Alterations in the formation of cyclic nucleotides and prostaglandins in the lower urinary tract of the diabetic rabbit

Smooth Muscle Insulin Receptor Deletion Causes Voiding Dysfunction: A Mechanism for Diabetic Bladder Dysfunction

Diabetic bladder dysfunction (DBD) is the most common complication in diabetes. Myogenic abnormalities are common in DBD; however, the underlying mechanisms leading to these remain unclear. To understand the importance of smooth muscle insulin receptor (IR)-mediated signaling in the pathogenesis of DBD, we conditionally deleted it to achieve either heterozygous (SMIR+/-) or homozygous (SMIR-/-) deletion in smooth muscle cells. Despite impaired glucose and insulin tolerance seen with SMIR-/- mice, both SMIR+/- and SMIR-/- mice exhibited normal blood glucose and plasma insulin levels. Interestingly, these mice had abnormal voiding phenotypes, that included urinary frequency and small voids, and bladder smooth muscle (BSM) had significantly diminished contraction force. Morphology revealed a dilated bladder with thinner BSM layer, and BSM bundles were disorganized with penetrating interstitial tissue. Deletion of IR elevated FoxO and decreased mTOR protein expression, which further decreased the expression of Chrm3, P2x1, Sm22, and Cav1.2, crucial functional proteins for BSM contraction. Furthermore, we determined the expression of adiponectin in BSM, and deletion of IR in BSM inhibited adiponectin-mediated signaling. In summary, disruption of IR-mediated signaling in BSM caused abnormalities in proliferation and differentiation, leading to diminished BSM contractility and a voiding dysfunction phenotype that recapitulates human DBD.

Berberine improves neurogenic contractile response of bladder detrusor muscle in streptozotocin-induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Coptidis Rhizoma has been used to treat diabetes mellitus for more than 1400 years in China. Berberine, one of the main alkaloids of Coptidis Rhizoma, is a principal antidiabetic component of Coptidis Rhizoma. To investigate the effects of berberine on impaired neurogenic contractility of detrusor muscle from urinary bladder of rats with early stage diabetes.

MATERIALS AND METHODS

The detrusor muscle strips were isolated from urinary bladders of streptozotocin-induced diabetic rats, 5% sucrose-induced diuretic rats or normal rats, and were placed in organ bath. The contractions induced by electrical field stimulation (EFS), carbachol, KCl, adenosine triphosphate, and the effects of berberine on those contractions were measured.

RESULTS

The EFS- or KCl-induced contraction of detrusor muscle was significantly decreased in diabetic rats as compared with diuretic or normal rats. Atropine and suramin inhibited EFS-induced contraction. In diabetic rats, the atropine sensitive components were decreased in EFS-induced contraction of detrusor muscle, and the adenosine triphosphate-induced contraction was significantly increased. The carbachol-induced contrations were not different among groups. Berberine significantly potentiated EFS-induced contractions of detrusor muscle both from normal and diabetic rats, but the potentiated effect of BBR was more sensitive to atropine in diabetic rats. Berberine also potentiated adenosine triphosphate-induced contraction of detrusor muscle, but did not change carbachol- or KCl-induced contraction.

CONCLUSION

The neurogenic contraction of urinary bladder detrusor muscle is decreased while purinergic contraction of bladder detrusor muscle is increased in rats with early stage diabetes. Berberine increases the neurogenic contractile response to EFS possibly via both presynaptic increasing neurotransmitters release and postsynaptic potentiation of purinergic transmitter-regulated response in rat urinary bladder detrusor; and in diabetic rats, berberine increases neurogenic contractile response mainly via the presynaptic increasing acetylcholine release.

