Vitiligo, reactive oxygen species and T-cells

Abstract

The acquired depigmenting disorder of vitiligo affects an estimated 1% of the world population and constitutes one of the commonest dermatoses. Although essentially asymptomatic, the psychosocial impact of vitiligo can be severe. The cause of vitiligo remains enigmatic, hampering efforts at successful therapy. The underlying pathogenesis of the pigment loss has, however, been clarified to some extent in recent years, offering the prospect of effective treatment, accurate prognosis and rational preventative strategies. Vitiligo occurs when functioning melanocytes disappear from the epidermis. A single dominant pathway is unlikely to account for all cases of melanocyte loss in vitiligo; rather, it is the result of complex interactions of biochemical, environmental and immunological events, in a permissive genetic milieu. ROS (reactive oxygen species) and H2O2 in excess can damage biological processes, and this situation has been documented in active vitiligo skin. Tyrosinase activity is impaired by excess H2O2 through oxidation of methionine residues in this key melanogenic enzyme. Mechanisms for repairing this oxidant damage are also damaged by H2O2, compounding the effect. Numerous proteins and peptides, in addition to tyrosinase, are similarly affected. It is possible that oxidant stress is the principal cause of vitiligo. However, there is also ample evidence of immunological phenomena in vitiligo, particularly in established chronic and progressive disease. Both innate and adaptive arms of the immune system are involved, with a dominant role for T-cells. Sensitized CD8+ T-cells are targeted to melanocyte differentiation antigens and destroy melanocytes either as the primary event in vitiligo or as a secondary promotive consequence. There is speculation on the interplay, if any, between ROS and the immune system in the pathogenesis of vitiligo. The present review focuses on the scientific evidence linking alterations in ROS and/or T-cells to vitiligo.

Photosensitization of peptides and proteins by pterin derivatives

“…In vitiligo, a skin disorder characterized by a defective protection against UV radiation due to the acquired loss of constitutional pigmentation [19], H 4 Bip metabolism is altered [20]. Dihydro and oxidized pterin derivatives accumulate in the affected tissues at concentrations that are significantly higher than those reported for healthy cells [20,21].…”

Redox Regulation of T-Cell Function: From Molecular Mechanisms to Significance in Human Health and Disease

“…Biochemical, neurological, environmental, genetic, and immunological factors have all been associated with the activation of vitiligo (87). Moreover, a melanocytespecific T-cell-mediated immune response has been implicated in the development of vitiligo.…”

Reactive Oxygen Species, Vascular Noxs, and Hypertension: Focus on Translational and Clinical Research

“…Most experimental models of hypertension exhibit some degree of oxidative stress (48,67,93,95,236). Moreover, mice with reduced antioxidant enzyme systems and those deficient in NADPH oxidase have higher blood pressures than those with intact systems.…”

“…In fact, despite extensive data in the literature implicating a role for ROS and oxidative stress in many chronic diseases, such as cardiovascular disease, diabetes, cancer, and kidney disease, there are very few clinical conditions that are directly due to altered ROS levels. These include vitiligo, neurodegenerative diseases, and progeria (67,99,117,145,172,216). With regard to clinical hypertension, most studies examining ROS are based on associations between plasma or urine markers of oxidative stress and blood pressure.…”