Expression of calcineurin in podocytes in response to endoplasmic reticulum stress in diabetic nephropathy

Abstract

To investigate the regulation of calcineurin (CaN) by endoplasmic reticulum stress (ERS) in podocytes in vitro and in vivo at the stage microalbuminuria in diabetic nehropathy (DN). The urinary albumin excretions of C57BLKS/J (Lepr) db/db and db/m mice at the ages of 6, 9, and 12 weeks were measured. The expressions of CaN and synaptopodin of these mice were observed. In immortalized mouse podocytes, the expression of podocyte CaN incubated with different concentrations of paltimate was quantitatively determined by real-time PCR. The changes of CaN incubated with paltimate with or without ursodeoxy-cholic acid (UDCA) were analyzed by confocal microscopy and Western blotting. As urine protein increased, the expression of CaN was enhanced and the expression of synaptopodin was reduced in early stage DN db/db mice potocytes. In immortalized mouse podocytes, as the concentrations of palmitate increased, CaN mRNA increased. By confocal microscopy, the fluorescence intensity of CaN increased in palmitate treatment group. After co-incubation with palmitate and UDCA, the fluorescence intensity decreased. The similar results were shown by Western blotting. At the stage of microalbuminuria in DN, ERS in podocytes up-regulates the expression of CaN.