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Manoharan I, Shanmugam A, Ramalingam M, Patel N, Thangaraju M, Ande S, Pacholczyk R, Prasad PD, Manicassamy S. The Transcription Factor RXRα in CD11c+ APCs Regulates Intestinal Immune Homeostasis and Inflammation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2023; 211:853-861. [PMID: 37477694 PMCID: PMC10538854 DOI: 10.4049/jimmunol.2200909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 07/05/2023] [Indexed: 07/22/2023]
Abstract
APCs such as dendritic cells and macrophages play a pivotal role in mediating immune tolerance and restoring intestinal immune homeostasis by limiting inflammatory responses against commensal bacteria. However, cell-intrinsic molecular regulators critical for programming intestinal APCs to a regulatory state rather than an inflammatory state are unknown. In this study, we report that the transcription factor retinoid X receptor α (RXRα) signaling in CD11c+ APCs is essential for suppressing intestinal inflammation by imparting an anti-inflammatory phenotype. Using a mouse model of ulcerative colitis, we demonstrated that targeted deletion of RXRα in CD11c+ APCs in mice resulted in the loss of T cell homeostasis with enhanced intestinal inflammation and increased histopathological severity of colonic tissue. This was due to the increased production of proinflammatory cytokines that drive Th1/Th17 responses and decreased expression of immune-regulatory factors that promote regulatory T cell differentiation in the colon. Consistent with these findings, pharmacological activation of the RXRα pathway alleviated colitis severity in mice by suppressing the expression of inflammatory cytokines and limiting Th1/Th17 cell differentiation. These findings identify an essential role for RXRα in APCs in regulating intestinal immune homeostasis and inflammation. Thus, manipulating the RXRα pathway could provide novel opportunities for enhancing regulatory responses and dampening colonic inflammation.
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Affiliation(s)
- Indumathi Manoharan
- Georgia Cancer Center, Augusta University, Augusta, GA, USA
- Department of Biochemistry and Molecular Biology, Augusta University, Augusta, GA, USA
| | | | | | - Nikhil Patel
- Department of Pathology, Augusta University, Augusta, GA USA
| | - Muthusamy Thangaraju
- Department of Biochemistry and Molecular Biology, Augusta University, Augusta, GA, USA
| | - Satyanarayana Ande
- Georgia Cancer Center, Augusta University, Augusta, GA, USA
- Department of Biochemistry and Molecular Biology, Augusta University, Augusta, GA, USA
| | | | - Puttur D. Prasad
- Department of Biochemistry and Molecular Biology, Augusta University, Augusta, GA, USA
| | - Santhakumar Manicassamy
- Georgia Cancer Center, Augusta University, Augusta, GA, USA
- Department of Biochemistry and Molecular Biology, Augusta University, Augusta, GA, USA
- Department of Medicine, Augusta University, Augusta, Georgia, USA
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2
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Asai N, Ethridge AD, Fonseca W, Yagi K, Rasky AJ, Morris SB, Falkowski NR, Huang YJ, Huffnagle GB, Lukacs NW. A steroid-resistant cockroach allergen model is associated with lung and cecal microbiome changes. Physiol Rep 2023; 11:e15761. [PMID: 37403414 PMCID: PMC10320043 DOI: 10.14814/phy2.15761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 05/30/2023] [Accepted: 06/15/2023] [Indexed: 07/06/2023] Open
Abstract
The pathogenesis of asthma has been partially linked to lung and gut microbiome. We utilized a steroid-resistant chronic model of cockroach antigen-induced (CRA) asthma with corticosteroid (fluticasone) treatment to examine lung and gut microbiome during disease. The pathophysiology assessment demonstrated that mucus and airway hyperresponsiveness were increased in the chronic CRA with no alteration in the fluticasone (Flut)-treated group, demonstrating steroid resistance. Analysis of mRNA from lungs showed no decrease of MUC5AC or Gob5 in the Flut-treated group. Furthermore, flow-cytometry in lung tissue showed eosinophils and neutrophils were not significantly reduced in the Flut-treated group compared to the chronic CRA group. When the microbiome profiles were assessed, data showed that only the Flut-treated animals were significantly different in the gut microbiome. Finally, a functional analysis of cecal microbiome metabolites using PiCRUSt showed several biosynthetic pathways were significantly enriched in the Flut-treated group, with tryptophan pathway verified by ELISA with increased kynurenine in homogenized cecum samples. While the implications of these data are unclear, they may suggest a significant impact of steroid treatment on future disease pathogenesis through microbiome and associated metabolite pathway changes.
