Beta-adrenergic receptor activation in immortalized human urothelial cells stimulates inflammatory responses by PKA-independent mechanisms

β3 Relaxant Effect in Human Bladder Involves Cystathionine γ-Lyase-Derived Urothelial Hydrogen Sulfide

It is now well established that the urothelium does not act as a passive barrier but contributes to bladder homeostasis by releasing several signaling molecules in response to physiological and chemical stimuli. Here, we investigated the potential contribution of the hydrogen sulfide (H2S) pathway in regulating human urothelium function in β3 adrenoceptor-mediated relaxation. The relaxant effect of BRL 37344 (0.1–300 µM), a selective β3 adrenoceptor agonist, was evaluated in isolated human bladder strips in the presence or absence of the urothelium. The relaxant effect of BRL 37344 was significantly reduced by urothelium removal. The inhibition of cystathionine-γ-lyase (CSE), but not cystathionine-β-synthase (CBS), significantly reduced the BRL 37344 relaxing effect to the same extent as that given by urothelium removal, suggesting a role for CSE-derived H2S. β3 adrenoceptor stimulation in the human urothelium or in T24 urothelial cells markedly increased H2S and cAMP levels that were reverted by a blockade of CSE and β3 adrenoceptor antagonism. These findings demonstrate a key role for urothelium CSE-derived H2S in the β3 effect on the human bladder through the modulation of cAMP levels. Therefore, the study establishes the relevance of urothelial β3 adrenoceptors in the regulation of bladder tone, supporting the use of β3 agonists in patients affected by an overactive bladder.

Sympathetic Nerve Hyperactivity in the Spleen: Causal for Nonpathogenic-Driven Chronic Immune-Mediated Inflammatory Diseases (IMIDs)?

Immune-Mediated Inflammatory Diseases (IMIDs) is a descriptive term coined for an eclectic group of diseases or conditions that share common inflammatory pathways, and for which there is no definitive etiology. IMIDs affect the elderly most severely, with many older individuals having two or more IMIDs. These diseases include, but are not limited to, type-1 diabetes, obesity, hypertension, chronic pulmonary disease, coronary heart disease, inflammatory bowel disease, and autoimmunity, such as rheumatoid arthritis (RA), Sjőgren's syndrome, systemic lupus erythematosus, psoriasis, psoriatic arthritis, and multiple sclerosis. These diseases are ostensibly unrelated mechanistically, but increase in frequency with age and share chronic systemic inflammation, implicating major roles for the spleen. Chronic systemic and regional inflammation underlies the disease manifestations of IMIDs. Regional inflammation and immune dysfunction promotes targeted end organ tissue damage, whereas systemic inflammation increases morbidity and mortality by affecting multiple organ systems. Chronic inflammation and skewed dysregulated cell-mediated immune responses drive many of these age-related medical disorders. IMIDs are commonly autoimmune-mediated or suspected to be autoimmune diseases. Another shared feature is dysregulation of the autonomic nervous system and hypothalamic pituitary adrenal (HPA) axis. Here, we focus on dysautonomia. In many IMIDs, dysautonomia manifests as an imbalance in activity/reactivity of the sympathetic and parasympathetic divisions of the autonomic nervous system (ANS). These major autonomic pathways are essential for allostasis of the immune system, and regulating inflammatory processes and innate and adaptive immunity. Pathology in ANS is a hallmark and causal feature of all IMIDs. Chronic systemic inflammation comorbid with stress pathway dysregulation implicate neural-immune cross-talk in the etiology and pathophysiology of IMIDs. Using a rodent model of inflammatory arthritis as an IMID model, we report disease-specific maladaptive changes in β₂-adrenergic receptor (AR) signaling from protein kinase A (PKA) to mitogen activated protein kinase (MAPK) pathways in the spleen. Beta₂-AR signal "shutdown" in the spleen and switching from PKA to G-coupled protein receptor kinase (GRK) pathways in lymph node cells drives inflammation and disease advancement. Based on these findings and the existing literature in other IMIDs, we present and discuss relevant literature that support the hypothesis that unresolvable immune stimulation from chronic inflammation leads to a maladaptive disease-inducing and perpetuating sympathetic response in an attempt to maintain allostasis. Since the role of sympathetic dysfunction in IMIDs is best studied in RA and rodent models of RA, this IMID is the primary one used to evaluate data relevant to our hypothesis. Here, we review the relevant literature and discuss sympathetic dysfunction as a significant contributor to the pathophysiology of IMIDs, and then discuss a novel target for treatment. Based on our findings in inflammatory arthritis and our understanding of common inflammatory process that are used by the immune system across all IMIDs, novel strategies to restore SNS homeostasis are expected to provide safe, cost-effective approaches to treat IMIDs, lower comorbidities, and increase longevity.

