Studying Ganoderma lucidum as a source of molecular inducers of autophagy
Artigo de Conferência
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resumo
Autophagy is one of the three main mechanisms of
programmed cell death[1]. One of the basis of cancer
therapy is to induce death of tumour cells. There are several
clinically approved molecules that induce cell death[2,3], but
unfortunately not all tumours highly resistant to cell death
respond to the existing therapies. Therefore, the search
for new molecules capable of inducing tumour cell death
is an area of growing interest. In this context, modulators
of autophagy have become very attractive in recent years.
Previous work performed by some of us has shown that
methanolic extracts of the medicinal mushroom Ganoderma
lucidum were modulators of cellular autophagy[4]. The
aim of the present work was to further understand the
cellular mechanisms involved in the autophagy modulation
and to identify bioactive compounds responsible for this
modulation.
A methanolic extract obtained by cold extraction (-20ºC) from
G. lucidum was studied with respect to its ability to induce
autophagy in a gastric adenocarcinoma cell line (AGS). The
presence of autophagic vacuoles was observed following
transfection of cells with a mCherry-LC3 expression vector
and the levels of some autophagic proteins were analysed
by Western Blot. Cells were also treated with the lysossomal protease inhibitors E-64d/pepstatin together with the
extract, in order to confirm if the extract induced autophagy
or a decrease in the autophagic flux. The levels of the
autophagic proteins after this treatment were also evaluated
by Western Blot.
An increase in the autophagic vacuoles was observed in
cells treated with the extract (concentrations corresponding
to the GI50 and 2×GI50) 24h before transfection with the
mCherry-LC3 vector. In addition, treatment of cells with
the same concentrations of the extract for 48h induced an
increase in the expression of LC3-II together with a slight
reduction in the levels of p62, particularly with the highest
concentration. Additionally, cells treated with the extract
together with E-64d/pepstatin expressed higher levels of
LC3-II and p62, when compared with cells treated only with
the extract, indicating that G. lucidum caused an induction of
autophagy rather than a decrease in the autophagic flux.
With these results we can conclude that the methanolic
extract from the mushroom G. lucidum may be a source of
compounds capable of inducing autophagy. Further studies
to identify the bioactive compounds present in the tested
extract and responsible for such activity are still ongoing.
