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Background: Factors leading to severe COVID-19 remain partially known. New biomarkers predicting COVID-19 severity that are also causally involved in disease pathogenesis could improve patient management and contribute to the development of innovative therapies. Autophagy, a cytosolic structure degradation pathway is involved in the maintenance of cellular homeostasis, degradation of intracellular pathogens and generation of energy for immune responses. Acyl-CoA binding protein (ACBP) is a key regulator of autophagy in the context of diabetes, obesity and anorexia. The objective of our work was to assess whether circulating ACBP levels are associated with COVID-19 severity, using proteomics data from the plasma of 903 COVID-19 patients. Methods: Somalogic proteomic analysis was used to detect 5000 proteins in plasma samples collected between March 2020 and August 2021 from hospitalized participants in the province of Quebec, Canada. Plasma samples from 903 COVID-19 patients collected during their admission during acute phase of COVID-19 and 295 hospitalized controls were assessed leading to 1198 interpretable proteomic profiles. Levels of anti-SARS-CoV-2 IgG were measured by ELISA and a cell-binding assay. Results: The median age of the participants was 59 years, 46% were female, 65% had comorbidities. Plasma ACBP levels correlated with COVID-19 severity, in association with inflammation and anti-SARS-CoV-2 antibody levels, independently of sex or the presence of comorbidities. Samples collected during the second COVID-19 wave in Quebec had higher levels of plasma ACBP than during the first wave. Plasma ACBP levels were negatively correlated with biomarkers of T and NK cell responses interferon-γ, tumor necrosis factor-α and interleukin-21, independently of age, sex, and severity. Conclusions: Circulating ACBP levels can be considered a biomarker of COVID-19 severity linked to inflammation. The contribution of extracellular ACBP to immunometabolic responses during viral infection should be further studied. [ABSTRACT FROM AUTHOR]

CD4 T cell activation induces dramatic changes to cellular metabolism for supporting their growth and differentiation into effector subsets. While the cytokines IL-4, TGF-β and IL-21 promote differentiation into Th9 cells, metabolic factors regulating this process remain poorly understood. To assess the role of lipid metabolism in human Th9 cell differentiation, naïve CD4 T cells were purified from blood of healthy volunteers and cultured in the presence or absence of compounds targeting PPAR-γ, acetyl-CoA-carboxylase 1 (ACC1), and AMP-activated protein kinase (AMPK) for four days. Th9 cell differentiation significantly increased PPARG expression, and the PPAR-γ agonist rosiglitazone suppressed IL-9 in a dose-dependent manner. The rosiglitazone-mediated suppression also occurred in the presence of the glucose metabolism inhibitor 2-deoxy-D-glucose, suggesting it was independent of glycolysis. On the other hand, the PPAR-γ antagonist GW9662 had no significant effect on IL-9 production. Next, the role of fatty acid synthesis was tested by treating cells with inhibitors of ACC1 (TOFA) or AMP-activated protein kinase (AMPK; dorsomorphin). We demonstrate reciprocal functions for these enzymes, as ACC1 inhibition substantially increased IL-9 production, whereas AMPK inhibition resulted in undetectable levels. TOFA also decreased expression of ACACA, the gene encoding ACC1, demonstrating regulation at the transcriptional level. Finally, combining TOFA treatment with exogenous oleic acid restored IL-9 back to the levels in control Th9 cultures, suggesting that ACC1 suppresses Th9 differentiation through fatty acid synthesis. Overall, our data demonstrate that lipid regulators associated with intracellular fatty acid accumulation suppress Th9 cell differentiation. These findings may have clinical implications for conditions associated with elevated IL-9 production. [ABSTRACT FROM AUTHOR]

Mitochondrial translation is essential to maintain mitochondrial function and energy production. Mutations in genes associated with mitochondrial translation cause several developmental disorders, and immune dysfunction is observed in many such patients. Besides genetic mutations, several antibiotics targeting bacterial ribosomes are well-established to inhibit mitochondrial translation. However, the effect of such antibiotics on different immune cells is not fully understood. Here, we addressed the differential effect of mitochondrial translation inhibition on different subsets of helper T cells (Th) of mice and humans. Inhibition of mitochondrial translation reduced the levels of mitochondrially encoded electron transport chain subunits without affecting their nuclear-encoded counterparts. As a result, mitochondrial oxygen consumption reduced dramatically, but mitochondrial mass was unaffected. Most importantly, we show that inhibition of mitochondrial translation induced apoptosis, specifically in Th2 cells. This increase in apoptosis was associated with higher expression of Bim and Puma, two activators of the intrinsic pathway of apoptosis. We propose that this difference in the sensitivity of Th1 and Th2 cells to mitochondrial translation inhibition reflects the intrinsic metabolic demands of these subtypes. Though Th1 and Th2 cells exhibit similar levels of oxidative phosphorylation, Th1 cells exhibit higher levels of aerobic glycolysis than Th2 cells. Moreover, Th1 cells are more sensitive to the inhibition of glycolysis, while higher concentrations of glycolysis inhibitor 2-deoxyglucose are required to induce cell death in the Th2 lineage. These observations reveal that selection of metabolic pathways for substrate utilization during differentiation of Th1 and Th2 lineages is a fundamental process conserved across species., (© 2024 John Wiley & Sons Ltd.)