Over expression of smooth muscle thin filament associated proteins in the bladder wall of diabetics

Potential role of oxidative stress in the pathogenesis of diabetic bladder dysfunction

Diabetes mellitus is a chronic metabolic disease, posing a considerable threat to global public health. Treating systemic comorbidities has been one of the greatest clinical challenges in the management of diabetes. Diabetic bladder dysfunction, characterized by detrusor overactivity during the early stage of the disease and detrusor underactivity during the late stage, is a common urological complication of diabetes. Oxidative stress is thought to trigger hyperglycaemia-dependent tissue damage in multiple organs; thus, a growing body of literature has suggested a possible link between functional changes in urothelium, muscle and the corresponding innervations. Improved understanding of the mechanisms of oxidative stress could lead to the development of novel therapeutics to restore the redox equilibrium and scavenge excessive free radicals to normalize bladder function in patients with diabetes.

Oxidative Stress: A Putative Link Between Lower Urinary Tract Symptoms and Aging and Major Chronic Diseases

Aging and major chronic diseases are risk factors for lower urinary tract symptoms (LUTS). On the other hand, oxidative stress (OS) is one of the fundamental mechanisms of aging and the development of chronic diseases. Therefore, OS might be a candidate mechanism linking these two clinical entities. This article aims to summarize the studies on the prevalence of LUTS, the role of OS in aging and chronic diseases, and the potential mechanisms supporting the putative link. A comprehensive literature search was performed to identify recent reports investigating LUTS and OS in major chronic diseases. In addition, studies on the impact of OS on the lower urinary tract, including bladder, urethra, and prostate, were collected and summarized. Many studies showed LUTS are prevalent in aging and major chronic diseases, including obesity, metabolic syndrome, diabetes, cardiovascular disease, hypertension, obstructive sleep apnea, autoimmune diseases, Alzheimer’s disease, and Parkinson’s disease. At the same time, OS is a key component in the pathogenesis of those chronic diseases and conditions. Recent studies also provided evidence that exacerbated OS can cause functional and/or structural changes in the bladder, urethra, and prostate, leading to LUTS. The reviewed data support the concept that OS is involved in multiple risk factors-associated LUTS, although further studies are needed to confirm the causative relationship. The specific ROS/RNS and corresponding reactions/pathways involved in chronic diseases and associated LUTS should be identified in the future and could serve as therapeutic targets.

Urothelial Senescence in the Pathophysiology of Diabetic Bladder Dysfunction-A Novel Hypothesis

Diabetic bladder dysfunction (DBD) is a well-recognized and common symptom affecting up to 50% of all diabetic patients. DBD has a broad range of clinical presentations ranging from overactive to underactive bladder symptoms that develops in middle-aged to elderly patients with long standing and poorly controlled diabetes. Low efficacy of current therapeutics and lifestyle interventions combined with high national healthcare costs highlight the need for more research into bladder dysfunction pathophysiology and novel treatment options. Cellular senescence is an age-related physiologic process in which cells undergo irreversible growth arrest induced by replicative exhaustion and damaging insults. While controlled senescence negatively regulates cell proliferation and promotes tissue regeneration, uncontrolled senescence is known to result in tissue dysfunction through enhanced secretion of inflammatory factors. This review presents previous scientific findings and current hypotheses that characterize diabetic bladder dysfunction. Further, we propose the novel hypothesis that cellular senescence within the urothelial layer of the bladder contributes to the pro-inflammatory/pro-oxidant environment and symptoms of diabetic bladder dysfunction. Our results show increased cellular senescence in the urothelial layer of the bladder; however, whether this phenomenon is the cause or effect of DBD is unknown. The urothelial layer of the bladder is made up of transitional epithelia specialized to contract and expand with demand and plays an active role in transmission by modulating afferent activity. Transition from normal functioning urothelial cells to secretory senescence cells would not only disrupt the barrier function of this layer but may result in altered signaling and sensation of bladder fullness; dysfunction of this layer is known to result in symptoms of frequency and urgency. Future DBD therapeutics may benefit from targeting and preventing early transition of urothelial cells to senescent cells.

Benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH), which causes lower urinary tract symptoms (LUTS), is a common diagnosis among the ageing male population with increasing prevalence. Many risks factors, both modifiable and non-modifiable, can increase the risk of development and progression of BPH and LUTS. The symptoms can be obstructive (resulting in urinary hesitancy, weak stream, straining or prolonged voiding) or irritative (resulting in increased urinary frequency and urgency, nocturia, urge incontinence and reduced voiding volumes), or can affect the patient after micturition (for example, postvoid dribble or incomplete emptying). BPH occurs when both stromal and epithelial cells of the prostate in the transitional zone proliferate by processes that are thought to be influenced by inflammation and sex hormones, causing prostate enlargement. Patients with LUTS undergo several key diagnostic investigations before being diagnosed with BPH. Treatment options for men with BPH start at watchful waiting and progress through medical to surgical interventions. For the majority of patients, the starting point on the treatment pathway will be dictated by their symptoms and degree of bother.

Interaction of Caveolin-3 and HCN is involved in the pathogenesis of diabetic cystopathy

A growing body of research suggests that impaired bladder Cajal-like interstitial cells (ICCs) are a important component in the pathogenesis of diabetes-induced bladder dysfunction, although the molecular mechanisms have not been illustrated completely. The purpose of this study was to examine whether the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in ICCs-DM were responsible for the detrusor weak contractility of Diabetic cystopathy (DCP) and to study the possible mechanism of regulating the expression and function of HCN channels. HCN channels expression were decreased at the mRNA and protein levels. Forskolin (FSK), which can elevate intracellular cAMP levels, increased the density of the hyperpolarization-activated current and intracellular calcium concentration in both normal control (NC) rats and DCP rats, but the sensitivity of FSK on HCN channels was clearly down-regulated in DCP rats. The loss of caveolae and caveolin was in accordance with the decrease in HCN channels. Caveolin-3 co-localizes with and affects the expression and function of HCN. Taken together, these results indicate that the loss of caveolae and HCN channels in ICCs-DM is important in the pathogenesis of DCP. Increasing the number of caveolae to enhance the function of HCN channels may represent a viable target for the pharmacological treatment of DCP.

Effect of oxidative stress on the expression of thin filament-associated proteins in gastric smooth muscle cells

Thin filament-associated proteins such as calponin, caldesmon, and smoothelin are believed to regulate acto-myosin interaction and thus, muscle contraction. Oxidative stress has been found to affect the normal contractile behavior of smooth muscle and is involved in the pathogenesis of a number of human diseases such as diabetes mellitus, hypertension, and atherosclerosis. However, very little is known about the effect of oxidative stress on the expression of smooth muscle contractile proteins. The aim of the current study is to investigate the effect of oxidative stress on the expression of thin filament-associated proteins in rat gastric smooth muscle. Single smooth muscle cells of the stomach obtained from Sprague-Dawley rats were used. Muscle cells were treated with hydrogen peroxide (H2O2) (500 μM) for 30 min or the peroxynitrite donor 3-morpholinosydnonimine (SIN-1) (1 mM) for 90 min to induce oxidative stress. Calponin, caldesmon, and smoothelin expressions were measured via specifically designed enzyme-linked immunosorbent assay. We found that exposure to exogenous H2O2 or incubation of dispersed gastric muscle cells with SIN-1 significantly increased the expression of calponin, caldesmon, and smoothelin proteins. In conclusion: oxidative stress increases the expression of thin filament-associated proteins in gastric smooth muscle, suggesting an important role in gastrointestinal motility disorders associated with oxidative stress.

