Towards application of water extract from heat-killed Lactococcus lactis H61 as a cosmetic ingredient.

We previously reported that oral administration of heat-killed Lactococcus lactis H61 improves certain human skin properties. For topical application of this strain, we reasoned that a bacterial cell extract obtained with an aqueous solvent could be readily formulated as a cosmetic ingredient. In the present study, we characterized the water extract from heat-killed H61. The extract had inhibitory activity for angiotensin-converting enzyme, which is known as suppression of inflammation of skin, and absorbed electromagnetic radiation in the UVB range. UVB-irradiated normal human epidermal keratinocytes (NHEKs) had lower viability than nonirradiated NHEKs. The NHEK survival rate was significantly higher in cells treated with the extract at 10 mg dried cells per ml prior to UVB exposure than in untreated cells or cells treated with lower extract concentrations. At this concentration, the extract also inhibited the production of interleukin-8 induced by UVB. The extract did not protect against hydrogen peroxide-induced cell damage. These data indicate that topical application of the H61 extract alleviates UVB damage and reduces inflammation in skin cells. The present study expands the potential application of strain H61 to its use as a cosmetic ingredient in addition to its use in the food industry.