Endophilin A2-mediated alleviation of endoplasmic reticulum stress-induced cardiac injury involves the suppression of ERO1α/IP3R signaling pathway.

Cardiac injury upon myocardial infarction (MI) is the leading cause of heart failure. The present study aims to investigate the role of EndoA2 in ischemia-induced cardiomyocyte apoptosis and cardiac injury. In vivo, we established an MI mouse model by ligating the left anterior descending (LAD) coronary artery, and intramyocardial injection of adenoviral EndoA2 (Ad-EndoA2) was used to overexpress EndoA2. In vitro, we used the siRNA and Ad-EndoA2 transfection strategies. Here, we reported that EndoA2 expression was remarkably elevated in the infarct border zone of MI mouse hearts and neonatal rat cardiomyocytes (NRCMs) stimulated with oxygen and glucose deprivation (OGD) which mimicked ischemia. We showed that intramyocardial injection of Ad-EndoA2 attenuated cardiomyocyte apoptosis and reduced endoplasmic reticulum (ER) stress in response to MI injury. Using siRNA for knockdown and Ad-EndoA2 for overexpression, we validated that knockdown of EndoA2 in NRCMs exacerbated OGD-induced NRCM apoptosis, whereas overexpression of EndoA2 attenuates OGD-induced cardiomyocyte apoptosis. Mechanistically, knockdown of EndoA2 activated ER stress response, which increases ER oxidoreductase 1α (ERO1α) and inositol 1, 4, 5-trisphosphate receptor (IP3R) activity, thus led to increased intracellular Ca2+ accumulation, followed by elevated calcineurin activity and nuclear factor of activated T-cells (NFAT) dephosphorylation. Pretreatment with the IP3R inhibitor 2-Aminoethoxydiphenylborate (2-APB) attenuated intracellular Ca2+ accumulation, and pretreatment with the Ca2+ chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) or the calcineurin inhibitor Cyclosporin A (CsA) inhibited EndoA2-knockdown-induced NRCM apoptosis. Overexpression of EndoA2 led to the opposite effects by suppressing ER-stress-mediated ERO1α/IP3R signaling pathway. This study demonstrated that EndoA2 protected cardiac function in response to MI via attenuating ER-stress-mediated ERO1α/IP3R signaling pathway. Targeting EndoA2 is a potential therapeutic strategy for the prevention of postinfarction-induced cardiac injury and heart failure.

EndophilinA2 protects against angiotensin II-induced cardiac hypertrophy by inhibiting angiotensin II type 1 receptor trafficking in neonatal rat cardiomyocytes.

Cardiac hypertrophy is one of the major risk factors for chronic heart failure. The role of endophilinA2 (EndoA2) in clathrin-mediated endocytosis and clathrin-independent endocytosis is well documented. In the present study, we tested the hypothesis that EndoA2 protects against angiotensin II (Ang II)-induced cardiac hypertrophy by mediating intracellular angiotensin II type 1 receptor (AT1-R) trafficking in neonatal rat cardiomyocytes (NRCMs). Cardiac hypertrophy was evaluated by using cell surface area and quantitative RT-PCR (qPCR) analyses. For the first time, we found that EndoA2 attenuated cardiac hypertrophy and fibrosis induced by Ang II. Moreover, EndoA2 inhibited apoptosis induced by excessive endoplasmic reticulum stress (ERS), which accounted for the beneficial effects of EndoA2 on cardiac hypertrophy. We further revealed that there was an interaction between EndoA2 and AT1-R.The expression levels of EndoA2, which inhibits AT1-R transport from the cytoplasm to the membrane, and the interaction between EndoA2 and AT1-R were obviously decreased after Ang II treatment. Furthermore, Ang II inhibited the co-localization of AT1-R with GRP-78, which was reversed by EndoA2 overexpression. In conclusion, our results suggested that EndoA2 plays a role in protecting against cardiac hypertrophy induced by Ang II, possibly by inhibiting AT1-R transport from the cytoplasm to the membrane to suppress signal transduction.

