cyclic-gmp and Ureteral-Obstruction

The pyeloureteral function is to transport urine from the kidneys into the ureter toward the urinary bladder for storage until micturition. A set of mechanisms collaborates to achieve this purpose: the basic process regulating ureteral peristalsis is myogenic, initiated by active pacemaker cells located in the renal pelvis. Great emphasis has been given to hydrodynamic factors, such as urine flow rate in determining the size and pattern of urine boluses which, in turn, affect the mechanical aspects of peristaltic rhythm, rate, amplitude, and baseline pressure. Neurogenic contribution is thought to be limited to play a modulatory role in ureteral peristalsis. The myogenic theory of ureteral peristalsis can be traced back to Engelmann (1) who was able to localize the peristaltic pressure wave's origin in the renal pelvis and suggested that the ureteral contraction impulse passes from one ureteral cell to another, the whole ureter working as a functional syncitium. Recent studies of ureteral biomechanics, smooth muscle cell electrophysiology, membrane ionic currents, cytoskeletal components and pharmacophysiology much improved our understanding of the mechanism of how the urine bolus is propelled, how this process is disturbed in pathological states, and what could be done to improve it.

Topics: Action Potentials; Animals; Biological Clocks; Biomechanical Phenomena; Cyclic AMP; Cyclic GMP; Humans; Mechanotransduction, Cellular; Peristalsis; Pressure; rho-Associated Kinases; Ureter; Ureteral Obstruction; Urination

Renal fibrosis is an important factor for end-stage renal failure. However, only few therapeutic options for its treatment are established. Zaprinast, a phosphodiesterase 5 inhibitor, and serelaxin, the recombinant form of the naturally occurring hormone relaxin, are differently acting modulators of cyclic guanosine monophosphate (cGMP) signaling. Both agents enhance cGMP availability in kidney tissue. These substances alone or in combination might interfere with the development of kidney fibrosis. Therefore, we compared the effects of combination therapy with the effects of monotherapy on renal fibrosis. Renal fibrosis was induced by unilateral ureteral obstruction (UUO) for 7 days in wild-type (WT) and cGKI knockout (KO) mice. Renal antifibrotic effects were assessed after 7 days. In WT, zaprinast and the combination of zaprinast and serelaxin significantly reduced renal interstitial fibrosis assessed by α-SMA, fibronectin, collagen1A1, and gelatinases (MMP2 and MMP9). Intriguingly in cGKI-KO, mRNA and protein expression of fibronectin and collagen1A1 were reduced by zaprinast, in contrast to serelaxin. Gelatinases are not regulated by zaprinast. Although both substances showed similar antifibrotic properties in WT, they distinguished in their effect mechanisms. In contrast to serelaxin which acts both on Smad2 and Erk1, zaprinast did not significantly diminish Erk1/2 phosphorylation. Interestingly, the combination of serelaxin/zaprinast achieved no additive antifibrotic effects compared to the monotherapy. Due to antifibrotic effects of zaprinast in cGKI-KO, we hypothesize that additional cGKI-independent mechanisms are supposed for antifibrotic signaling of zaprinast.

Topics: Animals; Cyclic GMP; Cyclic GMP-Dependent Protein Kinase Type I; Drug Therapy, Combination; Fibrosis; Kidney; Kidney Diseases; Mice; Mice, Knockout; Phosphodiesterase 5 Inhibitors; Purinones; Recombinant Proteins; Relaxin; Signal Transduction; Ureteral Obstruction

This study was designed to examine whether natriuretic peptide/natriuretic peptide receptor-A (NPR-A) system attenuates renal fibrosis in a unilateral ureteral obstruction (UUO) model and also examined the mechanism involved.. Three groups were studied: untreated UUO in wild-type mice; untreated UUO in NPR-A KO mice; and ANP treated (0.05 microg/kg/min) UUO in wild-type mice. We measured histological and immunohistochemical findings (alpha-SMA and F4/80), tissue cGMP levels, various mRNA expression levels by real-time PCR analysis, and transcription factor levels (AP-1 and NF-kappaB) in renal tissue.. Compared with wild-type UUO mice, NPRA-KO UUO mice had abnormal morphological findings (fibrous area: +26%, alpha-SMA expression: +30%) with lower tissue cGMP levels and increases in the mRNA expression levels of TGF-beta, collagen I, collagen III, PAI-1, renin and angiotensinogen, whereas there were no differences in F4/80 positive cells or the mRNA expression levels of ICAM-1, osteopontin, or MCP-1 between the two groups. In contrast, ANP pre-treatment significantly improved morphological changes with increase of tissue cGMP levels and reduction in the mRNA expression level of TGF-beta, collagen I, collagen III, PAI-1, ICAM-1, osteopontin, MCP-1, renin, and angiotensinogen. NPRA-KO UUO mice had higher AP-1 levels than wild-type UUO mice and ANP pre-treatment reduced AP-1 and NF-kappaB activity.. The endogenous natriuretic peptide/NPR-A system may inhibit renal fibrosis partly via inhibition of the angiotensin/AP-1/TGF-beta/collagen pathway and exogenous ANP pre-treatment may inhibit it partly via both the angiotensin/AP-1/TGF-beta/collagen and NF-kappaB/inflammatory pathways.

