Role of α- and ß-adrenergic signaling in phenotypic targeting: significance in benign and malignant urologic disease.

The urinary tract is highly innervated by autonomic nerves which are essential in urinary tract development, the production of growth factors, and the control of homeostasis. These neural signals may become dysregulated in several genitourinary (GU) disease states, both benign and malignant. Accordingly, the autonomic nervous system is a therapeutic target for several genitourinary pathologies including cancer, voiding dysfunction, and obstructing nephrolithiasis. Adrenergic receptors (adrenoceptors) are G-Protein coupled-receptors that are distributed throughout the body. The major function of α1-adrenoceptors is signaling smooth muscle contractions through GPCR and intracellular calcium influx. Pharmacologic intervention of α-and ß-adrenoceptors is routinely and successfully implemented in the treatment of benign urologic illnesses, through the use of α-adrenoceptor antagonists. Furthermore, cell-based evidence recently established the antitumor effect of α1-adrenoceptor antagonists in prostate, bladder and renal tumors by reducing neovascularity and impairing growth within the tumor microenvironment via regulation of the phenotypic epithelial-mesenchymal transition (EMT). There has been a significant focus on repurposing the routinely used, Food and Drug Administration-approved α1-adrenoceptor antagonists to inhibit GU tumor growth and angiogenesis in patients with advanced prostate, bladder, and renal cancer. In this review we discuss the current evidence on (a) the signaling events of the autonomic nervous system mediated by its cognate α- and ß-adrenoceptors in regulating the phenotypic landscape (EMT) of genitourinary organs; and (b) the therapeutic significance of targeting this signaling pathway in benign and malignant urologic disease. Video abstract.

Catecholamine response during haemodynamically stable upright posture in individuals with and without tilt-table induced vasovagal syncope.

AIM: Changes in circulating catecholamine concentrations during vasovagal faints have been the subject of considerable study. However, whether catecholamines are part of the triggering mechanism, or principally reflect attempted compensation for an evolving circulatory crisis is unknown. To address this issue, we determined whether the circulating catecholamine response to upright posture differs among patients with and without inducible vasovagal faints at a time when there is no detectable haemodynamic compromise. METHODS AND RESULTS: Blood samples for measurement of adrenaline and noradrenaline (Norepi) concentrations were obtained in the baseline state, and at both 2-3 min and 4-6 min of upright posture in 22 patients undergoing head-up tilt-table testing for evaluation of syncope of unknown cause. In 11 individuals tilt-testing induced syncope at >5 min head-up posture (Group 1). In 11 other individuals tilt testing did not result in syncope (Group 2). Supine arterial catecholamine levels were comparable in the two groups. However, adrenaline concentrations during upright posture tended to be greater at 2-3 min and were significantly greater at 4-6 min in Group 1 than in Group 2 (P< 0.01). These differences occurred in the absence of significant intergroup differences in mean arterial pressure or cardiac cycle lengths. Norepi concentrations also increased in both groups, but without significant differences. CONCLUSION: Circulating adrenaline concentrations in posturally induced vasovagal faints rise more rapidly in vasovagal fainters than in comparably posturally stressed non-fainters, and were significantly greater in fainters prior to either detectable haemodynamic compromise or diminution of circulating Norepi levels. These findings suggest that a premonitory rise in adrenaline concentrations occurs in vasovagal fainters unassociated with an evolving circulatory crisis.

Induction and subcellular localization of protein kinase C isozymes following renal ischemia.

