RESUMEN
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.
Asunto(s)
Colitis , Factores de Transcripción , Animales , Ratones , Colon , Citocinas/metabolismo , Homeostasis , Inflamación , Mucosa Intestinal , Intestinos/patología , Ratones Endogámicos C57BL , Receptor alfa X Retinoide , Factores de Transcripción/metabolismoRESUMEN
Extraintestinal manifestations are common in inflammatory bowel disease and involve several organs, including the kidney. However, the mechanisms responsible for renal manifestation in inflammatory bowel disease are not known. In this study, we show that the Wnt-lipoprotein receptor-related proteins 5 and 6 (LRP5/6) signaling pathway in macrophages plays a critical role in regulating colitis-associated systemic inflammation and renal injury in a murine dextran sodium sulfate-induced colitis model. Conditional deletion of the Wnt coreceptors LRP5/6 in macrophages in mice results in enhanced susceptibility to dextran sodium sulfate colitis-induced systemic inflammation and acute kidney injury (AKI). Furthermore, our studies show that aggravated colitis-associated systemic inflammation and AKI observed in LRP5/6LysM mice are due to increased bacterial translocation to extraintestinal sites and microbiota-dependent increased proinflammatory cytokine levels in the kidney. Conversely, depletion of the gut microbiota mitigated colitis-associated systemic inflammation and AKI in LRP5/6LysM mice. Mechanistically, LRP5/6-deficient macrophages were hyperresponsive to TLR ligands and produced higher levels of proinflammatory cytokines, which are associated with increased activation of MAPKs. These results reveal how the Wnt-LRP5/6 signaling in macrophages controls colitis-induced systemic inflammation and AKI.
Asunto(s)
Lesión Renal Aguda , Colitis , Microbioma Gastrointestinal , Enfermedades Inflamatorias del Intestino , Microbiota , Lesión Renal Aguda/metabolismo , Animales , Colitis/inducido químicamente , Citocinas/metabolismo , Sulfato de Dextran/toxicidad , Inflamación/metabolismo , Enfermedades Inflamatorias del Intestino/metabolismo , Riñón/metabolismo , Proteína-5 Relacionada con Receptor de Lipoproteína de Baja Densidad/genética , Proteína-5 Relacionada con Receptor de Lipoproteína de Baja Densidad/metabolismo , Proteína-6 Relacionada a Receptor de Lipoproteína de Baja Densidad/genética , Proteína-6 Relacionada a Receptor de Lipoproteína de Baja Densidad/metabolismo , Macrófagos/metabolismo , Ratones , Ratones Endogámicos C57BL , Vía de Señalización Wnt/genéticaRESUMEN
Dendritic cells (DCs) are professional APCs that play a crucial role in initiating robust immune responses against invading pathogens while inducing regulatory responses to the body's tissues and commensal microorganisms. A breakdown of DC-mediated immunological tolerance leads to chronic inflammation and autoimmune disorders. However, cell-intrinsic molecular regulators that are critical for programming DCs to a regulatory state rather than to an inflammatory state are not known. In this study, we show that the activation of the TCF4 transcription factor in DCs is critical for controlling the magnitude of inflammatory responses and limiting neuroinflammation. DC-specific deletion of TCF4 in mice increased Th1/Th17 responses and exacerbated experimental autoimmune encephalomyelitis pathology. Mechanistically, loss of TCF4 in DCs led to heightened activation of p38 MAPK and increased levels of proinflammatory cytokines IL-6, IL-23, IL-1ß, TNF-α, and IL-12p40. Consistent with these findings, pharmacological blocking of p38 MAPK activation delayed experimental autoimmune encephalomyelitis onset and diminished CNS pathology in TCF4ΔDC mice. Thus, manipulation of the TCF4 pathway in DCs could provide novel opportunities for regulating chronic inflammation and represents a potential therapeutic approach to control autoimmune neuroinflammation.
