Inhibitory effects of nicorandil on rat mesangial cell proliferation via the protein kinase G pathway

Nicorandil, Gastrointestinal Adverse Drug Reactions and Ulcerations: A Systematic Review

INTRODUCTION

Nicorandil is a popular anti-anginal drug in Europe and Japan. Apart from some common adverse drug reactions (ADR), its safety is satisfactory. Several reports have suggested a link between nicorandil, gastrointestinal (GI) ulceration and fistulas. The review aims to critically appraise, synthesize and present the available evidence of all known GI ADR per anatomical location.

METHODS

The study complied with the PRISMA statement. Literature and pharmacovigilance databases were used to provide rate and/or calculate parameters (median age, median dose, history of symptoms, length of therapy and healing time after withdrawal of the drug). Differences in distribution of quantitative variables were analyzed via Mann-Whitney test. Correlation between quantitative variables was assessed with a Spearman's correlation coefficient. A p value <0.05 was significant.

RESULTS

Oral ulcerations occur in 0.2% of the subjects, anal ulcerations are present between 0.07% and 0.37% of patients. Oral and distal GI involvements are the most common ADR (28-29% and 27-31% of all GI ADR, respectively). The hepatobiliary system, the pancreas and salivary glands are not affected by nicorandil exposure. The time to develop oral ulcerations is 74 weeks among people on <30 mg/day compared to only 7.5 weeks in individuals on higher regimens (p = 0.47). There is a significant correlation between dose and ulcer healing time (Spearman's 0.525, p < 0.001).

CONCLUSIONS

Ulcerative disease is a very commonly reported GI ADR. A delayed ulcerative tendency supports the hypothesis of an ulcerogenic metabolite. Nicorandil seems to act as a cause of the ulcerations, but appears to also work in synergy with other promoting factors. Whether the action of the metabolites relies on a specific mechanism or a simple chemical ulceration is still to be established.

Colitis generates remote antinociception in rats: the role of the L-arginine/NO/cGMP/PKG/KATP pathway and involvement of cannabinoid and opioid systems

OBJECTIVE AND DESIGN

The aim of this study was to investigate the possible involvement of the NO/cGMP/PKG/KATP+ pathway, cannabinoids and opioids in remote antinociception associated with 2,4,6-trinitrobenzene sulph onic acid (TNBS)-induced colitis.

METHODS

TNBS-induced colitis was induced by intracolonic administration of 20 mg of TNBS in 50% ethanol. After induction, carrageenan (500 μg/paw) or prostaglandin (PG) E2 (100 ng/paw) was injected in the rat's plantar surface and hypersensitivity was evaluated by the electronic von Frey test. Rats were pre-treated with L-Noarg one hour before carrageenan injection. L-Arginine was given 10 min before L-Noarg injections. ODQ, KT 5823, glibenclamide (Glib), naloxone and AM 251 or AM 630 were administered 30 min prior to carrageenan or PGE2 treatments.

RESULTS

Colitis induction by TNBS reduced PGE2 or carrageenan-induced hypersensitivity. Antinociception produced by TNBS-induced colitis was reversed significantly (P<0.05) by L-Noarg, ODQ, KT 5823, glibenclamide, naloxone, AM251 and AM630 treatments.

CONCLUSIONS

TNBS-induced colitis causes antinociception in the rat paw. This disorder appears to be mediated by activation of the NO/cGMP/PKG/KATP pathway, endocannabinoids and endogenous opioids. This information may contribute to a better understanding of peripheral neurological dysfunctions occurring in Crohn's disease.

