bluuebunny/crossref_metadata_2025 huggingface dataset:
Angiotensin type 2 receptors (AT2R) over expression in the nucleus of the solitary tract (NTS) attenuate renovascular hypertension
Authors: Blanch Graziela Torres , Freiria-Oliveira Andre Henrique , Li Hongwei , Colombari Eduardo , Sumners Colin , Colombari Debora S. A.
Published: June 2021

We have demonstrated that AT2R overexpression in the NTS decreases mean arterial pressure (MAP) in normotensive rats. The aim of the present study was to investigate the effects of AT2R overexpression in the NTS in two kidney 1 clip (2K1C) hypertensive rats. Holtzman male rats (150–180 g, n = 5–6/group) were implanted with telemetry transducers into the abdominal aorta followed by a silver clip implant in the left renal artery. Three weeks after the 2K1C surgery the NTS was microinjected (200 nl/site, 5 sites) with either adeno‐associated virus vector AAV2‐CBA‐AT2R (1×108 gc) or AAV2‐CBA‐eGFP (1×109 gc) for the over expression of AT2R or GFP, respectively. At that time period, rats were hypertensive (134±3 mmHg light period and 133±4 mmHg dark period) compared to baseline levels (light period: 101±3 mmHg; dark period: 110±5 mmHg). Three to 4 weeks after the NTS injections (6–7 weeks after 2K1C), at which time AT2R or GFP expression has reached maximal (and stable) levels, MAP reached values of 171±10 mmHg light period and 190±8 mmHg dark period in GFP rats. In the AT2R transduced 2K1C rats, the increase in MAP was significantly lower compared to GFP animals (151±6 mmHg light period; 153±7 mmHg dark period: p<0.05 vs. GFP group). These results suggest that overexpression of AT2R in the NTS impairs the development of renovascular hypertension.

Supported by: PNPD/CAPES, CNPq and NIH Grant HL 076803
Central infusion of a nitric oxide donor restores baroreflex control of heart rate in heart failure
Authors: Ramchandra Rohit , Hood Sally G , May Clive N
Published: June 2021

One of the hallmarks of heart failure (HF) is increased sympathetic nerve activity (SNA) to the heart and the kidney as well as depressed baroreflex control of heart rate (HR), but the mechanisms responsible remain unclear. We hypothesized that HF is associated with a reduction in central levels of NO synthase and that restoration of central NO levels in HF animals would be beneficial. Arterial pressure, HR, cardiac and renal SNA were recorded simultaneously in conscious sheep, at least 4 days after surgery in normal (n=7) and HF animals (n=7). HF was associated with a significant decrease in the levels of NO synthase in the brainstem (n=3). HF sheep had significant increases in baseline cardiac SNA levels and baroreflex control of HR was impaired. Intracerebroventricular (ICV) infusion of sodium nitroprusside (500 μg/ml/hr for 150 mins) led to a significant decrease in cardiac SNA in both normal (to 72 ± 10% of controland HF sheep (to 80± 6% of control. In addition there was a significant increase in the gain of baroreflex control of HR (from −2.28 ± 0.75 to −3.02 ± 10 bpm/mmHg, p<0.05), but there was no change in the normals. In contrast to cardiac SNA, there was no change in the baseline levels or baroreflex control of renal SNA in either group of animals. In conclusion, our data indicate an important role for NO in modulating baseline levels and baroreflex control of cardiac SNA.
Comparison of the cardiovascular effects produced by interference with GABA transmission in the left and right sides of dorsomedial hypothalamus in conscious rats
Authors: Fontes Marco Antônio Peliky , Oliveira Aline Cristina
Published: June 2021

In anesthetized rats activation of neurons in the right DMH (RDMH) evoked by bicuculline methiodide (BMI) caused greater tachycardia when compared to left DMH (LDMH) [Xavier et al, Neuroscience 2009]. In this study, we evaluated whether the same results can be obtained in awake animals. Experiments were approved (Protocol 160/2011) and performed using male Wistar rats (290–330g) submitted to implantation of unilateral guide cannula targeted to DMH. Five days after, the femoral artery was cannulated for recording of cardiovascular parameters. After one day to recovery, these animals were submitted to unilateral nanoinjection of BMI (10pmol/100nl) into RDMH (n=7) or LDMH (n=7). In group 1, BMI was injected into RDMH and in group 2, BMI was injected into LDMH. In both groups, injection of BMI into the DMH produced increases in HR (Δ RDMH: 141 ± 15 bpm and LDMH: 125 ± 15 bpm) accompanied by changes in MAP (Δ RDMH: 18 ± 2 mmhg and LDMH: 16 ± 2 mmHg). No significant difference between groups was found. However, when we compared the time course of the tachycardia evoked by BMI, we observed that the duration of effect evoked by RDMH activation lasted almost twice as long as evoked by the LDMH (RDMH: 38 ± 3 min and LDMH: 20 ± 3 min; P=0.0033). These results corroborate our previous data suggesting that the RDMH exert a prominent control on chronotropism. Support: CAPES, FAPEMIG, CNPq.
Long term enhancement of cerebral vascular resistance in spontaneously hypertensive rats produces short term pressor responses and long term re‐modelling of cerebral circulation
Authors: Baquero Ana Maria Alviar , Barrett Carolyn , Guild Sarah-Jane , Malpas Simon , Paton Julian FR
Published: June 2021

