gamma-Linolenic acid and eicosapentaenoic acid induce modifications in mitochondrial metabolism, reactive oxygen species generation, lipid peroxidation and apoptosis in Walker 256 rat carcinosarcoma cells.
The polyunsaturated fatty acids gamma-linolenic acid (GLA) and eicosapentaenoic acid (EPA) are cytotoxic to tumour cells. GLA inhibits Walker 256 tumour growth in vivo, causing alterations in mitochondrial ultrastructure and cellular metabolism. The objective of the present study was to investigate the mechanisms behind fatty acid inhibition of Walker 256 tumour growth under controlled in vitro conditions. At a concentration of 150 microM, both GLA and EPA caused a decrease in cell proliferation and an increase in apoptotic index. Increases in reactive oxygen species (ROS) and lipid peroxide production were identified, as well as alterations in energy metabolism and the deposition of large amounts of triacylglycerol in the form of lipid droplets. Mitochondrial respiratory chain complexes I+III and IV had significantly decreased activity and mitochondrial membrane potential was greatly diminished. Intracellular ATP concentrations were maintained at 70-80% of control values despite the decreased mitochondrial function, which may be in part due to increased utilisation of glucose for ATP generation. Cytochrome c release from mitochondria was found, as was caspase-3-like activation. DNA fragmentation in situ revealed many apoptotic events within the cell population. The mechanism(s) by which ROS and lipid peroxides induce apoptosis remains unclear, but the effects of GLA and EPA appear to involve the mitochondrial pathway of apoptosis induction leading to cytochrome c release, caspase activation, loss of mitochondrial membrane potential and DNA fragmentation.
Colquhoun
A
A
Departamento de Histologia e Embriologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Brazil. alison@usp.br
Schumacher
R I
RI
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002279:Carcinoma 256, Walker; D002455:Cell Division / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D015118:Eicosapentaenoic Acid / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D017965:gamma-Linolenic Acid / Q000494:pharmacology*
D017382:Reactive Oxygen Species; D019344:Lactic Acid; D017965:gamma-Linolenic Acid; D015118:Eicosapentaenoic Acid; D005947:Glucose