Increased SS bonds in chronic solar elastosis: a study with N-(7-dimethylamino-4-methyl-3-coumarinyl) maleimide...

We have studied the distribution of SH groups and SS linkages in solar elastosis, in comparison with that in aged and juvenile sun-unexposed skin, using N-(7-dimethylamino-4-methyl-3-coumarinyl) maleimide (DACM) stain. In heavy solar elastosis we found increased fluorescence for SS bonds in the upper and middle reticular dermis in the elastotic masses; these were separated from the epidermis by a network of actinically-damaged, SS-positive elastic fibers, showing irregularly and variously interwoven oxytalan and elaunic fibers. These latter, unlike the elastotic masses, revealed also SH groups. In moderate and weak elastosis, where the thick irregular masses were absent, the fluorescence for SH and SS linkages was present in equal proportions in the altered elastic fibers; collagen bundles revealed only fluorescence for SS bonds. Aged and juvenile sun-unexposed skin showed the same proportions of SH and SS linkages in the changed elastic fibers. Collagen bundles of aged and juvenile skin showed fluorescence for SS bonds; SH groups were present on a few collagen fibers only in aged skin. Our results are consistent with opinion supporting an elastic origin of elastotic degeneration, which could be the consequence of a defect, due to chronic solar exposure, in one of the steps--degradation or synthesis--of metabolic turnover of elastic fibers, resulting in abnormal and excessive polypeptide chains extremely rich in disulfide bonds.