Furocoumarins potentiate UVA-induced DNA damage in skin melanocytes.

Epidemiological studies have found that high citrus fruit consumption was associated with higher risk of skin cancer. Citrus fruits and some vegetables contain furocoumarins, which may interact with ultraviolet radiation to induce skin cancer. We aimed to determine the effects of two furocoumarins, including 8-methoxypsoralen (8-MOP) and 6',7'-dihydroxybergamottin (DHB), on UVA-induced DNA damage in human epidermal melanocytes, the origin of melanoma. Our hypothesis was that these dietary furocoumarins increase UVA-induced DNA damage in melanocytes, compared to cells exposed to UV alone. We incubated melanocytes with 8-MOP or DHB, followed by exposure to physiological doses of UVA radiation. We used Western blots to quantify the UVA-induced DNA damage measured by the fraction of phosphorylated histone variant H2AX (γH2AX), which is a marker of DNA damage, relative to total H2AX (γH2AX/H2AX) in the presence or absence of furocoumarins. To quantify the UVA-induced change in γH2AX/H2AX, we calculated the UVA:Control ratio as the ratio of γH2AX/H2AX in UVA-exposed cells to that in cells without UVA (control). The mean UVA:Control ratios were borderline significantly higher for cells treated with 8-MOP and significantly higher for cells treated with DHB, compared to that of untreated cells. This study suggests that furocoumarins (particularly 8-MOP and DHB) enhance UVA-induced DNA damage in melanocytes, which is a potential novel mechanism for citrus and furocoumarins to elevate the risk of skin cancer.

An insulin-regulated arrestin domain protein controls hepatic glucagon action.

Glucagon signaling is essential for maintaining normoglycemia in mammals. The arrestin fold superfamily of proteins controls the trafficking, turnover, and signaling of transmembrane receptors as well as other intracellular signaling functions. Further investigation is needed to understand the in vivo functions of the arrestin domain-containing 4 (ARRDC4) protein family member and whether it is involved in mammalian glucose metabolism. Here, we show that mice with a global deletion of the ARRDC4 protein have impaired glucagon responses and gluconeogenesis at a systemic and molecular level. Mice lacking ARRDC4 exhibited lower glucose levels after fasting and could not suppress gluconeogenesis at the refed state. We also show that ARRDC4 coimmunoprecipitates with the glucagon receptor, and ARRDC4 expression is suppressed by insulin. These results define ARRDC4 as a critical regulator of glucagon signaling and glucose homeostasis and reveal a novel intersection of insulin and glucagon pathways in the liver.

Host and primary tumor factors for the development of multiple cutaneous squamous cell carcinomas among a retrospective cohort in Rhode Island.

INTRODUCTION: Risk factors for a primary cutaneous squamous cell carcinoma (CSCC) are well-established; however, the host and primary tumor risk factors for subsequent CSCC have not been fully explored. METHODS: We performed a retrospective chart review of patients diagnosed with CSCC in an academic dermatology clinic in Rhode Island from 2016-2019. Logistic regression was used to evaluate the associations between host factors and multiple CSCC and between primary tumor characteristics and the risk of subsequent CSCC. Adjusted odds ratios (aORs) and 95% CIs were calculated. RESULTS: A total of 1312 patients with CSCC diagnoses were included. Host risk factors significantly associated with multiple CSCCs included: aged >80 years (aOR, 2.18; 95% CI, 1.46-3.31); history of: solid organ transplant (aOR, 2.41; 95% CI, 1.20-4.80); skin cancer (aOR, 1.96; 95% CI, 1.52-2.54); other cancer (aOR, 1.49; 95% CI, 1.11-2.00); family history of skin cancer (aOR, 1.36; 95% CI, 1.03-1.78); and actinic keratosis (aOR, 1.52; 95% CI, 1.18-1.95). Tumor location, diameter, histologic differentiation, and treatment were not significant predictors of subsequent CSCCs. LIMITATIONS: Study patients were predominantly White and from a single institution, limiting the generalizability of results. CONCLUSIONS: Certain host characteristics were associated with the development of subsequent CSCC, which may inform clinical guidelines for follow-up.