Abstract
Pulmonary hypertension (PH) is a common but dangerous complication in chronic obstructive pulmonary disease (COPD). We hypothesized that dysregulation in the T helper type 17 (Th17) compartment could contribute to the development of COPD-associated PH (COPD-PH). To investigate this hypothesis, patients with COPD-PH and age- and sex-matched healthy controls were recruited, and their circulating CD4+ T cells were activated using anti-CD3/CD28 antibodies. The frequency of interleukin-17 (IL-17) -secreting cells was significantly higher in COPD-PH patients than in healthy controls. The secretion of IL-17 was significantly higher from COPD-PH CD4+ T cells than from control CD4+ T cells, whereas the secretion of interferon-γ and IL-4 was not significantly different. The expression of transforming growth factor-β, on the other hand, was significantly higher in healthy controls than in COPD-PH patients. Activated CD4+ T cells from COPD-PH patients also presented significantly lower forkhead box P3 (FOXP3) and higher retinoic acid receptor-related orphan C2 (RORC2) expression than CD4+ T cells from healthy controls. In both controls and patients, a negative correlation between RORC2 and FOXP3 was found, ex vivo and after CD3/CD28 activation. The serum IL-6 level was slightly higher in COPD-PH patients than in controls, but the IL-6 transcription by monocytes was comparable in COPD-PH patients and controls. Interestingly, CD4+ T cells from COPD-PH patients presented significantly higher levels of Kirsten rat sarcoma viral oncogene homolog and neuroblastoma RAS viral oncogene homolog than CD4+ T cells from healthy controls. Inhibiting Ras-GTPases using farnesylthiosalicylic acid significantly reduced the ratio of RORC2/FOXP3 expression in CD4+ T cells. Overall, we demonstrated that an imbalance of Th17/regulatory T cells was a hallmark of COPD-PH.