Green tea catechins decrease oxidative stress in surgical menopause-induced overactive bladder in a rat model

Abstract

What's known on the subject? and What does the study add? Ovary hormone deficiency and the age-related changes in post-menopausal women are subjected to a number of urological dysfunctions, including overactive bladder syndrome. Green tea is a popular healthy drink worldwide and its extract catechin has strong anti-inflammatory and antioxidant properties. EGCG, the major type of catechin, is an antioxidant polyphenol flavonoid isolated from green tea. EGCG supplement could prevent ovariectomy-induced bladder dysfunction in a dose-related manner through its anti-oxidant, anti-fibrosis and anti-apoptosis effects.

Objective: To evaluate whether green tea extract, epigallocatechin gallate (EGCG), could prevent ovariectomy-induced overactive bladder (OAB) and to investigate its antioxidant, anti-apoptotic and anti-fibrosis effects.

Materials and methods: In all, 48 female Sprague-Dawley rats were divided into four groups. After bilateral ovariectomy, the first group served as the ovariectomy control, the second group received EGCG 1 µM/kg daily i.p. injection after ovariectomy surgery, and the third group received EGCG 10 µM/kg daily i.p. injection. The fourth group was taken as the sham without ovariectomy surgery. The rats were killed after 6 months after ovariectomy surgery. Cystometrograms were performed for the measure of bladder overactivity. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) assay was used to evaluate apoptotic cells. Western immunoblots were performed to determine the expressions of inflammatory markers, apoptosis-associated proteins and oxidative stress markers.

Results: Long-term ovariectomy significantly increased non-voiding contractions and decreased bladder compliance. Treatment with EGCG significantly increased bladder compliance and diminished non-voiding contractions. Ovariectomy significantly increased apoptotic cells and enhanced interstitial fibrosis in bladders. The expression of caspase-3 significantly increased, while that of Bcl-2 notably decreased after ovariectomy. Inflammatory and fibrosis markers, TGF-β, fibronectin and type I collagen expressions were significantly increased after 6 months of ovariectomy surgery. Treatment with EGCG significantly decreased TGF-β and type I collagen expressions. Oxidative stress markers, nitrotyrosine and protein carbonylation levels were significantly increased in the ovariectomy group. EGCG could attenuate this oxidative damage in dose-dependent fashion.

Conclusions: Ovariectomy increased oxidative damage, enhanced voiding frequency and decreased bladder compliance. EGCG could restore ovariectomy-induced bladder dysfunction in a dose-dependent fashion through antioxidant, anti-fibrosis and anti-apoptosis effects.