Intrarenal transfer of an intracellular fluorescent fusion of angiotensin II selectively in proximal tubules increases blood pressure in rats and mice

Abstract

Li XC, Cook JL, Rubera I, Tauc M, Zhang F, Zhuo JL. Intrarenal transfer of an intracellular fluorescent fusion of angiotensin II selectively in proximal tubules increases blood pressure in rats and mice. Am J Physiol Renal Physiol 300: F1076 -F1088, 2011. First published February 9, 2011 doi:10.1152/ajprenal.00329.2010.-The present study tested the hypothesis that intrarenal adenoviral transfer of an intracellular cyan fluorescent fusion of angiotensin II (ECFP/ ANG II) selectively in proximal tubules of the kidney increases blood pressure by activating AT1 (AT1a) receptors. Intrarenal transfer of ECFP/ANG II was induced in the superficial cortex of rat and mouse kidneys, and the sodium and glucose cotransporter 2 (sglt2) promoter was used to drive ECFP/ANG II expression selectively in proximal tubules. Intrarenal transfer of ECFP/ANG II induced a time-dependent, proximal tubule-selective expression of ECFP/ANG II in the cortex, which peaked at 2 wk and was sustained for 4 wk. ECFP/ANG II expression was low in the glomeruli and the entire medulla and was absent in the contralateral kidney or extrarenal tissues. At its peak of expression in proximal tubules at day 14, ANG II was increased by twofold in the kidney (P Ͻ 0.01) and more than threefold in proximal tubules (P Ͻ 0.01), but remained unchanged in plasma or urine. Systolic blood pressure was increased in ECFP/ANG II-transferred rats by 28 Ϯ 6 mmHg (P Ͻ 0.01), whereas fractional sodium excretion was decreased by 20% (P Ͻ 0.01) and fractional lithium excretion was reduced by 24% (P Ͻ 0.01). These effects were blocked by losartan and prevented in AT1a knockout mice. Transfer of a scrambled ECFP/ANG IIc had no effects on blood pressure, kidney, and proximal tubule ANG II, or sodium excretion. These results provide evidence that proximal tubule-selective transfer of an intracellular ANG II fusion protein increases blood pressure by activating AT1a receptors and increasing sodium reabsorption in proximal tubules. adenoviral gene delivery; G protein-coupled receptors; intracrine peptides; losartan; renin-angiotensin-aldosterone system; urinary sodium excretion THE RENIN-ANGIOTENSIN SYSTEM (RAS) is long recognized to exist and function as dual extracellular (endocrine and/or paracrine) and intracellular (or intracrine) vasoactive hormonal systems. The extracellular system includes circulating and local tissue ANG II, which plays the classic roles of ANG II through activation of cell surface G protein-coupled ANG II receptors (GPCRs) (6,21,30,35). The intracellular system includes intracellularly formed ANG II (1-5, 8 -10, 12, 19, 40) and extracellular ANG II internalized through type 1 (AT 1 ) receptor-mediated endocytosis (14,15,18,19,25,27,39). The roles of circulating and paracrine ANG II and G protein-coupled signaling transduction mechanisms via activation of cell surface receptors have been extensively studied (6,21,30,35). By contrast, whether intracellular ANG II may induce any physiological effects remains largely unknown. The slow progress in our under...

Intracellular angiotensin II activates rat myometrium

“…Whether or not the location of functional angiotensin II receptors plays a role in these differences it is not known. While most of evidence for functional intracellular angiotensin II receptors is provided by in vitro, or ex vivo studies, very recently, an elegant study using an innovative approach established the physiological in vivo effects of cytoplasmic angiotensin II-AT 1 interaction on proximal tubule epithelial function (27). The authors used adenoviral transfer of intracellular cyan fluorescent fusion of angiotensin II selectively in proximal tubules and provided evidence that trapping angiotensin II intracellulary increased the blood pressure in rats and mice (46).…”

Intracellular Endothelin Type B Receptor-driven Ca2+ Signal Elicits Nitric Oxide Production in Endothelial Cells

“…Endothelial cell-specific ET B knock-out mice exhibit decreased endogenous release of NO and increased plasma endothelin-1 (60). Innovative approaches previously employed to demonstrate that another intracrine, angiotensin II, increases blood pressure upon intracellular trapping at the kidney level (55,61), may also prove useful in the case of ET-1. Should our findings be supported by in vivo data, selective targeting of ET B agonists to the endothelial cytosol may prove therapeutically beneficial in cardiovascular disorders associated with dysfunction of ET-1/NO pathway.…”

Renin-angiotensin system in the kidney: What is new?

“…An alternative way for the intracellular source of Ang Ⅱ is the internalization of extracellular Ang Ⅱ after binding to the AT1 surface receptor [82,83] . Not all internalized Ang Ⅱ-AT1 complex is degraded in lysosomes, thereby increasing its concentration within the cell, and the AT1 receptor may be relocated to other organelles, including the nucleus [101,[104][105][106][107][108] . Indeed, subcellular localization of 125 I-labeled Ang Ⅱ in the pig kidney indicates that Ang Ⅱ generation is predominantly extracellular, followed by AT1 receptor-mediated endocytosis leading to higher intracellular Ang Ⅱ levels [109] .…”

“…Although many have demonstrated different Ang Ⅱ intracellular effects, the precise role of intracellular Ang Ⅱ in nephron segments remains poorly understood. Renal intracellular Ang Ⅱ increases blood pressure and decreases 24 h urinary Na + excretion in rats and mices [89,105] , suggesting that, like intrarenal Ang Ⅱ, intracellular Ang Ⅱ within the kidney also increases Na + reabsorption and blood pressure.…”