Prostaglandin E1 Attenuates Pulmonary Artery Remodeling by Activating Phosphorylation of CREB and the PTEN Signaling Pathway

The depletion of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) and phosphatase and tensin homolog (PTEN) is the critical mediator of pulmonary arterial hypertension (PAH). We hypothesized that the activation of phosphorylated CREB (pCREB) and PTEN could inhibit the AKT signaling pathway to attenuate pulmonary arterial remodeling in rats with monocrotaline-induced PAH. We observed decreased PTEN and pCREB in idiopathic PAH versus control tissue. We reduced PTEN using small interfering RNA in human control pulmonary arterial smooth muscle cells (PASMCs) and observed an increase in pAKT. Consistent with PTEN knockdown in PASMCs, prostaglandin E1 (PGE1) induced pCREB expression to stimulate PTEN protein expression and inhibited pAKT in a time- and dose-dependent manner. The enhanced proliferation and migration of PASMCs following PTEN knockdown were significantly inhibited by PGE1 treatment. The PGE1-induced elevation of PTEN expression in PTEN-depleted PASMCs was decreased by the application of a PKA inhibitor and a CBP-CREB interaction inhibitor. Supplementation with a novel emulsion composition comprising PGE1 in rats with monocrotaline-induced PAH prevented pulmonary arterial remodeling and improved hemodynamics via the induced expression of PTEN. We conclude that PGE1 recruits pCREB/PTEN to decrease the migration and proliferation of PASMCs associated with PAH. This finding elucidates a relevant underlying mechanism of the PGE1/CREB/PTEN signaling pathway to prevent progressive PAH.

Urothelium update: how the bladder mucosa measures bladder filling

AIM

This review critically evaluates the evidence on mechanoreceptors and pathways in the bladder urothelium that are involved in normal bladder filling signalling.

METHODS

Evidence from in vitro and in vivo studies on (i) signalling pathways like the adenosine triphosphate pathway, cholinergic pathway and nitric oxide and adrenergic pathway, and (ii) different urothelial receptors that are involved in bladder filling signalling like purinergic receptors, sodium channels and TRP channels will be evaluated. Other potential pathways and receptors will also be discussed.

RESULTS

Bladder filling results in continuous changes in bladder wall stretch and exposure to urine. Both barrier and afferent signalling functions in the urothelium are constantly adapting to cope with these dynamics. Current evidence shows that the bladder mucosa hosts essential pathways and receptors that mediate bladder filling signalling. Intracellular calcium ion increase is a dominant factor in this signalling process. However, there is still no complete understanding how interacting receptors and pathways create a bladder filling signal. Currently, there are still novel receptors investigated that could also be participating in bladder filling signalling.

CONCLUSIONS

Normal bladder filling sensation is dependent on multiple interacting mechanoreceptors and signalling pathways. Research efforts need to focus on how these pathways and receptors interact to fully understand normal bladder filling signalling.

β3-Adrenoceptor agonists for overactive bladder syndrome: Role of translational pharmacology in a repositioning clinical drug development project

β3-Adrenoceptor agonists were originally considered as a promising drug class for the treatment of obesity and/or type 2 diabetes. When these development efforts failed, they were repositioned for the treatment of the overactive bladder syndrome. Based on the example of the β3-adrenoceptor agonist mirabegron, but also taking into consideration evidence obtained with ritobegron and solabegron, we discuss challenges facing a translational pharmacology program accompanying clinical drug development for a first-in-class molecule. Challenges included generic ones such as ligand selectivity, species differences and drug target gene polymorphisms. Challenges that are more specific included changing concepts of the underlying pathophysiology of the target condition while clinical development was under way; moreover, a paucity of public domain tools for the study of the drug target and aspects of receptor agonists as drugs had to be addressed. Nonetheless, a successful first-in-class launch was accomplished. Looking back at this translational pharmacology program, we conclude that a specifically tailored and highly flexible approach is required. However, several of the lessons learned may also be applicable to translational pharmacology programs in other indications.

