Intracavernosal Pressure/mean Arterial Pressure Research Articles

Role of mechanotransduction mediated by YAP/TAZ in the treatment of neurogenic erectile dysfunction with low-intensity pulsed ultrasound.

Erectile dysfunction (ED) and weakness of the penis are processes related to hemodynamic alteration. Low-intensity pulsed ultrasound (LIPUS), as a new mechanical modality for the treatment of ED, deserves to be explored in depth for the biomechanical mechanisms it exerts. The aim of this study was to explore the role of YAP/TAZ-mediated mechanotransduction in mechanical therapy for the treatment of neurogenic erectile dysfunction (NED). Forty-two male SD rats (12 w old) were randomly divided into sham-operated (n=14), bilateral cavernous nerve injury (BCNI, n=14), and LIPUS-treated (n=14) groups. Intracavernosal pressure/mean arterial pressure (ICP/MAP) was measured 14 and 28 days after treatment. Penile tissue specimens were collected for pathological examination, and the changes in YAP, TAZ, connective tissue growth factor (CTGF), CYR61, LATS1, and p38 mitogen-activated protein kinase expression levels were assessed by Western blot, real-time quantitative polymerase chain reaction (RT-qPCR) and immunological staining. Compared with BCNI, LIPUS significantly improved ICP/MAP levels and enhanced histopathological changes. The penile expression levels of YAP, TAZ, CTGF, and CYR61 were significantly downregulated in the BCNI group (p<0.01), and LIPUS upregulated the expression levels of these proteins (p<0.05). The expression levels of p-LATS1 and LATS1 were not significantly different among the groups (p>0.05). Interestingly, the expression level of p-p38/p38 significantly increased in BCNI rats (p<0.05), which was reversed by LIPUS treatment (p<0.05). However, the p38 inhibitor SB203580 did not change the expression of YAP/TAZ in rat primary smooth muscle cells or mouse MOVAS cells (p>0.05). LIPUS can effectively improve penile erectile function in NED rats. The underlying mechanism may be related to the regulation of YAP/TAZ-mediated mechanotransduction. However, the upstream regulatory signal may differ from the classical Hippo pathway.

Bradykinin B1 receptor antagonist protects against cold stress-induced erectile dysfunction in rats.

Erectile dysfunction (ED) demonstrates seasonal variation with higher rates in winter, and we hypothesize that endothelial damage in erectile tissue caused by bradykinin receptor B1 (B1R) might be detrimental to this change. To find out direct correlations between cold stress and ED, through which to further investigate the functional roles of B1R in erectile tissue and to elucidate the therapeutic roles of the B1R antagonist in a cold stress-induced ED rat model. Cold stress rat models are established through long-term intermittent exposure to low temperature. After their erectile function was assessed, ED rats were treated with the B1R antagonist through intraperitoneal injection. Penile tissues were obtained at the end of the experiment after measurement of intracavernosal pressure/mean arterial pressure (ICP/MAP); the location and distribution of cytokine expression were determined by immunohistochemistry; cytokine levels and NOS and CD31 expression were detected by Western blotting; and collagen fibers and smooth muscles were observed through Masson staining. Cold stress impairs erectile function, and the B1R antagonist protects against it. We observed decreased erection frequency, prolonged erection latency time, decreased ICP/MAP, overexpression of B1R, increased expression of cytokines on cavernous sinus endothelium, and increased levels of collagen fibers/smooth muscles on erectile tissue in response to cold stress. Also, NOS and CD31 expression was downregulated. B1R antagonist treatment shows enhanced erectile function through increased erection frequency, shortened erection latency time, and increased ICP/MAP. Also, it reduces collagen fibers/smooth muscles, TNF-α, TGF-β1, and IL-6 and upregulates the expression of nNOS and CD31. Our findings cast new light on the correlations between cold stress and erectile function and potential new applications of existing B1R antagonist drugs in the field of ED. Our data support that cold stress impairs erectile function. B1R-mediated, cytokine-induced corpus cavernosum fibrosis and endothelial damage might be the main reason behind it, and B1R inhibition protects against fibrosis and endothelial damage. Other ways of B1R antagonist blocking methods in different types of ED still need to be investigated. Long-term intermittent cold stress impairs erectile function, and B1R-mediated, cytokine-induced corpus cavernosum fibrosis and endothelial damage might be the main reason behind it. B1R inhibition also protects against fibrosis and endothelial damage. Our data support the hypothesis that cold stress impairs erectile function and that B1R blockade ameliorates the symptoms of ED, possibly by reversing fibrosis and endothelial damage in erectile tissue.