Cushing (1901, Bull Johns Hopk Hosp 12, 290‐) discovered that acute increases in cerebral vascular resistance produced hypertension. Based on the Cushing response we propose that hypertension may result from elevated cerebral vascular resistance. We sought to determine the effect of occluding both vertebral and the right common carotid artery (3‐vessel occlusion or 3‐VO) on arterial pressure in spontaneously hypertensive rats (SHR). Given that this strain already has narrowed vertebro‐basilar arteries (Cates et al. 2011; J. Appl. Physiol. 111, 149‐), we hypothesised that the pressor response in the SHR would be larger than that in the Wistar rat. 3‐VO in SHR (n=7) produced a pressor response of 23±3mmHg, which compared with 15±2mmHg in normotensive rats (n=5). Arterial pressure returned to control levels by 8–11 days after 3‐VO. In the SHR there was marked cerebral vessel re‐modelling including dilatation of the right posterior communicating artery (+63%) and ventral spinal artery (+54%) seen from day 11 post 3‐VO. The degree of re‐modelling was associated with the magnitude of the pressure response. 3‐VO in the SHR produces a significant pressor effect and arteriogenesis of cerebral vessels that is associated with a subsequent near normalisation of arterial pressure. Cerebral vascular resistance plays a major role in determining arterial pressure set‐point in the SHR. MRC and BHF funded research.
Autonomic control in a rat model of sepsis induced by cecal ligation and puncture
Authors: Veiga Glaucia Raquel Luciano , Oyama Lila Missay , Fazan Rubens , Pontes Roberto , Campos Ruy , Bergamaschi Cassia
Published: June 2021

The aim of this study was to evaluate cardiovascular parameters: blood pressure (BP), heart rate (HR) and BP and HR variability, renal sympathetic nerve activity (RSNA) and baroreflex control of HR in animals submitted to the experimental model of sepsis induced by cecal ligation and puncture compared to sham rats. Male Wistar rats were submitted to sepsis (CLP) and studied 24 or 48h later (n=8/group). BP and HR were recorded in conscious rats and spectral analysis in the frequency domain was performed. Baroreflex was evaluated by changes infusion of vasoactive drugs. Although no differences in BP was observed, RSNA was significantly decreased in both sepsis groups compared to Sham (Sham 92.5±6 × Sepsis 24hrs 58.5±6 × Sepsis 48hrs 62.6±9 pps). In both sepsis groups it was observed a significant increased in LF (low frequency) to HR (Sham 15±2 × Sepsis 24hrs 25±4 and Sepsis 48hrs 23±6 mmHg2) and a decrease in HF (high frequency) (Sham 85±2 × Sepsis 24hrs 75±4 × Sepsis 48hrs 77±6 un). The sensitivity of baroreflex gain of HR was increased in Sepsis 24hrs compared to sham (Sepsis 24hrs −4.35±0.45 and Sham −2.03±0.14 bpm/mmHg). Taken altogether the present study suggest that the fall in RSNA in sepsis was accompanied by an increase in LF and baroreceptor sensitivity, such adjustments are apparently independent of BP changes and maybe involved in the sepsis evolution. Supported by: CNPq, FAPESP
Differential pattern of splanchnic and lumbar sympathetic nerve activity to stimulation of rostral ventrolateral medulla in sedentary versus physically active rats
Authors: Subramanian Madhan , Azar Toni , Mueller Patrick J
Published: June 2021

The rostral ventrolateral medulla (RVLM) is involved in normal and pathological increases in sympathetic nerve activity (SNA). For example, enhanced responses to stimulation of the RVLM occur in sedentary compared to physically active rats. RVLM neurons can also drive SNA differentially and may in turn contribute to the “sympathetic signature” in hypertension. However, the impact of physical (in)activity on differential regulation of SNA by the RVLM is unknown. In Inactin anesthetized sedentary or active rats (running wheels, 10–14 wks), mean arterial pressure (MAP), splanchnic (sSNA) and lumbar sympathetic nerve activity (LSNA) were recorded simultaneously. Microinjections of glutamate (30 nl, 10 mM) were performed in a three dimensional grid pattern in the pressor region of the RVLM. Glutamate increased sSNA and LSNA differentially depending on the location of injection and whether animals were sedentary or active. These data suggest that differential regulation of sympathetic outflow by the RVLM is altered by sedentary or physically active conditions and may play a role in modifying the sympathetic signature of certain disease states. (R01HL096787)
Astrocytes influence neurosecretory and presympathetic hypothalamic neurons via activation of extrasynaptic NMDARs negatively coupled to A‐type K+ channels
Authors: Naskar Krishna , Stern Javier E.
Published: June 2021

We recently showed that activation of extrasynaptic NMDARs (eNMDARs) by ambient glutamate under astrocyte control, inhibited the voltage‐gated K+ current IA in non‐identified neurosecretory neurons. Here, we aimed to address i) whether the eNMDAR/IA coupling is present in identified neurosecretory vasopressin (VP) and PVN‐RVLM presympathetic neurons, ii) the biophysical properties of IA targeted by eNMDAR, and iii) the functional consequence of the eNMDAR/IA coupling on neuronal firing activity. Patch clamp recordings were obtained from identified eGFP‐VP SON and PVN‐RVLM neurons. We found that activation of eNMDAR following astrocyte glutamate transporter block (DHK 300 μM) inhibited IA in ~70% of VP and ~50% of PVN‐RVLM neurons (~30% and ~ 25% inhibition, respectively P<0.05) Activation of eNMDARs shifted IA voltage dependence of inactivation to more hyperpolarized membrane potentials (ΔV1/2 inactivation ~−20 mV). Finally, the eNMDAR/IA coupling strengthened neuronal input/output function (i.e., leftward shift, more firing at less stimulation). Collectively, our results show that activation of eNMDARs, both in neurosecretory and presympathetic neurons, inhibits IA function, enhancing in turn neuronal excitability. Thus, the eNMDAR/IA coupling stands as a functionally relevant target by which astrocytes influence hypothalamic neurohumoral outflow. Supported by RO1 HL 090948.
Blunted Responses of Renal Sympathetic Nerve Activity to C‐type Natriuretic Peptide in the PVN of Rats with Heart Failure
Authors: Xu Bo , Zheng Hong , Patel Kaushik P
Published: June 2021

