RESUMO
COVID-19 is a disease of dysfunctional immune responses, but the mechanisms triggering immunopathogenesis are not established. The functional plasticity of macrophages allows this cell type to promote pathogen elimination and inflammation or suppress inflammation and promote tissue remodeling and injury repair. During an infection, the clearance of dead and dying cells, a process named efferocytosis, can modulate the interplay between these contrasting functions. Here, we show that engulfment of SARS-CoV-2-infected apoptotic cells exacerbates inflammatory cytokine production, inhibits the expression of efferocytic receptors, and impairs continual efferocytosis by macrophages. We also provide evidence supporting that lung monocytes and macrophages from severe COVID-19 patients have compromised efferocytic capacity. Our findings reveal that dysfunctional efferocytosis of SARS-CoV-2-infected cell corpses suppresses macrophage anti-inflammation and efficient tissue repair programs and provides mechanistic insights for the excessive production of pro-inflammatory cytokines and accumulation of tissue damage associated with COVID-19 immunopathogenesis.
Assuntos
COVID-19 , SARS-CoV-2 , Anti-Inflamatórios/farmacologia , Apoptose , Humanos , Macrófagos/metabolismo , FagocitoseRESUMO
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with a hyperinflammatory state and lymphocytopenia, a hallmark that appears as both signature and prognosis of disease severity outcome. Although cytokine storm and a sustained inflammatory state are commonly associated with immune cell depletion, it is still unclear whether direct SARS-CoV-2 infection of immune cells could also play a role in this scenario by harboring viral replication. We found that monocytes, as well as both B and T lymphocytes, were susceptible to SARS-CoV-2 infection in vitro, accumulating double-stranded RNA consistent with viral RNA replication and ultimately leading to expressive T cell apoptosis. In addition, flow cytometry and immunofluorescence analysis revealed that SARS-CoV-2 was frequently detected in monocytes and B lymphocytes from coronavirus disease 2019 (COVID-19) patients. The rates of SARS-CoV-2-infected monocytes in peripheral blood mononuclear cells from COVID-19 patients increased over time from symptom onset, with SARS-CoV-2-positive monocytes, B cells, and CD4+ T lymphocytes also detected in postmortem lung tissue. These results indicated that SARS-CoV-2 infection of blood-circulating leukocytes in COVID-19 patients might have important implications for disease pathogenesis and progression, immune dysfunction, and virus spread within the host.
Assuntos
COVID-19 , SARS-CoV-2 , Síndrome da Liberação de Citocina , Humanos , Leucócitos Mononucleares , MonócitosRESUMO
Severe cases of COVID-19 are characterized by a strong inflammatory process that may ultimately lead to organ failure and patient death. The NLRP3 inflammasome is a molecular platform that promotes inflammation via cleavage and activation of key inflammatory molecules including active caspase-1 (Casp1p20), IL-1ß, and IL-18. Although participation of the inflammasome in COVID-19 has been highly speculated, the inflammasome activation and participation in the outcome of the disease are unknown. Here we demonstrate that the NLRP3 inflammasome is activated in response to SARS-CoV-2 infection and is active in COVID-19 patients. Studying moderate and severe COVID-19 patients, we found active NLRP3 inflammasome in PBMCs and tissues of postmortem patients upon autopsy. Inflammasome-derived products such as Casp1p20 and IL-18 in the sera correlated with the markers of COVID-19 severity, including IL-6 and LDH. Moreover, higher levels of IL-18 and Casp1p20 are associated with disease severity and poor clinical outcome. Our results suggest that inflammasomes participate in the pathophysiology of the disease, indicating that these platforms might be a marker of disease severity and a potential therapeutic target for COVID-19.
Assuntos
COVID-19/patologia , COVID-19/virologia , Inflamassomos/metabolismo , SARS-CoV-2/fisiologia , Índice de Gravidade de Doença , Apoptose , Comorbidade , Citocinas/biossíntese , Humanos , Pulmão/patologia , Monócitos/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Mudanças Depois da Morte , Resultado do TratamentoRESUMO
Severe COVID-19 patients develop acute respiratory distress syndrome that may progress to cytokine storm syndrome, organ dysfunction, and death. Considering that neutrophil extracellular traps (NETs) have been described as important mediators of tissue damage in inflammatory diseases, we investigated whether NETs would be involved in COVID-19 pathophysiology. A cohort of 32 hospitalized patients with a confirmed diagnosis of COVID-19 and healthy controls were enrolled. The concentration of NETs was augmented in plasma, tracheal aspirate, and lung autopsies tissues from COVID-19 patients, and their neutrophils released higher levels of NETs. Notably, we found that viable SARS-CoV-2 can directly induce the release of NETs by healthy neutrophils. Mechanistically, NETs triggered by SARS-CoV-2 depend on angiotensin-converting enzyme 2, serine protease, virus replication, and PAD-4. Finally, NETs released by SARS-CoV-2-activated neutrophils promote lung epithelial cell death in vitro. These results unravel a possible detrimental role of NETs in the pathophysiology of COVID-19. Therefore, the inhibition of NETs represents a potential therapeutic target for COVID-19.
