Involvement of ERK1/2 kinase in insulin-and thrombin-stimulated vascular smooth muscle cell proliferation

The versatile role of Serpina3c in physiological and pathological processes: a review of recent studies

Murine Serpina3c belongs to the family of serine protease inhibitors (Serpins), clade "A" and its human homologue is SerpinA3. Serpina3c is involved in some physiological processes, including insulin secretion and adipogenesis. In the pathophysiological process, the deletion of Serpina3c leads to more severe metabolic disorders, such as aggravated non-alcoholic fatty liver disease (NAFLD), insulin resistance and obesity. In addition, Serpina3c can improve atherosclerosis and regulate cardiac remodeling after myocardial infarction. Many of these processes are directly or indirectly mediated by its inhibition of serine protease activity. Although its function has not been fully revealed, recent studies have shown its potential research value. Here, we aimed to summarize recent studies to provide a clearer view of the biological roles and the underlying mechanisms of Serpina3c.

The orphan receptor GPRC5B activates pro-inflammatory signaling in the vascular wall via Fyn and NFκB

BACKGROUND AND AIMS

Atherosclerosis is driven by an inflammatory process of the vascular wall. The novel orphan G-protein coupled receptor 5B of family C (GPRC5B) is involved in drosophila sugar and lipid metabolism as well as mice adipose tissue inflammation. Here, we investigated the role of GPRC5B in the pro-atherogenic mechanisms of hyperglycemia and vascular inflammation.

METHODS

Immortalized and primary endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) were used for stimulation with high glucose or different cytokines. Adenoviral- or plasmid-driven GPRC5B overexpression and siRNA-mediated knockdown were performed in these cells to analyze functional and mechanistic pathways of GPRC5B.

RESULTS

In ECs and VSMCs, stimulation with high glucose, TNFα or LPS induced a significant upregulation of endogenous GPRC5B mRNA and protein levels. GPRC5B overexpression and knockdown increased and attenuated, respectively, the expression of the pro-inflammatory cytokines TNFα, IL-1β, IL-6 as well as the pro-atherogenic vascular adhesion molecules ICAM-1 and VCAM-1. Furthermore, the expression and activity of the metalloproteinase MMP-9, a component of atherosclerotic plaque stabilization, were significantly enhanced by GPRC5B overexpression. Mechanistically, GPRC5B increased the phosphorylation of ERK1/2 and activated NFκB through a direct interaction with the tyrosine kinase Fyn.

CONCLUSIONS

Our findings demonstrate that GPRC5B is upregulated in response to high glucose and pro-inflammatory signaling. GPRC5B functionally modulates the inflammatory activity in cells of the vascular wall, suggesting a pro-atherogenic GPRC5B-dependent positive feedback loop via Fyn and NFκB. Thus, GPRC5B warrants further attention as a novel pharmacological target for the treatment of vascular inflammation and possibly atherogenesis.

Baicalin Alleviates Thrombin-Induced Inflammation in Vascular Smooth Muscle Cells

Atherosclerosis (AS) is a chronic inflammatory disease of the arterial intima. As AS represents the most common type of vascular disease, it affects millions of individuals and is a source of high morbidity and mortality rates worldwide. Overwhelming evidence indicates that AS-related inflammation is mediated by proinflammatory cytokines, chemokines, adhesion molecules and inflammatory signaling pathways, with each of these factors being shown to play critical roles during the entire progression of AS. While a number of drugs have been approved for use in the treatment of AS, their benefits are modest, which underscores the urgency for the development of new drug therapies. In part, these deficits in effective drugs can be attributable to the lack of a clear understanding of the molecular mechanisms of AS. In this study, we investigate the capacity for thrombin to trigger inflammation and induce cell proliferation in vascular smooth muscle cells (VSMCs). We then assessed the effects of baicalin and its potential mechanisms on VSMC inflammation as induced by thrombin. Baicalin, which is a natural bioactive compound of S. baicalensis Georgi (SBG), exerted a protective effect against thrombin-induced VSMC inflammation as resulting from the upregulation of PAR-1. This protection as exerted by baicalin appears to reside in its capacity to produce an inhibitory effect on the thrombin-induced activation of the ERK1/2 pathway. These findings suggest that baicalin may be a promising candidate for the treatment of atherosclerosis.

