Apigenin-induced apoptosis in A375 and A549 cells through selective action and dysfunction of mitochondria.
We isolated apigenin (5,7,4'-trihydroxy flavone) from ethanolic extract of Lycopodium clavatum (LC) used as a homeopathic mother tincture for treatment of various diseases. We assessed the anticancer potentials of the compound using human malignant melanoma cell line A375 and a lung carcinoma cell line A549 and focussed on its putative molecular mechanism of action on apoptosis induction. We examined the cytotoxicity of apigenin in both cancer cells and normal peripheral blood mononuclear cells (PBMC). A375 cells were more prone to apigenin-induced apoptosis, as compared with A549 cells after 24 h of treatment, while PBMC showed little or no cytotoxicity to apigenin. We also evaluated the effects of apigenin on interaction with DNA by comparative analysis of circular dichroism spectral data and melting temperature profiles (Tm) of calf thymus DNA (CT-DNA) treated with or without apigenin. Reactive oxygen species (ROS) accumulation in mitochondria, super-oxide dismutase and total thiol group (GSH) activities were also analyzed. The apoptotic process involved mitochondrial pathway associated with apigenin-DNA interaction, DNA fragmentation, ROS accumulation, cytochrome c (cyt c) release and mitochondrial transmembrane potential depolarization, Bax, caspase 3, 9, PARP, up-regulation, Bcl-2 down-regulation and down-regulation of cyt c in the mitochondrial fraction. Results of mitochondrial inner membrane swelling measurements, intracellular ADP/ATP ratio and ATPase activity showed that in A549 cells, apigenin did not appear to directly target the mitochondrial oxidative phosphorylation system but rather acted at an upstream step to activate the mitochondrial apoptotic pathway. However, apigenin could directly target and impair mitochondrial function in A375 cells by breaking down their oxidative phosphorylation system. Collectively, these results suggest that apigenin exhibits anticancer potential in A375 and A549 cells that may be mediated through DNA interaction, damage and mitochondrial dysfunction either by direct or indirect action on mitochondrial oxidative phosphorylation system.
Cytogenetics and Molecular Biology Laboratory, Department of Zoology, University of Kalyani, Kalyani 741235,  India.
Sreemanti
S
Das
Jayeeta
J
Das
Asmita
A
Samadder
Naoual
N
Boujedaini
Anisur Rahman
AR
Khuda-Bukhsh
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000970:Antineoplastic Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D047310:Apigenin / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D003603:Cytotoxins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects*; D006801:Humans; D032502:Lycopodium / Q000737:chemistry; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D008928:Mitochondria / Q000378:metabolism* / Q000473:pathology; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010936:Plant Extracts / Q000737:chemistry; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
D000970:Antineoplastic Agents; D003603:Cytotoxins; D010936:Plant Extracts; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D000244:Adenosine Diphosphate; D047310:Apigenin; D000255:Adenosine Triphosphate; D045304:Cytochromes c; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053453:Caspase 9