Immunoglobulins from scleroderma patients inhibit the muscarinic receptor activation in internal anal sphincter smooth muscle cells

Managing gastrointestinal manifestations in systemic sclerosis, a mechanistic approach

INTRODUCTION

Systemic sclerosis (SSc) is a connective tissue disease with heterogeneous presentation. Gastrointestinal (GI) complications of SSc are characterized by esophageal reflux, abnormal motility, and microbiome dysbiosis, which impact patient quality of life and mortality. Preventative therapeutics are lacking, with management primarily aimed at symptomatic control.

AREAS COVERED

A broad literature review was conducted through electronic databases and references from key articles. We summarize the physiology of gastric acid production and GI motility to provide context for existing therapies, detail the current understanding of SSc-GI disease, and review GI medications studied in SSc. Finally, we explore new therapeutic options. We propose a management strategy that integrates data on drug efficacy with knowledge of disease pathophysiology, aiming to optimize future therapeutic targets.

EXPERT OPINION

SSc-GI complications remain a challenge for patients, clinicians, and investigators alike. Management presently focuses on treating symptoms and minimizing mucosal damage. Little evidence exists to suggest immunosuppressive therapy halts progression of GI involvement or reverses damage, leaving many unanswered questions about the optimal clinical approach. Further research focused on identifying patients at risk for GI progression, and the underlying mechanism(s) that drive disease will provide opportunities to prevent long-term damage, and significantly improve patient quality of life.

Autoantibodies Targeting G-Protein-Coupled Receptors: Pathogenetic, Clinical and Therapeutic Implications in Systemic Sclerosis

Systemic sclerosis (SSc) is a multifaceted connective tissue disease whose aetiology remains largely unknown. Autoimmunity is thought to play a pivotal role in the development of the disease, but the direct pathogenic role of SSc-specific autoantibodies remains to be established. The recent discovery of functional antibodies targeting G-protein-coupled receptors (GPCRs), whose presence has been demonstrated in different autoimmune conditions, has shed some light on SSc pathogenesis. These antibodies bind to GPCRs expressed on immune and non-immune cells as their endogenous ligands, exerting either a stimulatory or inhibitory effect on corresponding intracellular pathways. Growing evidence suggests that, in SSc, the presence of anti-GPCRs antibodies correlates with specific clinical manifestations. Autoantibodies targeting endothelin receptor type A (ETAR) and angiotensin type 1 receptor (AT1R) are associated with severe vasculopathic SSc-related manifestations, while anti-C-X-C motif chemokine receptors (CXCR) antibodies seem to be predictive of interstitial lung involvement; anti-muscarinic-3 acetylcholine receptor (M3R) antibodies have been found in patients with severe gastrointestinal involvement and anti-protease-activated receptor 1 (PAR1) antibodies have been detected in patients experiencing scleroderma renal crisis. This review aims to clarify the potential pathogenetic significance of GPCR-targeting autoantibodies in SSc, focusing on their associations with the different clinical manifestations of scleroderma. An extensive examination of functional autoimmunity targeting GPCRs might provide valuable insights into the underlying pathogenetic mechanisms of SSc, thus enabling the development of novel therapeutic strategies tailored to target GPCR-mediated pathways.

Beyond very early systemic sclerosis: deciphering pre‑scleroderma and its trajectories to open new avenues for preventive medicine

The identification of individuals with systemic sclerosis in an oligosymptomatic phase preceding the very early manifestations of the disease represents a challenge in the search for a new window of opportunity in systemic sclerosis. This phase could be identified in a clinical scenario as the pre-scleroderma phase, in which the disease would still be far from systemic sclerosis-related fibrotic or irreversible manifestations in skin or organs. In this Personal View, we discuss parameters and candidate definitions for a conceptual framework of pre-scleroderma, from the identification of populations at risk to autoantibodies and their potential functional activities. We discuss how this new paradigm of pre-scleroderma could represent a game-changing approach in the management of systemic sclerosis, allowing the treatment of patients at high risk of organ involvement or skin fibrosis before such events occur.

Rapid improvement of systemic sclerosis-associated intestinal pseudo-obstruction with intravenous immunoglobulin administration

OBJECTIVES

SSc is an autoimmune disease characterized by excessive fibrosis in multiple organs, including the gastrointestinal (GI) tract. GI symptoms of SSc such as intestinal pseudo-obstruction (IPO) are often refractory to conventional intervention and can result in longer in-hospital stay or even increased mortality. We aimed to summarize the insights to date regarding the efficacy of IVIG against GI symptoms of SSc to unveil what we should focus on in future studies.

METHODS

Herein we report the response of GI symptoms in three cases with SSc-myositis overlap who received IVIG administration. We also conducted a systematic literature review to summarize previous reports regarding the efficacy of IVIG upon the GI manifestations of SSc, according to the PRISMA 2020 guideline.

RESULTS

The case series demonstrated remarkable and rapid improvement of GI symptoms, including IPO, after IVIG administration. The literature review revealed that previous reports also support the efficacy and safety of IVIG against GI manifestations of SSc. However, they were all retrospective studies and lacking description of the short-term outcome after IVIG administration with objective and quantitative metrics.

CONCLUSION

IVIG seems to be a promising therapeutic option for the management of GI symptoms in SSc, including IPO. Investigators should focus more on short-term outcomes to properly assess the therapeutic benefit of IVIG, ideally using reliable quantitative measures in a multicentre randomized placebo-controlled setting.

Systemic sclerosis gastrointestinal dysmotility: risk factors, pathophysiology, diagnosis and management

Nearly all patients with systemic sclerosis (SSc) are negatively affected by dysfunction in the gastrointestinal tract, and the severity of gastrointestinal disease in SSc correlates with high mortality. The clinical complications of this dysfunction are heterogeneous and include gastro-oesophageal reflux disease, gastroparesis, small intestinal bacterial overgrowth, intestinal pseudo-obstruction, malabsorption and the requirement for total parenteral nutrition. The abnormal gastrointestinal physiology that promotes the clinical manifestations of SSc gastrointestinal disease throughout the gastrointestinal tract are diverse and present a range of therapeutic targets. Furthermore, the armamentarium of medications and non-pharmacological interventions that can benefit affected patients has substantially expanded in the past 10 years, and research is increasingly focused in this area. Here, we review the details of the gastrointestinal complications in SSc, tie physiological abnormalities to clinical manifestations, detail the roles of standard and novel therapies and lay a foundation for future investigative work.

Gastrointestinal Tract Considerations Part I

The upper gastrointestinal (GI) tract is frequently involved in systemic sclerosis (SSc) and may impact quality of life, physical function and survival. Although we are currently very proactive in terms of screening for heart and lung involvement, patients with SSc are not routinely screened for GI involvement. This review details the available investigations for common upper GI symptoms in SSc, including dysphagia, reflux and bloating and provides advice as to how to integrate these investigations into current clinical care.

