IL-8 May be Used as an in vitro Marker for Human Eye Tolerance

Abstract

Abstract: : Purpose: Development of alternative methods to replace the Draize rabbit eye irritation test is an important challenge for the European cosmetic industry. The Draize test was the "gold standard" in validation studies but there is a real need for comparison of in vitro data with human ones. For many years we develop a human corneal cell line as a tool for assessing eye irritation. Our purpose was to evaluate our in-house in vitro method for its ability to predict human eye effects. So we compare in vitro responses with human data obtained in controlled eye tolerance study. Methods: 12 make up removers were evaluated clinically after a standardized application, with a complete ophthalmological examination including objective and subjective signs on 24 subjects. In vitro studies were performed on a human corneal epithelial cell line. At least 6 dilutions of make up removers were applied on cells to determine IC50 (mg of product that produced a 50% cell death). The pro- inflammatory IL-8 cytokine release was quantified on cell supernatants. Osmolality was determined on each dilution. A principal component analysis was conducted to study relationship between the different variables (ingredients vs in vitro test, ingredients vs clinical study and in vitro vs clinical study). Results: In vitro results showed that cytotoxicity and IL-8 release were found independent. Cytotoxicity was not related with clinical observations, but IL-8 release displayed a good correlation with itching, burning and bulbar conjunctival redness. Osmolality. of undiluted make up removers gave similar results. Conclusions: Comparison between human corneal epithelial cell’s responses and human data obtained in controlled eye tolerance study shows that IL-8 released in vitro seems to be related to redness, stinging and burning. This pro- inflammatory cytokine might be useful to classify formulations according to their human eye tolerance. It is interesting to notice that -in contrast to this results- a previous study on 35 other formulations displayed a good correlation between in vivo Draize classification and cytotoxicity -but not with IL8 released alone The relevance of IL8 as a marker of human eye tolerance has to be confirmed with the other products and by increasing the number of studied data. Relationships between osmolality and IL8 released need to be investigated. This work illustrates the interest to use human cells in a validation approach.

Keywords: ocular irritancy/toxicity testing • clinical research methodology • cornea: tears/tear film/dry eye