Calcitonin gene-related peptide mediates an inflammatory response in Schwann cells via cAMP-dependent ERK signaling cascade

AIMS

Calcitonin gene-related peptides (CGRP), an endogenous neuropeptide, play an important role in the development of neuroinflammation by acting upon its receptor. The CGRP receptor immunoreactivity was identified on Schwann cells. However the effects of CGRP on Schwann cells are unknown and the exact signaling mechanisms associated with CGRP receptor activation related to Schwann cells inflammatory responses are not well understood. We investigated the effect of CGRP on CGRP receptor activation mediates a proinflammatory signaling response in Schwann cells.

MAIN METHODS

CGRP-induced ERK-MAPK phosphorylation and proinflammatory cytokines, interleukin-1 beta (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor (TNF-α) expressions were measured by immune blotting. We also used specific antagonist and inhibitors to confirm the exactly signaling pathway including CGRP (8-37), SQ 22536 and H-89.

KEY FINDINGS

Treatment with CGRP demonstrated a significant generation of IL-1β and IL-6 but not in the level of TNF-α. In addition, there was a temporal increase in the activated form of ERK caused by CGRP that was prevented after pretreatment with CGRP (8-37), SQ 22536 and H-89. Furthermore, use of the CGRP (8-37), ERK inhibitor PD 98059, SQ 22536 or H-89 abolished the CGRP mediated increase in IL-1β.

SIGNIFICANCE

This investigation provides evidence for a novel CGRP activation on Schwann cells that mediates inflammatory response by increasing of IL-1β and IL-6 expression. CGRP activates the cAMP-PKA-ERK signaling cascade leading to IL-1β production. These results support the notion that CGRP may play a direct role to initiate inflammatory processes in the peripheral nervous system.

Regulation of Calcium-Independent Phospholipase A2 Expression by Adrenoceptors and Sterol Regulatory Element Binding Protein-Potential Crosstalk Between Sterol and Glycerophospholipid Mediators

Calcium-independent phospholipase A2 (iPLA2) is an 85-kDa enzyme that releases docosahexaenoic acid (DHA) from glycerophospholipids. DHA can be metabolized to resolvins and neuroprotectins that have anti-inflammatory properties and effects on neural plasticity. Recent studies show an important role of prefrontal cortical iPLA2 in hippocampo-prefrontal cortical LTP and antidepressant-like effect of the norepinephrine reuptake inhibitor (NRI) antidepressant, maprotiline. In this study, we elucidated the cellular mechanisms through which stimulation of adrenergic receptors could lead to increased iPLA2 expression. Treatment of SH-SY5Y neuroblastoma cells with maprotiline, another tricyclic antidepressant with noradrenaline reuptake inhibiting properties, nortriptyline, and the adrenergic receptor agonist, phenylephrine, resulted in increased iPLA2β mRNA expression. This increase was blocked by inhibitors to alpha-1 adrenergic receptor, mitogen-activated protein (MAP) kinase or extracellular signal-regulated kinase (ERK) 1/2, and sterol regulatory element-binding protein (SREBP). Maprotiline and phenylephrine induced binding of SREBP-2 to sterol regulatory element (SRE) region on the iPLA2 promoter, as determined by electrophoretic mobility shift assay (EMSA). Together, results indicate that stimulation of adrenoreceptors causes increased iPLA2 expression via MAP kinase/ERK 1/2 and SREBP, and suggest a possible mechanism for effect of CNS noradrenaline on neural plasticity and crosstalk between sterol and glycerophospholipid mediators, that may play a role in physiological or pathophysiological processes in the brain and other organs.