Pathogenetic rationale for prescribing menopausal hormone therapy for systemic sclerosis

Systemic scleroderma (SS) is characterized by dysregulation of the innate and adaptive immune systems, vasculopathy, and generalized fibrosis. As with most autoimmune diseases, women predominate among patients, who get sick 3–14 times more often than men. It is assumed that gender differences and modulation of sex hormones are essential in the pathogenesis of SS. Estrogens are able to influence the immune response, have a vasodilating effect and stimulate the synthesis of collagen in the skin. The development of SS leads to a significant decrease in the quality of life, psychological disorders associated with changes in appearance, as well as the need for lifelong medication with the frequent development of side effects. Age-related estrogen deficiency associated with the onset of menopause is accompanied by a decrease in the quality of life and, in some cases, a change in the clinical manifestations of somatic diseases. This review considers the impact of menopause and menopausal hormone therapy (MHT) on the course and clinical manifestations of systemic scleroderma. It is noted that SS in some cases is accompanied by an early onset of menopause. The use of MHT is not associated with the progression of cutaneous fibrosis, and may also improve the vascular manifestations of SS.

Gastrointestinal involvement in systemic sclerosis: pathogenesis, assessment and treatment

PURPOSE OF REVIEW

The majority of patients with systemic sclerosis (SSc) will experience involvement of their gastrointestinal over the course of their disease. Despite the high prevalence of gastrointestinal involvement in SSc, the strategies pertaining to the assessment and treatment for this clinical dimension of SSc have historically been limited. However, the present review highlights recent research contributions that enhance our understanding of SSc-GI patient subsets and provides updates on pathogenic mechanisms of disease, assessment and symptom-directed management.

RECENT FINDINGS

In the past few years, several studies have identified risk factors for more severe gastrointestinal disease in SSc and have provided insight to optimize diagnosis and management of SSc-GI symptoms. This article also provides a review of currently available investigations and therapies for individual SSc-GI disease manifestations and reflects on actively evolving areas of research, including our understanding the role of the gut microbiome in SSc.

SUMMARY

Here, we provide important updates pertaining to the risk stratification, assessment, diagnosis and management of SSc patients with gastrointestinal symptoms. These findings provide opportunities to enhance patient care and highlight exciting opportunities for future research.

Urinary incontinence in systemic sclerosis: a prospective multicentre cohort study

Investigate the natural history of urinary incontinence (UI) in systemic sclerosis (SSc) and assess its impact on quality of life (QoL). A longitudinal, international observational study followed 189 patients with SSc for a median duration of 5 years (IQR: 4.8–5.3). Presence, subtype and severity of UI, hospital admission and QoL were assessed using serial self-administered questionnaires. Mortality data came from national death registries. Multilevel mixed-effect logistic regressions explored factors associated with UI. Cox models adjusted the effects of UI on hospitalization and death for age, sex and subtype of SSc. Mean annual rates of new-onset UI and remission were 16.3% (95%CI 8.3%–24.2%) and 20.8% (95%CI 12.6–29.1), respectively. Among UI patients, 57.9% (95%CI 51.8–64.0) changed from one UI subtype to another. Between annual questionnaires, the severity of UI was the same in 51.1% (95%CI 40.8–61.4), milder or resolved in 35.2% (95%CI 25.3–44.9), and worse in 13.8% (95%CI 6.7–20.9). Anti-centromere antibodies, digestive symptoms, sex, age, neurological or urological comorbidities, diuretics and puffy fingers were all associated with UI. The two strongest predictors of UI and UI subtypes were a recent UI episode and the subtype of previous leakage episodes. UI at inclusion was not associated with hospital admission (adjusted HR: 1.86; 95%CI 0.88–3.93), time to death (aHR: 0.84; 95%CI 0.41–1.73) or change in QoL over time. Self-reported UI among SSc patients is highly dynamic: it waxes and wanes, changing from one subtype to another over time.

Pathogenetic Aspects of Systemic Sclerosis: A View Through the Prism of B Cells

Systemic sclerosis (SSc) is a rare fibrotic rheumatic disease, associated with psychological distress and increased morbidity and mortality due to skin involvement and internal organ damage. The current understanding of the complex pathogenesis is yet incomplete and disease therapeutic algorithms are far from optimal. Immunologic aberrations are considered key factors for the disease, along with vascular involvement and excess fibrosis. Adaptive immunity and its specialized responses are an attractive research target and both T and B cells have been extensively studied in recent years. In the present review, the focus is placed on B cells in SSc. B cell homeostasis is deranged and B cell subsets exhibit an activated phenotype and abnormal receptor signaling. Autoantibodies are a hallmark of the disease and the current perception of their diagnostic and pathogenetic role is analyzed. In addition, B cell cytokine release and its effect on immunity and fibrosis are examined, together with B cell tissue infiltration of the skin and lung. These data support the concept of targeting B cells as part of the therapeutic plan for SSc through well designed clinical trials.

Evidence for the presence and release of BDNF in the neuronal and non-neuronal structures of the internal anal sphincter

BACKGROUND

Data on the neuromodulatory effects of brain-derived neurotrophic factor (BDNF) in the gastrointestinal tract were recently reported, but there are still no data on the presence, distribution, and release of BDNF in the gastrointestinal tract, including the internal anal sphincter (IAS).

METHODS

We examined the presence and distribution of BDNF and its receptor TrkB in the different IAS structures (neuronal and non-neuronal) via immunohistochemical and immunocytochemical analyses. We also monitored the release of BDNF in an IAS muscle bath (consisting of smooth muscle cells [SMCs], myenteric plexus, and submucosal plexus) before and after different agonists, and electrical field stimulation in the absence and presence of neurotoxin tetrodotoxin.

KEY RESULTS

BDNF/TrkB was found to be present in all layers of the IAS, especially the smooth muscle, mucosa, myenteric plexus, and submucosal plexus. Detailed analyses revealed a significant colocalization between BDNF and TrkB in different structures, especially in the smooth muscle, the SMCs, and both plexuses. Data further showed higher levels of BDNF in the cytosol and that of TrkB toward the periphery of the SMCs.

CONCLUSIONS & INFERENCES

These studies showed that BDNF/TrkB was present not only in the enteric nervous system (ENS), but also in the SMCs. For the neuromodulatory effects, BDNF is released locally from the ENS ((myenteric (10.01 ± 0.23 pg/ml) and submucosal plexus (9.05 ± 0.51 pg/ml)) and the SMCs (18.63 ± 1.63 pg/ml). Collectively, these findings have pathophysiological and therapeutic implications regarding the role of BDNF/TrkB in the IAS-associated rectoanal motility disorders.

Targeting Systemic Sclerosis from Pathogenic Mechanisms to Clinical Manifestations: Why IL-6?

Systemic sclerosis (SS) is a chronic autoimmune disorder, which has both cutaneous and systemic clinical manifestations. The disease pathogenesis includes a triad of manifestations, such as vasculopathy, autoimmunity, and fibrosis. Interleukin-6 (IL-6) has a special role in SS development, both in vascular damage and in the development of fibrosis. In the early stages, IL-6 participates in vascular endothelial activation and apoptosis, leading to the release of damage-associated molecular patterns (DAMPs), which maintain inflammation and autoimmunity. Moreover, IL-6 plays an important role in the development of fibrotic changes by mediating the transformation of fibroblasts into myofibroblasts. All of these are associated with disabling clinical manifestations, such as skin thickening, pulmonary fibrosis, pulmonary arterial hypertension (PAH), heart failure, and dysphagia. Tocilizumab is a humanized monoclonal antibody that inhibits IL-6 by binding to the specific receptor, thus preventing its proinflammatory and fibrotic actions. Anti-IL-6 therapy with Tocilizumab is a new hope for SS patients, with data from clinical trials supporting the favorable effect, especially on skin and lung damage.

