Arterioles Of Rats Research Articles

The Effects of Black Garlic on Ovarian Malondialdehyde, Oviduct Muscle, and Endometrial Arterioles in Smoke-Exposed Rats

The effect of cigarette smoke exposure on reproductive health has been widely studied, showing various physiological disorders induced by free radicals and oxidative stress. This study aimed to assess the protective effect of ethanol extract of black garlic (Allium sativum) on some reproductive parameters of female rats Rattus norvegicus exposed to subacute cigarette smoke. A proper experimental method with a post-test-only control group design was used, involving 25 rats divided into five groups with three different doses of the extract. The rats were exposed to cigarette smoke and then treated for 28 days. Results showed a significant decrease in ovarian Malondialdehyde levels and increased fallopian tube smooth muscle thickness in the extract-treated group. In addition, black garlic extract successfully increased the number of endometrial arterioles in the group exposed to cigarette smoke and extract, in contrast to the group exposed to cigarette smoke only. This study concludes that black garlic extract has the potential to be a protective agent against oxidative damage in the reproductive system of rats exposed to cigarette smoke, with effectiveness that depends on the dose of extract given. Further studies should investigate the long-term effects and optimal dosing of black garlic extract in humans. Additionally, exploring the molecular mechanisms behind its protective properties could enhance its application in reproductive health management.

CXCR7 promotes pulmonary vascular remodeling via targeting p38/MMP2 pathway in pulmonary arterial hypertension.

A hallmark feature of pulmonary arterial hypertension (PAH) is the excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) in the pulmonary arteries. The exact role of C-X-C motif chemokine ligand 12 (CXCL12)/chemokine receptor type 7 (CXCR7) in the PASMCs remains unknown. This study was conducted to investigate CXCR7's role in p38/MMP2 pathway and its effect on PASMCs. In this study, we examined the expression profile of CXCL12/CXCR7 in both hypoxic rats and PASMCs. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was used to measure the level of proliferation in PASMCs. Enzyme-linked immunosorbent assay (ELISA) and western blotting assays were applied to investigate the protein expression of the related molecules. We found that a high level of CXCR7 was correlated with remodeled pulmonary arterioles in hypoxic rats. Moreover, CXCR7 protein levels were significantly increased by the induction of CXCL12, indicating that the CXCL12-CXCR7 axis participates in PAH. During hypoxia-PAH, CXCR7 inhibition reduces right ventricular systolic pressure (RVSP), the Fulton index, and pulmonary arteriosclerosis remodeling. Further study indicated inhibition CXCR7 reduced PASMCs by downregulating MMP2, via p38 MAPK pathway. It was additionally found that CXCL12/CXCR7 stimulated the phosphorylation of the p38 MAPK pathway, which was a contributing factor to the decrease in MMP2 expression following preconditioning with SB203580, which inhibited p38 MAPK. In summary, these findings suggest that CXCL12/CXCR7 plays a critical role in PAH, the therapy of which can be developed further by targeting its potential targets.

5-HT7 receptors mediate dilation of rat cremaster muscle arterioles in vivo.

Serotonin (5-HT) infusion in vivo causes hypotension and a fall in total peripheral resistance. However, the vascular segment and the receptors that mediate this response remain in question. We hypothesized that 5-HT7 receptors mediate arteriolar dilation to 5-HT in skeletal muscle microcirculation. Cremaster muscles of isoflurane-anesthetized male Sprague-Dawley rats were prepared for in vivo microscopy of third- and fourth-order arterioles and superfused with physiological salt solution at 34°C. Quantitative real-time PCR (RT-PCR) was applied to pooled samples of first- to third-order cremaster arterioles (2-4 rats/sample) to evaluate 5-HT7 receptor expression. Topical 5-HT (1-10 nmols) or the 5-HT1/7 receptor agonist, 5-carboxamidotryptamine (10-30 nM), dilated third- and fourth-order arterioles, responses that were abolished by 1 μM SB269970, a selective 5-HT7 receptor antagonist. In contrast, dilation induced by the muscarinic agonist, methacholine (100 nmols) was not inhibited by SB269970. Serotonin (10 nmols) failed to dilate cremaster arterioles in 5-HT7 receptor knockout rats whereas arterioles in wild-type litter mates dilated to 1 nmol 5-HT, a response blocked by 1 μM SB269970. Quantitative RT-PCR revealed that cremaster arterioles expressed mRNA for 5-HT7 receptors. 5-HT7 receptors mediate dilation of small arterioles in skeletal muscle and likely contribute to 5-HT-induced hypotension, in vivo.

