ATP-sensitive Potassium Channel Blocker Research Articles

Ivermectin Exerts Anticonvulsant Effects Against Status Epilepticus Induced by Lithium-Pilocarpine in Rats via GABAA Receptor and Neuroinflammation Modulation: Possible Interaction of Opioidergic Pathways and KATP Channel with Nitrergic System.

Status epilepticus (SE) is a critical medical emergency marked by persistent or rapidly repeating seizures, posing a threat to life. Using the lithium-pilocarpine-induced SE model, we decide to evaluate the anti-seizure effects of ivermectin as a positive allosteric modulator of GABAA receptor and the underlying mechanisms involved. Lithium chloride was injected intraperitoneally at a dose of 127 mg/kg, followed by the administration of pilocarpine at a dose of 60 mg/kg after a 20-h interval in order to induce SE. Subsequently, the rats received varying amounts of ivermectin (0.3, 1, 3, 5, and 10 mg/kg, i.p.) 30 min before the onset of SE. To study the underlying molecular mechanisms, we had pharmacological interventions of diazepam (1 mg/kg), glibenclamide and nicorandil as ATP-sensitive potassium channel blocker and opener (both 1 mg/kg, i.p.), naltrexone and morphine, as opioid receptor antagonist and agonist (1 mg/kg and 0.5 mg/kg, i.p., respectively). In addition, three nitric oxide inhibitors, namely, L-NAME (10 mg/kg, i.p.), 7-NI (30 mg/kg, i.p.), and aminoguanidine (100 mg/kg, i.p.), were administered to the rats in the experiment. Finally, we use ELISA and western blotting, respectively, to examine the amounts of pro-inflammatory cytokines (TNF-α and IL-1β), nitrite, and GABAA receptors in the rat hippocampal tissue. The study found that ivermectin, at doses of 3, 5, and 10 mg/kg, exerts anti-seizure effects and decrease Racine's scale SE score. Interestingly glibenclamide and naltrexone reduced the anti-seizure effects of ivermectin, and from other hand diazepam, nicorandil, morphine, L-NAME, 7-NI, and aminoguanidine, enhance the effects when co-administrated with subeffective dose of ivermectin. Additionally, the study found that ivermectin decreased the elevated levels of TNF-α and IL-1β following SE, while increased the reduced expression of GABAA receptors. Overall, these findings suggest that ivermectin has anti-seizure effects in a SE seizure which may be mediated by the modulation of GABAergic, opioidergic, and nitrergic pathways and KATP channels.

Participation of the cannabinoid system and the NO/cGMP/KATP pathway in serotonin-induced peripheral antinociception

It has already been shown that serotonin can release endocannabinoids at the spinal cord level, culminating in inhibition of the dorsal horn. At the peripheral level, cannabinoid receptors modulate primary afferent neurons by inhibiting calcium conductance and increasing potassium conductance. Studies have shown that after the activation of opioid receptors and cannabinoids, there is also the activation of the NO/cGMP/KATP pathway, inducing cellular hyperpolarization. In this study, we evaluated the participation of the cannabinoid system with subsequent activation of the NO/cGMP/KATP pathway in the peripheral antinociceptive effect of serotonin. The paw pressure test of mice was used in animals that had their sensitivity to pain increased due to an intraplantar injection of PGE2 (2 μg). Serotonin (250 ng/paw), administered locally in the right hind paw, induced antinociceptive effect. CB1 and CB2 cannabinoid receptors antagonists, AM251 (20, 40 and 80 μg) and AM630 (25, 50 and 100 μg), respectively, reversed the serotonin-induced antinociceptive effect. MAFP (0.5 μg), an inhibitor of the FAAH enzyme that degrades anandamide, and JZL184 (3.75 μg), an inhibitor of the enzyme MAGL that degrades 2-AG, as well as the VDM11 (2.5 μg) inhibitor of anandamide reuptake, potentiated the antinociceptive effect induced by a low dose (62. 5 ng) of serotonin. In the evaluation of the participation of the NO/cGMP/KATP pathway, the antinociceptive effect of serotonin was reversed by the administration of the non-selective inhibitor of NOS isoforms L-NOarg (12.5, 25 and 50 μg) and by the selective inhibitor for the neuronal isoform LNPA (24 μg), as well as by the soluble guanylate cyclase inhibitor ODQ (25, 50 and 100 μg). Among potassium channel blockers, only Glibenclamide (20, 40 and 80 μg), an ATP-sensitive potassium channel blocker, reversed the effect of serotonin. In addition, intraplantar administration of serotonin (250 ng) was shown to induce a significant increase in nitrite levels in the homogenate of the plantar surface of the paw of mice. Taken together, these data suggest that the antinociceptive effect of serotonin occurs by activation of the cannabinoid system with subsequent activation of the NO/cGMP/KATP pathway.

