Nitric Oxide-cyclic Guanosine Monophosphate Pathway Research Articles

Nicorandil, a Nitric Oxide Donor and ATP-Sensitive Potassium Channel Opener, Protects Against Dystrophin-Deficient Cardiomyopathy.

Dystrophin-deficient cardiomyopathy is a growing clinical problem without targeted treatments. We investigated whether nicorandil promotes cardioprotection in human dystrophin-deficient induced pluripotent stem cell (iPSC)-derived cardiomyocytes and the muscular dystrophy mdx mouse heart. Dystrophin-deficient iPSC-derived cardiomyocytes had decreased levels of endothelial nitric oxide synthase and neuronal nitric oxide synthase. The dystrophin-deficient cardiomyocytes had increased cell injury and death after 2 hours of stress and recovery. This was associated with increased levels of reactive oxygen species and dissipation of the mitochondrial membrane potential. Nicorandil pretreatment was able to abolish these stress-induced changes through a mechanism that involved the nitric oxide-cyclic guanosine monophosphate pathway and mitochondrial adenosine triphosphate-sensitive potassium channels. The increased reactive oxygen species levels in the dystrophin-deficient cardiomyocytes were associated with diminished expression of select antioxidant genes and increased activity of xanthine oxidase. Furthermore, nicorandil was found to improve the restoration of cardiac function after ischemia and reperfusion in the isolated mdx mouse heart. Nicorandil protects against stress-induced cell death in dystrophin-deficient cardiomyocytes and preserves cardiac function in the mdx mouse heart subjected to ischemia and reperfusion injury. This suggests a potential therapeutic role for nicorandil in dystrophin-deficient cardiomyopathy.

Current management of pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a vascular disease of unknown aetiology, characterised by an abnormal thickening of the arterial wall that is responsible for an increase in pulmonary vascular resistance. The haemodynamic consequence of PAH is an increased afterload for the right ventricle and, eventually, right heart failure. When untreated, PAH has a grim prognosis with a median survival of about 2 to 4 years from diagnosis. In the last 10 years new orally administered compounds have demonstrated clinical efficacy in controlled trials using various surrogate endpoints to survival. Although the disease remains without cure until now, the available phase III trials have allowed evidence-based recommendations for the medical management of these patients to be established. It appears, however, that none of the compounds from the three main therapeutic classes, endothelin receptor antagonists, agents acting on the nitric oxide-cyclic guanosine monophosphate pathway (including phosphodiesterase type 5 inhibitors and guanylate cyclase stimulator), and prostanoid receptor agonists are able alone to control disease progression in every patient. Therefore combination therapy with two or three drugs may be necessary in a significant number of patients in order to maintain patients in, or bring them to, a low risk profile. Several recent studies have now validated this approach for specific double or triple drug regimens. It remains, however, unclear whether an upfront combination is preferable to a sequential step-up approach based on clinical response. In addition, some specific combination therapies have failed to demonstrate superiority to single drug alone in randomised controlled trials. Besides PAH-specific treatment, the place of nonspecific pharmaceutical and nonpharmaceutical treatment has been also recently clarified.

Involvement of nitric oxide-cyclic guanosine monophosphate pathway in the antidepressant-like effect of tropisetron and ondansetron in mice forced swimming test and tail suspension test

Antidepressant-like effects of 5-hydroxytryptamine subtype 3 (5-HT3) antagonists including tropisetron and ondansetron have been previously demonstrated in the literature. It was reported that stimulation of 5-HT3 receptors activate the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway, which is involved in regulation of behavioral and emotional functions. In our study, treating animals with tropisetron (5, 10, and 30mg/kg) and ondansetron (0.01 and 0.1µg/kg) significantly decreased the immobility time in forced swimming test (FST) and tail-suspension test (TST). Co-administration of subeffective doses of tropisetron (1mg/kg) and ondansetron (0.001µg/kg) with subeffective dose of l-NAME (10mg/kg, nonselective NO synthase (NOS) inhibitor) and 7-nitroindazole (25mg/kg, neural NOS inhibitor) exerted antidepressant-like effect in FST and TST, while aminoguanidine (50mg/kg, inducible NOS inhibitor) did not enhance the antidepressant-like effect of 5-HT3 antagonists. Besides, l-arginine (750mg/kg, NO precursor) and sildenafil (5mg/kg, phosphodiesterase inhibitor) suppressed the anti-immobility effect of 5-HT3 antagonists. None of the treatments altered the locomotor behavior of mice in open-field test. Also, hippocampal (but not cortical) nitrite level was significantly lower in tropisetron and ondansetron-treated mice compared with saline-injected mice. Also, co-administration of 7-nitroindazole with tropisetron or ondansetron caused a significant decrease in hippocampal nitrite levels. In conclusion, we suggest that antidepressant-like effect of tropisetron and ondansetron are partially mediated by modulation of NO-cGMP pathway.

