Expression of HSP 70 and its mRNAS during ischemia-reperfusion in the rat bladder

Hydrogen sulfide-induced relaxation of the bladder is attenuated in spontaneously hypertensive rats

PURPOSE

To compare hydrogen sulfide (H₂S)-induced relaxation on the bladder between normotensive and spontaneously hypertensive rat (SHR), we evaluated the effects of H₂S donors (GYY4137 and NaHS) on the micturition reflex and on the contractility of bladder tissues. We also investigated the content of H₂S and the expression levels of enzymes related to H₂S biosynthesis [cystathionine β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (MPST), and cysteine aminotransferase (CAT)] in the bladder.

METHODS

Eighteen-week-old male normotensive Wistar rats and SHRs were used. Under urethane anesthesia, the effects of intravesically instilled GYY4137 (10^-8, 10^-7 and 10^-6 M) on the micturition reflex were evaluated by cystometry. The effects of NaHS (1 × 10^-8-3 × 10^-4 M) were evaluated on carbachol (10^-5 M)-induced pre-contracted bladder strips. Tissue H₂S content was measured by the methylene blue method. The expression levels of these enzymes were investigated by Western blot.

RESULTS

GYY4137 significantly prolonged intercontraction intervals in Wistar rats, but not in SHRs. NaHS-induced relaxation on pre-contracted bladder strips was significantly attenuated in SHRs compared with Wistar rats. The H₂S content in the bladder of SHRs was significantly higher than that of Wistar rats. CBS, MPST and CAT were detected in the bladder of Wistar rats and SHRs. The expression levels of MPST in the SHR bladder were significantly higher than those in the Wistar rat bladder.

CONCLUSION

H₂S-induced bladder relaxation in SHRs is impaired, thereby resulting in a compensatory increase of the H₂S content in the SHR bladder.

Protective effect of edaravone, a free-radical scavenger, on ischaemia-reperfusion injury in the rat testis

OBJECTIVE

To investigate the effect of edaravone, a radical scavenger, on ischaemia-reperfusion (I-R) injury in the testes.

MATERIALS AND METHODS

Eight-week-old male Sprague-Dawley rats were allocated to one of four groups: a no-drug group subjected to induction of 30-min of ischaemia and 60-min reperfusion; two drug groups administered edaravone at 1 or 10 mg/kg intraperitoneal and then subjected to 30-min ischaemia and 60-min reperfusion; and a sham-operated control group administered edaravone at 10 mg/kg intraperitoneal. To induce testicular I-R, the right testis was exposed outside of the body and the testicular artery was clamped with a small clip for 30 min. Blood flow and nitric oxide (NO) release were monitored in real time simultaneously with a laser Doppler flowmeter and an NO-selective electrode, respectively. After death the tissue levels of NO(2)-NO(3) (a marker of NO production), malondialdehyde (a marker of lipid peroxidation), 8-hydroxydeoxyguanosine (a marker of oxidative DNA damage), myeloperoxidase (a marker of neutrophil infiltration), and heat-shock protein 70 (HSP 70) and its mRNA were measured. The testicular tissue was also analysed histologically.

RESULTS

Clamping the testicular artery resulted in a decrease of blood flow to 0-5% of the basal level measured before clamping. NO release was increased during clamping and gradually recovered to the basal level on removing the clip. Interestingly, the peak of NO release in rats of the no-drug group occurred at the start of reperfusion, while that in the high-dose drug group occurred several minutes later. The levels of NO(2)-NO(3), malondialdehyde, 8-hydroxydeoxyguanosine, myeloperoxidase and HSP 70 and its mRNA, and histological variables, were significantly greater in the no-drug I-R group than in the control, and these variables were ameliorated by treatment with edaravone.

CONCLUSION

These results indicate that edaravone reduces the oxidative stress and prevents the testicular damage induced by I-R.

Oxidative stress reduces the muscarinic receptor function in the urinary bladder

AIMS

Several pathophysiological conditions in the urinary bladder, for example, ischemia/reperfusion and inflammation are characterized by the formation of reactive oxygen species (ROS). The ROS are highly toxic because they can destroy proteins, DNA, and lipids. The aim of this study was to investigate the effect of oxidative stress on excitation-contraction coupling of detrusor smooth muscle.

MATERIALS AND METHODS

Smooth muscle strips were dissected from pig urinary bladder and mounted in organ baths. Oxidative stress was mimicked by the addition of Cumene hydroperoxide (CHP), a lipophilic hydroperoxide, to the organ baths. Contractile responses to electrical field stimulation (EFS: 4-32 Hz), carbachol (10(-8)-3 x 10(-5) M), potassium (65.3 mM), and ATP (1 mM) were monitored before and after the addition of CHP.

RESULTS

Responses of detrusor strips to EFS were for the greater part based on neurogenic stimulation and the release of acetylcholine. CHP diminished contractile responses to EFS and carbachol to the same extent. The pD(2) value of the carbachol concentration-response curve decreased significantly after exposure to 0.1 mM, 0.4 mM, 0.8 mM CHP. Furthermore the maximal effect obtained with carbachol was significantly reduced after 0.1 mM, 0.4 mM, and 0.8 mM CHP treatment. Contractions induced by potassium and ATP were significantly less affected by oxidative stress compared to EFS- and carbachol-induced responses of comparable amplitude.

CONCLUSIONS

The results of our study demonstrate that oxidative stress induced by CHP affects pig bladder contractility. The muscarinic receptor signaling system is severely damaged. L-type calcium channels and the contractile system are less affected and cholinergic nerves remain largely unaffected.

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