Effect of PACAP on sweat secretion by immortalized human sweat gland cells.

The process of sweating plays an important role in the human body, including thermoregulation and maintenance of the environment and health of the skin. It is known that the conditions of hyperhidrosis and anhidrosis are caused by abnormalities in sweat secretion and can result in severe skin conditions such as pruritus and erythema, which significantly reduce the patient's quality of life. However, there are many aspects of the signaling mechanisms in the process of sweating that have not been clarified, and no effective therapies or therapeutic agents have yet been discovered. Previously, it was reported that pituitary adenylate cyclase-activating polypeptide (PACAP) promotes sweating, but details of the underlying mechanism has not been clarified. We used immortalized human eccrine gland cells (NCL-SG3 cell) to investigate how sweat secretion is induced by PACAP. Intracellular Ca2+ levels were increased in these cells following their exposure to physiological concentrations of PACAP. Intracellular Ca2+ was not elevated when cells were concomitantly treated with PA-8, a specific PAC1-R antagonist, suggesting that PAC1-R is involved in the elevation of intracellular Ca2+ levels in response to PACAP treatment. Furthermore, immunocytochemistry experiments showed that aquaporin-5 was translocated from the cytoplasm to the cell membrane by PACAP. These results suggest that PACAP acts on eccrine sweat glands to promote sweat secretion by translocation of aquaporin-5 to the cell membrane in response to increased levels of intracellular Ca2+. These findings also provide a solid basis for future research initiatives to develop new therapies to treat sweating disorders.

Management of Primary Focal Hyperhidrosis: An Algorithmic Approach.

Hyperhidrosis (HH) is defined as perspiration beyond the level required to maintain temperature regulation. HH affects nearly 4.8% of the population in the United States. It can have a great impact on patient’s quality of life by disturbing daily activity, performance, confidence, social interactions, and mental health. In the majority of patients with HH (93%), the etiology of excess sweating is idiopathic, which classifies it as primary focal HH. Mild HH may be controlled with topical antiperspirants and lifestyle modifications. Based on the location of involvement, iontophoresis and botulinum toxin may be considered if the patient does not respond to topical therapies. Despite minimizing sweating, chronic use of systemic anticholinergics, in particular oxybutynin, may result in detrimental adverse effects such as dementia. Local surgery, radiofrequency, microwave, and lasers are other potential modalities for HH. Sympathectomy can be a last resort for the treatment of focal HH of the palmar, plantar, axillary, and craniofacial areas after failure of less invasive therapeutic options. In this review, we conducted a comprehensive search in the PubMed electronic database to summarize an algorithmic approach for the treatment of HH. This can help broaden options for managing this difficult disease. J Drugs Dermatol. 20(5): doi:10.36849/JDD.5774.

Optical Measurements of Sweat for in Vivo Quantification of CFTR Function in Individual Sweat Glands.

Optical measurement of CFTR-dependent sweat secretion stimulated by a beta-adrenergic cocktail (C-phase) vs. CFTR-independent sweat secretion induced by methacholine (M-phase) can discriminate cystic fibrosis (CF) patientts from controls and healthy carriers by the ratio of sweat rate in the C-phase vs. the M-phase (C/M ratio). However, image analysis is experimentally demanding and time-consuming. Here, sweat droplet number (SDN) in the C-phase, corresponding to the number of sweat-secreting glands, was a statistically significant predictor for detecting the effects of CFTR-targeted therapy. We show that in 44 non-CF subjects and 110 CF patients, SDN in the C-phase provides a linear readout of CFTR function that is more sensitive than that using the C/M ratio. In CF patients, increased SDN in the C-phase during treatment with (LUMA/IVA) was associated with a trend toward improved lung function (FEV1). Our method is suitable for multicenter monitoring of the effects of CFTR modulators.

Melatonin induces a stimulatory action on the scrotal skin components of Soay ram in the non-breeding season.