A systematic review of intracavernosal injection of mesenchymal stem cells for diabetic erectile dysfunction

BACKGROUND As current erectile dysfunction (ED) treatments are limited, other treatment such as stem cells should be explored. Hence, this study aimed to review the sources, method of administration, and therapeutic effect of mesenchymal stem cells (MSCs) for diabetic ED treatment.&#x0D; METHODS All relevant articles regarding the use of MSCs for diabetic ED were searched in PubMed and Google Scholar databases from December 15, 2019 to January 1, 2020 published in the past 10 years. The keywords were “mesenchymal stem cells” and “diabetic ED”. The selection and critical appraisal of the studies were discussed. Diabetic ED was evaluated for functional and structural outcome. Functional outcome in animal studies was assessed by intracavernosal pressure/mean arterial pressure (ICP/MAP) ratio, meanwhile the structural outcome was done microscopically. In human study, the assessments were done using international index of erectile function score (IIEF-5) to erection hardness score and penile Doppler ultrasonography.&#x0D; RESULTS There were 10 animal studies and 3 human studies. The studies used MSCs from adipose (n = 6), bone marrow (n = 4), placenta (n = 1), umbilical cord (n = 1), and muscle tissue (n = 1). The MSCs were administrated through intracavernosal injection in all studies. In all animal studies, functional outcome was improved, shown in higher ICP/MAP ratio. Microscopically, there were an increase of cavernosal endothelial cells, vascular endothelial growth factor, nitric oxide synthase, and smooth muscle cells. In human studies, IIEF-5 and erection hardness score were improved. Peak systolic velocity was also higher.&#x0D; CONCLUSIONS MSCs may be a promising therapy for diabetic ED; however, long-term safety concerns still need further investigations.

N-acetylcysteine maintains penile length and erectile function in bilateral cavernous nerve crush rat model by reducing penile fibrosis.

Penile length shortening and erectile dysfunction are common complications after radical prostatectomy. Various methods have been used to maintain erectile function, but less attention has been paid to preserving penis length. N-acetylcysteine (NAC) has the effect of antioxidation and antifibrotic, which may be beneficial to improve those postoperative complications. This study investigated the effect of NAC on maintaining the penile length and the erectile function after bilateral cavernous nerve crush (BCNC) and its underlying mechanism. Twenty-four male rats were randomly divided into three groups: control group, BCNC group, and BCNC + NAC group. NAC or equal volume of saline was daily administrated by intragastric gavage for 4 weeks. The initial and end penile lengths were measured. Intracavernosal pressure/mean arterial pressure (ICP/MAP) ratio was calculated to assess erectile function. Hematoxylin–eosin staining, Masson's trichrome staining, immunohistochemistry, and Western blot were performed to explore cellular and molecular changes of the penis. Compared to the BCNC group, the penile length, ICP/MAP ratio and smooth muscle/collagen ratio in the BCNC + NAC group were improved significantly (all P < 0.05), and the expressions of endothelial nitric oxide synthase, α-smooth muscle actin, glutathione, and glutathione peroxidase 1 were significantly increased after NAC treated (all P < 0.05), along with the decreased expressions of hypoxia-inducible factor-1α, transforming growth factor-β1, collagen I, collagen III, collagen IV, malonaldehyde, and lysine oxidase (all P < 0.05). This study demonstrated that NAC could maintain penile length and partly improve erectile function. Possible mechanism is directly and/or indirectly related to antihypoxic and antifibrosis.

The protective effect of Ferula elaeochytris on age-related erectile dysfunction

Ethnopharmacological relevanceFerula elaeochytris Korovin (FE) is a perennial medicinal plant of Apiaceae family. Ferula elaeochytris Korovin, known as ‘Çakşır’ in Anatolia, is widely used as an aphrodisiac as well as antioxidant, anti-inflammatory, and anti-diabetic.Aim of the study: Erectile dysfunction (ED) is a serious public health problem that has a high prevalence and negatively affects the quality of life in elderly men. In the treatment and prophylaxis of many diseases, because of widely increasing use of plant extracts as therapeutic agents, preclinical studies related to plant extracts are becoming more important by the day. In this study, we aimed to investigate the protective effect of Ferula elaeochytris Korovin (FE) root extract on age-related ED. Materials and methodsSeventy-two male Wistar albino rats were equally divided into four groups: 4-month aged rats (Y), 24-month aged rats (AG), and FE-administered (20 and 40 mg/kg/day; oral gavage; over 8 weeks) 24-month aged rats (AG + FE). The measurements included: changes in smooth muscle cells and collagen fibrils, tumor necrosis factor alpha (TNF-α), penile neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) expression, serum testosterone concentrations (ST), neurogenic- and endothelial-dependent relaxations of the corpus cavernosum (CC), intracavernosal pressure/mean arterial pressure (ICP/MAP), area under the curve (total ICP), total antioxidant status (TAS), and total oxidant status (TOS) on corpus cavernosal tissue. ResultsThese results have an important role in the development of ED. ICP/MAP, total ICP, eNOS/nNOS expressions and ST levels increased in AG+40 mg FE group compared to the AG group, whereas TNF-α levels decreased and oxidative and antioxidant parameters balanced. ConclusionsOur findings show that FE may have a useful effect on decelerating the development of age-related ED.

