The induction of apoptosis in human cervical carcinoma (HeLa) cells by gamma-linolenic acid.
A high concentration (50 micrograms/ml) of gamma-linolenic acid (GLA) induced morphological lesions typical of apoptosis, as well as DNA fragmentation, in HeLa cells. A lower concentration of GLA (20 micrograms/ml), caused an increased proliferating cell nuclear antigen (PCNA) labelling, with 92.7% cells positive, compared to 27.7% at a concentration of 50 micrograms/ml GLA. In correlation with these results, the number of cells with degraded DNA below the G0/G1 peak increased significantly in the 50 micrograms/ml GLA-treated cells, but increased only slightly in cells exposed to the lower level of GLA. The high levels of PCNA induced by 20 micrograms/ml GLA, in both G1 and S phases, may indicate a state of DNA repair synthesis, whilst at the higher concentration of GLA, most of the cells became apoptotic. Since apoptosis is associated with the deregulation of c-Myc expression, and as the Raf-1-MAP kinase cascade activates the expression of c-Myc and c-Jun, we investigated the effects of 20 and 50 micrograms/ml GLA on the Raf-1, c-Myc and c-Jun levels, and on the activity of MAP kinase. The results showed that 50 micrograms/ml GLA lowered the activity of MAP kinase. As expected with the decreased MAP kinase activity in the cells exposed to the higher level GLA, the c-Jun levels were also lowered. The levels of c-Myc, however, were increased. It is therefore possible that the deregulated expression of c-Myc in the HeLa cells exposed to the high level of GLA (50 micrograms/ml) may contribute to the induction of apoptosis in HeLa cells.
de Kock
M
M
Department of Physiology, Medical University of Southern Africa.
Lottering
M L
ML
Grobler
C J
CJ
Viljoen
T C
TC
le Roux
M
M
Seegers
J C
JC
D017209:Apoptosis / Q000187:drug effects*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D053938:DNA Fragmentation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D016193:G1 Phase / Q000187:drug effects; D006367:HeLa Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D018809:Proliferating Cell Nuclear Antigen / Q000187:drug effects / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000187:drug effects / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000187:drug effects / Q000235:genetics; D019908:Proto-Oncogene Proteins c-raf; D016196:S Phase / Q000187:drug effects; D014158:Transcription, Genetic; D017965:gamma-Linolenic Acid / Q000494:pharmacology*
D018809:Proliferating Cell Nuclear Antigen; D011518:Proto-Oncogene Proteins; D016755:Proto-Oncogene Proteins c-jun; D016271:Proto-Oncogene Proteins c-myc; D017965:gamma-Linolenic Acid; D004247:DNA; D000242:Cyclic AMP; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases