Hypothesis on the Mechanisms Involved in the Enhancement of PGF2aInduced Contractions by Gingerol

The hypothesis on the mechanism involved in the potentiation or enhancement of PGF2o-induced contraction by gingerol or diabetic state in mice mesenteric veins is illustrated in Figure 13.8. In normal mesenteric veins, the exogenous prostaglandin (i.e., PGF2o) acts on the prostaglandin receptors and induces contraction of the vascular smooth muscle. Gingerol activates the cyclooxygenase in the endothelial cells, increasing the synthesis of prostaglandins, thus causing potentiation of prostaglandin-induced contraction. On the other hand, leukotriene acts on the leukotriene receptors and induces contraction of the smooth muscle. Gingerol inhibits the leukotriene-induced contraction, and this may be due to the inhibition of the leukotriene receptors but is not due to the inhibition of lipoxygenase in the endothelial cells. Similar results were observed in the guinea lung wherein the inhibition of leukotriene receptors converts the synthesis of arachidonic acid to the production of prostaglandins (PGE2, PGI2, and PGF2o) via the cyclooxygenase pathway (Mong et al., 1986).

The diabetic state damages the endothelial cells and disturbs the microvascular function. This may be related to the alterations in the synthesis of prostanoids and leukot-rienes in the diabetic state (Harrison et al., 1978; Silberbauer et al., 1979; Roth et al., 1984). In the diabetic mesenteric vein (Figure 13.8), the prostaglandin-induced con-

Figure 13.8 Potentiation or enhancement of PGF2o-induced contraction by gingerol or diabetic state in mice mesenteric veins. EC, endothelial cells; SMC, smooth muscle cells; PG, prostaglandin; LT, leukotriene; PG-R, prostaglandin receptor; LT-R, leukotriene receptor; COX, cyclooxygenase; LOX, lipoxygenase.

Figure 13.8 Potentiation or enhancement of PGF2o-induced contraction by gingerol or diabetic state in mice mesenteric veins. EC, endothelial cells; SMC, smooth muscle cells; PG, prostaglandin; LT, leukotriene; PG-R, prostaglandin receptor; LT-R, leukotriene receptor; COX, cyclooxygenase; LOX, lipoxygenase.

traction was significantly enhanced compared to that in the normal vein. The enhancement of the prostaglandin contractile response was significantly suppressed by lipoxygenase inhibitors but not by cycloxygenase inhibitors, suggesting the activation of the lipoxygenase in the diabetic state. The downregulation of the leukotriene receptors may, in turn, cause the upregulation of the prostaglandin receptors and the enhancement of the PG contractile response. It is assumed that the diabetic state induces an imbalance in the regulation of eicosanoid receptors in the vascular smooth muscle; however, this requires further investigation.

(±)-(6)-Gingerol also potentiated the contractile response to PGF2a in diabetic mice mesenteric vein (see Figure 13.8). The extent of potentiation was not significantly different from that in the normal vein. The results suggest that the mechanism involved in the potentiation of the PGF2a contractile response by (±)-(6)-gingerol is the same in normal and diabetic mesenteric veins; that is, via the cyclooxygenase pathway.

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Aromatherapy Ambiance

Aromatherapy Ambiance

Aromatherapy, a word often associated with calm, sweet smelling and relaxing surroundings. Made famous for its mostly relaxing indulgent  feature, using aromatherapy has also been known to be related to have medicinal qualities.

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