Carbenoxolone inhibits TRPV4 channel-initiated oxidative urothelial injury and ameliorates cyclophosphamide-induced bladder dysfunction

Abstract

Carbenoxolone (CBX) is a clinically prescribed drug for the treatment of digestive ulcer and inflammation. It is also a widely used pharmacological inhibitor of several channels in basic research. Given that the overactivity of several channels, including those inhibitable by CBX, underlies bladder dysfunction, we tested the potential therapeutic application and mechanism of CBX in the treatment of voiding dysfunction. In a mouse model of cystitis induced by cyclophosphamide (CYP), CBX administration prevented the CYP-elicited increase in bladder weight, oedema, haemorrhage, and urothelial injury. CBX also greatly improved micturition pattern, as manifested by the apparently decreased micturition frequency and increased micturition volume. Western blot results showed that CBX suppressed CYP-induced increase in protein carbonyls, COX-2, and iNOS. Further analysis using cultured urothelial cells revealed that acrolein, the major metabolite of CYP, caused protein oxidation, p38 activation, and urothelial injury. These effects of acrolein were reproduced by TRPV4 agonists and significantly prevented by antioxidant NAC, p38 inhibitor SB203580, TRPV4 antagonist RN-1734, and CBX. Further studies showed that CBX potently suppressed TRPV4 agonist-initiated calcium influx and subsequent cell injury. CBX attenuated CYP-induced cystitis in vivo and reduced acrolein-induced cell injury in vitro, through mechanisms involving inhibition of TRPV4 channels and attenuation of the channel-mediated oxidative stress. CBX might be a promising agent for the treatment of bladder dysfunction.

Keywords: TRPV4; bladder dysfunction; calcium; carbenoxolone; oxidative stress; p38 activation.