Abstract: FR-PO352
Complete Pik3c3 Deletion in Renal Proximal Tubule Cells Causes AKI Leading to CKD
Session Information
- CKD: Mechanisms - II
November 08, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: CKD (Non-Dialysis)
- 2103 CKD (Non-Dialysis): Mechanisms
Authors
- Liu, Ting, Medical College of Georgia at Augusta University, Augusta, Georgia, United States
- Yuan, Jialing, Medical College of Georgia at Augusta University, Augusta, Georgia, United States
- Humphreys, Benjamin D., Washington University School of Medicine, Clayton, Missouri, United States
- Dai, Caihong, Medical College of Georgia at Augusta University, Augusta, Georgia, United States
- Chen, Jian-Kang, Medical College of Georgia at Augusta University, Augusta, Georgia, United States
Background
Renal proximal tubules form the bulk of the kidney and are particularly sensitive to ischemic, toxic, and metabolic stress contributing to the pathogenesis of kidney disease. Class 3 phosphatidylinositol 3-kinase (Pik3c3) is the only PI3-kinase evolutionarily conserved from yeast to humans. However, the role of Pik3c3 in the proximal tubules in adult kidneys is unknown.
Methods
We generated a Pik3c3 gene-floxed mouse and crossed it with SLC34a1.CreERT2 mice to produce tamoxifen (TAM)-inducible renal proximal tubule cell (RPTC)-specific Pik3c3 heterozygous (Het) and homozygous knockout (KO) mice for comparison with appropriate control (Ctrl) littermates. Pik3c3 deletion was not induced until the mice reached 8 weeks old.
Results
Our data revealed that the proximal tubule expresses the highest level of Pik3c3 among all renal tubule segments. The Het mice are fertile and normal. However, the KO mice exhibited marked RPTC injury, indicated by cytoplasmic vacuolization, nuclear condensation and fragmentation as well as TUNEL-positive cells in the proximal tubules, leading to cell death and infiltration of inflammatory cells (including neutrophils) within 13 days after TAM induction of Pik3c3 deletion. Subsequently, the KO mice developed chronic kidney disease (CKD), evidenced by marked proliferation of a-smooth muscle actin-positive myofibroblasts, persistent infiltration of inflammatory cells (including macrophages and lymphocytes), and tubulointerstitial fibrosis, with elevated serum creatinine and BUN, after 3 months of Pik3c3 deletion. Mechanistically, in vivo animal studies and in vitro RPTC culture studies unveiled strikingly increased levels of LC3II/I, LAMP1 and activation of the initiator caspase 12 and the effector caspase 3 in response to Pik3c3 inactivation.
Conclusion
Our data indicate that complete Pik3c3 deletion in RPTC disturbed the endocytic and autophagic pathways and disrupted the homeostasis of intracellular protein sorting, leading to intracellular vacuolation and cell death involving activation of caspases 12 and 3. This study not only reveals an essential role of Pik3c3 in maintaining the homeostasis and survival of proximal tubule cells, but also provides a new model of progressive CKD.
Funding
- NIDDK Support