Fifteen adult Soay rams were employed in this study to investigate the effect of melatonin on the scrotal skin using histological, histochemical, and morphometrical analysis. The results revealed that the melatonin treated group showed a significant increase in the thickness of the epidermis, the cross-sectional area of blood capillaries and nerve fibers compared with the control one. In addition, obvious hypertrophy and hyperplasia were detected in the sebaceous glands in association with a significant increase in the number and diameter of apocrine sweat glands with well-developed secretory activity. S100 protein and cytokeratin-19 strongly stained the basal cells of sebaceous glands in the melatonin treated group incomparable to the control group. Moreover, the nerve fibers were intensively immunoreacted for S100 and cytokeratin proteins in the melatonin treated group in contrast to the control one. A high number of telocytes (TCs) could be identified in the treated group around the nerve fibers and blood vessels in the dermis. The number of Langerhans cells showed a significant increase in the melatonin groups that were identified by MHC II and PGP 9.5 within the epidermal layer. Furthermore, a significant increase in the number of dendritic cells was identified in the melatonin group, which were distributed within the dermis, around hair follicles, sebaceous glands, and sweat glands and were strongly expressed PGP-9.5, MHC-II, VAMP, SNAP, keratin-5, and cytokeratin-19 immunoreactivity. Notably, Merkel cells showed a significant increase in the number in the melatonin group that could be stained against nestin, SNAP, and VAMP. On the other hand, the secretory granules in sweat glands were exhibited a strong positive reactivity for synaptophysin in melatonin group. The current study showed that the administration of melatonin induced a stimulatory effect on keratinocytes, non-keratinocytes, sebaceous and sweat glands, hair follicles, as well as the vascular, neuronal, and cellular constituents of the dermis.

Biochemical and structural cues of 3D-printed matrix synergistically direct MSC differentiation for functional sweat gland regeneration.

Mesenchymal stem cells (MSCs) encapsulation by three-dimensionally (3D) printed matrices were believed to provide a biomimetic microenvironment to drive differentiation into tissue-specific progeny, which made them a great therapeutic potential for regenerative medicine. Despite this potential, the underlying mechanisms of controlling cell fate in 3D microenvironments remained relatively unexplored. Here, we bioprinted a sweat gland (SG)-like matrix to direct the conversion of MSC into functional SGs and facilitated SGs recovery in mice. By extracellular matrix differential protein expression analysis, we identified that CTHRC1 was a critical biochemical regulator for SG specification. Our findings showed that Hmox1 could respond to the 3D structure activation and also be involved in MSC differentiation. Using inhibition and activation assay, CTHRC1 and Hmox1 synergistically boosted SG gene expression profile. Together, these findings indicated that biochemical and structural cues served as two critical impacts of 3D-printed matrix on MSC fate decision into the glandular lineage and functional SG recovery.

Botulinum toxin: Pharmacology and injectable administration for the treatment of primary hyperhidrosis.

Hyperhidrosis is a dermatological condition defined by excessive sweating beyond thermoregulatory needs with significant effects on patients' quality of life. Hyperhidrosis is categorized as primary or secondary: primary hyperhidrosis is mostly focal and idiopathic, whereas secondary hyperhidrosis is commonly generalized and caused by an underlying medical condition or use of medications. Various surgical and nonsurgical therapies exist for primary hyperhidrosis. Although botulinum toxin is one of the deadliest toxins known, when used in small doses, it is one of the most effective therapies for primary hyperhidrosis. Botulinum toxin injections are widely used as a second-line primary hyperhidrosis treatment option once topical treatment strategies have failed. This article provides an overview of the commercially available botulinum toxin formulations and their applications in the treatment of primary hyperhidrosis.

Prurigo nodularis as a sweat gland/duct-related disorder: resolution associated with restoration of sweating disturbance.

Little attention has been given to the involvement of sweat glands/ducts in the pathogenesis of prurigo nodularis (PN). According to recent studies, PN is likely to develop under conditions characterized by dry skin, such as atopic dermatitis (AD), suggesting a strong impact of skin dryness on PN development. No therapeutic modalities produced complete resolution of PN without exacerbations. We previously reported that increases in skin dryness by sweating disturbance could initiate the development of AD. We investigated whether sweating responses were impaired in refractory PN lesions; and, if so, we asked whether the PN lesions could resolve by restoring sweating disturbance. Using the impression mold technique, which allows an accurate quantification of individual sweat gland/duct activity, we examined basal sweating under quiescent conditions and inducible sweating responses to thermal stimulus in PN lesions and normal-appearing skin in the same patients before and after treatment with a moisturizer or topical corticosteroids. Sweating disturbance, either basal or inducible, was most profoundly detected in the "hub" structure corresponding to the center of PN papule before the treatment. This sweating disturbance was immunohistochemically associated with the leakage of sweat into the dermis. This disturbance was restored by treatment with a moisturizer. Our limitations include a relatively small patient cohort and lack of blinding. Sweating disturbance could be one of the aggravating factors of PN development. Refractory PN with low skin hydration may resolve by restoring sweating disturbance.