Asunto(s)
Encefalomielitis Autoinmune Experimental , Células TH1 , Animales , Células Dendríticas , Ratones , Ratones Endogámicos C57BL , Células Th17 , Factor de Transcripción 4RESUMEN
For decades, lactate has been considered an innocuous bystander metabolite of cellular metabolism. However, emerging studies show that lactate acts as a complex immunomodulatory molecule that controls innate and adaptive immune cells' effector functions. Thus, recent advances point to lactate as an essential and novel signaling molecule that shapes innate and adaptive immune responses in the intestine and systemic sites. Here, we review these recent advances in the context of the pleiotropic effects of lactate in regulating diverse functions of immune cells in the tissue microenvironment and under pathological conditions.
Asunto(s)
Células Dendríticas/inmunología , Ácido Láctico/inmunología , Macrófagos/inmunología , Animales , Autoinmunidad , Proteínas de Ciclo Celular/inmunología , Humanos , Inmunomodulación , Infecciones/inmunología , Enfermedades Inflamatorias del Intestino/inmunología , Transportadores de Ácidos Monocarboxílicos/inmunología , Neoplasias/inmunología , Receptores Acoplados a Proteínas G/inmunologíaRESUMEN
DNA damage, induced by either chemical carcinogens or environmental pollutants, plays an important role in the initiation of colorectal cancer. DNA repair processes, however, are involved in both protecting against cancer formation, and also contributing to cancer development, by ensuring genomic integrity and promoting the efficient DNA repair in tumor cells, respectively. Although DNA repair pathways have been well exploited in the treatment of breast and ovarian cancers, the role of DNA repair processes and their therapeutic efficacy in colorectal cancer is yet to be appreciably explored. To understand the role of DNA repair, especially homologous recombination (HR), in chemical carcinogen-induced colorectal cancer growth, we unraveled the role of RAD51AP1 (RAD51-associated protein 1), a protein involved in HR, in genotoxic carcinogen (azoxymethane, AOM)-induced colorectal cancer. Although AOM treatment alone significantly increased RAD51AP1 expression, the combination of AOM and dextran sulfate sodium (DSS) treatment dramatically increased by several folds. RAD51AP1 expression is found in mouse colonic crypt and proliferating cells. RAD51AP1 expression is significantly increased in majority of human colorectal cancer tissues, including BRAF/KRAS mutant colorectal cancer, and associated with reduced treatment response and poor prognosis. Rad51ap1-deficient mice were protected against AOM/DSS-induced colorectal cancer. These observations were recapitulated in a genetically engineered mouse model of colorectal cancer (ApcMin /+ ). Furthermore, chemotherapy-resistant colorectal cancer is associated with increased RAD51AP1 expression. This phenomenon is associated with reduced cell proliferation and colorectal cancer stem cell (CRCSC) self-renewal. Overall, our studies provide evidence that RAD51AP1 could be a novel diagnostic marker for colorectal cancer and a potential therapeutic target for colorectal cancer prevention and treatment. IMPLICATIONS: This study provides first in vivo evidence that RAD51AP1 plays a critical role in colorectal cancer growth and drug resistance by regulating CRCSC self-renewal.
Asunto(s)
Autorrenovación de las Células , Neoplasias Colorrectales/tratamiento farmacológico , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/fisiología , Resistencia a Antineoplásicos , Fluorouracilo/farmacología , Células Madre Neoplásicas/efectos de los fármacos , Proteínas de Unión al ARN/metabolismo , Proteínas de Unión al ARN/fisiología , Animales , Antimetabolitos Antineoplásicos/farmacología , Apoptosis , Estudios de Casos y Controles , Proliferación Celular , Neoplasias Colorrectales/metabolismo , Neoplasias Colorrectales/patología , Proteínas de Unión al ADN/genética , Humanos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Células Madre Neoplásicas/metabolismo , Células Madre Neoplásicas/patología , Pronóstico , Proteínas de Unión al ARN/genética , Tasa de Supervivencia , Células Tumorales CultivadasRESUMEN
Crohn's disease (CD) and ulcerative colitis are two main clinically defined forms of chronic inflammatory bowel disease (IBD). Chronic intestinal inflammation is inextricably linked to colitis-associated colon carcinogenesis (CAC). Patients with ulcerative colitis (UC) and Crohn's disease (CD) have an increased risk of colon cancer. Our understanding of IBD and IBD-associated colon carcinogenesis depends largely on rodent models. AOM-DSS-induced colitis-associated colon cancer in mice is the most widely used and accepted model that can recapitulate the human IBD-associated colon cancer. Here, we have provided detailed protocols of this mouse model of experimentally induced chronic intestinal inflammation-associated colon cancer. We will also discuss the protocols for the isolation and analysis of inflammatory immune cells from the colon.