Transcutaneous electrical nerve stimulation (TENS) improves the diabetic cytopathy (DCP) via up-regulation of CGRP and cAMP

The objective of this study was to investigate the effects and mechanism of Transcutaneous Electrical Nerve Stimulation (TENS) on the diabetic cytopathy (DCP) in the diabetic bladder. A total of 45 rats were randomly divided into diabetes mellitus (DM)/TENS group (n = 15), DM group (n = 15) and control group (n = 15). The rats in the DM/TENS and TENS groups were electronically stimulated (stimulating parameters: intensity-31 V, frequency-31 Hz, and duration of stimulation of 15 min) for three weeks. Bladder histology, urodynamics and contractile responses to field stimulation and carbachol were determined. The expression of calcitonin gene-related peptide (CGRP) was analyzed by RT-PCR and Western blotting. The results showed that contractile responses of the DM rats were ameliorated after 3 weeks of TENS. Furthermore, TENS significantly increased bladder wet weight, volume threshold for micturition and reduced PVR, V% and cAMP content of the bladder. The mRNA and protein levels of CGRP in dorsal root ganglion (DRG) in the DM/TENS group were higher than those in the DM group. TENS also significantly up-regulated the cAMP content in the bladder body and base compared with diabetic rats. We conclude that TENS can significantly improve the urine contractility and ameliorate the feeling of bladder fullness in DM rats possibly via up-regulation of cAMP and CGRP in DRG.

Dysregulation of cGMP-dependent protein kinase 1 (PKG-1) impairs erectile function in diabetic rats: influence of in vivo gene therapy of PKG1?

OBJECTIVES

To investigate the expression of cGMP-dependent protein kinase 1 (PKG1)alpha and PKG1beta in the corpus cavernosum, and to evaluate the effect of adenoviral gene transfer of PKG1alpha to the erectile compartment on erectile function in a rat model of diabetes.

MATERIALS AND METHODS

Diabetic (DM; induced by streptozotocin) male Sprague Dawley rats were transfected with adenoviruses (AdCMVbetagal or AdCMVPKG1alpha, in 10 rats each) 2 months after the induction of DM. Intracavernosal pressure (ICP) during stimulation of the cavernosal nerve (CN) was assessed, and compared with mean arterial pressure (MAP). Erectile tissue was harvested for Western blot analysis, immunohistochemistry and total PKG activity. Ten age-matched rats without DM served as the control.

RESULTS

Compared to controls, AdCMVbetagal-transfected DM rats had significantly lower peak ICP responses, ICP/MAP ratios, and filling rates during CN stimulation. In DM rats transfected with AdCMVPKG1alpha, peak ICP, ICP/MAP ratios and filling rates were significantly better than in DM rats transfected with the reporter gene. As assessed by Western blot and immunohistochemistry, expression of PKG1alpha and PKG1beta was lower in corporal tissue from DM AdCMVbetagal-transfected rats than in controls. PKG1alpha expression was improved after AdCMVPKG1alpha gene therapy. Total PKG activity was lower in DM rat corporal tissue than in controls, and PKG1alpha gene transfer significantly improved DM corporal PKG activity to a value greater than in the control.

CONCLUSION

PKG1alpha and PKG1beta activities are reduced in the erectile tissue of the diabetic rat, and gene transfer of PKG1alpha to the penis restored PKG activity and erectile function in vivo in diabetic rats. Gene therapy procedures targeting PKG1alpha might be an interesting future therapeutic approach to overcome diabetic erectile dysfunction resistant to oral pharmacotherapy.

Effects of coffee and caffeine on bladder dysfunction in streptozotocin-induced diabetic rats

AIM

To explore the effects and mechanisms of caffeine and coffee on bladder dysfunction in streptozotocin-induced diabetic rats.

METHODS

Sprague-Dawley male rats were divided randomly into 4 groups: control, diabetes mellitus (DM), DM with coffee treatment, and DM with caffeine treatment. The diabetic rat was induced by intraperitoneal injection of streptozotocin (60 mg/kg). After 7 weeks of treatment with coffee and caffeine, cystometrogram, contractile responses to electrical field stimulation (EFS) and acetylcholine (ACh), and cyclic AMP (cAMP) concentration of the bladder body and base were measured.

