Abstract: SA-PO806
Twist1 in Kidney Epithelium but Not Macrophages Propagates Aristolochic Acid Nephropathy
Session Information
- Molecular Mechanisms of CKD - III
October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: CKD (Non-Dialysis)
- 1903 CKD (Non-Dialysis): Mechanisms
Authors
- Ren, Jiafa, Duke University Medical Center, Durham, North Carolina, United States
- Wen, Yi, Southeast University, Nanjing, China
- Lu, Xiaohan, Duke University, Durham, North Carolina, United States
- Privratsky, Jamie, Duke University Medical Center, Durham, North Carolina, United States
- Crowley, Steven D., Duke University Medical Center, Durham, North Carolina, United States
Background
Aristolochic acid, the causative agent in Chinese herbal and Balkan nephropathies, triggers persistent tubular injury and interstitial inflammation culminating in renal fibrosis. The transcription factor Twist1 induces pro-fibrotic gene expression programs in renal tubular cells (RTCs) but suppresses pro-fibrotic cytokines in macrophages. To discriminate these opposing, cell-specific actions of Twist1 in CKD, we subjected mice with RTC- or macrophage-specific Twist1 deficiency to chronic aristolochic acid nephropathy (AAN).
Methods
Mice with a floxed allele for the gene encoding Twist1 were backcrossed to the injury prone 129/SvEv strain and bred with 129/SvEv Ksp-Cre or LysM-Cre mice to yield Twist1 “KKO” or “MKO” mice with RTC- or macrophage-specific Twist1 deletion, respectively. AA (5mg/kg IP) was injected into Twist1 KKO, Twist1 MKO, and wild-type (WT) littermate control mice every other day for 12 days.
Results
5 weeks after the last AA injection, Twist1 KKO mice compared to WTs had attenuated CKD as measured by BUN (41 ± 4 vs 52 ± 3 mg/dl; p = 0.035), blinded injury scores of PAS stains (2.0 ± 0.3 vs 2.9 ± 0.2; p = 0.038), and renal NGAL mRNA levels (0.6 ± 0.1 vs 1.0 ± 0.1; p = 0.036). Twist1 deletion in RTCs ameliorated kidney fibrosis as exhibited by reduced mRNA for Col-I (0.69 ± 0.05 vs 1.00 ± 0.09; p = 0.022) and TGF-β1 (0.81 ± 0.05 vs 1.00 ± 0.05; p = 0.019) and decreased protein levels of fibronectin (0.60 ± 0.03 vs 1.00 ± 0.07; p< 0.001) and α-SMA (0.55 ± 0.06 vs 1.00 ± 0.06; p＜0.001). Twist1 in RTCs also secondarily regulated innate immune responses in the kidney as Twist1 KKO kidneys showed reduced mRNA expression for the macrophage chemokine CCL2 (0.72 ± 0.07 vs 1.00 ± 0.10; p = 0.046) and cytokine TNF-a (0.73 ± 0.08 vs 1.00 ± 0.08; p = 0.038). Accordingly, flow cytometric analysis after 5 weeks of AAN revealed reduced numbers of CD64+ (45906 ± 5279 vs 62986 ± 4822; p = 0.03) and F4/80+ (49949 ± 4441 vs 65581 ± 5005; p = 0.033) CD11b+Ly6G- macrophages in the Twist1 KKO kidneys versus WT controls. By contrast, robust deletion of Twist1 directly from myeloid cells in the Twist1 MKO cohort (>80%, p < 0.0001) had no impact at 5 weeks on renal tubular injury, interstitial fibrosis, or local inflammation.
Conclusion
Twist1 in RTCs rather than in myeloid cells regulates chronic inflammation and injury in the kidney during AAN.
Funding
- NIDDK Support