Abstract 19708: Reductive Metabolism of Carnosine Conjugates Attenuates the Formation of Advanced Lipoxidation Products
Cardiovascular oxidative stress results in the oxidation of membrane lipids and the generation of reactive carbonyl species (RCS). The RCS react with proteins to form advanced lipoxidation products (ALEs), which are known to be generated during ischemia and heart failure and trigger inflammation. Although RCS such as acrolein and 4-hydroxy-trans-2-nonenal (HNE) form covalent adducts with endogenous quenchers such as carnosine (CAR) and histidine (HIS), the significance of this metabolism is unclear. Because their aldehyde group is unbound and therefore CAR-RCS and HIS-RCS conjugates can react and cross link proteins, we evaluated the role of aldose reductase (AR), a member of aldo-keto reductase family, in the reduction of CAR and HIS-acrolein conjugates. Mass spectrometric analysis of purified CAR and HIS-acrolein conjugates incubated with recombinant AR showed a significant reduction of CAR-acrolein conjugates to their corresponding alcohols. In comparison with heart and skeletal muscle of wild-type C57BL/6 mice, reduction of CAR-acrolein adducts in tissues from AR-null mice was 20-50 % lower (p <0.001). The abundance of reduced endogenous CAR-acrolein conjugates, generated by incubating acrolein with muscle homogenates, was significantly lower in WT (20-30 %, P<0.001) than in AR-null (5-10%) tissue. Profiling of HIS containing peptides in urine by highly sensitive and selective Hybrid FT Mass spectrometer showed that the CAR-acrolein conjugate is hydrolyzed to HIS-acrolein by carnosinase present in the plasma. Quantitative profiling of WT and AR-null urine samples showed 5-8 fold decrease in the reduced form of HIS-acrolein in the AR-null vs WT. mice. Oxy-blot analysis of heart and muscle homogenates incubated with CAR - acrolein showed that the CAR-acrolein protein adducts were 2-3 fold, (P<0.01) lower in the WT than AR-null mice. These data indicate that the quenching of RCS by CAR is not sufficient to prevent ALE formation and that reduction by AR is essential for attenuating the formation of protein aldehyde adducts during oxidative stress.
- © 2010 by American Heart Association, Inc.