Differential antigen expression between human apocrine sweat glands and eccrine sweat glands.

Bromhidrosis has a great negative impact on personal occupation and social psychology. It is not yet clear whether bromhidrosis is caused by apocrine sweat glands or the co-action of apocrine sweat glands and eccrine sweat glands. To distinguish between apocrine sweat glands and eccrine sweat glands, specific antigen markers for apocrine sweat glands and eccrine sweat glands must be found first. In the study, we detected the expression of K7, K18, K19, Na+-K+-2Cl- cotransporter 1 (NKCC1), carbonic anhydrase II (CAII), Forkhead transcription factor a1 (Foxa1), homeobox transcription factor engrailed homeobox1 (En1), gross cystic disease fluid protein-15 (GCDFP-15), mucin-1 (MUC-1), cluster of differentiation 15 (CD15) and apolipoprotein (APOD) in eccrine sweat glands and apocrine sweat glands by immunofluorescence staining. The results showed that K7, K18, K19, Foxa1, GCDFP-15 and MUC-1 were expressed in both apocrine and eccrine sweat glands, CD15 and APOD were only expressed in apocrine sweat glands, and CAII, NKCC1 and En1 were only expressed in eccrine sweat glands. We conclude that CD15 and APOD can serve as specific markers for apocrine sweat glands, while CAII, NKCC1 and En1 can serve as specific markers for eccrine sweat glands to differentiate the two sweat glands.

[Research advances on the regulatory mechanism of sweat secretion ion channels of eccrine sweat glands].

Sweat glands are widely distributed in human skin, among which eccrine sweat glands play major roles in heat dissipation and sweat secretion. Sweat secretion is mainly regulated by nervous system and includes two processes of secretion of secretory coil and reabsorption of sweat duct, involving various ion channels and proteins such as calcium ion channel, potassium ion channel, sodium-potassium-chloride co-transporter 1, Best2 protein, aquaporin 5, cystic fibrosis transmembrane conductance regulator, and epithelial sodium ion channel. This paper reviews the nerve conduction system and various ion channels involved in sweat secretion of exocrine sweat glands in order to provide a theoretical basis for the study of regeneration, repair, and transformation of stem cells.

Foxa1 mediates eccrine sweat gland development through transcriptional regulation of Na-K-ATPase expression.

Eccrine sweat glands (ESGs) perform critical functions in temperature regulation in humans. Foxa1 plays an important role in ESG maturation and sweat secretion. Its molecular mechanism, however, remains unknown. This study investigated the expression of Foxa1 and Na-K-ATPase (NKA) in rat footpads at different development stages using immunofluorescence staining, qRT-PCR, and immunoblotting. Also, bioinformatics analysis and Foxa1 overexpression and silencing were employed to evaluate Foxa1 regulation of NKA. The results demonstrated that Foxa1 was consistently expressed during the late stages of ESGs and had a significant role in secretory coil maturation during sweat secretion. Furthermore, the mRNA abundance and protein expression of NKA had similar accumulation trends to those of Foxa1, confirming their underlying connections. Bioinformatics analysis revealed that Foxa1 may interact with these two proteins via binding to conserved motifs in their promoter regions. Foxa1 gain-of-function and loss-of-function experiments in Foxa1-modified cells demonstrated that the activities of NKA were dependent on the presence of Foxa1. Collectively, these data provided evidence that Foxa1 may influence ESG development through transcriptional regulation of NKA expression.

Physiological mechanisms determining eccrine sweat composition.

