Urothelial antigen-specific CD4+ T cells function as direct effector cells and induce bladder autoimmune inflammation independent of CD8+ T cells

The NLRP3 Inflammasome Inhibitor Dapansutrile Attenuates Cyclophosphamide-Induced Interstitial Cystitis

Interstitial cystitis (IC)/bladder pain syndrome (BPS), hereafter referred together as IC, is a clinical syndrome characterized by sterile inflammation in the bladder. While the etiology and pathophysiology of IC remain unclear, it may involve autoimmunity in light of the significant role played by the NLRP3 inflammasome. However, the effect of NLRP3 inhibitors including dapansutrile (Dap) on IC had not been explored previously. Here, we investigated the effect of Dap in the cyclophosphamide (CYP)-induced experimental mouse model of IC, which results in functional and histological alterations confined to the urinary bladder (UB) comparable to that of clinical IC. CYP-induced mice treated with Dap exhibited improved UB pathology and reductions in inflammation scores and the frequency and the number of mast cells and neutrophils, relative to mice that received CYP alone. Dap- and CYP-treated mice also exhibited infiltration of T cells in the spleen and iliac lymph nodes (ILNs) and a concurrent significant decrease (p<0.01) in CXCR3⁺CD8⁺ T cells in the UB, induction of systemic and mucosal dendritic cells (DCs), and reduced levels of systemic proinflammatory cytokines, as compared to CYP alone. We also observed decreases in the expression of several signaling pathways regulators, including interleukin-1 beta (IL-1β), NLRP3, caspase-1, nuclear factor kappa B (NF-κB), and inducible nitric oxide synthase (iNOS) in the UB of CYP- and Dap-treated mice, relative to those receiving CYP alone. Taken together, these results suggest that Dap suppresses IC through the reduction of CXCR3⁺T cells, mast cells, and neutrophils in the UB and induces DCs as a protective measure. The present study identifies the mechanisms underlying the amelioration of IC by the NLRP3 inhibitor Dap and may provide an avenue for a potential therapeutic agent for the treatment of IC.

The Roles of T cells in Bladder Pathologies

T lymphocytes play important roles in the skin and mucosal surfaces such as the gut and lung. Until recently the contributions of T cells to mammalian bladder immunity were largely unknown. With newer techniques, including single-cell RNA sequencing and reporter mice, an understanding is emerging of T cell roles in bladder diseases (bacterial infections, bladder cancer, chronic inflammation). In these pathologies, many bladder T cell responses can be harmful to the host through suboptimal clearance of bacteria or cancer cells, or by modulating autoinflammation. Recent findings suggest that T cell behavior might be influenced by resident T cell interactions with the bladder microbiota and other immunostimulants. Thus, regulating bladder T cell functions could emerge as a putative immunotherapy to treat some bladder diseases.

Interstitial cystitis/bladder pain syndrome: The evolving landscape, animal models and future perspectives

Interstitial cystitis/bladder pain syndrome is a debilitating condition of unknown etiology characterized by persistent pelvic pain with lower urinary tract symptoms and comprises a wide variety of potentially clinically useful phenotypes with different possible etiologies. Current clinicopathological and genomic evidence suggests that interstitial cystitis/bladder pain syndrome should be categorized by the presence or absence of Hunner lesions, rather than by clinical phenotyping based on symptomatology. The Hunner lesion subtype is a distinct inflammatory disease with proven bladder etiology characterized by epithelial denudation and enhanced immune responses frequently accompanied by clonal expansion of infiltrating B cells, with potential engagement of infection. Meanwhile, the non-Hunner lesion subtype is a non-inflammatory disorder with little evidence of bladder etiology. It is potentially associated with urothelial malfunction and neurophysiological dysfunction, and frequently presents with somatic and/or psychological symptoms, that commonly result in central nervous sensitization. Animal models of autoimmune cystitis and neurogenic sensitization might serve as disease models for the Hunner lesion and non-Hunner lesion subtypes, respectively. Here, we revisit the taxonomy of interstitial cystitis/bladder pain syndrome according to current research, and discuss its potential pathophysiology and representative animal models. Categorization of interstitial cystitis/bladder pain syndrome based on cystoscopy is mandatory to design optimized treatment and research strategies for each subtype. A tailored approach that specifically targets the characteristic inflammation and epithelial denudation for the Hunner lesion subtype, or the urothelial malfunction, sensitized/altered nervous system and psychosocial problems for the non-Hunner lesion subtype, is essential for better clinical management and research progress in this complex condition.

