bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Interaction between Thyroid Receptor Interacting Protein 13 with Tetratricopeptide Repeat Domain 5 Regulates p53 Activity in Murine Inner Medullary Collecting Duct Cells
Authors: Hama Taketsugu , Pressly Jeffrey David , O'Brien Shannon , Park Frank
Published: November 2023

Renal epithelial cells adapt to biological stressors to maintain their normal biological function. Repair pathways are initiated within the damaged tubular epithelial cells and allow for recovery from the biological stress, whereas more severe injury may circumvent the recovery phase by activating programmed cell death pathways. Emerging evidence has uncovered that thyroid receptor interacting protein 13 (TRIP13) may play a crucial role in the repair process of genomic DNA following damage stimuli. Towards this end, our lab has recently identified increased production of Trip13 transcript levels in renal tubular epithelial cells following acute kidney injury, but there is a paucity of data regarding its mechanism of action in the kidney. In this study we investigated the relationship between TRIP13 and p53, a pivotal transcription factor that acts as a central hub for signal transduction pathways to direct a multifaceted signaling output following biological stress. To investigate the effect of TRIP13 in response to DNA damage, we initially exposed genetic knockdown of TRIP13 in murine inner medullary collecting duct cells to H2O2, which is known to induce double strand breaks. We demonstrated a significant reduction in cell numbers by 40–50% compared to IMCD‐Ctrl and also revealed increased levels of phospho‐p53 (Serine 15) and total p53 following H2O2 insult compared to the IMCD‐Ctrl cells. To further investigate the mechanism by which TRIP13 induces p53 levels and/or activity, we pursued a yeast two‐hybrid screen approach to identify new protein‐protein interactions that could participate in this response. Our yeast two‐hybrid approach identified a protein, tetratricopeptide repeat domain 5 (TTC5), which is known to function as a stress‐inducible transcription p53 cofactor to augment p53 expression, stability and/or activity. Confirmation of a direct interaction between TRIP13 and TTC5 was demonstrated using co‐immunoprecipitation techniques. Moreover, fluorescent microscopy revealed that TRIP13 was largely localized to the cytoplasm with modest signals from the nucleus. In the presence of over‐expressed TTC5, TRIP13 was strongly detected in the nucleus. Western blotting using nuclear fractionation revealed that p53 induction was reduced in overexpression of EGFP‐TRIP13 and myc‐TTC5 compared to control conditions. Thus, our data suggests that TRIP13 interacts with TTC5 to reduce p53 activity following DNA damage.

Support or Funding Information

This study was funded by NIH RO1‐DK90123, and UTHSC seed grant program.
CT20p induced autophagy in breast cancer cells can be overcome by co‐treatment with 3‐methyladenine to maximize cell death
Authors: Lee Michael William , Moskowitz Chad , Perez J. Manuel , Khaled Annette
Published: November 2023

Triple‐negative breast cancer is an aggressive form of cancer that is highly resistant to current treatments and has a high rate of recurrence. The CT20p peptide is a novel therapeutic that can target and kill triple‐negative breast cancer cells. In this study, we investigated one of the biological effects of CT20p in MDA‐MB‐231 triple negative breast cancer cell. We discovered that as a result of CT20p's inhibition of essential cellular processes, such as cell attachment, autophagy, as protective response, was induced. Thus, we sought to determine if inhibiting the autophagic process could accelerate and enhance the cell killing ability of CT20p. As proof in principle, combination of the autophagy inhibitor 3‐methyladenine together with CT20p increased the amount of cell death among MDA‐MB‐231 cells compared to CT20p alone, indicating that simultaneous targeting of the autophagy pathway is a viable method to maximize cell death via CT20p.
EMERGENCE OF APOPTOTIC FEATURES AFTER GLCINE CYTOPROTECTION AGAINST ATP DEPLETION‐INDUCED NECROTIC KILLING OF RAT HEPATOCYTES
Authors: Li Li , Lemasters John J
Published: November 2023

Glycine protects hepatocytes from injuries caused by toxins, hypoxia and ischemia. However, the mechanisms by which glycine exerts its cytoprotection remain elusive. In excitable cells like neurons, glycine binding to its receptor can trigger influx of chloride. Although the existence and molecular composition of a glycine receptor in non‐excitable cells is not clear, cell lines with no expression of glycine receptor proteins have either attenuated or no protection by glycine (Pan et al., Biochem. J. 390, 447). Another model has been proposed that protection is through blockage of non‐specific plasma membrane pores by glycine (Nishimura and Lemasters, Cell Death Differ. 8, 850). To further understand the mechanism of glycine protection, we studied killing of rat hepatocytes by carbonyl cyanide m‐chlorophenyl hydrazone (CCCP), a mitochondrial uncoupler. After CCCP (15 μM), hepatocytes started to die in a progressive manner after a latency time of 15–95 min. After 6 h, necrotic cell death approached 100% by the criterion of nuclei staining with propidium iodide (PI). Glycine (3 mM) strongly protected rat hepatocytes against CCCP toxicity: cell killing was both delayed and decreased to approximately 30% over 6 h. After expression of a genetically encoded chloride biosensor, no significant difference in chloride concentration was observed with and without glycine after CCCP. However, glycine caused a dramatic change in cell death behavior. In the absence of glycine, hepatocytes died in a membrane‐bursting manner, and fluorescence of the chloride biosensor rapidly disappeared, indicating leakage of cellular contents. In the presence of glycine, hepatocytes began to shrink substantially, beginning at approximately the same time necrotic cell death would otherwise have occurred. After CCCP in the absence of glycine, plasma membrane staining by Alexa488‐Annexin V occurred simultaneously with PI staining of nuclei. With CCCP plus glycine, hepatocytes first stained by Annexin V as shrinkage began and only hours later by PI. Rhodamine‐dextran labeling of lysosomes showed that lysosomal leakage accompanied cell shrinkage and Annexin V labeling in the presence of glycine. These findings indicate that features of apoptotic cell death (Annexin V labeling, cell shrinkage) emerge when onset of necrotic cell death is suppressed by glycine in ATP‐depleted hepatocytes. Lysosomal permeabilization may promote the apparent activation of apoptotic pathways.
BNIP3 Regulation of Intracellular Calcium
Authors: Field Jared , da Silva Rosa Simone , Mughal Wajihah , Hai Yan , Gordon Joseph , Diehl‐Jones William L
Published: November 2023

