Renal microvascular function is an essential element in the control of glomerular capillary pressure, glomerular filtration rate (GFR) and sodium excretion. Salt-sensitive hypertensive patients exhibit a blunted pressure-natriuretic response, and susceptibility to hypertensive renal injury, possibly arising from impaired hemodynamic control. Our laboratory has an established interest in the mechanisms involved in controlling renal blood flow and GFR. Project 2 will examine a novel hypothesis that chronic elevation of dietary salt modifies the renal microvascular response to endothelin-1 (ET-1) to facilitate salt excretion through receptorspecific pathways. Recent studies establish that ETA receptors contribute to salt-sensitive hypertension, whereas ETB receptors stimulate endothelium-dependent vasorelaxation and inhibit sodium reabsorption. However, ETB receptor physiology is complex as they can produce opposing vasoconstriction and vasodilation within the pre-glomerular circulation. We have shown that afferent arterioles of rats fed a high salt diet exhibit a marked rightward shift in ET-1-mediated vasoconstriction and attenuated autoregulatory reactivity (preliminary data), which may involve ETB receptors. These novel observations suggest that the salt-induced enhancement of ETB receptor expression reduces autoregulatory sensitivity to facilitate ETB receptor mediated excretion of salt. While this may have a positive effect in the short-term, reduced autoregulatory efficiency does leave the kidney vulnerable to other hemodynamic insults, like hypertension, that may hasten the progression to renal injury. Therefore, it is important to establish the role of ETB receptors in the afferent arteriolar response to high salt. The central hypothesis for Project 2 is that a high salt diet enhances ETB receptor-specific pathways to promote afferent arteriolar dilation, blunt autoregulatory efficiency and facilitate sodium excretion. We propose to address this central hypothesis by investigating three specific aims.
Aim 1 will test the hypotheses that a high salt diet enhances afferent arteriolar ETBdependent vasorelaxation resulting in increased GFR and that this effect is prevented by ETB receptor deficiency.
Aim 2 will test the hypothesis that a high salt diet blunts autoregulatory efficiency through mechanisms linked to ETB receptor activation.
Aim 3 will test the hypothesis that a high salt diet changes ETB receptor activity to blunt autoregulatory efficiency by reducing afferent arteriolar reactivity to P2 or PI receptor activation via ATP or adenosine, respectively. These studies will provide unique insights into how the kidney responds to salt to facilitate NaCI excretion.
The Program Project focuses on elucidating mechanisms by which the kidney controls sodium excretion, and therefore, has direct relevance to the serious health problem of salt-dependent hypertension and kidney disease. The Administrative Core plays an important role in coordinating these activities, which is particularly important in the current program due to the integration of basic and clinical science
| Kang, Kyu-Tae; Sullivan, Jennifer C; Pollock, Jennifer S (2018) Superoxide Dismutase Activity in Small Mesenteric Arteries Is Downregulated by Angiotensin II but Not by Hypertension. Toxicol Res 34:363-370 |
| De Miguel, Carmen; Sedaka, Randee; Kasztan, Malgorzata et al. (2018) Tauroursodeoxycholic acid (TUDCA) abolishes chronic high salt-induced renal injury and inflammation. Acta Physiol (Oxf) :e13227 |
| Johnston, Jermaine G; Pollock, David M (2018) Circadian regulation of renal function. Free Radic Biol Med 119:93-107 |
| Guan, Z; Wang, F; Cui, X et al. (2018) Mechanisms of sphingosine-1-phosphate-mediated vasoconstriction of rat afferent arterioles. Acta Physiol (Oxf) 222: |
| De Miguel, Carmen; Hamrick, William C; Hobbs, Janet L et al. (2017) Endothelin receptor-specific control of endoplasmic reticulum stress and apoptosis in the kidney. Sci Rep 7:43152 |
| Gohar, Eman Y; Kasztan, Malgorzata; Pollock, David M (2017) Interplay between renal endothelin and purinergic signaling systems. Am J Physiol Renal Physiol 313:F666-F668 |
| Guan, Zhengrong; Singletary, Sean T; Cha, Haword et al. (2016) Pentosan polysulfate preserves renal microvascular P2X1 receptor reactivity and autoregulatory behavior in DOCA-salt hypertensive rats. Am J Physiol Renal Physiol 310:F456-65 |
| Hyndman, Kelly Anne; Dugas, Courtney; Arguello, Alexandra M et al. (2016) High salt induces autocrine actions of ET-1 on inner medullary collecting duct NO production via upregulated ETB receptor expression. Am J Physiol Regul Integr Comp Physiol 311:R263-71 |
| Heimlich, J Brett; Speed, Joshua S; O'Connor, Paul M et al. (2016) Endothelin-1 contributes to the progression of renal injury in sickle cell disease via reactive oxygen species. Br J Pharmacol 173:386-95 |
| Davenport, Anthony P; Hyndman, Kelly A; Dhaun, Neeraj et al. (2016) Endothelin. Pharmacol Rev 68:357-418 |
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