An Immunogenic Peptide, T2 Induces Interstitial Cystitis/Painful Bladder Syndrome: an Autoimmune Mouse Model for Interstitial Cystitis/Painful Bladder Syndrome

The exact pathophysiology of interstitial cystitis/painful bladder syndrome is unknown; however, autoimmunity is a valid theory. We developed an autoimmune chronic cystitis model by administration of the medium dose of immunogenic peptide T2. Sixty female C57BL/6 mice were divided into six groups. The control group was not treated with any reagent. CFA group was injected with CFA + normal saline, homogenate group with bladder homogenate + CFA, low-dose group with low dose of T2 peptide + CFA, medium dose group with the medium dose of T2 peptide + CFA, and high-dose group with the high dose of T2 peptide + CFA. Micturition habits, withdrawal frequencies of mice, and bladders weight were measured for each group. Hematoxylin and eosin staining and toluidine blue staining were used to investigate bladder inflammation and mast cells accumulation, respectively. T cells infiltration in the bladder tissues and serum TNF-α level were measured by using immunohistochemistry and ELISA, respectively. Mice immunized with the medium dose of T2 peptide (0.225 mg/ml) were extremely sensitive to the applied force, showed greater urine frequencies, and higher bladder weights. Histologic examination revealed severe edema and inflammation in bladder tissues of medium-dose group. Extensive infiltration of T cells in bladder tissues, elevated TNF-α, and increased mast cells accumulation were observed in medium-dose group as compared to that in other groups. EAC mice model established by injecting the medium dose of T2 (0.225 mg/ml) mimics all the symptoms and pathophysiologic characteristics of IC/PBS. We believe that this model can help us to investigate the pathogenesis of IC/PBS.

Evidence for the Role of Mast Cells in Cystitis-Associated Lower Urinary Tract Dysfunction: A Multidisciplinary Approach to the Study of Chronic Pelvic Pain Research Network Animal Model Study

Bladder inflammation frequently causes cystitis pain and lower urinary tract dysfunction (LUTD) such as urinary frequency and urgency. Although mast cells have been identified to play a critical role in bladder inflammation and pain, the role of mast cells in cystitis-associated LUTD has not been demonstrated. Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic and debilitating inflammatory condition of the urinary bladder characterized by the hallmark symptoms of pelvic pain and LUTD. In this study we investigated the role of mast cells in LUTD using a transgenic autoimmune cystitis model (URO-OVA) that reproduces many clinical correlates of IC/BPS. URO-OVA mice express the membrane form of the model antigen ovalbumin (OVA) as a self-antigen on the urothelium and develop bladder inflammation upon introduction of OVA-specific T cells. To investigate the role of mast cells, we crossed URO-OVA mice with mast cell-deficient Kit^W-sh mice to generate URO-OVA/Kit^W-sh mice that retained urothelial OVA expression but lacked endogenous mast cells. We compared URO-OVA mice with URO-OVA/Kit^W-sh mice with and without mast cell reconstitution in response to cystitis induction. URO-OVA mice developed profound bladder inflammation with increased mast cell counts and LUTD, including increased total number of voids, decreased mean volume voided per micturition, and decreased maximum volume voided per micturition, after cystitis induction. In contrast, similarly cystitis-induced URO-OVA/Kit^W-sh mice developed reduced bladder inflammation with no mast cells and LUTD detected. However, after mast cell reconstitution URO-OVA/Kit^W-sh mice restored the ability to develop bladder inflammation and LUTD following cystitis induction. We further treated URO-OVA mice with cromolyn, a mast cell membrane stabilizer, and found that cromolyn treatment reversed bladder inflammation and LUTD in the animal model. Our results provide direct evidence for the role of mast cells in cystitis-associated LUTD, supporting the use of mast cell inhibitors for treatment of certain forms of IC/BPS.

