Oxodesmosine and isooxodesmosine, candidates of oxidative metabolic intermediates of pyridinium cross-links in elastin

We isolated two new dihydrooxopyridine crosslinks, oxodesmosine (OXD) and i sooxodesmosine (IOXD) from the acid hydrolysates of the bovine aortic elast in, OXD and IOXD were identified to have N-substituted 1,2-dihydro-2-oxopyr idine and N-substituted 1,4-dihydro-4-oxopyridine skeletons, respectively, with three alpha -amino acid groups and mass of 495 (C23H37N5O7). These str uctures and distribution indicated that OXD and IOXD are oxidative metaboli tes generated from desmosine (DES) and isodesmosine (IDE), respectively, by reactive oxygen species (ROS), Effects of ROS derived from divalent metal (Fe2+, Cu2+)/H2O2 on DES, IDE, OXD, and IOXD in elastin were investigated. Changes in the contents of these cross-links in elastin were observed by us ing reverse-phase HPLC with UV detection. The time- and pH-dependent format ion of OXD and reduction of DES and IDE in elastin by Cu2+/H2O2 Fe2+/H2O2 w ere observed. OXD was found to be formed from DES by Fe2+/H2O2. No formatio n of IOXD was observed under the conditions of oxidation examined. By using a model compound of IDE, however, we found that 4-pyridone could be formed by Fe2+/H2O2. Elastin incubated in Cu2+/H2O2 was also solubilized dependen t on solution pH and the concentration of H2O2. These results suggest that oxidative degradation of elastin with cross-links results in its weakening, followed by its solubilization, Pyridinium cross-links, such as DES and ID E, may be oxidatively metabolized by ROS, further changing to dihydrooxopyr idine cross-links such as OXD and IOXD, respectively. (C) 2001 Academic Pre ss.