KV7 Channel Expression and Function Within Rat Mesenteric Endothelial Cells

Abstract

Background and Purpose: Arterial diameter is dictated by the contractile state of the vascular smooth muscle cells (VSMCs), which is modulated by direct and indirect inputs from endothelial cells (ECs). Modulators of KCNQ-encoded kV7 channels have considerable impact on arterial diameter and these channels are known to be expressed in VSMCs but not yet defined in ECs. However, expression of kV7 channels in ECs would add an extra level of vascular control. This study aims to characterize the expression and function of KV7 channels within rat mesenteric artery ECs.Experimental Approach: In rat mesenteric artery, KCNQ transcript and KV7 channel protein expression were determined via RT-qPCR, immunocytochemistry, immunohistochemistry and immunoelectron microscopy. Wire myography was used to determine vascular reactivity.Key Results: KCNQ transcript was identified in isolated ECs and VSMCs. KV7.1, KV7.4 and KV7.5 protein expression was determined in both isolated EC and VSMC and in whole vessels. Removal of ECs attenuated vasorelaxation to two structurally different KV7.2-5 activators S-1 and ML213. KIR2 blockers ML133, and BaCl2 also attenuated S-1 or ML213-mediated vasorelaxation in an endothelium-dependent process. KV7 inhibition attenuated receptor-dependent nitric oxide (NO)-mediated vasorelaxation to carbachol, but had no impact on relaxation to the NO donor, SNP.Conclusion and Implications: In rat mesenteric artery ECs, KV7.4 and KV7.5 channels are expressed, functionally interact with endothelial KIR2.x channels and contribute to endogenous eNOS-mediated relaxation. This study identifies KV7 channels as novel functional channels within rat mesenteric ECs and suggests that these channels are involved in NO release from the endothelium of these vessels.

Kidney Injury Causes Accumulation of Renal Sodium That Modulates Renal Lymphatic Dynamics

“…Our data show that a high-sodium environment also reduced phosphorylated SPAK compared with the baseline sodium control group (Figure 5C) [21]. Among the vasoactive factors, eNOS is a major endothelial-derived mechanism regulating lymphatic dynamics, which is regulated by activity of NKCC1 [23]. Exposing LECs to a high-sodium environment caused a sig-nificant reduction in eNOS activity as measured by the amount of phosphorylated eNOS protein (Figure 6A).…”

“…Although kidneys are central in Na+ homeostasis, little is understood about Na+ effects on renal lymphatics. The current studies provide new insights into regulation of renal lymphatic network by showing (1) proteinuric kidney injury increases renal Na+ by 23 Na/1H MRI and direct sampling of renal lymphatic fluid shows elevated Na+ concentration while plasma Na+ is unchanged (2) high Na+ and furosemide inhibition of NKCC1 decrease lymphatic vessel contraction amplitude and ejection fraction in isolated renal lymphatic vessels, (3) a high Na+ environment decreases phosphorated-NKCC1, phosphorylated SPAK, an upstream kinase, and phosphorylated eNOS, a downstream vasoactive factor, and (4) a high Na+ environment together with renal injury contribute to a blunted lymphatic response in PAN-injured kidneys.…”

“…Noninvasive imaging by 23 Na/1H MRI showed that proteinuric kidney injury leads to accumulation of sodium and water in the in vivo kidneys. This new observation reflects advances in multi-nuclear imaging technology that exploit endogenous 23 Na, the second most abundant magnetic nuclei in living systems [25].…”

“…Such studies have been primarily limited by a lack of methodology for sodium quantification in vivo. Recent developments in noninvasive sodium imaging by 23 Na-MRI provide an attractive tool for quantifying kidney sodium content in vivo. Moreover, although kidney disease is regularly accompanied by lymphatic vessel hyperplasia [7][8][9][10][11][12][13][14], whether disease-induced lymphangiogenesis is accompanied by disrupted renal lymphatic vessel dynamics is unknown.…”

Sexual dimorphism in prostacyclin‐mimetic responses within rat mesenteric arteries: A novel role for KV7.1 in shaping IP receptor‐mediated relaxation

“…Immunocytochemistry with an antibody for K V 7.1 validated by overexpression studies (Figure S1) showed a significant reduction in total cell fluorescence (A.U) in Kcnq1 morpholino‐transfected arteries when compared to mismatch control (Figure 5a–c). Functionally, arteries incubated with mismatch control produced a significantly greater relaxant response to 300 nmol·L −1 K V 7.1 activator ML277 (Baldwin et al, 2020; Yu et al, 2013) compared to Kcnq1 morpholino‐transfected arteries (Figure 5d). Similarly, relaxation produced by 1 μmol·L −1 MRE‐269 was greater in arteries transfected with mismatch control morpholino when compared Kcnq1 morpholino‐transfected arteries (Figure 5e).…”