Alpha-melanocyte-stimulating hormone modulates activation of NF-kappa B and AP-1 and secretion of interleukin-8 in human dermal fibroblasts. Böhm M,Schulte U,Kalden H,Luger T A Annals of the New York Academy of Sciences Alpha-melanocyte-stimulating hormone (alpha-MSH) has evolved as a mediator of diverse biological activities in an ever-growing number of non-melanocytic cell types. One mechanism by which alpha-MSH exerts its effects is modulation of AP-1 and NF-kappa B. These two transcription factors also play an important role in fibroblasts, in extracellular matrix composition, and in cytokine expression. By use of electric mobility shift assays, we demonstrate that alpha-MSH (10(-6) to 10(-14) M) activates AP-1 in human dermal fibroblasts, whereas coincubation with interleukin-1 beta (IL-1 beta) results in suppression of its activation. alpha-MSH also induces activation of NF-kappa B but does not modulate DNA binding on costimulation with IL-1 beta. Since AP-1 and NF-kappa B are key elements in controlling interleukin-8 (IL-8) transcription, human fibroblasts were treated with alpha-MSH and IL-1 beta for 24 hours, and cytokine levels in the supernatants were measured by ELISA. alpha-MSH alone had little effect, whereas coincubation with IL-1 beta led to marked downregulation of IL-8 secretion (at most 288 +/- 152 ng/mL) when compared to treatment with IL-1 beta alone (919 +/- 157 ng/mL). Our results indicate that alpha-MSH exerts modulatory effects on the activation of NF-kappa B and AP-1, and that it can regulate chemokine secretion in human dermal fibroblasts. These effects of alpha-MSH may have important regulatory functions in extracellular matrix composition, wound healing, or angiogenesis. 10.1111/j.1749-6632.1999.tb08685.x

New mechanistic insights into coupled binuclear copper monooxygenases from the recent elucidation of the ternary intermediate of tyrosinase. FEBS letters Tyrosinase is the most predominant member of the coupled binuclear copper (CBC) protein family. The recent trapping and spectroscopic definition of the elusive catalytic ternary intermediate (enzyme/O /monophenol) of tyrosinase dictates a monooxygenation mechanism that revises previous proposals and involves cleavage of the μ-η :η -peroxide dicopper(II) O-O bond to accept the phenolic proton, followed by monophenolate coordination to copper concomitant with aromatic hydroxylation by the non-protonated μ-oxo. Here, we compare and contrast previously proposed and current mechanistic models for monophenol monooxygenation of tyrosinase. Next, we discuss how these recent insights provide new opportunities towards uncovering structure-function relationships in CBC enzymes, as well as understanding fundamental principles for O activation and reactivity by bioinorganic active sites. 10.1002/1873-3468.14503