Functional significance of non-neuronal acetylcholine in skin epithelia

Molecular and functional changes in neutrophilic granulocytes induced by nicotine: a systematic review and critical evaluation

Background

Over 1.1 billion people smoke worldwide. The alkaloid nicotine is a prominent and addictive component of tobacco. In addition to tumors and cardiovascular disorders, tobacco consumption is associated with a variety of chronic-inflammatory diseases. Although neutrophilic granulocytes (neutrophils) play a role in the pathogenesis of many of these diseases, the impact of nicotine on neutrophils has not been systematically reviewed so far.

Objectives

The aim of this systematic review was to evaluate the direct influence of nicotine on human neutrophil functions, specifically on cell death/damage, apoptosis, chemotaxis, general motility, adhesion molecule expression, eicosanoid synthesis, cytokine/chemokine expression, formation of neutrophil extracellular traps (NETs), phagocytosis, generation of reactive oxygen species (ROS), net antimicrobial activity, and enzyme release.

Material and methods

This review was conducted according to the PRISMA guidelines. A literature search was performed in the databases NCBI Pubmed® and Web of Science™ in February 2023. Inclusion criteria comprised English written research articles, showing in vitro studies on the direct impact of nicotine on specified human neutrophil functions.

Results

Of the 532 originally identified articles, data from 34 articles were finally compiled after several evaluation steps. The considered studies highly varied in methodological aspects. While at high concentrations (>3 mmol/l) nicotine started to be cytotoxic to neutrophils, concentrations typically achieved in blood of smokers (in the nmol/l range) applied for long exposure times (24-72h) supported the survival of neutrophils. Smoking-relevant nicotine concentrations also increased the chemotaxis of neutrophils towards several chemoattractants, elevated their production of elastase, lipocalin-2, CXCL8, leukotriene B4 and prostaglandin E2, and reduced their integrin expression. Moreover, while nicotine impaired the neutrophil phagocytotic and anti-microbial activity, a range of studies demonstrated increased NET formation. However, conflicting effects were found on ROS generation, selectin expression and release of β-glucuronidase and myeloperoxidase.

Conclusion

Nicotine seems to support the presence in the tissue and the inflammatory and selected tissue-damaging activity of neutrophils and reduces their antimicrobial functions, suggesting a direct contribution of nicotine to the pathogenesis of chronic-inflammatory diseases via influencing the neutrophil biology.

Axillary Hidradenitis Suppurativa: A Comparison between Two Perforator Flap Reconstructive Approaches after Radical Surgical Management

Background

Axillary hidradenitis suppurativa (HS) can result in significant functional impairment in both personal and professional lives. Stage 3 HS requires radical surgical treatment. Flap reconstruction allows for faster healing and better functional and aesthetic outcomes. We compared the results of thoracodorsal artery perforator (TDAP) and propeller inner arm artery perforator (IAAP) flap reconstructions after radical surgical treatment of axillary HS.

Methods

We conducted a retrospective study that included 13 consecutive patients who underwent stage 3 axillary HS treatment between August 2015 and January 2023. Seven patients underwent reconstruction by islanded TDAP flaps, whereas six patients underwent reconstruction by propeller IAAP flaps, with one patient undergoing bilateral reconstruction. The data collected from the patient records included age, gender, smoking status, body mass index, comorbidities, operative time, defect size, flap size, hospital stay, and complications.

Results

Although not statistically significant (P = 0.1923), a higher rate of flap complications is reported here with propeller IAAP flaps (42.86 %), whereas islanded TDAP flaps had no flap complications (0%). We found a statistically significant difference in operative time (P = 0.0006), defect size (P = 0.0064), and flap size (P = 0.0012) between the two groups. All patients exhibited satisfactory functional and aesthetic outcomes. Fourteen flaps were performed in total; only one case exhibited recurrence (7.14%).

Conclusion

After radical surgical management, both islanded TDAP and propeller IAAP flap reconstructions offer excellent outcomes for stage 3 axillary HS. We strongly encourage our peers to consider performing perforator flaps over secondary healing for these patients with a major functional impairment.

Hidradenitis suppurativa and follicular occlusion syndrome: Where is the pathogenetic link?

The follicular occlusion tetrad complex encompasses several entities (hidradenitis suppurativa, acne conglobata, dissecting cellulitis of the scalp, and pilonidal cyst) that share common clinical features, risk factors, and pathophysiology. Follicular occlusion is a crucial triggering mechanism in the etiology in each of these disorders, leading to development of distinctive skin lesions such as deep-seated nodules, abscesses, comedones, and draining sinuses, often with accompanying scarring. Despite the fact that the follicular occlusion tetrad components manifest multiple similarities, they also exhibit many differences among themselves and require individual approaches and treatment.

