ACSL5 promotes lipid deposition and lipoapoptosis in proximal tubular epithelial cells of diabetic kidney disease

Background: Lipoapoptosis in Proximal tubular epithelial cells (PTCs) are substantial in the etiology of diabetic kidney disease (DKD), yet the underlying mechanisms warrant further investigation. Acyl-CoA synthetase long-chain family member 5 (ACSL5) facilitates the formation of acyl-CoA, however, the precise role of ACSL5 in lipoapoptosis of PTCs in DKD remains inconclusive.

Methods: Transcriptomic data analysis identified the hub gene Acsl5 associated with lipid metabolism in DKD. The expression of ACSL5 was examined in high-fat diet/streptozotocin (HFD/STZ)-induced diabetic mice and high glucose/ palmitic acid (HGPA)-induced mouse proximal tubular epithelial cell (BUMPT). Oil Red O staining, free fatty acids (FFA) ELISA assay, Western Blot, and morphological changes were employed to assess lipid deposition and lipoapoptosis. Furthermore, knockdown and overexpression of ACSL5 were conducted in BUMPT cells, followed by morphological assessment, Oil Red O staining, FFA ELISA assay and Western Blot analysis. Using the ChEA3 database, we predicted that STAT3 may transcriptionally regulate ACSL5. Subsequently, we knocked down STAT3 and evaluated Acsl5 expression via RT-qPCR. Additionally, we investigated whether STAT3 modulates the impact of ACSL5 on lipoapoptosis through Western Blot analysis.

Results: We demonstrated, for the first time, a notable upregulation of ACSL5 expression in PTCs in HFD/STZ-induced diabetic mice, accompanied by increased the expression of FATP2, lipid accumulation and heightened lipoapoptosis. In HGPA-treated BUMPT cells, ACSL5 knockdown reduced the expression of FATP2, lipid deposition and lipoapoptosis, whereas its overexpression elevated the expression of FATP2 and exacerbated these effects. These findings strongly suggest that ACSL5 may exacerbate lipoapoptosis in PTCs within a diabetic milieu. From a molecular mechanism perspective, ACSL5 expression decreased after Stat3 knockdown. Concurrent knockdown of Stat3 and overexpression of Acsl5 led to a mitigation of lipoapoptosis compared to sole Acsl5 overexpression. Furthermore, STAT3 promotes the activation of ACSL5 promoter under HGPA conditions.

Conclusions: In summary, our research identified ACSL5 as an important contributor exacerbating lipoapoptosis in the renal proximal tubules within diabetic environments. In addition, we found that ACSL5 is transcriptionally regulated by STAT3.