Circulating and Urinary Concentrations of Malondialdehyde in Aging Humans in Health and Disease: Review and Discussion.

(1) Background: Malondialdehyde (MDA) is a major and stable product of oxidative stress. MDA circulates in the blood and is excreted in the urine in its free and conjugated forms, notably with L-lysine and L-serine. MDA is the most frequently measured biomarker of oxidative stress, namely lipid peroxidation. Oxidative stress is generally assumed to be associated with disease and to increase with age. Here, we review and discuss the literature concerning circulating and excretory MDA as a biomarker of lipid peroxidation in aging subjects with regard to health and disease, such as kidney disease, erectile dysfunction, and COVID-19. (2) Methods: Scientific articles, notably those reporting on circulating (plasma, serum) and urinary MDA, which concern health and disease, and which appeared in PubMed were considered; they formed the basis for evaluating the potential increase in oxidative stress, particularly lipid peroxidation, as humans age. (3) Results and Conclusions: The results reported in the literature thus far are contradictory. The articles considered in the present study are not supportive of the general view that oxidative stress increases with aging. Many functions of several organs, including the filtration efficiency of the kidneys, are physiologically reduced in men and women as they age. This effect is likely to result in the apparent "accumulation" of biomarkers of oxidative stress, concomitantly with the "accumulation" of biomarkers of an organ's function, such as creatinine. How free and conjugated MDA forms are transported in various organs (including the brain) and how they are excreted in the urine via the kidney is not known, and investigating these questions should be the objective of forthcoming studies. The age- and gender-related increase in circulating creatinine might be a useful factor to be taken into consideration when investigating oxidative stress and aging.

Fibrotic Diseases of the Human Urinary and Genital Tract: Current Understanding and Potential Strategies for Treatment.

Fibrosis is a disease condition characterized by abnormalities of the extracellular matrix, such as accumulation of the transforming growth factor ß, infiltration by myofibroblasts, deposition of collagen, and a generalized dysregulation of collagen maturation. It can severely impair the function of organs by replacing normal tissue with a highly collagenized matrix, thereby reducing the elasticity and compliance of tissues. Fibrotic diseases of the genitourinary tract present relevant problems in healthcare, and their principles of pathophysiology remain unclarified; hence, the armamentarium for prevention and treatment is limited. These diseases include renal fibrosis, Peyronie's disease and ureteral and urethral strictures due to perturbations in the process of wound healing in response to injuries. Such deteriorations may contribute to obstructive uropathies or sexual dysfunction. This review provides a brief overview of the most frequent fibrotic diseases of the genitourinary system and of how the pathophysiology is related to symptoms, and also highlights potential therapeutic strategies to address the abnormal deposition of collagen. Although the understanding of factors associated with fibrotic conditions of the urinary and genital tract is still limited, some beneficial advances have been made. Further research will serve to provide a more comprehensive insight into factors responsible for the development of fibrotic tissue deposition.

Is cortisol an endogenous mediator of erectile dysfunction in the adult male?

Background: It has been speculated for decades whether there is a significance of the adrenal corticosteroid cortisol in the process of male sexual function, including the control of sexual arousal and penile erection. In order to investigate further the role of the adrenocorticotropic axis in the physiological process of penile erection, we aimed to determine the course of cortisol in the cavernous and systemic blood through different stages of sexual arousal in patients suffering from erectile dysfunction (ED) in comparison to a cohort of healthy males. Methods: Fifty-four healthy adult males and 45 patients with ED were presented sexually explicit visual material in order to elicit tumescence and (in the healthy males) rigid erection. Blood was collected from the cavernous space (corpus cavernosum penis, CC) and a cubital vein (CV) at different stages of the sexual arousal cycle as indicated by the penile stages flaccidity, tumescence, rigidity (attained only by the healthy males) and detumescence. Cortisol (µg/dL serum) was measured using a radioimmunometric assay (RIA). Results: In healthy males, cortisol decreased in both the cavernous and systemic blood with the beginning of sexual stimulation (CV: 15 to 13, CC: 16 to 13). At detumescence, in the systemic circulation, no alterations in cortisol levels were registered, whereas it decreased further in the CC (to 12). In the ED patients, no significant changes in cortisol were noticed in the systemic and cavernous blood. Conclusions: The findings indicate that cortisol might act as an antagonist of the normal sexual response cycle of the adult male. A dysregulation of the secretion and/or degradation of the hormone might well play a role in the manifestation of ED.

