Yongsheng Gong

Apelin inhibits the proliferation and migration of rat PASMCs via the activation of PI3K/Akt/mTOR signal and the inhibition of autophagy under hypoxia

Apelin is highly expressed in the lungs, especially in the pulmonary vasculature, but the functional role of apelin under pathological conditions is still undefined. Hypoxic pulmonary hypertension is the most common cause of acute right heart failure, which may involve the remodeling of artery and regulation of autophagy. In this study, we determined whether treatment with apelin regulated the proliferation and migration of rat pulmonary arterial smooth muscle cells (SMCs) under hypoxia, and investigated the underlying mechanism and the relationship with autophagy. Our data showed that hypoxia activated autophagy significantly at 24 hrs. The addition of exogenous apelin decreased the level of autophagy and further inhibited pulmonary arterial SMC (PASMC) proliferation via activating downstream phosphatidylinositol‐3‐kinase (PI3K)/protein kinase B (Akt)/the mammalian target of Rapamycin (mTOR) signal pathways. The inhibition of the apelin receptor (APJ) system by siRNA abolished the inhibitory effect of apelin in PASMCs under hypoxia. This study provides the evidence that exogenous apelin treatment contributes to inhibit the proliferation and migration of PASMCs by regulating the level of autophagy.

Percutaneous Biphasic Electrical Stimulation for Treatment of Obstructive Sleep Apnea Syndrome

In this paper, we study the effect of stimulation of the genioglossus with percutaneous biphasic electrical pulses on patients with the obstructive sleep apnea syndrome (OSAS). The experiment was conducted in 22 patients clinically diagnosed with OSAS. The patients were monitored with polysomnography (PSG) in the trial. When the sleep apnea was detected, the genioglossus was stimulated with percutaneous biphasic electrical pulses that were automatically regulated by a microcontroller to achieve the optimal effect. The percutaneous biphasic electrical stimulation caused contraction of the genioglossus, forward movement of the tongue, and relieving of the glossopharyngeal airway obstruction. The SaO, apnea time, hypoxemia time, and change of respiratory disturbance index (RDI) were compared in patients with treatment and without treatment. With percutaneous biphasic electrical stimulation of the genioglossus, the OSAS patients showed apnea time decreased , RDI decreased , and SaO increased . No tissue injury or major discomfort was noticed during the trial. The stimulation of genioglossus with percutaneous biphasic electrical current pulse is an effective method for treating OSAS.

Chronic intermittent hypoxia induces atherosclerosis by NF-κB-dependent mechanisms

Chronic intermittent hypoxia (CIH) causes atherosclerosis in mice fed a high cholesterol diet (HCD). The mechanisms by which CIH promotes atherosclerosis are incompletely understood. This study defined the mechanistic role of NF-κB pathway in CIH+HCD induced atherosclerosis. Wild type (WT) and mice deficient in the p50 subunit of NF-κB (p50-KO) were fed normal chow diet (ND) or HCD, and exposed to sham or CIH. Atherosclerotic lesions on the en face aortic preparation and cross-sections of aortic root were examined. In WT mice, neither CIH nor HCD exposure alone caused, but CIH+HCD caused evident atherosclerotic lesions on both preparations after 20weeks of exposure. WT mice on ND and exposed to CIH for 35.6weeks did not develop atherosclerotic lesions. P50 gene deletion diminished CIH+HCD induced NF-κB activation and abolished CIH+HCD induced atherosclerosis. P50 gene deletion inhibited vascular wall inflammation, reduced hepatic TNF-α level, attenuated the elevation in serum cholesterol level and diminished macrophage foam cell formation induced by CIH+HCD exposure. These results demonstrate that inhibition of NF-κB activation abrogates the activation of three major atherogenic mechanisms associated with an abolition of CIH+HCD induced atherosclerosis. NF-κB may be a central common pathway through which CIH+HCD exposure activates multiple atherogenic mechanisms, leading to atherosclerosis.