PURPOSE: The purpose of this paper is to review the physiological mechanisms determining eccrine sweat composition to assess the utility of sweat as a proxy for blood or as a potential biomarker of human health or nutritional/physiological status. METHODS: This narrative review includes the major sweat electrolytes (sodium, chloride, and potassium), other micronutrients (e.g., calcium, magnesium, iron, copper, zinc, vitamins), metabolites (e.g., glucose, lactate, ammonia, urea, bicarbonate, amino acids, ethanol), and other compounds (e.g., cytokines and cortisol). RESULTS: Ion membrane transport mechanisms for sodium and chloride are well established, but the mechanisms of secretion and/or reabsorption for most other sweat solutes are still equivocal. Correlations between sweat and blood have not been established for most constituents, with perhaps the exception of ethanol. With respect to sweat diagnostics, it is well accepted that elevated sweat sodium and chloride is a useful screening tool for cystic fibrosis. However, sweat electrolyte concentrations are not predictive of hydration status or sweating rate. Sweat metabolite concentrations are not a reliable biomarker for exercise intensity or other physiological stressors. To date, glucose, cytokine, and cortisol research is too limited to suggest that sweat is a useful surrogate for blood. CONCLUSION: Final sweat composition is not only influenced by extracellular solute concentrations, but also mechanisms of secretion and/or reabsorption, sweat flow rate, byproducts of sweat gland metabolism, skin surface contamination, and sebum secretions, among other factors related to methodology. Future research that accounts for these confounding factors is needed to address the existing gaps in the literature.

K31 as a novel marker for clear secretory cells in human eccrine sweat glands.

K31 was previously considered as one of the hair keratins. During a study on differential markers between hair follicles and eccrine sweat glands, we observed that K31 was expressed in eccrine sweat gland cells in a scattered pattern, similar to the distribution of dark or clear secretory cells. To investigate the precise cell localization of K31 in human eccrine sweat glands and find new marker for eccrine sweat gland cells, human skin samples were fixed, paraffined and sectioned. The serial sections were stained for K31, dark secretory cell marker gross cystic disease fluid protein 15 (GCDFP15) and clear secretory cell marker carbonic anhydrase II (CAII). The exact cell localization of K31 was detected by double immunofluorescence staining of K31 and a serial of cell-specific markers, and further by dual stain using a combination of periodic acid-Schiff (PAS) and immunofluorescence for K31 and GCDFP15. The expression pattern of K31-positive cells was similar to that of CAII-positive cells but was different from that of GCDFP15-positive staining in serial sections. Double immunofluorescent staining showed that K31-positive cells co-expressed K7 and CAII, but not S100P, α-SMA or GCDFP15. Dual stain by combined PAS and immunofluorescence showed that K31-positive cells are negative for PAS staining. We conclude that K31 is a previously unreported eccrine clear cell marker that allows for distinction between clear and dark secretory cells, as well as between secretory coils and ducts of eccrine sweat glands in human eccrine sweat glands.

Integrated Transcriptomic and Proteomic Analysis of Human Eccrine Sweat Glands Identifies Missing and Novel Proteins.

The eccrine sweat gland is an exocrine gland that is involved in the secretion of sweat for control of temperature. Malfunction of the sweat glands can result in disorders such as miliaria, hyperhidrosis and bromhidrosis. Understanding the transcriptome and proteome of sweat glands is important for understanding their physiology and role in diseases. However, no systematic transcriptome or proteome analysis of sweat glands has yet been reported. Here, we isolated eccrine sweat glands from human skin by microdissection and performed RNA-seq and proteome analysis. In total, ∼138,000 transcripts and ∼6,100 proteins were identified. Comparison of the RNA-seq data of eccrine sweat glands to other human tissues revealed the closest resemblance to the cortex region of kidneys. The proteome data showed enrichment of proteins involved in secretion, reabsorption, and wound healing. Importantly, protein level identification of the calcium ion channel TRPV4 suggests the importance of eccrine sweat glands in re-epithelialization of wounds and prevention of dehydration. We also identified 2 previously missing proteins from our analysis. Using a proteogenomic approach, we identified 7 peptides from 5 novel genes, which we validated using synthetic peptides. Most of the novel proteins were from short open reading frames (sORFs) suggesting that many sORFs still remain to be annotated in the human genome. This study presents the first integrated analysis of the transcriptome and proteome of the human eccrine sweat gland and would become a valuable resource for studying sweat glands in physiology and disease.

Expression and localization of Forkhead transcription factor A1 in the three-dimensional reconstructed eccrine sweat glands.

