Relaxation Of Aorta Research Articles

Potentiation of Acetylcholine-Induced Relaxation of Aorta in Male UC Davis Type 2 Diabetes Mellitus (UCD-T2DM) Rats: Sex-Specific Responses.

Previous reports suggest that diabetes may differentially affect the vascular beds of females and males. The objectives of this study were to examine whether there were (1) sex differences in aortic function and (2) alterations in the relative contribution of endothelium-derived relaxing factors in modulating aortic reactivity in UC Davis Type 2 Diabetes Mellitus (UCD-T2DM) rats. Endothelium-dependent vasorelaxation (EDV) in response to acetylcholine (ACh) was measured in aortic rings before and after exposure to pharmacological inhibitors. Relaxation responses to sodium nitroprusside were assessed in endothelium-denuded rings. Moreover, contractile responses to phenylephrine (PE) were measured before and after incubation of aortic rings with a nitric oxide synthase (NOS) inhibitor in the presence of indomethacin. Metabolic parameters and expression of molecules associated with vascular and insulin signaling as well as reactive oxygen species generation were determined. Diabetes slightly but significantly impaired EDV in response to ACh in aortas from females but potentiated the relaxation response in males. The potentiation of EDV in diabetic male aortas was accompanied by a traces of nitric oxide (NO)- and prostanoid-independent relaxation and elevated aortic expression of small- and intermediate conductance Ca2+-activated K+ channels in this group. The smooth muscle sensitivity to NO was not altered, whereas the responsiveness to PE was significantly enhanced in aortas of diabetic groups in both sexes. Endothelium-derived NO during smooth muscle contraction, as assessed by the potentiation of the response to PE after NOS inhibition, was reduced in aortas of diabetic rats regardless of sex. Accordingly, decreases in pAkt and peNOS were observed in aortas from diabetic rats in both sexes compared with controls. Our data suggest that a decrease in insulin sensitivity via pAkt-peNOS-dependent signaling and an increase in oxidative stress may contribute to the elevated contractile responses observed in diabetic aortas in both sexes. This study demonstrates that aortic function in UCD-T2DM rats is altered in both sexes. Here, we provide the first evidence of sexual dimorphism in aortic relaxation in UCD-T2DM rats.

New Therapeutic Insight into the Effect of Ma Huang Tang on Blood Pressure and Renal Dysfunction in the L-NAME-Induced Hypertension

In this study, we evaluated the effect of a traditional herbal formula, Ma Huang Tang (MHT), on blood pressure and vasodilation in a rat model of NG‐nitro‐L‐arginine methylester- (L-NAME-) induced hypertension. We found that MHT-induced vascular relaxation in a dose-dependent manner in rat aortas pretreated with phenylephrine. However, pretreatment of endothelium-intact aortic rings with L‐NAME, an inhibitor of nitric oxide synthesis (NOS), or 1H‐[1, 2, 4]‐oxadiazole‐[4, 3‐α]‐quinoxalin‐1‐one (ODQ), an inhibitor of soluble guanylyl cyclase, significantly abolished vascular relaxation induced by MHT. MHT also increased the production of guanosine 3′,5′-cyclic monophosphate (cGMP) in the aortic rings pretreated with L-NAME or ODQ. To examine the in vivo effects of MHT, Sprague Dawley rats were treated with 40 mg/kg/day L-NAME for 3 weeks, followed by administration of 50 or 100 mg/kg/day MHT for 2 weeks. MHT was found to significantly normalize systolic blood pressure and decreased intima-media thickness in aortic sections of rats treated with L-NAME compared to that of rats treated with L-NAME alone. MHT also restored the L-NAME-induced decrease in vasorelaxation response to acetylcholine and endothelial nitric oxide synthase (eNOS) and endothelin-1 (ET-1) expression. Furthermore, MHT promoted the recovery of renal function, as indicated by osmolality, blood urea nitrogen (BUN) levels, and creatinine clearance. These results suggest that MHT-induced relaxation in the thoracic aorta is associated with activation of the nitric oxide/cGMP pathway. Furthermore, it provides new therapeutic insights into the regulation of blood pressure and renal function in hypertensive patients.