Necrotizing enterocolitis is the most common gastrointestinal emergency affecting low‐birth weight premature infants, with an incidence between 3% and 10% in infants less than 1500 grams, and mortality ranging from 15% to 30%. The pathogenesis of NEC is not clearly defined, but is likely a multifactorial disease wherein intestinal ischemia and hypoxia play fundamental roles. The hypoxia‐inducible death gene Bnip3 has been recently identified as a key regulator of NEC, yet the molecular mechanisms surrounding Bnip3‐induced enterocyte necrosis are not fully defined. Calcium‐mediated opening of the mitochondrial permeability transition pore (mPTP) has been identified as an important precursor event to necrotic cell death. Therefore, we tested the hypothesis that Bnip3 initiates calcium‐dependent PTP opening in cultured cells. We demonstrate that expression of Bnip3 increases mitochondrial calcium content, determined by Rhod2 staining, and that this effect is attenuated by expression of the inhibitory alternative splice variant Bnip3ΔEx3. Consistent with these findings, Bnip3 expression opens the mPTP, which was also prevented by Bnip3ΔEx3. Using organelle‐targeted calcium indicators, we found that Bnip3ΔEx3 did not inhibit Bnip3‐induced calcium release from the endoplasmic reticulum. However, Bnip3ΔEx3 expression re‐directed calcium release and promoted nuclear accumulation of calcium. These novel findings indicate that Bnip3ΔEx3 may protect cells from necrosis by promoting calcium‐dependent signaling pathways that converge on the nucleus, and provide a novel mechanism that may serve to protect enterocytes from hypoxic injury during NEC.

Support or Funding Information

Athabasca University

Children's Hospital Research Institute of Manitoba

Natural Sciences and Engineering Research Council of Canada
5‐methoxytryptophan Prevents High‐Glucose Induced Mesenchymal Stem cell Senescence through Alteration of Lysosome Mass
Authors: Chang Tzu‐Ching , Shiue Ying‐Chang , Hsu Min‐Fen , Wu Kenneth K.
Published: November 2023

Bone marrow‐derived mesenchymal stem cells (BMSCs) have great therapeutic potential for many diseases. However, stressful environment may lead BMSCs to premature senescence, resulting in altered cellular characteristics and functions. We had recently reported that high glucose (HG) stress induced BMSC senescence via up‐regulating autophagy. Inhibition of ROS activity with N‐acetylcysteine prevented BMSCs from HG‐induced autophagy and senescence. In this study, we have determined the role of 5‐methoxytryptophan (5‐MTP) on preventing HG‐induced BMSC senescence. 5‐MTP was detected in the conditioned medium (CM) of BMSCs cultured at low glucose (LG) and reduced in CM of cells cultured at HG. Exogenous addition of 5‐MTP reduced p21 and p16 expression in HG‐induced senescent BMSCs. Moreover, 5‐MTP attenuated the activity of senescence associated‐β‐galactocidase (SA‐β‐gal) in HG‐BMSC. Since lysosomes have a crucial role on cellular senescence, we evaluated the effect of 5‐MTP on lysosome by lysotracker staining. Lysotracker‐positive cells were increased in HG‐BMSCs compared to LG‐BMSCs. 5‐MTP addition abrogated lysosome increase in HG‐BMSCs. Our data also revealed that 5‐MTP reduced the glycosylation of LAMP‐1, a membrane protein of lysosome which is involved in lysosome stabilization, in HG‐BMSCs. Like the effects of 5‐MTP, inhibition of LAMP‐1 glycosylation with endoH in HG‐BMSCs attenuated the lysosome mass and SA‐β‐gal activity. Furthermore, both 5‐MTP and endoH could suppress the inflammatory cytokine, IL‐6, secretion from HG‐BMSCs. Taken together, these results indicate that 5‐MTP prevents BMSCs from high glucose‐induced senescence and secretory phenotype, which may be mediated by altering lysosome hemostasis.

Support or Funding Information

MOST‐103‐2321‐B‐039‐006
Disruption of the Mouse Tip110 Gene Leads to Early Post‐implantation Lethality and Prohibits Embryonic Stem Cell Development
Authors: Whitmill Amanda Jade , He Johnny
Published: November 2023

