Genetic and Cellular Response to Unilateral Ischemia of the Rabbit Urinary Bladder

Effects of Lycopene Attenuating Injuries in Ischemia and Reperfusion

Tissue and organ ischemia can lead to cell trauma, tissue necrosis, irreversible damage, and death. While intended to reverse ischemia, reperfusion can further aggravate an ischemic injury (ischemia-reperfusion injury, I/R injury) through a range of pathologic processes. An I/R injury to one organ can also harm other organs, leading to systemic multiorgan failure. A type of carotenoid, lycopene, has been shown to treat and prevent many diseases (e.g., rheumatoid arthritis, cancer, diabetes, osteoporosis, male infertility, neurodegenerative diseases, and cardiovascular disease), making it a hot research topic in health care. Some recent researches have suggested that lycopene can evidently ameliorate ischemic and I/R injuries to many organs, but few clinical studies are available. Therefore, it is essential to review the effects of lycopene on ischemic and I/R injuries to different organs, which may help further research into its potential clinical applications.

Expression of nerve growth factor immunoreactivity and messenger RNA in ischemic urinary bladder

AIMS

The bladder contractile dysfunction resulting from acute ischemia may be attributed to nerve growth factor (NGF) overexpression. This study was conducted to evaluate the acute and mid-term effects of bladder ischemia on the temporal expression of NGF immunoreactivity and mRNA.

MATERIALS AND METHODS

Bladder ischemia was induced by ligation of bilateral vesical arteries in female rats. We examined the NGF content of bladder detrusor muscle at 1 day, 1 week and 4 weeks after artery ligation. Immunoreactivity of NGF was studied by immunofluorescent staining and Western blot. The NGF mRNA was analyzed by real-time polymerase chain reaction.

RESULTS

The immunofluorescence of NGF at 1 week and 4 weeks was significantly reduced when compared to sham-operated group (P < 0.05). This decreased tendency was also found in Western blot test. An increased expression of NGF mRNA was noted at 1 day, 1 week and 4 weeks, but had no significant change when compared to sham-operated group (P > 0.05).

CONCLUSIONS

Our study showed bilateral vesical artery ligation may cause damage of detrusor muscle and there is decreased NGF immunofluorescence and elevated NGF mRNA in bladder suggesting an expression disparity following ischemia.

Effect of partial bladder outlet obstruction on nitrotyrosine levels and their correlation with contractile function

AIMS

It has been demonstrated that partial bladder outlet obstruction (PBOO) causes free radical generation that, in turn, results in cellular and subcellular damage. We tested the hypothesis that nitration of proteins is associated with contractile dysfunctions in obstructive bladder disease.

METHODS

Thirty rabbits were subjected to 1-28 days of partial outlet obstruction. Sham operated rabbits served as controls. Western blotting was used to determine the amount of nitrotyrosine level at the protein level. At each time point, isolated strips of bladder body were mounted in individual baths and the contractile response to field stimulation (FS), carbachol, and KCl determined.

RESULTS

Bladder weight increased rapidly during the first 7 days and then increased slowly thereafter. There was a fourfold increase in the amount of nitrotyrosine in the 7 day obstructed groups when compared to sham controls and the levels remain elevated at 14 and 28 days of obstruction. Contractile dysfunction in response to FS (8 and 32 Hz) was noted as early as 1 day after obstruction and increased progressively over the study period. The decrease in response to carbachol and KCl was significant only after 3 days of obstruction and the progressive increase in dysfunction was slower than with FS.

CONCLUSIONS

PBOO is accompanied by an increase in nitrotyrosine, a marker of free radical damage. Simultaneously there was a progressive decrease in contractility of detrusor smooth muscles (DSMs). Nitrotyrosine may be usable as a marker of free radical damage and reperfusion injury.

Altered Nitric Oxide Synthase, Arginase and Ornithine Decarboxylase Activities, and Polyamine Synthesis in Response to Ischemia of the Rabbit Detrusor

PURPOSE

Little is known about L-arginine catabolism following ischemia in the bladder. We examined the changes in nitric oxide synthase, arginase and ornithine decarboxylase activity, polyamine biosynthesis and the ability to produce nitric oxide following ischemia of the rabbit bladder.

