We investigated the pharmacologic effects of the antioxidant Vitamin E (alpha-tocopherol [alpha-toc]) in airway inflammation induced by inhaled endotoxin. A preparation of alpha-toc incorporated in liposomes was administered intraperitoneally in mice 1 h after exposure of aerosolized endotoxin. Injection of 50 mg alpha-toc/kg significantly decreased the number of neutrophils in airspaces and prevented lung injury, monitored both as decreased lactate dehydrogenase activity in airways and reduced lung edema when compared with animals treated with plain liposomes. Immunofluorescence staining of lung tissue revealed that treatment with alpha-toc decreased the number of neutrophils in lung interstitium, whereas the number in lung blood vessels and peripheral blood did not differ between mice treated with alpha-toc and control mice. Our results indicate that alpha-toc downmodulates the migration of neutrophils across the endothelial barrier, but in contrast to strong anti-inflammatory drugs such as corticosteroids, without inhibition of transcription factors involved in the early inflammatory response (nuclear factor-kappaB/activator protein-1). Neither was the endotoxin-induced expression of proinflammatory cytokines in lung tissue downregulated. Treatment with a combination of alpha-toc and a suboptimal dose of 0.5 mg/kg dexamethasone enhanced the effect, suggesting that alpha-toc, in combination with low doses of corticosteroids, might be effective for therapeutic treatment of acute lung injury.

SUMMARYInhalation of bacterial endotoxin induces an acute inflammation in the lower respiratory tract. In this study, the anti-inflammatory effects of the anti-oxidant N-acetylcysteine (NAC) and the glucocorticoid dexamethasone were investigated in mice exposed to aerosolized endotoxin (lipopolysaccharide (LPS)). Powerful reduction of neutrophils in bronchoalveolar lavage fluid (BALF) was obtained by a single i.p. injection of dexamethasone (10 mg/kg), whereas treatment with NAC only resulted in reduction of neutrophils when administered at a high dose (500 mg/kg). Measurement of cytokine and chemokine expression in lung tissue revealed a significant decrease of tumour necrosis factor-alpha, IL-1a , IL-1b , IL-6, IL-12p40, and MIP-1a mRNA when mice where treated with dexamethasone but not when treated with NAC. Analysis of oxidative burst demonstrated a remarkable reduction of oxygen radicals in BALF neutrophils after treatment with dexamethasone, whereas the effect of NAC was not significantly different from that in untreated animals. In conclusion, dexamethasone exerted both anti-inflammatory and anti-oxidative effects in acute airway inflammation, probably by blocking early events in the inflammatory cascade. In contrast, treatment with NAC resulted in a weak reduction of the inflammatory response but no inhibition of proinflammatory cytokines or reduction of oxidative burst in neutrophils. These results demonstrate dramatic differences in efficiency and also indicate that the two drugs have different actions. Combined treatment with NAC and dexamethasone revealed an additive action but no synergy was observed.

The pathogenesis of lung injury by exposure to highly toxic sulfur and nitrogen mustards involves alkylating damage of the respiratory epithelium followed by an acute inflammatory response and lung edema. The acute phase is followed by long-term respiratory complications characterized by bronchitis, lung fibrosis, and airway hyperreactivity. In this study, we utilized a mouse model for airway inflammation induced by inhalation exposure to the alkylating nitrogen mustard melphalan, in order to investigate possible beneficial treatment effects by the corticosteroid dexamethasone. In addition, we investigated therapeutic efficacy of liposome-encapsuled vitamin E, an antioxidant formulation previously shown to be efficient in counteracting inflammatory conditions. Influx of inflammatory cells to airways, edema formation, and expression of different cytokines were analyzed 6 and 18 hours after exposure to melphalan. In order to evaluate long-term lung effects, we also investigated collagen deposition and accumulation of lymphocytes at 2 and 4 weeks after exposure. A single intraperitoneal injection of dexamethasone (10 mg/kg body weight) 1 hour after melphalan exposure significantly reduced interleukin (IL)-1 and IL-6 in bronchoalveolar lavage fluid (BALF) and diminished the acute airway inflammation. Our results also indicate that early single-dose treatment with dexamethasone protects against long-term effects observed 2-4 weeks after melphalan exposure, as indicated by reduced lymphocytic response in airways and decreased collagen deposition. Furthermore, our results indicate that also vitamin E (50 mg/kg) reduces acute inflammatory cell influx, and suppresses collagen formation in lung tissue, indicating that this drug could be used in combination with corticosteroids for protection against chemical-induced lung injury.

Recruitment of neutrophils to lung tissue and airspaces is a hallmark of inflammatory events following inhalation of endotoxins. We studied the role of different lymphocyte subsets in this inflammation, which is assumed to primarily involve the innate immune system. Inhalation of aerosolized Escherichia coli lipopolysaccharide (LPS) in mice induced a dose-dependent increase in neutrophils in bronchoalveolar lavage fluid, reaching a maximum after 12 h at a low dose and after 24 h at a high dose. Profiles of gene expression in lung tissue indicated an early (2 h) and transient onset of proinflammatory cytokines and chemokines by a low dose of LPS, while a high dose caused more delayed and sustained (6 to 12 h) activation. Gamma interferon, interleukin-2 (IL-2), RANTES, and the alpha chain of the IL-2 receptor were not expressed at a low dose, whereas a high dose of LPS induced a strong expression of these genes, indicating a dose-dependent activation of T cells. A similar pattern was observed for IL-17, supporting a contribution of T cells to the neutrophilic inflammation only at high-dose exposure to LPS. The involvement of lymphocytes in the inflammatory response was further studied using mice with functional deficiencies in defined lymphocyte subsets. Both gammadelta T-cell- and B-cell-deficient mice displayed a response similar to that of the corresponding wild-type strains. Selective depletion of NK cells by in vivo administration of the pk136 antibody did not significantly affect the recruitment of neutrophils into airspaces. Thus, neither NK cells, B cells, nor gammadelta T cells appeared to participate in the host response, suggesting that among the lymphocyte subsets, alphabeta T cells are exclusively involved in endotoxin-induced airway inflammation.

The results in our animal model indicate that high-velocity BABT induce circulatory and respiratory dysfunction, and in some cases even transient cerebral functional disturbances.