Control of p53 and p21 (WAF1) expression during unilateral ureteral obstruction

Long-term unilateral ureteral obstruction (UUO) initiates a series of renal events leading to proliferation of interstitial fibroblasts and proliferation/repair of tubular cells. This is evidenced by significant increases in proliferating cell nuclear antigen (PCNA) positive nuclei during UUO. Several pathologic settings requiring DNA replication and/or DNA repair are dependent upon the expression of p53 and at least one of two p53-dependent proteins, termed p21 (also called WAF1) and GADD45. We therefore sought to determine if p53, p21, (WAF1) or GADD45 mRNA levels were changed in obstruction. There was a progressive increase in the amount of p53 mRNA and p21 (WAF1) mRNA at 1, 3, 5 and 8 days of continuous UUO. The amount of GADD45 mRNA was found not to change. Treatment of the experimental animals with an ACE inhibitor on day 4 through day 8 of UUO significantly blunted the increase in p53 and p21 (WAF1) expression. ACE inhibitor treatment also significantly decreased the number of PCNA-positive renal cell nuclei during UUO. These results suggest that during ureteral obstruction the p53 and p21 (WAF1) genes are activated. ACE inhibitor treatment reduces p53 and p21 (WAF1) expression. This reduction is at least in part due to an inhibition of interstitial cell proliferation.