Abstract: FR-PO221

Cytoprotective Role of Autophagy in Angiotensin II-Induced Podocyte Apoptosis

Session Information

Category: Cell Biology

  • 202 Apoptosis, Proliferation, Autophagy, Cell Senescence, Cell Transformation

Author

  • Ha, Tae-Sun, Chungbuk National University College of Medicine, Cheongju-si, Korea (the Republic of)
Background

Autophagy and apoptosis are two cellular processes through which injured and aging cells or organelles are eliminated. Angiotensin II (Ang II) induces podocyte injury resulting in apoptosis in vitro and in vivo. However, the relationship between autophagy and apoptosis in Ang II-induced podocyte injury is unknown and the role of Ang II-induced autophagy in podocyte survival or death remains unclear. We investigated the sequential relationship between autophagy and apoptosis in Ang II-induced podocytes as well as the role of PI3-kinase.

Methods

Mouse podocytes were incubated in media containing various concentrations of Ang II and at different incubation times. Cell survival/death-modifying reagents and Atg5 siRNA were applied. The changes of podocyte autophagy and apoptosis were observed by electron microscopy, confocal imaging, western blotting, TUNEL, and FACS assay according to the presence of Ang II.

Results

Ang II enhanced the podocyte expression of the autophagic proteins, LC3A/B-II and beclin-1, and also increased the number of autophagosomes compared with control cells at early phase of 12 hours in a dose-dependent manner. This pro-autophagic effect of Ang II was inhibited by pretreatment with 3-methyladenine (3-MA), a PI3-kinase class III inhibitor. Atg5 siRNA reduced LC3 puncta levels and increased the number of apoptotic podocytes over that observed with Ang II treatment at 12 hours. Thereafter, the Ang II-induced enhancement in autophagy decreased, whereas, podocyte apoptosis appeared later at 24 hours in concentration- and time-dependent manners in FACS and TUNEL assays. 3-MA and LY294002 further increased Ang II-induced podocyte apoptosis. Suppression of autophagy by Atg5 siRNA could induce podocyte apoptosis and further augment high-dose Ang II-induced podocyte apoptosis.

Conclusion

We suggest that Ang II induced autophagy in mouse podocytes prior to apoptosis as an early adaptive cytoprotective mechanism for podocyte survival after Ang II treatment and the imbalance between autophagy and apoptosis causes podocyte injury.

Funding

  • Government Support - Non-U.S.