Effect of indole alkaloids from roots of Rauvolfia ligustrina in the noradrenergic neurotransmission.

The new glucosyl sarpagan alkaloid designated as 21(R*)-(O-ß-glucosyl)-hydroxy-sarpagan-17-oic acid, along with eleven known alkaloids were isolated from a soluble alkaloidal fraction from the ethanol extract of Rauvolfia ligustrina. Their structures were elucidated by interpretation of spectroscopic data (1D and 2D NMR), HRESIMS experiment, GIAO 13C NMR calculations, and comparison with literature data. All the isolated alkaloids were screened by their neuroinhibitory effects using the electrically stimulated mice vas deferens bioassay. Compounds 1, 2 and 9 presented a potent inhibitory effect in the neurotransmission while 3 and 11 showed an acute neuroexcitatory effect. Compound 10 exhibited a very effective post-synaptic inhibitory activity.

PKB is a central molecule in the modulation of Na+-ATPase activity by albumin in renal proximal tubule cells.

Evidence points to a possible role of tubular sodium reabsorption in worsening renal injury. Proximal tubule (PT) albumin overload is a critical process in the development of tubule-interstitial injury (TII), and consequently in progression of renal disease. We studied the possible correlation between changes in albumin concentration in the lumen of PT with modification of Na+-ATPase activity. An albumin overload animal model and LLC-PK1 cells as a model of PT cells were used. Albumin overload was induced by intraperitoneal injection of BSA in 14-week-old male Wistar rats. An increase in sodium clearance, fractional excretion of sodium, proteinuria, ratio between urinary protein and creatinine, and albuminuria were observed. These observations indicate that there could be a correlation between an increase in albumin in the lumen of PTs and renal sodium excretion. We observed that the activity of both Na+-ATPase and (Na++K+)ATPase decreased in the renal cortex of an albumin overload animal model. Using LLC-PK1 cells as a model of PT cells, inhibition of Na+-ATPase activity was observed with higher albumin concentrations, similar to that observed in the animal model. The inhibition of protein kinase B by higher albumin concentration was found to be a critical step in the inhibition of Na+-ATPase activity. Interestingly, activation of the ERK1/2/mTORC1/S6K pathway was required for protein kinase B inhibition. This mechanism leads to a decrease in protein kinase C activity and, consequently to inhibition of Na+-ATPase activity. Taken together, our results indicate that the molecular mechanism underlying the modulation of PT Na+-ATPase activity by albumin overload involves activation of the ERK1/2/mTORC1/S6K pathway, which leads to inhibition of the mTORC2/PKB/PKC pathway. Our findings contribute to better understanding regarding handing of renal Na+ induced by albumin overload in the lumen of PTs and, consequently, in the progression of renal disease.

Post-weaning Exposure to High-Fat Diet Induces Kidney Lipid Accumulation and Function Impairment in Adult Rats.

Aim: We investigated the kidney morphofunctional consequences of high-fat diet intake since post-weaning in adult rats. Main Methods: Male Wistar rats were divided into two groups: ND (normal diet; n = 10) and HD (high-fat diet; n = 10). The high-fat diet was introduced post-weaned and animals were followed for 8 weeks. Key Findings: HD group did not change body weight gain even though food consumption has decreased with no changes in caloric consumption. The HD group showed glucose intolerance and insulin resistance. The glomerular filtration rate (GFR) was decreased in vivo (ND: 2.8 ± 1.01; HD: 1.1 ± 0.14 ml/min) and in the isolated perfusion method (34% of decrease). Renal histological analysis showed a retraction in glomeruli and an increase in kidney lipid deposition (ND: 1.5 ± 0.17 HD: 5.9 ± 0.06%). Furthermore, the high-fat diet consumption increased the pro-inflammatory cytokines IL-6 (ND: 1,276 ± 203; HD: 1,982 ± 47 pg/mL/mg) and IL-1b (ND: 97 ± 12 HD: 133 ± 5 pg/mL/mg) without changing anti-inflammatory cytokine IL-10. Significance: Our study provides evidence that high-fat diet consumption leads to renal lipid accumulation, increases inflammatory cytokines, induces glomeruli retraction, and renal dysfunction. These damages observed in the kidney could be associated with an increased risk to advanced CKD in adulthood suggesting that reduction of high-fat ingestion during an early period of life can prevent metabolic disturbances and renal lipotoxicity.

