Cellular immune response against tropomyosin isoform 5 in ulcerative colitis

The yin and yang of B cells in a constant state of battle: intestinal inflammation and inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract, defined by a clinical relapse-remitting course. Affecting people worldwide, the origin of IBD is still undefined, arising as a consequence of the interaction between genes, environment, and microbiota. Although the root cause is difficult to identify, data clearly indicate that dysbiosis and pathogenic microbial taxa are connected with the establishment and clinical course of IBD. The composition of the microbiota is shaped by plasma cell IgA secretion and binding, while cytokines such as IL10 or IFN-γ are important fine-tuners of the immune response in the gastrointestinal environment. B cells may also influence the course of inflammation by promoting either an anti-inflammatory or a pro-inflammatory milieu. Here, we discuss IgA-producing B regulatory cells as an anti-inflammatory factor in intestinal inflammation. Moreover, we specify the context of IgA and IgG as players that can potentially participate in mucosal inflammation. Finally, we discuss the role of B cells in mouse infection models where IL10, IgA, or IgG contribute to the outcome of the infection.

Musculoskeletal manifestations in inflammatory bowel disease: a revisit in search of immunopathophysiological mechanisms

Inflammatory bowel diseases are chronic inflammatory disorders of multiple organ systems, primarily involving the gut, with chronic relapsing and remitting course. Musculoskeletal involvement is the most common extraintestinal manifestation. Distinct cell-mediated and humoral immunopathophysiological mechanisms have been identified underlying gut and joint inflammation in patients with inflammatory bowel disease and arthritis. Genetic polymorphisms in genes coding for NOD2 and IL12/IL23 complex lead to impaired antigenic handling in the gut and local immune dysregulation. The gut-synovial axis hypothesis implicates both environmental and host factors acting as triggers to initiate inflammation in genetically predisposed individuals, leading to priming of Th1 and Th17 lymphocytes in the gut and subsequent homing to the synovial tissue. Similar to gut, antibody-dependent cell-mediated cytotoxicity and complement-mediated cell lysis may also contribute to the joint damage. Involvement of peripheral joints occurs in 2 distinct manners, one being oligoarticular asymmetric arthritis associated with active disease and the other being polyarticular symmetric involvement of small joints. The axial involvement may include asymptomatic sacroiliitis, inflammatory back pain, and ankylosing spondylitis, running an independent clinical course. Noninflammatory involvement of the musculoskeletal system may present as osteopenia, osteonecrosis, fibromyalgia, or myopathies, leading to significant impact on quality of life.

Mesalamine suppresses the expression of TC22, a novel tropomyosin isoform associated with colonic neoplasia

Although a protective role for mesalamine against colon cancer in ulcerative colitis has been shown epidemiologically, its molecular mechanism is unknown. We cloned and sequenced a novel human tropomyosin (hTM) isoform, TC22, which is an alternatively spliced variant of normal epithelial hTM isoform 5 (hTM5), identical apart from 25 C-terminal amino acids. TC22 is expressed in 100% of colorectal carcinoma but is not expressed in normal colon epithelial cells. To explore a molecular mechanism of chemoprevention, we examined the effect of mesalamine on TC22 expression using LS180 colon cancer cells. Expression of hTM5 and TC22 was investigated at the protein and gene levels by fluorescence-activated cell sorting and real-time reverse transcription-polymerase chain reaction. Small interference RNA (siRNA) against the TC22 variant were transfected into LS180 colon cancer cells, reducing protein and transcript levels by 45 to 50%. Mesalamine or sulfasalazine (2 mM), but not sulfapyridine, significantly (p < 0.02-0.006) reduced the expression of the TC22 transcript and significantly (p < 0.05 to <0.0002) reduced the expression of TC22 protein in a dose-dependent and reversible manner. Rosiglitazone, a specific peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist, similarly and significantly (p < 0.002) reduced TC22 protein expression. A polymerase chain reaction array of 84 cancer-related genes performed on TC22 siRNA-transfected cells demonstrated a significant (more than two times) change in targets involved in apoptosis, adhesion, angiogenesis, and tissue remodeling. We conclude that mesalamine, sulfasalazine, and rosiglitazone significantly reduced the cellular expression of TC22, implicating PPARgamma in this modulation. Similar suppression of TC22 by siRNA produced gene level changes on several critical carcinogenic pathways. These findings suggest a novel antineoplastic molecular effect of mesalamine.