Different mechanisms for lead acetate, aluminum and cadmium sulfate in rat corpus cavernosum.

Some heavy metals show adverse vascular and neurological effects, however, their effect on erection is underestimated. This study aims to investigate the effect of Pb, Cd and Al on erectile function and their potential mechanism of action in rats. Measurement of intracavernosal pressure/mean arterial pressure (ICP/MAP) changes elicited by electrical stimulation of cavernous nerve in anesthetized rats treated with Pb-acetate, Al-sulfate, or Cd-sulfate acutely, and subacutely for 7 days. Serum creatinine, testosterone, TBARs, GSH levels and metal accumulation in corpus cavernosum were measured. Pb, Al and Cd significantly reduced ICP/MAP in rats after acute (2,10-2,10 and 1,3 mg/kg respectively) and sub-acute (3, 3, and 1mg/kg/day respectively) treatments. They selectively accumulated in the corpus cavernosum reaching 25.107 ± 2.081 μg/g wet weight for Pb, 1.029 ± 0.193 for Cd, 31.343 ± 1.991 for Al, compared to 7.084 ± 1.517, 0.296 ± 0.067, and 8.86 ± 1.115 as controls respectively. Serum creatinine levels were not altered. Cd and Al significantly reduced testosterone level to 0.483 ± 0.059 and 0.419 ± 0.037 ng/ml respectively compared to 0.927 ± 0.105 ng/ml as control. Aluminum elevated TBARs significantly by 27.843%. The acute anti-erectile action of Pb was blocked by non-selective NOS and GC inhibitors and potassium channel blocker. Lead also masked the potentiatory effect of l-arginine and diazoxide on ICP/MAP. No interaction with muscarinic or nicotinic modulators was observed. Pb, Cd and Al show anti-erectile effect independent on renal injury. They don not modulate cholinergic nor ganglionic transmission in corpus cavernosum. Pb may inhibit NO/cGMP/K+channel pathway. The effect of Cd and Al but not Pb seems to be hormonal dependent.

Erectile dysfunction in heart failure rats is associated with increased neurogenic contractions in cavernous tissue and internal pudendal artery

The rates of erectile dysfunction (ED) in heart failure (HF) are extremely high. This study tested the hypothesis that rats with HF display ED and that HF leads to increased sympathetic-mediated contractile tone of the cavernous tissue and/or internal pudendal arteries (IPA) as potential mechanisms contributing to ED. HF was induced in Wistar rats by ligation of the left anterior descending coronary artery. Changes in the ratio of intracavernosal pressure/mean arterial pressure (ICP/MAP) after electrical stimulation of major pelvic ganglion were determined in vivo. Cavernosal and IPA contractions were induced by electric field stimulation (EFS) and phenylephrine. RhoA, Rho kinase 2 (ROCK 2) and myosin phosphatase target protein 1 (MYPT-1) protein expression and phosphorylation levels were also determined. HF rats display impaired erectile function represented by decreased ICP/MAP responses. EFS-mediated contractions were increased by HF in cavernous tissue and IPA. Contractions induced by phenylephrine were increased in cavernous tissue of HF rats, but decreased in IPA rings. Moreover, HF decreased RhoA protein expression, but increased ROCK 2 and MYPT-1 phosphorylation levels in cavernous tissue. In conclusion, rats with HF induced by myocardial infarction display ED in vivo and increased sympathetic-mediated contractile responses in cavernous tissue and IPA. Increased sympathetic-mediated contractile responses were associated with increased ROCK 2 and MYPT-1 phosphorylation in cavernosal tissue, suggesting the involvement of ROCK signaling pathway in ED genesis. Our findings suggest new mechanisms linking HF to ED, providing potential therapeutic targets for treating ED associated to HF.

Chronic ethanol consumption induces erectile dysfunction: Role of oxidative stress.