Volume expansion produces a reflex decrease in renal sympathetic nerve activity (RSNA) that is mediated by the paraventricular nucleus (PVN). C‐type natriuretic peptide (CNP) has the attributes to be a potential candidate as a mediator of sympathoinhibition in the PVN. First, we determined the presence of CNP receptors (NPR‐C) on PVN neurons that projected to the rostral ventrolateral medulla (RVLM). The retrogradely transported tracers, green fluorescent latex microspheres, were microinjected into the RVLM and found primarily colocolized with NPR‐C in parvocellular neurons of the PVN. Second, of the 19 spontaneously active neurons recorded in the PVN in normal rats with extracellular single‐unit recording in vivo, 6 units were antidromically activated from the RVLM. Picoinjection of CNP significantly decreased the basal discharge in 5/6 PVN‐RVLM neurons, and in 6/13 neurons that were not antidromically activated from the RVLM. There were no significant changes after picoinjection of artificial cerebrospinal fluid. Third, microinjection of CNP into the PVN significantly decreased RSNA, means arterial pressure (MAP) and heart rate (HR). Fourth, microinjection of CNP into the PVN produced significantly attenuated responses (in RSNA 56%, MAP 69%, HR 75% of sham rats) in rats with chronic heart failure (CHF). Consistent with these observations, the expressions of NPR‐C in the PVN were decreased in CHF rats. These results suggest an altered inhibitory role for CNP in the PVN of rats with CHF.
Expression of angiotensin type 1A receptors in C1 neurons of the rostral ventrolateral medulla is required for the pressor response to angiotensin II
Authors: Allen Andrew Mark , Jancovski Nikola , Choong Yan-Ting , Carter David A , Gurley Susan B , Chen Daian , Bassi Jaspreet Kaur
Published: June 2021

Angiotensin II (AngII) acts via its type 1A receptor (AT1AR) in the rostral ventrolateral medulla (RVLM) to modulate blood pressure. Whilst AngII is known to excite RVLM C1 neurons, it is not known whether this is sufficient for the pressor response in vivo. Using an AT1AR promoter GFP mouse we examined expression within RVLM. Mice (n=3) were anesthetized and perfused with 4% paraformaldehyde for immunohistochemical detection of GFP and tyrosine hydroxylase (TH). To determine whether AT1ARs in C1 neurons are necessary for the pressor response to AngII in RVLM, lentivirus expressing either Cre‐recombinase (Cre)(n=6) or GFP (n=6) controlled by a phox2 promoter was injected into the RVLM, in adult transgenic mice with a conditional AT1AR allele (AT1ARfl/fl). Four weeks after viral injection, blood pressure was recorded in anesthetized mice. Ang II (50 nL of 1 mM) and glutamate (10 nL of 10 mM) were injected into the RVLM. Immunohistochemistry revealed that the majority of C1 neurons expressed the AT1AR. A small number of AT1AR‐expressing non‐ C1 neurons were observed. Cre expression in the RVLM of AT1ARfl/fl mice did not affect the response to glutamate but attenuated the response to AngII (Cre: 3±(SD)3.4 mmHg; GFP: 17±(SD)5.2 mmHg P<0.001). Expression of the AT1AR occurs endogenously in C1 neurons and is essential for the pressor response to AngII in the RVLM. Supported by the NHMRC (Australia).
Aldosterone (Aldo) Interacts with PKA, MAPKs and PLC Pathway to Sensitize Angiotensin (ANG) II‐Induced Hypertension
Authors: Xue Baojian , Zhang Zhongming , Guo Fang , Johnson Alan Kim
Published: June 2021

Previous studies using an Induction‐Delay‐Expression (I‐D‐E) experimental design have demonstrated that one‐week Aldo pre‐treatment can sensitize the brain to produce an enhanced hypertensive response to subsequent ANGII. The amplified pressor effects are associated with elevated mRNA expression of RAAS components in the lamina terminalis (LT). The present study was to determine the signaling mechanisms involved in the sensitizing effects of Aldo on the brain. During I Aldo (750 ng/h) or saline was delivered sc for 1 wk. The rats then rested for 1 wk (D). Then the tissues along LT were collected at the end of D for determining activation of PKA, MAPKs or PLC pathway.

The week of Aldo treatment during I had no effect on BP during I and D. However, Aldo treatment during I induced a significant increase in phosphorylated cAMP response element‐binding protein (CREB, 1.5 fold), extracellular signal‐regulated kinase (ERK, 1.8 fold), or phospholipase C (PLC, 1.8 fold) in the LT. Moreover, Aldo infusion resulted in a significant increase in mRNA (1.5 fold) and protein (1.3 fold) expression of brain‐derived neurotrophic factor (BDNF) as compared with the saline treated rats. The results indicate that Aldo pre‐treatment may facilitate the development of ANG II‐induced hypertension by acting through a sensitization process involving PKA, MAPKs or PLC pathway.
Central cholinergic or angiotensinergic activation facilitates the pressor responses to glutamate injected into the RVLM
Authors: Gomide Joelma Maria Cardoso , Gasparini Silvia , De Luca Laurival Antonio , de Almeida Colombari Debora Simoes , De Paula Patricia Maria , Moreira Thiago Santos , Menani Jose Vanderlei
Published: June 2021

In the present study, we investigated the cardiovascular responses produced by the injections of L‐glutamate into the rostroventrolateral medulla (RVLM) in conscious rats that previously received injections of carbachol (cholinergic agonist) or angiotensin II (ANG II) injected into the lateral ventricle (LV). Male Holtzman rats (280–320 g, n = 8, baseline mean arterial pressure = 117 ± 4 mmHg and baseline heart rate = 400 ± 17 bpm) with stainless steel guide‐cannulas implanted unilaterally in the LV and in the RVLM were used. The pressor response produced by the injections of L‐glutamate (5 nmol/100 nl) into the RVLM increased by pre‐treating the rats with carbachol (4 nmol/1 μl) or ANG II (50 ng/1 μl) icv (59 ± 3 and 68 ± 5 mmHg, respectively) compared to the control responses produced by L‐glutamate injected into the RVLM combined with saline icv (37 ± 3 mmHg). The pressor responses produced by the injection of carbachol or ANG II icv reached the maximum of 56 ± 3 and 44 ± 3 mmHg, respectively and they were reduced to 9 ± 2 and 6 ± 3 mmHg immediately before the injection of glutamate into the RVLM. Injection of carbachol or ANG II icv and L‐glutamate into the RVLM alone or combined produced no significant changes in the heart rate. These results suggest that central cholinergic or angiotensinergic activation facilitates the pressor response produced by glutamatergic activation of the RVLM.

