Affinin (Spilanthol), Isolated from Heliopsis longipes, Induces Vasodilation via Activation of Gasotransmitters and Prostacyclin Signaling Pathways

Abstract

Heliopsis longipes roots have been widely used in Mexican traditional medicine to relieve pain, mainly, toothaches. Previous studies have shown that affinin, the major alkamide of these roots, induces potent antinociceptive and anti-inflammatory activities. However, the effect of H. longipes root extracts and affinin on the cardiovascular system have not been investigated so far. In the present study, we demonstrated that the dichloromethane and ethanolic extracts of H. longipes roots, and affinin, isolated from these roots, produce a concentration-dependent vasodilation of rat aorta. Affinin-induced vasorelaxation was partly dependent on the presence of endothelium and was significantly blocked in the presence of inhibitors of NO, H₂S, and CO synthesis (N^G-nitro-l-arginine methyl ester (l-NAME), dl-propargylglycine (PAG), and chromium mesoporphyrin (CrMP), respectively); K⁺ channel blockers (glibenclamide (Gli) and tetraethyl ammonium (TEA)), and guanylate cyclase and cyclooxygenase inhibitors (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and indomethacin (INDO), respectively). Our results demonstrate, for the first time, that affinin induces vasodilation by mechanisms that involve gasotransmitters, and prostacyclin signaling pathways. These findings indicate that this natural alkamide has therapeutic potential in the treatment of cardiovascular diseases.

Keywords: Heliopsis longipes; affinin; gasotransmitters; prostacyclin; rat aorta; vasodilation.

Figure 1

Diagram of the isolation of affinin from the dichloromethane extract of H. longipes roots.

Figure 2

Chemical structure of affinin, the major alkamide in H. longipes roots.

Figure 3

(A) Vasodilator effect of the dichloromethane extract (HLDE), the ethanolic extract (HLEE), and affinin from Heliopsis longipes roots on intact aortic rings. Acetylcholine (ACh) was used as positive control; (B) Concentration-response curves of the vasodilator effect of affinin in the presence (E+) and absence (E−) of endothelium. Values are expressed as mean ± standard error of the mean (SEM) (n = 6); + p < 0.01.

Figure 4

(A) Vasodilator effect of affinin in the absence (control) and presence of PAG (1 mM), chromium mesoporphyrin (CrMP, 15 µM), N^G-nitro-l-arginine methyl ester (l-NAME, 100 µM), and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 µM) in rat aortic rings; (B) Vasodilator effect of affinin in the absence (control) and presence of glibenclamide (Gli, 10 µM) and tetraethyl ammonium (TEA, 1 mM) in rat aortic rings. Values are expressed as mean ± SEM (n = 6); + p < 0.01; * p < 0.001.

Figure 5

Vasodilatory effect of affinin in the absence (control) and presence of indomethacin (INDO, 10 µM) in rat aortic rings. Values are expressed as mean ± SEM (n = 6); * p < 0.001.

Figure 6

Pathways involved in the vasodilator effect of affinin. PLA₂, phospholipase A₂; AA, arachidonic acid; COX, cyclooxygenase; eNOS, endothelial NO synthase; HO2, heme-oxygenase 2; CSE, cystathionine-γ-lyase; sGC, soluble guanylate cyclase; PKG, protein kinase G; AC, adenylate cyclase; PKA, protein kinase A; K⁺ Ch, K⁺ channel; P-MLC, phosphorylated myosin light chain. Black upwards arrow, increased levels; Black downwards arrows, decreased levels. ?, pathway that remains to be confirmed.