Interleukin-17A contributes to myocardial ischemia/reperfusion injury by regulating cardiomyocyte apoptosis and neutrophil infiltration.

OBJECTIVES: This study tested whether interleukin (IL)-17A is involved in the pathogenesis of mouse myocardial ischemia/reperfusion (I/R) injury and investigated the mechanisms. BACKGROUND: Inflammatory processes play a major role in myocardial I/R injury. We recently identified IL-17A as an important cytokine in inflammatory cardiovascular diseases such as atherosclerosis and viral myocarditis. However, its role in myocardial I/R injury remains unknown. METHODS: The involvement of IL-17A was assessed in functional assays in mouse myocardial I/R injury by neutralization/repletion or genetic deficiency of IL-17A, and its mechanism on cardiomyocyte apoptosis and neutrophil infiltration were further studied in vivo and in vitro. RESULTS: Interleukin-17A was elevated after murine left coronary artery ligation and reperfusion. Intracellular cytokine staining revealed that γδT lymphocytes but not CD4(+) helper T cells were a major source of IL-17A. Anti-IL-17A monoclonal antibody treatment or IL-17A knockout markedly ameliorated I/R injury, as demonstrated by reduced infarct size, reduced cardiac troponin T levels, and improved cardiac function. This improvement was associated with a reduction in cardiomyocyte apoptosis and neutrophil infiltration. In contrast, repletion of exogenous IL-17A induced the opposite effect. In vitro study showed that IL-17A mediated cardiomyocyte apoptosis through regulating the Bax/Bcl-2 ratio, induced CXC chemokine-mediated neutrophil migration and promoted neutrophil-endothelial cell adherence through induction of endothelial cell E-selectin and inter-cellular adhesion molecule-1 expression. CONCLUSIONS: IL-17A mainly produced by γδT cells plays a pathogenic role in myocardial I/R injury by inducing cardiomyocyte apoptosis and neutrophil infiltration.

Impaired thymic export and apoptosis contribute to regulatory T-cell defects in patients with chronic heart failure.

OBJECTIVE: Animal studies suggest that regulatory T (T(reg)) cells play a beneficial role in ventricular remodeling and our previous data have demonstrated defects of T(reg) cells in patients with chronic heart failure (CHF). However, the mechanisms behind T(reg-)cell defects remained unknown. We here sought to elucidate the mechanism of T(reg-)cell defects in CHF patients. METHODS AND RESULTS: We performed flow cytometry analysis and demonstrated reduced numbers of peripheral blood CD4(+)CD25(+)FOXP3(+)CD45RO(-)CD45RA(+) naïve T(reg) (nT(reg)) cells and CD4(+)CD25(+)FOXP3(+)CD45RO(+)CD45RA(-) memory T(reg) (mT(reg)) cells in CHF patients as compared with non-CHF controls. Moreover, the nT(reg)/mT(reg) ratio (p<0.01), CD4(+)CD25(+)FOXP3(+)CD45RO(-) CD45RA(+)CD31(+) recent thymic emigrant T(reg) cell (RTE-T(reg)) frequency (p<0.01), and T-cell receptor excision circle levels in T(reg) cells (p<0.01) were lower in CHF patients than in non-CHF controls. Combined annexin-V and 7-AAD staining showed that peripheral T(reg) cells from CHF patients exhibited increased spontaneous apoptosis and were more prone to interleukin (IL)-2 deprivation- and CD95 ligand-mediated apoptosis than those from non-CHF individuals. Furthermore, analyses by both flow cytometry and real-time polymerase chain reaction showed that T(reg)-cell frequency in the mediastinal lymph nodes or Foxp3 expression in hearts of CHF patients was no higher than that of the non-CHF controls. CONCLUSION: Our data suggested that the T(reg)-cell defects of CHF patients were likely caused by decreased thymic output of nascent T(reg) cells and increased susceptibility to apoptosis in the periphery.

Atorvastatin upregulates regulatory T cells and reduces clinical disease activity in patients with rheumatoid arthritis.

In this study, we investigated the hypothesis that regulatory T cells (T(reg)) are involved in the immunomodulatory effects of statins on rheumatoid arthritis (RA) patients. The 12-week study cohort consisted of 55 RA patients and 42 control subjects allocated to either a group treated with atorvastatin (AT) (20 mg/day) or a non-AT group. T(reg) numbers, suppressive function, serum inflammatory markers, and disease activity were evaluated before and after the therapy. Furthermore, the effects of AT on the frequency and suppressive function of T(reg) were determined in vitro. Our data revealed that the suppressive function of T(reg) from RA patients significantly decreased compared with that of control subjects. AT significantly reduced erythrosedimentation, C-reactive protein, and disease activity. Concomitantly, T(reg) numbers and suppressive functions were significantly improved by AT. Consistent with the in vivo experiments, AT promoted the generation of T(reg) from primary T cells and enhanced preexisting T(reg) function in vitro. Moreover, we showed that PI3K-Akt-mTOR and ERK signal pathways were involved in the induction of T(reg) by AT. In conclusion, AT significantly increased T(reg) numbers and restored their suppressive function in the RA patients, and this may be relevant in the modulation of uncontrolled inflammation in this disorder.