Co-upregulation of Toll-like receptors 2 and 6 on peripheral blood cells in patients with obstructive sleep apnea

Purpose: Toll-like receptor (TLR) 2 can heterodimerise with TLR6 to detect diacylated lipoproteins. Hypoxia inducible factor-1 α co-ordinates selective induction of TLR2 and TLR6 during persistent hypoxia. We hypothesized that TLR 2/6 co-expression may be upregulated by chronic intermittent hypoxia with re-oxygenation (IHR) in obstructive sleep apnea (OSA). Methods: TLR2/6 expressions on blood immune cells were measured in 144 patients with sleep-disordered breathing (SDB), including primary snoring (PS, n = 24), moderate to severe OSA (MSO, n = 60), very severe OSA (VSO, n = 36), and very severe OSA on continuous positive airway pressure (CPAP) treatment (VSOC, n = 24). An in vitro IHR experiment was also undertaken. Results: Patients in both the MSO and VSO groups had increased TLR2/6 co-expression on CD16⁺ neutrophil than those in the PS group. Patients in the VSOC group had reduced TLR2/6 co-expression on neutrophil than those in either the MSO or VSO group. Blood absolute neutrophil count was positively but weakly correlated with TLR2/6 co-expression on neutrophil. TLR2/6 co-expressions on both CD14⁺ monocyte and CD3⁺CD4⁺T helper cell, and TLR2 expressions on both monocyte and T helper cell in SDB patients with low Minimum SaO₂ (≦70 %) were all higher than those with high Minimum SaO₂. In vitro IHR for 1–4 days resulted in TLR2/6 co-upregulation on both neutrophil and monocyte. Conclusions: OSA patients had increased TLR2/6 co-expressions on blood immune cells, which were related to their immune cell counts and could be reversed with CPAP treatment. In vitro IHR could induce TLR2/6 co-upregulation.