LRP1 protects against excessive superior mesenteric artery remodeling by modulating angiotensin II-mediated signaling.

Vascular smooth muscle cells (vSMCs) exert a critical role in sensing and maintaining vascular integrity. These cells abundantly express the low-density lipoprotein receptor-related protein 1 (LRP1), a large endocytic signaling receptor that recognizes numerous ligands, including apolipoprotein E-rich lipoproteins, proteases, and protease-inhibitor complexes. We observed the spontaneous formation of aneurysms in the superior mesenteric artery (SMA) of both male and female mice in which LRP1 was genetically deleted in vSMCs (smLRP1-/- mice). Quantitative proteomics revealed elevated abundance of several proteins in smLRP1-/- mice that are known to be induced by angiotensin II-mediated (AngII-mediated) signaling, suggesting that this pathway was dysregulated. Administration of losartan, an AngII type I receptor antagonist, or an angiotensinogen antisense oligonucleotide to reduce plasma angiotensinogen concentrations restored the normal SMA phenotype in smLRP1-/- mice and prevented aneurysm formation. Additionally, using a vascular injury model, we noted excessive vascular remodeling and neointima formation in smLRP1-/- mice that was restored by losartan administration. Together, these findings reveal that LRP1 regulates vascular integrity and remodeling of the SMA by attenuating excessive AngII-mediated signaling.

Perivascular Adipose Tissue Compensation for Endothelial Dysfunction in the Superior Mesenteric Artery of Female SHRSP.Z-Leprfa/IzmDmcr Rats.

Regulation of arterial tone by perivascular adipose tissue (PVAT) differs between sexes. In male SHRSP.Z-Leprfa/IzmDmcr rats (SHRSP.ZF), PVAT exerts a compensatory relaxation effect for the loss of endothelium-mediated vasorelaxation, which occurs during the early stages of metabolic syndrome. However, this effect deteriorates by 23 weeks of age. Here, therefore, we compared the effects of PVAT in female and male SHRSP.ZF. Acetylcholine-induced relaxation in superior mesenteric artery without PVAT did not differ between 23-week-old females and males. However, the presence of PVAT enhanced relaxation in 23-week-old females, but not in males. The mRNA levels of angiotensin II type 1 receptor (AT1R) in PVAT did not differ between sexes, but AT1R-associated protein (ATRAP) and apelin levels were higher in females than in males. We observed a positive relationship between differences in artery relaxation with and without PVAT and ATRAP or apelin mRNA levels. In 30-week-old females, PVAT-enhanced relaxation disappeared, and mRNA levels of AT1R increased, while apelin levels decreased compared to 23-week-old females. These results demonstrated that in SHRSP.ZF, PVAT compensation for endothelium dysfunction extended to older ages in females than in males. Apelin and AT1R/ATRAP expression in PVAT may be predictors of favorable effects.

Anthocyanins Activate Membrane Estrogen Receptors With Nanomolar Potencies to Elicit a Nongenomic Vascular Response Via NO Production.

Background The vascular pharmacodynamics of anthocyanins is only partially understood. To examine whether the anthocyanin-induced vasorelaxation is related to membrane estrogen receptor activity, the role of ERα or GPER antagonism was ascertained on anthocyanins or 17-ß estradiol-(E2) induced vasodilatations and NO production. Methods and Results The rat arterial mesenteric bed was perfused with either anthocyanins or corresponding 3-O-glycosides, or E2, to examine rapid concentration-dependent vasorelaxations. The luminally accessible fraction of NO in mesenteric perfusates before and after anthocyanins or E2 administration was quantified. Likewise, NO-DAF signal detected NO production in primary endothelial cells cultures incubated with anthocyanins or E2 in the absence and presence of ERα (ICI 182,780) or GPER (G-36) selective antagonists. Anthocyanins or corresponding glycosides elicited, within minutes, vasodilation with nanomolar potencies; half maximal anthocyanin response reached 50% to 60% efficacy, in contrast to acetylcholine. The vasorelaxation is of rapid onset and exclusively endothelium-dependent; NOS inhibition annulled the vasorelaxation. The delphinidin vascular response was not modified by 100 nmol/L atropine but significantly attenuated by joint application of ICI plus G-36 (52±4.6 versus 8.5±1.5%), revealing the role of membrane estrogen receptors. Moreover, the anthocyanin or E2-induced NO production was antagonized up to 70% by these antagonists. NO-DAF signal elicited by anthocyanins was annulled by NOS inhibition or by ICI plus G-36 addition. Conclusions The biomedical effect of anthocyanins or 3-O-glycosylates derivatives contained in naturally purple-colored foods or berries is due to increased NO production, and not to the phytochemical's antioxidant potential, highlighting the nutraceutical role of natural products in cardiovascular diseases.

