Helicobacter pylori and skin autoimmune diseases

Abstract

Autoimmune skin diseases are characterized by dysregulation of the immune system resulting in a loss of tolerance to skin self-antigen(s). The prolonged interaction between the bacterium and host immune mechanisms makes Helicobacter pylori (H. pylori) a plausible infectious agent for triggering autoimmunity. Epidemiological and experimental data now point to a strong relation of H. pylori infection on the development of many extragastric diseases, including several allergic and autoimmune diseases. H. pylori antigens activate cross-reactive T cells and induce autoantibodies production. Microbial heat shock proteins (HSP) play an important role of in the pathogenesis of autoimmune diseases because of the high level of sequence homology with human HSP. Eradication of H. pylori infection has been shown to be effective in some patients with chronic autoimmune urticaria, psoriasis, alopecia areata and Schoenlein-Henoch purpura. There is conflicting and controversial data regarding the association of H. pylori infection with Behçet’s disease, scleroderma and autoimmune bullous diseases. No data are available evaluating the association of H. pylori infection with other skin autoimmune diseases, such as vitiligo, cutaneous lupus erythematosus and dermatomyositis. The epidemiological and experimental evidence for a possible role of H. pylori infection in skin autoimmune diseases are the subject of this review.

Key Words: Autoimmune, Skin, Helicobacter pylori, Infection

Core tip: Epidemiological and experimental data now point to a strong relation of Helicobacter pylori (H. pylori) infection on the development of many autoimmune diseases. Eradication of H. pylori infection was shown to be effective in some patients with chronic autoimmune urticaria, psoriasis, alopecia areata and Schoenlein-Henoch purpura. There is conflicting and controversial data regarding the association of H. pylori infection with Behçet’s disease, scleroderma and autoimmune bullous diseases. No data are available evaluating the association of H. pylori infection with vitiligo, cutaneous lupus erythematosus and dermatomyositis. A possible role of H. pylori infection in skin autoimmune diseases is the subject of this review.

INTRODUCTION

The association between infection and autoimmunity has been progressively defined over the past 25 years. Since Helicobacter pylori (H. pylori) identification in 1983, an increasing amount of knowledge has collected, with this pathogen having been directly involved in the pathogenesis of several dermatological diseases[1]. H. pylori is a widely prevalent microbe, with nearly 50% of the western world and over 80% of those living in developing countries infected[2]. The bacteria has the amazing ability to persist in infected individuals for many decades and have closely co-existed with humans at least since they first migrated out of East Africa approximately 60000 years ago[3]. Epidemiological and experimental data now point to a strong relation of H. pylori infection on the development of many extragastric diseases, including several allergic and autoimmune diseases[4].

The epidemiological and experimental evidence for a possible role of H. pylori infection in skin autoimmune diseases are the subject of this review.

IMMUNOMODULARY MECHANISMS OF H. PYLORI IN AUTOIMMUNE DISEASES

Various mechanisms have been proposed in an attempt to explain the extra intestinal autoimmune manifestations of H. pylori infections.

Autoimmune diseases are characterized by dysregulation of the immune system resulting in a loss of tolerance to self-antigens. The exact etiology for the majority of these diseases is unknown; however, complex process, including genetic predisposition, hormonal balance and environmental factors such as infectious agents are believed to play a pivotal role[4]. The inflammatory response to H. pylori infection can lead to the development of antigen-antibody complexes or cross-reactive antibodies resulting in autoimmunity[5]. H. pylori induced molecular mimicry can also result in both humoral and cell-mediated autoimmune reactions with the development of organ specific and systemic immunopathology[6].

Infection with H. pylori elicits a significant immunomodulation, that are typically triggered by chronic inflammation[7] and results in a primarily Th1 T-cell response, resulting in the production of interleukin (IL)-2 and interferon gamma[8]. This chronic infection is also characterized be higher local and systemic levels of proinflammatory cytokines such as tumor necrosis factor-α, IL-6, IL-10, and IL-8[9]. H. pylori chronic infection can also result in uncontrolled growth and proliferation of CD5+ B-cells, which produce polyreactive and auto-reactive IgM and IgG3 antibodies[10].

Several recent reports have implicated T regulatory cells (Tregs) and dendritic cells (DCs) with tolerogenic activity in mediating the systemic immunomodulatory effects of H. pylori infection[11]. Evidence for a functional role for Tregs and Treg-derived cytokines in promoting H. pylori-induced immunomodulation has been provided in experimental infection models[12,13]. Inducible Tregs, which are generated in the periphery are believed to initiate and maintain peripheral immune tolerance through the induction of anergy, deletion of autoreactive T-cells and the instruction and differentiation of inducible Tregs[14]. These tolerogenic DCs function by converting naive T-cells into FoxP3+ Tregs through antigen presentation in the absence of co-stimulatory signals or cytokines[14,15] and appears to play a central role in the induction and maintenance of H. pylori-specific immune tolerance and immunomodulation[16]. H. pylori also holds an ability to intensely reprogram DCs toward tolerogenicity by efficiently inducing FoxP3 expression in naive T-cells in a tumor growth factor (TGF)-β-dependent manner[17,18].

