Impact of Renal Pelvic Denervation on Systemic Hemodynamics and Neurohumoral Changes in a Porcine Model.

INTRODUCTION: The blood pressure (BP) response to arterial renal denervation (RDN) is variable. METHODS: This study examined the effectiveness of renal pelvic denervation (RPD) on BP, heart rate (HR), norepinephrine (NE), and histopathology in 42 swine. NE levels were measured immediately, 7, 14, 30, and 90 days after RPD. Intra-arterial BP and HR were measured throughout RPD and after 14 days in 5 swine. RESULTS: During the procedure, RPD immediately reduced systolic BP (-20.6 ± 18.3 mm Hg), diastolic BP (-6.0 ± 8.3 mm Hg), and HR (-5.4 ± 5.6 bpm), which remained decreased at follow-up. The porcine kidneys had a mean NE reduction of 76% directly post procedure and 60% after 7 days, 64% after 14 days, 57% after 30 days, and 65% after 90 days. Histopathological examination confirmed nerve ablation. CONCLUSIONS: These preliminary findings suggest that the renal pelvis nerve ablation is an encouraging target for RDN. Clinical trials are required to test the feasibility of RPD in human hypertension.

Does glucagon-like peptide-1 induce diuresis and natriuresis by modulating afferent renal nerve activity?

Glucagon-like peptide-1 (GLP-1), an incretin hormone, has diuretic and natriuretic effects. The present study was designed to explore the possible underlying mechanisms for the diuretic and natriuretic effects of GLP-1 via renal nerves in rats. Immunohistochemistry revealed that GLP-1 receptors were avidly expressed in the pelvic wall, the wall being adjacent to afferent renal nerves immunoreactive to calcitonin gene-related peptide, which is the dominant neurotransmitter for renal afferents. GLP-1 (3 µM) infused into the left renal pelvis increased ipsilateral afferent renal nerve activity (110.0 ± 15.6% of basal value). Intravenous infusion of GLP-1 (1 µg·kg-1·min-1) for 30 min increased renal sympathetic nerve activity (RSNA). After the distal end of the renal nerve was cut to eliminate the afferent signal, the increase in efferent renal nerve activity during intravenous infusion of GLP-1 was diminished compared with the increase in total RSNA (17.0 ± 9.0% vs. 68.1 ± 20.0% of the basal value). Diuretic and natriuretic responses to intravenous infusion of GLP-1 were enhanced by total renal denervation (T-RDN) with acute surgical cutting of the renal nerves. Selective afferent renal nerve denervation (A-RDN) was performed by bilateral perivascular application of capsaicin on the renal nerves. Similar to T-RDN, A-RDN enhanced diuretic and natriuretic responses to GLP-1. Urine flow and Na+ excretion responses to GLP-1 were not significantly different between T-RDN and A-RDN groups. These results indicate that the diuretic and natriuretic effects of GLP-1 are partly governed via activation of afferent renal nerves by GLP-1 acting on sensory nerve fibers within the pelvis of the kidney.

H2O2 generated by NADPH oxidase 4 contributes to transient receptor potential vanilloid 1 channel-mediated mechanosensation in the rat kidney.

The presence of NADPH oxidase (Nox) in the kidney, especially Nox4, results in H2O2 production, which regulates Na(+) excretion and urine formation. Redox-sensitive transient receptor potential vanilloid 1 channels (TRPV1s) are distributed in mechanosensory fibers of the renal pelvis and monitor changes in intrapelvic pressure (IPP) during urine formation. The present study tested whether H2O2 derived from Nox4 affects TRPV1 function in renal sensory responses. Perfusion of H2O2 into the renal pelvis dose dependently increased afferent renal nerve activity and substance P (SP) release. These responses were attenuated by cotreatment with catalase or TRPV1 blockers. In single unit recordings, H2O2 activated afferent renal nerve activity in response to rising IPP but not high salt. Western blots revealed that Nox2 (gp91(phox)) and Nox4 are both present in the rat kidney, but Nox4 is abundant in the renal pelvis and originates from dorsal root ganglia. This distribution was associated with expression of the Nox4 regulators p22(phox) and polymerase δ-interacting protein 2. Coimmunoprecipitation experiments showed that IPP increases polymerase δ-interacting protein 2 association with Nox4 or p22(phox) in the renal pelvis. Interestingly, immunofluorescence labeling demonstrated that Nox4 colocalizes with TRPV1 in sensory fibers of the renal pelvis, indicating that H2O2 generated from Nox4 may affect TRPV1 activity. Stepwise increases in IPP and saline loading resulted in H2O2 and SP release, sensory activation, diuresis, and natriuresis. These effects, however, were remarkably attenuated by Nox inhibition. Overall, these results suggest that Nox4-positive fibers liberate H2O2 after mechanostimulation, thereby contributing to a renal sensory nerve-mediated diuretic/natriuretic response.

