Effects of Kynurenic Acid on the Rat Aorta Ischemia-Reperfusion Model: Pharmacological Characterization and Proteomic Profiling.

Kynurenic acid (KYNA) is derived from tryptophan, formed by the kynurenic pathway. KYNA is being widely studied as a biomarker for neurological and cardiovascular diseases, as it is found in ischemic conditions as a protective agent; however, little is known about its effect after ischemia-reperfusion in the vascular system. We induced ischemia for 30 min followed by 5 min reperfusion (I/R) in the rat aorta for KYNA evaluation using functional assays combined with proteomics. KYNA recovered the exacerbated contraction induced by phenylephrine and relaxation induced by acetylcholine or sodium nitroprussiate in the I/R aorta, with vessel responses returning to values observed without I/R. The functional recovery can be related to the antioxidant activity of KYNA, which may be acting on the endothelium-injury prevention, especially during reperfusion, and to proteins that regulate neurotransmission and cell repair/growth, expressed after the KYNA treatment. These proteins interacted in a network, confirming a protein profile expression for endothelium and neuron repair after I/R. Thus, the KYNA treatment had the ability to recover the functionality of injured ischemic-reperfusion aorta, by tissue repairing and control of neurotransmitter release, which reinforces its role in the post-ischemic condition, and can be useful in the treatment of such disease.

Tadalafil treatment improves cardiac, renal and lower urinary tract dysfunctions in rats with heart failure.

Tadalafil, a phosphodiesterase-5 (PDE5) inhibitor, shown to exert a protection to heart failure (HF) associated damage or lower urinary tract symptoms (LUTS). Thus, we investigated the contribution of tadalafil chronic treatment in the alterations of LUTS in HF rats. Male rats were subjected to aortocaval fistula model for HF induction. Echocardiography, cystometric, renal function and redox cell balance, as well as concentration-response curves to carbachol, KCl, ATP and frequency-response curves to electrical field stimulation (EFS) were evaluated in Sham, HF, Tadalafil and HF-Tadalafil (12 weeks endpoint) groups. HF group to present increased in left-ventricle (LV) mass and in LV end-diastolic- and LV end-systolic volume, with a decreased ejection fraction. Tadalafil treatment was able to decrease in hypertrophy and improve the LV function restoring cardiac function. For micturition function (in vivo), HF animals shown an increase in basal pressure, threshold pressure, no-voiding contractions and decreased bladder capacity, being that the tadalafil treatment restored the cystometric parameters. Contractile mechanism response (in vitro) to carbachol, KCl, ATP and EFS in the detrusor muscles (DM) were increased in the HF group, when compared to Sham group. However, tadalafil treatment restored the DM hypercontractility in the HF animals. Moreover, renal function as well as the oxidative mechanism was impaired in the HF animals, and the tadalafil treatment improved all renal and oxidative parameters in HF group. Our data shown that tadalafil has potential as multi-therapeutic drug and may be used as a pharmacological strategy for the treatment of cardiovascular, renal and urinary dysfunctions associated with HF.

Increased cavernosal relaxations in sickle cell mice priapism are associated with alterations in the NO-cGMP signaling pathway.

