Cyclic GMP modulates the expression of Gi protein and adenylyl cyclase signaling in vascular smooth muscle cells

We have recently shown that the nitric oxide (NO) donor, SNAP, decreased the expression of Giα proteins and associated functions in vascular smooth muscle cells. Because NO stimulates soluble guanylyl cyclase and increases the levels of guanosine 3′,5′-cyclic monophosphate (cGMP), the present studies were undertaken to investigate whether cGMP can also modulate the expression of Gi proteins and associated adenylyl cyclase signaling. A10 vascular smooth muscle cells (VSMCs) and primary cultured cells from aorta of Sprague Dawley rats were used for these studies. The cells were treated with 8-bromoguanosine 3′,5′-cyclic monophosphate (8Br-cGMP) for 24 h and the expression of Giα proteins was determined by immunobloting techniques. Adenylyl cyclase activity was determined by measuring [³²P]cAMP formation for [α-³²P]ATP. Treatment of cells with 8-Br-cGMP (0.5 mM) decreased the expression of Giα-2 and Giα-3 by about 30–45%, which was restored towards control levels by KT5823, an inhibitor of protein kinase G. On the other and hand, the levels of Gsα protein were not altered by this treatment. The decreased expression of Giα proteins by 8Br-cGMP treatment was reflected in decreased Gi functions. For example, the inhibition of forskolin (FSK)-stimulated adenylyl cyclase activity by low concentrations of GTPγS (receptor-independent Gi functions) was significantly decreased by 8Br-cGMP treatment. In addition, exposure of the cells to 8Br-cGMP also resulted in the attenuation of angiotensin (Ang) II- and C-ANP_4–23 (a ring-deleted analog of atrial natriuretic peptide [ANP]-mediated inhibition of adenylyl cyclase activity (receptor-dependent functions of Gi). On the other hand, Gsα-mediated stimulations of adenylyl cyclase by GTPγS, isoproterenol and FSK were significantly augmented in 8Br-cGMP-treated cells. These results indicated the 8Br-cGMP decreased the expression of Giα proteins and associated functions in VSMCs. From these studies, it can be suggested that 8Br-cGMP-induced decreased levels of Gi proteins and resultant increased levels of cAMP may be an additional mechanism through which cGMP regulates vascular tone and thereby blood pressure.     

Chitinase 3-like 1 gene-329G/A polymorphism, plasma concentration and risk of coronary heart disease in a Chinese population

Background

The chitinase-like 1 protein, YKL-40, is involved in inflammation and tissue remodeling. Patients with coronary heart disease (CHD) and acute myocardial infarction have elevated levels of serum YKL-40. The goal of the present study was to investigate whether the chitinase-like 1 gene-329G/A variant (rs10399931) confers susceptibility to CHD, and whether it is associated with the clinical phenotype and severity of disease.

Methods

We performed a case-control study of 410 unrelated CHD patients (coronary stenosis ≥ 50% or documented myocardial infarction) and 442 controls from China. A ligase detection reaction was used to determine a single-nucleotide polymorphism in rs10399931. The genotypic and allelic associations of this single-nucleotide polymorphism with CHD, phenotypes and severity were also evaluated. Plasma levels of YKL-40 were measured using ELISA assays.

Results

Three genotypes, CC, CT, and TT, existed in rs10399931 and there were no significant differences found in either the genotypic or allelic frequencies between the CHD cases and controls. Patients with CHD had higher YKL-40 levels compared to controls and those with acute myocardial infarction had the highest levels of YKL-40 compared to patients with either stable or unstable angina pectoris (all p < 0.01). Rs10399931 affected neither the main anthropometric or metabolic characteristics, nor did there exists any association between rs10399931 and the severity of coronary lesions assessed by Gensini scores (all p > 0.05).

Conclusions

Our results do not support that rs10399931 is associated with clinical phenotypes of CHD and the extent of coronary lesions; however, YKL-40 levels are higher in CHD patients and associated with its clinical phenotypes.     

The miR-182/SORT1 axis regulates vascular smooth muscle cell calcification in vitro and in vivo

Arterial calcification is a common feature of cardiovascular disease. Sortilin is involved in the development of atherosclerosis, but the specific mechanism is unclear. In this study, we established calcification models in vivo and in vitro by using vitamin D₃ and β-glycerophosphate, respectively. In vivo, the expression of SORT1 was up-regulated and the expression of miR-182 was down-regulated in calcified arterial tissues. Meanwhile there was a negative correlation between SORT1 expression and miR-182 levels. In vitro, downregulating SORT1 expression using shRNA inhibited β-glycerophosphoric induced vascular smooth muscle cells (VSMCs) calcification. Moreover, reduced sortilin levels followed transfection of miR-182 mimics, whereas there was a significant increase in sortilin levels after transfection of miR-182 inhibitors. A luciferase reporter assay confirmed that SORT1 is the direct target of miR-182. Our study suggests that SORT1 plays a vital role in the development of arterial calcification and is regulated by miR-182.     