Bladder function in mice with inducible smooth muscle-specific deletion of the manganese superoxide dismutase gene

Manganese superoxide dismutase (MnSOD) is considered a critical component of the antioxidant systems that protect against oxidative damage. We are interested in the role of oxidative stress in bladder detrusor smooth muscle (SM) in different disease states. In this study, we generated an inducible, SM-specific Sod2(-/-) mouse model to investigate the effects of MnSOD depletion on the function of the bladder. We crossbred floxed Sod2 (Sod2(lox/lox)) mice with mice containing heterozygous knock-in of a gene encoding a tamoxifen-activated Cre recombinase in the SM22α promoter locus [SM-CreER(T2)(ki)(Cre/+)]. We obtained Sod2(lox/lox),SM-CreER(T2)(ki)(Cre/+) mice and injected 8-wk-old males with 4-hydroxytamoxifen to induce Cre-mediated excision of the floxed Sod2 allele. Twelve weeks later, SM-specific deletion of Sod2 and depletion of MnSOD were confirmed by polymerase chain reaction, immunoblotting, and immunohistochemistry. SM-specific Sod2(-/-) mice exhibited normal growth with no gross abnormalities. A significant increase in nitrotyrosine concentration was found in bladder SM tissue of SM-specific Sod2(-/-) mice compared with both wild-type mice and Sod2(+/+), SM-CreER(T2)(ki)(Cre/+) mice treated with 4-hydroxytamoxifen. Assessment of 24-h micturition in SM-specific Sod2(-/-) mice revealed significantly higher voiding frequency compared with both wild-type and SM-specific Cre controls. Conscious cystometry revealed significantly shorter intercontraction intervals and lower functional bladder capacity in SM-specific Sod2(-/-) mice compared with wild-type mice. This novel model can be used for exploring the mechanistic role of oxidative stress in organs rich in SM in different pathological conditions.

Differential expression of smooth muscle regulatory proteins in the uterosacral ligaments of women with uterine prolapse

OBJECTIVE

To compare smooth muscle regulatory protein expression in the uterosacral ligament (USL) of women with and without uterine prolapse.

STUDY DESIGN

USLs ligament were sampled in women with (n = 9) or without (n = 9) uterine prolapse. Caldesmon, smooth muscle actin (SMA), myosin heavy chain, and zinc finger protein messenger RNA expression was assessed by quantitative real-time polymerase chain reaction. Immunohistochemistry and digital image analysis were used to determine protein expression.

RESULTS

Caldesmon messenger RNA expression and the ratio of caldesmon-SMA messenger RNA expression was significantly increased in the USL from women with uterine prolapse compared with women without prolapse (caldesmon mean +/- standard deviation messenger RNA, 0.81 +/- 0.46 vs 0.39 +/- 0.16; P = .01 and caldesmon-SMA messenger RNA ratio, mean +/- standard deviation, 0.11 +/- 0.04 vs 0.07 +/- 0.02; P = .01). In addition, the ratio of caldesmon-SMA staining was significantly increased in women with uterine prolapse compared with women without prolapse (mean +/- standard deviation, 0.44 +/- 0.28 vs 0.28 +/- 0.16; P = .03).

CONCLUSION

Uterine prolapse is associated with an increased ratio of caldesmon-SMA actin expression.

Diabetic bladder dysfunction: current translational knowledge

PURPOSE

Diabetes mellitus, a metabolic disorder caused by an absolute or relative deficiency of insulin, is a debilitating and costly disease with multiple serious complications. Lower urinary tract complications are among the most common complications of diabetes mellitus. The most common, bothersome lower urinary tract complication of diabetes mellitus is diabetic cystopathy or diabetic bladder dysfunction. We reviewed the current translational knowledge of diabetic bladder dysfunction.

MATERIALS AND METHODS

We performed a search of the English literature through PubMed. The key words used were diabetes and bladder dysfunction or cystopathy. Our data and perspective are provided for consideration of the future direction of research.

RESULTS

Despite traditional recognition of diabetic bladder dysfunction as a voiding problem characterized by poor emptying and overflow incontinence, recent clinical and experimental evidence indicate storage problems such as urgency and urge incontinence in diabetes mellitus cases. Recent experimental evidence from studies of diabetic bladder dysfunction in small animal models of diabetes mellitus show a temporal effect on diabetic bladder dysfunction. Early phase diabetes mellitus causes compensated bladder function and the late phase causes decompensated bladder function. The temporal theory could plausibly provide the scientific road map to correlate clinical and experimental findings, and identify the role of mechanisms such as polyuria, hyperglycemia, oxidative stress, autonomic neuropathy and decompensation of the bladder contractile apparatus in the creation of clinical and experimental manifestations of diabetic bladder dysfunction.

