Quantitative ion determination in eccrine sweat gland cells correlates to sweat reduction of antiperspirant actives

Abstract

Objective Axillary wetness represents an unwanted effect of the physiologically vital sweating mechanism, especially when it becomes excessive. Cosmetic products reducing sweat secretion rely on aluminium salts as the active ingredient acting by physically blocking the sweat gland. Driven by the interest to better understand the sweat mechanism and to develop alternative technologies against excessive sweating a search for an effective testing approach started as up to now, cost‐ and time‐consuming in vivo studies represent the standard procedure for testing and identifying these alternatives. Material and methods The herein described in vitro test system is based on the measurement of intracellular changes of the ion equilibrium in cultured eccrine sweat gland cells. Subsequently, in vivo studies on the back of volunteers were conducted to verify the sweat‐reducing effect of in vitro newly discovered substance. Results In this study, we describe an effective cell‐based in vitro method as a potent tool for a more targeted screening of alternatives to aluminium salts. Testing the commonly used aluminium chlorohydrate as one example of an aluminium‐based active in this screening procedure, we discovered a distinct influence on the ion equilibrium: Intracellular levels of sodium ions were decreased while those of chloride increased. Screening of various substances revealed a polyethyleneimine, adjusted to pH 3.5 with hydrochloric acid, to evoke the same alterations in the ion equilibrium as aluminium chlorohydrate. Subsequent in vivo studies showed its substantial antiperspirant action and confirmed the high efficiency of the polyethyleneimine solution in vivo. Further, specific investigations connecting the chloride content of the tested substances with the resulting sweat reduction pointed towards a substantial impact of the chloride ions on sweating. Conclusion The newly described in vitro cell‐based screening method represents an effective means for identifying new antiperspirant actives and suggests an additional biological mechanism of action of sweat‐reducing ingredients which is directed towards unbalancing of the ion equilibrium inside eccrine sweat gland cells.

A novel cell line from human eccrine sweat gland duct cells for investigating sweating physiology

“…Reactivity of SV40T‐transduced 1D10 duct‐derived cells was established by treating those cells with previously published aluminium chlorohydrate (ACH) alternative PEI‐HCl [46]. Matching reported results obtained in eSG co‐culture cells, application of PEI‐HCl also triggered reduction of [Na + ] i with concomitant elevation of [Cl − ] i in both, parental and 1D10 duct‐derived cells.…”

“…The basic idea for establishing an immortalized duct cell line in cosmetics research was its unlimited use in screening procedures for the identification of alternative antiperspirant actives. The establishment of such a test procedure was recently published by our group [46]. When relying on limited primary cell material donor‐dependent variations would be induced.…”

“…To assess the reaction of selected SV40T‐transduced 1D10 duct‐derived cells their intracellular sodium and chloride ion concentrations ([Na + ] i and [Cl − ] i , respectively) were tracked using ion‐sensitive fluorescent probes. Therefore, 1D10 cell cultures in P22 were treated with previously analysed test substance polyethyleneimine pH‐adjusted with hydrochloric acid (PEI‐HCl) [46]. As controls, primary parental, duct‐derived cells in passage 6 were carried along and treated with the same DMEM‐based solution containing 0.2% of PEI‐HCl (Figure 5).…”

“…Relative intracellular concentrations of the cation sodium [Na + ] i and the anion chloride [Cl − ] i were determined in monolayer cells of primary and transduced duct cells as previously described by our group [46]. Treatment of duct cells to assess their functionality occurred with polyethyleneimine adjusted to pH 3.5 with HCl (PEI‐HCl) (BASF, Ludwigshafen, Germany).…”

“…With regard to scientific research addressable with those cell lines, an in vitro eSG cell-based screening approach was recently developed by us to identify alternatives replacing aluminium salts in cosmetics. While contributing to the knowledge of the mechanism of action of aluminium salts it also revealed some promising substance candidates as alternative actives [46]. However, this screening relied on the usage of primary cells with a limited lifespan due to induction of replicative senescence after a few weeks of continuous culture.…”