NF-kappaB signaling mediates vascular smooth muscle endothelin type B receptor expression in resistance arteries

Endothelin receptor B enhances liver injury and pro-inflammatory responses by increasing G-protein-coupled receptor kinase-2 expression in primary biliary cholangitis

Severe diseases like cirrhosis and liver failure can be developed from primary biliary cholangitis (PBC). Endothelin-2 (EDN2) and endothelin receptor B (EDNRB) are related to the pathogenesis of PBC. However, the roles of EDN2 and EDNRB in PBC-related liver injury and inflammation along with molecular mechanisms are poorly defined. In this study, histopathologic alterations of liver tissues were assessed through hematoxylin-eosin staining. Alanine transaminase (ALT), alkaline phosphatase (ALP), aspartate transaminase (AST), and γ-Glutamyltranspetidase (GGT) (4 liver function indexes) serum levels were detected with corresponding activity assay kits. Also, we determined the levels of M2 subtype anti-mitochondrial antibody (AMA-M2), interferon-gamma (IFN-γ), and tumor-necrosis factor alpha (TNFα) in serum with ELISA assay. Later, RT-qPCR assay was used to measure the expression of genes at mRNA levels, while western blotting and immunohistochemical techniques were used to detect protein levels of genes. Our results showed that the liver tissues of PBC patients and mice presented with severe hepatocyte injury and inflammatory cell infiltration as well as destruction of intrahepatic small bile ducts. ALP, AST, ALT, GGT, AMA-M2, IFN-γ, and TNF-α serum levels were higher in PBC patients and mice. Besides, EDN2 and EDNRB were highly expressed in serums and livers of PBC patients and mice. EDNRB potentiated PBC-related liver injury and pro-inflammatory responses, as evidenced by observation of serious liver pathologic injury and increased serum levels of ALP, AST, ALT, AMA-M2, IFN-γ, and TNF-α in PBC mice following EDNRB overexpression. EDNRB overexpression or activation via its agonist IRL-1620 TFA triggered liver injury and pro-inflammatory responses, increased GRK2 expression and induced NF-κB expression and activation in wild-type mice. EDNRB knockdown or inhibition by Bosentan alleviated liver damage and inflammation, reduced GRK2 expression, and inhibited NF-κB in PBC mice. These findings suggested EDNRB loss or inhibition weakened liver injury and pro-inflammatory responses by down-regulating GRK2 and inhibiting the NF-κB pathway in PBC mice.

Inhibitors of the MAPK/ NF-κB pathway attenuate the upregulation of the ETB receptor mediated by high glucose in vascular smooth muscle cells

BACKGROUND

Increased vascular smooth muscle cell (VSMC) endothelin type B (ET_B) receptor expression is involved in cardiovascular diseases. High glucose (HG) in diabetes is closely related to cardiovascular complications. Although diabetes upregulates VSMC endothelin subtype B (ET_B) receptors, its mechanism is still unclear. Our aim is to investigate the mechanism of HG-induced ET_B receptors in VSMCs.

METHODS

Rat superior mesenteric arteries (SMAs) without endothelium were cultured in medium without serum for 24 h. HG with or without mitogen-activated protein kinase (MAPK) signaling pathway inhibitors and downstream nuclear factor-kappaB (NF-κB) inhibitors was coincubated with SMAs. A sensitive myograph detected the contractile responses to sarafotoxin 6c. Western blotting and immunofluorescence staining were used to determine protein expression.

RESULTS

HG promoted the expression of VSMC ET_B receptors in rat SMAs and enhanced the ET_B receptor-induced contractile response. The results showed that HG increased vascular smooth muscle cell (VSMC) ET_B receptor expression and ET_B receptor-induced contractile responses in rat SMAs. Both extracellular signal-related kinase 1 and 2 (ERK1/2) inhibitors (U0126) and P38 inhibitors (SB203580) significantly inhibited HG-increased VSMC ET_B receptors. However, a C-jun terminal kinase (p-JNK) inhibitor (SP600125) did not affect HG- upregulated VSMC ET_B receptors. Further study showed that NF-κB using an IκB kinase inhibitor (wedelolactone) also significantly inhibited HG-increased VSMC ET_B receptors.