HIV‐1 Tat‐interacting protein of 110 kDa, Tip110, has roles in tumor antigen presentation, pre‐mRNA splicing, transcription of viral and host genes (e.g. HIV‐1 LTR and androgen receptor), and protein degradation. Tip110 is also known to be up‐regulated in a variety of cancers and to regulate and/or interact with a variety of transcription factors, oncogenes, and pluripotency factors such as YB1, USP4, USP15, CMYC, GATA2, OCT4, SOX2 and NANOG. As such, Tip110 can effect proliferation, apoptosis, and the cell cycle when knocked down in vitro. However, Tip110 function in embryonic development remains largely uncharacterized. One early study has shown that loss of a Tip110 ortholog leads to embryonic lethality in zebrafish. Our studies have shown that transgenic mice lacking expression of a functional Tip110 protein die several days post‐implantation in vivo. Tip110 loss does not impair embryo growth from the zygote to the blastocyst stage in vivo nor does it impair the blastocysts ability to implant into the uterine lining in vivo. However, long‐term culture of blastocysts in vitro reveals that Tip110 loss impairs both blastocyst outgrowth formation and derivation of mouse embryonic stem cells (mESC) from blastocysts in vitro. In this case, blastocyst outgrowths lacking Tip110 develop initially in synchrony with their Tip110 expressing counterparts but diminish in both size and survivability with long‐term culture. In vivo embryos can survive until the post‐implantation stage where they will eventually perish. The premature death of these embryos is characterized by a clear retardation in embryonic development resulting in underdeveloped or completely resorbed mouse embryos around 8.5 days post coitum (dpc). The underdeveloped embryos possess clear features of premature developmental arrest between 8.5 and 9.5 dpc including failure of anterior and posterior neuropore closure, lack of characteristic s‐shaped looping of the heart, minimal somatogenesis, and diminished formation of yolk‐sac blood islands. Microarray analysis of Tip110−/− cells derived from mouse blastocysts is currently underway to determine the specific underlying mechanisms that lead to cell death in Tip110−/− mESCs and embryos.
Multisensory Integration in the Developing Brain of the Xenopus laevis Tadpole
Authors: Carrillo Oscar A , Truszkowski Torrey
Published: November 2023

Perception of meaningful experiences requires that we combine multiple sensory modalities through a process called multisensory integration (MSI). Previous work on the mammalian superior colliculus has revealed the phenomenology of MSI, but little is known about the underlying biophysical mechanisms. In the Xenopus laevis tadpole, a homologue of the superior colliculus, the optic tectum, is directly involved in MSI and is an emerging model for the study of MSI. NMDA receptors (NMDARs) can serve as coincidence detectors in neurons allowing for non‐linear integration of synaptic input, so we hypothesized that NMDARs may play important roles in mediating single‐neuron MSI and, thus, blocking NMDA receptors will stunt MSI in tectal neurons. We also predict that low‐intensity multisensory stimuli undergo greater MSI than high‐intensity multisensory stimuli. We employed multisensory behavioral experiments and electrophysiological recordings to address these questions. Behavioral results indicate that multisensory stimuli not only result in significantly greater startle responses than unisensory stimuli, but that tadpoles use MSI to a greater extent when both stimuli are low‐intensity as compared to one of the stimuli being high‐intensity. Electrophysiology results indicate that low‐intensity multisensory stimuli have greater signal enhancement (5.57 ±1.01) than high‐intensity multisensory stimuli (1.17 ±0.06). Additionally, the low‐intensity multisensory stimuli group has greater MSI (3.18 ±0.68) than the NMDA‐antagonist group (1.34 ±0.34). These preliminary findings suggest that MSI is more useful for enhancing low‐intensity multisensory stimuli and that the NMDA receptor is at least partially involved with MSI on a cellular level.

Support or Funding Information

American Physiological Society, National Institute of Neurological Disorders and Stroke
Bardet‐Biedl Syndrome 1 Gene in the Ventromedial Hypothalamus is Required for Energy Homeostasis
Authors: Rouabhi Mohamed , Guo Deng Fu , Rahmouni Kamal
Published: November 2023

Bardet‐Biedl Syndrome (BBS) is a cilia‐related disorder characterized by many clinical features including obesity. Global deletion of individual Bbs genes recapitulates many of the phenotypes associated with human BBS including obesity. In addition, our laboratory has demonstrated that conditional deletion of the Bbs1 gene throughout the nervous system lead to the development of obesity in mice. The ventromedial hypothalamus (VMH) is a key nucleus in the regulator of energy balance, but the role and contribution of the Bbs1 gene in the VMH with regards to obesity is not known. To address this, we specifically ablated the Bbs1 gene in the VMH. This was achieved by crossing genetically modified mice bearing the Bbs1 gene flanked by Lox‐P sites (Bbs1fl/fl) with mice expressing Cre recombinase selectively in the VMH, driven by the steroidogenic factor 1 (SF1) promoter (SF1Cre). First and to validate specificity of Cre‐recombinase, a td‐Tomato reporter mouse was used. As expected, Cre recombinase, indicated by td‐Tomato expression, occurred only in the VMH where SF1 expressing neurons reside. Next, growth curves of SF1Cre/Bbs1fl/fl mice and littermate controls, from 4 to 25 weeks of age, was compiled. Interestingly, mice lacking the Bbs1 gene in the VMH (SF1Cre/Bbs1fl/fl mice) developed obesity. Indeed, although body weight was not different at young ages (4–6 weeks), after 7 weeks of age SF1Cre/Bbs1fl/fl mice start gaining more weight than littermate controls. At the end of study, body weight of SF1Cre/Bbs1fl/fl mice (males: 43.2±2.8g and females: 31.3±2.9g) was significantly (P<0.05) elevated compared to control littermates (males: 36.7±1.7g and females: 25.7±2.2g). Of note, heterozygous mice lacking one copy of the Bbs1 gene in SF1 neurons (SF1Cre/Bbs1fl/wt) had body weights (males: 41.1±2.2g and females: 29.4±1.0g) intermediate to SF1Cre/Bbs1fl/fl mice and controls. Finally, individual daily and cumulative food intake over 4 days was obtained. SF1Cre/Bbs1fl/fl mice exhibited hyperphagia as indicated by the significantly (P<0.05) increased daily food intake (4.06±0.15g) relative to WT littermates (3.55±0.15g). We concluded that Bbs1 gene in the VMH is necessary for the regulation of energy homeostasis.
Brain Epithelial Sodium Channel Contributes to Thirst Stimulated by Hypernatremia
Authors: Nation Haley L. , Simmonds Sarah S. , Stocker Sean D.
Published: November 2023

