Smoke inhalation enhances early alveolar leukocyte responsiveness to endotoxin

Background: Pulmonary dysfunction after smoke inhalation and thermal injury is associated with excessive morbidity and mortality. The purpose of this study was to evaluate alveolar leukocyte function after thermal injury and smoke inhalation. Methods: Twenty-one patients with thermal injury only (n = 8); thermal injury and smoke inhalation injury (n = 8); and nonburned controls (n = 5) were assessed by means of bronchoscopically directed lavage (bronchoalveolar lavage [BAL]) on the first and fourth days postinjury. BAL-isolated pulmonary leukocytes were assessed for number, composition, viability, and production of tumor necrosis factor (TNF)α, interleukin (IL)-8, and IL-6 in response to 100 ng/mL of lipopolysaccharide (LPS) (mean ± SEM; significance at p < 0.05). Results: Six of eight Smoke patients had gross evidence of lung injury. On day 1, Smoke and Burn BAL isolates yielded greater cell counts than Control (10.6 vs. 4.5 vs. 2.4 × 10⁶/mL). Smoke macrophages on day 1 produced more TNFα (1.2 vs. 0.2 ng/mL), IL-6 (8.0 vs. 1.9 ng/ mL), and IL-8 (85 vs. 32 ng/mL) after LPS stimulation compared with respective unstimulated (0 ng/mL of LPS) day-1 Smoke cells. LPS-stimulated Burn cells on day 1 produced more IL-8 (150 vs. 62 ng/mL) but not TNFα (0.4 vs. 0.25 ng/mL) or IL-6 (1.8 vs. 0.69 ng/mL), when compared with respective unstimulated Burn cells. By day 4, LPS-stimulated Smoke and Burn cells produced significantly more TNFα (Smoke, 0.41 vs. 0.16 ng/mL; Burn, 0.87 vs. 0.51 ng/mL) and IL-6 (Smoke, 2.5 vs. 0.47 ng/mL; Burn, 4.1 vs. 1.47 ng/mL), but not IL-8 (Smoke, 51.1 vs. 51.1 ng/mL; Burn, 54.4 vs. 55.6 ng/mL), compared with respective unstimulated day-4 cells. Conclusion: Smoke inhalation induces a massive influx of alveolar leukocytes that are primed for an early, enhanced LPS-activated cytokine response compared with alveolar leukocytes isolated after burn injury alone or normal controls.