Incorporation of Nitroprusside on Silica Nanoparticles-A Strategy for Safer Use of This NO Donor in Therapy.

Silica-based nanoparticles have been developed as powerful platforms for drug delivery and might also prevent undesired side effects of drugs. Here, a fast method to synthesize positively charged mesoporous silica nanoparticles (ζ = 20 ± 0.5 mV, surface area = 678 m2 g-1, and 2.3 nm of porous size) was reported. This nanomaterial was employed to anchor sodium nitroprusside (SNP), a vasodilator drug with undesired cyanide release. A remarkable incorporation of 323.9 ± 7.55 µmol of SNP per gram of nanoparticle was achieved, and a series of studies of NO release were conducted, showing efficient release of NO along with major cyanide retention (ca. 64% bound to nanoparticle). Biological assays with mammalian cells showed only a slight drop in cell viability (13%) at the highest concentration (1000 µM), while SNP exhibited an LC50 of 228 µM. Moreover, pharmacological studies demonstrated similar efficacy for vasodilation and sGC-PKG-VASP pathway activation when compared to SNP alone. Altogether, this new SNP silica nanoparticle has great potential as an alternative for wider and safer use of SNP in medicine with lower cyanide toxicity.

Thiocarbonyl-bound metallonitrosyl complexes with visible-light induced DNA cleavage and promising vasodilation activity.

Nitric oxide has been involved in many key biological processes such as vasodilation, platelet aggregation, apoptosis, memory function, and this has drawn attention to the development of exogenous NO donors. Metallonitrosyl complexes are an important class of these compounds. Here, two new ruthenium nitrosyl complexes containing a thiocarbonyl ligand, with the formula cis-[Ru(phen)2(L)(NO)](PF6)3 (phen = phenantroline, L = thiourea or thiobenzamide), were synthesized and characterized by electronic spectroscopy, FTIR, NMR, mass spectrometry and voltammetric techniques. Theoretical calculations using Density Functional Theory (DFT) and Time-dependent Density Functional Theory (TD-DFT) were also used and further supported the characterizations of these complexes. An efficient release of nitric oxide by blue light was validated using a NO/HNO probe: 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, known as cPTIO. Interestingly, the complex containing thiourea cleaved DNA even in the dark, while both complexes showed great DNA photocleavage activity in blue light. This process might work mainly through NO and hydroxyl radical production. Additionally, these complexes showed promising vasodilator activity, whose mechanism of action was investigated using N-Nitro-l-arginine methyl ester hydrochloride (L-NAME) and 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and compared to sodium nitroprusside. Both compounds were indeed NO-mediated heme-dependent activators of soluble guanylate cyclase. Additionally, they did not show any significant cytotoxicity against cancer cell lines U87 and GBM02. Altogether, these results supported both complexes having potential pharmacological applications that deserve further studies.

Effects of cardiotonic steroids on isolated perfused kidney and NHE3 activity in renal proximal tubules.

Cardiotonic steroids (CS) are known as modulators of sodium and water homeostasis. These compounds contribute to the excretion of sodium under overload conditions due to its natriuretic property related to the inhibition of the renal Na+/K+-ATPase (NKA) pump α1 isoform. NHE3, the main route for Na+ reabsorption in the proximal tubule, depends on the Na+ gradient generated by the NKA pump. In the present study we aimed to investigate the effects of marinobufagin (MBG) and telocinobufagin (TBG) on the renal function of isolated perfused rat kidney and on the inhibition of NKA activity. Furthermore, we investigated the mechanisms for the cardiotonic steroid-mediated natriuretic effect, by evaluating and comparing the effects of bufalin (BUF), ouabain (OUA), MBG and TBG on NHE3 activity in the renal proximal tubule in vivo. TBG significantly increased GFR, UF, natriuresis and kaliuresis in isolated perfused rat kidney, and inhibits the activity of NKA at a much higher rate than MBG. By stationary microperfusion technique, the perfusion with BUF, OUA, TBG or MBG promoted an inhibitory effect on NHE3 activity, whereas BUF was the most effective agent, and demonstrated a dose-dependent response, with maximal inhibition at 50nM. Furthermore, our data showed the role of NKA-Src kinase pathway in the inhibition of NHE3 by CS. Finally, a downstream step, MEK1/2-ERK1/2 was also investigated, and, similar to Src inhibition, the MEK1/2 inhibitor (U0126) suppressed the BUF effect. Our findings indicate the involvement of NKA-SRc-Kinase-Ras-Raf-ERK1/2 pathway in the downregulation of NHE3 by cardiotonic steroids in the renal proximal tubule, promoting a reduction of proximal sodium reabsorption and natriuresis.