A novel non-vascular system to treat resistant hypertension.

AIMS: To evaluate in a preclinical model the utility of a monopolar electrode catheter delivering radiofrequency (RF) energy placed into the renal pelvis in order to treat resistant hypertension (RH). METHODS AND RESULTS: Sixteen female domestic swine weighing 60-65 kg underwent renal pelvic denervation via ureteral access. Three animals were euthanised immediately after delivery of RF energy; five animals were allowed to survive for seven days, six animals were allowed to survive for 14 days and two animals were allowed to survive for 30 days. Renal cortical norepinephrine levels were measured in all groups of animals. Histopathology of the treated zone was performed to confirm nerve damage. Renal cortical tissue was harvested for determination of tissue norepinephrine by HPLC. The kidneys were then profusion-fixed and harvested for histopathologic analysis. Mean reduction of norepinephrine levels was 60.4% compared to control. Histopathology confirmed nerve ablation in the treated zone. CONCLUSIONS: In this small, preclinical study, we introduce a new non-vascular system to treat resistant hypertension. If the current clinical experience confirms efficacy and safety, this approach may be one way to treat patients who cannot be treated with the standard percutaneous arterial devices.

Renal sensory and sympathetic nerves reinnervate the kidney in a similar time-dependent fashion after renal denervation in rats.

Efferent renal sympathetic nerves reinnervate the kidney after renal denervation in animals and humans. Therefore, the long-term reduction in arterial pressure following renal denervation in drug-resistant hypertensive patients has been attributed to lack of afferent renal sensory reinnervation. However, afferent sensory reinnervation of any organ, including the kidney, is an understudied question. Therefore, we analyzed the time course of sympathetic and sensory reinnervation at multiple time points (1, 4, and 5 days and 1, 2, 3, 4, 6, 9, and 12 wk) after renal denervation in normal Sprague-Dawley rats. Sympathetic and sensory innervation in the innervated and contralateral denervated kidney was determined as optical density (ImageJ) of the sympathetic and sensory nerves identified by immunohistochemistry using antibodies against markers for sympathetic nerves [neuropeptide Y (NPY) and tyrosine hydroxylase (TH)] and sensory nerves [substance P and calcitonin gene-related peptide (CGRP)]. In denervated kidneys, the optical density of NPY-immunoreactive (ir) fibers in the renal cortex and substance P-ir fibers in the pelvic wall was 6, 39, and 100% and 8, 47, and 100%, respectively, of that in the contralateral innervated kidney at 4 days, 4 wk, and 12 wk after denervation. Linear regression analysis of the optical density of the ratio of the denervated/innervated kidney versus time yielded similar intercept and slope values for NPY-ir, TH-ir, substance P-ir, and CGRP-ir fibers (all R(2) > 0.76). In conclusion, in normotensive rats, reinnervation of the renal sensory nerves occurs over the same time course as reinnervation of the renal sympathetic nerves, both being complete at 9 to 12 wk following renal denervation.

Is the pelviureteric junction an anatomical entity?