Asunto(s)
Colitis Ulcerosa/patología , Neoplasias Asociadas a Colitis/patología , Neoplasias del Colon/patología , Animales , Colitis Ulcerosa/inducido químicamente , Colon/patología , Enfermedad de Crohn/inducido químicamente , Enfermedad de Crohn/patología , Sulfato de Dextran/farmacología , Modelos Animales de Enfermedad , Femenino , Enfermedades Inflamatorias del Intestino/inducido químicamente , Enfermedades Inflamatorias del Intestino/patología , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
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-ß-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 ß-catenin-IL-10 axis. Accordingly, conditional activation of ß-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-ß-catenin-IL-10 signaling pathway in intestinal APCs in resolving chronic intestinal inflammation and protecting against CAC in response to the commensal flora.
Asunto(s)
Células Presentadoras de Antígenos/inmunología , Colitis/inmunología , Neoplasias del Colon/inmunología , Microbioma Gastrointestinal/inmunología , Interleucina-10/inmunología , Vía de Señalización Wnt/inmunología , beta Catenina/inmunología , Animales , Células Presentadoras de Antígenos/patología , Colitis/complicaciones , Colitis/genética , Colitis/patología , Neoplasias del Colon/etiología , Neoplasias del Colon/genética , Neoplasias del Colon/prevención & control , Microbioma Gastrointestinal/genética , Interleucina-10/genética , Ratones , Ratones Transgénicos , Proteínas de Neoplasias/genética , Vía de Señalización Wnt/genética , beta Catenina/genéticaRESUMEN
RAD51-associated protein 1 (RAD51AP1) plays an integral role in homologous recombination by activating RAD51 recombinase. Homologous recombination is essential for preserving genome integrity and RAD51AP1 is critical for D-loop formation, a key step in homologous recombination. Although RAD51AP1 is involved in maintaining genomic stability, recent studies have shown that RAD51AP1 expression is significantly upregulated in human cancers. However, the functional role of RAD51AP1 in tumor growth and the underlying molecular mechanism(s) by which RAD51AP1 regulates tumorigenesis have not been fully understood. Here, we use Rad51ap1-knockout mice in genetically engineered mouse models of breast cancer to unravel the role of RAD51AP1 in tumor growth and metastasis. RAD51AP1 gene transcript was increased in both luminal estrogen receptor-positive breast cancer and basal triple-negative breast cancer, which is associated with poor prognosis. Conversely, knockdown of RAD51AP1 (RADP51AP1 KD) in breast cancer cell lines reduced tumor growth. Rad51ap1-deficient mice were protected from oncogene-driven spontaneous mouse mammary tumor growth and associated lung metastasis. In vivo, limiting dilution studies provided evidence that Rad51ap1 plays a critical role in breast cancer stem cell (BCSC) self-renewal. RAD51AP1 KD improved chemotherapy and radiotherapy response by inhibiting BCSC self-renewal and associated pluripotency. Overall, our study provides genetic and biochemical evidences that RAD51AP1 is critical for tumor growth and metastasis by increasing BCSC self-renewal and may serve as a novel target for chemotherapy- and radiotherapy-resistant breast cancer. SIGNIFICANCE: This study provides in vivo evidence that RAD51AP1 plays a critical role in breast cancer growth and metastasis by regulating breast cancer stem cell self-renewal.