Mitochondria and renal microvascular dysfunction following ischemia-reperfusion in rats

The pathophysiological mechanisms underlying ischemia-reperfusion (IR) induced acute kidney injury (AKI) remain poorly understood. Preglomerular microvessels (PGMV), specifically afferent arterioles, possess an intrinsic autoregulatory ability that is vital for ensuring stable renal hemodynamics. Our recent study indicates that renal autoregulation is impaired in IR rats due to reactive oxygen species (ROS) accumulation. We hypothesized that mitochondria-derived ROS (mtROS) in preglomerular microvessels contribute to renal autoregulatory impairment in IR rats. Blood-perfused juxtamedullary nephron experiments were performed on kidneys of male Sprague-Dawley rats 24 hours after IR induction (60-min, bilateral renal artery clamping). Afferent arteriolar autoregulation was assessed as perfusion pressure (PP) was increased from 65 to 170 mmHg in 15 mmHg increments. Afferent arterioles of sham-operated control rats (n=7) established pressure-mediated autoregulatory responses. Baseline diameter (100 mmHg) averaged 13.2±0.4 μm and increased to 114±4% of baseline when PP decreased from 100 to 65 mmHg. Diameter decreased to 65±3% of baseline when PP increased to 170 mmHg. In contrast, afferent arterioles from IR rats lost autoregulatory capability and remained between 90 and 100% of baseline diameter over 65-170 mmHg (n=8). Addition of Mito-Tempo (mitochondria-targeted antioxidant, 0.1 mM, n=3) to the perfusate restored autoregulation in IR rats at lower PP (65-125 mmHg, P>0.05 vs sham) and partially restored it over 140-170 mmHg. Superfusion with oligomycin (ATP synthase inhibitor, 2.5 μM) in normal kidneys evoked vasodilation to 178±13% baseline and blunting of autoregulatory reactivity. Renal autoregulation is linked to ATP-sensitive P2X1-receptor signaling. Changes in ATP-induced intracellular calcium concentration ([Ca2+]i) were assessed in isolated PGMV myocytes using Fura-2 fluorescent dye. IR markedly attenuated [Ca2+]i responses to 10 and 100 μM ATP by 46±11% and 57±15%, respectively (P<0.05, n=3-4 rats/group), and blunted ATP-induced afferent arteriolar vasoconstriction ( P<0.05 vs. sham, n=3/group). IR markedly increased the fluorescence intensity of mitoROS (MitoSOX™ kit) in PGMV compared to sham rats. Mitochondrial respiratory function was assessed using High Resolution Respirometry in freshly isolated PGMV (n=3/group). IR significantly reduced basal respiration (20±4 vs. 58±9 pmol/s·ml in sham, P<0.05) and oxidative phosphorylation capacity (51±10 vs. 219±37 pmol/s·ml in sham, P<0.05). The percentage of ATP-linked respiration was also reduced in PGMV of IR (60±2% vs. 75±2% in sham, P<0.05). In conclusion, mitochondria of PGMV are involved in regulating renal microvascular tone and autoregulation. IR leads to autoregulatory dysfunction by causing mitochondrial dysfunction in PGMV, increased mtROS production and suppression of ATP-dependent calcium signaling. This study is supported by grants R01DK106500. 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.

Upregulation of Piezo2 in the mesangial, renin, and perivascular mesenchymal cells of the kidney of Dahl salt-sensitive hypertensive rats and its reversal by esaxerenone.

The recent discovery of mechanosensitive ion channels has promoted mechanobiological research in the field of hypertension and nephrology. We previously reported Piezo2 expression in mouse mesangial and juxtaglomerular renin-producing cells, and its modulation by dehydration. This study aimed to investigate how Piezo2 expression is altered in hypertensive nephropathy. The effects of the nonsteroidal mineralocorticoid receptor blocker, esaxerenone, were also analyzed. Four-week-old Dahl salt-sensitive rats were randomly assigned to three groups: rats fed a 0.3% NaCl diet (DSN), rats fed a high 8% NaCl diet (DSH), and rats fed a high salt diet supplemented with esaxerenone (DSH + E). After six weeks, DSH rats developed hypertension, albuminuria, glomerular and vascular injuries, and perivascular fibrosis. Esaxerenone effectively decreased blood pressure and ameliorated renal damage. In DSN rats, Piezo2 was expressed in Pdgfrb-positive mesangial and Ren1-positive cells. Piezo2 expression in these cells was enhanced in DSH rats. Moreover, Piezo2-positive cells accumulated in the adventitial layer of intrarenal small arteries and arterioles in DSH rats. These cells were positive for Pdgfrb, Col1a1, and Col3a1, but negative for Acta2 (αSMA), indicating that they were perivascular mesenchymal cells different from myofibroblasts. Piezo2 upregulation was reversed by esaxerenone treatment. Furthermore, Piezo2 inhibition by siRNA in the cultured mesangial cells resulted in upregulation of Tgfb1 expression. Cyclic stretch also upregulated Tgfb1 in both transfections of control siRNA and Piezo2 siRNA. Our findings suggest that Piezo2 may have a contributory role in modulating the pathogenesis of hypertensive nephrosclerosis and have also highlighted the therapeutic effects of esaxerenone on salt-induced hypertensive nephropathy. Mechanochannel Piezo2 is known to be expressed in the mouse mesangial cells and juxtaglomerular renin-producing cells, and this was confirmed in normotensive Dahl-S rats. In salt-induced hypertensive Dahl-S rats, Piezo2 upregulation was observed in the mesangial cells, renin cells, and notably, perivascular mesenchymal cells, suggesting its involvement in kidney fibrosis.

