bluuebunny/crossref_metadata_2025 huggingface dataset:
Leptin modulates orexin‐mediated functions at the behavioral and cellular level in mice
Authors: Grundschober Christophe , Delerue Fabien , Prinssen Eric , Moreau Jean‐Luc , Wettstein Joseph G , Lopez‐Lopez Cristina
Published: June 2021

The two orexin hypothalamic neuropeptides play an important role in energy homeostasis as well as arousal and narcolepsy. Leptin is putatively involved in the regulation of orexin neuronal activity. Using neurochemical, behavioral and histological methods the in vivo and in vitro interactions between the leptin and orexin systems were studied. Results indicate that there are higher levels of serum orexin A and increased locomotor activity during the active period of the light‐dark cycle in female as compared to male mice. Both elevated orexin serum levels and locomotion were decreased following subchronic exposure to a physiological dose of leptin (100 μg/kg/day, sc, minipump) in female mice. In addition, stereological brain analysis revealed that leptin reduced the number of orexin immunoreactive neurons in the lateral hypothalamus of female but not male mice. Leptin also reduced the activation of these neurons in both genders as measured by c‐fos activation. Further mechanistic studies in a mouse hypothalamic cell line revealed that AMPK, a kinase involved in metabolic regulation, could be the transducer of this leptin control of orexin neurons. In summary, these data support the notion that the leptin and orexin systems interact centrally, and indicate how leptin could modulate the orexin‐mediated regulation of vigilance states.
Guinea pig hippocampal 5‐HT1E receptors: a tool for selective drug development
Authors: Klein Michael Thomas , Smith Carol , Toohey Nicole , Teitler Milt
Published: June 2021

Recent studies have indicated that the 5‐HT1ER, discovered in human brain tissue (Leonhardt et al, 1989), is not expressed in mouse or rat brain, but is expressed in guinea pig brain (Bai et al, 2004). Thus there have been few reports on 5‐HT1ER drug development. In order to establish an animal model that will allow 5‐HT1ER drug development we identified regions of the guinea pig brain that when homogenized exhibit 5‐CT, mesulergine, and sumatriptan ‐insensitive 3H5‐HT binding (characteristic of the 5‐HT1ER). The hippocampus was determined to have a receptor density sufficiently high for further analysis. In hippocampal homogenates, 100nM 5‐CT, 30nM ritanserin, and 100nM LY344864 were used to block high‐affinity 3H5‐HT binding at non‐1E binding sites. The Kd value of 3H5‐HT was found to be 5.7±0.7nM which is indistinguishable from the cloned receptor Kd of 5.7±0.6nM. Drug affinities for the hippocampal and cloned 5‐HT1ER binding were identical. These findings indicate the 3H‐5‐HT binding is specific to the guinea pig 5‐HT1ER and levels of receptors can be determined in various brain tissues. Autoradiographical analysis and signal transduction studies of 5‐HT1ER in guinea pig brain can thus be determined. This should provide important insights into possible functions of the 5‐HT1ER receptor and may predict the possible therapeutic potential of selective h5‐HT1ER agonists and antagonists.

(Supported by MH56650)
Ultrafine particulates decrease left ventricular performance after ischemia‐reperfusion
Authors: Moll David , Lindsay John , Lord Kevin C , Dellinger Barry , Dugas Tammy , Varner Kurt
Published: June 2021

Epidemiological studies show a correlation between increased airborne particulates and hospitalization for cardiovascular events, especially in at risk populations. Ultrafine particles (UFP, <100 nm diam) generated from the combustion of hazardous wastes can contain stable free radicals. Given the link between oxidative stress and cardiac disease, we hypothesized that exposure to UFP may exacerbate left ventricular (LV) dysfunction produced by ischemia reperfusion (I/R). Male Brown Norway rats were pretreated (24 hr) i.t. with UFP containing CuO and dichlorobenzene (DCB, 8 mg/kg), silica UFP (8 mg/kg) or vehicle. Rats were anesthetized, ventilated and a pressure volume (PV) catheter placed in the LV. After baseline measures, the LAD was ligated for 90s and released. PV loops were generated 1–60 min post I/R. At 1 min post I/R, control and DCB‐treated rats showed decreased dP/dt max, increased tau, and increased end diastolic volume. Ejection fraction was unchanged in control and reduced in DCB‐treated rats (−45%). LV performance in control rats returned to baseline by 30 min. In DCB‐treated rats LV performance steadily declined for 60 min before stabilizing at reduced levels (dP/dt, −45%; tau, +38%; EF −50% vs baseline). These data indicate that prior exposure to UFP may pose a significant risk in persons with cardiac ischemia. Support: NIH P20‐RR018766
ANTECEDENT HYDROGEN SULFIDE ELICITS AN ANTI‐INFLAMMATORY PHENOTYPE IN POSTISCHEMIC MURINE SMALL INTESTINE: ROLE OF p38 MAPK
Authors: Yusof Mozow , Kalogeris Theodore , Gaskin F. Spencer , Korthuis Ronald J.
Published: June 2021

Recent work indicates that the activation of a number of kinases, such as p38 MAPK, plays a critical role in the development of preconditioned states. This MAPK is activated by dual phosphorylation on a Thr‐Gly‐Tyr motif in response to a number of stimuli implicated as triggers for preconditioning. We recently demonstrated that preconditioning with an exogenous hydrogen sulfide (H2S) donor (NaHS‐PC) 24 h prior to ischemia and reperfusion (I/R) causes postcapillary venules to shift to an anti‐inflammatory phenotype in C57Bl/6 wild‐type mice such that these vessels fail to support leukocyte rolling (LR) and leukocyte adhesion (LA) during reperfusion. Since H2S has been shown to increase p38 MAPK phosphorylation, we postulated that the anti‐inflammatory effects induced by exogenous H2S might be elicited through activation of this kinase. Our results show that pharmacologic inhibition of p38 MAPK by either of SB203580 or SK80062 inhibitors abolished the protective effects of late phase NaHS‐PC in C57Bl/6 WT mice to limit LR and LA induced by I/R 24 hrs after preconditioning. Our data supports the notion that activation of p38MAPK mediates the effects of NaHS‐PC. Supported by AA14945 and DK43785.
Cerebrovascular dilatory and protective effects of VIP in newborn piglets
Authors: Zimmermann Aliz , Lenti Laura , Domoki Ferenc , David Kis , Olah Orsolya , Toth Gabor , Busija David W , Bari Ferenc
Published: June 2021

