sildenafil-citrate and Hemolysis

Ischemic priapism is a common but underrecognized morbidity affecting about 33% of adult men with sickle cell disease (SCD). The onset of priapism occurs in the prepubertal period and tends to be recurrent with increasing age. Significantly, priapism is associated with an unrecognized high burden of mental duress and sexual dysfunctions. The diagnosis of priapism is clinical. Many episodes of priapism will resolve spontaneously, but when an episode lasts longer than 4 hours, the episode is considered a urologic emergency requiring quick intervention with either corporal aspiration or shunt surgery. Only 3 randomized clinical trials (stilbesterol, ephedrine or etilefrine, and sildenafil) have been conducted for secondary priapism prevention in SCD. All 3 trials were limited with small sample sizes, selection biases, and inconclusive results after completion. The current molecular understanding of the pathobiology of priapism suggests a relative nitric oxide (NO) deficiency secondary to chronic hemolysis in SCD and associated phosphodiesterase type 5 dysregulation. We posit an increase in NO levels will restore the normal homeostatic relationship between voluntary erection and detumescence. Currently, 2 randomized phase 2 trials (1 double-blind, placebo-controlled trial and 1 open-label, single-arm intervention) are being conducted for secondary priapism prevention in men at high risk for recurrent priapism (NCT03938454 and NCT05142254). We review the epidemiology and pathobiology of priapism, along with mechanistic therapeutic approaches for secondary prevention of priapism in SCD.

Topics: Adult; Anemia, Sickle Cell; Clinical Trials, Phase II as Topic; Etilefrine; Hemolysis; Humans; Male; Priapism; Randomized Controlled Trials as Topic; Sildenafil Citrate

Topics: Heart-Assist Devices; Hemolysis; Humans; Pulmonary Circulation; Sildenafil Citrate; Thromboembolism

Topics: Heart-Assist Devices; Hemolysis; Humans; Pulmonary Circulation; Sildenafil Citrate; Thromboembolism

Low-level hemolysis (LLH) after left ventricular assist device implantation contributes to thromboembolic events (TE). Free plasma hemoglobin (fHb) scavenges nitric oxide (NO), which causes endothelial dysfunction and activates platelets. fHb also interacts with von Willebrand factor (vWF). We hypothesized that improved hemodynamic and enhanced NO signaling in HeartMate II (HMII) patients with LLH taking the phosphodiesterase-5 inhibitor sildenafil may reduce the risk of TE.From 2011 to 2015, 83 patients underwent HMII implantation. Patients with LLH as defined by elevated lactate dehydrogenase (400 < LDH ≤ 700 U/L) at hospital discharge were identified. Patients were categorized into 4 groups: 1) LLH + sildenafil, 2) LLH no sildenafil, 3) no LLH + sildenafil, and 4) no LLH no sildenafil. Adverse event-free survival was compared between the groups.Thirty-four patients (40.9%) were discharged with LLH and 22 (64.7%) of them took sildenafil. LDH and fHb remained significantly elevated in both LLH groups compared to the no LLH patients (P < 0.0001). Overall incidence of pump thrombosis (PT) was 4.8% and of ischemic stroke (IS) was 8.4%. HMII patients with LLH not on sildenafil had higher risk of TE (hazard ratio (HR): 14.4, 95%-CI: 1.8-117.1, P = 0.001). vWF activity and bleeding incidence did not differ between the LLH and no LLH patients. Mean pulmonary artery pressure and pulmonary vascular resistance decreased significantly in HMII taking sildenafil (P < 0.0001) while cardiac index increased (P < 0.0001).Sildenafil treatment among HMII patients with LLH reduced the risk of thromboembolic events and significantly improved and decompressed the pulmonary circulation during HMII support.

Topics: Aged; Case-Control Studies; Female; Follow-Up Studies; Heart-Assist Devices; Hemolysis; Humans; Male; Middle Aged; Phosphodiesterase 5 Inhibitors; Postoperative Complications; Pulmonary Circulation; Retrospective Studies; Sildenafil Citrate; Thromboembolism; Treatment Outcome

Persistent low-level hemolysis (LLH) during continuous-flow mechanical circulatory support is associated with subsequent thrombosis. Free hemoglobin from ongoing hemolysis scavenges nitric oxide (NO) to create an NO deficiency which can augment platelet function leading to a prothrombotic state. The phosphodiesterase-5 inhibitor, sildenafil, potentiates NO signaling to inhibit platelet function. Accordingly, we investigated the association of sildenafil administration and thrombotic events in patients with LLH during Heart Mate II support.. A single-center review of all patients implanted with a Heart Mate II who survived to discharge (n=144). LLH was defined by a discharge lactate dehydrogenase level of 400 to 700 U/L. Patients were categorized as (1) LLH not on sildenafil, (2) LLH on sildenafil, (3) no LLH not on sildenafil, and (4) no LLH on sildenafil. Age, sex, platelet count, and mean platelet volume were similar between groups. Seventeen patients had either device thrombosis or ischemic stroke. Presence of LLH was associated with a greater risk of thrombosis (adjusted hazard ratio, 15; 95% confidence interval, 4.5-50;. Sildenafil is associated with reduced device thrombosis and ischemic stroke during ongoing LLH on Heart Mate II support.