INTRODUCTION: Priapism is defined as prolonged and persistent penile erection, unassociated with sexual interest or stimulation, and is one of the many serious complications associated with sickle cell disease (SCD). AIM: The aim of this study was to evaluate the role of the NO-cGMP signaling pathway in priapism in Berkeley murine model of SCD (SS). METHODS: SS mice and C57BL/6 mice (control) penile tissues were removed and the erectile tissue within the corpus cavernosum (CC) was surgically dissected free. The strips were mounted in 10 mL organ baths containing Krebs solution at 37 degrees C (95% O(2), 5% CO(2), pH 7.4), and vertically suspended between two metal hooks. MAIN OUTCOME MEASURES: Cumulative concentration-response curves were constructed for acetylcholine (ACh; endothelium-dependent responses), sodium nitroprusside (SNP; endothelium-independent relaxations) and BAY 41-2272 (a potent activator of NO-independent site of soluble guanylate cyclase) in CC precontracted with phenylephrine. Cavernosal responses induced by frequency-dependent electrical field stimulation (EFS) were also carried out to evaluate the nitrergic cavernosal relaxations. RESULTS: In SS mice, ACh-induced cavernosal relaxations were leftward shifted by 2.6-fold (P < 0.01) that was accompanied by increases in the maximal responses (78 +/- 5% and 60 +/- 3% in SS and C57B6/6J mice, respectively). Similarly, SNP- and BAY 41-2272-induced CC relaxations were leftward shifted by approximately 3.3- and 2.2-fold (P < 0.01) in SS mice, respectively. A significant increase in maximal responses to SNP and BAY 41-2272 in SS mice was also observed (113 +/- 6% and 124 +/- 5%, respectively) compared with C57B6/6J mice (83 +/- 4% and 99 +/- 2%, respectively). The EFS-induced cavernosal relaxations were also significantly higher SS mice. CONCLUSION: These results showed that SS mice exhibit amplified corpus carvenosum relaxation response mediated by NO-cGMP signaling pathway. Intervention in this signaling pathway may be a potential therapeutic target to treat SCD priapism.

Molecular evidence of tissue remodeling in an animal model of heart failure.

Heart failure (HF) is the final common pathway of many cardiovascular diseases. Metalloproteinases and their inhibitors, such as MMP9 and TIMP-1, assist in maintaining the extracellular matrix, leading to tissue remodeling observed after HF. Previous studies have shown that L-Arginine (LA) appears to have beneficial effects for the treatment of HF, contributing to vasodilation, the reestablishment of the endothelial function and an increase in muscle contractile force. This study analyzed heart tissue remodeling in an animal model of HF induced by aortocaval fistula (ACF) and submitted to LA treatment. After 4 weeks of ACF, animals were treated with LA for 4 weeks (SHAM-LA, HF-LA) or for 8-12 weeks with saline (SHAM, HF8, HF12). Rats were euthanized and the hearts removed for histological processing. The samples were stained with Hematoxylin-Eosin (HE), Masson's Thichome (MT), or submitted to immunohistochemistry (IHC) for MMP9 and TIMP-1. Light microscopy analysis showed cardiac striated muscle without fibrosis in all experimental groups. Immunostaining of MMP9 and TIMP-1 were positive for all experimental groups. LA administration significatively reduced MMP9 content after HF. These data indicate molecular changes in metalloproteinases expression prior to tissue remodeling and point out LA as an adjuvant therapy to pharmacological treatment of patients with HF.

A novel experimental model of erectile dysfunction in rats with heart failure using volume overload.

BACKGROUND: Patients with heart failure (HF) display erectile dysfunction (ED). However, the pathophysiology of ED during HF remains poorly investigated. OBJECTIVE: This study aimed to characterize the aortocaval fistula (ACF) rat model associated with HF as a novel experimental model of ED. We have undertaken molecular and functional studies to evaluate the alterations of the nitric oxide (NO) pathway, autonomic nervous system and oxidative stress in the penis. METHODS: Male rats were submitted to ACF for HF induction. Intracavernosal pressure in anesthetized rats was evaluated. Concentration-response curves to contractile (phenylephrine) and relaxant agents (sodium nitroprusside; SNP), as well as to electrical field stimulation (EFS), were obtained in the cavernosal smooth muscle (CSM) strips from sham and HF rats. Protein expression of endothelial NO synthase (eNOS) and neuronal NO synthase (nNOS) and phosphodiestarese-5 in CSM were evaluated, as well as NOX2 (gp91phox) and superoxide dismutase (SOD) mRNA expression. SOD activity and thiobarbituric acid reactive substances (TBARs) were also performed in plasma. RESULTS: HF rats display erectile dysfunction represented by decreased ICP responses compared to sham rats. The neurogenic contractile responses elicited by EFS were greater in CSM from the HF group. Likewise, phenylephrine-induced contractions were greater in CSM from HF rats. Nitrergic response induced by EFS were decreased in the cavernosal tissue, along with lower eNOS, nNOS and phosphodiestarese-5 protein expressions. An increase of NOX2 and SOD mRNA expression in CSM and plasma TBARs of HF group were detected. Plasma SOD activity was decreased in HF rats. CONCLUSION: ED in HF rats is associated with decreased NO bioavailability in erectile tissue due to eNOS/nNOS dowregulation and NOX2 upregulation, as well as hypercontractility of the penis. This rat model of ACF could be a useful tool to evaluate the molecular alterations of ED associated with HF.