Investigate the effects of chronic ethanol consumption on erectile function and on the corpus cavernosum (CC) reactivity to endothelin-1 (ET-1). Male Wistar rats were treated with ethanol (20% v/v) for six weeks. Ethanol-treated rats showed impaired erectile function represented by decreased intracavernosal pressure/mean arterial pressure (ICP/MAP) responses. Ethanol consumption increased the contractile response induced by ET-1 in the isolated CC. Tiron increased ET-1-induced contraction in CC from control and ethanol-treated rats. No differences in the maximal contraction to ET-1 were observed after incubation of CC with PEG-catalase. SC560 and SC236 increased ET-1-induced contraction in CC from ethanol-treated rats. Y27632 reduced the contraction induced by ET-1 in CC from control and ethanol-treated rats. Ethanol increased plasma TBARS, superoxide anion (O2(-)) levels and intracellular reactive oxygen species (ROS) generation in the rat CC. Reduced hydrogen peroxide (H2O2) levels in CC and increased catalase (CAT) activity in plasma and CC were detected after treatment with ethanol. Ethanol decreased superoxide dismutase (SOD) activity in the rat CC. Increased expression of COX-1 was observed in CC from ethanol-treated rats. Treatment with ethanol decreased COX-2 expression but did not alter the expression of Nox1, RhoA and p-RhoA (ser(188)) in the rat CC. The major new findings of our study are that ethanol consumption induces erectile dysfunction (ED) and increases the contraction induced by ET-1 in the rat CC by a mechanism that involves decreased generation of H2O2 and vasodilator prostanoids as well as increased activation of the RhoA/Rho-kinase pathway.

The effects of new herbal formula (KBMSI-2) on penile erection and expression of nitric oxide synthase isoforms in streptozotocin-induced diabetic rat model.

To investigate the effects of new herbal formula (KBMSI-2) on erectile dysfunction in streptozotocin (STZ)-induced diabetic rat model. Twenty four Sprague-Dawley male rats were randomly divided into three groups; control (n=8), diabetes model (n=8), diabetes + KBMSI-2 200 mg/kg treatment (n=8) groups. The diabetes induced groups received a single intraperitoneal injection of STZ. Distilled water was administered in the control and model groups. To investigate the penile erection, intracavernosal pressure (ICP) and intracavernosal pressure/mean arterial pressure (ICP/MAP) were recorded in all groups. Serial sections of the penis were used to perform Masson's trichrome stain. The expression of neuronal nitric oxide synthase (nNOS), endothelial NOS (eNOS) and cyclic guanosine monophosphate (cGMP) concentration in the isolated corpus cavernosum were analyzed by Western blotting. Peak ICP/MAP ratio was increased in the KBMSI-2 treatment group compared with the model group (P<0.05). Masson's trichrome staining confirmed that the smooth muscle component was increased in the KBMSI-2 treatment group compared with the model group (P<0.05). The nNOS, eNOS and cGMP expression of KBMSI-2 200 mg/kg treatment group was increased compared with the model group (P<0.05). This study showed that herbal formula of KBMSI-2 improved the erectile function by preserving the smooth muscle content and inhibiting the fibrosis of the corpus cavernosum in STZ-induced diabetic rat model.

Lead acetate may cause erectile dysfunction by modulating NO/cGMP pathway in rat corpus cavernosum

Despite the fact that metal toxicity has been widely reported in industrial toxicological studies, very little has been reported about the effect of lead exposure on erectile function. This study investigated the effect of lead on erectile function in rats and aimed to preliminarily test the mechanisms by which it might affect erection. Rats were injected with lead acetate (0.25-2 mg/kg) intraperitoneally for 21 days. Intracavernosal pressure/mean arterial pressure (ICP/MAP) next to nerve stimulation; nitrite/nitrate; malonaldehyde; and reduced glutathione levels and superoxide dismutase activity in the corpus cavernosum, kidney, and brain were measured in addition to creatinine, urea, and testosterone. For acute studies, rats were injected intravenously with lead acetate, and then ICP/MAP was recorded for 45 min. Subacute treatment significantly reduced erection with significant elevation of malonaldehyde and reduction of nitrite/nitrate levels in the corpus cavernosum. In acute studies, lead (2 and 5 mg/kg) reduced neurogenic erections by 28.42 ± 3.76 and 96.84 ± 8.52%, respectively, an effect that was masked in the presence of NG-nitro-L-arginine, tetraethyl ammonium, or methylene blue, but not zinc protoporphyrine, and reversed by vitamin C and partially by sildenafil. Lead acetate may inhibit the erectile process in rats. Besides its prooxidant effect and consequent inactivation of nitric oxide, lead may negatively modulate the action of nitric oxide on guanylate cyclase and potassium channels.

