RESUMEN
Triggering receptor expressed on myeloid cells-2 (TREM2) is a cell surface receptor on macrophages and microglia that senses and responds to disease-associated signals to regulate the phenotype of these innate immune cells. The TREM2 signaling pathway has been implicated in a variety of diseases ranging from neurodegeneration in the central nervous system to metabolic disease in the periphery. Here, we report that TREM2 is a thyroid hormone-regulated gene and its expression in macrophages and microglia is stimulated by thyroid hormone and synthetic thyroid hormone agonists (thyromimetics). Our findings report the endocrine regulation of TREM2 by thyroid hormone, and provide a unique opportunity to drug the TREM2 signaling pathway with orally active small-molecule therapeutic agents.
Asunto(s)
Acetatos/farmacología , Encefalomielitis Autoinmune Experimental/tratamiento farmacológico , Glicoproteínas de Membrana/genética , Microglía/efectos de los fármacos , Fenoles/farmacología , Receptores Inmunológicos/genética , Receptores X Retinoide/genética , Hormonas Tiroideas/farmacología , Acetatos/síntesis química , Animales , Sitios de Unión , Encéfalo/efectos de los fármacos , Encéfalo/inmunología , Encéfalo/patología , Encefalomielitis Autoinmune Experimental/genética , Encefalomielitis Autoinmune Experimental/inmunología , Encefalomielitis Autoinmune Experimental/patología , Regulación de la Expresión Génica , Humanos , Inmunidad Innata , Macrófagos/efectos de los fármacos , Macrófagos/inmunología , Macrófagos/patología , Glicoproteínas de Membrana/antagonistas & inhibidores , Glicoproteínas de Membrana/inmunología , Ratones , Ratones Endogámicos C57BL , Microglía/inmunología , Microglía/patología , Modelos Moleculares , Fenoles/síntesis química , Fenoxiacetatos/farmacología , Regiones Promotoras Genéticas , Unión Proteica , Conformación Proteica en Hélice alfa , Conformación Proteica en Lámina beta , Dominios y Motivos de Interacción de Proteínas , ARN Mensajero/antagonistas & inhibidores , ARN Mensajero/genética , ARN Mensajero/inmunología , Receptores Inmunológicos/antagonistas & inhibidores , Receptores Inmunológicos/inmunología , Elementos de Respuesta , Receptores X Retinoide/química , Receptores X Retinoide/metabolismo , Transducción de SeñalRESUMEN
Triggering receptor expressed on myeloid cells-2 (TREM2) is a cell surface receptor on macrophages and microglia that senses and responds to disease associated signals to regulate the phenotype of these innate immune cells. The TREM2 signaling pathway has been implicated in a variety of diseases ranging from neurodegeneration in the central nervous system to metabolic disease in the periphery. We report here that TREM2 is a thyroid hormone regulated gene and its expression in macrophages and microglia is stimulated by thyroid hormone. Both endogenous thyroid hormone and sobetirome, a synthetic thyroid hormone agonist drug, suppress pro-inflammatory cytokine production from myeloid cells including macrophages that have been treated with the SARS-CoV-2 spike protein which produces a strong, pro-inflammatory phenotype. Thyroid hormone agonism was also found to induce phagocytic behavior in microglia, a phenotype consistent with activation of the TREM2 pathway. The thyroid hormone antagonist NH-3 blocks the anti-inflammatory effects of thyroid hormone agonists and suppresses microglia phagocytosis. Finally, in a murine experimental autoimmune encephalomyelitis (EAE) multiple sclerosis model, treatment with Sob-AM2, a CNS-penetrating sobetirome prodrug, results in increased Trem2 expression in disease lesion resident myeloid cells which correlates with therapeutic benefit in the EAE clinical score and reduced damage to myelin. Our findings represent the first report of endocrine regulation of TREM2 and provide a unique opportunity to drug the TREM2 signaling pathway with orally active small molecule therapeutic agents.
RESUMEN
X-linked adrenoleukodystrophy (X-ALD) is a rare, genetic disease in which increased very long chain fatty acids (VLCFAs) in the central nervous system (CNS) cause demyelination and axonopathy, leading to neurological deficits. Sobetirome, a potent thyroid hormone agonist, has been shown to lower VLCFAs in the periphery and CNS. In this study, two pharmacological strategies for enhancing the effects of sobetirome were tested in Abcd1 KO mice, a murine model with the same inborn error of metabolism as X-ALD patients. First, a sobetirome prodrug (Sob-AM2) with increased CNS penetration lowered CNS VLCFAs more potently than sobetirome and was better tolerated with reduced peripheral exposure. Second, co-administration of thyroid hormone with sobetirome enhanced VLCFA lowering in the periphery but did not produce greater lowering in the CNS. These data support the conclusion that CNS VLCFA lowering in Abcd1 knockout mice is limited by a mechanistic threshold related to slow lipid turnover.
Asunto(s)
Acetatos/uso terapéutico , Adrenoleucodistrofia/tratamiento farmacológico , Fenoles/uso terapéutico , Profármacos/uso terapéutico , Hormonas Tiroideas/uso terapéutico , Miembro 1 de la Subfamilia D de Transportador de Casetes de Unión al ATP/genética , Adrenoleucodistrofia/genética , Adrenoleucodistrofia/metabolismo , Animales , Modelos Animales de Enfermedad , Ácidos Grasos/metabolismo , Femenino , Humanos , Errores Innatos del Metabolismo Lipídico/tratamiento farmacológico , Errores Innatos del Metabolismo Lipídico/genética , Errores Innatos del Metabolismo Lipídico/metabolismo , Masculino , Ratones , Ratones NoqueadosRESUMEN
Oligodendrocyte processes wrap axons to form neuroprotective myelin sheaths, and damage to myelin in disorders, such as multiple sclerosis (MS), leads to neurodegeneration and disability. There are currently no approved treatments for MS that stimulate myelin repair. During development, thyroid hormone (TH) promotes myelination through enhancing oligodendrocyte differentiation; however, TH itself is unsuitable as a remyelination therapy due to adverse systemic effects. This problem is overcome with selective TH agonists, sobetirome and a CNS-selective prodrug of sobetirome called Sob-AM2. We show here that TH and sobetirome stimulated remyelination in standard gliotoxin models of demyelination. We then utilized a genetic mouse model of demyelination and remyelination, in which we employed motor function tests, histology, and MRI to demonstrate that chronic treatment with sobetirome or Sob-AM2 leads to significant improvement in both clinical signs and remyelination. In contrast, chronic treatment with TH in this model inhibited the endogenous myelin repair and exacerbated disease. These results support the clinical investigation of selective CNS-penetrating TH agonists, but not TH, for myelin repair.