Multidrug resistance proteins preferentially regulate natriuretic peptide-driven cGMP signalling in the heart and vasculature.

cGMP underpins the bioactivity of NO and natriuretic peptides and is key to cardiovascular homeostasis. cGMP-driven responses are terminated primarily by PDEs, but cellular efflux via multidrug resistance proteins (MRPs) might contribute. Herein, the effect of pharmacological blockade of MRPs on cGMP signalling in the heart and vasculature was investigated in vitro and in vivo. Proliferation of human coronary artery smooth muscle cells (hCASMCs), vasorelaxation of murine aorta and reductions in mean arterial BP (MABP) in response to NO donors or natriuretic peptides were determined in the absence and presence of the MRP inhibitor MK571. The ability of MRP inhibition to reverse morphological and contractile deficits in a murine model of pressure overload-induced heart failure was also explored. MK571 attenuated hCASMC growth and enhanced the anti-proliferative effects of NO and atrial natriuretic peptide (ANP). MRP blockade caused concentration-dependent relaxations of murine aorta and augmented responses to ANP (and to a lesser extent NO). MK571 did not decrease MABP per se but enhanced the hypotensive actions of ANP and improved structural and functional indices of disease severity in experimental heart failure. These beneficial actions of MRP inhibition were associated with a greater intracellular:extracellular cGMP ratio in vitro and in vivo. MRP blockade promotes the cardiovascular functions of natriuretic peptides in vitro and in vivo, with more modest effects on NO. MRP inhibition may have therapeutic utility in cardiovascular diseases triggered by dysfunctional cGMP signalling, particularly those associated with altered natriuretic peptide bioactivity. This article is part of a themed issue on cGMP Signalling in Cell Growth and Survival. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.11/issuetoc.

Coptisine Attenuates Diabetes-Associated Endothelial Dysfunction through Inhibition of Endoplasmic Reticulum Stress and Oxidative Stress.

Coptisine is the major bioactive protoberberine alkaloid found in Rhizoma Coptidis. Coptisine reduces inflammatory responses and improves glucose tolerance; nevertheless, whether coptisine has vasoprotective effect in diabetes is not fully characterized. Conduit arteries including aortas and carotid arteries were obtained from male C57BL/6J mice for ex vivo treatment with risk factors (high glucose or tunicamycin) and coptisine. Some arterial rings were obtained from diabetic mice, which were induced by high-fat diet (45% kcal% fat) feeding for 6 weeks combined with a low-dose intraperitoneal injection of streptozotocin (120 mg/kg). Functional studies showed that coptisine protected endothelium-dependent relaxation in aortas against risk factors and from diabetic mice. Coptisine increased phosphorylations of AMPK and eNOS and downregulated the endoplasmic reticulum (ER) stress markers as determined by Western blotting. Coptisine elevates NO bioavailability and decreases reactive oxygen species level. The results indicate that coptisine improves vascular function in diabetes through suppression of ER stress and oxidative stress, implying the therapeutic potential of coptisine to treat diabetic vasculopathy.

Punicalagin Attenuates Disturbed Flow-Induced Vascular Dysfunction by Inhibiting Force-Specific Activation of Smad1/5.

BackgroundPathophysiological vascular remodeling in response to disturbed flow with low and oscillatory shear stress (OSS) plays important roles in atherosclerosis progression. Pomegranate extraction (PE) was reported having anti-atherogenic effects. However, whether it can exert a beneficial effect against disturbed flow-induced pathophysiological vascular remodeling to inhibit atherosclerosis remains unclear. The present study aims at investigating the anti-atherogenic effects of pomegranate peel polyphenols (PPP) extraction and its purified compound punicalagin (PU), as well as their protective effects on disturbed flow-induced vascular dysfunction and their underlying molecular mechanisms.MethodsThe anti-atherogenic effects of PPP/PU were examined on low-density lipoprotein receptor knockout mice fed with a high fat diet. The vaso-protective effects of PPP/PU were examined in rat aortas using myograph assay. A combination of in vivo experiments on rats and in vitro flow system with human endothelial cells (ECs) was used to investigate the pharmacological actions of PPP/PU on EC dysfunction induced by disturbed flow. In addition, the effects of PPP/PU on vascular smooth muscle cell (VSMC) dysfunction were also examined.ResultsPU is the effective component in PPP against atherosclerosis. PPP/PU evoked endothelium-dependent relaxation in rat aortas. PPP/PU inhibited the activation of Smad1/5 in the EC layers at post-stenotic regions of rat aortas exposed to disturbed flow with OSS. PPP/PU suppressed OSS-induced expression of cell cycle regulatory and pro-inflammatory genes in ECs. Moreover, PPP/PU inhibited inflammation-induced VSMC dysfunction.ConclusionPPP/PU protect against OSS-induced vascular remodeling through inhibiting force-specific activation of Smad1/5 in ECs and this mechanism contributes to their anti-atherogenic effects.

Selective Phosphodiesterase 1 Inhibition Ameliorates Vascular Function, Reduces Inflammatory Response, and Lowers Blood Pressure in Aging Animals.

