BRG1 Deficiency Promotes Cardiomyocyte Inflammation and Apoptosis by Activating the cGAS-STING Signaling in Diabetic Cardiomyopathy.

Brahma-related gene 1 (BRG1) has been implicated in the repair of DNA double-strand breaks (DSBs). Downregulation of BRG1 impairs DSBs repair leading to accumulation of double-stranded DNA (dsDNA). Currently, the role of BRG1 in diabetic cardiomyopathy (DCM) has not been clarified. In this study, we aimed to explore the function and molecular by which BRG1 regulates DCM using mice and cell models. We found that BRG1 was downregulated in the cardiac tissues of DCM mice and in cardiomyocytes cultured with high glucose and palmitic acid (HG/PA), which was accompanied by accumulation of dsDNA and activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway. shRNA-mediated Brg1 knockdown aggravated DCM mice cardiac functions, enhanced dsDNA accumulation, cGAS-STING signaling activation, which induced inflammation and apoptosis. In addition, the results were further verified in HG/PA-treated primary neonatal rat cardiomyocytes (NRCMs). Overexpression of BRG1 in NRCMs yielded opposite results. Furthermore, a selective cGAS inhibitor RU.521 or STING inhibitor C-176 partially reversed the BRG1 knockdown-induced inflammation and apoptosis in vitro. In conclusion, our results demonstrate that BRG1 is downregulated during DCM in vivo and in vitro, resulting in cardiomyocyte inflammation and apoptosis due to dsDNA accumulation and cGAS-STING signaling activation. Therefore, targeting the BRG1-cGAS-STING pathway may represent a novel therapeutic strategy for improving cardiac function of patients with DCM.

Mesenchymal Stem Cell-Derived Exosomes Attenuate Murine Cytomegalovirus-Infected Pneumonia via NF-κB/NLRP3 Signaling Pathway.

Reactivation and infection with cytomegalovirus (CMV) are frequently observed in recipients of solid organ transplants, bone marrow transplants, and individuals with HIV infection. This presents an increasing risk of allograft rejection, opportunistic infection, graft failure, and patient mortality. Among immunocompromised hosts, interstitial pneumonia is the most critical clinical manifestation of CMV infection. Recent studies have demonstrated the potential therapeutic benefits of exosomes derived from mesenchymal stem cells (MSC-exos) in preclinical models of acute lung injury, including pneumonia, ARDS, and sepsis. However, the role of MSC-exos in the pathogenesis of infectious viral diseases, such as CMV pneumonia, remains unclear. In a mouse model of murine CMV-induced pneumonia, we observed that intravenous administration of mouse MSC (mMSC)-exos reduced lung damage, decreased the hyperinflammatory response, and shifted macrophage polarization from the M1 to the M2 phenotype. Treatment with mMSC-exos also significantly reduced the infiltration of inflammatory cells and pulmonary fibrosis. Furthermore, in vitro studies revealed that mMSC-exos reversed the hyperinflammatory phenotype of bone marrow-derived macrophages infected with murine CMV. Mechanistically, mMSC-exos treatment decreased activation of the NF-κB/NLRP3 signaling pathway both in vivo and in vitro. In summary, our findings indicate that mMSC-exo treatment is effective in severe CMV pneumonia by reducing lung inflammation and fibrosis through the NF-κB/NLRP3 signaling pathway, thus providing promising therapeutic potential for clinical CMV infection.

Necroptosis contributes to the cyclosporin A-induced cytotoxicity in NRK-52E cells.

Cyclosporin A (CsA) induces renal tubular epithelial cells apoptosis and necrosis following in vitro exposure. The mechanisms of CsA-induced apoptosis have been studied intensively, whereas the mechanisms of necrosis remain to be elucidated. Necroptosis has been described as programmed necrosis. This study investigated the ability of CsA to induce necroptosis in the rat tubular cell line NRK-52E. The NRK-52E cells were incubated with CsA for 24 hours with or without necrostatin-1 (Nec-1). The majority of the NRK-52E cells died of necrosis as indicated by LDH leakage, Hoechst 33342/PI staining, and flow cytometry analysis. Cell death was significantly reduced by Nec-1 pretreated before CsA exposure. CsA-induced apoptosis and necrosis were also compared in NRK-52E cells with or without knockdown of receptor interaction protein 3 (RIP3) expression using small interfering RNA. Moreover, the role of reactive oxygen species (ROS) in CsA-induced cell death was also attempted. The result suggests that necroptosis contributes to the CsA-induced cytotoxicity in NRK-52E cells. Meanwhile, RIP3 and ROS are involved in CsA-induced necroptosis. To our knowledge, this is the first report on necroptosis in CsA-induced renal tubular cell death pathways, which might offer a novel protective target for CsA nephrotoxicity.

Protective effect of 2-deoxy-D-glucose on the cytotoxicity of cyclosporin A in vitro.