Increases in plasma NaCl concentrations or osmolality are sensed by specialized neurons in the hypothalamus and subsequently stimulate thirst, vasopressin secretion, and increase blood pressure. However, the exact mechanism by which these neurons sense changes in NaCl concentrations or osmolality has not yet been identified. Central administration of the non‐voltage gated sodium channel antagonist, benzamil, attenuates neuroendocrine and pressor responses to central NaCl infusion. Interestingly, a major target of benzamil is the epithelial sodium channel (ENaC), and the ENaC is highly expressed in several sodium‐ or osmosensing areas of the hypothalamus. Therefore, the purpose of the present study was to test the hypothesis that the ENaC contributes to osmoregulatory responses including thirst stimulated by hypernatremia or hyperosmolality. To test this hypothesis, we generated male mice (10–15 weeks of age) with brain‐specific deletion of the various ENaC subunits by breeding ENaCαlox/lox or ENaCϒlox/lox to NestinCre strains. Cumulative water intakes were measured in response to injection (10μL per 1 g body weight, sc) of 0.15M, 0.3M, or 0.5M NaCl. Injection of NaCl produced concentration‐dependent increases in water intake across all strains. However, ENaCαlox/loxNestinCre (n=6) versus ENaCαlox/lox (n=10) mice ingested significantly less water after injection of 0.3M NaCl (0.12±0.03 vs 0.17±0.02mL, respectively; P<0.05) and 0.5M NaCl (0.21±0.04 vs 0.31±0.02mL, respectively; P<0.01). Injection of 0.15M NaCl did not increase water intake in either strain (0.02±0.01 vs 0.01±0.01mL, respectively). In marked contrast, ENaCϒlox/loxNestinCre (n=12) versus ENaCϒlox/lox (n=10) mice ingested similar amount of water after injection of 0.15M (0.05±0.02 vs 0.01±0.01mL, respectively), or 0.5M NaCl (0.31±0.02 vs 0.33±0.03mL, respectively). A second set of experiments were performed to determine whether the ENaC contributes to thirst stimulated by hyperosmolality rather than hypernatremia. Injection of 0.7M mannitol (dissolved in 0.15M NaCl) stimulated similar increases in water intake between ENaCαlox/loxNestinCre versus ENaCαlox/lox mice (0.25±0.02 vs 0.27±0.05mL, respectively) as well as ENaCϒlox/loxNestinCre versus ENaCϒlox/lox mice (0.31±0.03 vs 0.31±0.03mL, respectively). Collectively, these data demonstrate that the ENaCα subunit, but not ENaCϒ subunit, contributes to thirst stimulated by hypernatremia but not hyperosmolality and may represent a putative channel in the brains ability to detect sodium changes.
BRIEF ISOCAPNIC HYPEROXIA INCREASES SYMPATHETIC VASCULAR TRANSDUCTION DURING SYMPATHOEXCITATORY MANEUVERS IN HEALTHY HUMANS
Authors: Silva Bruno M. , Machado Alessandro C. , Vianna Lauro C. , Barbosa Thales C. , Prodel Eliza , Fernandes Igor A. , Nobrega Antonio C.
Published: November 2023

Oxygen supplementation is fundamental in medical care to avoid hypoxia. However, excessive use of oxygen is common in clinical practice, which has been associated with adverse cardiovascular events. Vasoconstriction and, consequently, increase in systemic vascular resistance (SVR) is a clinically relevant side effect of hyperoxia. But interestingly, muscle sympathetic nerve activity (MSNA) does not change or even decreases during hyperoxia. Thus, we hypothesized that hyperoxia increases the ability of muscle sympathetic nerve activity (MSNA) to effect vascular responses (i.e., sympathetic vascular transduction ‐ SPVT), particularly when MSNA is elevated. Healthy young men, aged 18–40 years, were submitted to 3 minutes of rest (n = 6), 3 minutes of post exercise ischemia (PEI; n = 8), and 2 minutes of cold pressor test (CPT; n = 6). Each protocol was conducted in isocapnic normoxia (21% O2; control) and isocapnic hyperoxia (100% O2), in random order. Respiratory rate was controlled using a metronome and tidal volume using verbal feedback to yield similar ventilation between and within protocols. This was done to minimize the influence of ventilation on cardiovascular variables and MSNA. Respiration (metabolic analyzer), hemodynamics (electrocardiogram and finger photoplethysmography), and MSNA (microneurography) were continuously recorded. SPVT was estimated by the ratio between mean values of SVR and MSNA total activity. At rest, hyperoxia did not change cardiac output (CO), SVR, mean arterial pressure (MAP), MSNA total activity, and SPVT. During PEI, hyperoxia decreased CO (Δ −10 ± 3%, mean ± SEM, P = 0.01) and increased SVR (Δ 16 ± 6%, P = 0.03). As a result, MAP did not change. Besides, hyperoxia decreased MSNA total activity (Δ −20 ± 6%, P < 0.01) and increased SPVT (Δ 49 ± 12%, P = 0.05). During CPT, hyperoxia tended to decrease CO (Δ −11 ± 5%, P = 0.08), tended to increase SVR (Δ 18 ± 8%, P = 0.08), and did not change MAP. Moreover, hyperoxia decreased MSNA total activity (Δ −12 ± 10%, P < 0.01) and increased SPVT (Δ 39 ± 11%, P = 0.05). In conclusion, brief isocapnic hyperoxia did not increase SPVT during rest, but increased SPVT during sympathoexcitatory maneuvers in healthy humans.

