An in vitro study of the pro‑apoptotic properties of green tea polyphenols in neoplastic cell lines


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Lakshman Nalluri1, David Jamieson3, Trevor Jackson3, Lisa Lee-Jones2

1Northumbria University, Newcastle-upon-Tyne, UK, 2Manchester Metropolitan University, Manchester, UK, 3Newcastle University, Newcastle-upon-Tyne, UK

Abstract

Background

Green tea polyphenols have received much attention from the research community, nutritionists, and public due to their antioxidant, anti-inflammatory and chemopreventive properties. This study investigated the pro-apoptotic properties of green tea extract and its constituent polyphenols, (epigallocatechin-3-gallate, epicatechin, epicatechin-3-gallate, epigallocatechin) in a variety of neoplastic cell lines of haematological and melanocytic origins.

Method

Apoptosis was assessed using a combination of approaches, in cells treated with green tea extract (0.0073, 0.073, 0.73 mg/mL) or polyphenols for 24, 48, 72 and 96 hours. Detection of phosphatidylserine on the surface of apoptotic cells was undertaken using annexin V by flow cytometry. Changes in chromatin morphology, plasma membrane damage, and other morphological features of apoptosis was achieved using vital dyes. Internucleosomal cleavage was detected by gel electrophoresis of DNA.

Results

The level of apoptosis induction by green tea extract differed according to the cell line used; U-937 and HP6002 being most sensitive (72% apoptosis after 72 hours), and THP-1 least sensitive (62%). However all cell lines demonstrated apoptosis induction in a dose and time-dependent manner. Plasma membrane “blebbing” was prominent in all concentrations and times studied, whereas pyknosis, karyorrhexis and apoptotic laddering were more prevalent in cells treated for longer time periods (48 -96 h) at 0.73 mg/mL. Flow cytometric analysis revealed the order of effectiveness of different polyphenols to induce apoptosis were EGC>EGCG>ECG>EC.

Conclusion

This study demonstrated that green tea induce high levels of apoptosis in a variety of cancer cells in vitro, suggesting a role in treatment in addition to chemoprevention.

Background

Green tea polyphenols have received much attention from the research community, nutritionists, and public due to their antioxidant, anti-inflammatory and chemopreventive properties. This study investigated the pro-apoptotic properties of green tea extract and its constituent polyphenols, (epigallocatechin-3-gallate, epicatechin, epicatechin-3-gallate, epigallocatechin) in a variety of neoplastic cell lines of haematological and melanocytic origins.

Method

Apoptosis was assessed using a combination of approaches, in cells treated with green tea extract (0.0073, 0.073, 0.73 mg/mL) or polyphenols for 24, 48, 72 and 96 hours. Detection of phosphatidylserine on the surface of apoptotic cells was undertaken using annexin V by flow cytometry. Changes in chromatin morphology, plasma membrane damage, and other morphological features of apoptosis was achieved using vital dyes. Internucleosomal cleavage was detected by gel electrophoresis of DNA.

Results

The level of apoptosis induction by green tea extract differed according to the cell line used; U-937 and HP6002 being most sensitive (72% apoptosis after 72 hours), and THP-1 least sensitive (62%). However all cell lines demonstrated apoptosis induction in a dose and time-dependent manner. Plasma membrane “blebbing” was prominent in all concentrations and times studied, whereas pyknosis, karyorrhexis and apoptotic laddering were more prevalent in cells treated for longer time periods (48 -96 h) at 0.73 mg/mL. Flow cytometric analysis revealed the order of effectiveness of different polyphenols to induce apoptosis were EGC>EGCG>ECG>EC.

Conclusion

This study demonstrated that green tea induce high levels of apoptosis in a variety of cancer cells in vitro, suggesting a role in treatment in addition to chemoprevention.

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