Pro-Resolving Effects of Resolvin D<sub>2</sub> in LTD<sub>4</sub> and TNF-α Pre-Treated Human Bronchi

<div><p>Inflammation is a major burden in respiratory diseases, resulting in airway hyperresponsiveness. Our hypothesis is that resolution of inflammation may represent a long-term solution in preventing human bronchial dysfunctions. The aim of the present study was to assess the anti-inflammatory effects of RvD<sub>2</sub>, a member of the D-series resolving family, with concomitant effects on ASM mechanical reactivity. The role and mode of action of RvD<sub>2</sub> were assessed in an <i>in vitro</i> model of human bronchi under pro-inflammatory conditions, induced either by 1 μM LTD<sub>4</sub> or 10 ng/ml TNF-α pre-treatment for 48h. TNF-α and LTD<sub>4</sub> both induced hyperreactivity in response to pharmacological stimuli. Enhanced 5-Lipoxygenase (5-LOX) and cysteinyl leukotriene receptor 1 (<a href="" target="_blank">CysLTR1</a>) detection was documented in LTD<sub>4</sub> or TNF-α pre-treated human bronchi when compared to control (untreated) human bronchi. In contrast, RvD<sub>2</sub> treatments reversed 5-LOX/β-actin and CysLTR1/β-actin ratios and decreased the phosphorylation levels of AP-1 subunits (c-Fos, c-Jun) and p38-MAP kinase, while increasing the detection of the ALX/FPR2 receptor. Moreover, various pharmacological agents revealed the blunting effects of RvD<sub>2</sub> on LTD<sub>4</sub> or TNF-α induced hyper-responsiveness. Combined treatment with 300 nM RvD<sub>2</sub> and 1 μM WRW4 (an ALX/FPR2 receptor inhibitor) blunted the pro-resolving and broncho-modulatory effects of RvD<sub>2</sub>. The present data provide new evidence regarding the role of RvD<sub>2</sub> in a human model of airway inflammation and hyperrresponsiveness.</p></div>