Acetylcholine-induced Relaxation Research Articles

Isoflurane increases the activity of the vascular matrix metalloproteinase-2 in non-pregnant rats and increases the nitric oxide metabolites in pregnancy.

Surgeries that require general anesthesia occur in 1.5-2% of gestations. Isoflurane is frequently used because of its lower possibility of affecting fetal growth. Therefore, we examined the isoflurane anesthesia-induced effects on maternal hemodynamic and vascular changes. We hypothesized that isoflurane would enhance endothelium-dependent vasodilation as a consequence of increased nitric oxide and decreased metalloproteinases (MMPs). Female rats (n = 28) were randomized into 4 groups (7 rats/group): conscious (non-anesthetized) non-pregnant group, non-pregnant anesthetized group, conscious pregnant group, and pregnant anesthetized group. Anesthesia was performed on the 20th pregnancy day, and hemodynamic parameters were monitored. Nitric oxide metabolites, gelatinolytic activity of MMP-2 and MMP-9, and the vascular function were assessed. Isoflurane caused no significant hemodynamic changes in pregnant compared with non-pregnant anesthetized group. Impaired acetylcholine-induced relaxations were observed only in conscious non-pregnant group (by approximately 62%) vs 81% for other groups. Phenylephrine-induced contractions were greater in endothelium-removed aorta segments of both pregnant groups (with or without isoflurane) compared with non-pregnant groups. Higher nitric oxide metabolites were observed in anesthetized pregnant in comparison with the other groups. Reductions in the 75 kDa activity and concomitant increases in 64 kDa MMP-2 isoforms were observed in aortas of pregnant anesthetized (or not) groups compared with conscious non-pregnant group. Isoflurane anesthesia shows stable effects on hemodynamic parameters and normal MMP-2 activation in pregnancy. Furthermore, there were increases in nitric oxide bioavailability, suggesting that isoflurane provides protective actions to the endothelium in pregnancy.

In utero exposure to maternal diabetes exacerbates dietary sodium intake-induced endothelial dysfunction by activating cyclooxygenase 2-derived prostanoids.

Prenatal exposure to maternal diabetes has been recognized as a significant cardiovascular risk factor, increasing the susceptibility to the emergence of conditions such as high blood pressure, atherosclerosis, and heart disease in later stages of life. However, it is unclear if offspring exposed to diabetes in utero have worse vascular outcomes on a high-salt (HS) diet. To test the hypothesis that in utero exposure to maternal diabetes predisposes to HS-induced vascular dysfunction, we treated adult male wild-type offspring (DM_Exp, 6 mo old) of diabetic Ins2+/C96Y mice (Akita mice) with HS (8% sodium chloride, 10 days) and analyzed endothelial function via wire myograph and cyclooxygenase (COX)-derived prostanoids pathway by ELISA, quantitative PCR, and immunochemistry. On a regular diet, DM_Exp mice did not manifest any vascular dysfunction, remodeling, or inflammation. However, HS increased aortic contractility to phenylephrine and induced endothelial dysfunction (analyzed by acetylcholine-induced endothelium-dependent relaxation), vascular hydrogen peroxide production, COX2 expression, and prostaglandin E2 (PGE2) overproduction. Interestingly, ex vivo antioxidant treatment (tempol) or COX1/2 (indomethacin) or COX2 (NS398) inhibitors improved or reverted the endothelial dysfunction in DM_Exp mice fed a HS diet. Finally, DM_Exp mice fed with HS exhibited greater circulating cytokines and chemokines accompanied by vascular inflammation. In summary, our findings indicate that prenatal exposure to maternal diabetes predisposes to HS-induced vascular dysfunction, primarily through the induction of oxidative stress and the generation of COX2-derived PGE2. This supports the concept that in utero exposure to maternal diabetes is a cardiovascular risk factor in adulthood.NEW & NOTEWORTHY Using a unique mouse model of prenatal exposure to maternal type 1 diabetes, our study demonstrates the novel observation that prenatal exposure to maternal diabetes results in a predisposition to high-salt (HS) dietary-induced vascular dysfunction and inflammation in adulthood. Mechanistically, we demonstrated that in utero exposure to maternal diabetes and HS intake induces vascular oxidative stress, cyclooxygenase-derived prostaglandin E2, and inflammation.