Based on these observations, it is now accepted; that the presence or absence of H. pylori infection may influence the risk of developing of several autoimmune conditions, include immune-mediated dermatological diseases[19].

H. pylori and chronic urticaria

Urticaria is widely regarded as a heterogeneous group of diseases that share a distinct skin reaction pattern, i.e., the development of urticarial skin lesions[20]. Chronic spontaneous urticaria (CU) is defined as wheals arising spontaneously without any external physical stimuli and the disease lasts > 6 wk[20]. It is accepted that autoimmune mechanisms are involved in the pathogenesis of CU; and different pathogenic autoantibodies, namely causing a release of histamine, after reaction with IgE epitopes, or with the α-chain of Fc epsilon RI receptors, is considered[21]. Assessment of these autoantibodies in clinical practice is performed by the autologous serum skin test (ASST) and by immunoassay, while a positive ASST correlates with CU exacerbation[22]. The role of H. pylori infection in CU is still a matter of debate, although the association between CU and H. pylori has been found by some research groups[23-28].

The pathogenetic mechanisms by which H. pylori may induce urticaria are far from being clear and several hypotheses have been developed regarding the link with the bacteria and CU. The immunomodulatory role of H. Pylori infection in CU is a subject of intensive studies. For instance, IgG and IgA antibodies to 19-kDa H. pylori-associated lipoprotein was found to play a role in the pathogenesis of CU[29]. When IgA-, IgG-, and IgE- mediated immune responses against H.pylori antigens were analyzed, some bacterial immunoresponsive proteins were identified in cases of CU[30]. Moreover, H.pylori is causing excessive consumption of complement by specific antibodies produced against the bacterium, contributing to the pathogenesis of CU[31]. Generally, different strains of H. pylori may elicit different pathogenic responses[32]. In some cases specific IgE antibodies to H. pylori antigens have been described, both in active CU[33] and in complete remission after H. pylori eradication[34]. Significantly increased gastric juice eosinophil cationic protein (ECP) and gastric eosinophil infiltration were described in H. pylori infected CU patients[35]. Furthermore, H. pylori eradication results in a significant decrease in gastric juice ECP and gastric eosinophil infiltration only in CU patients[36]. CU is associated with a systemic inflammatory response, whereas the acute-phase response is manifested by increased circulating IL-6, which varies along with C-reactive protein changes and may be related to the urticarial activity[23].

The best evidence of H. pylori comes from studies investigating CU in which CU clinically improved in many patients with H.pylori infection after its eradication[24,37,38]. We recently observed that H. pylori eradication in CU patients, who are resistant to antihistamine medications, reduces clinical severity of CU through attenuation of low grade systemic inflammation[39].

Several studies evaluated a possible relationship between endoscopic gastrointestinal findings and CU using gastroduodenoscopy. In most patients with CU and H. pylori infection, endoscopic evaluation showed mostly mild to moderate gastric inflammation, but very few cases of gastric or duodenal ulcers were identified[29,35].

Recently, we described several cases of CU triggered by eradication of H. pylori[40]. Perhaps the systemic effects of the pathogen’s eradication involve some kind of immunomodulation activating autoimmune mechanisms of CU[40].

Consequently, the recent critical appraisal of the 10 trials, utilizing the Grading of Recommendations Assessment, Development, and Evaluation approach, showed that the benefit of H. pylori eradication in patients with CU is weak and conflicting[41]. For this reason, a decision to proceed with this management should be considered carefully in the context of relative harms/burdens and benefits, as well as patient values and preferences[41].

H. pylori and psoriasis

Psoriasis is an autoimmune disease which affects 1%-3% of population[42]. Latest immunological studies have increased our understanding of the pathogenesis of psoriasis. Recently, it has been suggested that of H. pylori infection might be a triggering factor in psoriasis[43,44]. H. pylori infections were considerably more common in psoriasis patients than in healthy controls[43,45]. Several investigators reported cases in which psoriatic lesions cleared up following the eradication of H. pylori infections[45-47]. Further clinical and basic studies are needed to confirm this association and its pathophysiological mechanisms.

H. pylori and scleroderma

Over the last 20 years increasing evidence has accumulated to implicate infectious agents in the etiology of systemic sclerosis (SSc). The most recent research on the involvement of bacterial infections in the pathogenesis of SSc focuses H. pylori[48,49]. Several studies reported higher prevalence of H. Pylori infection in patients with SSc, than in healthy[50-51]. Moreover, most of the patients in these studies were infected with CagA strain of H. pylori as compared to infected controls. H. pylori infection was also associated with higher SSc activity[52]. At this time it is unclear, whether H. pylori eradication can improve the disease activity and skin involvement in SSc patients.

