Critical Role of Antimicrobial Peptide Cathelicidin for Controlling Helicobacter pylori Survival and Infection.

The antimicrobial peptide cathelicidin is critical for protection against different kinds of microbial infection. This study sought to elucidate the protective action of cathelicidin against Helicobacter pylori infection and its associated gastritis. Exogenous cathelicidin was found to inhibit H. pylori growth, destroy the bacteria biofilm, and induce morphological alterations in H. pylori membrane. Additionally, knockdown of endogenous cathelicidin in human gastric epithelial HFE-145 cells markedly increased the intracellular survival of H. pylori. Consistently, cathelicidin knockout mice exhibited stronger H. pylori colonization, higher expression of proinflammatory cytokines IL-6, IL-1ß, and ICAM1, and lower expression of the anti-inflammatory cytokine IL-10 in the gastric mucosa upon H. pylori infection. In wild-type mice, H. pylori infection also stimulated gastric epithelium-derived cathelicidin production. Importantly, pretreatment with bioengineered Lactococcus lactis that actively secretes cathelicidin significantly increased mucosal cathelicidin levels and reduced H. pylori infection and the associated inflammation. Moreover, cathelicidin strengthened the barrier function of gastric mucosa by stimulating mucus synthesis. Collectively, these findings indicate that cathelicidin plays a significant role as a potential natural antibiotic for H. pylori clearance and a therapeutic agent for chronic gastritis.

Dihydrotanshinone, a lipophilic component of Salvia miltiorrhiza (danshen), relaxes rat coronary artery by inhibition of calcium channels.

AIM OF THE STUDY: Dihydrotanshinone is a lipophilic component of the medicinal herb Salvia miltiorrhiza (danshen) belonging to the family of Labiatae. In this study, we have investigated the mechanisms of its relaxant effect on rat-isolated coronary artery. MATERIALS AND METHODS: Rat coronary artery rings were precontracted with 1 microM 5-hydroxytryptamine (5-HT). Involvement of endothelium-dependant mechanisms were investigated by pretreatment of the artery rings with a cyclooxygenase inhibitor flurbiprofen (10 microM), a nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 100 microM), a muscarinic receptor antagonist atropine (100 nM), and by mechanical removal of the endothelium. Involvement of endothelium-independent mechanisms was investigated in endothelium-denuded artery rings pretreated with a beta-adrenoceptor antagonist propranolol (100 nM), an adenylyl cyclase inhibitor 9-(tetrahydro-2-furanyl)-9H-purine-6-amine (SQ22536, 100 microM), a guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ,10 microM), and a potassium channel inhibitor tetraethylammonium (TEA, 10 mM). Involvement of Ca(2+) channels was investigated in artery rings incubated with Ca(2+)-free buffer and primed with 1 microM 5-HT for 5 min prior to adding CaCl(2) to elicit contraction. RESULTS: Dihydrotanshinone relaxed the 5-HT-precontracted coronary artery rings with an IC50 value of 10.39+/-1.69 microM. None of the above inhibitors or antagonists tested produced a significant change on the vasorelaxant effect of dihydrotanshinone, except ODQ caused a 50% reduction. Pre-incubation of the artery rings for 10 min with dihydrotanshinone (100 microM) abolished the CaCl(2)-induced vasoconstriction. CONCLUSIONS: These findings suggest that inhibition of Ca(2+) influx in the vascular smooth muscle cells is important for the vasorelaxant effect of dihydrotanshinone, and it is independent of pathways involving the endothelium, muscarinic receptors, beta-adrenoceptors, adenylyl cyclase, and guanylyl cyclase.

Mechanisms of the dilator action of cryptotanshinone on rat coronary artery.