Hydrochlorothiazide Potentiates Contractile Activity of Mouse Cavernosal Smooth Muscle.

INTRODUCTION: Hydrochlorothiazide has a negative influence on penile erection but little is known about the mechanism(s) involved. AIMS: To characterize the effects of this diuretic on mouse corpus cavernosum (CC) smooth muscle in vitro and ex vivo. METHODS: CC strips of C57BL/6 mice (12-16 weeks old) were mounted in organ baths containing Krebs-Henseleit solution and tissue reactivity was evaluated. Expression of genes encoding diuretic targets and enzymes involved in penile erection were evaluated by polymerase chain reaction. MAIN OUTCOME MEASURES: Stimulation-response curves to phenylephrine (10 nmol/L-100 µmol/L) or to electrical field stimulation (1-32 Hz) were constructed, with or without hydrochlorothiazide. Strips of CC from mice after long-term hydrochlorothiazide treatment (6 mg/kg/day for 4 weeks) with or without amiloride (0.6 mg/kg/day for 4 weeks) in vivo also were studied. Nitric oxide and Rho-kinase pathways were evaluated. RESULTS: Hydrochlorothiazide (100 µmol/L) increased the maximum response to phenylephrine by 64% in vitro. This effect was unaffected by the addition of indomethacin (5 µmol/L) but was abolished by N((ω))-nitro-L-arginine methyl ester (100 µmol/L). Hydrochlorothiazide (100 µmol/L) potentiated electrical field stimulation-induced contraction in vitro, but not ex vivo. Long-term treatment with hydrochlorothiazide increased the maximum response to phenylephrine by 60% and resulted in a plasma concentration of 500 ± 180 nmol/L. Amiloride (100µmol/L) caused rightward shifts in concentration-response curves to phenylephrine in vitro. Long-term treatment with hydrochlorothiazide plus amiloride did not significantly increase the maximum response to phenylephrine (+13%). Reverse transcriptase polymerase chain reaction did not detect the NaCl cotransporter in mouse CC. Hydrochlorothiazide did not change Rho-kinase activity, whereas amiloride decreased it in vitro and ex vivo (approximately 18% and 24% respectively). A 40% decrease in Rock1 expression also was observed after long-term treatment with hydrochlorothiazide plus amiloride. CONCLUSION: Hydrochlorothiazide potentiates contraction of smooth muscle from mouse CC. These findings could explain why diuretics such as hydrochlorothiazide are associated with erectile dysfunction.