Sildenafil citrate improves erectile function after castration in a rat model

The administration of phosphodiesterase 5 inhibitor commencing at the time of castration might preserve erectile function. To determine if sildenafil citrate treatment could improve erectile function after castration. To determine if sildenafil citrate treatment reduces collagenisation and apoptosis in erectile tissue after castration. In all, 60 Sprague-Dawley rats were studied; the rats were divided into the following groups: sham - no orchidectomy (S), control - orchidectomy only (O) and treatment - orchidectomy plus sildenafil treatment (V), with 10 rats per group. Erectile haemodynamics assessment was done at 7 days (S7, O7, V7) and at 28 days (S28, O28, V28) yielding a total of six groupings. Functional assessment measured the mean maximum intracavernosal pressure-mean arterial pressure (ICP/MAP) ratio. TUNEL assay was used to define apoptotic indices (AIs) and Masson's trichrome staining was used to evaluate smooth muscle-collagen (SM-C) ratios. The S28 group had the highest and the O7 group the lowest ICP/MAP ratio, at a mean (sd) of 70 (6)% and 36 (6)%, respectively. Both treatment groups, V7 [42 (12)%] and V28 [49 (13)%] showed statistically significant improvements over their corresponding control groups: O7 [36 (6)%] and O28 [37 (9)%] (P < 0.05). However, ICP/MAP values for V7 and V28 remained significantly below the S28 group (P < 0.001). There were no significant differences in ICP/MAP values between the 28-day and 7-day ICP/MAP ratios within each group (S, O, V). There were no significant differences in SM-C ratio between the O and V groups (O7 vs V7, P = 0.45; O28 vs V28, P = 0.16). There were no significant differences in AIs between the O and V groups (O7 vs V7, P = 0.54; O28 vs V28, P = 0.8). Daily treatment with sildenafil improved erectile function in rats after castration. ICP/MAP ratios increased significantly in the treatment groups compared with the control groups with the greatest erectile function occurring 28 days from administration. In this series of experiments the improved erectile function recovery with sildenafil after surgical castration cannot be explained by smooth muscle protection and decreased collagenisation. The improved erectile function with sildenafil after surgical castration cannot be explained by reduced apoptosis in erectile tissue.

Effect of icarisid II on diabetic rats with erectile dysfunction and its potential mechanism via assessment of AGEs, autophagy, mTOR and the NO–cGMP pathway

Erectile dysfunction (ED) is a major complication of diabetes mellitus. Icariin has been shown to enhance erectile function through its bioactive form, icarisid II. This study investigates the effects of icarisid II on diabetic rats with ED and its potential mechanism via the assessment of advanced glycosylation end products (AGEs), autophagy, mTOR and the NO-cGMP pathway. Icarisid II was extracted from icariin by an enzymatic method. In the control and diabetic ED groups, rats were administered normal saline; in the icarisid II group, rats were administered icarisid II intragastrically. Erectile function was evaluated by measuring intracavernosal pressure/mean arterial pressure (ICP/MAP). AGE concentrations, nitric oxide synthase (NOS) activity and cGMP concentration were assessed by enzyme immunoassay. Cell proliferation was analysed using methyl thiazolyl tetrazolium assay and flow cytometry. Autophagosomes were observed by transmission electron microscopy, monodansylcadaverine staining and GFP-LC3 localisation. The expression of NOS isoforms and key proteins in autophagy were examined by western blot. Our results have shown that Icarisid II increased ICP/MAP values, the smooth muscle cell (SMC) growth curve, S phase and SMC/collagen fibril (SMC/CF) proportions and decreased Beclin 1 (P<0.05). Icarisid II significantly increased the proliferative index and p-p70S6K(Thr389) levels and decreased the numbers of autophagosomes and the levels of LC3-II (P<0.01). Icarisid II decreased AGE concentrations and increased cGMP concentration, NOS activity (P<0.05) and cNOS levels (P<0.01) in the diabetic ED group. Therefore, Icarisid II constitutes a promising compound for diabetic ED and might be involved in the upregulation of SMC proliferation and the NO-cGMP pathway and the downregulation of AGEs, autophagy and the mTOR pathway.