CONCLUSION

In conclusion, HG upregulated the VSMC ET_B receptor by activating the ERK1/2- or P38- NF-κB signaling pathway.

PM2.5 upregulates rat mesenteric arteries 5-HT2A receptor via inflammatory-mediated mitogen-activated protein kinases signaling pathway

Fine particulate matter (PM_2.5 ) is an important environmental risk factor for cardiovascular diseases. However, little is known about the effects of PM_2.5 on arteries. The present study investigated whether PM_2.5 alters 5-hydroxytryptamine (5-HT) receptor expression and inflammatory mediators on rat mesenteric arteries, and examined the underlying mechanisms. Isolated rat mesenteric arteries segments were cultured with PM_2.5 in the presence or absence of ERK1/2, JNK, and p38 pathway inhibitors. Contractile reactivity was monitored by a sensitive myograph. The expression of 5-HT_2A/1B receptors and inflammatory mediators were studied by a real-time polymerase chain reaction and/or by immunohistochemistry. The phosphorylation of mitogen-activated protein kinases (MAPK) pathway was detected by Western blot. Compared with the fresh or culture alone groups, 1.0 μg/mL PM_2.5 cultured for 16 hours significantly enhanced contractile response induced by 5-HT and increased 5-HT_2A receptor mRNA and protein expressions, indicating PM_2.5 upregulates 5-HT_2A receptor. SB203580 (p38 inhibitor) and U0126 (ERK1/2 inhibitor) significantly decreased PM_2.5 -induced elevated contraction and mRNA and protein expression of 5-HT_2A receptor. Cultured with PM_2.5 significantly increased the mRNA expression of inflammatory mediators (NOS2, IL-1β, and TNF-α), while SB203580 decreased mRNA expression level of NOS2, IL-1β, and TNF-α. SP600125 (JNK inhibitor) decreased mRNA expression level of TNF-α and IL-1β. After PM_2.5 exposure, the phosphorylation of p38 and ERK1/2 protein were increased. SB203580 and U0126 inhibited the PM_2.5 caused increased phosphorylation protein of p38 and ERK1/2. In conclusion, PM_2.5 induces inflammatory-mediated MAPK pathway in artery which subsequently results in enhanced vascular contraction responding to 5-HT via the upregulated 5-HT_2A receptors.

Cardioprotective Efficacy of Coriandrum sativum (L.) Seed Extract in Heart Failure Rats Through Modulation of Endothelin Receptors and Antioxidant Potential

The present study aimed to evaluate the therapeutic and prophylactic potential of Coriandrum sativum extract in isoproterenol-induced heart failure (HF) in Wistar rats. Two weeks after the isoproterenol administration, rats developed severe impairment in left ventricular functions, reduced baroreflex sensitivity, and significant alteration in hemodynamic parameters and lipid profile. HF rats also exhibited enhanced lipid peroxidation and increased expression of endothelin receptors (ET_A and ET_B). Therapeutic and prophylactic treatment with C. sativum extract significantly (p < .05) improved the left ventricular functions and hemodynamic parameters and increased baroreflex sensitivity. It also inhibited lipid peroxidation, improved lipid profile, and downregulated the expression of endothelin receptors. Simvastatin treatment showed a similar cardioprotective effect. Our results suggest that C. sativum extract provides significant protection from heart failure possibly due to its ability to improve left ventricular functions and baroreflex sensitivity, attenuate lipid peroxidation, and modulate the expression of endothelin receptors.

Effects of Coriandrum Sativum Extract and Simvastatin in Isopreterenol Induced Heart Failure in Rats