Uroguanylin modulates (Na++K+)ATPase in a proximal tubule cell line: Interactions among the cGMP/protein kinase G, cAMP/protein kinase A, and mTOR pathways.

BACKGROUND: The natriuretic effect of uroguanylin (UGN) involves reduction of proximal tubule (PT) sodium reabsorption. However, the target sodium transporters as well as the molecular mechanisms involved in these processes remain poorly understood. METHODS: To address the effects of UGN on PT (Na(+)+K(+))ATPase and the signal transduction pathways involved in this effect, we used LLC-PK1 cells. The effects of UGN were determined through ouabain-sensitive ATP hydrolysis and immunoblotting assays during different experimental conditions. RESULTS: We observed that UGN triggers cGMP/PKG and cAMP/PKA pathways in a sequential way. The activation of PKA leads to the inhibition of mTORC2 activity, PKB phosphorylation at S473, PKB activity and, consequently, a decrease in the mTORC1/S6K pathway. The final effects are decreased expression of the α1 subunit of (Na(+)+K(+))ATPase and inhibition of enzyme activity. CONCLUSIONS: These results suggest that the molecular mechanism of action of UGN on sodium reabsorption in PT cells is more complex than previously thought. We propose that PKG-dependent activation of PKA leads to the inhibition of the mTORC2/PKB/mTORC1/S6K pathway, an important signaling pathway involved in the maintenance of the PT sodium pump expression and activity. GENERAL SIGNIFICANCE: The current results expand our understanding of the signal transduction pathways involved in the overall effect of UGN on renal sodium excretion.

Non-nitric oxide based metallovasodilators: synthesis, reactivity and biological studies.

There is an increasing number of compounds developed to target one or more pathways involved in vasodilation. Some studies conducted with azaindole and indazole derivatives showed cardiovascular activity associated with these compounds. Fast and easy structural modification of these organic molecules can be achieved using metal complexes promoting a much larger spatial change than organic strategies, potentially leading to novel drugs. Here, we have prepared a series of complexes with a formula cis-[RuCl(L)(bpy)(2)]PF(6), where L = 7-azaindole (ain), 5-azaindole (5-ain), 4-azaindole (4-ain), indazole (indz), benzimidazole (bzim) or quinoline (qui), which were characterized by spectroscopic and electrochemical techniques (CV, DPV). These compounds showed reasonable stability exhibiting photoreactivity only at low wavelength along with superoxide scavenger activity. Cytotoxicity assays indicated their low activity preliminarily supporting in vivo application. Interestingly, vasodilation assays conducted in rat aorta exhibited great activity that largely improved compared to free ligands and even better than the well-studied organic compound (BAY 41-42272), with IC(50) reaching 55 nM. These results have validated this strategy opening new opportunities to further develop cardiovascular agents based on metallo-bicyclic rings.

A new structurally atypical bradykinin-potentiating peptide isolated from Crotalus durissus cascavella venom (South American rattlesnake).