Expression and distribution of the transient receptor potential cationic channel ankyrin 1 (TRPA1) in the human seminal vesicles.

Background and Aims: The transient receptor potential cationic channel ankyrin 1 (TRPA1), a channel protein permeable to most divalent cations, has been suggested to play a role in mechano-afferent/efferent signaling (including the release of neurotransmitters) in the human urinary tract (bladder, prostate, and urethra). To date, only a few studies have addressed the expression of this receptor in male and female reproductive tissues. The present study aimed to evaluate human seminal vesicles (SVs)  for the expression and localization of TRPA1. Methods: SV tissue was obtained from 5 males who had undergone pelvic surgery due to malignancies of the prostate or urinary bladder. The expression of messenger ribonucleic acid (mRNA) specifically encoding for the TRPA1 protein was elucidated by means of reverse transcriptase polymerase chain reaction (RT-PCR). Using immunohistochemical methods, the distribution of TRPA1 was examined in relation to the endothelial and neuronal nitric oxide synthases (eNOS, nNOS) and the neuropeptides calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP). Results: RT-PCR revealed signals related to the expected molecular size of 656 bp. Immunohistochemistry demonstrated that TRPA1 is located in nerves running through the smooth muscle portion of the SV. Here, the protein is in part co-localized with nNOS and CGRP, whereas no co-localization with VIP was registered. Dot-like signals specific for TRPA1 were observed in the cytoplasm of epithelial cells lining the lumen of glandular spaces. The epithelial layer also presented staining for eNOS. The smooth musculature appeared free of immunosignals for TRPA1. Conclusion: The results convincingly show the expression of TRPA1 in nerve endings as well as in epithelial cells of the SV. Based on its location in epithelial cells, TRPA1 might be involved in the mechanism of the NO/cyclic guanosine monophosphate (GMP)-mediated signaling and also the control of secretory function (mediated by cyclic GMP) in the human SV.

[Metanephric adenoma, a benign variant of Wilms' tumour: case report of an extremely rare kidney tumour and literature survey]. / Das metanephrische Adenom - eine benigne Variante des Wilms-Tumors - Ein Fallbericht eines sehr seltenen Nierentumors mit Literaturübersicht.

Rare benign tumours of the kidney comprise a group of very different histogenetic entities. We report a case of a 53-year-old woman who underwent laparoscopic nephrectomy because of a renal mass. The diagnosis of a rare and benign metanephric adenoma was confirmed by histopathology. With less than 200 documented cases, the metanephric adenoma described here is a rarity in everyday urological practice and cannot be distinguished from a malignant tumour of the kidney by clinical examination and/or imaging without histological assessment.

An advanced method for the immunohistochemical detection of nitric oxide synthase (NOS) in the female genital tract.

The expression of nitric oxide synthase (NOS) in male and female urogenital tissues has been investigated by using conventional light microscopical immunoperoxidase staining. We present an improved immunohistochemical method for the specific and simultaneous detection of endothelial and neuronal NOS (eNOS/nNOS) in vaginal tissue. Specific antibodies have been used in combination with the tyramide signal amplification method. We found a subepithelial meshwork of varicose nerve fibers. A subpopulation of fibers presented immunoreactivity specific for nNOS. Epithelial cells also showed cytoplasmatic labeling for nNOS. Arteries presenting signals for eNOS in their endothelial layer were found in close proximity to nNOS-positive nerve fibers.

Re-evaluation of the immunohistochemical distribution of isoforms of nitric oxide synthase in the human prostate: A light and electron microscopical study.