Financial support: FAPESP, CNPq.
Baroreflex rhythms regulate synaptic amplification in sympathetic ganglia
Authors: Springer Mitchell G. , Horn John P.
Published: June 2021

Analysis of baroreflex regulation of blood pressure has concentrated on the cardiovascular system and renal function together with sensory transduction and CNS integration. This study focuses instead on ganglionic synapses. To test the hypothesis that rhythmic preganglionic activity increases ganglionic gain, we used dynamic clamp to stimulate sympathetic neurons with patterns of virtual synaptic activity. Experiments employed whole‐cell patch recordings from rat neurons in primary culture (P15 – 20; superior cervical ganglion). Cardiac periodicity was simulated using a heart rate of 5 Hz and random preganglionic activity that alternated between 0 and 5 Hz (20% duty cycle, average presynaptic firing rate = 1 Hz). The 40 s stimulus template included 1 primary nicotinic synapse whose strength was 3 times threshold synaptic conductance and 8 secondary synapses set to 90% threshold‐gsyn. In response to the template, neurons fired at 2.4±0.1 Hz, (equivalent to a gain of 2.4±0.1). With 4 secondary's gain was 1.8±0.1. The templates generated bursts of synaptic activity in almost every cardiac cycle and action potentials in 34 – 43% of cycles. Bursts of spikes occurred in <3% of cycles. Removal of periodicity reduced gain by 24%. These results mimic human microneurographic data, show that ganglionic integration can double the sympathetic outflow and that baroreceptor entrainment increases ganglionic gain.
Monitoring neurovascular coupling in the hypothalamic supraoptic nucleus in an in vitro slice preparation
Authors: Du Wenting , Kim Ki Jung , Stern Javier E , Filosa Jessica Andrea
Published: June 2021

While much effort has been placed in understanding neurovascular coupling (NVC) in the brain, most studies have focused on the cortex or hippocampus. Thus in this study we characterized the response of parenchymal arterioles from the supraoptic nucleus (SON) of the hypothalamus which contains oxytocin and vasopressin neurons critically involved in reproductive and fluid/electrolyte homeostasis. The SON is characterized for having a dense capillary network and astrocytes with dynamic processes which retract/expand in an activity‐dependent manner providing a unique model to study the consequences of neuro‐glial structural remodeling in NVC. SON arterioles were cannulated and perfused to induce myogenic tone. Compared to cortical arterioles, SON arterioles had higher tone and flow‐dependent vasoconstriction. In a separate group, vascular tone was induced following bath application of the thromboxane agonist U46619. Increased firing activity evoked in single patched neurons resulted in dilations (40.54 %). Moreover, electrical field stimulation induced two types of responses: dilations (9.5 %) or localized smooth muscle cell constrictions with no apparent changes in vessel diameter. Given the multiplicity of neuropeptides locally release from SON neuronal dendrites we are currently investigating their relative contribution to these activity‐dependent vascular responses. NIH 1R01HL089067.
Cerebral autoregulation is enhanced at higher levels of exercise intensity
Authors: Falvo Michael , Witkowski Jaclyn , Serrador Jorge
Published: June 2021

Cerebral blood flow (CBF) changes in response to exercise are intensity dependent, but it is unclear how well cerebral autoregulation (CA) is maintained at higher intensities. We had ten healthy subjects perform cycle exercise at 50%, 85%, and 115% of their ventilatory threshold (Vt) as well as delta 90 for a 5 minute bout. CBF (transcranial Doppler), mean arterial pressure (MAP), heart rate and ventilatory response were measured continuously throughout, and exercise responses were compared to baseline values. CA was calculated via transfer‐function (0.04 – 0.5 Hz) gain between MAP and mean CBF velocity and analyzed via repeated measures ANOVA. CBF and MAP significantly increased from baseline (59.24±5.3 cm/s, 90.6±6.4 mmHg) to exercise (64.83±5.8 cm/s, 103.81±6.3 mmHg). We observed minimal changes in gain during submaximal intensities (i.e. 50–115%Vt), but saw a significant decrease in gain from baseline (1.57±0.28) to exercise (0.63±0.23) as intensity increased (i.e. delta90). We interpret this significant interaction (baseline/exercise x intensity) as evidence of improved CA during high‐intensity exercise. Therefore, during high levels of exercise CBF is adequately maintained despite greater effort and increased cerebral metabolism.
Effects of medullary administration of nitric oxide precursor on cardiovascular responses and neurotransmission during static exercise in stroke rats
Authors: Ally Ahmmed , Phattanarudee Siripan , Shafique Ehtesham , Maher Timothy
Published: June 2021

Rats with a 90‐min left middle cerebral artery occlusion followed by 24‐hour reperfusion (MCAO), pressor responses during muscle contractions were attenuated, as were glutamate in the left rostral ventrolateral medulla (RVLM) and left caudal VLM (CVLM), but GABA increased in left RVLM and CVLM (Brain Res. 2002: 952). This study determined the effects of L‐arginine (L‐Arg), a nitric oxide (NO) precursor, within the RVLM or CVLM on cardiovascular activity and glutamate/GABA levels during static exercise in left‐sided MCAO rats. Microdialysis of L‐Arg into the left RVLM further attenuated pressor and heart rate (HR) responses, decreased glutamate and increased GABA levels during muscle contractions. Administration of N(G)‐monomethyl‐L‐arginine, an NO‐synthase inhibitor, reversed the effects. In contrast, L‐Arg administration into left CVLM potentiated pressor and HR responses, increased glutamate and decreased GABA levels during muscle contractions. However, simultaneous L‐Arg microdialysis into left RVLM and CVLM elicited responses similar to those following its infusion into RVLM. Results suggest that NO within the RVLM and CVLM plays an important role in modulating cardiovascular responses and glutamate/GABA neurotransmission during static exercise following stroke, and that the RVLM‐NO mechanism has a dominant effect in medullary regulation of cardiovascular function.
Central Hypothalamic Pathways Mediating Stress Responsiveness Vary in Different Rat Strains
Authors: Knuepfer Mark M , Busauskas Marius , Langasek Julie , Willingham Laura
Published: June 2021