Topics: Brain Ischemia; Chi-Square Distribution; Disease-Free Survival; Heart Failure; Heart-Assist Devices; Hemolysis; Humans; Kaplan-Meier Estimate; Mean Platelet Volume; Phosphodiesterase 5 Inhibitors; Proportional Hazards Models; Prosthesis Design; Protective Factors; Retrospective Studies; Risk Factors; Sildenafil Citrate; Stroke; Time Factors; Treatment Outcome

Recent research suggests that priapism in sickle cell disease (SCD) is due to dysregulation of penile erection homeostasis including alteration of nitric oxide synthase (NOS) and phosphodiesterase type 5 (PDE5) activities by excessive levels of reactive oxygen species (ROS) released during hemolysis. It is unknown if subacute exposure to hemolysis is sufficient or if chronic reconditioning of erectile tissues is required for perturbation of homeostatic pathways and whether PDE5 inhibitor (PDE5I) treatment can restore erectile homeostasis in the subacute setting.. The aim of this study was to investigate the effects of subacute hemolysis (3-month exposure) on priapism and NO pathway regulation.. Mice underwent bone marrow transplantation with either SCD (BM-SS) or wild-type (WT) bone marrow. BM-SS mice were treated with sildenafil 100 mg/kg/day. We measured intracavernous pressure (ICP) measurements with or without cavernous nerve stimulation following bone marrow transplantation to assess for priapism.. ICP and frequency of erections were assessed. Penile tissues were analyzed for NOS, protein kinase G (PKG), PDE5, and ROS activities.. BM-SS mice demonstrated a priapism phenotype. PDE5I treatment reduced the frequency of erections in BM-SS mice (1.7 ± 1.1 vs. 5.5 ± 2.8 erections per hour, P < 0.05). Penile tissues from BM-SS mice demonstrated decreased NOS, PKG, PDE5 and elevated ROS activities compared with that of control mice. PDE5I treatment increased NOS (11.6 ± 1.3% vs. 7.8 ± 2.3%, P < 0.05) and PDE5 (76.3 ± 9.8% vs. 52.3 ± 11.1%, P < 0.05) activities and decreased ROS activity (137.8 ± 12.1% vs. 199.1 ± 11.3%, P < 0.05) compared with non-PDE5I treated BM-SS mice. PKG activity was increased beyond control levels with PDE5I treatment (158.4 ± 10.3%, P < 0.05).. Short-term hemolysis is sufficient to establish a priapism phenotype and results in loss of erectile function. PDE5I treatment ameliorates priapism, in part, because of restored NO balance with decreased ROS generation and increased PDE5 activity.

Topics: Acute Disease; Anemia, Sickle Cell; Animals; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Hemolysis; Male; Mice; Mice, Transgenic; Nitric Oxide Synthase; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Priapism; Signal Transduction; Sildenafil Citrate

Evans syndrome is a rare cause of hemolysis in pediatric patients. The authors describe two severely affected patients who had previously been heavily treated, and who subsequently developed severe pulmonary hypertension. Both patients were successfully managed by a combination of immunosuppression and anti-pulmonary hypertension treatment. The first patient to present, case A, received an allogeneic bone marrow transplant with subsequent cure of both Evans syndrome and pulmonary hypertension and is now on a weaning dose of sildenafil. Case B is being worked up for allogeneic bone marrow transplantation. The authors speculate that the pulmonary hypertension was caused by the underlying immune dysregulation and hemolysis and that Evans syndrome joins the list of other hemolytic anemias that cause pulmonary hypertension, such as sickle cell disease, thalassemia, and paroxysmal nocturnal hemoglobinuria. However, they suggest a vasculitic process as the main cause.

Topics: Anemia, Hemolytic, Autoimmune; Bone Marrow Transplantation; Child; Child, Preschool; Female; Hemolysis; Humans; Hypertension, Pulmonary; Infant; Piperazines; Purines; Purpura, Thrombocytopenic, Idiopathic; Sildenafil Citrate; Sulfones; Syndrome; Transplantation, Homologous; Vasodilator Agents

Increased platelet activation is recognized in patients with sickle cell disease (SCD), but its pathogenesis and clinical relevance remain uncertain. Pulmonary arterial hypertension (PAH), an important complication of SCD, is characterized by a proliferative pulmonary vasculopathy, in situ thrombosis, and vascular dysfunction related to scavenging of nitric oxide (NO) by hemoglobin released into blood plasma during intravascular hemolysis. We investigated links between platelet activation, PAH and NO scavenging in patients with SCD. Platelet activation marked by activated fibrinogen receptor correlated to the severity of PAH (r = 0.58, P < .001) and to laboratory markers of intravascular hemolysis, such as reticulocyte count (r = 0.44, P = .02). In vitro exposure of platelets to pathologically relevant concentrations of cell-free hemoglobin promoted basal- and agonist-stimulated activation and blocked the inhibitory effects on platelet activation by an NO donor. In patients with SCD, administration of sildenafil, a phosphodiesterase-5 inhibitor that potentiates NO-dependent signaling, reduced platelet activation (P = .01). These findings suggest a possible interaction between hemolysis, decreased NO bioavailability, and pathologic platelet activation that might contribute to thrombosis and pulmonary hypertension in SCD, and potentially other disorders of intravascular hemolysis. This supports a role for NO-based therapeutics for SCD vasculopathy. This trial was registered at www.clinicaltrials.gov as no. NCT00352430.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Adult; Anemia, Sickle Cell; Female; Flow Cytometry; Hemoglobins; Hemolysis; Humans; Hypertension, Pulmonary; Male; Nitric Oxide; Phosphodiesterase Inhibitors; Piperazines; Platelet Activation; Purines; Sildenafil Citrate; Sulfones; Thrombosis