Jacob Rajfer

Nitric Oxide as a Mediator of Relaxation of the Corpus Cavernosum in Response to Nonadrenergic, Noncholinergic Neurotransmission

Abstract Background. Nitric oxide has been identified as an endothelium-derived relaxing factor in blood vessels. We tried to determine whether it is involved in the relaxation of the corpus cavernosum that allows penile erection. The relaxation of this smooth muscle is known to occur in response to stimulation by nonadrenergic, noncholinergic neurons. Methods. We studied strips of corpus cavernosum tissue obtained from 21 men in whom penile prostheses were inserted because of impotence. The mounted smooth-muscle specimens were pretreated with guanethidine and atropine and submaximally contracted with phenylephrine. We then studied the smooth-muscle relaxant responses to stimulation by an electrical field and to nitric oxide. Results. Electrical-field stimulation caused a marked, transient, frequency-dependent relaxation of the corpus cavernosum that was inhibited in the presence of N-nitro-L-arginine and N-amino-L-arginine, which selectively inhibit the biosynthesis of nitric oxide from L-arginine. The a...

Nitric oxide and cyclic GMP formation upon electrical field stimulation cause relaxation of corpus cavernosum smooth muscle.

In the presence of functional adrenergic and cholinergic blockade, electrical field stimulation relaxes corpus cavernosum smooth muscle by unknown mechanisms. We report here that electrical field stimulation of isolated strips of rabbit corpus cavernosum promotes the endogenous formation and release of nitric oxide (NO), nitrite, and cyclic GMP. Corporal smooth muscle relaxation in response to electrical field stimulation, in the presence of guanethidine and atropine, was abolished by tetrodotoxin and potassium-induced depolarization, and was markedly inhibited by NG-nitro-L-arginine, NG-amino-L-arginine, oxyhemoglobin, and methylene blue, but was unaffected by indomethacin. The inhibitory effects of NG-substituted analogs of L-arginine were nearly completely reversed by addition of excess L-arginine but not D-arginine. Corporal smooth muscle relaxation elicited by electrical field stimulation was accompanied by rapid and marked increases in tissue levels of nitrite and cyclic GMP, and all responses were nearly abolished by NG-nitro-L-arginine. These observations indicate that penile erection may be mediated by NO generated in response to nonadrenergic-noncholinergic neurotransmission.

QUERCETIN IN MEN WITH CATEGORY III CHRONIC PROSTATITIS: A PRELIMINARY PROSPECTIVE, DOUBLE-BLIND, PLACEBO-CONTROLLED TRIAL

OBJECTIVES The National Institutes of Health (NIH) category III chronic prostatitis syndromes (nonbacterial chronic prostatitis and prostatodynia) are common disorders with few effective therapies. Bioflavonoids have recently been shown in an open-label study to improve the symptoms of these disorders in a significant proportion of men. The aim of this study was to confirm these findings in a prospective randomized, double-blind, placebo-controlled trial. METHODS Thirty men with category IIIa and IIIb chronic pelvic pain syndrome were randomized in a double-blind fashion to receive either placebo or the bioflavonoid quercetin 500 mg twice daily for 1 month. The NIH chronic prostatitis symptom score was used to grade symptoms and the quality-of-life impact at the start and conclusion of the study. In a follow-up unblind, open-label study, 17 additional men received 1 month of a supplement containing quercetin, as well as bromelain and papain (Prosta-O), which enhance bioflavonoid absorption. RESULTS Two patients in the placebo group refused to complete the study because of worsening symptoms, leaving 13 placebo and 15 bioflavonoid patients for evaluation in the blind study. Both the quercetin and placebo groups were similar in age, symptom duration, and initial symptom score. Patients taking placebo had a mean improvement in NIH symptom score from 20.2 to 18.8 (not significant), while those taking the bioflavonoid had a mean improvement from 21.0 to 13.1 (P = 0.003). Twenty percent of patients taking placebo and 67% of patients taking the bioflavonoid had an improvement of symptoms of at least 25%. In the 17 patients who received Prosta-Q in the open-label study, 82% had at least a 25% improvement in symptom score. CONCLUSIONS Therapy with the bioflavonoid quercetin is well tolerated and provides significant symptomatic improvement in most men with chronic pelvic pain syndrome.