Others have reported that the dorsomedial hypothalamus (DMH) mediates certain cardiovascular responses to behavioral stress. We sought to determine whether this variability is strain dependent and whether different stressors are similarly dependent on the DMH. We compared responses to cocaine (5 mg/kg, iv) with startle responses to 1 cm deep ice cold water (CWS) in Brown‐Norway (BN) and Dahl salt sensitive (DSS) rats. BN and DSS rats were instrumented for recording arterial pressure and for measuring blood flow changes in the abdominal aorta (hindquarters or Hq) and the superior mesenteric (Ms) artery using Doppler flowmetry. We calculated changes in vascular resistance (R) in animals. BN rats had greater increases in MsR (visceral) and HqR (skeletal muscle) to cocaine than DSS. In contrast, DSS rats had greater increases in MsR in response to CWS than BN rats. Microinjection of muscimol (80 pmol in 100 nl) in the DMH attenuated the increase in MsR in BN but not DSS rats in response to cocaine but not to CWS. DMH stimulation with kainate (10 pmol in 100 nl) elicited greater Ms vasoconstriction in BN compared to DSS rats. We conclude that there are unique strain‐dependent pathways mediating regional vascular resistance for specific stressors. The BN is more dependent on DMH in mediating cocaine‐induced visceral vasoconstriction. Supported by USPHS DA017371 and HL091440.
ACE2 reduces hyperglycemia by preventing pancreatic renin angiotensin system over‐activation in high fat diet‐fed mice
Authors: Chhabra Kavaljit H. , Pedersen Kim B , Shenoy Vinayak , Raizada Mohan K. , Lazartigues Eric
Published: June 2021

An over‐active pancreatic renin‐angiotensin system (RAS)could be involved in the High‐fat diet (HFD) mediated type 2 diabetes (T2D). ACE2, a carboxypeptidase, appears to be beneficial against RAS over‐activation. We hypothesized that pancreatic ACE2 might protect against HFD‐induced T2D. Pancreatic ACE2 activity (FU/min/mg protein) and angiotensin‐II (Ang‐II) levels (ng/g of tissue)were assessed in 5‐month old C57BL/6J mice (N=4/group) fed with HFD for 12 weeks. HFD‐fed mice had lower ACE2 activity (2053 ±469 vs. 4623 ±274)and higher pancreatic Ang‐II levels (2.73 ±0.5vs. 0.91 ±0.3)vs. regular diet‐fed mice(P<0.05), confirming RAS over‐activation. To assess therapeutic potential of ACE2, we treated HFD‐fed mice with a lentivirus coding for mACE2 or GFP (pancreas injection, 10^6 TU/ml) at the 13th week of HFD‐feeding. Three weeks later, ACE2‐injected mice exhibited reduced Ang‐II levels (2.11±0.3 vs. 3.38±0.2) and higher ACE2 activity (3632±117 vs.1971±332)in the pancreas accompanied with reduced fasting blood glucose (177 ±15 vs. 243 ±18mg/dl) and improved glucose tolerance (AUC= 42968±1029 vs.51904±937 mg/dl*120 min.)vs. GFP‐treated mice(P<0.05. Our data show that HFD leads to pancreatic RAS over‐activation that can be reversed by increasing local ACE2 activity, thus improving glycemic control. Hence, ACE2 could be a promising therapeutic target for managing HFD‐induced T2D.
A combinatorial genetic approach identifies a significant locus that controls elevated heart rate in mice
Authors: Ilushkina Irina A. , Smolock Elaine M. , Gerloff Janice , Glazko Galina , Murashev Arkady N. , Lusis Aldons J. , Korshunov Vyacheslav A.
Published: June 2021

Elevated heart rate (HR) is a risk factor for cardiovascular diseases. The goal of the study was to use a combination of quantitative trait locus (QTL) and genome‐wide association studies (GWAS) to map hemodynamic traits in mice. QTL analyses were performed in a C3HeBxSJL backcross (n=134). GWAS were done using the hybrid mouse diversity panel (HMDP; 30 inbred strains). HR and systolic blood pressure (SBP) were measured by the tail cuff method. HR was approximately 80 beats/min higher in SJL compared to C3HeB. There was a significant distribution of the HR (536–763 beats/min) in N2 mice. We discovered a highly significant QTL (LOD=6.7, p<0.001) on chromosome 7 (41cM) for HR in the C3HeBxSJL backcross. In the HMDP (n=5–6/strain) we found that HR (beats/min) ranged from 546±12 in C58/J strain to 717±7 in MA/MyJ mice. SBP (mmHg) ranged from 99±6 in I/LnJ to 149±2 in SWR/J mice. GWAS for HR recognized over 100 significant loci (‐log[p‐value]≥6). We found fourteen SNPs that are localized within 10 known genes. Importantly, a significant locus on mouse chromosome 7 co‐localized with the QTL for elevated HR found in the C3HeBxSJL backcross. GWAS for SBP identified two SNPs on chromosome 16. In summary, we used a combined genetic approach to identify a novel elevated heart rate locus on mouse chromosome 7. This study was supported by Russian Federation Program #2011‐1.5‐501‐006‐ 024 and NIH HL105623 (VAK); NIH HL30568 and HL42488 (AJL)
Interaction of human MATE1 and MATE2‐K with N‐Butylpyridinium chloride and other cationic Ionic liquids
Authors: Martinez-Guerrero Lucy Jazmin , Wright Stephen
Published: June 2021