Nicorandil protects against ischaemia-reperfusion injury in newborn rat kidney

Ischaemia-reperfusion injury (IRI) is the predominant cause of acute kidney injury. Nevertheless, the underlying molecular mechanisms are still unclear. The current study investigated the effects of nicorandil on ATP-sensitive potassium (KATP) channels and the potential signal transduction pathway(s) in a rat kidney IRI model and in cultured tubular HK-2 cells subjected to oxygen and glucose deprivation/reoxygenation (OGD/R) injury. The standard procedure for IRI was performed in newborn rat kidneys. Pretreatment with nicorandil (10 mg/kg) 2 h prior to induction of IRI improved renal function, attenuated tubule damage, and prevented apoptosis of tubule cells, infiltration of neutrophils and macrophages, and production of inflammatory cytokines interleukin (IL)-6, IL-17 and tumour necrosis factor-α. Ischaemia-reperfusion-induced reduction of KIR6.2 was restored to normal levels by nicorandil. The activation of the phosphoinositide-3-kinase (PI3K)-Akt-nuclear factor (NF)-κB axis was detected in this rat kidney IRI model, which was blocked by nicorandil. The renoprotection of nicorandil against IRI was abolished by its inhibitor glibenclamide (1 mg/kg). Similar results were obtained in OGD/R-damaged HK-2 cells. Taken together, our findings demonstrated the specific renoprotective role of nicorandil in the newborn rat IRI kidney by decreasing the production of inflammatory cytokines, and restoring the expression of KIR6.2 potentially through the PI3K-Akt-NF-κB axis.

Type II, but not type I, cGMP-dependent protein kinase reverses bFGF-induced proliferation and migration of U251 human glioma cells

Previous data have shown that the type II cGMP‑dependent protein kinase (PKG II) inhibits the EGF‑induced MAPK signaling pathway. In order to thoroughly investigate PKG, it is necessary to elucidate the function of another type of PKG, PKG I. The aim of this study was to investigate the possible inhibitory effect of PKG II and PKG I activity on the basic fibroblast growth factor (bFGF)‑induced proliferation and migration of U251 human glioma cells and the possible underlying mechanisms. U251 cells were infected with adenoviral constructs encoding cDNA of PKG I (Ad‑PKG I) or PKG II (Ad‑PKG II) to increase the expression levels of PKG I or PKG II and then treated with 8‑Br‑cGMP and 8‑pCPT‑cGMP, respectively, to activate the enzyme. An MTT assay was used to detect the proliferation of the U251 cells. The migration of the U251 cells was analyzed using a Transwell migration assay. Western blot analysis was used to detect the phosphorylation/activation of the fibroblast growth factor receptor (FGFR), MEK and ERK and the nuclear distribution of p-ERK. The results showed that bFGF treatment increased the proliferation and migration of U251 cells, accompanied by increased phosphorylation of FGFR, MEK and ERK. Furthermore, the nuclear distribution of p-ERK increased following bFGF treatment. Increasing the activity of PKG II through infection with Ad-PKG II and stimulation with 8-pCPT-cGMP significantly attenuated the aforementioned effects of the bFGF treatment, while increased PKG I activity did not inhibit the effects of bFGF treatment. These data suggest that increased PKG II activity attenuates bFGF‑induced proliferation and migration by inhibiting the MAPK/ERK signaling pathway, whereas PKG I does not.

Evaluation of the effects of nicorandil and its molecular precursor (without radical NO) on proliferation and apoptosis of 786-cell

Nicorandil is a nitric oxide (NO) donor used in the treatment of angina symptoms. It has also been reported to protect cells and affect the proliferation and death of cells in some tissues. The molecules that interfere with these processes can cause dysfunction in healthy tissues but can also assist in the therapy of some disorders. In this study we examined the effect of nicorandil and of the molecular precursor that does not have the NO radical (N-(beta-hydroxyethyl) nicotinamide) on the cell proliferation and death of human renal carcinoma cells (786-O) under normal oxygenation conditions. The molecular precursor was used in order to analyze the effects independents of NO. In the cytotoxicity test, nicorandil was shown to be cytotoxic at very high concentrations and it was more cytotoxic than its precursor (cytotoxic at concentrations of 2,000 and 3,000 μg/mL, respectively). We propose that the lower cytotoxicity of the precursor is due to the absence of the NO radical. In this study, the cells exposed to nicorandil showed neither statistically significant changes in cell proliferation nor increases in apoptosis or genotoxicity. The precursor generated similar results to those of nicorandil. We conclude that nicorandil causes no changes in the proliferation or apoptosis of the cell 786-O in normal oxygenation conditions. Moreover, the lack of NO radical in the precursor molecule did not show a different result, except in the cell cytotoxicity.

Nicorandil ameliorates ischaemia-reperfusion injury in the rat kidney

BACKGROUND AND PURPOSE

Nicorandil, an ATP-sensitive potassium (K(ATP) ) channel opener and nitric oxide donor, is used in the treatment of angina and acute heart failure. Here we investigated the effects of two K(ATP) channel openers, nicorandil and cromakalim on ischaemia reperfusion (I-R) injury in the kidney.