Potassium Ion Channel Modulation as a Potential Remedy for Cadmium-induced Hypertension

Objective: Hypertension remains a chief non-communicable lifestyle disease that is negatively associated with dietary cadmium (Cd). The exact mechanism of Cd toxicity and the mitigating role of potassium supplementation are not fully known, hence, this study aimed to investigate their effects on the aorta. Hypothesis: We hypothesized that potassium supplementation can modulate Cd-induced vascular dysfunction. Method: Six cohorts of control, Cd-exposed, and potassium supplemented male Sprague-Dawley rats were selected. Hypertension was induced using cadmium chloride (2.5 or 5 mg/kg b.w.). Blood pressure was measured twice weekly. Reactivity to pharmacological agents with and without potassium ion channel modulation was assessed in thoracic aortic rings after eight weeks, using an organ bath set-up. Data: Statistical analysis was done using one-way analysis of variance and the results were reported as mean ± standard error of the mean. The Games-Howell or Bonferroni post hoc test was used for multiple comparisons. Summary of Results: Cadmium significantly (p<0.05) elevated systolic, diastolic, mean arterial, and pulse pressures, reduced (p<0.001) phenylephrine-induced contraction mostly via BKCa channels, and augmented (p<0.05) sodium nitroprusside-induced relaxation via K-ATP, KV, and KIR channels, without affecting acetylcholine-induced relaxation. Potassium supplementation ameliorated these effects via KIR and BKCa channels. Conclusions: The results indicate that modulation of potassium ion channels in the vasculature might provide therapeutic management for environmentally-induced hypertension and should be further explored. Funding source: The Mona Campus Committee for Research and Publications and Graduate Awards, School for Graduate Studies and Research, University of the West Indies. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The soluble (pro)renin receptor promotes a preeclampsia-like phenotype both in vitro and in vivo.

Preeclampsia is classified as new-onset hypertension coupled with gross endothelial dysfunction. Placental (pro)renin receptor ((P)RR) and plasma soluble (P)RR (s(P)RR) are elevated in patients with preeclampsia. Thus, we aimed to interrogate the role (P)RR may play in the pathogenesis of preeclampsia. Human uterine microvascular endothelial cells (HUtMECs, n = 4) were cultured with either; vehicle (PBS), 25-100 nM recombinant s(P)RR, or 10 ng/ml TNF-a (positive control) for 24 h. Conditioned media and cells were assessed for endothelial dysfunction markers via qPCR, ELISA, and immunoblot. Angiogenic capacity was assessed through tube formation and adhesion assays. Additionally, pregnant rats were injected with an adenovirus overexpressing s(P)RR from mid-pregnancy (day 8.5), until term (n = 6-7 dams/treatment). Maternal and fetal tissues were assessed. HUtMECs treated with recombinant s(P)RR displayed increased expression of endothelial dysfunction makers including vascular cell adhesion molecule-1, intracellular adhesion molecule-1, and endothelin-1 mRNA expression (P = 0.003, P = 0.001, P = 0.009, respectively), along with elevated endothelin-1 protein secretion (P < 0.001) compared with controls. Recombinant s(P)RR impaired angiogenic capacity decreasing the number of branches, total branch length, and mesh area (P < 0.001, P = 0.004, and P = 0.009, respectively), while also increasing vascular adhesion (P = 0.032). +ADV rats exhibited increased systolic (P = 0.001), diastolic (P = 0.010), and mean arterial pressures (P = 0.012), compared with -ADV pregnancies. Renal arteries from +ADV-treated rats had decreased sensitivity to acetylcholine-induced relaxation (P = 0.030), compared with -ADV pregnancies. Our data show that treatment with s(P)RR caused hypertension and growth restriction in vivo and caused marked endothelial dysfunction in vitro. These findings demonstrate the significant adverse actions of s(P)RR on vascular dysfunction that is characteristic of the preeclamptic phenotype.

The difference in endothelium-dependent relaxation components in proximal and distal thoracic aorta regions of male rats.

Aorta, the largest vessel in the body, is generally considered anatomically homogeneous, yet spatial functional differences exist. In our study, we conducted a comprehensive analysis by reexamining public RNA-SEQ data, comparing expression patterns between thoracic and abdominal aorta. Additionally, we measured acetylcholine-induced relaxations of the different regions of thoracic aorta in Wistar Rats. Our results revealed a distinct percentage difference in acetylcholine-induced relaxation in the proximal and distal segments of the thoracic aorta (p = 1.14e-4). To explain this variation, we performed differential expression analysis of previously published RNA-sequencing data between thoracic and abdominal aorta, which showed 497 differentially expressed genes between these locations. From results of RNA-Seq analysis, we draw a hypothesis that differential expressions of the potassium inward rectifying channels (KIR) and voltage gated calcium channels (VGCC) presumably located on SMC, with higher expression in the distal thoracic segments in comparison with the proximal thoracic segments of aorta, can explain differences in acetylcholine-induced relaxation. Notably, specific blockade of KIR eliminated differences between the proximal and distal regions of thoracic aorta, underscoring their significance in understanding the spatial nuances in aortic behavior, also blockade of VGCC, shows a higher effect on basal tone, in distal region of thoracic aorta in comparison with proximal.