BACKGROUND: We have previously reported that the expression of the receptor for activated C kinase (RACK1) is induced post-ischemia/preperfusion injury to the kidney, and activation of protein kinase C (PKC) protects renal cells from hypoxic injury. This study was done to determine whether the induced expression of RACK1 is accompanied by changes in the level of expression and subcellular distribution of PKC isozymes. METHODS: Ischemia/reperfusion injury resulting in acute renal failure was induced by 60 minutes of bilateral renal artery clamping in rats. The expression levels and translocation of various PKC isozymes between soluble and particulate fractions in whole kidney homogenates were demonstrated by immunoblot analysis. The expression pattern of the various PKC isozymes in the kidney postinjury was performed by immunohistochemistry. RESULTS: PKC alpha, beta II, and zeta were induced and translocated from the soluble fraction to the particulate fraction post-injury. Immunolocalization showed PKC alpha, beta II, and zeta expression to be induced in the proximal tubule epithelial cell (PTEC) at 0 to 30 minutes post-ischemia/reperfusion injury (IRI). At one-day postinjury, the alpha isozyme was translocated to the plasma membrane of the undamaged PTEC, while it was translocated to the nucleus in damaged PTEC. PKC beta II expression was along the basal and lateral side of the undamaged PTEC, while it was distributed in the cytoplasm of sloughed cells in the damaged PTEC. PKC zeta expression at one day was along the apical side of the damaged PTEC. At seven-days postinjury, the expressions of the alpha and zeta isozymes were localized to the plasma membrane of the regenerating PTEC and the expression of PKC beta II isozyme to certain interstitial cells. CONCLUSION: The induced expression, translocation, and the intracellular spatial distributions of the enzymes suggest that they may mediate multiple processes during IRI.

Inhibition of poly(ADP-ribose) polymerase attenuates ischemic renal injury in rats.

The enzyme, poly(ADP-ribose) polymerase (PARP), effects repair of DNA after ischemia-reperfusion (I/R) injury to cells in nerve and muscle tissue. However, its activation in severely damaged cells can lead to ATP depletion and death. We show that PARP expression is enhanced in damaged renal proximal tubules beginning at 6-12 h after I/R injury. Intraperitoneal administration of PARP inhibitors, benzamide or 3-amino benzamide, after I/R injury accelerates the recovery of normal renal function, as assessed by monitoring the levels of plasma creatinine and blood urea nitrogen during 6 days postischemia. PARP inhibition leads to increased cell proliferation at 1 day postinjury as assessed by proliferating cell nuclear antigen and improves the histopathological appearance of kidneys examined at 7 days postinjury. Furthermore, inhibition of PARP increases levels of ATP measured at 24 h postischemia compared with those in vehicle-treated animals. Our data indicate that PARP activation is a part of the cascade of molecular events that occurs after I/R injury in the kidney. Although caution is advised, transient inhibition of PARP postischemia may constitute a novel therapy for acute renal failure.

Expression of CD27 and ischemia/reperfusion-induced expression of its ligand Siva in rat kidneys.

BACKGROUND: Studies identifying genes that are differentially expressed following induction of acute ischemic injury have been useful in delineating the pathophysiology of acute renal failure. METHODS: A differential cDNA library screening technique was used to identify genes that are differentially expressed in rat kidney following induction of acute ischemic renal injury. RESULTS: Levels of mRNA with a high homology to that coding for Siva, a human proapoptotic protein, were increased approximately 4.5-fold in kidneys obtained from rats within 12 hours following ischemia, compared to kidneys from sham-operated rats. A partial cDNA sequence for the rat protein (rat Siva) was determined that overlaps 92% of the human open reading frame. The cDNA sequence predicts a protein 177 amino acids in length with 76% homology to human Siva. Levels of rat Siva in kidneys were elevated at one, five and seven days post-ischemia were not different from those in kidneys from sham-operated controls. In situ hybridization demonstrated that rat Siva mRNA was expressed in cells lining damaged sections in the S3 segment of the proximal tubule at 12 hours and one day post-ischemia. At five and seven days, Siva mRNA was located in epithelial cells of regenerating tubules including in papillary proliferations. TdT-mediated dUTP-biotin nick end-labeling (TUNEL)-positive cells colocalized with cells containing Siva mRNA. CD27, the receptor for Siva was localized by immunohistochemistry to sloughed cells in the lumens of damaged S3 segments at 12 hours post-ischemia and to cells within papillary proliferations at five days post-injury. CONCLUSIONS: Siva that is produced within the kidney could be a mediator of apoptosis post-ischemia via an interaction with CD27.

