Inhibition of Acute Phase Inflammation by Laminaria japonica through Regulation of iNOS-NF-κB Pathway

Laminaria japonica has been frequently used as food supplements in many of the Asian countries and as a drug in traditional oriental medicine. This research investigated the effects of Laminaria japonica extract (LJE) on acute phase inflammation in a carrageenan-induced paw edema model, as assessed by histomorphometric and immunohistochemical analyses. The effect of LJE was also evaluated in Raw264.7 cells stimulated with lipopolysaccharide (LPS) in the aspect of the inhibition of nitric oxide (NO), prostaglandin E2 (PGE2), and proinflammatory cytokines production. NO, PGE2, tumor necrosis factor (TNF)- α , interleukin-1 β , and interleukin-6 contents were assayed by ELISA, and inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 expressions were determined by western blot analyses. In rats, LJE treatment inhibited carrageenan-induced paw edema formation and infiltration of inflammatory cells in H&E staining. LJE treatment prevented the ability of LPS to increase the levels of iNOS and COX-2 protein in a concentration-dependent manner. Consistently, LJE suppressed the production of TNF- α , interleukin-1 β , and interleukin-6. Treatment of the cells with LJE caused inhibition of inhibitor of κ B α phosphorylation induced by LPS, suggesting LJE repression of nuclear factor- κ B activity by LPS. In conclusion, this study shown here may be of help to understand the action mechanism of LJE and the anti-inflammatory use of L. japonica.