Bladder function in mice with inducible smooth muscle-specific deletion of the manganese superoxide dismutase gene

Abstract

Manganese superoxide dismutase (MnSOD) is considered a critical component of the antioxidant systems that protect against oxidative damage. We are interested in the role of oxidative stress in bladder detrusor smooth muscle (SM) in different disease states. In this study, we generated an inducible, SM-specific Sod2(-/-) mouse model to investigate the effects of MnSOD depletion on the function of the bladder. We crossbred floxed Sod2 (Sod2(lox/lox)) mice with mice containing heterozygous knock-in of a gene encoding a tamoxifen-activated Cre recombinase in the SM22α promoter locus [SM-CreER(T2)(ki)(Cre/+)]. We obtained Sod2(lox/lox),SM-CreER(T2)(ki)(Cre/+) mice and injected 8-wk-old males with 4-hydroxytamoxifen to induce Cre-mediated excision of the floxed Sod2 allele. Twelve weeks later, SM-specific deletion of Sod2 and depletion of MnSOD were confirmed by polymerase chain reaction, immunoblotting, and immunohistochemistry. SM-specific Sod2(-/-) mice exhibited normal growth with no gross abnormalities. A significant increase in nitrotyrosine concentration was found in bladder SM tissue of SM-specific Sod2(-/-) mice compared with both wild-type mice and Sod2(+/+), SM-CreER(T2)(ki)(Cre/+) mice treated with 4-hydroxytamoxifen. Assessment of 24-h micturition in SM-specific Sod2(-/-) mice revealed significantly higher voiding frequency compared with both wild-type and SM-specific Cre controls. Conscious cystometry revealed significantly shorter intercontraction intervals and lower functional bladder capacity in SM-specific Sod2(-/-) mice compared with wild-type mice. This novel model can be used for exploring the mechanistic role of oxidative stress in organs rich in SM in different pathological conditions.

Regulation of Spontaneous Contractions in Intact Rat Bladder Strips and the Effects of Hydrogen Peroxide

“…Our results suggest that Ca 2+ influx, Rho kinase activation, and SK channel deactivation may play important roles in the spontaneous contractions in intact bladder strips, whereas only latter two mechanisms may be involved in H 2 O 2 -induced augmentation of spontaneous contractions. Previous studies indicated that excessive accumulation of ROS [ 17 – 19 , 57 ] and enhanced spontaneous contractions [ 5 , 6 , 14 ] are related to OAB, indicating high levels of ROS may contribute to the enhanced spontaneous contractions. The current study explored the potential mechanisms of the H 2 O 2 -induced augmentation of spontaneous contractions through pharmacological approach.…”

“…Therefore, the elevated levels of ROS have been proposed to contribute to OAB [ 17 , 18 ]. More directly, we generated an inducible, smooth muscle-specific manganese superoxide dismutase (MnSOD) gene knockout mouse model recently [ 19 ]. We found the depletion of MnSOD caused oxidative stress in the bladder and the mice presented bladder overactivity [ 19 ].…”

“…More directly, we generated an inducible, smooth muscle-specific manganese superoxide dismutase (MnSOD) gene knockout mouse model recently [ 19 ]. We found the depletion of MnSOD caused oxidative stress in the bladder and the mice presented bladder overactivity [ 19 ]. Higher levels of spontaneous activity were found in detrusor muscle strips from humans and animals with OAB [ 5 , 6 ].…”

Functional and morphological alterations of the urinary bladder in type 2 diabetic FVBdb/db mice

“…Twenty-four hour urination behavior measurement was performed using mouse micturition chambers with a wire mesh bottom designed by Med Associates Inc. (St. Albans, VT) (Liu et al, 2015). The mice were placed in the micturition chambers.…”

“…A suprapubic catheter was implanted 2 days prior to cystometry (Liu et al, 2015). Under anesthesia, the bladder was exposed and a circular purse string suture of 7-0 silk was used on the dome of bladder.…”