P53 AND P21 (WAF1 CIP1) MESSENGER-RNA EXPRESSION ASSOCIATED WITH DNA-DAMAGE AND REPAIR IN ACUTE IMMUNE-COMPLEX ALVEOLITIS IN MICE/

The tumor suppresser p53 is a cell cycle checkpoint protein that contr ibutes to the preservation of genetic stability by mediating either a G1 arrest or apoptosis in response to DNA damage. p53 causes growth ar rest through transcriptional activation of the cyclin-dependent kinase inhibitor p21. During p53-mediated suppression of cell proliferation, p21 is important for coordinating cell cycle progression, DNA replica tion, and repair of damaged DNA. The purpose of this study is to inves tigate the expression of p53 and p21 mRNA in association with DNA dama ge and normal repair in acute immune complex alveolitis in mice. Male ICR mice were injected intravenously with IgG antibodies against oval albumin, aerosolized with oval albumin solution, and killed at 4, 6, 1 2, 24, and 48 hours and 1 week after aerosolization. We assessed the e xpression of p53 and p21 mRNA by reverse transcriptase (RT)-PCR and by RT in situ PCR. We also assessed DNA damage by terminal deoxynucleoti dyl transferase mediated biotin-dUTP nick-end-labeling (TUNEL) and by gel electrophoresis of DNA extracted from lung tissues. The results of RT-PCR and RT in situ PCR showed that p53 and p21 mRNA were concurren tly up-regulated at 4 to 48 hours after aerosolization in alveolar epi thelial cells. Bronchial and alveolar epithelial cells were positively stained by TUNEL in this period but not at 1 week after aerosolizatio n or in control mice. The result of electrophoretic analysis of DNA wa s compatible with that of TUNEL. These studies suggest that the respon ses of p53 and p21 mRNA are associated with physiologic processes of D NA damage and repair in acute immune complex alveolitis in mice.