Potential Role for Combined Subtype-Selective Targeting of M1 and M3 Muscarinic Receptors in Gastrointestinal and Liver Diseases

Despite structural similarity, the five subtypes comprising the cholinergic muscarinic family of G protein-coupled receptors regulate remarkably diverse biological functions. This mini review focuses on the closely related and commonly co-expressed M₁R and M₃R muscarinic acetylcholine receptor subtypes encoded respectively by CHRM1 and CHRM3. Activated M₁R and M₃R signal via G_q and downstream initiate phospholipid turnover, changes in cell calcium levels, and activation of protein kinases that alter gene transcription and ultimately cell function. The unexpectedly divergent effects of M₁R and M₃R activation, despite similar receptor structure, distribution, and signaling, are puzzling. To explore this conundrum, we focus on the gastrointestinal (GI) tract and liver because abundant data identify opposing effects of M₁R and M₃R activation on the progression of gastric, pancreatic, and colon cancer, and liver injury and fibrosis. Whereas M₃R activation promotes GI neoplasia, M₁R activation appears protective. In contrast, in murine liver injury models, M₃R activation promotes and M₁R activation mitigates liver fibrosis. We analyze these findings critically, consider their therapeutic implications, and review the pharmacology and availability for research and therapeutics of M₁R and M₃R-selective agonists and antagonists. We conclude by considering gaps in knowledge and other factors that hinder the application of these drugs and the development of new agents to treat GI and liver diseases.

Fecal incontinence and scleroderma: Pathogenesis and unmet needs

Scleroderma is a chronic autoimmune disorder involving multiple organs and very commonly the gastrointestinal (GI) system; nevertheless, data on the involvement of the anal sphincter and consequent faecal incontinence (FI) are inadequate. FI in scleroderma was first reported in 1994 by Engel and colleagues, but its impact of added health care costs and declining quality of life (QoL) is poorly determined. Up to 40% of patients with GI involvement complain of FI, however, the quality of data available is poor owing to majority of the studies being retrospective and case reports or series of small study size. A direct involvement of internal anal sphincter muscularis propria has been demonstrated on anorectal ultrasound imaging suggesting a thin, atrophic or scarred internal sphincter. Treatment guidelines for incontinence in scleroderma are mainly symptomatic, with radical surgeries burdened by poor outcomes. Sacral neuromodulation is being used with good outcomes in a subgroup of patients, but larger, controlled studies are required to assess its efficacy on symptoms and prognosis.

Anti-vinculin antibodies in scleroderma (SSc): a potential link between autoimmunity and gastrointestinal system involvement in two SSc cohorts

BACKGROUND

Systemic sclerosis (SSc) is an autoimmune disorder and commonly presents with vascular system involvement and motility disorders in the gastrointestinal (GI) tract. Vinculin is a cytoskeletal protein that plays major roles in cell-cell adhesion and is expressed in the neuromuscular apparatus of the gut. Antibodies to vinculin have been identified as a biomarker of irritable bowel syndrome (IBS). Our aim was to evaluate serum anti-vinculin antibodies in patients with SSc.

METHODS

Patients were recruited from two SSc centers: group I (GI-enriched group), University of Leeds, UK, and Group II (vascular predominant), University of California, Los Angeles. Serum samples of patients recruited from two SSc centres, Group I ( GI enriched group), University of Leeds, UK and Group II (Vascular predominant), University of California, Los Angeles) were collected. Samples from age- and sex-matched healthy volunteers (N = 88) were used as controls.

RESULTS

Group I (GI-enriched group, N = 83) patients were 58 [50-67] years old; 83% were females with a median body mass index (BMI) of 20.3 (21.2 ± 4.5) [18-23]. Group II (vascular-enriched group, N = 72) patients were 58 [50-67] years old; 80% were female, and BMI was 23.9 (21.3-26.9). More subjects in group I had prominent GI involvement (N = 55, 66%) than group II (12, 16%), p ˂ 0.0001. Anti-vinculin antibody levels in SSc group I (1.3 [0.9]) were significantly higher than in HC (0.7 [0.8]; p = 0.002). When pooled, circulating anti-vinculin levels in both SSc groups remained significantly higher than in the HC group (p = 0.02). Higher anti-vinculin levels were associated with higher GI-visual analogue scale (GI-VAS) scores and specifically with GI-VAS scores of ≥ 4 (p < 0.0001).

CONCLUSION

This study demonstrates that elevated anti-vinculin antibody levels are common in SSc and suggests a potential link between increased anti-vinculin levels and GI tract symptoms.

KEY POINTS

• Anti-vinculin antibodies are elevated in systemic sclerosis and are relatively common. • In these SSc patients, anti-vinculin antibodies are associated with higher levels of GI symptoms in SSc. • A potential link between anti-vinculin antibodies and vascular system involvement was shown.

Putative functional pathogenic autoantibodies in systemic sclerosis

Systemic sclerosis (scleroderma, SSc) is a systemic disease characterized by vascular lesions, fibrosis, and circulating autoantibodies. A complex interplay between innate and adaptive immunity, and with regard to the latter, between humoral and cellular immunity, is believed to be involved in SSc pathogenesis. Lately, close attention has been paid to the role of B cells which, once activated, release profibrotic cytokines, promote profibrotic Th2 differentiation, and produce autoantibodies. Several novel interesting autoantibodies, targeting antigens within the extracellular matrix or on the cell surface, rather than the nuclear antigens of canonical SSc-autoantibodies, have been recently described in patients with SSc. As they show stimulatory or inhibitory activity or react with structures involved in the pathogenesis of SSc lesions, they can be considered as potentially pathogenic. In this paper, we will review those which have been better characterized.

The Pathogenesis of Systemic Sclerosis: An Understanding Based on a Common Pathologic Cascade across Multiple Organs and Additional Organ-Specific Pathologies

Systemic sclerosis (SSc) is a multisystem autoimmune and vascular disease resulting in fibrosis of various organs with unknown etiology. Accumulating evidence suggests that a common pathologic cascade across multiple organs and additional organ-specific pathologies underpin SSc development. The common pathologic cascade starts with vascular injury due to autoimmune attacks and unknown environmental factors. After that, dysregulated angiogenesis and defective vasculogenesis promote vascular structural abnormalities, such as capillary loss and arteriolar stenosis, while aberrantly activated endothelial cells facilitate the infiltration of circulating immune cells into perivascular areas of various organs. Arteriolar stenosis directly causes pulmonary arterial hypertension, scleroderma renal crisis and digital ulcers. Chronic inflammation persistently activates interstitial fibroblasts, leading to the irreversible fibrosis of multiple organs. The common pathologic cascade interacts with a variety of modifying factors in each organ, such as keratinocytes and adipocytes in the skin, esophageal stratified squamous epithelia and myenteric nerve system in gastrointestinal tract, vasospasm of arterioles in the heart and kidney, and microaspiration of gastric content in the lung. To better understand SSc pathogenesis and develop new disease-modifying therapies, it is quite important to understand the complex pathogenesis of SSc from the two distinct perspectives, namely the common pathologic cascade and additional organ-specific pathologies.

Intestinal hypomotility in systemic sclerosis: a histological study into the sequence of events

OBJECTIVES

The pathogenesis of intestinal involvement in systemic sclerosis (SSc) is thought to be a sequential process (vascular, neuronal, and consecutive muscular impairment), but understanding of the underlying histological changes and how they translate to symptoms, is still lacking. Therefore, we systematically investigated histological characteristics of SSc in the intestines, compared to controls.