MATERIALS AND METHODS

Bladder ischemia was created by ligation of a unilateral bladder artery. At various time points, that is 1, 4, 8, 24, 48 and 72 hours following ligation, the bladders were excised and harvested for determinations.

RESULTS

Constitutive nitric oxide synthase, inducible nitric oxide synthase arginase and ornithine decarboxylase activities increased with time, peaking at 48 hours without significant differences between the ligated and nonligated sides in the whole layer. Arginase and ornithine decarboxylase increased mainly in the muscularis following ischemia. Also, putrescine in the muscularis was significantly higher than in the mucosa 48 hours following ischemia. Baseline nitrite/nitrate production in the whole detrusor on the ligated side at 24 hours was significantly lower than that in the normal detrusor. However, nor-hydroxyarginine as an arginase inhibitor and L-arginine increased nitrite/nitrate production in the ischemic detrusor without changing in the normal detrusor. This increasing effect of nor-hydroxyarginine was abolished by nitroarginine methylester as a nitric oxide synthase inhibitor.

CONCLUSIONS

Enzymes related to L-arginine catabolism were involved in the early events of ischemic bladder. Arginase may have 2 independent roles, that is 1) activation of arginase/ornithine decarboxylase/polyamines pathways in the muscle injury and remodeling following ischemia, and 2) endogenous negative regulation of nitric oxide production by limiting the L-arginine substrate for nitric oxide synthase.

Low-dose tadenan protects the rabbit bladder from bilateral ischemia/ reperfusion-induced contractile dysfunction

Recent studies indicate that focal ischemia/reperfusion (I/R) can cause the contractile dysfunctions induced in animal models of partial bladder outlet obstruction. Tadenan (Pygeum africanum) pretreatment can prevent the rabbit bladder from developing the contractile and biochemical dysfunctions induced by partial outlet obstruction, possibly by protecting the bladder from ischemic injury. The current study was designed to determine whether pre-treating rabbits with a clinically relevant dose of Tadenan could prevent the bladder from developing the contractile dysfunctions that are induced by bilateral ischemia followed by reperfusion. New Zealand White rabbits were separated into two groups. One group was pre-treated by oral gavage for 3 weeks with Tadenan (3.0 mg/kg body wt./ day). The second group was treated with vehicle (peanut oil). Five rabbits from each group were subjected to either bilateral ischemia for 1 or 3 h and than reperfused for either 1 h or 1 week. Five rabbits from each group were subjected to sham surgery and run with each of the experimental groups. The results of the current study show that Tadenan pretreatment at the clinically relevant dose of 3.0 mg/kg body wt./day protected the bladder from the contractile dysfunctions induced by bilateral ischemia followed by reperfusion. These data are consistent with the assertion that Tadenan therapy in both rabbits and humans acts by protecting the bladder smooth muscle against cellular damage caused by ischemia and reperfusion.

Acute intravesical infusion of a cobalt solution stimulates a hypoxia response, growth and angiogenesis in the rat bladder

PURPOSE

Experimental partial bladder outlet obstruction of rats induces a bladder growth and remodeling process similar to that in humans with benign prostatic hyperplasia. Previously we have proposed that bladder hypoxia associated with partial bladder outlet obstruction is a stimulus of this bladder growth process. We report our results of testing the acute effects of a simple chemical agent (cobaltous ion) known to mimic hypoxia in the rat bladder. We measured its ability to effect bladder gene expression, angiogenesis and growth processes.

MATERIALS AND METHODS

Adult rats were divided into 2 groups. One group (controls) received intravesical saline 3 times for 30 minutes in 6 days and the other received intravesical saline with 100 microM. CoCl(2) at the same times. All animals also received continuous infusion of BrdU for the 6-day period through an implanted osmotic pump. Portions of the bladders from these rats were fixed, sectioned, stained for microscopic analysis and immunohistochemically stained to identify BrdU positive cells and vascular elements via factor VIII staining. Other portions were frozen, extracted for proteins and the proteins were comparatively analyzed for the expression of hypoxia inducible factor-1alpha and vascular endothelial growth factor on Western blots.