The promoting role of Cx43 on the proliferation and migration of arterial smooth muscle cells for angiotensin II-dependent hypertension

BACKGROUND

Recent studies have shown that endothelin-1 and angiotensin II (AngII) can increase gap junctional intercellular communication (GJIC) by activating Mitogen-activated protein kinases (MAPKs) pathway. However, not only the precise interaction of AngII with Connexin43(Cx43) and the associated functions remain unclear, but also the regulatory role of Cx43 on the AngII-mediated promotion proliferation and migration of VSMCs is poorly understood.

MATERIAL AND METHODS

Our research applicated pressure myography measurements, immunofluorescence and Western blot analyses to investigate the changes in physiological indicators in spontaneously hypertensive rats (SHRs) and AngII-stimulated proliferation and migration of A7r5 SMCs(Rat vascular smooth muscle cells). The aim was to elucidate the role of CX43 in hypertension induced by AngII.

RESULTS

Chronic ramipril (angiotensin converting enzyme inhibitor) management for SHRs significantly attenuated blood pressure and blood vessel wall thickness, also reduced contraction rate in the cerebral artery. The cerebral artery contraction rates, mRNA and protein expression of Cx43, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) protein expression in the SHR + ramipril and SHR + ramipril + carbenoxolone (CBX, Cx43 specific blocker) groups were significantly lower than those in the SHR group. Cx43 protein expression and Ser368 phosphorylated Cx43 protein levels increased significantly in AngII-stimulated A7r5 cells. However, the levels of phosphorylated Cx43 decreased after pre-treatment with candesartan (AT1 receptor blocker), GF109203X (protein kinase C (PKC) blocker) and U0126 (mitogen-activated protein kinases/extracellular signal-regulated kinase1/2(MEK/ERK1/2)-specific blocker) in AngII-stimulated A7r5 cells. Cx43 was widely distributed in the cell membrane, nucleus, and cytoplasm of the SMCs. Furthermore, pre-treatment of the AngII- stimulated A7r5 cells with Gap26 (Cx43 blocker) significantly inhibited cell migration and decreased the expression levels of MEK1/2, ERK1/2, P-MEK1/2, and P-ERK1/2.

CONCLUSION

Our research confirms that Cx43 plays an important role in the regulation of proliferation and migration of VSMCs via MEK/ERK and PKC signal pathway in AngII-dependent hypertension.

PINK1/Parkin-mediated mitophagy promotes apelin-13-induced vascular smooth muscle cell proliferation by AMPKα and exacerbates atherosclerotic lesions

Aberrant proliferation of vascular smooth muscle cells (VSMC) is a critical contributor to the pathogenesis of atherosclerosis (AS). Our previous studies have demonstrated that apelin-13/APJ confers a proliferative response in VSMC, however, its underlying mechanism remains elusive. In this study, we aimed to investigate the role of mitophagy in apelin-13-induced VSMC proliferation and atherosclerotic lesions in apolipoprotein E knockout (ApoE-/-) mice. Apelin-13 enhances human aortic VSMC proliferation and proliferative regulator proliferating cell nuclear antigen expression in dose and time-dependent manner, while is abolished by APJ antagonist F13A. We observe the engulfment of damage mitochondria by autophagosomes (mitophagy) of human aortic VSMC in apelin-13 stimulation. Mechanistically, apelin-13 increases p-AMPKα and promotes mitophagic activity such as the LC3I to LC3II ratio, the increase of Beclin-1 level and the decrease of p62 level. Importantly, the expressions of PINK1, Parkin, VDAC1, and Tom20 are induced by apelin-13. Conversely, blockade of APJ by F13A abolishes these stimulatory effects. Human aortic VSMC transfected with AMPKα, PINK1, or Parkin and subjected to apelin-13 impairs mitophagy and prevents proliferation. Additional, apelin-13 not only increases the expression of Drp1 but also reduces the expressions of Mfn1, Mfn2, and OPA1. Remarkably, the mitochondrial division inhibitor-1(Mdivi-1), the pharmacological inhibition of Drp1, attenuates human aortic VSMC proliferation. Treatment of ApoE-/- mice with apelin-13 accelerates atherosclerotic lesions, increases p-AMPKα and mitophagy in aortic wall in vivo. Finally, PINK1-/- mutant mice with apelin-13 attenuates atherosclerotic lesions along with defective in mitophagy. PINK1/Parkin-mediated mitophagy promotes apelin-13-evoked human aortic VSMC proliferation by activating p-AMPKα and exacerbates the progression of atherosclerotic lesions.