The prevalence of hyper- and hypothyroidism in patients with ulcerative colitis

BACKGROUND

The association between ulcerative colitis and thyroid disorders has been previously reported. However, most reports consist of single case description, and a systematic assessment of this relationship has only sporadically been investigated.

AIMS

To study a cohort of patients with ulcerative colitis to establish the prevalence of hyper- and hypothyroidism.

MATERIAL AND METHODS

During a four-year period, we studied thyroid function in 162 ulcerative colitis patients (62 men, 100 women, age range 18-78 years).

RESULTS

Thyroid dysfunction was present in 4 patients (2.5%) of the overall population and was represented by both hypo- (3 patients) and hyperthyroidism (1 patient). The incidence of this kind of thyroid dysfunction was significantly (p=0.03) lower than that found in a large (more than 5000 subjects) control group.

CONCLUSIONS

We conclude that the prevalence of hyper-/hypothyroidism is relatively low in patients with ulcerative colitis, at least in our country, and does not justify a systematic investigation of the thyroid function, except in selected cases, probably those with scarce or no response to standard therapeutic measures.

Alterations in the immunohistochemical expression of Das-1 and CG-3 in colonic mucosal biopsy specimens helps distinguish ulcerative colitis from Crohn disease and from other forms of colitis

Distinction between ulcerative colitis (UC) and Crohn disease (CD) in mucosal biopsies is often difficult. Das-1 and CG-3 are monoclonal antibodies directed against an unknown colonic epithelial protein and human tropomyosin isoform-5, respectively, both show altered expression in patients with UC. In this study, we evaluated the utility of Das-1 and CG-3 in distinguishing UC from CD and from other types of colitis. One colonic biopsy specimen from each of 85 patients with confirmed UC (n=25), CD (n=15), lymphocytic (n=15), collagenous (n=15), and ischemic (n=15) colitis, and also 10 samples from normal controls, were stained for Das-1 and CG-3 using standard techniques. Reactivity for Das-1 and CG-3 was noted to be absent or present, and the location (ie, surface+/-crypt epithelium) and degree (weak or strong) of CG-3 staining was recorded. Loss of Das-1 staining occurred more frequently in UC (96%) compared with CD (20%), lymphocytic (20%), collagenous (13%), and ischemic colitis (0%) cases, as well as controls (10%, P<0.001 for all comparisons). CG-3 positivity in crypt epithelium was significantly more common in UC (52%) compared with the other groups (P< or =0.02 for all comparisons). The combination of strong crypt CG-3 staining and loss of Das-1 staining was noted in 44% of UC cases, but not in any other type of colitis (P=0.003 for all comparisons). We conclude that the patterns of Das-1 and CG-3 staining in colonic mucosal biopsies may be clinically useful in distinguishing UC from CD and from other colitidies.

Effect of eradication of Helicobacter pylori on the histology and cellular phenotype of gastric intestinal metaplasia

BACKGROUND & AIMS

Eradication of Helicobacter pylori appears to reduce gastric cancer incidence. We examined the effect of successful H pylori therapy on histology, phenotype of gastric intestinal metaplasia (GIM) (complete vs incomplete), and expression of several biomarkers related to carcinogenesis.

METHODS

Ninety-six H pylori-positive patients from Japan were treated successfully and followed up prospectively over 4 years with yearly endoscopy and were classified into 3 groups: group CG, chronic gastritis without GIM (n = 36); group IM, chronic gastritis with GIM (n = 33); group DYS, and GIM with dysplasia/cancer in a different location of the stomach (n = 27). A total of 288 endoscopic procedures were performed. Histology, mucin-histochemistry, and immunoperoxidase assays using monoclonal antibodies (mAbs) for cell phenotype (monoclonal antibody Das-1/colonic) and for neoplasia (TC22 and p53) were performed.

RESULTS

The GIM histologic score was higher in group DYS than in group IM (P < .05) and group CG (P < .0001). The GIM scores did not change in groups IM and DYS over 4 years. mAb Das-1 reactivity was higher in group DYS (63%) than in group IM (39%) and group GC (0%). After eradication of H pylori, mAb Das-1 reactivity disappeared in 40% of patients (P < .0001) despite the unchanged GIM scores, and regression of TC22-4 was noted in the same patients.