CONCLUSIONS

Diabetic bladder dysfunction includes time dependent manifestations of storage and emptying problems. Identifying mechanistic pathways would lead to the identification of therapeutic intervention.

Early inhibition of EGFR signaling prevents diabetes-induced up-regulation of multiple gene pathways in the mesenteric vasculature

Diabetes mellitus is associated with vascular complications including an impairment of vascular function and alterations in the reactivity of blood vessels to vasoactive hormones. However, the signaling mechanisms leading to vascular dysfunction in diabetes are not fully understood. This microarray-based study was designed to identify differential gene expression between the normal and diabetic mesenteric vasculature and to investigate the effect of inhibiting epidermal growth factor receptor (EGFR) signaling on global gene expression in the mesenteric bed of streptozotocin (STZ)-induced diabetic rats. Transcriptome analysis was performed in triplicate using oligonucleotide microarrays housing 10,000 rat genes on the mesenteric bed of normal, diabetic, and diabetic rats treated with AG1478, a selective inhibitor of EGFR. Four weeks of diabetes led to a profound alteration in gene expression within the mesenteric bed with 1167 of the 3074 annotated genes being up-regulated and 141 genes down-regulated by at least 2-fold. The up-regulated gene ontologies included receptor tyrosine kinases, G-protein coupled receptors and ion channel activity. In particular, significant overexpressions of colipase, phospholipase A2, carboxypeptidases, and receptor tyrosine kinases such as EGFR, erbB2 and fibroblast growth factor receptor were observed in diabetes mesenteric vasculature. A 4-week intraperitoneal treatment of diabetic animals with AG1478 (1.2 mg/kg/alt diem) beginning on the same day as STZ injection prevented up-regulation of the majority (approximately 95%) of the genes associated with STZ diabetes including those apparently "unrelated" to the known EGFR pathway without correction of hyperglycemia. These results suggest that activation of EGFR signaling is a key initiating step that leads to induction of multiple signaling pathways in the development of diabetes-induced vascular dysfunction. Thus, therapeutic targeting of EGFR may represent a novel strategy for the prevention and/or treatment of vascular dysfunction in diabetes.

Caldesmon expression is decreased in women with anterior vaginal wall prolapse: a pilot study

INTRODUCTION AND HYPOTHESIS

The purpose of this study is to compare vaginal caldesmon expression in women with and without anterior vaginal wall prolapse.

METHODS

Vaginal tissues were sampled in women with (n = 11) or without (n = 11) vaginal wall prolapse. Caldesmon messenger RNA (mRNA) expression was assessed by quantitative real-time polymerase chain reaction. Immunohistochemistry and digital image analysis were used to determine caldesmon protein expression in the histologic sections.

RESULTS

There were no significant differences in demographic data between the two groups. Caldesmon mRNA expression was significantly decreased in the vaginal tissue from women with anterior vaginal wall prolapse compared to women without prolapse [(caldesmon mean +/- SD mRNA expression in relative units) 0.03 +/- 0.03 vs 0.17 +/- 0.17, P = 0.02]. The fractional area of nonvascular caldesmon staining in the vagina of women with anterior vaginal wall prolapse was significantly decreased compared to women without prolapse [mean +/- SD (0.09 +/- 0.04 vs 0.16 +/- 0.09, P = 0.03)].

CONCLUSIONS

Vaginal caldesmon expression is significantly decreased in women with anterior vaginal wall prolapse compared to normal subjects.