Inhibitory effect of sildenafil on pyloric sphincter from streptozotocin-diabetic rats: role of no-cGMP transduction pathway

Long-standing and poorly controlled diabetes may result disturbances in gastrointestinal function of which gastroparesis is one of the more common. Previous studies have shown that nitric oxide-cyclic guanosine monophosphate transduction pathway has a regulatory role in gastrointestinal motility. But, this drive is adversely affected by diabetes mellitus. Sildenafil, as a selective inhibitor of cyclic guanosine monophosphate-selective phosphodiesterase type 5, has also beneficial effect in diabetic patients with gastrointestinal symptoms. In this study, we aimed to investigate the effect of sildenafil and its underlying mechanisms on pylorus motility of diabetic rats. Acetylcholine (10−8–10−3 M) produced concentration-dependent contraction responses that is significantly attenuated by sildenafil (10−6 M) incubation. On the other hand, sildenafil elicited relaxant effect in rat pylorus precontracted by acetylcholine. The relaxant responses to sildenafil partially, but significantly, inhibited by nitric oxide synthase blocker N-nitro-L-arginine methyl ester (L-NAME, 10−4 M) or soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10−5 M). These results demonstrated that sildenafil continue to relax diabetic rat pylorus despite a nitric oxide-cyclic guanosine monophosphate pathway inhbition. Hence, other mechanisms (calcium dynamics, acetylcholine metabolism) may also contribute to its relaxant effect. The results also suggest the potential use of sildenafil for improving gastroparesis in diabetic patients.

NMDA Receptors and the L-Arginine–Nitric Oxide–Cyclic Guanosine Monophosphate Pathway Are Implicated in the Antidepressant-Like Action of the Ethanolic Extract fromTabebuia avellanedaein Mice

Bark infusion of Tabebuia avellanedae Lorentz ex Griseb is consumed in tropical America folk medicine for the treatment of several diseases, including depressive disorders. It was recently demonstrated that the extract from this plant has antidepressant properties. The present study was aimed at investigating the contribution of N-methyl-D-aspartate (NMDA) receptors and the L-arginine-nitric oxide (NO)-cyclic guanosine 3'5'-monophosphate (cGMP) pathway to the antidepressant-like action of the ethanolic extract from T. avellanedae (EET) in the tail suspension test (TST). The anti-immobility effect of the extract (30 mg/kg, orally [p.o.]) was prevented by pretreatment of mice with NMDA (0.1 pmol/site, intracerebroventicular [i.c.v.]), L-arginine (750 mg/kg, intraperitoneally [i.p.]), and sildenafil (5 mg/kg, i.p.). Additionally, the combination of MK-801 (0.01 mg/kg, p.o.), 7-nitroindazole (25 mg/kg, i.p.), and 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ) (30 pmol/site, i.c.v.) with a subeffective dose of EET (1 mg/kg, p.o.) produced a synergistic antidepressant-like effect in the TST, without causing significant alterations in the locomotor activity. Moreover, the administration of an effective dose of EET (30 mg/kg, p.o.) produced a reduction in NOx levels in the cerebral cortex. Conversely, a subeffective dose of EET (1 mg/kg, p.o.) caused no changes in the cortical NOx levels. Results suggest that the antidepressant-like effect of EET in the TST is dependent on a blockade of NMDA receptor activation and inhibition of NO-cGMP synthesis, significantly extending literature data about the antidepressant-like action of this plant and reinforcing the notion that this plant may be useful in the management of depressive disorders.

Methylene Blue for Distributive Shock: A Potential New Use of an Old Antidote

Methylene blue is used primarily in the treatment of patients with methemoglobinemia. Most recently, methylene blue has been used as a treatment for refractory distributive shock from a variety of causes such as sepsis and anaphylaxis. Many studies suggest that the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway plays a significant role in the pathophysiology of distributive shock. There are some experimental and clinical experiences with the use of methylene blue as a selective inhibitor of the NO-cGMP pathway. Methylene blue may play a role in the treatment of distributive shock when standard treatment fails.

