CHRNA1 promotes the pathogenesis of primary focal hyperhidrosis

Highlights

• CHRNA1 upregulation is a characteristic of the sweat glands of PFH patients and hyperhidrosis mice.

• Silencing of CHRNA1 decreased sweat secretion and the number of sweat secretory granules of hyperhidrosis mice.

• Serum acetylcholine and AQP5 and CACNA1C expression in sweat glands were reduced by siCHRNA1.

Abstract

The aim of the study was to elucidate the involvement of cholinergic receptor nicotinic alpha 1 subunit (CHRNA1) in the pathogenesis of primary focal hyperhidrosis (PFH). The hyperhidrosis mouse model was constructed using pilocarpine injection. The expression levels of CHRNA1 in sweat gland tissues of PFH patients and hyperhidrosis mice were compared using Western blots and quantitative real-time PCR (qRT-PCR) analyses. Sweat secretion in hyperhidrosis mice treated with small-interfering RNA (siRNA) targeting CHRNA1 (si-CHRNA1) or non-specific siRNA were compared. Sweat secretory granules in the sweat gland cells of hyperhidrosis mice were examined using transmission electron microscopy. The serum level of acetylcholine was measured using enzyme-linked immunosorbent assay, while markers associated with PFH, including Aquaporin 5 (AQP5) and Calcium Voltage-Gated Channel Subunit Alpha1 C (CACNA1C), were assessed using immunohistochemical assay and Western blots. Brain-derived neurotrophic factor (BDNF) and Neuregulin 1 (NRG-1) in sympathetic ganglia axons of hyperhidrosis mice were quantified using Western blots. CHRNA1 up-regulation is a characteristic of the sweat glands of PFH patients and Hyperhidrosis mice. Silencing CHRNA1 decreased sweat secretion and the number of sweat secretory granules of hyperhidrosis mice. Serum acetylcholine, as well as AQP5 and CACNA1C expression in the sweat glands, was reduced by siCHRNA1. BDNF1 and NRG-1 levels in the sympathetic ganglia axons were also attenuated by siCHRNA1 treatment. CHRNA1 up-regulation is a potential biomarker of PFH and downregulating CHRNA1 could alleviate the symptoms of PFH through inactivating the sympathetic system.

Introduction

Hyperhidrosis refers to excessive sweating in local, regional or the entire body, that can be caused by neurological, infectious, endocrine or pharmacological factors, as well as unknown causes therefore considered idiopathic in some cases (McConaghy and Fosselman, 2018). Primary focal hyperhidrosis (PFH) refers to local or regional hyperhidrosis and is distinguished by sweating in one or more sites including the hands, axillae, feet, forehand, or face, in addition to the crown or inguinal region (Smith and Pariser, 2018). PFH can be exacerbated by factors including stress, heat, gustatory and olfactory stimuli. PFH severely affects quality of life and work efficiencies and may even lead to serious psychological disorders if left untreated for a long period of time. It has been reported about 1.4% of the US population suffer from PFH (Lin et al., 2020). Thus far, treatments for PFH are limited to symptom alleviation, and precision medicine targeting molecular mechanisms driving PFH pathogenesis is limited. It is imperative to develop molecular targets for PFH treatment and elucidate their mechanisms of action.

An important pathological cause of PFH is the dysfunction of the autonomous sympathetic nervous system. Previous studies have shown that PFH is associated with up-regulation of acetylcholine receptor subunits, choline acetyltransferase and vasoactive intestinal peptide in the thoracic sympathetic ganglia (de Moura et al., 2013). A PFH-related gene on chromosome 2q31.1 has been identified through exome sequencing and genome-wide single nucleotide polymorphism chain scan analysis in a PPH-001 family of patients with familial inheritance (Chen et al., 2015). In combination with the Mapviewer database analysis of National Center for Biotechnology Information (NCBI), 30 genes with clearly defined functions have been identified as potential targets. Among them, cholinergic receptor nicotinic alpha 1 subunit (CHRNA1), which regulates the binding and gating of acetylcholine neurotransmitters, stood out due to its role in the sympathetic nervous system (Heckmann et al., 1996). Previously, dysregulated CHRNA1 levels were found to be associated with multiple neuromuscular disorders, such as congenital myasthenic syndrome (Abath Neto et al., 2017), myasthenia gravis (Li et al., 2017) and multiple pterygium syndrome (Vogt et al., 2008). More importantly, the CHRNA1 gene expression has been found to be significantly higher in the thoracic sympathetic ganglia of patients with hand sweating than normal subjects (Hurst et al., 2013). Acetylcholine blockers have been used to treat patients with PFH (Haider and Solish, 2005), and the enhanced expression of CHRNA1 gene may be one of the mechanisms underlying excessive sweat secretion.

Herein, we set out to elucidate the role of CHRNA1 in PFH by testing whether CHRNA1 was up-regulated in sweat gland tissues of PFH patients, and hyperhidrosis mice. The therapeutic potential of CHRNA1 silencing using small-interfering RNA (siRNA) was assessed in mice to evaluate whether this treatment alleviated PFH symptoms and reduced the level of PFH biomarker molecules. We showed that CHRNA1 up-regulation was a potential biomarker of PFH and down-regulating CHRNA1 was effective in alleviating the symptoms of PFH through inactivating the sympathetic system. Our study for the first time reports a link between the up-regulated CHRNA1 and PFH and could shed light on the potential of CHRNA1 as a therapeutic target in treating PFH.