Diminished nitric oxide-cGMP-mediated relaxation plays a crucial role in cardiovascular aging, leading to decreased vasodilation, vascular hypertrophy and stiffening, and ultimately, cardiovascular dysfunction. Aging is the time-related worsening of physiologic function due to complex cellular and molecular interactions, and it is at least partly driven by DNA damage. Genetic deletion of the DNA repair enzyme ERCC1 endonuclease in Ercc1Δ/- mice provides us an efficient tool to accelerate vascular aging, explore mechanisms, and test potential treatments. Previously, we identified the cGMP-degrading enzyme phosphodiesterase 1 as a potential treatment target in vascular aging. In the present study, we studied the effect of acute and chronic treatment with ITI-214, a selective phosphodiesterase 1 inhibitor on vascular aging features in Ercc1Δ/- mice. Compared with wild-type mice, Ercc1Δ/- mice at the age of 14 weeks showed decreased reactive hyperemia, diminished endothelium-dependent and -independent responses of arteries in organ baths, carotid wall hypertrophy, and elevated circulating levels of inflammatory cytokines. Acute ITI-214 treatment in organ baths restored the arterial endothelium-independent vasodilation in Ercc1Δ/- mice. An 8-week treatment with 100 mg/kg per day ITI-214 improved endothelium-independent relaxation in both aorta and coronary arteries, at least partly restored the diminished reactive hyperemia, lowered the systolic and diastolic blood pressure, normalized the carotid hypertrophy, and ameliorated inflammatory responses exclusively in Ercc1Δ/- mice. These findings suggest phosphodiesterase 1 inhibition would provide a powerful tool for nitric oxide-cGMP augmentation and have significant therapeutic potential to battle arteriopathy related to aging. SIGNIFICANCE STATEMENT: The findings implicate the key role of phosphodiesterase 1 in vascular function and might be of clinical importance for the prevention of mortalities and morbidities related to vascular complications during aging, as well as for patients with progeria that show a high risk of cardiovascular disease.

Butyrate protects endothelial function through PPARδ/miR-181b signaling

Reports of the beneficial roles of butyrate in cardiovascular diseases, such as atherosclerosis and ischemic stroke, are becoming increasingly abundant. However, the mechanisms of its bioactivities remain largely unknown. In this study, we explored the effects of butyrate on endothelial dysfunction and its potential underlying mechanism. In our study, ApoE-/- mice were fed with high-fat diet (HFD) for ten weeks to produce atherosclerosis models and concurrently treated with or without sodium butyrate daily. Thoracic aortas were subsequently isolated from C57BL/6 wild-type (WT), PPARδ-/-, endothelial-specific PPARδ wild-type (EC-specific PPARδ WT) and endothelial-specific PPARδ knockout (EC-specific PPARδ KO) mice were stimulated with interleukin (IL)-1β with or without butyrate ex vivo. Our results demonstrated that butyrate treatment rescued the impaired endothelium-dependent relaxations (EDRs) in thoracic aortas of HFD-fed ApoE-/- mice. Butyrate also rescued impaired EDRs in IL-1β-treated thoracic aorta ring ex vivo. Global and endothelial-specific knockout of PPARδ eliminated the protective effects of butyrate against IL-1β-induced impairment to EDRs. Butyrate abolished IL-1β-induced reactive oxygen species (ROS) production in endothelial cells while the inhibitory effect was incapacitated by genetic deletion of PPARδ or pharmacological inhibition of PPARδ. IL-1β increased NADPH oxidase 2 (NOX2) mRNA and protein expressions in endothelial cells, which were prevented by butyrate treatment, and the effects of butyrate were blunted following pharmacological inhibition of PPARδ. Importantly, butyrate treatment upregulated the miR-181b expression in atherosclerotic aortas and IL-1β-treated endothelial cells. Moreover, transfection of endothelial cells with miR-181b inhibitor abolished the suppressive effects of butyrate on NOX2 expressions and ROS generation in endothelial cells. To conclude, butyrate prevents endothelial dysfunction in atherosclerosis by reducing endothelial NOX2 expression and ROS production via the PPARδ/miR-181b pathway.

Chronic stress induced perivascular adipose tissue impairment of aortic function and the therapeutic effect of exercise.