Efficacy and Safety of Botulinum Toxin A in Axillary Bromhidrosis and Associated Histological Changes in Sweat Glands: A Prospective Randomized Double-Blind Side-by-Side Comparison Clinical Study.

BACKGROUND: The efficacy of botulinum toxin A (BTX-A) therapy in axillary hyperhidrosis has been documented; however, there are a few studies reporting the efficacy of BTX-A in treating axillary bromhidrosis. The histological changes occurring in sweat glands after BTX-A treatment are also unknown. OBJECTIVE: The authors report on the efficacy and safety of BTX-A in the treatment of axillary bromhidrosis and on the histological changes in sweat glands after BTX-A treatment. MATERIALS AND METHODS: Nineteen patients were included in this study. The patients were administered BTX-A injection in one axilla and sterile normal saline as placebo in the other axilla. The degree of malodor was evaluated subjectively by the patients before and 3 months after treatment. Sweat secretion was quantified by the gravimetric method. All patients underwent standard apocrinectomy in both axillary regions. RESULTS: The mean degree of malodor and mean sweat production in the BTX-A-treated axilla were significantly lower than those in the control axilla (2.42 vs 8.00; p < .0001 and 13.33 vs 33.75 mg/min; p = .0028, respectively) at 3 months after therapy. The histological studies showed apocrine sweat glands with atrophic changes and hypoplasia in treated axilla. CONCLUSION: BTX-A injection is an easy, fast, noninvasive method of treating axillary bromhidrosis.

Six-Month Comparative Analysis Monitoring the Progression of the Largest Diameter of the Sweating Inhibition Halo of Different Botulinum Toxins Type-A.

BACKGROUND: Excessive sweating is a clinical condition that can be improved with type-A botulinum toxin (BTX-A). OBJECTIVES: To evaluate and compare the largest diameter of sweating inhibition halo (SIH) of 5 different commercially available BTX-A, in five different doses, in a 6-month-long clinical evaluation. METHODS: Twenty-five adult female volunteers were injected in the dorsal trunk area with both 100 units (100UI) and 500 units (500UI) BTX-A products, reconstituted in a ratio of 1:2.5 IU, respectively. Products were applied in five different concentrations (1:2.5U, 2:5U, 3:7.5U, 4:10U, and 5:12.5U). After 30, 60, 90, 120, 150, and 180 days, a starch-iodine test was performed to obtain the largest diameter of each SIH. RESULTS: The higher the number of units used, the larger the SIH p < 0.05 for all BTX-A. However, Botox®, Botulift®, Dysport®, and Prosigne® have pretty likewise SIH along the study, with some few differences for some doses and months between one and another. However, Xeomin® is the BTX-A with the smallest SIH, in comparison with all others, in any dose and period. CONCLUSIONS: Differences were observed among all brands of BTX-As, based on dose and time after injection. Xeomin® provides the smallest SIH in comparison with others BTX-A.

Sweat rate analysis of ivacaftor potentiation of CFTR in non-CF adults.

To determine if ivacaftor (Kalydeco) influences non-CF human CFTR function in vivo, we measured CFTR-dependent (C-sweat) and CFTR-independent (M-sweat) rates from multiple identified sweat glands in 8 non-CF adults. The two types of sweating were stimulated sequentially with intradermal injections of appropriate reagents; each gland served as its own control via alternating off-on drug tests on both arms, given at weekly intervals with 3 off and 3 on tests per subject. We compared drug effects on C-sweating stimulated by either high or low concentrations of ß-adrenergic cocktail, and on methacholine-stimulated M-sweating. For each subject we measured ~700 sweat volumes from ~75 glands per arm (maximum 12 readings per gland), and sweat volumes were log-transformed for statistical analysis. T-tests derived from linear mixed models (LMMs) were more conservative than the familiar paired sample t-tests, and show that ivacaftor significantly increased C-sweating stimulated by both levels of agonist, with a larger effect in the low cocktail condition; ivacaftor did not increase M-sweat. Concurrent sweat chloride tests detected no effect of ivacaftor. We conclude that ivacaftor in vivo increases the open channel probability (PO) of WT CFTR, provided it is not already maximally stimulated.