Support or Funding Information

São Paulo Research Foundation (FAPESP), National Counsel of Technological and Scientific Development (CNPq), and Research Support Foundation of the State of Rio de Janeiro (FAPERJ).
Time Course of Structural and Functional Adaptations of Mesenteric Resistance Vasculature after High Thoracic Spinal Cord Injury
Authors: Popok David , West Christopher , Frias Barbara , Laher Ismail , Krassioukov Andrei
Published: November 2023

Background

Spinal cord injury (SCI) disrupts autonomic pathways and consequently perturbs cardiovascular homeostasis. Injuries above T6 results in loss of descending sympathetic control of the splanchnic vasculature. Blood pressure regulation is impaired resulting in resting hypotension and episodic hypertension, the latter of which is known as a life threatening condition called autonomic dysreflexia (AD). These fluctuations in arterial blood pressure following SCI may also result in dysfunction and maladaptive remodelling at the level of the splanchnic resistance vasculature.

Objective

To examine the time course of structural and functional adaptations of resistance mesenteric vasculature in a complete T3 transection rodent model.

Design/Method

15 male Wistar rats were randomly assigned to three groups: T3 SCI 1 Week (n=5), T3 SCI 1 Month (n=5), and Uninjured Control (n=5). Functional and structural assessment of primary mesenteric arteries were assessed ex vivo using a pressure myograph system. In addition to vessel morphology and myogenic tone, functional assessment of vasocontractility was assessed using α1 adrenoceptor agonist phenylephrine (PE) and methoxamine (MET).

Results

Myogenic tone is significantly impaired in the T3 SCI 1 Week and T3 SCI 1 Month groups compared to the Uninjured Control group (p = 0.0212 and p=0.0059, respectively). EC50 values were extrapolated from PE dose response curves and were lower for both the T3 SCI 1 Week and T3 SCI 1 Month groups compared to the Uninjured Control group (p<0.0001 and p=0.0004, respectively). There are no significant differences found between EC50 values determined for MET. Wall thickness is decreased and vessel diameter is increased in the T3 SCI 1 Month group compared to the Uninjured Control group (p=0.0221 and p=0.066, respectively).

Conclusion

Hypersensitivity to the α1 adrenoceptor agonist PE but not MET suggest deficiency in the reuptake of norepinephrine in resistance mesenteric vasculature. Decreased wall thickness, in addition to an increased vessel diameter may suggest chronic outward hypotrophic remodelling.

Support or Funding Information

This research was funded by the Canadian Institute of Health Research and the Heart and Stroke Foundation of BC and Yukon.
Ca2+ Transients In And Release Of Norepinephrine From Sympathetic Varicosities In Rat Mesenteric Small Arteries – Importance For Force Development
Authors: Aalkjaer Christian , Tarasova Olga , Nilsson Holger
Published: November 2023

The role of Ca2+ in the sympathetic varicosity in the vascular wall for transmitter release is only inferred from the effect of Ca2+ channel blockers.

Here we measured Ca2+ transients directly in nervefibers (confocal microscopy after loading of a Ca2+ sensitive dye into the nerves selectively or into nerves and Schwann cells), norepinephrine (NE) release and in isolated rat mesenteric small arteries.

Electrical field stimulation caused a frequency dependent increase of nerve Ca2+, NE release and force development. All three effects were blocked by 100 nM ω‐Conotoxin GVIA and by tetrodotoxin. In arteries where both nerves and Schwann cells were loaded areas where nuclear stain demonstrated the presence of nuclei, field stimulation had little effect on Ca2+, while response to ATP was seen. In contrast ATP had little effect on Ca2+ transients in nerves, where good responses to field stimulation were seen. Acetylcholine (10 μM) caused complete inhibition of field stimulation induced Ca2+ increase, NE release and force development, while 4‐aminopyridine (10 μM) increased all three paramters 2–3 times.

It is possible to image Ca2+ in neurons and in Schwann cells in the vascular wall. Acetylcholine induced reduction in NE release is associated with decreased Ca2+ and 4‐AP induced increase of NE release is associated with increased Ca2+ probably mediated by K+ channels belonging to the Kv3 family.

Support or Funding Information

Danish Heart Foundation, Danish Research Council, Lundbeck Foundation
Baroreflex Function and Salt Sensitivity Among Normotensives
Authors: Matthews Evan Lee , Coyle Dana E , Brian Michael S , Edwards David G , Stocker Sean D , Farquhar William B
Published: November 2023

High degrees of salt sensitivity among normotensive individuals increases the risk for cardiovascular disease and death. Salt sensitive rodent models display impaired baroreflex sensitivity, a trait thought to contribute to poor cardiovascular health. Thus, we hypothesized that increased salt sensitivity (SS) in normotensive humans would be associated with decreased cardiac baroreflex sensitivity (CBRS) and decreased high frequency heart rate variability (HF‐HRV). Eighty‐seven healthy normotensive men and women completed 1 week of high (300mmol/day) and 1 week of low (20mmol/day) dietary sodium (random order) with 24hr mean arterial pressure (MAP) assessed on the last day of each diet. The change in 24hr MAP from low to high sodium was used as an index of SS. Of these 87 individuals, 50 agreed to return to the lab for testing under a habitual sodium intake condition. Eight were excluded from this analysis due to the presence of ectopic heart beats. Thus 42 (24 males) are presented in this analysis (age 39±2yrs [range 22–60yrs], BMI 24.3±0.5kg/m2, MAP 83±1mmHg, HR 59±1bpm, habitual urine sodium 93±7mmol/24hr). Electrocardiogram derived R‐R interval and beat‐by‐beat systolic blood pressure (SBP) were measured during 5 minutes of supine rest. Cardiac baroreflex analysis via the sequencing method was used to determine up sequence (concurrent increase in R‐R interval and SBP) and down sequence (concurrent decrease in R‐R interval and SBP) baroreflex sensitivity. Time domain heart rate variability analysis was performed using a fast Fourier transformation focusing on high frequency power. Linear regression analysis between SS and the variables of interest was performed. Among this cohort of normotensive adults, SS was associated with decreased HF‐HRV (r = −0.349, p = 0.046) and tended to be associated with decreased up sequence CBRS (r = −0.309, p = 0.096). However, multiple regression analysis accounting for age revealed that there was no relationship between SS and either HF‐HRV (age adjusted p=0.369) or up sequence CBRS (age adjusted p=0.712). Thus, these data suggest that the relation between increased SS and decreased HF‐HRV and CBRS is largely driven by the association of SS with age.