Previously studies showed that Forkhead transcription factor A1 (FoxA1) was associated with sweat secretion. To investigate the expression and localization of FoxA1 in the three-dimensional (3D) reconstructed eccrine sweat glands, eccrine sweat gland cells were transplanted subcutaneously into nude mice with Matrigel, and at 2, 3, 4, 5, 6, 8, 10 and 12 weeks post-transplantation, the reconstructed eccrine sweat glands were removed and immunostained for FoxA1 and co-immunostained for FoxA1 and eccrine sweat markers, K7, carbonic anhydrase II (CA Ⅱ), gross cystic disease fluid protein-15 (GCDFP-15) and α-smooth muscle actin (α-SMA), and FoxA1 and sweat secretion-related proteins, Na+-K+-ATPase α and Na+-K+-2Cl- cotransporter 1 (NKCC1). The results showed that FoxA1-positive cells weren't detected until 3 weeks post-implantation, a time point of the differntiation of secretory coil-like structures. From the fourth week on, the number of FoxA1-positive cells increased and thereafter maintained at a high number. Double immunofluorescence staining showed that FoxA1-positive cells co-expressed dark cell marker GCDFP-15 and myoepithelial cell marker α-SMA, as well as secretion-related proteins, Na+-K+-ATPase α and NKCC1 in both the native and reconstructed eccrine sweat glands. In conclusion, FoxA1 might be related to the development and differentiation of secretory coil-like structures, as well as the secretory function of the 3D reconstructed eccrine sweat glands.

Lymphomatoid papulosis with folliculotropism, eccrinotropism and neurotropism.

The histopathological characteristics of lymphomatoid papulosis (LyP) vary. Currently, 6 subtypes have been reported, including a new subtype with perifollicular infiltration and different degrees of folliculotropism of CD30+ atypical lymphocytes, known as follicular LyP. However, LyP pathologically manifesting with folliculotropism, eccrinotropism and neurotropism has been rarely reported. We present a case of LyP showing CD30+ atypical lymphocytes around the hair follicle, eccrine gland and nerve fiber, with varying degrees of infiltrates. The pathological characteristics of folliculotropism and eccrinotropism are often associated with mycosis fungoides (MF). This case suggests that differential diagnosis is necessary when atypical lymphocytes infiltrate the follicle and eccrine gland. As folliculotropism and eccrinotropism can occur in both MF and LyP, it may represent a conceptual intersection between the 2 disease processes.

Homeobox transcriptional factor engrailed homeobox 1 is expressed specifically in normal and neoplastic sweat gland cells.

AIMS: A number of homeobox transcriptional factors are utilised as organ-specific markers in the histopathological diagnosis of neoplasms. We have screened a homeobox gene that is expressed specifically in normal sweat gland cells and is useful for the histopathological diagnosis of sweat gland neoplasms. METHODS AND RESULTS: By screening an open database resource of The Human Protein Atlas, 37 genes among the 235 homeobox transcriptional factors were found to be expressed specifically in the skin. Among those 37 genes, the engrailed homeobox 1 (En1) was expressed in normal eccrine glands but not in the epidermal keratinocytes. Expression of En1 was found throughout the eccrine glands, but not in the apocrine secretory coils, sebaceous glands or hair follicles. Expression of En1 was examined immunohistochemically in 111 cases of cutaneous epithelial neoplasms. All nine cases of poroma, seven cases of spiradenoma and six cases of syringoma, which are considered to differentiate towards eccrine glands, showed positive nuclear staining in most of the tumour cells. Sebaceous gland and hair follicle tumours were immunonegative. En1 was expressed focally in the epidermal neoplasms of seborrheic keratosis and squamous cell carcinoma. CONCLUSION: Engrailed homeobox 1 was expressed specifically in normal eccrine glands and was expressed in most of the tumour cells of sweat gland neoplasms with eccrine gland differentiation. En1 was expressed focally in epidermal neoplasms; however, it was absent in sebaceous or hair follicle neoplasms. These findings will help in the histopathological diagnosis as well as understanding of the histogenesis of sweat gland neoplasms.

Neural control of sweat secretion: a review.

