Alpha1-adrenergic receptors mediate bladder overactivity induced by cold stress in rats with bladder outlet obstruction

METTL3-dependent m6A modification mediates bladder remodeling after partial bladder outlet obstruction through CCN2 activation

AIMS

N6-methyladenosine (m6A) modification is a critical posttranscriptional event in gene regulation. Thus, identifying methyltransferase, demethylase, or m6A binding protein-mediated m6A modifications in cancer or noncancer transcriptomes has become a promising novel strategy for disease therapy development. However, novel insights into m6A modification in partial bladder outlet obstruction (pBOO) and detailed information about the drivers of bladder remodeling remain to be elucidated. Here, we first characterized the m6A modification landscape in pBOO and investigated potential actionable pharmaceutical targets for future therapies.

METHODS

We generated an improved animal model of pBOO in SD rats with urethral meatus stricture induced by suturing. Urodynamic investigations and cystometry were carried out to evaluate the physiologic changes elicited by pBOO. Whole-transcriptome sequencing (RNA-seq) and m6A-modified RNA immunoprecipitation sequencing (MeRIP-seq) were subsequently performed to analyze the expression pattern associated with bladder remodeling in pBOO.

RESULTS

The cystometric evaluation of bladder function demonstrated obvious increases in pressure-related parameters in the pBOO group. Hematoxylin and eosin staining and Masson's trichrome staining validated the occurrence of bladder remodeling. A global elevation in m6A RNA methylation levels was observed in parallel to a increased expression of METTL3 in the pBOO group. High-throughput sequencing revealed the differences in expression patterns between the pBOO and sham-operated groups. Furthermore, potential m6A-modified genes, including CCN2, may serve as new pharmaceutical targets to reverse bladder remodeling.

CONCLUSIONS

Exploring the roles of m6A-modified genes identified as associated with bladder remodeling by integrating RNA-seq and MeRIP-seq data can offer new insights for developing promising treatments for pBOO patients.

α1 -Blocker inhibits non-voiding contractions and decreases the level of intravesical prostaglandin E2 in rats with partial bladder outlet obstruction

OBJECTIVES

To elucidate the mechanism of action of the α₁ -blocker, naftopidil, in partial bladder outlet obstruction animals, by studying non-voiding contractions, and the levels of mediators were measured with resiniferatoxin treatment.

METHODS

A total of 35 female Wistar rats were randomly divided into a sham or bladder outlet obstruction group, and rats in each group were given vehicle or resiniferatoxin. Incomplete urethral ligation was applied to the bladder outlet obstruction group. After cystometry, the intravesical level of prostaglandin E₂ and adenosine 5'-triphosphate was measured in the instilled perfusate collected. Naftopidil was given at the time of cystometry.

RESULTS

In bladder outlet obstruction rats, non-voiding contractions, bladder capacity, and the intravesical levels of prostaglandin E₂ and adenosine 5'-triphosphate were markedly increased compared with sham rats. Naftopidil decreased non-voiding contractions, enlarged the bladder capacity, and decreased the intravesical levels of prostaglandin E₂ and adenosine 5'-triphosphate. Resiniferatoxin enhanced non-voiding contractions. The effects of naftopidil on non-voiding contractions and the intravesical level of prostaglandin E₂ , but not adenosine 5'-triphosphate, were tolerant to resiniferatoxin.

CONCLUSIONS

In bladder outlet obstruction rats, one cause of generation of non-voiding contractions might be bladder wall distension, but not transient receptor potential cation channel V1. The increase in intravesical prostaglandin E₂ might also be associated with the generation of non-voiding contractions. Naftopidil inhibits the increase in non-voiding contractions and decreases the intravesical level of prostaglandin E₂ , which are independent of transient receptor potential cation channel V1.

The pharmacology of α1-adrenoceptor subtypes

This review examines the functions of α₁-adrenoceptor subtypes, particularly in terms of contraction of smooth muscle. There are 3 subtypes of α₁-adrenoceptor, α_1A- α_1B- and α_1D-adrenoceptors. Evidence is presented that the postulated α_1L-adrenoceptor is simply the native α_1A-adrenoceptor at which prazosin has low potency. In most isolated tissue studies, smooth muscle contractions to exogenous agonists are mediated particularly by α_1A-, with a lesser role for α_1D-adrenoceptors, but α_1B-adrenoceptors are clearly involved in contractions of some tissues, for example, the spleen. However, nerve-evoked responses are the most crucial physiologically, so that these studies of exogenous agonists may overestimate the importance of α_1A-adrenoceptors. The major α₁-adrenoceptors involved in blood pressure control by sympathetic nerves are the α_1D- and the α_1A-adrenoceptors, mediating peripheral vasoconstrictor actions. As noradrenaline has high potency at α_1D-adrenceptors, these receptors mediate the fastest response and seem to be targets for neurally released noradrenaline especially to low frequency stimulation, with α_1A-adrenoceptors being more important at high frequencies of stimulation. This is true in rodent vas deferens and may be true in vasopressor nerves controlling peripheral resistance and tissue blood flow. The α_lA-adrenoceptor may act mainly through Ca²⁺ entry through L-type channels, whereas the α_1D-adrenoceptor may act mainly through T-type channels and exhaustable Ca²⁺ stores. α₁-Adrenoceptors may also act through non-G-protein linked second messenger systems. In many tissues, multiple subtypes of α-adrenoceptor are present, and this may be regarded as the norm rather than exception, although one receptor subtype is usually predominant.

Functional roles of bladder α1-adrenoceptors in the activation of single-unit primary bladder afferent activity in rats

OBJECTIVES

To clarify the involvement of bladder α1-adrenoceptors (α1-ARs) in afferent pathways by investigating the effects of silodosin and BMY7378, selective α1A- or α1D-AR antagonists, respectively, on single-unit afferent nerve fibre activity (SAA) of the primary bladder afferent nerves and their relationship with bladder microcontractions in rats.

MATERIALS AND METHODS

A total of 63 female Sprague-Dawley rats were anaesthetized with urethane. The SAA of Aδ and C fibres generated from the left L6 dorsal roots was determined using electrical stimulation of the left pelvic nerve and bladder distension. After measuring baseline SAA during constant filling cystometry, the procedure was repeated with i.v. (0.3-30 μg/kg) or intravesical (10 μm) administration of each antagonist. In separate rats, the bladder was filled with saline until the intravesical pressure reached 30 cmH2 O, and was kept under isovolumetric conditions, then the recording was performed with i.v.-administered vehicle and silodosin (0.3 μg/kg).

RESULTS

A total of Aδ fibres and 33 C fibres were isolated from 63 rats. The SAA of Aδ fibres, but not C fibres, were dose-dependently decreased after both i.v. and intravesical administrations of each of the antagonists. In the experiments under bladder isovolumetric conditions, silodosin administration significantly decreased the SAA of Aδ fibres, but not C fibres, compared with vehicle administration. There were no significant effects on either the mean basal bladder pressure or microcontractions.

CONCLUSION

The present study suggests that both α1A- or α1D-ARs in the rat bladder are involved in the activation of the bladder mechanosensory Aδ fibres during bladder filling, and that this activation may not be related to bladder microcontractions.