Heart failure is a syndrome, caused due to structural and functional cardiac abnormalities, characterized by changes in the hemodynamic and neurohumoral mechanisms. It is becoming a major health burden worldwide. More effective therapies are desperately needed. Coriandrum sativum (C. sativum), a traditional spice crop has been known to possess many biological and medicinal properties. The present study was designed to investigate the cardioprotective efficacy of C. sativum in rat model of isoproterenol induced heart failure. Heart failure was produced by injecting isoproterenol subcutaneously (85 mg/kg twice at an interval of 24 h). Oral efficacy of seed extract was assessed on hemodynamic profile, antioxidant enzyme activities, lipid peroxidation, lipid profile, atherogenic indices, mRNA and protein expression of endothelin receptors (ETA and ETB) and histopathology. Treatment of heart failure rats with C. sativum orally (1g/kg b.wt) improved the altered hemodynamics, restored the cardiac antioxidant enzymes armory, attenuated oxidative stress, improved lipid profile, lowered atherogenic indices, decreased the levels of ETA and ETB receptor mRNA and protein, and restored the cardiac morphology. In conclusion, our results suggest C. sativum to be a cardioprotective agent in heart failure, possibly by the virtue of its ability to alleviate oxidative stress, improve lipid profile and endothelial dysfunction.

Downregulation of Thromboxane A2 Receptor Occurs Mainly via Nuclear Factor-KappaB Signaling Pathway in Rat Renal Artery

Thromboxane A₂ (TXA₂) acts on TXA₂ receptors (TP) to regulate renal artery blood flow and subsequently contributes to the pathogenesis of renal ischemia. The present study was designed to examine if nuclear factor-kappaB (NF-κB) signaling pathway is involved in the downregulation of TP receptors in rat renal artery. Rat renal artery segments were organ cultured for 6 or 24 h. Downregulation of TP receptors was monitored using myograph (contractile function), real-time PCR (receptor mRNA), and immunohistochemistry (receptor protein). Specific inhibitors (MG-132 and BMS345541) for NF-κB signaling pathway were used to dissect the underlying molecular mechanisms involved. Compared to fresh (noncultured) segments, organ culture of the renal artery segments for 24 h induced a significant rightward shift of U46619 (TP receptor agonist) contractile response curves (pEC₅₀: 6.89 ± 0.06 versus 6.48 ± 0.04, P < 0.001). This decreased contractile response to U46619 was paralleled with decreased TP receptor mRNA and protein expressions in the renal artery smooth muscle cells. Specific inhibitors (MG-132 and BMS345541) for NF-κB signaling pathway significantly abolished the decreased TP protein expression and receptor-mediated contractions. In conclusion, downregulation of TP receptors in the renal artery smooth muscle cells occurs mainly via the NF-κB signaling pathway.

Cyclosporin A upregulates ETB receptor in vascular smooth muscle via activation of mitogen-activating protein kinases and NF-κB pathways

Hypertension is one of the most frequent complications of solid organ transplantation, and cyclosporin A (CsA) plays a predominant role in the pathophysiology of post-transplant hypertension. However, the exact molecular mechanisms of CsA-induced hypertension remain obscure. We previously showed that CsA increased the mRNA expression and contractile function of endothelin B (ETB) receptor in vascular smooth muscle cells. The present study was designed to investigate the underlying mechanisms of CsA-induced upregulation of ETB receptor in vasculature. Rat mesenteric arteries were incubated with CsA in an organ culture system, and results showed that CsA enhanced ETB receptor mRNA in the time- and dose-dependent manner, and increased protein expression levels of ETB receptor after treatment with CsA 10(-5)M for 6h. Furthermore, CsA induced phosphorylation of extracellular regulated protein kinases 1 and 2 (ERK1/2), p38, and translocation of nuclear factor-kappaB (NF-κB) p65 in vasculature. Blocking ERK1/2, p38, or NF-κB activation with their specific inhibitors markedly attenuated CsA-induced upregulation of ETB receptor mRNA expression and protein levels, and ETB receptor-mediated contraction. In summary, this study showed that mitogen-activating protein kinases (ERK1/2 and p38) and the downstream transcriptional factor NF-κB pathways were involved in CsA-induced upregulation of ETB receptor in arterial smooth muscle cells.