Evaluation of the component’s contribution in endothelium-dependent acetylcholine-induced relaxation of the rat aorta

The regulation of rat aorta vascular tone involves various factors, including endothelium-derived hyperpolarization factor (EDHF), nitric oxide (NO), prostaglandins, and sensory nerves. While these elements can function independently, their pathways intersect at various points, complicating the assessment of their individual contributions. The aim of this study was to establish the numerical contributions of EDHF, NO, prostaglandins, and also the effect of the sensory nerve on acetylcholine-induced relaxation on the background of phenylephrine preconstriction using contraction and relaxation measurements in Wistar rat thoracic aorta. EDHF, whose action is mediated through potassium channels, emerges as a crucial regulator. Blockage of inward rectifier potassium (KIR) channels integral to EDHF significantly abolishes 50% of the relaxation amplitude in comparison to control conditions. Endothelial TRPV4 channel, exhibiting a fine-tuning role, contributes to a 25% reduction in the amplitude of acetylcholine-induced relaxation in comparison to control relaxation. NO demonstrates its vasodilatory prowess, with NO blockage eliminating 77% of the residual relaxation effect after KIR blockage. Blockage of prostaglandin functions, modulated by cyclooxygenase 1, reduces relaxation by 44% in comparison to control relaxation. Desensitization of sensory nerves with capsaicin, shows a minor yet significant role, in the reduction of acetylcholine-induced relaxation amplitude by 10%. In conclusion, we established that the main element of acetylcholine-induced relaxation is EDHF with approximately 50% of relaxation amplitude depending on it.

(247) A Rat Model for Bipolar Androgen Therapy is Evaluated for Its Effects on Erectile Dysfunction after Castration

Abstract Introduction Prostate cancer (PCa), an androgen-dependent tumor and one of the most prevalent cancers in males, has traditionally been treated with androgen suppression. In recent years, bipolar androgen treatment (BAT) has emerged as a potential therapeutic approach for men with metastatic castrate-resistant PCa. The control of testosterone (T) between castration and supraphysiological levels inhibits the proliferation of cancer cells and slows the progression of cancer. Furthermore, while there has been prior research between T and erectile function, there is no evidence linking BAT and erectile dysfunction (ED). Objective The purpose of the current investigation was to determine if BAT therapy was effective in treating ED in a castration-prone rat model. Methods Sprague-Dawley rats (n=30) were randomly divided into four groups: 1) Control, 2) Control rats-received BAT treatment, 3) castrated Rats, and 4) castrated rats-received BAT treatment. The rats were castrated by making bilateral scrotal incisions. A subcutaneous injection of testosterone propionate (250 mg/kg/week, intramuscular) was administered four weeks following castration. Four weeks after the initial dose, the second dose of the medication was given in the same manner. By stimulating the cavernous nerve, the intracavernosal pressure (ICP) to mean arterial pressure (MAP) ratio and total ICP were determined. Corpus cavernosum (CC) strips were used as in vitro preparations for evaluating the relaxant and contractile responses. Nitric oxide synthase (nNOS) and endothelial NOS (eNOS) protein expression was analyzed using Western blotting. Using Masson trichrome staining, the location of the smooth muscle in relation to the collagen was identified. Results Castrated rats' prostate weight was reduced when compared to uncastrated rats (P&amp;lt; 0.001). Compared to controls and castrated rats, BAT marginally boosted prostate weight reduction. The ICP/MAP ratio and total ICP for 7.5 V were lowest in castrated rats (P&amp;lt; 0.001 vs. controls). BAT enhanced ICP/MAP and total ICP responses (P&amp;lt;0.01 vs. castrated rats). In vitro, endothelium-dependent acetylcholine-induced relaxation at 1 nM (P 0.05 vs controls), endothelium-independent sodium nitroprusside-induced relaxation at 1 nM (P 0.01 vs controls), electrical field stimulation-induced relaxant response at 20 Hz (P&amp;lt;0.05 vs. controls) and sildenafil-induced relaxation at 10 M (P 0.05 vs controls) were all reduced in the CC strips from the castrated group. Additionally, the castrated group showed increased neurogenic contractile response at 40 Hz and the contractile response to phenylephrine at 1 mM (P 0.001 vs. controls). The variations in the relaxation and contractile responses were returned by BAT. The smooth muscle cell-to-collagen ratio and nNOS and eNOS protein expression were both markedly reduced in castrated rats, though BAT reversed these modifications. Conclusions The results of the study show that BAT improves neurogenic relaxation, endothelium relaxation, sildenafil-induced relaxing of the CC, and changes in penile morphology after castration. BAT might be a cutting-edge therapeutic approach for patients with castration-resistant prostate cancer who have an ED route. Disclosure No.

Nitric oxide, endothelium-derived hyperpolarizing factor, and smooth muscle-dependent mechanisms contribute to magnesium-dependent vascular relaxation in mouse arteries.