Targeting Metabolic Syndrome in Hidradenitis Suppurativa by Phytochemicals as a Potential Complementary Therapeutic Strategy

Hidradenitis suppurativa (HS) is a chronic inflammatory disease characterized by the appearance of painful inflamed nodules, abscesses, and pus-draining sinus tracts in the intertriginous skin of the groins, buttocks, and perianal and axillary regions. Despite its high prevalence of ~0.4-1%, therapeutic options for HS are still limited. Over the past 10 years, it has become clear that HS is a systemic disease, associated with various comorbidities, including metabolic syndrome (MetS) and its sequelae. Accordingly, the life expectancy of HS patients is significantly reduced. MetS, in particular, obesity, can support sustained inflammation and thereby exacerbate skin manifestations and the chronification of HS. However, MetS actually lacks necessary attention in HS therapy, underlining the high medical need for novel therapeutic options. This review directs attention towards the relevance of MetS in HS and evaluates the potential of phytomedical drug candidates to alleviate its components. It starts by describing key facts about HS, the specifics of metabolic alterations in HS patients, and mechanisms by which obesity may exacerbate HS skin alterations. Then, the results from the preclinical studies with phytochemicals on MetS parameters are evaluated and the outcomes of respective randomized controlled clinical trials in healthy people and patients without HS are presented.

The Epidermal Keratinocyte as a Therapeutic Target for Management of Diabetic Wounds

Diabetes mellitus (DM) is an important cause of chronic wounds and non-traumatic amputation. The prevalence and number of cases of diabetic mellitus are increasing worldwide. Keratinocytes, the outermost layer of the epidermis, play an important role in wound healing. A high glucose environment may disrupt the physiologic functions of keratinocytes, resulting in prolonged inflammation, impaired proliferation, and the migration of keratinocytes and impaired angiogenesis. This review provides an overview of keratinocyte dysfunctions in a high glucose environment. Effective and safe therapeutic approaches for promoting diabetic wound healing can be developed if molecular mechanisms responsible for keratinocyte dysfunction in high glucose environments are elucidated.

Hidradenitis Suppurativa: The Influence of Gender, the Importance of Trigger Factors and the Implications for Patient Habits

Hidradenitis suppurativa (HS) is a debilitating, chronic, inflammatory skin disease primarily affecting apocrine gland-rich areas of the body. On the one hand, the presence of triggering factors-some identified, others only hypothesized-may initiate or perpetuate the pathogenic process of HS. In addition to cigarette smoking and diet, other trigger factors, including choice of clothing, are frequently observed in clinical practice. On the other hand, the presence of disease may influence habits of HS patients. Indeed, high incidences of sexual and sleep impairment have been reported in these patients. Consequently, alcohol and substance abuse may be a coping strategy for the emotional and psychological disease burden. Furthermore, a greater awareness of gender differences in HS may be important for dermatologists in their own clinical practice (i.e., pregnancy and breastfeeding). Consequently, in this loop interaction, comprehensive knowledge of all factors involved is crucial for the management of HS patients. Thus, the objective of this review is to (i) discuss the influence of gender on HS, (ii) summarize the most frequent triggering factors of HS and (iii) analyze the impact of HS on patient habits.

Practical Guidelines for Managing Patients With Hidradenitis Suppurativa: An Update

Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease that is characterized by the formation of comedones, papules, nodules, abscesses and sinus tracts in the axillary, inframammary, groin, and gluteal areas. Up to 3.8% of the Canadian population has HS, though due to a lack of awareness of HS, many patients are initially misdiagnosed and do not receive adequate treatment early on in the disease course. Once a diagnosis of HS is made, developing an effective management plan can be a dilemma for many providers. There is significant variability in response to any given therapy within the HS patient population and many HS patients have other medical comorbidities which must be taken into consideration. The aim of this review is to provide a practical approach for all healthcare providers to diagnose and manage HS and its associated comorbidities. A sample electronic medical record template for HS management was developed by the Canadian Hidradenitis Suppurativa Foundation Executive Board and is intended for use in clinical settings. This will help to increase collaboration between primary healthcare providers, dermatologists, and other medical specialists and ultimately improve the quality of care that HS patients receive.

Phytotherapeuthics Affecting the IL-1/IL-17/G-CSF Axis: A Complementary Treatment Option for Hidradenitis Suppurativa?

Hidradenitis suppurativa (HS; also designated as acne inversa) is a chronic inflammatory disease characterized by painful skin lesions that occur in the axillary, inguinal, gluteal and perianal areas of the body. These lesions contain recurring deep-seated, inflamed nodules and pus-discharging abscesses and fistulas. Affecting about 1% of the population, this common disease has gained appropriate clinical attention in the last years. Associated with numerous comorbidities including metabolic syndrome, HS is considered a systemic disease that severely impairs the quality of life and shortens life expectancy. Therapeutic options for HS are limited, comprising long-term antibiotic treatment, the surgical removal of affected skin areas, and neutralization of TNF-α, the only approved systemic treatment. Novel treatment options are needed to close the therapeutic gap. HS pathogenesis is increasingly better understood. In fact, neutrophilic granulocytes (neutrophils) seem to be decisive for the development of the purulent destructive skin inflammation in HS. Recent findings suggest a key role of the immune mediators IL-1β, IL-17A and G-CSF in the migration into and activation of neutrophils in the skin. Although phytomedical drugs display potent immunoregulatory properties and have been suggested as complementary therapy in several chronic disorders, their application in HS has not been considered so far. In this review, we describe the IL-1/IL-17/G-CSF axis and evaluate it as potential target for an integrated phytomedical treatment of HS.

