Ultraviolet (UV) irradiation of the skin is related to the development of skin cancer. UVB also causes DNA damage in the form of cyclobutane pyrimidine dimers (CPDs), which can result in stable mutations. Toll-like receptor 4 (TLR4), a component of innate immunity, plays a key role in cancer. Previous studies from our laboratory have observed that TLR4 deficiency resulted in the repair of UVB-induced DNA damage, inhibition of UVB-induced immune suppression, and carcinogenesis. In this study, we determined the efficacy of TLR4 antagonist TAK-242 in regulation of UVB-induced DNA damage, inflammation, and tumor development. Our results indicate that TAK-242 treatment increased the expression of xeroderma pigmentosum group A (XPA) mRNA, resulting in the repair of UVB-induced CPDs in skin of SKH-1 mice. Treatment with TAK-242 also inhibited the activation of NLR family pyrin domain containing 3 (NLRP3) in UVB-exposed skin of SKH-1 mice. Cutaneous carcinogenesis was significantly reduced in mice treated with TAK-242 in comparison to vehicle-treated mice. The proinflammatory cytokines IL-1β, IL-6, and TNF-α were also found to be significantly greater in vehicle-treated mice than TAK-242-treated mice. Finally, treatment with TAK-242 augmented anti-tumor immune responses in mice. Our data provide further evidence that activation of the TLR4 pathway promotes the development of UV-induced non-melanoma skin cancer mediated at least in part on its negative effects on DNA damage. Moreover, treatment with the TLR4 inhibitor TAK-242 may be effective for prevention of skin cancer.

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Hidradenitis suppurativa (HS) is a chronic inflammatory condition characterized by the formation of nodules, abscesses, and sinus tracts with tunnels that primarily involves the skin folds. HS affects approximately 1% of the population, but its pathogenesis is unclear. Dysbiosis of skin microbiome is a major cause of HS and alterations of microbiome composition and diversity can be seen in the skin of patients with HS. These disruptions may contribute to the immune dysfunction seen in HS. Understanding these alterations and their contributions to the pathogenesis of HS could help guide future treatment. In addition to dysbiosis promoting immune dysregulation, HS may promote dysbiosis via differences in expression of antimicrobial peptides (AMPs). In this review, we have discussed the role of skin and gut microbiome in manifestation of HS and the consequences of dysbiosis on the immune system.