Abstract 135: Alubuminuria Causes Disorder of Cytochrome P450 Metabolism of Arachidonic Acid in the Kidney of Nephrotic Rats

Alubuminuria is an aggravating factor for chronic kidney disease. Fatty acids bound to albumin are overloaded to the proximal tubules in alubuminuria and contribute to tubulointerstitial damage. It is known not only the β-oxidation ability but the ability of cytochrome P450 (CYP) metabolism of arachidonic acid (AA) is high in the kidney. Epoxyeicosatrienoic acids synthesized primarily by CYP2C and 20-hydroxyeicosatetraenoic acid synthesized by CYP4A affect tubular function and renal circulation. However, it isn’t clear CYP metabolism of AA would change in alubuminuria. The study tested changes of CYP metabolism of AA in the kidney of nephrotic rats. Sprague-Dawley rat (SD) and Nagase Analbuminemic rat (NAR) with inherited hypoalbuminemia were used and nephrotic syndrome was induced by Puromycin Aminonucleoside (PAN; 100 mg/kg, iv). Rats were randomly divided into four groups; (1) SD group; (2) SD treated with PAN group (PAN group); (3) NAR group; (4)NAR treated with PAN group (NAR+PAN group). Rats were killed on the 14th day and urinary 8OHdG, a marker of oxidative stress in the kidney, and urinary NAG, a marker of proximal tubular cell damage, were measured. The protein level of enzymes in the kidney was analyzed by Western blot and immunohistochemistry. Compared with the SD group, albuminuria, 8OHdG and NAG increased respectively to 847%, 154% and 903% in the PAN group, and Western blot showed the protein levels of CYP2C23 and CYP4A decreased to 45% and 49% without change of the protein level of PPARα, a nuclear receptor regulating fatty acid metabolism, in the PAN group. Immunohistochemistry showed the localization of CYP2C23 and CYP4A in the proximal tubule and confirmed the results by Western blot. Otherwise, we could find no difference in albuminuria, tubulointerstitial damage and the protein level of CYP2C23 between the NAR group and the NAR+PAN group. Compared with the NAR group, the protein level of CYP4A decreased to 68% in the NAR+PAN group. Alubuminuria caused tubulointerstitial damage and decreased the expressions of CYP2C23 and CYP4A in the nephrotic kidney. This study suggested the disorder of CYP metabolism of AA would affect renal circulation in alubuminuria and CYP4A would be affected by anything except alubuminuria in PAN rats.