Periodic mechanical stress activates EGFR-dependent Rac1 mitogenic signals in rat nucleus pulpous cells via ERK1/2

The mitogenic effects of periodic mechanical stress on nucleus pulpous cells have been studied extensively but the mechanisms whereby nucleus pulpous cells sense and respond to mechanical stimulation remain a matter of debate. We explored this question by performing cell culture experiments in our self-developed periodic stress field and perfusion culture system. Under periodic mechanical stress, rat nucleus pulpous cell proliferation was significantly increased (p < 0.05 for each) and was associated with increases in the phosphorylation and activation of EGFR, Rac1, and ERK1/2 (p < 0.05 for each). Pretreatment with the ERK1/2 selective inhibitor PD98059 reduced periodic mechanical stress-induced nucleus pulpous cell proliferation (p < 0.05 for each), while the activation levels of EGFR and Rac1 were not inhibited. Proliferation and phosphorylation of ERK1/2 were inhibited after pretreatment with the Rac1 inhibitor NSC23766 in nucleus pulpous cells in response to periodic mechanical stress (p < 0.05 for each), while the phosphorylation site of EGFR was not affected. Inhibition of EGFR activity with AG1478 abrogated nucleus pulpous cell proliferation (p < 0.05 for each) and attenuated Rac1 and ERK1/2 activation in nucleus pulpous cells subjected to periodic mechanical stress (p < 0.05 for each). These findings suggest that periodic mechanical stress promotes nucleus pulpous cell proliferation in part through the EGFR-Rac1-ERK1/2 signaling pathway, which links these three important signaling molecules into a mitogenic cascade.

Role of the extracellular signal-regulated kinase 1/2 signaling pathway in the process of thrombin-promoting airway remodeling in ovalbumin-allergic rats

CONTEXT

Although it is recognized that thrombin plays a key role in airway remodeling during chronic asthma. In a previous study, we have proved that thrombin promotes airway remodeling via PAR-1 in OVA-allergic rats, but little is known about intracellular signaling pathway involved in the event.

OBJECTIVE

In this study, we intend to explore the impact of pERK1/2 signaling pathway on the process of thrombin-induced airway remodeling in OVA-allergic rats.

MATERIALS AND METHODS

A rat model of chronic asthma was set up by systemic sensitization and repeated challenge to OVA. The doses of thrombin, recombinant hirudin, PAR-1 inhibitor ER-112780-06, and pERK1/2 inhibitor PD98059 varied for different groups. The expression of pERK1/2 was analyzed by western blot and RT-PCR. Secretion of TGF-β1 and IL-6 was detected by ELISA.

RESULTS

The expression of pERK1/2 was higher in the airway of asthmatic rats than those of normal rats, and was significantly increased by thrombin treatment but decreased by thrombin-inhibitor treatment. Airway remodeling was enhanced by thrombin but weakened by pERK1/2 inhibitor. Expression of growth factors and IL-6 in asthmatic rats was significantly increased by thrombin treatment and decreased by thrombin-inhibitor treatment and pERK1/2 inhibitor treatment.

CONCLUSION

These results suggest that ERK1/2 signaling pathway may play an important role in the process of thrombin-promoting airway remodeling in OVA-allergic rats, and pERK1/2 inhibitor effectively inhibits the process.