Effects of Kynurenic acid on the rat aorta ischemia—reperfusion model: pharmacological characterization and proteomic profiling

Kynurenic acid (KYNA) is derived from tryptophan, formed by the kynurenic pathway. KYNA is being widely studied as a biomarker for neurological and cardiovascular diseases, as it is found in ischemic conditions as a protective agent; however, little is known about its effect after ischemia-reperfusion in the vascular system. We induced ischemia for 30 min followed by 5 min reperfusion (I/R) in the rat aorta for KYNA evaluation using functional assays combined with proteomics. KYNA recovered the exacerbated contraction induced by phenylephrine and relaxation induced by acetylcholine or sodium nitroprussiate in the I/R aorta, with vessel responses returning to values observed without I/R. The functional recovery can be related to the antioxidant activity of KYNA, which may be acting on the endothelium-injury prevention, especially during reperfusion, and to proteins that regulate neurotransmission and cell repair/growth, expressed after the KYNA treatment. These proteins interacted in a network, confirming a protein profile expression for endothelium and neuron repair after I/R. Thus, the KYNA treatment had the ability to recover the functionality of injured ischemic-reperfusion aorta, by tissue repairing and control of neurotransmitter release, which reinforces its role in the post-ischemic condition, and can be useful in the treatment of such disease

Urinary Bladder Dysfunction in Transgenic Sickle Cell Disease Mice.

BACKGROUND: Urological complications associated with sickle cell disease (SCD), include nocturia, enuresis, urinary infections and urinary incontinence. However, scientific evidence to ascertain the underlying cause of the lower urinary tract symptoms in SCD is lacking. OBJECTIVE: Thus, the aim of this study was to evaluate urinary function, in vivo and ex vivo, in the Berkeley SCD murine model (SS). METHODS: Urine output was measured in metabolic cage for both wild type and SS mice (25-30 g). Bladder strips and urethra rings were dissected free and mounted in organ baths. In isolated detrusor smooth muscle (DSM), relaxant response to mirabegron and isoproterenol (1nM-10µM) and contractile response to (carbachol (CCh; 1 nM-100µM), KCl (1 mM-300mM), CaCl2 (1µM-100mM), α,ß-methylene ATP (1, 3 and 10 µM) and electrical field stimulation (EFS; 1-32 Hz) were measured. Phenylephrine (Phe; 10nM-100µM) was used to evaluate the contraction mechanism in the urethra rings. Cystometry and histomorphometry were also performed in the urinary bladder. RESULTS: SS mice present a reduced urine output and incapacity to produce typical bladder contractions and bladder emptying (ex vivo), compared to control animals. In DSM, relaxation in response to a selective ß3-adrenergic agonist (mirabegron) and to a non-selective ß-adrenergic (isoproterenol) agonist were lower in SS mice. Additionally, carbachol, α, ß-methylene ATP, KCl, extracellular Ca2+ and electrical-field stimulation promoted smaller bladder contractions in SS group. Urethra contraction induced by phenylephrine was markedly reduced in SS mice. Histological analyses of SS mice bladder revealed severe structural abnormalities, such as reductions in detrusor thickness and bladder volume, and cell infiltration. CONCLUSIONS: Taken together, our data demonstrate, for the first time, that SS mice display features of urinary bladder dysfunction, leading to impairment in urinary continence, which may have an important role in the pathogenesis of the enuresis and infections observed the SCD patients.

Sickling cells, cyclic nucleotides, and protein kinases: the pathophysiology of urogenital disorders in sickle cell anemia.

Sickle cell anemia is one of the best studied inherited diseases, and despite being caused by a single point mutation in the HBB gene, multiple pleiotropic effects of the abnormal hemoglobin S production range from vaso-occlusive crisis, stroke, and pulmonary hypertension to osteonecrosis and leg ulcers. Urogenital function is not spared, and although priapism is most frequently remembered, other related clinical manifestations have been described, such as nocturia, enuresis, increased frequence of lower urinary tract infections, urinary incontinence, hypogonadism, and testicular infarction. Studies on sickle cell vaso-occlusion and priapism using both in vitro and in vivo models have shed light on the pathogenesis of some of these events. The authors review what is known about the deleterious effects of sickling on the genitourinary tract and how the role of cyclic nucleotides signaling and protein kinases may help understand the pathophysiology underlying these manifestations and develop novel therapies in the setting of urogenital disorders in sickle cell disease.