Support or Funding Information

Research supported by NIH R01 HL104106, & ACSM Foundation Research Grant.
Exercise Training Improves the Arterial Baroreflex Function in Hypertensive Rats
Authors: Pan Yan‐Xia , Hong Lin , Zhao Xiao‐Lin , Lin Cheng
Published: November 2023

Objective

To investigate the influence of exercise training on the arterial baroreflex and its central mechanisms in spontaneously hypertensive rats (SHR).

Methods

Twenty male SHR and 24 normotensive Wistar rats were randomly assigned into control group (C) or exercise training (E) group. All experimental procedures were in conformance with the FASEB Statement of Principles for the use of animals in research and education. Exercise training was performed on a treadmill for 8 weeks. Systolic blood pressure and heart rate were measured by tail‐cuff method. Baroreflex sensitivity(BRS) was determined by intravenous injection of phenylephrine (PE) and sodium nitroprusside (SNP). Alterations in the BRS were evaluated before and after intracerebroventricular administration of superoxide dismutase (SOD) mimetic Tempol or SOD inhibitor DETC. Malondialdehyde (MDA) content, total antioxidant capacity (T‐AOC), superoxide dismutase (SOD) and catalase (CAT) antioxidant enzyme activities in the hypothalamus were measured to assess oxidative state.

Results

Before exercise training, systolic blood pressure in two groups of SHR was obviously higher than those in normotensive Wistar rats (P<0.01). Exercise training significantly decreased heart rate in SHR and Wistar rats and systolic blood pressure in SHR alone. The BRS of control SHR was significantly lower than that of normotensive Wistar rats [PE: (0.89 ± 0.22) vs. (1.96 ± 0.23) bpm/mmHg, P <0.001; SNP: (0.62 ± 0.10 ) vs. (1.32 ± 0.23) bpm/mmHg, P<0.001). Exercise training significantly improved the BRS of SHR. Compared with control SHR, the BRS of the trained SHR was significantly increased [PE: (1.31 ± 0.26 ) vs. (0.89±0.22) bpm/mmHg, P <0.001 SNP: (1.22 ± 0.25) vs. (0.62±0.10)bpm/mm Hg, P <0.01). Intracerebroventricular infusion of DETC abolished the beneficial effect of exercise training on the BRS in SHR rats (P<0.05) and significantly decreased the BRS in two Wistar groups (P < 0.05). In contrast, Tempol greatly improved the BRS in two SHR groups (P<0.05) and normalized the BRS of the trained SHR. Exercise training decreased MDA content in the hypothalamus of SHR by 27% (P<0.05), but increased T‐AOC, SOD and CAT activities by 74%, 41% and 62%, respectively (P<0.05). In addition, exercise training decreased MDA content in the hypothalamus of Wistar by 40% (P<0.05), but increased T‐AOC, SOD and CAT activities by 72%, 30% and 51%, respectively (P<0.05).

Conclusions

Central oxidative stress depresses the arterial baroreflex, and exercise training –induced reduction of central oxidative stress contributes to improved arterial baroreflex function in SHR by the enhancement of antioxidant enzyme activity and antioxidant capacity in the brain.

Support or Funding Information

the National Natural Science Foundation of China (No.81372111)

the Natural Science Foundation of Fujian Province (No. J01339)
Effect of electroacupuncture on cardiac excitability during sympathoexcitation induced by acute ischemia and left stellate ganglion stimulation in a porcine model
Authors: Zhou Wei , Takamiya Tatsuo , Yamamoto Kento , Mahajan Aman
Published: November 2023

Augmentation of cardiac sympathetic tone during myocardial ischemia has been shown to increase myocardial O2 demand and infarct size as well as induce arrhythmias. We have previously demonstrated that electroacupuncture (EA) mitigates myocardial ischemia‐reperfusion injury by modulation of cardiac norepinephrine release. The purpose of this study is to determine the effects of EA on cardiac excitability evaluated by measurement of activation recovery interval (ARI) and heart rate variability (HRV) by using power spectral analysis. A median sternotomy was performed to expose the heart and the left stellate ganglion (LSG). Acute myocardial ischemia (AMI) was induced by ligation of left descending coronary artery. A 56‐electrode was placed on the heart to record ARI, a surrogate measure of action potential duration. AMI with LSG stimulation significantly shortened ARI by 5.4% and increased dispersion by 160% as well as increased LF/HF from 0.31 to 1.18 (n.u.). 30 min of EA significantly attenuated the ARI shortening (1.7% vs. 5.4%) and dispersion (104% vs. 160%) as well as decreased the LF/HF from 1.18 to 0.70 (n.u.) with decreased LF components from 46.5±3.5 to 27.2±4.1(n.u.) and increased HF components from 38.5 to 49.2 (n.u.). In conclusion, EA modulates the cardiac excitability through inhibition of sympathetic nerve system and activation of parasympathetic nerve system.

