Abstract P2047: Human Renal Proximal Tubule Cells Cultured Under High Salt Conditions Increase Angiotensin Type 2 Receptor Abundance In Secreted Exosomes

Abstract

The dopamine type 1 (D 1 R) and angiotensin type 2 (AT 2 R) are both natriuretic receptors that regulate renal sodium homeostasis. Aberrant D 1 R and AT 2 R mechanisms are implicated in hypertension, salt-sensitive hypertension, and in normotensive salt sensitives. Increased AT 2 R recruitment to the plasma membrane has been shown to occur when the D 1 R is stimulated by dopamine and increases with increased extracellular and intracellular sodium. RPTCs secrete exosomes which are plasma membrane vesicles between 50 and 90 nm in diameter and which encapsulate proteins and microRNA from the cell. We hypothesized that exosomal AT 2 R may reflect plasma membrane abundance of the RPTCs responding to the exposure to increased sodium. This study examined the abundance of the AT 2 R found on the surface of these exosomes in response to changing salt concentrations. Immortalized hRPTC were treated in serum free media cultured overnight with either an additional 50 mM sodium chloride or choline chloride as an osmotic equivalent, and exosomes were purified and concentrated from cell culture supernatant. The exosomes were then captured with magnetic lectin affinity beads and immunostained with fluorescent AT 2 R that increased in high salt conditions compared to vehicle control treated cells (VEH 71,884±7099 RFU, n=17, 190 mM Sodium, 94,180±5487 RFU, n=16, p= 0.018, t-test). The increase levels of AT 2 R are appropriate for their natriuretic activity. Future work will examine this response as it relates to salt sensitivity and inverse salt sensitivity of blood pressure as we previously reported using miRNA.