The nitric oxide-cyclic GMP-KATP channels pathway contributes to the effects of montelukast against gastric damage induced by ethanol

The leukotrienes, lipid mediators, have a role in gastric damage induced by ethanol. Here, the gastroprotective effect of montelukast, an antagonist of the leukotriene receptor, and the involvement of the NO-cGMP-KATP channel pathway, were evaluated in gastric damage induced by ethanol in rats. For this, l-arginine, l-NAME, methylene blue (guanylate cyclase inhibitor), sildenafil, diazoxide, or glibenclamide (ATP-sensitive potassium channel blocker) were administered 30 min before montelukast (0.1, 1, 10, and 20 mg/kg, by mouth [p.o.]). After 1 h, to induce gastric damage, the rats received absolute ethanol (4 mL/kg, p.o.), and then microscopic, macroscopic, and pro-inflammatory parameters (TNF-α and IL-1β) were assessed. Results obtained here revealed that montelukast significantly attenuated the macroscopic and microscopic lesions induced by ethanol. Montelukast also reduced IL-1β and TNF-α levels. It was also observed that NOS inhibitor (l-NAME), methylene blue, and glibenclamide inhibited the effects of montelukast in the stomach. Moreover, the NO precursor (l-arginine), the PDE-5 inhibitor (sildenafil), and a potassium channel opener (diazoxide) before montelukast produced gastroprotective effects. In conclusion, the effect of montelukast against gastric lesions induced by ethanol is mediated, at least in part, through the pathway of the NO-cGMP-KATP channel.

The role of L-arginine/NO/cGMP/KATP channel pathway in the local antinociceptive effect of berberine in the rat formalin test.

Berberine is an isoquinoline alkaloid naturally produced by several types of plants. Berberine has extensive pharmacological effects, such as anti-diabetic, anti-inflammatory, and antioxidant effects. In the current study, we assess the antinociceptive effects of berberine and its association with the l-arginine (l-Arg)/NO/cGMP/KATP channel pathway via intraplantar administration in rats. To examine the antinociceptive properties of berberine, the formalin test was conducted. The number of rat paw flinches was counted for an h. l-Arg (precursor of nitric oxide, 3-30 μg/paw), l-NAME (NO synthase inhibitor, 10 and 100 μg/paw), methylene blue (guanylyl cyclase inhibitor, 100 and 200 μg/paw), and glibenclamide (ATP-sensitive potassium channel blocker, 10 and 30 μg/paw) were locally injected, respectively, into the right hind paws of rats as a pre-treatment before berberine injection to understand how the l-Arg/NO/cGMP/KATP pathway plays a role in the antinociceptive effect of berberine. The ipsilateral injection of berberine into the right paw (0.1-100 μg/paw) showed a dose-dependent antinociceptive effect in both the first and second phases of the formalin test, almost similar to morphine (25 μg/paw). Intraplantar injection of l-Arg (30 µg/paw) increased the antinociceptive effect of berberine in the second phase. In addition, injection of l-NAME, methylene blue, and glibenclamide caused a reduction in the antinociceptive effect of berberine throughout the second phase in a dose-dependent manner. However, the antinociceptive effects of berberine in the first phase of the rat formalin test were not affected by this pathway. As a novel local antinociceptive agent, berberine can exert a peripheral antinociceptive effect via the l-Arg/NO/cGMP/KATP channel pathway.

PS-BPB03-2: VASORELAXANT-MEDIATED ANTIHYPERTENSIVE EFFECT OF THE SEED AQUEOUS EXTRACT OF AFRAMOMUM PRUINOSUM GAGNEP. (ZINGIBERACEAE)

Objective: Despite the existing therapies, arterial hypertension is still a prevalent and a worldwide major public health concern, prompting the search for new therapeutic alternatives. The present study investigated the antihypertensive and the related mechanisms of action of the seed aqueous extract of Aframomum pruinosum (AEAP), a plant used in Cameroon traditional medicine against cardiovascular ailments. Design and method: Male Wistar rats were rendered hypertensive by chronic oral administration of L-NAME (30 mg/kg/day) for three consecutive weeks, and hypertensive rats were selected and treated with L-NAME alone or in combination with AEAP at doses of 75 or 150 mg/kg/day for an additional 3 consecutive weeks. Captopril (25 mg/kg/day, p.o) was used as reference drug. Blood pressure and heart rate were monitored weekly. At the end of the experiment, the heart was harvested, weighed, and sections of cardiac tissue were stained with hematoxylin and eosin for histological analysis. Cumulative concentrations of the aqueous extract (3, 10, 30, 100, and 300 μg/mL) were tested on intact or endothelium-denuded aorta rings precontracted with norepinephrine (NE; 1 μM) or KCl (90 mM) in absence or presence of L-NAME (a nitric oxide synthase inhibitor, 100 μM), indomethacin (a prostaglandin synthesis inhibitor; 10 μM), methylene blue (a guanylate cyclase inhibitor, 1 μM), tetraethylammonium (TEA; a non-specific potassium channel blocker; 5 μM) or glibenclamide (an ATP-sensitive potassium channel blocker; 10 μM). The contractile response to NE, or CaCl2 was also assessed in the presence or absence of the plant extract. Results: AEAP completely reversed (p < 0.001) L-NAME-induced elevated systolic and diastolic blood pressure, and increased heart rate. AEAP partially reversed cardiac hypertrophy, leucocyte infiltration, and prevent cardiac necrosis. AEAP induced a concentration-dependent vasorelaxant effect on NE- and KCl-evoked contraction with EC50 values of 13.46 and 49.37 μg/mL, respectively. Removal of the endothelium and the preincubation of aorta rings with L-NAME significantly (p < 0.05) reduced the vasorelaxant effect of the plant extract, while indomethacin and methylene blue had no effect (p > 0.05). Glibenclamide, similar to TEA, significantly (p < 0.001) inhibited the vasorelaxant response to AEAP. Also, the extract significantly (p < 0.01 and p < 0.001) inhibited NE- and CaCl2-induced contraction. Conclusion: AEAP possesses antihypertensive effects that are at least partially mediated by its vasorelaxant activity. Nitric oxide release, opening of KATP channels, blockade of alpha-1 receptors, and inhibition of Ca2+ influx account for this vasorelaxant activity.