Support or Funding Information

Department Fund
The Correlation between Heart Rate Variability and Diet
Authors: Murray Olivia , Vick Robert
Published: November 2023

Heart function can be affected by lifestyle choices. Heart rate variability (HRV) is the variation in the time interval between heartbeats and can be used as a means to assess cardiac health (Stein & Kleiger 1999). A high HRV is indicative of good cardiac health and increased parasympathetic activity, while a low HRV has been associated with poor outcomes in adults (Kristal‐Boneh et al. 1995). This study investigated the correlation between overall diet and HRV. Thirty‐two participants aged 18–22 years old were recruited based on their diet. Diets represented in this study included vegetarian, dairy‐free, and gluten‐free, as well as participants that had no dietary restrictions, to act as controls. A 5‐minute electrocardiogram (ECG) was performed on each participant. Software supplied by ADInstruments was used to generate a spectral analysis of HRV by applying a Fast Fourier Transformation (FFT). Frequencies were subdivided as Very Low Frequency (VLF) and Low Frequency (LF), which correlates to a combination of sympathetic and parasympathetic effects, and High Frequency (HF), which correlates to parasympathetic effects. Time domain and frequency domain measures of HRV were analyzed through SPSS Statistics software. No significant differences between the diet groups were found; however, there were differences in the standard deviation of all normal RR intervals (SDRR) of each group (vegetarian = 104.66 ms, gluten‐free = 81.5 ms, healthy = 66.34 ms, unhealthy = 59.13 ms, and control = 87.07 ms). A moderate negative correlation was found between consumption of fast food and frequency HRV measures (HF power: r = −.397, p = .024), indicating that with increasing fast food consumption, there is an increasing risk for an adverse cardiac outcome. In general, diet does seem to result in small differences in HRV, especially between the unhealthy diet group, which is characterized by high consumption of red meat, fast food, alcohol, and sweets, and the vegetarian diet group, specifically for the LF domain (p=0.17). Additionally, after sorting the data through time domains rather than FFT, it was found that the vegetarian group had a SDRR greater than 100 ms, correlating with a low risk of cardiac problems as determined by previous parameters (Torres et al. 2008).

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Funding was obtained through the Elon University Undergraduate Research Program and the Elon College Fellows Program.
Leptin Facilitates Phrenic and Abdominal Nerve Activity During Chemoreflex Activation
Authors: Bassi Mirian , Furuya Werner Issau , Zoccal Daniel Breseghello , Menani José Vanderlei , de Almeida Colombari Débora Simões , Colombari Eduardo
Published: November 2023

Leptin acts in the central nervous system (CNS) enhancing chemorespiratory responses by mechanisms not yet completely understood. In the present study, we evaluated the pulmonary ventilation and the activity of the phrenic and abdominal nerves during activation of chemoreflex in rats treated chronically with leptin. Juvenile Holtzman rats (22–28 day old) received leptin (40 mg/day/7 days) or saline infusion subcutaneously. On the 6th day of infusion, pulmonary ventilation was recorded by whole body plethysmography and on the seventh day, nerve activity was recorded in the in situ heart‐brainstem preparation. The chemoreflex response was activated by KCN (0.04%) or hypercapnia (10% CO2). In both preparations, ventilation or nerve activities were recorded before and during chemoreflex activation. Leptin reduced the gain of body weight (30 ± 9 g vs. saline: 49 ± 2 g, p <0.05). Ventilation increased more during hypercapnia in rats treated with leptin infusion (1284 ± 109 ml.kg−1.min−1, vs. saline: 967 ± 66 ml.kg−1.min−1, p <0.05). In the in situ preparation, the increased activity of the phrenic and abdominal nerve produced by the activation of chemoreflex with KCN was strongly potentiated by leptin (45% ± 9 and 263 ± 83% vs. saline: 17 ± 3% and 93 ± 45% respectively, p <0.05). Similar increased responses were observed during hypercapnia in the in situ preparation. The results suggest that leptin enhances the chemoreflex response increasing inspiratory and expiratory activities.

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FAPESP; CNPQ; AND PNPD‐CAPES.
Renal Afferent Peptidergic Neurons – What are Primary Stimuli ?
Authors: Ditting Tilmann , Rodinova Kristina , Loosen Sonja , Hilgers Karl , Ott Christian , Schmieder Roland E , Amann Kerstin , Veelken Roland
Published: November 2023

Renal afferent nerve fibers comprise a complicated neuro‐paracrine regulatory system significantly influencing the sympathetic nervous system in health and disease, We wanted to test the hypothesis that the activity of renal afferent neuronal units is primarily altered by inflammatory processes in cardiovascular disease.

As inflammatory model, normotensive renal inflammation (Thy‐1) was induced by i.v. injection of 1.75 mg/kg BW Thy‐1 antibody to rats, hypertension by unilateral clipping of one renal artery (2K1Cl model) in rats 3 weeks prior to experiments. Controls were sham‐treated, respectively. Retrograde labelling (DiI) allowed the identification of renal afferent neurons situated in the dorsal root ganglion (DRG) (Th11‐L2). Patch clamp recordings, i.e. current clamp allowed to characterize neurons as highly active or “tonic”, i.e. sustained action potential (AP) firing versus low active or “phasic”, i.e. <5 APs according to their firing response to current injections. Electrophysiological parameters and AP properties were determined in all experimental groups and controls, proteinuria and renal morphology assessed for all kidneys.