IL-1β enhances vascular smooth muscle cell proliferation and migration via P2Y2 receptor-mediated RAGE expression and HMGB1 release

Vascular smooth muscle cells (VSMCs) are the major cell type in blood vessel walls, and their proliferation and migration play important roles in the development of atherosclerosis. Recently, it has been reported that IL-1β mediates the inflammatory response through the upregulation of the P2Y2 receptor (P2Y2R). Thus, we examined the role of P2Y2R in IL-1β-mediated proliferation and migration of VSMCs and the underlying molecular mechanisms. VSMCs were pretreated with IL-1β for 24h to upregulate P2Y2R expression. The cells were then stimulated with UTP or ATP for the indicated times, and cell proliferation and migration and the related signaling pathways were examined. The equipotent P2Y2R agonists ATP and UTP enhanced proliferation, RAGE expression and HMGB1 secretion in IL-1β-pretreated VSMCs. Additionally, pretreatment with IL-1β enhanced UTP-mediated VSMC migration and MMP-2 release, but these effects were not observed in the P2Y2R-siRNA- or RAGE-siRNA-transfected VSMCs. Next, the signaling molecules involved in P2Y2R-mediated cell proliferation and migration were determined. The ERK, AKT, PKC, Rac-1 and ROCK2 pathways were involved in UTP-induced cell proliferation and migration, MMP-2 and HMGB1 secretion and RAGE expression in the IL-1β-pretreated VSMCs. UTP induced the phosphorylation of ERK, AKT and PKC and the translocation of Rac-1 and ROCK2 from cytosol to membrane as well as stress fiber formation, which were markedly increased in the IL-1β-pretreated VSMCs but not in the P2Y2R-siRNA-transfected VSMCs. These results demonstrate that pro-inflammatory cytokines associated with atherosclerosis, such as IL-1β, can accelerate the process of atherosclerosis through the upregulation of P2Y2R.

Rosiglitzone suppresses angiotensin II-induced production of KLF5 and cell proliferation in rat vascular smooth muscle cells

Krüppel-like factor (KLF) 5, which initiates vascular smooth muscle cell (VSMC) proliferation, also participates in Angiotensin (Ang) II-induced vascular remodeling. The protective effect of rosiglitazone on vascular remodeling may be due to their impact on VSMC proliferation. However, the underlying mechanisms involved remain unclear. This study was designed to investigate whether the antiproliferation effects of rosiglitazone are mediated by regulating Ang II/KLF5 response. We found that, in aortas of Ang II-infused rats, vascular remodeling and KLF5 expression were markedly increased, and its target gene cyclin D1 was overexpressed. Co-treatment with rosiglitazone diminished these changes. In growth-arrested VSMCs, PPAR-γ agonists (rosiglitazone and 15d-PGJ2) dose-dependently inhibited Ang II-induced cell proliferation and expression of KLF5 and cyclin D1. Moreover, these effects were attenuated by the PPAR-γ antagonists GW9662, bisphenol A diglycidyl ether and PPAR-γ specific siRNA. Furthermore, rosiglitazone inhibited Ang II-induced phosphorylation of protein kinase C (PKC) ζ and extracellular signal-regulated kinase (ERK) 1/2 and activation of early growth response protein (Egr). In conclusion, in Ang II-stimulated VSMCs, rosiglitazone might have an antiproliferative effect through mechanisms that include reducing KLF5 expression, and a crosstalk between PPAR-γ and PKCζ/ERK_1/2/Egr may be involved in. These findings not only provide a previously unrecognized mechanism by which PPAR-γ agonists inhibit VSMC proliferation, but also document a novel evidence for the beneficial vascular effect of PPAR-γ activation.