Effects of different vasopressors on the contraction of the superior mesenteric artery and uterine artery in rats during late pregnancy.

BACKGROUND: Hypotension after neuraxial anaesthesia is one of the most common complications during caesarean section. Vasopressors are the most effective method to improve hypotension, but which of these drugs is best for caesarean section is not clear. We assessed the effects of vasopressors on the contractile response of uterine arteries and superior mesenteric arteries in pregnant rats to identify a drug that increases the blood pressure of the systemic circulation while minimally affecting the uterine and placental circulation. METHODS: Isolated ring segments from the uterine and superior mesenteric arteries of pregnant rats were mounted in organ baths, and the contractile responses to several vasopressor agents were studied. Concentration-response curves for norepinephrine, phenylephrine, metaraminol and vasopressin were constructed. RESULTS: The contractile response of the mesenteric artery to norepinephrine, as measured by the pEC50 of the drug, was stronger than the uterine artery (5.617 ± 0.11 vs. 4.493 ± 1.35, p = 0.009), and the contractile response of the uterine artery to metaraminol was stronger than the mesenteric artery (pEC50: 5.084 ± 0.17 vs. 4.92 ± 0.10, p = 0.007). There was no statistically significant difference in the pEC50 of phenylephrine or vasopressin between the two blood vessels. CONCLUSIONS: In vitro experiments showed that norepinephrine contracts peripheral blood vessels more strongly and had the least effect on uterine artery contraction. These findings support the use of norepinephrine in mothers between the time of neuraxial anaesthesia and the delivery of the foetus.

Sorafenib not only impairs endothelium-dependent relaxation but also promotes vasoconstriction through the upregulation of vasoconstrictive endothelin type B receptors.

As a VEGF-targeting agent, sorafenib has been used to treat a number of solid tumors but can easily lead to adverse vascular effects. To elucidate the underlying mechanism, rat mesenteric arteries were subjected to organ cultured in the presence of different concentrations of sorafenib (0, 3, 6 and 9 mg/L) with or without inhibitors (U0126, 10-5 M; SB203580, 10-5 M; SP200126, 10-5 M) of MAPK kinases, and then acetylcholine- or sodium nitroprusside-induced vasodilation and sarafotoxin 6c-induced vasoconstriction were monitored by a sensitive myograph. The NO synthetases, the nitrite levels, the endothelial marker CD31,the ETB and ETA receptors and the phosphorylation of MAPK kinases were studied. Next, rats were orally administrated by sorafenib for 4 weeks (7.5 and 15 mg/kg/day), and their blood pressure, plasma ET-1, the ETB and ETA receptors and the phosphorylation of MAPK kinases in the mesenteric arteries were investigated. The results showed that sorafenib impairs endothelium-dependent vasodilation due to decreased NO levels and the low expression of eNOS and iNOS. Weak staining for CD31 indicated that sorafenib induced endothelial damage. Moreover, sorafenib caused the upregulation of vasoconstrictive ETB receptors, the enhancement of ETB receptor-mediated vasoconstriction and the activation of JNK/MAPK. Blocking the JNK, ERK1/2 and p38/MAPK signaling pathways by using the inhibitors significantly abolished ETB receptor-mediated vasoconstriction. Furthermore, it was observed that the oral administration of sorafenib caused an increase in blood pressure and plasma ET-1, upregulation of the ETB receptor and the activation of JNK in the mesenteric arteries. In conclusion, sorafenib not only impairs endothelium-dependent vasodilatation but also enhances ETB receptor-mediated vasoconstriction, which may be the causal factors for hypertension and other adverse vascular effects in patients treated with sorafenib.

Exposure to maternal diabetes induces endothelial dysfunction and hypertension in adult male rat offspring.