METHODS

Autopsy material from the small bowel and colon was used for histological semiquantitative evaluation of the vasculature, enteric nervous system, interstitial cells of Cajal (ICC), and muscle layers, using a combination of histochemical and immunohistochemical stainings, according to guidelines of the Gastro 2009 International Working Group.

RESULTS

Vascular changes were most frequently encountered, represented by intima fibrosis in both arteries and small vessels, and represented by venous dilatation. Second, generalized fibrosis of the circular muscle layer was significantly more found in SSc patients than in controls. Third, reduction of submucosal nerve fibers and myenteric neurons was shown in the colon of four SSc patients, which may explain severe symptoms of intestinal dysmotility. The density of myenteric ICC network was decreased in the small bowel of SSc patients.

CONCLUSIONS

The postulated sequential processes of intestinal involvement in SSc could not be supported by our histological evaluation. The interpatient diversity suggests that parallel processes occur, explaining the variety of histological features and clinical symptoms. Key Points • Histological analysis showed vascular changes, fibrosis in the muscularis propria, and reduction of the ENS and ICC network in the intestines of SSc patients. • Pathophysiological mechanisms leading to intestinal dysmotility in SSc may be parallel rather than sequential. • The interpatient diversity suggests parallel pathophysiological processes, explaining the variety of histological features and clinical symptoms.

Antibodies to the Muscarinic Acetylcholine Receptor M3 in Primary Biliary Cholangitis Inhibit Receptor Function on Cholangiocytes

Background and Aims: In primary biliary cholangitis (PBC), antibodies to a peptide of the muscarinic acetylcholine receptor 3 (mAChR3) have been described. Since the mAChR3 is expressed on cholangiocytes and mAChR3-signaling is involved in the pathogenesis of chronic inflammatory biliary diseases, we wanted to investigate whether anti-mAChR3-antibodies influence the function of the receptor and the proliferative response of cholangiocytes. Methods: Immunoglobulins were isolated by ammonium sulfate precipitation using sera from patients with PBC (n = 63) and with other chronic liver disorders (n = 150). All immunoglobulins were analyzed by a luminometric assay using Chinese hamster ovary (CHO) cells overexpressing the mAChR3 and cholangiocytes (TFK-1-cells) expressing the receptor constitutively. Cell proliferation was measured by ³H-thymidine assay. PBC patients were also analyzed in the follow-up. Results: Antibodies inhibiting the mAChR3 were found in 49 and 79% of PBC patients using CHO-cells or TFK-1-cells, respectively, but only in up to 26% of controls (p < 0.01). Stimulatory antibodies were hardly detected. Antibody reactivity only marginally changed during the course of the disease, independently of the choice of treatment (ursodeoxycholic acid, immunosuppressive therapy, or no medication). There was no correlation with laboratory, clinical or histological parameters, but the antibodies were more frequently found in PBC patients with a benign course (96%) than in patients with active disease progressing to late stages within 10 years (57%; p < 0.01). Proliferation of cells was not influenced by immunoglobulins from PBC-patients. Conclusion: Sera from patients with PBC contain inhibitory antibodies to the mAChR3 on cholangiocytes (TFK-1 cells) without influencing TFK-1-cell proliferation. These antibodies were predominantly observed in patients with non-progressing PBC.

Pathogenic roles of autoantibodies in systemic sclerosis: Current understandings in pathogenesis

The potential pathogenic role for autoantibodies in systemic sclerosis has captivated researchers for the past 40 years. This review answers the question whether there is yet sufficient knowledge to conclude that certain serum autoantibodies associated with systemic sclerosis contribute to its pathogenesis. Definitions for pathogenic, pathogenetic and functional autoantibodies are formulated, and the need to differentiate these autoantibodies from natural autoantibodies is emphasized. In addition, seven criteria for the identification of pathogenic autoantibodies are proposed. Experimental evidence is reviewed relevant to the classic systemic sclerosis antinuclear autoantibodies, anti-topoisomerase I and anticentromere, and to functional autoantibodies to endothelin 1 type A receptor, angiotensin II type 1 receptor, muscarinic receptor 3, platelet-derived growth factor receptor, chemokine receptors CXCR3 and CXCR4, estrogen receptor α, and CD22. Pathogenic evidence is also reviewed for anti-matrix metalloproteinases 1 and 3, anti-fibrillin 1, anti-IFI16, anti-eIF2B, anti-ICAM-1, and anti-RuvBL1/RuvBL2 autoantibodies. For each autoantibody, objective evidence for a pathogenic role is scored qualitatively according to the seven pathogenicity criteria. It is concluded that anti-topoisomerase I is the single autoantibody specificity with the most evidence in favor of a pathogenic role in systemic sclerosis, followed by anticentromere. However, these autoantibodies have not been demonstrated yet to fulfill completely the seven proposed criteria for pathogenicity. Their contributory roles to the pathogenesis of systemic sclerosis remain possible but not yet conclusively demonstrated. With respect to functional autoantibodies and other autoantibodies, only a few criteria for pathogenicity are fulfilled. Their common presence in healthy and disease controls suggests that major subsets of these immunoglobulins are natural autoantibodies. While some of these autoantibodies may be pathogenetic in systemic sclerosis, establishing that they are truly pathogenic is a work in progress. Experimental data are difficult to interpret because high serum autoantibody levels may be due to polyclonal B-cell activation. Other limitations in experimental design are the use of total serum immunoglobulin G rather than affinity-purified autoantibodies, the confounding effect of other systemic sclerosis autoantibodies present in total immunoglobulin G and the lack of longitudinal studies to determine if autoantibody titers fluctuate with systemic sclerosis activity and severity. These intriguing new specificities expand the spectrum of autoantibodies observed in systemic sclerosis. Continuing elucidation of their potential mechanistic roles raises hope of a better understanding of systemic sclerosis pathogenesis leading to improved therapies.

Detecting gastrointestinal manifestations in patients with systemic sclerosis using anti-gAChR antibodies

BACKGROUND

Patients with systemic sclerosis (SSc) complicated by gastrointestinal dysmotility are difficult to treat and have high mortality. To clarify the pathogenesis of gastrointestinal manifestations, we aimed to demonstrate the association among the clinical features of SSc, the serological markers, the autoantibodies against nicotinic acetylcholine receptor at autonomic ganglia (gAChR).

METHODS

Fifty patients were enrolled and divided into two groups according to the presence or absence of gastrointestinal manifestations, and the characteristics were analyzed between these two groups. We measured biomarkers and the autoantibodies against two gAChRα3 and β4 subunits to test sera samples. Furthermore, patients were classified based on the presence or absence of anti-gAChR autoantibodies, and their clinical features were compared.

RESULTS

In patients with SSc and gastrointestinal manifestations, digital ulcers were more frequent (p = 0.050) and VEGF expression was significantly higher (p = 0.038). Seven subjects with SSc were seropositive for α3 subunit, whereas one patient was seropositive for β4 subunit. The mean level of anti-gAChRα3 autoantibodies in SSc patients with gastrointestinal manifestations was significantly higher than that in SSc patients without gastrointestinal manifestations (p = 0.001). The group of patients with SSc and gAChR autoantibodies had significantly higher endostatin levels (p = 0.046).

