We examined the effect of ultraviolet (UV) irradiation on the expression of cyclooxygenases in cultured HaCaT keratinocytes and in human skin in vivo. UVB irradiation (10 and 50 mJ/cm2) and hydrogen peroxide (200 micromol/L) increased cyclooxygenase-2 mRNA expression in HaCaT keratinocytes. No clear expression of cyclooxygenase-1 mRNA was detected in either control or stimulated HaCaT cells. Genistein, a tyrosine kinase inhibitor, suppressed both the basal and stimulated expression of cyclooxygenase-2 in HaCaT cells. UVB-induced cyclooxygenase-2 mRNA expression was partly inhibited by the antioxidant N-acetylcysteine and by H-7, a non-specific inhibitor of protein kinase C. Solar-simulated irradiation (40 mJ/cm2) was found to induce in vivo both cyclooxygenase-2 mRNA and protein expression in human skin, whereas the expression of cyclooxygenase-1 mRNA remained at the basal level. Our results show that cyclooxygenase-2 expression is induced by UV irradiation and suggest that tyrosine kinases and reactive oxygen intermediates are involved in this induction of cyclooxygenase-2.

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Recently, the proto-oncogenes bcl-2 and bax have emerged as important regulators of the apoptotic form of cell death. We examined UV irradiation-elicited apoptosis and regulation of bcl-2 and bax expression both in vivo in human skin and in vitro in HeLa cells. Using flow cytometric analysis, HeLa cells were found to undergo apoptosis at the 12-h time-point after exposure to UVB irradiation (100 mJ/cm2). The expression of bcl-2 mRNA was found to decrease after a single dose of UVB radiation (doses 10-200 mJ/cm2). In contrast, the expression of bax mRNA was not significantly changed. When human skin was irradiated with a single dose of solar-simulated radiation (40 mJ/cm2), Bcl-2-positive cells were significantly reduced in the epidermis at the 3- and 6-h time-points. Our results suggest that UV irradiation downregulates bcl-2 expression both in vitro at the mRNA level and in vivo at the protein level, and that downregulation of bcl-2 constitutes a mechanism of potential importance in UV-induced apoptosis in human epidermis.

Calciphylaxis (CPX) is a rare calcifying thrombotic vasculopathy responsible for painful necrotic ulcers, with a high mortality rate, and its management is often difficult. Recently, intravenous infusions of sodium thiosulfate (STS) have shown efficacy. The aim of this study was to assess the efficacy of intralesional STS (IL STS) in four patients. Our aim was to assess the efficacy of IL STS in a prospective mono-centric open study that included four patients with a biopsy-proven cutaneous CPX. Four women (55-84 years old, mean age: 71·2 years) with a uremic (n = 1) or non-uremic CPX (n = 3) and primary hyperparathyroidism induced by teriparatide or after the initiation of oral anti-vitamin K were treated by IL STS (250 mg/ml). The injections were performed around the ulcers, on the active borders, once or twice a week and then at 1-2 weeks intervals. The injected quantity varied from 1·5 to 15 ml. Pain usually improved after two series of injections. Clinical response was visible after 2 weeks. Three patients (75%) healed completely or almost completely. A failure was observed in the last patient who also had lower limb arteriopathy. The main side effect was the pain during injections. IL STS is an interesting alternative therapeutic option in the management of CPX necrotic ulcers with limited side effects. Larger studies are warranted to precisely define its place, its administration procedure and the patients who could benefit from it.