VIP dilates cerebral vessels and is protective against ischemic brain damage, but the mechanisms of these actions have not been investigated in the newborn. VIP and pituitary adenylate cyclase activating polypeptide (PACAP) are structurally related neurotransmitters potentially acting on common receptors. We tested if 1) VIP‐induced cerebral vasodilation is mediated by a) cyclooxygenase (COX), b) nitric oxide synthase (NOS) or c) PACAP‐receptors; 2) VIP preserves cerebrovascular responsiveness after I/R. Pial arteriolar diameter was measured by intravital microscopy in newborn piglets equipped with closed cranial windows. VIP (10−9−10−6M) caused a significant, dose‐dependent pial arteriolar dilation that was blocked by the non‐selective COX‐inhibitor, indomethacin, only at 10−9−10−8M VIP, was unaffected by the NOS inhibitor, L‐NAME, and reduced by the PACAP antagonists, PACAP 6–27 and 6–38. VIP (10−9M, 20 min before I/R) preserved the endothelium‐dependent response to hypercapnia, but not the neuronal‐dependent reactivity to NMDA. We conclude that 1) vasodilator effect of VIP partially involves COX and common receptors with PACAP and 2) VIP protects cerebrovascular endothelial function against I/R. Supported by the Hungarian Scientific Research Fund (OTKA K63401 and K68976) and the Hungarian Health Science Board (ETT 194042006).
Renal ischemia‐reperfusion injury (I/R) is prevented by adrenal glands removal
Authors: Ramírez Victoria , Trujillo Joyce , Valdez Rafael , Cruz Cristino , Gamba Gerardo , Bobadilla Norma A.
Published: June 2021

We showed that spironolactone (Sp) prevented I/R injury by mechanisms that include preservation of renal blood flow (RBF), reestablishment of UNO2/NO3V, reduction of lipoperoxidation and cell apoptotic death, suggesting that aldosterone participates in promoting renal injury in this model. However, renal protection conferred by Sp could potentially due to unknown mechanisms. To evaluate if Sp renoprotection is mediated by blocking aldosterone actions, the effect of adrenalectomy (Adx) prior I/R injury was evaluated.

Three groups of 7 rats were studied. Sham operated; rats underwent 20 min of bilateral ischemia and reperfusion (24h); Adx rats, 3 days before I/R. To prevent hypoglycemia in Adx rats, physiological doses of glucocorticoids were given. In collected urine samples, creatinine clearance (CrC), n‐acetil‐beta‐d‐glucosaminidasa (NAG) and protein excretion (Prot) were measured. After 24h, mean arterial pressure and renal blood flow (RBF) were recorded and one kidney was fixed for histopathological evaluation.

As expected, I/R induced renal dysfunction as compared to sham group that was characterized by reduction of RBF (4±0.4 vs. 7±0.2) and CrC (0.4±0.1 vs. 1.5±±0.2). At histological level, I/R produced severe tubular necrosis and increased Prot (46.7±3.9 vs. 10.4±1.2) and NAG excretion (0.6±0.1 vs. 0.2±0.02). In contrast, in Adx group RBF and CrC were not affected by I/R (7.3±0.4 and 1.4±0.2 respectively). Moreover, histological signs of tubular injury were not observed, effect that was associated with NAG and Prot normalization.

Our data show that aldosterone plays a central role in the pathogenesis of renal I/R injury and pointed out to Sp as a promising tool for renal protection against I/R.
Role of Angiotensin II internalization in the activation of Proximal Tubule Angiotensinogen
Authors: Gonzalez‐Villalobos Romer A , Satou Ryousuke , Kobori Hiroyuki , Navar L. Gabriel
Published: June 2021

Angiotensin (Ang) II increases the expression of angiotensinogen (AGT) mRNA and protein by proximal tubules (PT) in the kidney; however the molecular mechanisms are unclear. Because Ang II internalization regulates several actions of this hormone in PT cells, studies were performed to determine if Ang II internalization is required for activation of AGT expression in these cells. Immortalized rat PT cells (IRPTCs) were exposed to Ang II (1 nM, 1 hour), with or without an AT1R blocker (candesartan, 10 μM), or an endocytosis inhibitor (PAO, 0.1 μM) before mRNA collection. AGT mRNA expression was determined by qRT‐PCR. Ang II internalization was determined by exposing cells to fluorescent‐Ang II (Alexa488‐Ang II, 100 nM, 15–240 min) and detecting intracellular fluorescent signal with an epifluorescence microscope. Ang II increased AGT expression by 20% (1.21 ± 0.19 vs. 1.00 in controls, p<0.05). This effect was both AT1R‐dependent and endocytosis‐dependent as it was prevented by candesartan (0.89 ± 0.24, NS) and by PAO respectively (0.93 ± 0.04, NS). Microscopy studies demonstrated that Ang II is internalized in a time‐dependent manner, with a signal shift from the cell membrane to the perinuclear area after 1 hour. In conclusion, Ang II internalization by PT cells is required for activation of the AGT gene, and this effect is concomitant with a signal shift that suggests Ang II translocation to perinuclear compartments.