CONCLUSIONS

This study is the first to demonstrate that clinical characteristics of SSc patients with seropositivity for gAChR autoantibodies. Patients with SSc have circulating autoantibodies against gAChR, which may contribute to gastrointestinal manifestations associated with this disease, suggesting that gAChR-mediated autonomic neurotransmission may provide a pathomechanism for gastrointestinal dysmotility in SSc.

Ganglionic Acetylcholine Receptor Antibodies and Autonomic Dysfunction in Autoimmune Rheumatic Diseases

Autonomic neuropathy has been reported in autoimmune rheumatic diseases (ARD) including Sjögren’s syndrome, systemic sclerosis, rheumatoid arthritis, and systemic lupus erythematosus. However, the pathophysiological mechanism underlying autonomic dysfunction remains unknown to researchers. On the other hand, autoimmune autonomic ganglionopathy (AAG) is an acquired immune-mediated disorder, which causes dysautonomia that is mediated by autoantibodies against ganglionic acetylcholine receptors (gAChRs). The purpose of this review was to describe the characteristics of autonomic disturbance through previous case reports and the functional tests used in these studies and address the importance of anti-gAChR antibodies. We have established luciferase immunoprecipitation systems to detect antibodies against gAChR in the past and determined the prevalence of gAChR antibodies in various autoimmune diseases including AAG and rheumatic diseases. Autonomic dysfunction, which affects lower parasympathetic and higher sympathetic activity, is usually observed in ARD. The anti-gAChR antibodies may play a crucial role in autonomic dysfunction observed in ARD. Further studies are necessary to determine whether anti-gAChR antibody levels are correlated with the severity of autonomic dysfunction in ARD.

BDNF augments rat internal anal sphincter smooth muscle tone via RhoA/ROCK signaling and nonadrenergic noncholinergic relaxation via increased NO release

Presently, there are no studies examining the neuromodulatory effects of brain-derived neurotropic factor (BDNF) on the basal internal anal sphincter (IAS) tone and nonadrenergic noncholinergic (NANC) relaxation. To examine this, we determined the neuromuscular effects of BDNF on basal IAS smooth muscle tone and the smooth muscle cells (SMCs) and the effects of NANC nerve stimulation before and after high-affinity receptor tyrosine kinase receptor B (TrkB) antagonist K252a. We also investigated the mechanisms underlying BDNF-augmented increase in the IAS tone and NANC relaxation. We found that BDNF-increased IAS tone and SMC contractility were TTX resistant and attenuated by K252a. TrkB-specific agonist 7,8-dihydroxyflavone, similar to BDNF, also produced a concentration-dependent increase in the basal tone, whereas TrkB inhibitors K252a and ANA-12 produced a decrease in the tone. In addition, BDNF produced leftward shifts in the concentration-response curves with U46619 and ANG II (but not with bethanechol and K⁺ depolarization), and these shifts were reversed by K252a. Effects of Y27632 and Western blot data indicated that the BDNF-induced increase in IAS tone was mediated via RhoA/ROCK. BDNF-augmented NANC relaxation by electrical field stimulation was found to be mediated via the nitric oxide (NO)/soluble guanylate cyclase (sGC) pathway rather than via increased sensitivity to NO. In conclusion, the net effect of BDNF was that it caused an increase in the basal IAS tone via RhoA/ROCK signaling. BDNF also augmented NANC relaxation via NO/sGC. These findings may have relevance to the role of BDNF in the pathophysiology and therapeutic targeting of the IAS-associated rectoanal motility disorders.NEW & NOTEWORTHY These studies for the first time to our knowledge demonstrate that increased levels of brain-derived neurotrophic factor (BDNF; conceivably released from smooth muscle cells and/or the enteric neurons) has two major effects. First, BDNF augments the internal anal sphincter (IAS) tone via tyrosine kinase receptor B/thromboxane A2-receptor, angiotensin II receptor type 1/RhoA/ROCK signaling; and second, it increases nonadrenergic noncholinergic relaxation via nitric oxide/soluble guanylate cyclase. These studies may have relevance in therapeutic targeting in the anorectal motility disorders associated with the IAS.

Gastrointestinal involvement in systemic sclerosis: diagnosis and management

PURPOSE OF REVIEW

This review provides important updates in systemic sclerosis (SSc)-related gastrointestinal disease, with a particular focus on the diagnosis and management of dysmotility.

RECENT FINDINGS

In the past 2 years, several studies were published that present interesting diagnostic insights into SSc and gastrointestinal dysmotility. Studies focusing on new therapies and the novel application of existing therapies, both in SSc and non-SSc-associated gastrointestinal dysmotility syndromes, demonstrate progress in the management of these challenging complications.

SUMMARY

SSc gastrointestinal disease is heterogeneous in its clinical presentation, which presents a challenge in diagnosis and management. Objective studies may help to identify patterns of gastrointestinal dysmotility and more specifically target therapy. A variety of drugs are now available or are under study in the management of gastrointestinal dysmotility, such as prucalopride, intravenous immunoglobulin, pyridostigmine, linaclotide, relamorelin, and others. These drugs may improve symptoms and quality of life in SSc gastrointestinal patients. Combination therapies are also under study. Electroacupuncture, dietary intervention (e.g. medical nutrition therapy, low FODmap diet), and medical cannibus may also play a role in alleviating patient symptoms; however, more data are needed to define the role of these interventions in SSc.

Systemic sclerosis and urinary symptoms: a complex pathophysiology

Lower urinary tract symptoms (LUTS) have long been overlooked in systemic sclerosis (SSc). However, they are out of proportion of what would be expected based on age, sex, and presence of usual risk factors. Thus, there must be specific scleroderma-related mechanisms to result in LUTS. Fibrosis, nervous involvement (notably, dysautonomia), early signs of menopauses, and functional restriction play certainly a role, but available evidence shows inconsistent results. Thus, these factors are not sufficient to explain all aspect of LUTS in SSc. In vitro experiments point out a promising alternative mechanism, already observed in other rheumatologic diseases: an antibody-mediated etiology. However, more research is needed to better understand the pathophysiology of LUTS in SSc and develop specific treatment.

Gastrointestinal and Hepatic Disease in Systemic Sclerosis

Although classification criteria for systemic sclerosis (SSc) do not incorporate gastrointestinal tract (GIT) manifestations often present in this disease, the GIT is the most common internal organ involved. Pathophysiology of GIT involvement is thought to be similar to other organs in SSc with fibroproliferative vascular lesions of small arteries and arterioles, increased production of profibrotic growth factors, and alterations of innate, humoral, and cellular immunity. These processes result in neuropathy progressing to myopathy with eventual fibrosis. Proper diagnostics and therapeutics for SSc-GIT involvement require the treating physician to have an understanding of an integrated approach and potential medication adverse effects.