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Affiliation(s)
- Nobuhiro Asai
- Department of PathologyUniversity of MichiganAnn ArborMichiganUSA
| | - Alexander D. Ethridge
- Department of PathologyUniversity of MichiganAnn ArborMichiganUSA
- Immunology Graduate ProgramUniversity of MichiganAnn ArborMichiganUSA
| | - Wendy Fonseca
- Department of PathologyUniversity of MichiganAnn ArborMichiganUSA
| | - Kazuma Yagi
- Department of PathologyUniversity of MichiganAnn ArborMichiganUSA
| | - Andrew J. Rasky
- Department of PathologyUniversity of MichiganAnn ArborMichiganUSA
| | - Susan B. Morris
- Department of PathologyUniversity of MichiganAnn ArborMichiganUSA
| | - Nicole R. Falkowski
- Division of Pulmonary and Critical Medicine, Department of MedicineUniversity of MichiganAnn ArborMichiganUSA
| | - Yvonne J. Huang
- Division of Pulmonary and Critical Medicine, Department of MedicineUniversity of MichiganAnn ArborMichiganUSA
| | - Gary B. Huffnagle
- Immunology Graduate ProgramUniversity of MichiganAnn ArborMichiganUSA
- Division of Pulmonary and Critical Medicine, Department of MedicineUniversity of MichiganAnn ArborMichiganUSA
- Mary H. Weiser Food Allergy CenterUniversity of MichiganAnn ArborMichiganUSA
- Department of Molecular, Cellular and Developmental BiologyUniversity of MichiganAnn ArborMichiganUSA
| | - Nicholas W. Lukacs
- Department of PathologyUniversity of MichiganAnn ArborMichiganUSA
- Immunology Graduate ProgramUniversity of MichiganAnn ArborMichiganUSA
- Mary H. Weiser Food Allergy CenterUniversity of MichiganAnn ArborMichiganUSA
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Garo LP, Ajay AK, Fujiwara M, Gabriely G, Raheja R, Kuhn C, Kenyon B, Skillin N, Kadowaki-Saga R, Saxena S, Murugaiyan G. MicroRNA-146a limits tumorigenic inflammation in colorectal cancer. Nat Commun 2021; 12:2419. [PMID: 33893298 PMCID: PMC8065171 DOI: 10.1038/s41467-021-22641-y] [Citation(s) in RCA: 63] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 03/24/2021] [Indexed: 02/07/2023] Open
Abstract
Chronic inflammation can drive tumor development. Here, we have identified microRNA-146a (miR-146a) as a major negative regulator of colonic inflammation and associated tumorigenesis by modulating IL-17 responses. MiR-146a-deficient mice are susceptible to both colitis-associated and sporadic colorectal cancer (CRC), presenting with enhanced tumorigenic IL-17 signaling. Within myeloid cells, miR-146a targets RIPK2, a NOD2 signaling intermediate, to limit myeloid cell-derived IL-17-inducing cytokines and restrict colonic IL-17. Accordingly, myeloid-specific miR-146a deletion promotes CRC. Moreover, within intestinal epithelial cells (IECs), miR-146a targets TRAF6, an IL-17R signaling intermediate, to restrict IEC responsiveness to IL-17. MiR-146a within IECs further suppresses CRC by targeting PTGES2, a PGE2 synthesis enzyme. IEC-specific miR-146a deletion therefore promotes CRC. Importantly, preclinical administration of miR-146a mimic, or small molecule inhibition of the miR-146a targets, TRAF6 and RIPK2, ameliorates colonic inflammation and CRC. MiR-146a overexpression or miR-146a target inhibition represent therapeutic approaches that limit pathways converging on tumorigenic IL-17 signaling in CRC.