Venom glands of some snakes synthesize bradykinin-potentiating peptides (BPP's) which increase bradykinin-induced hypotensive effect and decrease angiotensin I vasopressor effect by angiotensin-converting enzyme (ACE) inhibition. The present study shows a new BPP (BPP-Cdc) isolated from Crotalus durissus cascavella venom: Pro-Asn-Leu-Pro-Asn-Tyr-Leu-Gly-Ile-Pro-Pro. Although BPP-Cdc presents the classical sequence IPP in the C-terminus, it has a completely atypical N-terminal sequence, which shows very low homology with all other BPPs isolated to date. The pharmacological effects of BPP-Cdc were compared to BBP9a from Bothrops jararaca and captopril. BPP-Cdc (1 µM) significantly increased BK-induced contractions (BK; 1 µM) on the guinea pig ileum by 267.8% and decreased angiotensin I-induced contractions (AngI; 10 nM) by 62.4% and these effects were not significantly different from those of BPP9a (1 µM) or captopril (200 nM). Experiments with 4-week hypertensive 2K-1C rats show that the vasopressor effect of AngI (10 ng) was decreased by 50 µg BPP-Cdc (69.7%), and this result was similar to that obtained with 50 µg BPP9a (69.8%). However, the action duration of BPP-Cdc (60 min) was 2 times greater than that of BPP-9a (30 min). On the other hand, the hypotensive effect of BK (250 ng) was significantly increased by 176.6% after BPP-Cdc (50 µg) administration, value 2.5 times greater than that obtained with BPP9a administered at the same doses (71.4%). In addition, the duration of the action of BPP-Cdc (120 min) was also at least 4 times greater than that of BPP-9a (30 min). Taken together, these results suggest that BPP-Cdc presents more selective action on arterial blood system than BPP9a. Besides the inhibition of ACE, it may present other mechanisms of action yet to be elucidated.

Isolation, homology modeling and renal effects of a C-type natriuretic peptide from the venom of the Brazilian yellow scorpion (Tityus serrulatus).

Mammalian natriuretic peptides (NPs) have been extensively investigated for use as therapeutic agents in the treatment of cardiovascular diseases. Here, we describe the isolation, sequencing and tridimensional homology modeling of the first C-type natriuretic peptide isolated from scorpion venom. In addition, its effects on the renal function of rats and on the mRNA expression of natriuretic peptide receptors in the kidneys are delineated. Fractionation of Tityus serrulatus venom using chromatographic techniques yielded a peptide with a molecular mass of 2190.64 Da, which exhibited the pattern of disulfide bridges that is characteristic of a C-type NP (TsNP, T. serrulatus Natriuretic Peptide). In the isolated perfused rat kidney assay, treatment with two concentrations of TsNP (0.03 and 0.1 µg/mL) increased the perfusion pressure, glomerular filtration rate and urinary flow. After 60 min of treatment at both concentrations, the percentages of sodium, potassium and chloride transport were decreased, and the urinary cGMP concentration was elevated. Natriuretic peptide receptor-A (NPR-A) mRNA expression was down regulated in the kidneys treated with both concentrations of TsNP, whereas NPR-B, NPR-C and CG-C mRNAs were up regulated at the 0.1 µg/mL concentration. In conclusion, this work describes the isolation and modeling of the first natriuretic peptide isolated from scorpion venom. In addition, examinations of the renal actions of TsNP indicate that its effects may be related to the activation of NPR-B, NPR-C and GC-C.

Natriuretic effect of bufalin in isolated rat kidneys involves activation of the Na+-K+-ATPase-Src kinase pathway.

Bufadienolides are structurally related to the clinically relevant cardenolides (e.g., digoxin) and are now considered as endogenous steroid hormones. Binding of ouabain to Na(+)-K(+)-ATPase has been associated, in kidney cells, to the activation of the Src kinase pathway and Na(+)-K(+)-ATPase internalization. Nevertheless, whether the activation of this cascade also occurs with other cardiotonic steroids and leads to diuresis and natriuresis in the isolated intact kidney is still unknown. In the present work, we perfused rat kidneys for 120 min with bufalin (1, 3, or 10 µM) and measured its vascular and tubular effects. Thereafter, we probed the effect of 10 µM 3-(4-chlorophenyl)1-(1,1-dimethylethyl)-1H-pyrazolo[3,4-d]pyrimidin-4amine (PP2), a Src family kinase inhibitor, and 1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio] butadiene (UO126), a highly selective inhibitor of both MEK1 and MEK2, on bufalin-induced renal alterations. Bufalin at 3 and 10 µM profoundly increased several parameters of renal function in a time- and/or concentration-dependent fashion. At a concentration that produced similar inhibition of the rat kidney Na(+)-K(+)-ATPase, ouabain had a much smaller diuretic and natriuretic effect. Although bufalin fully inhibited the rat kidney Na(+)-K(+)-ATPase in vitro, its IC(50) (33 ± 1 µM) was threefold higher than the concentration used ex vivo and all its renal effects were blunted by PP2 and UO126. Furthermore, the phosphorylated (activated) ERK1/2 expression was increased after bufalin perfusion and this effect was totally prevented after PP2 pretreatment. The present study shows for the first time the direct diuretic, natriuretic, and kaliuretic effects of bufalin in isolated rat kidney and the relevance of Na(+)-K(+)-ATPase-mediated signal transduction.

