RESUMO
Heme is an essential molecule expressed in many tissues where it plays key roles as the prosthetic group of several proteins involved in vital physiological and metabolic processes such as gas and electron transport. Structurally, heme is a tetrapyrrole ring containing an atom of iron (Fe) in its center. When released into the extracellular milieu, heme exerts several deleterious effects, which make it an important player in infectious and noninfectious hemolytic diseases where large amounts of free heme are observed such as malaria, dengue fever, ß-thalassemia, sickle cell disease and ischemia-reperfusion. Our recent work has uncovered an unappreciated cellular response triggered by heme or Fe, one of its degradation products, on macrophages, which is the formation of protein aggregates known as aggresome-like induced structres (ALIS). This response was shown to be fully dependent on ROS production and the activation of the transcription factor NFE2L2/NRF2. In addition, we have demonstrated that heme degradation by HMOX1/HO-1 (heme oxygenase 1) is required and that Fe is essential for the formation of ALIS, as heme analogs lacking the central atom of Fe are not able to induce these structures. ALIS formation is also observed in vivo, in a model of phenylhydrazine (PHZ)-induced hemolysis, indicating that it is an integral part of the host response to excessive free heme and that it may play a role in cellular homeostasis.
Assuntos
Heme/farmacologia , Ferro/farmacologia , Agregados Proteicos/efeitos dos fármacos , Animais , Humanos , Modelos BiológicosRESUMO
Diabetes mellitus (DM) encompasses a multitude of secondary disorders, including heart disease. One of the most frequent and potentially life threatening disorders of DM-induced heart disease is ventricular tachycardia (VT). Here we show that toll-like receptor 2 (TLR2) and NLRP3 inflammasome activation in cardiac macrophages mediate the production of IL-1ß in DM mice. IL-1ß causes prolongation of the action potential duration, induces a decrease in potassium current and an increase in calcium sparks in cardiomyocytes, which are changes that underlie arrhythmia propensity. IL-1ß-induced spontaneous contractile events are associated with CaMKII oxidation and phosphorylation. We further show that DM-induced arrhythmias can be successfully treated by inhibiting the IL-1ß axis with either IL-1 receptor antagonist or by inhibiting the NLRP3 inflammasome. Our results establish IL-1ß as an inflammatory connection between metabolic dysfunction and arrhythmias in DM.
Assuntos
Diabetes Mellitus Experimental/imunologia , Interleucina-1beta/imunologia , Macrófagos/imunologia , Miócitos Cardíacos/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/imunologia , Taquicardia Ventricular/imunologia , Receptor 2 Toll-Like/imunologia , Potenciais de Ação , Animais , Antirreumáticos/farmacologia , Arritmias Cardíacas/etiologia , Arritmias Cardíacas/imunologia , Arritmias Cardíacas/metabolismo , Cálcio/metabolismo , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Caspase 1/metabolismo , Diabetes Mellitus Experimental/complicações , Diabetes Mellitus Experimental/metabolismo , Inflamassomos/antagonistas & inibidores , Proteína Antagonista do Receptor de Interleucina 1/farmacologia , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Camundongos , Camundongos Transgênicos , Contração Miocárdica , Miócitos Cardíacos/imunologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/antagonistas & inibidores , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Potássio/metabolismo , Receptores de Interleucina-1/antagonistas & inibidores , Receptores de Interleucina-1/genética , Receptores de Interleucina-1/imunologia , Taquicardia Ventricular/etiologia , Taquicardia Ventricular/metabolismo , Receptor 2 Toll-Like/genéticaRESUMO
Hemolytic diseases include a variety of conditions with diverse etiologies in which red blood cells are destroyed and large amounts of hemeproteins are released. Heme has been described as a potent proinflammatory molecule that is able to induce multiple innate immune responses, such as those triggered by TLR4 and the NLRP3 inflammasome, as well as necroptosis in macrophages. The mechanisms by which eukaryotic cells respond to the toxic effects induced by heme to maintain homeostasis are not fully understood, however. Here we describe a previously uncharacterized cellular response induced by heme: the formation of p62/SQTM1 aggregates containing ubiquitinated proteins in structures known as aggresome-like induced structures (ALIS). This action is part of a response driven by the transcription factor NRF2 to the excessive generation of reactive oxygen species induced by heme that results in the expression of genes involved in antioxidant responses, including p62/SQTM1. Furthermore, we show that heme degradation by HO-1 is required for ALIS formation, and that the free iron released on heme degradation is necessary and sufficient to induce ALIS. Moreover, ferritin, a key protein in iron metabolism, prevents excessive ALIS formation. Finally, in vivo, hemolysis promotes an increase in ALIS formation in target tissues. Our data unravel a poorly understood aspect of the cellular responses induced by heme that can be explored to better understand the effects of free heme and free iron during hemolytic diseases such as sickle cell disease, dengue fever, malaria, and sepsis.