Magnesium (Mg2+ ) is a vasorelaxant. The underlying physiological mechanisms driving this vasorelaxation remain unclear. Studies were designed to test the hypothesis that multiple signaling pathways including nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) in endothelial cells as well as Ca2+ antagonization and TRPM7 channels in vascular smooth muscle cells mediate Mg2+ -dependent vessel relaxation. To uncover these mechanisms, force development was measured exvivo in aorta rings from mice using isometric wire myography. Concentration responses to Mg2+ were studied in intact and endothelium-denuded aortas. Key findings were confirmed in second-order mesenteric resistance arteries perfused exvivo using pressure myography. Effects of Mg2+ on NO formation were measured in Chinese Hamster Ovary (CHO) cells, isolated mesenteric vessels, and mouse urine. Mg2+ caused a significant concentration-dependent relaxation of aorta rings. This relaxation was attenuated significantly in endothelium-denuded aortas. The endothelium-dependent portion was inhibited by NO and cGMP blockade but not by cyclooxygenase inhibition. Mg2+ stimulated local NO formation in CHO cells and isolated mesenteric vessels without changing urinary NOx levels. High extracellular Mg2+ augmented acetylcholine-induced relaxation. SKCa and IKCa channel blockers apamin and TRAM34 inhibited Mg2+ -dependent relaxation. The endothelium-independent relaxation in aorta rings was inhibited by high extracellular Ca2+ . Combined blockade of NO, SKCa , and IKCa channels significantly reduced Mg2+ -dependent dilatation in mesenteric resistance vessels. In mouse conductance and resistance arteries Mg2+ -induced relaxation is contributed by endothelial NO formation, EDHF pathways, antagonism of Ca2+ in smooth muscle cells, and additional unidentified mechanisms.

Portulaca Oleracea L. (Purslane) Extract Protects Endothelial Function by Reducing Endoplasmic Reticulum Stress and Oxidative Stress through AMPK Activation in Diabetic Obese Mice.

Portulaca oleracea L. (purslane) is a food and a traditional drug worldwide. It exhibits anti-inflammatory, anti-oxidative, anti-tumor, and anti-diabetic bioactivities; but its activity on diabetic-associated endothelial dysfunction is unknown. This study aimed to investigate the effect of purslane on endothelial function and the underlying mechanisms. Male C57BL/6 mice had 14-week ad libitum access to a high-fat rodent diet containing 60% kcal% fat to induce obesity and diabetes whereas purslane extract (200 mg/kg/day) was administered during the last 4 weeks via intragastric gavage. Primary rat aortic endothelial cells and isolated mouse aortas were cultured with a risk factor, high glucose or tunicamycin, together with purslane extract. By ESI-QTOF-MS/MS, flavonoids and their glycoside products were identified in the purslane extract. Exposure to high glucose or tunicamycin impaired acetylcholine-induced endothelium-dependent relaxations in aortas and induced endoplasmic reticulum (ER) stress and oxidative stress with the downregulation of 5' AMP-activated protein kinase (AMPK)/ endothelial nitric oxide synthase (eNOS) signaling. Co-incubation with purslane significantly ameliorated these impairments. The effects of purslane were abolished by Compound C (AMPK inhibitor). Four-week purslane treatment ameliorated aortic relaxations, ER stress, and oxidative stress in diabetic obese mice. This study supported that purslane protected endothelial function, and inhibited ER stress and oxidative stress in vasculature through AMPK/eNOS activation, revealing its therapeutic potential against vascular complications in diabetes.

Abstract 13047: The Modulatory Effects of Perivascular Adipose Tissue on the Renal Arterial Vasorelaxation and Its Relationship With Kidney Function in Metabolic Syndrome

Metabolic syndrome (MetS) is a cluster condition that increases the risk of cardiovascular diseases and type 2 diabetes. Perivascular adipose tissue (PVAT) regulates the arterial tone. We have demonstrated that the renal arterial PVAT enhances the vasorelaxation response in MetS model strains, SHRSP.Z- Lepr fa /IzmDmcr rats (SPZF) and SHR/NDmcr-cp rats (CP). Furthermore, we have found that overactivation of angiotensin II type 1 receptor (AT1R) signaling and a decrease in apelin levels in PVAT leads to a decline in compensatory PVAT effects. MetS is associated with chronic kidney disease, and the dysfunction of the PVAT favoring the vasorelaxation response could be a reason for kidney disease development. Therefore, we investigated the relationship between PVAT function and kidney function using MetS model rats.Renal arteries were isolated from the male and female SPZF and CP at 23 weeks of age. Vasorelaxation and mRNA transcript levels in PVAT were examined using organ bath methods and quantitative real-time polymerase chain reaction, respectively. Systolic blood pressure (sBP) was measured using a tail-cuff method. Insulin, glucose, and creatinine in the serum and protein in the urine were measured using commercial kits and eGFR, and the HOMA-IR were calculated.sBP was higher in SPZF than CP, but lower in females than males. HOMA-IR and urine protein levels were the lowest, while eGFR and enhancing effects of PVAT on acetylcholine-induced relaxations were the highest in female CP among the groups. eGFR was negatively correlated with sBP, HOMA-IR, and urinary protein levels. The enhancements of relaxations by PVAT were negatively correlated with sBP, HOMA-IR, and AT1R activity in PVAT.This study suggests that the insulin resistance and high blood pressure are associated with PVAT dysfunction, resulting from AT1 activation in PVAT, while it does not support the hypothesis that the disappearance of the effects of PVAT directly leads to kidney dysfunction.