Hypotensive effects of the Crotalus durissus cascavella venom: involvement of NO.

Crotalus durissus cascavella is a snake native of northeastern Brazil. The aim of the study was to investigate the effects of C. d. cascavella venom on rat mean arterial pressure and vascular reactivity in the mesenteric vascular bed. The venom evoked a dose-dependent decrease in mean arterial pressure, cardiac and respiratory frequency with increased plasma nitrite levels. L-NAME (10 mg/kg) blunted both the hypotension and increased nitrite production observed after the venom administration. To investigate the effects of C. d. cascavella in resistance vessels, the vascular mesenteric bed was studied, and the results suggested that the hypotensive effect of the venom is not dependent on a direct vasodilatory activity. In conclusion, C. d. cascavella venom presented indirect hypotensive effects with the involvement of nitric oxide.

Role of SRC family kinase in extracellular renal cyclic guanosine 3',5'-monophosphate- and pressure-induced natriuresis.

cGMP functions as an extracellular (paracrine) messenger acting at the renal proximal tubule and is an important modulator of pressure-natriuresis (P-N). The signaling pathway activated by cGMP in the tubule cell basolateral membrane remains unknown. We hypothesized that renal interstitial microinfusion of cGMP (50 nmol/kg per minute) or P-N would be accompanied by increased renal protein levels of phospho-Src (Tyr 416) and that the natriuresis would be decreased by Src inhibition. Renal interstitial cGMP-induced natriuresis was blocked by Src inhibitor PP2 (2.0±0.4 versus 0.5±0.01 µEq/g per minute; P<0.001). The inactive analog of PP2, PP3, had no effect on cGMP-induced natriuresis. SU6656, another Src inhibitor, also inhibited cGMP-induced natriuresis (2.0±0.4 versus 1.02±0.01 µEq/g per minute; P<0.001). Renal interstitial cGMP infusion increased phospho-Src protein levels 5.6-fold at 15 minutes and 6.8-fold at 30 minutes compared with vehicle infusion but returned toward basal levels after 60 minutes. PP2 also blunted P-N (3.1±0.1 versus 1.1±0.3 µEq/g per minute; P<0.01) despite a similar increase in blood pressure. PP3 had no effect on P-N. Phospho-Src protein levels increased during P-N in vehicle- (1.8-fold) and PP3-treated (2.1-fold) groups compared with the sham-operated group. PP2 blocked the pressure-induced increase in renal phospho-Src protein levels. PP2 had no effect on renal hemodynamics but decreased both fractional excretion of Na(+) and lithium. Both extracellular cGMP and increased renal perfusion pressure increased renal phospho-Src protein levels and induced natriuresis in an Src-dependent manner, demonstrating that Src is an important downstream signaling molecule for extracellular cGMP-induced natriuresis.

Anthelmintic effect of Eucalyptus staigeriana essential oil against goat gastrointestinal nematodes.

The aim of this study was to evaluate the anthelmintic efficacy of Eucalyptus staigeriana essential oil (EsEO). The in vitro effects of EsEO were determined through the egg hatching test and the inhibition of larval development of Haemonchus contortus. The oil was subjected to acute and subacute toxicity rodents. The in vivo effects were determined through fecal egg count reduction test in goats. 1.35 and 5.4 mgml(-1) EsEO inhibited 99.27 and 99.20% H. contortus egg hatching and larval development. In subacute toxicity of EsEO, all parameters were found to be in the normal range, and histopathological analysis of organs did not present alterations. EsEO efficacy against goat gastrointestinal nematodes was 76.57% at 15th day after treatment. E. staigeriana essential oil showed in vitro and in vivo anthelmintic activity.

The relaxation induced by uroguanylin and the expression of natriuretic peptide receptors in human corpora cavernosa.