The adverse environment in early life can modulate adult phenotype, including blood pressure. Our previous study shows, in a rat streptozotocin (STZ)-induced maternal diabetes model, fetal exposure to maternal diabetes is characterized by established hypertension in the offspring. However, the exact mechanisms are not known. Our present study found, as compared with male control mother offspring (CMO), male diabetic mother offspring (DMO) had higher blood pressure with arterial dysfunction, i.e., decreased acetylcholine (Ach)-induced vasodilation. But there is no difference in blood pressure between female CMO and DMO. The decreased Ach-induced vasodilation was related to decreased nitric oxide (NO) production in the endothelium, not NO sensitivity in vascular smooth muscle because sodium nitroprusside (SNP)-mediated vasodilation was preserved; there was decreased NO production and lower eNOS phosphorylation in male DMO. The reactive oxygen species (ROS) level was increased in male DMO than CMO; normalized ROS levels with tempol increased NO production, normalized Ach-mediated vasodilation, and lowered blood pressure in male DMO rats. It indicates that diabetic programming hypertension is related to arterial dysfunction; normalizing ROS might be a potential strategy for the prevention of hypertension in the offspring.

MARCKS mediates vascular contractility through regulating interactions between voltage-gated Ca2+ channels and PIP2.

Phosphatidylinositol 4,5-bisphosphate (PIP2) acts as substrate and unmodified ligand for Gq-protein-coupled receptor signalling in vascular smooth muscle cells (VSMCs) that is central for initiating contractility. The present work investigated how PIP2 might perform these two potentially conflicting roles by studying the effect of myristoylated alanine-rich C kinase substrate (MARCKS), a PIP2-binding protein, on vascular contractility in rat and mouse mesenteric arteries. Using wire myography, MANS peptide (MANS), a MARCKS inhibitor, produced robust contractions with a pharmacological profile suggesting a predominantly role for L-type (CaV1.2) voltage-gated Ca2+ channels (VGCC). Knockdown of MARCKS using morpholino oligonucleotides reduced contractions induced by MANS and stimulation of α1-adrenoceptors and thromboxane receptors with methoxamine (MO) and U46619 respectively. Immunocytochemistry and proximity ligation assays demonstrated that MARCKS and CaV1.2 proteins co-localise at the plasma membrane in unstimulated tissue, and that MANS and MO reduced these interactions and induced translocation of MARCKS from the plasma membrane to the cytosol. Dot-blots revealed greater PIP2 binding to MARCKS than CaV1.2 in unstimulated tissue, with this binding profile reversed following stimulation by MANS and MO. MANS evoked an increase in peak amplitude and shifted the activation curve to more negative membrane potentials of whole-cell voltage-gated Ca2+ currents, which were prevented by depleting PIP2 levels with wortmannin. This present study indicates for the first time that MARCKS is important regulating vascular contractility and suggests that disinhibition of MARCKS by MANS or vasoconstrictors may induce contraction through releasing PIP2 into the local environment where it increases voltage-gated Ca2+ channel activity.

Total resuscitative endovascular balloon occlusion of the aorta causes inflammatory activation and organ damage within 30 minutes of occlusion in normovolemic pigs.

BACKGROUND: Resuscitative endovascular balloon occlusion of the aorta (REBOA) causes physiological, metabolic, end-organ and inflammatory changes that need to be addressed for better management of severely injured patients. The aim of this study was to investigate occlusion time-dependent metabolic, end-organ and inflammatory effects of total REBOA in Zone I in a normovolemic animal model. METHODS: Twenty-four pigs (25-35 kg) were randomized to total occlusion REBOA in Zone I for either 15, 30, 60 min (REBOA15, REBOA30, and REBOA60, respectively) or to a control group, followed by 3-h reperfusion. Hemodynamic variables, metabolic and inflammatory response, intraperitoneal and intrahepatic microdialysis, and plasma markers of end-organ injuries were measured during intervention and reperfusion. Intestinal histopathology was performed. RESULTS: Mean arterial pressure and cardiac output increased significantly in all REBOA groups during occlusion and blood flow in the superior mesenteric artery and urinary production subsided during intervention. Metabolic acidosis with increased intraperitoneal and intrahepatic concentrations of lactate and glycerol was most pronounced in REBOA30 and REBOA60 during reperfusion and did not normalize at the end of reperfusion in REBOA60. Inflammatory response showed a significant and persistent increase of pro- and anti-inflammatory cytokines during reperfusion in REBOA30 and was most pronounced in REBOA60. Plasma concentrations of liver, kidney, pancreatic and skeletal muscle enzymes were significantly increased at the end of reperfusion in REBOA30 and REBOA60. Significant intestinal mucosal damage was present in REBOA30 and REBOA60. CONCLUSION: Total REBOA caused severe systemic and intra-abdominal metabolic disturbances, organ damage and inflammatory activation already at 30 min of occlusion.