Magnetic Resonance Imaging of Hidradenitis Suppurativa: A Focus on the Anoperineal Location

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease involving apocrine-bearing sites. It is characterized by recurrent painful nodules and abscesses that potentially rupture, resulting in sinus tract formation, fistulas, and scarring. HS tends to be found in the intertriginous areas (i.e., the axillary, inguinal, and perianal areas of the body). HS may be uncommon for radiologists because its diagnosis is usually based on clinical assessment. However, diagnosis based solely on clinical manifestations can underestimate the severity of HS. Ultrasonography and MRI play a critical adjunct role in determining the severity and extent of the disease and greatly aid its management. Given that MRI is an effective imaging tool, its role in the analysis of severe and anogenital HS lesions merits considerable attention. Unfortunately, anoperineal HS imposes diagnostic dilemmas. It has multiple symptoms and presentations and often mimics other diseases in the intertriginous areas. Therefore, a thorough understanding of HS is essential to avoid delayed diagnoses. This review highlights the typical MRI imaging features and staging of HS, emphasizing on the anoperineal location. The review also differentiates the disease from mimics to facilitate the prompt delivery of appropriate treatment and improve patients’ quality of life.

Insights into hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a chronic, debilitating, inflammatory skin disorder with a prevalence of around 1% and a profound impact on patients' quality of life. Characteristic lesions such as inflammatory nodules, abscesses, and sinus tracts develop in the axillae, inguinal, and gluteal areas, typically during or after puberty. A complex interplay of genetic predisposition, hormonal factors, obesity, and smoking contributes to development and maintenance of the disease. HS is considered to arise from an intrinsic defect within the hair follicle, leading to follicular plugging, cyst formation, and subsequent rupture that in turn induce an acute inflammatory response characterized by elevated levels of IL-1β, IL-17, and TNF. Over time, acute lesions transition into chronic disease, with active draining sinus tracts accompanied by extensive fibrosis. HS is associated with other immune-mediated inflammatory diseases, metabolic and cardiovascular disorders, and psychiatric comorbidities. Treatment of HS often requires a combination of antibiotic or immunosuppressing therapies and surgical intervention. Nonetheless, the currently available treatments are not universally effective, and many drugs, which are often repurposed from other inflammatory diseases, are under investigation. Studies into the early stages of HS may yield treatments to prevent disease progression; yet, they are hampered by a lack of appropriate in vitro and animal models.

Hidradenitis Suppurativa: Host-Microbe and Immune Pathogenesis Underlie Important Future Directions

Hidradenitis suppurativa (HS) is an inflammatory disease of the skin with a chronic, relapsing-remitting course. The pathogenesis of the disease is poorly understood and involves multiple factors, including genetics, environment, host-microbe interactions, and immune dysregulation. In particular, the composition of the cutaneous microbiome shifts as the disease progresses, although it is unclear whether this is a primary or secondary process. Trials with immunomodulatory therapy elucidate the role of specific immune pathways and cytokine signaling in disease mechanism, such as TNF-α, IL-1β, IL-12, IL-17, IL-23, and complement. Future studies should continue examining the causes of and contributing factors to microbial changes and immune dysregulation in HS pathogenesis.

Botulinum Neurotoxin Type A in the Treatment of Facial Seborrhea and Acne: Evidence and a Proposed Mechanism

Intradermal injection of botulinum neurotoxin is a frequently performed procedure in aesthetic dermatology to improve facial skin tone, texture, fine wrinkles, and enlarged pores. In practice, botulinum neurotoxin type A is also used to reduce skin oiliness of the face. There is increasing evidence that acetylcholine plays specific roles in sebum production, suggesting that botulinum neurotoxin type A may reduce sebum production by interfering with cholinergic transmission between sebaceous glands and autonomic nerve terminals. Botulinum neurotoxins can also inhibit several pathogenetic components of acne development, suggesting that botulinum neurotoxins can be used as a safe and effective treatment modality for acne and other skin disorders related to overactivity of sebaceous glands. This review aims to explore the current evidence behind the treatment of facial seborrhea and acne with botulinum neurotoxin type A.

Insights into the Pathogenesis of HS and Therapeutical Approaches

Hidradenitis suppurativa (HS) is a debilitating, chronic, (auto)inflammatory disease primarily affecting apocrine gland-rich areas of the body. Although pathogenic mechanisms responsible for HS have not yet been fully elucidated, it is a multifactorial process whose main target is the terminal follicle. The role of the inflammatory process (and consequently of cytokine milieu) and of several other factors (genetics, lifestyle, hormonal status, microbiome, innate and adaptive immune systems) involved in HS pathogenesis has been investigated (and often defined) over the years with a view to transferring research results from bench to bedside and describing a unique and universally accepted pathogenetic model. This review will update readers on recent advances in our understanding of HS pathogenesis and novel (potential) medical therapies for patients with moderate-to-severe HS.

