This report contains the experimental data obtained during the in vitro evaluation of the antiinflammatory activity of AVOMULS® LOW, after stimulation with Tumor Necrosis Factor alpha (TNF-α), in human keratinocytes.

Cytokines are small (5 to 20 kDa) proteins known to play an important role in the immune system; in particular they are able to influence the activation, maturation, growth and differentiation of several cell populations.

Among the wide cytokine family, one could be particularly identified as the most direct and reliable marker of inflammation: IL-8 (Harada et al., 1994). IL-8 is a member of the C-X-C chemokine family (the acronyme is related to the structural motif cysteine-amino acid-cysteine in the amino-terminal portion of the cytokine); it is not produced constitutively, but its secretion is promoted in an inflammatory environment in response to other cytokines earlier involved in the acute phase response (IL-1a, IL-1b, TNF-a, INF-g) (Wilmer et al., 1995).

Its pivotal function is to play a chemoattractant role, mainly towards polymorphonuclear neutrophils and lymphocytes (Larsen et al., 1989), but also towards basophils, inducing histamine secretion in these cells (Wilmer et al., 1995). Specifically, it seems to be involved in leukocyte adherence to endothelial cells and diapedesis. Moreover, it could also exert an effect in activating immune cells and promoting angiogenesis (Moore et al., 1998); it causes granule exocytosis from neutrophils and increases cytosolic free calcium, determining a remodelling in neutrophil morphology which pairs to the surface membrane remodelling and the increased expression of adhesion molecules, like CD11b/CD18 (complement receptor type 3) CD11c/CD18 and complement receptor type I (Baggiolini et al., 1992).

IL-8 production has been demonstrated in a wide variety of cells, including monocytes, T lymphocytes, neutrophils, vascular endothelial cells, dermal fibroblasts, hepatocytes, chondrocytes, synovial cells and keratinocytes (Harada et al., 1994). Its secretion is particularly active in chronic inflammation conditions, such as rheumatoid arthritis, inflammatory bowel diseases, and, for skin, diseases like psoriasis (Schroder et al., 1992) or palmoplantar pustolosis (Ozawa et al., 2005), where its mRNA expression has been identified as prominent therapeutic option (Kerr et al., 2011).

Thus, measurement of this cytokine in an in vitro model represents a useful and sensitive tool to assess the anti-inflammatory effect of a cosmetic product, in particular way in a key regulatory cell type of dermal integrity as normal human dermal fibroblasts (NHDF) (Buken et al., 2019).