INTRODUCTION: Receptors for natriuretic peptides have been demonstrated as potential targets for the treatment of male erectile dysfunction. AIM: This study investigates the relaxant effects of the atrial natriuretic peptide (ANP) and uroguanylin (UGN), and expression of natriuretic peptide receptors on strips of human corpora cavernosa (HCC). MAIN OUTCOME MEASURES: Quantitative analysis of natriuretic receptor expression and relaxation of precontracted strips were used to assess the membrane-bound guanylate cyclase-cyclic guanosine monophosphate (cGMP) pathway in HCC strips. METHODS: HCC was obtained from a cadaver donor at the time of collection of organs for transplantation (14-47 years) and strips were mounted in organ baths for isometric studies. RESULTS: ANP and UGN both induced concentration-dependent relaxation on HCC strips with a maximal response attained at 300 nM, corresponding to 45.4±4.0% and 49±4.8%, respectively. The relaxation is not affected by 30 µM 1H-[1,2,4]oxaolodiazolo[4,3-a]quinoxalin-1-one (ODQ) (a soluble guanylate cyclase inhibitor), but it is significantly blocked by 10 µM isatin, a nonspecific particulate guanylate cyclase (pGC) inhibitor. UGN was unable to potentiate electrical field stimulation (EFS) or acetylcholine-induced relaxations. The potential role of pGC activation and cGMP generation in this effect is reinforced by the potentiation of this effect by phosphodiesterase-5 inhibitor vardenafil (55.0±7.5-UGN vs. 98.6±1.4%-UGN+vardenafil; P<0.05). The relaxant effect was also partially (37.6%) blocked by the combination iberitoxin-apamin but was insensitive to glybenclamide. The expression of guanylate cyclase receptors (GC-A, GC-B, GC-C) and the expression of the natriuretic peptide "clearance" receptor (NPR-C) were confirmed by real-time polymerase chain reaction. The exposure of HCC strips to ANP (1 µM) and UGN (10 µM) significantly increased cGMP, but not cyclic adenosine monophosphate (cAMP) levels. CONCLUSIONS: UGN relaxes HCC strips by a guanylate cyclase and K(ca)-channel-dependent mechanism. These findings obtained in HCC reveal that the natriuretic peptide receptors are potential targets for the development of new drugs for the treatment of erectile dysfunction.

High-salt intake primes the rat kidney to respond to a subthreshold uroguanylin dose during ex vivo renal perfusion.

In a variety of animal models, uroguanylin causes diuresis, natriuresis and kaliuresis and is found in larger concentrations in the urine compared to controls after oral salt intake or in conditions of excess salt and fluid retention. It has been proposed that uroguanylin functions as an intestinal natriuretic hormone following intake of meals high in salt content. In the present work, we examined if 10 days of salt ingestion resulted in an enhanced response to uroguanylin in the isolated perfused rat kidney. Rats were given normal water, 1% NaCl (HS1%), or 2% NaCl (HS2%) for 10 days, at which time the right kidneys were surgically removed and perfused with a modified Krebs-Henseleit solution for 30 min. After a 30-min control period, the kidneys were perfused with a modified Krebs-Henseleit solution containing 0.06 microM uroguanylin for an additional 90 min. Compared to vehicle-matched time controls, 0.06 microM uroguanylin perfusion of kidneys from rats maintained on HS2% resulted in a significantly increased urine flow (UF; from 0.17+/-0.01 to 0.23+/-0.01, after 60 min, n=6, P<0.05), fractional Na(+) excretion (%E(Na+); from 16.6+/-0.7 to 30+/-2, after 60 min, n=6, P<0.05), fractional K(+) excretion (%E(K+); from 20.5+/-0.58 to 37.4+/-2.1, after 60 min, n=6, P<0.05), and fractional Cl(-) excretion increased from 18.16+/-0.52 to 35.2+/-2.0 at 60 min, n=6, P<0.05. With the exception of a significant increase in the %E(K)(+), no other effect was observed in the kidneys from the rats maintained on HS1%, and no significant effects were seen in those that were maintained on normal water. The effect of a higher dose (0.6 microM) of uroguanylin on urinary flow, sodium or potassium excretion was also significantly increased by 2% NaCl (HS2%) treatment (P<0.05). We also observed an expressive upregulation of the GC-C and a slight downregulation of the GC-A receptor in high-salt treated rats. These data demonstrate that prolonged salt ingestion primes the kidney to enhanced renal responses to uroguanylin.