Asunto(s)
Neoplasias de la Mama/patología , Autorrenovación de las Células/genética , Proteínas de Unión al ADN/deficiencia , Neoplasias Mamarias Animales/patología , Animales , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/terapia , Proteínas de Unión al ADN/genética , Modelos Animales de Enfermedad , Activación Enzimática , Femenino , Humanos , Neoplasias Pulmonares/secundario , Neoplasias Mamarias Animales/metabolismo , Neoplasias Mamarias Animales/terapia , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Células Madre Neoplásicas , Proteínas de Unión al ARN/genética , Recombinasa Rad51/metabolismo , Neoplasias de la Mama Triple Negativas/metabolismo , Neoplasias de la Mama Triple Negativas/patología , Regulación hacia ArribaRESUMEN
Dendritic cells (DCs) control the strength and quality of antigen-specific adaptive immune responses. This is critical for launching a robust immunity against invading pathogens while maintaining a state of tolerance to self-antigens. However, this also represents a fundamental barrier to anti-tumor immune responses and cancer immunotherapy. DCs in the tumor microenvironment (TME) play a key role in this process. The factors in the TME and signaling networks that program DCs to a regulatory state are not fully understood. Recent advances point to novel mechanisms by which the canonical Wnt signaling cascade in DCs regulates immune suppression, and the same pathway in tumors is associated with the evasion of anti-tumor immunity. Here, we review these recent advances in the context of the pleiotropic effects of the Wnts in shaping anti-tumor immune responses by modulating DC functions. In addition, we will discuss how Wnt/ß-catenin pathway in DCs can be targeted for successful cancer immunotherapy.
Asunto(s)
Células Dendríticas/inmunología , Células Dendríticas/metabolismo , Inmunidad/inmunología , Microambiente Tumoral/inmunología , Microambiente Tumoral/fisiología , Vía de Señalización Wnt/inmunología , Humanos , Inmunoterapia , Neoplasias/inmunología , Transducción de Señal/inmunología , beta Catenina/inmunología , beta Catenina/metabolismoRESUMEN
MYCN amplification drives the development of neuronal cancers in children and adults. Given the challenge in therapeutically targeting MYCN directly, we searched for MYCN-activated metabolic pathways as potential drug targets. Here we report that neuroblastoma cells with MYCN amplification show increased transcriptional activation of the serine-glycine-one-carbon (SGOC) biosynthetic pathway and an increased dependence on this pathway for supplying glucose-derived carbon for serine and glycine synthesis. Small molecule inhibitors that block this metabolic pathway exhibit selective cytotoxicity to MYCN-amplified cell lines and xenografts by inducing metabolic stress and autophagy. Transcriptional activation of the SGOC pathway in MYCN-amplified cells requires both MYCN and ATF4, which form a positive feedback loop, with MYCN activation of ATF4 mRNA expression and ATF4 stabilization of MYCN protein by antagonizing FBXW7-mediated MYCN ubiquitination. Collectively, these findings suggest a coupled relationship between metabolic reprogramming and increased sensitivity to metabolic stress, which could be exploited as a strategy for selective cancer therapy. SIGNIFICANCE: This study identifies a MYCN-dependent metabolic vulnerability and suggests a coupled relationship between metabolic reprogramming and increased sensitivity to metabolic stress, which could be exploited for cancer therapy.See related commentary by Rodriguez Garcia and Arsenian-Henriksson, p. 3818.
Asunto(s)
Neuroblastoma , Serina , Vías Biosintéticas , Carbono , Línea Celular Tumoral , Niño , Glicina , Humanos , Proteína Proto-Oncogénica N-MycRESUMEN
Aberrant Wnt/ß-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 ß-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.
Asunto(s)
Células Presentadoras de Antígenos/inmunología , Microbioma Gastrointestinal/inmunología , Inmunidad Mucosa/inmunología , Mucosa Intestinal/inmunología , Vía de Señalización Wnt/inmunología , Animales , Colitis Ulcerosa/inmunología , Colitis Ulcerosa/microbiología , Colon/inmunología , Colon/microbiología , Homeostasis/inmunología , Inflamación/inmunología , Mucosa Intestinal/microbiología , Ratones , Ratones Endogámicos C57BL , Ratones TransgénicosRESUMEN
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-1ß, 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.