Induction of calcyclin after ischemic injury to rat kidney.

Genes differentially expressed after acute renal ischemic injury were identified using differential display-polymerase chain reaction (DD-PCR). Messenger RNA for calcyclin, a member of the S100 family of calcium-binding proteins, is increased in kidneys by 6 h following ischemic injury to rats compared with sham surgery. The level of calcyclin mRNA is increased 10-fold by 1 day postinjury and declines thereafter. In situ hybridization demonstrates little calcyclin mRNA in kidneys of sham-operated rats. However, calcyclin protein is present in glomeruli and distal tubules (DT). Compared with kidneys from sham-operated controls, both calcyclin mRNA and protein expression are increased at 1-3 days following ischemic injury in the thick ascending limb of Henle, the DT, and in damaged regenerating segments of proximal tubules. By 7 days postischemia there is a reduction in mRNA and protein expression. Calcyclin could play a role in the regulation of renal cell proliferation and regeneration in the recovery process after acute ischemic injury.

Ischemia-induced receptor for activated C kinase (RACK1) expression in rat kidneys.

Differential display-polymerase chain reaction (DD-PCR) was used to identify genes that are expressed in kidney following induction of acute ischemic renal injury. The receptor for activated C kinase (RACK1) mRNA expression in kidneys obtained from rats 12 h following ischemia is enhanced twofold compared with sham-operated rats. The maximal enhancement of expression (3.3-fold) is at 7 days following reperfusion. Expression remains elevated at 14 days. RACK1 transcripts and protein are localized to the damaged and regenerating segments of proximal tubules. At 1 day following injury, RACK1 protein is present in the epithelial cells of the damaged S3 segment and in cells sloughed into the tubular lumen. By 5 days following injury, RACK1 protein expression is enhanced in the regenerating cells relining the injured tubules of the S3 segment and in papillary proliferations within regenerating tubules. Increased expression of RACK1 could enhance the activity of PKC and, in so doing, regulate the process of regeneration of the proximal tubule following ischemic renal injury.

Abnormal postpartum renal development and cystogenesis in the bcl-2 (-/-) mouse.

Mice deficient for B cell leukemia/lymphoma gene 2 [bcl-2(-/-) mice] manifest congenital renal hypoplasia and develop multicystic kidney disease and renal failure postnatally. To characterize postpartum renal development, to identify the cellular origin of the cysts, and to provide insight into the role that bcl-2 deficiency plays in the cystogenic process, we examined the morphology of kidneys from bcl-2 (-/-) mice and wild-type littermates [bcl-2 (+/+)] from birth (P0) to postpartum day 28 (P28), determined whether abnormalities of cellular proliferation and apoptosis accompany cyst development, and characterized expression of the bcl-2-related protein, bax. Between P0 and P7, kidneys from bcl-2 (-/-) and bcl-2 (+/+) mice undergo a comparable increase in weight and have similar histological appearances. However, during the next 2 wk of life, weight gain in kidneys from bcl-2 (-/-) mice is reduced compared with that in kidneys from bcl-2 (+/+) animals, and cysts develop in tubules with staining characteristics of proximal tubule, distal tubule/medullary thick ascending limb of Henle's loop, and collecting duct. Unaffected glomeruli and proximal tubules in kidneys of bcl-2 (-/-) mice undergo compensatory growth. Cystogenesis is accompanied by enhanced incorporation of 5-bromo-2'-deoxyuridine in cells within cortex and medulla and apoptosis of cells within cysts and in the renal interstitium. Bax protein is expressed in the distal tubule in kidneys of bcl-2 (+/+) and bcl-2 (-/-) mice and in some, but not all cysts. We conclude that abnormal regulation of DNA synthesis and apoptosis accompany cystogenesis in bcl-2 (-/-) mice during postpartum kidney development. Continued expression of bax could enhance apoptotic cell death.