Role of PI3K/Akt/mTOR pathway-mediated macrophage autophagy in affecting the phenotype transformation of lung fibroblasts induced by silica dust exposure

SIRT5 Inhibits Mitophagy and Inflammation of Hypoxia-Induced Pulmonary Hypertension by Regulating the Desuccinylation of PDK1

Hypoxia-induced pulmonary hypertension (HPH), a consequence of lung pathologies, is linked to changes in immune responses and inflammation. SIRT5 is recognized as the only enzyme capable of removing succinyl groups. The focus of this research was to explore the involvement of SIRT5 in HPH and to elucidate the associated mechanisms. Models simulating HPH were created in both living organisms and controlled laboratory settings under conditions of low oxygen. To investigate autophagy, transmission electron microscopy (TEM) was employed for ultrastructural analysis, while reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot were used to measure the expression of autophagy-related genes. Cell viability was determined using the cell counting kit-8 (CCK-8) assay. The concentrations of inflammatory cytokines were quantified using ELISA, and flow cytometry was applied to evaluate reactive oxygen species (ROS) levels. To explore the interaction between PDK1 and SIRT5, co-immunoprecipitation (Co-IP) followed by Western blot analysis was conducted. Findings revealed that low oxygen conditions prompted mitophagy and elevated levels of both mRNA and proteins associated with this process in experiments conducted in organisms as well as in cellular models. Under conditions of low oxygen, the expression of SIRT5 was found to be reduced. Hypoxia enhanced cell viability, ROS level, angiogenesis-related protein levels, and inflammatory cytokine levels in pulmonary microvascular endothelial cells (PMVECs), effects that were reversed upon SIRT5 overexpression. Mechanistically, SIRT5 interacted with PDK1, desuccinylating PDK1 and thereby inhibiting mitophagy and inflammation associated with HPH. In conclusion, SIRT5 inhibited mitophagy and inflammation in HPH by regulating the desuccinylation of PDK1, potentially offering effective therapeutic strategies for treating HPH.

Bone marrow mesenchymal stem cell-derived extracellular vesicles alleviate diabetes-exacerbated atherosclerosis via AMPK/mTOR pathway-mediated autophagy-related macrophage polarization

INTRODUCTION

Bone marrow-derived mesenchymal stem cell-derived extracellular vesicles (BMSC-EVs) are widely used for therapeutic purposes in preclinical studies. However, their utility in treating diabetes-associated atherosclerosis remains largely unexplored. Here, we aimed to characterize BMSC-EV-mediated regulation of autophagy and macrophage polarization.

METHODS

EVs were isolated from the supernatant of cultured BMSCs and characterized with transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blotting. A diabetes-related atherosclerotic ApoE-/- mouse model was established through feeding with a high-fat diet (HFD) and streptozotocin (STZ). Histopathological analyses were carried out using Oil Red O, H&E, and Masson staining of the aorta. TEM and immunohistochemistry (IHC) were applied to evaluate autophagy, and immunofluorescence (IF) was used to identify macrophage polarization. RAW264.7 macrophages were induced with oxidized low-density lipoprotein (ox-LDL) and high glucose (HG), co-cultured with BMSC-EVs, and analyzed for macrophage proliferation, migration, and foam cell formation. RAW264.7 cells were transduced with autophagy marker mRFP-GFP-LC3 lentivirus and analyzed with IF and western blotting.

RESULTS

Diabetic mice (DA group) had larger aortic plaque areas and lower collagen content than the HFD mice. BMSC-EV treatment significantly reduced blood glucose, LDL levels, and aortic plaque areas while increasing collagen content. BMSC-EV-treated aortas contained a higher number of autophagosomes/autolysosomes, with increased expression of LC3BII correlating with decreased P62 levels and a lower proportion of M1 macrophages. In vitro, BMSC-EVs inhibited proliferation, migration, and foam cell formation in ox-LDL and HG-induced activated RAW264.7 cells. These effects were reversed by the autophagy blocker bafilomycin A1. Consistent with the in vivo findings, BMSC-EVs elevated levels of the autophagy-related protein LC3BII/I and decreased P62 in ox-LDL and HG-induced RAW264.7 cells. These cells also expressed the M1 macrophage markers CD86 and iNOS, but showed reduced expression of the M2 marker Arg-1. Further, BMSC-EVs decreased AMPKα and mTOR phosphorylation levels, which were blocked by the AMPK inhibitor compound C.

CONCLUSIONS

BMSC-EVs attenuate diabetes-exacerbated atherosclerosis by inhibiting vascular macrophage proliferation, migration, and foam cell formation via AMPK/mTOR signaling-regulated autophagy and macrophage polarization. BMSC-EVs thus hold promise as therapeutic agents for atherosclerosis.

RNA Expression of MMP12 Is Strongly Associated with Inflammatory Bowel Disease and Is Regulated by Metabolic Pathways in RAW 264.7 Macrophages

Macrophage metalloelastase or matrix metalloproteinase-12 (MMP12) is a macrophage-specific proteolytic enzyme involved in the physiopathology of many inflammatory diseases, including inflammatory bowel disease. Although previously published data suggested that the modulation of MMP12 in macrophages could be a determinant for the development of intestinal inflammation, scarce information is available on the mechanisms underlying the regulation of MMP12 expression in those phagocytes. Therefore, in this study, we aimed to delineate the association of MMP12 with inflammatory bowel disease and the molecular events leading to the transcriptional control of this metalloproteinase. For that, we used publicly available transcriptional data. Also, we worked with the RAW 264.7 macrophage cell line for functional experiments. Our results showed a strong association of MMP12 expression with the severity of inflammatory bowel disease and the response to relevant biological therapies. In vitro assays revealed that the inhibition of mechanistic target of rapamycin complex 1 (mTORC1) and the stimulation of the AMP-activated protein kinase (AMPK) signaling pathway potentiated the expression of Mmp12. Additionally, AMPK and mTOR required a functional downstream glycolytic pathway to fully engage with Mmp12 expression. Finally, the pharmacological inhibition of MMP12 abolished the expression of the proinflammatory cytokine Interleukin-6 (Il6) in macrophages. Overall, our findings provide a better understanding of the mechanistic regulation of MMP12 in macrophages and its relationship with inflammation.