PHYTOCHEMICALS AND CANCER PREVENTIVE PATHWAYS: EFFECTS OF GENETIC AND EPIGENETIC FACTORS
Location: Diet, Genomics and Immunology Lab
Title: Effect of resveratrol and zinc on intracellular zinc status in normal human prostate epithelial cells
Submitted to: American Journal of Physiology - Cell Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 16, 2009
Publication Date: June 24, 2009
Citation: Zhang, J., Wu, M., Schoene, N.W., Cheng, W., Wang, T.T., Alshatwi, A.A., Alsaif, M., Lei, K.Y. 2009. Effect of resveratrol and zinc on intracellular zinc status in normal human prostate epithelial cells. American Journal of Physiology - Cell Physiology. 297(3):C632-644.
Interpretive Summary: The molecular affects of phytochemicals on normal as well as cancerous cells remain largely unknown. ARS and University of Maryland scientists evaluated the influence of the grape-derived phytochemical resveratrol on cellular zinc status. Normal human prostate epithelial (NHPrE) cells were treated with different levels of resveratrol and zinc. Reductions in cell growth (similar to growth that occurs in cancers) were correlated with increasing amounts of resveratrol (2.5-10 microM). Strikingly, resveratrol treatment at 5 and 10 microM resulted in a dramatic increase in cell zinc concentration. Resveratrol at the highest level tested(10 microM) resulted in cell growth inhibition in a cell culture system. Additional studies demonstrated complex interactions between resveratrol and zinc ions in the cell. Other analyses revealed that free zinc in the cell increased when resveratrol increased culture medium. Furthermore, increases in cell zinc were associated with increases in reactive oxygen species (ROS), known to increase carcinogenesis, and cells aged more in cells treated with 2.5 or 10 microM resveratrol. Taken together, increases in total cell zinc content may induce ROS and cell aging, while the elevated levels of cell zinc induced by resveratrol enhance ROS and aging effects. This work provides novel information for research scientists interested in molecular targets and mechanism(s) of action of grape-derived phytochemical(s), and serves as an important basis for future investigation of targets of cell growth and signaling. This work will benefit basic as well as translational research science.
To evaluate the influence of resveratrol on cellular zinc status, normal human prostate epithelial (NHPrE) cells were treated with 6 levels of resveratrol (0, 0.5, 1, 2.5, 5 and 10 microM) and 4 levels of zinc [0, 4, 16, and 32 microM for zinc-deficient (ZD), zinc-normal (ZN), zinc-adequate (ZA), and zinc supplemented (ZS), respectively]. A progressive reduction in cell growth was observed in cells treated with increasing amounts of resveratrol (2.5-10 microM). Strikingly, resveratrol treatment at 5 and 10 microM resulted in a dramatic increase in cellular total zinc concentration, especially in ZS cells. Flow cytometric study indicated that resveratrol (10 microM) treatment induced a G2/M arrest in association with the observed cell growth inhibition. Data from an in vitro experiment using zinquin as an indicator of intracellular free Zn(II) status demonstrated complex interactions between resveratrol and zinc ion. Fluorescent spectrofluorometry and fluorescent microscopic analyses revealed that intracellular labile free zinc was progressively elevated from ~2-fold in ZS cells with no resveratrol to multi-fold increases in ZA and ZS cells with 10 microM resveratrol treatment compared to their corresponding ZN cells. Furthermore, increases in cellular zinc status were associated with elevated levels of reactive oxygen species (ROS) and senescence as evidenced by morphological and histochemical changes in cells treated with 2.5 or 10 microM resveratrol, especially in ZA and ZS cells. Taken together, increases in total cellular zinc may induce ROS and senescence, while the elevated level of intracellular free labile zinc may enhance this ROS and senescence inducing effect.