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Affiliation(s)
- Lucien P Garo
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
- Boston University School of Medicine, Boston, MA, USA
| | - Amrendra K Ajay
- Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Mai Fujiwara
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Galina Gabriely
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Radhika Raheja
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Chantal Kuhn
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Brendan Kenyon
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Nathaniel Skillin
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Ryoko Kadowaki-Saga
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Shrishti Saxena
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Gopal Murugaiyan
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
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Swafford D, Shanmugam A, Ranganathan P, Manoharan I, Hussein MS, Patel N, Sifuentes H, Koni PA, Prasad PD, Thangaraju M, Manicassamy S. The Wnt-β-Catenin-IL-10 Signaling Axis in Intestinal APCs Protects Mice from Colitis-Associated Colon Cancer in Response to Gut Microbiota. THE JOURNAL OF IMMUNOLOGY 2020; 205:2265-2275. [PMID: 32917787 DOI: 10.4049/jimmunol.1901376] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 08/17/2020] [Indexed: 12/21/2022]
Abstract
Loss of immune tolerance to gut microflora is inextricably linked to chronic intestinal inflammation and colitis-associated colorectal cancer (CAC). The LRP5/6 signaling cascade in APCs contributes to immune homeostasis in the gut, but whether this pathway in APCs protects against CAC is not known. In the current study, using a mouse model of CAC, we show that the LRP5/6-β-catenin-IL-10 signaling axis in intestinal CD11c+ APCs protects mice from CAC by regulating the expression of tumor-promoting inflammatory factors in response to commensal flora. Genetic deletion of LRP5/6 in CD11c+ APCs in mice (LRP5/6ΔCD11c) resulted in enhanced susceptibility to CAC. This is due to a microbiota-dependent increased expression of proinflammatory factors and decreased expression of the immunosuppressive cytokine IL-10. This condition could be improved in LRP5/6ΔCD11c mice by depleting the gut flora, indicating the importance of LRP5/6 in mediating immune tolerance to the gut flora. Moreover, mechanistic studies show that LRP5/6 suppresses the expression of tumor-promoting inflammatory factors in CD11c+ APCs via the β-catenin-IL-10 axis. Accordingly, conditional activation of β-catenin specifically in CD11c+ APCs or in vivo administration of IL-10 protected LRP5/6ΔCD11c mice from CAC by suppressing the expression of inflammatory factors. In summary, in this study, we identify a key role for the LRP5/6-β-catenin-IL-10 signaling pathway in intestinal APCs in resolving chronic intestinal inflammation and protecting against CAC in response to the commensal flora.
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Affiliation(s)
- Daniel Swafford
- Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Arulkumaran Shanmugam
- Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | | | - Indumathi Manoharan
- Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Mohamed S Hussein
- Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Nikhil Patel
- Department of Pathology, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Humberto Sifuentes
- Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Pandelakis A Koni
- Parker Institute for Cancer Immunotherapy, San Francisco, CA 94129; and
| | - Puttur D Prasad
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Muthusamy Thangaraju
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Santhakumar Manicassamy
- Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA 30912; .,Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912.,Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912
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5
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Harusato A, Viennois E, Etienne-Mesmin L, Matsuyama S, Abo H, Osuka S, Lukacs NW, Naito Y, Itoh Y, Li JD, Merlin D, Gewirtz AT, Denning TL. Early-Life Microbiota Exposure Restricts Myeloid-Derived Suppressor Cell-Driven Colonic Tumorigenesis. Cancer Immunol Res 2019; 7:544-551. [PMID: 30782668 DOI: 10.1158/2326-6066.cir-18-0444] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Revised: 12/07/2018] [Accepted: 02/15/2019] [Indexed: 12/28/2022]
Abstract
Gut microbiota and their metabolites are instrumental in regulating homeostasis at intestinal and extraintestinal sites. However, the complex effects of prenatal and early postnatal microbial exposure on adult health and disease outcomes remain incompletely understood. Here, we showed that mice raised under germ-free conditions until weaning and then transferred to specific pathogen-free (SPF) conditions harbored altered microbiota composition, augmented inflammatory cytokine and chemokine expression, and were hyper-susceptible to colitis-associated tumorigenesis later in adulthood. Increased number and size of colon tumors and intestinal epithelial cell proliferation in recolonized germ-free mice were associated with augmented intratumoral CXCL1, CXCL2, and CXCL5 expression and granulocytic myeloid-derived suppressor cell (G-MDSC) accumulation. Consistent with these findings, CXCR2 neutralization in recolonized germ-free mice completely reversed the exacerbated susceptibility to colitis-associated tumorigenesis. Collectively, our findings highlight a crucial role for early-life microbial exposure in establishing intestinal homeostasis that restrains colon cancer in adulthood.
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Affiliation(s)
- Akihito Harusato
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia. .,Department of Gastroenterology, North Medical Center, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Emilie Viennois
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia
| | - Lucie Etienne-Mesmin
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia.,UMR454 MEDIS, Université Clermont Auvergne/INRA, Clermont-Ferrand, France
| | - Shingo Matsuyama
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia
| | - Hirohito Abo
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia
| | - Satoru Osuka
- Department of Neurosurgery, Emory University, Atlanta, Georgia
| | - Nicholas W Lukacs
- Department of Pathology, University of Michigan, Ann Arbor, Michigan
| | - Yuji Naito
- Department of Molecular Gastroenterology and Hepatology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Yoshito Itoh
- Department of Molecular Gastroenterology and Hepatology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Jian-Dong Li
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia
| | - Didier Merlin
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia.,Atlanta Veterans Affairs Medical Center, Decatur, Georgia
| | - Andrew T Gewirtz
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia
| | - Timothy L Denning
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia.