Topics: Animals; Crosses, Genetic; Cyclic GMP; Fibrosis; Fluorescent Dyes; Immunohistochemistry; Indoles; Kidney Diseases; Mice; Mice, Inbred C57BL; Mice, Knockout; Natriuretic Peptides; Receptors, Atrial Natriuretic Factor; Renin-Angiotensin System; RNA, Messenger; Ureteral Obstruction

Progression of renal injury after relief of unilateral ureteral obstruction (UUO) has been demonstrated. Nitric oxide (NO) may be an effective intervention due to its vasodilatory, antifibrotic, and anti-apoptotic effects. Herein, we used dietary L-arginine (ARG) supplementation in a UUO relief model.. This study comprised group 1, control (no treatment). All other rats were subject to 3-day UUO, which was then relieved, and the rats maintained for 7 additional days. Group 2, no additional treatment; group 3, L-ARG; group 4, L-NAME, NO synthase inhibitor; group 5, ARG and L-NAME. Urinary NO(2/3) was quantified. GFR and ERPF were measured at day 10. Interstitial fibrosis and fibroblast expression, macrophage infiltration, tubular apoptosis, and proliferation, NOS expression, and the levels of tissue TGF-beta were evaluated.. Urinary NO(2/3) was significantly increased by ARG treatment and decreased by L-NAME. GFR and ERPF measured 7 days following relief were not significantly different in the previously obstructed kidneys (POK) of groups 2 and 3. L-NAME significantly reduced GFR and ERPF in the POK. ARG significantly reduced apoptosis, macrophage infiltration, and fibroblast expression in the POK. L-NAME exacerbated the effects on apoptosis and fibroblasts. Fibrosis was minimal in groups 1 through 3, but was significantly increased by L-NAME. ARG did not affect renal NOS expression and tissue TGF-beta1 levels.. Dietary ARG supplementation during UUO relief did not improve ERPF or GFR. However, renal damage, including fibrosis, apoptosis, and macrophage infiltration was significantly improved by ARG treatment. This suggests that increasing NO availability could be beneficial in the setting of UUO relief.

Topics: Animals; Arginine; Cyclic GMP; Dietary Supplements; Enzyme Inhibitors; Fibroblasts; Fibrosis; Glomerular Filtration Rate; In Situ Nick-End Labeling; Kidney; Macrophages; Male; NG-Nitroarginine Methyl Ester; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitrites; Organ Size; Proliferating Cell Nuclear Antigen; Rats; Rats, Sprague-Dawley; Transforming Growth Factor beta; Transforming Growth Factor beta1; Ureteral Obstruction

As several studies indirectly suggest that inhibiting the intracellular breakdown of cyclic nucleotides may inhibit fibrogenesis, this study used membrane permeable cyclic nucleotide analogues to examine the role of cAMP and cGMP signaling pathways in the regulation of renal fibroblast function. Fibroblasts were isolated by explant outgrowth culture of rat kidneys post unilateral ureteric obstruction. Subcultured cells were exposed to 10- 1,000 microM of the cyclic nucleotide analogues 8-bromo-cAMP (8br-cAMP) and 8-bromo-cGMP (8br-cGMP). Functional parameters examined included mitogenesis (thymidine incorporation), collagen synthesis (proline incorporation), myofibroblast differentiation (Western blotting for alpha-smooth muscle actin; alpha-SMA) and expression of CTGF (Northern blotting), a TGF-beta(1)-driven immediate early response gene. Serum-stimulated mitogenesis was decreased 27 +/- 4% by 100 microM 8br-cAMP (p < 0.01), 49 +/- 6% by 1,000 microM 8br-cAMP (p < 0.001) and 43 +/- 7% by 1,000 microM 8br-cGMP (p < 0.01). 1,000 microM 8br-cAMP and 8br-cGMP reduced basal collagen synthesis by 80 +/- 5 and 60 +/- 21% respectively (both p < 0.05). Maximum dose of 8br-cAMP but not 8br-cGMP inhibited basal expression of the differentiation marker alpha-SMA by 43 +/- 33 (p < 0.05), resulted in a more rounded cell morphology and reduced expression of CTGF by 39 +/- 24% (p < 0.05). Measurement of mitochondrial activity confirmed that effects were independent of cell toxicity. In conclusion, cyclic nucleotides inhibit fibrogenesis in vitro. Strategies which elevate intracellular cyclic nucleotide concentrations may therefore be therapeutically valuable in preventing the proliferation and activation of fibroblasts in progressive renal disease.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Actins; Animals; Cell Division; Cells, Cultured; Collagen; Connective Tissue Growth Factor; Cyclic AMP; Cyclic GMP; DNA; Fibroblasts; Fibrosis; Immediate-Early Proteins; Intercellular Signaling Peptides and Proteins; Kidney; Nucleotides, Cyclic; Rats; Ureteral Obstruction