SaRNA Guided iNOS Up-Regulation Improves Erectile Function of Diabetic Rats

Promoter targeted saRNAs mediate sequence specific up-regulation of gene expression. We explored the therapeutic effect of RNA activation mediated iNOS gene activation on improving erectile function in a rat model of diabetes mellitus. An optimal saRNA sequence specific for iNOS promoter was cloned into an adenoviral vector, resulting in AdU6/shiNOS and AdU6/shControl. The corresponding viruses were used to transduce cultured rat cavernous smooth muscle cells. Streptozotocin induced diabetes models were established in rats and used to test the effects of intracavernous delivery of iNOS saRNA viruses on erectile function. iNOS expression in the cavernous smooth muscle cells or penile tissue of treated rats was assessed by reverse transcriptase-polymerase chain reaction and Western blot. Cyclic guanosine monophosphate was analyzed by enzyme-linked immunosorbent assay. Intracavernous pressure in response to cavernous nerve stimulation was measured using a data acquisition system on post-injection days 1, 3, 5, 7, 10 and 14. Adenovirus mediated expression of iNOS saRNA caused sustained up-regulation of iNOS in cavernous smooth muscle cells. Intracavernous injection of AdU6/shiNOS activated iNOS expression in vivo and significantly increased peak intracavernous pressure in streptozotocin induced diabetic rats via nitric oxide/intracellular cyclic guanosine monophosphate activation. Results show that saRNA mediated iNOS over expression in the penis can restore erectile function in streptozocin diabetic rats via the nitric oxide-cyclic guanosine monophosphate pathway.

Latest treatment for lower urinary tract dysfunction: Therapeutic agents and mechanism of action

Recent studies suggest that antimuscarinics might suppress bladder afferent activity by blocking muscarinic receptors in the urothelium, myofibroblasts and detrusor, thereby improving overactive bladder symptoms. β(3)-Adrenoceptors are predominantly expressed in the human bladder and mediate relaxation of detrusor muscle. β(3)-Adrenoceptor agonists increase bladder capacity and prolong micturition interval. It is assumed that β(3)-adrenoceptor agonists could exert an inhibitory effect on bladder afferent through β(3)-adrenoceptors in the urothelium and detrusor, which eventually improve the symptom of urgency. Mirabegron is a potent and selective β(3)-adrenoceptor agonist. A Japanese phase 3 study showed that mirabegron has excellent efficacy and safety for treating overactive bladder. α(1)-Adrenoceptor antagonists (α(1)-blockers) have become a mainstay of male lower urinary tract symptoms treatment. The α(1)(A) subtype is known to mediate functional obstruction as a result of benign prostatic enlargement. Recent studies have suggested that α(1)(A)-adrenoceptors are additionally involved in the generation of storage symptoms. The α(1)(D) subtype is thought to play a role in the facilitation of voiding reflex; that is; storage symptoms. α(1)-Blockers often fail to alleviate overactive bladder symptoms. In this context, combination therapy with α(1)-blockers and antimuscarinics has been recommended. Treatment with 5α-reductase inhibitor for 1 year improves urinary symptoms and flow rate by reducing prostatic volume in men with benign prostatic enlargement. A pooled analysis showed that the long-term (2 or 4 years) treatment with 5α-reductase inhibitor reduced the rate of progression to acute urinary retention and surgery. Combination therapy with 5α-reductase inhibitor and α(1)-blocker was shown to provide a rapid improvement in lower urinary tract symptoms, and reduce the relative risk of acute urinary retention and benign prostatic hyperplasia-related surgery. Phosphodiesterase inhibitors might target a nitric oxide-cyclic guanosine monophosphate pathway in the prostate, urethra and bladder. Phosphodiesterase-5 inhibitors (sildenafil or tadalafil) were shown to provide clinically relevant improvements in both male lower urinary tract symptoms and erectile dysfunction.