In nephritic rats, the number of neurons with a tonic, more active response pattern decreased significantly (43,4% vs. 64,8%, p<0.05) as compared to controls. Interestingly. in renovascular hypertension (2K1Cl model, n=92) only neurons with projections to the clipped kidney showed a significant decrease in tonic firing pattern (30.6% [23/75]), whereas the non‐clipped kidney showed an unaffected proportion of tonically firing neurons (67.5% [50/74], p<0.05) as compared to controls. There was no increase in blood pressure (BP) in Thy‐1 animals, hence confounding effects of BP were unlikely. RI rats exhibited albuminuria (61±6 μg/24h), infiltration of macrophages in the interstitium (26 ± 4 cells/high‐power field) and glomeruli (3.7±0.6 cells/glomerular cross‐section) as signs of active renal inflammation. In contrast, in 2K1Cl animals BP was increased to 180/100 mmHg, but no signs of renal inflammation could be detected as in Thy‐1 rats.

In contrast to our hypothesis inflammation per se (and especially hypertension) may play less important roles for the decreased activity pattern of afferent renal neuron as seen in our experiments. Rather altered perfusion occurring in a clipped kidney with renal stenosis and likely also present in nephritis might be of pivotal importance.

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Deutsche Forschungsgemeinschaft
Cardiovascular Autonomic Tone in Rats with Heart Failure Treated with Allogeneic Mesenchymal Stem Cells
Authors: Morais Sharon DBV , Lataro Renata Maria , Silva Carlos Alberto Aguiar , Meirelles Lindolfo S , Fazan Rubens , Salgado Helio Cesar
Published: November 2023

Autonomic imbalance with lower cardiac vagal tone and sympathetic overactivity is a trademark of heart failure (HF) in either patients or experimental models of this disease. We evaluated the effect of bone marrow mesenchymal stem cells (MSC) on cardiovascular autonomic function in rats with chronic HF, induced by myocardial infarction (MI). Male Wistar rats were subjected to surgical ligation of left coronary artery to induce MI. After 7 days they were intravenously treated with MSC (106cels/250μL, N=11), or vahicle (saline, N=13). Control (non‐infarcted, N=14) rats were also evaluated. Five weeks after MI rats were implanted with subcutaneous electrodes for electrocardiogram (ECG). After 48 h, conscious freely moving rats underwent to basal ECG recording for 60 min hereafter received intravenous injection of methyl‐atropine followed by propranolol (or vice versa) to evaluate cardiac autonomic tone. Changes in heart rate (HR) elicited by methyl‐atropine and propranolol were considered as cardiac vagal and sympathetic tones, respectively. HR interval was similar among groups (313±6, 312±6 and 300±6 bpm). Surprisingly cardiac sympathetic tone was similar among groups (9±3, 14±3 and 11±4 bpm). On the other hand, cardiac vagal tone was significantly lower in saline‐treated infarcted rats (53±7 bpm) as compared to non‐infarcted control counterparts (84±7 bpm). MSC‐treated infarcted animals showed same vagal tone as control rats (97±10 bpm). Moreover, intrinsic HR, i.e. HR after double autonomic receptors blockade, was lower in non‐treated (saline) infarcted rats (344±5 bpm) as compared to control and to MSC‐treated infarcted rats (365±5 and 371±7 bpm). In conclusion, our data demonstrate that MSC therapy was effective to improve cholinergic autonomic tone of the heart and intrinsic HR.

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FAPESP, CNPq, FAEPA
Obstructive sleep apnea impairs insulin resistance in metabolic syndrome patients with normal levels of glucose
Authors: Cepeda Felipe Xerez , Rodrigues Sara , Dutra‐Marques Akothirene CB , Carvalho Jefferson Cabral , Toschi‐Dias Edgar , Jordão Camila Paixão , Rondon Maria Urbana , Alves Maria Janieire N.N. , Lorenzi‐Filho Geraldo , Trombetta Ivani Credidio
Published: November 2023

Intermittent hypoxia, a hallmark of obstructive sleep apnea (OSA), impairs glucose metabolism. Systemic inflammation is one mechanism involved in this impairment. Since OSA is highly prevalent in metabolic syndrome patients (MetS), we tested the hypotheses that: 1) Even with normal glucose levels, the presence of OSA in MetS worsens insulin sensitivity (IS); 2) The minimal oxygen saturation (Minimum SaO2) during polysomnography is associated with inflammation; and 3) The inflammation is associated with (IS). Thirty one newly diagnosed MetS (ATP III) with fasting glucose <100mg/dL were divided into: MetS+OSA (n=12, 46±3y) and MetS‐OSA (n=19, 42±2y), and compared with healthy control (C, n=11, 49±2y). OSA was characterized by apnea‐hypopnea index (AHI) >15 events/h. The pro‐inflammatory marker C‐reactive protein (CRP) was examined. We evaluated the IS by HOMA‐IR. All groups were similar in glucose levels. Both MetS groups were similar in MetS risk factors and different than C. MetS+OSA had similar to MetS‐OSA, but is higher than C for HOMA‐IR (4.1±0.5 vs. 3.0±0.4 and C, 2.0±0.2, respectively, P<0.01). Interestingly, in the MetS+OSA we found an association with Minimum SaO2 with PCR (R=−0.71; P<0.001). Moreover, the PCR was associated with HOMA‐IR (R=−0.62; P<0.001). In conclusion, our data suggest that the overlap of OSA in patients with MetS with normal levels of glucose impairs IS which may be explained, at least in part, inflammation as a response for the chronic intermittent hypoxia oxygen desaturation during sleep

Support or Funding Information

This study was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP# 2011/17533‐6 ) and, in part, by Fundação Zerbini.

Felipe X Cepeda was supported by FAPESP# 2015/03274‐0,

Sara Rodrigues was supported by FAPESP# 2013/15323‐0,

Edgar Toschi‐Dias was supported by FAPESP# 2013/07651‐7.