Other studies focused on a role of H. pylori infection in the development of Raynaud’s phenomenon and Sjögren syndrome in SSc. At least, in primary Raynaud’s phenomenon, eradication of H. pylori infection was associated with complete remission in some and with a reduction in symptoms in most of the treated patients[53,54].

Kalabay et al[55] explained the pathophysiologic association of H. pylori infection in SSc by the disturbed gastrointestinal motility in patients with SSc and H. pylori induced immune dysregulation, aggravating the course of SSc. Additional studies are necessary to elucidate the pathogenesis and confirm the association between H. pylori and SSc.

H. pylori and alopecia areata

Alopecia areata (AA) is an autoimmune T-cell mediated disease directed against the hair follicle, with an estimated lifetime risk of 1.7% among the general population[56]. While one group of investigators found higher prevalence of H. pylori infection in patients with AA[57], other studies failed to confirm this association[58,59]. However, recently a case of a 43-year-old man with an 8-mo history of AA of the scalp and beard and concomitant H. pylori infection was presented, with complete remission from AA after H. pylori eradication[60].

Further controlled trials are necessary to investigate the association between AA and H. pylori infection.

H. pylori and vasculitis

There is some evidence of an association of H. pylori infection with various vasculitides.

Behçet’s disease (BD) is a multisystem inflammatory disorder characterized by recurrent oral aphthous ulcers, genital ulcers, uveitis, and skin lesions. The etiology of BD remains unknown, but epidemiologic findings suggest that an autoimmune process is triggered by an infectious or environmental agent in a genetically predisposed individual[61,62]. As for the most other autoimmune disorders, the Th1-type polarization is significant in BD[62] with increased numbers of activated γδ T lymphocytes[63].

A genetic susceptibility for both BD and H. pylori infection has been implicated by the fact that H. pylori infection is endemic in most of the countries in which BD is also highly prevalent[64].

While the prevalence of H. pylori IgG seropositivity was not significantly higher in the patients with BD compared to the controls, an eradication of H. pylori significantly decreased clinical manifestations of BD, such as oral, genital ulcerations and cutaneous lesions[65]. Other studies did not find differences in upper gastrointestinal endoscopy findings, prevalence and eradication rates of H. pylori between BD and control groups[66]. More trials are necessary to check the association between H. pylori and BD.

Schoenlein-Henoch purpura (SHP) is a leukocytoclastic vasculitis of small vessels and is characterized by IgA deposition in the affected tissues[67]. SHP is the most common vasculitic disorder affecting children, but is less common in adults[68]. Since 1995, when Reinauer et al[69] first described the case of SHP and H. pylori positive gastritis; where after H. pylori eradication therapy, the clinical manifestations of SHP were resolved, several analogous case reports have been described[70-74]. In general, the relationship of H. pylori infection and SHP may be underestimated. Randomised controlled trials are necessary to confirm a relationship between H. pylori and SHP and to evaluate the usefulness of H. pylori eradication therapy in SHP.

H. pylori and autoimmune bullous diseases

Autoimmune bullous diseases (AIBD) are a heterogeneous group of disorders, which includes pemphigus, pemphigoid, epidermolysis bullosa acquisita, dermatitis herpetiformis, linear immunoglobulin A disease, and multiple autoimmune syndrome[75]. AIBD are characterized with a genetic predisposition, which promotes the production of auto-antibodies targeted against different components of the epidermal desmosome and hemidesmosome[76]. There are no published studies investigating the association between AIBD and H. pylori, though a contributing role of this pathogen in inducing bullous pemphigoid has been suggested by some authors[77]. Recently, Matsuo et al[78] reported on the remission of sublamina densa-type linear IgA bullous dermatosis after H. pylori eradication.

In a study looking at serological evidence of various infectious agents in patients with AIBD (Pemphigus and bullous pemphigoid), H. pylori IgG antibodies were reported to be more common in patients as compared to controls[79]. Clinical trials are necessary to confirm preliminary observations.

CONCLUSION

Autoimmune skin diseases are characterized by dysregulation of the immune system resulting in a loss of tolerance to skin self-antigen(s). The prolonged interaction between the bacterium and host immune mechanisms make H. pylori a plausible infectious agent for triggering autoimmunity. H. pylori antigens were found to activate cross-reactive T cells and induce autoantibodies production. Moreover, microbial heat shock proteins (HSP) play an important role of in the pathogenesis of autoimmune diseases because of the high level of sequence homology with human HSP.

Eradication of H. pylori infection has been shown to be effective in some patients with chronic autoimmune urticaria, psoriasis, alopecia areata and Schoenlein-Henoch purpura. There is conflicting and controversial data regarding the association of H. pylori infection with BD, scleroderma and autoimmune bullous diseases. No data are available evaluating the association of H. pylori infection with other skin autoimmune diseases, such as vitiligo, cutaneous lupus erythematosus and dermatomyositis. Epidemiological and clinical studies are necessary to investigate the association between H. pylori and these diseases.