Endothelin A receptors mediate relaxation of guinea pig internal anal sphincter through cGMP pathway

Estradiol mediates relaxation of porcine lower esophageal sphincter

Most pregnant women have symptoms of gastroesophageal reflux disease (GERD) during pregnancy. Postmenopausal hormone replacement therapy is associated with GERD. The effects of estradiol on lower esophageal sphincter (LES) motility and GERD are not clearly known. The purpose of this study is to investigate the effects of estradiol on the motility of the porcine LES. Relaxations of clasp and sling strips of porcine LES caused by estradiol were measured using isometric transducers. We investigated the mechanism of estradiol-induced relaxation of the porcine LES using tetraethylammonium, apamine, iberiotoxin, glibenclamide, KT5720, KT5823, NG-nitro-l-arginine, tetrodotoxin, and ω-conotoxin GVIA. Reverse transcription polymerase chain reaction (PCR) analysis and immunohistochemistry (IHC) were performed to determine the existence of the G protein-coupled estrogen receptor (GPER) in the porcine LES. In endothelin-1-precontracted porcine LES strips, estradiol caused marked relaxations in a concentration-dependent manner. The mechanism of estradiol-induced relaxation on the porcine LES was associated with the potassium channel. Reverse transcription PCR analysis and IHC revealed that GPER was expressed in the sling and clasp fibers of the porcine LES. This finding suggests that GPER mediates the relaxation of the porcine LES. Estradiol may play a role in LES motility.

Mechanism of resveratrol-induced relaxation of the guinea pig fundus

BACKGROUND

Resveratrol is a polyphenolic compound that can be isolated from plants and also is a constituent of red wine. Resveratrol induces relaxation of vascular smooth muscle and may prevent cardiovascular diseases.

PURPOSE

Impaired gastric accommodation plays an important role in functional dyspepsia and fundic relaxation and is a therapeutic target of functional dyspepsia. Although drugs for fundic relaxation have been developed, these types of drugs are still rare. The purpose of this study was to investigate the relaxant effects of resveratrol in the guinea pig fundus.

STUDY DESIGN

We studied the relaxant effects of resveratrol in the guinea pig fundus. In addition, we investigated the mechanism of resveratrol-induced relaxation on the guinea pig fundus by using tetraethylammonium (a non-selective potassium channel blocker), apamine (a selective inhibitor of the small conductance calcium-activated potassium channel), iberiotoxin (an inhibitor of large conductance calcium-activated potassium channels), glibenclamide (an ATP-sensitive potassium channel blocker), KT 5720 (a cAMP-dependent protein kinase A inhibitor), KT 5823 (a cGMP-dependent protein kinase G inhibitor), NG-nitro-L-arginine (a competitive inhibitor of nitric oxide synthase), tetrodotoxin (a selective neuronal Na⁺ channel blocker), ω-conotoxin GVIA (a selective neuronal Ca²⁺ channel blocker) and G-15 (a G-protein coupled estrogen receptor antagonist).

RESULTS

The results of this study showed that resveratrol has potent and dose-dependent relaxant effects on the guinea pig fundic muscle. In addition, the results showed that resveratrol-induced relaxation of the guinea pig fundus occurs through nitric oxide and ATP-sensitive potassium channels.

CONCLUSION

This study provides the first evidence concerning the relaxant effects of resveratrol in the guinea pig fundic muscle strips. Furthermore, resveratrol may be a potential drug to relieve gastrointestinal dyspepsia.

Mechanism of resveratrol-induced relaxation in the human gallbladder

BACKGROUND

Resveratrol is a polyphenolic compound extracted from plants and is also a constituent of red wine. Resveratrol produces relaxation of vascular smooth muscle and may prevent cardiovascular diseases. Although resveratrol has been reported to cause relaxation of the guinea pig gallbladder, limited data are available about the effect of resveratrol on the gallbladder smooth muscle in humans. The purpose of this study was to investigate the relaxation effects of resveratrol in human gallbladder muscle strips.

METHODS

We studied the relaxant effects of resveratrol in human gallbladder. In addition, we also investigated mechanism of resveratrol-induced relaxation in human gallbladder by tetraethylammonium (a non-selective potassium channels blocker), iberiotoxin (an inhibitor of large conductance calcium-activated potassium channel), glibenclamide (an ATP-sensitive potassium channel blocker), charybdotoxin (an inhibitor of large conductance calcium-activated potassium channels and slowly inactivating voltage-gated potassium channels), apamine (a selective inhibitor of the small conductance calcium-activated potassium channel), KT 5720 (a cAMP-dependent protein kinase A inhibitor), KT 5823 (a cGMP-dependent protein kinase G inhibitor), NG-Nitro-L-arginine (a competitive inhibitor of nitric oxide synthase), tetrodotoxin (a selective neuronal Na⁺ channel blocker), and ω-conotoxin GVIA (a selective neuronal Ca²⁺ channel blocker).