‘Ionic Liquids’ (ILs; salts in the liquid state) are seeing increasing use in industrial applications and, consequently, are of increasing interest with respect to their potential toxicity. Three cationic ILs (NBuPy‐Cl, Bmim‐Cl and BmPy‐Cl) have been shown to be excreted in the urine of rats and mice and are inhibitors of the human ortholog of the Organic Cation Transporter, hOCT2, which is the entry step for secretion of type I OCs across the basolateral membrane of renal proximal tubule (RPT) cells. In the present study we assessed the interaction of these model ILs with the human Multidrug and Toxin Extrusion transporters, hMATE1 and hMATE2‐K, which mediate the apical exit of OCs from RPT cells into the filtrate. The uptake of [3H]1‐methyl‐4‐phenylpyridinium ([3H]MPP) and [3H]triethylmethylammonium ([3H]TEMA) into Chinese hamster ovary CHO cells that stably expressed hMATE1 or hMATE2‐K was inhibited by the model ILs with comparatively high affinity (IC50 values from 3 to 70 μM). In addition, all three ILs trans‐stimulated MATE's mediated [3H]MPP efflux, supporting the conclusion that these model ILs are transported substrates as well as inhibitors of the human MATE homologs. Together, these data suggest that cationic ILs are secreted by the human kidney through the OCT2‐MATE1/2‐K pathway, and that inhibition of MATE transporters by ILs may influence the pharmacokinetics of (at least) some cationic drugs.
Differential adrenergic signaling in the regulation of renal blood flow in rats with heart failure
Authors: Schiller Alicia Marie , Wang Han-Jun , Zucker Irving H
Published: June 2021

Chronic heart failure (CHF) is a disease characterized by an overactive sympathetic nervous system. The kidney is especially vulnerable to these adaptations, and responds, in part, with a decrease in renal blood flow (RBF). The purpose of this study was to determine the effects of the α1 adrenergic receptor agonist phenylephrine (PE) and the nonselective adrenergic receptor agonist norepinephrine (NE) on RBF in sham and CHF animals. CHF was induced by coronary artery ligation. Anesthetized animals were instrumented with a renal flow probe and a catheter in the aorta close to the renal bifurcations. Changes in RBF were measured in response to intra‐aortic infusions of increasing doses of PE (5, 10, and 20 μg/kg) and NE (8 and 16 μg/kg). Renal cortices from CHF and sham animals were sieved to obtain a vascular‐enriched preparation. CHF animals exhibited a blunted change in RBF in response to intra‐aortic infusion of PE compared to sham animals at all concentrations. Conversely, CHF animals exhibited an increased sensitivity to NE. To determine if the changes in blood flow in response to ligand correlated to differential expression of the targeted receptors western blotting on sieved lysate was performed. Preliminary western blotting data indicate that relative amounts of β1 adrenergic receptor were significantly decreased in CHF animals compared to sham. Results of this study suggest that changes in RBF during CHF are due in part to alterations in adrenergic receptor signaling.
Early life stress‐induced exaggerated AngII aortic vasoconstriction is transmitted to the F1 generation
Authors: Loria Analia S , Cunningham Tayler , Pollock Jennifer S.
Published: June 2021

Previously, we showed that maternal separation (MS), a model of early life stress, reduces creatinine clearance (Ccr) and enhances angiotensin II (AngII)‐induced aortic vasoconstriction via reduced nitric oxide (NO) buffering in male rats. We hypothesized that this phenotype would be transmitted to the first generation (F1) of male offspring from MS parents. Normally‐reared rats (12 weeks old) from either MS (MSF1) or control WKY parents were placed in metabolic cages. Food and water intake, body weight, and Ccr were all similar in control and MSF1 rats. Wire myography was performed to assess aortic vasoconstrictive responses to AngII in the presence and absence of the NO synthase inhibitor (L‐NAME, 100 μM, 15 min). Aorta from MSF1 compared to control rats showed greater sensitivity (log EC50: −8.51±0.14 vs. −7.93±0.12, p<0.05) and exaggerated vasoconstriction to AngII (9.38±0.8 vs. 4.8±0.3 % KCl, p<0.05). Exacerbated AngII‐induced constriction due the pre‐incubation with L‐NAME, was greater in aorta from control compared to MSF1 rats (delta % max constriction: 34.7±4.3 vs. 13.2±2.1, p<0.05). KCl induced aortic vasoconstriction was similar in control and MSF1 rats. These data indicate that the MSF1 rats maintains the vascular phenotype with reduced aortic NO buffering to AngII‐induced vasoconstriction, thus, suggesting a role for an epigenetic mechanism(s).
Combining whole transcriptome expression with SILAC to investigate mTOR inhibition in cultured baboon fetal proximal tubule cells
Authors: Nakamura Michiyo , Cox Laura A , Glenn Jeremy P , Pardo Sammy , Habib Samy , Weintraub Susan P , Nijland Mark J
Published: June 2021

Maternal nutrition during pregnancy influences fetal growth and postnatal health. The developing mammalian kidney is sensitive to alterations in its nutrient environment. The mammalian target of rapamycin (mTOR) signaling system acts as a nutrient sensor and key component of the cell stress response. We have combined transcriptomic and proteomic approaches to investigating inhibition of mTOR signaling in fetal baboon renal epithelial cells (PTC) in culture.

Fetal PTCs were isolated at 0.5G from 5 fetal baboons. Equal numbers of cells were plated in 6 well plates containing standard culture medium or medium containing stable isotope‐labeled arginine and lysine (SILAC). Rapamycin (1 nM) or vehicle was added at 60% confluence and equal numbers of cells harvested 24h later. Transcriptome (Illumina BeadChip) and proteome (HPLC‐ESI‐MS/MS) analyses were performed. The union of transcripts for differentially expressed proteins detected by SILAC and differentially expressed genes detected by BeadChip was analyzed using ontology enrichment analysis.

Ontologies down‐regulated by rapamycin include translation initiation, elongation and termination, protein complex disassembly, ribosome biosynthesis and assembly, Golgi vesicle budding and S‐adenosylmethionine biosynthesis and metabolism.

We conclude that fetal baboon PTCs exhibit classic responsiveness to mTOR signaling inhibition.
Circadian expression of H,K‐ATPase type 2 contributes to the stability of plasma K+ levels
Authors: Crambert Gilles , Centeno Gabriel , Firsov Dmitri , Salhi Amel
Published: June 2021

Maintenance by the kidney of stable plasma K+ values is crucial, as the latter control muscle and nerve activity. Inability to do so, induced hyper‐ or hypokalemia both related to heart dysfunctions, muscle weakness and neurological disorders.

Since renal K+ excretion is regulated by the circadian clock we aimed to identify the ion transporters involved in this process.

