Element contents in seaweed products and cytotoxicity on breast cancer cell linesDuangjai Muangratt
( M.Sc. )
This study aims to determine the concentrations of elements in commercial seaweed products and to assess their cytotoxic effects. Sixty-eight edible seaweed products available in Thai markets during Feb 2009-June 2010 were examined in this study. Seaweed products were digested with concentrated nitric acid by using microwave system and analyzed by using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). In general, analyzed seaweeds contained both essential elements (calcium (Ca) and manganese (Mn)) and toxic elements (arsenic (As), cadmium (Cd) and lead (Pb)). Among these samples, 97% and 83% of total seaweed samples contained levels of contaminated As and Cd above the regulation values (3 mg/kg dry weight (DW) for inorganic As, and 0.5 mg/kg DW for Cd, respectively). Therefore, three seaweed samples, containing different levels of As (35-46 mg/kg DW) and Cd (0.7-3.2 mg/kg DW), and also polyphenolic compounds, were selected and extracted with water in order to study for their biological effects using human breast cancer cell lines,T47D and MDA-MB231. MTT cell viability assay revealed that analyzed seaweed extracts possessed in vitro cytotoxic effect on both cell lines. However, higher cytotoxicity was evidenced in the hormone-dependent estrogen receptor alpha (ERα)-positive T47D cells compared to that observed in hormone-independent (ER)-negative MDA-MB231 cells. The observed cytotoxicity of seaweed extract may be due to the effects of seaweed itself, effect of contaminants, or their combinatory effects. Thus, cytotoxic effects of single and combination of arsenic and cadmium at concentrations equivalent to those detected in 1 to 20 mg/ml seaweed extract were investigated. In both cell lines, cytotoxicity was detected with arsenite treatments but not cadmium treatments. The combined treatment of arsenite and cadmium concentrations equivalent to that detected in 1 to 20 mg/ml seaweed extract induced cytotoxic effect at the same level as arsenite treatment alone on the two tested cell lines. Estrogenic activity of seaweed was examined by estrogen responsive element (ERE) transcriptional activation using breast cancer cells transfected with ERE-luciferase reporter, T47D-KBluc cells. Seaweed extract demonstrated estrogenic activity either in presence or absence of estradiol (E2). However, anti-estrogenic activity was detected at dose of 10 mg/ml in presence of E2. Furthermore, risk assessment analysis of 68 seaweed products revealed that total intakes of Ca, Mn, As, Cd and Pb were below the recommendations (UL, TDI, PTMI and PTWI) with the average consumption of 14.6 g/day of seaweeds.
Element, calcium, manganese, arsenic, cadmium, lead, seaweed, cytotoxic effect, T47D, MDA-MB231, estrogenic activity, breast cancer