BACKGROUND: Humans have 4 million exocrine sweat glands, which can be classified into two types: eccrine and apocrine glands. Sweat secretion, a constitutive feature, is directly involved in thermoregulation and metabolism, and is regulated by both the central nervous system (CNS) and autonomic nervous system (ANS). OBJECTIVES: To explore how sweat secretion is controlled by both the CNS and the ANS and the mechanisms behind the neural control of sweat secretion. METHODS: We conducted a literature search on PubMed for reports in English from 1 January 1950 to 31 December 2016. RESULTS AND CONCLUSIONS: Acetylcholine acts as a potent stimulator for sweat secretion, which is released by sympathetic nerves. ß-adrenoceptors are found in adipocytes as well as apocrine glands, and these receptors may mediate lipid secretion from apocrine glands for sweat secretion. The activation of ß-adrenoceptors could increase sweat secretion through opening of Ca2+ channels to elevate intracellular Ca2+ concentration. Ca2+ and cyclic adenosine monophosphate play a part in the secretion of lipids and proteins from apocrine glands for sweat secretion. The translocation of aquaporin 5 plays an important role in sweat secretion from eccrine glands. Dysfunction of the ANS, especially the sympathetic nervous system, may cause sweating disorders, such as hypohidrosis and hyperhidrosis.

Lipoid proteinosis: A case with distinct histopathological and radiological findings.

Lipoid proteinosis is a rare inherited genodermatosis characterized by hyaline deposits in various tissues. Clinically, it manifests with cutaneous as well as extracutaneous features. Periodic acid-Schiff (PAS)-reactive hyaline deposits in the upper dermis, with localization around blood vessels and eccrine sweat glands, in particular, is the histopathological hallmark finding. On brain imaging, bilateral symmetrical temporal lobe calcifications are considered to be pathognomonic of this disorder. We report a case of lipoid proteinosis in which hyaline deposits were present in the papillary and reticular dermis, without being seen at the periphery of eccrine sweat glands, along with dystrophic calcification. Magnetic resonance imaging (MRI) of brain revealed hydrocephalus, subependymal heterotropia and absent splenium of corpus callosum with no evidence of temporal lobe calcification. Thus, our case highlights the inherent diverse nature of lipoid proteinosis.

Serum is an indispensable factor in the maintenance of the biological characteristics of sweat gland cells.

The tolerance of sweat gland cells for in vitro amplification and subcultivation is low as they are somatic cells. The present study aimed to formulate an optimal medium for the culture of human eccrine sweat gland cells (HESGCs) and to establish a method for induction of HESGCs proliferation, whilst maintaining the characteristics of sweat gland cells. HESGCs cultured in sweat gland (SG):keratinocyte growth medium­2 (KGM­2) (1:1) medium had a higher proliferation rate and a stable morphology compared with cells cultured in SG and KGM­2 medium only. Reverse transcription­quantitative polymerase chain reaction indicated that cells cultured in the SG:KGM­2 (1:1) medium exhibited higher expression levels of α­smooth muscle actin, keratin (K)77, carcinoembryonic antigen, K8, K18, ectodysplasin A receptor, c­Myc, Kruppel­like factor 4 and octamer­binding transcription factor 4 compared with cells cultured in SG only or KGM­2 only medium. Three­dimensional culture analysis revealed that HESGCs cultured in SG:KGM­2 1:1 medium differentiated into sweat gland­like structures, whereas cells cultured in KGM­2 only medium underwent cornification. The present study also determined that the maintenance of the biological characteristics of HESGCs occurred due to the presence of fetal bovine serum (FBS). Cells cultured in medium without FBS differentiated into keratinocytes. Therefore, the SG:KGM­2 (1:1) medium may be a suitable culture medium for HESGCs. In conclusion, this mixed medium is a valuable compound and should be considered to be a potential supplemental medium for HESGCs.

SOX10 immunohistochemistry in sweat ductal/glandular neoplasms.