Effects of tobacco and vaping on the skin

Cigarette and electronic cigarette use are significant public health concerns across the United States. Tobacco use remains the single most preventable cause of morbidity and mortality in the world. Electronic cigarettes initially emerged as a better alternative to conventional cigarettes and for promoting smoking cessation; however, current evidence reveals similar deleterious health implications caused by both products on almost all organ systems, including the skin. Recognition of the cutaneous manifestations associated with cigarette and electronic cigarette use is essential for dermatologists in current clinical practice. Dermatologists play a vital role in educating and counseling patients on smoking cessation. We specifically highlight the cutaneous consequences of conventional cigarette smoking and electronic cigarettes on dermatologic disease.

[Clinical, pathology-associated and molecular biomarkers of hidradenitis suppurativa/acne inversa]

Hidradenitis suppurativa/acne inversa is a scarring disease of the intertrigines that is now intensively researched. Improved pathogenetic understanding has led to the introduction of tumor necrosis factor alpha (TNF‑α) inhibition, which represents a major advance over traditional broad immunosuppression and antibiotic administration. In addition, a wide range of newer and promising treatments is or is about to be clinically evaluated. These include various specific antibodies against cytokines and the complement system and small molecules. Successful use of the individual drugs depends on the stratification of suitable patient groups with the help of clinically relevant biomarkers. While molecular investigations have shown a number of possible biomarkers and/or therapeutic target molecules, the detection of robust predictive biomarkers is still in its initial phase. In summary, the therapeutic options for hidradenitis suppurativa/acne inversa are improving through the introduction of new drugs, possibly in combination with surgical interventions, whereby the possibilities for predictive therapeutic decisions through the discovery of biomarkers would revolutionize the chances of therapeutic success.

Association of hidradenitis suppurativa with Crohn’s disease

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disorder characterized by recurrent nodules, abscesses, and sinus tracts. Crohn’s disease (CD) is characterized by inflammation of the entire digestive tract and belongs to the group of inflammatory bowel diseases, and there are many extraintestinal manifestations, among which hidradenitis suppurativa is one of the rare extraintestinal manifestations. There appears to be a strong association between CD and HS based on clinical and histological similarities (sinus tract development, granulomatous inflammation, and scarring), intersections in pathogenesis (genetic loci, immune dysregulation mechanisms, and microbiome changes), and commonality in treatment. In this review, we summarize recent studies on the association between HS and CD.

Does smoking affect your skin?

Smoking has a negative influence on human beings. Carcinogens detected in smoke can increase the risk of developing chronic disorders, cancer and premature death. Nicotine can also affect dermatological diseases such as psoriasis, hidradenitis suppurativa, chronic dermatoses, alopecia, lupus erythematosus, polymorphous light eruption, skin cancer and tobacco-associated oral lesions. Advanced education at a doctor's surgery in various medical occupations can change the bad habits and protect people from the consequences.

Quality-of-Life Impairment among Patients with Hidradenitis Suppurativa: A Cross-Sectional Study of 1795 Patients

The chronic, inflammatory skin disorder hidradenitis suppurativa (HS) is associated well documented negative influences on patients' quality of life (QoL). The aim of this study was to present more robust data on patients' QoL impairment by demographic data and its correlation with well-known HS risk factors on a cohort of 1795 German patients. The instrument used for measuring QoL in this study was the Dermatology Life Quality Index (DLQI). Overall, patients reported a very large effect of HS on their QoL (mean DLQI: 13.2 ± 8.1 points), and 22% of the analyzed population even reported to consider the effect as extremely large. Women tended to experience significantly higher impairment than men (p < 0.001). QoL impairment correlated positively with pain (r = 0.581, p < 0.001), HS severity (measured by the International Hidradenitis Suppurativa Severity Score System (IHS4)) as well as Hurley. Neck involvement tended to decrease QoL significantly more than any other location (14.7 ± 8.3 points). This study confirms the enormous influence of HS on patients' QoL in a large cohort. Knowledge of QoL impairment in such patients is crucial for proper understanding and holistic management of this disease.

Hidradenitis suppurativa; classification, remedies, etiology, and comorbidities; a narrative review

Hidradenitis suppurativa (HS) is a chronic inflammatory skin condition that is more common in females, especially during puberty and menopause. These inflammatory lesions include painful deep-seated nodules and abscesses, draining sinus tracts, and fibrotic scars. This article is a narrative review to explain whole disease aspects, including complication, causes, epidemiology, history, classification, prognosis, comorbidities, the effect of sex hormone, and potent treatments. Most patients with HS, who are not aware of their primary disease, visit primary care physicians to superinfection lesions instead of specialists. If these physicians suspect HS, their illness will not get misdiagnosed. This brief and comprehensive information in this article may help doctors to decide better about the same situation.

High Glucose Restraint of Acetylcholine-Induced Keratinocyte Epithelial-Mesenchymal Transition Is Mitigated by p38 Inhibition

Non-neuronal acetylcholine (Ach) plays important roles in various aspects of cell biology and homeostasis outside the neural system. Keratinocytes (KCs) have a functional cholinergic mechanism, suggesting that they respond to Ach. However, the physiological role and mechanism by which Ach modulates wound KC behavior in both nondiabetic and diabetic conditions are unexplored. We found an enrichment in neurotransmitter-related pathways in microdissected-migrating nondiabetic and diabetic KCs. We showed that Ach upregulated TGFβRII through Src-extracellular signal‒regulated kinase 1/2 pathway to potentiate TGFβ1-mediated epithelial‒mesenchymal transition in normoglycemic condition. Unexpectedly, KCs were nonresponsive to the elevated endogenous Ach in a hyperglycemic environment. We further showed that the activation of p38 MAPK in high glucose condition interferes with Src-extracellular signal‒regulated kinase 1/2 signaling, resulting in Ach resistance that could be rescued by inhibiting p38 MAPK. A better understanding of the cholinergic physiology in diabetic KCs could improve wound management and care. The finding suggests that mitigating the inhibitory effect of diabetic wound microenvironment has a direct clinical implication on the efficacy and safety of various wound healing agents to improve chronic diabetic wounds.