Work supported by NIH grants P20RR017659, HL26371 (LGN), (R01DK072408) (HK), and the COSEHC Warren Trust Fellowship award (RAGV).
Increased oxidative stress diminishes NO‐mediated vasodilatation initiated by aldosterone in arterioles
Authors: Heylen Erwan , Sun Dong , Kaley Gabor
Published: June 2021

There is increasing evidence that aldosterone has a significant impact on cardiovascular function. In the present study, we investigated direct vasoreactivity to aldosterone in resistance vessels. Mesenteric arterioles were isolated from normal Wistar rats and pressurized at 80 mmHg intravascular pressure in a no‐flow condition. Aldosterone (10−12 to 10−8M) elicited a dose‐dependent vasodilator response, which was significantly inhibited by administration of spironolactone (10−7 M), mineralocorticoid receptor antagonist, removal of the endothelium or inhibition of NO synthesis by Nω‐nitro‐L‐arginine methyl ester (3×10−4M). At a concentration of 10−7M, aldosterone elicited a reduced dilation, which was converted to a vasoconstriction after removal of the endothelium and a greater dilatation after scavenging superoxide with Tempol (10−4M) or inhibition of NAD(P)H‐oxidase with apocynin (10−4M). Intraluminal administration of aldosterone (10−7M) elicited a significantly greater and prolonged vasodilatation than extraluminal administration. These data suggest that the effects of aldosterone on resistance vessels depend on its concentration. In a physiological concentration, aldosterone increases arteriolar diameter via an endothelial NO‐mediated mechanism; however, in pathological concentrations, aldosterone increases oxidative stress, which may reduce NO bioavailability. (Supported by NIH HL‐43023, HL‐68813 and HL‐070653)
Enhancement of cardiac baroreflex sensitivity in acute hypovolemia is abolished in vasopressin V1a receptor knockout mice
Authors: Masuki S. , Koshimizu T. , Zhang B. , Higuchi K. , Tsujimoto G. , Nose H.
Published: June 2021

To assess the role of vasopressin V1a receptor (V1a‐R) in baroreflex control of heart rate (HR) in acute hypovolemia, mean arterial pressure (MAP) and HR were measured in freely moving V1a‐R knockout (KO, n = 6) and wild type mice (WT, n = 5) in 3 conditions; before and after 0.39 ml of blood draw, and after blood recovery. The treatments of blood draw and recovery were accomplished in 4 min each, followed by the 5‐min measurement, respectively. A double lumen catheter was chronically placed in the femoral artery for MAP measurement, drug infusion, and blood draw and recovery. Baroreflex sensitivity of HR (BRS‐HR) was determined by bolus infusion of phenylephrine at the 1.5th min of each condition. MAP (mmHg) was 119 ± 3 in WT and 112 ± 3 in KO before blood draw (P = 0.1), and decreased by 24 ± 4 in KO more than 8 ± 1 in WT after blood draw (P = 0.01). There were no differences in HR (~520 beats/min) before blood draw and the increase after blood draw (~140) between WT and KO (P > 0.3). BRS‐HR (HR/MAP, beats/min/mmHg) was −3.0 ± 0.5 in WT and −6.1 ± 1.9 in KO before blood draw (P = 0.2), and increased to −7.2 ± 1.2 in WT after blood draw (P < 0.05) but, in contrast, decreased to −1.6 ± 0.4 in KO (P < 0.05; KO vs WT, P = 0.001). After blood recovery, BRS‐HR was restored immediately in both groups. Thus, BRS‐HR was enhanced by acute hypovolemia in WT but the response was abolished in KO, suggesting that V1a‐R was involved in enhanced BRS‐HR in acute hypovolemia.
CARDIOVASCULAR EFFECTS OF ACETYLCHOLINE MICROINJECTED INTO THE VENTROLATERAL PERIAQUEDUCTAL GRAY AREA OF RATS.
Authors: Deolindo Milena Vieira , Pelosi Gislaine Garcia , de aguiar Correa Fernando Morgan
Published: June 2021

INTRODUCTION

The periaqueductal gray area (PAG) is a mesencephalic region that is involved in the modulation of cardiovascular changes associated with behavioural responses. Among the neurotransmitters present in the PAG, acetylcholine (Ach) is also known to be involved in central cardiovascular control. In the present study, we attempted to study the cardiovascular effects of the microinjection of Ach into the ventrolateral portion of the PAG (vlPAG) of rats.

METHODS: Male Wistar rats were used. Guide cannulas were implanted in the vlPAG for drug injection and a polyethylene catheter was implanted into the femoral artery for arterial pressure (AP) and heart rate (HR) recording using a computerized acquisition system. RESULTS: The injection of different doses of Ach (27 and 81nmol/50nL) into the vlPAG of unanaesthetized rats caused dose‐related depressor responses accompanied by bradycardia. However, the injection of different doses of Ach (27 and 81nmol/50nL) into the vlPAG of anaesthetized rats caused dose‐related depressor responses accompanied by tachycardia.

CONCLUSION: The present results indicate that activation of cholinergic receptors within the vlPAG can evoke cardiovascular responses in rats.

FINANCIAL SUPPORT: CNPq and Fapesp (05/57227‐0)
Scheduled sampling of cardiovascular parameters: how often should one collect data?
Authors: Guild Sarah‐Jane , Barrett Carolyn J , McBryde Fiona D , Van Vliet Bruce N , Malpas Simon C
Published: June 2021

Long‐term measurement of variables such as heart rate (HR), blood pressure (BP) and sympathetic nerve activity (SNA) via telemetry in laboratory animals has become indispensable in cardiovascular physiology. Due to the significant amount of data recorded and battery life limitations many researchers use acquisition software to intermittently collect data over short time periods at scheduled time points. The question is how much data does one need to collect to accurately reflect the underlying average value?

Three separate days (0000–2400) of HR, BP and integrated renal SNA data were used from each of 6 rabbits. Each day's data (collected as 2s averages) were resampled according to 60 sampling protocols to investigate both the quantity of data collected and the number of sampling periods, e.g. 4 hours sampling per day could be two 2 hour or twenty–four 10 minute periods.

The error in estimating the actual mean was calculated for each sampling protocol by comparing each day's estimated mean with that calculated using the complete data set for that day. The results show that the error in estimating the daily mean of SNA using a given protocol is approximately double that of BP and HR and good estimations (<2% error) can be achieved by scheduled sampling, particularly if short sampling periods are spread throughout the day. Supported by the Health Research Council of New Zealand and University of Auckland Research Committee.
Assessment of potential hypertensive risk during circuit training in normotensive and hypertensive subjects.
Authors: Margonato Vittoria
Published: June 2021

Combined aerobic‐anaerobic exercise seem to be a valid not pharmacological way to reduce hypertension. Circuit training (CT) is often used to train normotensive (N) and hypertensive (H) subjects, but not all the circuits are equal and some exercises could be dangerous for H.