Liraglutide attenuates high glucose-induced abnormal cell migration, proliferation, and apoptosis of vascular smooth muscle cells by activating the GLP-1 receptor, and inhibiting ERK1/2 and PI3K/Akt signaling pathways

Background

As a new anti-diabetic medicine, Liraglutide (LIRA), one of GLP-1 analogues, has been found to have an anti-atherosclerotic effect. Since vascular smooth muscle cells (VSMCs) play pivotal roles in the occurrence of diabetic atherosclerosis, it is important to investigate the role of LIRA in reducing the harmful effects of high-glucose (HG) treatment in cultured VSMCs, and identifying associated molecular mechanisms.

Methods

Primary rat VSMCs were exposed to low or high glucose-containing medium with or without LIRA. They were challenged with HG in the presence of phosphatidylinositol 3-kinase (PI3K), extracellular signal-regulated kinase (ERK)1/2, or glucagon-like peptide receptor (GLP-1R) inhibitors. Cell proliferation and viability was evaluated using a Cell Counting Kit-8. Cell migration was determined by Transwell migration and scratch wound assays. Flow cytometry and Western blotting were used to determine apoptosis and protein expression, respectively.

Results

Under the HG treatment, VSMCs exhibited increased migration, proliferation, and phosphorylation of protein kinase B (Akt) and ERK1/2, along with reduced apoptosis (all p < 0.01 vs. control). These effects were significantly attenuated with LIRA co-treatment (all p < 0.05 vs. HG alone). Inhibition of PI3K kinase and ERK1/2 similarly attenuated the HG-induced effects (all p < 0.01 vs. HG alone). GLP-1R inhibitors effectively reversed the beneficial effects of LIRA on HG treatment (all p < 0.05).

Conclusions

HG treatment may induce abnormal phenotypes in VSMCs via PI3K and ERK1/2 signaling pathways activated by GLP-1R, and LIRA may protect cells from HG damage by acting on these same pathways.

The effects of pleiotrophin in proliferative diabetic retinopathy

Pleiotrophin (PTN), a secreted, multifunctional cytokine, is involved in angiogenic, fibrotic and neurodegenerative diseases. However, little is known about its effects on diabetic retinopathy, a neurovascular disease. To investigate the role of PTN in proliferative diabetic retinopathy (PDR), PTN concentration in the vitreous was evaluated in PDR patients and non-diabetic controls. PTN expression was observed in epiretinal membranes from patients. PTN knockdown was performed using small interfering (si)RNA, and the effects on retinal pigment epithelium (RPE) cells and human umbilical vascular endothelia cells (HUVECs) were observed in vitro under hyperglycemic and hypoxic conditions. Cell attachment, proliferation, migration, tube formation, cell cycle, apoptosis, extracellular signal-regulated kinase 1/2 (ERK 1/2) phosphorylation, and VEGF levels were studied. The vitreous PTN concentration in PDR patients was higher than that in non-diabetic controls, and PTN was highly expressed in the fibrovascular membranes of PDR patients. Under hyperglycemic and hypoxic conditions, PTN knockdown reduced cell attachment, proliferation, migration, and tube formation and induced cell cycle arrest and apoptosis in vitro. Mechanically, PTN depletion decreased ERK 1/2 phosphorylation. Recombinant PTN up regulated the concentration of VEGF in vitro, which can be attenuated by the ERK 1/2 inhibitor. Taken together, our results implied that elevated PTN in PDR patients might participate in the critical processes of the development of PDR, most likely playing roles in angiogenesis and proliferation, possibly by activating the ERK 1/2 pathway and regulating VEGF secretion. These findings provide new insight into the roles of PTN in PDR and suggest that PTN may become a new target for therapeutic intervention in PDR.