Intestinal Involvement in Systemic Sclerosis: A Clinical Review

Systemic sclerosis (SSc) is a chronic systemic disease characterized by microvasculopathy, autoantibodies, and extensive fibrosis. Intestinal involvement is frequent in SSc and represents a significant cause of morbidity. The pathogenesis of intestinal involvement includes vascular damage, nerve dysfunction, smooth muscle atrophy, and fibrosis, causing hypomotility, which leads to small intestinal bacterial overgrowth (SIBO), malabsorption, malnutrition, diarrhea, pseudo-obstruction, constipation, pneumatosis intestinalis, and fecal incontinence. Manifestations are often troublesome and reduce quality of life and life expectancy. Assessment of intestinal involvement includes screening for small intestine hypomotility, malnutrition, SIBO, and anorectal dysfunction. Current management of intestinal manifestations is largely inadequate. Patients with diarrhea are managed with low-fat diet, medium-chain triglycerides, avoidance of lactulose and fructose, and control of bacterial overgrowth with antibiotics for SIBO. In diarrhea/malabsorption, bile acid sequestrant and pancreatic enzyme supplementation may help, and nutritional support is needed. General measures are applied for constipation, and intestine rest plus antibiotics for pseudo-obstruction. Fecal incontinence is managed with measures for associated SIBO, or constipation, and with behavioral therapies. Pneumatosis intestinalis is usually an incidental finding that does not require any specific treatment. Immunomoduation should be considered early in intestinal involvement. Multidisciplinary approach of intestinal manifestations in SSc by gastroenterologists and rheumatologists is required for optimum management.

Gastrointestinal Manifestations of Systemic Sclerosis

Systemic sclerosis (SSc) is a rare autoimmune disease characterized by fibroproliferative alterations of the microvasculature leading to fibrosis and loss of function of the skin and internal organs. Gastrointestinal manifestations of SSc are the most commonly encountered complications of the disease affecting nearly 90% of the SSc population. Among these complications, the esophagus and the anorectum are the most commonly affected. However, this devastating disorder does not spare any part of the gastrointestinal tract (GIT), and includes the oral cavity, esophagus, stomach, small and large bowels as well as the liver and pancreas. In this review, we present the current understanding of the pathophysiologic mechanisms of SSc including vasculopathy, endothelial to mesenchymal transformation as well as the autoimmune pathogenetic pathways. We also discuss the clinical presentation and diagnosis of each part of the GIT affected by SSc. Finally, we highlight the latest developments in the management of this disease, addressing the severe malnutrition that affects this vulnerable patient population and ways to assess and improve the nutritional status of the patients.

Gut microbiota profile in systemic sclerosis patients with and without clinical evidence of gastrointestinal involvement

Recent evidence suggests that there is a link between the gut microbial community and immune-mediated disorders. Systemic sclerosis (SSc) is an autoimmune disease characterized by immunonological abnormalities, vascular lesions, and extensive fibrosis. Since the gastrointestinal tract is one of the organs most involved, the goal of this study was to explore the composition of the intestinal microbiota in SSc patients with (SSc/GI+) and without gastrointestinal involvement (SSc/GI-) in comparison to healthy controls (HC). The fecal bacterial composition was investigated by Illumina sequencing of 16 S rRNA gene amplicons. The fecal microbiota of SSc/GI+ subjects was characterized by higher levels of Lactobacillus, Eubacterium and Acinetobacter compared with healthy controls, and lower proportions of Roseburia, Clostridium, and Ruminococcus. The gut microbiota of SSc/GI- subjects was more similar to the microbiota of HC than to that of SSc/GI+ subjects albeit Streptococcus salivarius was over-represented in SSc/GI- fecal samples compared with both SSc/GI+ subjects and controls. Our study reveals microbial signatures of dysbiosis in the gut microbiota of SSc patients that are associated with clinical evidence of gastrointestinal disease. Further studies are needed to elucidate the potential role of these perturbations in the onset and progression of systemic sclerosis, and gastrointestinal involvement in particular.

Agonistic antibodies in systemic sclerosis

Systemic sclerosis (SSc) is characterized by microangiopathy, excessive fibrosis, and the presence of circulating autoantibodies to several cellular and extracellular components. The role of autoimmunity in generating the clinical and pathologic phenotypes in SSc has been long debated and is still matter of controversy. Distinct specificities of antinuclear antibodies (ANAs) are selectively detected in SSc patients and are associated with unique disease manifestations, but do not have a proven pathogenic role. A new group of autoantibodies reactive with cell surface receptors have been identified in SSc patients. They have been shown to directly activate pathways that may contribute to tissue and vascular damage. As such, they are proposed to have a role as agonistic autoantibodies in SSc. According to Koch's third postulate, the autoantibodies in question should cause disease when introduced into a healthy subject. Therefore, our review will focus on those autoantibodies for which agonistic activity has already been demonstrated not only in vitro, but, at least partly, also in vivo. These include the antibodies anti-endothelial cells (AECA), anti-Platelet-Derived Growth Factor Receptor (PDGFR), anti-Angiotensin II type 1 receptor (AT1R) and anti-endothelin-1 type A receptor (ETaR). In this review, we will discuss also a class of antagonistic autoantibodies, the anti-muscarinic-3 receptor (M3R) antibodies, since they seem to fulfill the aforementioned requirements.

Role of anti-receptor autoantibodies in pathophysiology of scleroderma

The pathophysiology of SSc-mediated organ damage is complex and not well understood. Hallmarks of the disease include skin thickening, vasculopathy and gastrointestinal dysmotility. Diverse anti-nuclear antibodies can be used as biomarkers for classification and prognosis, but their role in producing tissue pathology/organ dysfunction is not established. In contrast, antibodies against cell surface receptors for platelet derived growth factor, angiotensin II, endothelin A, ICAM-1, and type 3 muscarinic acetyl choline receptors may play a major role in skin thickening, vasoconstriction/pulmonary and renal hypertension, ischemia and gastrointestinal dysmotility, respectively. In addition, antibodies to an inhibitory B-lymphocyte surface molecule, CD 22, may allow increased production of other autoantibodies. Each of these types of antibodies have been reported in some SSc patients, and laboratory studies suggest signaling pathways and mechanisms by which they may contribute to disease activity. However, we are far from a consensus on their importance. Additional epidemiologic, mechanistic and physiologic studies are needed. Confirmation of the roles of anti-receptor antibodies and identification of the signaling pathways by which they alter cellular functions would have major implications for treatment of SSc, both in terms of targeting autoantibodies and the cells that produce them, and in the use of small molecules which inhibit their pernicious effects.

Review article: pathogenesis and clinical manifestations of gastrointestinal involvement in systemic sclerosis

BACKGROUND

Gastrointestinal tract (GIT) involvement is a common cause of debilitating symptoms in patients with systemic sclerosis (SSc). There are no disease modifying therapies for this condition and the treatment remains symptomatic, largely owing to the lack of a clear understanding of its pathogenesis.

AIMS

To investigate novel aspects of the pathogenesis of gastrointestinal involvement in SSc. To summarise existing knowledge regarding the cardinal clinical gastrointestinal manifestations of SSc and its pathogenesis, emphasising recent investigations that may be valuable in identifying potentially novel therapeutic targets.

METHODS

Electronic (PubMed/Medline) and manual Google search.

RESULTS

The GIT is the most common internal organ involved in SSc. Any part of the GIT from the mouth to the anus can be affected. There is substantial variability in clinical manifestations and disease course and symptoms are nonspecific and overlapping for a particular anatomical site. Gastrointestinal involvement can occur in the absence of cutaneous disease. Up to 8% of SSc patients develop severe GIT symptoms. This subset of patients display increased mortality with only 15% survival at 9 years. Dysmotiity of the GIT causes the majority of symptoms. Recent investigations have identified a novel mechanism in the pathogenesis of GIT dysmotility mediated by functional anti-muscarinic receptor autoantibodies.