Combined effect of sildenafil and guanethidine, propranolol or verapamil on erectile function in rats

This study aims to further elucidate the role of adrenergic transmission in erection and to highlight whether adrenergic transmission in the penis modulates sildenafil's action. Measurement of intracavernosal pressure in the anesthetized rat model. Guanethidine (3 and 6 mg/kg) potentiated intracavernosal pressure/mean arterial pressure (ICP/MAP) rises in response to cavernous nerve stimulation by 4.375 ± 0.425 and 18.375 ± 1.085% respectively. Propranolol did the opposite. In presence of guanethidine, sildenafil (0.01, 0.1 and 1 mg/kg) potentiated ICP/MAP responses by 81.571 ± 4.918%, 147.83 ± 10.864% and 279.285 ± 23.053% at 1 Hz compared to 22.277 ± 2.139%, 123.571 ± 8.443% and 186.25 ± 13.542% respectively in the absence of guanethidine. Propranolol inhibited the effect sildenafil at all frequencies of stimulation. Verapamil exhibited a pro-erectile action and potentiated the effect of sildenafil (0.01, 0.1 and 1 mg/kg) on erectile responses corresponding to 85.25 ± 6.716%, 146 ± 11.288% and 221.571 ± 19.032% respectively compared to 26.011 ± 1.911%, 87.142 ± 8.73% and 182.2 ± 16.921% in its absence. This study provides functional evidence that inhibition of sympathetic tone peripherally results in enhancement of erectile function. β-adrenergic receptors seem to play an important role in erection. The combination of sildenafil and guanethidine or verapamil could have a potential advantage on erectile function but propranolol may mask the effect of sildenafil on erectile function.

Evaluation of vitamin E in the treatment of erectile dysfunction in aged rats

AimsThe present study aims to elucidate the role of oxidative stress in erectile dysfunction associated with aging and to investigate the effect of treatment with vitamin E in this respect. Main methodsRats were divided into four groups: young (3-month-old), aged rats (18-month-old), aged rats given 80IU of vitamin E/rat/day for 21-days, aged rats given 5mg/kg of sildenafil/day for 21-days. Intracavernosal pressure/mean arterial pressure (ICP/MAP), nitric oxide production, TBARS, GSH levels and SOD activity in corpus cavernosum were measured. Key findingsSignificant decrease in ICP/MAP was observed in aged rats at both low and high frequency of stimulation. Significant increase in ICP/MAP was observed in aged rats treated with vitamin E over the range of 0.8 to 5Hz but young control values were not restored. Percentage potentiation of ICP/MAP than aged group at 0.8Hz was 326±41.3% and 897±72.2% for vitamin E and sildenafil respectively. Decreased levels of NO2/NO3 and SOD activity in the penile tissue observed with aging were elevated back to control by either vitamin E or sildenafil. Penile concentration of TBARS was 20.86±0.83 for aged rats vs. 11.39±0.79nmol/g tissue for young controls. Both vitamin E and sildenafil reduced penile TBARS in aged rats. SignificanceThis study proves that antioxidant therapy with vitamin E ameliorates the age-associated erectile dysfunction. Sildenafil may exert some antioxidant properties which add to the advantages of its long-term use. The effect of combinations of low-dose sildenafil and vitamin E on age-associated erectile dysfunction merits to be studied.

Activation of muscarinic receptors inhibits neurogenic nitric oxide in the corpus cavernosum

The functional role of cholinergic transmission in erection is still far from being fully elucidated. This work aims to further elucidate the modulatory role of neostigmine on NO in the corpus cavernosum and to highlight whether cholinergic transmission in the penis modulates sildenafil action. The isolated rabbit corpus cavernosum and measurement of intracavernosal pressure in the anesthetized rat model were used. Neostigmine (0.02mg/kg) reduced increase of intracavernosal pressure/mean arterial pressure (ICP/MAP) next to cavernous nerve stimulation. Higher doses (0.06 and 0.4mg/kg) potentiated ICP/MAP rise and atropine (1.5 and 10mg/kg) did the opposite. In vitro, neostigmine (10−5 and 10−4M) potentiated neurogenic relaxations and this effect was significantly inhibited by hexamethonium (10−4M) or Nω-propyl-l-arginine (3×10−5M) and partially but significantly reduced in the presence of atropine. Lower dose neostigmine (10−7M), inhibited electrically induced relaxation over the range of 1–4Hz, atropine (10−6M) almost abolished this inhibitory effect as well as NG-nitro-l-arginine (10−5M). It was also significantly reduced by selective nNOS inhibitor Nω-propyl-l-arginine (3×10−5M). Nicotine (10−4M) significantly potentiated electrically induced relaxations amounting to 84.625±8.06% at 1Hz and potentiated the effect of sildenafil synergistically. Hexamthonium did the opposite. The potentiatory effect of sildenafil on neurogenic erection was significantly reduced by low dose neostigmine both in vitro and in vivo. This study provides evidence that muscarinic receptors may modulate NO synthesis in nitrergic nerves by inhibiting nNOS and high level of cholinergic stimulation may activate nicotinic receptors to promote erection probably by potentiating NO synthesis in nitrergic nerves.

