Comparison of the cytotoxic effects of β-sitosterol oxides and a cholesterol oxide, 7β-hydroxycholesterol, in cultured mammalian cells

Abstract

Phytosterols are plant sterols found in foods such as oils, nuts and vegetables. Phytosterols, in the same way as cholesterol, contain a double bond and are susceptible to oxidation. The objective of the present study was to assess the potential toxic effects of b-sitosterol oxides on U937 cells. The effects of increasing concentrations (0-120 mM) of b-sitosterol oxides on cellular cytotoxicity, apoptosis, antioxidant status and genotoxicity was assessed over 12, 24 and 48 h exposure periods. Following 12 h, the viability of cells treated with 120 mM-b-sitosterol oxides was reduced to 51·7 % relative to control. At 24 and 48 h, both 60 and 120 mM-b-sitosterol oxides caused a significant decrease in cell viability. For comparison, a decrease in viability of cells treated with a cholesterol oxide, 7b-hydroxycholesterol (7b-OH, 30 mM), was evident at 24 h. An increase in apoptotic cells, assessed using Hoechst 33342, indicates that the mode of cell death in U937 cells following exposure to 7b-OH (30 mM) and b-sitosterol oxides (60 and 120 mM) was by apoptosis. The increase in apoptotic cells after 12 h following treatment with 120 mM-b-sitosterol oxides was accompanied by a decrease in cellular glutathione. Similarly, 7b-OH (30 mM) treatment resulted in decreased glutathione at 12 h. Catalase activity was not affected by any of the treatments. b-Sitosterol oxides had no genotoxic effects on U937 and V79 cells as assessed by the comet and sister chromatid exchange assays respectively. In general, the results indicate that thermally oxidised derivatives of b-sitosterol demonstrate similar biological effects as 7b-OH in U937 cells, but at higher concentrations.

Different apoptotic mechanisms are involved in the antiproliferative effects of 7β-hydroxysitosterol and 7β-hydroxycholesterol in human colon cancer cells

“…24 Cholesterol oxides and a mixture of b-sitosterol/campesterol oxides were examined for their cytotoxic effects on a macrophage-derived cell line (C57BL/6). All compounds exhibited similar cytotoxicity as indicated by LDH leakage, cell viability and mitochondria dehydrogenase activity, although oxyphytosterols exerted less severe effects than cholesterol oxides.…”

“…21,22 It was reported that they cause cellular damage in cultured macrophage-derived cell lines 23 and that hydroxysitosterol induces apoptosis of U937 cells, accompanied by a reduction of cellular glutathione. 24 Furthermore, numerous studies reported atherogenic 25,26 and cytotoxic properties [27][28][29][30] of cholesterol oxides, leading to apoptosis or necrosis in various cell types. 24,[31][32][33] They may also exert their effects by lowering cholesterol availability for cell membrane formation by inhibiting 3-hydroxy-methylglutaryl coenzyme A reductase (HMG-CoA reductase), a key enzyme in cholesterol synthesis.…”

“…24 Furthermore, numerous studies reported atherogenic 25,26 and cytotoxic properties [27][28][29][30] of cholesterol oxides, leading to apoptosis or necrosis in various cell types. 24,[31][32][33] They may also exert their effects by lowering cholesterol availability for cell membrane formation by inhibiting 3-hydroxy-methylglutaryl coenzyme A reductase (HMG-CoA reductase), a key enzyme in cholesterol synthesis. 34 Cholesterol oxides bind to specific membrane receptors or cytosolic binding proteins, leading to the perturbation of cholesterol synthesis.…”

Oxidation of β-sitosterol and campesterol in sunflower oil upon deep- and pan-frying of French fries

“…However, several aspects of the possible toxic effects of POP are still to be elucidated (Tomoyori et al 2004;Lea et al 2004). Maguire et al (2003) reported that β-sitosterol oxides exhibit less severe but similar toxicity patterns to those found for COP. On the other hand, Lea et al (2004) concluded that POP do not exhibit a genotoxic potential.…”

“…1) could have toxic effects on human organisms similar to those of cholesterol oxidation products (COP) (Garcia-Cruset et al 2002). POP were shown to be accumulated in the serum and liver of mice (Tomoyori et al 2004), and to have cytotoxic effects on mammalian cells (Maguire et al 2003). POP were identified in the plasma of human subjects in amounts ranging from 4.80 to 57.2 ng/mL (Grandgirard et al 2004).…”