Effect and mechanism of PCSK9 on lipid homeostasis and cell damage of podocytes / 中华肾脏病杂志

ABSTRACT

Objective:To evaluate the effect of proprotein convertase subtilisin/kexin type 9 (PCSK9) on lipid homeostasis and cellular injury of podocytes, and to clarify its mechanism.Methods:Twelve-week old C57BL/6 wild-type mice ( n=10) and PCSK9 knockout ( PCSK9 KO) mice ( n=10) were selected as the animal models. The renal tissues were taken after perfusion through heart. Mouse podocytes were transfected with PCSK9 siRNA to downregulate PCSK9 expression. BODIPY 493/503 staining was performed for evaluating lipid accumulation, and standard transmission electron microscopy (TEM) was used to observe the foot process of podocytes, the shape of mitochondria and lipid droplet in podocytes. TUNEL staining was carried out to evaluate cell apoptosis in glomerulus. The parameters about mitochondria function (key enzymes such as PGC-1α, CPT-1 and Acox-1) and apoptosis were quantified through qPCR and western blotting. Results:The lipid accumulation in glomerulus of PCSK9 KO mice were more serious than controls. The expression of PGC-1α protein and PGC-1α, CPT-1 and Acox-1 mRNA in PCSK9 KO mouse kidney tissues were decreased than controls (all P<0.05), and mitochondria swelling and cristae disappearance in podocytes of PCSK9 KO mice were observed. In PCSK9 KO group, the foot process of podocytes partially fused and disappeared, and the apoptosis index increased compared with the control group ( P<0.05). In vitro, compared with the control group, the lipid accumulation was more significant, transcription level of key enzymes related to mitochondrial function was decreased, mitochondrial structure was damaged and the apoptosis index was increased in cultured podocyte PCSK9 siRNA group (all P<0.05). Conclusions:PCSK9 is involved in the lipid homeostasis of podocytes. The decrease of PCSK9 results in the increase of intracellular lipid accumulation, accompanied by the mitochondrial structure damage and disfunction of podocytes, and leads to cell apoptosis.