RESULTS

Bladders infused with CoCl(2) showed extensive expansion of the submucosal region, which was significant compared with that in saline infused bladders. Cells in this expanded region as well as cells within the urothelium were found to be extensively labeled with BrdU, in contrast to control bladders, which had rare BrdU labeled cells in any region. Immunohistochemical analysis for factor VIII showed that the submucosal region of cobalt treated rats contained numerous small vessels and microvessels that were not apparent in controls. These cellular changes were consistent with our finding of increased hypoxia inducible factor-1alpha and vascular endothelial growth factor protein expression in cobalt treated bladders compared with controls.

CONCLUSIONS

Acute intravesical instillation of cobalt ion solution into the rat bladder initiated a hypoxia response accompanied by increased bladder angiogenesis and growth. This finding supports the idea that hypoxia is a stimulus for bladder growth subsequent to partial bladder outlet obstruction.

Microcirculation of the urinary bladder in a rat model of ischemia-reperfusion-induced cystitis

OBJECTIVES

To determine the microcirculatory disturbances in a rat model of ischemia-reperfusion-induced cystitis using intravital fluorescence videomicroscopy.

METHODS

Twenty male Sprague-Dawley rats were used for the experiments. In 10 animals, warm ischemia of the bladder was induced for 60 minutes. After 30 minutes of reperfusion, microvascular macromolecular leakage, leukocyte-endothelial cell interactions, venular red blood cell velocity, functional capillary density, and the arteriolar and venular diameters were determined by intravital videomicroscopy. In addition, the intravesical pressure and macrohemodynamic parameters were assessed during the experiments. Sham-operated animals served as the controls (n = 10).

RESULTS

After ischemia-reperfusion, the numbers of rolling and firmly adherent leukocytes in the postcapillary venules were significantly increased. Venular red blood cell velocity and functional capillary density, as well as the arteriolar and venular diameters, were significantly decreased. The macromolecular leakage had increased in both arterioles and venules.

CONCLUSIONS

After ischemia-reperfusion, inflammatory reactions and microcirculatory failure were observed in the urinary bladder. This study targeted the microcirculatory consequences of cystitis using intravital videomicroscopy. Because the parameters investigated are relevant not only for ischemia-reperfusion of the urinary bladder but also for cystitis caused by other stimuli, this model represents a novel tool in the field of inflammation research in urology.

Effect of doxazosin on rat urinary bladder function after partial outlet obstruction

Hypoxia induced by partial outlet obstruction is believed to play a major role in both the hypertrophic and degenerative effects of partial outlet obstruction. Doxazosin (dox) is a clinically effective alpha-adrenergic antagonist used in the treatment of symptomatic benign prostatic hyperplasia (BPH). Although the major therapeutic effect of the agent is believed to occur on the smooth muscle components of the prostate by reducing prostatic urethral resistance and thus improving emptying, dox may have part of its clinical action via effects mediated by other actions, including via spinal alpha-adrenergic receptors or direct effects on the bladder, possibly via inhibition of vascular alpha receptors. The specific aim of the current study was to determine whether dox pretreatment on rats affects blood flow to the bladder and reduces the level of bladder dysfunction induced by partial outlet obstruction. In part 1, eight rats were separated into two groups of four rats each. Group 1 received oral administration of dox (30 mg/kg) for 4 weeks; group 2 received vehicle (5% dimethyl sulfoxide). After 4 weeks of treatment, blood flow studies were performed using fluorescent microspheres and the bladders excised, frozen, and submitted to Interactive Medical Technologies (IMT) for blood flow analysis. In part 2, 32 adult male rats were separated into four groups of eight rats each. Groups 1 and 2 received oral administration of dox (30 mg/kg) for 4 weeks, groups 3 and 4 received vehicle (5% dimethyl sulfoxide). At 4 weeks, the rats in groups 1 and 3 received partial outlet obstructions and treatment continued for an additional 2 weeks. After 6 weeks of treatment (total), each rat was anesthetized, the bladder excised, weighed, and isolated strips mounted and contractility studies performed. 1) Four weeks pretreatment of rats with dox increased blood flow to the bladder in both the control and obstructed groups. 2) Partial outlet obstruction induced a mild decrease in blood flow. 3) The magnitude of the increased bladder weight in the vehicle-treated obstructed group was significantly greater than in the dox-treated obstructed group. 4) Partial outlet obstruction resulted in significant decreases in the contractile response to field stimulation in both treated and non-treated rats. The magnitude of the decreased response was significantly greater in the non-treated rats. 5) The response to potassium chloride was significantly reduced by partial outlet obstruction in the vehicle-treated group but not in the dox-treated group. 6) The time to maximal tension was significantly increased in response to carbachol, adenosine triphosphate, and potassium chloride. However, the magnitude of the increase was significantly greater for the vehicle-treated obstructed groups stimulated by potassium chloride than for the dox-treated groups. Dox treatment of rats increased blood flow to the bladder and reduced the severity of the response to partial outlet obstruction. These beneficial effects would be due to pharmacological effects on alpha-adrenergic systems outside those present in the prostate. These include effects on blood flow to the bladder, effects on the micturition centers of the central nervous system, spinal reflexes, and alpha-adrenergic receptors in the urethra and bladder.