OBJECTIVE: The concept of the pelviureteric junction has existed for more than a century and yet there is no clear anatomical definition of this junction. This systematic review addresses the question of whether the human pelviureteric junction is a discrete anatomical entity. METHODS: A systematic literature review was undertaken to investigate the normal gross and microscopic anatomy of the pelviureteric junction using the electronic databases MEDLINE, PubMed, Cochrane Library and Google Scholar. RESULTS: In most individuals there is a gradual transition between the renal pelvis and ureter with no external features indicating the presence of a discrete pelviureteric 'junction'. Internally, however, luminal mucosal folds are prominent in this region. There is no consensus on the arrangement of muscle fibers at the pelviureteric junction (which may be age-dependent) although some studies suggest a focal thickening in the muscle wall consistent with physiological observations suggesting a high pressure zone capable of regulating urine flow. Studies of innervation have shown no evidence of specialization at this site. CONCLUSIONS: There is some evidence that a pelviureteric region can be delineated anatomically and physiologically. However, although it may be a useful clinical concept, there is no sound anatomical basis for an actual pelviureteric junction.

Distribution of Cajal like cells and innervation in intrinsic ureteropelvic junction obstruction.

OBJECTIVES: C-kit positive interstitial cells of Cajal (ICC)-like cells are defined as pacemaker cells in the ureter, which produce and coordinate peristaltic motility. To investigate the changes in ICC-like cells and innervation in segments of intrinsic uretero-pelvic junction (UPJ) obstruction. MATERIAL AND METHODS: Full thickness specimens obtained from UPJ segments (n = 77) were divided into 3 groups. Group I included 32 intrinsic UPJ obstruction segments, separated into 3 subgroups: Group Ia (proximal), Group Ib (obstruction, intermediate) and Group Ic (distal segments). Group II included 30 normal UPJ segments derived from the nephrectomy specimens. In Group III, 15 UPJ segments of chronic obstruction were analyzed. Formalin fixed, paraffin embedded specimens from UPJs were analyzed immunohistochemically for CD117, S100 and synaptophysin protein expression in nerve plexus and ganglionic cells in the neuromuscular junction. RESULTS: Group Ib showed significantly decreased (p < 0.05) positive staning with c-kit protooncogene protein (CD117), S100 and synaptophysin proteins compared with Group Ia and Group Ic. ICC-like cells were observed in increased number (p < 0.05) in Group Ia compared to Groups II and III. Group Ib had lower synaptophysin positivity compared to Group II. CONCLUSIONS: The findings support the hypothesis of decreased innervation in the etiopathogenesis of intrinsic UPJ obstruction. Increased number of ICC-like cells in Group Ia suggests that peristaltic activity is higher in pelvicalyceal region.

Dietary sodium modulates the interaction between efferent and afferent renal nerve activity by altering activation of α2-adrenoceptors on renal sensory nerves.

Activation of efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA), which then reflexively decreases ERSNA via activation of the renorenal reflexes to maintain low ERSNA. The ERSNA-ARNA interaction is mediated by norepinephrine (NE) that increases and decreases ARNA by activation of renal α(1)-and α(2)-adrenoceptors (AR), respectively. The ERSNA-induced increases in ARNA are suppressed during a low-sodium (2,470 ± 770% s) and enhanced during a high-sodium diet (5,670 ± 1,260% s). We examined the role of α(2)-AR in modulating the responsiveness of renal sensory nerves during low- and high-sodium diets. Immunohistochemical analysis suggested the presence of α(2A)-AR and α(2C)-AR subtypes on renal sensory nerves. During the low-sodium diet, renal pelvic administration of the α(2)-AR antagonist rauwolscine or the AT1 receptor antagonist losartan alone failed to alter the ARNA responses to reflex increases in ERSNA. Likewise, renal pelvic release of substance P produced by 250 pM NE (from 8.0 ± 1.3 to 8.5 ± 1.6 pg/min) was not affected by rauwolscine or losartan alone. However, rauwolscine+losartan enhanced the ARNA responses to reflex increases in ERSNA (4,680 ± 1,240%·s), and renal pelvic release of substance P by 250 pM NE, from 8.3 ± 0.6 to 14.2 ± 0.8 pg/min. During a high-sodium diet, rauwolscine had no effect on the ARNA response to reflex increases in ERSNA or renal pelvic release of substance P produced by NE. Losartan was not examined because of low endogenous ANG II levels in renal pelvic tissue during a high-sodium diet. Increased activation of α(2)-AR contributes to the reduced interaction between ERSNA and ARNA during low-sodium intake, whereas no/minimal activation of α(2)-AR contributes to the enhanced ERSNA-ARNA interaction under conditions of high sodium intake.