Combination of BAY 60-4552 and Vardenafil Exerts Proerectile Facilitator Effects in Rats With Cavernous Nerve Injury: A Proof of Concept Study for the Treatment of Phosphodiesterase Type 5 Inhibitor Failure

BackgroundRadical prostatectomy (RP) is frequently responsible for erectile dysfunction (ED). Post-RP patients often show a failure to respond to phosphodiesterase type 5 (PDE5) inhibitors. ObjectiveThe acute effect of BAY 60-4552, the soluble guanylate cyclase (sGC) stimulator, and vardenafil were evaluated alone or in combination on erectile responses to electrical stimulation of the cavernous nerve (ES CN) in rats with cavernous nerve (CN) crush injury–induced ED. Design, setting, and participantsMale adult Sprague-Dawley rats underwent laparotomy (sham, n=10) or bilateral CN crush injury (n=56). After 3 wk of recovery, erectile function was evaluated under urethane anaesthesia following ES CN at different frequencies. MeasurementsThe acute effects of intravenous (IV) injection of vehicle, vardenafil 0.03mg/kg, BAY 60-4552 0.03mg/kg or 0.3mg/kg, or a BAY 60-4552 0.03mg/kg plus vardenafil 0.03mg/kg combination were evaluated in CN-crushed rats. Results and limitationsBilateral CN crush injury followed by a 3-wk recovery period decreased erectile responses to ES CN by about 50%. In CN-crushed rats, IV vardenafil 0.03mg/kg and BAY 60-4552 (0.03 or 0.3mg/kg) increased erectile responses to ES CN to the same extent: Δ intracavernosal pressure/mean arterial pressure (ICP/MAP) at 10Hz ES CN was 21±1% after vehicle, 25±3% (p<0.001) after vardenafil, and 26±5% and 27±5% after BAY 60-4552 0.03mg/kg (p<0.01) and 0.3mg/kg (p<0.001), respectively. The combination of vardenafil with BAY 60-4552 in CN-crushed rats totally restored erectile responses to ES CN equivalent to sham rats (ΔICP/MAP at 10Hz ES CN: 34±4% after BAY 60-4552/vardenafil combination vs 39±4% in sham rats; not significant). ConclusionsThe present study supports the concept that the combined administration of a sGC stimulator, BAY 60-4552, and vardenafil provides synergistic beneficial effects and might therefore salvage patients who experience treatment failures with PDE5 inhibitors after RP.

The Effects of New Herbal Formula (KBMSI-1) on the Penile Erection and Corpus Cavernosum in Streptozotocin-induced Diabetic Rats

Purpose: The aim of this study was to investigate the effects of new herbal formula (KBMSI-1) on erectile dysfunction in streptozotocin-induced diabetic rat model. Materials and Methods: We used male Sprague-Dawley rats aged 12 weeks and divided into three groups; control (n=8), diabetes (DM) (n=8), DM +KBMSI-1 200 mg/kg treatment (n=8) groups. The DM groups received a single intraperitoneal injection of streptozotocin (STZ). Distilled water was administered in the control and DM group. To investigate the penile erection, intracavernosal pressure (ICP) and intracavernosal pressure/mean arterial pressure (ICP/MAP) were recorded in all groups. Serial sections of the penis were used to perform Masson's trichrome stain. We analyzed the expression of nNOS and eNOS concentration in the isolated corpus cavernosum by western blotting. Results: Peak ICP/MAP ratio was markedly increased in the treatment group with KBMSI-1 compared with DM group (p <0.05). Masson's trichrome staining of corpus cavernosum showed increase in smooth muscle volume and the regular arrangement of collagen fibers in KBMSI-1 treatment group compared with DM group. Western blot analysis revealed that the penile expressions of nNOS and eNOS protein were significantly higher in KBMSI-1-treated group than in DM group. Conclusions: This study showed that herbal formulation of KBMSI-1 enhances the penile erection and the level of eNOS and nNOS expression of penile corpus cavernosum in streptozotocin-induced diabetic rat model.