Objective of the study, conducted in accordance with Basic Principles of the Declaration of Helsinki, was: assessing the trend of blood pressure response of N and H during a CT session; defining which exercises in a CT are most safe for H; verifying the possible risks of a CT session to rise excessively blood pressure in H. Methods. 10 N and 10 H moderately trained males were enrolled. Arterial blood pressure was measured at rest and at the end of each exercise. Heart rate was recorded by a heart rate monitor. Subjects performed a 7 CT stations: bike 65–70–75% of HRmax,, leg press, leg extention, leg curl and squat. Results. Mean arterial blood pressure was significantly higher in H respect N. No difference was detected for leg‐extension and for bike 75% HRmax diastolic pressure. Leg curl, leg‐extension, leg press and bike at 65%HRmax resulted clinically safe. Bike at 70–75% HRmax and isometric squat overcame the upper limit of clinically safe exercise. Conclusions: It is necessary to monitor blood pressure during a CT programme as bike (70–75% of HRmax) and isometric squat evidenced a potential risk for H subjects.
Reciprocal neuronal projections between arcuate and ventrolateral periaqueductal gray participate in long‐lasting EA inhibition of reflex blood pressure elevation
Authors: Li Peng , Tjen‐A‐Looi Stephanie C. , Guo Zhi Ling , Longhurst John C
Published: June 2021

We have shown the prolonged inhibition of electroacupuncture (EA) on reflex elevations of blood pressure (BP). EA activates the arcuate nucleus (ARC) that sends excitatory projection to ventrolateral periaqueductal gray (vlPAG), in turn, inhibits cardiovascular sympathetic premotor neurons in the medulla. This study investigated the role of a reciprocal neural circuit between the vlPAG and ARC. In alpha‐chloralose anesthetized cats recordings showed that injection of DL‐homocysteic acid (DLH, 4 nM, 50 nl) into vlPAG facilitated the ARC neuronal response to splanchnic nerve stimulation over 40 min. Injection of kainic acid (KA, 1 mM, 50 nl) into the vlPAG blocked the long‐lasting EA (P5‐6 overlying median nerve) excitation on ARC neurons. The EA inhibition on reflex‐induced elevation of BP could be blocked by microinjection of glutamate receptor antagonist, kynurenic acid (KYN) into the ARC. The EA excitation of vlPAG neurons also was blocked by microinjection of glutamate NMDA and non‐NMDA receptor antagonists, CNQX and AP‐5 as well as by atropine. Retrograde morphological studies using colored microspheres (six rats) showed the reciprocal neuronal projections between ARC and vlPAG that contain glutamate. These data demonstrated that the long‐lasting EA inhibition is partly due to the ARC‐vlPAG excitatory neural circuitry involving glutamate and acetylcholine. (Supported by HL‐63313, ‐72125)
Role of Forebrain TRPV1 Receptors in Body Fluid Homeostasis
Authors: Taylor Anna Caitlynn , McCarthy John J , Stocker Sean D
Published: June 2021

Neurons of the organum vasculosum of the lamina terminalis mediate thirst and the secretion of antidiuretic hormone during hypernatremia. The osmosensitivity of these neurons is mediated by the transient receptor potential vanilloid‐type 1 (TRPV1) receptor. Therefore, we hypothesized that TRPV1 −/− versus wild‐type (WT) mice would have blunted thirst responses to osmotic dependent stimuli. TRPV1−/− versus WT mice ingested similar amounts of water after sc injection (0.5 ml) of 0.5 M NaCl (0.55±0.2 vs 0.53±0.03 mL) or 1.0 M NaCl (1.44±0.05 vs 1.25±0.05 mL). Overnight water deprivation produced similar increases in water intake between TRPV1−/− and WT mice (1.23±0.05 vs 1.01±0.06 mL). The ingestion of water stimulated by sole access to 2% NaCl for 48 hrs was not different between TRPV1−/− and WT mice (0.67±0.07 vs 0.76±0.06 mL). Hypovolemia produced by the diuretic furosemide (2.5 mg, sc) stimulated similar increases in water intake between TRPV1−/− and WT mice (0.63±0.03 vs 0.79±0.04 mL). Isoproterenol (0.4 μg, sc) also produced similar increases in water intake between TRPV1−/− and WT mice (0.27±0.02 vs 0.31±0.03 mL). TRPV1−/− mice were confirmed by PCR and the lack of an irritant response to capsaicin. These findings suggest that TRPV1 receptors are not necessary for osmotically‐driven thirst and may not be candidate ion channels that permit the brain to detect changes in systemic sodium concentration.
Acid‐Sensing Ion Channel‐1a Differentially Contributes to Blood Pressure and Heart Rate Responses to Hypoxia and Hypercapnia
Authors: Sabharwal Rasna , Wemmie John A , Abboud Francois M , Chapleau Mark W
Published: June 2021

Hypoxia and hypercapnia influence blood pressure (BP) and heart rate (HR) through multiple mechanisms including chemoreflex activation, central neural actions, and peripheral effects on heart and vasculature. Acid‐Sensing Ion Channel‐1 (ASIC1) is expressed in tissues implicated in hypoxia‐ and/or acid‐sensing including carotid body glomus cells, and sensory and central neurons. We hypothesized that ASIC1a contributes to BP and HR responses to hypoxia and hypercapnia. BP and HR were recorded by telemetry in ASIC1a−/− (n=5) and wild‐type (WT) mice (n=9) before and during 10‐min exposures to hypoxia (10% O2) and hypercapnia (5 and 10% CO2). Mean BP and HR during normoxia did not differ in ASIC1a−/− and WT mice (127±3 vs. 117±4 mmHg, 707±18 vs. 712±34 bpm). HR increased transiently during hypoxia in WT and ASIC1a−/− mice (+35±14 and +48±11 bpm), and then decreased over time as did BP. The hypoxia‐induced bradycardia and hypotension were significantly enhanced in ASIC1a−/− mice vs. WT (see Table, *P<0.05). Sustained hypercapnia also decreased HR and BP in WT mice. Notably, CO2‐hypotension did not occur in ASIC1a−/− mice despite an enhanced bradycardia (Table).