EXPERIMENTAL APPROACH

Right nephrectomy was performed in 8-week-old male Sprague-Dawley rats and they were then divided into six groups: control group; I-R, including 30 min of left renal ischaemia followed by 24 h of reperfusion; I-R groups plus nicorandil 3 or 10 mg·kg⁻¹ i.p.; and I-R groups plus cromakalim 100 or 300 µg·kg⁻¹ i.p. After reperfusion, renal function was estimated by serum creatinine (SCr), urinary albumin:creatinine ratio (ACR) and urinary β2-microglobulin (β2-MG). Levels of K(ATP) channel subtypes were investigated by Western blot. Kidney sections were stained for 4-hydroxy-2-nonenal and 8-hydroxy-2'-deoxyguanosine.

KEY RESULTS

Renal I-R induced significant increases in SCr, ACR and β2-MG levels compared with the control animals. Treatment with K(ATP) channel openers reduced urinary β2-MG levels, raised by I-R. Both K(IR) 6.1 and K(IR) 6.2 channels were expressed. Expression of K(IR) 6.2 channels in the I-R group was lower than in the control group, which was restored to normal by treatment with K(ATP) channel openers. Histologically, severe acute tubular damage was observed in the I-R kidney and this damage was ameliorated by K(ATP) channel openers, dose-dependently.

CONCLUSIONS AND IMPLICATIONS

ATP-sensitive potassium channel openers protected against proximal tubule damage after I-R injury. Nicorandil could represent a powerful additional component in the treatment of patients undergoing partial nephrectomy or renal transplantation.

Protein kinase G as a therapeutic target for the treatment of metastatic colorectal cancer

Colorectal cancer is a leading cause of cancer-related death in the world and there is an urgent need for new strategies to combat this disease. Findings from several independent laboratories have converged on cGMP signaling as an exciting new therapeutic target, but the mechanisms remain controversial. A key intracellular effector of cGMP is protein kinase G (PKG). This article reviews the scientific literature concerning PKG effects on tumor development and progression, and discusses possible strategies for its exploitation in future cancer therapies. Studies from several independent laboratories have described novel anti-tumor effects of PKG in colon cancer cells that include inhibition of tumor growth and angiogenesis. While more preclinical research is warranted to better understand signaling mechanisms, these properties support the notion that PKG is a novel cancer target.

Involvement of the nitric oxide-cyclic GMP-protein kinase G-K+ channel pathway in the antihyperalgesic effects of bovine lactoferrin in a model of neuropathic pain

The possible involvement of the nitric oxide (NO)-cyclic GMP (cGMP)-protein kinase G (PKG) pathway on bovine lactoferrin (BLF)-induced spinal antihyperalgesic activity was elucidated in sciatic nerve injured rats. Intrathecal BLF reduced thermal hyperalgesia in a dose-dependent manner. Pretreatment with NG-L-nitro-arginine methyl ester (L-NAME, non-specific inhibitor of NO synthase), 7-nitroindazole (7-NI, neuronal NO synthase inhibitor), 1H-[1,2,4]-oxadiazolo [4,3-a] quinoxalin-1-one (ODQ, guanylyl-cyclase inhibitor), (9S, 10R, 12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2, 9-dimethyl-1-oxo-9, 12-epoxy-1H-diindolo-[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid methyl ester (KT-5823, specific PKG inhibitor) or glybenclamide (ATP-sensitive K+ channel blocker), but not NG-D-nitro-arginine methyl ester (D-NAME, an inactive enantiomer of l-NAME), d-Phe-Cys-Tyr-d-Trp-Orn-Thr-NH2 (CTOP, selective mu-opioid receptor antagonist) or naloxone (nonselective opioid receptor antagonist) prevented BLF-induced antihyperalgesia. Data suggest that BLF-induced spinal antihyperalgesia could be due to activation of the NO-cGMP-PKG-K+ channel pathway and it is not mediated by mu-opioid receptor in a model of neuropathic pain.