What is the central question of this study? Thoracic perivascular adipose tissue (tPVAT) is known to, in part, regulate aortic function: what are the effects of unpredictable chronic mild stress (UCMS) on the tPVAT regulation of aortic function and what is the role of exercise training in alleviating the potential negative actions of UCMS on tPVAT? What is the main finding and its importance? UCMS causes tPVAT to disrupt endothelium-dependent dilatation, increases inflammatory cytokine production and diminishes tPVAT-adiponectin. Exercise training proved efficacious in preventing tPVAT-mediated disruption of aortic function. The data support a tPVAT mechanism through which chronic stress negatively impacts vascular health, which adds to our knowledge of how psychological disorders might increase the risk of cardiovascular disease. Chronic stress is a major risk for cardiovascular disease. Perivascular adipose tissue (PVAT) has been shown to regulate vascular function; however, the impact of chronic stress and the comorbidity of metabolic syndrome (MetS) on thoracic (t)PVAT is unknown. Additionally, aerobic exercise training (AET) is known to combat the pathology of MetS and chronic stress, but the role of tPVAT in these actions is also unknown. Therefore, the purpose of this study was to examine the effects of unpredictable chronic mild stress (UCMS) on the tPVAT regulation of aortic function and the preventative effect of AET. Lean (LZR) and obese (OZR) Zucker rats (16-17weeks old) were exposed to 8weeks of UCMS with and without treadmill exercise (AET). In LZR, UCMS impaired aortic endothelium-dependent dilatation (EDD) (assessed ex vivo by wire myography) and aortic stiffness (assessed by elastic modulus) with no change in OZR subject to UCMS. However, both LZR and OZR UCMS tPVAT impaired EDD compared to respective controls. LZR and OZR subject to UCMS had higher oxidative stress production, diminished adiponectin and impaired aortic nitric oxide levels. Divergently, UCMS induced greater inflammatory cytokine production in LZR UCMS tPVAT, but not in OZR UCMS tPVAT. AET prevented the tPVAT impairment of aortic relaxation with UCMS in LZR and OZR. Additionally, AET reduced aortic stiffness in both LZR and OZR. These beneficial effects on tPVAT regulation of the aorta are likely due to AET preservation of adiponectin, reduced oxidative stress and inflammation, and enhanced nitric oxide. UCMS impaired tPVAT-regulated aortic function in LZR, and augmented MetS-induced EDD in OZR. Conversely, AET in combination with UCMS largely preserved aortic function and the tPVAT environment, in both groups.

In Aged Females, the Enhanced Pressor Response to Angiotensin II Is Attenuated By Estrogen Replacement via an Angiotensin Type 2 Receptor-Mediated Mechanism.

[Figure: see text].

Endothelial mineralocorticoid receptor deletion ablates leptin‐induced cardiovascular and fetal growth preeclampsia characteristics in pregnant mice

Obesity increases the risk for preeclampsia (PE), a hypertensive syndrome of pregnancy characterized by placental ischemia. Obese PE patients demonstrate increases in plasma leptin levels in midgestation due to increased placental leptin production. We have shown that pregnancy increases endothelial mineralocorticoid receptor (ECMR) expression and that ECMR mediates leptin-induced endothelial dysfunction and hypertension in nonpregnant females. We therefore hypothesized that ECMR deletion protects from the development endothelial dysfunction, hypertension and fetal growth restriction in pregnant leptin-infused mice. Pregnant ECMR+/+ (WT) and ECMR-/- (KO) littermate mice were infused with vehicle or leptin (N=4-6/group) by osmotic minipump (0.9mg/kg/day, s.c.) from GD11-18 and thoracic aortas assessed for vascular function by wire myography. Separate groups (N=1-2/group) were implanted with radiotelemeters for systolic blood pressure (BP) measurement. Leptin decreased pup weight (0.86±0.04g WT vs 0.52±0.11g WT+lep, *P<0.05) and placental efficiency (9.7±0.7 WT vs 7.9±0.6 WT+lep, pup/placenta weight ratio, *P<0.05) indicating fetal growth restriction. ECMRdeletion prevented leptin-mediated decreases in pup weight (0.91±0.06g KO vs 1.0±0.07g KO+lep) and placental efficiency (9.6±0.5 KO vs 9.4±1.2 KO+lep). Preliminary data shows that prior to leptin infusion (GD8-11) all groups demonstrated similar BP and circadian rhythm of BP. Leptin infusion increased BP and ablated circadian rhythm (GD11-18, 114 mmHg WT vs 137 mmHg WT+lep), however, ECMR deletion blunted leptin-induced BP increases (112 KO mmHg vs 120 mmHg KO+lep) and preserved circadian rhythm. Leptin infusion reduced endothelial function (acetylcholine-mediated relaxation) in aortas of WT, but not KO, pregnant mice (2-way ANOVA, repeated measures, *P<0.05). Relaxation to acetylcholine with LNAME showed restoration of endothelial function in KO+lep mice was NO-dependent. In addition, ECMR deletion protected pregnant mice from leptin-induced increases in vascular α1 receptor-mediated constriction (phenylephrine) (*P<0.05). Endothelial-independent relaxation to sodium nitroprusside was similar across all groups. Moreover, ECMR deletion protected from leptin-mediated increases in placental mRNA expression of: sFlt-1 (WT+leptin: 1.2±0.03-fold from WT, *P<0.05, KO+leptin: 1.1±0.1-fold change from KO), HIF1α (WT+leptin: 1.6±0.1-fold, P=0.09, KO+leptin: 1.5±0.2-fold) and galectin 3 (WT+leptin: 3.2±0.5-fold, *P<0.05, KO+leptin: 0.8±0.1-fold). Collectively, these data indicate that ECMR deletion decreases BP, improves vascular function and placental function in association with increased vascular NO bioavailability and fetal growth in an obesity-associated, leptin-infusion model of PE.