Asunto(s)
Colitis/metabolismo , Homeostasis/fisiología , Ácido Láctico/metabolismo , Receptores de Superficie Celular/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Animales , Citocinas/metabolismo , Modelos Animales de Enfermedad , Femenino , Macrófagos/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Células TH1/metabolismoRESUMEN
Recently, impressive technical advancements have been made in the isolation and validation of mammary stem cells and cancer stem cells (CSC), but the signaling pathways that regulate stem cell self-renewal are largely unknown. Furthermore, CSCs are believed to contribute to chemo- and radioresistance. In this study, we used the MMTV-Neu-Tg mouse mammary tumor model to identify potential new strategies for eliminating CSCs. We found that both luminal progenitor and basal stem cells are susceptible to genetic and epigenetic modifications, which facilitate oncogenic transformation and tumorigenic potential. A combination of the DNMT inhibitor 5-azacytidine and the HDAC inhibitor butyrate markedly reduced CSC abundance and increased the overall survival in this mouse model. RNA-seq analysis of CSCs treated with 5-azacytidine plus butyrate provided evidence that inhibition of chromatin modifiers blocks growth-promoting signaling molecules such as RAD51AP1 and SPC25, which play key roles in DNA damage repair and kinetochore assembly. Moreover, RAD51AP1 and SPC25 were significantly overexpressed in human breast tumor tissues and were associated with reduced overall patient survival. In conclusion, our studies suggest that breast CSCs are intrinsically sensitive to genetic and epigenetic modifications and can therefore be significantly affected by epigenetic-based therapies, warranting further investigation of combined DNMT and HDAC inhibition in refractory or drug-resistant breast cancer. Cancer Res; 76(11); 3224-35. ©2016 AACR.
Asunto(s)
Azacitidina/farmacología , Neoplasias de la Mama/prevención & control , Carcinoma Basocelular/prevención & control , ADN (Citosina-5-)-Metiltransferasas/antagonistas & inhibidores , Histona Desacetilasa 1/antagonistas & inhibidores , Inhibidores de Histona Desacetilasas/farmacología , Células Madre Neoplásicas/efectos de los fármacos , Animales , Antimetabolitos Antineoplásicos/farmacología , Apoptosis , Biomarcadores de Tumor/genética , Western Blotting , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Carcinoma Basocelular/metabolismo , Carcinoma Basocelular/patología , Proliferación Celular , ADN (Citosina-5-)-Metiltransferasa 1 , Quimioterapia Combinada , Femenino , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Técnicas para Inmunoenzimas , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos NOD , Ratones Desnudos , Ratones SCID , Células Madre Neoplásicas/metabolismo , Células Madre Neoplásicas/patología , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Células Tumorales CultivadasRESUMEN
Epidemiological studies have linked increased incidence of inflammatory diseases and intestinal cancers in the developed parts of the world to the consumption of diets poor in dietary fibers and rich in refined carbohydrates. Gut bacteria residing in the intestinal lumen exclusively metabolize dietary fibers. Butyrate, propionate and acetate, which are collectively called short-chain fatty acids (SCFAs), are generated by fermentation of dietary fibers by gut microbiota. Evidences indicate that SCFAs are key players in regulating beneficial effect of dietary fibers and gut microbiota on our health. SCFAs interact with metabolite-sensing G protein-coupled receptors GPR41, GPR43 and GPR109A expressed in gut epithelium and immune cells. These interactions induce mechanisms that play a key role in maintaining homeostasis in gut and other organs. This review summarizes the protective roles of GPR41, GPR43 and GPR109A in dietary fibers-, gut microbiota- and SCFAs-mediated suppression of inflammation and carcinogenesis in gut and other organs.