Aetiology and pathogenesis of hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory disorder. Patients develop inflamed nodules and abscesses and, at later stages of disease, epithelialized tunnels and scars in skinfolds of axillary, inguinal, gluteal and perianal areas. Quality of life is affected due to severe pain, purulent secretion, restricted mobility and systemic involvement. Genetics and lifestyle factors including smoking and obesity contribute to the development of HS. These factors lead to microbiome alteration, subclinical inflammation around the terminal hair follicles, and infundibular hyperkeratosis, resulting in plugging and rupture of the follicles. Cell-damage-associated molecules and propagating bacteria trigger inflammation and lead to massive immune cell infiltration that clinically manifests as inflamed nodules and abscesses. The immune system plays a key role also in the progression and chronification of skin alterations. Innate proinflammatory cytokines (e.g. interleukin-1β and tumour necrosis factor-α), mediators of activated T helper (Th)1 and Th17 cells (e.g. interleukin-17 and interferon-γ), and effector mechanisms of neutrophilic granulocytes, macrophages and plasma cells are involved. Simultaneously, skin lesions contain anti-inflammatory mediators (e.g. interleukin-10) and show limited activity of Th22 and regulatory T cells. The inflammatory vicious circle finally results in pain, purulence, tissue destruction and scarring. Chronic inflammation in patients with HS is also frequently detected in organs other than the skin, as indicated by their comorbidities. All these aspects represent a challenge for the development of therapeutic approaches, which are urgently needed for this debilitating disease. This scholarly review focuses on the causes and pathogenetic mechanisms of HS and the potential therapeutic value of this knowledge.

Botulinum Toxin Type B for Hidradenitis Suppurativa: A Randomised, Double-Blind, Placebo-Controlled Pilot Study

Background

Botulinum toxin (BTX) is a potent neurotoxin with a long history of therapeutic application in neurological and dermatological conditions, with a strong efficacy and safety profile.

Objective

Our aim was to assess whether intradermal injection with BTX-B is an effective treatment for hidradenitis suppurativa (HS).

Methods

Twenty patients with HS stage I–III disease, according to Hurley’s classification, were consecutively included for treatment with either a placebo or BTX-B. At the next intervention after 3 months, all participants received the active substance and another follow-up at 6 months. The primary outcome was quality of life, measured using the Dermatology Life Quality Index (DLQI), while secondary outcomes were the visual analogue scale (VAS) for pain in the worst boil and HS-related impairment of general health (VAS), as well as changes in physician-reported disease activity assessed as the number of total lesions, and reported adverse effects of treatment.

Results

The DLQI improved from a median of 17 at baseline to 8 at 3 months in the BTX-B group, compared with a reduction from 13.5 to 11 in the placebo group (p <0.05). Improvement of the patients’ own ratings of symptoms and a reduction in total lesions supplemented the primary outcome. Fifty-five percent of the study population reported some degree of hyperhidrosis.

Conclusion

BTX-B improves the quality of life in patients with HS. Furthermore, comorbidity between HS and hyperhidrosis is suggested.

Trial Registration

ClinicalTrials.gov identifier: NCT03103074.

Hidradenitis suppurativa

Hidradenitis suppurativa (HS; also designated as acne inversa) is a chronic inflammatory disorder, which affects the intertriginous skin and is associated with numerous systemic comorbidities. The estimated prevalence of HS is ~1% in most studied countries. Typically starting in early adulthood, cutaneous inflamed nodules, abscesses and pus-discharging tunnels develop in axillary, inguinal, gluteal and perianal body sites. The comorbidities of HS include metabolic and cardiovascular disorders, which contribute to reduced life expectancy. A genetic predisposition, smoking, obesity and hormonal factors are established aetiological factors for HS. Cutaneous changes seem to start around hair follicles and involve activation of cells of the innate and adaptive immune systems, with pivotal roles for pro-inflammatory cytokines such as tumour necrosis factor, IL-1β and IL-17. The unrestricted and chronic immune response eventually leads to severe pain, pus discharge, irreversible tissue destruction and scar development. HS has profound negative effects on patients' quality of life, which often culminate in social withdrawal, unemployment, depression and suicidal thoughts. The therapeutic options for HS comprise antibiotic treatment, neutralization of tumour necrosis factor and surgical intervention together with lifestyle modification. Nevertheless, there is an enormous need for awareness of HS, understanding of its pathogenesis and novel treatments.