Role of the PKA regulatory subunit RIα in the contractile tone of the aorta

Protein kinase A (PKA) is a key enzyme activated by binding of cAMP. PKA induces smooth muscle relaxation and vasodilatation. The PKA-RIα knock-in heterozygous mice, [R368X]/[+] (KI), leading to the generation of a truncated RIα and the repression of PKA activation (Le Stunff et al., 2017, J Bone Miner Res ) may help decipher the contribution of PKA-RIα in vascular system which has remained elusive. Our aim is to document the expression of PKA-RIα in mouse aorta and to decipher its role in arterial tone by using wild-type (WT) and KI mice. Aortas were harvested from adult male WT and KI mice. PKA subunits expressions were studied by immunoblot. Vascular reactivity was tested by mounting the aorta on a wire-myograph. The internal circumference (IC) was recorded. Concentration-contractile responses were performed for K + (20–120 mM), U46619 (1 nM–3 μM) and phenylephrine (PE, 1 nM–3 μM). Vasorelaxant responses to acetylcholine (ACh, 1 nM–10 μM) and to L858051 (adenylate cyclase activator, 10 nM–30 μM) were studied in aorta contracted with PE. All groups included 5–6 mice. In WT aorta, the anti-PKA-RIα antibody yielded a signal at 49 kDa, as expected. In KI mice, mutant allele expression was confirmed by an additional signal at 47 kDa. RIIα and Cα expressions were similar in both strains. IC was 20% smaller in KI mice than in WT. The contractile response to K + and PE were similar in both groups, whereas the response to U46619 was stronger in mutant aorta with a higher E max . ACh and L858051 relaxed aortas similarly in both groups. These preliminary data show that PKA-RIα is expressed in mouse aorta. The smaller IC of aorta in [R368X]/[+] mice is consistent with their smaller size (Le Stunff et al.). The stronger constriction to U46619 in mutant mice may be explained by reduced PKA activity compared to WT. The similar relaxation to L858051 in mutant mice maybe due to redundancy of PKA-RIα in mouse aorta.

Effects of sitagliptin on ß-adrenoceptor mediated relaxation in streptozotocin-diabetic rat aorta

Background/aim Dipeptidyl peptidase-4 (DPP4) inhibitors, a class of oral antidiabetic drugs, have been shown to be protective on the vascular system because of their antiinflammatory, antiatherosclerotic, and vasodilatory effects. ß 2-adrenoceptors (ß 2-ARs) mediate the vasorelaxation in the aorta. However, ß 3-adrenoceptor-mediated relaxation has not been studied in diabetic aorta yet. Thus, we aimed to study the effect of sitagliptin treatment on ß 2- and ß3-adrenoceptor-mediated relaxations in the diabetic rat aorta.Materials and methods Eight-week old Sprague Dawley rats were divided into three groups: control, diabetic, sitagliptin treated diabetic. Diabetes was induced by injection of streptozotocin (35 or 40 mg/kg, intraperitoneally). After 10 weeks of diabetes, some of the diabetic rats were treated with sitagliptin (orally, 10mg/kg/day). ß2- and ß 3-AR-mediated relaxation responses were evaluated by using isoprenaline and CL 316,243, respectively. ß3-AR-mediated relaxation experiments were repeated in presence of L-NAME. Western blotting and immunohistochemistry were performed to determine the abundance of ß3-adrenoceptor and endothelial nitric oxide synthase (eNOS).Results The isoprenaline-mediated relaxation response was impaired in the diabetic group and sitagliptin treatment did not improve it. There was no significant change in CL316,243 mediated-relaxation or protein expression of ß 3-ARs among the groups. However, the ratio of phosphorylated eNOS/NOS protein was increased markedly in the sitagliptin treated group, which points the stimulating effect of this drug towards the eNOS pathway. Conclusion Our results indicate that sitagliptin treatment does not alter ß- AR-mediated relaxation in streptozotocin-diabetic rat aorta; however, it significantly stimulates the eNOS pathway. Future studies are needed to clarify the relationship between the eNOS pathway and DPP-4 inhibition.