Enhancing glucose flux into sweat by increasing paracellular permeability of the sweat gland.

Non-invasive wearable biosensors provide real-time, continuous, and actionable health information. However, difficulties detecting diluted biomarkers in excreted biofluids limit practical applications. Most biomarkers of interest are transported paracellularly into excreted biofluids from biomarker-rich blood and interstitial fluid during normal modulation of cellular tight junctions. Calcium chelators are reversible tight junction modulators that have been shown to increase absorption across the intestinal epithelium. However, calcium chelators have not yet been shown to improve the extraction of biomarkers. Here we show that for glucose, a paracellularly transported biomarker, the flux into sweat can be increased by >10x using citrate, a calcium chelator, in combination with electroosmosis. Our results demonstrate a method of increasing glucose flux through the sweat gland epithelium, thereby increasing the concentration in sweat. Future work should examine if this method enhances flux for other paracellularly transported biomarkers to make it possible to detect more biomarkers with currently available biosensors.

Prolonged and localized sweat stimulation by iontophoretic delivery of the slowly-metabolized cholinergic agent carbachol.

BACKGROUND: Continuous non-invasive sampling and sensing of multiple classes of analytes could revolutionize medical diagnostics and wearable technologies, but also remains highly elusive because of the many confounding factors for candidate biofluids such as interstitial fluid, tears, saliva, and sweat. Eccrine sweat biosensing has seen a recent surge in demonstrations of wearable sampling and sensing devices. However, for subjects at rest, access to eccrine sweat is highly limited and unpredictable compared to saliva and tears. OBJECTIVE: Reported here is a prolonged and localized sweat stimulation by iontophoretic delivery of the slowly-metabolized nicotinic cholinergic agonist carbachol. METHODS: Presented here are detailed measurements of natural baseline sweat rates across multiple days, confirming a clear need for localized sweat stimulation. Iontophoresis was performed with either carbachol or pilocarpine in order to stimulate sweat in subjects at rest. Furthermore, improved methods of quantifying sweat generation rates (nL/min/gland) are demonstrated. RESULTS: In-vivo testing reveals that carbachol stimulation can surpass a major goal of 24-h sweat access, in some cases providing more than an order of magnitude longer duration than stimulation with commonly-used pilocarpine. Also demonstrated is reduction of the traditional iontophoretic dosage for sweat stimulation (<5.25-42mC/cm2). This increases the viability of repeated dosing as demonstrated herein, and for carbachol is as much as 100-1000X less than used for other applications. CONCLUSION: This work is not only significant for wearable sweat biosensing technology, but could also have broader impact for those studying topical skin products, antiperspirants, textiles and medical adhesives, nerve disorders, the effects of perspiration on skin-health, skin related diseases such as idiopathic pure sudomotor failure and hyperhidrosis, and other skin- and perspiration-related applications.

Ivacaftor restores CFTR-dependent sweat gland fluid secretion in cystic fibrosis subjects with S945L alleles.

BACKGROUND: To determine in vivo effects of CFTR modulators on mutation S945L. METHODS: We measured effects of CFTR modulators on CFTR-dependent sweating ('C-sweat') in two pancreatic sufficient cystic fibrosis (CF) subjects. S1 (S945L/G542X) took ivacaftor and S2 (S945L/F508del) took ivacaftor+tezacaftor. Sweating was stimulated pharmacologically to produce sequentially both CFTR-independent (methacholine stimulated) M-sweat and C-sweat; and the ratio of these was compared. Sweat secretion was measured with two methods: real time secretory rate quantitative recording and by optically measuring the growth of sweat bubbles under oil from multiple identified glands. RESULTS: Using the quantitative recorder, we saw zero C-sweat secretion off-drug, but when on-drug the C-sweat responses for both subjects were comparable to those seen in carriers. The on-drug response was further quantified using the sweat bubble method. Each subject again showed robust C-sweat responses, with C-sweat/M-sweat ratios~half of the ratio determined for a cohort of 40 controls tested under identical conditions. CONCLUSION: These in vivo results, consistent with prior in vitro findings, indicate that the drug treatments restore near-normal function to S945L-CFTR, and support the use of ivacaftor as a treatment for CF patients who carry this allele.