RESULTS

The bladder weight, volume threshold for micturition and post-void residual volume (PVR) in the diabetic rats were significantly higher compared to those in the control animals. Coffee or caffeine treatment significantly reduced the bladder weight, bladder capacity and PVR in the diabetic rats. DM caused significant decreases in cAMP concentration of the bladder and coffee and caffeine caused upregulation of cAMP content in the diabetic bladder. In addition, coffee and caffeine tended to normalize the altered detrusor contractile responses to EFS and ACh in the diabetic rats.

CONCLUSION

These results indicate that caffeine and coffee may have beneficial effects on bladder dysfunction in the early stage of diabetes by increasing cAMP content in the lower urinary tract, recovering the micturition reflex and improving the detrusor contractility.

Phosphodiesterase 5 in the female pig and human urethra: morphological and functional aspects

OBJECTIVE

To characterize the distribution of phosphodiesterase 5 (PDE-5), cGMP and cGMP-dependent protein kinase I (PKG1), and to evaluate the effect of pharmacological inhibition of PDE-5 in isolated preparations of pig and human urethra, as the nitric oxide (NO)/cGMP pathway generates the main inhibitory signals to reduce resistance in the bladder outlet and urethra during emptying of the bladder.

MATERIALS AND METHODS

After obtaining ethics committee approval, urethral specimens were obtained from three female patients during cystectomy, and from young female pigs. The specimens were prepared for immunohistochemical investigations and for functional studies in organ baths. Effects of sildenafil, vardenafil and tadalafil (1 nm to 30 microm) were studied in l-noradrenaline (1 microm)-activated or spontaneously contracted preparations, and on relaxations induced by electrical-field stimulation (EFS). Levels of cGMP were determined by radioimmunoassay.

RESULTS

After stimulation with the NO donor, DETA NONO-ate (1 mm), there was greater cGMP-immunoreactivity (IR) in urethral and vascular smooth muscles. There was a wide distribution of cGMP- and vimentin-positive interstitial cells between pig urethral smooth muscle bundles. There was also cGMP-IR within NO-synthase-IR endothelium. There was PDE-5 IR within the urethral and vascular smooth muscle cells, but also in vascular endothelial cells that expressed cGMP-IR. In pig and human sections, there was strong PKG1-IR in alpha-actin-IR urethral smooth muscle cells that also contained IR for cGMP. Sildenafil, vardenafil and tadalafil caused mean (sem) concentration-dependent relaxations of the pig urethra which, at 30 microm, were 80 (3)% (11 samples), 81 (5)% (12 samples) and 64 (4)% (10 samples) of the spontaneous tone. The relaxation of L-noradrenaline-contracted female human urethra was 100% in response to 10 microm sildenafil, and 85 (15)% and 47 (13)% for 30 microm of vardenafil and tadalafil, respectively (three samples). Vardenafil or sildenafil (30 microm) doubled cGMP levels in pig specimens. There were no effects on cGMP levels with tadalafil. EFS (1-32 Hz) caused l-NG-nitroarginine-sensitive relaxations of pig urethral muscle that were increased in amplitude and duration by PDE-5 inhibition. At 0.1 microm, sildenafil, vardenafil or tadalafil significantly prolonged the mean (sem) duration of the relaxation at 4 Hz by 55 (19)%, 45 (14)% and 51 (12)%, respectively.

CONCLUSIONS

PDE-5-, cGMP- and PKG1-IR is widely distributed in human and pig urethral tissues. Nerve-induced relaxations of urethral preparations were enhanced at low concentrations of sildenafil, vardenafil and tadalafil, whereas there were direct smooth muscle-relaxant actions of the PDE-5 inhibitors at high concentrations. Inhibition of PDE-5 might be an interesting option to facilitate cGMP-mediated relaxation of the outflow region.

Female pig urethral tone is dependent on Rho guanosine triphosphatases and Rho-associated kinase

PURPOSE

Circular smooth muscle of the urethra generates spontaneous myogenic tone of relevance for the maintenance of continence. We tested if Rho guanosine triphosphatases (GTPases) and Rho-associated kinase (ROK) are involved in the generation of urethral tone.