The present study aimed to investigate the mechanism underlying the protective effect of 2-deoxy-D-glucose (2-DG) on the cytotoxicity of cyclosporin A (CsA) in vitro using NRK-52E cells. Staining with Hoechst 33342/propidium iodide prior to flow cytometric analysis was performed to assess the rate of cellular apoptosis and necrosis induced by CsA. The expression levels of lactate dehydrogenase (LDH), caspase 3, receptor-interacting protein kinase 3 (RIP3), reactive oxygen species (ROS), glutathione (GSH) and malondialdehyde (MDA) were detected using colorimetry, ELISA, western blotting or flow cytometric analysis to determine the protective effects of 2-DG on CsA-induced cell death. The results demonstrated that 2-DG inhibited the release of LDH, the activation of caspase 3 and the generation of ROS induced by CsA, but had no effect on the expression of RIP3. Treatment with 2-DG increased the expression of GSH and decreased the expression of MDA in dose-dependent manner, and reduced the rate of the cellular apoptosis and necrosis induced by CsA. Therefore, 2-DG inhibited CsA-induced cellular apoptosis and necrosis, possibly by reducing the production of ROS. Inhibiting the activation of caspase 3 is one of the protective mechanisms of 2-DG, however, the expression of RIP3 remained unaltered following treatment with 2-DG. Whether 2-DG inhibits the CsA-induced necrosis and apoptosis by inhibiting the RIP3 signaling pathway remains to be elucidated.

Protective effects of 2-deoxy-D-glucose on nephrotoxicity induced by cyclosporine A in rats.

OBJECTIVE: This study aims to explore the protective effect mechanism of 2-deoxy-D-glucose on nephrotoxicity of cyclosporin A in vivo. METHOD: Renal toxicity of SD rats model induced by CsA was established. Serum creatinine, blood urea nitrogen, urine NAG, GSH and MDA were determined and the histopathological changes of rat renal cortex were observed to explore the protective effects of 2-DG on CsA-induced nephrotoxicity. RESULTS: Serum creatinine, BUN and urinary NAG of rats were significantly changed in experimental groups. Pathological results showed that there was obvious renal tubular injury in model group, however, the renal injury was significantly reduced in pre-treated with 2-DG. CONCLUSIONS: 2-DG had obvious protective effect on nephrotoxicity especially with high dose. This protective effect could be related to the reduction of ROS induced by CsA. However, 2-DG had no effect on the expression of RIP3.

Endoplasmic reticulum stress mediates aristolochic acid I-induced apoptosis in human renal proximal tubular epithelial cells.

Aristolochic acid (AA), derived from the Aristolochia species, has been associated with aristolochic acid nephropathy (AAN), which has emerged as a worldwide disease. Aristolochic acid I (AAI) is the main ingredient of AA, and the underlying mechanisms for AAI-induced nephrotoxicity are still unclear. In this study, we investigated whether endoplasmic reticulum (ER) stress was involved in AAI-induced nephrotoxicity. The results showed that treatment of HK-2 cells (a human proximal tubular epithelial cell line) with AAI caused an increase in eukaryotic initiation factor-2α (eIF2α) phosphorylation, X-box binding protein 1 (XBP1) mRNA splicing and the expression of glucose-regulated protein (GRP) 78 and CAAT/enhancer-binding protein-homologous protein (CHOP). These events represent typical markers of the ER stress-related signaling pathway. Pretreatment with 4-phenylbutyrate (4-PBA) or salubrinal (Sal) significantly inhibited AAI-induced apoptosis, indicating the role of ER stress in AAI-induced apoptosis. In addition, AAI-induced cell death followed an increase of reactive oxygen species (ROS) formation in HK-2 cells. Pretreatment with N-acetyl cysteine (NAC) or glutathione (GSH) significantly inhibited AAI-induced ER stress proteins and cell death, suggesting that ROS mediate AAI-induced ER stress. Taken together, these results suggest that the ER stress response is involved in apoptosis induced by AAI in HK-2 cells, thus offering a new insight into the nephrotoxicity of AAI.

The endoplasmic reticulum stress response is involved in apoptosis induced by aloe-emodin in HK-2 cells.

Aloe-emodin (AE; 1,8-dihydroxy-3-hydroxymethyl-9,10-anthracenedione) is one of the primary active compounds in total rhubarb anthraquinones (TRAs), which induce nephrotoxicity in rats. However, it is still not known whether AE has a similar effect on human kidney cells. In this study, 3-(4,5,-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays showed that AE decreases the viability of HK-2 cells (a human proximal tubular epithelial cell line) in a dose- and time-dependent manner. AE induced G2/M arrest of cell cycle in HK-2 cells, which was detected with propidium iodide (PI) staining. This apoptosis was further investigated by Hoechst staining, transmission electron microscopy (TEM), DNA fragmentation, and Annexin V/PI staining. Apoptosis of the cells was associated with caspase 3 activation, which was detected by Western blot analysis and a caspase activity assay. In addition, changes in the endoplasmic reticulum (ER) ultrastructure as observed by TEM showed the effects of AE on ER. Treatment with AE also resulted in an increase in eukaryotic initiation factor-2α (eIF-2α) phosphorylation, X-box binding protein 1 (XBP1) mRNA splicing, c-Jun N-terminal kinase (JNK) phosphorylation, glucose-regulated protein (GRP) 78 and CAAT/enhancer-binding protein-homologous protein (CHOP) accumulation. These results suggest that AE induces ER stress in HK-2 cells, which is involved in AE-induced apoptosis. In conclusion, AE induces apoptosis in HK-2 cells, and the ER stress is involved in AE-induced apoptosis in vitro. The implications of the toxic effects of AE for clinical use are unclear and these findings should be taken into account in the risk assessment for human exposure.