Activation of endothelin A receptors contributes to impaired responsiveness of renal mechanosensory nerves in congestive heart failure.

Increasing renal pelvic pressure results in PGE2-mediated release of substance P, leading to increases in afferent renal nerve activity (ARNA) and natriuresis, that is, a renorenal reflex response. The renorenal reflexes are impaired in congestive heart failure (CHF). Impairment of the renorenal reflexes may contribute to the increased renal sympathetic nerve activity and sodium retention in CHF. Endothelin (ET)-1 contributes to the pathological changes in cardiac and renal function in CHF. Therefore, we examined whether the ETA receptor antagonist BQ123 altered the responsiveness of renal mechanosensory nerves in CHF. The ARNA responses to increasing renal pelvic pressure were suppressed in CHF but not in sham-CHF rats. In CHF, increasing renal pelvic pressure by 7.5 mm Hg before and during renal pelvic perfusion with BQ123 increased ARNA 12% +/- 3% and 21% +/- 3% (p < 0.05 vs. vehicle). In isolated renal pelvises from CHF rats, PGE2 increased substance P release from 5 +/- 0 to 7 +/- 1 pg/min without BQ123 and from 4 +/- 1 to 9 +/- 1 pg/min with BQ123 in the bath (p < 0.01 vs. vehicle). BQ123 had no effect on the ARNA responses or substance P release in sham-CHF. In conclusion, activation of ETA receptors contributes to the impaired responsiveness of renal mechanosensory nerves in CHF rats by a mechanism(s) at the renal sensory nerve endings.

Extracellular matrix degradation and reduced neural density in children with intrinsic ureteropelvic junction obstruction.

OBJECTIVES: To investigate the extracellular matrix microenvironment and nerve supply of ureteropelvic junctions (UPJs) in children with intrinsic UPJ obstruction. Congenital UPJ obstruction is the most common cause of neonatal hydronephrosis. Although many studies investigating the molecular changes within this segment have been performed, the underlying mechanisms of UPJ obstruction are still unclear. METHODS: Specimens were obtained from 21 children with a mean age of 103.2 months undergoing dismembered pyeloplasty. Control samples included 9 archival specimens from age-matched children without any history of urologic disease. Paraffin-embedded sections were immunostained to detect matrix metalloproteinase 2 (MMP-2), tenascin C (TN-C), and S-100 (for the neuronal supply). Expression patterns were investigated using semiquantitative high-power field magnification analyses, and the MMP-2 and TN-C immunoreactivity were scored. Differences between the 2 groups were examined statistically. RESULTS: All UPJ specimens displayed a resolved muscular coat and replacement of smooth muscle cells by connective tissue. The degree of MMP-2 expression representing matrix turnover was statistically significantly elevated. Similarly, TN-C expression was found to be higher in obstructed specimens. Additionally, the mean S-100 staining was lower than in controls. Although S-100-positive nerve-fibers were more predominant in the adventitia with minimal submucosal and absent intramuscular staining in patient specimens, they were abundant in both adventitia and submucosa with minimal intramuscular staining in the controls. CONCLUSIONS: In intrinsic UPJ obstruction samples, a dissolved smooth muscular coat and an overexpression of extracellular matrix proteins, together with depleted nerve supply, was demonstrable.

Spontaneous electrical and Ca2+ signals in the mouse renal pelvis that drive pyeloureteric peristalsis.

