Niacinamide leave-on formulation provides long-lasting protection against bacteria in vivo.

Antimicrobial peptides (AMPs) form a part of the skin's innate immune system. Their primary activity is to provide antimicrobial benefits and hence protect from infections. AMPs that are present on human skin include psoriasin (S100A7), RNase 7, lysozyme, LL-37 and defensins. Niacinamide is a well-known cosmetic ingredient that has been used traditionally for multiple skin benefits. Recent data indicate that niacinamide treatment can boost AMPs in human gut epithelial cells and in neutrophils. Treatment with niacinamide in mice also provided protection from skin infections by enhancing AMPs. In this article, we find that treatment with niacinamide formulation provides long-lasting protection against bacteria, potentially through the activation of an AMP response.

Melanocyte-keratinocyte interaction induces calcium signalling and melanin transfer to keratinocytes.

Physical contact between melanocytes and keratinocytes is a prerequisite for melanosome transfer to occur, but cellular signals induced during or after contact are not fully understood. Herein, it is shown that interactions between melanocyte and keratinocyte plasma membranes induced a transient intracellular calcium signal in keratinocytes that was required for pigment transfer. This intracellular calcium signal occurred due to release of calcium from intracellular stores. Pigment transfer observed in melanocyte-keratinocyte co-cultures was inhibited when intracellular calcium in keratinocytes was chelated. We propose that a 'ligand-receptor' type interaction exists between melanocytes and keratinocytes that triggers intracellular calcium signalling in keratinocytes and mediates melanin transfer.