Therapeutic modulation of urinary bladder function: multiple targets at multiple levels

Storage dysfunction of the urinary bladder, specifically overactive bladder syndrome, is a condition that occurs frequently in the general population. Historically, pathophysiological and treatment concepts related to overactive bladder have focused on smooth muscle cells. Although these are the central effector, numerous anatomic structures are involved in their regulation, including the urothelium, afferent and efferent nerves, and the central nervous system. Each of these structures involves receptors for—and the urothelium itself also releases—many mediators. Moreover, hypoperfusion, hypertrophy, and fibrosis can affect bladder function. Established treatments such as muscarinic antagonists, β-adrenoceptor agonists, and onabotulinumtoxinA each work in part through their effects on the urothelium and afferent nerves, as do α1-adrenoceptor antagonists in the treatment of voiding dysfunction associated with benign prostatic hyperplasia; however, none of these treatments are specifically targeted to the urothelium and afferent nerves. It remains to be explored whether future treatments that specifically act at one of these structures will provide a therapeutic advantage.

Autonomic nervous control of the urinary bladder

The autonomic nervous system plays an important role in the regulation of the urinary bladder function. Under physiological circumstances, noradrenaline, acting mainly on β(3) -adrenoceptors in the detrusor and on α(1) (A) -adrenoceptors in the bladder outflow tract, promotes urine storage, whereas neuronally released acetylcholine acting mainly on M(3) receptors promotes bladder emptying. Under pathophysiological conditions, however, this system may change in several ways. Firstly, there may be plasticity at the levels of innervation and receptor expression and function. Secondly, non-neuronal acetylcholine synthesis and release from the urothelium may occur during the storage phase, leading to a concomitant exposure of detrusor smooth muscle, urothelium and afferent nerves to acetylcholine and noradrenaline. This can cause interactions between the adrenergic and cholinergic system, which have been studied mostly at the post-junctional smooth muscle level until now. The implications of such plasticity are being discussed.

Identification of novel competing β2AR phospho-extracellular signal regulated kinase 1/2 signaling pathways in human trabecular meshwork cells

PURPOSE

β-Adrenergic receptor (βAR) agonists reduce intraocular pressure (IOP) by increasing aqueous outflow through the trabecular meshwork (TM). However, although this effect is well established, the specific signaling mechanisms responsible are less clear. To address this, the current study examined βAR signaling in primary human trabecular meshwork cells (HTMCs), specifically, focusing on the effect of βAR activation on the extracellular signal regulated kinases 1/2 (ERK).

METHODS

HTMCs were cultured and assessed for βAR expression by both immunofluorescence and reverse-transcription-polymerase chain reaction. The effect of βAR activation on ERK phosphorylation was examined in these cells by In-Cell Western™ analysis. Pharmacological approaches were used to characterize the mechanism of the βAR effect on ERK.

RESULTS

Treatment of HTMCs with the nonselective βAR agonist, isoproterenol (ISO), decreased the basal phospho-ERK (pERK) level, through actions at the β2AR. The response was insensitive to pertussis toxin (PTx), but pretreatment with cholera toxin (CTx) resulted in a reversal of the response, such that ISO treatment instead increased pERK, thus implicating Gα(s) in the inhibitory pERK response. The adenylyl cyclase activator, forskolin, also decreased pERK, suggesting the involvement of adenylyl cyclase and cAMP, whereas a protein kinase A (PKA) inhibitor, H-89, blocked both ISO and forskolin-mediated pERK inhibition in HTMCs. Finally, a closer examination of the pERK increase generated in the presence of CTx demonstrated that it was also insensitive to PTx, and appeared to have differing rank orders of efficacy for various βAR agonists compared with the inhibitory pERK pathway in HTMCs.

CONCLUSION

A novel β(2)AR-signaling pathway leading to a decrease in pERK, which was dependent on Gα(s), cAMP, and PKA, was identified in HTMCs. A competing β(2)AR signaling pathway resulting in increased pERK was also identified. Since βAR effects on aqueous humor (AH) outflow have been linked to cAMP, and inhibition of ERK in TM cells has recently been suggested as increasing AH outflow, our findings suggest that the inhibitory β(2)AR-pERK pathway likely represents the mechanism by which βAR agonists decrease IOP. The presence of a competing β(2)AR-ERK activation pathway in the same cells suggests that this is an ideal system for the development and validation of functionally selective β(2)AR agonists.