Angiotensin II Type 1 Receptor Antagonist Azilsartan Restores Vascular Reactivity Through a Perivascular Adipose Tissue-Independent Mechanism in Rats with Metabolic Syndrome.

PURPOSE: Perivascular adipose tissues (PVAT) are involved in the regulation of vascular tone. In mesenteric arteries, the compensatory vasodilatory effects of PVAT appear when vascular relaxation is impaired and disappear at around 23 weeks of age in SHRSP.Z-Leprfa/IzmDmcr (SHRSP.ZF) rats with metabolic syndrome (MetS). The renin-angiotensin system is involved in the development of endothelium and vascular dysfunction. Therefore, we investigated whether azilsartan, a potent angiotensin II type 1 (AT1) receptor antagonist, can protect against the deterioration of the PVAT compensatory vasodilator function that occurs with aging in MetS. METHODS: Two age groups of SHRSP.ZF rats (13 and 20 weeks of age) were administered azilsartan or vehicle through oral gavage once daily for 10 weeks. The vasodilation response of the isolated superior-mesenteric arteries upon addition of endothelium-dependent and -independent agonists was determined in the presence or absence of PVAT using organ bath methods. RESULTS: In vivo treatment with azilsartan improved the acetylcholine-induced vasodilation in mesenteric arteries with and without PVAT at both time-points. The mRNA levels of AT1 receptor and AT1 receptor-associated protein were unchanged in PVAT upon azilsartan treatment. Furthermore, in vitro treatment with azilsartan (0.1 and 0.3 µM for 30 min) did not affect the compensatory effect of PVAT on vasodilation in response to acetylcholine in SHRSP.ZF rat mesenteric arteries. CONCLUSIONS: Our results provide evidence supporting the use of azilsartan for the long-term protection against vascular dysfunctions in MetS. Azilsartan did not improve the dysfunction of PVAT-mediated modulation of vascular tone during MetS. The protective effect of azilsartan is mediated by restoring the endothelium- and vascular smooth muscle-mediated mechanisms.

Functional circuitry of neuro-immune communication in the mesenteric lymph node and spleen.

The peripheral nervous system is an active participant in immune responses capable of blocking aberrant activation of a variety of immune cells. As one of these neuro-immune circuits, the cholinergic anti-inflammatory pathway has been well established to reduce the severity of several immunopathologies. While the activation of this pathway by vagal nerve stimulation requires sympathetic innervation of the spleen, the neuro-immune circuitry remains highly controversial. Neuro-immune pathways in other lymphoid tissues such as mesenteric lymph nodes (MLN) that are critical to the surveillance of the small intestine and proximal colon have not been assessed. Using conditionally expressed Channelrhodopsin, selective stimulation of sympathetic post-ganglionic neurons in the superior mesenteric ganglion (SMG) prevented macrophage activation and LPS-induced TNFα production in the spleen and MLN, but not in the inguinal LN. Site selective stimulation of the SMG induced the release of norepinephrine, resulting in ß2AR dependent acetylcholine release in the MLN and spleen. VNS-evoked release of norepinephrine and acetylcholine in the MLN and spleen was significantly reduced using selective optogenetic blockade applied at the SMG. Additionally, this optogenetic blockade restored LPS-induced TNFα production, despite VNS. These studies identify the superior mesenteric ganglion as a critical node in a neuro-immune circuit that can inhibit immune function in the MLN and the spleen.

Tetrahydroxystilbene glucoside-induced relaxation of the superior mesenteric artery via both endothelium-dependent and endothelium-independent mechanisms.

Tetrahydroxystilbene glucoside (TSG) is the main water-soluble component in Polygonum multiflorum Thunb, and it has many cardioprotective effects. Although TSG is able to relax blood vessels, its relaxation of rat superior mesenteric arteries and the underlying mechanism of this process are not clearly understood. The aim of the present study was to use in vivo and in vitro models to investigate the arterial relaxation effect of TSG on rat superior mesenteric arteries and the mechanisms involved. We found that TSG concentration-dependently relaxed the superior mesenteric artery with or without endothelium. The vasorelaxation induced by TSG is not related to the vasodilator derived factor NO but is rather by the inhibition of COX-2 activity and decreased TXA2. We also found that the vasorelaxation induced by TSG was attenuated by 4­AP. Moreover, TSG also inhibited the contraction induced by an increase in external calcium concentration in Ca2+-free medium plus KCl (60 mM). These results suggest that TSG induces relaxation in mesenteric arterial rings through an endothelium-dependent pathway that involves the inhibition of COX-2 activity and decreased in TXA2 and through an endothelium-independent pathway via opening of a voltage-dependent K+ channel, blockade of Ca2+ influx and release of intracellular Ca2+.

