Present and future treatment strategies for pulmonary arterial hypertension : focus on phosphodiesterase-5 inhibitors

The effects of sildenafil citrate on urinary podocin and nephrin mRNA expression in an L-NAME model of pre-eclampsia

We investigated the effects of sildenafil citrate (SC) on podocyturia in N ^ω-nitro-L-arginine methyl ester hydrochloride (L-NAME) model of pre-eclampsia (PE). One hundred and twenty Sprague-Dawley rats (SDR) were divided into five groups like pregnant control (PC), early-onset PE (EOPE), late-onset PE(LOPE), early and late-onset PE with SC-treated groups [EOPE (SC); LOPE (SC)]. PE was induced in SDR by oral administration of L-NAME in drinking water for 4-8 days for EOPE and 8-14 day for LOPE. The blood pressure, urine volume and total urine protein were increased in EOPE and LOPE groups when compared to PC, and all the above parameters decreased in EOPE (SC) and LOPE (SC) groups when compared to EOPE and LOPE groups, respectively. The EOPE and LOPE groups showed an increase in urinary nephrin mRNA and podocin mRNA levels compared to PC group. Increases in serum and renal soluble fms-like tyrosine kinase-1 (sFlt-1) expression levels and decreases in renal vascular endothelial growth factor (VEGF) expression and serum placenta growth factor (PlGF) levels were observed in EOPE and LOPE groups when compared to PC group. In addition, decreases in serum and renal sFlt-1 expression levels and increases in renal VEGF expression and serum PlGF levels were observed in EOPE (SC) and LOPE (SC) groups when compared to EOPE and LOPE groups, respectively. The light microscopy showed that the renal tissue of L-NAME-treated rats had extensive glomerular damage, tubular damage and infiltration by mononuclear cells when compared to PC group. Therefore, SC ameliorated podocyturia through its effects on the antiangiogenic/angiogenic status in this animal model.

Vasoactive Therapy in Systemic Sclerosis: Real-life Therapeutic Practice in More Than 3000 Patients

OBJECTIVE

Vasculopathy is a key factor in the pathophysiology of systemic sclerosis (SSc) and the main cause for Raynaud phenomenon (RP), digital ulcers (DU), and/or pulmonary arterial hypertension (PAH). It is so far unknown how patients with SSc are treated with vasoactive agents in daily practice. To determine to which extent patients with SSc were treated with different vasoactive agents, we used data from the German Network for Systemic Scleroderma registry.

METHODS

The data of 3248 patients with SSc were analyzed.

RESULTS

Patients were treated with vasoactive drugs in 61.1% of cases (1984/3248). Of these, 47.6% received calcium channel inhibitors, followed by 34.2% treated with angiotensin-converting enzyme (ACE) inhibitors, 21.1% treated with intravenous (IV) prostanoids, 10.1% with pentoxifylline, 8.8% with angiotensin 1 receptor antagonists (AT1RA), 8.7% with endothelin 1 receptor antagonists (ET1RA), 4.1% with phosphodiesterase type 5 (PDE5) inhibitors, and 5.3% with others. Patients with RP received vasoactive therapy in 63.3% of cases, with DU in 70.1%, and with PAH in 78.2% of cases. Logistic regression analysis revealed that patients with PAH were significantly more often treated with PDE5 inhibitors and ET1RA, and those with DU with ET1RA and IV prostanoids. In addition, 41.8% of patients were treated with ACE inhibitors and/or AT1RA. Patients registered after 2009 received significantly more often ET1RA, AT1RA, and IV prostanoids compared with patients registered prior to 2005.

CONCLUSION

These data clearly indicate that many patients with SSc do not yet receive sufficient vasoactive therapy. Further, in recent years, a marked change of treatment regimens can be observed.

