Hypothesis / aims of study
Cyclophosphamide (CYP) is a non-specific broad-spectrum anticancer drug commonly used in chemotherapy. However, CYP causes serious and uncomfortable side effects in patients including hemorrhagic cystitis. The cystitis is characterized by bladder inflammation and bleeding, pelvic pain, and lower urinary tract symptoms such as increased urinary frequency and urgency. These symptoms seriously affect the treatment tolerance and prognosis of patients [1]. However, before and during chemotherapy with CYP, there are only symptomatic treatments for the cystitis. Therefore, critical approaches for preventing CYP-induced cystitis are urgently needed.
Hydrogen sulfide (H2S) is the third endogenous gasotransmitter besides carbon monoxide and nitric oxide, and plays key roles in several physiological functions including anti-inflammation, antioxidation and cytoprotection [2]. Moreover, H2S is believed to play an important role in formation of visceral pain [3]. Therefore, H2S might be a promising therapeutic target for CYP-induced cystitis to improve tolerability of chemotherapy with CYP. However, effects of H2S on CYP-induced cystitis have not been investigated yet.
Therefore, in this study, we aimed to evaluate the effects of an H2S donor (NaHS) pretreatment on urinary bladder dysfunction in rats with CYP-induced cystitis.
Study design, materials and methods
Male Wistar rats (290-320 g) were used.
The rats were divided into four groups: Vehicle + Saline (n = 8), Vehicle + CYP (n = 9), NaHS 3 + CYP (n = 10), and NaHS 10 + CYP (n = 8). The rats were treated with daily intraperitoneal (ip) injections of vehicle (saline, 1 ml/kg) or NaHS (3 or 10 μmol/kg) in saline solution for 7 days. CYP (150 mg/kg, ip) or saline (5 ml/kg, ip) had been injected two days before the cystometry.
One day after the final administration of vehicle or NaHS, under urethane-anesthesia (0.8 g/kg, ip), a catheter was inserted into the rat bladder via the bladder dome. One hour after stabilization, single and continuous cystometry were performed by intavesical instillation of saline at a constant flow rate (4.0 ml/h) via the bladder catheter to measure intravesical pressure. At the end of the study, bladders of all rats were isolated and weighted.
Results
(1) Compared to the control group (Vehicle + Saline), the Vehicle + CYP group showed decreased body weight and increased bladder weight and bladder to body weight ratio (BBR). However, treatment with NaHS at each dose showed no effect on these CYP-induced changes (Table 1).
(2) In continuous cystometry, compared to the control group (Vehicle + Saline), in the Vehicle + CYP group, the intercontraction intervals (ICI) and bladder compliance (Comp) were significantly decreased, and the number of non-voiding contractions (NVCs) was significantly increased (Table 1 and Fig. 1). In ths NaHS 3 + CYP group, threshold pressure (TP) was significantly increased compared to the Vehicle + Saline group, but the number of NVCs was significantly decreased compared to the Vehicle + CYP group (Table 1 and Fig. 1). In the NaHS 10 + CYP group, ICI and Comp were significantly increased and the number of NVCs was significantly decreased compared to the Vehicle + CYP group (Table 1 and Fig. 1). There was no significant difference in maximum voiding pressure (MVP) among four groups (Table.1 and Fig. 1). In single cystometry, there was no significant difference in post-voiding residual volume (Rv) among four groups (data not shown).
Interpretation of results
Due to the toxicity of CYP, CYP-treated rats showed body weight loss and bladder weight and BBR increases, while NaHS treatment (3 and 10 μmol/kg) had no effect on these CYP-induced changes. These data suggest that NaHS may have no direct effect on CYP-induced toxicity on the whole body or the bladder. CYP injection significantly reduced ICI and Comp and increased the number of NVCs without changing Rv, suggesting that CYP successfully induced urinary frequency with low bladder distensibility and detrusor overactivity in rats. Both doses of NaHS significantly attenuated the CYP-induced increase in NVCs, suggesting that NaHS could suppress the CYP-induced detrusor overactivity. Moreover, NaHS at a dose of 10 μmol/kg also attenuated the CYP-induced reduction in ICI and Comp, indicating that NaHS partially improved the urinary frequency with low bladder distensibility in CYP-treated rats. These results indicate that NaHS pretreatment at a dose of 10 μmol/kg/day for 7 days showed protective effect on urinary dysfunction in CYP-treated rats.