Elsevier

Free Radical Biology and Medicine

Volume 53, Issue 10, 15 November 2012, Pages 1886-1893
Free Radical Biology and Medicine

Original Contribution
NAD(P)H:quinone oxidoreductase 1 protects bladder epithelium against painful bladder syndrome in mice

https://doi.org/10.1016/j.freeradbiomed.2012.08.584Get rights and content

Abstract

Painful bladder syndrome (PBS), or interstitial cystitis, is a poorly understood chronic disease that is characterized by thinning of the bladder epithelium and intense pain. Here we demonstrate that NAD(P)H:quinone oxidoreductase 1−/− (NQO1−/−) mice developed in our laboratory represent a new animal model of PBS. NQO1 is known to protect against physiological stress as well as protecting transcription factors against proteasomal degradation. In this study we demonstrate that NQO1 is necessary for bladder epithelium integrity and to prevent the development/progression of PBS. We observed downregulation of energy metabolism, adhesion, and apoptotic signaling cascades, which led to mitochondrial aberrations and profound alterations in energy metabolism, increased susceptibility to reactive oxygen species generation, and apoptosis in luminal epithelium in NQO1−/− mice that were absent in wild-type mice. These pathophysiological changes led to the incidence of PBS in NQO1−/− mice. Altogether, the results demonstrate for the first time that NQO1 is an endogenous factor in protection against PBS.

Highlights

► A mouse model for painful bladder syndrome in aged female NQO1−/− mice was developed. ► NQO1−/− mouse bladders showed painful bladder syndrome-like ulcerations. ► NQO1 loss led to alterations in bladder mitochondrial structure and energy metabolism. ► Loss of NQO1 also increased apoptosis that led to painful bladder syndrome. ► We conclude that NQO1 protects against painful bladder syndrome.

Section snippets

Mice

C57/BL6 mice containing or lacking NQO1 were characterized previously [12] and were housed in our animal housing facility and provided with chow and water ad libitum. Mice were sacrificed according to IACUC-approved protocols.

Morphological examination f ladders

Whole bladders from age-matched mice of both sexes; ages 6, 12, and 24 weeks; and wild-type, NQO1−/−, and NQO1+/− heterozygous genotypes were collected from isoflurane-euthanized mice and examined for the absence and presence of PBS using dissecting microscopic,

PBS dependence on NQO1 gene copy number

We observed that, whereas in wild-type bladders the luminal epithelium was intact at both 6 and 24 weeks, the luminal epithelium in bladders from NQO1−/− mice had a profound loss of integrity from 6 to 24 weeks of age, as visualized by H&E staining (Fig. 1A). Similarly, in trichrome-stained tissue sections we observed a detachment of the luminal epithelium from the underlying basolateral layer in NQO1−/− mice at 24 weeks of age, which was not present at 6 weeks or at any age in wild-type mice (

Discussion

Previously, animal models have been generated that mimic certain aspects of PBS pathophysiology [23], [24], [25]. These included an autoimmune cystitis model [23], cathelicidin peptide-induced bladder inflammation [24], and more recently an APF-based inhibition of bladder epithelial repair model [25]. These models temporarily mimic some aspects of PBS and are not based on the knockdown of a susceptible marker as developed by us in this report. The published models [23], [24], [25] are unrelated

Conclusions

In conclusion, we generated a mouse model of PBS, which showed that NQO1 is an endogenous factor in protection against PBS in female mice and possibly in male mice. Both NQO1−/− and NQO1+/− mice demonstrated symptoms of PBS. Disruption of the NQO1 gene in mice led to increased reactive oxygen species, alterations in factors regulating energy metabolism and adhesion, and loss of mitochondrial structures including cristae structures. These together resulted in increased apoptotic cell death and

Acknowledgments

We thank Dr. Suresh Niture and Phillip Shelton for helpful discussions/suggestions. This work was supported by NIH Grant RO1 ES007943. B.A.P. was partly supported by Training Grant ES007263. There is a patent pending on this work.

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    Present address: Center for Chemical Biology, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, Andhra Pradesh, India.

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