BACKGROUND: SOX10 is a newer Schwannian and melanocytic marker that has generated great interest for its relative sensitivity and specificity in the diagnosis of neural crest-derived tumors. Previous studies with SOX10 have shown positive immunohistochemical expression in cutaneous eccrine glands and negative expression in eccrine ducts, apocrine glands and hair follicles. Thus, we hypothesized that some sweat gland tumors of presumed eccrine origin would be positive for SOX10, whereas apocrine-derived sweat gland tumors would not. METHODS: A mouse monoclonal anti-SOX10 (clone BC34: Biocare Medical; Concord, California) immunohistochemical antibody was performed on various sweat gland tumors and basal cell carcinoma. RESULTS: SOX10 showed positivity in spiradenomas (13/13), cylindromas (9/10), hidradenoma papilliferum (10/10), syringocystadenoma papilliferum (8/10), apocrine adenomas (8/10), and negativity in poromas (0/12), syringomas (0/10), and basal cell carcinomas (0/13). There was mixed staining of hidradenomas (6/15). CONCLUSIONS: SOX10 immunohistochemistry may be of utility in distinguishing some of the varying adnexal tumors from each other, and from basal cell carcinoma (BCC), but given the staining of both apocrine and eccrine tumors, does not seem to provide information as to their origins as either eccrine or apocrine tumors.

Nicotinic receptor activation augments muscarinic receptor-mediated eccrine sweating but not cutaneous vasodilatation in young males.

NEW FINDINGS: What is the central question of this study? Acetylcholine released from cholinergic nerves can activate both muscarinic and nicotinic receptors. Although each receptor can independently induce cutaneous vasodilatation and eccrine sweating, it remains to be elucidated whether the two receptors interact in order to mediate these responses. What is the main finding and its importance? We show that although nicotinic receptor activation does not modulate muscarinic cutaneous vasodilatation, it lowers the muscarinic receptor agonist threshold at which onset for eccrine sweating (augmentation of muscarinic eccrine sweating) occurs in young men in normothermic resting conditions. These results provide new insights into the physiological significance of nicotinic receptors in the regulation of cutaneous perfusion and eccrine sweating. Acetylcholine released from cholinergic nerves can activate both muscarinic and nicotinic receptors; each is known independently to induce cutaneous vasodilatation and eccrine sweating in humans. However, it is not known whether the two receptors interact in order to mediate cutaneous vasodilatation and eccrine sweating. In 10 young men (27 ± 6 years old), cutaneous vascular conductance and sweat rate were evaluated at intradermal microdialysis sites that were continuously perfused with either lactated Ringer's solution (control) or three different concentrations of nicotine (0.1, 1 and 10 mm), a nicotinic receptor agonist. Co-administration of methacholine, a muscarinic receptor agonist, was performed at all skin sites in a dose-proportional fashion (0.0125, 0.25, 5, 100 and 2000 mm, each for 25 min). Administration of nicotine alone caused dose-dependent transient increases in cutaneous vascular conductance and sweat rate (all P ≤ 0.05), which thereafter returned to pre-nicotine levels, except that a portion of transient responses remained with continuous administration of 10 mm nicotine (both P ≤ 0.05). Cutaneous vascular conductance was increased by administration of ≥0.25 mm methacholine at the control site, and this response was likewise observed in the presence of co-administration of all doses of nicotine used (all P ≤ 0.05). Sweat rate at the control site was increased by administration of ≥0.25 mm methacholine, but the lowest dose of methacholine (0.0125 mm) was able to increase sweat rate in the presence of 10 mm nicotine (P ≤ 0.05). We conclude that nicotinic receptor activation lowers the muscarinic receptor agonist threshold for eccrine sweating (augmentation of muscarinic sweating) but does not affect muscarinic cutaneous vasodilatation in young men in normothermic resting conditions.

Pituitary adenylate cyclase-activating polypeptide promotes eccrine gland sweat secretion.

BACKGROUND: Sweat secretion is the major function of eccrine sweat glands; when this process is disturbed (paridrosis), serious skin problems can arise. To elucidate the causes of paridrosis, an improved understanding of the regulation, mechanisms and factors underlying sweat production is required. Pituitary adenylate cyclase-activating polypeptide (PACAP) exhibits pleiotropic functions that are mediated via its receptors [PACAP-specific receptor (PAC1R), vasoactive intestinal peptide (VIP) receptor type 1 (VPAC1R) and VPAC2R]. Although some studies have suggested a role for PACAP in the skin and several exocrine glands, the effects of PACAP on the process of eccrine sweat secretion have not been examined. OBJECTIVES: To investigate the effect of PACAP on eccrine sweat secretion. METHODS: Reverse transcriptase-polymerase chain reaction and immunostaining were used to determine the expression and localization of PACAP and its receptors in mouse and human eccrine sweat glands. We injected PACAP subcutaneously into the footpads of mice and used the starch-iodine test to visualize sweat-secreting glands. RESULTS: Immunostaining showed PACAP and PAC1R expression by secretory cells from mouse and human sweat glands. PACAP immunoreactivity was also localized in nerve fibres around eccrine sweat glands. PACAP significantly promoted sweat secretion at the injection site, and this could be blocked by the PAC1R-antagonist PACAP6-38. VIP, an agonist of VPAC1R and VPAC2R, failed to induce sweat secretion. CONCLUSIONS: This is the first report demonstrating that PACAP may play a crucial role in sweat secretion via its action on PAC1R located in eccrine sweat glands. The mechanisms underlying the role of PACAP in sweat secretion may provide new therapeutic options to combat sweating disorders.

