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Malik F, Kumar A, Bhushan S, Khan S, Bhatia A, Suri KA, Qazi GN, Singh J.
Apoptosis. 2007 Nov;12(11):2115-33
Reactive oxygen species
generation and mitochondrial dysfunction in the apoptotic cell death of human
myeloid leukemia HL-60 cells by withaferin A with concomitant protection
by N-acetyl cysteine.
Division of Pharmacology, Indian Institute of Integrative Medicine, Council
of Scientific and Industrial Research, Canal Road, Jammu-Tawi 180001, India.
Induction of apoptosis in cancer cells has become the major focus of
anti-cancer therapeutics development. WithaferinA, a major chemical constituent
of Withania somnifera, reportedly shows cytotoxicity in a variety of tumor cell
lines while its molecular mechanisms of action are not fully understood. We
observed that withaferinA primarily induces oxidative stress in human leukemia
HL-60 cells and in several other cancer cell lines. The withanolide induced
early ROS generation and mitochondrial membrane potential (Deltapsi(mt)) loss,
which preceded release of cytochrome c, translocation of Bax to mitochondria and
apoptosis inducing factor to cell nuclei. These events paralleled activation of
caspases -9, -3 and PARP cleavage. WA also activated extrinsic pathway
significantly as evidenced by time dependent increase in caspase-8 activity
vis-à-vis TNFR-1 over expression. WA mediated decreased expression of Bid may be
an important event for cross talk between intrinsic and extrinsic signaling.
Furthermore, withaferinA inhibited DNA binding of NF-kappaB and caused nuclear
cleavage of p65/Rel by activated caspase-3. N-acetyl-cysteine rescued all these
events suggesting thereby a pro-oxidant effect of withaferinA. The results of
our studies demonstrate that withaferinA induced early ROS generation and
mitochondrial dysfunction in cancer cells trigger events responsible for
mitochondrial -dependent and -independent apoptosis pathways.
PMID: 17874299
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