4-PBA inhibits LPS-induced inflammation through regulating ER stress and autophagy in acute lung injury models

Acute lung injury (ALI) is a common clinical disorder that causes substantial health problems worldwide. An excessive inflammatory response is the central feature of ALI, but the mechanism is still unclear, especially the role of endoplasmic-reticulum (ER) stress and autophagy. To identify the cellular mechanism of lung inflammation during lipopolysaccharide (LPS)-induced mouse model of ALI, we investigated the influence of classic ER stress inhibitor 4-phenyl butyric acid (4-PBA) on ER stress and autophagy, which partially affect the activation of inflammation, both in LPS-induced ALI mouse model and human alveolar epithelial cell model. We demonstrated that 4-PBA, which further prevented the activation of the NF-κB pathway, decreased the release of the pro-inflammatory mediators IL-1β, TNF-α and IL-6, significantly inhibited LPS-activated ER stress. Moreover, it was found that autophagy was also decreased by the treatment of 4-PBA, which may play a protective role in ALI models through the classical AKT/mTOR signaling pathway. Inhibition of autophagy by 3-MA exacerbates cytotoxicity induced by LPS in A549 alveolar epithelial cells. Taken together, our study indicated that ER stress is a key promoter in the induction of inflammation by LPS, the protective effect of 4-PBA is related to the inhibition of ER stress and autophagy in LPS-induced ALI models. Furthermore, the role of autophagy that contributes to cell survival may depend on the activation of ER stress.

The Apelin-APJ Axis Is an Endogenous Counterinjury Mechanism in Experimental Acute Lung Injury

BACKGROUND Although the mechanisms and pathways mediating ARDS have been studied extensively, less attention has been given to the mechanisms and pathways that counteract injury responses. This study found that the apelin-APJ pathway is an endogenous counterinjury mechanism that protects against ARDS. METHODS Using a rat model of oleic acid (OA)-induced ARDS, the effects of ARDS on apelin and APJ receptor expressions and on APJ receptor binding capacity were examined. The protective effect of activating the apelin-APJ pathway against OA- or lipopolysaccharide (LPS)-induced ARDS was evaluated. RESULTS ARDS was coupled to upregulations of the apelin and APJ receptor. Rats with OA-induced ARDS had higher lung tissue levels of apelin proprotein and APJ receptor expressions; elevated plasma, BAL fluid (BALF), and lung tissue levels of apelin-36 and apelin-12/13; and an increased apelin-APJ receptor binding capacity. Upregulation of the apelin-APJ system has important pathophysiologic function. Stimulation of the apelin-APJ signaling using receptor agonist apelin-13 alleviated, whereas inhibition of the apelin-APJ signaling using receptor antagonist [Ala]-apelin-13 exacerbated, OA-induced lung pathologies, extravascular lung water accumulation, capillary-alveolar leakage, and hypoxemia. The APJ receptor agonist inhibited, and the APJ receptor antagonist augmented, OA-induced lung tissue and BALF levels of tumor necrosis factor-α and monocyte chemoattractant protein-1, and plasma and lung tissue levels of malondialdehyde. Postinjury treatment with apelin-13 alleviated lung inflammation and injury and improved oxygenation in OA- and LPS-induced lung injury. CONCLUSIONS The apelin-APJ signaling pathway is an endogenous anti-injury and organ-protective mechanism that is activated during ARDS to counteract the injury response and to prevent uncontrolled lung injury.

Blunted inflammation mediated by NF-κB activation in hippocampus alleviates chronic normobaric hypoxia-induced anxiety-like behavior in rats

This study aims to investigate whether inflammation mediated by NF-κB activation is involved in the induction of anxiety-like behavior in chronic normobaric hypoxia (CNH) exposed rats and to investigate the underlying mechanism. To this end, rats were exposed in a normobaric hypoxic chamber with a fraction of inspired oxygen (FIO2) of ∼ 10%, 23 h/d, continues for 2 weeks. Anxiety-like behavior was tested by elevated plus maze and open field, inflammatory response, nucleus translocation of NF-κB, and signaling pathway in hippocampus were examined. CNH induced a significant increase of anxiety- like behavior and inflammation responses, which were ameliorated by NF-κB inhibitor, PDTC pretreatment, suggesting that the anxiogenic effect induced by inflammation is through NF-κB activation. CNH treatment significantly increased nucleus translocation of p65 and p105 in hippocampus, which was suppressed by PDTC pretreatment. In addition, CNH treatment significantly increased Iba-1, iNOS, COX-2, and p-PKA in hippocampus, which were blocked by PDTC pretreatment, suggesting CNH may activate microglia cells in hippocampus through NF-κB pathway. In conclusion, our results illustrate a mechanism that, activation of NF-κB in hippocampus may trigger the proinflammatory response of microglia cells, and iNOS-PKA pathway may involve in anxiogenic effect in CNH exposed rats.

