The present finding shows for the first time that there is enhanced

protein expression of the Cu/Zn- and Mn-SOD isoforms as the same time that there is enhanced production of the superoxide anion in the pulmonary artery of rats exposed in vivo to PM2.5. It was previously demonstrated that PM2.5 exposure causes oxidative stress in aortic tissue and in macrophages ( Wan et al., 2010). In addition, in macrophages cell, in vitro PM GSK-3 inhibitor exposure enhances gene expression of Cu/Zn-SOD ( Wan et al., 2010) and the protein expression of the antioxidant enzymes catalase and heme oxygenase-1 ( Xiao et al., 2003). Therefore, enhanced expression of SOD isoforms could be a secondary mechanism activated in response to enhanced superoxide anion production induced by PM2.5 as a protective pathway. The proinflammatory cytokines IL-1β, IL-6 and TNF-α have emerged as biomarkers and mediators of oxidative stress and endothelial dysfunction in several cardiovascular diseases (Ungvari et al., 2003 and Wan et al., 2010). In the present study, we observed that pulmonary arteries from urban PM2.5-exposed animals showed enhanced TNF-α protein expression despite there being no changes in IL1-β and IL-6. Thus, inhaled PM2.5 could directly induce endothelial dysfunction

by stimulating TNF-α protein synthesis. This hypothesis is in agreement with a prior study demonstrating that acute in vitro exposure to fine manufactured PM increases the release of TNF-α in isolated rat pulmonary this website G protein-coupled receptor kinase arteries and dexamethasone (an anti-inflammatory drug) prevented the reduction of acetylcholine-induced

relaxation in these vessels ( Courtois et al., 2008). It is known that the pro-inflammatory cytokine TNF-α can impair eNOS gene and protein expression, thus reducing NO synthesis ( Anderson et al., 2004). In the present study we found a significant negative correlation between TNF-α protein expression and maximal relaxation to acetylcholine in pulmonary arteries from in vivo PM2.5-exposed rats, suggesting that the higher TNF-α protein expression induced by air pollution is strongly related with the endothelial dysfunction of pulmonary circulation. Deposition of PM on alveolar epithelium induces infiltration of inflammatory cells, thus increasing the release of local proinflammatory factors that can reach pulmonary and systemic circulation and trigger secondary inflammation (Seaton et al., 1995). Moreover, elemental components of PM per se or after macrophage phagocytosis can pass through the alveolar-capillary membrane and induce peripheral effects ( Lehnert, 1992). Our findings for peripheral blood provide no evidence for extrapulmonary activity of inhaled particles within the time of exposure and at the concentration evaluated in the present study. PM2.