The effect of montelukast, a leukotriene receptor antagonist, on the acetic acid-induced model of colitis in rats: Involvement of NO-cGMP-KATP channels pathway.

Inflammatory bowel disease is a chronic autoimmune disorder that may involve entire gastrointestinal tract. The leukotrienes have a role as mediators in the pathophysiology of colitis. Here, we investigated the effect of a leukotriene receptor antagonist, montelukast, and also the role of the NO-cGMP-KATP channel pathway in acetic acid-induced colitis. Rectal administration of acetic acid (4%) was used for induction of colitis in rats. To investigate our hypothesis, the rats were intraperitoneally pre-treated with L-NAME (NOS inhibitor), L-arginine, sildenafil, methylene blue, glibenclamide, or diazoxide 15 min before treatment with montelukast (5–20 mg/kg, i. p.), for three consecutive days. Then, microscopic, macroscopic, and inflammatory parameters were evaluated. Montelukast reduced the microscopic and macroscopic damage induced by acetic acid. Montelukast also reduced the level of IL-1β and TNF-α. We also showed that the effects of montelukast were significantly attenuated by L-NAME, methylene blue (guanylate cyclase inhibitor), and an ATP-sensitive potassium channel blocker (glibenclamide). Also, the administration of L-arginine, sildenafil, and diazoxide before montelukast produced protective effect. In conclusion, the pathway of the NO-cGMP-KATP channel is involved in the protective effect of montelukast in acetic acid-induced colonic tissue damage.

The effects of ATP sensitive potassium channel (KATP) opener and blockers on Bcl-2, Bax, and Cyt-c gene expression levels in epileptic rats

In this study, it was aimed to investigate the gene expression levels of Bcl-2, Bax, and cytochrome c (Cyt-c), in the cortex region of pinacidil as a KATP channel opener and glibenclamide as a blocker on penicillin model epilepsy. Male Wistar-Albino rats were used. A total of 4 main groups were formed: Control, Epilepsy, Epilepsy-opener, and Epilepsy-blocker groups, then three-time points were formed subgroups (1st day, 4th, and 8th). 48 rats were used in total. The epileptic focus was created by intracortical administration of penicillin at a dose of 500 IU/2 μl. Cortex is removed from all animals and cyt c, Bcl-2, and Bax gene expression levels were determined by qPCR. The SPSS 21 program was used for statistics. Bcl-2 and Bax gene expression levels were increased in the cortex regions of rats with epilepsy (p<0.05). Bcl-2, Bax gene expression levels, which increased due to epilepsy with the effect of KATP channels opened with pinacidil, returned to normal levels in the epilepsy opener group (p<0.05). Bcl-2 gene expression level, which was increased as a result of epilepsy due to the effect of KATP channels closed with glibenclamide, was higher than in the control and epilepsy-opener groups (p<0.05). Bcl-2 and Bax gene expression levels are increased in the cortex region due to epilepsy indicates that the apoptotic pathway could be activated. This study also It has been shown that the apoptotic pathway activated by epilepsy can be inactivated by pinacidil.

The role of potassium channels in the proliferation and migration of endometrial adenocarcinoma HEC1-A cells.

Endometrial cancer is the most common gynecological cancer in developed countries. Potassium channels, which have many types, are suggested to play a major role in cancer progression. However, their role in endometrial cancer has not been fully investigated. We aimed to demonstrate whether the ATP-sensitive potassium channel blocker glibenclamide, voltage-sensitive potassium channel blocker 4-aminopyridine, non-selective (voltage-sensitive and calcium-activated) potassium channels blocker tetraethylammonium and potassium chloride (KCl) have any effect on the proliferation and migration of HEC1-A cells. Proliferation and migration were evaluated by real-time cell analysis (xCELLigence system) and wound healing assays, respectively. Proliferation was reduced by glibenclamide (0.1 and 0.2mM, P < 0.05 and P < 0.01, respectively), 4-aminopyridine (10 and 20mM, P < 0.001) and tetraethylammonium (10 and 20mM, P < 0.01 and P < 0.001, respectively). However, KCl did not change the proliferation. Migration was reduced by glibenclamide (0.01, 0.1 and 0.2mM, P < 0.001, P < 0.001 and P < 0.01, respectively) and 4-aminopyridine (10 and 20mM, P < 0.05 and P < 0.01, respectively). Tetraethylammonium did not change migration. However, KCl reduced it (10, 25 and 50mM, P < 0.05, P < 0.01 and P < 0.01, respectively). Both proliferation and migration were reduced by glibenclamide and 4-aminopyridine. However, tetraethylammonium only reduced proliferation and KCl only reduced migration. Potassium channels have an important role in HEC1-A cell proliferation and migration and potassium channel blockers needs to be further investigated for their therapeutic effect in endometrial cancer.

