2760 - Role of ATP Binding Cassette Subfamily A Member 1 (ABCA1) in Renal Toxicity

A. Ahmad¹, M. Alnukhali¹, M. Ali¹, A. Sloan², R. Levy³, Y. Zeidan⁴, S. Merscher⁵, A. Fornoni⁶, S. M. Welford⁷, and A. Pollack⁸; ¹Department of Radiation Oncology, University of Miami/Sylvester Comprehensive Cancer Center, Miami, FL, Miami, FL, ²Peggy and Harold Katz Family Drug Discovery Center and Katz Family Division of Nephrology and Hypertension, Department of Medicine, University of Miami, Miami, Florida, USA, Miami, FL, ³Department of Microbiology and Immunology, University of Miami Miller School of Medicine and Sylvester Comprehensive Cancer Center, University of Miami, Miami, FL, USA., Miami, FL, ⁴Lynn Cancer Institute, Baptist Health South Florida, Boca Raton, FL, ⁵Department of Medicine/Division of Nephrology and Hypertension, University of Miami School of Medicine, Miami, FL, ⁶Katz Family Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, FL, ⁷Case Western Reserve University, Cleveland, OH, ⁸Department of Radiation Oncology, University of Miami/Sylvester Comprehensive Cancer Center, Miami, FL

Purpose/Objective(s): Cisplatin-induced kidney damage, compounded by radiation therapy, leads to acute kidney injury (AKI) and chronic kidney disease (CKD), necessitating renal replacement therapies. We hypothesize that chemoradiotherapy-induced ABCA1 deficiency may disturb cholesterol metabolism, making podocytes susceptible and cancer cells resistant to treatment-induced injury. Materials/

Methods: To assess podocyte response to radiation, cultured podocytes were exposed to varying doses of radiation, and their cell index was monitored using a real-time cell index assay (RTCA). Cisplatin-induced podocytopathy was evaluated by treating an androgen-sensitive human prostate adenocarcinoma cell line (LNCaP) and human kidney cells (podocytes) with Cisplatin (10µM) ± ABCA1 inducer (GW3965; Sigma; 10µM) in an e-plate reader for 24 hours.,. Nuclear membrane fluidity was measured using an Abcam Membrane Fluidity Kit (ab189819) on nuclei isolated from ABCA1scrabmle (SC) and siABCA1 cell lines with PDA and pluronic F-127. Mice received bilateral kidney X-irradiation (4Gy, 14Gy, or fractionated 6x5Gy), and changes in ABCA1 expression and podocyte count were quantified using IHC.
Results: The podocyte index was significantly decreased post 4 Gy (5.1±0.4 vs. 4.8± 0.2, p<0.0492) and further reduced at 8Gy (4.8±0.2 vs. 3.8± 0.25, p<0.0098), indicating a dose-dependent decrease in podocyte survival after RT. Cisplatin treatment alone reduces LNCaP (2.06±0.6 vs. 1.1± 0.1, p<0.0001) and podocyte differentiation (4.3±0.2 vs. 0.5± 0.1, p<0.0001). However, LXR agonist treatment enhances Cisplatin efficacy against LNCaP (2.06±0.2 vs. 0.53± 0.2, p<0.0001) and increases podocyte growth (6.06±0.3 vs. 2.1± 0.3, p<0.0001). Nuclear membrane fluidity assay indicates a significant reduction in podocyte nuclear membrane fluidity in siABCA1 podocytes compared to ABCA1 scramble podocytes(0.53±0.1 vs. 0.3± 0.08, p<0.0113) [3]. In vivo, studies show a decrease in ABCA1 expression in tubular and glomerular cells, including podocytes, after 4 Gy (21.69±4.8 vs. 11.47± 3.1, p<0.0001), which was further reduced after 14 Gy but not significantly (11.47±3.1 vs. 10.2± 3.8, p<0.8326). Fractionated 6x5Gy also resulted in a significant reduction in ABCA1 expression (21.69±4.7 vs. 12.73± 3.8, p<0.0001), with a lesser reduction compared to single dose 14Gy, though insignificant (10.2±3.9 vs. 12.73± 3.8, p< 0.3360).
Conclusion: Our findings indicate that ABCA1 deficiency makes podocytes susceptible and cancer cells resistant to radiation injury. Targeting pathways associated with ABCA1-mediated cholesterol metabolism might offer a promising approach to alleviate kidney injury while improving the effectiveness of cancer treatment.