A novel mutation of ALK2, L196P, found in the most benign case of fibrodysplasia ossificans progressiva activates BMP-specific intracellular signaling equivalent to a typical mutation, R206H

Naphthoquinone derivatives have been reported to possess various pharmacological activities, such as antiplatelet, anticancer, antifungal, and antiviral properties. In this study, we investigated the effects of a newly-synthesized naphthoquinone derivative, 2-decylamino-5,8-dimethoxy-1,4-naphthoquinone (2-decylamino-DMNQ), on VSMC proliferation and examined the molecular basis of the underlying mechanism. In a dose-dependent manner, 2-decylamino-DMNQ inhibited PDGF-stimulated VSMC proliferation with no apparent cytotoxic effect. While 2-decylamino-DMNQ did not affect PDGF-Rβ or Akt, it did inhibit the phosphorylation of Erk1/2 and PLCγ1 induced by PDGF. Moreover, 2-decylamino-DMNQ suppressed DNA synthesis through the arrest of cell cycle progression at the G₀/G₁ phase, including the suppression of pRb phosphorylation and a decrease in PCNA expression, which was related to the downregulation of cell cycle regulatory factors, such as cyclin D1/E and CDK 2/4. It was demonstrated that both U0126, an Erk1/2 inhibitor, and U73122, a PLCγ inhibitor, increased the proportion of cells in the G₀/G₁ phase of the cell cycle. Thus, these results suggest that 2-decylamino DMNQ has an inhibitory effect on PDGF-induced VSMC proliferation and the mechanism of this action is through cell cycle arrest at the G₀/G₁ phase. This may be a useful tool for studying interventions for vascular restenosis in coronary revascularization procedures and stent implantation.     

Alpha-lipoic acid regulates the autophagy of vascular smooth muscle cells in diabetes by elevating hydrogen sulfide level

Dysfunctional vascular smooth muscle (VSM) plays a vital role in the process of atherosclerosis in patients with type 2 diabetes mellitus (T2DM). Alpha-lipoic acid (ALA) can prevent the altered VSM induced by diabetes. However, the precise mechanism underlying the beneficial effect of ALA is not well understood. This study aimed to determine whether ALA ameliorates VSM function by elevating hydrogen sulfide (H₂S) level in diabetes and whether this effect is associated with regulation of autophagy of VSM cells (VSMCs). We found decreased serum H₂S levels in Chinese patients and rats with type 2 diabetes mellitus (T2DM). ALA treatment could increase H₂S level, which reduced the autophagy-related index and activation of the 5′-monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway, thereby protecting vascular function in rats with T2DM. Propargylglycine (PPG), a cystathionine-γ-lyase inhibitor, could weaken the ALA effect. In cultured VSMCs, high glucose level also reduced H₂S level, upregulated the autophagy-related index and activated the AMPK/mTOR pathway, which were reversed by concomitant application of sodium hydrosulfide (NaHS, an H₂S donor) or ALA. The protective effect of NaHS or ALA was attenuated by rapamycin (an autophagy activator), 5-amino-1-β-d-ribofuranosyl-imidazole-4-carboxamide (an AMPK activator) or PPG. In contrast, Compound C (an AMPK inhibitor) enhanced the effect of ALA or NaHS. ALA may have a protective effect on VSMCs in T2DM by elevating H₂S level and downregulating autophagy via the AMPK/mTOR pathway. This study provides a new target for addressing diabetic macroangiopathy.     

亮氨酸脑啡肽抑制培养大鼠主动脉平滑肌细胞增殖

实验以培养的ＳＤ大鼠胸主动脉平滑肌细胞为模型,用四唑盐比色地及＾３Ｈ－ＴｄＲ掺入技术动态观察发现亮氨酸脑啡肽可显著抑制血管平滑肌细胞的增殖及ＤＮＡ的合成,阿片受体阻断剂纳洛酮对ＶＳＭＣｓ的增殖及ＤＮＡ的合成无影响,但ＮＡＬ可拮抗亮氨酸脑啡肽对ＶＳＭＣｓ增殖的抑制作用。     

Synthetic retinoid Am80 inhibits interaction of KLF5 with RARα through inducing KLF5 dephosphorylation mediated by the PI3K/Akt signaling in vascular smooth muscle cells

Krüppel-like factor 5 (KLF5) is known to physically interact with retinoic acid receptor-α (RARα). Here, we show that Am80 inhibited the interaction between KLF5 and RARα and this inhibitory effect was accompanied by the dephosphorylation of KLF5 in VSMCs. Treating VSMCs with LY294002, the PI3K/Akt inhibitor, abrogated Am80-induced KLF5 dephosphorylation and reversed Am80-induced suppression of interaction between KLF5 and RARα, whereas treating vascular smooth muscle cells (VSMCs) with SB203580, the p38 kinase inhibitor, attenuated the interaction between KLF5 and RARα. Constitutively active p38 kinase MKK6b infection prevented the KLF5 dephosphorylation induced by Am80. In conclusion, Am80 induces KLF5 dephosphorylation by activating PI3K/Akt signaling, and inhibits KLF5 phosphorylation by blocking p38 signaling, subsequently leading to the suppression of interaction of KLF5 with RARα.

Structured summary

MINT-7013243: Klf5 (uniprotkb:Q66HP1) physically interacts (MI:0218) with RAR alpha (uniprotkb:Q9QWJ1) by anti bait coimmunoprecipitation (MI:0006)