Nitric Oxide is a Potent Relaxant of Human and Rabbit Corpus Cavernosum

Nitric oxide (NO) caused a potent, marked, and transient relaxation of precontracted strips of corpus cavernosum isolated from humans and rabbits. The relaxation response elicited by NO was very similar to the relaxation evoked by electrical field stimulation via the nonadrenergic-noncholinergic pathway. Sodium nitroprusside, nitroglycerin, and S-nitroso-N-acetylpenicillamine, which are nitrovasodilators known to generate NO, also caused marked concentration-dependent relaxation of corpus cavernosum. Relaxant responses to NO were enhanced by the cyclic GMP phosphodiesterase inhibitor M&B 22,948 and inhibited by oxyhemoglobin. Similarly, relaxation of corpus cavernosum in response to electrical field stimulation or acetylcholine was enhanced by M&B 22,948 and inhibited by oxyhemoglobin. NO stimulated cyclic GMP formation in corpus cavernosum and a close positive correlation was found between the magnitudes of relaxation and cyclic GMP formation. The data suggest that NO-elicited activation of guanylate cyclase and cyclic GMP formation represents the signal transduction mechanism responsible for relaxation and nonadrenergic-noncholinergic-mediated penile erection. These observations indicate that NO is a potent relaxant of human and rabbit corpus cavernosum and support our hypothesis that endogenous NO is the principal mediator of penile erection caused by nonadrenergic-noncholinergic stimulation.

The efficacy and safety of tadalafil: an update.

To provide an update on the efficacy and safety of tadalafil, a phosphodiesterase‐5 inhibitor, in the treatment of erectile dysfunction (ED).

Hormonal therapy of cryptorchidism. A randomized, double-blind study comparing human chorionic gonadotropin and gonadotropin-releasing hormone

Abstract We conducted a randomized, double-blind study comparing intranasal gonadotropin-releasing hormone (1.2 mg per day for 28 days) with parenteral human chorionic gonadotropin (3300 IU per week for four weeks) in the treatment of cryptorchidism in 33 boys one to five years old (29 with unilateral and 4 with bilateral cryptorchidism). Testicular descent into the scrotum occurred in 3 of the 16 patients (19 percent) treated with gonadotropin-releasing hormone and in 1 of the 17 (6 percent) treated with human chorionic gonadotropin (P = 0.23). The mean luteinizing hormone and testosterone levels were similar in both groups before treatment. During treatment, the testosterone levels were significantly increased in both groups, but higher levels occurred in the group treated with human chorionic gonadotropin (P<0.05). In a parallel (but uncontrolled) study of five boys with retractile testes (defined as a nonscrotal testis that could be manipulated into the bottom of the scrotum) who were originally exclu...

Chronic daily tadalafil prevents the corporal fibrosis and veno-occlusive dysfunction that occurs after cavernosal nerve resection

Associate Editor

Effect of nitric oxide on the differentiation of fibroblasts into myofibroblasts in the Peyronie's fibrotic plaque and in its rat model.

