A TGFBR2/SMAD2/DNMT1/miR-145 negative regulatory loop is responsible for LPS-induced sepsis

The critical roles of TGFBR2/Smad2 signaling have been established in LPS-induced sepsis, however, the underlying mechanisms by which TGFBR2/Smad2 signaling was regulated in LPS-induced sepsis are still confused. Here, miRNA-based on RNA-sequencing dataset revealed that miR-145 was significantly decreased in human umbilical vein endothelial cells (HUVECs) following LPS treatment. Bioinformatics, luciferase reporter and RNA immune co-precipitation (RIP) assays showed that miR-145 could directly target TGFBR2 and thus inactivated TGFBR2/Smad2 axis. On the contrary, luciferase reporter and chromatin immunoprecipitation (ChIP) analysis showed that Smad2 could directly bind to DNA methyltransferase 1 (DNMT1), the upregulation of which led to miR-145 promoter hypermethylation and downregulation of miR-145 expression, conversely promoting TGFBR2 expression. Notably, knockdown of TGFBR2 partially rescued the inhibition on miR-145 expression induced by LPS treatment. Additionally, we found that knockdown of TGFBR2 or overexpression of miR-145 attenuated LPS-induced sepsis and prolonged the overall survival of septic mice. Furthermore, TGFBR2 overexpression abrogated miR-145 overexpression-mediated attenuation on LPS-induced sepsis. Our results demonstrate the TGFBR2/SMAD2/DNMT1/miR-145 negative regulatory loop is responsible for LPS-induced sepsis.