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The Amine-Containing Cutaneous Irritant Heptylamine Inhibits the Volume-Regulated Anion Channel and Mobilizes Intracellular Calcium in Normal Human Epidermal Keratinocytes

Laboratoire de Neurophysiologie Cellulaire, Centre National de la Recherche Scientifique Unité Mixte de Recherche 6150, Université de la Méditerranée, Marseille, France (M.R., P.D., M.C.); Eurofins/ATS, Z. I. des Milles, ACTIMART, Aix en Provence, France (C.C.)

Many amines are skin irritants and cause contact dermatitis. However, little is known about their mechanisms of action in keratinocytes except that they induce the release of the inflammatory mediators cytokines and ATP. Here, we tested whether volume-regulated anion channels (VRACs) in primary cultures of normal human epidermal keratinocytes are modulated by the referenced amine-containing cutaneous irritant heptylamine. Under isotonic conditions, we isolated the VRAC current (I_VRAC) from other conductances using a high Ca²⁺-buffering internal solution. I_VRAC ran up after patch rupturing and reached a plateau within 15 min. It was reversibly and dose-dependently inhibited by heptylamine with an IC₅₀ value of 260 µM. Cell-swelling caused by the application of a hypotonic solution increased 2.7-fold I_VRAC and reduced the inhibition of VRAC by heptylamine with a dose-response curve shifted approximately 10-fold to the right. In addition, we showed, using cell-attached patch recordings, that adding heptylamine to the bath inhibited VRAC activity. This suggests that heptylamine diffuses into the membrane to inhibit VRAC. Finally, we demonstrated that heptylamine induced Ca²⁺-store depletion and that VRAC inhibition was not caused by the increase in cytosolic Ca²⁺. Taken together, these results identify heptylamine as a blocker of VRAC and suggest that Ca²⁺-store depletion may be involved in mechanisms of irritant contact dermatitis caused by heptylamine.

Address correspondence to: Dr. Marcel Crest, Laboratoire de Neurophysiologie Cellulaire, CNRS UMR 6150, IFR Jean Roche, Faculté de Médecine, Université de la Méditerranée, Boulevard Pierre Dramard, 13916, Marseille Cedex 20, France. E-mail: marcel.crest{at}univmed.fr