SIRT5-mediated desuccinylation prevents mitochondrial dysfunction in Alveolar epithelial cells senescence and Pulmonary fibrosis

Background Senescence of alveolar epithelial cells (AEC) is a key event in the occurrence and development of Idiopathic pulmonary fibrosis (IPF). The pathogenic mechanisms that underlie the effects of AEC senescence remain largely unexplained. Some age-related diseases have an etiology that is related to mitochondrial dysfunction induced by excessive lysine succinylation (Ksucc). Excessive Ksucc levels can be removed by SIRT5 to maintain mitochondrial homeostasis. Aims The aim of this study was to determine the effects of SIRT5-mediated de-Ksucc on mitochondrial function and pulmonary fibrosis after AEC senescence Methods The expressions of Ksucc and SIRT5 were observed by western blot and immunofluorescence. The mitochondrial morphology of aging AEC was observed by Transmission electron microscopy (TEM). The effect of SIRT5-mediated desuccinylation on mitochondrial function and aging fibrotic effect was determined by using SA‐β‐gal, mitoSOX, and MitoTracker staining. liquid chromatography with tandem mass spectrometry (LC-MS/MS) to perform the first global profiling of Ksucc in lung tissues with IPF patients. The changes of candidate key proteins and Ksucc sites related to energy metabolism in IPF lung tissues were analyzed by using the clusters of orthologous groups of proteins (COG), Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene ontology (GO). Specific succinylated proteins were validated by parallel reaction monitoring (PRM). Results AEC in the lungs of IPF patients exhibit a marked accumulation of dysmorphic and dysfunctional mitochondria and excessive Ksucc levels. These mitochondrial abnormalities in AEC of normal mice with advancing age were associated with the downregulation of SIRT5. Increase SIRT5 expression in aging AEC maintains mitochondrial function and reduces fibrotic effects of AEC senescence in established bleomycin (BLM)-aging mouse model. 1964 Ksucc sites in 628 proteins were identified and specific succinylated proteins (GRHPR, HSD17B8) were closely related to mitochondria functions in the IPF lungs. SIRT5 down-regulate the Ksucc level of GRHPR and HSD17B8 in the AEC aging model. Conclusions HyperKsucc is the basis of mitochondrial dysfunction in the AEC senescence and SIRT5 alleviates the pulmonary fibrosis induced by AEC senescence by stabilizing the mitochondrial function.