Opioidergic regulation of contractile activity of lymphatic vessels

The aim is to study the effect of endogenous opioid peptides on the contractile activity of lymphatic vessels in the white rat. Materials and methods . Under isometric conditions, the dynamics of spontaneous contractile activity of isolated annular segments of rat lymphatic vessels under the action of endogenous opioid peptides (beta-endorphin and endomorphin-1) was record; possible mechanisms of opiates action were studied. Results . The range of β-endorphin level 1×10 –11 –1×10 –8 M resulted in a decrease of the minute productivity of the lymphatic vessels, by 22%, mainly due to a decreasing of single contractions frequency. In the presence of blockers of voltage-gated and ATP-sensitive potassium channels and blockers of eNOS, the inhibitory effect was not manifest. Endomorphin-1, used in the concentration range of 1×10 –10 –1×10 –8 M, stimulated the contractile activity of the lymphatic vessels by an average of 15 %. The stimulatory effect was not manifest when using endomorphin-1 in the presence of a selective NK1 receptor antagonist. Conclusions . The inhibitory effect of β-endorphin is associated with the activation of voltage-dependent and ATP-sensitive potassium channels, endothelium-(NO)-dependent mechanisms. The action of endomorphin-1, stimulating lymphangionic motility, can be carry out through interaction with NK receptors.

In Vivo and in Vitro Anti-Inflammatory Activities of Extracts of Pandiaka angustifolia (Vahl.) Hepper (Amaranthaceae) Used in Traditional Medicine in Burkina Faso

Background: Pandiaka angustifolia Valh Hepper (Amaranthaceae) whole plant is used in folk Burkinabe’s medicine to treat ailments with an inflammatory component. Previous studies revealed the antioxidant capacity, xanthine oxidase, and lipoxygenase inhibitory activities of the plant, but to the best of our knowledge, its anti-inflammatory activities were not reported before. Therefore, this study was designed to evaluate the anti-inflammatory and analgesic activity of P. Angustifolia hexane and aqueous extracts using in vitro enzymatic methods and in vivo methods and verify the best anti-inflammatory extract implication in KATP pathways. Experiments: acute toxicity of the plant was conducted under OECD 423 guidelines. Phospholipase and cyclooxygenases were pro-inflammatory enzymes used to evaluate in vitro anti-inflammatory effects of plant extracts while carrageenan induced edema method was used to evaluate the anti-edematous activity and acetic acid inducing writhing method to evaluate the non-morphine analgesic effect of herbal mixture. ATP sensitive K+ channel assay was performed in vivo using the glibenclamide as ATP-sensitive potassium channel (KATP) blocker. Results: enzymatic inhibition assays revealed that both hexane and aqueous extracts of P. angustifolia were good inhibitors against sPLA2 activity with IC50 values of 14.23 ± 0. 72 µg/mL and 11.56 ± 0.11 µg/mL, respectively. Aqueous extract presented the best inhibition for COX-1 (IC50 = 24.76 ±0. 51 µg/mL) while hexane extract concentration that inhibit 50% of COX-2 was lesser than those of aqueous extract. P. angustifolia aqueous extract orally administrated to NMRI mice caused no death at the dose of 3000 mg/kg b.w indicating that the plant toxicity is low. While hexane extract was unable to reduce Carrageenan-induced edema, ethanolic extract were significantly active when extract was orally administrated. Non-morphine analgesic activity evaluation revealed that ethanolic extract was more efficient on writhing reduction than hexane extract. Nociception effect of the plant is linked with its effects on K+ ATP sensitive channels. Conclusion: Results indicate that the anti-inflammatory potential of P. angustifolia may be due to its polar phytoconstituents and observed pharmacological activities provide the scientific basis for the medicinal use of the plant in the treatment of ailment associated with inflammation.

Anticontractile Effect of Perivascular Adipose Tissue But Not of Endothelium Is Enhanced by Hydrogen Sulfide Stimulation in Hypertensive Pregnant Rat Aortae.

Perivascular adipose tissue (PVAT) modulates the vascular tone. Hydrogen sulfide (H2S) is synthetized by cystathionine gamma-lyase (CSE) in brown PVAT. Modulation of vascular contractility by H2S is, in part, adenosine triphosphate (ATP)-sensitive potassium channels dependent. However, the role of PVAT-derived H2S in hypertensive pregnancy (HTN-Preg) is unclear. Therefore, we aimed to examine the involvement of H2S in the anticontractile effect of PVAT in aortae from normotensive and hypertensive pregnant rats. To this end, phenylephrine-induced contractions in the presence and absence of PVAT and endothelium in aortae from normotensive pregnant (Norm-Preg) and HTN-Preg rats were investigated. Maternal blood pressure, fetal-placental parameters, angiogenesis-related biomarkers, and H2S levels were also assessed. We found that circulating H2S is elevated in hypertensive pregnancy associated with angiogenic imbalance, fetal and placental growth restrictions, which revealed that there is H2S pathway activation. Moreover, under stimulated H2S formation PVAT, but not endothelium, reduced phenylephrine-induced contractions in aortae from HTN-Preg rats. Also, H2S synthesis inhibitor abolished anticontractile effects of PVAT and endothelium. Furthermore, anticontractile effect of PVAT, but not of endothelium, was eliminated by ATP-sensitive potassium channels blocker. In accordance, increases in H2S levels in PVAT and placenta, but not in aortae without PVAT, were also observed. In conclusion, anticontractile effect of PVAT is lost, at least in part, in HTN-Preg aortae and PVAT effect is ATP-sensitive potassium channels dependent in normotensive and hypertensive pregnant rat aortae. PVAT but not endothelium is responsive to the H2S stimulation in hypertensive pregnant rat aortae, implying a key role for PVAT-derived H2S under endothelial dysfunction.