Hidradenitis Suppurativa: Current Understanding of Pathogenic Mechanisms and Suggestion for Treatment Algorithm

Hidradenitis suppurativa is one of the most distressing dermatological conditions and has a significant negative impact on patients' quality of life. However, the exact pathogenic mechanisms remain incompletely understood and-therefore-efficient therapies are still lacking. The current manuscript focuses on new findings on its pathogenic mechanisms and aims to provide practical therapy recommendations.

The importance of the neuro-immuno-cutaneous system on human skin equivalent design

The skin is a highly complex organ, responsible for sensation, protection against the environment (pollutants, foreign proteins, infection) and thereby linked to the immune and sensory systems in the neuro-immuno-cutaneous (NIC) system. Cutaneous innervation is a key part of the peripheral nervous system; therefore, the skin should be considered a sensory organ and an important part of the central nervous system, an 'active interface' and the first connection of the body to the outside world. Peripheral nerves are a complex class of neurons within these systems, subsets of functions are conducted, including mechanoreception, nociception and thermoception. Epidermal and dermal cells produce signalling factors (such as cytokines or growth factors), neurites influence skin cells (such as via neuropeptides), and peripheral nerves have a role in both early and late stages of the inflammatory response. One way this is achieved, specifically in the cutaneous system, is through neuropeptide release and signalling, especially via substance P (SP), neuropeptide Y (NPY) and nerve growth factor (NGF). Cutaneous, neuronal and immune cells play a central role in many conditions, including psoriasis, atopic dermatitis, vitiligo, UV-induced immunosuppression, herpes and lymphomas. Therefore, it is critical to understand the connections and interplay between the peripheral nervous system and the skin and immune systems, the NIC system. Relevant in vitro tissue models based on human skin equivalents can be used to gain insight and to address impact across research and clinical needs.

An update on the pathogenesis of hidradenitis suppurativa: implications for therapy

INTRODUCTION

Hidradenitis suppurativa is a chronic, inflammatory disease characterized by painful nodules, abscesses, and sinuses in the intertriginous areas, with significant associated comorbidities. The pathogenesis remains unclear, although advances have been made in understanding the disease process. Management of the disease is challenging, with a wide range of treatment options available with variable clinical response. Areas covered: This review discusses the most updated studies on the complex pathogenic mechanisms of hidradenitis suppurativa and the relevant literature on the current treatment options for this condition. Expert commentary: There is increasing evidence supporting the role of Th17 cells and enhanced expression of IL-17 and IL-1β, which represent potential targets for therapy. Bacteria and biofilms are likely contributory but secondary drivers of inflammation. There is also evolving evidence to suggest the presence of systemic comorbidities associated with HS, which underlie the importance of better understanding the pathogenesis and treatment of this disease.

Incidence of hidradenitis suppurativa among tobacco smokers: a population-based retrospective analysis in the U.S.A

BACKGROUND

The relationship between tobacco use and hidradenitis suppurativa (HS) is controversial.

OBJECTIVES

To determine the incidence of HS among tobacco smokers.

METHODS

Retrospective cohort analysis identifying incident HS cases among adult tobacco smokers and nonsmokers sampled from a demographically heterogeneous population-based sample of over 50 million unique patients across all census regions in the U.S.A.

RESULTS

We identified 3 924 310 tobacco smokers, which included 7860 patients newly diagnosed with HS. Tobacco smokers diagnosed with HS were most commonly aged 18-39 years (3795 of 7860; 48·3%), women (5640 of 7860; 71·8%), white (5200 of 7860; 66·2%) and those with body mass index (BMI) ≥ 30 (5690 of 7860; 72·4%). Overall incidence of HS was 0·20% (7860 of 3 924 310) among tobacco smokers and 0·11% (8430 of 8 027 790) among nonsmokers (P < 0·001). Incidence was greatest among tobacco smokers who were aged 30-39 years (0·35%), women (0·28%), African Americans (0·46%) and those with BMI ≥ 30 (0·33%). The overall adjusted odds of developing HS was 1·90 (95% confidence interval 1·84-1·96) among tobacco smokers, compared with nonsmokers (P < 0·001). HS incidence among tobacco smokers remained increased within each demographic subgroup.

CONCLUSIONS

Incidence of HS appears to be doubled among tobacco smokers. These findings may support evidence-based counselling efforts for the cessation of smoking in populations at risk for HS.

Hidradenitis suppurativa, a review of pathogenesis, associations and management. Part 1

Hidradenitis suppurativa is a chronic, painful, autoinflammatory condition resulting in nodules, abscesses and sinus tracts. We present an evidence-based review providing new understanding of the pathogenesis of hidradenitis suppurativa and associated comorbidities. By the nature of their speciality, dermatologists are uniquely positioned to investigate and treat patients with this condition. Data collected from a subspecialty hidradenitis suppurativa clinic (N = 106) and experiences thereof are discussed in this review.

Inflammatory Mechanisms in Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic relapsing disease of follicular occlusion that causes immense clinical and psychosocial morbidity when refractory to treatment. HS is no longer considered a disease of primary infectious etiology, although bacteria play a role. There is increasing evidence that HS is associated with immune dysregulation, based on its clinical association with other immune-mediated disorders, by its response to biologic therapy in the clinical arena, and from molecular research. This article summarizes what is known in relation to the inflammatory pathways in HS.