DNA REPAIR DEFECT IN SMOOTH MUSCLE CELL REPRODUCES FEATURES OF AGE-RELATED VASCULAR DISEASE IN MICE

Objective: DNA damage and repair responses have been implicated in age-related vascular disease. Evidence in mice shows that deletion of the Ercc1 gene, encoding an endonuclease that participates in several DNA repair systems, leads to features of accelerated ageing. It is not known from which cell type the vascular aging effect of Ercc1 deletion originates. A possibility is local DNA damage in vascular smooth muscle cells (VSMC). We determined features of vascular aging in a mouse model with specific Ercc1 deletion in smooth muscle cells (SMC-KO). Design and method: 12 SMC-KO and 13 Wild-type (WT) littermates were generated using alpha SM22-Cre driven cre-lox deletion of Ercc1. Blood pressure (BP) and in vivo vasodilation (reactive hyperemia: RH) were measured at the age of 22 and 23 weeks respectively. Mice were sacrificed at 24 weeks. Thoracic aorta and iliac artery endothelium-dependent (ED) and –independent (EI) relaxation were assessed (wire myograph). Results: There was no significant difference in BP between WT and SMC-KO. RH was decreased in SMC-KO vs. WT by 73% (P = 0.008). In SMC-KO mice maximal relaxation in iliac arteries to acetylcholine (ED) and sodium nitroprusside donor (EI) were decreased as compared to WT (ED: 48.04 ± 6.80 vs. 86.16 ± 3.68, P = 0.001; EI: 79.84 ± 4.04 vs. 93.78 ± 2.13, P = 0.022). In aorta similar observations were made (ED: 17.11 ± 2.29 vs. 73.42 ± 4.29, P = 0.0001; EI 55.87 ± 4.77 vs. 69.01 ± 5.17, p = 0.007). When added in the organ bath ITI-214 acutely increased aortic EI relaxation both in WT (from 69.01 ± 5.17 to 80.53 ± 2.05, P = 0.006) and SMC-KO (from 55.87 ± 4.77 to 67.17 ± 3.70, P = 0.084). Conclusions: Local DNA damage in SMC causes a decrease of vasodilator responses. This effect is blood pressure-independent. Given that responses to sodium nitroprusside, a nitric oxide (NO) donor, and PDE1, a cGMP-metabolising enzyme, were both involved, most probably a decline of NO-cGMP signalling is involved.

Improved Endothelium-Dependent Relaxation of Thoracic Aorta in Niclosamide-Treated Diabetic Rats.

Diabetes-induced endothelial dysfunction is critical for the development of diabetic cardiovascular complications. The aim of this study was to investigate the effect of niclosamide (Nic) on vascular endothelial dysfunction in streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats were injected with a single intraperitoneal injection of STZ (75mg/kg) to induce type 1 diabetes, and Nic (10mg/kg) was intraperitoneally administered per day for 4weeks. Endothelial function was evaluated as carbachol (CCh, an endothelium-dependent vasodilator)-evoked relaxation in the experiments performed on isolated thoracic aortas. The changes in the protein expressions of phosphorylated eNOS at serine 1177 (p-eNOSSer1177) and phosphorylated VASP at serine 239 (p-VASPSer239) of the rat aortas were analyzed by western blotting to determine whether NO/cGMP signaling is involved in the mechanism of Nic. STZ-injected rats had higher fasting blood glucose and less body weight compared to control rats (p < 0.05). Nic treatment did not affect blood glucose levels or body weights of the rats. CCh-induced endothelium-dependent relaxation of the aortic rings was significantly decreased in diabetic rats compared to control (Emax = 66.79 ± 7.41% and 90.28 ± 5.55%, respectively; p < 0.05). CCh-induced relaxation response was greater in Nic-treated diabetic rats compared to diabetic rats (Emax = 91.56 ± 1.20% and 66.79 ± 7.41%, respectively; p < 0.05). Phosphorylation of eNOS and VASP in aortic tissues was significantly reduced in diabetic rats, which were markedly increased by Nic treatment (p < 0.05). We demonstrated that Nic improved endothelial dysfunction possibly through the activation of NO/cGMP signaling without affecting hyperglycemia in diabetic rats. Our results suggesting that Nic has potential of repurposing for diabetic cardiovascular complications.

Vascular Inflammation and Dysfunction in Lupus-Prone Mice-IL-6 as Mediator of Disease Initiation.

Background: Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease and patients are under an increased risk for cardiovascular (CV) events and mortality. The increased CV risk for patients with SLE seems to be caused by a premature and accelerated atherosclerosis, attributable to lupus-specific risk factors (i.e., increased systemic inflammation, altered immune status), apart from traditional CV risk factors. To date, there is no established experimental model to explore the pathogenesis of this increased CV risk in SLE patients. Methods: Here we investigated whether MRL-Faslpr mice, which develop an SLE-like phenotype, may serve as a model to study lupus-mediated vascular disease. Therefore, MRL-Faslpr, MRL-++, and previously generated Il6−/− MRL-Faslpr mice were used to evaluate vascular changes and possible mechanisms of vascular dysfunction and damage. Results: Contrary to MRL-++ control mice, lupus-prone MRL-Faslpr mice exhibited a pronounced vascular and perivascular leukocytic infiltration in various organs; expression of pro-inflammatory cytokines in the aorta and kidney was augmented; and intima-media thickness of the aorta was increased. IL-6 deficiency reversed these changes and restored aortic relaxation. Conclusion: Our findings demonstrate that the MRL-Faslpr mouse model is an excellent tool to investigate vascular damage in SLE mice. Moreover, IL-6 promotes vascular inflammation and damage and could potentially be a therapeutic target for the treatment of accelerated arteriosclerosis in SLE.