We conclude that ASIC1a mediates hypercapnia‐induced hypotension but opposes the CO2‐bradycardia. In contrast, ASIC1a‐dependent mechanisms oppose hypoxia‐induced hypotension and bradycardia. The results suggest that ASIC1a may contribute to autonomic responses and to the direct cardiac and vascular effects of hypoxia and hypercapnia in a differential manner. (AHA 0725771Z, HL14388)
Pharmacological inhibition of nitric oxide synthase increases sympathetic nerve activity in healthy humans
Authors: Young Colin N. , Fisher James P. , Gallagher Kevin M. , Fadel Paul J.
Published: June 2021

Animal studies have indicated that nitric oxide (NO) is a key signaling molecule involved in the tonic restraint of central sympathetic outflow from the brainstem. Extension of these findings to humans has been difficult since experimental systemic NO synthase (NOS) inhibition rapidly increases blood pressure (BP) from the removal of endothelial‐dependent vasodilation and activates an arterial baroreflex‐mediated sympathoinhibitory response. Thus, to overcome this confounding inhibitory influence of the baroreflex we measured skin SNA, which is not under baroreceptor control. Seven healthy subjects (26 ± 3 yr) were studied before, during and 90 minutes after a 60 minute intravenous infusion of the NOS inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME; 4mg/kg). Skin SNA and BP were continuously measured. Mean BP was increased from baseline at the end of the L‐NAME infusion (Δ15 ± 2 mmHg; P<0.05) and remained elevated at 90 minutes post infusion (Δ16 ± 1 mmHg; P<0.05). Similarly, skin SNA was elevated at the end of the L‐NAME infusion (ΔTotal Area 133 ± 59 au; P<0.05) and this increase was maintained at 90 minutes post infusion (ΔTotal Area 209 ± 70 au; P<0.05). Importantly, skin SNA remained unchanged during time control experiments. These preliminary findings suggest that pharmacological inhibition of NOS increases SNA and supports a role of NO in central sympathetic control in humans. Supported by NIH DK076636.
Protein Tyrosine Phosphatase 1B is a negative regulator of alpha‐adrenergic vasoconstriction in mouse aorta
Authors: de Chantemele Eric Belin , Ketsawatsomkron Pimonrat , Marrero Mario , Stepp David
Published: June 2021

Protein tyrosine phosphatases, such as 1B (PTP1B) act as counter‐regulators of tyrosine kinases to modulate signal transduction. While tyrosine kinases are involved in vascular function, effects of PTP1B on vascular reactivity are unknown. We hypothesized that PTP1B modulates aortic contraction. Aortic contraction was examined by myography using PTP1B knockout (KO) mice and Balb/C controls (CON). PTP1B deletion reduced blood pressure (CON: 112±2 vs KO: 106±2mmHg, p<0.05). Phenylephrine (PE)‐induced maximum contraction was reduced in KO mice (CON: 96.3±12 vs KO: 57.7±9% of KCl, p<0.05) with no effect on KCl or serotonin (5HT)‐mediated contraction. To analyze the mechanisms involved, contraction to PE, 5HT and KCl were conducted in the presence of PKC (Calphostin C), ERK1/2 (PD98059) and ROK inhibitors (Y27632). Inhibitors had no effect on the 5HT, KCL‐mediated contraction suggesting lack of dependence on PKC, MAPK and ROK. PKC inhibition reduced similarly contraction to PE in CON and KO mice. The inhibitory effects of PD98059 (CON: 12.6±16 vs KO: 55.7±11%, p<0.05) and Y27632 (CON: 48.6±9 vs KO: 70.2±6%, p<0.05) were higher in KO mice arguing for a higher involvement of MAPK and ROK in PE‐induced contraction in KO mice. These data identify PTP1B as a novel negative regulator of adrenergic contraction in vascular smooth muscle via MAPK and ROK signaling and may explain reduced blood pressure in PTP1B KO mice.
Age‐related changes in vasoconstrictor response to heat in skeletal muscle arteries
Authors: Kluess Heidi A , Buckwalter John B , DeLorey Darren S , Clifford Philip S
Published: June 2021

Aging reduces skeletal muscle blood flow, but the mechanism remains unclear. The hypothesis was that aging results in less heat‐induced attenuation of vasoconstriction and this is attributable to decreased sensitivity of P2X receptors to heat. Femoral arteries from 28 young (2–3 months old) and 23 old (24 months old) rats were prepared for wire myography. Dose response curves for the P2X agonist, αβ‐methylene ATP (mATP: 10−7 to 10−3M), the α1‐agonist, phenylephrine (PE: 10−7 to 10−4M), the smooth muscle constrictor, potassium chloride (KCl: 20 to 80mM), and field stimulation (2–60Hz for 144 impulses) were performed at bath temperatures of 37°C and 41°C. The response to mATP was attenuated with heat in young (37°C: 0.95±0.14; 41°C: 1.48±0.12 g/log M mATP; p<0.05) and old (37°C: 1.05±0.16; 41°C: 1.67±0.20 g/log M mATP; p<0.05) femoral arteries. Phenylephrine dose response curves were not heat sensitive in young arteries, but were potentiated with 41°C in old arteries (p<0.05). KCl dose response curves were potentiated by 41°C in the young (37°C: 2.10±0.25; 41°C: 2.67±0.19g peak tension; p<0.05) and old arteries (37°C: 1.95±0.22; 41°C: 2.53±0.10g peak tension; p<0.05). The tension produced by field stimulation was attenuated by a greater amount in old (−78±10%) than in young (−43±12%). Heat‐induced attenuation of vasoconstriction via P2X receptors is preserved in old femoral arteries. Unexpectedly, old femoral arteries exhibit heat potentiation of α1‐receptor mediated vasoconstriction.
The hydrogen sulfide donor IK‐1001 protects against hepatic reperfusion injury in a murine model: evidence for a gender difference
Authors: Mebel Elise , Szabo Csaba , Toombs Christopher
Published: June 2021