Asunto(s)
Fibras de la Dieta/metabolismo , Ácidos Grasos Volátiles/metabolismo , Microbioma Gastrointestinal/fisiología , Neoplasias Intestinales/fisiopatología , Receptores Acoplados a Proteínas G/metabolismo , Acetatos/metabolismo , Animales , Butiratos/metabolismo , Carcinogénesis/metabolismo , Humanos , Inflamación/metabolismo , Propionatos/metabolismo , Receptores de Superficie Celular/metabolismo , Receptores Nicotínicos/metabolismoRESUMEN
PURPOSE: Hemochromatosis, an iron-overload disease, occurs as adult and juvenile types. Mutations in hemojuvelin (HJV), an iron-regulatory protein and a bone morphogenetic protein (BMP) coreceptor, underlie most of the juvenile type. Hjv(-/-) mice accumulate excess iron in retina and exhibit aberrant vascularization and angiomas. A succinate receptor, GPR91, is pro-angiogenic in retina. We hypothesized that Hjv(-/-) retinas have increased BMP signaling and increased GPR91 expression as the basis of angiomas. METHODS: Expression of GPR91 was examined by qPCR, immunofluorescence, and Western blot in wild-type and Hjv(-/-) mouse retinas and pRPE cells. Influence of excess iron and BMP6 on GPR91 expression was investigated in ARPE-19 cells, and wild-type and Hjv(-/-) pRPE cells. Succinate was used to activate GPR91 and determine the effects of GPR91 signaling on VEGF expression. Signaling of BMP6 was studied by the expression of Smad1/5/8 and pSmad4, and the BMP-target gene Id1. The interaction of pSmad4 with GPR91 promoter was studied by ChIP. RESULTS: Expression of GPR91 was higher in Hjv(-/-) retinas and RPE than in wild-type counterparts. Unexpectedly, BMP signaling was increased, not decreased, in Hjv(-/-) retinas and RPE. Bone morphogenetic protein 6 induced GPR91 in RPE, suggesting that increased BMP signaling in Hjv(-/-) retinas was likely responsible for GPR91 upregulation. Exposure of RPE to excess iron and succinate as well as BMP6 and succinate increased VEGF expression. Bone morphogenetic protein 6 promoted the interaction of pSmad4 with GPR91 promoter in RPE. CONCLUSIONS: G-protein-coupled receptor 91 is a BMP6 target and Hjv deletion enhances BMP signaling in retina, thus underscoring a role for excess iron and hemochromatosis in abnormal retinal vascularization.
Asunto(s)
Proteína Morfogenética Ósea 6/metabolismo , Modelos Animales de Enfermedad , Regulación de la Expresión Génica/fisiología , Hemocromatosis/congénito , Receptores Acoplados a Proteínas G/genética , Retina/metabolismo , Animales , Western Blotting , Línea Celular , Inmunoprecipitación de Cromatina , Técnica del Anticuerpo Fluorescente Indirecta , Hemocromatosis/genética , Hemocromatosis/metabolismo , Humanos , Ratones , Ratones Noqueados , ARN/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Epitelio Pigmentado de la Retina/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal , Regulación hacia ArribaRESUMEN
SLC6A14 mediates Na(+)/Cl(-)-coupled concentrative uptake of a broad-spectrum of amino acids. It is expressed at low levels in many tissues but up-regulated in certain cancers. Pharmacological blockade of SLC6A14 causes amino acid starvation in estrogen receptor positive (ER+) breast cancer cells and suppresses their proliferation in vitro and in vivo. In the present study, we interrogated the role of this transporter in breast cancer by deleting Slc6a14 in mice and monitoring the consequences of this deletion in models of spontaneous breast cancer (Polyoma middle T oncogene-transgenic mouse and mouse mammary tumour virus promoter-Neu-transgenic mouse). Slc6a14-knockout mice are viable, fertile and phenotypically normal. The plasma amino acids were similar in wild-type and knockout mice and there were no major compensatory changes in the expression of other amino acid transporter mRNAs. There was also no change in mammary gland development in the knockout mouse. However, when crossed with PyMT-Tg mice or MMTV/Neu (mouse mammary tumour virus promoter-Neu)-Tg mice, the development and progression of breast cancer were markedly decreased on Slc6a14(-/-) background. Analysis of transcriptomes in tumour tissues from wild-type mice and Slc6a14-null mice indicated no compensatory changes in the expression of any other amino acid transporter mRNA. However, the tumours from the null mice showed evidence of amino acid starvation, decreased mTOR signalling and decreased cell proliferation. These studies demonstrate that SLC6A14 is critical for the maintenance of amino acid nutrition and optimal mammalian target of rapamycin (mTOR) signalling in ER+ breast cancer and that the transporter is a potential target for development of a novel class of anti-cancer drugs targeting amino acid nutrition in tumour cells.