Transcriptome analysis of mesenteric arterioles changes and its mechanisms in cirrhotic rats with portal hypertension

Portal hypertension (PHT) is a major cause of liver cirrhosis. The formation of portosystemic collateral vessels and splanchnic vasodilation contribute to the development of hyperdynamic circulation, which in turn aggravates PHT and increases the risk of complications. To investigate the changes in mesenteric arterioles in PHT, cirrhotic rat models were established by ligating the common bile ducts. After 4 weeks, the cirrhotic rats suffered from severe PHT and splanchnic hyperdynamic circulation, characterized by increased portal pressure (PP), cardiac output (CO), cardiac index (CI), and superior mesenteric artery (SMA) flow. Mesenteric arterioles in cirrhotic rats displayed remarkable vasodilation, vascular remodeling, and hypocontractility. RNA sequencing was performed based on these findings. A total of 1,637 differentially expressed genes (DEGs) were detected, with 889 up-regulated and 748 down-regulated genes. Signaling pathways related to vascular changes were enriched, including the vascular endothelial growth factor (VEGF), phosphatidylinositol-3-kinase-AKT (PI3K-AKT), and nuclear factor kappa light chain enhancer of activated B cells (NF-κB) signaling pathway, among others. Moreover, the top ten hub genes were screened according to the degree nodes in the protein–protein interaction (PPI) network. Functional enrichment analyses indicated that the hub genes were involved in cell cycle regulation, mitosis, and cellular response to oxidative stress and nitric oxide (NO). In addition, promising candidate drugs for ameliorating PHT, such as resveratrol, were predicted based on hub genes. Taken together, our study highlighted remarkable changes in the mesenteric arterioles of cirrhotic rats with PHT. Transcriptome analyses revealed the potential molecular mechanisms of vascular changes in splanchnic hyperdynamic circulation.

Abstract 10336: Phase 3 Anticancer Agent, RRx-001, Ameliorates Hypoxia-Induced Pulmonary Hypertension

Introduction: The hallmark features of pulmonary artery hypertension (PAH), for which hypoxia is a trigger, are vascular remodeling, elevated pulmonary blood pressure, oxidative stress, and right ventricular hypertrophy. RRx-001 is a minimally toxic Phase 3 anticancer agent with anti-oxidative, anti-inflammatory, nitric oxide-donating, and anti-proliferative properties. This study aimed to investigate the effect of RRx-001 on intermittent hypoxia-induced PAH in rats. Hypothesis: RRx-001 attenuates PAH Methods: Male Wistar rats (180-220 g) were divided into four groups (n=6 per group): normoxic control, hypoxic with vehicle treatment (2 weeks breathing an atmosphere containing 10% oxygen), hypoxic treated with oral endothelin-1 receptor inhibitor, bosentan, 50 mg/kg per day for 2 weeks during hypoxia and one intravenous dose of 5mg/kg RRx-001 given the day before the start of the hypoxia. After sacrifice, hearts and lungs were removed and harvested for analyses. Results: RRx-001 and bosentan, separately, significantly attenuated hypoxia-induced increases in right ventricular systolic pressure and right ventricular hypertrophy in PAH rats vs. vehicle. RRx-001 and bosentan, separately, also significantly decreased the thickening of pulmonary artery media and decreased the muscularization of pulmonary arterioles in PAH rats and the wall thickness/external diameter ratio of the pulmonary arteries vs. vehicle. Conclusions: RRx-001 significantly reduced right ventricular systolic pressure and pulmonary remodeling in a rat model of PAH, which potentially makes it a new therapeutic option for this dread disease. As a next step, combination of RRx-001 and bosentan will be attempted.

Synemin promotes pulmonary artery smooth muscle cell phenotypic switch in shunt-induced pulmonary arterial hypertension.