Up until today, there are still uncertainties regarding the occurrence of isoforms of the nitric oxide synthase (eNOS, nNOS) in the human prostate. While nNOS was exclusively seen in slender nerve fibres branching within the transition zone, eNOS was reported in glandular structures and also in small vessels interspersing the tissue. This study aimed to re-evaluate by means of light and electron microscopy (LM, EM), the distribution of eNOS and nNOS in the transition zone of the human prostate. Tissue specimens were obtained from 16 patients who underwent surgery for pelvic malignancies. Using specific antibodies in conjunction with advanced fixation and staining procedures, the occurrence of eNOS and nNOS was investigated. nNOS was detected in nerve fibres interspersing the tissue and was also seen in glandular structures. EM revealed that in glandular epithelial cells immunoreaction for nNOS was limited to the cytoplasmic compartment. Vascular endothelial cells of small vessels transversing glandular structures significantly stained for eNOS, while epithelial layers of prostatic glandules appeared free of eNOS. The results implicate that, in the prostate, nNOS is a mediator of stromal and glandular tissue function, and counteract the assumption of eNOS activity in glandular epithelial cells as a source of NO synthesis.

Expression of Phosphodiesterase (PDE) Isoenzymes in the Human Male and Female Urethra.

PURPOSE: Although it has been supposed that the NO/cyclic GMP system produces inhibitory signals to reduce the resistance of the bladder outlet and urethra during the micturition phase, little is known on the mechanisms controlling the function of urethral smooth muscle. The aim of the present study was to examine in the male and female urethra the expression of phosphodiesterase (PDE) isoenzymes, known as key proteins of the cyclic GMP/AMP signaling. METHODS: Urethral tissue was obtained from 4 female cadavers and 7 male patients (who had undergone gender reassignment surgery). The expression of mRNA encoding for PDE1A, 1B, 1C, 2A, 4B, 4D, 5A, 10A and 11A was investigated by means of real-time polymerase chain reaction. Western blot (WB) analysis was conducted to detect PDE isoenzymes. RESULTS: RT-PCR revealed relevant amounts of mRNA encoding for PDE1A, 2A, 4B, 5A, 10A and 11A in male and female urethral tissue. The expression of PDE1A, 2A, 4B and 10A was 2-fold higher in the female than in the male urethra, whereas the expression of PDE11A mRNA was 7-fold higher in the male tissue. In the WB experiments, immunosignals specific for PDE1A, PDE4A and 4B and PDE11A were of higher degree in the female than the male tissue specimens, while an almost equivocal expression of PDE2A, PDE5A and PDE10A was registered. CONCLUSION: On the level of mRNA and function proteins, different patterns of expression of PDE isoenzymes were registered in human male and female urethra. Future studies may clarify whether inhibition of PDE isoenzymes is likely to facilitate the relaxation of the outflow region in both sexes.

The Use of Vasoactive Drugs in the Treatment of Male Erectile Dysfunction: Current Concepts.

It is widely accepted that disorders of the male (uro)genital tract, such as erectile dysfunction (ED) and benign diseases of the prostate (lower urinary tract symptomatology or benign prostatic hyperplasia), can be approached therapeutically by influencing the function of both the vascular and non-vascular smooth muscle of the penile erectile tissue or the transition zone/periurethral region of the prostate, respectively. As a result of the discovery of nitric oxide (NO) and cyclic guanosine monophosphate (GMP) as central mediators of penile smooth muscle relaxation, the use of drugs known to increase the local production of NO and/or elevate the intracellular level of the second messenger cyclic GMP have attracted broad attention in the treatment of ED of various etiologies. Specifically, the introduction of vasoactive drugs, including orally active inhibitors of the cyclic GMP-specific phosphodiesterase (PDE) 5, has offered great advantage in the pharmacotherapy of ED and other diseases of the genitourinary tract. These drugs have been proven efficacious with a fast on-set of action and an improved profile of side-effects. This review summarizes current strategies for the treatment of ED utilizing the application of vasoactive drugs via the oral, transurethral, topical, or self-injection route.

Emerging drugs to target lower urinary tract symptomatology (LUTS)/benign prostatic hyperplasia (BPH): focus on the prostate.

