Anti-inflammatory and anti-oxidants activities of Ferula szowitsiana L. (F. szowitsiana) were shown in ancient texts and assayed by modern studies. However, immunomodulatory properties of the plant are poorly understood.
The effects of F. szowitsiana extract (10, 40 and 160 µg/ml), dexamethasone and vehicle were investigated on nitric oxide (NO) level, cell proliferation, and cytokines (IL-4, IL10 and IFN-γ) expression at gene and protein levels in non-stimulated and phytohaemagglutinin-stimulated human lymphocytes (n = 15 in each group).
Cell proliferation, cytokines secretion, NO production and levels of genes expression were significantly inhibited but IFN-γ/IL-4 and IL-10/IL-4 ratios (T helper 1/Th2 and Treg/Th2 balances respectively) were increased by dexamethasone and all three concentrations of the extract compared to control group in stimulated lymphocytes (P < 0.001 for all cases). The effect of three concentrations of the extract in all experiments was significantly lower than dexamethasone (P < 0.001 for all cases).
The extract of F. szowitsiana concentration-dependently decreased NO level but increased Th/Th and T/Th ratios toward Th and T. These results suggest the therapeutic potential of the plant’s extract in inflammatory diseases with dominant Th2 polarization such as asthma or cancers.

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