Although considerable progress has been made in the diagnosis and treatment of congenital heart disease-associated pulmonary heart hypertension (CHD-PAH), the clinical prognosis and overall survival of patients with CHD-PAH remain poor. Therefore, the molecular pathogenesis of CHD-PAH requires further investigation. The intermediate filament protein synemin (SYN) is reported to modulate phenotypic alterations and varicose vein development, but there is little understanding of its exact functions in CHD-PAH. SYN expression in the pulmonary arterioles of CHD-PAH patients and shunt-induced PAH rat models was evaluated using immunohistochemistry and western blot. Cell counts and Transwell migration assays were used to assess the effect of SYN on the proliferation and migration capability of human pulmonary smooth muscle cells (hPASMCs). Adeno-associated viruses (AAVs) have been used to suppress SYN expression in the pulmonary arterioles of rats. Such rats were further used to construct a shunt-induced PAH animal model to investigate the function of SYN in PAH and pulmonary vascular remodelling. Compared with the normal control group, SYN expression was found to be clearly up-regulated in the remodelled pulmonary arterioles of CHD-PAH and shunt-induced PAH rat models. In addition, SYN suppression increased the expression of hPASMC contractile-phenotype markers and decreased the expression of synthetic phenotype markers, in contrast to the control group. SYN suppression also dramatically attenuated the proliferation and migration capability of hPASMCs. Conversely, SYN overexpression promoted phenotypic switch, proliferation, and migration of hPASMCs, whereas these effects were notably alleviated by the protein kinase B (AKT) inhibitor MK-2206. Furthermore, we confirmed that SYN suppression mitigated PAH and pulmonary vascular remodelling induced by high blood flow in vivo. Our findings indicated that SYN may represent a promising therapeutic target in the treatment of CHD-PAH.

Apela gene therapy alleviates pulmonary hypertension in rats

AbstractPulmonary artery hypertension (PAH) is a common disease that threatens human health. At present, no treatment can cure PAH, and the prognosis is poor. Therefore, it is important to determine new targets for PAH treatment. Recently, a novel endogenous ligand Apela (ELABELA/Toddler/ELA32) of apelin peptide jejunum (APJ) receptor was identified as a possible PAH target. This study explored the potential effect of Apela gene therapy on rats with PAH. An AAV‐ELA32 recombinant expression vector was constructed by molecular cloning. Purified adeno‐associated virus (AAV) was injected into monocrotaline (MCT)‐induced PAH rats via tail vein 1 and 2 weeks after modeling. Apela gene therapy significantly reduced the increased right ventricular systolic pressure and N‐terminal pro‐brain natriuretic peptide (NT‐proBNP) in PAH rats. The results of histopathology and immunofluorescence showed that Apela gene therapy not only reduced the rate of pulmonary arteriole muscularization and media thickening in PAH rats but also inhibited the endothelial‐to‐mesenchymal transition of the pulmonary arteriole. Western blotting showed that Apela gene therapy up‐regulated the expression of KLF2/eNOs and BMPRII/SMAD4 in pulmonary arterioles of PAH rats. Overall, the results show that Apela gene therapy can inhibit pulmonary arteriolar vascular remodeling and reduce pulmonary artery pressure in PAH rats. These effects may be related to KLF2/eNOs and BMPRII/SMAD4 signaling pathways. The apelinergic system may be a potential new target for the prevention and treatment of PAH.

N-Methyl-D-Aspartic Acid Receptor-Mediated Vasodilation Is Attenuated in the Retinas of Diabetic Rats

Purpose Activation of N-methyl-d-aspartic acid (NMDA) receptors enhances nitric oxide (NO) production in retinal neuronal cells, and in turn, NO released from neuronal cells induces glial cell-mediated dilation of retinal arterioles in rats. The purpose of this study was to examine how neuronal cell-dependent, glial cell-mediated vasodilation is impacted in diabetic rat retinas. Methods Diabetes was induced in 6-week-old male Wistar rats by combining streptozotocin injection and D-glucose feeding. Two weeks later, the dilator function of retinal arterioles was assessed. Results Compared with non-diabetic rats, the dilator responses of retinal arterioles induced by intravitreal injection of NMDA and NOR3, an NO donor, were reduced in diabetic rats. Following the blockade of large-conductance Ca2+-activated K+ (BKCa) channels with iberiotoxin, no significant difference in the retinal vasodilator response to NOR3 was observed between non-diabetic and diabetic rats. Intravitreal injection of 14,15-epoxyeicosatrienoic acid, a vasodilatory factor released from glial cells, dilated retinal arterioles, and the response was diminished by diabetes. Conclusion These findings suggest that the impaired BKCa channel function in vascular cells is responsible for the diminished neuronal cell-dependent, glial cell-mediated dilation of retinal arterioles during the early stage of diabetes.

