Alveolar macrophages modulate stromal derived factor-1 α expression in a murine acute lung injury model

Abstract

This study evaluated the pulmonary expression of stromal derived factor-1 alpha (SDF-1α) in a murine lipopolysaccharide (LPS) model of acute lung injury. Methods. C57BL/6J mice ( n = 6/time point) underwent intratracheal injection of 100 mcg LPS and were sacrificed 0, 4, 6, 12, 24, 48, and 72 h postinjection. SDF-1 levels were measured by ELISA on whole lung lysate and compared as pg SDF-1/ng total protein ± SEM using Student’s t-test. Immunohistochemistry was conducted to characterize the cells responsible for differential expression of SDF-1 in LPS lung injury. Results. SDF-1 levels are increased an order of magnitude at 48 h postinjury as compared with earlier time points. Immunohistochemistry for SDF-1 and the macrophage-specific marker antigen F4/80 demonstrates co-localization of signal for both antibodies within the same cell. There is no co-localization of signal for SDF-1 and thyroid transcription factor-1, a specific marker for type II pneumocytes within the murine lung. Conclusions. LPS injury in the murine lung increases alveolar macrophage specific expression of SDF-1, reaching a peak by our measurements at 48 h postinjection. This is the first report of alveolar macrophage expression of SDF-1, in addition to the first report of SDF-1 modulation in the acute inflammatory cascade. TABLE—ABSTRACT P23 Time point (h) SDF-1 (pg/ng total protein) Time point (h) SDF-1 (pg/ng total protein) 0 0.01 ± 0.00 24 0.05 ± 0.04 4 0.04 ± 0.02 48 ∗ 0.38 ± 0.05 6 0.03 ± 0.02 72 0.12 ± 0.12 12 0.02 ± 0.02 ∗ P < 0.05 versus 0, 4, 6, 12, 24, and 74 hours.