MATERIALS AND METHODS

Small circular strips of female pig urethra were dissected out and mounted for recording isometric force. The effect of pharmacological agents known to modulate the activity of Rho GTPases or ROK was examined. The intracellular calcium concentration was measured using fura-2.

RESULTS

Urethral tone was abolished by removing extracellular calcium or by adding the calcium antagonist felodipine. The decrease in force was closely related to a decrease in intracellular calcium concentration, indicating that tone depends on membrane associated mechanisms. Toxin B, which inactivates Rho GTPases, and Y 27632, which inhibits ROK, completely abolished tone in the female pig urethra. The latter effect occurred without any change in the intracellular calcium concentration.

CONCLUSIONS

The results suggests that urethral tone depends on activity in G-protein coupled pathways and inhibition of this activity is sufficient for urethral tone relaxation. Thus, to our knowledge a new pathway in the generation of urethral tone, which might be acted on by autonomic nerves during micturition, has been identified.

Urethral dysfunction in diabetic rats

PURPOSE

We investigated the effects of diabetes mellitus (DM) on urethral relaxation mechanisms during reflex bladder contractions in rats.

MATERIALS AND METHODS

Five weeks after streptozotocin injection (65 mg/kg intraperitoneally) the effects of DM on urethral relaxation mechanisms were evaluated by simultaneous recordings of intravesical pressure under isovolumetric conditions and urethral perfusion pressure (UPP) using urethane anesthesia.

RESULTS

In diabetic rats the UPP nadir during urethral relaxation and intravesical pressure thresholds for inducing urethral relaxation were significantly higher (199% and 92%, respectively) than in normal rats, while baseline UPPs were not significantly different. The mean rate and amplitude of high frequency oscillations of urethral striated muscle in diabetic rats were also significantly lower (17% and 64%, respectively) compared with normal rats. Following alpha-bungarotoxin treatment to eliminate striated muscle sphincter contractions intravenous administration of L-arginine (200 mg/kg) [corrected] , the substrate of nitric oxide (NO) synthase, decreased the UPP nadir (36% and 22%, in diabetic and normal rats) as well as intravesical pressure thresholds (49% and 22%, respectively). The effect was greater (61% to 126%) in diabetic rats than in normal rats. In each group of rats the effect of L-arginine was inhibited by Nomega-nitro-L-arginine (100 mg/kg intravenously) [corrected], a NO synthase inhibitor.

CONCLUSIONS

During reflex bladder contractions streptozotocin induced diabetic rats exhibited smooth and striated muscle dysfunctions of the urethral outlet. L-arginine therapy, which could augment urethral smooth muscle relaxation by increasing NO production, may be useful for partially restoring the urethral relaxation mechanism in DM.

Does type 2 diabetes mellitus delay renal failure in autosomal dominant polycystic kidney disease?

Autosomal dominant polycystic kidney disease (ADPKD) is a common renal disease without an effective therapeutic intervention to delay renal failure. Within kindreds, renal dysfunction often develops at a similar age in affected individuals, although there are known modifying factors. Two kindreds with ADPKD have shown a striking pattern of delayed onset of renal insufficiency in those individuals also suffering from type 2 diabetes mellitus. Eight nondiabetic patients with ADPKD had onset of dialysis or renal death at ages 38-52 years, (mean +/- SEM 46 +/- 1.9, n = 7) as compared with four diabetics who started dialysis or are still off dialysis at the age of 61 +/- 2.8 years (p < 0.01). Two of the four diabetics still have reasonable renal function at age 61 and 66. The diabetes was diagnosed at age 32 +/- 2 years and was treated with oral hypoglycemics for 19 +/- 2 years before institution of insulin. Cardiovascular disease dominated the clinical picture in the diabetics. In conclusion, onset of renal failure in ADPKD was delayed for over 15 years in individuals who also suffered from type 2 diabetes mellitus, in two ADPKD kindreds. Possible mechanisms are discussed, including glibenclamide inhibition of the cystic fibrosis transmembrane conductance regulator. The striking delay associated with type 2 diabetes mellitus in ADPKD induced renal failure should be evaluated further.