Asunto(s)
Sistemas de Transporte de Aminoácidos , Proliferación Celular , Eliminación de Gen , Neoplasias Mamarias Experimentales/metabolismo , Proteínas de Neoplasias/metabolismo , Proteínas de Transporte de Neurotransmisores en la Membrana Plasmática , Transducción de Señal , Animales , Sistemas de Liberación de Medicamentos , Femenino , Neoplasias Mamarias Experimentales/dietoterapia , Neoplasias Mamarias Experimentales/genética , Neoplasias Mamarias Experimentales/patología , Ratones , Ratones Noqueados , Proteínas de Neoplasias/genética , Serina-Treonina Quinasas TOR/genética , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
Mammary stem/progenitor cells (MaSCs) maintain self-renewal of the mammary epithelium during puberty and pregnancy. DNA methylation provides a potential epigenetic mechanism for maintaining cellular memory during self-renewal. Although DNA methyltransferases (DNMTs) are dispensable for embryonic stem cell maintenance, their role in maintaining MaSCs and cancer stem cells (CSCs) in constantly replenishing mammary epithelium is unclear. Here we show that DNMT1 is indispensable for MaSC maintenance. Furthermore, we find that DNMT1 expression is elevated in mammary tumours, and mammary gland-specific DNMT1 deletion protects mice from mammary tumorigenesis by limiting the CSC pool. Through genome-scale methylation studies, we identify ISL1 as a direct DNMT1 target, hypermethylated and downregulated in mammary tumours and CSCs. DNMT inhibition or ISL1 expression in breast cancer cells limits CSC population. Altogether, our studies uncover an essential role for DNMT1 in MaSC and CSC maintenance and identify DNMT1-ISL1 axis as a potential therapeutic target for breast cancer treatment.
Asunto(s)
Neoplasias de la Mama/genética , Carcinogénesis/genética , ADN (Citosina-5-)-Metiltransferasas/genética , Proteínas con Homeodominio LIM/genética , Glándulas Mamarias Animales/metabolismo , Neoplasias Mamarias Experimentales/genética , Células Madre Neoplásicas/metabolismo , Factores de Transcripción/genética , Animales , Western Blotting , Neoplasias de la Mama/metabolismo , Línea Celular , Línea Celular Tumoral , ADN (Citosina-5-)-Metiltransferasa 1 , ADN (Citosina-5-)-Metiltransferasas/metabolismo , Metilación de ADN , Regulación hacia Abajo , Femenino , Humanos , Proteínas con Homeodominio LIM/metabolismo , Células MCF-7 , Glándulas Mamarias Animales/citología , Glándulas Mamarias Animales/crecimiento & desarrollo , Neoplasias Mamarias Experimentales/metabolismo , Ratones , Microscopía Fluorescente , Células Madre Neoplásicas/citología , Células Madre/metabolismo , Factores de Transcripción/metabolismoRESUMEN
NaCT (SLC13A5) is a Na(+)-coupled transporter for Krebs cycle intermediates and is expressed predominantly in the liver. Human NaCT is relatively specific for citrate compared with other Krebs cycle intermediates. The transport activity of human NaCT is stimulated by Li(+), whereas that of rat NaCT is inhibited by Li(+). We studied the influence of Li(+) on NaCTs cloned from eight different species. Li(+) stimulated the activity of only NaCTs from primates (human, chimpanzee, and monkey); by contrast, NaCTs from nonprimate species (mouse, rat, dog, and zebrafish) were inhibited by Li(+). Caenorhabditis elegans NaCT was not affected by Li(+). With human NaCT, the Li(+)-induced increase in transport activity was associated with the conversion of the transporter from a low-affinity/high-capacity type to a high-affinity/low-capacity type. H(+) was able to substitute for Li(+) in eliciting the stimulatory effect. The amino acid Phe500 in human NaCT was critical for Li(+)/H(+)-induced stimulation. Mutation of this amino acid to tryptophan (F500W) markedly increased the basal transport activity of human NaCT in the absence of Li(+), but the ability of Li(+) to stimulate the transporter was almost completely lost with this mutant. Substitution of Phe500 with tryptophan in human NaCT converted the transporter from a low-affinity/high-capacity type to a high-affinity/low-capacity type, an effect similar to that of Li(+) on the wild-type NaCT. These studies show that Li(+)-induced activation of NaCT is specific for the transporter in primates and that the region surrounding Phe500 in primate NaCTs is important for the Li(+) effect.