Common Pitfalls in Some of the Experimental Studies in Erectile Function and Dysfunction: A Consensus Article

Experimental studies investigating physiology of erectile function and pathophysiology erectile dysfunction employ several in vitro and in vivo techniques. As the field of sexual medicine expanding, the proper conduct of such techniques is becoming an even more important necessity than before. This review article aims to guide scientists, particularly young researchers and new comers in the field, toward employment of these techniques in an appropriate, timely, and competent fashion. The authors reviewed the existing available published articles on the following topics: intracavernosal pressure measurements, cavernous nerve injury models, nitric oxide-cyclic guanosine monophosphate pathway, hypertension- and smoking-induced erectile dysfunction models, and stem cells. The authors present a consensus on how to best perform these models and techniques and also highlight the pitfalls. The authors hope that this article will assist and encourage young scientists in the field and that similar articles covering other important models will be also available to them soon.

VEGF genetic polymorphisms affect the responsiveness to sildenafil in clinical and postoperative erectile dysfunction

Vascular endothelial growth factor (VEGF) is a cytokine involved in angiogenesis and is closely related to the nitric oxide-cyclic guanosine monophosphate pathway, a target for sildenafil. We investigated for the first time whether three clinically relevant polymorphisms in the VEGF gene are associated with altered responsiveness to sildenafil treatment in postoperative erectile dysfunction (PED) and clinical erectile dysfunction (CED). We determined VEGF genotypes for three polymorphisms in VEGF promoter: -2578C>A (rs699947), -1154G>A (rs1570360) and -634G>C (rs2010963) in 126 patients with erectile dysfunction (ED; 66 patients with PED and 60 patients with CED). The patients were classified as good or poor responders to sildenafil (GR and PR groups, respectively) according to their responses with basis on the changes in five-item version of the International Index for Erectile Function (5-IIEF). We found an association of the -1154AA genotype with PR in both PED and CED patients (P<0.05), whereas the -2578AA and the -2578CA genotypes were associated with PR only in the CED group (P<0.05). The AAG haplotype was more common in PR than in GR patients (38% versus 20%, respectively; P=0.032) in the CED group, thus increasing the risk for a worse response to sildenafil (odds ratio, OR=2.33, 95% confidence interval, CI=1.07-5.09). However, this finding does not resist to Bonferroni's correction (P>0.0125). Our results indicate that VEGF polymorphisms affect the responsiveness of PED and CED patients to sildenafil. These findings may help to improve the therapy of patients with ED.

The role of the NMDA receptors and l-arginine–nitric oxide–cyclic guanosine monophosphate pathway in the antidepressant-like effect of duloxetine in the forced swimming test

Duloxetine is a selective serotonin and noradrenaline reuptake inhibitor used as antidepressant. However, its mechanisms of action are not fully understood. This study investigated the effect of duloxetine in the mouse forced swimming test (FST) and in the tail suspension test (TST) and the involvement of the NMDA receptors and the l-arginine–NO–cGMP pathway in its effect in the FST. Duloxetine reduced the immobility time both in the FST and in the TST (dose range of 1–30mg/kg, i.p.), without changing locomotion in an open-field. Duloxetine administered orally (1–30mg/kg) also reduced the immobility time in the FST. The effect of duloxetine (10mg/kg, p.o.) in the FST was prevented by pre-treatment with NMDA (0.1pmol/site, i.c.v.), d-serine (30μg/site, i.c.v.), (l-arginine (750mg/kg, i.p.), S-nitroso-N-acetyl-penicillamine (SNAP, 25μg/site, i.c.v) or sildenafil (5mg/kg, i.p.). The administration of MK-801 (0.001mg/kg, i.p.), 7-nitroindazole (50mg/kg, i.p.), methylene blue (20mg/kg, i.p.) or 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ) (30pmol/site i.c.v.) in combination with a sub-effective dose of duloxetine (0.3mg/kg, p.o.) reduced the immobility time in the FST. Moreover, the administration of duloxetine (10mg/kg) produced a reduction in NOx levels in the hippocampus and cerebral cortex. Altogether the results suggest that the effect of duloxetine in the FST is dependent on either a blockade of NMDA receptors or an inhibition of NO. In addition, our results further reinforce the role of NMDA receptors and l-arginine–NO–cGMP pathway, besides the monoaminergic systems, in the mechanism of action of current prescribed antidepressant agents.

Tadalafil in pulmonary hypertension: May be more than seen?