Abstract 106: Vascular Dysfunction In The Mesenteric Resistance Arteries Occurs Prior To The Occurrence Of Early-onset Alzheimer’S Disease In A Sex-dependent Manner

Alzheimer’s Disease (AD) and cardiovascular diseases (CVDs) are a major cause ofdisability and death among the older population. Familial Alzheimer’s Disease (FAD) islinked with an early onset AD (EOAD) pathology (&lt;65years) that manifests throughpathogenic mutations in the presenilin (PSEN)1 and PSEN2 genes, leading to theincreased production of central amyloid β (Aβ) peptides. There is increasing evidencethat elevated blood pressure and peripheral arterial stiffness contribute to thedevelopment and increase the risk of β-amyloid deposition in the brain leading to cognitivedecline later in life. We hypothesized that peripheral vascular remodeling and vasculardysfunction in the aorta and mesenteric resistance arteries (MRA) would be observedprior to the development of EOAD. The MRA of male and female C57Bl/6J (control) andAD mice (B6. CApptm1DboTg(APPswe,PSEN1dE9)85Dbo) at 9-weeks-old were isolatedprior to the onset of AD. Acetylcholine-induced relaxation (1pM-30μM) andphenylephrine-induced contraction (0.1nM-30μM) were evaluated using wire myography.Pulse wave velocity (PWV) and H&amp;E staining were used to measure vascular stiffnessand morphology, respectively. Data were analyzed as non-linear curve regression andmaximum response (Rmax) using the Student t test ( p &lt;0.05*). MRA from AD miceshowed impaired relaxation in both males (Rmax: control 90±0.9 vs. AD 59±6.4* %, n=3-4) and females (Rmax: control 90±2.8 vs. AD 70±8.3*%, n=4-6). Interestingly,phenylephrine-induced contraction was reduced in arteries from males (Rmax: control11.7±0.9 vs . AD 7.7±0.8* mN, n=3-4), but not in arteries from females (Rmax: control9.3±1.3 vs. AD 8.1±0.6 mN, n=6-7). However, no differences were observed in the aortawall thickness in the male (control 51.8±2.9 vs. AD 72±9.2 μm, n=3-4), or female (control63.7±9.8 vs. AD 54±4.8μm, n=2-3) AD mice, as well as the PWV analysis from male ADmice (control 2.41±0.44 vs. AD 4.05±1.4 mm/ms, n=6). These data suggest that thechanges observed in the peripheral microvasculature prior to the onset of AD could laterhave direct effects on cerebral blood flow leading to areas of altered blood perfusion andmicrovascular damage, thus contributing to the genesis and maintenance of AD.

Hyperandrogenism Protects Against High Blood Pressure by Nongenomic Mechanisms and Obesity Causes Hypertension in Females with Polycystic Ovary Syndrome

ABSTRACT Background Androgens induce vasorelaxation and reduce blood pressure in different mammals, including humans. Most women with polycystic ovary syndrome (PCOS), with hyperandrogenism, are obese and exhibit hypertension; thus, the fact that androgens increase blood pressure (BP) is controversial. Our aim was to determine whether hypertension is produced by androgen excess and/or obesity. Methods Experiments were performed in dehydroepiandrosterone; (DHEA, s.c)-induced PCOS model. BP from nonobese and obese rats with PCOS (fed a normal or high-fat diet, respectively) was evaluated weekly for 10 weeks by plethysmography and compared between them. We determined whether androgen receptors are responsible for androgen action on BP in rats with PCOS; a group of DHEA-treated rats was implanted with pellets of an antiandrogen and was compared with nonobese rats with PCOS. Isometric tension from aortas of nonobese and obese rats was recorded and compared to explore the integrity of the vascular endothelium when acetylcholine-induced endothelium-dependent vascular relaxation on phenylephrine contraction. Additionally, BP was obtained from 30 women diagnosed with PCOS: nonobese (BMI ≤25) and obese women (BMI ≥35) and compared with healthy counterparts; 15 obese and 15 nonobese women. Results Nonobese rats and women with PCOS showed hypotension, while obese rats and women with PCOS displayed hypertension. Healthy obese women were hypertensive and nonobese women remained normotensive. Antiandrogen did not modify the BP values in nonobese rats with PCOS, and obese rats with PCOS revealed marked endothelial dysfunction. Conclusions Our findings show that obesity is responsible for hypertension in PCOS and partial endothelial damage was observed, which may contribute to elevated BP. Remarkably, hyperandrogenism is capable of regulating BP to low values that are androgen receptor-independent.