Correlation between nuclear factor κB activity and pulmonary artery pressure in a rat high pulmonary blood flow model

The aim of the present study was to investigate the correlation between nuclear factor-κB (NF-κB) activity and pulmonary artery pressure in the pulmonary artery endothelial cells of high pulmonary blood flow rat models. A total of 50 four-week-old male Wistar rats were randomly divided into four groups: Surgery shunt group (Tn, n=15); surgery + pyrollidine dithiocarbamate (PDTC) administration group (Ti, n=15); sham control group (Co, n=10) and negative control group (Cn, n=10). The 30 rats of the Ti and Tn groups underwent carotid artery-external jugular vein anastomosis; the 15 rats in the Ti group were injected with PDTC intraperitoneally 1 h prior to surgery for a two-week continuous infusion. After 12 weeks of feeding ad libitum, right ventricular systolic pressure and NF-κB activity in the pulmonary artery endothelial cells of the rats were measured. The NF-κB activity of the Tn group was significantly higher than that of the Cn group (P<0.01) and the NF-κB activity of the Ti group was lower than that of the Cn group (P<0.01); however, no significant difference was observed between the Co and Cn groups. The increased activity of NF-κB was an important factor in the pulmonary vasoconstriction and structural remodeling of rats with high pulmonary blood flow.

Phenotypic alterations in human saphenous vein culture induced by tumor necrosis factor-alpha and lipoproteins: a preliminary development of an initial atherosclerotic plaque model

Background

Atherosclerosis is a chronic progressive inflammatory disease of blood vessels particularly the arteries. The development of atherosclerotic plaques or atherogenesis is a complex process that is influenced by cardiovascular risk factors such as vascular inflammation and dyslipidemia. This study demonstrates the ability of tumor necrosis factor-alpha (TNF-α) and low density lipoproteins (LDL) to induce atherosclerotic plaque in human saphenous vein (HSV) organ culture.

Methods

Normal HSV segments, from male patients who had coronary bypass graft, were cultured in DMEM containing 5% heat inactivated fetal bovine serum. TNF-α (5 ng/ml) was applied in combination with native LDL (nLDL) or oxidized LDL (oxLDL) at the dose of 50 μg/ml for 14 days. The phenotypic changes of the organ cultures characteristic of initial atherosclerotic plaques were evaluated. The effect of anti-atherogenic agent, 17-β estradiol (E₂), was also determined.

Results

Histologic, histomorphometric, and immunohistochemical examinations revealed that HSV rings stimulated with TNF-α + nLDL or TNF-α + oxLDL can exhibit the essential morphological features of atherogenesis, including fibrous cap formation, cholesterol clefts, evident thickening of the intimal layer, increased proliferation of smooth muscle cells (SMC) and migration to the subendothelial layer, significant SMC foam cell formation, and increased expression of adhesion molecules in the vascular wall. Addition of E₂ (50 nM) to the culture significantly modulated the critical changes. Consistently, mRNA profiling of the HSV model revealed that 50 of 84 genes of atherosclerosis were up-regulated.

Conclusions

Phenotypic changes characteristic of the initial development of atherosclerotic plaques can be induced in HSV organ culture.

Redox state alters anti-cancer effects of wedelolactone

Wedelolactone is one of the active plant polyphenolic compounds. Anti-tumor effects of this drug have been demonstrated recently. We have described that wedelolactone acts as catalytic inhibitor of DNA topoisomerase IIα. The aim of this study was to further characterize the mechanism of its anti-tumor effects. We showed that wedelolactone inhibits binding of DNA topoisomerase IIα to plasmid DNA and antagonizes formation of etoposide-induced DNA cleavage complex. The inhibition of topoisomerase IIα by wedelolactone is reversible by excess of the enzyme but not DNA. The in vitro inhibitory effect of wedelolactone on the topoisomerase IIα activity is redox-dependent as it diminished in the presence of reducing agents. Cytotoxicity of wedelolactone was partially inhibited by N-acetylcysteine and glutathione ethyl ester in breast cancer MDA-MB-231 and MDA-MB-468 cells while the inhibitory effect of catalase was observed only in the former cell line. Finally, we found that wedelolactone can be oxidized in the presence of copper ions resulting in DNA strand break and abasic site formation in vitro. However, wedelolactone induced neither DNA damage in MDA-MB-231 cells nor mutations in bacterial cells detectable by Ames test suggesting that wedelolactone may not be an effective inducer of DNA damage. We conclude that the topoisomerase IIα inhibitory- and DNA damaging activities of wedelolactone in vitro depend on its redox state. Pro-oxidant activity could, however, explain only part of wedelolactone-induced cytotoxicity. Therefore, the major cellular target(s) of wedelolactone and the exact mechanism of wedelolactone-induced cytotoxicity still remain to be identified.