Relaxation of rabbit corpus cavernosum smooth muscle and aortic vascular endothelium induced by new nitric oxide donor substances of the nitrosyl-ruthenium complex.

INTRODUCTION: Endothelial dysfunction characterized by endogenous nitric oxide (NO) deficiency made 56% of patients affected with erectile dysfunction decline treatment with PDE-5 inhibitors. New forms of treatment are currently being developed for this group of patients. MATERIALS AND METHODS: The study compared the effect of sodium nitroprusside (SNP) and two substances of the nitrosyl-ruthenium complex, cis-[Ru(bpy)2(SO3)(NO)]PF-6-9 ("FONO1") and trans-[Ru(NH3)4(caffeine)(NO)]C13 ("LLNO1") on relaxation of rabbit corpus cavernosum smooth muscle and aortic vascular endothelium. The samples were immersed in isolated baths and precontracted with 0.1 microM phenylephrine (PE) and the corresponding relaxation concentration/response curves were plotted. In order to investigate the relaxation mechanisms involved, 100 microM ODQ (a soluble guanylate cyclase-specific inhibitor), 3 microM or 10 microM oxyhemoglobin (an extracellular NO scavenger) or 1 mM L-cysteine (a nitrosyl anion-specific scavenger) was added to the samples. RESULTS: All the NO donors tested produced a significant level of relaxation in the vascular endothelium. In corpus cavernosum samples, FONO1 produced no significant effect, but LLNO1 and SNP induced dose-dependent relaxation with comparable potency (pEC50 = 6.14 +/- 0.08 and 6.4 +/- 0.14, respectively) and maximum effect (Emax = 82% vs. 100%, respectively). All NO donors were found to activate soluble guanylate cyclase, since the addition of the corresponding inhibitor (100 microM ODQ) completely neutralized the relaxation effect observed. The addition of oxyhemoglobin reduced the relaxation effect, but did not inhibit it completely. In aortic vascular endothelium 3 microM oxyhemoglobin decreased the relaxation effect by 26% on the average, while 10 microM oxyhemoglobin reduced it by over 52%. The addition of 100 microM L-cysteine produced no significant inhibiting effect. CONCLUSIONS: These results suggest that LLNO1 and FONO1 are potent vasodilators. LLNO1 was shown to induce a significant level of relaxation in rabbit corpus cavernosum. The substances tested were shown to activate soluble guanylate cyclase and release intracellular NO.

Renal and vascular effects of the natriuretic peptide isolated from Crotalus durissus cascavella venom.

Crotalus durissus cascavella is a snake that is usually found in the scrublands of northeast Brazil. The components of its venom may have effects on the vascular and renal systems. Recently, a new bradykinin inhibitory peptide has been identified in the venom of the Crotalinae family. The aim of the present study was to investigate the renal and vascular effects of the natriuretic peptide isolated from the venom of Crotalus durissus cascavella (NP2_Casca). The chromatographic profile showed the fractionation of substances identified as convulxin, gyroxin, crotoxin and crotamine, as well as fractions V and VI. The electrophoretic profile of fraction V consisted of several bands ranging from approximately 6kDa to 13kDa, while fraction VI showed only two main electrophoretic bands with molecular weights of approximately 6 and 14kDa. Reverse-phase chromatography showed that NP2_Casca corresponds to about 18% of fraction VI and that this fraction is the main natriuretic peptide. NP2_Casca was compared to other natriuretic peptides from other sources of snake venom. All amino acid sequences that were compared showed a consensus region of XGCFGX, XLDRIX and XSGLGCX. The group treated with NP2_Casca showed an increase in perfusion pressure, renal vascular resistance, urinary flow and glomerular filtration rate. The percent of total and proximal tubular transport of sodium was reduced significantly after administration of the peptide. The mean arterial pressure showed a dose-dependent decrease after infusion of NP2_Casca, and an increase in nitrite production. In the aortic ring assay, NP2_Casca caused a relaxant effect in endothelium-intact thoracic aortic rings precontracted with phenylephrine in the presence and absence of isatin. NP2_Casca failed to relax the aortic rings precontracted with an isosmotic potassium Krebs-Henseleit solution. In conclusion, the natriuretic peptide isolated from Crotalus durissus cascavella venom produced renal and vascular effects. NP2_Casca reduced total and proximal sodium tubular transport, leading to an increase in sodium excretion, thereby demonstrating a diuretic action. A hypotensive effect was displayed in an arterial pressure assay, with an increase in nitrite production, suggesting a possible vasoactive action.