1. Peristalsis in the smooth muscle cell (SMC) wall of the pyeloureteric system is unique in physiology in that the primary pacemaker resides in a population of atypical SMCs situated near the border of the renal papilla. 2. Atypical SMCs display high-frequency Ca(2+) transients upon the spontaneous release of Ca(2+) from inositol 1,4,5-trisphosphate (IP(3))-dependent stores that trigger cation-selective spontaneous transient depolarizations (STDs). In the presence of nifedipine, these Ca(2+) transients and STDs seldom propagate > 100 mum. Synchronization of STDs in neighbouring atypical SMCs into an electrical signal that can trigger action potential discharge and contraction in the typical SMC layer involves a coupled oscillator mechanism dependent on Ca(2+) entry through L-type voltage-operated Ca(2+) channels. 3. A population of spindle- or stellate-shaped cells, immunopositive for the tyrosine receptor kinase kit, is sparsely distributed throughout the pyeloureteric system. In addition, Ca(2+) transients and action potentials of long duration occurring at low frequencies have been recorded in a population of fusiform cells, which we have termed interstitial cells of Cajal (ICC)-like cells. 4. The electrical and Ca(2+) signals in ICC-like cells are abolished upon blockade of Ca(2+) release from either IP(3)- or ryanodine-dependent Ca(2+) stores. However, the spontaneous Ca(2+) signals in atypical SMCs or ICC-like cells are little affected in W/W(-v) transgenic mice, which have extensive lesions of their intestinal ICC networks. 5. In summary, we have developed a model of pyeloureteric pacemaking in which atypical SMCs are indeed the primary pacemakers, but the function of ICC-like cells has yet to be determined.

Dietary sodium modulates the interaction between efferent renal sympathetic nerve activity and afferent renal nerve activity: role of endothelin.

Increasing efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA), which in turn decreases ERSNA via activation of the renorenal reflexes in the overall goal of maintaining low ERSNA. We now examined whether the ERSNA-induced increases in ARNA are modulated by dietary sodium and the role of endothelin (ET). The ARNA response to reflex increases in ERSNA was enhanced in high (HNa)- vs. low-sodium (LNa) diet rats, 7,560 +/- 1,470 vs. 900 +/- 390%.s. The norepinephrine (NE) concentration required to increase PGE(2) and substance P release from isolated renal pelvises was 10 pM in HNa and 6,250 pM in LNa diet rats. In HNa diet pelvises 10 pM NE increased PGE(2) release from 67 +/- 6 to 150 +/- 13 pg/min and substance P release from 6.7 +/- 0.8 to 12.3 +/- 1.8 pg/min. In LNa diet pelvises 6,250 pM NE increased PGE(2) release from 64 +/- 5 to 129 +/- 22 pg/min and substance P release from 4.5 +/- 0.4 to 6.6 +/- 0.7 pg/min. In the renal pelvic wall, ETB-R are present on unmyelinated Schwann cells close to the afferent nerves and ETA-R on smooth muscle cells. ETA-receptor (R) protein expression in the renal pelvic wall is increased in LNa diet. In HNa diet, renal pelvic administration of the ETB-R antagonist BQ788 reduced ERSNA-induced increases in ARNA and NE-induced release of PGE(2) and substance P. In LNa diet, the ETA-R antagonist BQ123 enhanced ERSNA-induced increases in ARNA and NE-induced release of substance P without altering PGE(2) release. In conclusion, activation of ETB-R and ETA-R contributes to the enhanced and suppressed interaction between ERSNA and ARNA in conditions of HNa and LNa diet, respectively, suggesting a role for ET in the renal control of ERSNA that is dependent on dietary sodium.

The effects of ureteral obstruction on Cajal-like cells in rats.