β-adrenoceptor agonist effects in experimental models of bladder dysfunction

β-adrenoceptor stimulation can enhance the storage function of the urinary bladder by acting on detrusor smooth muscle tone, mediator release from the urothelium and/or afferent nerve activity. In humans this may occur predominantly if not exclusively via the β₃-subtype. The effects of β-adrenoceptor agonists including several β₃-selective agonists have been studied in vitro and in vivo, in healthy animals of both genders and various age groups and in a wide range of animal (mostly rat) models of genetic or acquired bladder dysfunction. Such models included bladder irritation by intravesical instillation of acetic acid or prostaglandin E₂, bladder outlet obstruction, stroke, diabetes, spontaneously hypertensive rats, and NO synthase inhibition. Across all of these models β-adrenoceptor agonists had effects consistent with improved bladder storage function. β₃-adrenoceptor effects are resistant to agonist-induced desensitization in many cell types, but whether this also applies to the human bladder is unknown. The efficacy of β-adrenoceptor agonists appears to be largely unaffected by common polymorphisms of the β₃-adrenoceptor gene. Taken together these findings suggest that β₃-adrenoceptor agonists may become useful drugs for the treatment of bladder storage dysfunction, a view supported by recent phase III clinical studies for one such agent, mirabegron.

β-Adrenergic receptor subtype expression in myocyte and non-myocyte cells in human female bladder

β(3)-Adrenergic receptor agonists are currently under clinical development for the treatment of overactive bladder, a condition that is prevalent in postmenopausal women. These agents purportedly relax bladder smooth muscle through a direct action at the myocyte β(3)-receptor. The aim of this study was to examine the expression of the individual beta-adrenergic receptors in full thickness sections from ageing human female bladder. We obtained a series of rabbit polyclonal antibodies generated against each of the three β-adrenergic receptors, and validated their receptor specificity in CHOK1 cells expressing each of the individual receptors. Immunostaining for β(1), β(2), and β(3) were each more prominent in the urothelium than in the detrusor, with all receptors expressed in the same cell types, indicating co-expression of all three receptors throughout the urothelium in addition to the detrusor. Staining of all receptors was also observed in suburothelial myofibroblast-like cells, intramural ganglion cells, and in Schwann cells of intramural nerves. The β(3)-receptor in the human urothelium appears to be functional, as two different selective β(3)-receptor agonists, TAK677 and BRL37344, stimulate cAMP formation in URO tsa cells. Densitometry analysis indicates a persistent expression of all receptors throughout the bladder with increasing age, with the exception of the β(2)-receptor in the urothelium of the trigone, which appears to decrease slightly in older women. These data indicate that β(3)-receptor expression is maintained with age, but may function in concert with other β-receptors. Activation of the myocyte receptor may be influenced by action on non-myocyte structures including the intramural ganglion cells and myofibroblasts.

Pro-inflammatory responses in human monocytes are beta1-adrenergic receptor subtype dependent

Stress induced circulating catecholamines are hypothesized to selectively activate adrenergic receptors (ARs) on immunocompetent cells modulating their inflammatory response to trauma or environmental toxins. We characterized changes in expression of a pro-inflammatory cytokine modulated by beta-AR activation in human primary and immortalized monocytes that had been simultaneously stimulated with lipopolysaccharide (LPS). Results from cytokine antibody arrays demonstrated that half-maximal effective concentrations of the selective beta-AR agonist isoproterenol (Iso) qualitatively increased LPS-mediated expression of the soluble cytokine, interleukin-1beta (IL-1beta). Semi-quantitative immunoblot techniques confirmed a synergistic increase of IL-1beta production in both LPS stimulated THP-1 cells and primary human monocytes co-incubated with Iso. Immunoblot techniques as well as radioligand binding studies were also used to characterize the heterogeneous expression of beta(1)- and beta(2)-AR subtypes on THP-1 cells. beta-AR activation is classically associated with generation of cAMP in many tissues and cell types. Therefore, using the method of Schild, we generated Iso concentration-response curves in the presence of fixed subtype-selective beta-AR antagonist concentrations to demonstrate that beta(1)-AR activation was exclusively linked with the generation of cAMP in THP-1 cells. Furthermore, use of a selective kinase inhibitor demonstrated that Iso potentiated the expression of soluble IL-1beta through activation of cAMP-dependent protein kinase A. Finally, discriminating concentrations of subtype-selective beta-AR antagonists revealed that beta(1)-AR stimulation alone accounted for the synergistic production of IL-1beta in LPS stimulated monocytes co-incubated with Iso. These results demonstrate a unique synergistic pro-inflammatory response mediated through a beta(1)-AR cAMP-dependent mechanism in LPS-challenged monocytic cells.