CONCLUSIONS

H pylori eradication does not reduce the histologic GIM score, but changes the cellular phenotype of GIM. This change of phenotype may be an important factor in the reduction of cancer incidence after eradication of H pylori.

Tropomyosin-based regulation of the actin cytoskeleton in time and space

Tropomyosins are rodlike coiled coil dimers that form continuous polymers along the major groove of most actin filaments. In striated muscle, tropomyosin regulates the actin-myosin interaction and, hence, contraction of muscle. Tropomyosin also contributes to most, if not all, functions of the actin cytoskeleton, and its role is essential for the viability of a wide range of organisms. The ability of tropomyosin to contribute to the many functions of the actin cytoskeleton is related to the temporal and spatial regulation of expression of tropomyosin isoforms. Qualitative and quantitative changes in tropomyosin isoform expression accompany morphogenesis in a range of cell types. The isoforms are segregated to different intracellular pools of actin filaments and confer different properties to these filaments. Mutations in tropomyosins are directly involved in cardiac and skeletal muscle diseases. Alterations in tropomyosin expression directly contribute to the growth and spread of cancer. The functional specificity of tropomyosins is related to the collaborative interactions of the isoforms with different actin binding proteins such as cofilin, gelsolin, Arp 2/3, myosin, caldesmon, and tropomodulin. It is proposed that local changes in signaling activity may be sufficient to drive the assembly of isoform-specific complexes at different intracellular sites.

Tropomyosins in human diseases: ulcerative colitis

Ulcerative colitis (UC) is a form of chronic inflammatory bowel disease (IBD) that almost always affects the rectal mucosa and variable length of the colon in continuity and at times mucosa of the entire colon. It is not caused by any specific pathogen. Genetics, environmental factors and altered immune responses to dietary macromolecules, colonic bacteria and cellular proteins have been implicated in the pathogenesis of UC. Autoimmune response against cytoskeletal, microfilament protein tropomyosin (Tm) seems to play an important role in the pathogenesis of UC. The predominant colonic epithelial Tm isoform, hTm5, can induce both humoral (B-cells) and cellular (T-cells) response in patients with UC. Such responses are not seen in normal subjects and disease control subjects, such as patients with Crohn's disease (CD, another type of IBD) and patients with lupus. A novel observation that hTm5 is expressed on colon epithelial cell surface but not on small intestinal epithelial cells provides evidence for presentation to immune effector cells. This surface expression of hTm5 seems to be facilitated by a colon epithelial cell membrane associated protein, CEP, that acts as a chaperone for the trans-migration of hTm5 to the surface and both hTm5 and CEP are then released outside the cell. Both CEP and hTm5 expression are increased with pro-inflammatory cytokine, such as gamma-interferon. hTm5 expression in UC mucosa is also significantly increased compared to normal. Finally, autoantibodies against hTm5 observed both in circulation and in the colon mucosa of patients with UC are pathogenic causing colon epithelial cell destruction by antibody and complement mediated cytolysis.

Human tropomyosin isoforms in the regulation of cytoskeleton functions

Over the past two decades, extensive molecular studies have identified multiple tropomyosin isoforms existing in all mammalian cells and tissues. In humans, tropomyosins are encoded by TPM1 (alpha-Tm, 15q22.1), TPM2 (beta-Tm, 9p13.2-p13.1), TPM3 (gamma-Tm, 1q21.2) and TPM4 (delta-Tm, 19p13.1) genes. Through the use of different promoters, alternatively spliced exons and different sites of poly(A) addition signals, at least 22 different tropomyosin cDNAs with full-length open reading frame have been cloned. Compelling evidence suggests that these isoforms play important determinants for actin cytoskeleton functions, such as intracellular vesicle movement, cell migration, cytokinesis, cell proliferation and apoptosis. In vitro biochemical studies and in vivo localization studies suggest that different tropomyosin isoforms have differences in their actin-binding properties and their effects on other actin-binding protein functions and thus, in their specification ofactin microfilaments. In this chapter, we will review what has been learned from experimental studies on human tropomyosin isoforms about the mechanisms for differential localization and functions of tropomyosin. First, we summarize current information concerning human tropomyosin isoforms and relate this to the functions of structural homologues in rodents. We will discuss general strategies for differential localization oftropomyosin isoforms, particularly focusing on differential protein turnover and differential isoform effects on other actin binding protein functions. We will then review tropomyosin functions in regulating cell motility and in modulating the anti-angiogenic activity of cleaved high molecular weight kininogen (HKa) and discuss future directions in this area.