OBJECTIVE: To determine the changes in number and morphology of interstitial cells of Cajal (ICC)-like cells (ICC-LC) at the ureteropelvic junction (UPJ) of rats after experimental distal ureteral obstruction. MATERIALS AND METHODS: Of a total of 109 rats, 20 served as controls (C), 20 underwent sham-operations (SH) and 69 were in the study (S) groups. The UPJs were extracted initially in the C and SH groups, and 7, 14, 30, 60 and 90 days after ligation of the distal ureter in the study groups (S1, S2, S3, S4 and S5, respectively). The sections stained by c-kit anticore were studied under a light microscope. RESULTS: The mean number of ICC-LC was 4.55+/-2.21 in C, 5.15+/-3.51 in SH, 7.40+/-6.88 in S1, 21.16+/-19.03 in S2, 12.63+/-8.16 in S3, 10.40+/-5.09 in S4, and 10.9+/-6.33 in S5. There was a statistically significant increase in ICC-LC in the study groups, except S1, compared to the C and SH groups. No significant difference was detected in Cajal cell morphology and distribution pattern between groups. CONCLUSIONS: Based on the changes in number of ICC-LC at the UPJ after obstruction of the distal ureter compared with the limited data available in the literature, we suggest that ICC-LC have a close relationship with motility of the ureter.

Interdependent regulation of afferent renal nerve activity and renal function: role of transient receptor potential vanilloid type 1, neurokinin 1, and calcitonin gene-related peptide receptors.

Our previous studies have shown that the activation of the transient receptor potential vanilloid type 1 (TRPV1) expressed in the renal pelvis leads to an increase in ipsilateral afferent renal nerve activity (ARNA) and contralateral renal excretory function, but the molecular mechanisms of TRPV1 action are largely unknown. This study tests the hypothesis that activation of receptors of neurokinin 1 (NK1) or calcitonin gene-related peptide (CGRP) by endogenously released substance P (SP) or CGRP following TRPV1 activation, respectively, governs TRPV1-induced increases in ARNA and renal excretory function. Capsaicin (CAP; 0.04, 0.4, and 4 nM), a selective TRPV1 agonist, administered into the renal pelvis dose-dependently increased ARNA. CAP (4 nM)-induced increases in ipsilateral ARNA or contralateral urine flow rate (Uflow) and urinary sodium excretion (UNa) were abolished by capsazepine (CAPZ), a selective TRPV1 antagonist, or 2-[1-imino-2-(2-methoxyphenyl)ethyl]-7,7-diphenyl-4-perhydroisoindolone (3aR,7aR) (RP67580) or cis-2-(diphenylmethyl)-N-[(2-iodophenyl)-methyl]-1 azabicyclo[2.2.2]octan-3-amine (L703,606), selective NK1 antagonists, but not by CGRP8-37, a selective CGRP receptor antagonist. Both SP (7.4 nM) and CGRP (0.13 muM) increased ARNA, Uflow, or UNa, and increases in these parameters induced by CGRP but not SP were abolished by CAPZ. CAP at 4 nM perfused into the renal pelvis caused the release of SP and CGRP, which was blocked by CAPZ but not by RP67580, L703,606, or CGRP8-37. Immunofluorescence results showed that NK1 receptors were expressed in sensory neurons in dorsal root ganglion and sensory nerve fibers innervating the renal pelvis. Taken together, our data indicate that NK1 activation induced by SP release upon TRPV1 activation governs TRPV1 function and that a TRPV1-dependent mechanism is operant in CGRP action.

Transient receptor potential vanilloid type 1 channels act as mechanoreceptors and cause substance P release and sensory activation in rat kidneys.

Stimulation of capsaicin receptors results in an increase in afferent renal nerve activity (ARNA), but it is unclear how capsaicin contributes to sensory activation intrarenally. Here, we studied the relationships between capsaicin receptor activation, substance P (SP) release, and the sensory response in the rat renal pelvis. Immunoblots showed that one of the capsaicin receptors, transient receptor potential vanilloid type 1 channel (TRPV1), was found in various renal tissues and was especially abundant in the renal pelvis, where most sensory nerve fibers originate. Interestingly, immunolabeling showed colocalization of TRPV1, SP, and the panneuronal marker PGP9.5 in the renal pelvis. Electrophysiological recordings showed that SP and capsaicin activated the same mechanosensitive ARNA in a single-unit preparation. Intrapelvic administration of capsaicin or a specific TRPV1 agonist, resiniferatoxin, resulted in a dose-dependent increase in multi-unit ARNA and SP release, and these effects were blocked by the TRVP1 blocker capsazepine. Inhibition of the SP receptor by L-703,606 largely prevented capsaicin- or resiniferatoxin-induced ARNA. Capsazepine also prevented intrapelvic pressure (IPP)-dependent ARNA activation and contralateral diuresis/natriuresis in the renorenal reflex at an IPP of 20 mmHg, but had no effect at an IPP of 50 mmHg. These data indicate that TRPV1, a low-pressure baroreceptor, is present in the renal pelvis and exclusively regulates neuropeptide release from primary renal afferent C-fibers in response to mechanostimulation.

