Abstract 022: Proteasome Inhibition Prevents Renal Inflammation and Hypertension by Abrogation of Dendritic Cell Autoantigen Presentation

Abstract

Reactive oxygen species (ROS) have been shown to be important mediators of hypertension. Isolevuglandins (isoLG) are oxidation products of fatty acids that adduct to lysine residues of proteins. Our prior data suggest that isoLG-adducted proteins are presented by dendritic cells (DCs) and activate T-cells resulting in hypertension. Identification of the source and mechanism of presentation of isoLG adducts is critical for the development of therapies targeting this process. Antigens formed intracellularly are processed by the proteasome and presented to CD8 + T cells in MHC class I (MHC-I). We hypothesize that within DCs, isoLG-adducted peptides are processed by the proteasome and presented in MHC-I. Treatment of mouse DCs with the oxidant tert-butyl hydroperoxide (TBHP) increased levels of isoLG-adducts on the DC surface, as detected by flow cytometry, from 1.3 x 10 3 to 11.4 x 10 3 /10 6 DCs (N = 9, P < 0.01). Co-treatment of mouse DCs with TBHP and proteasome inhibitors (PIs) bortezomib (BTZ) or MG132 attenuated surface isoLG-adduct levels when compared to TBHP alone (2.7 x 10 3 or 3.5 x 10 3 vs 11.4 x 10 3 /10 6 DCs, N = 9, P < 0.001). Moreover, using flow cytometry-based fluorescence resonance energy transfer, we found that isoLG-adducted peptides and MHC-I interact at the intermolecular level on mouse DCs, suggesting that IsoLG-modified peptides are presented within MHC-I. Co-treatment of these cells with TBHP and BTZ attenuated this interaction compared with TBHP treatment alone (2.9 x 10 3 vs 32.7 x 10 3 /10 6 DCs, N = 9, P < 0.001). Next, mice were treated with angiotensin II (ang II) with or without co-treatment with BTZ. Co-treated animals exhibited reduced mean systolic blood pressure (161.7 ± 7.2 vs 122.9 ± 17.9 mmHg, N = 4-5, P < 0.05) and a reduction in renal macrophages (13.4 x 10 3 vs 6.57 x 10 3 DCs/Kidney, N = 4-5, P < 0.001) and DCs (129.4 x 10 3 vs 79.9 x 10 3 DCs/Kidney, N = 4-5, P < 0.05). These studies provide evidence that the proteasome processes isoLG adducts into peptides that are presented within MHC -I, and that proteasome inhibitors can not only block this process, but in doing so, can reduce renal inflammation and lower blood pressure. Efforts to inhibit processing and presentation of isoLG-modified peptides may therefore have therapeutic benefit in hypertension.