The role of iNKT cells and receptors for advanced glycation end products (RAGE) in lung ischemia-reperfusion injury

Pulmonary ischemia-reperfusion (IR) injury entails an inflammatory cascade that is characterized by a biphasic response involving early activation of T cells and macrophages and a later phase involving activation of epithelial cells, endothelial cells and neutrophils. To study the detailed role of T cells in lung IR injury, an in vivo hilar clamp model of lung IR was used wherein C57BL/6 wild-type (WT), Rag-1 knockout (Rag-1 -/- , deficient in T and B cells) and Jα18 -/- (iNKT cell deficient) mice underwent sham thoracotomy or lung IR (1hr left hilar occlusion and 2hrs reperfusion). Lung dysfunction and injury (proinflammatory cytokine production, lung edema, vascular permeability, neutrophil infiltration and activation) were significantly attenuated in Rag-/- 1 and Jα18 -/- mice compared to WT controls. Furthermore, reconstitution of Jα18 -/- mice with CD4+ iNKT cells from WT mice, but not IL-17 -/- mice, completely restored lung dysfunction and injury after lung IR. Flow cytometry and ELISPOT data confirmed IL-17 production by CD4+ iNKT cells after lung IR. Taken together, this data confirms a pivotal role of CD4+ iNKT cells and iNKT cell-derived IL-17 in the pathogenesis of lung IR injury. To further define specific signaling mechanisms involved in iNKT cell activation and subsequent IL-17 production, we investigated the role of receptor for advanced glycation end products (RAGE) and high mobility group box 1 (HMGB1), a RAGE ligand, on iNKT cell activation. RAGE -/- mice were significantly protected from lung dysfunction and injury after IR compared to WT mice. Treatment with recombinant HMGB1 significantly exacerbated lung dysfunction and injury after IR in WT mice but not in RAGE -/- mice. Furthermore, adoptive transfer of RAGE -/- iNKT cells to Jα18 -/- ii mice resulted in significant attenuation of lung dysfunction, injury and IL-17 production compared to Jα18 -/- mice reconstituted with WT iNKT cells. Moreover, in vitro studies confirmed that alveolar macrophages were a prominent source of HMGB1 and induces IL-17 production from WT iNKT cells but not RAGE -/- iNKT cells. Taken together, these data indicate that iNKT cells play a pivotal role in initiating inflammation after IR via IL- 17 production, which is regulated by the HMGB1/RAGE axis.

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