To investigate the modulation of lung local immune responses of hesperidin (HES) on the acute lung inflammation induced by LPS in vivo. Mice were challenged with intratracheal lipopolysaccharide (100 microg) 30 min before with treatment hesperidin (200 mg/kg oral administration) or vehicle. After 4 and 24 h, bronchoalveolar lavage fluid was obtained to measure proinflammatory (TNF-alpha, IL-1 beta, IL-6), anti-inflammatory (IL-10, IL-4, IL-12) cytokines, chemokines (KC, MCP-1 and MIP-2), total cell counts, nitric oxide production, and proteins. Lung histology was performed in inflated-fixed lungs. Hesperidin downregulate the LPS-induced expression of TNF-alpha, IL-1 beta, IL-6, KC, MIP-2, MCP-1, and IL-12. It also enhanced the production of IL-4, IL-10. Total leukocyte counts; nitric oxide production, iNOS expression, and proteins were significantly decreased by hesperidin. In vitro, HES suppressed the expression of IL-8 on A549 cells and THP-1 cells, the expression of TNF-alpha, IL-1 beta, and IL-6 on THP-1 cells, the expression of ICAM-1 and VCAM-1 on A549 cells which effect cell adhesion function. The suppression of those molecules is controlled by NF-kappaB and AP-1, which are activated by I kappa B and MAPK pathways. HES inhibits those pathways, thereby suppressing the expression of IL-8, TNFalpha, IL-1 beta, IL-6, IL-12, ICAM-1 and VCAM-1. This study indicates that HES had a markedly immunomodulatory effect in a clinically relevant model of ARDS. Nevertheless, further investigations are required to determine the potential clinical usefulness of HES in the adjunctive therapy of ARDS.