Tacrolimus(FK-506) Nephrotoxicity and the Effect of alpha-Tocopherol in the Rat Renal Isograft

Hong, In Chul; Yoo, Chang Hyun; Jeong, Hyeon Joo; Kim, Hye Young; Kim, Soon Il; Moon, Jang Il; Kim, Yu Seun; Park, Kiil

Abstract

There have been many reports about oxygen free radical injury as a pathogenetic mechanism of CyA nephrotoxicity, but few reports have investigated the relationship between Tacrolimus(FK-506) nephrotoxicity and oxygen free radical injury. Therefore, we decided to evaluate the relationship between Tacrolimus nephrotoxicity and oxygen free radicals, to examine the protective effect of alpha-tocopherol as an antioxidant, and finally to determine the histological changes of these injuries. En bloc resection of the left kidney, left renal artery including a portion of aorta, left renal vein with vena cava, and left ureter including a portion of bladder from male Lewis rats was done, and then preserved in UW solution and stored in the refrigerator at 4oC for 24 hours. After right nephrectomy in the recipients, the harvested organs were transplanted into the right peritoneal cavity using end-to-side anastomoses of the aorta and inferior vena cava between the recipient and donor under a microscope. Also, end-to-end anastomosis of the partly-resected bladders was made between the recipient and donor. After transplantations, rats were divided into 4 groups(I~IV). 2 mg of Tacrolimus per kilogram body weight was injected intramuscularly daily into groups II and III. alpha-Tocopherol was injected intraperitoneally daily in the amount of 20 mg/kg from 2 days prior to transplantation in groups III and IV. The control group(I) received the same amount of saline. 5 or 6 rats from each group were sacrificed at 3 days, 7 days, and 14 days after transplantation, respectively. The grafted and native kidneys were removed for histopathologic examination and the measurement of malondialdehyde(MDA) using a modified TBA method(Ohkawa). Both morphologic renal tubular injury and the increase of MDA due to cold ischemia-reperfusion were highest at 3 days after transplantation, then were alleviated after 7 days. The inhibitory effect of alpha-tocopherol to renal tubular damage from cold ischemia-reperfusion began to appear after 1 week, and was distinct 2 weeks after transplantation. The degree of renal tubular damage was the most severe in Tacrolimus nephrotoxicity, and the frequency of tubulointerstitial nephritis increased with the passage of time, as compared with the ischemia-reperfusion injury(group I). With alpha-tocopherol treatment, ischemia-reperfusion injury as well as Tacrolimus nephrotoxicity was decreased or healed 2 weeks after transplantation, and the amount of MDA was markedly decreased after 1 week. In summary, Tacrolimus nephrotoxicity prolonged the duration of acute tubular necrosis and caused tubulointerstitial nephritis in the rat renal isograft model, which may be the result of aggravation of ischemia-reperfusion injury. That the renal damage due to cold ischemia-reperfusion and Tacrolimus administration was reduced by alpha- tocopherol, indicates that oxidative injury is a pathogenetic mechanism of Tacrolimus nephrotoxicity in this model.