Vasorelaxant Activity and Inhibitory Effects on Leukocyte Function of a Flavanoid Compound from Kaempferia Parviflora

Abstract

The rhizomes of Kaempferia parviflora (K. parviflora) (Zingiberaceae) have been
used in Thai traditional medicine for gastrointestinal disorders, pain, allergy, and
inflammation. The alcoholic infusion of its rhizome has also been used as a tonic for
rectifying male impotence. Ethanolic extract of K. parviflora was reported to exhibit acute
anti-inflammatory activities in the rat paw edema model (unpublished data) and vasorelaxant
activity in isolated rat aortic rings. The purposes of this study were to investigate the effects
of a flavanoid compound from K. Parviflora, (VR-F6/1) on vasorelaxant activity, the
expression of ICAM-1 on human umbilical vein endothelial cells (HUVEC), CD62-L and
Mac-1 on neutrophils, human neutrophil functional responsiveness and T-lymphocyte
proliferation. VR-F6/1 was primarily investigated for its cytotoxic effects on HUVECs,
neutrophils and T-lymphocytes using XTT cytotoxicity assay. The vasorelaxant activity of
VR-F6/1 was assessed using myography technique. The effects of VR-F6/1 on fMLP-induced
L-selectin shedding and Mac-1 expression on neutrophils were assessed using flow
cytometry. Human neutrophil functional responsiveness was determined by measuring fMLPinduced
chemotaxis, superoxide anion generation (SAG), and MPO release. PHA-induced-Tlymphocyte
proliferation was quantified by [H3] thymidine incorporation. Viability of
HUVECs, neutrophils, and T-lymphocytes were not significantly affected by VR- F6/1 (1-
100 μg/ml) (IC50>1000 μM). VR-F6/1 concentration-dependently caused acute relaxation of
isolated mouse mesenteric arteries. VR-F6/1 (10 μM) inhibited ICAM-1 expression on
HUVECs, and inhibited fMLP-induced L-selectin shedding and Mac-1 surface expression on
neutrophils. VR-F6/1 concentration-dependently inhibited fMLP-induced chemotaxis, SAG,
and MPO production in neutrophils. VR-F6/1 also significantly inhibited PHA-induced Tlymphocyte
proliferation in a concentration-dependent manner. These findings suggest that
anti-inflammatory activity of VR-F6/1 might be, in part, attributable to inhibition of ICAM-1
expression on HUVEC, inhibition of CD62L shedding and Mac-1 surface expression on
neutrophils, neutrophil chemotaxis and SAG as well as T-lymphocyte proliferation. This
study also demonstrates an acute vasorelaxant activity of VR-F6/1 where nitric oxide may
mediate the effect.