OBJECTIVES: The benign prostatic syndrome, comprising lower urinary tract symptomatology secondary to benign prostatic hyperplasia/enlargement, represents a major health care issue in westernized countries. The pharmacological management involves alpha-adrenoceptor antagonists, intervention into the hormonal control of prostate growth using inhibitors of the enzyme 5-alpha-reductase, and stimulation of the nitric oxide/cyclic GMP pathway by tadalafil, an inhibitor of the phosphodiesterase type 5. METHODS: This review summarizes the achievements which have been made in the development of drug candidates assumed to offer opportunities as beneficial treatment options in the management of the benign prostatic syndrome. RESULTS: A review of the literature has revealed that the line of development is focusing on drugs interfering with peripheral neuromuscular/neuronal mechanisms (nitric oxide donor drugs, agonists/antagonists of endogenous peptides, botulinum toxin, NX-1207), the steroidal axis (cetrorelix) or the metabolic turn-over (lonidamine), as well as the combination of drugs already established in the treatment of lower urinary tract symptomatology/benign prostatic hyperplasia (phosphodiesterase 5 inhibitor plus alpha-adrenoceptor antagonist). CONCLUSION: Many research efforts have provided the basis for the development of new therapeutic modalities for the management of lower urinary tract dysfunctions, some of which might be offered to the patients in the near future.

Arginase enzymes in the human prostate: A molecular biological and immunohistochemical approach.

The nitric oxide (NO) pathway plays a role in maintaining the function of the prostate. An impairment in the activity of the NO system may have an impact in the manifestation of lower urinary tract symptomatology and benign prostatic hyperplasia. Arginase enzymes (Arg) counteract the generation of NO by depleting the intracellular pool of L-arginine, known to be the substrate of the NO synthases. This study investigated the expression of arginase type I and II in the human prostate. Nondiseased prostate tissue was obtained during pelvic surgeries (prostatectomy, cystoprostatectomy). Tissue sections were exposed to antibodies directed against Arg I and II, cGMP, the phosphodiesterase 5 and nNOS. The expression of mRNA transcripts encoding for Arg I and Arg II was investigated using molecular biology. Reverse transcriptase polymerase chain reaction (RT-PCR) revealed the presence of mRNA encoding for Arg I and II, immunofluorescence specific for Arg I was seen in the stromal smooth musculature, and labelling for PDE5 and cyclic GMP was also observed. Nerve fibres containing nNOS were identified running across the smooth musculature. Immunostainings for Arg II did not yield signals. These findings are in support of the notion that, in the prostate, Arg is involved in the modulation of the activity of the NO system.

Development and validation of GC-MS methods for the comprehensive analysis of amino acids in plasma and urine and applications to the HELLP syndrome and pediatric kidney transplantation: evidence of altered methylation, transamidination, and arginase activity.

We developed and validated gas chromatography-mass spectrometry (GC-MS) methods for the simultaneous measurement of amino acids and their metabolites in 10-µL aliquots of human plasma and urine. De novo synthesized trideutero-methyl esters were used as internal standards. Plasma proteins were precipitated by acidified methanol and removed by centrifugation. Supernatants and native urine were evaporated to dryness. Amino acids were first esterified using 2 M HCl in methanol and then amidated using pentafluoropropionic anhydride for electron-capture negative-ion chemical ionization. Time programmes were used for the gas chromatograph oven and the selected-ion monitoring of specific anions. The GC-MS methods were applied in clinical studies on the HELLP syndrome and pediatric kidney transplantation (KTx) focusing on L-arginine-related pathways. We found lower sarcosine (N-methylglycine) and higher asymmetric dimethylarginine (ADMA) plasma concentrations in HELLP syndrome women (n = 7) compared to healthy pregnant women (n = 5) indicating altered methylation. In plasma of pediatric KTx patients, lower guanidinoacetate and homoarginine concentrations were found in plasma but not in urine samples of patients treated with standard mycophenolate mofetil-based immunosuppression (MMF; n = 22) in comparison to matched patients treated with MMF-free immunosuppression (n = 22). On average, the global arginine bioavailability ratio was by about 40% lower in the MMF group compared to the EVR group (P = 0.004). Mycophenolate, the major pharmacologically active metabolite of MMF, is likely to inhibit the arginine:glycine amidinotransferase (AGAT), and to enhance arginase activity in leukocytes and other types of cell of MMF-treated children.

