Identification of AMD3100 (Plerixafor) as a potential lead compound for chlorine toxicity

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PROJECT SUMMMARY/ABSTRACT Statement of problem: Chlorine (Cl2) gas is the most common inhalational irritant in the United States, which results in serious adverse effects including lung injury and death. Previous studies by the PI and others have demonstrated that migration and homing of leukocytes (neutrophils and macrophages) into lungs play a critical role in lung morbidity and mortality post Cl2 gas exposure. The binding of the chemokine ligand, stromal- derived-factor-1 (SDF-1), to the C-X-C chemokine receptor type 4 (CXCR4) on lung immune, epithelial, and endothelial cells promote the migration of leukocytes from the circulation to lungs. The SDF-1/CXCR4 axis also propagates the activation and survival of leukocytes in the lungs. Our preliminary data shows that both SDF-1 and CXCR4 levels are elevated in the lungs of Cl2 exposed animals. Therefore, our hypothesis is that SDF- 1/CXCR4 axis is involved in the migration, homing, and survival of leukocytes in lung post exposure to Cl2 and therefore inhibiting this axis by an FDA approved compound, AMD3100 (Plerixafor), would attenuate Cl2- induced lung morbidity and mortality. Specific aims: 1) Establish the role of SDF-1/CXCR4 axis in Cl2-induced lung leukocyte migration, activation, and survival. 2) Optimize the dosage regimen of AMD3100 for Cl2 toxicity. 3) Delineate the mechanisms of SDF-1/CXCR4 regulation post-Cl2 exposure. Experimental approach: C57BL/6 mice will be exposed to Cl2 gas (500ppm, 30min) and then the SDF-1 concentration in broncholaveolar lavage fluid and the CXCR4 surface expression on the alveolar leukocytes and whole lung tissue will be measured over time. It will also be analyzed whether, the SDF-1/CXCR4 axis mediates Cl2 dependent migration, activation, and survival of lung leukocytes. Next the Cl2 exposed mice will be administered a clinically safe dose (0.01-0.16 mg/kg) of AMD3100 intramuscularly and the indices of acute and chronic lung injury and mortality will be measured. Finally, the role of Cl2-induced hemolysis and hypoxia in the regulation of lung SDF-1 and CXCR4 levels post Cl2 exposure will be studied in vitro and in vivo. Anticipated results: We anticipate that AMD3100 will attenuate leukocyte translocation to lungs and subsequently mitigate lung injury and improve survival in mice exposed to Cl2. Innovation: The study is the first to propose the use of a novel, FDA-approved, small molecule compound, AMD3100, to mitigate lung injury and mortality post exposure to Cl2 gas. AMD3100 may be beneficial in mitigating lung injury post exposure to other toxic gases such as bromine and phosgene, which are also associated with hemolysis and increased migration of leukocytes into lung.