Alteration of Skin Mechanical Properties in Patients Undergoing Botulinum Toxin Type A Injections of Forehead Rhytides

BACKGROUND

Although application of botulinum toxin type A (BTX-A) for the treatment of forehead rhytides has become very popular, the effects of its intramuscular injections on the skin mechanical properties remain unclear.

OBJECTIVES

We prospectively investigated the alterations in the mechanical properties of the skin of patients who received intramuscular injections of botulinum toxin A (BTX-A) for forehead rhytides and compared two injection doses.

METHODS

Of the 42 enrolled patients, one randomly assigned half received intramuscular injections of two units (group I), and the other half received four units (group II) of BTX-A in each injection point. The baseline and post-treatment skin mechanical parameters, including gross elasticity (R2), net elasticity (R5), viscoelastic ratio (R6) and biological elasticity (R7), were measured using the Cutometer(®) and compared.

RESULTS

Treatment with BTX-A resulted in significant overall alterations in the mechanical properties of skin at the injection sites of both treatment groups during the 16-week period, and no significant differences were observed between groups. Significant decreases in biological elasticity, net elasticity and viscoelasticity properties were observed at 2 weeks follow-up and began to recover at that time. All of the skin mechanical properties recovered to baseline levels by 16 weeks of follow-up in both dosage groups, which indicates that the higher dosage (4 units) did not delay relapse compared to the two-unit dosage.

CONCLUSIONS

We concluded that intramuscular injections of BTX-A significantly regulated the gross elasticity, net elasticity, functional elasticity and viscoelastic elasticity at the injection point over a radius of 1.5 cm at 2, 4 and 8 weeks follow-up. The alteration in the skin measurements had completely diminished by the 16-week follow-up.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Acetylcholine induces fibrogenic effects via M2/M3 acetylcholine receptors in non-alcoholic steatohepatitis and in primary human hepatic stellate cells

BACKGROUND

The parasympathetic nervous system (PNS), via neurotransmitter acetylcholine (ACh), modulates fibrogenesis in animal models. However, the role of ACh in human hepatic fibrogenesis is unclear.

AIMS

We aimed to determine the fibrogenic responses of human hepatic stellate cells (hHSC) to ACh and the relevance of the PNS in hepatic fibrosis in patients with non-alcoholic steatohepatitis (NASH).

METHODS

Primary hHSC were analyzed for synthesis of endogenous ACh and acetylcholinesterase and gene expression of choline acetyltransferase and muscarinic ACh receptors (mAChR). Cell proliferation and fibrogenic markers were analyzed in hHSC exposed to ACh, atropine, mecamylamine, methoctramine, and 4-diphenylacetoxy-N-methylpiperidine methiodide. mAChR expression was analyzed in human NASH scored for fibrosis.

RESULTS

We observed that hHSC synthesize ACh and acetylcholinesterase and express choline acetyltransferase and M1-M5 mAChR. We also show that M2 was increased during NASH progression, while both M2 and M3 were found upregulated in activated hHSC. Furthermore, endogenous ACh is required for hHSC basal growth. Exogenous ACh resulted in hHSC hyperproliferation via mAChR and phosphoinositide 3-kinase and Mitogen-activated protein kinase kinase (MEK) signaling pathways, as well as increased fibrogenic markers.

CONCLUSION

We show that ACh regulates hHSC activation via M2 and M3 mAChR involving the phosphoinositide 3-kinase and MEK pathways in vitro. Finally, we provide evidence that the PNS may be involved in human NASH fibrosis.

Pathophysiology of hidradenitis suppurativa: An update

The pathogenesis of hidradenitis suppurativa (HS) or acne inversa is not completely understood. Recent research has led to greater insight into the mechanisms involved in the disease. The primary defect in HS pathophysiology rests with the hair follicle. Follicular occlusion, followed by follicular rupture, and a foreign body-type immune response are necessary conditions for the development of clinical HS. A specific genetic signature and environmental factors, such as cigarette smoking, microbial colonization, and adiposity, all contribute to the HS phenotype. Translational research focused on the inflammatory mechanisms involved in HS is needed to develop novel therapeutic options for this debilitating disease.

Hidradenitis Suppurativa: A Guide for the Practicing Physician

Hidradenitis suppurativa is a chronic inflammatory disease of apocrine gland-bearing skin. Although immunologic derangements, genetic predisposition, obesity, and smoking are likely important factors, the pathogenesis of the disease and the effect of available treatments on disease course have not been fully elucidated. In the absence of proper treatment, chronic inflammation results in diffuse scarring and a wide array of complications, including the development of cutaneous squamous cell carcinoma. This severe and chronic disease can have detrimental effects on self-esteem and quality of life. No ideal treatment regimen has been defined, but several therapies have been found to reduce lesion severity and improve symptoms. We reviewed the literature through July 2014 for existing treatments. Published articles were obtained via systematic review of medical databases (PubMed, Embase, Google Scholar) and scrutiny of citation lists using the search terms "hidradenitis suppurativa" and "acne inversa". Given the scarce literature on treatment strategies, we also reviewed data from any case reports or prospective and retrospective studies that were located. On the basis of the existing literature, we provide an evidence-based algorithm for the management of this disease in the primary care setting. More research is needed to evaluate the comparative effectiveness of topical and systemic treatments and to better understand the pathogenesis, natural history, and subtypes of hidradenitis suppurativa.