The myofibroblast shares phenotypic features of both fibroblasts and smooth muscle cells. It plays a critical role in collagen deposition and wound healing and disappears by apoptosis when the wound is closed. Its abnormal persistence leads to hypertrophic scar formation and other fibrotic conditions. Myofibroblasts are present in the fibrotic plaque of the tunica albuginea (TA) of the penis in men with Peyronies disease (PD), a localized fibrosis that is accompanied by a spontaneous induction of the inducible nitric oxide synthase (iNOS), also observed in the TGFbeta1-elicited, PD-like lesion in the rat model. iNOS expression counteracts fibrosis, by producing nitric oxide (NO) that reduces collagen deposition in part by neutralization of profibrotic reactive oxygen species. In this study we investigated whether fibroblast differentiation into myofibroblasts is enhanced in the human and rat PD-like plaque and in cultures of human tissue fibroblasts. We also examined whether NO reduces this cell differentiation and collagen synthesis. The myofibroblast content in the fibroblast population was measured by quantitative immunohistochemistry as the ratio between alpha-smooth muscle actin (ASMA; myofibroblast marker) and vimentin (general fibroblast marker) levels. We found that myofibroblast content was considerably increased in the human and TGFbeta1-induced rat plaques as compared to control TA. Inhibition of iNOS activity by chronic administration of L-iminoethyl-L-lysine to rats with TGFbeta1-induced TA lesion increased myofibroblast abundance and collagen I synthesis measured in plaque and TA homogenates from animals injected with a collagen I promoter construct driving the expression of beta-galactosidase. Fibroblast differentiation into myofibroblasts occurred with passage in the cell cultures from the human PD plaque, but was minimal in cultures from the TA. Induction of iNOS in PD and TA cultures with a cytokine cocktail and a NO donor, S-nitroso-N-acetyl penicillamine (SNAP), was detected by immunohistochemistry. Both treatments reduced the total number of cells and the number of ASMA positive cells, whereas only SNAP decreased collagen I immunostaining. These results support the hypotheses that myofibroblasts play a role in the development of the PD plaque and that the antifibrotic effects of NO may be mediated at least in part by the reduction of myofibroblast abundance and lead to a reduction in collagen I synthesis.

Myostatin short interfering hairpin RNA gene transfer increases skeletal muscle mass

Myostatin negatively regulates skeletal muscle growth. Myostatin knockout mice exhibit muscle hypertrophy and decreased interstitial fibrosis. We investigated whether a plasmid expressing a short hairpin interfering RNA (shRNA) against myostatin and transduced using electroporation would increase local skeletal muscle mass.

Long-Term Continuous Treatment with Sildenafil Ameliorates Aging-Related Erectile Dysfunction and the Underlying Corporal Fibrosis in the Rat

Abstract Aging-related erectile dysfunction is characterized by a loss of smooth muscle cells (SMCs) and fibrosis in the corpora cavernosa, and functionally by corporal veno-occlusive dysfunction (CVOD). Phosphodiesterase 5 (PDE5A) inhibitors, in part via upregulating inducible nitric oxide synthase (NOS2A), have antifibrotic properties in penile tissues. We aimed to determine whether in the aged rat the chronic long-term treatment with sildenafil ameliorates corporal SMC loss and fibrosis, stimulates NOS2A induction, and corrects the associated CVOD. Aged male rats (20 mo old) received sildenafil in their drinking water (20 mg/kg per day) or plain water for 45 days, and untreated young rats (5 mo old) served as controls (n = 8 per group). CVOD was assessed by dynamic infusion cavernosometry (DIC). Collagen:SMC (Masson trichrome) and collagen III:I (picrosirius red) ratios, SMC content (alpha-smooth muscle actin [ACTA2]), cell proliferation (proliferating nuclear antigen [PCNA]), apoptotic death (TUNEL), and NOS2A induction were measured by histochemistry and immunohistochemistry followed by quantitative image analysis. Collagen content was determined by hydroxyproline assay, and transforming growth factor beta-1 (TGFB1); xanthine oxidoreductase (XDH); ACTA2; NOS2A; and the Rho kinase inhibitor protein tyrosine phosphatase, nonreceptor type 11 (PTPN11), and activator, VAV, were measured by quantitative Western blot. In the aged rats treated with sildenafil, the erectile response by DIC was normalized, and the corporal SMC:collagen ratio and SMC number were increased. In addition, sildenafil reduced the corporal collagen content without affecting the collagen III:I ratio, increased the PCNA:apoptosis ratio, and stimulated NOS2A induction, although there was no effect on XDH, TGFB1, PTPN11, or VAV levels. These data show that long-term PDE5A treatment corrected CVOD in the aged rat and partially reversed the aging-related fibrosis and loss of SMC in the corpora cavernosa without affecting TGFB1 or PTPN11 levels, which are markers of oxidative stress. It may be speculated that similar effects may be achieved with this paradigm in men.