Royal jelly increases peripheral circulation by inducing vasorelaxation through nitric oxide production under healthy conditions.

AIMS: Royal jelly (RJ) has a variety of reported biological activities, including vasorelaxation and blood pressure-lowering effects. Although functional foods are positively used for health, the effects of RJ on the cardiovascular system in healthy individuals have not been well studied. Therefore, we investigated the mechanisms underlying the vasorelaxation effects of RJ in healthy control rats to evaluate whether the peripheral circulation was increased. MAIN METHODS: We used fresh RJ to examine the vasorelaxation effects and related mechanisms in Wistar rats using organ bath techniques. Furthermore, we measured changes in tail blood circulation, systolic blood pressure (sBP), and heart rate (HR) after the oral administration of RJ to control rats and nitro-l-arginine methyl ester (l-NAME)-treated rats (0.5 mg/ml dissolved in distilled drinking water for 1 week). Concentrations of acetylcholine (ACh) in the RJ were measured using a commercial kit. KEY FINDINGS: RJ caused vasorelaxation of isolated rat aortas and superior mesenteric arteries, and this effect was inhibited by atropine (10-5 M, 15 min) or L-NAME (10-4 M, 20 min) and endothelium-denuded arterial ring preparations. Oral RJ increased tail blood flow and mass in control rats 1 h after treatment without affecting velocity, sBP, or HR. These effects were not observed in L-NAME-treated rats. RJ contained approximately 1000 µg/g of ACh. SIGNIFICANCE: The present study demonstrated that RJ is composed of muscarinic receptor agonist(s), likely ACh, and induces vasorelaxation through nitric oxide (NO) production from the vascular endothelium of healthy rats, leading to increased tail blood circulation. Thus, fresh RJ may improve peripheral circulation in healthy individuals.

Organ-specific changes in vascular reactivity and roles of inducible nitric oxide synthase and endothelin-1 in a rabbit endotoxic shock model.

BACKGROUND: Hemorrhagic shock-induced changes in vascular reactivity appear organ-specific. In the present study, we examined the hypothesis that vascular reactivity induced by septic shock similarly displays organ-specific differences and is regulated by inducible nitric oxide synthase (iNOS) and endothelin-1 (ET-1). METHODS: Endotoxic shock was induced in rabbits by administration of lipopolysaccharide (LPS) (1 mg/kg), and organ specificity of vascular reactivity of superior mesenteric artery (SMA), celiac artery (CA), and left renal artery (LRA) as well as the potential involvement of iNOS and ET-1 examined. RESULTS: Vascular reactivity of SMA, CA, and LRA was increased at the early stages and decreased at the late stages after LPS administration. Superior mesenteric artery showed the greatest decrease in vascular reactivity in response to norepinephrine (NE) (34.9%) and acetylcholine (Ach; 32.3%), followed by LRA (NE, 33.7%; Ach, 30.5%) and CA (NE, 16.2%), whereas the relaxation reactivity of CA in response to Ach was increased to 159%. The mRNA and protein levels of iNOS and ET-1 in SMA, CA, and LRA were not affected at the early stages of endotoxic shock after LPS administration but significantly increased at the late stages. Expression levels were higher in SMA than CA and LRA and negatively correlated with the decrease in vascular reactivity. The iNOS and ET-1 inhibitors, aminoguanidine (20 mg/kg) and PD-142893 (0.02 mg/kg), respectively, induced significant improvements in vascular reactivity and organ perfusion and stabilized the hemodynamic parameters in rabbits subjected to endotoxic shock. CONCLUSION: Changes in vascular reactivity during endotoxic shock are organ-specific. Differential expression patterns of iNOS and ET-1 in different blood vessels contribute to the organ specificity of vascular reactivity. LEVEL OF EVIDENCE: Therapeutic study, level II.

High Glucose Upregulated Vascular Smooth Muscle Endothelin Subtype B Receptors via Inhibition of Autophagy in Rat Superior Mesenteric Arteries.