Berberine ameliorates vascular dysfunction by a global modulation of lncRNA and mRNA expression profiles in hypertensive mouse aortae.

The current study investigated the mechanism underlying the therapeutic effects of berberine in the vasculature in hypertension. Angiotensin II (Ang II)-loaded osmotic pumps were implanted in C57BL/6J mice with or without berberine administration. Mouse aortae were suspended in myograph for force measurement. Microarray technology were performed to analyze expression profiles of lncRNAs and mRNAs in the aortae. These dysregulated expressions were then validated by qRT-PCR. LncRNA-mRNA co-expression network was constructed to reveal the specific relationships. Ang Ⅱ resulted in a significant increase in the blood pressure of mice, which was suppressed by berberine. The impaired endothelium-dependent aortic relaxation was restored in hypertensive mice. Microarray data revealed that 578 lncRNAs and 554 mRNAs were up-regulated, while 320 lncRNAs and 377 mRNAs were down-regulated in the aortae by Ang Ⅱ; both were reversed by berberine treatment. qRT-PCR validation results of differentially expressed genes (14 lncRNAs and 6 mRNAs) were completely consistent with the microarray data. GO analysis showed that these verified differentially expressed genes were significantly enriched in terms of "cellular process", "biological regulation" and "regulation of biological process", whilst KEGG analysis identified vascular function-related pathways including cAMP signaling pathway, cGMP-PKG signaling pathway, and calcium signaling pathway etc. Importantly, we observed that lncRNA ENSMUST00000144849, ENSMUST00000155383, and AK041185 were majorly expressed in endothelial cells. The present results suggest that the five lncRNAs ENSMUST00000144849, NR_028422, ENSMUST00000155383, AK041185, and uc.335+ might serve critical regulatory roles in hypertensive vasculature by targeting pivotal mRNAs and subsequently affecting vascular function-related pathways. Moreover, these lncRNAs were modulated by berberine, therefore providing the novel potential therapeutic targets of berberine in hypertension. Furthermore, lncRNA ENSMUST00000144849, ENSMUST00000155383, and AK041185 might be involved in the preservation of vascular endothelial cell function.

C-type natriuretic peptide-induced relaxation through cGMP-dependent protein kinase and SERCA activation is impaired in two kidney-one clip rat aorta

AimsHypertension underlies endothelial dysfunction, and activation of vasorelaxation signaling with low dependence on nitric oxide (NO) represents a good alternative for vascular modulation. C-type natriuretic peptide (CNP) causes relaxation by increasing cyclic guanosine 3′,5′-monophosphate (cGMP) or Gi-protein activation through its natriuretic peptide receptor-B or -C, respectively. We have hypothesized that CNP could exerts its effects and could overcome endothelial dysfunction in two kidney-one clip (2K-1C) hypertensive rat aorta. Here, we investigate the intracellular signaling involved in CNP effects in hypertension. Materials and methodsThe 2K-1C hypertension was induced in male Wistar rats (200 g). CNP-induced vascular relaxation and cGMP production were investigated in rat thoracic aortas. The natriuretic peptide receptor-B and -C localization was evaluated by immunofluorescence. Calcium mobilization was assessed in endothelial cells from rat aortas. Key findingsCNP induced similar relaxation in normotensive and 2K-1C hypertensive rat aortas, which increased after endothelium removal. CNP-induced relaxation involved natriuretic peptide receptor-B and -C activation in 2K-1C rats. Nitric oxide synthase (NOS) and soluble guanylyl cyclase (sGC) counter-regulated CNP-particulate GC (pGC) activation in aortas. CNP reduced endothelial calcium and increased cGMP production, which was lower in 2K-1C. CNP-induced cGMP-dependent protein kinase (PKG) and sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) activation was impaired in 2K-1C rat aorta. SignificanceOur results indicated CNP triggered relaxation through its natriuretic peptide receptor-B and -C in 2K-1C rat aortas, and that CNP-induced relaxation overcomes endothelial dysfunction in hypertension. In addition, NOS and sGC activities counter-regulate CNP-pGC activation to induce vascular relaxation.

