Regulation of chemokine expression by cyclosporine a in alveolar macrophages exposed to hypoxia and reoxygenation

Background. We have recently demonstrated a role for selected chemokines in a rat model of lung ischemia reperfusion injury (LIRI). We have further shown that pretreatment with cyclosporine A (CSA) is protective. The precise cellular events regulating this model are unknown. The alveolar macrophage (AM) is a key effector cell in multiple models of acute lung injury, and it likely plays a central role in LIRI as well. The present studies were undertaken to determine whether CSA functions in part by modifying the chemokine response of AMs to hypoxia and reoxygenation in vitro. Methods. Alveola macrophages were rendered hypoxic (0.5%) for 2 hours and reoxygenated for 6 hours. The secreted chemokine content in the media was quantified by enzyme-linked immunosorbent assay, and nuclear protein was analyzed after electro-mobility shift assay. When employed, CSA was administered 30 minutes before hypoxia. Results. Alveolar macrophages demonstrated a marked increase in the secretion of the chemokines, MIP-2, MIP-1α, CINC, and MCP-1, in response to hypoxia and reoxygenation. This increase was dependent on mRNA transcription and de novo protein synthesis. It was also blocked by a specific inhibitor of the nuclear translocation factor, NF-κB. Pretreatment with CSA (500 ng/mL) significantly reduced expression of chemokines and activation of NF-κB. Conclusions. Cyclosporine A attenuates the chemokine response of AMs in vitro to hypoxia and reoxygenation at the pretranscriptional level through modulation of NF-κB. These findings suggest the potential mechanism of action of CSA's protective effects in lung ischemia reperfusion injury.