Asunto(s)
Compuestos de Litio/farmacología , Simportadores/metabolismo , Animales , Transporte Biológico , Caenorhabditis elegans , Línea Celular , Citratos/metabolismo , Perros , Femenino , Humanos , Macaca mulatta , Ratones , Mutación , Oocitos/metabolismo , Pan troglodytes , Ratas , Especificidad de la Especie , Simportadores/genética , Xenopus laevis , Pez CebraRESUMEN
Commensal gut microflora and dietary fiber protect against colonic inflammation and colon cancer through unknown targets. Butyrate, a bacterial product from fermentation of dietary fiber in the colon, has been implicated in this process. GPR109A (encoded by Niacr1) is a receptor for butyrate in the colon. GPR109A is also a receptor for niacin, which is also produced by gut microbiota and suppresses intestinal inflammation. Here we showed that Gpr109a signaling promoted anti-inflammatory properties in colonic macrophages and dendritic cells and enabled them to induce differentiation of Treg cells and IL-10-producing T cells. Moreover, Gpr109a was essential for butyrate-mediated induction of IL-18 in colonic epithelium. Consequently, Niacr1(-/-) mice were susceptible to development of colonic inflammation and colon cancer. Niacin, a pharmacological Gpr109a agonist, suppressed colitis and colon cancer in a Gpr109a-dependent manner. Thus, Gpr10a has an essential role in mediating the beneficial effects of gut microbiota and dietary fiber in colon.
Asunto(s)
Carcinogénesis/inmunología , Colitis/inmunología , Colon/inmunología , Neoplasias del Colon/prevención & control , Células Epiteliales/inmunología , Receptores Acoplados a Proteínas G/metabolismo , Receptores Nicotínicos/metabolismo , Animales , Butiratos/inmunología , Diferenciación Celular/efectos de los fármacos , Células Cultivadas , Colitis/complicaciones , Colitis/tratamiento farmacológico , Colon/microbiología , Colon/patología , Neoplasias del Colon/etiología , Células Dendríticas/inmunología , Susceptibilidad a Enfermedades , Células Epiteliales/efectos de los fármacos , Interleucina-10/metabolismo , Interleucina-18/genética , Interleucina-18/metabolismo , Activación de Linfocitos/efectos de los fármacos , Macrófagos/inmunología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microbiota , Niacina/administración & dosificación , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/inmunología , Receptores Nicotínicos/genética , Receptores Nicotínicos/inmunología , Transducción de Señal/efectos de los fármacos , Subgrupos de Linfocitos T/inmunología , Linfocitos T Reguladores/inmunologíaRESUMEN
BACKGROUND: Nutrient levels are known to influence the development of osteoarthritis (OA), presumably by modulating levels of matrix biosynthesis and degradation. These processes may be affected by ascorbic acid (AA), an antioxidant which acts as a cofactor for numerous biochemical reactions and is essential for post-translational modifications of collagen. In this study we examined the expression of SVCT2, the only known Sodium coupled vitamin C transporter isoform present in articular cartilage, in human articular cartilage explants derived from both normal and osteoarthritis articular cartilage. METHODS: OA1 and OA3 human articular cartilage was carefully dissected and macroscopically graded for degeneration via the Collins scale. The tissue samples were histologically examined by Hematoxylin and Eosin and Safranin O and Fast Green staining. SVCT2 expression analysis was performed at mRNA level by quantitative real time PCR and at a protein level by immunohistochemistry. RESULTS: Our quantitative real time PCR showed marked variation in the expression of SVCT2 in human osteoarthritic articular cartilage. SVCT2 expression was significantly down-regulated (p = 0.0001) in the Collins grade 3 (OA3) compared to Collins grade 1 (OA1) tissue. Furthermore, slides stained with fluorescent antibodies to SVCT2 demonstrated greatly reduced fluorescence for the SVCT2 transporter on the chondrocyte plasma membrane in the osteoarthritic tissue samples. CONCLUSIONS: These findings demonstrate that the expression of SVCT2 transporter is significantly altered in human osteoarthritic tissues (OA3). The modulation of this transporter could therefore potentially influence the prevention, management and treatment of osteoarthritis.