Age-Related Dysfunction of the Lacrimal Gland and Oxidative Stress

An imbalance between free radical generation and radical scavenging antioxidant systems results in oxidative stress, which has been associated with cell injury observed in many age-related diseases. The superoxide dismutase (SOD) family is a major antioxidant system, and deficiency of Cu,Zn-superoxide dismutase-1 (Sod1) in mice leads to many different phenotypes that resemble accelerated aging. In this study we examined the morphologic features and the secretory functions of the lacrimal glands in Sod1(-/-) mice. Lacrimal glands showed atrophy of acinar units; fibrosis; infiltration with CD4(+) T cells, monocytes, and neutrophils; increased staining with both 4-hydroxy-2-nonenal and 8-hydroxy-2'-deoxyguanosine; increases in apoptotic cells; and the presence of the epithelial-mesenchymal transition in senescent Sod1(-/-) mice. Electron microscopy findings revealed evidence of epithelial-mesenchymal transition, presence of swollen and degenerated mitochondria, and the presence of apoptotic cell death in the lacrimal glands of senescent Sod1(-/-) mice. These alterations were also associated with the accumulation of secretory vesicles in acinar epithelial cells, decreased production of both stimulated and nonstimulated tears, and a decline in total protein secretion from the lacrimal glands. Our results suggest that Sod1(-/-) mice may be a good model system in which to study the mechanism of reactive oxygen species-mediated lacrimal gland alterations.