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6
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Swafford D, Shanmugam A, Ranganathan P, Hussein MS, Koni PA, Prasad PD, Thangaraju M, Manicassamy S. Canonical Wnt Signaling in CD11c + APCs Regulates Microbiota-Induced Inflammation and Immune Cell Homeostasis in the Colon. THE JOURNAL OF IMMUNOLOGY 2018; 200:3259-3268. [PMID: 29602775 DOI: 10.4049/jimmunol.1701086] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 03/08/2018] [Indexed: 12/14/2022]
Abstract
Aberrant Wnt/β-catenin signaling occurs in several inflammatory diseases, including inflammatory bowel disease and inflammatory bowel disease-associated colon carcinogenesis. However, its role in shaping mucosal immune responses to commensals in the gut remains unknown. In this study, we investigated the importance of canonical Wnt signaling in CD11c+ APCs in controlling intestinal inflammation. Using a mouse model of ulcerative colitis, we demonstrated that canonical Wnt signaling in intestinal CD11c+ APCs controls intestinal inflammation by imparting an anti-inflammatory phenotype. Genetic deletion of Wnt coreceptors, low-density lipoprotein receptor-related proteins 5 and 6 (LRP5/6) in CD11c+ APCs in LRP5/6ΔCD11c mice, resulted in enhanced intestinal inflammation with increased histopathological severity of colonic tissue. This was due to microbiota-dependent increased production of proinflammatory cytokines and decreased expression of immune-regulatory factors such as IL-10, retinoic acid, and IDO. Mechanistically, loss of LRP5/6-mediated signaling in CD11c+ APCs resulted in altered microflora and T cell homeostasis. Furthermore, our study demonstrates that conditional activation of β-catenin in CD11c+ APCs in LRP5/6ΔCD11c mice resulted in reduced intestinal inflammation with decreased histopathological severity of colonic tissue. These results reveal a mechanism by which intestinal APCs control intestinal inflammation and immune homeostasis via the canonical Wnt-signaling pathway.
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Affiliation(s)
- Daniel Swafford
- Georgia Cancer Center, Augusta University, Augusta, GA 30912
| | | | | | | | - Pandelakis A Koni
- Georgia Cancer Center, Augusta University, Augusta, GA 30912.,Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912; and.,Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Puttur D Prasad
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912; and
| | - Muthusamy Thangaraju
- Georgia Cancer Center, Augusta University, Augusta, GA 30912.,Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912; and
| | - Santhakumar Manicassamy
- Georgia Cancer Center, Augusta University, Augusta, GA 30912; .,Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912; and.,Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912
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7
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Ranganathan P, Shanmugam A, Swafford D, Suryawanshi A, Bhattacharjee P, Hussein MS, Koni PA, Prasad PD, Kurago ZB, Thangaraju M, Ganapathy V, Manicassamy S. GPR81, a Cell-Surface Receptor for Lactate, Regulates Intestinal Homeostasis and Protects Mice from Experimental Colitis. THE JOURNAL OF IMMUNOLOGY 2018; 200:1781-1789. [PMID: 29386257 DOI: 10.4049/jimmunol.1700604] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 12/18/2017] [Indexed: 01/29/2023]
Abstract
At mucosal sites such as the intestine, the immune system launches robust immunity against invading pathogens while maintaining a state of tolerance to commensal flora and ingested food Ags. The molecular mechanisms underlying this phenomenon remain poorly understood. In this study, we report that signaling by GPR81, a receptor for lactate, in colonic dendritic cells and macrophages plays an important role in suppressing colonic inflammation and restoring colonic homeostasis. Genetic deletion of GPR81 in mice led to increased Th1/Th17 cell differentiation and reduced regulatory T cell differentiation, resulting in enhanced susceptibility to colonic inflammation. This was due to increased production of proinflammatory cytokines (IL-6, IL-1β, and TNF-α) and decreased expression of immune regulatory factors (IL-10, retinoic acid, and IDO) by intestinal APCs lacking GPR81. Consistent with these findings, pharmacological activation of GPR81 decreased inflammatory cytokine expression and ameliorated colonic inflammation. Taken together, these findings identify a new and important role for the GPR81 signaling pathway in regulating immune tolerance and colonic inflammation. Thus, manipulation of the GPR81 pathway could provide novel opportunities for enhancing regulatory responses and treating colonic inflammation.