Autophagy plays an important role in cardiovascular diseases. High glucose (HG) upregulates endothelin subtype B (ETB) receptors in vascular smooth muscle cells (VSMCs). However, it is unclear as to whether autophagy is involved in HG-induced upregulation of ETB receptors in VSMCs. The present study was designed to examine the hypothesis that HG upregulates ETB receptors by inhibiting autophagy in VSMCs. We studied HG-treated rat superior mesenteric artery (SMA) without endothelium in the presence and absence of 5-aminoimidazole-4-carboxamide 1-ß-D-ribofuranoside (AICAR), rapamycin, or MHY1485 for 24 hr. We measured contractile responses to sarafotoxin 6c (S6c) (an ETB receptor agonist) using a sensitive myograph. Levels of protein expression were determined using Western blotting. HG impaired autophagy and increased the levels of ETB receptor protein expression and ETB receptor-mediated contractile responses to S6c in SMA. However, these effects were reversed by AICAR (an agonist of adenosine monophosphate [AMP]-activated protein kinase [AMPK]) and rapamycin (an inhibitor of mammalian target of rapamycin [mTOR]). However, MHY1485 (an agonist of mTOR) did not upregulate the AICAR-inhibited ETB receptor-mediated contractile responses or ETB receptor protein expression in the presence of HG. These data suggest that HG upregulated ETB receptors by inhibiting autophagy in VSMCs via AMPK and mTOR signaling pathways.

Homocysteine up-regulates ETB receptors via suppression of autophagy in vascular smooth muscle cells.

The change of autophagy is implicated in cardiovascular diseases (CVDs). Homocysteine (Hcy) up-regulates endothelin type B (ETB) receptors in vascular smooth muscle cells (VSMCs). However, it is unclear whether autophagy is involved in Hcy-induced-up-regulation of ETB receptors in VSMCs. The present study was designed to examine the hypothesis that Hcy up-regulates ETB receptors by inhibiting autophagy in VSMCs. Hcy treated the rat superior mesenteric artery (SMA) without endothelium in the presence and absence of AICAR, rapamycin or MHY1485 for 24 h. The contractile responses to sarafotoxin 6c (S6c) (an ETB receptor agonist) were studied using a sensitive myograph. Levels of protein expression were determined using Western blot analysis. Punctate staining of LC3B was exanimated by immunofluorescence using confocal microscopy. The results showed that Hcy inhibited AMPK, and activated mTOR, followed by impairing autophagy, and increased the levels of ETB receptor protein expression and the ETB receptor-mediated contractile responses to S6c in SMA without endothelium. However, these effects were reversed by AICAR or rapamycin. Additionally, MHY1485 up-regulated the AICAR-inhibited ETB receptor-mediated contractile response and the levels of ETB receptor protein expression in presence of Hcy. In conclusion, this suggested that Hcy up-regulated ETB receptors by inhibiting autophagy in VSMCs via AMPK/mTOR signaling pathway.

The Curcumin-Induced Vasorelaxation in Rat Superior Mesenteric Arteries.

BACKGROUND: Curcumin (Cur) is a natural lipophilic polyphenol compound extracted from the rhizome of turmeric. Recently, protective effect of Cur on cardiovascular system is paid close attention. Some researches demonstrated that Cur could induce vascular relaxation in many arterial beds. However, relaxant effect of Cur on rat superior mesenteric artery is not clear. This present study will investigate the vasorelaxant effect of Cur on rat superior mesenteric arteries and the mechanisms involved. METHODS: The isometric tension of rat superior mesenteric arterial rings was recorded by a sensitive myograph system in vitro. The vasodilation of Cur at various concentrations (range: 10-8-10-4 M) on potassium chloride (KCl; 60 mmol/L)-precontracted or phenylephrine hydrochloride (PE; 10 µmol/L)-precontracted arterial rings were observed. We also observed vasorelaxant effect of Cur on KCl (60 mM)-preconstricted rat superior mesenteric arterial rings after incubating the inhibitors of endothelial mechanism, including the endothelial nitric oxide synthase inhibitor Nω-nitro-L-arginine methyl ester, the guanylate cyclase inhibitor 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one, and the cyclooxygenase inhibitor indomethacin, and inhibitors of potassium ion channel, including 4-aminopyridine (Voltage-sensitive K+ channel blockers), and tetraethylammonium chloride (Ca2+ activated K+ channel blockers), and BaCl2 (Inward rectifying K+ channel blockers), and glibenclamide (ATP -sensitive K+ channel blockers), respectively. The effects of Cur are expressed as percentage of relaxation from the precontraction induced by KCl (60 mmol/L) or PE (10 µmol/L). The Emax value refers to the maximum relaxation. The pD2 value refers to the negative logarithmic value of the drug concentration that produces 50% Emax. RESULTS: Cur concentration dependently relaxed the superior mesenteric artery rings with endothelium precontracted by PE (Emax = 84.33 ± 1.11 and pD2 = 5.03 ± 0.02) or KCl (Emax = 80.96 ± 2.12% and pD2 = 4.32 ± 0.01). The vasorelaxant effect of Cur on the superior mesenteric artery rings relied on endothelium partially. Indomethacin (5 µM) significantly inhibited the effect. However, 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (10 µM) and Nω-nitro-L-arginine methyl ester (100 µM) had no effect on the action. In artery rings without endothelium, vasorelaxation induced by Cur was attenuated by 4-aminopyridine (100 µM). However, barium chloride dehydrate (10 µM), glibenclamide (10 µM), and traethylammonium chloride (1 mM) did not affect vasorelaxation induced by Cur. Moreover, Cur also significantly inhibited contraction induced by increasing external calcium in Ca2+-free medium plus K+ (60 mM) and releasing intracellular Ca2+ in the Ca2+-free solution. CONCLUSIONS: Our results suggested that Cur induces relaxation in superior mesenteric arterial rings through an endothelium-dependent pathway, involving prostanoid, and also through an endothelium-independent pathway, opening K+ channel, and blockade of Ca2+ influx and intracellular Ca2+ release.