IK‐1001 is a parenteral sulfide donor that recently entered human trials. Published literature shows sulfide to be protective in myocardial ischemia. We explored the potential protective effects in hepatic ischemia. C57/B6 mice were anesthetized and a midline laparotomy was performed to expose the liver. Mice were treated with heparin to prevent clotting after which a micoaneurysm clip was applied to the hepatic artery and portal vein to create liver ischemia. In the last 5 minutes of a 45 minute occlusion, vehicle or IK‐1001 (2.3 mg/kg) was injected into inferior vena cava. The clips were removed to restore hepatic blood flow which was confirmed visually. The abdominal incision was closed and animals were recovered. At 5‐hours reperfusion, blood was collected to measure serum alanine aminotransferase (ALT). In vehicle treated male animals, ALT was 841 ± 261 U/L (n=10). With IK‐1001, ALT was reduced to 582 U/L ± 71 % (p<0.048) n=10. Interestingly, when studies were repeated in female mice, the degree of injury appeared reduced (497 ± 69 U/L, n=4) in comparison to male mice and no significant reduction in ALT was noted when female mice were treated with IK‐1001 (493 ± 185 U/L, n=8). We conclude that administration of IK‐1001 at the time of reperfusion results in liver protection as measured by ALT. In female mice, comparable ischemia did not appear to produce comparable injury and may explain a lack of benefit of IK‐1001 in females.
Effect of ischemia‐reperfusion on O‐GlcNAcylation of specific proteins in isolated rat hearts
Authors: Laczy Boglarka , Wilson Landon , Brocks Charlye A , Marchase Richard B , Chatham John C
Published: June 2021

We have shown that increasing the level of O‐linked‐N‐acetylglucosamine (O‐GlcNAc) on proteins protects the heart against ischemia‐reperfusion injury; however, the specific proteins altered by O‐GlcNAc have yet to be determined. Isolated perfused hearts from male rats (n=5–9/groups) were subjected to 10 min no‐flow ischemia (ISC) or ISC followed by 60 min reperfusion (I/R). Overall protein O‐GlcNAc levels, determined by anti‐O‐GlcNAc immunoblots, were increased following ISC (p<0.05) compared to normoxic controls. Using MALDI‐TOF we identified proteins in two bands in which O‐GlcNAc levels significantly increased during ISC and subsequently decreased following I/R and one band that increased only following I/R. The proteins in the O‐GlcNAc positive bands that increased during ISC were identified as glycogen phosphorylase b and mitochondrial aconitase. The protein in the O‐GlcNAc band that increased with I/R was identified as the cytoskeletal protein vinculin. Vinculin and aconitase were subsequently immunoprecipitated and both were found to be O‐GlcNAc positive by immunoblot analysis. Further studies are needed to determine the effect of O‐GlcNAc on the function of these proteins and how this influences the response to I/R. NIH grants: HL067464 and HL079364.
A New Cardioprotective Strategy to Salvage Myocardium from Reperfusion Injury: Combination PAR1 Inhibition and PAR2 Activation at Reperfusion
Authors: Jiang Rong , Deneve Jeremiah , Eldaif Shady , Wang Ningping , Zhao Zhi‐Qing , Guyton Robert A. , Vinten‐Johansen Jakob
Published: June 2021

Protease activated receptors (PAR) play contrasting roles in ischemic‐reperfusion: PAR1 activation is deleterious while PAR2 activation may exert protection. This study tested the hypothesis that the combination of PAR1 inhibition and PAR2 activation exerts enhanced cardioprotection. Methods: In open‐chest rats, the left coronary artery was occluded for 30 min and reperfused for 3 hours. Rats were randomly assigned to: 1) Control: saline 1 ml/Kg; 2) PAR1 antagonist BMS 200261 1mg/Kg; 3) PAR2 agonist peptide (PAR2 AP) SLIGRL‐NH2 1 mg/Kg; 4) BMS 200261 + PAR2 AP: each 1mg/Kg. All drugs were given 5 min before reperfusion. Results: Area at risk (33%‐38%) was comparable. Compared to control, infarct size was significantly reduced in both BMS 200261 and PAR2 AP groups (40.7 ?2.7* and 37.2 ?2.3* vs 55.8 ?2.4). The combination of BMS 200261 and PAR2 AP further reduced infarct size (28.0 ?3.6*?). Conclusions: 1) Either inhibition of PAR1 or activation of PAR2 specifically at reperfusion is cardioprotective in vivo; 2) the combination of the two approaches is significantly more effective in reducing infarct size. * P < 0.05 vs. control. ?P < 0.05 vs. PAR 2 AP or BMS group.
Isoflurane causes powerful second window of protection (SWOP) against myocardial stunning in the dog
Authors: Saad Maged M , Goanzalez Joaquin B , Crystal George J , Kim Song‐Jung
Published: June 2021

Despite intensive investigation, the ability of isoflurane (ISO) to cause SWOP in the myocardium remains a matter of debate. We tested the hypothesis that inhalation of ISO can reduce extent of myocardial stunning produced by ischemia 24 hours later. The findings with ISO were compared to those with ischemic preconditioning (IPC) produced by a 10 min coronary artery occlusion (CAO). 8 mongrel dogs were chronically instrumented to measure wall thickening (WT) in the left ventricle. In group 1 (n=4), dogs inhaled 1 MAC (1.4 %) ISO for 60 min, after which time they were allowed to recover for 24 hrs and studied in the conscious state. A 10 min CAO was induced and the recovery of WT was monitored for 24 hrs. In group 2 (n=4), dogs underwent IPC, induced by a 10 min CAO; 24 hrs later they were subjected to another 10 min CAO. The recovery of WT following the initial occlusion served as control (CON) for the effects of both ISO and IPC. CAO caused akinesis in all groups. Three hours of reperfusion were required for complete recovery of WT in the ISO and IPC. At this time WT remained significantly depressed (−25±4%) in CON; between 12 and 24 hrs of reperfusion was required for complete recovery. We conclude that isoflurane has powerful SWOP effects against myocardial stunning and that this effect is comparable to ischemic preconditioning in the dog.
Ischemic damage to the mitochondrial electron transport chain favors opening of the permeability transition pore
Authors: Chen Qun , Lesnefsky Edward
Published: June 2021

Myocardial ischemia (ISC) damages the electron transport chain (ETC). Blockade of the ETC during ISC at complex I with amobarbital (AMO) protects against ETC damage during ISC and decreases necrosis measured after reperfusion (REP). Opening of the mitochondrial permeability transition pore (MPTP) is a key mechanism of REP injury. We hypothesized that ischemic ETC damage leads to MPTP opening as a mechanism of REP injury. Isolated rabbit hearts were perfused for 15 min. followed by 30 min. stop‐flow ISC at 37°C (ISC alone) or given 2.5 mM AMO for 1 min. immediately before ISC. Subsarcolemmal mitochondria (SSM) were isolated after ISC. AMO treatment protected respiration (nAO/mg/min) with glutamate (complex I) and TMPD‐ascorbate (complex IV) as substrates. MPTP opening was assessed by detecting mitochondrial swelling by 200 uM calcium (% change of AU/mg/min). AMO inhibition of ETC during ISC attenuated swelling of SSM. Protection of the ETC during ISC significantly decreased MPTP opening. Ischemic damage to ETC promotes MPTP opening as a mechanism of mitochondrial‐dependent cardiac injury during REP, translating ischemic ETC damage into REP injury.