In control mice, the renal mRNA expression of the H,K‐ATPase type 2 (HKA2) is 25% higher during rest compared to the activity period. Conversely, under dietary K+ restriction, HKA2 expression is ~ 40% higher during the activity period. This reversal suggests that HKA2 contributes to the circadian regulation of K+ homeostasis. Compared to their wild‐type littermate (WT), HKA2‐ null mice on a normal diet have a 2‐fold higher K+ renal excretion during rest. Under K+ restriction, their urinary K+ loss is 40% higher during the activity period. This inability to excrete K+ “on time” is reflected in plasma K+ values, which vary by 12 % between activity and rest periods in HKA2‐null mice but remain stable in WT. Analysis of the circadian expression of HKA2 regulators suggests that Nrf2 but not progesterone contributes to its rhythmicity. Therefore, HKA2 acts to maintain the circadian rhythm of urinary K+ excretion and preserve stable plasma K+ values throughout the day.
Retrograde signaling does not mediate sodium excretion during dorsal column stimulation
Authors: Tschautscher Craig Franz , Knoblich Penny
Published: June 2021

Prior work found an increase in renal sodium excretion in male spontaneously hypertensive rats (SHR) following dorsal spinal column stimulation (DCS) at the spinal segment of the left renal sensory nerves (T12–T13). General sympathetic tone, and renal blood flow were unaltered by DCS. The effects of dorsal rhizotomy on the DCS‐induced renal sodium excretion was investigated in male SHR. SHR were randomly assigned to one of the following groups: no‐stimulation (NS), stimulation (S), no stimulation + Rhizotomy (NS+R), and Stimulation + Rhizotomy (S+R). Stimulated rats received DCS during the 2nd of five 15‐min. collection periods. Blood pressure was measured via a carotid artery cannula, and urine was collected via a bladder cannula. A standard stimulation parameter of 66% of the motor threshold (0.2 msec duration and 50 Hz) was used. Urine sodium was analyzed using flame photometry. Sodium excretion was significantly elevated in periods 3 and 4 in the S group when compared with corresponding periods in the NS group. Sodium excretion was significantly elevated in period 5 in the S+R group when compared with the NS+R. There were no differences between the S+R and the S groups. The DSC‐induced increase in sodium excretion is independent of retrograde signaling in the renal nerves. This research was funded by a departmental grant, in the Department of the Biological Sciences, Minnesota State University, Mankato, MN
Co‐localization of Dynorphin with inducible cAMP element repressor (ICER) in the supraoptic nucleus
Authors: Bengs Heather Denise , Rangel Yolanda , Franklin Cynthia , Toney Glenn M , Gottlieb Helmut B
Published: June 2021

The endogenous kappa (κ) opioid agonist, Dynorphin, and its receptors have been shown to be present at the supraoptic nucleus (SON) as well as co‐localized within vasopressin secretory vesicles. Central administration of U50, κ agonist, increases ICER expression at the level of the SON, which may play a role in modulating vasopressin release. This study examined central κ‐mediated changes in ICER expression in SON neurons expressing Dynorphin. Rats were implanted with an ICV cannula for microinjection of drug/vehicle, and each was acclimated to a metabolic cage for collection of urine during the experimental protocol. Tissue sections through SON were processed for ICER using commercially available polyclonal anti‐ICER and Dynorphin antibodies. U50 (1μg/5μl) significantly increased water free diuresis and ICER staining in the SON as compared to control (all P < 0.05). ICER‐ir staining significantly increased in Dynorphin positive cells of SON. These results raise the possibility that ICER activation could be an important substrate through which κ opioids mediate magnocellular neuron inhibition to suppress vasopressin secretion. Understanding the role of the ICER transcription factor in regulating SON neuronal activity could provide new and potentially important insight into mechanisms of water and electrolyte homeostasis in health and disease. Supported by 1SC2 HL104639 (HBG).
Renal handling of potassium in a Sus scrofa model of acute hemorrhagic shock
Authors: Uyehara Catherine FT , Golden Patrick J , Ichimura Wayne M , Murata Lee-Ann M , Sato Aileen K , Hernandez Claudia A
Published: June 2021

Hyperkalemia associated with acute hemorrhagic shock has recently been associated with increased mortality, yet the timeframe and mechanism in the development of this hyperkalemia is not well understood. We examined whether hyperkalemia may develop due to alteration of the renal handling of water and electrolytes in the first minutes of hemorrhage. Acute rapid hemorrhage (1 to 3 ml/kg/min) in juvenile Yorkshire cross pigs (n=7, 33±3 kg body weight) was induced resulting in a 55±4% decrease in mean arterial pressure and an oxygen debt of 50±12 ml/kg over 30 minutes. Within five minutes of the start of hemorrhage plasma potassium increased, reaching 6.6±0.3 mEq/l by 30 min of hemorrhage. Accompanying a 50% drop in cardiac index were decreases in urine flow (28.5±5.3 to 4.5±2.3 μl/kg/min), creatinine clearance, and osmotic clearance. Despite an increase in circulating vasopressin, a decrease in tubular water reabsorption occurred in conjunction with an overall rise in plasma osmolality. Plasma aldosterone was unchanged in this acute period, but the trans tubular potassium gradient decreased with the antidiuresis caused by a drop in renal filtration. Results indicate that the drastic hemodynamic changes during acute severe shock override the normal influence of vasopressin and aldosterone on renal handling of water and potassium excretion, thus contributing to the hyperkalemia.
Effect of Oryeongsan on hypertonic stress‐induced water channel expression and apoptosis in renal collecting duct cells
Authors: Lee So Min , Lee Yun Jung , Yoon Jung Joo , Kang Dae Gill , Lee Ho Sub
Published: June 2021

