Effects of 12-lipoxygenase and angiotensinII on p21, p27 and p57 in rat diabetic glomeruli

Objective To investigate the effects of 12-lipoxygenase (12-LO) and angiotensin Ⅱ(AngⅡ) 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 AngⅡ 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+AngⅡ 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. AngⅡ increased p27 protein expression in glomeruli 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 AngⅡ may induce only p27 expression. Key words: Diabetic nephropathies; Angiotensin Ⅱ; Arachidonate 12-lipoxygenase; Cyclin-dependent kinase inhibitor proteins