Aims/hypothesis B cell CLL/lymphoma 2 (BCL-2)-interacting cell death suppressor (BIS), known as an anti-stress and antiapoptotic

protein, has been reported to modulate susceptibility to oxidative stress. This study investigated the potential role of

BIS as an antioxidant protein in diabetic nephropathy.

Methods Diabetes was induced in BIS-heterozygote (BIS-HT) mice via streptozotocin injections and the resulting phenotypes

were compared with those of BIS-wild-type (BIS-WT) mice over the 20 weeks following diabetes induction.

Results Renal injuries, represented by increased plasma creatinine levels and increased albuminuria, were greater in diabetic

BIS-HT mice than in diabetic BIS-WT mice, and were accompanied by a significant increase in reactive oxygen

species (ROS) and oxidative stress markers. Moreover, renalpathological changes and the apoptotic process were accelerated

in diabetic BIS-HT mice compared with diabetic BIS-WT mice with the same degree of hyperglycaemia; all

were restored by 4-hydroxy-2,2,6,6-tetramethylpiperidine-Noxyl (tempol) treatment. The levels of NADPH oxidase and

related proteins were not significantly higher in diabetic BIS-HT mice compared with diabetic BIS-WT mice. However,

levels of superoxide dismutase (SOD)1 and SOD2 increased on the induction of diabetes in BIS-WT mice but not in BIS-HT

mice, correlating with the total SOD activity. An in vitro study showed that knockdown of BIS production also resulted in

impaired induction of SOD activity as well as SOD levels in HK-2 and NMS cells, concomitant with significant ROS

accumulation.

Conclusion/interpretation Our results suggest that the decreased antioxidant capacity of BIS aggravates diabetic nephropathy

in diabetic BIS-HT mice, possibly as a result of the disruption in the regulation of SOD protein quality under oxidative stress.