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Affiliation(s)
| | | | - Daniel Swafford
- Georgia Cancer Center, Augusta University, Augusta, GA 30912
| | | | - Pushpak Bhattacharjee
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430
| | | | - Pandelakis A Koni
- Georgia Cancer Center, Augusta University, Augusta, GA 30912.,Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30901.,Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30901; and
| | - Puttur D Prasad
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30901; and
| | - Zoya B Kurago
- Dental College of Georgia, Augusta University, Augusta, GA 30912
| | - Muthusamy Thangaraju
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30901; and
| | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430
| | - Santhakumar Manicassamy
- Georgia Cancer Center, Augusta University, Augusta, GA 30912; .,Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30901
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Manoharan I, Suryawanshi A, Hong Y, Ranganathan P, Shanmugam A, Ahmad S, Swafford D, Manicassamy B, Ramesh G, Koni PA, Thangaraju M, Manicassamy S. Homeostatic PPARα Signaling Limits Inflammatory Responses to Commensal Microbiota in the Intestine. THE JOURNAL OF IMMUNOLOGY 2016; 196:4739-49. [PMID: 27183583 DOI: 10.4049/jimmunol.1501489] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 03/25/2016] [Indexed: 12/28/2022]
Abstract
Dietary lipids and their metabolites activate members of the peroxisome proliferative-activated receptor (PPAR) family of transcription factors and are critical for colonic health. The PPARα isoform plays a vital role in regulating inflammation in various disease settings, but its role in intestinal inflammation, commensal homeostasis, and mucosal immunity in the gut are unclear. In this study, we demonstrate that the PPARα pathway in innate immune cells orchestrates gut mucosal immunity and commensal homeostasis by regulating the expression of IL-22 and the antimicrobial peptides RegIIIβ, RegIIIγ, and calprotectin. Additionally, the PPARα pathway is critical for imparting regulatory phenotype in intestinal macrophages. PPARα deficiency in mice led to commensal dysbiosis in the gut, resulting in a microbiota-dependent increase in the expression of inflammatory cytokines and enhanced susceptibility to intestinal inflammation. Pharmacological activation of this pathway decreased the expression of inflammatory cytokines and ameliorated colonic inflammation. Taken together, these findings identify a new important innate immune function for the PPARα signaling pathway in regulating intestinal inflammation, mucosal immunity, and commensal homeostasis. Thus, the manipulation of the PPARα pathway could provide novel opportunities for enhancing mucosal immunity and treating intestinal inflammation.
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Affiliation(s)
| | | | - Yuan Hong
- Cancer Center, Augusta University, Augusta, GA 30912
| | | | | | - Shamim Ahmad
- Cancer Center, Augusta University, Augusta, GA 30912
| | | | | | - Ganesan Ramesh
- Vascular Biology Center, Augusta University, Augusta, GA 30912
| | - Pandelakis A Koni
- Cancer Center, Augusta University, Augusta, GA 30912; Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912; and
| | - Muthusamy Thangaraju
- Cancer Center, Augusta University, Augusta, GA 30912; Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Santhakumar Manicassamy
- Cancer Center, Augusta University, Augusta, GA 30912; Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912; and Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912
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9
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Immunity and Tolerance Induced by Intestinal Mucosal Dendritic Cells. Mediators Inflamm 2016; 2016:3104727. [PMID: 27034589 PMCID: PMC4789473 DOI: 10.1155/2016/3104727] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 02/02/2016] [Accepted: 02/08/2016] [Indexed: 12/25/2022] Open
Abstract
Dendritic cells present in the digestive tract are constantly exposed to environmental antigens, commensal flora, and invading pathogens. Under steady-state conditions, these cells have high tolerogenic potential, triggering differentiation of regulatory T cells to protect the host from unwanted proinflammatory immune responses to innocuous antigens or commensals. On the other hand, these cells must discriminate between commensal flora and invading pathogens and mount powerful immune response against pathogens. A potential result of unbalanced tolerogenic versus proinflammatory responses mediated by dendritic cells is associated with chronic inflammatory conditions, such as Crohn's disease, ulcerative colitis, food allergies, and celiac disease. Herein, we review the dendritic cell population involved in mediating tolerance and immunity in mucosal surfaces, the progress in unveiling their development in vivo, and factors that can influence their functions.
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