In this study, we have investigated the actions of cryptotanshinone, an active, lipophilic component of the medicinal herb danshen (Salvia miltiorrhiza), on rat isolated coronary artery rings precontracted with 1 microM 5-hydroxytryptamine (5-HT) and its action compared to the ethanol-extractable fraction of the herb. Extraction of the ethanol-soluble fraction from danshen provided a yield of 1%. The amount of cryptotanshinone determined in this ethanol extract was 3.682%, and it was 6 times more potent than the extract in relaxing 5-HT-precontracted coronary artery rings; IC(50) values were 2.65+/-0.15 microg/ml and 15.82+/-1.07 microg/ml, respectively. Involvement of endothelium-dependant mechanisms in their dilator effects were investigated by pretreatment of the artery rings with a cyclooxygenase inhibitor flurbiprofen (10 microM), a nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 100 microM), a muscarinic receptor antagonist atropine (100 nM), and by mechanical removal of the endothelium; none of these procedures produced a significant change on their dilator actions. Involvement of endothelium-independent mechanisms was investigated in endothelium-denuded artery rings pretreated with a beta-adrenoceptor antagonist propranolol (100 nM), an adenylyl cyclase inhibitor 9-(tetrahydro-2-furanyl)-9H-purine-6-amine (SQ22536, 100 microM), a guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 microM), and a potassium channel inhibitor tetraethylammonium (TEA, 100 mM); these also produced no change on their dilator actions. The possible involvement of Ca(2+) channels was investigated in artery rings incubated with Ca(2+)-free buffer and primed with 1 microM 5-HT for 5 min prior to adding CaCl(2) to elicit contraction. The danshen ethanol extract (100 microg/ml) abolished the CaCl(2)-induced vasoconstriction, whereas, cryptotanshinone (30 microg/ml) produced 59% inhibition. These findings suggest their vasorelaxant effects are independent of pathways mediated by the endothelium, muscarinic receptors, beta-adrenoceptors, adenylyl cyclase, and guanylyl cyclase, whereas, inhibition of Ca(2+) influx in the vascular smooth muscle cells is important for their vasodilator actions. The high vasodilator potency and the quantity of salvianolic acid B contained in danshen ethanolic extract suggest it is an important constituent in this medicinal herb.

Salvianolic acid B, an aqueous component of danshen (Salvia miltiorrhiza), relaxes rat coronary artery by inhibition of calcium channels.

In this study, we have investigated the mechanism of action through which salvianolic acid, a constituent of the medicinal herb danshen (Salvia miltiorrhiza), causes relaxation of isolated coronary artery rings precontracted with 1 microM 5-hydroxytryptamine (5-HT). The vasorelaxant effects of salvianolic acid B were also compared with the aqueous extract of danshen. Extraction of the water-soluble fraction from danshen provided a yield of 17.5%. The amount of salvianolic acid B determined in this aqueous extract was 3.9%, and the extract was 6.3 times less potent than salvianolic acid B in relaxing 5-HT-precontracted coronary artery rings; IC(50) values were 930.3+/-133.5 microg/ml and 147.9+/-17.4 microg/ml, respectively. Removal of the endothelium did not significantly affect their vasodilator potencies; IC(50) values were 842.1+/-123.8 mictog/ml and 160.3+/-25.9 microg/ml. On the other hand, a potassium channel inhibitor tetraethylammonium (TEA, 10 mM) shifted their concentration-response curves by 1.7 and 2.9 folds. The possible involvement of Ca(2+) channels was investigated in artery rings incubated with Ca(2+)-free buffer and primed with 1 microM 5-HT or 60 mM KCl for 5 min prior to adding CaCl(2) to elicit contraction. In 5-HT-primed preparations, 2 mg/ml danshen aqueous extract and 0.72 mg/ml salvianolic acid B abolished the CaCl(2)-induced vasoconstriction, whereas, in KCl-primed preparations, 10 mg/ml danshen aqueous extract and 1.44 mg/ml salvianolic acid B produced 90% inhibition. These findings suggest the vasorelaxant effects of danshen aqueous extract and salvianolic acid B were produced by inhibition of Ca(2+) influx in the vascular smooth muscle cells. The opening of K(+) channels had a minor contribution to their effects, but endothelium-dependent mechanisms were not involved. The high vasodilator potency and the quantity of salvianolic acid B contained in danshen aqueous extract suggest it is an important vasodilator constituent in this medicinal herb.