Intermedin modulates hypoxic pulmonary vascular remodeling by inhibiting pulmonary artery smooth muscle cell proliferation

BACKGROUND Hypoxic pulmonary arterial hypertension (PAH) is a disabling disease with limited treatment options. Hypoxic pulmonary vascular remodeling is a major cause of hypoxic PAH. Pharmacological agents that can inhibit the remodeling process may have great therapeutic value. OBJECTIVE To examine the effect of intermedin (IMD), a new calcitonin gene-related peptide family of peptide, on hypoxic pulmonary vascular remodeling. METHODS Rats were exposed to normoxia or hypoxia (∼10% O(2)), or exposed to hypoxia and treated with IMD, administered by an implanted mini-osmotic pump (6.5 μg/rat/day), for 4 weeks. The effects of IMD infusion on the development of hypoxic PAH and right ventricle (RV) hypertrophy, on pulmonary vascular remodeling, on pulmonary artery smooth muscle cell (PASMC) proliferation and apoptosis, and on the activations of l-arginine nitric oxide (NO) pathway and endoplasmic reticulum stress apoptotic pathway were examined. RESULTS Rats exposed to hypoxia developed PAH and RV hypertrophy. IMD treatment alleviated PAH and prevented RV hypertrophy. IMD inhibited hypoxic pulmonary vascular remodeling as indicated by reduced wall thickness and increased lumen diameter of pulmonary arterioles, and decreased muscularization of distal pulmonary vasculature in hypoxia-exposed rats. IMD treatment inhibited PASMC proliferation and promoted PASMC apoptosis. IMD treatment increased tissue level of constitutive NO synthase activity and tissue NO content in lungs, and enhanced l-arginine uptake into pulmonary vascular tissues. IMD treatment increased cellular levels of glucose-regulated protein (GRP) 78 and GRP94, two major markers of endoplasmic reticulum (ER) stress, and increased caspase-12 expression, the ER stress-specific caspase, in lungs and cultured PASMCs. CONCLUSIONS These results demonstrate that IMD treatment attenuates hypoxic pulmonary vascular remodeling, and thereby hypoxic PAH mainly by inhibiting PASMC proliferation. Promotion of PASMC apoptosis may also contribute to the inhibitory effect of IMD. Activations l-arginine-NO pathway and of ER stress-specific apoptosis pathway could be the mechanisms mediating the anti-proliferative and pro-apoptotic effects of IMD.

Chronic Normobaric Hypoxia Induces Pulmonary Hypertension in Rats: Role of NF-κB

To investigate whether nuclear factor-kappa B (NF-κB) activation is involved in chronic normobaric hypoxia-induced pulmonary hypertension (PH), rats were treated with saline or an NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC, 150 mg/kg, sc, twice daily), and exposed to normoxia or chronic normobaric hypoxia with a fraction of inspired oxygen of ∼0.1 for 14 days. Lung tissue levels of NF-κB activity, and interleukin (IL)-1β, IL-6, and cyclooxygenase-2 mRNAs, were determined, and mean pulmonary arterial pressure, right ventricular hypertrophy, and right heart function were evaluated. Compared to the normoxia exposure group, rats exposed to chronic normobaric hypoxia showed an increased NF-κB activity, measured by increased nuclear translocation of p50 and p65 proteins, an increased inflammatory gene expression in the lungs, elevated mean pulmonary arterial blood pressure and mean right ventricular pressure, right ventricular hypertrophy, as assessed by right ventricle-to-left ventricle plus septum weight ratio, and right heart dysfunction. Treatment of hypoxia-exposed rats with PDTC inhibited NF-κB activity, decreased pulmonary arterial blood pressure and right ventricular pressure, and ameliorated right ventricular hypertrophy and right heart dysfunction. Hypoxia exposure increased protein kinase C activity and promoted pulmonary artery smooth muscle cell proliferation in vitro. Our data suggest that NF-κB activation may contribute to chronic normobaric hypoxia-induced PH.

