A cream based on Aquaphilus dolomiae extracts alleviates non-histaminergic pruritus in humans

Itch is a symptom of many skin diseases. At least two pathways of itch have been described: a histaminergic and a non-histaminergic pathway. The latter is activated by cowhage, a tropical plant with spicules that, upon skin contact, release mucunain, a cysteine protease serving as a ligand for the protease-activated receptor 2 (PAR-2) [1]. In humans, PAR-2, expressed by mechanically-sensitive C fibres and keratinocytes, is involved in the development of inflammation and itch in atopic dermatitis (AD) [2]. In AD patients, a dysregulation of PAR-2 has been documented in both sensory fibres and epidermal keratinocytes [3]. Moreover, PARs are involved in sensitization to itch, particularly in hyperknesis (enhanced itch to a normally itchy stimulus), and alloknesis (itch elicited by an innocuous touch stimulus) [4]. The cowhage model of itch is suitable for the study of itch because it resembles the characteristics of pruritus in chronic dermatoses, such as AD [5, 6]. Few topical drugs have shown efficacy against chronic itch, and very few topical agents targeting non-histaminergic itch pathways have been studied [5, 6]. We performed a prospective, placebo-controlled study in order to evaluate the effects of a cream, based on a biologic extract from culture of Aquaphilus dolomiae, on the intensity of evoked itch in healthy subjects. The Gram-negative bacteria strain I-4290, Aquaphilus dolomiae, isolated from Avene Spring water (Southwest France), has been fully characterized, regarding genotyping and phenotyping, and this information has been deposited at the CNCM (Collection Nationale de Cultures de Microorganismes Institut Pasteur Paris) [7].