Cytotoxic effects of oxysterols produced during ozonolysis of cholesterol in murine GT1-7 hypothalamic neurons.
Ozone present in the photochemical smog or generated at the inflammatory sites is known to oxidize cholesterol and its 3-acyl esters. The oxidation results in the formation of multiple "ozone-specific" oxysterols, some of which are known to cause abnormalities in the metabolism of cholesterol and exert cytotoxicity. The ozone-specific oxysterols have been shown to favor the formation of atherosclerotic plaques and amyloid fibrils involving pro-oxidant processes. In the present communication, cultured murine GT1-7 hypothalamic neurons were studied in the context of cholesterol metabolism, formation of reactive oxygen species, intracellular Ca2 + levels and cytotoxicity using two most commonly occurring cholesterol ozonolysis products, 3beta- hydroxy-5-oxo-5,6-secocholestan-6-al (ChSeco) and 5beta, 6beta-epoxy-cholesterol (ChEpo). It was found that ChSeco elicited cytotoxicity at lower concentration (IC50 = 21 +/- 2.4 microM) than did ChEpo (IC50 = 43 +/- 3.7 microM). When tested at their IC50 concentrations in GT1-7 cells, both ChSeco and ChEpo resulted in the generation of ROS, the magnitude of which was comparable. N-acetyl-l-cysteine and Trolox attenuated the cytotoxic effects of ChSeco and ChEpo. The intracellular Ca2 + levels were not altered by either ChSeco or ChEpo. Methyl-beta-cyclodextrins, which cause depletion of cellular cholesterol, prevented ChSeco- but not ChEpo-induced cytotoxicity. The cell death caused by ChEpo, but not ChSeco, was prevented by exogenous cholesterol. Although oxidative stress plays a significant role, the results of the present study indicate differences in the pathways of cell death induced by ChSeco and ChEpo in murine GT1-7 hypothalamic neurons.
Sathishkumar
K
K
Department of Environmental Toxicology, The Health Research Center, Southern University and A&M College, Baton Rouge, LA 70813, USA.
Murthy
Subramanyam N
SN
Uppu
Rao M
RM
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D010126:Ozone / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D047392:beta-Cyclodextrins / Q000378:metabolism
D017382:Reactive Oxygen Species; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D010126:Ozone; D002784:Cholesterol; D002118:Calcium