Mentored Phase: A long-term goal of the mentor, Dr. David Pollock, is to elucidate the role of ET-1 in salt sensitive hypertension. Recently, it was demonstrated that the interstitium of the skin is an important 4 reservoir for Na+, and defects in this storage capacity occurs in salt sensitive hypertension. While mechanisms are not fully understood, preliminary data suggest that vascular endothelial cell derived ET-1 plays a role in skin Na+ storage and clearance during a high salt intake. Therefore, the central hypothesis of the mentored phase is that increases in extrarenal vascular ET-1 influences blood pressure by increasing skin Na+ storage and clearance in response to high salt intake. To test this hypothesis, a vascular endothelial cell specific ET-1 knockout mouse (VEET KO) will be utilized. The first specific aim will determine if vascular ET-1 mediates pathways that regulate Na+ storage and clearance in response to a high salt intake. These include skin interstitial Na+ concentration, macrophages and lymphocytes, tonicity-responsive enhancer binding protein, vascular endothelial growth factor c, and lymph vessel hyperplasia. It is expected that increasing salt intake will lead to increases in each of these factors, and this will be abolished n VEET KO mice. Previous studies indicate that loss of any of these regulatory pathways results in salt sensitive hypertension, however VEET KO mice are hypotensive. It is believed that this is due to lack of ET-1 in renal vasculature, which would increase renal function will isolate the role of extrarenal vascular ET-1 in blood pressure regulation. Question 3 will address this question through the transplant of kidneys from control mice with intact vascular ET-1 into VEET KO mice, a manipulation that is expected to cause salt sensitive hypertension. Independent Phase: Several lines of evidence suggest that increased ET-1 mediates cardiovascular disease associated with obesity; however, preliminary data and previous studies on cultured adipocytes suggest that reduced ETA and/or increased ETB receptor activation on adipocytes produce a favorable environment that leads to obesity. Accordingly, the overall hypothesis of the independent phase is that an imbalance between ETA/ETB receptor signaling in adipocytes creates a favorable environment that leads to obesity. The second specific aim will determine if reductions in ETA and/or increases in ETB receptor expression and function in adipocytes can lead to obesity. This will be tested through in vitro experiments on cultured adipocytes as well as knocking out ETA receptors specifically in adipose tissue of mice.
Specific aim 2 will also determine if reduced ETA and/or increases in ETB receptor expression and function occurs in obesity. This will be tested by determining if ET-1 receptor expression, binding, and signaling is altered in adipose tissue of lean and obese human subjects. The third specific aim will determine if metabolic and dietary factors, such as leptin and western diet, cause an imbalance of ET-1 signaling in adipose tissue. ET-1 production, as well as ET-1 receptor expression and binding will be determined in adipose tissue of ob/ob and db/db mice and animals chronically fed a high fat diet. The goals of the proposed studies will undoubtedly shed light on mechanistic pathways by which ET-1 influences blood pressure and obesity, two prevalent risk factors for cardiovascular disease.

Public Health Relevance

Cardiovascular disease (CVD) is the number one cause of death in the world. Hypertension and obesity are two highly associated diseases that are risk factors for CVD. This project focuses on how dysfunction in endothelin-1 related pathways can contribute to the development and maintenance of hypertension and obesity with hopes that findings from this study will lead to new therapeutic targets to combat this escalating health epidemic.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Career Transition Award (K99)
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NHLBI Mentored Transition to Independence Review Committee (MTI)
Program Officer
Huang, Li-Shin
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University of Alabama Birmingham
Internal Medicine/Medicine
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United States
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Speed, Joshua S; Hyndman, Kelly A; Roth, Kaehler et al. (2018) High dietary sodium causes dyssynchrony of the renal molecular clock in rats. Am J Physiol Renal Physiol 314:F89-F98
Becker, Bryan K; Speed, Joshua S; Powell, Mackenzie et al. (2017) Activation of neuronal endothelin B receptors mediates pressor response through alpha-1 adrenergic receptors. Physiol Rep 5:
Gohar, Eman Y; Kasztan, Malgorzata; Becker, Bryan K et al. (2017) Ovariectomy uncovers purinergic receptor activation of endothelin-dependent natriuresis. Am J Physiol Renal Physiol 313:F361-F369
Kasztan, Malgorzata; Fox, Brandon M; Speed, Joshua S et al. (2017) Long-Term Endothelin-A Receptor Antagonism Provides Robust Renal Protection in Humanized Sickle Cell Disease Mice. J Am Soc Nephrol 28:2443-2458
Becker, Bryan K; Feagans, Amanda C; Chen, Daian et al. (2017) Renal denervation attenuates hypertension but not salt sensitivity in ETB receptor-deficient rats. Am J Physiol Regul Integr Comp Physiol 313:R425-R437
Gohar, Eman Y; Speed, Joshua S; Kasztan, Malgorzata et al. (2016) Activation of purinergic receptors (P2) in the renal medulla promotes endothelin-dependent natriuresis in male rats. Am J Physiol Renal Physiol 311:F260-7
De Miguel, Carmen; Speed, Joshua S; Kasztan, Malgorzata et al. (2016) Endothelin-1 and the kidney: new perspectives and recent findings. Curr Opin Nephrol Hypertens 25:35-41
Jin, Chunhua; Speed, Joshua S; Pollock, David M (2016) High salt intake increases endothelin B receptor function in the renal medulla of rats. Life Sci 159:144-147
Speed, Joshua S; Hyndman, Kelly A (2016) In vivo organ specific drug delivery with implantable peristaltic pumps. Sci Rep 6:26251
Johnston, Jermaine G; Speed, Joshua S; Jin, Chunhua et al. (2016) Loss of endothelin B receptor function impairs sodium excretion in a time- and sex-dependent manner. Am J Physiol Renal Physiol 311:F991-F998

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