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Abstract: PO1834

Toll-Like Receptor 4 (TLR4) an Effector of Renal Inflammation and Sodium (Na) Transport

Session Information

Category: Hypertension and CVD

  • 1403 Hypertension and CVD: Mechanisms

Authors

  • Oliveira, Karin Carneiro de, Stony Brook University Renaissance School of Medicine, Stony Brook, New York, United States
  • Repetti, Robert Lawrence, Stony Brook University Renaissance School of Medicine, Stony Brook, New York, United States
  • Rohatgi, Rajeev, Northport VA Medical Center, Northport, New York, United States
Background

Na sensitivity of blood pressure (BP) is risk factor for cardiovascular mortality compared to Na resistant subjects. In addition, constrained cholesterol (chol) efflux is novel predictor for future cardiovascular events. Dysregulation of ABCA1, a chol efflux protein, is implicated in hypertension and kidney disease while ABCA1 ablation in macrophages stimulates TLR4 dependent inflammation. We surmised that tubular ABCA1 depletion similarly enhances TLR4 dependent inflammation in a model of Na sensitivity.

Methods

Transgenic mice (TgPAX8rtTA;tetO-Cre/+), which express CRE in tubular epithelia when fed doxycycline, were bred with mice expressing floxed ABCA1 to generate mice deficient in tubular ABCA1 (FF). Western blotting was performed on whole kidney protein lysate, renal plasma membrane (PM), and mpkCCD cells. Amiloride sensitive short-circuit current (AIsc) was measured in shear and static exposed mpkCCD cells.

Results

FF mice are phenotypically consistent with Na sensitivity (abstract# 3600350). FF and littermate controls (WT) mice fed a chol enriched diet for 6 weeks, a low Na and a high Na diet for 1 week were euthanized and kidneys extracted. Steady-state protein expression of NLRP3 inflammasome increased in ABCA1 deficient (1.5±0.1; n=7 p<0.05) vs. WT kidneys (1.0±0.1; n=5); however, TLR4, a receptor that stimulates NLRP3, was unchanged. Western blot of renal PM showed enhanced TLR4 abundance in FF (1.9±0.3; n=3; p<0.05) vs. WT (1.0±0.2; n=3) kidneys. Because Na enriched diets augment urine volume, tubular flow, and, thus fluid shear stress (FSS), 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 10 µM basolateral TAK242, a TLR4 antagonist. FSS (n=9; 1.6±0.2, p<0.05) and 5 µM PSC (n=6; 1.7±0.2, p<0.05), an ABCA1 inhibitor, also induced NLRP3 protein abundance compared to static cells (n=9; 1.0±0.1) and (n=5, 1.0±0.1), respectively.

Conclusion

ABCA1 tubular deficiency enhances TLR4 PM localization and activation in kidney to induce NLRP3 while a cell model confirms that FSS and reduced ABCA1 stimulate NLRP3 abundance. TLR4 also regulates FSS-induced ENaC-dependent Na transport.

Funding

  • Veterans Affairs Support