Regulatory T cells suppress autoreactive CD4+ T cell response to bladder epithelial antigen

AIM: To investigate the role of regulatory T (Treg) cells in CD4⁺ T cell-mediated bladder autoimmune inflammation.

METHODS: Urothelium-ovalbumin (URO-OVA)/OT-II mice, a double transgenic line that expresses the membrane form of the model antigen (Ag) OVA as a self-Ag on the urothelium and the OVA-specific CD4⁺ T cell receptor specific for the I-A^b/OVA_323-339 epitope in the periphery, were developed to provide an autoimmune environment for investigation of the role of Treg cells in bladder autoimmune inflammation. To facilitate Treg cell analysis, we further developed URO-OVA^GFP-Foxp3/OT-II mice, a derived line of URO-OVA/OT-II mice that express the green fluorescent protein (GFP)-forkhead box protein P3 (Foxp3) fusion protein.

RESULTS: URO-OVA/OT-II mice failed to develop bladder inflammation despite the presence of autoreactive CD4⁺ T cells. By monitoring GFP-positive cells, bladder infiltration of CD4⁺ Treg cells was observed in URO-OVA^GFP-Foxp3/OT-II mice. The infiltrating Treg cells were functionally active and expressed Treg cell effector molecule as well as marker mRNAs including transforming growth factor-β, interleukin (IL)-10, fibrinogen-like protein 2, and glucocorticoid-induced tumor necrosis factor receptor (GITR). Studies further revealed that Treg cells from URO-OVA^GFP-Foxp3/OT-II mice were suppressive and inhibited autoreactive CD4⁺ T cell proliferation and interferon (IFN)-γ production in response to OVA Ag stimulation. Depletion of GITR-positive cells led to spontaneous development of bladder inflammation and expression of inflammatory factor mRNAs for IFN-γ, IL-6, tumor necrosis factor-α and nerve growth factor in URO-OVA^GFP-Foxp3/OT-II mice.

CONCLUSION: Treg cells specific for bladder epithelial Ag play an important role in immunological homeostasis and the control of CD4⁺ T cell-mediated bladder autoimmune inflammation.

Clonality, activated antigen-specific CD8(+) T cells, and development of autoimmune cholangitis in dnTGFβRII mice

There are several murine models described with features similar to human primary biliary cirrhosis (PBC). Among these models, the one which has the closest serologic features to PBC is a mouse with a T-cell-restricted expression of the dominant negative transforming growth factor β receptor type II (dnTGFβRII). Our work has demonstrated that CD8(+) T cells from dnTGFβRII mice transfer autoimmune cholangitis to Rag1(-/-) recipients. However, it remained unclear whether the autoimmune cholangitis was secondary to an intrinsic function within CD8(+) T cells or due to the abnormal TGFβR environment within which CD8(+) T cells were generated. To address this mechanistic issue, we used our dnTGFβRII, OT-I/Rag1(-/-) , OT-II/Rag1(-/-) mice and in addition generated OT-I/dnTGFβRII/Rag1(-/-) , and OT-II/dnTGFβRII/Rag1(-/-) mice in which the entire T-cell repertoire was replaced with ovalbumin (OVA)-specific CD8(+) or CD4(+) T cells, respectively. Importantly, neither the parental OT-I/dnTGFβRII/Rag1(-/-) mice and/or OT-II/dnTGFβRII/Rag1(-/-) mice developed cholangitis. However, adoptive transfer demonstrated that only transfer of CD8(+) T cells from dnTGFβRII mice but not CD8(+) T cells from OT-I/Rag1(-/-) mice or from OT-I/dnTGFβRII/Rag1(-/-) mice transferred disease. These data were not secondary to an absence of CD4(+) T cell help since a combination of CD8(+) T cells from OT-I/dnTGFβRII/Rag1(-/-) and CD4(+) T cells from OT II/dnTGFβRII/Rag1(-/-) or CD8(+) T cells from OT-I/dnTGFβRII/Rag1(-/-) with CD4(+) T cells from OT-II/Rag1(-/-) mice failed to transfer disease.

CONCLUSION

Defective TGFβRII signaling, in addition to clonal CD8(+) T cells that target biliary cells, are required for induction of autoimmune cholangitis.