Autoantibodies against human tropomyosin isoform 5 in ulcerative colitis destroys colonic epithelial cells through antibody and complement-mediated lysis

INTRODUCTION

Patients with ulcerative colitis (UC) have IgG1 antibodies in serum and colon against human tropomyosin isoform 5 (hTM5), a cytoskeletal microfilament protein found intracellularly and on the surface of colonic epithelial cells (EC). These antibodies may be pathogenic in UC.

METHODS

Sera from patients with UC (n=110) or Crohn's disease (CD) (n=50) and from healthy individuals (Hl) (n=30) were preincubated with recombinant hTM5 or bovine serum albumin (BSA), then cultured for 4h with (51)Cr-labelled colonic adenocarcinoma cells (LS180). Cytotoxicity was determined by (51)Cr release assay.

RESULTS

All serum samples lysed up to 36% of LS180 cells regardless of the source of the serum. However, adding hTM5 to UC, but not to CD or HI, sera reduced cytotoxicity by up to 75%. This hTM5-induced inhibition of cytotoxicity was found especially with sera from UC patients with active disease, and was found even after total colectomy. The hTM5-induced inhibition was mediated by purified IgG from UC sera. Complement was involved since hTM5-induced inhibition of cytotoxicity declined with either heat inactivation of the sera or premixing sera with Fc fragments.

CONCLUSIONS

This study shows that hTM5-specific IgG autoantibodies present in UC sera destroy LS180 cells by antibody and complement-mediated lysis. Such a phenomenon was not seen in CD or HI. This suggests an autoantigenic role of hTM5 and anti-hTM5 antibodies in the pathogenesis of UC. This observation may lead to novel diagnostic and therapeutic possibilities.

Autoimmunity against human tropomyosin isoforms in ulcerative colitis: localization of specific human tropomyosin isoforms in the intestine and extraintestinal organs

BACKGROUND

Tropomyosins (TMs) are microfilament cytoskeletal proteins, and 5 major human TM isoforms (hTM1-5) are described. hTMs, particularly isoform 5 (hTM5), is capable of inducing autoantibodies and T-cell response in ulcerative colitis (UC). However, cellular localization of hTM isoforms in the colon and in extraintestinal organs commonly involved in UC is unknown.

METHODS

Using isoform-specific monoclonal antibodies, we localized hTMs through immunoperoxidase assay in normal colon (n = 12), small intestine (n = 14), esophagus (n = 10), skin (n = 19), eye (n = 12), gallbladder (n = 16), liver, including bile duct at the porta hepatis (n = 4), lungs (n = 4), and pancreas (n = 4).

RESULTS

There is intense expression of hTM5, but not other isoforms, in the epithelium of the colon, gallbladder, and skin. In the eye, hTM5 is expressed only in the nonpigmented ciliary epithelium. Although extrahepatic and interlobar large ductal biliary epithelium was positive, bile canaliculi at the portal tract are negative. The immunoreactivity in epithelial cells from these organs is diffuse cytoplasmic and along the periphery. In colon epithelium, there is intense expression along basolateral areas and luminal (apical) surface. In the small intestinal epithelium, however, hTM5 expression is weak and distinctly different than in the colon. hTM5 was not detected in the squamous epithelium of the esophagus, although it was strongly positive in the skin. hTM1, hTM2, and hTM3 are localized predominantly in smooth muscle of the intestine and blood vessel wall but not the epithelium. HTM4 is localized in the endothelial cells and basement membrane of the colonic epithelium.

CONCLUSIONS

hTM5 is the predominant isoform in the epithelium of colon and extraintestinal organs commonly involved in UC. The unique expression of hTM5 may allow its interaction with effector immune cells involved in the immunopathogenesis of UC and its extraintestinal manifestations.

