κ-opioid receptor activation protects against myocardial ischemia-reperfusion injury via AMPK/Akt/eNOS signaling activation

This study aims to investigate the effect of κ-opioid receptor activation on myocardial ischemia and reperfusion(I/R) injury and elucidate the underlying mechanisms. Myocardial I/R rat model and simulated I/R cardiomyocytes model were established. In vivo study showed that U50,488 H improved cardiac function, reduced myocardial infarct size and serum cTnT significantly. The effect of U50,488 H was abolished by nor-BNI(a κ-opioid receptor antagonist), Compound C(an AMPK inhibitor), Akt inhibitor and L-NAME(an eNOS inhibitor). AICAR, an AMPK activator, mimicked the effect of U50,488 H. U50,488 H up-regulated p-AMPK, p-Akt, and p-eNOS, which were abolished by nor-BNI. AICAR increased p-Akt and p-eNOS, which was abolished by Compound C. In vitro study showed that U50,488 H increased p-AMPK, p-Akt, and p-eNOS via κ-OR activation. The effect of U50,488 H on p-AMPK was abolished by compound C, but not Akt inhibitor and L-NAME. The effect of U50,488 H on p-Akt was abolished by compound C and Akt inhibitor, but not L-NAME. AICAR increased p-Akt and p-eNOS, which was abolished by Akt inhibitor, but not L-NAME. U50,488 H and AICAR also increased the viability of cardiomyocytes subjected to simulated I/R, the effects of U50,488 H and AICAR were blocked by nor-BNI, Compound C, Akt inhibitor, and L-NAME, respectively. In conclusion, κ-OR activation confers cardioprotection via AMPK/Akt/eNOS signaling.

Anticonvulsant activity of Pseudospondias microcarpa (A. Rich) Engl. hydroethanolic leaf extract in mice: The role of excitatory/inhibitory neurotransmission and nitric oxide pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Pseudospondias microcarpa (A. Rich) Engl. is a plant used for managing various diseases including central nervous system disorders.

AIM OF THE STUDY

This study explored the anticonvulsant activity of P. microcarpa hydroethanolic leaf extract (PME) as well as possible mechanism(s) of action in animal models.

METHODS

Effects of PME was assessed in electroconvulsive (the maximal electroshock and 6-Hz seizures) and chemoconvulsive (pentylenetetrazole-, picrotoxin-, isoniazid-, 4-aminopyridine-, and strychnine-induced seizures) models of epilepsy. In addition, effect of the extract on the nitric oxide pathway and GABA_A receptor complex was evaluated.

RESULTS

The extract (30, 100 and 300mgkg^-1, p.o.) significantly delayed the onset as well as decreased the duration and frequency of pentylenetetrazole-, picrotoxin- and strychnine-induced seizures. In addition, PME pre-treatment significantly improved survival in the 4-aminopyridine- and isoniazid-induced seizure tests. Furthermore, the extract protected against 6-Hz psychomotor seizures but had no effect in the maximal electroshock test. The anticonvulsant effect of PME (100mgkg^-1, p.o.) was also reversed by pre-treatment with flumazenil, L-arginine or sildenafil. However, L-NAME or methylene blue (MB) augmented its effect.

CONCLUSION

Results show that PME has anticonvulsant activity and may probably be affecting GABAergic, glycinergic, NMDA, K⁺ channels and nitric oxide-cGMP pathways to exert its effect.

Vasculoprotective and vasodilatation effects of herbal formula (Sahatsatara) and piperine in spontaneously hypertensive rats

BACKGROUND

The herbal formula (Sahatsatara, STF), the Thai traditional poly-herbal recipe, has been used for treatment of muscle pain, anti-flatulence and numbness on hands and feet, with the caution when used in hypertensive patients. However, there is no scientific evidence to prove its effects on cardiovascular system. Piperine is the proposed major active compound in STF. It is shown to have antihypertensive effect in the L-NAME-induced endothelial dysfunction rats.

PURPOSE

This study investigated the pharmacokinetics, mechanism of action, as well as the hemodynamic and vasoactive effect and toxicity of STF and piperine using spontaneously hypertensive rats (SHR) and normal Wistar rats (NWR).

METHODS

The amount of piperine in STF was measured by ultra performance liquid chromatography (UPLC). SHR and NWR were gavaged with piperine (50mg/kg/day) or STF (100, 300, or 1000mg/kg/day) alone or together with L-NAME (in drinking water) for 28 days. Hemodynamic effects were monitored by noninvasive tail cuff every 7 days. Vasorelaxation effect on the thoracic aorta in organ chamber was observed through force transducer at the end of the experiment. Biochemical parameters for kidney and liver toxicity were measured. In addition, pharmacokinetic study was performed using non-compartment analysis.