Vasorelaxation endothelium-independent of the ethyl acetate phase from aerial parts of Solanum paludosum Moric. envolves channels-calcium L-type blockade

Previous results showed the ethyl acetate phase (SP-AcOEt), obtained from aerial parts of Solanum paludosum, relaxed the aorta isolated in the endothelium-dependent and -independent manner. The vasorelaxant effects of SP-AcOEt was not characterized on aorta rings endothelium-denuded, thus this work aimed to elucidate the mechanisms endothelium-independent vasorelaxation on rat isolated aorta. The aorta was isolated from Wistar rats and mounted in glass baths containing 6 mL of normal Krebs physiological solution with pH at 7.4. The preparation was maintained at 37ºC and bubbled continuously with a mixture of 95% O2 and 5% CO2. Aortic rings were maintained for 1 hour by a resting tension of 1g and next were contracted with phenylephrine after the sustained contraction ACh was added to access the integrity of the endothelium. SP-AcOEt relaxed pre-contracted aorta by KCl-30mM or -80mM in a similar manner, suggesting blockade CaV, but not channel-K+ participating. SP-AcOEt also inhibited the contraction induced by CaCl2 and relaxed pre-contracted aorta by (±)-BayK8644 (EC50 = 16.9±1.3 μg/mL), which confirms the involvement of L-type CaV blockade. SP-AcOEt presented vasorelaxation endothelium-independent that involves L-type CaV blockade.

Pirfenidone Is a Vasodilator: Involvement of KV7 Channels in the Effect on Endothelium-Dependent Vasodilatation in Type-2 Diabetic Mice.

Endothelial cell dysfunction and fibrosis are associated with worsening of the prognosis in patients with cardiovascular disease. Pirfenidone has a direct antifibrotic effect, but vasodilatation may also contribute to the effects of pirfenidone. Therefore, in a first study we investigated the mechanisms involved in the relaxant effect of pirfenidone in rat intrapulmonary arteries and coronary arteries from normal mice. Then in a second study, we investigated whether pirfenidone restores endothelial function in the aorta and mesenteric arteries from diabetic animals. From 16–18-week old normal male C57BL/6 mice and normoglycemic (db/db+), and type 2 diabetic (db/db) male and female mice, arteries were mounted in microvascular isometric myographs for functional studies, and immunoblotting was performed. In rat pulmonary arteries and mouse coronary arteries, pirfenidone induced relaxations, which were inhibited in preparations without endothelium. In mouse coronary arteries, pirfenidone relaxation was inhibited in the presence of a nitric oxide (NO) synthase inhibitor, NG-nitro-l-arginine (L-NOARG), a blocker of large-conductance calcium-activated potassium channels (BKCa), iberiotoxin, and a blocker of KV7 channels, XE991. Patch clamp studies in vascular smooth muscle revealed pirfenidone increased iberiotoxin-sensitive current. In the aorta and mesenteric small arteries from diabetic db/db mice relaxations induced by the endothelium-dependent vasodilator, acetylcholine, were markedly reduced compared to db/db + mice. Pirfenidone enhanced the relaxations induced by acetylcholine in the aorta from diabetic male and female db/db mice. An opener of KV7 channels, flupirtine, had the same effect as pirfenidone. XE991 reduced the effect of pirfenidone and flupirtine and further reduced acetylcholine relaxations in the aorta. In the presence of iberiotoxin, pirfenidone still increased acetylcholine relaxation in aorta from db/db mice. Immunoblotting for KV7.4, KV7.5, and BKCa channel subunits were unaltered in aorta from db/db mice. Pirfenidone failed to improve acetylcholine relaxation in mesenteric arteries, and neither changed acetylcholine-induced transient decreases in blood pressure in db/db+ and db/db mice. In conclusion, pirfenidone vasodilates pulmonary and coronary arteries. In coronary arteries from normal mice, pirfenidone induces NO-dependent vasodilatation involving BKCa and KV7 channels. Pirfenidone improves endothelium-dependent vasodilatation in aorta from diabetic animals by a mechanism involving voltage-gated KV7 channels, a mechanism that may contribute to the antifibrotic effect of pirfenidone.

Dietary chlorogenic acid ameliorates oxidative stress and improves endothelial function in diabetic mice via Nrf2 activation.

ObjectivesChlorogenic acid (CGA) is an antioxidant dietary factor. We investigated the effects of CGA on endothelial cell dysfunction in diabetic mice and the mechanistic role of nuclear factor erythroid-related factor 2 (Nrf2) in the antioxidant effect of CGA.MethodsDiabetic (db/db) mice were fed normal chow or chow containing 0.02% CGA for 12 weeks. Human umbilical vein endothelial cells (HUVECs) and mouse aortas were treated with normal or high glucose.ResultsCGA treatment induced upregulation of Nrf2 in HUVECs in a dose-dependent manner. CGA pretreatment prevented reactive oxygen species generation and preserved nitric oxide bioavailability in HUVECs and aortas from wild-type but not Nrf2−/− mice. CGA improved endothelium-dependent relaxation in high glucose-treated aortas from wild-type and db/db mice, but not Nrf2−/− mice. Dietary CGA improved endothelium-dependent relaxation in db/db mice.ConclusionsCGA ameliorates endothelial dysfunction in diabetic mice through activation of the Nrf2 anti-oxidative pathway.