Thrombin stimulates VSMC proliferation through an EGFR-dependent pathway: involvement of MMP-2

In this study, the role of epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK1/2), heparin-binding EGF-like growth factor (HB-EGF), general metalloproteinases, matrix metalloproteinases-2 (MMP-2) in mediating the mitogenic action of thrombin in rat vascular smooth muscle cells (VSMC) was investigated. The incubation of rat VSMC with thrombin (1 U/ml) for 5 min resulted in significant (p < 0.001) increase of ERK1/2 phosphorylation by 8.7 ± 0.9-fold, EGFR phosphorylation by 8.5 ± 1.3-fold (p < 0.001) and DNA synthesis by 3.6 ± 0.4-fold (p < 0.001). Separate 30-min pretreatments with EGFR tyrosine kinase irreversible inhibitor, 10 µM PD169540 (PD), and 20 µM anti-HB-EGF antibody significantly reduced thrombin-stimulated EGFR and ERK1/2 phosphorylation by 81, 72 % and by 48 and 61 %, respectively. Furthermore, the same pretreatments with PD or anti-HB-EGF antibody reduced thrombin-induced VSMC proliferation by 44 and 45 %, respectively. In addition, 30-min pretreatments with 10 µM specific MMP-2 inhibitor significantly reduced thrombin-stimulated phosphorylation of both EGFR and ERK1/2 by 25 %. Moreover, the same pretreatment with MMP-2 inhibitor reduced thrombin-induced VSMC proliferation by 45 %. These results show that the thrombin-induced DNA synthesis correlates with the level of ERK1/2 activation rather than EGFR activation. These results further suggest that thrombin acts through EGFR and ERK 1/2 signaling pathways involving MMP-2 to upregulate proliferation of VSMC.

ATP stimulates PGE(2)/cyclin D1-dependent VSMCs proliferation via STAT3 activation: role of PKCs-dependent NADPH oxidase/ROS generation

Vascular smooth muscle cells (VSMCs) that function as synthetic units play important roles in cardiovascular diseases. Extracellular nucleotides, such as ATP, have been shown to act via activation of P2 purinoceptors implicated in various inflammatory diseases, we hypothesized that extracellular nucleotides contribute to vascular diseases via up-regulation of inflammatory proteins, including cyclooxygenase-2 (COX-2) and cytosolic phospholipase A2 (cPLA2) in VSMCs. However, the mechanisms of ATP-induced cPLA2 and COX-2 expression and PGE2 synthesis remain largely unclear. We showed that pretreatment with the inhibitors of STAT3 (CBE), NADPH oxidase [diphenyleneiodonium chloride (DPI) or apocynin (APO)], ROS [N-acetyl-l-cysteine (NAC)], and PKC (Ro-318220, Gö6983, or Rottlerin) or transfection with siRNAs of STAT3 and p47(phox) markedly inhibited ATPγS-induced cPLA2 and COX-2 mRNA/protein expression and promoter activity and PGE2 secretion. ATPγS further stimulated PKC, p47(phox), and STAT3 translocation. Moreover, ATPγS-induced STAT3 phosphorylation and translocation was inhibited by pretreatment with the inhibitors of PKC, NADPH oxidase, and ROS. ATPγS enhanced NADPH oxidase activity and ROS generation in VSMCs, which were reduced by pretreatment with Ro-318220, Gö6983, or Rottlerin. Finally, we found that ATPγS significantly induced cyclin D1 expression and VSMCs proliferation, which were inhibited by pretreatment with NAC, APO, DPI, Ro-318220, Gö6983, Rottlerin, or CBE or transfection with siRNAs of COX-2 and cyclin D1. We also demonstrated that ATPγS induced cyclin D1 expression via a PGE2-dependent pathway. These results suggested that ATPγS-induced cPLA2/COX-2 expression and PGE2 secretion is mediated through a PKC/NADPH oxidase/ROS/STAT3-dependent pathway in VSMCs.

Examining the role of insulin in the regulation of cardiovascular health

A substantial body of evidence has reported that insulin has direct actions on the cardiovascular system independent of its systemic effects on plasma glucose or lipids. In particular, insulin regulates endothelial synthesis of the vasoactive mediators nitric oxide and endothelin-1, yet the importance of this in the maintenance of cardiovascular health remains poorly understood. Recent studies using animals with targeted downregulation of insulin signaling in vascular tissues are improving our understanding of the role of insulin in vascular health. This article focuses on the direct actions of insulin in cardiovascular tissues, with particular emphasis on the molecular mechanisms of insulin action on endothelial function. The potential contribution of impaired vascular insulin action to the cardiovascular complications of diabetes will also be discussed.