RESULTS

The present study showed that resveratrol has relaxant effects in human gallbladder muscle strips. In addition, we found that resveratrol-induced relaxation in human gallbladder is associated with nitric oxide, ATP-sensitive potassium channel, and large conductance calcium-activated potassium channel pathways.

CONCLUSIONS

This study provides the first evidence concerning the relaxant effects of resveratrol in human gallbladder muscle strips. Furthermore, these results demonstrate that resveratrol is a potential new drug or health supplement in the treatment of biliary colic.

Delonix regia Leaf Extract (DRLE): A Potential Therapeutic Agent for Cardioprotection

Delonix regia (Boj. Ex. Hook) is a flowering plant in the pea family found in tropical areas and its leaves are used informally to treat diseases in folk medicine. However, the cardioprotective effects in this plant are still unclear. In this study, we found that the Delonix regia leaf extract (DRLE) (400 mg/kg/d) can reduce the mortality rate in an isoproterenol (ISO)-induced heart injury and hypertrophy mouse model. Decreased serum levels of creatine phosphokinase, LDH, GOT, TNF-alpha and increased nitric oxide levels were found in DRLE-treated ISO-injured mice. In the in vitro study, the porcine coronary artery exhibited vasodilation effect induced by DRLE in a dose-dependent manner. In the DRLE toxic test, overdose of DRLE showed the high safety in normal mice and may have the ability to remove the metabolic wastes in blood. In conclusion, we demonstrated for the first time that DRLE has the cardioprotective effects by activating the vasodilation through NO pathway and preventing the myocyte injury via inhibition of TNF-alpha pathway. We suggest that DRLE may act as a promising novel herbal medicine for cardioprotection.

Proteinase-activated receptor-1 (PAR1) and PAR2 mediate relaxation of guinea pig internal anal sphincter

Activation of proteinase-activated receptor-1 (PAR1) and PAR2 stimulates contraction of the rat but relaxation of the guinea pig colon. The aim of the present study was to investigate PAR effects on internal anal sphincter (IAS) motility. We measured relaxation of isolated muscle strips from the guinea pig IAS caused by PAR agonists using isometric transducers. Reverse transcription polymerase chain reaction (RT-PCR) was performed to determine the existence of PAR. In the IAS, thrombin and PAR1 peptide agonists TFLLR-NH2 and SFLLRN-NH2 evoked moderate to marked relaxation in a concentration-dependent manner. In addition, trypsin and PAR2 peptide agonists 2-furoyl-LIGRLO-NH2, SLIGRL-NH2 and SLIGKV-NH2 produced relaxation. In contrast, both PAR1 and PAR2 inactive control peptides did not elicit relaxation. Furthermore, the selective PAR1 antagonist vorapaxar and PAR2 antagonist GB 83 specifically inhibited thrombin and trypsin-induced relaxations, respectively. RT-PCR revealed the presence of PAR1 and PAR2 in the IAS. This indicates that PAR1 and PAR2 mediate the IAS relaxation. The relaxant responses of TFLLR-NH2 and trypsin were attenuated by N(omega)-Nitro-L-arginine (L-NNA), indicating involvement of NO. These responses were not affected by tetrodotoxin, implying that the PAR effects are not neurally mediated. On the other hand, PAR4 agonists GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2 did not cause relaxation or contraction, suggesting that PAR4 is not involved in the sphincter motility. Taken together, these results demonstrate that both PAR1 and PAR2 mediate relaxation of the guinea pig IAS through the NO pathway. PAR1 and PAR2 may regulate IAS tone and might be potential therapeutic targets for anal motility disorders.

The effect of topical anal captopril on resting anal pressure in healthy volunteers: the first human pilot study

BACKGROUND

Previous laboratory studies have shown that angiotensin II is produced locally in the rat internal anal sphincter causing potent contraction. The aim of this first human study was to evaluate the safety and manometric effects of topical application of captopril (an ACE inhibitor) on the resting anal pressure in healthy adult volunteers.

METHODS

Ten volunteers, mean age 32.5 years (range, 19-48 years), underwent anorectal manometric evaluation of the mean anal resting pressure (MRAP) and the length of the high-pressure zone (HPZ) before 20 and 60 min after topical application of captopril (0.28 %) cream. Cardiovascular variables (systolic blood pressure, diastolic blood pressure and pulse) were measured before and for up to 1 h after cream application. Side effects were recorded. Adverse events and patient comfort after the cream application were evaluated within a 24-h period by completing a questionnaire.

RESULTS

There was no significant change overall in MRAP following captopril administration, although in half the patients, there were reductions in MRAP after treatment. Half the patients had a reduction in the mean resting HPZ length; however, there was no overall difference between pre- and post-treatment values. There was no effect on basic cardiovascular parameters and no correlation between manometric and cardiovascular variables.

CONCLUSIONS

Topical application of captopril cream may result in a reduction in MRAP in volunteers without anorectal disease. Its use is associated with minimal side effects. It may be a new potential therapeutic option in the treatment of anal fissure. Further studies are required to determine the optimal concentration, dose and frequency of application.