Fibroblast heterogeneity and its implications for engineering organotypic skin models in vitro

Advances in cell culture methods, multidisciplinary research, clinical need to replace lost skin tissues and regulatory need to replace animal models with alternative test methods has led to development of three dimensional models of human skin. In general, these in vitro models of skin consist of keratinocytes cultured over fibroblast-populated dermal matrices. Accumulating evidences indicate that mesenchyme-derived signals are essential for epidermal morphogenesis, homeostasis and differentiation. Various studies show that fibroblasts isolated from different tissues in the body are dynamic in nature and are morphologically and functionally heterogeneous subpopulations. Further, these differences seem to be dictated by the local biological and physical microenvironment the fibroblasts reside resulting in "positional identity or memory". Furthermore, the heterogeneity among the fibroblasts play a critical role in scarless wound healing and complete restoration of native tissue architecture in fetus and oral mucosa; and excessive scar formation in diseased states like keloids and hypertrophic scars. In this review, we summarize current concepts about the heterogeneity among fibroblasts and their role in various wound healing environments. Further, we contemplate how the insights on fibroblast heterogeneity could be applied for the development of next generation organotypic skin models.

Hidradenitis suppurativa

Hidradenitis suppurativa is a chronic relapsing disorder of the folliculopilosebaceous units (FPSUs). Its negative impact on quality of life is extreme, mainly due to the lack of early recognition, accurate diagnosis, and appropriate management. The support structure of the FPSUs is defective. Under the influence of endogenous reproductive hormones, exogenous hormones, androgens and their precursors in dairy products, and other dietary factors, the follicular unit is plugged and distended by retained keratin. Friction, shearing forces, and pressure lead to rupture and leakage of the ductal contents from the weakened FPSU, causing an inflammatory reaction mediated mainly by the innate immune system. Therapy requires patient comprehension and cooperation, counseling, aggressive hormonal and dietary modification, avoidance of the trauma that leads to rupture, active multimodal anti-inflammatory therapy, and early unroofing and debridement. The full therapeutic program is needed to avoid the aggressive surgery required if the condition is not diagnosed early and managed appropriately.

Hidradenitis suppurativa: viewpoint on clinical phenotyping, pathogenesis and novel treatments

Hidradenitis suppurativa (HS) is an inflammatory, debilitating follicular skin disease with recurring flare-ups. The painful, deep-seated, inflamed lesions in the inverse areas of the body cause severe discomfort, and hence, serious psycho-social and economic costs. HS is common, but often misdiagnosed and mechanistically poorly understood. Furthermore, HS is notoriously difficult to treat resulting in a high unmet medical need. To provoke debate, rational experimentation and initiate strategic studies, we here present a concise viewpoint on seven topics: the diagnosis of HS, the role of mechanical friction, the critical importance of accurate clinical subgrouping, smoking and obesity, the role of bacteria, and our comprehensive view on HS pathogenesis with a central role for keratin clearance, and novel treatment approaches.

Can animal skin diseases or current transgenic mice serve as a model for hidradenitis suppurativa?

The pathogenesis of hidradenitis suppurativa (HS) is still enigmatic, and a valid animal model for HS is currently not available. The recent discovery of γ-secretase mutations in a subpopulation of patients with HS suggested γ-secretase transgenic mice as a model for HS pathogenesis. However, the discrepancies between human HS and these mice are daunting. We critically review cases of animal HS and transgenic γ-secretase mouse models for HS and discuss the criteria which should be met for a representative pathogenic model.

Smoking and the skin

Cigarette smoking has been associated with significant morbidity affecting all systems of the body, including the integumentary system. We review the many dermatologic hazards of tobacco use. It is important to distinguish between the effects of tobacco smoke from effects of pure nicotine on the skin. All skin cells express several subtypes of the nicotinic class of acetylcholine receptors, including the α7 receptor. Many chronic dermatoses are affected by smoking either negatively or positively. Elucidation of positive associations with a particular disease can lead to improvement from smoking cessation, whereas inverse correlation may lead to development of a disease-specific treatment with nicotinergic agonists.

The channel physiology of the skin

During embryonic development, the skin, the largest organ of the human body, and nervous system are both derived from the neuroectoderm. Consequently, several key factors and mechanisms that influence and control central or peripheral nervous system activities are also present and hence involved in various regulatory mechanisms of the skin. Apparently, this is the case for the ion and non-ion selective channels as well. Therefore, in this review, we shall focus on delineating the regulatory roles of the channels in skin physiology and pathophysiology. First, we introduce key cutaneous functions and major characteristics of the channels in question. Then, we systematically detail the involvement of a multitude of channels in such skin processes (e.g. skin barrier formation, maintenance, and repair, immune mechanisms, exocrine secretion) which are mostly defined by cutaneous non-neuronal cell populations. Finally, we close by summarizing data suggesting that selected channels are also involved in skin diseases such as e.g. atopic dermatitis, psoriasis, non-melanoma cancers and malignant melanoma, genetic and autoimmune diseases, etc., as well as in skin ageing.