I read an interesting article about the superiority of tadalafil over tempol via its antioxidant capacity on acute hypoxia-induced pulmonary hypertension (PH) model. Rashid et al. investigated and compared the antioxidant capacity of specific phosphodiesterase type-5 (PDE5) inhibitor, tadalafil, with superoxide dismutase mimetic and an efficient free radical scavenging agent tempol in acute hypoxia-induced PH model. They demonstrated that tadalafil was superior to tempol in inhibiting hypoxia-induced rise in right ventricular systolic pressure (RVSP) without producing any fall in mean arterial pressure. Also, tadalafil was shown to partially prevent oxidative stress. In conclusion, Rashid et al. highlighted the superiority of tadalafil especially in the settings of chronic hypoxia-induced PH. Monocrotaline (MCT)-induced PH is the other widely accepted animal model in PH studies. MCT is a member of the pyrrolizidine alkaloid family of plant toxins, which induces a delayed, yet progressive vascular injury resulting in PH in rats, dogs and monkeys. It is recognized that the initial reaction to MCT-induced PH is injury to the endothelial cells that precedes media hypertrophy in small size pulmonary arteries, and leads to an increase in pulmonary artery disease. These alterations in morphology largely mimic the primary PH in humans. We have recently compared the effects of three commercially available PDE5 inhibitors: sildenafil, vardenafil and tadalafil in rat MCT-induced PH model. It has been briefly demonstrated that vardenafil was more effective than sildenafil and tadalafil in this model. Vardenafil relaxes pulmonary artery rings in pulmonary hypertensive group through nitric oxide (NO)-cyclic guanosine monophosphate (NO-cGMP)-independent pathway. Neither sildenafil nor tadalafil achieves to induce relaxation response in pulmonary artery rings when NO-cGMP pathway inhibitor (NO synthase inhibitor, L-NAME and soluble guanylyl cyclase inhibitor, ODQ) incubations were used. This superiority potentially results from the differences in the heterocyclic ring system of vardenafil. Biochemical potencies (affinities) of these compounds for PDE5 have been determined by half maximal inhibitory concentration (IC50) and dissociation rate (KD), respectively, were the following: sildenafil (3.7 + 1.4, 3.7 + 0.29 nM), tadalafil (1.8 + 0.40, 1.9 + 0.37 nM), vardenafil (0.091 + 0.031, 0.27 + 0.01 nM), and it has been clearly demonstrated that vardenafil was the most potent inhibitor of PDE-5 because of its slow dissociation rate. Although tadalafil has an advantage over sildenafil and vardenafil because of its longer duration of action, tadalafil did not significantly alter the time to exercise treadmill test-induced ischemia compared with placebo in subjects with coronary artery disease. It is well-known that PH and coronary artery disease share similar risk factors, including endothelial dysfunction, diminishing of NO production and increased oxidative stress. This study is also in agreement with the others demonstrating that tadalafil was less effective than sildenafil and vardenafil in reducing the infarct size. In other preparations such as rat aorta-penile arteries and rabbit isolated pulmonary artery–corpus cavernosum tissue, vardenafil was shown to be more potent than other PDE5 inhibitors in relaxing the vascular tissues and preparations. These discrepancies may be attributed to experimental model, protocols or preparations difference employed in these studies. Also, these studies demonstrated that vardenafil has some beneficial effects in addition to its PDE5 inhibitory activity (e.g. activation of some ion channels or blocking of calcium influx).

Acute atorvastatin treatment exerts antidepressant-like effect in mice via the l-arginine–nitric oxide–cyclic guanosine monophosphate pathway and increases BDNF levels

Atorvastatin is a synthetic and lipophilic statin that presents a good effect in decreasing cholesterol levels and is safe and well tolerated. Population-based studies have suggested a positive role of statins in reducing depression risk. This study aimed at investigating the atorvastatin effect in the tail suspension test (TST) and in the forced swimming test (FST). The participation of NMDA receptors and L-arginine-NO-cGMP in an atorvastatin antidepressant-like effect in the TST was evaluated. Acute atorvastatin administration (0.1-30 mg/kg) reduced the immobility time both in TST and FST. A similar effect was observed by using imipramine as a positive control in the TST and FST (1 and 0.1-1 mg/kg, p.o., respectively). An atorvastatin (0.1 mg/kg) antidepressant-like effect was prevented by the pretreatment of mice with NMDA (0.1 pmol/site, i.c.v.), L-arginine (750 mg/kg, i.p.) or sildenafil (5 mg/kg, i.p.). The administration of MK-801 (0.001 mg/kg, i.p.), ketamine (0.1 mg/kg, i.p.), 7-nitroindazole (50 mg/kg, i.p.), methylene blue (20 mg/kg, i.p.), or ODQ (30 pmol/site i.c.v.) in combination with a subeffective dose of atorvastatin (0.01 mg/kg, p.o.) reduced the immobility time in the TST compared to drugs alone, showing the participation of the pathway L-arginine-NO-cGMP. The administration of drugs did not produce any significant alteration in locomotor activity in the open-field test. Acute atorvastatin treatment (0.1-10.0 mg/kg, v.o.) increased the hippocampal BDNF levels, which is an effect that has not been observed in imipramine-treated mice. These results demonstrate that atorvastatin exerts an antidepressant-like effect and point to dependence on the inhibition of NMDA receptors and NO-cGMP synthesis, and on the increase of hippocampal BDNF levels.

