Cysteine, histidine and glycine exhibit anti-inflammatory effects in human coronary arterial endothelial cells

Abstract

The activation of nuclear factor-kappa B (NF-κB) in vascular endothelial cells may be involved in vascular pathogeneses such as vasculitis or atherosclerosis. Recently, it has been reported that some amino acids exhibit anti-inflammatory effects. We investigated the inhibitory effects of a panel of amino acids on cytokine production or expression of adhesion molecules that are involved in inflammatory diseases in various cell types. The activation of NF-κB was determined in human coronary arterial endothelial cells (HCAECs) because NF-κB modulates the production of many cytokines and the expression of adhesion molecules. We examined the inhibitory effects of the amino acids cysteine, histidine and glycine on the induction of NF-κB activation, expression of CD62E (E-selectin) and the production of interleukin (IL)-6 in HCAECs stimulated with tumour necrosis factor (TNF)-α. Cysteine, histidine and glycine significantly reduced NF-κB activation and inhibitor κBα (IκBα) degradation in HCAECs stimulated with TNF-α. Additionally, all the amino acids inhibited the expression of E-selectin and the production of IL-6 in HCAECs, and the effects of cysteine were the most significant. Our results show that glycine, histidine and cysteine can inhibit NF-κB activation, IκBα degradation, CD62E expression and IL-6 production in HCAECs, suggesting that these amino acids may exhibit anti-inflammatory effects during endothelial inflammation.

Fig. 1

Inhibitory effect of amino acids on nuclear factor-kappa B (NF-κB) activation measured using enzyme-linked immunosorbent assay (ELISA) in human coronary arterial endothelial cells (HCAECs) stimulated with tumour necrosis factor (TNF)-α (2 ng/ml) for 30 min. Data (n = 6) are presented as mean ± standard error of the mean. *P < 0·05; **P < 0·01; ***P < 0·001, compared to cells stimulated with TNF-α. #P < 0·001, compared to non-treated cells.

Fig. 2

Effects of amino acids on tumour necrosis factor (TNF)-α-induced inhibitor κBα (IκBα) degradation analysed by Western blotting of human coronary arterial endothelial cells (HCAECs) (a). β-Actin was used as an internal control (b). TNF-α stimulation induced degradation of IκBα, and the peak occurred 10 min after stimulation in HCAECs. Pretreatment with 20 mm of histidine or cysteine inhibited IκBα degradation compared to TNF-α-stimulated cells at 10 min compared to non-treated cells. Similar results were obtained in three independent experiments. Representative blots are shown.

Fig. 3

Inhibitory effects of amino acids on CD62E (E-selectin) expression analysed by flow cytometry in human coronary arterial endothelial cells (HCAECs) stimulated with (black column) or without (white column) tumour necrosis factor (TNF)-α (2 ng/ml) for 2 h. Data (n = 6) are presented as the mean ± standard error of the mean. *P < 0·05; **P < 0·001, compared to cells stimulated with TNF-α. #P < 0·001, compared to non-treated cells.

Fig. 4

Inhibitory effects of amino acids on interleukin (IL)-6 production analysed by enzyme-linked immunosorbent assay (ELISA) in human coronary arterial endothelial cells (HCAECs) stimulated with (black column) or without (white column) tumour necrosis factor (TNF)-α (2 ng/ml) for 6 h. Data (n = 6) are presented as mean ± standard error of the mean. *P < 0·001, compared to cells stimulated with TNF-α. #P < 0·001, compared to culture fluid from non-treated cells.