Exercise Training Attenuates Radiation‐Induced Impairments in Endothelium‐Dependent Vasodilation of Coronary Arterioles in Rats

BackgroundRadiation is an important and effective anti‐cancer therapy, but is associated with many side effects. Radiation exposure may cause damage to the heart and coronary vasculature. Exercise training is currently being investigated in cancer research as a treatment or adjuvant to anti‐cancer therapies, and has been shown to mitigate deleterious changes in coronary vascular function, such as with aging. We hypothesized that impairments in endothelium‐dependent vasodilation of coronary resistance arterioles that occur in response to radiation exposure would be mitigated with exercise training.Methods12 male Fischer 344 rats (3‐4 months old) were randomly assigned to one of four groups: control (CON; n=3), exercise (EX; n=3), control radiated (RAD; n=3), or exercise radiated (EX RAD; n=3). After increasing intensity over the first 3 weeks, EX and EX RAD animals ran on a motorized treadmill 5 days/week for 60 minutes/day, at an intensity of 15 m/min and 15° incline for the remainder of 12 weeks of training. After the conclusion of exercise training, all groups of animals were subjected 2 Gy whole body radiation by X‐Rad 350 x‐ray irradiator and euthanized within 8 hours. Hearts were harvested and left anterior descending (LAD) arteriole sections were isolated and fixed on glass pipets. Vessels were pressurized at 60 cm H2O. Once a minimum of 20% tone was developed, vessels were exposed to cumulative doses of bradykinin (10‐13‐10‐7 M), an endothelium‐dependent vasodilator, and vessel diameter was recorded at each dose.ResultsNo differences were detected for CON vs. EX or CON vs. EX RAD. Vasodilation for RAD was significantly reduced vs. CON (p = 0.007). EX RAD was significantly increased vs. RAD (p = 0.025).ConclusionsThere were no differences between CON and EX; however, vasodilation was impaired for radiated animals, suggesting even one dose of 2 Gy radiation can cause significant impairment in endothelium‐dependent vasodilation of coronary arterioles. Exercise training attenuated this impairment and restored endothelium‐dependent vasodilation to levels not different from control animals. These findings are significant, given that exercise training may be used as a simple and safe method to preserve coronary arteriole function in patients receiving radiation therapy.

Sex Difference in Autoregulatory Responses of Juxtamedullary Afferent Arterioles Following Ischemia‐Reperfusion in Rats

Renal ischemia‐reperfusion (IR) is a major cause of acute kidney injury (AKI). Renal autoregulation protects the kidney from ischemia at low arterial pressure and hyperperfusion at high arterial pressure. Female rats are more protected against AKI than male rats. We reported that IR impaired autoregulatory behavior of afferent arterioles (AA) in male rats 24 hours and 1‐week post‐IR. We hypothesize that AA autoregulatory control in IR‐induced AKI (IR‐AKI) is better preserved in female rats compared to males. IR was induced in female rats by bilateral renal arterial clamping for 60 minutes followed by reperfusion for 24 hours or 1 week. Autoregulatory responses were assessed using the in vitro blood‐perfused juxtamedullary nephron preparation during step increases in perfusion pressure (PP) from 65 to 170 mmHg at 15 mmHg intervals in sham‐operated and IR rats 24 hours and 1‐week post‐IR. AA from sham rats exhibited pressure‐dependent vasoreactivity. Baseline AA diameter averaged 12.1±1.4 µm in shams (n=3) 24 hours post‐surgery. Diameter increased to 112±2% of baseline when PP decreased from 100 to 65 mmHg and decreased to 70±6% of baseline when PP increased to 170 mmHg (P<0.05), indicating intact autoregulation. Conversely, baseline diameter in IR rats (n=5) averaged 10.0±1.4 µm and remained relatively unaltered during PP changes averaging between 98‐102% (P>0.05) of baseline, indicating impaired autoregulation. Shams 1 week post‐IR (n=3) exhibited autoregulatory responses similar to 24‐hour shams. Intriguingly, autoregulatory responses normalized within 1 week in female IR rats (n=3) though these rats still maintained increased urine output over 1 week (P<0.05). Diameter increased to 110±4% of baseline at 65 mmHg and decreased to 82±4% at 170 mmHg (P<0.05) of baseline (9.4±1.2 µm, n=3). mRNA expression of NADPH oxidase (NOX) subunits and the inflammatory chemokine (C‐C motif) Ligand 2 (CCL2) were measured in isolated preglomerular microvessels (PGMV, n=4‐8/group). Only p67phox expression in PGMV increased in female IR rats 24 hours post‐IR compared to elevation of all three of the NOX subunits (gp91phox, p67phox, and p47phox) to male IR rats. IR significantly increased CCL2 mRNA expression in female PGMV 7‐fold and 3‐fold at 24 hours and 1‐week post‐IR, respectively, compared to shams (P<0.05). mRNA expression increased less in females than males (9‐fold at 24 hours and 6‐fold at 1 week after IR, respectively). In conclusion, autoregulatory behavior in female rats is significantly blunted, 24 hours post‐IR and normalized 1‐week post‐IR, in contrast, all male IR rats exhibited blunted autoregulatory behavior 24 hours and 1‐week post‐IR. Increased CCL2 mRNA expression parallels the dimorphism of AA autoregulatory reactivity following IR, suggesting that elevated CCL2 could mediate IR‐induced AA autoregulatory dysfunction. Overall, these results suggest a sexual dimorphism in the renal microvascular response to IR injury and that female rats may possess innate protection against IR‐AKI.

