Abstract 253: Abdominal Aortic Aneurysms: Protein Targets for Autoimmunity
Objectives: The vast majority of Abdominal Aortic Aneurysm (AAA) patients have a history of smoking. The current hypothesis is that smoking induces post-translational protein modifications within the abdominal aorta resulting in site-specific antigenic targets for humoral immunity, and leads to a complex inflammatory milieu that ultimately gives rise to mature AAAs.
Methods: Plasma samples from patients with AAAs were separated by smoking status (Non-smoker = NS [n = 5]; Smoker = S [n = 15]; Prior Smoker = PS [n = 36]). Aortic wall was harvested from AAA (n = 5) and healthy control aorta (n = 5). Membrane proteins were extracted from AAA aortas by phase separation and bound to affinity columns. Plasma from NS, S, and PS groups was passed through these columns to isolate immunoglobulins (eluted IgGs). Duplicate samples of pooled control aortic tissue proteins underwent electrophoresis for Western blotting and Coomassie staining. Western blots were developed with eluted IgGs from the NS, S, and PS groups as well as IgGs from healthy volunteers as negative control. The Western blots were analyzed for differences in banding patterns between NS and S or PS groups and the corresponding proteins from Coomassie stained gels were excised for Mass Spectrometry (LC-MS/MS analysis).
Results: Western blot experiments revealed a ∼38 kD band in NS but no correlating band in S and PS groups, as well as ∼22 kD and ∼33 kD bands present in S and PS but no correlating bands in the NS group. LC-MS/MS analysis of these 3 bands identified the encompassed proteins as having sequence homologies with TROPOMYOSIN 1, TROPOMYOSIN 2, TRANSGELIN, INTEGRIN BETA-1, VERSICAN, PEROXIREDOXIN 2 and OSTEOGLYCIN (Mimecan), and that these proteins differed in relative abundance between the three groups.
Conclusions: We identified putative proteins in normal human aortas that could represent autoimmune targets leading to AAA development. The discrepancy between the molecular weights of putative targets and the bands used for LC-MS/MS analysis possibly reflects post-translational processing of the larger parent protein resulting in auto-antigenicity.
- © 2012 by American Heart Association, Inc.