A sequence upstream of canonical PDZ-binding motif within CFTR COOH-terminus enhances NHERF1 interaction.

The development of cystic fibrosis transmembrane conductance regulator (CFTR) targeted therapy for cystic fibrosis has generated interest in maximizing membrane residence of mutant forms of CFTR by manipulating interactions with scaffold proteins, such as sodium/hydrogen exchange regulatory factor-1 (NHERF1). In this study, we explored whether COOH-terminal sequences in CFTR beyond the PDZ-binding motif influence its interaction with NHERF1. NHERF1 displayed minimal self-association in blot overlays (NHERF1, Kd = 1,382 ± 61.1 nM) at concentrations well above physiological levels, estimated at 240 nM from RNA-sequencing and 260 nM by liquid chromatography tandem mass spectrometry in sweat gland, a key site of CFTR function in vivo. However, NHERF1 oligomerized at considerably lower concentrations (10 nM) in the presence of the last 111 amino acids of CFTR (20 nM) in blot overlays and cross-linking assays and in coimmunoprecipitations using differently tagged versions of NHERF1. Deletion and alanine mutagenesis revealed that a six-amino acid sequence 1417EENKVR1422 and the terminal 1478TRL1480 (PDZ-binding motif) in the COOH-terminus were essential for the enhanced oligomerization of NHERF1. Full-length CFTR stably expressed in Madin-Darby canine kidney epithelial cells fostered NHERF1 oligomerization that was substantially reduced (∼5-fold) on alanine substitution of EEN, KVR, or EENKVR residues or deletion of the TRL motif. Confocal fluorescent microscopy revealed that the EENKVR and TRL sequences contribute to preferential localization of CFTR to the apical membrane. Together, these results indicate that COOH-terminal sequences mediate enhanced NHERF1 interaction and facilitate the localization of CFTR, a property that could be manipulated to stabilize mutant forms of CFTR at the apical surface to maximize the effect of CFTR-targeted therapeutics.

Proteomic profiling of eccrine sweat reveals its potential as a diagnostic biofluid for active tuberculosis.

PURPOSE: Excessive sweating is a common symptom of the disease and an unexplored biofluid for TB diagnosis; we conducted a proof-of-concept study to identify potential diagnostic biomarkers of active TB in eccrine sweat. EXPERIMENTAL DESIGN: We performed a global proteomic profile of eccrine sweat sampled from patients with active pulmonary TB, other lung diseases (non-TB disease), and healthy controls. A comparison of proteomics between Active-TB, Non-TB, and Healthy Controls was done in search for potential biomarkers of active TB. RESULTS: Sweat specimens were pooled from 32 active TB patients, 27 patients with non-TB diseases, and 24 apparently healthy controls, all were negative for HIV. Over 100 unique proteins were identified in the eccrine sweat of all three groups. Twenty-six proteins were exclusively detected in the sweat of patients with active TB while the remaining detected proteins overlapped between three groups. Gene ontology evaluation indicated that the proteins detected uniquely in sweat of active TB patients were involved in immune response and auxiliary protein transport. Gene products for cellular components (e.g. ribosomes) were detected only in active TB patients. Data are available via ProteomeXchange with identifier PXD003224. CONCLUSIONS AND CLINICAL RELEVANCE: Proteomics of sweat from active TB patients is a viable approach for biomarker identification, which could be used to develop a nonsputum-based test for detection of active TB.