Effect of KATP channel blocker glibenclamide on levcromakalim-induced headache.

Administration of ATP-sensitive potassium channel opener levcromakalim triggers headache in healthy volunteers and migraine attacks in migraine patients. Here, we investigated the effect of ATP-sensitive potassium channel blocker glibenclamide on levcromakalim-induced headache in healthy volunteers. In a randomized, double-blind, placebo-controlled, three-way cross-over study, 15 healthy volunteers aged 18-40 years were randomly allocated to receive glibenclamide and levcromakalim (day 1), glibenclamide and placebo (day 2), and placebo and placebo (day 3) on three different days separated by at least 1 week. The primary endpoints were the difference in incidence of headache and the difference in area under the curve for headache intensity scores (0-12 hours) between the days. Fifteen healthy volunteers completed the 3 days of the study. More participants (12/15, 80%) developed headache on the glibenclamide-levcromakalim day compared to the glibenclamide-placebo day (5/15, 33%) (p = 0.01; mean difference 47%; 95% confidence interval 18-75%) and compared to the placebo-placebo day (1/15, 7%) (p = 0.001; mean difference 73%; 95% confidence interval 48-99%). We found no difference in headache incidence between glibenclamide-placebo day and placebo-placebo day (p = 0.12; mean difference 27%; 95% confidence interval 1.3-52%). The area under the curve for headache intensity was significantly larger on the glibenclamide-levcromakalim day compared to the glibenclamide-placebo day (p = 0.003); and compared to the placebo-placebo day (p = 0.001). We found no difference in the area under the curve between the glibenclamide-placebo day compared to the placebo-placebo day (p = 0.07). The median time to onset for headache after levcromakalim infusion with glibenclamide pretreatment was delayed (180 min) compared to levcromakalim without pretreatment (30 min) from a previously published study. Glibenclamide administration did not cause headache, and glibenclamide pretreatment did not prevent levcromakalim-induced headache. However, glibenclamide delayed the onset of levcromakalim-induced headache. More selective blockers are needed to further elucidate the role of the ATP-sensitive potassium channel in headache initiation.Trial Registration: ClinicalTrials.gov NCT03886922.

H2S donor GYY4137 ameliorates paclitaxel-induced neuropathic pain in mice

Paclitaxel-induced neuropathic pain (PINP) is a dose-limiting side effect that largely affects the patient’s quality of life and may limit the use of the drug as a chemotherapeutic agent for treating metastatic breast cancer and other solid tumors. Recently, a putative role for the gaseous mediator hydrogen sulfide (H2S) in nociception modulation has been suggested. The aim of the present study was to investigate the potential efficacy of the slow release H2S donor GYY4137 to alleviate and prevent PINP. Female BALB/c mice that were intraperitoneally (i.p.) injected with paclitaxel (2 mg/kg) for 5 consecutive days developed thermal hyperalgesia, cold and mechanical allodynia and had reduced of H2S, generation in the spinal cord and paw skin. Treatment of mice with established thermal hyperalgesia with GYY4137 or the analgesic positive control drug gabapentin produced antihyperalgesic activities. The antihyperalgesic activity of GYY4137 was antagonized by the ATP sensitive potassium channels (KATP channels) blocker glibenclamide. Co-treatment with GYY4137 and paclitaxel prevented the paclitaxel-induced decrease in H2S, generation as well as the paclitaxel-induced thermal hyperalgesia, cold allodynia and mechanical allodynia. GYY4137 enhanced paclitaxel's anti-proliferative effects against the breast cancer cell line MCF-7. The present results suggest that GYY4137 alleviates paclitaxel-induced thermal hyperalgesia, via KATP channels. GYY4137 prevents PINP possibly by blocking the paclitaxel-induced reduction in the generation of H2S, in the tissues, while enhancing the anti-cancer activity of paclitaxel, and therefore warrants further research as a candidate for prevention of PINP in clinical settings.

Gastroprotective effects of N-acylarylhydrazone derivatives on ethanol-induced gastric lesions in mice are dependent on the NO/cGMP/KATP pathway