Simulated hyperglycemia in rat cardiomyocytes: A proteomics approach for improved analysis of cellular alterations

Diabetic hyperglycemia can lead to stress-related cellular apoptosis of cardiac tissue. However, the mechanism by which hyperglycemia inflicts this damage on the structure and function of the heart is unclear. In this study, we examined the relationship between proteome alterations, mitochondrial function, and major biochemical and electrophysiological changes affecting cardiac performance during simulated short-term hyperglycemia. Two-dimensional comparative proteomics analysis of rat hearts perfused with glucose at high (30 mM) or control (5.5 mM) levels revealed that glucose loading alters cardiomyocyte proteomes. It increased expression levels of initial enzymes of the tricarboxylic acid cycle, and of enzymes of fatty acid beta-oxidation, with consequent up-regulation of enzymes of mitochondrial electron transport. It also markedly decreased expression of enzymes of glycolysis and the final steps of the tricarboxylic acid cycle. Glucose loading increased the rate of Bax-independent apoptosis. High glucose increased the duration of the action potential and elevated level of intracellular cytoplasmic calcium. Surprisingly, glucose loading did not influence levels of nitric oxide or mitochondrial superoxide in isolated cardiomyocytes. In summary, short-term simulated hyperglycemia attenuated expression of many anti-apoptotic proteins. This effect was apparently mediated via alterations in multiple biochemical pathways that collectively increased apoptotic susceptibility.

Using gene chips to identify organ-specific, smooth muscle responses to experimental diabetes: potential applications to urological diseases

OBJECTIVE

To identify early diabetes-related alterations in gene expression in bladder and erectile tissue that would provide novel diagnostic and therapeutic treatment targets to prevent, delay or ameliorate the ensuing bladder and erectile dysfunction.

MATERIALS AND METHODS

The RG-U34A rat GeneChip (Affymetrix Inc., Sunnyvale, CA, USA) oligonucleotide microarray (containing approximately 8799 genes) was used to evaluate gene expression in corporal and male bladder tissue excised from rats 1 week after confirmation of a diabetic state, but before demonstrable changes in organ function in vivo. A conservative analytical approach was used to detect alterations in gene expression, and gene ontology (GO) classifications were used to identify biological themes/pathways involved in the aetiology of the organ dysfunction.

RESULTS

In all, 320 and 313 genes were differentially expressed in bladder and corporal tissue, respectively. GO analysis in bladder tissue showed prominent increases in biological pathways involved in cell proliferation, metabolism, actin cytoskeleton and myosin, as well as decreases in cell motility, and regulation of muscle contraction. GO analysis in corpora showed increases in pathways related to ion channel transport and ion channel activity, while there were decreases in collagen I and actin genes.

CONCLUSIONS

The changes in gene expression in these initial experiments are consistent with the pathophysiological characteristics of the bladder and erectile dysfunction seen later in the diabetic disease process. Thus, the observed changes in gene expression might be harbingers or biomarkers of impending organ dysfunction, and could provide useful diagnostic and therapeutic targets for a variety of progressive urological diseases/conditions (i.e. lower urinary tract symptoms related to benign prostatic hyperplasia, erectile dysfunction, etc.).

Increased basal phosphorylation of detrusor smooth muscle myosin in alloxan-induced diabetic rabbit is mediated by upregulation of Rho-kinase β and CPI-17

Urinary bladder dysfunction caused by the alteration of detrusor smooth muscle (DSM) is one of the complications of diabetes. It is well established that smooth muscle contractility is regulated by an elevation of cytosolic Ca2+ via myosin light chain (MLC) phosphorylation. However, recent studies have shown the modulation of MLC phosphorylation without a rise in Ca2+ in smooth muscle and that two key molecules (Rho-kinase and CPI-17) are involved in the regulation of calcium sensitization. This study investigates the effect of diabetes on DSM calcium sensitization. Diabetes was induced by alloxan in New Zealand White rabbits, and age-matched rabbits given 5% sucrose in the drinking water served as control for diuresis. Two-dimensional gel electrophoresis showed that basal MLC phosphorylation level was significantly higher in diabetic animals than normal or diuretic controls, and Rho-kinase-specific inhibitor, Y-27632, decreased MLC phosphorylation level. Adding Y-27632 to bethanechol-precontracted DSM strips can induce muscle relaxation, but it occurred much more slowly in diabetic samples compared with controls. RT-PCR, Western blot analysis, and immunohistochemistry revealed the overexpression of Rho-kinase β and CPI-17 at both mRNA and protein levels in response to diabetes. In conclusion, our results demonstrate that Rho-kinase contributes to DSM MLC phosphorylation and there is a higher basal MLC phosphorylation level in diabetic DSM. Our results also suggest that this high basal MLC phosphorylation may be due to the upregulation of Rho-kinase and CPI-17. Thus Rho-kinase- and CPI-17-mediated Ca2+ sensitization might play a role in diabetes-induced alteration of the detrusor contractility and bladder dysfunction.

