Citation

  • Authors: Przepiórska K. et al.
  • Year: 2022
  • Journal: Mol Neurobiol
  • Applications: in vitro / siRNA / INTERFERin
  • Cell type: Mouse primary neocortical cells

Method

To inhibit the expression of the Becn1 and Atg7 genes in neocortical cells, specific Becn1 and Atg7 siRNAs (Santa Cruz Biotechnology Inc., USA) were used as previously described. The siRNAs (at a final concentration of 50 nM) containing transfection reagent (INTERFERin) were applied in antibiotic-free medium for 7 h. After transfection, the culture medium was replaced with standard medium containing antibiotics, and neuronal cells were incubated until the next day of the experiment. Control cells were transfected with negative siRNA, i.e., scrambled sequence that did not lead to specific degradation of any known cellular mRNA. To verify the mRNA silencing, we measured the expression levels of specific mRNAs. As previously described, Becn1 and Atg7 expression levels decreased by 68% and 57%, respectively.

Abstract

Amorfrutin B is a selective modulator of the PPARγ receptor, which has recently been identified as an effective neuroprotective compound that protects brain neurons from hypoxic and ischemic damage. Our study demonstrated for the first time that a 6-h delayed post-treatment with amorfrutin B prevented hypoxia/ischemia-induced neuronal apoptosis in terms of the loss of mitochondrial membrane potential, heterochromatin foci formation, and expression of specific genes and proteins. The expression of all studied apoptosis-related factors was decreased in response to amorfrutin B, both during hypoxia and ischemia, except for the expression of anti-apoptotic BCL2, which was increased. After post-treatment with amorfrutin B, the methylation rate of the pro-apoptotic Bax gene was inversely correlated with the protein level, which explained the decrease in the BAX/BCL2 ratio as a result of Bax hypermethylation. The mechanisms of the protective action of amorfrutin B also involved the inhibition of autophagy, as evidenced by diminished autophagolysosome formation and the loss of neuroprotective properties of amorfrutin B after the silencing of Becn1 and/or Atg7. Although post-treatment with amorfrutin B reduced the expression levels of Becn1, Nup62, and Ambra1 during hypoxia, it stimulated Atg5 and the protein levels of MAP1LC3B and AMBRA1 during ischemia, supporting the ambiguous role of autophagy in the development of brain pathologies. Furthermore, amorfrutin B affected the expression levels of apoptosis-focused and autophagy-related miRNAs, and many of these miRNAs were oppositely regulated by amorfrutin B and hypoxia/ischemia. The results strongly support the position of amorfrutin B among the most promising anti-stroke and wide-window therapeutics.

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