Influence of green tea constituents on cultured porcine luteinized granulosa cell functions

A Sirotkin,N Maruniakova,A Harrath,A Kádasi,S Alwasel,R Grossmann

doi:10.22358/jafs/104705/2019

Abstract

The aim of the study was to examine the action of green tea polyphenols (GTPP) and their main constituent, epigallocatechin-3-gallate (EGCG), on porcine ovarian granulosa cells. For this purpose, the effect of GTPP and EGCG on cultured porcine ovarian granulosa cell functions, including proliferation, apoptosis, steroidogenesis and response to insulin-like growth factor I (IGF-I) was examined. Proliferation (the accumulation of proliferating cell nuclear antigen (PCNA) and cyclin B1), apoptosis (the accumulation of bax and caspase 3) and the release of steroid hormones (progesterone and testosterone) were evaluated by using immunocytochemistry and enzyme immunoassay. The addition of both GTPP and EGCG reduced the percentage of both PCNA- and cyclin B1-positive cells, increased the proportion of cells containing bax and caspase 3 and stimulated progesterone release. GTPP had a biphasic effect on testosterone output – stimulating at dose 1 μg/ml and inhibiting at doses 10 and 100 μg/ml, whilst EGCG did not affect testosterone secretion. IGF-I, when administered alone, promoted % of cells containing PCNA, suppressed bax accumulation, and stimulated progesterone release (only at dose 100 ng/ml). Testosterone release increased after the addition of IGF-I at 1 ng/ml, but decreased after IGF-I addition at 10 or 100 ng/ml. Both GTPP and EGCG suppressed or even reversed the effects of IGF-I on percentage of PCNA-positive cells, bax, testosterone output, and promoted IGF-I action on progesterone release. These observations suggested the inhibitory actions of green tea constituents on porcine ovarian granulosa cell functions were mediated through various regulatory mechanisms: suppression of the ovarian cell cycle in the S and G2 phases; promotion of cytoplasmic apoptosis; alteration of steroid hormone release; and, predominantly, prevention of the action of the hormonal stimulator IGF-I on ovarian cells. It can be also suggested that the major GTPP effects may result from the presence of EGCG.

Highlights

In China the medicinal use of green tea (Camellia sinensis L., Theaceae) is dated 4700 years back
The progesterone release was increased after addition of green tea polyphenols (GTPP) regardless used dose (Figure 2I), after EGCG addition the increase was stated only after the highest dose (Figure 2J)
GTPP and EGCG action on basic ovarian granulosa cell functions. It was observed a decrease in the proportion of cells containing both PCNA and cyclin B1 after the addition of both GTPP and EGCG, which suggested that these green tea constituents inhibit ovarian granulosa cell proliferation

Summary

Introduction

In China the medicinal use of green tea (Camellia sinensis L., Theaceae) is dated 4700 years back. Even drinking green tea is regarded to be generally healthful practice (Cooper, 2012). Clinical, and epidemiological studies have reported health and therapeutic benefits of this tea, which are mainly provided by green tea polyphenols (GTPP), especially the polyphenol epigallocatechin-3-gallate (EGCG). The use of herbs, including anti-microbial green tea, as additives in livestock nutrition has been suggested as a novel alternative to antibiotics. Despite many potential benefits, the consumption of green tea and its constituent molecules should be evaluated in the context of possible reproduction-related consequences (Basini et al, 2005)

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