Smooth muscle cell apoptosis and defective neural development in congenital ureteropelvic junction obstruction.

PURPOSE: We assessed the smooth muscle cell apoptosis along with changes in cellular and extracellular components of the ureteropelvic junction in 23 patients with unilateral obstruction and compared them with 25 autopsies from ureteropelvic junction regions of age matched cadavers. MATERIALS AND METHODS: Tissue specimens obtained from pyeloplasty were divided into 3 sections-renal pelvis above the obstruction, obstructed ureteropelvic junction and ureter below the obstructed region. For the control group the normal ureteropelvic junctions of age matched infants were autopsied. In paraffin embedded sections we determined myocyte apoptosis index (using TUNEL assay), and the amount of muscular components and nerve terminals (using image analysis techniques after immunohistochemical staining). The collagen and elastin fibers were specifically stained for evaluation of changes in extracellular matrix. RESULTS: Smooth muscle cell apoptosis index was significantly increased at the site of ureteropelvic junction obstruction (5.68 +/- 0.18) compared to normal autopsied ureteropelvic junctions (3.60 +/- 0.11) and 2 other sections of obstructed ureteropelvic junction complex (renal pelvis 4.73 +/- 0.16, and ureter 3.97 +/- 0.16). The number of nerve terminals and the percentage of muscular component were significantly lower at the obstructed segments of affected patients compared to normal ureteropelvic junctions. Meanwhile, collagen fibers formed a significantly higher proportion of ureteral wall at the site of obstruction. Interestingly, there was negative correlation between myocyte apoptosis indices and number of nerve endings as well as amount of muscular components at the site of ureteropelvic junction obstruction. However, positive correlations were found between smooth muscle cell apoptosis and the percentage of collagen and elastin fibers. CONCLUSIONS: Our findings suggest an important role for myocyte apoptosis and defective neural development in the pathogenesis of congenital ureteropelvic junction obstruction that could pave the road for the emergence of new therapeutic modalities.

Diuresis and natriuresis caused by activation of VR1-positive sensory nerves in renal pelvis of rats.

To test the hypothesis that activation of the vanilloid receptor 1 (VR1) expressed in sensory nerves innervating the renal pelvis leads to diuresis and natriuresis, a selective VR1 receptor agonist, capsaicin (2.4 nmol), or vehicle was perfused intravenously or into the left renal pelvis of anesthetized rats at a rate without changing renal perfusion pressure. Mean arterial pressure was not altered by capsaicin administered intravenously or into the renal pelvis. Capsaicin perfusion into the left renal pelvis but not intravenously caused significant increases in urine flow rate and urinary sodium excretion bilaterally in a dose-dependent manner, which were abolished by capsazepine, a selective VR1 receptor antagonist, given ipsilaterally to the renal pelvis or by ipsilateral renal denervation. Capsaicin given intravenously or into the left renal pelvis increased plasma calcitonin gene-related peptide levels to the same extent. Increased plasma calcitonin gene-related peptide levels induced by capsaicin (68.9+/-2.8 pg/mL) perfusion into the renal pelvis was prevented either by capsazepine (22.5+/-10.1 pg/mL) given ipsilaterally into the renal pelvis or by ipsilateral renal denervation (25.9+/-2.3 pg/mL). Taken together, our data show that unilateral activation of VR1-positive sensory nerves innervating the renal pelvis leads to bilateral diuresis and natriuresis via a mechanism that is independent of plasma calcitonin gene-related peptide levels. These data suggest that VR1-positive sensory nerves in the kidney enhance renal excretory function, a mechanism that may be critically involved in sodium and fluid homeostasis.