The gastroprotective effects of N-acylarylhydrazone derivatives on ethanol-induced gastric lesions in mice were investigated with respect to the NO/cGMP/KATP pathway. To investigate our hypothesis, the mice were intraperitoneally pretreated with glibenclamide, L-NAME, or ODQ 30 min before treatment with DMSO, LASSBio-294 (1, 2, and 4 mg/kg, p.o.), LASSBio-897 (0.5, 1, and 2 mg/kg, p.o.), or omeprazole. After 1 h, the mice received absolute ethanol (4 ml/kg) by gavage to induce gastric mucosal lesions, and the microscopic and macroscopic parameters were evaluated. GSH (non-protein sulfhydryl groups) and MDA (malondialdehyde) concentrations, hemoglobin levels, nitric oxide production, myeloperoxidase (MPO) activity, and TNF-α and IL-1β levels were also analyzed in the stomach after absolute ethanol administration. Pretreatment with LASSBio-294 or LASSBio-897 significantly reduced the microscopic and macroscopic lesion area. The compounds restored the GSH, MDA, and hemoglobin levels and reduced MPO activity. Moreover, the compounds significantly reduced nitrate and nitrite concentrations in the stomach samples after ethanol administration. Molecular docking studies revealed that LASSBio-294 and LASSBio-897 interact with active sites of the eNOS (endothelial nitric oxide synthase) enzymes through hydrogen bonds. LASSBio-294 and LASSBio-897 also reduced TNF-α and IL-1β levels. It was observed that a NO synthase inhibitor, an ATP-sensitive potassium channel blocker, and a guanylate cyclase inhibitor significantly reversed the gastroprotective effects of these compounds. Thus, the gastroprotective effect of LASSBio-294 and LASSBio-897 against gastric lesions is mediated through the NO/cGMP cascade, followed by blocking of the KATP channels.

Dexmedetomidine attenuates the induction and reverses the progress of 6-hydroxydopamine- induced parkinsonism; involvement of KATP channels, alpha 2 adrenoceptors and anti-inflammatory mechanisms

BackgroundStudies have shown that dexmedetomidine (DEX), a potent α2-adrenoceptors agonist provides neuroprotection through suppression of inflammatory response. In present study, we examined effect of DEX and its underlying mechanisms on the induction and progress of 6-OHDA- induced Parkinsonism in rat. Material and methodsThe 6-OHDA was injected into the medial forebrain bundle of right hemisphere by stereotaxic surgery and then, behavioral tests carried out within second, fourth, sixth and eighth weeks post-surgery. All treatments were started before the toxin and continued to eight weeks afterwards. Striatal levels of dopamine, TNF-α and IL-6 were measured within the eighth week after the toxin by enzyme-linked immunosorbent assay kits. ResultsDEX at dose of 50 μg/kg attenuated significantly the intensity of 6-OHDA- induced behavioral symptoms in the second week post-surgery. DEX also attenuated remarkably 6-OHDA- induced reduction in striatal dopamine level. These effects were also observed in rats treated by both DEX and yohimbine (YOH), a selective α2-adrenoceptors antagonist but were not observed in rats treated by both of DEX and glibenclamide (Glib), an ATP-sensitive potassium (KATP) channels blocker. DEX also reversed the progressive increase in intensity of the behavioral symptoms and reversed 6-OHDA- induced overproduction of TNF-α and IL-6. These effects were reversed by YOH but not Glib. ConclusionOur findings indicate that DEX attenuates the induction and reverses the progress of 6-OHDA- induced Parkinsonism through activation of KATP channels and α2-adrenoceptors, respectively. Through activation of α2-adrenoceptors, DEX also exerts anti-inflammatory effect which is possibly another mechanism underlying the DEX's antiparkinsonism effect.

Effects of Gasotransmitters on Membrane Elasticity and Microrheology of Erythrocytes

Erythrocytes change their micromechanical properties associated with membrane viscoelasticity when they perform the transport function. There is some evidence that this is due to the influence of signaling molecules, including such gasotransmitters as nitrogen oxide (NO) and hydrogen sulfide (H2S). The aim of this study was to investigate the changes in microrheology of human erythrocytes under the influence of donors and stimulants of endogenous formation of gasotransmitters. The erythrocyte deformability, assessed by the elongation index of erythrocytes (EIE), and aggregation parameters, the indices of aggregation of erythrocytes (IAE), of washed cells were recorded after their incubation with sodium nitroprusside (SNP); sodium hydrosulfide (NaHS), the donor of H2S; 1H-[1,2,4]-oxadiazolo [4,3-a] quinoxalin-l-one (ODQ), an inhibitor of soluble guanylate cyclase; L-arginine and N-nitroarginine methyl ester (L-NAME), a substrate and an inhibitor of NO synthase, respectively; and glibenclamide (GBC ), the blocker of ATP-sensitive potassium channels. In addition, the resealed ghosts of erythrocytes were prepared, incubated with the above compounds, and the change in their deformability was evaluated. EIE increased by 8–11% (p < 0.01) and IAE decreased by 11–26% (p < 0.01) after the incubation of erythrocytes with SNP and NaHS, respectively. L-arginine and SNP exerted similar microrheological effects, which were eliminated by L-NAME or ODQ. GBC caused an increase in EIE by 8% (p < 0.05); the effects of GBC and NaHS were not additive. Incubation of the erythrocyte ghosts with SNP, L-arginine and NaHS was accompanied by a moderate but significant increase in membrane elasticity (p < 0.05). The obtained results indicate that the donors and stimulators of gasotransmitters NO and H2S moderately increase deformability of erythrocytes and markedly reduce their aggregability. The experiments on the erythrocyte ghosts suggest the existence of a direct effect of gasotransmitters on the viscoelastic properties of the membrane of these cells, which is independent of cGMP.