Imatinib Mesylate (Gleevec) as Protein-tyrosine Kinase Inhibitor Elicits Smooth Muscle Relaxation in Isolated Human Prostatic Tissue

To evaluate the mechanism of action of imatinib mesylate (Gleevec), a protein tyrosine kinase inhibitor on the human prostate with benign prostatic hyperplasia. Prostate samples were obtained from 16 patients with benign prostatic hyperplasia (mean age 68.3 ± 1.9 years), who had undergone transurethral prostatectomy. In tissue bath studies, cumulative concentration-response curves were constructed for imatinib after precontraction with 120 mM KCl. Imatinib-induced relaxation was quantitated in tissues treated with l-N(G)-Nitroarginine Methyl Ester (l-NAME) (an inhibitor of nitric oxide synthase) or 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (a soluble guanylyl cyclase inhibitor). Two K+ channel blockers (adenosine triphosphate [K(ATP)] and Large-conductance Ca(2+)-activated K(+) channels [BK(Ca2+)] channels) were also evaluated as antagonists of imatinib-induced relaxation and repeated in the presence of the α-adrenergic receptor blocker alfuzosin. An electrical field stimulation (1-20 Hz, 5 ms, 5 seconds, 60 V)-induced contractile response was performed on strips incubated with imatinib (10(-3) M). KCl-induced contractions in human prostatic tissue were significantly inhibited by imatinib (maximal response 84.9 ± 4.5%) and were attenuated by l-NAME (42%, P < .001) and ODQ (43%, P < .001). This relaxant effect was also suppressed by glibenclamide (adenosine triphosphate-sensitive K+ channel blocker, 41%, P < .001) and tetraethylammonium (BK(Ca2+) channel blocker, 24%, P < .05). Imatinib induced prostatic smooth muscle relaxation in vitro. This effect was suppressed by l-NAME and ODQ, showing a dependence on the nitric oxide-cyclic guanosine monophosphate pathway and modulated by the K(ATP) and BK(Ca2+) K+ channels. Our findings suggest that imatinib can augment relaxation of human prostatic tissues by way of a novel ligand-protein tyrosine kinase signaling pathway.

Antidepressant-like effect of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol, a putative trace amine receptor ligand involves l-arginine–nitric oxide–cyclic guanosine monophosphate pathway

1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol is a novel putative trace amine receptor modulator hypothesized to be useful for treatment–resistant depression. In our previous study, we have demonstrated the antidepressant-like effect of this molecule in mouse forced swim and tail suspension tests and shown to act via modulating the levels of norepinephrine, serotonin and dopamine. The present study attempts to explore the involvement of l-arginine–nitric oxide–cyclic guanosine monophosphate pathway in the antidepressant-like effect of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol in the mouse forced swim test. The antidepressant-like action of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol (8 mg/kg, i.p) was reversed by pretreatment with L-arginine (750 mg/kg, i.p.), a nitric oxide precursor. In contrast, pretreatment with methylene blue (a soluble guanlyate cyclase inhibitor and nitric oxide synthase (NOS) inhibitor) or 7-nitroindazole (a specific neuronal NOS inhibitor) potentiated the antidepressant-like effect of sub-effective dose of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol (2 mg/kg, i.p.) in this test model. Furthermore, the antidepressant-like effect of this molecule (8 mg/kg, i.p.) was reversed by sildenafil (5 mg/kg, i.p.), a phosphodiesterase inhibitor. In conclusion, the antidepressant-like action of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol involved L-arginine–nitric oxide–cyclic guanosine monophospate signaling pathway.