Temporal differences in bladder dysfunction caused by diabetes, diuresis, and treated diabetes in mice

Diabetic bladder dysfunction is a common complication of diabetes mellitus (DM) with poorly understood natural history. This study examined the temporal changes in bladder function 3, 9, 12, and 20 wk after induction of DM by streptozotocin (STZ) in male C57BL/6 mice compared with that in age-matched diabetic mice treated with insulin, 5% sucrose-induced diuretic mice, and sham-treated control mice. Conscious cystometrograms of mice were examined in addition to the measurements of micturition cycle. Diabetes resulted in decreased body weight. Bladder weight, urine output, bladder capacity, and compliance increased in the DM and diuretic groups. Peak voiding pressure (PVP) increased initially in both DM and diuretic mice. However, in DM mice, PVP dropped dramatically at and after 12 wk. Similar changes in the capacity, compliance, and emptying ability of the bladder were seen during the first 9 wk of the diabetes or diuresis, whereas significant decline in the emptying ability of the bladder was only seen in diabetes after 12 wk of disease in mice. Long-term insulin replacement effectively reversed most changes in bladder function. These results suggest that the transition from a compensated to a decompensated bladder dysfunction occurs 9-12 wk after induction of DM in mice by STZ.

Detection of a progesterone-dependent secretory protein synthesized by cat endometrium

Uterine flushings and culture media from endometrial explants incubated in the presence of radiolabeled amino acids were analyzed using one-(1-D) and two-dimensional (2-D) gel electrophoresis to identify proteins synthesized by the endometrium and subsequently released into the uterine lumen. 1-D and 2-D analyses of uterine flushings and culture media of endometrial explants obtained from 7- to 11-day pregnant cats (pre-implantation) showed a Mr 30,000 protein that appeared on 2-D gels as a family of macromolecules with isoelectric points between 6.5 and 7.0. This family of macromolecules was also present in the culture media of implantation-site tissue obtained from 12- to 16-day pregnant cats and of nonimplantation-site endometrium obtained form 12- to 28-day pregnant cats. The Mr 30,000 protein was absent in uterine flushings and culture media from estrous and 3- to 5-day-pregnant cats. In ovariectomized, steroid-treated animals, the Mr 30,000 protein was only detected in flushings and media from those animals treated with progesterone, regardless of the presence or absence of estradiol-priming and/or simultaneous estradiol treatment. In daily flushings obtained from ovariectomized, steroid-treated cats equipped with an indwelling uterine catheter, the Mr 30,000 protein was absent during the 14 days of estradiol treatment and was first detected 3-4 days after the onset of estradiol plus progesterone treatment. This protein was not detected in serum from estrous, 9-day pregnant, ovariectomized, and ovariectomized, steroid-treated animals. This study shows that 1) a progesterone-dependent protein, with an approximate molecular weight of 30,000 and an isoelectric point of 6.5-7.0, first appears within the uterine lumen soon after the arrival of the blastocyst and continues to be present during implantation; 2) the synthesis and release of the Mr 30,000 protein is dependent on progesterone regardless of the presence or absence of estradiol; and 3) the onset of secretion of the Mr 30,000 protein requires 3-4 days of continuous progesterone treatment in the estradiol-primed cat.