The 27-kDa heat shock protein confers cytoprotective effects through a beta 2-adrenergic receptor agonist-initiated complex with beta-arrestin

Heat shock proteins represent an emerging model for the coordinated, multistep regulation of apoptotic signaling events. Although certain aspects of the biochemistry associated with heat shock protein cytoprotective effects are known, little information is found describing the regulation of heat shock protein responses to harmful stimuli. During screening for noncanonical beta adrenergic receptor signaling pathways in human urothelial cells, using mass spectroscopy techniques, an agonist-dependent interaction with beta-arrestin and the 27-kDa heat shock protein was observed in vitro. Formation of this beta-arrestin/Hsp27 complex in response to the selective beta adrenergic receptor agonist isoproterenol, was subsequently confirmed in situ by immunofluorescent colocalization studies. Radioligand binding techniques characterized a homogeneous population of the beta2 adrenergic receptor subtype expressed on these cells. Using terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling, immunoblot analysis and quantitation of caspase-3 activity to detect apoptosis, preincubation of these cells with isoproterenol was found to be sufficient for protection against programmed cell death initiated by staurosporine. RNA interference strategies confirmed the necessity for Hsp27 as well as both beta-arrestin isoforms to confer this cytoprotective consequence of beta adrenergic receptor activation in this cell model. As a result, these studies represent the first description of an agonist-dependent relationship between a small heat shock protein and beta-arrestin to form a previously unknown antiapoptotic "signalosome."

Do gene polymorphisms alone or in combination affect the function of human beta3-adrenoceptors?

BACKGROUND AND PURPOSE

beta(3)-Adrenoceptors mediate many important physiological functions, for example, in the urinary bladder. The corresponding gene is polymorphic, and the W64R (Trp64Arg) single nucleotide polymorphism has been associated with disease states such as obesity, type 2 diabetes and bladder dysfunction. While these clinical data suggest that the 64R variant is hypofunctional, previous in vitro studies in which this variant was generated by site-directed mutagenesis and subsequent transfection have not consistently confirmed this.

EXPERIMENTAL APPROACH

We transfected the wild-type human beta(3)-adrenoceptor and the 64R variant and also the more recently discovered 265M and 306F variants as well as 64R/265M and 64R/306F double mutants into human embryonic kidney cells and selected clones expressing the receptors at a density of about 100 fmol mg protein(-1). Receptor activation was measured by cAMP accumulation and ligand affinity by radioligand binding. Desensitisation was assessed as alterations of cAMP responses after prolonged agonist treatment.

KEY RESULTS

Neither mutated receptor exhibited alterations in efficacy or potency for cAMP accumulation for any of five agonists (isoprenaline, noradrenaline, YM 178, FK 4664, CGP 12 177). In competition binding studies, the mutations did not affect the ability of any agonist to bind to the receptor. Wild-type receptors and the 64R variant exhibited similar isoprenaline-induced functional desensitization during a 24 h treatment.

CONCLUSIONS AND IMPLICATIONS

None of the polymorphisms tested here significantly altered the interaction of isoprenaline, noradrenaline, YM 178, FK 4664 or CGP 12 177 with the human beta(3)-adrenoceptor when expressed at near physiological levels in a human cell line.