Cochlospermum regium (Mart. ex Schrank) Pilg.: Evaluation of chemical profile, gastroprotective activity and mechanism of action of hydroethanolic extract of its xylopodium in acute and chronic experimental models

Ethnopharmacological relevanceCochlospermum regium (Bixaceae) is a native shrub of Brazil and its xylopodium (infusion/decoction) is being used for the treatment of gastritis, ulcers, arthritis, intestinal infections, gynaecological infections, skin diseases, among others. The aim of the present study was to evaluate the gastroprotective/antiulcer activity and the mechanism of action of hydroethanolic extract of C. regium xylopodium (HECr), using in vitro and in vivo models. Additionally, phytochemical constituents were identified by high-performance liquid chromatography (HPLC). Materials and methodsC. regium xylopodium was macerated with ethanol/water to obtain the HECr. The phytochemical characterisation was carried out by HPLC. The antiulcer efficacy of HECr (25, 100 and 400 mg/kg, p.o.) was evaluated using acute acidified ethanol (HCl/EtOH), piroxicam and water immersion-induced experimental ulcer models. Chronic gastric ulcer healing activity of HECr was evaluated through acetic acid (99.8%) – induced model. Histological analysis and myeloperoxidase (MPO), glutathione (GSH), catalase (CAT) activities were also evaluated in chronic ulcer induced gastric tissues. The plausible mode of action of the HECr was assessed by estimation of gastric wall mucus production and the role of gastric secretion in pylorus ligature. The animals were also pre-treated with various inhibitors which includes indomethacin (10 mg/kg, p.o.) a selective inhibitor of cyclooxygenase, L-NAME (10 mg/kg, i.p.), an inhibitor of nitric oxide synthase, glibenclamide, a ATP-sensitive potassium channels (K+ATP) blocker (5 mg/kg, p.o.) or yohimbine (2 mg/kg, i.p.), an α2-adrenergic receptor antagonist. In vitro, Helicobacter pylori action was done by broth microdilution method. ResultsThe HPLC analysis data revealed the presence of gallic acid, rutin, myricetin, morin and kaempferol. HECr promoted protective effect against acute ulcers induced by HCl/EtOH with inhibitions of 47.52% (p < 0.01) and 62.69% (p < 0.001) at 100 and 400 mg/kg, and in piroxicam by 34.11% (p < 0.05), 49.14% (p < 0.01) and 61.34% (p < 0.001), at 25, 100 or 400 mg/kg, respectively, and in water restraint stress by 78.26% inhibition, p < 0.001, at the dose of 400 mg/kg when compared to the vehicle control group respectively. In the chronic gastric ulcer model, HECr (25, 100 and 400 mg/kg p.o.) significantly (p < 0.001) decreased the injured area by 58.80%, 77.87% and 71.10% respectively. Histological examination indicated that oral treatment of HECr promoted healing of gastric lesions by regenerating gastric mucosa layer with less inflammatory cells. HECr augmented the GSH, CAT activities and reduced MPO level. The pre-treatment with HECr increased the gastric wall mucus production. It also significantly altered the gastric secretion parameters by causing the reduction in the gastric juice volume, elevated the pH level and reduced the total acidity at all doses tested when compared with the vehicle group. HECr at the most active dose (100 mg/kg) reversed completely the reduction of PGs, NO production, closure of K+ATP- channels and α2-adrenoreceptor blockage – induced damages. In microdilution assay, the HECr showed good anti-Helicobacter pylori effect with MIC = 100 µg/mL. ConclusionThe HECr presented preventive and curative effects in the experimental gastric ulcer models, besides good anti-Helicobacter pylori activity, which supports the traditional medicinal use of the xylopodium of this plant for gastrointestinal diseases. The underlying mechanisms of this antiulcerogenic/antiulcer action involve, at least, augmentation of mucus production, inhibition of gastric secretion, stimulation of PGs and NO synthesis. And that it involves activation of K+ATP channels and α-2-adrenergic receptors, in addition to an antioxidant activity, probably due to the presence of gallic acid and flavonoids in HECr.

Airway smooth muscle relaxant activity of Cordia dodecandra A. DC. mainly by cAMP increase and calcium channel blockade

Ethnopharmacological relevanceThe fight against chronic respiratory diseases needs the exploration of new active compounds with properties that contribute to diminish the symptoms or resolve the disease alongside current therapy. Materials and methodsEight extracts obtained from the bark and leaves of a Mayan medicinal plant used to treat asthma, Cordia dodecandra A. DC., were investigated for their relaxant effect on rat isolated tracheal rings pre-contracted with carbachol [1 µM]. The underlying functional mode of action of the most effective extract was assessed and the chromatographic fingerprints of more active extracts were analyzed. ResultsThe dichloromethane bark extract (DECd-b) was the most effective and potent (Emax= 87.57 ± 1.32 %; EC50 = 392.7 ± 5.18 µg/mL). DECd-b relaxant effect was maximized in presence of isoproterenol (β-adrenergic agonist, [10 µM]) and theophylline (phosphodiesterase unspecific inhibitor, [10 µM]). DECd-b also showed efficient relaxation of KCl [80 mM]-induced contraction and inhibition of CaCl2-induced contraction. Pre-incubation with propranolol (non-selective β-adrenergic antagonist, [10 µM]), SQ22536 (adenylyl cyclase inhibitor; [100 µM]), ODQ (guanylyl cyclase inhibitor; [10 µM]), l-NAME (nitric oxide synthase inhibitor; [10 µM]), indomethacin (a cyclooxygenase unspecific inhibitor; [10 µM]), glibenclamide (ATP-sensitive potassium channel blocker; [10 µM]) and 2-aminopyridine (voltage-gated potassium channel blocker [100 µM]) did not modify the DECd-b relaxant-effect curve. The chromatographic analysis of DECd-b suggests the cordiaquinones presence with double conjugated bounds such as menaquinone. ConclusionsResults suggest that DECd-b induces relaxation mainly by cAMP increase and Ca2+ channel blockade. The chromatographic profiles and UV spectrum of DECd-b and HECd-l suggest the presence of molecules with structure of meroterpenoid naphthoquinones. This work report scientific evidence of C. dodecandra medicinal specie, which contributes to the pharmacological and phytochemical background of C. dodecandra providing an added value to the traditional use of this specie.