Whether the postobstructive diuresis can in part be related to an altered regulation of Dendroaspis natriuretic peptide (DNP) was investigated. Male Sprague-Dawley rats were bilaterally obstructed of their ureters. Control group was with sham ureteral obstruction. Forty-eight h later, tissue levels of DNP immunoreactivity were determined in the plasma, heart, and kidneys. Urine samples were collected in some rats under anesthesia. The plasma DNP immunoreactivity was significantly increased by 45% in the experimental group. The tissue levels of DNP immunoreactivity in the atrium, ventricle, or kidneys did not significantly differ between the experimental and control groups. The urinary flow and sodium excretion rate were 3- to 4-fold increased in the experimental group. The urinary DNP excretion was also increased in the experimental group, which was positively correlated with the urinary volume and sodium excretion. The urinary excretion of cGMP was 2- to 3-fold increased in the experimental group. These results indicate that an enhanced DNP activity may in part be causally related to the postobstructive diuresis.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Elapid Venoms; Immunohistochemistry; Intercellular Signaling Peptides and Proteins; Kidney; Male; Myocardium; Peptides; Rats; Rats, Sprague-Dawley; Ureteral Obstruction

RBF and GFR are decreased in kidneys after ipsilateral unilateral ureteral obstruction (UUO) for 24 h. Despite net vasoconstriction, vasodilatory mechanisms respond to counterbalance the vasoconstriction: the inhibition of nitric oxide synthase activity is associated with a greater reduction in RBF with ipsilateral UUO. To determine whether the stimulation of soluble guanylyl cyclase differs between glomeruli from obstructed kidneys and normal kidneys, cGMP was measured after stimulation by 10(-3) M sodium nitroprusside (SNP) in glomeruli isolated from the kidneys of Sprague-Dawley rats after 24 h of UUO or sham operation. The generation of intracellular and extracellular (EC) cGMP (femtomoles of cGMP/100 glomeruli/per hour) was measured by RIA. After incubation with SNP, the EC accumulation of cGMP by UUO glomeruli was significantly greater than that by glomeruli from sham-operated rats (P < 0.05). When glomerular studies were repeated in the presence of the phosphodiesterase inhibitor isobutyl methylxanthine, there was no difference in the EC accumulation of cGMP. The direct measurement of cGMP hydrolysis by phosphodiesterase was significantly less in glomerular homogenate from UUO rats compared with sham-operated rats (P < 0.05). When 10(-5) M losartan, an angiotensin II receptor inhibitor, was included in glomerular incubations, there was a significant decrease in the EC glomerular cGMP response to SNP in UUO glomeruli (P < 0.05). This attenuated response was abolished by the addition of isobutyl methylxanthine. The addition of angiotensin II did not alter the accumulation of cGMP by UUO or sham glomeruli. These studies indicate that decreased phosphodiesterase activity in UUO glomeruli contributes to the enhanced accumulation of EC glomerular cGMP after the stimulation of soluble guanylyl cyclase by SNP. In addition, angiotensin II receptors modulate this response, suggesting a role for soluble guanylyl cyclase in countering angiotensin-mediated vasoconstriction due to UUO.

Topics: Angiotensin II; Angiotensin Receptor Antagonists; Animals; Antihypertensive Agents; Biphenyl Compounds; Cyclic GMP; Imidazoles; Kidney Glomerulus; Losartan; Male; Nitroprusside; Phosphoric Diester Hydrolases; Rats; Rats, Sprague-Dawley; Tetrazoles; Ureteral Obstruction; Vasoconstrictor Agents

Following 24 h of ureteral obstruction in the rat, renal blood flow and glomerular filtration rate are markedly depressed. The effect of saline loading on post-obstructive glomerular filtration (GFR) was studied in 15 female Sprague-Dawley rats in the awake state, 4 h following the release of 24 h of unilateral ureteral obstruction. Group I (n = 8) received 39 microliters min-1 of 0.9% saline only for 1 h prior to study and Group II (n = 7) received 78 microliters min-1 of 0.9% saline for the whole 4 h prior to study. The Cin and CPAH of the post-obstructed kidney were significantly reduced over control values in both groups. Saline loading (Group II) resulted in an improvement in Cin in the post-obstructed kidney compared with group I (3.22 +/- 0.14 vs. 2.19 +/- 0.14 ml/min/kg BW, P less than 0.001). This was independent of any change in CPAH. In two further groups of rats the saline loading protocol was shown to cause a rise in the excretion of urinary cGMP in the post-obstructed kidney, but not the contralateral control kidney. In addition, administration of exogenous atriopeptin (1-24) to non-saline loaded animals resulted in a qualitatively similar alteration in renal function to saline loading, namely a rise in Cin and an increase in excretion of cGMP by the post-obstructed kidney, and no change in CPAH.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Atrial Natriuretic Factor; Cyclic GMP; Female; Glomerular Filtration Rate; Isotonic Solutions; Kidney; Rats; Rats, Inbred Strains; Renal Circulation; Sodium Chloride; Ureteral Obstruction