Peripheral antinociceptive effect of pertussis toxin: activation of the arginine/NO/cGMP/PKG/ ATP-sensitive K channel pathway

The aim of the present study was to determine the effect of pertussis toxin (PTX) on inflammatory hypernociception measured by the rat paw pressure test and to elucidate the mechanism involved in this effect. In this test, prostaglandin E(2) (PGE(2)) administered subcutaneously induces hypernociception via a mechanism associated with neuronal cAMP increase. Local intraplantar pre-treatment (30 min before), and post-treatment (5 min after) with PTX (600 ng/paw1, in 100 microL) reduced hypernociception induced by prostaglandin E(2) (100 ng/paw, in 100 microL, intraplantar). Furthermore, local intraplantar pre-treatment (30 min before) with PTX (600 ng/paw, in 100 microL) reduced hypernociception induced by DbcAMP, a stable analogue of cAMP (100 microg/paw, in 100 microL, intraplantar), which indicates that PTX may have an effect other than just G(i)/G(0) inhibition. PTX-induced analgesia was blocked by selective inhibitors of nitric oxide synthase (L-NMMA), guanylyl cyclase (ODQ), protein kinase G (KT5823) and ATP-sensitive K(+) channel (Kir6) blockers (glybenclamide and tolbutamide). In addition, PTX was shown to induce nitric oxide (NO) production in cultured neurons of the dorsal root ganglia. In conclusion, this study shows a peripheral antinociceptive effect of pertussis toxin, resulting from the activation of the arginine/NO/cGMP/PKG/ATP-sensitive K(+) channel pathway.

Ghrelin reduces voltage-gated potassium currents in GH3 cells via cyclic GMP pathways

Ghrelin is an endogenous growth hormone secretagogue (GHS) causing release of GH from pituitary somatotropes through the GHS receptor. Secretion of GH is linked directly to intracellular free Ca(2+) concentration ([Ca(2+)]i), which is determined by Ca(2+) influx and release from intracellular Ca(2+) storage sites. Ca(2+) influx is via voltage-gated Ca(2+) channels, which are activated by cell depolarization. Membrane potential is mainly determined by transmembrane K(+) channels. The present study investigates the in vitroeffect of ghrelin on membrane voltage-gated K(+) channels in the GH3 rat somatotrope cell line. Nystatin-perforated patch clamp recording was used to record K(+) currents under voltage-clamp conditions. In the presence of Co(2+) (1 mM, Ca(2+) channel blocker) and tetrodotoxin (1 microM, Na(+) channel blocker) in the bath solution, two types of voltage-gated K(+) currents were characterized on the basis of their biophysical kinetics and pharmacological properties. We observed that transient K(+) current (IA) represented a significant proportion of total K(+) currents in some cells, whereas delayed rectifier K(+) current (IK) existed in all cells. The application of ghrelin (10 nM) reversibly and significantly decreased the amplitude of both IA and IK currents to 48% and 64% of control, respectively. Application of apamin (1 microM, SK channel blocker) or charybdotoxin (1 microM, BK channel blocker) did not alter the K(+) current or the response to ghrelin. The ghrelin-induced reduction in K(+) currents was not affected by PKC and PKA inhibitors. KT5823, a specific PKG inhibitor, totally abolished the K+ current response to ghrelin. These results suggest that ghrelin-induced reduction of voltage-gated K(+) currents in GH3 cells is mediated through a PKG-dependent pathway. A decrease in voltage-gated K(+) currents may increase the frequency, duration, and amplitude of action potentials and contribute to GH secretion from somatotropes.

An anti-tumor role for cGMP-dependent protein kinase

This study compared Type-1 cGMP-dependent protein kinase (PKG) expression in normal and tumor tissues and examined PKG function in tumor growth. Studies with a cDNA array revealed that PKG expression was reduced in many tumors compared to respective normal tissue. This decrease in PKG expression was confirmed using quantitative RT-PCR and western blotting of matched colon specimens from normal epithelium and tumor tissue, and also in colon derived cell lines where luciferase reporter analysis revealed that the decreased expression occurred at the transcriptional level. Using SW620 colon carcinoma cells engineered for inducible expression of PKG1beta, it was found that exogenous PKG1beta lead to decreased tumor growth and invasiveness in nude mouse xenografts.