Relaxation of rabbit corpus cavernosum smooth muscle and aortic vascular endothelium induced by new nitric oxide donor substances of the nitrosyl-ruthenium complex

INTRODUCTION: Endothelial dysfunction characterized by endogenous nitric oxide (NO) deficiency made 56 percent of patients affected with erectile dysfunction decline treatment with PDE-5 inhibitors. New forms of treatment are currently being developed for this group of patients. MATERIALS AND METHODS: The study compared the effect of sodium nitroprusside (SNP) and two substances of the nitrosyl-ruthenium complex, cis-[Ru(bpy)2(SO3)(NO)]PF-6-9 ("FONO1”) and trans-[Ru(NH3)4(caffeine)(NO)]C13 ("LLNO1”) on relaxation of rabbit corpus cavernosum smooth muscle and aortic vascular endothelium. The samples were immersed in isolated baths and precontracted with 0.1 µM phenylephrine (PE) and the corresponding relaxation concentration/response curves were plotted. In order to investigate the relaxation mechanisms involved, 100 µM ODQ (a soluble guanylate cyclase-specific inhibitor), 3 µM or 10 µM oxyhemoglobin (an extracellular NO scavenger) or 1 mM L-cysteine (a nitrosyl anion-specific scavenger) was added to the samples. RESULTS: All the NO donors tested produced a significant level of relaxation in the vascular endothelium. In corpus cavernosum samples, FONO1 produced no significant effect, but LLNO1 and SNP induced dose-dependent relaxation with comparable potency (pEC50 = 6.14 ± 0.08 and 6.4 ± 0.14, respectively) and maximum effect (Emax = 82 percent vs. 100 percent, respectively). All NO donors were found to activate soluble guanylate cyclase, since the addition of the corresponding inhibitor (100 µM ODQ) completely neutralized the relaxation effect observed. The addition of oxyhemoglobin reduced the relaxation effect, but did not inhibit it completely. In aortic vascular endothelium 3 µM oxyhemoglobin decreased the relaxation effect by 26 percent on the average, while 10 µM oxyhemoglobin reduced it by over 52 percent. The addition of 100 µM L-cysteine produced no significant inhibiting effect. CONCLUSIONS: These results suggest that LLNO1...

Role of phospholipase A2 and tyrosine kinase in Clostridium difficile toxin A-induced disruption of epithelial integrity, histologic inflammatory damage and intestinal secretion.

Clostridium difficile-associated disease causes diarrhea to fulminant colitis and death. We investigated the role of phospholipase A2 (PLA2) inhibitors, aristolochic acid (AA), bromophenacyl bromide (BPB) and quinacrine (QUIN) on the C. difficile toxin A-induced disruption of epithelial integrity, histologic inflammatory damage and intestinal secretion. Toxin A caused severe hemorrhagic and inflammatory fluid secretion at 6-8 h in rabbit ileal segments, an effect that was significantly inhibited by QUIN (71%, P < 0.01), AA (87%, P < 0.000l) or by BPB (51%, P < 0.01). The secretory effect of toxin A was also inhibited in segments adjacent to those with AA (89%, P < 0.01). Furthermore, QUIN or AA substantially reduced the histologic damage seen after 6-8 h in rabbit ileal segments. The cyclooxygenase inhibitor, indomethacin, also significantly inhibited (96%; n = 6) the secretory effects of toxin A in ligated rabbit intestinal segments. The destruction by toxin A of F-actin at the tight junctions of T-84 cell monolayers was not inhibited by AA or BPB. AA or QUIN had no effect on the T-84 cell tissue resistance reduction over 8-24 h after toxin A exposure. All the inhibitors were shown to be effective in the doses administered direct in ileal loops to inhibit PLA2 activity. The data suggest that PLA2 is involved in the major pathway of toxin A-induced histologic inflammatory damage and hemorrhagic fluid secretion.