Aquaporin‐2 (AQP2), a family of water channels, plays an important role in the urinary concentrating process and regulation of water balance in the kidney. Oryeongsan (ORS, Wulingsan) has been reported to possess renal protective effects from renal diseases such as diabetes‐induced renal damage, nephrocalcinosis. This study was conducted to evaluate the inhibitory effect of ORS on hypertonic stress‐induced AQP2 expression and apoptosis in inner medullary collecting duct cell lines (IMCD‐3). Hypertonic stress (175 mM NaCl) increased AQP2 expression, ORS attenuated the hypertonicity‐induced increase in protein and mRNA levels in a concentration‐dependent manner. Pretreatment with ORS attenuated hypertonicity‐induced cell death. Hypertonicity increased serum‐ and glucocorticoid‐inducible protein kinase (Sgk1) phosphorylation, however, ORS attenuated the hypertonicity‐induced Sgk1 activation. Tonicity‐responsive enhancer binding protein (TonEBP) mRNA was also recovered by ORS under hypertonic stress. Hypertonicity increased cAMP levels and the changes were blocked by ORS. On the other hand, hypertonic stress‐induced Bax or caspase‐3 expression was decreased by ORS, resulting in anti‐apoptotic effect. These results provided evidence that the beneficial effect of ORS in water balance and apoptosis against in vitro hypertonic stress of renal collecting ducts.
Role of aldosterone on Sympathetic hyperactivity in renovascular hypertensive rats
Authors: Lincevicius Gisele Silverio , Shimoura Caroline Gusson , Nishi Erika Emy , Bergamaschi Cassia , Campos Ruy
Published: June 2021

Increased renal sympathetic nerve activity (rSNA) and baroreflex dysfunction are involved in the pathophysiology of renovascular hypertension. Most of these effects are believed to be mediated by increased Angiotensin (Ang II) endogenous level. Considering that Ang II enhance aldosterone release, the aim of the present study was to evaluate the effects on cardiovascular function of chronic mineralocorticoid receptor blockade with spironolactone (spiro, 200 mg/Kg/Day, orally) for 1 week by the 6th week after left renal artery clipping (2K1C) compared to sham group treated or not with spiro Spiro produced reduction (p<0.05) of 12% in mean arterial pressure (from 194±4, n=18 to 171±8 mmHg, n=15) and 35% in rSNA (from 147±9, n=6 to 96±10 spikes/s, n=8) of 2K1C group. In the 2K1C group, the water intake (control: 30±2, n=5; 2K1C: 49±4 mL, n=16) and urine excretion (control: 13±0.4, n=5; 2K1C: 38±3 mL, n=16) were significantly increased compared to control group, however, spiro did not alter these parameters. Furthermore, spiro treatment significantly increased the baroreflex sensitivity for rSNA in both treated groups (control: − 0.3±0.04, n=6; control + spiro: −0.9±0.03, n=5; 2K‐1C: −0.2±0.03, n=5; 2K1C + spiro: −0.4±0.03 spikes/s/mmHg, n=5). Our data suggest that aldosterone is involved in the sympathoexcitation and rSNA baroreflex impairment in the renovascular model of hypertension. Supported by FAPESP/CNPq
Expression of Renin Angiotensin System (RAS) Components in Npr1 Gene‐Disrupted mice
Authors: Periyasamy Ramu , Das Subhankar , Pandey Kailash N
Published: June 2021

Disruption of the Npr1 gene (coding for GC‐A/NPRA) exhibits increased BP, congestive heart failure, cardiac and renal hypertrophy in mice. The objective of the present study was to evaluate the effect of RAS components in Npr1 gene‐disrupted and gene‐duplicated mice kidney. The study was performed utilizing adult mice aged 6 month with different copies of Npr1 gene [homozygous null mutant, 0‐copy (−/−), heterozygous mutant (+/−; 1‐copy), wild‐type (+/+; 2‐copy) and gene‐duplicated (++/++; 4‐copy)]. The results showed that complete disruption of Npr1 gene causes a significant elevation of BP by 30 ± 2.4mmHg as compared with the 2‐copy control mice. On the other hand, the 4‐copy mice showed lowered BP when compared with wild‐type mice. A significant increase in (pro)renin receptor (3.5‐fold), angiotensin‐converting enzyme (ACE; 4.5‐fold), and angiotensin II type 1 receptor (AT1R; 3.0‐fold) levels was observed in the kidney of 0‐copy mice as compared with 2‐copy control mice. In contrast, 4‐copy mice showed decreased expressions of (pro)renin (2‐fold), ACE (1.5‐fold) and AT1R (1.5‐fold). In addition, the expression level of ACE2 was decreased by 2‐fold in 0‐copy mice when compared with the control mice. The present findings demonstrate that complete disruption of Npr1 gene causes a significant increased expression of (pro)renin receptor, ACE, and AT1R, which together may contribute towards the increase of BP.
Inflammation and disruption of the mucosal architecture in claudin‐7‐deficient mice
Authors: Chen Yan-Hua , Lu Zhe , Ding Lei , Foreman Oded , Tatum Rodney , Lu Qun , Renegar Randall , Cao Jian
Published: June 2021

Integrity of the intestinal epithelium is required for nutrition absorption and defense against pathogens. Multiple claudins are expressed along the gastrointestinal tract, but little is known about their functions. We generated claudin‐7‐deficient (Cldn7−/−) mice and examined their intestines by histology, molecular and cellular biology, as well as biochemistry approaches. Cldn7−/− mice died around 9 days after birth and had severe intestinal defects that included mucosal ulcerations, epithelial cell sloughing and terminal bleeding. Intestines of Cldn7−/− mice produced significantly higher levels of cytokines, NF‐kappa B and COX‐2. In addition, deletion of Cldn7 resulted in the striking upregulation of MMP‐3 and MMP‐7 in Cldn7−/− intestines. Electron microscopy analysis showed that intestines of Cldn7−/− mice had intercellular gaps and cell‐matrix loosening. Biotin tracer leakage was observed in the intestinal epithelial cells of Cldn7−/− mice at postnatal day 5. Most importantly, Cldn7 deletion reduced the expression and altered the localization of integrin a2; disrupted the formation of claudin‐7/integrin a2/claudin‐1 complexes that normally form in epithelial basolateral compartments of intestines. Our study reveals a novel function of claudin‐7 in cell‐matrix interactions and presents a new animal model to study the intestinal inflammation and inflammatory bowel disease in humans.