Taxifolin Reduces Blood Pressure via Improvement of Vascular Function and Mitigating the Vascular Inflammatory Response in Spontaneously Hypertensive Rats.

The effect of a 10-day-long treatment with taxifolin (TAX, 20 mg/kg/day p.o.) was investigated on spontaneously hypertensive rats (SHRs) with a focus on the vascular functions of isolated femoral arteries and thoracic aortas. TAX reduced blood pressure in SHRs. In femoral arteries, TAX increased acetylcholine-induced relaxation, reduced the maximal NA-induced contraction, and reduced acetylcholine-induced endothelium-dependent contraction (EDC); however, TAX had no effect on the vascular reactivity of isolated thoracic aortas. In addition, TAX elevated the total nitric oxide synthase (NOS) activity and iNOS protein expression but reduced cyclooxygenase-2 (COX2) protein expression in the tissue of the abdominal aorta without changes in Nos2 and Ptgs2 gene expressions. TAX also increased the gene expression of the anti-inflammatory interleukin-10 (Il10). In addition, in vitro studies showed that TAX has both electron donor and H atom donor properties. However, TAX failed to reduce superoxide production in the tissue of the abdominal aorta after oral administration. In conclusion, our results show that a decrease in the blood pressure in TAX-treated SHRs might be attributed to improved endothelium-dependent relaxation and reduced endothelium-dependent contraction. In addition, the results suggest that the effect of TAX on blood pressure regulation also involves the attenuation of COX2-mediated pro-inflammation and elevation of anti-inflammatory pathways.

Mechanism of Social Stress-Related Erectile Dysfunction in Mice: Impaired Parasympathetic Neurotransmission and Ketamine.

This study aimed to investigate the mechanism underlying social stress (SS)-induced erectile dysfunction (ED) and evaluate the effects of a single subanesthetic dose of ketamine on SS-related ED. Male FVB mice were exposed to retired male C57BL/6 mice for 60 min daily over a 4-week period. In the third week, these FVB mice received intraperitoneal injections of either saline (SSS group) or ketamine (SSK group). Erectile function was assessed by measuring the intracavernosal pressure (ICP) during electrical stimulation of the major pelvic ganglia. Corpus cavernosum (CC) strips were utilized for wire myography to assess their reactivity. Both SSS and SSK mice exhibited significantly lower ICP in response to electrical stimulation than control mice. SS mice showed increased contractility of the CC induced by phenylephrine. Acetylcholine-induced relaxation was significantly reduced in SSS and SSK mice. Sodium nitroprusside-induced relaxation was higher in SSS mice compared to control and SSK mice. Nicotine-induced neurogenic and nitric oxide-dependent relaxation was significantly impaired in both SSS and SSK mice. An immunohistochemical analysis revealed co-localization of tyrosine hydroxylase and neuronal nitric oxide synthase-immunoreactive fibers in the CC. These findings highlight the complex nature of SS-related ED and suggest the limited efficacy of ketamine as a therapeutic intervention.

Effects of beetroot juice supplementation on vascular functional and structural changes in aged mice.

This study investigated whether beetroot juice (BRJ) ingestion ameliorates aging-induced functional and structural changes in vasculature. Aged mice (98-100 weeks old) were supplemented with BRJ (nitrate: 3.5 mmol/L) or drinking water for 4 weeks and compared with young mice (12-15 weeks old). The vasorelaxant response of isolated aortas to acetylcholine was markedly weaker in aged mice than in young mice, but the attenuated relaxation was significantly improved in BRJ-supplemented aged mice. The acetylcholine-induced relaxation was completely abolished by Nω -nitro-l-arginine methyl ester in all groups. Additionally, the response to sodium nitroprusside was comparable among the three groups. The aortic medial thickness was significantly greater in aged mice than in young mice, and BRJ supplementation did not suppress this thickening. Plasma nitrate levels were significantly higher in BRJ-supplemented aged mice than in non-supplemented aged mice. Conversely, non-supplemented aged mice had high plasma levels of thiobarbituric acid-reactive substances, but the levels were suppressed in BRJ-supplemented aged mice. These findings suggest that BRJ ingestion improves vascular endothelial dysfunction associated with aging, at least in part, by enhancing nitric oxide bioavailability and reducing oxidative stress. Therefore, beetroot ingestion may be a highly useful self-medication option to prevent vascular aging.

Piezo1 Mediates Vasodilation Induced by Acute Hyperglycemia in Mouse Renal Arteries and Microvessels.