Apigenin C-glycosides of Microcos paniculata protects lipopolysaccharide induced apoptosis and inflammation in acute lung injury through TLR4 signaling pathway.

Acute lung injury (ALI) and its more severe form acute respiratory distress syndrome (ARDS) are life-threatening conditions with high morbility and mortality, underscoring the urgent need for novel treatments. Leaves of the medicinal herb Microcos paniculata have been traditionally used for treating upper airway infections, by virtue of its content of flavonoids such as apigenin C-glycosides (ACGs). C-glycosides have been shown to exert strong anti-inflammatory properties, although their mechanism of action remains unknown. Herein, hypothesizing that ACGs from M. paniculata inhibit progression of ALI, we used the experimental model of lipopolysaccharide (LPS)-induced ALI in BALB/c mice to evaluate the therapeutic potential of purified ACGs. Our results showed that M. paniculata ACGs inhibited lung inflammation in animals undergoing ALI. The protective effects of ACGs were assessed by determination of cytokine levels and in situ analysis of lung inflammation. ACGs reduced the pulmonary edema and microvascular permeability, demonstrating a dose-dependent down-regulation of LPS-induced TNF-α, IL-6 and IL-1ß expression in lung tissue and bronchoalveolar lavage fluid, along with reduced apoptosis. Moreover, metabolic profiling of mice serum and subsequent Ingenuity Pathway Analysis suggested that ACGs activated protective protein networks and pathways involving inflammatory regulators and apoptosis-related factors, such as JNK, ERK1/2 and caspase-3/7, suggesting that ACGs-dependent effects were related to MAPKs and mitochondrial apoptosis pathways. These results were further supported by evaluation of protein expression, showing that ACGs blocked LPS-activated phosphorylation of p38, ERK1/2 and JNK on the MAPKs signaling, and significantly upregulated the expression of Bcl-2 whilst down-regulated Bax and cleaved caspase-3. Remarkably, ACGs inhibited the LPS-dependent TLR4 and TRPC6 upregulation observed during ALI. Our study shows for the first time that ACGs inhibit acute inflammation and apoptosis by suppressing activation of TLR4/TRPC6 signaling pathway in a murine model of ALI. Our findings provide new evidence for better understanding the anti-inflammatory effects of ACGs. In this regard, ACGs could be exploited in the development of novel therapeutics for ALI and ARDS.

Autophagy is involved in the protective effect of endophilin A2 on H2O2-induced apoptosis in H9C2 cardiomyocytes.

Apoptosis plays a critical role in normal embryonic development and tissue homeostasis regulation. EndophilinA2 (EndoA2) is widely reported to regulate endocytosis. Additionally, EndoA2 has been demonstrated to be involved in tumor metastasis, neuroregulation and vascular function. In this study, we used siRNA and Ad-EndoA2 transfection strategy to investigate whether EndoA2 provides a protective effect against apoptosis induced by H2O2 in H9C2 cardiomyocytes and the underlying mechanisms. We found that EndoA2 siRNA knockdown promoted H2O2-induced apoptosis in H9C2 cardiomyocytes, evidenced by decreased cell number, increased apoptotic cells, and activation of caspase-3. In contrast, EndoA2 overexpression showed the opposite effects and inhibited H2O2-induced apoptosis in H9C2 cardiomyocytes. Further studies revealed that EndoA2 overexpression strengthened autophagy, evidenced by the increased LC3 II/I ratio and P62 degradation, whereas EndoA2 siRNA knockdown produced the opposite effects. Furthermore, we revealed that there was an interaction between Bif-1 and Beclin-1. Upon H2O2 treatment, the association of Bif-1 and Beclin-1 remarkably increased. EndoA2 overexpression further promoted the binding of Bif-1 with Beclin-1, whereas EndoA2 siRNA knockdown reduced this association. These data strongly suggested that EndoA2 inhibited H2O2-induced apoptosis in H9C2 cardiomyocytes, possibly by promoting Bif-1 to form a complex with Beclin-1 and strengthening autophagy. This study provides a novel target for heart diseases.