Stimulation of neural stem cell proliferation by inhibition of phosphodiesterase 5

The involvement of nitric oxide (NO) and cyclic GMP (cGMP) in neurogenesis has been progressively unmasked over the last decade. Phosphodiesterase 5 (PDE5) specifically degrades cGMP and is highly abundant in the mammalian brain. Inhibition of cGMP hydrolysis by blocking PDE5 is a possible strategy to enhance the first step of neurogenesis, proliferation of neural stem cells (NSC). In this work, we have studied the effect on cell proliferation of 3 inhibitors with different selectivity and potency for PDE5, T0156, sildenafil, and zaprinast, using subventricular zone-(SVZ-) derived NSC cultures. We observed that a short- (6 h) or a long-term (24 h) treatment with PDE5 inhibitors increased SVZ-derived NSC proliferation. Cell proliferation induced by PDE5 inhibitors was dependent on the activation of the mitogen-activated protein kinase (MAPK) and was abolished by inhibitors of MAPK signaling, soluble guanylyl cyclase, and protein kinase G. Moreover, sildenafil neither activated ERK1/2 nor altered p27^Kip1 levels, suggesting the involvement of pathways different from those activated by T0156 or zaprinast. In agreement with the present results, PDE5 inhibitors may be an interesting therapeutic approach for enhancing the proliferation stage of adult neurogenesis.

Phosphodiesterase-5 inhibitor, tadalafil, protects against myocardial ischemia/reperfusion through protein-kinase g-dependent generation of hydrogen sulfide

BACKGROUND

Tadalafil is a novel long-acting inhibitor of phosphodiesterase-5. Because cGMP-dependent protein kinase (PKG) signaling plays a key role in cardioprotection, we hypothesized that PKG activation with tadalafil would limit myocardial ischemia/reperfusion (I/R) injury and dysfunction. Additionally, we contemplated that cardioprotection with tadalafil is mediated by hydrogen sulfide (H(2)S) signaling in a PKG-dependent fashion.

METHODS AND RESULTS

After baseline transthoracic echocardiography (TTE), adult ICR mice were injected i.p. with vehicle (10% DMSO) or tadalafil (1 mg/kg) with or without KT5823 (KT, PKG blocker, 1 mg/kg) or dl-propargylglycine (PAG, Cystathionine-gamma-lyase [CSE, H(2)S-producing enzyme] blocker; 50 mg/kg) 1 hour before coronary artery ligation for 30 minutes and reperfusion for 24 hours, whereas C57BL wild-type and CSE-knockout mice were treated with either vehicle or tadalafil. After reperfusion, TTE was performed and hearts were collected for infarct size (IS) measurement using TTC staining. Survival was increased with tadalafil (95%) compared with control (65%, P<0.05). Infarct size was reduced with tadalafil (13.2+/-1.7%) compared to vehicle (40.6+/-2.5%; P<0.05). KT and PAG abolished tadalafil-induced protection (IS: 39.2+/-1% and 51.2+/-2.4%, respectively) similar to genetic deletion of CSE (47.2+/-5.1%). Moreover, tadalafil preserved fractional shortening (FS: 31+/-1.5%) compared to control (FS: 22+/-4.8%, P<0.05). Baseline FS was 44+/-1.7%. KT and PAG abrogated the preservation of LV function with tadalafil by decline in FS to 17+/-1% and 23+/-3%, respectively. Compared to vehicle, myocardial H(2)S production was significantly increased with tadalafil and was abolished with KT.

CONCLUSIONS

PKG activation with tadalafil limits myocardial infarction and preserves LV function through H(2)S signaling.

A systematic review of experimental and clinical studies of sildenafil citrate for intrauterine growth restriction and pre-term labour

Sildenafil could be an alternative in the treatment of intrauterine growth retardation (IUGR) and premature delivery. In order to systematically review the reproductive-related effects of sildenafil, a search was made on PubMed and the Science Citation Index for studies evaluating the effects of sildenafil on uterine vessels or myometrium either in vitro or in experimental animal models as well as for any clinical trial or case reporting the outcome of pregnant women treated with sildenafil. The information was obtained from: three in vitro studies, five studies performed in experimental animal models, four studies on women with fertility and sterility disorders receiving 100 mg/day of sildenafil intravaginally, and two case reports of pregnant women who received sildenafil for the treatment of pulmonary hypertension. Incubation with sildenafil of different in vitro preparations resulted in vasodilator and uterine relaxant effects. No evidence of teratogenicity was observed in the studies performed in mice, rats and dogs. Sildenafil increased fetal weight in rats. In women, contradictory results on uterine blood flow and endometrial development were reported after the intravaginal administration of sildenafil. No adverse fetal outcomes were reported in the two pregnant women with pulmonary hypertension receiving sildenafil late in their pregnancy. In conclusion, there is still limited information about the efficacy of sildenafil for the treatment of IUGR and premature delivery. However, studies in experimental animal models and two human case reports have reported no deleterious effects on the mother or offspring.