Targeted Genomic Disruption of H-Ras Induces Hypotension Through a NO-cGMP-PKG Pathway–Dependent Mechanism

The aim of the present experiments was to evaluate the differences in arterial pressure between H-Ras lacking mice and control mice and to analyze the mechanisms involved in the genesis of the differences. H-Ras lacking mice and mouse embryonic fibroblasts from these animals were used. Blood pressure was measured using 3 different methods: direct intraarterial measurement in anesthetized animals, tail-cuff sphygmomanometer, and radiotelemetry. H-Ras lacking mice showed lower blood pressure than control animals. Moreover, the aorta protein content of endothelial nitric oxide synthase, soluble guanylyl cyclase, and cyclic guanosine monophosphate-dependent protein kinase was higher in H-Ras knockout mice than in control animals. The activity of these enzymes was increased, because urinary nitrite excretion, sodium nitroprusside-stimulated vascular cyclic guanosine monophosphate synthesis, and phosphorylated vasoactive-stimulated phosphoprotein in aortic tissue increased in these animals. Furthermore, mouse embryonic fibroblasts from H-Ras lacking mice showed higher cyclic guanosine monophosphate-dependent protein kinase promoter activity than control cells. These results strongly support the upregulation of the nitric oxide-cyclic guanosine monophosphate pathway in H-Ras-deficient mice. Moreover, they suggest that H-Ras pathway could be considered as a therapeutic target for hypertension treatment.

Adrenomedullin relaxes rat uterine artery: mechanisms and influence of pregnancy and estradiol.

Uterine arteries play a major role in regulating uteroplacental blood flow. Failure to maintain blood flow to the uteroplacental compartment during pregnancy often results in intrauterine growth retardation. Immunohistochemical staining of adrenomedullin (AM), an endogenous vasoactive peptide, in uterine artery was intense in pregnant compared to nonpregnant rats, but it is not known whether AM directly relaxes uterine artery or not. In this study, we elucidated the mechanisms of uterine artery relaxation by AM and its regulation by pregnancy and female sex steroids. AM was able to relax uterine artery, and this relaxation was influenced positively by pregnancy and estradiol as evidenced by the increased pD(2) and E(max) values of AM. Both pregnancy and estradiol treatment to ovariectomized rats amplified RAMP(3) expression in uterine arteries while progesterone had no effect. AM-induced uterine artery relaxation is predominantly endothelium-dependent. The AM receptor antagonist CGRP(8-37) is more potent than AM(22-52) in inhibiting the AM relaxation, indicating the involvement of AM(2) receptor subtype. Moreover, AM uses the classical nitric oxide-cyclic guanosine monophosphate pathway along with K(Ca) channels to mediate the vasodilatory effect in uterine artery. In conclusion, sensitivity of uterine artery to AM-induced relaxation is increased with pregnancy or estradiol treatment by increasing RAMP(3) expression, suggesting an important role for AM in regulating the uterine hemodynamics, probably maintaining uterine blood flow during pregnancy and in pre- and postmenopausal cardiovascular adaptation differences.

Apelin Attenuates Hyperoxic Lung and Heart Injury in Neonatal Rats

Apelin, a potent vasodilator and angiogenic factor, may be a novel therapeutic agent in neonatal chronic lung disease, including bronchopulmonary dysplasia. To determine the beneficial effect of apelin in neonatal rats with hyperoxia-induced lung injury, a model for premature infants with bronchopulmonary dysplasia. The cardiopulmonary effects of apelin treatment (62 μg/kg/d) were studied in neonatal rats by exposure to 100% oxygen, using two treatment strategies: early concurrent treatment during continuous exposure to hyperoxia for 10 days and late treatment and recovery in which treatment was started on Day 6 after hyperoxic injury for 9 days and continued during the 9-day recovery period. We investigated in both models the role of the nitric oxide-cyclic guanosine monophosphate (cGMP) pathway in apelin treatment by specific inhibition of the nitric oxide synthase activity with N(ω)-nitro-L-arginine methyl ester (L-NAME, 25 mg/kg/d). Parameters investigated include survival, lung and heart histopathology, pulmonary fibrin deposition and inflammation, alveolar vascular leakage, lung cGMP levels, right ventricular hypertrophy, and differential mRNA expression in lung and heart tissue. Prophylactic treatment with apelin improved alveolarization and angiogenesis, increased lung cGMP levels, and reduced pulmonary fibrin deposition, inflammation, septum thickness, arteriolar wall thickness, and right ventricular hypertrophy. These beneficial effects were completely absent in the presence of L-NAME. In the injury-recovery model apelin also improved alveolarization and angiogenesis, reduced arteriolar wall thickness, and attenuated right ventricular hypertrophy. Apelin reduces pulmonary inflammation, fibrin deposition, and right ventricular hypertrophy, and partially restores alveolarization in rat pups with neonatal hyperoxic lung injury via a nitric oxide synthase-dependent mechanism.