High glucose upregulates endothelin type B receptors in vascular smooth muscle cells via the downregulation of Sirt1.

Silent information regulator family protein 1 (Sirt1) has recently gained attention for its protective effects against diabetic and cardiovascular diseases (CVDs). Vascular smooth muscle endothelin type B (ETB) receptors are involved in the pathogenesis of CVDs and diabetes. The aim of present study was to explore whether Sirt1 is involved in high glucose (HG)-mediated regulation of ETB receptors in rat superior mesenteric arteries (SMA). The rat SMA segments were cultured in the presence and absence of HG with or without the activator of Sirt1 and specific inhibitor for the extracellular signal-regulated protein kinase 1/2 (ERK1/2) for 24 h. Following organ culture, the contractile responses to sarafotoxin 6c were studied using a sensitive myograph, and the ETB receptor protein expression level was determined using western blotting. The results demonstrated that HG induced upregulation of ETB receptor expression and increased receptor-mediated vasoconstriction in SMA. Resveratrol (Res; a Sirt1 activator) concentration-dependently inhibited the HG-induced upregulation of ETB receptor expression and receptor-mediated vasoconstriction. Additionally, these effects could also be abolished by an inhibitor of the ERK1/2 signaling pathway. Furthermore, upregulation of ERK1/2 phosphorylation induced by HG was inhibited by Res. In conclusion, HG upregulated ETB receptors by downregulating Sirt1 and subsequently activating the ERK1/2 signaling pathways in the organ culture SMA.

ACPA and JWH-133 modulate the vascular tone of superior mesenteric arteries through cannabinoid receptors, BKCa channels, and nitric oxide dependent mechanisms.

BACKGROUND: Some cannabinoids, a family of compounds derived from Cannabis sativa (marijuana), have previously shown vasodilator effects in several studies, a feature that makes them suitable for the generation of a potential treatment for hypertension. The mechanism underlying this vasodilator effect in arteries is still controversial. In this report, we explored how the synthetic cannabinoids ACPA (CB1-selective agonist) and JWH-133 (CB2-selective agonist) regulate the vascular tone of rat superior mesenteric arteries. METHODS: To screen the expression of CB1 (Cannabinoid receptor 1) and CB2 (Cannabinoid receptor 2) receptors in arterial rings or isolated smooth muscle cells obtained from the artery, immunocytochemistry, immunohistochemistry, and confocal microscopy were performed. In addition, the effects on vascular tone induced by the two cannabinoids were tested in isometric tension experiments in rings obtained from superior mesenteric arteries. The participation of voltage and calcium-activated potassium channel of big conductance (BKCa) and the role of nitric oxide (NO) release on the vascular effects induced by ACPA and JWH-133 were tested. RESULTS: CB1 and CB2 receptors were highly expressed in the rat superior mesenteric artery, in both smooth muscle and endothelium. The vasodilation effect shown by ACPA was endothelium-dependent through a mechanism involving CB1 receptors, BKCa channel activation, and NO release; meanwhile, the vasodilator effect of JWH-133 was induced by the activation of CB2 receptors located in smooth muscle and by a CB2 receptor-independent mechanism inducing NO release. CONCLUSIONS: CB1 and CB2 receptor activation in superior mesenteric artery causes vasorelaxation by mechanisms involving BKCa channels and NO release.