Similarities and differences in the autonomic control of airway and urinary bladder smooth muscle

The airways and the urinary bladder are both hollow organs serving very different functions, i.e. air flow and urine storage, respectively. While the autonomic nervous system seems to play only a minor if any role in the physiological regulation of airway tone during normal breathing, it is important in the physiological regulation of bladder smooth muscle contraction and relaxation. While both tissues share a greater expression of M2 than of M3 muscarinic receptors, smooth muscle contraction in both is largely mediated by the smaller M3 population apparently involving phospholipase C activation to only a minor if any extent. While smooth muscle in both tissues can be relaxed by beta-adrenoceptor stimulation, this primarily involves beta2-adrenoceptors in human airways and beta3-adrenoceptors in human bladder. Despite activation of adenylyl cyclase by either subtype, cyclic adenosine monophosphate plays only a minor role in bladder relaxation by beta-agonists; an important but not exclusive function is known in airway relaxation. While airway beta2-adrenoceptors are sensitive to agonist-induced desensitization, beta3-adrenoceptors are generally considered to exhibit much less if any sensitivity to desensitization. Gene polymorphisms exist in the genes of both beta2- and beta3-adrenoceptors. Despite being not fully conclusive, the available data suggest some role of beta2-adrenoceptor polymorphisms in airway function and its treatment by receptor agonists, whereas the available data on beta3-adrenoceptor polymorphisms and bladder function are too limited to allow robust interpretation. We conclude that the distinct functions of airways and urinary bladder are reflected in a differential regulation by the autonomic nervous system. Studying these differences may be informative for a better understanding of each tissue.

Expression and functional role of beta-adrenoceptors in the human urinary bladder urothelium

We investigated the presence of beta-adrenoceptor subtypes in human urinary bladder urothelium and examined whether beta-adrenoceptors in the urothelium modulate the relaxation responses of isolated human detrusor strips to a beta-adrenoceptor agonist. Expression of beta1-, beta2-, and beta3-adrenoceptor mRNA in urothelium and detrusor smooth muscle was determined by reverse transcription-polymerase chain reaction, and the distribution of beta1-, beta2-, and beta3-adrenoceptors in human urinary bladder urothelium were examined by immunohistochemistry. Paired human longitudinal detrusor strips with and without an intact urothelium were suspended in organ baths to construct concentration-response curves to isoproterenol. The possible involvement of urothelium-derived nitric oxide (NO) in this response was examined in additional experiments with urothelium-intact strips in the presence of NG-nitro-L-arginine methylester (L-NAME). Results confirmed the expression of beta1-, beta2-, and beta3-adrenoceptors in the human urinary bladder urothelium. Further, the presence of the urothelium caused a parallel rightward shift of the concentration-response curve to isoproterenol with a significant reduction in potency (pEC50). L-NAME failed to exert any significant effect on the relaxation response to isoproterenol in the urothelium-intact strips. These results confirm the presence of beta1-, beta2-, and beta3-adrenoceptors in human urinary bladder urothelium. Further, they suggest that urothelial beta-adrenoceptors induce the release of a urothelium-derived factor which inhibits the beta-adrenoceptor agonist-induced relaxation of the human detrusor smooth muscle and that this inhibitory mechanism might not involve NO.

Expression of cyclooxygenase-2 in urinary bladder in rats with cyclophosphamide-induced cystitis

These studies examined the expression of cyclooxygenase-2 (COX-2) expression in the urothelium and suburothelial space and detrusor from rats treated with cyclophosphamide (CYP) to induce acute (4 h), intermediate (48 h), or chronic (10-day) cystitis. Western blot analysis and immunohistochemistry were used to demonstrate COX-2 expression. In whole mount preparations of urinary bladder, nerve fibers in the suburothelial plexus, and inflammatory cell infiltrates were characterized for COX-2 expression after CYP-induced cystitis. COX-2 expression significantly (P <or= 0.01) increased in the urothelium + suburothelium and detrusor smooth muscle with acute, intermediate, and chronic (10-day) CYP-induced cystitis, but expression in urothelium + suburothelium was significantly greater. CYP-induced upregulation of COX-2 showed by immunostaining in the urothelium + suburothelium was similar to that observed with Western blot analysis and also demonstrated COX-2 inflammatory cell infiltrates (CD86+) and nerve fibers (PGP+) in the suburothelial plexus. Although COX-2 expression was significantly (P <or= 0.01) increased in detrusor smooth muscle, immunohistochemistry failed to demonstrate an obvious change in COX-2-immunoreactivity (IR) in detrusor muscle, but COX-2 inflammatory infiltrates were present throughout the detrusor. COX-2-IR nerve fibers exhibited increased density in the suburothelial plexus with acute or chronic CYP-induced cystitis. COX-2-IR macrophages (CD86+) were present throughout the urinary bladder with acute and chronic CYP-induced cystitis. These studies demonstrate cellular targets in the urinary bladder where COX-2 inhibitors may act.

