Abstract: FR-PO409
Renal ABCA1 Deficiency Induces TLR4 that Regulates Epithelial Sodium Channel (ENaC)
Session Information
- Hypertension and CVD: Basic
November 03, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Hypertension and CVD
- 1601 Hypertension and CVD: Basic
Authors
- Carneiro de Oliveira, Karin, Icahn School of Medicine at Mount Sinai, New York, New York, United States
- Wei, Yuan, Icahn School of Medicine at Mount Sinai, New York, New York, United States
- Repetti, Robert Lawrence, Northport VA Medical Center, Northport, New York, United States
- Rohatgi, Rajeev, James J Peters VA Medical Center, Bronx, New York, United States
Background
Na sensitive blood pressure (BP) and restricted cholesterol (chol) efflux are risk factors for cardiovascular mortality. In preliminary studies, renal tubular ablation of ABCA1, a chol efflux protein, leads to greater systolic BP (SBP) vs control (WT) mice, while a low Na diet quenches this difference. Moreover, toll-like receptor 4 (TLR4) is stimulated by chol and associated with Na sensitive models. We hypothesize that TLR4 contributes to cation transport in an ABCA1 deficient model.
Methods
Transgenic mice, which express a doxycycline inducible CRE in tubules, were bred with mice expressing floxed ABCA1 to produce mice deficient in ABCA1 (FF). Western blotting of kidney and cortical collecting duct (mpkCCD) cell lysate was performed. Immunofluorescence (IF) was performed on kidneys and amiloride sensitive short-circuit current (AIsc) measured in mpkCCD cells.
Results
Mice were fed a 1% chol diet (X 6 weeks), a low Na and a high Na diet for 1 week each and then euthanized and kidneys extracted. TLR4 expression was enhanced in FF (1.9±0.3; n=3; p<0.05) vs. WT (1.0±0.2; n=3) kidneys. Phospho-ERK(pERK) was 2.3±1.3 (p=0.052) fold greater in FF(n=5) than WT(n=5) kidneys. IF of kidneys localized pERK to CDs while TLR4 was seen in CDs and non-CDs. Next, mpkCCD cells were incubated with PSC833 (PSC, 5 μM), an ABCA1 inhibitor, which increased abundance of pERK, (1.7±0.3; n=4; p<0.05) vs. untreated cells (1.0±0.2; n=4). Dual TLR4 antagonist (TAK242 10μM) and PSC suppressed γ-ENAC expression vs. untreated and PSC alone. While TAK242 did not affect AIsc in untreated mpkCCD cells, TAK242 repressed AIsc in PSC treated mpkCCD (11.2±2.2 μA/cm2; n=6; p<0.05) vs PSC alone (17.1±3.1 μA/cm2). Fluid shear stress (FSS) induces pERK, and ERK inhibition suppresses flow-induced in Na absorption (Repetti et al. 2021). The role of TLR4 signaling on FSS mediated Na transport was tested in mpkCCD cells. The AIsc in FSS (0.4 dynes/cm2) exposed cells was greater (40.8±2.1 μA/cm2;n=20, p<0.05) than in static cells (26.7±1.6 μA/cm2; n=20) and the FSS induced AIsc was reduced (31.5±2.6 μA/cm2; n=18, p<0.05 vs FSS exposed cells) by TAK242.
Conclusion
ABCA1 deficiency induces TLR4 and pERK abundance in renal CD while in mpkCCD cells exposed to FSS or ABCA1 inhibition sensitizes them to TLR4 dependent AIsc. We speculate repression of chol efflux enhances TLR4 dependent activation of pERK and AIsc.
Funding
- Veterans Affairs Support