Impaired substance P release from renal sensory nerves in SHR involves a pertussis toxin-sensitive mechanism.

Stretching the renal pelvic wall activates renal mechanosensory nerves by a PGE2-mediated release of substance P via activation of the cAMP-PKA pathway. Renal pelvic ANG II modulates the responsiveness of renal sensory nerves by suppressing the PGE2-mediated activation of adenylyl cyclase via a pertussis toxin (PTX)-sensitive mechanism. In SHR, activation of renal mechanosensory nerves is impaired. This is due to suppressed release of substance P in response to increased pelvic pressure. The present study was performed to investigate whether the PGE2-mediated release of substance P was suppressed in SHR vs. WKY and, if so, whether the impaired PGE2-mediated release of substance P was due to ANG II activating a PTX-sensitive mechanism. In an isolated renal pelvic wall preparation, PGE2, 0.14 microM, increased substance P release from 9 +/- 3 to 22 +/- 3 pg/min (P < 0.01) in Wistar-Kyoto rats (WKY), but had no effect in spontaneously hypertensive rats (SHR). A tenfold higher concentration of PGE2, 1.4 microM, was required to increase substance P release in SHR, from 7 +/- 1 to 22 +/- 3 pg/min (P < 0.01). In SHR, treating renal pelvises with losartan enhanced the release of substance P produced by subthreshold concentration of PGE2, 0.3 microM, from 16 +/- 2 to 26 +/- 3 pg/min (P < 0.01). Likewise, treating renal pelvises with PTX enhanced the PGE2-mediated release of substance P from 10 +/- 1 to 33 +/- 3 pg/min (P < 0.01) in SHR. In WKY, neither losartan nor PTX had an effect on the release of substance P produced by subthreshold concentrations of PGE2, 0.03 microM. In conclusion, the impaired responsiveness of renal sensory nerves in SHR involves endogenous ANG II suppressing the PGE2-mediated release of substance P via a PTX-sensitive mechanism.

Angiotensin blocks substance P release from renal sensory nerves by inhibiting PGE2-mediated activation of cAMP.

Activation of renal sensory nerves involves PGE2-mediated release of substance P (SP) via activation of the cAMP-PKA pathway. The PGE2-mediated SP release is suppressed by a low- and enhanced by a high-sodium (Na+) diet, suggesting an inhibitory effect of ANG. We now examined whether ANG II is present in the pelvic wall and inhibits PGE2-mediated SP release by blocking PGE2-mediated increases in cAMP. ANG II levels in renal pelvic tissue were 710 +/- 95 and 260 +/- 30 fmol/g tissue in rats fed a low- and high-Na+ diet, respectively. In a renal pelvic preparation from high-Na+-diet rats, 0.14 microM PGE2 produced an increase in SP release from 7 +/- 1 to 19 +/- 3 pg/min that was blocked by 15 nM ANG II. Treating pelvises with pertussis toxin (PTX) abolished the effects of ANG II. In pelvises from low-Na+ rats, neither basal nor bradykinin-mediated SP release was altered by PGE2. However, the bradykinin-mediated release of SP was enhanced by the permeable cAMP analog CPT-cAMP, from 4 +/- 1 to 11 +/- 2 pg/min, a response similar to that in normal-Na+-diet rats. In vivo, renal pelvic administration of PGE2 enhanced the afferent renal nerve activity (ARNA) response to bradykinin in normal- but not in low-Na+ diet rats. CPT-cAMP produced similar enhancement of the ARNA responses to bradykinin in normal- and low-Na+-diet rats, 1,670 +/- 490 and 1,760 +/- 400%.s (area under the curve of ARNA vs. time). Similarly, the ARNA responses to increases in renal pelvic pressure were similarly enhanced by CPT-cAMP in normal- and low-Na+-diet rats. In conclusion, renal pelvic ANG II modulates the responsiveness of renal sensory nerves by suppressing PGE2-mediated activation of adenylyl cyclase via a PTX-sensitive mechanism.