Diesel exhaust particles induce apoptosis via p53 and Mdm2 in J774A.1 macrophage cell line

Diesel exhaust particles (DEP) are known to cause cardiopulmonary diseases due to their proinflammatory and cytotoxic effects. Continuous exposure to DEP potentiates chronic inflammatory processes and acute symptomatic responses in the respiratory tract. Recent studies have emphasized that alveolar cell apoptosis is a crucial step in chronic inflammation and lung injury. The phenomenon of apoptosis is a key event that successfully clears damaged cells, and its failure leads to the development of more serious diseases, such as lung cancer. The mechanism and molecular target of DEP-induced apoptosis in the respiratory tract remain unclear. In this study, J774A.1 macrophage cells were used to investigate the p53-mediated apoptotic pathway induced by DEP exposure. The results showed that murine double minute 2 (Mdm2), a negative regulator of p53, was downregulated at the protein level by DEP exposure. In contrast, the pro-apoptotic protein Bcl-2-associated X protein (Bax), an endogenous target of p53-dependent transcriptional activation, was continuously upregulated at the mRNA and protein levels by DEP exposure. Furthermore, pifithrin-alpha (p53 inhibitor) blocked DEP-induced apoptosis as well as p53 activation. Taken together, the findings of the present study suggest that DEP trigger apoptosis in J774A.1 macrophage cells via the activation of p53, followed by Bax.