The effect of bladder outflow obstruction on detrusor blood flow changes during the voiding cycle in conscious pigs

PURPOSE

We monitored detrusor blood flow in pigs with bladder outflow obstruction.

MATERIALS AND METHODS

Partial urethral obstruction was created in 9 immature, female large white pigs with an implanted ring, and 10 normal animals were used for comparison. Urodynamic parameters and detrusor blood flow were measured using chronically implanted access catheters and laser Doppler fibers. Repeated recordings were made from each animal while it was lightly sedated.

RESULTS

The animals with implanted rings developed prolonged, high pressure voiding contractions in association with poor urinary flow, indicating bladder outflow obstruction, and had evidence of detrusor instability. In obstructed and normal animals detrusor blood flow was maintained during bladder filling. Elevated detrusor pressure during voiding significantly decreased blood flow to similar levels in each group. The duration of the ischemic period was much greater in obstructed animals.

CONCLUSIONS

Bladder outflow obstruction is associated with repeated episodes of prolonged detrusor ischemia which may account for the biochemical and neuronal alterations in such bladders.

Smooth muscle fatigue due to repeated urinary bladder neurostimulation: an in vivo study

The presented study investigates the influence of different pause lengths between two consecutive stimulations of the S3 roots on intravesical pressure during bladder neurostimulation. In eight male foxhounds (aged 7-18 months), laminectomy and placement of a modified Brindley electrode were performed. In four series with different pause lengths between two consecutive stimulations (1, 3, 5, and 15 min), the maximum intravesical pressure was measured during stimulation. The changes in intravesical pressure were registered in these four series, each series with six stimulations. A 15-min interval elapsed before the commencement of each series. In the series with a pause length of 15 min, the consecutive stimulations did not result in significant changes in maximum intravesical pressure. In the 5-min series, a significant decrease in intravesical pressure was not observed after the third stimulation. In the 3-min series, a significant decrease was seen at almost every stimulation (average decrease of 3.8% per stimulation) and in the 1-min series, a significant decrease was also observed at almost every stimulation (average decrease of 5.9% per stimulation). The results of repeated bladder neurostimulation demonstrate that the maximum intravesical pressure is dependent on the pause length between two consecutive stimulations. The detrusor muscle showed reversible and short-lived signs of fatigue. This implies the importance of a minimum 5-min interval between two subsequent stimulations. A pause length <5 min leads to a falsification of the results and thus to lower validity of the investigation.

Acute increase in blood flow to the rat bladder subsequent to partial bladder outlet obstruction