SSM
Glutamate
TMPD‐asc
Swelling

ISC (n=5)
110±9
360±21
15.1±3.4

AMO (n=4)
185±29*
554±17*
4.0±1.8*

±SEM; *p<0.05 vs. ISC
Myocardial SIRT1 expression following endurance and resistance exercise training in young and old rats
Authors: Cross Whitney L. , Roby Mackenzie A. , Deschenes Michael R. , Harris M. Brennan
Published: June 2021

Previous studies indicate a link between caloric restriction, SIRT1 expression, and longevity. It has been suggested that the metabolic stress of exercise may also alter SIRT1 expression. Therefore, we evaluated the effects of two different modes of exercise training on myocardial SIRT1 protein expression in young and old rats. In the first study, young (8 mo) and old (24 mo) Fisher 344 rats were subjected to a progressive treadmill training program for 10 wks ending at 60 min/day, 15 m/min, 0% grade. Myocardial SIRT1 expression was not significantly different (P>0.05) between young and old rats. However, endurance training resulted in a significant (P<0.05) decrease in myocardial SIRT1 protein expression. In the second study, young (5 mo) and old (22 mo) Fisher 344 rats were resistance trained by ladder climbing for 8 wks. Animals began by lifting 50% body weight and ended the training protocol lifting 276±6% body weight (young) and 141±12% body weight (old). Again, we observed no effect of age on myocardial SIRT1 expression. However, in contrast to endurance training, resistance training resulted in no significant (P>0.05) change in SIRT1 expression. The results of this study demonstrate that exercise‐induced changes in myocardial SIRT1 expression are dependent on the mode of training.

Supported by Borgenicht Program for Aging Studies and Exercise Science (MBH), AHA SDG 0430157N (MBH), and the NIA (MRD).
Protein and mRNA expression of mitochondrial transcription factors TFB1M, TFB2M and TFAM in elite athletes
Authors: Sundberg Carl Johan , Norrbom Jessica , Rundqvist Helene , Wallman Susanna , Jansson Eva , Gustafsson Thomas
Published: June 2021

The aim of the present study was to investigate mRNA and protein levels of mitochondrial transcription factors Tfam, TFB1M and TFB2M in individuals with high oxidative capacity (elite athletes) compared to normally trained individuals, as well as the effect of 5 weeks of exercise in healthy males.

Method: Skeletal muscle biopsies were obtained from the vastus lateralis muscle at rest from 12 males with high oxidative capacity, 9 moderately trained male controls and 12 healthy males before and after 10 days and 5 weeks of one‐legged knee extension exercise. One leg exercised with restricted blood flow (R‐leg), the other with non‐restricted blood (NR‐leg) flow.

Results: mRNA expression of TFB1M and TFB2M was increased after 10 days and 5 weeks of exercise in the R‐leg. Moreover, higher mRNA expression of both TFB1M and TFB2M was detected in elite athletes compared to moderately active individuals. No differences in TFAM mRNA were observed.

Conclusion: This suggests that metabolic perturbation, induced by regular contractile activity, or a higher oxidative status have long‐term effects on steady state mRNA expression of TFB1M and TFB2M but not on Tfam. Protein analyses could not detect any differences in TFB1M and TFB2M between elite athletes and moderately active individuals. However, TFAM protein expression was significantly higher in the elite athletes.
12‐weeks of Aquatic Exercise Training modifies mTOR signaling following Essential Amino Acid + Carbohydrate Ingestion in Older Subjects
Authors: Christian Dreyer Hans , John Drummond Micah , Fujita Satoshi , Rasmussen Blake , Volpi Elena
Published: June 2021

Essential amino acid (EAA) ingestion can stimulate muscle protein synthesis in young and older subjects. In older subjects however, the addition of carbohydrate (CHO) (EAA+CHO) blunts the anabolic response as compared to young subjects and may be due to dysregulation of the insulin signaling pathway. Recent evidence shows that a single bout of aerobic exercise, performed within 24hrs, restores the anabolic response in older muscle following insulin infusion.

PURPOSE: To determine if 12 weeks of aquatic exercise training would similarly maintain the EAA+CHO‐induced anabolic response in older muscle.

METODS: Immunoblotting methods were used to determine mTOR signaling, at 1 and 2h post EAA + CHO ingestion pre and post‐training.

RESULTS: Our preliminary results from 5 older subjects demonstrate that mTOR phosphorylation is more robust at 1hr post EAA+CHO ingestion following 12 weeks of aquatic training (P<0.05) while there was no change in the phosphorylation status of Akt, S6K1, 4E‐BP1, and eEF2 after training.

CONCLUSIONS: Our preliminary findings suggest that mTOR phosphorylation is significantly greater 1hr post EAA+CHO ingestion following 12 weeks of aquatic exercise training as compared to pre‐training. This may provide potential evidence for a beneficial exercise training adaptation which improves the ability of older individuals to respond more efficiently to anabolic nutrients.

