Tissue-derived proinflammatory effect of adenosine A_2B receptor in lung ischemia–reperfusion injury

Objective

Ischemia–reperfusion injury after lung transplantation remains a major source of morbidity and mortality. Adenosine receptors have been implicated in both pro- and anti-inflammatory roles in ischemia–reperfusion injury. This study tests the hypothesis that the adenosine A_2B receptor exacerbates the proinflammatory response to lung ischemia–reperfusion injury.

Methods

An in vivo left lung hilar clamp model of ischemia–reperfusion was used in wild-type C57BL6 and adenosine A_2B receptor knockout mice, and in chimeras created by bone marrow transplantation between wild-type and adenosine A_2B receptor knockout mice. Mice underwent sham surgery or lung ischemia–reperfusion (1 hour ischemia and 2 hours reperfusion). At the end of reperfusion, lung function was assessed using an isolated buffer-perfused lung system. Lung inflammation was assessed by measuring proinflammatory cytokine levels in bronchoalveolar lavage fluid, and neutrophil infiltration was assessed via myeloperoxidase levels in lung tissue.

Results

Compared with wild-type mice, lungs of adenosine A_2B receptor knockout mice were significantly protected after ischemia–reperfusion, as evidenced by significantly reduced pulmonary artery pressure, increased lung compliance, decreased myeloperoxidase, and reduced proinflammatory cytokine levels (tumor necrosis factor-α; interleukin-6; keratinocyte chemoattractant; regulated on activation, normal T-cell expressed and secreted; and monocyte chemotactic protein-1). Adenosine A_2B receptor knockout→adenosine A_2B receptor knockout (donor→recipient) and wild-type→ adenosine A_2B receptor knockout, but not adenosine A_2B receptor knockout→wild-type, chimeras showed significantly improved lung function after ischemia–reperfusion.

Conclusions

These results suggest that the adenosine A_2B receptor plays an important role in mediating lung inflammation after ischemia–reperfusion by stimulating cytokine production and neutrophil chemotaxis. The proinflammatory effects of adenosine A_2B receptor seem to be derived by adenosine A_2B receptor activation primarily on resident pulmonary cells and not bone marrow-derived cells. Adenosine A_2B receptor may provide a therapeutic target for prevention of ischemia–reperfusion-related graft dysfunction in lung transplant recipients.

CTSNet classification: 9, 12, 38.1

Abbreviations and Acronyms: A₁R, A₁ receptor, A_2AR, A_2A receptor, A_2BR, A_2B receptor, A₃R, A₃ receptor, A_2BR^−/−, A_2BR knockout, BAL, bronchoalveolar lavage, KC, keratinocyte chemoattractant, IL, interleukin, IR, ischemia–reperfusion, MPO, myeloperoxidase, RANTES, regulated on activation, normal T-cell expressed and secreted, TNF, tumor necrosis factor, WT, wild-type