Accumulation of tropomyosin isoform 5 at the infection sites of host cells during Cryptosporidium invasion

The actin cytoskeleton of host cells has been implicated in Cryptosporidium invasion. However, the underlying mechanism of how actin filaments and associated proteins modulate this process remains unclear. In this study, we use in vitro cultured cell lines, human ileocecal adenocarcinoma HCT-8 and Chinese hamster ovary (CHO), and an in vivo mouse model to investigate the roles of tropomyosin isoforms in Cryptosporidium invasion. Using isoform-specific monoclonal antibodies, we found that the major human tropomyosin (hTM) isoforms expressed in HCT-8 cells are hTM4 and hTM5. HCT-8 cells also express hTM1 at low levels but not hTM2 and hTM3. During Cryptosporidium parvum infection, hTM5 colocalized to the infection sites with a novel parasite membrane protein, CP2. Neither hTM1 nor hTM4 accumulated at infection sites. Similarly, a high level of TM5 and varying amounts of TM4 accumulated at the C. parvum infection sites in CHO cells. CHO cells overexpressing hTM5 exhibit a significantly higher percent of mature meronts early in the infection process relative to CHO cells or CHO cells overexpressing a tropomyosin mutant, chimeric isoform hTM5/3. These results suggest that functional TM5 enhances Cryptosporidium invasion of host cells. In C. parvum-infected mice, accumulation and rearrangement of TM5 and TM4 were detected throughout the infected ileum. Similarly, in the Cryptosporidium muris-infected mice, TM5 accumulated in discrete regions of the epithelial cells of gastric glands and in the oocyst-laden stomach gland lumen. Cryptosporidium infection appears to rearrange and recruit host TM isoforms in both culture cells and in the mouse. Localized accumulation of tropomyosin at the infection sites may facilitate parasite invasion.

Current therapeutic recommendations: infliximab for ulcerative colitis

Randomized, controlled studies have shown that infliximab, the chimeric anti-tumor necrosis factor alpha (TNF-alpha) antibody, is effective for the treatment of active and fistulizing Crohn's disease. Because infliximab is beneficial in patients with Crohn's disease, in whom other therapies have failed, it has been postulated that infliximab may also be helpful in patients with ulcerative colitis. Many investigators have studied the effectiveness of infliximab in ulcerative colitis, mainly in patients who are refractory to corticosteroids. Unfortunately, these studies have not yielded a conclusive answer to the efficacy of infliximab in inducing remission in patients with severe ulcerative colitis. However, some have reported excellent results and others less effective, with the overall data being inconclusive. The purpose of this review is to summarize the current literature on the use of infliximab in ulcerative colitis, as well as to provide insight into the possible mechanisms of why it may or may not work in these difficult-to-treat patients.

Tropomyosin expression in the ileal pouch: a relationship with the development of pouchitis in ulcerative colitis

OBJECTIVE

Human tropomyosin isoform 5 (hTM5) is a cytoskeletal protein expressed in normal epithelial cells, predominantly in the colon. An autoimmune response toward hTM5 has been reported in ulcerative colitis (UC). Whether hTM5 expression in the ileum is involved in pouchitis is unknown. We assessed hTM5 expression on ileal epithelial cells at surgery and subsequently on development of pouchitis in UC.

METHODS

In a prospective longitudinal study, 28 UC patients undergoing ileal pouch procedures were included. Biopsy samples were taken from the rectum at surgery, as well as from the ileal pouch at surgery and at 6 months. The specimens were stained by immunoperoxidase using the anti-hTM5 monoclonal antibody CG3. Pouchitis was assessed by the Pouchitis Disease Activity Index and hTM5 expression on a scale of 0-3.

RESULTS

At surgery, in rectal samples, hTM5 expression was strong in all epithelial cells including the luminal surface, whereas in ileal samples hTM5 was not expressed or focally expressed only in the goblet cells. At 6 months, the ileum was found to have undergone morphological changes, becoming similar to the colon and showing shortening or reduced number of villi. These changes were associated with a diffuse hTM5 staining in the goblet cells and in the nongoblet epithelial cells lining the crypts and the lumen. The hTM5 score was related to the Pouchitis Disease Activity Index at 6 months (r = 0.82; p = 0.01).

CONCLUSIONS

Expression of hTM5 shows a different pattern in the ileal pouch in UC after surgery. This event is associated with morphological changes of the ileum toward colonic epithelium, related to the development of pouchitis.

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