Type 4 phosphodiesterase inhibitor suppresses experimental bladder inflammation

5-Aminolevulinic acid has the potential to prevent bladder dysfunction in cyclophosphamide-induced hemorrhagic cystitis

OBJECTIVES

To investigate the effects of pretreatment with 5-aminolevulinic acid hydrochloride combined with sodium ferrous citrate on bladder dysfunction in cyclophosphamide-induced hemorrhagic cystitis in rats.

METHODS

Male Wistar rats (340-460 g) were pretreated with vehicle or with 5-aminolevulinic acid hydrochloride combined with sodium ferrous citrate (100/157 or 300/471 mg/kg/day, po) once daily for 7 days before cystometry. Saline or cyclophosphamide (150 mg/kg, ip) was administered 2 days before cystometry. Cystometry was performed under urethane anesthesia (0.8 g/kg, ip) via a catheter inserted into the bladder. After cystometry, bladder tissues were collected to perform hematoxylin and eosin staining for pathological evaluation (neutrophil infiltration, edema, and bleeding scores), and for enzyme-linked immunosorbent assay and real-time polymerase chain reaction for investigating tissue levels of myeloperoxidase, and mRNA levels of haem oxygenase-1 as a cytoprotective molecule.

RESULTS

Compared to controls, cyclophosphamide induced a shorter intercontraction interval, lower bladder compliance, increased number of non-voiding contractions, and increased pathological scores and myeloperoxidase expression in the bladder. Pretreatment with 5-aminolevulinic acid hydrochloride combined with sodium ferrous citrate (300/471 mg/kg/day) significantly improved cyclophosphamide-induced intercontraction interval shortening and increases in number of non-voiding contractions and neutrophil infiltration/bleeding scores and enhanced haem oxygenase-1 expression in the bladder. In addition, cyclophosphamide-induced decreases in bladder compliance and increases in myeloperoxidase were not detected with 5-aminolevulinic acid hydrochloride combined with sodium ferrous citrate pretreatment.

CONCLUSIONS

Pretreatment with 5-aminolevulinic acid expects protective effects on bladder dysfunction in cyclophosphamide-induced hemorrhagic cystitis by improving inflammatory changes in bladder tissues perhaps via up-regulation of haem oxygenase-1.

Changes in the expression and function of the PDE5 pathway in the obstructed urinary bladder

Our study aims to explore changes in bladder contractility and the phosphodiesterase type 5 (PDE5) signalling pathway in response to partial bladder outlet obstruction (PBOO). A surgically induced male rat PBOO model and human obstructed bladder tissues were used. Histological changes were examined by H&E and Masson's trichrome staining. Bladder strip contractility was measured via organ bath. The expressions of nitric oxide synthase (NOS) isoforms, PDE5, muscarinic cholinergic receptor (CHRM) isoforms and PDE4 isoforms in bladder were detected by RT‐PCR and Western blotting. The immunolocalization of the PDE5 protein and its functional activity were also determined. PBOO bladder tissue exhibited significant SM hypertrophy and elevated responsiveness to KCl depolarization and the muscarinic receptor agonist carbachol. NOS isoforms, PDE5, CHRM2, CHRM3 and PDE4A were up‐regulated in obstructed bladder tissue, whereas no change in PDE4B and PDE4D isoform expression was observed. With regard to PDE5, it was expressed in the SM bundles of bladder. Interestingly, obstructed bladder exhibited less relaxation responsiveness to sodium nitroprusside (SNP), but an exaggerated PDE5 inhibition effect. The up‐regulation of PDE5 could contribute to the lack of effect on Q_max for benign prostatic hyperplasia/lower urinary tract symptom (BPH/LUTS) patients treated with PDE5 inhibitors. Moreover, PDE5 (with presence of NO) and PDE4 may serve as new therapeutic targets for bladder diseases such as BPH‐induced LUTS and overactive bladder (OAB).

Phosphodiesterase type 4 inhibition enhances nitric oxide- and hydrogen sulfide-mediated bladder neck inhibitory neurotransmission

Nitric oxide (NO) and hydrogen sulfide (H₂S) play a pivotal role in nerve-mediated relaxation of the bladder outflow region. In the bladder neck, a marked phosphodiesterase type 4 (PDE4) expression has also been described and PDE4 inhibitors, as rolipram, produce smooth muscle relaxation. This study investigates the role of PDE4 isoenzyme in bladder neck gaseous inhibitory neurotransmission. We used Western blot and double immunohistochemical staining for the detection of NPP4 (PDE4) and PDE4A and organ baths for isometric force recording to roflumilast and tadalafil, PDE4 and PDE5, respectively, inhibitors in pig and human samples. Endogenous H₂S production measurement and electrical field stimulation (EFS) were also performed. A rich PDE4 and PDE4A expression was observed mainly limited to nerve fibers of the smooth muscle layer of both species. Moreover, roflumilast produced a much more potent smooth muscle relaxation than that induced by tadalafil. In porcine samples, H₂S generation was diminished by H₂S and NO synthase inhibition and augmented by roflumilast. Relaxations elicited by EFS were potentiated by roflumilast. These results suggest that PDE4, mainly PDE4A, is mostly located within nerve fibers of the pig and human bladder neck, where roflumilast produces a powerful smooth muscle relaxation. In pig, the fact that roflumilast increases endogenous H₂S production and EFS-induced relaxations suggests a modulation of PDE4 on NO- and H₂S-mediated inhibitory neurotransmission.

The role of TSG-6 and uroplakin III in bladder pain syndrome/ interstitial cystitis in rats and humans

Objectives

We investigated the relationship between the expression of tumor necrosis factor-inducible gene 6 (TSG-6) with inflammation and integrity of the bladder epithelium in the bladder tissues of patients with bladder pain syndrome/interstitial cystitis (BPS/IC) and the mechanism of action using a rat model of BPS/IC.

Materials and Methods

Expression of TSG-6 and uroplakin III was determined by immuno- histochemistry of bladder biopsy samples from control human subjects and patients with verified BPS/IC. Our rat model of BPS/IC was employed to measure the perfusion of bladders with hyaluronidase, and assessment of the effect of TSG-6 administration on disease progression. Treatment effects were assessed by measurement of metabolic characteristics, RT-PCR of TGR-6 and interleukin-6, bladder histomorphology, and immunohistochemistry of TGR-6 and uroplakin III.

Results

The bladders of patients with BPS/IC had lower expression of uroplakin III and higher expression of TSG-6 than controls. Rats treated with hyaluronidase for 1 week developed the typical signs and symptoms of BPS/IC, and rats treated with hyaluronidase for 4 weeks had more serious disease. Administration of TSG-6 reversed the effects of hyaluronidase and protected against disease progression.

Conclusion

Our results indicate that TSG-6 plays an important role in maintaining the integrity of the bladder epithelial barrier.