The role of the urothelium in mediating bladder responses to isoprenaline

OBJECTIVES

To investigate whether the responses of the pig bladder to isoprenaline (a nonselective beta-adrenoceptor agonist) are influenced by the presence of an intact urothelium and whether any influence might be attributed to the release of nitric oxide (NO), since stimulation of beta-adrenoceptors induces a direct relaxation of detrusor smooth muscle and beta-adrenoceptors are also present on the urothelium.

MATERIAL AND METHODS

Paired (in the presence or absence of urothelium) longitudinal strips of pig bladder dome were set up in tissue baths and the developed tension recorded. Relaxation responses to isoprenaline were examined after pre-contraction with carbachol. The inhibitory effects of isoprenaline were examined by comparing responses to carbachol in the absence and presence of isoprenaline. To examine a possible role for NO, similar experiments were performed in the presence of the NO synthase inhibitor N(G)-nitro-L-arginine (L-NNA).

RESULTS

In the presence of the urothelium, both the potency (pEC(50)) and the maximum contractile responses to carbachol were depressed. In relaxation experiments, isoprenaline relaxed carbachol pre-contracted tissues by approximately 75%, and the potency and maximum relaxation were similar in the absence and presence of the urothelium. In the inhibition experiments, the presence of isoprenaline caused rightward parallel shifts of the concentration-response curves to carbachol, but isoprenaline did not influence the maximum contractions. In the presence of the urothelium there was a greater shift with 0.1 microm isoprenaline than in denuded tissues. Incubation with L-NNA did not affect the influence of the urothelium on responses to isoprenaline in any experimental group.

CONCLUSIONS

The relaxation responses of the bladder to isoprenaline do not appear to involve the urothelium or NO release in vitro. However, contractile responses to carbachol were inhibited in the presence of an intact urothelium, and this might reflect the release of an inhibitory factor other than NO.

Beta2 adrenergic receptor activation stimulates pro-inflammatory cytokine production in macrophages via PKA- and NF-kappaB-independent mechanisms

Activation of the beta(2) adrenergic receptor (beta(2)AR) located on macrophages has been reported to possess anti-inflammatory properties, inhibiting nuclear factor kappaB (NF-kappaB) activation and cytokine production induced by pro-inflammatory stimuli. Here, we show that activation of the beta(2)AR in the absence of pro-inflammatory stimuli produced up to an 80- and 8-fold increase in IL-1beta and IL-6 transcripts, respectively, in the RAW 264.7 murine macrophage cell line. This increase in mRNA expression was accompanied by a significant increase in IL-1beta and IL-6 protein production. Pre-treatment of RAW cells with pharmacological inhibitors of protein kinase A (PKA) or NF-kappaB pathway failed to block this cytokine increase. Instead, the beta(2)AR-mediated increase in cytokines required activation of both the B-raf-ERK1/2 and p38 pathways. Treatment of RAW cells with the exchange protein directly activated by cAMP (EPAC) agonist also resulted in the up-regulation of IL-1beta and IL-6 transcripts. Examination of the main transcription factors downstream of the ERK1/2 and p38 signaling revealed that beta(2)AR activation resulted in the stimulation of CRE-, but not C/EBPbeta-, ETS-, or NF-kappaB-dependent transcription. Western blot analysis further showed that among the transcription factors which recognize the CRE-binding site, ATF-1 and ATF-2 but not CREB proteins were phosphorylated in an ERK1/2- and p38-dependent manner. Collectively, these results demonstrate that beta(2)ARs possess pro-inflammatory properties and that their activation leads to IL-1beta and IL-6 production through ERK1/2- and p38-dependent activation of ATF-1 and ATF-2 transcription factors.