Gasdermin-D activation by SARS-CoV-2 triggers NET and mediate COVID-19 immunopathology.

BACKGROUND: The release of neutrophil extracellular traps (NETs) is associated with inflammation, coagulopathy, and organ damage found in severe cases of COVID-19. However, the molecular mechanisms underlying the release of NETs in COVID-19 remain unclear. OBJECTIVES: We aim to investigate the role of the Gasdermin-D (GSDMD) pathway on NETs release and the development of organ damage during COVID-19. METHODS: We performed a single-cell transcriptome analysis in public data of bronchoalveolar lavage. Then, we enrolled 63 hospitalized patients with moderate and severe COVID-19. We analyze in blood and lung tissue samples the expression of GSDMD, presence of NETs, and signaling pathways upstreaming. Furthermore, we analyzed the treatment with disulfiram in a mouse model of SARS-CoV-2 infection. RESULTS: We found that the SARS-CoV-2 virus directly activates the pore-forming protein GSDMD that triggers NET production and organ damage in COVID-19. Single-cell transcriptome analysis revealed that the expression of GSDMD and inflammasome-related genes were increased in COVID-19 patients. High expression of active GSDMD associated with NETs structures was found in the lung tissue of COVID-19 patients. Furthermore, we showed that activation of GSDMD in neutrophils requires active caspase1/4 and live SARS-CoV-2, which infects neutrophils. In a mouse model of SARS-CoV-2 infection, the treatment with disulfiram inhibited NETs release and reduced organ damage. CONCLUSION: These results demonstrated that GSDMD-dependent NETosis plays a critical role in COVID-19 immunopathology and suggests GSDMD as a novel potential target for improving the COVID-19 therapeutic strategy.

Beneficial effects of colchicine for moderate to severe COVID-19: a randomised, double-blinded, placebo-controlled clinical trial.

OBJECTIVE: To evaluate whether the addition of colchicine to standard treatment for COVID-19 results in better outcomes. DESIGN: We present the results of a randomised, double-blinded, placebo-controlled clinical trial of colchicine for the treatment of moderate to severe COVID-19, with 75 patients allocated 1:1 from 11 April to 30 August 2020. Colchicine regimen was 0.5 mg thrice daily for 5 days, then 0.5 mg twice daily for 5 days. The primary endpoints were the need for supplemental oxygen, time of hospitalisation, need for admission and length of stay in intensive care unit and death rate. RESULTS: Seventy-two patients (36 for placebo and 36 for colchicine) completed the study. Median (and IQR) time of need for supplemental oxygen was 4.0 (2.0-6.0) days for the colchicine group and 6.5 (4.0-9.0) days for the placebo group (p<0.001). Median (IQR) time of hospitalisation was 7.0 (5.0-9.0) days for the colchicine group and 9.0 (7.0-12.0) days for the placebo group (p=0.003). At day 2, 67% versus 86% of patients maintained the need for supplemental oxygen, while at day 7, the values were 9% versus 42%, in the colchicine and the placebo groups, respectively (log rank; p=0.001). Two patients died, both in placebo group. Diarrhoea was more frequent in the colchicine group (p=0.26). CONCLUSION: Colchicine reduced the length of both, supplemental oxygen therapy and hospitalisation. The drug was safe and well tolerated. Once death was an uncommon event, it is not possible to ensure that colchicine reduced mortality of COVID-19. TRIAL REGISTRATION NUMBER: RBR-8jyhxh.

Inflammasomes are activated in response to SARS-CoV-2 infection and are associated with COVID-19 severity in patients.

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.

SARS-CoV-2-triggered neutrophil extracellular traps mediate COVID-19 pathology.

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.

Impaired Pulmonary Function is an Additional Potential Mechanism for the Reduction of Functional Capacity in Clinically Stable Fontan Patients.

Central factors negatively affect the functional capacity of Fontan patients (FP), but "non-cardiac" factors, such as pulmonary function, may contribute to their exercise intolerance. We studied the pulmonary function in asymptomatic FP and its correlations with their functional capacity. Pulmonary function and cardiopulmonary exercise tests were performed in a prospective study of 27 FP and 27 healthy controls (HC). Cardiovascular magnetic resonance was used to evaluate the Fontan circulation. The mean age at tests, the mean age at surgery, and the median follow-up time of FP were 20(±6), 8(±3), and 11(8-17) years, respectively. Dominant ventricle ejection fraction was within normal range. The mean of peak VO2 expressed in absolute values (L/min), the relative values to body weight (mL/kg/min), and their predicted values were lower in FP compared with HC: 1.69 (±0.56) vs 2.81 (±0.77) L/min; 29.9 (±6.1) vs 41.5 (±9.3) mL/kg/min p < 0.001 and predicted VO2 Peak [71% (±14) vs 100% (±20) p < 0.001]. The absolute and predicted values of the forced vital capacity (FVC), forced expiratory volume in one second (FEV1), inspiratory capacity (IC), total lung capacity (TLC), diffusion capacity of carbon monoxide of the lung (DLCO), maximum inspiratory pressure (MIP), and sniff nasal inspiratory pressure (SNIP) were also significantly lower in the Fontan population compared to HC. An increased risk of restrictive ventilatory pattern was found in patients with postural deviations (OD:10.0, IC:1.02-97.5, p = 0.042). There was a strong correlation between pulmonary function and absolute peak VO2 [FVC (r = 0.86, p < 0.001); FEV1 (r = 0.83, p < 0.001); IC (r = 0.84, p < 0.001); TLC (r = 0.79, p < 0.001); and DLCO (r = 0.72, p < 0.001). The strength of the inspiratory muscles in absolute and predicted values was also reduced in FP [-79(±28) vs -109(±44) cmH2O (p = 0.004) and 67(±26) vs 89(±36) % (p = 0.016)]. Thus, we concluded that the pulmonary function was impaired in clinically stable Fontan patients and the static and dynamic lung volumes were significantly reduced compared with HC. We also demonstrated a strong correlation between absolute Peak VO2 with the FVC, FEV1, TLC, and DLCO measured by complete pulmonary test.