Dapagliflozin, sildenafil and their combination in monocrotaline-induced pulmonary arterial hypertension

BackgroundDapagliflozin, a selective inhibitor of sodium-glucose cotransporter 2 (SGLT2), can reduce cardiovascular events and mortality in patients with heart failure. A number of mechanisms have been proposed to explain the beneficial effects of SGLT2 inhibitors. The purpose of this study was to determine whether dapagliflozin can improve pulmonary vascular remodelling and the efficacy of dapagliflozin as an add-on therapy to sildenafil in rats with pulmonary arterial hypertension (PAH).MethodsA monocrotaline (MCT)-induced PAH rat model was used in our study. MCT-injected rats were randomly divided into four groups and treated for 3 weeks with daily per os treatment with vehicle, dapagliflozin (1 mg/kg/day), sildenafil (25 mg/kg/day), or a combination of dapagliflozin (1 mg/kg/day) and sildenafil (25 mg/kg/day). Haemodynamic measurements, histological analysis, enzyme-linked immunosorbent assay and western blotting analysis were employed to detect the changes in PAH rats after treatments.ResultsDapagliflozin significantly attenuated MCT-induced increases in right ventricular systolic pressure (RVSP) and right ventricular hypertrophy (RVH) in PAH rats. Dapagliflozin effectively decreased the thickening of pulmonary artery media and decreased the muscularization of pulmonary arterioles in PAH rats. Moreover, dapagliflozin attenuated nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome activation in lung tissues and the levels of interleukin-1β (IL-1β) and interleukin-18 (IL-18) in plasma. However, dapagliflozin as an add-on therapy to sildenafil in rats with PAH did not show a more pronounced beneficial effect on right ventricular systolic pressure and pulmonary vascular remodelling in MCT rats than sildenafil alone.ConclusionsDapagliflozin reduces right ventricular systolic pressure and pulmonary vascular remodelling in a rat model of PAH. However, combination therapy with dapagliflozin and sildenafil was not more effective than monotherapy with sildenafil in PAH rats.

Involvement of Gap Junctions in Acetylcholine-Induced Endothelium-Derived Hyperpolarization-Type Dilation of Retinal Arterioles in Rats.

An electrical communication between the endothelial and smooth muscle cells via gap junctions, which provides the signaling pathway known as endothelium-dependent hyperpolarization (EDH), plays a crucial role in controlling the vascular tone. In this study, we investigated the role of gap junctions in the acetylcholine (ACh)-induced EDH-type dilation of rat retinal arterioles in vivo. The dilator response was evaluated by measuring the diameter of retinal arterioles. Intravitreal injection of gap junction blockers (18β-glycyrrhetinic acid and carbenoxolone) reduced the ACh-induced dilation of retinal arterioles. Moreover, the retinal arteriolar response to ACh was attenuated by 18β-glycyrrhetinic acid under treatment with a combination of NG-nitro-L-arginine methyl ester (a nitric oxide (NO) synthase inhibitor; 30 mg/kg) and indomethacin (a cyclooxygenase inhibitor; 5 mg/kg). The NO- and prostaglandin-independent, EDH-related component of ACh-induced dilation of retinal arterioles was prevented by intravitreal injection of iberiotoxin, which inhibits large-conductance Ca2+-activated K+ channels. Furthermore, the combination of 18β-glycyrrhetinic acid and iberiotoxin produced greater attenuation in the EDH-related response than that by the individual agent. Treatment with 18β-glycyrrhetinic acid revealed no significant effect on NOR3 (an NO donor)-induced retinal vasodilator response. These results suggest that gap junctions contribute to the ACh-induced, EDH-type dilation of rat retinal arterioles in vivo.

Constrictor responses of cerebral resistance arterioles in male and female rats exposed to prenatal alcohol.

