Alpha B-crystallin in oxidative muscle fibers and its accumulation in ragged-red fibers: a comparative immunohistochemical and histochemical study in human skeletal muscle.

The alpha B-crystallin gene is abundantly expressed in the vertebrate lens and at lower levels in various non-lenticular tissues. Among the non-lenticular tissues, alpha B-crystallin is present at high levels in the heart and skeletal muscle. Using a specific antibody against alpha B-crystallin, the cellular localization of alpha B-crystallin was studied in biopsies of human skeletal muscles. Expression of alpha B-crystallin was observed in normal oxidative muscle fibers that show positive reactions for NADH-tetrazolium reductase and cytochrome c oxidase. In muscle diseases increased immunoreactivity for alpha B-crystallin was found in ragged-red fibers, which stained darkly with histochemistry for succinate dehydrogenase. Since alpha B-crystallin is related to small heat-shock proteins and can be induced by various stress conditions, the increased alpha B-crystallin immunoreactivity of ragged-red fibers could result from profound oxidative stress produced by the abnormal mitochondrial metabolism.