Endonuclease G (EndoG) Inhibits DNase I-Mediated Apoptosis and DNA Repair in Kidney Tubular Epithelial Cells During Cisplatin Injury
- AKI: Mechanisms - III
November 04, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 103 AKI: Mechanisms
- Basnakian, Alexei G., University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
- Li, Shenyang, Central Arkansas Veterans Healthcare System John L McClellan Memorial Veterans Hospital, Little Rock, Arkansas, United States
- Shelton, Randal Shane, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
- Fite, Todd, Central Arkansas Veterans Healthcare System John L McClellan Memorial Veterans Hospital, Little Rock, Arkansas, United States
We have previously shown that kidney tubular epithelial (KTE) endonuclease G (EndoG, EG) is induced by cisplatin and translocated from mitochondria to the nucleus during apoptosis. However, it is unknown whether EG causes apoptotic DNA fragmentation and how it leads to cell death. EG is the only apoptotic endonuclease found in the nucleus during apoptosis, has RNase activity, and induces inactive truncated isoform of another endonuclease, DNase I (DI).
We hypothesized that the role of EG in apoptosis depends on the presence of DI in the cell, and used cisplatin kidney injury in vitro and in vivo models to test this.
To our surprise, although EG was often present in TUNEL-positive nuclei of KTE cells in mice treated with cisplatin (20 mg/kg), it did not colocalize with DNA fragmentation measured by TUNEL or with endonuclease activity measured by a fluorescent probe in apoptotic nuclei in cultured KTE NRK-52E cells. EG overexpression in DI-positive NRK-52E cells showed EG was not cytotoxic but instead protective against cisplatin injury (60 µM) as determined by flow cytometry. EG overexpression induced alternative splicing and inactivation of DI. When the same experiment was repeated using DI-negative HCC1954 cells, EG was cytotoxic and promoted cisplatin-induced cell death. Further study showed that EG was induced but was not cytotoxic in cisplatin kidney injury in vivo. After injection of cisplatin, no protection in EG null mice versus wild-type (WT) mice was observed by BUN, SCr, or histology. EG induction by cisplatin in WT mice was associated with the decrease of native DI expression and the appearance of inactive truncated DI. In addition to DNase I inactivation, an overexpression of EG in mouse KTE TKPTS cells induced mRNA alternative splicing (inactivation) of several DNA repair genes.
This study showed that EG acts as a proapoptotic enzyme in the absence of DI and it is anti-apoptotic in the presence of DI in KTE cells and the kidney during cisplatin injury. In addition, the overexpression of EG causes inactivation of several DNA repair genes thus likely causing an aggravation of the cisplatin injury.
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