(1→3)-β-d-Glucan stimulates nitric oxide generation and cytokine mRNA expression in macrophages

Beta-glucans are known for their potent ability to induce nonspecific inflammatory reactions and are believed to play a role in bioaerosol-induced respiratory symptoms seen in both occupational and residential environments. Here, the ability of a (1→3)-β-d-glucan (Curdlan) to stimulate nitric oxide generation and cytokine mRNA expression in rat alveolar macrophages (AMs) and the murine monocyte/macrophage cell line, RAW 264.7 was investigated. Exposure to (1→3)-β-d-glucan (20, 100 and 500 μg/ml) induced a dose-dependent increase in the expression of inducible nitric oxide synthase mRNA and a release of nitric oxide into the culture medium in both rat AMs and RAW 264.7 cells. The mRNA expression of a number of other inflammatory mediators such as interleukin-1β, interleukin-6, tumor necrosis factor-α and cyclooxygenase-2 was also increased by the exposure to β-glucan. The capability of (1→3)-β-d-glucan (500 μg/ml) to induce mRNA synthesis of these various mediators were comparable to that of endotoxin (1 μg/ml). These results imply that (1→3)-β-d-glucan stimulates the generation of nitric oxide, cytokines and prostaglandins in macrophages and suggest the possibility that this may contribute to bioaerosol-induced respiratory symptoms seen in exposed individuals.