Acute hyperglycemia is a risk factor for developing acute kidney injury and poor renal outcome in critically ill patients, whereby the role of renal vasculature remains unclear. We hypothesize that hyperglycemia-associated hyperosmolarity facilitates vasodilation through Piezo1-mediated eNOS (endothelial NO synthase) activation. Vasoreactivity was analyzed using wire myography in isolated mouse mesenteric arteries and renal interlobar, and using microvascular perfusion in renal afferent arterioles and efferent arterioles, and vasa recta. Immunofluorescence and Western blot were used for molecular analyses of isolated mouse blood vessels and human umbilical vein endothelial cells. Pretreatment with hyperglycemia (44 mmol/L glucose; 4 hours) increased acetylcholine-induced relaxation in interlobar arteries and mesenteric arteries, which was prevented by eNOS inhibition using Nω-nitro-L-arginine methylester hydrochloride. Hyperosmotic mannitol solution had a similar effect. Hyperglycemia induced an immediate, Nω-nitro-L-arginine methylester hydrochloride-inhibitable dilation in afferent arterioles, efferent arterioles, and vasa recta, whereby stronger dilation in afferent arterioles compared to efferent arterioles. Hyperglycemia also increased glomerular filtration rate in mice. In human umbilical vein endothelial cells, hyperglycemia, and the Piezo1 activator Yoda-1 increased levels of Piezo1 protein, p-CaMKII (phosphorylated Ca2+/Calmodulin-dependent protein kinase type II), Akt, and p-eNOS (phosphorylated eNOS). The hyperglycemia effect could be prevented by inhibiting Piezo1 using GsMTx4 (Grammostola spatulata mechanotoxin 4) and CaMKII using KN93. Furthermore, in arteries and microvessels, inhibition of Piezo1 using GsMTx4 prevented the hyperglycemia -effect, while Yoda-1 caused relaxation and dilation, respectively. Results reveal that Piezo1 mediates renal vasodilation induced by hyperosmolarity in acute hyperglycemia. This mechanism may contribute to the pathogenesis of renal damage by acute hyperglycemia.

High-energy photons vs protons in their action on vascular function in rats

The goal of this work was to compare the effects of a photon (PTI) and proton/hadron (HTI) irradiation on rat’s cardiovascular system. Cardiovascular functions were studied in rats after PTI and HTI impact in the equivalent total absorbed dose of 6 Gy. Photons were delivered using 60Co gamma-rays (0.8 Gy min-1). The particle irradiation was done by using a 9,6×10-12 J proton beam accelerated in the U-240 isochronous cyclotron. Both PTI and HTI decreased the acetylcholine-induced relaxation in rat’s aorta smooth muscle (SM) and outward potassium currents in aortic SM cells on the 9th day post-irradiation but HTI appeared to produce a more profound effect. HTI had no significant effect on systolic blood pressure (SBP) in rats while PTI produced clearly defined systemic hypertension. HTI, unlike PTI, significantly increased the left ventricle pressure in Langendorff - perfused rat’s heart. Thus, the biological effects of PTI and HTI on rat’s aorta endothelium-dependent relaxation and net potassium currents in the SM cells appear to be similar, although the effects of HTI are more pronounced. However, PTI, unlike HTI, produced significant systemic hypertension.

Ghrelin improves endothelial function and reduces blood pressure in Ang II-induced hypertensive mice: Role of AMPK

ABSTRACT Background Endothelial dysfunction is a major pathophysiology observed in hypertension. Ghrelin, a key regulator of metabolism, has been shown to play protective roles in cardiovascular system. However, whether it has the effect of improving endothelial function and lowering blood pressure in Ang II-induced hypertensive mice remains unclear. Methods In this study, hypertension was induced by continuous infusion of Ang II with a subcutaneous osmotic pumps and ghrelin (30 μg/kg/day) was intraperitoneal injection for 4 weeks. Acetylcholine-induced endothelium-dependent relaxation in aortae was measured on wire myograph and superoxide production in mouse aortae was assessed by fluorescence imaging. Results We found that ghrelin had protective effects on Ang II-induced hypertension by inhibiting oxidative stress, increasing NO production, improving endothelial function, and lowering blood pressure. Furthermore, ghrelin activated AMPK signaling in Ang II-induced hypertension, leading to inhibition of oxidative stress. Compound C, a specific inhibitor of AMPK, reversed the protective effects of ghrelin on the reduction of oxidative stress, the improvement of endothelial function and the reduction of blood pressure. Conclusions our findings indicated that ghrelin protected against Ang II-induced hypertension by improving endothelial function and lowering blood pressure partly through activating AMPK signaling. Thus, ghrelin may be a valuable therapeutic strategy for hypertension.

Role of Dickkopf-3 in Blood Pressure Regulation in Mice and Hypertensive Rats.