Partial obstruction of the rat bladder outlet initiates a multi-step process during which the bladder progressively loses its functional ability. The first step in this progression is bladder hypertrophy; the organ dramatically increases in size and weight to compensate for the effects of obstruction. Unoperated female rats, age-matched, sham-obstructed rats, and rats that received a partial bladder outlet obstruction were studied. During the first 24 hours after partial bladder outlet obstruction, relative bladder blood flow was measured using a fluorescent microsphere infusion technique and laser Doppler imaging. Nitric oxide synthase (NOS) activities of control and obstructed rat bladder tissues were determined using an enzymatic assay that measures the conversion of (3)H-L-arginine to (3)H-L-citrulline. Using the microsphere infusion technique, a significant increase in blood flow to the obstructed rat bladder was observed during the first 24 hours after partial bladder outlet obstruction. Relative bladder blood flow increased approximately sixfold at 4 and 6 hours post-obstruction and remained elevated through 24 hours of obstruction. Sham operations (evaluated after 6 hours after surgery) resulted in a minor increase in blood flow that did not reach statistical significance. Relative blood flow to the spleen, measured in the same rats, was not significantly changed. Laser Doppler measurements also identified a significant increase in rat bladder blood flow after outlet obstruction and showed that increased blood flow could be detected as early as 1 hour post-obstruction. Interestingly, despite the significant differences in bladder blood flow between control and early post-obstructed rat bladders, NOS activities of control and obstructed rat bladders were comparable. The increase in bladder blood flow precedes the urothelial, fibroblast and smooth muscle cell hyperplasia, and the smooth muscle hypertrophy that occurs after obstruction. We propose that, in response to surgical induction of partial outlet obstruction, acute up-regulation of bladder blood flow may be an initiating factor for subsequent bladder cell proliferation and smooth muscle hypertrophy. Neurourol. Urodynam. 19:195-208, 2000.

Atherosclerosis-induced chronic ischemia causes bladder fibrosis and non-compliance in the rabbit

PURPOSE

The overall goal was to determine whether chronic ischemia and hypercholesterolemia interfere with bladder function and structure. The roles of atherosclerosis-induced chronic ischemia and hypercholesterolemia in bladder fibrosis and non-compliance were studied in the rabbit. The relationship between ischemia-induced changes in the expression of transforming growth factor-beta1 (TGF-beta1) and basic fibroblast growth factor (bFGF) and the severity of bladder fibrosis was also investigated.

MATERIALS AND METHODS

Male New Zealand White rabbits were divided into chronic bladder ischemia (CBI, n = 11), hypercholesterolemia (Hch, n = 8) and control (n = 8) groups. The CBI group underwent balloon endothelial injury of the iliac arteries and received a 0.5% cholesterol diet. The Hch group received a 0.5% cholesterol diet alone. The control group was placed on a regular diet. After 16 weeks, iliac artery and bladder wall blood flow measurements, cystometrograms (CMG) and aorto-iliac arteriograms were obtained in all animals. Iliac arteries and bladder tissues were processed for histological staining and computer-assisted histomorphometric image analysis. The expressions of TGF-beta1 and bFGF in bladder tissue were determined by immunohistochemical staining utilizing monoclonal antibodies.

RESULTS

At 16 weeks, arteriography and histology showed significant diffuse atherosclerotic occlusive disease of the aorto-iliac arteries in the CBI group. Iliac artery and bladder wall blood flows were significantly decreased in the CBI group compared with the Hch and control groups. Atherosclerosis-induced CBI shifted the volume-pressure curve to the left and caused severe bladder fibrosis. Hypercholesterolemia also caused fibrosis and non-compliance but to a much lesser extent compared with those caused by CBI. In histomorphometry, the percentage of detrusor smooth muscle was moderately decreased in the Hch group and severely decreased in the CBI group compared with the control group. In immunohistochemical stains of bladder tissues, bFGF expression was similar in the three groups of animals. TGF-beta1 expression was significantly greater in bladder tissues from the CBI group compared with the Hch and control groups.

CONCLUSIONS

Our studies show that atherosclerosis-induced chronic ischemia increases TGF-beta1 expression in the bladder leading to fibrosis, smooth muscle atrophy and non-compliance. Hypercholesterolemia also interferes with bladder structure and compliance but to a significantly lesser extent compared with CBI. Our studies suggest that arterial insufficiency and hypercholesterolemia, common aging-associated disorders, may play important roles in the pathophysiology of voiding dysfunction in the elderly.

Airway nerves and protein phosphatases

Much attention has focused on the important role played by phosphatases in the control of gene transcription, cell differentiation and memory regulation. It is also clear that phosphatases may regulate a number of biochemical pathways which can modulate cellular function. Of particular interest is the role of phosphatases in the control of neuronal function. Alterations in neuronal function may contributed to the heightened airways responsiveness observed in asthma to a number of physiological stimuli including distilled water, sulfur dioxide, metabisulfite, hypertonic saline, exercise, allergens, viruses and cold air. An understanding of the mechanisms which regulate the function of sensory nerves could have important clinical implications. In this review we will highlight a number of studies that have investigated the role of phosphatases in the regulation of airway nerve function.