Poly (I:C) impairs NO donor-induced relaxation by overexposure to NO via the NF-kappa B/iNOS pathway in rat superior mesenteric arteries.

Recent studies have suggested a link between vascular dysfunction and innate immune activation including toll-like receptors (TLRs), but the detailed mechanism remains unclear. Here we investigated whether poly (I:C) [a synthetic double-strand RNA recognized by TLR3, melanoma differentiation-associated gene 5 (MDA5), and retinoic acid-inducible gene I (RIG-I)] affected nitric oxide (NO)/cGMP-related vascular relaxation, one of the major cascades of relaxation, in rat superior mesenteric arteries. Using organ-cultured arteries, we found that poly (I:C) (30µg/mL for approximately 1 day) markedly reduced sodium nitroprusside (SNP)-induced relaxation (vs. vehicle); this was prevented by co-treatment with a TLR3 inhibitor. Relaxation induced by 8-Br cGMP (a phosphodiesterase (PDE)-resistant cGMP analogue) and the expression of proteins related to NO/cGMP signaling did not differ between vehicle- and poly (I:C)-treated groups. When PDEs were inhibited by IBMX (a nonselective PDE inhibitor), the SNP-induced relaxation was still greatly reduced in poly (I:C)-treated arteries (vs. vehicle). Poly (I:C) reduced SNP-stimulated cGMP production, but increased NO production and iNOS expression (vs. vehicle). The impairment of SNP-induced relaxation by poly (I:C) was prevented by co-treatment with either iNOS or a nuclear factor-kappa B (NF-κB) inhibitor. This effect induced by poly (I:C) appeared to be independent of oxidative stress. The SNP-induced relaxation was reduced in freshly isolated arteries by pre-incubation with SNP in a concentration-dependent manner. Poly (I:C) did not alter protein levels of TLR3, TRIF/TICAM-1, or phospho-IRF3/IRF3, whereas RIG-I and MDA5 were significantly upregulated (vs. vehicle). These results suggest that poly (I:C) impairs NO donor-induced relaxation in rat superior mesenteric arteries via overexposure to NO produced by the NF-κB/iNOS pathway.

Heteromeric TRPV4/TRPC1 channels mediate calcium-sensing receptor-induced nitric oxide production and vasorelaxation in rabbit mesenteric arteries.

Stimulation of calcium-sensing receptors (CaSR) by increasing the external calcium concentration (Ca2+]o) induces endothelium-dependent vasorelaxation through nitric oxide (NO) production and activation of intermediate Ca2+-activated K+ currents (IKCa) channels in rabbit mesenteric arteries. The present study investigates the potential role of heteromeric TRPV4-TRPC1 channels in mediating these CaSR-induced vascular responses. Immunocytochemical and proximity ligation assays showed that TRPV4 and TRPC1 proteins were expressed and co-localised at the plasma membrane of freshly isolated endothelial cells (ECs). In wire myography studies, increasing [Ca2+]o between 1 and 6mM induced concentration-dependent relaxations of methoxamine (MO)-induced pre-contracted tone, which were inhibited by the TRPV4 antagonists RN1734 and HC067047, and the externally-acting TRPC1 blocking antibody T1E3. In addition, CaSR-evoked NO production in ECs measured using the fluorescent NO indicator DAF-FM was reduced by RN1734 and T1E3. In contrast, [Ca2+]o-evoked perforated-patch IKCa currents in ECs were unaffected by RN1734 and T1E3. The TRPV4 agonist GSK1016790A (GSK) induced endothelium-dependent relaxation of MO-evoked pre-contracted tone and increased NO production, which were inhibited by the NO synthase inhibitor L-NAME, RN1734 and T1E3. GSK activated 6pS cation channel activity in cell-attached patches from ECs which was blocked by RN1734 and T1E3. These findings indicate that heteromeric TRPV4-TRPC1 channels mediate CaSR-induced vasorelaxation through NO production but not IKCa channel activation in rabbit mesenteric arteries. This further implicates CaSR-induced pathways and heteromeric TRPV4-TRPC1 channels in regulating vascular tone.