While it is known that dilation of cerebral arterioles to NOS‐dependent agonists is impaired in rats exposed to prenatal alcohol, no studies have examined the influence of prenatal alcohol on constrictor response of cerebral arterioles. Our goal was to determine whether constrictor responses of cerebral resistance arterioles are altered by prenatal exposure to alcohol and if any changes differed as a function of age or sex. We fed Sprague‐Dawley rat dams a liquid diet with or without alcohol (3% ethanol) for the duration of their pregnancy. We then examined reactivity of cerebral arterioles to thromboxane (U‐46619; 0.01 and 0.1 µM), arginine vasopressin (0.1 and 1 nM), and angiotensin II (1 and 10 µM) in four groups of offspring: control male and female, and prenatal alcohol male and female at two different ages (adolescent: 4–6 weeks old and adult: 14–16 weeks old). Constriction of cerebral arterioles to U‐46619 and AVP were similar in male and female rats regardless of exposure to prenatal alcohol and age. Similarly, adolescent male and female rats showed no difference to angiotensin II following prenatal exposure to alcohol. However, alcohol‐exposed females exhibited an unexpected dilation to the high concentration of angiotensin II in adulthood, which was absent in males. We suggest that the findings from these studies may have implications regarding the susceptibility of the brain to cerebral ischemic damage. We speculate that impaired vasodilation, coupled with preserved vasoconstriction, can lead to a scenario favoring a decrease in cerebral blood flow during times of increased metabolic demand.

Sex Differences in Exercise-Training-Related Functional and Morphological Adaptation of Rat Gracilis Muscle Arterioles

BackgroundThe cardiovascular effects of training have been widely investigated; however, few studies have addressed sex differences in arteriolar adaptation. In the current study, we examined the adaptation of the gracilis arterioles of male and female rats in response to intensive training.MethodsWistar rats were divided into four groups: male exercise (ME) and female exercise (FE) animals that underwent a 12-week intensive swim-training program (5 days/week, 200 min/day); and male control (MC) and female control (FC) animals that were placed in water for 5 min daily. Exercise-induced cardiac hypertrophy was confirmed by echocardiography. Following the training, the gracilis muscle arterioles were prepared, and their biomechanical properties and functional reactivity were tested, using pressure arteriography. Collagen and smooth muscle remodeling were observed in the histological sections.ResultsLeft ventricular mass was elevated in both sexes in response to chronic training. In the gracilis arterioles, the inner radius and wall tension increased in female animals, and the wall thickness and elastic modulus were reduced in males. Myogenic tone was reduced in the ME group, whereas norepinephrine-induced vasoconstriction was elevated in the FE group. More pronounced collagen staining was observed in the ME group than in the MC group. Relative hypertrophy and tangential stress of the gracilis arterioles were higher in females than in males. The direct vasoconstriction induced by testosterone was lower in females and was reduced as an effect of exercise in males.ConclusionThe gracilis muscle arteriole was remodeled as a result of swim training, and this adaptation was sex dependent.

Rosiglitazone restores nitric oxide synthase-dependent reactivity of cerebral arterioles in rats exposed to prenatal alcohol.

Prenatal exposure to alcohol leads to a greater incidence of many cardiovascular-related diseases, presumably via a mechanism that may involve increased oxidative stress. An agonist of peroxisome proliferator-activated receptor gamma (PPARγ; rosiglitazone) has been shown to suppress alcohol-induced neuroinflammation and oxidative stress. The goal of this study was to determine whether acute and chronic treatment with rosiglitazone could restore or prevent impaired nitric oxide synthase (NOS)-dependent responses of cerebral arterioles in male and female adult (14-16weeks old) rats exposed to alcohol in utero. We fed Sprague-Dawley dams a liquid diet with or without 3% ethanol for the duration of their pregnancy (21-23days). In the first series of studies, we examined the reactivity of cerebral arterioles to eNOS- (ADP), nNOS-dependent (NMDA), and NOS-independent agonists in male and female adult rats before and during acute (1hour) topical application of rosiglitazone (1µM). In a second series of studies, we examined the influence of chronic treatment with rosiglitazone (3mg/kg/day in drinking water for 2-3weeks) on the responses of cerebral arterioles in male and female adult rats exposed to alcohol in utero. We found that in utero exposure to alcohol similarly reduced responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in male and female adult rats. In addition, acute treatment of the male and female adult rats with rosiglitazone similarly restored this impairment in cerebral vascular function to that observed in controls. We also found that chronic treatment with rosiglitazone prevented impaired vascular function in male and female adult rats that were exposed to alcohol in utero. PPARγ activation may be an effective and relevant treatment to reverse or prevent cerebral vascular abnormalities associated with prenatal exposure to alcohol.

