Comparative effects of angiotensin II on the contractility of muscularis mucosae and detrusor in the pig urinary bladder

Insights into the associative role of hypertension and angiotensin II receptor in lower urinary tract dysfunction

In men, the lower urinary tract comprises the urinary bladder, urethra, and prostate, and its primary functions include urine storage and voiding. Hypertension is a condition that causes multi-organ damage and an age-dependent condition. Hypertension and the renin-angiotensin system activation are associated with the development of lower urinary tract dysfunction. Hypertensive animal models show bladder dysfunction, urethral dysfunction, and prostatic hyperplasia. In the renin-angiotensin system, angiotensin II and the angiotensin II type 1 receptor, which are expressed in the lower urinary tract, have been implicated in the pathogenesis of lower urinary tract dysfunction. Moreover, among the several antihypertensives, renin-angiotensin system inhibitors have proven effective in human and animal models of lower urinary tract dysfunction. This review aimed to elucidate the hitherto known mechanisms underlying the development of lower urinary tract dysfunction in relation to hypertension and the angiotensin II/angiotensin II type 1 receptor axis and the effect of renin-angiotensin system inhibitors on lower urinary tract dysfunction. Possible mechanisms through which hypertension or activation of Ang II/AT1 receptor axis causes LUTD such as bladder dysfunction, urethral dysfunction, and prostatic hyperplasia. LUT: lower urinary tract, LUTD: lower urinary tract dysfunction, AT1: angiotensin II type 1, ACE: angiotensin-converting enzyme.

Hypertension and urologic chronic pelvic pain syndrome: An analysis of MAPP-I data

BACKGROUND

Urologic chronic pelvic pain syndrome (UCPPS), which includes interstitial cystitis/bladder pain syndrome (IC/BPS) and chronic prostatitis (CP/CPPS), is associated with increased voiding frequency, nocturia, and chronic pelvic pain. The cause of these diseases is unknown and likely involves many different mechanisms. Dysregulated renin-angiotensin-aldosterone-system (RAAS) signaling is a potential pathologic mechanism for IC/BPS and CP/CPPS. Many angiotensin receptor downstream signaling factors, including oxidative stress, fibrosis, mast cell recruitment, and increased inflammatory mediators, are present in the bladders of IC/BPS patients and prostates of CP/CPPS patients. Therefore, we aimed to test the hypothesis that UCPPS patients have dysregulated angiotensin signaling, resulting in increased hypertension compared to controls. Secondly, we evaluated symptom severity in patients with and without hypertension and antihypertensive medication use.

METHODS

Data from UCPPS patients (n = 424), fibromyalgia or irritable bowel syndrome (positive controls, n = 200), and healthy controls (n = 415) were obtained from the NIDDK Multidisciplinary Approach to the Study of Chronic Pelvic Pain I (MAPP-I). Diagnosis of hypertension, current antihypertensive medications, pain severity, and urinary symptom severity were analyzed using chi-square test and t-test.

RESULTS

The combination of diagnosis and antihypertensive medications use was highest in the UCPPS group (n = 74, 18%), followed by positive (n = 34, 17%) and healthy controls (n = 48, 12%, p = 0.04). There were no differences in symptom severity based on hypertension in UCPPS and CP/CPPS; however, IC/BPS had worse ICSI (p = 0.031), AUA-SI (p = 0.04), and BPI pain severity (0.02). Patients (n = 7) with a hypertension diagnosis not on antihypertensive medications reported the greatest severity of pain and urinary symptoms.

CONCLUSION

This pattern of findings suggests that there may be a relationship between hypertension and UCPPS. Treating hypertension among these patients may result in reduced pain and symptom severity. Further investigation on the relationship between hypertension, antihypertensive medication use, and UCPPS and the role of angiotensin signaling in UCPPS conditions is needed.

The Dependence of Urinary Bladder Responses on Extracellular Calcium Varies Between Muscarinic, Histamine, 5-HT (Serotonin), Neurokinin, Prostaglandin, and Angiotensin Receptor Activation

With many common bladder diseases arising due to abnormal contractions, a greater understanding of the receptor systems involved may aid the development of future treatments. The aim of this study was to identify any difference in the involvement of extracellular calcium (Ca²⁺) across prominent contractile-mediating receptors within cells lining the bladder. Strips of porcine urothelium and lamina propria were isolated from the urinary bladder dome and mounted in isolated tissue baths containing Krebs-bicarbonate solution, perfused with carbogen gas at 37°C. Tissue contractions, as well as changes to the frequency and amplitude of spontaneous activity were recorded after the addition of muscarinic, histamine, 5-hydroxytryptamine, neurokinin-A, prostaglandin E2, and angiotensin II receptor agonists in the absence and presence of 1 µM nifedipine or nominally zero Ca²⁺ solution. The absence of extracellular Ca²⁺ influx after immersion into nominally zero Ca²⁺ solution, or the addition of nifedipine, significantly inhibited the contractile responses (p < 0.05 for all) after stimulation with carbachol (1 µM), histamine (100 µM), 5-hydroxytryptamine (100 µM), neurokinin-A (300 nM), prostaglandin E2 (10 µM), and angiotensin II (100 nM). On average, Ca²⁺ influx from extracellular sources was responsible for between 20–50% of receptor-mediated contractions. This suggests that although the specific requirement of Ca²⁺ on contractile responses varies depending on the receptor, extracellular Ca²⁺ plays a key role in mediating G protein-coupled receptor contractions of the urothelium and lamina propria.