Amelioration of apelin-13 in chronic normobaric hypoxia-induced anxiety-like behavior is associated with an inhibition of NF-κB in the hippocampus

Apelin, a small bioactive peptide, plays an important role in the pathogenesis of mood disorders through the endogenous ligand APJ. Although the anxiolytic effect of apelin is well established, the mechanisms are poorly understood. In this study, we hypothesized that apelin played an anxiolytic role in chronic normobaric hypoxia (CNH)-induced anxiety like behavior in mice, which might be associated with an inhibition of nuclear factor-κB (NF-κB) activation in the hippocampus. To this end, mice were exposed in a normobaric hypoxic chamber with a fraction of inspired oxygen (FIO2, ∼10%, 23h/d) with or without apelin-13 application (20 nmolkg-1d-1, i.p.), for 4 weeks. The anxiety-like behavior was tested by elevated plus maze and open field. Activities of NF-κB, microglial, and related signaling pathways in the hippocampus during this pathological process were examined. We found that CNH treatment decreased APJ but increased Iba-1 proteins expression, as well as nucleus translocation of p50 and p65 in the hippocampus, which were reversed by apelin-13 treatment. In addition, apelin-13 treatment ameliorated CNH-induced anxiety-like behavior in mice, suggesting anxiogenic effect of apelin-13 might be mediated by an inhibition of NF-κB activation in microglial of the hippocampus. Furthermore, apelin-13 treatment reversed p-CAMKII decrease in the hippocampus under CNH treatment. Apelin-13 treatment did not affect anxiety-like behavior and relative proteins expression in normoxia control mice. Finally, we found that rats with CNH treatment decreased APJ expression while enhanced NF-κB activation in the hippocampus, providing additional evidences that NF-κB activation in hippocampus in CNH-induced anxiety-like behavior in rats we reported previously might be associated with an inhibition of APJ activity. In conclusion, the present results illustrated that inhibition of APJ and promotion of NF-κB activation in the microglial of hippocampus might be involved in anxiogenic effect in CNH-exposed mice, and apelin-13 ameliorates CNH-induced anxiety-like behavior might be associated with an inhibition of NF-κB activation.

Cardiac β2-Adrenergic Receptor Phosphorylation at Ser355/356 Regulates Receptor Internalization and Functional Resensitization.

Previous studies have demonstrated that β2-adrenergic receptors (β2ARs) can be phosphorylated by G protein-coupled receptor kinases (GRKs) and protein kinase A (PKA), affecting β2AR internalization and desensitization. However, the exact physiological function of β2ARs in cardiomyocytes is unknown. In this study, we showed that neonatal mouse cardiomyocytes had different contraction and internalization responses to sustained or repeated, transient agonist stimulation. Specifically, short-time stimulation (10 min) with epinephrine or norepinephrine increased the cardiomyocyte contraction rate, reaching a maximum at 5 min, followed by a slow decline. When the agonist was re-added after a 60-min wash-out period, the increase in the cardiomyocyte contraction rate was similar to the initial response. In contrast, when cardiomyocytes were exposed continuously to epinephrine or norepinephrine for 60 min, the second agonist stimulation did not increase the contraction response. These results indicated that continuous β2AR stimulation caused functional desensitization. Phosphorylation of β2ARs at serine (Ser)355/356 GRK phosphorylation sites, but not at Ser345/346 PKA phosphorylation sites increased with continuous epinephrine stimulation for 60 min. Accordingly, β2AR internalization increased. Interestingly, β2AR internalization was blocked by mutations at the GRK phosphorylation sites, but not by mutations at the PKA phosphorylation sites. Furthermore, inhibition of β2AR dephosphorylation by okadaic acid, a phosphatase 2A inhibitor, impaired the recovery of internalized β2ARs and reduced the cardiomyocyte contraction rate in response to epinephrine. Finally, epinephrine treatment induced the physical interaction of β-arrestin with internalized β2ARs in cardiomyocytes. Together, these data revealed the essential role of the Ser355/356 phosphorylation status of β2ARs in regulating receptor internalization and physiological resensitization in neonatal cardiomyocytes to contraction functions.