Skin is the largest human organ and provides a first line of defense that includes physical, chemical, and immune mechanisms to combat environmental stress. Radiation is a prevalent environmental stressor. Radiation induced skin damage ranges from photoaging and cutaneous carcinogenesis from UV exposure, to treatment-limiting radiation dermatitis associated with radiotherapy, to cutaneous radiation syndrome, a frequently fatal consequence of exposures from nuclear accidents. The major mechanism of skin injury common to these exposures is radiation induced oxidative stress. Efforts to prevent or mitigate radiation damage have included development of antioxidants capable of reducing reactive oxygen species (ROS). Mitochondria are particularly susceptible to oxidative stress, and mitochondrial dependent apoptosis plays a major role in radiation induced tissue damage. We reasoned that targeting a redox cycling nitroxide to mitochondria could prevent ROS accumulation, limiting downstream oxidative damage and preserving mitochondrial function. Here we show that in both mouse and human skin, topical application of a mitochondrial targeted antioxidant prevents and mitigates radiation induced skin damage characterized by clinical dermatitis, loss of barrier function, inflammation, and fibrosis. Further, damage mitigation is associated with reduced apoptosis, preservation of the skin’s antioxidant capacity, and reduction of irreversible DNA and protein oxidation associated with oxidative stress.

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Alcoholics suffer from immune dysfunction that can impede vaccine efficacy. If ethanol (EtOH)-induced immune impairment is in part a result of direct exposure of immune cells to EtOH, then reduced levels of exposure could result in less immune dysfunction. As alcohol ingestion results in lower alcohol levels in skin than blood, we hypothesized that the skin immune network may be relatively preserved, enabling skin-targeted immunizations to obviate the immune inhibitory effects of alcohol consumption on conventional vaccines. We employed the two most common chronic EtOH mouse feeding models, the liver-damaging Lieber-DeCarli (LD) and liver-sparing Meadows-Cook (MC) diets, to examine the roles of EtOH and/or EtOH-induced liver dysfunction on alcohol related immunosuppression. Pair-fed mice were immunized against the model antigen ovalbumin (OVA) by DNA immunization or against flu by administering the protein-based influenza vaccine either systemically (IV, IM), directly to liver (hydrodynamic), or cutaneously (biolistic, ID). We measured resulting tissue EtOH levels, liver stress, regulatory T cell (Treg), and myeloid-derived suppressor cell (MDSC) populations. We compared immune responsiveness by measuring delayed-type hypersensitivity (DTH), antigen-specific cytotoxic T lymphocyte (CTL), and antibody induction as a function of delivery route and feeding model. We found that, as expected, and independent of the feeding model, EtOH ingestion inhibits DTH, CTL lysis, and antigen-specific total IgG induced by traditional systemic vaccines. On the other hand, skin-targeted vaccines were equally immunogenic in alcohol-exposed and non-exposed subjects, suggesting that cutaneous immunization may result in more efficacious vaccination in alcohol-ingesting subjects.

Alcohol abuse is associated with suppression of both of innate and adaptive immune systems. Functionally, several studies suggest that ETOH consumption polarizes immune responses away from Th1 responses toward Th2 skewed immunity. Understanding the mechanisms by which alcohol alters immune function is critical to the development of strategies to reverse these changes. Contact Hypersensitivity reactions are dendritic cell dependent, antigen specific, T cell-mediated immune responses triggered by skin exposure to haptens that become immunogenic after binding to peptides or proteins. We examined the impact of alcohol consumption on the response to Th1 skewing (DNCB) and Th2 skewing (FITC) contact sensitizers. Our studies suggest that ETOH consumption significantly inhibits CHS responses to the Th1 skewing sensitizer DNCB. In contrast, alcohol consumption did not diminish the CHS response triggered by the Th2 skewing sensitizer FITC. Importantly, the differential immune effects of ETOH consumption occurred independently of ETOH associated liver damage, as the results were similar in mice fed alternative alcohol diets that that did or did not induce liver damage. These results demonstrate specificity in ETOH-induced immunomodulation, and suggest strategies to prevent and treat ETOH associated immune dysfunction relevant to vaccination and immune mediated ETOH induced pathologies.