Possible protective effects of two different doses of cyanocobalamin against methotrexate nephrotoxicity in rats

Abstract 
   Nephrotoxicity is defined as rapid deterioration in kidney functions. It arises from direct exposure to drugs or their metabolites. Methotrexate is a famous chemotherapeutic drug with anti-inflammatory and immunosuppressive properties. A high-dose methotrexate-induced renal dysfunction can be life threatening. Cyanocobalamin, one of the forms of vitamin B12, acts as a coenzyme in the conversion of homocysteine to methionine in the cytosol, and the conversion of methylmalonyl-CoA to succinyl-CoA in the mitochondrion. This study is designed to examine the effect of cyanocobalamin in two different doses each co-administered with methotrexate at 20 mg/kg induced nephrotoxicity in rats through the involvement of Nrf2/keap1 molecular mechanism in this respect. Rats utilized in this study were randomized into 4 groups (ten rats per each group); Group 1- (Control) rats intraperitoneally injected with 0.5ml normal saline once daily for 7 consecutive days. Group 2- Rats intraperitoneally injected with 0.5ml normal saline once daily for 7 consecutive days; and at day 2, a single intraperitoneal dose of methotrexate (20mg/kg) is to be injected. Group 3- Rats intraperitoneally injected with a 0.5mg/kg cyanocobalamin once daily for 7 consecutive days, and at day 2, a single intraperitoneal dose of methotrexate (20mg/kg). Group 4- Rats intraperitoneally injected with a 2mg/kg cyanocobalamin once daily for 7 consecutive days, and at day 2, a single intraperitoneal dose of methotrexate (20mg/kg). Co-administration of cyanocobalamin at doses cyanocobalamin 0.5mg/kg and 2mg/kg with methotrexate showed significant  reduction  (P<0.05) in malondialdehyde, significant elevation (P<0.05)  in reduced glutathione level, significant upregulation in  renal Nrf2 expression and significant down regulation in renal keap1 expression each compared to corresponding levels in methotrexate-only treated group. In conclusion this study demonstrated that co-administration of cyanocobalamin at two different doses with MTX resulted in attenuation of its nephrotoxicity by the utilization of selected parameters. 
Keywords: Nephrotoxicity, methotrexate, cyanocobalamin, malondialdehyde, glutathione, Nrf2, Keap1.