The role of G protein coupled receptor kinases in neurocardiovascular pathophysiology

In coronary artery disease the G protein related kinases (GRKs) play a role in desensitization of β-adrenoreceptors (AR) after coronary occlusion. Targeted deletion and lowering of cardiac myocyte GRK-2 decreases the risk of post-ischemic heart failure (HF). Studies carried out in humans confirm the role of GRK-2 as a marker for the progression of HF after myocardial infarction (MI). The level of GRK-2 could be an indicator of β-AR blocker efficacy in patients with acute coronary syndrome. Elevated levels of GRK-2 are an early ubiquitous consequence of myocardial injury. In hypertension an increased level of GRK-2 was reported in both animal models and human studies. The role of GRKs in vagally mediated disorders such as vasovagal syncope and atrial fibrillation remains controversial. The role of GRKs in the pathogenesis of neurocardiological diseases provides an insight into the molecular pathogenesis process, opens potential therapeutic options and suggests new directins for scientific research.

Differential effects of formoterol on thrombin- and PDGF-induced proliferation of human pulmonary arterial vascular smooth muscle cells

Background

Increased pulmonary arterial vascular smooth muscle (PAVSM) cell proliferation is a key pathophysiological component of pulmonary vascular remodeling in pulmonary arterial hypertension (PH). The long-acting β₂-adrenergic receptor (β₂AR) agonist formoterol, a racemate comprised of (R,R)- and (S,S)-enantiomers, is commonly used as a vasodilator in chronic obstructive pulmonary disease (COPD). PH, a common complication of COPD, increases patients’ morbidity and reduces survival. Recent studies demonstrate that formoterol has anti-proliferative effects on airway smooth muscle cells and bronchial fibroblasts. The effects of formoterol and its enantiomers on PAVSM cell proliferation are not determined. The goals of this study were to examine effects of racemic formoterol and its enantiomers on PAVSM cell proliferation as it relates to COPD-associated PH.

Methods

Basal, thrombin-, PDGF- and chronic hypoxia-induced proliferation of primary human PAVSM cells was examined by DNA synthesis analysis using BrdU incorporation assay. ERK1/2, mTORC1 and mTORC2 activation were determined by phosphorylation levels of ERK1/2, ribosomal protein S6 and S473-Akt using immunoblot analysis.

Results

We found that (R,R) and racemic formoterol inhibited basal, thrombin- and chronic hypoxia-induced proliferation of human PAVSM cells while (S,S) formoterol had lesser inhibitory effect. The β₂AR blocker propranolol abrogated the growth inhibitory effect of formoterol. (R,R), but not (S,S) formoterol attenuated basal, thrombin- and chronic hypoxia-induced ERK1/2 phosphorylation, but had little effect on Akt and S6 phosphorylation levels. Formoterol and its enantiomers did not significantly affect PDGF-induced DNA synthesis and PDGF-dependent ERK1/2, S473-Akt and S6 phosphorylation in human PAVSM cells.

Conclusions

Formoterol inhibits basal, thrombin-, and chronic hypoxia-, but not PDGF-induced human PAVSM cell proliferation and ERK1/2, but has little effect on mTORC1 and mTORC2 signaling. Anti-proliferative effects of formoterol depend predominantly on its (R,R) enantiomer and require the binding with β₂AR. These data suggest that (R,R) formoterol may be considered as potential adjuvant therapy to inhibit PAVSM cell proliferation in COPD-associated PH.

Plasma leptin concentrations are greater in type II diabetic patients and stimulate monocyte chemotactic peptide-1 synthesis via the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway

Background

Leptin is an adipokine that is recently reported to be a biomarker of systemic inflammation. Although atherosclerosis causes cardiovascular diseases, it is not clear whether leptin contributes to the acceleration of this process. In this study, we investigated whether alterations of plasma leptin levels were related to diabetic nephropathy and systemic inflammation. In addition, we examined the physiologic action of leptin in cultured vascular smooth muscle cells (VSMCs).