Antinociceptive and anti-inflammatory properties of Tetracera alnifolia Willd. (Dilleniaceae) hydroethanolic leaf extract.

Background Tetracera alnifolia Willd. (Dilleniaceae) is used in traditional African Medicine for the treatment of headache, abdominal pain, and rheumatism. Hence, this study sought to investigate the antinociceptive and anti-inflammatory effects of the hydroethanolic leaf extract of T. alnifolia (HeTA) in rodents. Methods Antinociceptive activity was evaluated using the acetic acid-induced writhing, formalin-/capsaicin-induced paw licking and hot plate tests in mice. The contribution of opioidergic, l-arginine-nitric oxide, and ATP-sensitive potassium channel pathways in HeTA-induced antinociception was also evaluated. The anti-inflammatory effect was assessed using the carrageenan-induced paw edema, xylene ear edema, cotton pellet granuloma, and complete Freund's adjuvant (CFA)-induced arthritis in rats. Results HeTA (100, 200, and 400 mg/kg, p.o.) produced significant (p<0.05) decrease in mean number of acetic acid-induced writhing, time spent licking paw in formalin, and capsaicin tests as well as time course increase in nociceptive reaction latency in hot plate test. HeTA-induced antinociception was prevented by pretreatment of mice with naloxone (non-selective opioid receptor antagonist), l-arginine (nitric oxide precursor), or glibenclamide (ATP-sensitive potassium channel blocker). HeTA (100 mg/kg, p.o.) produced a significant anti-inflammatory effect against carrageenan-induced rat paw edema (1-5 h), xylene-induced ear edema, cotton pellet-induced granuloma formation, and CFA-induced arthritis in rats. The effects of HeTA in various models were similar to the effect of the standard reference drugs. Conclusions Findings from this study showed that HeTA possesses antinociceptive effect possibly mediated through peripheral opioid receptors with activation of l-arginine-nitric oxide and ATP-sensitive potassium channel pathway as well as anti-inflammatory activity.

Influence of Luehea divaricata Mart. extracts on peripheral vascular resistance and the role of nitric oxide and both Ca+2-sensitive and Kir6.1 ATP-sensitive K+ channels in the vasodilatory effects of isovitexin on isolated perfused mesenteric beds

BackgroundLuehea divaricata Mart. (Malvaceae) is an important medicinal species widely used by indigenous and riverside populations of the Brazilian Pantanal region. It has been shown that the several extracts obtained from leaves of this species have important cardioprotective effects. Nevertheless, the secondary metabolites responsible for this activity, as well as the molecular mechanisms responsible for their pharmacological effects remain unknown. PurposeTo carry out a biomonitoring study to identify possible active metabolites present in different ESLD fractions and evaluate the mechanisms responsible for the vasodilatory effects on isolated perfused mesenteric beds. MethodsFirst, ESLD was obtained from L. divaricata leaves and a liquid-liquid fractionation was performed. The resulting fractions were analyzed by liquid chromatography-mass spectrometry. Then, the possible vasodilatory effects of ESLD, chloroform, ethyl acetate, n-butanolic and aqueous fractions on perfused arterial mesenteric vascular beds were evaluated. Finally, the molecular mechanisms involved in vasodilator responses of the aqueous fraction and its chemical component, isovitexin, on the mesenteric arteriolar tone were also investigated. ResultsIn preparations with functional endothelium ESLD, n-butanolic, aqueous fraction and isovitexin dose-dependently reduced the perfusion pressure in mesenteric vascular beds. Endothelium removal or inhibition of nitric oxide synthase enzymes by L-NAME reduced the vasodilatory effects induced by aqueous fraction and isovitexin. Perfusion with nutritive solution containing 40 mM KCl abolished the vasodilatory effect of all aqueous fractions and Isovitexin doses. Treatment with glibenclamide, a Kir6.1 (ATP-sensitive) potassium channels blocker, tetraethylammonium, a non-selective KCa (calcium-activated) potassium channels blocker, or apamin, a potent blocker of small conductance Ca2+-activated (SK KCa) potassium channels reduced by around 70% vasodilation induced by all aqueous fractions and isovitexin doses. In addition, association of tetraethylammonium and glibenclamide, or L-NAME and glibenclamide, fully inhibited aqueous fraction and Isovitexin -induced vasodilation. ConclusionThis study showed that AqueFr obtained from Luehea divaricata and its metabolite - isovitexin - has important vasodilatory effects on MVBs. Apparently, these effects are dependent on endothelium-NO release and both SK KCa K+ channels and Kir6.1 ATP-sensitive K+ channels activation in the vascular smooth muscle.