Lysimachia clethroides Extract Promote Vascular Relaxation via Endothelium-Dependent Mechanism

Lysimachia clethroides is widely used in traditional herbal medicine for many purposes, especially for blood vessel-related diseases in Korea and East Asia. Experiments were undertaken to determine whether hydro-alcoholic extract obtained from L. clethroides (LCE) has vasorelaxant activity in the rat aorta rings and, if so, to elucidate the underlying mechanism. Rat aorta rings were suspended in organ chambers for the measurement of changes in isometric tension in the presence or absence of several inhibitors. LCE induced endothelium-dependent vasodilation (ED50 = 6.1 mug/mL) and that was abolished by nitric oxide synthase inhibitor, N-nitro-L-arginine, and guanylyl cyclase inhibitor, 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one, PI3-kinase inhibitor, wortmannin, and cell permeable superoxide dismutase. In addition, LCE decreased vessels contraction by phenylephrine. Prostaglandin synthesis inhibitor, indometacin, and inhibitors of endothelium-derived hyperpolarizing factor, charybdotoxin plus apamin, did not affect vasodilatory effect of LCE. In cultured endothelial cells, LCE-induced phosphorylation of serine 1177-endothelial nitric oxide synthase and serine 473-Akt. LCE inhibited strongly nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in smooth muscle cells and angiotensin II-induced contraction of rat aorta. Finally, increased oxidative stress in rat aorta-induced by angiotensin II is ameliorated by LCE. Taken together, LCE induces an endothelium-dependent vasodilation and might be involved, at least in part, the activation of the nitric oxide-cyclic guanosine monophosphate pathway. In addition, LCE decreases oxidative stress in aorta by inhibition of NADPH oxidase activity. The present findings indicate that LCE could be a candidate of herbal medicine for cardiovascular diseases associated with disturbed NO production and endothelial dysfunction.

A New Perfusion Model for Studying Erectile Function

The present study introduces a newly devised in vitro penile perfusion model, which allows the measurement of changes in intracavernosum pressure (ICP), tension, and cyclic nucleotides in penile tissue in a one-step procedure. We compared the penile perfusion model with the classical penile strip chamber model to develop the new model. We investigated the role of nitric oxide-cyclic guanosine monophosphate pathway in both systems activated by acetylcholine or electrical field stimulation (EFS). We measured cGMP (cyclic guanosine monophosphate) in the penile corpus cavernosum smooth muscle in both systems and perfusates in the penile perfusion model. We determined ICP, tension, and cGMP simultaneously in penile perfusion model during the experiments. Changes of tension and cGMP in both models, and of cGMP in perfusates and of ICP in penile perfusion model. In both systems, acetylcholine relaxed the phenylephrine-precontracted penile corpus cavernosum smooth muscle in a concentration-dependent manner. EFS decreased the tension in both models and ICP in the penile perfusion model in a frequency-dependent manner. Pretreatment with atropine, Nomega nitro-L-arginine-methyl ester (L-NAME), and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) blocked the acetylcholine-induced decrease in the tension in both models and ICP in penile perfusion model. Acetylcholine increased cGMP levels in the perfusate of penile perfusion model and the changes were attenuated by tetrodotoxin (TTX), atropine, L-NAME and ODQ. EFS increased cGMP levels of the penile corpus cavernosum smooth muscle of both models and the changes were attenuated by TTX, atropine, L-NAME, and ODQ. The results indicated that the responses of penile strip and perfused penile tissue to acetylcholine and EFS were very similar in both models in terms of tension and cGMP levels. Furthermore, the new model has more advantages over the classical penile strip chamber model in measuring intracavernosum metabolic changes and ICP without interruption of the procedure.