Methods

A total of 126 type 2 diabetic participants and 37 healthy controls were studied. The diabetic participants were divided into three groups according to stage of nephropathy. We investigated whether leptin induced monocyte chemotactic peptide-1 (MCP-1) synthesis through the mitogen-activated protein kinase (MAPK) pathway using cultured VSMCs.

Results

Plasma leptin concentrations were significantly higher in the diabetic group than in the controls. Plasma leptin levels were positively correlated with body mass index, fasting and postprandial blood glucose, hemoglobin A1c, total cholesterol, urinary albumin excretion, high-sensitivity C-reactive protein (hsCRP), and MCP-1 plasma levels, and negatively correlated with creatinine clearance values. In cultured VSMCs, leptin increased MCP-1 production in a dose-dependent manner, and this stimulating effect of leptin on MCP-1 expression was reversed by the MAPK (MEK) inhibitor PD98059. In addition, leptin stimulated the phosphorylation of MEK, extracellular signal–regulated kinase, and E26-like transcription factor, which are components of the MAPK pathway.

Conclusions

Overall, these findings suggest that activation of leptin synthesis may promote MCP-1 activation in a diabetic environment via the MAPK pathway in VSMCs and that it possibly contributes to the acceleration of atherosclerosis.

Thrombin and vascular inflammation

Vascular endothelium is a key regulator of homeostasis. In physiological conditions it mediates vascular dilatation, prevents platelet adhesion, and inhibits thrombin generation. However, endothelial dysfunction caused by physical injury of the vascular wall, for example during balloon angioplasty, acute or chronic inflammation, such as in atherothrombosis, creates a proinflammatory environment which supports leukocyte transmigration toward inflammatory sites. At the same time, the dysfunction promotes thrombin generation, fibrin deposition, and coagulation. The serine protease thrombin plays a pivotal role in the coagulation cascade. However, thrombin is not only the key effector of coagulation cascade; it also plays a significant role in inflammatory diseases. It shows an array of effects on endothelial cells, vascular smooth muscle cells, monocytes, and platelets, all of which participate in the vascular pathophysiology such as atherothrombosis. Therefore, thrombin can be considered as an important modulatory molecule of vascular homeostasis. This review summarizes the existing evidence on the role of thrombin in vascular inflammation.

Dehydroepiandrosterone-induced phosphorylation and translocation of FoxO1 depend on the mineralocorticoid receptor

In humans, dehydroepiandrosterone (DHEA), with its sulfate, is the most abundant adrenal steroid, whereas the rat adrenals are not capable of synthesizing this steroid. Circulating concentrations of DHEA sulfate lie in the millimolar range and those of DHEA in the subnanomolar range. DHEA exerts protective potential during vascular remodeling, although the underlying mechanisms of this protection are imperfectly defined. We hypothesized that physiological doses of DHEA alter signaling pathways that are of central importance for vascular integrity. We exposed human endothelial cells, vascular smooth muscle cells, and fibroblasts to DHEA (10(-6) to 10(-10) mol/L) and observed a dose- and time-dependent increase of extracellular signal-regulated kinases 1 and 2 activation. Similar results were observed in rat vascular smooth muscle cells. In addition, in rat vascular smooth muscle cells, we found altered phosphorylation and cellular translocation of the transcription factor FoxO1. Pharmacological blockade of the mineralocorticoid receptor (MR) with eplerenone or small interfering RNA-mediated MR-silencing prevented DHEA-induced extracellular signal-regulated kinase 1/2 phosphorylation and its effects on FoxO1. Of note, in a cell-based MR transactivation assay, we did not find any agonist effect of DHEA on MR activity. We conclude that DHEA induces early signaling events in vascular cells that might underlie the DHEA-mediated protection against vasculopathies. These effects are dependent on the MR, although the finding that DHEA fails to act as a direct MR agonist suggests that additional signaling proteins are involved. In this regard, DHEA may either interact with coeffectors to modify MR activity or serves as a ligand for a yet unknown receptor that might transactivate the MR.