Pgc-1α Promotes Phosphorylation, Inflammation, and Apoptosis in H9c2 Cells During the Early Stage of Lipopolysaccharide Induction

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family in physiological and pathophysiological process and diseases

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family (PGC-1s), consisting of three members encompassing PGC-1α, PGC-1β, and PGC-1-related coactivator (PRC), was discovered more than a quarter-century ago. PGC-1s are essential coordinators of many vital cellular events, including mitochondrial functions, oxidative stress, endoplasmic reticulum homeostasis, and inflammation. Accumulating evidence has shown that PGC-1s are implicated in many diseases, such as cancers, cardiac diseases and cardiovascular diseases, neurological disorders, kidney diseases, motor system diseases, and metabolic disorders. Examining the upstream modulators and co-activated partners of PGC-1s and identifying critical biological events modulated by downstream effectors of PGC-1s contribute to the presentation of the elaborate network of PGC-1s. Furthermore, discussing the correlation between PGC-1s and diseases as well as summarizing the therapy targeting PGC-1s helps make individualized and precise intervention methods. In this review, we summarize basic knowledge regarding the PGC-1s family as well as the molecular regulatory network, discuss the physio-pathological roles of PGC-1s in human diseases, review the application of PGC-1s, including the diagnostic and prognostic value of PGC-1s and several therapies in pre-clinical studies, and suggest several directions for future investigations. This review presents the immense potential of targeting PGC-1s in the treatment of diseases and hopefully facilitates the promotion of PGC-1s as new therapeutic targets.

Inhibition of Pyruvate Dehydrogenase Kinase 4 Protects Cardiomyocytes from lipopolysaccharide-Induced Mitochondrial Damage by Reducing Lactate Accumulation

Mitochondrial dysfunction is considered one of the major pathogenic mechanisms of sepsis-induced cardiomyopathy (SIC). Pyruvate dehydrogenase kinase 4 (PDK4), a key regulator of mitochondrial metabolism, is essential for maintaining mitochondrial function. However, its specific role in SIC remains unclear. To investigate this, we established an in vitro model of septic cardiomyopathy using lipopolysaccharide (LPS)-induced H9C2 cardiomyocytes. Our study revealed a significant increase in PDK4 expression in LPS-treated H9C2 cardiomyocytes. Inhibiting PDK4 with dichloroacetic acid (DCA) improved cell survival, reduced intracellular lipid accumulation and calcium overload, and restored mitochondrial structure and respiratory capacity while decreasing lactate accumulation. Similarly, Oxamate, a lactate dehydrogenase inhibitor, exhibited similar effects to DCA in LPS-treated H9C2 cardiomyocytes. To further validate whether PDK4 causes cardiomyocyte and mitochondrial damage in SIC by promoting lactate production, we upregulated PDK4 expression using PDK4-overexpressing lentivirus in H9C2 cardiomyocytes. This resulted in elevated lactate levels, impaired mitochondrial structure, and reduced mitochondrial respiratory capacity. However, inhibiting lactate production reversed the mitochondrial dysfunction caused by PDK4 upregulation. In conclusion, our study highlights the pathogenic role of PDK4 in LPS-induced cardiomyocyte and mitochondrial damage by promoting lactate production. Therefore, targeting PDK4 and its downstream product lactate may serve as promising therapeutic approaches for treating SIC.

RBM25 binds to and regulates alternative splicing levels of Slc38a9, Csf1, and Coro6 to affect immune and inflammatory processes in H9c2 cells

Background

Alternative splicing (AS) is a biological process that allows genes to be translated into diverse proteins. However, aberrant AS can predispose cells to aberrations in biological mechanisms. RNA binding proteins (RBPs), closely affiliated with AS, have gained increased attention in recent years. Among these RBPs, RBM25 has been reported to participate in the cardiac pathological mechanism through regulating AS; however, the involvement of RBM25 as a splicing factor in heart failure remains unclarified.

Methods

RBM25 was overexpressed in H9c2 cells to explore the target genes bound and regulated by RBM25 during heart failure. RNA sequencing (RNA-seq) was used to scrutinize the comprehensive transcriptional level before identifying AS events influenced by RBM25. Further, improved RNA immunoprecipitation sequencing (iRIP-seq) was employed to pinpoint RBM25-binding sites, and RT-qPCR was used to validate specific genes modulated by RBM25.

Results

RBM25 was found to upregulate the expression of genes pertinent to the inflammatory response and viral processes, as well as to mediate the AS of genes associated with cellular apoptosis and inflammation. Overlap analysis between RNA-seq and iRIP-seq suggested that RBM25 bound to and manipulated the AS of genes associated with inflammation in H9c2 cells. Moreover, qRT-PCR confirmed Slc38a9, Csf1, and Coro6 as the binding and AS regulatory targets of RBM25.

Conclusion

Our research implies that RBM25 plays a contributory role in cardiac inflammatory responses via its ability to bind to and regulate the AS of related genes. This study offers preliminary evidence of the influence of RBM25 on inflammation in H9c2 cells.

Sirtuin 1 alleviates microglia-induced inflammation by modulating the PGC-1α/Nrf2 pathway after traumatic brain injury in male rats

Microglial activation and the subsequent inflammatory response play important roles in the central nervous system after traumatic brain injury (TBI). Activation of the PGC-1α pathway is responsible for microglial activation after TBI. Our previous study demonstrated that SIRT1 alleviates neuroinflammation-induced apoptosis after TBI, and activation of the PGC-1α/Nrf2 pathway extenuates TBI-induced neuronal apoptosis. However, no study has investigated whether SIRT1 can affect the PGC-1α/Nrf2 pathway to induce microglial excitation and the subsequent neuroinflammatory response. Microglial activation and the levels of pro-inflammatory factors, namely, tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) were assessed to evaluate the neuroinflammatory response after TBI. To examine the effects of SIRT1, immunohistochemical staining and western blot analysis were used to observe the nuclear translocation and secretion of PGC-1α, as well as the activation of the PGC-1α/Nrf2 pathway. Treatment with the SIRT1 inhibitor sirtinol promoted microglial activation and pro-inflammatory factor expression (TNF-α, IL-6, and IL-1β) and inhibited PGC-1α and Nrf2 nuclear translocation and secretion after TBI, while treatment with the SIRT1 activator A3 had the opposite effects. The results of this study suggest that microglial activation, the subsequent neuroinflammatory response, and the PGC-1α/Nrf2 pathway play essential roles in secondary injury after TBI. These results indicate that SIRT1 protects neurons after TBI by inhibiting microglial activation and the subsequent inflammatory response, possibly by activating the PGC-1α/Nrf2 pathway.