CONCLUSIONS

Despite extensive investigation, the pathogenesis of gastrointestinal involvement in systemic sclerosis remains elusive. Although treatment currently remains symptomatic, an improved understanding of novel pathogenic mechanisms may allow the development of potentially highly effective approaches including intravenous immunoglobulin and microRNA based therapeutic interventions.

Efficacy of anorectal biofeedback in scleroderma patients with fecal incontinence: a case-control study

OBJECTIVE

To determine whether anorectal biofeedback therapy can improve the symptoms of fecal incontinence (FI) in patients with scleroderma when compared to patients with functional FI, and also whether there is any effect on anorectal physiology or quality of life (QOL). FI in patients with scleroderma is highly prevalent and is associated with significant loss of QOL. Biofeedback has been proven to be an effective treatment for functional FI, but there are no data to support its use in scleroderma.

MATERIALS AND METHODS

13 consecutive female patients (median age 59, IQR 47-65 years) with scleroderma, and 26 age- and parity-matched female patients with functional FI (disease controls, 2:1), underwent biofeedback therapy for management of FI. Fecal incontinence severity index (FISI), anorectal physiology, feeling of control and QOL were collected before and after 6 weeks of biofeedback therapy, with additional scoring repeated at 6-month follow-up.

RESULTS

After biofeedback treatment FISI, feeling of control and QOL significantly improved in both groups (p < 0.005). There was no difference in the degree in improvement in physiology, FISI or QOL between scleroderma patients and functional FI patients. Long-term improvement in FISI and control were seen in both groups and for QOL only in the scleroderma cohort (p < 0.05).

CONCLUSIONS

Patients with scleroderma benefit from biofeedback therapy to the same extent as that achieved in patients with functional FI. There are significant improvements in symptoms, physiology and QOL. Biofeedback is an effective, low-risk treatment option in this patient group.

Gastrointestinal Manifestations of Systemic Sclerosis

In patients with systemic sclerosis (SSc), gastrointestinal (GI) tract involvement is almost universal. Any segment of the GI tract from mouth to anus can be involved, and GI symptoms are a frequent cause of morbidity. In severe cases, GI tract involvement can progress to the point of malnutrition requiring parenteral nutrition. GI tract involvement in SSc contributes to disease-related mortality although mostly as a co-morbidity rather than direct cause of death. The review is intended to help address challenges in the assessment and treatment of GI tract involvement in SSc.

Role of muscarinic-3 receptor antibody in systemic sclerosis: correlation with disease duration and effects of IVIG

Gastrointestinal dysmotility in systemic sclerosis (SSc) is associated with autoantibodies against muscarinic-3 receptor (M3-R). We investigated the temporal course of the site of action of these autoantibodies at the myenteric neurons (MN) vs. the smooth muscle (SM) M3-R in relation to disease duration, and determined the role of intravenous immunoglobulin (IVIG) in reversing these changes. Immunoglobulins purified from SSc patients (SScIgG) were used to assess their differential binding to MN and SM (from rat colon) employing immunohistochemistry (IHC). Effect of SScIgG on neural and direct muscle contraction was determined by cholinergic nerve stimulation and bethanechol-induced SM contraction. Effects of IVIG and its antigen-binding fragment F(ab')2 on SScIgG binding were studied by enzyme-linked immunosorbent assay (ELISA) of rat colonic longitudinal SM myenteric plexus (LSMMP) lysate and to second extracellular loop peptide of M3-R (M3-RL2). SScIgG from all patients demonstrated significantly higher binding to MN than to SM. With progression of SSc duration, binding at MN and SM increased in a linear fashion with a correlation coefficient of 0.696 and 0.726, respectively (P < 0.05). SScIgG-mediated attenuation of neural and direct SM contraction also increased with disease duration. ELISA analysis revealed that IVIG and F(ab')2 significantly reduced SScIgG binding to LSMMP lysate and M3-RL2. Dysmotility in SSc occurs sequentially, beginning with SScIgG-induced blockage of cholinergic neurotransmission (neuropathy), which progresses to inhibition of acetylcholine action at the SM cell (myopathy). IVIG reverses this cholinergic dysfunction at the neural and myogenic receptors by anti-idiotypic neutralization of SScIgG.

Anal incontinence and vesico-sphincter events in systemic sclerosis: An epidemiologic bicentric cohort study

OBJECTIVE

To estimate the frequency and severity of anal incontinence and vesico-sphincter events, associated factors, and impact on the quality of life of patients with systemic sclerosis.

METHODS

Questionnaires assessing anal incontinence (Miller score), vesico-sphincter events (Urogenital Distress Inventory) and quality of life [Short Form Health Survey 36v2 (SF-36), and Hospital Anxiety and Depression Scale] were mailed to 139 patients with systemic sclerosis at the university hospitals of Besançon and Poitiers, France. Clinical data were collected from the medical records to identify risk factors.

RESULTS

Among the 121 (87%) responders, severe vesico-sphincter events or severe anal incontinence occurred in 3.4% and 12.4% of cases, respectively. Frequent urination (66.3%) and anal incontinence to gas (50.4%) were the most frequent symptoms. Anal incontinence was associated positively with vesico-sphincter events, unrelated to obstetrical factors. No correlations were seen with age, sex, or systemic sclerosis characteristics. In multivariate analysis, moderate or severe vesico-sphincter events was associated with higher anxiety and depression scores and lower SF-36 scores; the same results were observed for anal incontinence, but did not reach significance.

CONCLUSION

Vesico-sphincter events and anal incontinence are common in systemic sclerosis, and sometimes severe, with a potential negative impact in quality of life. These results will be confirmed by a case-control study with dynamic and manometric assessment, and could legitimate a systematic screening to ensure early therapy and multidisciplinary individual management.

Systemic Sclerosis: Gastrointestinal Disease and Its Management

The gastrointestinal tract, affecting more than 90% of patients, is the internal organ most frequently involved in systemic sclerosis. Any part of the gastrointestinal tract can be affected, from the mouth to the anus. Patients often experience reduced quality of life and impaired social life. Although only 8% have severe gastrointestinal involvement, mortality is high in those patients. Recent studies on the pathophysiology of the disease highlight new mechanisms to explain gastrointestinal dysmotility, but treatment remains symptomatic. This article reviews the pathophysiology of the gastrointestinal tract and discusses the investigation and management of the disease.

Role of SM22 in the differential regulation of phasic vs. tonic smooth muscle

Preliminary proteomics studies between tonic vs. phasic smooth muscles identified three distinct protein spots identified to be those of transgelin (SM22). The latter was found to be distinctly downregulated in the internal anal sphincter (IAS) vs. rectal smooth muscle (RSM) SMC. The major focus of the present studies was to examine the differential molecular control mechanisms by SM22 in the functionality of truly tonic smooth muscle of the IAS vs. the adjoining phasic smooth muscle of the RSM. We monitored SMC lengths before and after incubation with pFLAG-SM22 (for SM22 overexpression), and SM22 small-interfering RNA. pFLAG-SM22 caused concentration-dependent and significantly greater relaxation in the IAS vs. the RSM SMCs. Conversely, temporary silencing of SM22 caused contraction in both types of the SMCs. Further studies revealed a significant reverse relationship between the levels of SM22 phosphorylation and the amount of SM22-actin binding in the IAS and RSM SMC. Data showed higher phospho-SM22 levels and decreased SM22-actin binding in the IAS, and reverse to be the case in the RSM SMCs. Experiments determining the mechanism for SM22 phosphorylation in these smooth muscles revealed that Y-27632 (Rho kinase inhibitor) but not Gö-6850 (protein kinase C inhibitor) caused concentration-dependent decreased phosphorylation of SM22. We speculate that SM22 plays an important role in the regulation of basal tone via Rho kinase-induced phosphorylation of SM22.