Effect of ischemia-reperfusion on contractile function of rat urinary bladder: possible role of nitric oxide

Because there are increasing evidences that nitric oxide (NO) plays important roles in ischemia-reperfusion injury in several systems, we investigated the role of NO in ischemia-reperfusion injury of the rat urinary bladder. Rat abdominal aorta was clamped with a small clip to induce ischemia-reperfusion injury in the rat bladder dome. In functional studies, contractile responses to carbachol were cumulatively measured after the urinary bladder was treated with various duration (0, 30, 60, and 90 min) of ischemia. The injury of rat bladder functioning was dependent on ischemic periods. Significant decreases in the Emax (maximum contractile response) values were observed in the bladder subjected to 60 or 90 min ischemia. Furthermore, the subsequent 30 min reperfusion caused additional damages of the contractile response in bladder muscles. To investigate the role of NO in the ischemia (30 min)-reperfusion (30 min) injury, NG-nitro-L-arginine methylester (L-NAME) was injected intraperitoneally 30 min before the ischemia. Treatment of L-NAME (30 and 100 mg/kg) partly but significantly prevented the reduction contractile responses to carbachol of the rat bladder dome. In histological studies, the ischemia-reperfusion caused infiltration of leukocytes and rupture of microcirculation in the regions of submucosa and smooth muscle without a corresponding sloughing of mucosal cells. The histological damages were also prevented by treatment with L-NAME. Therefore, these data suggested that ischemia-reperfusion of the urinary bladder may result in dysfunction of the contractile response to autonomic nervous system and that nitric oxide may act as a cell/tissue damaging agent in ischemia-reperfusion injury.

Correlation of ischemia/reperfusion or partial outlet obstruction-induced spectrin proteolysis by calpain with contractile dysfunction in rabbit bladder

OBJECTIVES

In the rabbit, both experimental ischemia and partial outlet obstruction of the urinary bladder induce similar dysfunctions with regard to the contractile responses to both field (neuronal) stimulation and postsynaptic receptor stimulation. Circumstantial evidence indicates that the pathologic response to both conditions is related to two connected processes-tissue ischemia and reperfusion injury-that result in a marked increase in intracellular calcium ([Ca2+]i), followed by the activation of the Ca(2+)-dependent neutral protease calpain. Calpain activation results in the proteolysis of specific membrane proteins, including those of neuronal membranes (resulting in progressive denervation of the detrusor) and the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), resulting in the previously reported decrease in SERCA. The current study is designed to generate direct support for the theory that both ischemia and partial outlet obstruction result in the activation of calpain.

METHODS

Separate sets of rabbits were subjected to 1 or 2 hours of ischemia, followed by reperfusion for different lengths of time, or partial outlet obstruction for different lengths of time. We determined the state of calpain activation by quantitating tissue proteolysis of alpha-spectrin by Western blot analysis. Correlative organ bath studies were conducted to observe the contractile responses of bladder strips to field stimulation and bethanechol administration.

RESULTS

(1) Sixty minutes of ischemia followed by 30 minutes of reperfusion resulted in (a) a reduction in the contractile responses to field stimulation and bethanechol (89% and 57%, respectively), and (b) a 72% decrease in native alpha-spectrin, with a concomitant 300% increase in its breakdown products (BDPs). Neither alpha-spectrin nor its BDPs had returned to control levels after 72 hours of reperfusion. (2) Twenty-four hours after the creation of a partial obstruction, alpha-spectrin BDP levels were increased 330%, then gradually fell to 130% of control levels by 14 days after obstruction. Concomitantly, the native alpha-spectrin level was decreased 74% 24 hours after obstruction and remained low through 7 days after obstruction. At 14 days after obstruction, the alpha-spectrin levels had recovered to 75% of control levels.

CONCLUSIONS

These findings suggest that Ca(2+)-dependent proteolysis of the preferred calpain substrate alpha-spectrin in urinary bladder tissues is increased significantly by both ischemia/reperfusion and partial outlet obstruction. Temporally, proteolysis precedes the reduced muscle function resulting from these pathologic conditions.