This work was supported by a Pepper Pilot Project award
Hemodynamic and autonomic responses during psychological and physiological stressors in African American males prior to and following an aerobic training program
Authors: Bartels Matthew N , De Meersman Ronald E , Zion Adrienne , Sloan Richard , Rebmann Rebecca A , Bond Vernon
Published: June 2021

We compared the patterning of autonomic and blood pressure (BP) response to psychologic and physiologic stressors prior to and after an 8‐week aerobic training program. METHODS: 16 African American males underwent training and were compared to 16 controls matched for family history of hypertension, race, gender, body mass index, age and VO2. Heart rate (HR), brachial systolic BP and radial beat‐to‐beat BP were recorded during seated rest, cold pressor test, deep breathing and color‐conflict stressor. Spectral analyses of HR and SBP were used to derive baroreflex sensitivity (BRS) and parasympathetic (HFRR[nu]) and sympathetic vasomotor modulation (LFSBP[nu]). RESULTS: Trained individuals showed significant improvement (p<0.05) in BRS as measured by alpha index (msec/mmHg): 8(3) vs 14(3), rest; 9(7) vs 16(4), cold pressor; 13(7) vs 18(9), deep breathing; 8(4) vs 13(7), color conflict. HFRR[nu], LFSBP[nu] and arterial compliance also showed improvements. No significant changes were seen in controls. CONCLUSIONS: Findings indicate aerobic training improved autonomic and blood pressure profiles at rest and during stressors in a population at high risk for cardiovascular events. Support: VIDDA foundation.
Perilipin gene haplotype is associated with body fatness before and after endurance exercise training
Authors: Jenkins Nathan T , McKenzie Jennifer A , Damcott Coleen M , Hagberg James M
Published: June 2021

Perilipin proteins are known to regulate intracellular lipolysis in adipocytes. A haplotype of two perlipin gene (PLIN) single nucleotide polymorphisms (SNPs), 13041A>G and 14995A>T, has been previously associated with obesity risk. We hypothesized that this haplotype associates with body fatness phenotypes before and after a 6‐mo aerobic exercise training program in sedentary older men and women. The major haplotype group (n = 57), characterized by the dominant allele at both SNPs (A/A), had significantly lower body mass index (BMI) and percentage, trunk, and subcutaneous fat compared to all other haplotypes (collapsed into a single group, n = 44) before the training intervention (all p < 0.05). After training, BMI, percent and trunk fat remained lower in A/A individuals (p < 0.05), while subcutaneous fat did not differ between haplotype groups at follow‐up (p > 0.05) owing to a greater training‐induced decrease in subcutaneous fat in non‐carriers of the A/A haplotype (p < 0.05). Maximal O2 uptake (VO2max) relative to kg body mass was not different (p > 0.05) at baseline but was greater after training in A/A haplotype carriers (p < 0.05). This association was not found with VO2max after training expressed relative to kg lean mass (p > 0.05). We conclude that the A/A haplotype of these two PLIN SNPs associates with reduced body fatness before and after training.
Cyclooxygenase mRNA expression in human patellar tendon at rest and after exercise
Authors: Carroll Chad C , Jemiolo Bozena , Trappe Scott W , Døssing Simon , Kjaer Michael , Magnusson S Peter , Trappe Todd A
Published: June 2021

Exercise has been shown to acutely elevate several metabolic processes in tendon tissue, many of which are regulated by the cyclooxygenase (COX) enzymes. We measured the expression levels of COX‐1 (variants 1 and 2), COX‐2, and the recently discovered intron 1‐retaining COX‐1 variants (COX‐1b1, ‐1b2, ‐1b3) at rest and following resistance exercise (RE). Patellar tendon biopsy samples were taken from six individuals (3M, 3F) before and 4h following a bout of RE (3 sets of 10 repetitions at ~70% of 1RM) and from a separate six individuals (3M, 3F) before and 24h following RE and analyzed using real‐time RT‐PCR. The COX‐1 variants were the most abundant COX mRNAs before exercise and remained unchanged (p>0.05) following exercise. COX‐2 was also expressed in tendon at rest and was unchanged (p>0.05) following exercise. The intron 1‐retaining COX‐1 variants were not detectable in tendon tissue before or after exercise. Compared to our previous work in quadriceps skeletal muscle, the patellar tendon expressed much higher levels of COX‐1 and COX‐2, although the overall COX mRNA expression patterns were similar in skeletal muscle and tendon (COX‐1v2 > COX‐1v1, P<0.05; COX‐1:COX‐2 ≅ 4:1). These results suggest both COX‐1 and COX‐2 are constitutively expressed at relatively high levels in human patellar tendon and are likely targets of COX inhibiting drugs at rest and following physical activity.

NIH R01 AG020532 (TT)
Mitochondrial DNA rejuvenescence: Why Resist?
Authors: Safdar Adeel , Sule Lauren M , Kaczor Jan J , Tarnopolsky Mark A
Published: June 2021

We previously reported that satellite cells from older adults do not accumulate aging‐associated mitochondrial DNA (mtDNA) deletions (Safdar et al, 2007). Resistance (RES) training induces satellite cell activation and skeletal muscle hypertrophy, and is recommended as an effective countermeasure to sarcopenia in the elderly. We aimed to delineate the protective mechanism underlying this effect. Muscle biopsies were taken from the vastus lateralis of 16 older subjects (70 ± 5 y; 8 women) before and after 6 months of RES training and analyzed for protein content of electron transport chain (complex I ND6, complex III core protein 2, complex IV COX subunits –II and –IV, and complex V alpha subunit), antioxidant enzymes (Mn‐SOD, Cu/Zn‐SOD, and catalase), markers of mitochondrial abundance (citrate synthase CS) and oxidative damage (protein carbonyl PC, 4‐hydroxynonenal 4HNE, and total DNA 8‐hydroxy‐2‐deoxyguanosine 8‐OHdG), mtDNA deletions, as well as CS, COX, and catalase enzyme activity. RES training increased protein content of ND6, core protein 2, COX‐II, COX‐IV, complex V alpha subunit and catalase by 25%, 41%, 62%, 69%, 31%, and 95% respectively (P < 0.042), and COX and catalase enzyme activity by 79% and 89%, respectively (P < 0.028). RES training decreased mtDNA deletions (63%), PC (45%), 4‐HNE (29%), and total DNA 8‐OHdG (45%) content (P < 0.01). We conclude that the improvements in mitochondrial function occurred through RES training‐induced recruitment of satellite cells resulting in mitochondrial gene shifting and rejuvenescence in the skeletal muscle of older adults. We propose that RES training is a viable therapy to attenuate and/or “reverse” mitochondrial abnormalities associated with sarcopenia. (Funded by CIHR Institute of Aging, and Warren Lammert and Kathy Corkins).