C1q/TNF-related protein-9 ameliorates hypoxia-induced pulmonary hypertension by regulating secretion of endothelin-1 and nitric oxide mediated by AMPK in rats

Injury/dysfunction of the endothelium of pulmonary arteries contributes to hypoxia-induced pulmonary hypertension (HPH). We investigated whether C1q/tumor necrosis factor-related protein-9 (CTRP9), a newly identified cardiovascular agent, has protective roles in the development of HPH. HPH was induced in adult male rats by chronic hypobaric hypoxia. CTRP9 overexpression by adeno-associated virus (AAV)-CTRP9 transfection attenuated the increases in right ventricular systolic pressure, right ventricular hypertrophy index, and pulmonary arterial remodeling of rats under hypoxia. Importantly, CTRP9 overexpression improved endothelium-dependent vasodilation in pulmonary arterioles in HPH rats. CTRP9 overexpression enhanced expression of phosphorylated 5′-adenosine monophosphate-activated protein kinase (p-AMPK) and phosphorylated endothelial nitric oxide synthase (p-eNOS), and reduced phosphorylated extracellular signal-regulated protein kinase (p-ERK1/2) expression in pulmonary microvascular endothelial cells (PMVECs) of HPH rats. In cultured PMVECs, CTRP9 not only preserved the decrease of AMPK and eNOS phosphorylation level and nitric oxide (NO) production induced by hypoxia, but also blocked the increase in hypoxia-induced ERK1/2 phosphorylation level and endothelin (ET)-1 production. Furthermore, the effects of CTRP9 were interrupted by inhibitors or knockdown of AMPK. CTRP9 enhances NO production and reduces ET-1 production by regulating AMPK activation. CTRP9 could be a target for HPH.

Rosiglitazone Restores NOS‐Dependent Reactivity of Cerebral Arterioles in Rats Exposed to Prenatal Alcohol

Prenatal alcohol exposure (PAE) is known to have widespread clinical effects on fetal growth and development in humans, but effective treatments are yet unavailable due to our limited knowledge of the underlying pathological mechanisms or suitable molecular targets. Peroxisome proliferator-activated receptor gamma (PPARγ), a member of PPAR family of nuclear receptors present on vascular smooth muscle and endothelium, has been targeted in the treatment of several cardiovascular disease-related abnormalities. Rosiglitazone can activate the PPARγ isoform to bring about its anti-inflammatory and antioxidant potentials required for ameliorating the pathological state. Given that PAE is known to impair responses of cerebral arterioles potentially viaan alteration in oxidative stress, we examined whether acute and chronic treatment with rosiglitazone could restore impaired responses of the cerebral arterioles to NOS-dependent and -independent agonists in rats exposed to alcohol in utero. Twelve to sixteen weeks after birth, we examined reactivity of cerebral arterioles to eNOS- (ADP), nNOS-dependent (NMDA) and NOS-independent (nitroglycerin) agonists in male and female adult rats before and during one-hour-long acute application of rosiglitazone. We found that rosiglitazone enhanced responses of cerebral arterioles to ADP and NMDA in PAE rats when compared to control rats. We also examined the influence of chronic, oral treatment with rosiglitazone (2-3 weeks) on responses of cerebral arterioles in male and female adult rats exposed to alcohol in utero. We found that chronic treatment with rosiglitazone to prevent impaired cerebral vascular function in PAE rats, regardless of their gender. Overall, these studies suggest that PPARγ can restore impaired reactivity in cerebral arterioles to eNOS- and nNOS-dependent agonists during PAE. We speculate that PPARγ activation might be a promising treatment option to reverse the cerebral vascular abnormalities associated with in utero exposure to alcohol. We also believe that our findings may have important implications for the regulation of cerebral blood flow in those that suffer from symptoms associated with Fetal Alcohol Spectrum Disorders (FASD).

L-Citrulline ameliorates the attenuation of acetylcholine-induced vasodilation of retinal arterioles in diabetic rats

In our previous study, we found that the vasodilation of retinal arterioles induced by acetylcholine and BMS-191011, a large-conductance Ca2+-activated K+ (BKCa) channel opener, were diminished in diabetic rats. Currently, few agents ameliorate the impaired vasodilator responses of retinal blood vessels. Our recent finding that the intravenous infusion of L-citrulline dilated retinal arterioles, suggests that L-citrulline could be a potential therapeutic agent for circulatory disorders of the retina. In this study, we determined the effect of an oral L-citrulline treatment on impaired acetylcholine- and BMS-191011-induced vasodilation in the retinal arterioles of diabetic rats. To induce diabetes, rats were administered an intravenous dose of streptozotocin (65 mg/kg) and a 5% D-glucose solution as drinking water. The L-citrulline (2 g/kg/day) and L-arginine (2 g/kg/day) treatments commenced either 15 days before or just after the streptozotocin injection and continued throughout the experimental period. A 29-day treatment with L-citrulline, but not L-arginine, significantly ameliorated the impaired acetylcholine- and BMS-191011-induced retinal vasodilation in diabetic rats without affecting their plasma glucose levels. The 2-week L-citrulline treatment tended to ameliorate the dysfunction of the acetylcholine-induced retinal vasodilation in diabetic rats. In conclusion, these results showed that the retinal blood vessel dysfunction induced by diabetes mellitus could be prevented by the long-term administration of L-citrulline and suggest that the latter could play a potentially prophylactic role in diabetic retinopathy.