Peripheral analgesic blockade of hypernociception: activation of arginine/NO/cGMP/protein kinase G/ATP-sensitive K+ channel pathway

The final step in the direct restoration of the nociceptor threshold by peripheral administration of morphine and dipyrone was recently suggested to result from the opening of ATP-sensitive K(+) channels (K(ATP)(+)). This channel is known to be open either directly by cGMP or indirectly via protein kinase G (PKG) stimulation. In the present study, it was shown that the blockade was caused by a specific PKG inhibitor (KT5823) of the antinociceptive effect of morphine and dipyrone on acute hypernociception and of dipyrone on persistent hypernociception. It was also shown that, in both models, KT5823 prevented the peripheral antinociceptive effect of an analogue of cGMP, the nitric oxide (NO) donor (S-nitroso-n-acetyl-d,l-penicilamine). However, in acute hypernociception, KT5823 did not prevent the peripheral antinociceptive effect of diazoxide (a direct K(ATP)(+) opener). In persistent hypernociception, the sensitization plateau was induced by daily injections of prostaglandin E(2) (PGE(2), 100 ng) into the rat paw for 14 days. After cessation of PGE(2) injections, the pharmacological blockade of persistent hypernociception led to a quiescent phase in which a rather small stimulus restored the hypernociceptive plateau. In this phase, glibenclamide (which specifically closes K(ATP)(+)) fully restored persistent hypernociception, as did injection of PGE(2). Thus, the activation of the arginine/NO/cGMP pathway causes direct blockade of acute and persistent hypernociception by opening K(ATP)(+) via the stimulation of PKG. Analgesic stimulators of the neuronal arginine/NO/cGMP/PKG/K(ATP)(+) pathway constitute a previously undescribed well defined class of peripheral analgesics with a mechanism of action different from either glucocorticoids or inhibitors of cyclooxygenases.

A forskolin derivative, colforsin daropate hydrochloride, inhibits rat mesangial cell mitogenesis via the cyclic AMP pathway

A forskolin derivative, colforsin daropate hydrochloride (CDH), has been introduced as an inotropic agent that acts directly on adenylate cyclase to increase intracellular cyclic AMP (cAMP) levels and ventricular contractility, resulting in positive inotropic activity. We investigated the effects of CDH on rat mesangial cell (MC) proliferation. CDH (10(-7)-10(-5) mol/l) inhibited [(3)H]thymidine incorporation into cultured rat MCs in a concentration-dependent manner. CDH (10(-7)-10(-5) mol/l) also decreased cell numbers in a similar manner, and stimulated cAMP accumulation in MCs in a concentration-dependent manner. A protein kinase A inhibitor, H-89, abolished the inhibitory effects of CDH on MC mitogenesis. These findings suggest that CDH would inhibit the proliferation of rat MCs via the cAMP pathway.

Mesangial cell proliferation inhibitors for the treatment of proliferative glomerular disease

Mesangial cells (MC) serve a number of functions in the renal glomerular capillary including structural support of the capillary tuft, modulation of glomerular hemodynamics, and a phagocytic function allowing removal of macromolecules and immune complexes. The proliferation of MC is a prominent feature of glomerular disease including IgA nephropathy, membranoproliferative glomerulonephritis, lupus nephritis, and diabetic nephropathy. In experimental animal models of nephritis, MC proliferation frequently precedes and is linked to the increase of extracellular matrix in the mesangium and glomerulosclerosis. Reduction of MC proliferation in glomerular disease models by treatment with heparin, low-protein diet, or antibodies to platelet-derived growth factor (PDGF), have been shown to reduce extracellular matrix expansion and glomerulosclerotic changes. Therefore, MC proliferation inhibitors may offer therapeutic opportunities for the treatment of proliferative glomerular disease. It is also known that the MC proliferation is inhibited by many kinds of pharmacological drugs, for example, angiotensin converting enzyme (ACE) inhibitors, leukotriene D(4) (LTD(4)) antagonists, PDGF inhibitors, matrix metalloproteinases (MMP) inhibitors, 3-hydroxy-3 methyl glutaryl-coenzymeA (HMG-CoA) inhibitors, cyclin-dependent kinases (CDK) inhibitors, and others. This review summarizes the recently reported MC proliferation inhibitors with their pharmacological properties on the basis of their chemical structures.