Purinergic signaling modulates immune function and is involved in the immunopathogenesis of several viral infections. This study aimed to investigate alterations in purinergic pathways in coronavirus disease 2019 (COVID-19) patients. Mild and severe COVID-19 patients had lower extracellular adenosine triphosphate and adenosine levels, and higher cytokines than healthy controls. Mild COVID-19 patients presented lower frequencies of CD4 + CD25 + CD39 + (activated/memory regulatory T cell [mTreg]) and increased frequencies of high-differentiated (CD27 − CD28 − ) CD8 + T cells compared with healthy controls. Severe COVID-19 patients also showed higher frequencies of CD4 + CD39 + , CD4 + CD25 − CD39 + (memory T effector cell), and high-differentiated CD8 + T cells (CD27 − CD28 − ), and diminished frequencies of CD4 + CD73 + , CD4 + CD25 + CD39 + mTreg cell, CD8 + CD73 + , and low-differentiated CD8 + T cells (CD27 + CD28 + ) in the blood in relation to mild COVID-19 patients and controls. Moreover, severe COVID-19 patients presented higher expression of PD-1 on low-differentiated CD8 + T cells. Both severe and mild COVID-19 patients presented higher frequencies of CD4 + Annexin-V + and CD8 + Annexin-V + T cells, indicating increased T-cell apoptosis. Plasma samples collected from severe COVID-19 patients were able to decrease the expression of CD73 on CD4 + and CD8 + T cells of a healthy donor. Interestingly, the in vitro incubation of peripheral blood mononuclear cell from severe COVID-19 patients with adenosine

Aim: To investigate the impact of physical fitness on the mobilization of CD4 + CD25 − CD39 + and CD4 + CD25 + CD39 + T cells in response to acute exercise.Methods: Fifteen high physical fitness (25.3 ± 1.4 years) and 15 low physical fitness (26.1 ± 1.9 years) men performed a single bout of high-intensity interval exercise (HIIE, 10 bouts of 60 seconds at 85% HRmax intercepted by 75 seconds of recovery at 50% HRmax). Blood lymphocytes were isolated before, immediately after and 1 hour after exercise for assessment of cell surface expression of CD25, CD39, and CD73 on CD4 + T cells. Effector memory T cells (mTeff) were identified by CD4 + CD25 − CD39 + coexpression, and memory regulatory T cells (mTReg) were defined as CD4 + CD25 + CD39 + T cells.Results: Exercise increased CD4 + and CD4 + CD25 + T cell frequencies immediately after followed by a decrease bellow to baseline values at 1 hour after the bout in both low and high physical fitness groups. At baseline, the proportions of mTeff were higher, while mTreg were lower in low physical fitness individuals. The frequency of mTreg increased immediately after HIIE in both groups, and remained higher 1 hour after the bout. However, high physical fitness individuals presented higher mTreg frequency in all periods evaluated. A significantly mobilization of mTeff cells was identified in both groups immediately after HIIE. High physical fitness individuals displayed a decrease in mTeff cells bellow to baseline, while the frequency of mTeff remained higher in low physical fitness group 1 hour after the bout. The peripheral frequency of CD4 + CD25 + CD73 + T cells increased in a similar way immediately after the bout in both groups, returning to the baseline values 1 hour after exercise. No differences in CD4 + CD25 − CD73 + T cells were observed after HIIE in both groups. Conclusion:Our results highlight the impact of physical activity status in the redistribution of CD4 + T cells expressing ectonucleotidases in response to HIIE. K E Y W O R D Saerobic fitness, effector memory T cells, interval exercise, memory regulatory T cells

In this study, we evaluated the effects of autologous serum collected after two types of exercise on the in vitro inflammatory profile and T cell phenotype of resting peripheral blood mononuclear cells (PBMCs) in obese men. Serum samples and PBMCs were obtained from eight obese men who performed two exercise bouts—high intensity interval exercise (HIIE) and exhaustive exercise session to voluntary fatigue—in a randomized cross-over trial. Pre-exercise PBMCs were incubated with 50% autologous serum (collected before and after each exercise bout) for 4 h. In vitro experiments revealed that post-HIIE serum reduced the histone H4 acetylation status and NF-κB content of PBMCs and suppressed the production of both TNF-α and IL-6 by PBMCs, while increasing IL-10 production. Post-exhaustive exercise serum induced histone H4 hyperacetylation and mitochondrial depolarization in lymphocytes and increased TNF-α production. In vitro post-HIIE serum incubation resulted in an increase in the frequencies of CD4 + CTLA-4 + and CD4 + CD25+ T cells expressing CD39 and CD73. Post-exhaustive exercise serum decreased the frequency of CD4 + CD25 + CD73+ T cells but increased CD4 + CD25-CD39 + T cell frequency. Both post-exercise serums increased the proportions of CD4 + PD-1 + and CD8 + PD-1+ T cells. Blood serum factors released during exercise altered the immune response and T cell phenotype. The type of exercise impacted the immunomodulatory activity of the post-exercise serum on PBMCs.

We evaluated the impact of maximal exercise on oxidative stress and DNA damage in peripheral blood mononuclear cells (PBMC) from sedentary and exercised lean and obese men. PBMC were collected before, immediately and 1-h after exercise and exposed to hydrogen peroxide (H 2 O 2 ; 25 and 50 μM, 4 h). A leukocytosis was induced by maximal exercise immediately and 1-h after exercise in all groups. However, a lymphopenia was observed 1-h after exercise in the Sedentary obese group. In the control condition, low DNA damage index concomitant to increases in intracellular glutathione content (GSH) was identified immediately after exercise in all groups. However, higher DNA damage index and lipid peroxidation occurred 1-h after the bout in Sedentary and Exercised Obese groups. PBMC exposed to both H 2 O 2 25 and 50 μM experienced higher DNA damage and lipid peroxidation index immediately after exercise in all groups. Both lipid peroxidation and DNA damage index remained higher in PBMC of Sedentary Lean, Sedentary Obese, and Exercised obese groups obtained 1-h after exercise in both H 2 O 2 25 and 50 μM, with the highest values identified in PBMC from Sedentary Obese group. However, increases in GSH content were identified in treated PBMC from sedentary and exercised lean groups as well as exercised obese group 1-h after exercise. Habitual exercise confers increased resistance of PBMC to DNA damage induced by oxidative stress, reducing the detrimental effects of obesity.

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