Course of transforming growth factor ß1 in the systemic and cavernous blood of healthy males through different penile conditions.

Studies on erectile dysfunction (ED) have revealed a relationship between smooth muscle atrophy and the accumulation of collagen in the corpus cavernosum (CC). Transforming growth factor ß1 (TGF ß1) is a cytokine which has been proposed to be involved in the fibrotic process in the CC. We aimed to evaluate the course of TGF ß1 in the systemic and cavernous blood of 17 healthy males through different phases of the sexual arousal response (exemplified by the penile conditions flaccidity, tumescence, rigidity and detumescence). An enzyme-linked immunoassay was used to measure the concentration of TGF ß1 (ng/ml) in both the systemic and cavernous blood at the stages of flaccidity, tumescence and detumescence. TGF levels were significantly higher in the cavernous compartment than in the systemic blood. A linear decrease was evident in the cavernous blood when the flaccid penis became tumescent (24.3 ± 14.5 to 13.9 ± 6.5) and rigid (to 8.7 ± 3.1). At detumescence, TGF increased to 18.3 ± 10.4. In contrast, the levels in the systemic circulation remained unchanged. The results are in support of the hypothesis that the concentration of TGF ß1 in the CC is regulated by adequate blood flow and oxygenation.

Is ß-endorphin significant in the control of the male sexual response?

It has been assumed that ß-endorphin, belonging to the family of opiodergic neuropeptides, might facilitate the inhibition of the male sexual response; however, its role in the control of the penile erectile tissue remains to be elucidated. This study aimed to evaluate in healthy men the course of ß-endorphin in the systemic and cavernous blood through different stages of sexual arousal. Thirty-four (34) men were exposed to erotic stimuli to induce penile tumescence and rigidity. Blood was aspirated from the corpus cavernosum and a cubital vein during the penile conditions flaccidity, tumescence, rigidity and detumescence. Plasma levels of ß-endorphin were determined by means of radioimmunometric methods. The effects of ß-endorphin on isolated human penile erectile tissue were investigated in vitro. ß-endorphin did not induce a contractile response of the cavernous tissue or reverse the contraction induced by noradrenaline. ß-endorphin decreased in the systemic blood when the penis became tumescent and rigid and increased during detumescence. In the cavernous blood, no alterations in ß-endorphin concentrations were observed. The drop in ß-endorphin observed during tumescence and rigidity seems likely to reflect the inhibition of the opioidergic input with the beginning of sexual arousal.

Results, meta-analysis and a first evaluation of UNOxR, the urinary nitrate-to-nitrite molar ratio, as a measure of nitrite reabsorption in experimental and clinical settings.