Assuntos
Betacoronavirus/fisiologia , Infecções por Coronavirus/imunologia , Infecções por Coronavirus/virologia , Armadilhas Extracelulares/fisiologia , Pneumonia Viral/imunologia , Pneumonia Viral/virologia , Células A549 , Adulto , Enzima de Conversão de Angiotensina 2 , COVID-19 , Morte Celular , Infecções por Coronavirus/sangue , Infecções por Coronavirus/patologia , Células Epiteliais/patologia , Células Epiteliais/virologia , Feminino , Células HeLa , Humanos , Masculino , Ativação de Neutrófilo , Pandemias , Peptidil Dipeptidase A/metabolismo , Pneumonia Viral/sangue , Pneumonia Viral/patologia , SARS-CoV-2 , Serina Proteases/metabolismo , Sucção , Traqueia/imunologiaRESUMO
Macrophages are highly plastic cells, responding to diverse environmental stimuli to acquire different functional phenotypes. Signaling through MAPKs has been reported to regulate the differentiation of macrophages, but the role of ERK5 in IL-4-mediated M2 macrophage differentiation is still unclear. Here, we showed that the ERK5 signaling pathway plays a critical role in IL-4-induced M2 macrophage differentiation. Pharmacologic inhibition of MEK5, an upstream activator of ERK5, markedly reduced the expression of classical M2 markers, such as Arg-1, Ym-1, and Fizz-1, as well as the production of M2-related chemokines and cytokines, CCL22, CCL17, and IGF-1 in IL-4-stimulated macrophages. Moreover, pharmacologic inhibition of ERK5 also decreased the expression of several M2 markers induced by IL-4. In accordance, myeloid cell-specific Erk5 depletion (Erk5∆mye ), using LysMcre /Erk5f/f mice, confirmed the involvement of ERK5 in IL-4-induced M2 polarization. Mechanistically, the inhibition of ERK5 did not affect STAT3 or STAT6 phosphorylation, suggesting that ERK5 signaling regulates M2 differentiation in a STAT3 and STAT6-independent manner. However, genetic deficiency or pharmacologic inhibition of the MEK5/ERK5 pathway reduced the expression of c-Myc in IL-4-activated macrophages, which is a critical transcription factor involved in M2 differentiation. Our study thus suggests that the MEK5/ERK5 signaling pathway is crucial in IL-4-induced M2 macrophage differentiation through the induction of c-Myc expression.
Assuntos
Diferenciação Celular/imunologia , Interleucina-4/imunologia , MAP Quinase Quinase 5/imunologia , Sistema de Sinalização das MAP Quinases/imunologia , Macrófagos/imunologia , Proteína Quinase 7 Ativada por Mitógeno/imunologia , Proteínas Proto-Oncogênicas c-myc/imunologia , Animais , Antígenos de Diferenciação/genética , Antígenos de Diferenciação/imunologia , Diferenciação Celular/genética , Regulação da Expressão Gênica/imunologia , Interleucina-4/genética , MAP Quinase Quinase 5/genética , Sistema de Sinalização das MAP Quinases/genética , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Proteína Quinase 7 Ativada por Mitógeno/genética , Proteínas Proto-Oncogênicas c-myc/genética , Fator de Transcrição STAT3/genética , Fator de Transcrição STAT3/imunologia , Fator de Transcrição STAT6/genética , Fator de Transcrição STAT6/imunologiaRESUMO
Th17 cell differentiation and pathogenicity depend on metabolic reprogramming inducing shifts toward glycolysis. Here, we show that the pyruvate kinase M2 (PKM2), a glycolytic enzyme required for cancer cell proliferation and tumor progression, is a key factor mediating Th17 cell differentiation and autoimmune inflammation. We found that PKM2 is highly expressed throughout the differentiation of Th17 cells in vitro and during experimental autoimmune encephalomyelitis (EAE) development. Strikingly, PKM2 is not required for the metabolic reprogramming and proliferative capacity of Th17 cells. However, T cell-specific PKM2 deletion impairs Th17 cell differentiation and ameliorates symptoms of EAE by decreasing Th17 cell-mediated inflammation and demyelination. Mechanistically, PKM2 translocates into the nucleus and interacts with STAT3, enhancing its activation and thereby increasing Th17 cell differentiation. Thus, PKM2 acts as a critical nonmetabolic regulator that fine-tunes Th17 cell differentiation and function in autoimmune-mediated inflammation.
Assuntos
Autoimunidade/fisiologia , Inflamação/metabolismo , Piruvato Quinase/fisiologia , Fator de Transcrição STAT3/metabolismo , Células Th17/fisiologia , Animais , Diferenciação Celular , Encefalomielite Autoimune Experimental/metabolismo , Encefalomielite Autoimune Experimental/fisiopatologia , Citometria de Fluxo , Imunofluorescência , Camundongos , Camundongos Endogâmicos C57BL , Piruvato Quinase/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Células Th17/metabolismoRESUMO
The Chikungunya virus (CHIKV) is a re-emerging arbovirus, in which its infection causes a febrile illness also commonly associated with severe joint pain and myalgia. Although the immune response to CHIKV has been studied, a better understanding of the virus-host interaction mechanisms may lead to more effective therapeutic interventions. In this context, neutrophil extracellular traps (NETs) have been described as a key mediator involved in the control of many pathogens, including several bacteria and viruses, but no reports of this important protective mechanism were documented during CHIKV infection. Here we demonstrate that the experimental infection of mouse-isolated neutrophils with CHIKV resulted in NETosis (NETs release) through a mechanism dependent on TLR7 activation and reactive oxygen species generation. In vitro, mouse-isolated neutrophils stimulated with phorbol 12-myristate 13-acetate release NETs that once incubated with CHIKV, resulting in further virus capture and neutralization. In vivo, NETs inhibition by the treatment of the mice with DNase resulted in the enhanced susceptibility of IFNAR-/- mice to CHIKV experimental acute infection. Lastly, by accessing the levels of MPO-DNA complex on the acutely CHIKV-infected patients, we found a correlation between the levels of NETs and the viral load in the blood, suggesting that NETs are also released in natural human infection cases. Altogether our findings characterize NETosis as a contributing natural process to control CHIKV acute infection, presenting an antiviral effect that helps to control systemic virus levels.