Suppressive effects of Houttuynia cordata Thunb (Saururaceae) extract on Th2 immune response

Houttuynia cordata Thunb (Saururaceae), known as 'E-Sung-Cho' in Korea, has been traditionally used for the treatment of herpes simplex, chronic sinusitis, and allergy.

To investigate the inhibitory activity of Houttuynia cordata Thunb fractions (HcFs) on the T helper 2 (Th2) immune response, we evaluated the alternation of the release of Th2-type cytokines and chemokines such as interleukin (IL)-4 and IL-5, and thymus and activation-regulated chemokine (TARC/CCL17).

Ethanol fraction was obtained from dried and powdered whole plants of Houttuynia cordata Thunb using ethanol. The residue was diluted with water and was then successively partitioned with n-hexane, EtOAc and BuOH. HcFs include ethanol, n-hexane, EtOAc, BuOH and water fractions. RT-PCR and ELISA were performed to measure mRNA and protein expression of cytokines.

HcFs inhibited the expression of IL-4 and IL-5 in response to phorbol 12-myristate 13-acetate (PMA) and calcium ionophore (CaI) in Jurkat T cells and the human mast cell line, HMC-1. IL-4- and tumor necrosis factor-alpha (TNF-alpha)-induced TARC production was blocked by HcFs in skin fibroblast CCD-986sk cells, particularly by the ethanol extract of Hc. Stimulants included in PMA, phytohemagglutinin (PHA) and CaI, increased the mRNA level of CC chemokine receptor 4 (CCR4), a receptor of TARC, in Jurkat T cells, and the ethanol extract of HcF weakly blocked the increased mRNA level. However, the stimulants and ethanol extract had no effect on the CCR4 protein level. The ethanol extract inhibited TARC-induced migration, as well as basal migration of Jurkat T cells.

This study may show the usefulness of HcFs in the ethnopharmacological treatment of Th2-mediated or allergic inflammation, through the down-regulation of the production of Th2 cytokines and TARC, as well as cell migration.