We recently found that renal carbonic anhydrase (CA) is involved in the reabsorption of inorganic nitrite (NO2-), an abundant reservoir of nitric oxide (NO) in tissues and cells. Impaired NO synthesis in the endothelium and decreased NO bioavailability in the circulation are considered major contributors to the development and progression of renal and cardiovascular diseases in different conditions including diabetes. Isolated human and bovine erythrocytic CAII and CAIV can convert nitrite to nitrous acid (HONO) and its anhydride N2O3 which, in the presence of thiols (RSH), are further converted to S-nitrosothiols (RSNO) and NO. Thus, CA may be responsible both for the homeostasis of nitrite and for its bioactivation to RSNO/NO. We hypothesized that enhanced excretion of nitrite in the urine may contribute to NO-related dysfunctions in the renal and cardiovascular systems, and proposed the urinary nitrate-to-nitrite molar ratio, i.e., UNOxR, as a measure of renal CA-dependent excretion of nitrite. Based on results from clinical and experimental animal studies, here, we report on a first evaluation of UNOxR. We determined UNOxR values in preterm neonates, healthy children, and adults, in children suffering from type 1 diabetes mellitus (T1DM) or Duchenne muscular dystrophy (DMD), in elderly subjects suffering from chronic rheumatic diseases, type 2 diabetes mellitus (T2DM), coronary artery disease (CAD), or peripheral arterial occlusive disease (PAOD). We also determined UNOxR values in healthy young men who ingested isosorbide dinitrate (ISDN), pentaerythrityl tetranitrate (PETN), or inorganic nitrate. In addition, we tested the utility of UNOxR in two animal models, i.e., the LEW.1AR1-iddm rat, an animal model of human T1DM, and the APOE*3-Leiden.CETP mice, a model of human dyslipidemia. Mean UNOxR values were lower in adult patients with rheumatic diseases (187) and in T2DM patients of the DALI study (74) as compared to healthy elderly adults (660) and healthy young men (1500). The intra- and inter-variabilities of UNOxR were of the order of 50% in young and elderly healthy subjects. UNOxR values were lower in black compared to white boys (314 vs. 483, P = 0.007), which is in line with reported lower NO bioavailability in black ethnicity. Mean UNOxR values were lower in DMD (424) compared to healthy (730) children, but they were higher in T1DM children (1192). ISDN (3 × 30 mg) decreased stronger UNOxR compared to PETN (3 × 80 mg) after 1 day (P = 0.046) and after 5 days (P = 0.0016) of oral administration of therapeutically equivalent doses. In healthy young men who ingested NaNO3 (0.1 mmol/kg/d), UNOxR was higher than in those who ingested the same dose of NaCl (1709 vs. 369). In LEW.1AR1-iddm rats, mean UNOxR values were lower than in healthy rats (198 vs. 308) and comparable to those in APOE*3-Leiden.CETP mice (151).

S-Nitroso-N-acetyl-L-cysteine ethyl ester (SNACET) and N-acetyl-L-cysteine ethyl ester (NACET)-Cysteine-based drug candidates with unique pharmacological profiles for oral use as NO, H2S and GSH suppliers and as antioxidants: Results and overview.

S-Nitrosothiols or thionitrites with the general formula RSNO are formally composed of the nitrosyl cation (NO+) and a thiolate (RS-), the base of the corresponding acids RSH. The smallest S-nitrosothiol is HSNO and derives from hydrogen sulfide (HSH, H2S). The most common physiological S-nitrosothiols are derived from the amino acid L-cysteine (CysSH). Thus, the simplest S-nitrosothiol is S-nitroso-L-cysteine (CysSNO). CysSNO is a spontaneous potent donor of nitric oxide (NO) which activates soluble guanylyl cyclase to form cyclic guanosine monophosphate (cGMP). This activation is associated with multiple biological actions that include relaxation of smooth muscle cells and inhibition of platelet aggregation. Like NO, CysSNO is a short-lived species and occurs physiologically at concentrations around 1 nM in human blood. CysSNO can be formed from CysSH and higher oxides of NO including nitrous acid (HONO) and its anhydride (N2O3). The most characteristic feature of RSNO is the S-transnitrosation reaction by which the NO+ group is reversibly transferred to another thiolate. By this way numerous RSNO can be formed such as the low-molecular-mass S-nitroso-N-acetyl-L-cysteine (SNAC) and S-nitroso-glutathione (GSNO), and the high-molecular-mass S-nitrosol-L-cysteine hemoglobin (HbCysSNO) present in erythrocytes and S-nitrosol-L-cysteine albumin (AlbCysSNO) present in plasma at concentrations of the order of 200 nM. All above mentioned RSNO exert NO-related biological activity, but they must be administered intravenously. This important drawback can be overcome by lipophilic charge-free RSNO. Thus, we prepared the ethyl ester of SNAC, the S-nitroso-N-acetyl-L-cysteine ethyl ester (SNACET), from synthetic N-acetyl-L-cysteine ethyl ester (NACET). Both NACET and SNACET have improved pharmacological features over N-acetyl-L-cysteine (NAC) and S-nitroso-N-acetyl-L-cysteine (SNAC), respectively, including higher oral bioavailability. SNACET exerts NO-related activities which can be utilized in the urogenital tract and in the cardiovascular system. NACET, with high oral bioavailability, is a strong antioxidant and abundant precursor of GSH, unlike its free acid N-acetyl-L-cysteine (NAC). Here, we review the chemical and pharmacological properties of SNACET and NACET as well as their analytical chemistry. We also report new results from the ingestion of S-[15N]nitroso-N-acetyl-L-cysteine ethyl ester (S15NACET) demonstrating the favorable pharmacological profile of SNACET.

