Role of Bradykinin Type 2 Receptors in Human Sweat Secretion: Translational Evidence Does Not Support a Functional Relationship

A single-blind, randomized, crossover study on the efficacy of icatibant for sweating-induced dermal pain (icatibant for sweating-induced dermal pain)

INTRODUCTION

Severe dermal pain triggered by sweating stimuli, such as bathing, exercise, and mental stress, significantly affects patients' daily lives. The pathomechanism underlying the sweating-induced dermal pain remains poorly understood and there exists no standard treatment for such pain. This study aims to evaluate the effectiveness of icatibant as an analgesic, a bradykinin B2 receptor antagonist, in treating sweating-induced dermal pain, and to establish the role of bradykinin in pain induction.

METHODS/DESIGN

A multicenter, exploratory, crossover, single-blinded, placebo-controlled randomized, comparative study will be conducted to evaluate the efficacy of subcutaneous icatibant injection (30 mg) in treating sweating-induced dermal pain. Ten patients will be enrolled and assigned randomly in a 1:1 ratio to either the icatibant-placebo or placebo-icatibant groups. The primary endpoint is the change in the visual analog scale scores for dermal pain induced by thermal load before and after treatment with icatibant or placebo. Secondary endpoints include changes in the duration of dermal pain, blood and plasma histamine levels, serum angiotensin-converting enzyme levels, and histological evaluation of skin tissue samples at the site of dermal pain.

DISCUSSION

The effectiveness of icatibant against sweating-induced dermal pain would provide clear evidence for the involvement of the bradykinin-bradykinin B2 receptor pathway in the pathogenesis of this condition. This finding may contribute to a better understanding of the underlying mechanisms of dermal pain associated with sweating stimuli and has the potential to improve patients' quality of life by suggesting potential treatment options, specifically, using drugs that inhibit bradykinin or suppress its production.

The family of kallikrein-related peptidases and kinin peptides as modulators of epidermal homeostasis

The epidermis is the outermost skin layer and is part of one of the largest organs in the body; it is supported by the dermis, a network of fibrils, blood vessels, pilosebaceous units, sweat glands, nerves, and cells. The skin as a whole is a protective shield against numerous noxious agents, including microorganisms and chemical and physical factors. These functions rely on the activity of multiple growth factors, peptide hormones, proteases, and specific signaling pathways that are triggered by the activation of distinct types of receptors sited in the cell membranes of the various cell types present in the skin. The human kallikrein family comprises a large group of 15 serine proteases synthesized and secreted by different types of epithelial cells throughout the body, including the skin. At this site, they initiate a proteolytic cascade that generates the active forms of the proteases, some of which regulate skin desquamation, activation of cytokines, and antimicrobial peptides. Kinin peptides are formed by the action of plasma and tissue kallikreins on kininogens, two plasma proteins produced in the liver and other organs. Although kinins are well known for their proinflammatory abilities, in the skin they are also considered important modulators of keratinocyte differentiation. In this review, we summarize the contributions of the kallikreins and kallikrein-related peptidases family and those of kinins and their receptors in skin homeostasis, with special emphasis on their pathophysiological role.