Vascular endothelin receptor type B: structure, function and dysregulation in vascular disease

Endothelin-1 (ET-1) is a major regulator of vascular function, acting via both endothelin receptor type A (ET(A)R) and type B (ET(B)R). Although the role of ET(A)R in vascular smooth muscle (VSM) contraction has been studied, little is known about ET(B)R. ET(B)R is a G-protein coupled receptor with a molecular mass of ~50 kDa and 442 amino acids arranged in seven transmembrane domains. Alternative splice variants of ET(B)R and heterodimerization and cross-talk with ET(A)R may affect the receptor function. ET(B)R has been identified in numerous blood vessels with substantial effects in the systemic, renal, pulmonary, coronary and cerebral circulation. ET(B)R in the endothelium mediates the release of relaxing factors such as nitric oxide, prostacyclin and endothelium-derived hyperpolarizing factor, and could also play a role in ET-1 clearance. ET(B)R in VSM mediates increases in [Ca(2+)](i), protein kinase C, mitogen-activated protein kinase and other pathways of VSM contraction and cell growth. ET-1/ET(A)R signaling has been associated with salt-sensitive hypertension (HTN) and pulmonary arterial hypertension (PAH), and ET(A)R antagonists have shown some benefits in these conditions. In search for other pathogenetic factors and more effective approaches, the role of alterations in endothelial ET(B)R and VSM ET(B)R in vascular dysfunction, and the potential benefits of modulators of ET(B)R in treatment of HTN and PAH are being examined. Combined ET(A)R/ET(B)R antagonists could be more efficacious in the management of conditions involving upregulation of ET(A)R and ET(B)R in VSM. Combined ET(A)R antagonist with ET(B)R agonist may need to be evaluated in conditions associated with decreased endothelial ET(B)R expression/activity.

The role of tumor necrosis factor-α and TNF-α receptors in cerebral arteries following cerebral ischemia in rat

Background

Tumour necrosis factor-α (TNF-α) is a pleiotropic pro-inflammatory cytokine, which is rapidly upregulated in the brain after injury. TNF-α acts by binding to its receptors, TNF-R1 (p55) and TNF-R2 (p75), on the cell surface. The aim of this study was first to investigate if there is altered expression of TNF-α and TNF-α receptors in cerebral artery walls following global or focal ischemia, and after organ culture. Secondly, we asked if the expression was regulated via activation of the MEK-ERK1/2 pathway.

Methods

The hypothesis was tested in vivo after subarachnoid hemorrhage (SAH) and middle cerebral artery occlusion (MCAO), and in vitro by organ culture of isolated cerebral arteries. The localization and amount of TNF-α, TNF-α receptor 1 and 2 proteins were analysed by immunohistochemistry and western blot after 24 and 48 h of organ culture and at 48 h following SAH or MCAO. In addition, cerebral arteries were incubated for 24 or 48 h in the absence or presence of a B-Raf inhibitor (SB386023-b), a MEK- inhibitor (U0126) or an NF-κB inhibitor (IMD-0354), and protein expression evaluated.

Results

Immunohistochemistry revealed enhanced expression of TNF-α, TNF-R1 and TNF-R2 in the walls of cerebral arteries at 48 h after MCAO and SAH compared with control. Co-localization studies showed that TNF-α, TNF-R1 and TNF-R2 were primarily localized to the cell membrane and the cytoplasm of the smooth muscle cells (SMC). There was, in addition, some expression of TNF-R2 in the endothelial cells. Immunohistochemistry and western blot analysis showed that these proteins were upregulated after 24 and 48 h in culture, and this upregulation reached an apparent maximum at 48 h of organ culture. Treatment with U0126 significantly reduced the enhanced SMC expression of TNF-α, TNF-R1 and TNF-R2 immunoreactivities after 24 and 48 h of organ culture. The Raf and NF-κB inhibitors significantly reduced organ culture induced TNF-α expression while they had minor effects on the TNF-α receptors.

Conclusion

The present study shows that cerebral ischemia and organ culture induce expression of TNF-α and its receptors in the walls of cerebral arteries and that upregulation is transcriptionally regulated via the MEK/ERK pathway.