S-Nitroso-N-acetyl-L-cysteine ethyl ester (SNACET) and N-acetyl-L-cysteine ethyl ester (NACET)–Cysteine-based drug candidates with unique pharmacological profiles for oral use as NO, H2S and GSH suppliers and as antioxidants: Results and overview / 药物分析学报

S-Nitrosothiols or thionitrites with the general formula RSNO are formally composed of the nitrosylcation(NO+)and a thiolate(RS-),the base of the corresponding acids RSH.The smallest S-nitrosothiol isHSNO and derives from hydrogen sulfide(HSH,H2S).The most common physiological S-nitrosothiols arederived from the amino acid L-cysteine(CysSH).Thus,the simplest S-nitrosothiol is S-nitroso-L-cysteine(CysSNO).CysSNO is a spontaneous potent donor of nitric oxide(NO)which activates soluble guanylylcyclase to form cyclic guanosine monophosphate(cGMP).This activation is associated with multiplebiological actions that include relaxation of smooth muscle cells and inhibition of platelet aggregation.Like NO,CysSNO is a short-lived species and occurs physiologically at concentrations around 1 nM inhuman blood.CysSNO can be formed from CysSH and higher oxides of NO including nitrous acid(HONO)and its anhydride(N2O3).The most characteristic feature of RSNO is the S-transnitrosation reaction bywhich the NO+group is reversibly transferred to another thiolate.By this way numerous RSNO can beformed such as the low-molecular-mass S-nitroso-N-acetyl-L-cysteine(SNAC)and S-nitroso-glutathione(GSNO),and the high-molecular-mass S-nitrosol-L-cysteine hemoglobin(HbCysSNO)present in erythrocytesand S-nitrosol-L-cysteine albumin(AlbCysSNO)present in plasma at concentrations of theorder of 200 nM.All above mentioned RSNO exert NO-related biological activity,but they must be administeredintravenously.This important drawback can be overcome by lipophilic charge-free RSNO.Thus,we prepared the ethyl ester of SNAC,the S-nitroso-N-acetyl-L-cysteine ethyl ester(SNACET),fromsynthetic N-acetyl-L-cysteine ethyl ester(NACET).Both NACET and SNACET have improved pharmacologicalfeatures over N-acetyl-L-cysteine(NAC)and S-nitroso-N-acetyl-L-cysteine(SNAC),respectively,including higher oral bioavailability.SNACET exerts NO-related activities which can be utilized in theurogenital tract and in the cardiovascular system.NACET,with high oral bioavailability,is a strong antioxidantand abundant precursor of GSH,unlike its free acid N-acetyl-L-cysteine(NAC).Here,we reviewthe chemical and pharmacological properties of SNACET and NACET as well as their analytical chemistry.We also report new results from the ingestion of S-[15N]nitroso-N-acetyl-L-cysteine ethyl ester(S15NACET)demonstrating the favorable pharmacological profile of SNACET.

Expression and distribution of phosphodiesterase isoenzymes in the human male urethra.

