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.
ABSTRACT
Objectives To evaluate the role of PCSK9 (proprotein convertase subtilisin kexin type 9) on the lipid accumulation and kidney injury of C57BL/6 mice. Methods The 24 h urine of 12 weeks old wide type C57BL/6 mice and PCSK9 knockout (KO) mice were collected through a metabolic cage, followed by perfusion and sacrifice. Urinary microalbumin?to?creatinine ratio (UACr), total cholesterol and triglyceride in kidney tissues were measured by ELISA. BODIPY 493/503 staining and standard transmission electron microscopy (TEM) of kidney tissues was performed for evaluating lipid accumulation and podocyte foot effacement in the kidney. Kidney tissues were also evaluated by PAS stain and TUNNEL stain. PCSK9, podocin and nephrin were quantified through real?time PCR, and the Bcl?2, Bax and cleaved caspase 3 were evaluated by Western blotting. Results Total cholesterol and triglyceride contents were higher in the kidneys of PCSK9 KO mice than controls (P<0.05). The level of lipid accumulation in glomeruli and tubules through BODIPY 493/503 stain, and the amount of lipid drop in TEM were more serious in PCSK9 KO mice. UACr and podocyte foot process effacement were increased, and the transcription of podocin and nephrin were decreased in the kidneys of PCSK9 KO mice (all P<0.05). The expression of Bcl?2 was decreased, and Bax and cleavedcaspase 3 were increased in the kidney samples of PCSK9 KO mice. Conclusion PCSK9 might be reversely involved in lipid homeostasis and accumulation, resulting in injury and apoptosis in the kidneys of C57BL/6 mice.
ABSTRACT
Objective To investigate the effects of 12-lipoxygenase (12-LO) and angiotensin Ⅱ (Ang Ⅱ) on the CIP/KIP family of cyclin-dependent kinase inhibitors (CKIs) p21,p27 and p57 related to cell hypertrophy.Methods Mesangial cells were treated with high glucose for 24 hours and 48 hours respectively.12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] and Ang Ⅱ were infused to rats by osmotic mini-pump for 1 week and 2 weeks respectively.Rats fed high fat diet were received low dose streptozotocin (STZ) to make type 2 diabetes (DN).The rats were divided into normal control group,DN group,DN+Ang Ⅱ type 1 receptor blocker (ARB) group or 12-LO inhibitor (CDC) group.DN+ARB rats were treated by losartan for 6 weeks,and DN+CDC rats were treated for 8 weeks.Urine albumin and protein expressions of p21,p27 and p57 were detected by ELISA and Western blotting respectively.Glomeruli injury and expressions of p21 and p27 were detected by PAS staining and immunohistochemistry respectively.Results High glucose increased p21 and p27 protein expression in mesangial cells significantly compared with the relative control (all P ＜ 0.05),but had no effect on p57.Ang Ⅱ increased p27 protein expression in gloneruli significantly (P ＜ 0.05),but had no effect on p21 and p57 protein expression.12(S)-HETE increased both p21 and p27 protein expression in glomeruli significantly (all P ＜ 0.05),but had no effect on p57 protein expression.Blood glucose,kidney/body weight,urinary protein,and glomerular p21 and p27 protein expressions were increased in DN group (all P ＜ 0.05) compared with those in control group,with little change of p57 protein expression (P ＜ 0.05).Moreover,glomerular hypertrophy and extra cellular matrix accumulation were observed in DN group.However,urine protein,kidney/body weight,renal injury,but not blood glucose,were decreased in DN+ARB group and DN+CDC group compared with DN group respectively (P＜ 0.05).Further DN+CDC rats had decreased both p21 and p27 protein expressions in glomeruli,but DN+ ARB rats only had decreased p27 protein expression (all P ＜ 0.05).Conclusions 12-LO may induce both p21 and p27 protein expression in DN glomeruli,but Ang Ⅱ may induce only p27 expression.