Abstract 624: Induction of Oxidative Stress in Dendritic Cells Promotes Isoketal Formation and Activation of T Cells
We and others have previously shown that T cells play an important role in hypertension, but the mechanisms by which they are activated remains undefined. Dendritic cells present antigens and secrete cytokines that modify T cell polarization. The NADPH oxidase also contributes to hypertension via multiple mechanisms. We have found that dendritic cells (DCs) from ang II-infused mice have a 5-fold increase in superoxide production by NADPH oxidase. Superoxide catalyzes the formation of H2-isoprostanes, which rearrange to form reactive γ-ketoaldehydes termed isoketals that adduct to protein lysines which renders them immunogenic. We hypothesized that oxidative stress catalyzes the formation of isoketals which alters the function of dendritic cells leading to inflammation and hypertension. Thus, we exposed DCs from spleens of C57Bl/6 mice to tert-Butyl hydroperoxide (t-BHP) for 30 minutes. Using flow cytometry, we found that t-BHP exposure increased levels of isoketal-ligated proteins in the CD11b+/CD11c+ DCs population compared to control (19.6 ± 3.7 vs. 10.6 ± 2.5, respectively; P=0.035). Importantly, we found DCs exposed to t-BHP become capable of activating T cells. After exposure to this oxidant for 30 minutes, DCs were cultured with autologous T cells for 7 days and proliferation was monitored by carboxyfluorescein succinimidyl ester (CFSE) and flow cytometry. Exposure of DCs to t-BHP promoted a 4-fold increase in proliferation of autologous CD8+ T cells compared to controls. This was also associated with a modest proliferation of CD4+ T cells. Thus, hypertension promotes oxidative stress in DCs. Induction of oxidative stress in DCs leads to formation of highly reactive isoketals, which alters the function of endogenous proteins. Formation of isoketals in DCs leads to T cell and, in particular, CD8 activation. These findings provide a mechanism as to how T cells are activated in hypertension and provide insight into the inflammatory nature of this disease.
- © 2013 by American Heart Association, Inc.