Erectile Dysfunction in Young Non-Obese Type II Diabetic Goto-Kakizaki Rats is Associated with Decreased eNOS Phosphorylation at Ser1177

Diabetes mellitus (DM) is a risk factor for erectile dysfunction (ED). Although type 2 DM is responsible for 90-95% diabetes cases, type 1 DM experimental models are commonly used to study diabetes-associated ED. Goto-Kakizaki (GK) rat model is relevant to ED studies since the great majority of patients with type 2 diabetes display mild deficits in glucose-stimulated insulin secretion, insulin resistance, and hyperglycemia. We hypothesized that GK rats display ED which is associated with decreased nitric oxide (NO) bioavailability. Wistar and GK rats were used at 10 and 18 weeks of age. Changes in the ratio of intracavernosal pressure/mean arterial pressure (ICP/MAP) after electrical stimulation of cavernosal nerve were determined in vivo. Cavernosal contractility was induced by electrical field stimulation (EFS) and phenylephrine (PE). In addition, nonadrenergic-noncholinergic (NANC)- and sodium nitroprusside (SNP)-induced relaxation were determined. Cavernosal neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) mRNA and protein expression were also measured. GK diabetic rats display ED associated with decreased cavernosal expression of eNOS protein. GK rats at 10 and 18 weeks demonstrated impaired erectile function represented by decreased ICP/MAP responses. Ten-week-old GK animals displayed increased PE responses and no changes in EFS-induced contraction. Conversely, contractile responses to EFS and PE were decreased in cavernosal tissue from GK rats at 18 weeks of age. Moreover, GK rats at 18 weeks of age displayed increased NANC-mediated relaxation, but not to SNP. In addition, ED was associated with decreased eNOS protein expression at both ages. Although GK rats display ED, they exhibit changes in cavernosal reactivity that would facilitate erectile responses. These results are in contrast to those described in other experimental diabetes models. This may be due to compensatory mechanisms in cavernosal tissue to overcome restricted pre-penile arterial blood supply or impaired veno-occlusive mechanisms.

Functional inhibition of erectile process in rats by indomethacin

Despite the important role played by prostaglandins in the control of erection, the potential contribution of non-steroidal anti-inflammatory drugs in erectile dysfunction in experimental animals has not been investigated. We examined the effect of the selective COX-2 inhibitor, celexocib, and the non-selective COX-inhibitors, indomethacin and diclofenac on erectile process in vivo. Erectile responses to electrical stimulation of the cavernous nerve in anesthetized male rats were recorded after single and repeated administration and intracavernosal pressure/mean arterial pressure (ICP/MAP) was calculated. The effect on blood pressure during erection and total plasma nitrite/nitrate level was also investigated. Single-dose administration of indomethacin significantly reduced erectile responses to electrical stimulation at all frequencies tested; 15mg/kg further reduced ICP/MAP to 0.016±0.005 compared to 0.064±0.012 and 0.104±0.035 for indomethacin (5mg/kg) and control, respectively at 0.5Hz. Longer-term treatment with indomethacin completely abolished erectile responses at low frequencies and significantly reduced ICP/MAP at higher frequencies, accompanied by significant reduction in total plasma nitrite/nitrate level. Diclofenac reduced erectile responses only at low frequencies in contrast to celexocib that failed to negatively affect erectile responses. Indomethacin, and to a lower extent diclofenac, may adversely affect erectile responses in rats.

Dimethylarginine dimethylaminohydrolase in rat penile tissue: reduced enzyme activity is responsible for erectile dysfunction in a rat model of atherosclerosis

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), is mainly metabolized by NG,NG-dimethylarginine dimethylaminohydrolase (DDAH). We investigated whether altered cavernosal ADMA–DDAH metabolism might cause impairment of erection in rat model of atherosclerosis (AS). Male Sprague–Dawley rats (3 months old) were divided into an AS group and a normal control (Con) group (n=20 in each group). The AS rats received AS-prone treatment (6 weeks of 1% cholesterol diet plus early 2 weeks of NG-nitro-L-arginine methyl ester (3 mg ml−1 per day) treatment). After 6 weeks, rats underwent cavernosometry measuring the maximal intracavernosal pressure/mean arterial pressure (ICP/MAP) ratios as a surrogate marker of erectile function. The amount of cavernosal ADMA was assessed by immunoblot analysis and correlated with the ICP/MAP. Isoform-specific DDAH expression was compared by immunohistochemistry. Cavernosal DDAH and NOS activity were measured. Cavernosal malondialdehyde levels were assayed to determine the degree of lipid peroxidation. Compared to the controls, the AS rats had signs of impaired erectile function. Higher cavernosal ADMA was observed in the AS rats. The cavernosal ADMA had a moderately negative correlation with the ICP/MAP. Immunohistochemistry revealed the expression of both isoforms was not affected by the presence of AS. However, significantly diminished DDAH as well as NOS activity was observed in the AS group. In addition, elevated cavernosal malondialdehyde levels were noted in the AS rats. Our study showed that decreased cavernosal DDAH activity is the cause of cavernosal ADMA accumulation leading to reduced cavernosal NOS activity and impairment of erectile function.