RESULTS

The amount of piperine in STF was 1.29%w/w. Both STF and piperine did not affect blood pressure and heart rate in both SHR and NWR. Interestingly, STF and piperine increased acetylcholine-induced vasorelaxation of isolated thoracic aorta and have vascoluprotective effect in nitric oxide (NO) impaired rats. No liver or kidney toxicity was found in this study. Non-compartment pharmacokinetic analysis showed that the time to reach maximum concentration (T_max) of plasma piperine after administration of piperine and STF were 3.9 and 1.7h, respectively. This result suggested that piperine in the recipe had better absorption than the pure standard piperine.

CONCLUSIONS

STF had no effect on blood pressure in both SHR and NWR. However, it was able to relax isolated thoracic aorta and had the potential for vasculoprotective effect in hypertensive and NO impaired condition. The effects of STF were comparable to those of piperine.

Sex differences in the role of NADPH oxidases in endothelium-dependent vasorelaxation in porcine isolated coronary arteries

The present study examined whether vascular function, expression and activity of NADPH oxidases differ between sexes in porcine isolated coronary arteries (PCAs) using selective Nox inhibitors, ML-171 and VAS2870. Vascular responses of distal PCAs were examined under myographic conditions in the presence of a range of inhibitors. Nox activity in PCA homogenates was assessed using lucigenin-enhanced chemiluminescence. Protein expression of Nox1, Nox2 and Nox4 was compared using Western immunoblotting. The presence of ML-171 or DPI had no effect on the bradykinin-induced vasorelaxation in PCAs from females. In males, DPI shifted the EC50 2.8-fold to the right. In the presence of L-NAME and indomethacin, DPI and ML-171 had no effect in females, but enhanced the bradykinin-induced vasorelaxation in males. ML-171 had no effect on the forskolin-induced vasorelaxation but decreased the potency of U46619-induced tone in both sexes in the absence or presence of endothelium. VAS2870 had no effect on the bradykinin-induced vasorelaxation in both sexes but reduces the EDH-type response in males only. Nox activity was reduced by DPI and ML-171, but not VAS2870 in PCAs from both sexes. Protein expression of Nox1 and Nox2 in PCAs was higher in males compared to females whereas Nox4 was higher in females. Inhibition of Nox with ML-171 enhances while VAS2870 reduces the EDH-type response in PCAs from males but not females. This indicates that Nox-generated ROS play a role in the EDH-type response in males with differences attributed to the differential expression of Nox isoforms. This may underlie the greater oxidative stress observed in males.

Huperzia saururus Lam. Trevis. (Lycopodiaceae) facilitates ejaculation in spinal cord transected male rats

ETHNOPHARMACOLOGICAL RELEVANCE

Huperzia saururus (Lam.) Trevis. has an extensive ethnopharmacological use, mainly because of its aphrodisiac properties. The species is consumed as decoctions or infusions in traditional medicine. The purpose of the present research was to determine if Huperzia saururus is able to increase sexual potency by evaluating the ejaculatory response, in the presence of a decoction in spinal cord transected male rats.

MATERIALS AND METHODS

The fictive ejaculation model to record the rhythmic contractions of the bulbospongiosus muscles that accompany ejaculation as an indicator of ejaculation occurrence was used. Sexually experienced male Wistar rats were used. The activation of the fictive ejaculation by the i.v. administration of a decoction was tested, as well as the effects of the oxytocinergic, cholinergic, adrenergic and nitrergic antagonism upon the pro-ejaculatory activity of Huperzia saururus.

RESULTS

Decoction (3µg/animal) was able to activate the fictive ejaculation in spinal male rats, producing a statistically significant diminution on the latency of discharge parameter and a statistically significant augment for the number of discharges. Moreover, when sequential treatments using antagonists plus decoction were administered, the effects produced showed that prazosin prevent the pro-ejaculatory effect of the decoction and that the four antagonists assayed blocked the facilitatory effect of Huperzia saururus since the facilitation in the latency of response was prevented, and the number of discharges was reduced. Together these findings support the notion that the decoction exerts an aphrodisiac effect influencing the ejaculatory potency which is partially mediated by oxytocinergic, cholinergic, adrenergic and nitrergic spinal mechanisms.

CONCLUSION

In agreement to the ethnopharmacological uses, Huperzia saururus decoction has aphrodisiac properties by influence on the ejaculatory potency.