Oxidation of SOD1 in Skin Aging
Normal cell metabolism, particularly the activities of mitochondria, generates oxidizing molecules that react with proteins to disrupt their function. This damage occurs constantly, and is repaired constantly. Cells remove damaged proteins, undo oxidative changes, and make use of antioxidant enzymes such as SOD1 to prevent damage from occurring in the first place. With age, oxidation increases and becomes an important component of cell dysfunction. Here, researchers note that SOD1 itself can become oxidized and harmful, and discuss the importance of antioxidants disabled by oxidization in the growth of age-related oxidative stress in cells. The specific focus is on skin aging, but the points have relevance to all tissues.
As the body's primary barrier against environmental insults, the skin is continually exposed to oxidative stress, which may contribute to progressive proteotoxic stress. Excess reactive oxygen species (ROS) can overwhelm cellular protein-quality-control systems, promoting the accumulation of damaged and misfolded proteins, proteome instability, and eventual protein homeostasis (proteostasis) collapse. Superoxide dismutase 1 (SOD1), a Cu/Zn-dependent cytosolic antioxidant enzyme and key component of cellular defense against superoxide radicals, is itself vulnerable to oxidative modification. ROS-mediated post-translational oxidation of SOD1 may promote its misfolding and the formation of toxic protein species, potentially establishing a self-amplifying cycle of superoxide accumulation, further protein damage, and impaired cellular homeostasis.
In cutaneous cell types, including dermal fibroblasts and epidermal cells, these processes may be especially relevant to age-associated declines in proteostatic capacity and skin aging. This review distinguishes established skin-specific evidence from hypotheses extrapolated from other systems and synthesizes current evidence on the interplay among ROS-induced protein damage, proteostasis failure, SOD1 dysfunction, and cutaneous aging. We highlight the bidirectional relationship between proteostasis collapse and mitochondrial dysfunction, which may establish a self-reinforcing cycle of oxidative stress, cellular senescence, and chronic low-grade inflammation. These interconnected processes may converge to promote extracellular-matrix remodeling and tissue dysfunction, contributing to wrinkles, reduced elasticity, and impaired barrier function.