Measurement of smooth muscle function in the isolated tissue bath-applications to pharmacology research

Isolated tissue bath assays are a classical pharmacological tool for evaluating concentration-response relationships in a myriad of contractile tissues. While this technique has been implemented for over 100 years, the versatility, simplicity and reproducibility of this assay helps it to remain an indispensable tool for pharmacologists and physiologists alike. Tissue bath systems are available in a wide array of shapes and sizes, allowing a scientist to evaluate samples as small as murine mesenteric arteries and as large as porcine ileum - if not larger. Central to the isolated tissue bath assay is the ability to measure concentration-dependent changes to isometric contraction, and how the efficacy and potency of contractile agonists can be manipulated by increasing concentrations of antagonists or inhibitors. Even though the general principles remain relatively similar, recent technological advances allow even more versatility to the tissue bath assay by incorporating computer-based data recording and analysis software. This video will demonstrate the function of the isolated tissue bath to measure the isometric contraction of an isolated smooth muscle (in this case rat thoracic aorta rings), and share the types of knowledge that can be created with this technique. Included are detailed descriptions of aortic tissue dissection and preparation, placement of aortic rings in the tissue bath and proper tissue equilibration prior to experimentation, tests of tissue viability, experimental design and implementation, and data quantitation. Aorta will be connected to isometric force transducers, the data from which will be captured using a commercially available analog-to-digital converter and bridge amplifier specifically designed for use in these experiments. The accompanying software to this system will be used to visualize the experiment and analyze captured data.

Physiological and structural anorectal abnormalities in patients with systemic sclerosis and fecal incontinence

OBJECTIVE

Fecal incontinence is common in systemic sclerosis (SSc), but the underlying mechanisms are not fully understood. The objectives of this study were to characterize anorectal physiological and morphological defects in SSc patients and to correlate the results with incontinence symptoms.

MATERIALS AND METHODS

Twenty-five SSc patients underwent anorectal neurophysiological investigations, anal manometry, and ultrasound.

RESULTS

Eleven patients (44%) reported incontinence to solid or liquid feces, but no patient reported diarrhea. Increased fiber density (FD) was recorded in 78% of patients with and in 86% of patients without fecal incontinence not significant (NS). Incontinent patients had lower squeeze pressure (SP; median 49.5 mm Hg) in the high-pressure zone (HPZ) than continent patients (median 72 mm Hg; p = 0.01). In two of the incontinent patients, sonographic abnormalities of the internal anal sphincter (IAS) and the external anal sphincter (EAS) were present, whereas in another two patients isolated IAS abnormalities were seen. These four individuals had lower resting pressure at 1 cm and in the HPZ, and lower SP at 2 cm than patients with normal anorectal sonographic findings (p < 0.05).

CONCLUSION

Lower voluntary SP in incontinent patients and EAS sonographic abnormalities only in patients with incontinence suggest that the EAS is more important in maintaining fecal continence in SSc patients than has previously been reported. The finding of increased FD in most patients further supports involvement of the EAS function in SSc and could indicate previous nerve injury with consequent incomplete reinnervation.

Gastrointestinal involvement in systemic sclerosis

Systemic sclerosis is an autoimmune chronic disease characterised by microvascular, muscular and immunologic abnormalities that lead to progressive and systemic deposition of connective tissue in the skin and internal organs. The gastrointestinal tract is often overlooked by physicians but it is the most affected organ after the skin, from the mouth to the anus. Indeed, 80% of SSc patients may present with gastrointestinal involvement. Gastrointestinal manifestations range from bloating and heartburn to dysphagia and anorectal dysfunction to severe weight loss and malabsorption. However, the gastrointestinal involvement is rarely the direct cause of death, but has great impact on quality of life and leads to several comorbidities that subsequently affect patients' survival. Treatments, including nutritional support and prokinetics provide limited benefits and do not arrest the progressive course of the disease, but earlier detection of gastrointestinal involvement may reduce the risk of complications such as malnutrition.

Gastrointestinal complications of systemic sclerosis

Systemic sclerosis is an autoimmune disease characterized by progressive skin thickening and tightness. Pulmonary interstitial fibrosis and kidney damage are the most important indicators for mortality; however, the gastrointestinal tract is the most commonly damaged system. Virtually all parts of the gastrointestinal (GI) tract can be involved, although the esophagus is the most frequently reported. The mechanisms that cause such extensive damage are generally unclear, but vascular changes, immunological abnormalities, excessive accumulation of collagen in the submucosa, smooth muscle atrophy and neuropathy may participate because these are the most common histological findings in biopsies and autopsies. Most patients with GI tract involvement complain about dyspepsia, nausea, vomiting, abdominal bloating/distension, and fecal incontinence. These symptoms are generally mild during the early stage of the disease and are likely ignored by physicians. As the disease becomes more advanced, however, patient quality of life is markedly influenced, whereby malnutrition and shortened survival are the usual consequences. The diagnosis for systemic sclerosis is based on manometry measurements and an endoscopy examination. Supportive and symptomatic treatment is the main therapeutic strategy; however, an early diagnosis is critical for successful management.

Effects of scleroderma antibodies and pooled human immunoglobulin on anal sphincter and colonic smooth muscle function

BACKGROUND & AIMS

Patients with systemic sclerosis (SSc) have impairments in gastrointestinal smooth muscle function. The disorder has been associated with circulating antibodies to cholinergic muscarinic the type-3 receptor (M(3)-R). We investigated whether it is possible to neutralize these antibodies with pooled human IgGs (pooledhIgG).

METHODS

We studied the effects of IgGs purified from patients with SSc (SScIgGs) on cholinergic nerve stimulation in rat colon tissues. We also examined the effects of SScIgGs on M(3)-R activation by bethanechol (BeCh), M(3)-R occupancy, and receptor binding using immunofluorescence, immunoblot, and enzyme-linked immunosorbent analyses of human internal anal sphincter (IAS) smooth muscle cells, before and after administration of pooledhIgG. Functional displacement of M(3)-R occupancy by the SScIgGs was compared with that of other IgGs during the sustained phase of BeCh-induced contraction of intact smooth muscles from rats.

RESULTS

SScIgG significantly attenuated neurally mediated contraction and acetylcholine release in rat colon as well as BeCh-induced sustained contraction of the IAS smooth muscle. In immunofluorescence analysis, SScIgG co-localized with M(3)-R. In immunoblot and enzyme-linked immunosorbent analyses, M(3)-R loop-2 peptide and human IAS SMC membrane lysates bound significant amounts of SScIgG, compared with IgGs from healthy individuals and pooledhIgG. Binding was attenuated significantly by application of pooledhIgG, which by itself had no significant effect. Incubation of samples with pooledhIgG, or mixing pooledhIgG with SScIgG before administration to tissues, significantly reduced binding of SScIgG, indicating that pooledhIgG prevents SScIgG blockade of M(3)-R.

CONCLUSIONS

In studies of rat and human tissues, pooled human IgG prevent and reverses the cholinergic dysfunction associated with the progressive gastrointestinal manifestations of SSc by neutralizing functional M(3)-R antibodies present in the circulation of patients with SSc.