OBJECTIVE: To investigate the expression and distribution of phosphodiesterase (PDE) isoenzymes PDE1A, PDE2A, PDE4A, PDE4B, and PDE5A in human urethral tissue. METHODS: Specimens of penile urethra were obtained from male subjects who had undergone male-to-female sex reassignment surgery. Using immunohistochemistry (immunofluorescence), the occurrence of PDE1A, PDE2A, PDE4A, PDE4B, and PDE5A, the neuronal nitric oxide synthase, calcitonin gene-related peptide, and vasoactive intestinal polypeptide was examined in urethral sections. Cytosolic supernatants prepared from isolated human urethral tissue were subjected to Western blot analysis using specific anti-PDE antibodies. RESULTS: Immunosignals specific for PDE1A, 4A, 4B, and 5A were observed in the urethral smooth musculature. The smooth muscle bundles were seen innervated by slender nerve fibers, characterized by the expression of the neuronal nitric oxide synthase, calcitonin gene-related peptide, and vasoactive intestinal polypeptide. The expression of the PDE isoenzymes mentioned was confirmed by Western blotting. CONCLUSION: The results provide evidence for a significance of both the cyclic adenosine monophosphate and cyclic guanosine monophosphate signaling in the control of human urethral smooth muscle. The selective inhibition of PDE isoenzymes might represent a pharmacologic option to influence the function of smooth musculature in the human outflow region.

Phosphodiesterase isoenzymes in the human urethra: a molecular biology and functional study.

Experimental and clinical studies have suggested a role for phosphodiesterase (PDE) isoenzymes in the control of the human lower urinary tract. This study aimed to investigate the expression of PDE isoenzymes and the effects of PDE inhibitors (PDE-Is) in isolated human urethral smooth muscle (USM). The expression of messenger ribonucleic acid (mRNA) specifically encoding for PDE isoenzymes and isoforms (1A, 1B, 1C, 2A, 4A, 4B, 4C, 4D, 5A and 11A) was analyzed by means of reverse transcriptase polymerase chain reaction (RT-PCR). Using a tissue bath technique, the effects of vinpocetine (PDE1-I), erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride (EHNA-HCl=MEP1) (PDE2-I), rolipram (PDE4-I), sildenafil, vardenafil and tadalafil (PDE5-Is) (0.01-10µM) on the tension of USM induced by norepinephrine were investigated. The production of cyclic guanosine monophosphate (cyclic GMP) and cyclic adenosine monophosphate (cyclic AMP) was measured by means of radioimmunoassays. RT-PCR analysis revealed the expression of PDE1B, PDE1C, PDE4A, PDE4C, PDE4D, PDE5A and PDE11A. The tension induced by norepinephrine (NE) was reversed by the PDE inhibitors with the following rank order of efficacy: rolipram (mean: -39%)≥sildenafil (-35%)>vardenafil (-26%)>tadalafil (-20%)>vinpocetine (-16%)>MEP1 (-2%). The relaxing effects of the drugs were paralleled by an elevation in tissue levels of cyclic AMP and cyclic GMP. Selective inhibitors of PDE4 and PDE5 can antagonize the tension induced by alpha-adrenergic stimulation of USM. PDE inhibition might represent an interesting option to facilitate the relaxation of the human outflow region.

Melanocortin receptor agonists in the treatment of male and female sexual dysfunctions: results from basic research and clinical studies.

INTRODUCTION: Over the last 20 years, basic and clinical research activities studying the male and female sexual responses have led to several pharmacological options to treat male erectile dysfunction (ED) and female arousal and orgasmic disorders. While some strategies exclusively focus on peripheral mechanisms--such as nitric oxide/cyclic GMP signaling, which is known to play a role in the control of genital vascular and nonvascular smooth muscle--others have considered the central pathways involved in mediating arousal and orgasmic functions in females as well as the induction of penile erection in males. Aside from dopaminergic agonists, drugs known to target the central melanocortin system have also been assumed to have a promising potential in the treatment of female and male sexual dysfunctions. AREAS COVERED: The present review summarizes the achievements that have been made in the clinical development of melanocortin receptor (MCR) agonists (melanotan I, melanotan II, bremelanotide) for the treatment of symptoms of sexual arousal and orgasmic disorders in adult females and ED in males. EXPERT OPINION: The data available at present have facilitated our understanding of how the melanocortin pathway regulates both the male and female sexual functions. Indeed the data warrant further investigation to demonstrate the impact of the activation of MCRs by specific agonists on penile erection and female arousal and orgasm function.