Claudin-3 Loss Causes Leakage of Sweat from the Sweat Gland to Contribute to the Pathogenesis of Atopic Dermatitis.

The transfer of sweat to the skin surface without leakage is important for the homeostatic regulation of skin and is impaired in atopic dermatitis. Although the precise composition of the leakage barrier remains obscure, there is a large contribution from claudins, the major components of tight junctions. In humans, claudin-1, -3, and -15 are expressed on sweat ducts, and claudin-3 and -10 are expressed on secretory coils. Although only two claudins are expressed in murine sweat glands, we found that the expression of claudin-3 is conserved. Atopic dermatitis lesional skin had decreased claudin-3 expression in sweat glands, which was accompanied by sweat leakage. This critical role in water barrier function was confirmed in Cldn3-/- and Cldn3+/- mice and those with experimentally decreased claudin-3. Our results show the crucial role of claudin-3 in preventing sweat gland leakage and suggest that the pathogenesis of dermatoses accompanied by hypohidrosis involves abnormally decreased claudin-3.

Do nitric oxide synthase and cyclooxygenase contribute to sweating response during passive heating in endurance-trained athletes?

The aim of our study was to determine if habitual endurance training can influence the relative contribution of nitric oxide synthase (NOS) and cyclooxygenase (COX) in the regulation of sweating during a passive heat stress in young adults. Ten trained athletes and nine untrained counterparts were passively heated until oral temperature (as estimated by sublingual temperature, Tor) increased by 1.5°C above baseline resting. Forearm sweat rate (ventilated capsule) was measured at three skin sites continuously perfused with either lactated Ringer's solution (Control), 10 mmol/L NG -nitro-L-arginine methyl ester (L-NAME, non-selective NOS inhibitor), or 10 mmol/L ketorolac (Ketorolac, non-selective COX inhibitor) via intradermal microdialysis. Sweat rate was averaged for each 0.3°C increase in Tor Sweat rate at the L-NAME site was lower than Control following a 0.9 and 1.2°C increase in Tor in both groups (all P ≤ 0.05). Relative to the Control site, NOS-inhibition reduced sweating similarly between the groups (P = 0.51). Sweat rate at the Ketorolac site was not different from the Control at any levels of Tor in both groups (P > 0.05). Nevertheless, a greater sweat rate was measured at the end of heating in the trained as compared to the untrained individuals (P ≤ 0.05). We show that NOS contributes similarly to sweating in both trained and untrained individuals during a passive heat stress. Further, no effect of COX on sweating was measured for either group. The greater sweat production observed in endurance-trained athletes is likely mediated by factors other than NOS- and COX-dependent mechanisms.

Oxybutynin as an alternative treatment for hyperhidrosis.

Hyperhidrosis is the excessive production of sweating, which can be primary and focal or secondary to various pathologies. The exact cause of primary focal hyperhidrosis is still unknown, although a genetic basis is recognized, and its prevalence varies from 1% to 2.8%. The most affected sites are the armpits, palms, soles and face. It causes much discomfort, affects the quality of life, and is estimated to be undervalued by health professionals. Many treatment options are proposed, both clinical and surgical. The aim of this review is to focus on the treatment of hyperhidrosis with oxybutynin, an anticholinergic drug originally used to control overactive bladder.

A device to measure secretion of individual sweat glands for diagnosis of peripheral neuropathy.

There is a need for quantitative, precise assessment of small fiber peripheral nerve function. We tested a customized camera device and protocol designed to quantify secretions of individual sweat glands (SGs). Testing was performed on 178 healthy controls and 20 neuropathy subjects. Sweating was stimulated on a 2.25 cm2 skin area by iontophoresis of pilocarpine. The camera imaged sweat from 50 to 400 sweat ducts. We calculated secretion rate of individual SGs, total sweat volume, and number of secreting SGs at four body sites. Neuropathy subjects were tested at the two distal sites to demonstrate the device's capability to detect abnormal sudomotor function. Normal ranges were calculated for each body site. Neuropathy subjects had lower sweat rates per SG, lower total sweat, and lower SG density. The normal values decreased with advancing age, were lower in females, and differed between body sites. There was good agreement with repeat testing. The device provides reliable, precise quantitative measures of sweat secretion from single SGs for characterization of sudomotor nerve function in healthy control subjects and in subjects with known peripheral neuropathy. The test combines the capabilities of existing tests of sudomotor function while providing additional capabilities.