Identification of oxidative post-translational modification of serum albumin in patients with idiopathic pulmonary arterial hypertension and pulmonary hypertension of sickle cell anemia

Pulmonary hypertension (PH) in sickle cell anemia (SCA) is characterized by decreased nitric oxide bioavailability that might, in part, be related to oxidative stress. Oxidative post-translational modifications of plasma proteins may serve as hallmarks of disease severity and could result in altered protein function and structure. We hypothesized that serum albumin in patients with PH of SCA undergoes oxidative post-translational modification and that this modification may reflect important mediators of disease pathogenesis that are common to both idiopathic pulmonary arterial hypertension (IPAH) and PH of SCA. To explore this hypothesis, we studied albumin purified from the plasma of patients in four subject groups: SCA and PH, SCA steady-state without PH, IPAH, and normal volunteers. Purified albumin was analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). Using MALDI-TOFMS, we identified that an ion corresponding to a malondialdehyde (MDA)-modified albumin peptide was differentially present in patients with IPAH and PH of SCA. These results were confirmed by dot-blotting and Western analysis. We localized the site of MDA modification to albumin residue K159 using LC/MS/MS. Thus, we have identified an MDA modification of serum albumin that appears to be a common link between PH of SCA and IPAH. This finding supports the notion that oxidative stress modulates the pathogenesis of PH of SCA and suggests that this and other post-translational modifications may be important biomarkers of disease.

Sildenafil and vardenafil but not nitroglycerin limit myocardial infarction through opening of mitochondrial K(ATP) channels when administered at reperfusion following ischemia in rabbits

Phosphodiesterase-5 (PDE-5) inhibitors including sildenafil and vardenafil induce powerful preconditioning-like cardioprotective effect against ischemia/reperfusion injury through opening of mitochondrial K(ATP) channels in the heart. The goal of these studies was to demonstrate the protective effect of sildenafil and vardenafil on reperfusion injury and to compare it with the antianginal vasodilator nitroglycerin (NTG). In addition, we determined the role of mitochondrial K(ATP) channels in protection. Adult male New Zealand white rabbits were anesthetized and subjected to ischemia by 30 min of coronary artery occlusion followed by 3 h of reperfusion. Seven groups were studied. 1-Controls; 2-Sildenafil (total dose: 0.71 mg/kg; i.v.) infused for 65 min starting 5 min before reperfusion; 3-Sildenafil+5-hydroxydecanoate (5-HD, blocker of mitochondrial K(ATP) channel, total dose: 5 mg/kg) administered as 2 bolus injections; 4-Vardenafil (total dose: 0.014 mg/kg; iv) administered as in group 2; 5-Vardenafil+5-HD administered as in group 3; 6-5-HD administered as two bolus injections and 7-Nitroglycerin (NTG, total dose: 2 microg kg(-1) min(-1)) administered as in group 2. Infarct size was reduced in sildenafil (19.19+/-1.3%) as well as vardenafil (17.0+/-2.0%) treated groups as compared to controls (33.8+/-1.7%). However, NTG failed to confer similar cardioprotection (31.5+/-0.8%). 5-HD blocked the cardioprotective effects of sildenafil and vardenafil as shown by an increase in infarct size (34.0+/-1.1% and 28.3+/-1.9%, respectively). Both sildenafil and vardenafil protect the ischemic myocardium against reperfusion injury through a mechanism dependent on mitochondrial K(ATP) channel opening.