Dkk3 (Dickkopf-3) is a secreted glycoprotein known for its proapoptotic and angiogenic activity. The role of Dkk3 in cardiovascular homeostasis is largely unknown. Remarkably, the Dkk3 gene maps within a chromosome segment linked to the hypertensive phenotype in spontaneously hypertensive rats (SHR). We used Dkk3-/- mice or stroke-resistant (sr) and stroke-prone (sp) SHR to examine the role of Dkk3 in the central and peripheral regulation of blood pressure (BP). We used lentiviral expression vector to rescue Dkk3 in knockout mice or to induce Dkk3 overexpression or silencing in SHR. Genetic deletion of Dkk3 in mice enhanced BP and impaired endothelium-dependent acetylcholine-induced relaxation of resistance arteries. These alterations were rescued by restoring Dkk3 expression either in the periphery or in the central nervous system (CNS). Dkk3 was required for the constitutive expression of VEGF (vascular endothelium growth factor), and the action of Dkk3 on BP and endothelium-dependent vasorelaxation was mediated by VEGF-stimulated phosphatidylinositol-3-kinase pathway, leading to eNOS (endothelial NO synthase) activation both in resistance arteries and the CNS. The regulatory function of Dkk3 on BP was confirmed in SHR stroke-resistant and SHR stroke-prone in which was blunted in both resistance arteries and brainstem. In SHR stroke-resistant, lentiviral expression vector-induced Dkk3 expression in the CNS largely reduced BP, whereas Dkk3 knock-down further enhanced BP. In SHR stroke-prone challenged with a hypersodic diet, lentiviral expression vector-induced Dkk3 expression in the CNS displayed a substantial antihypertensive effect and delayed the occurrence of stroke. These findings demonstrate that Dkk3 acts as peripheral and central regulator of BP by promoting VEGF expression and activating a VEGF/Akt (protein kinase B)/eNOS hypotensive axis.

Administration of the KCa channel activator SKA-31 improves endothelial function in the aorta of atherosclerosis-prone mice

Atherosclerosis is a major risk factor for cardiovascular disease and is induced by hyperlipidemia and endothelial dysfunction (ED), leading to fatty plaque formation and impaired vascular function. Pharmacological activation of endothelial Ca 2+ -activated K + channels (KCa2.3 and KCa3.1) can oppose ED by enhancing endothelium-dependent vasodilation.We hypothesized that improving endothelial function will mitigate the development and/or severity of atherosclerosis in Apoe knockout (Apoe-/-) mice. Administration of the KCa channel activator SKA-31 was utilized to improve endothelial function in vivo.Experimentally, 8-week-old male Apoe-/- mice on a high fat diet (HFD) were administered one of three daily oral treatments for 12 weeks: the KCa channel activator SKA-31 (10 mg/kg), the KCa3.1 channel blocker senicapoc (40 mg/kg), or drug vehicle alone. Pharmacological inhibition of KCa3.1 channels is reported to reduce atherosclerosis in Apoe-/- mice and was utilized as a benchmark. Cardiac function was assessed by echocardiography under isoflurane anesthesia. Atherosclerotic lesions in the thoracic aorta were visualized by Oil-Red-O staining, and abdominal aortic contractility and relaxation were measured by wire myography in Apoe-/- mice and age/sex-matched wild-type C57BL/6 mice.At the end of drug treatment, left ventricular (LV) ejection fraction, fractional shortening, and LV posterior wall thickness were not different in Apoe-/- mice treated with either SKA-31 or senicapoc compared with vehicle. Oil-Red-O staining of the thoracic aorta and aortic arch revealed fatty plaque formation in Apoe-/- mice (~15% of area) compared with WT controls (&lt;1% of area), but neither SKA-31 nor senicapoc treatments reduced plaque formation vs. vehicle. Phenylephrine (PE)-evoked contraction of abdominal aortic rings was similar in WT and vehicle/drug treated Apoe-/- mice. Conversely, endothelium-dependent, acetylcholine-induced relaxation was significantly enhanced in PE-constricted aortic rings from SKA-31-treated mice (mean ± SD, 75.6 ± 21.1 %) vs. vehicle (51.2 ± 11.9 %, p=0.0024). Acetylcholine-induced relaxation was not improved by senicapoc administration. Relaxation induced by the smooth muscle vasodilator sodium nitroprusside was similar in WT and vehicle/drug treated Apoe-/- aortic rings. Summary: SKA-31 administration improved aortic endothelial function without reducing lesion density. Future studies will examine how SKA-31 improves endothelium-dependent relaxation and whether enhanced KCa channel activity (with SKA-31) in combination with lipid-lowering drugs (e.g., statins) can mitigate atherosclerosis more effectively. Enhancement of endothelial KCa channel activity may thus represent a viable stand-alone or “add-on” strategy to reduce morbidity and mortality associated with ED and atherosclerosis. Funding provided by the CIHR and NSERC This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.