brain | APS Undergraduate Researcher

This summer, I am very thankful to be a recipient of the Undergraduate Summer Research Fellowship (UGSRF). This fellowship has given me the opportunity to conduct research under the guidance of Dr. Justin Grobe at the University of Iowa. My research project studies the role of AT1a receptors on the vasopressin-producing cells found in the hypothalamus region of the brain.

Vasopressin (AVP) is a hormone, produced in the magnocellular neurons within the hypothalamus, playing a key role in maintaining homeostasis. This hormone maintains homeostasis by increasing blood pressure through upregulation of water reabsorption and vasoconstriction. The AT1a receptor responds to high levels of angiotensin II, ANGII, by constricting the cells with AT1a as part of the renin-angiotensin-aldosterone system, RAAS. A previous study conducted in our lab has shown AT1a receptor localization on vasopressin-producing cells in the supraoptic nucleus of the hypothalamus¹. In order to observe the role of AT1a receptors, the experiment compared the response of AT_1a^AVP-KO mice with control mice under the ICV infusion of ANGII or aCSF at 50ng/hr. Specifically, I am looking for responses in water-intake, urine output, blood pressure, and vasopressin secretion. This experiment will provide further insights to understand AVP secretion in response to brain RAAS and could potentially help prevent hypertension, exhibited patients with obesity, diabetes, and/or preeclampsia.

Figure 1: qPCR machine for gene expression analysis

I have learned many valuable skills from conducting research over the course of this summer thanks to my awesome mentors and principal investigator. They have devoted their time to teach me how to use Excel in analyzing the results of specific qPCR gene expressions and creating protocols for many experiments utilized in the lab. Nevertheless, there are many other essential skills that I have yet to learn such as interpreting results, reading scientific journals, and other lab protocols. They are important in all aspects of research but honing in these skills will require time and practice. For instance, several experiments that I performed yielded poor results and required additional extra time devoted towards troubleshooting the problem. Although frustrating at times, I have learned troubleshooting is one of the most important skills in research because not all the experiments will yield the desired results. While learning and refining my skills, the research project has progressed into the final stages towards completion and I am very excited to find out what results from the samples reveal regarding the role of AT1_Areceptors.

Figure 2: Tail-cuff system setup for blood pressure measurement

As a member of the lab during this summer, I have gained an insight into becoming a scientist. Every morning is devoted towards measuring the blood pressure in the mice cohorts, which need the measurements to be taken daily for three weeks prior to the surgery and two weeks after. The afternoon is spent performing qPCRs on specific genes from tissues collected earlier, analyzing data, learning new protocols, and/or reading publications pertaining to my research area. There are many basic aspects that scientists value greatly such as labeling tubes, checking the timer, and pipetting the exact amount of solutions. The focus on minute details is a trait developed over the years dedicated towards conducting research, and I have definitely noticed improvements in my attention to detail since I first began conducting research. In the next couple of weeks, I will have the opportunity to collect, organize, and analyze the results during the finals days of this experiment. I would like to again thank APS for the opportunity to conduct research at the University of Iowa this summer.

References

Linggonegoro D, Sandgren J, Claflin K, Perschbacher K, Ni J, Pearson N, Pierce G, Santillan M, Grobe J. Physiological Significance of Angiotensin AT1A Receptors in Vasopressin-Producing Cells of the Supraoptic Nucleus. Experimental Biology.
Guyton AC, Hall JE. Textbook of Medical Physiology. 10th ed. Philadelphia, PA: W.B. Saunders Company, 2010.

I am rising junior at the University of Iowa, majoring in biomedical engineering. I will be pursuing a biomechanics and biomaterials track with an interest in implant design and drug delivery. This summer, I had the opportunity to conduct research under my principal investigator, Dr. Justin Grobe, with the assistance of UGSRF fellowship funding by the American Physiological Society. My project investigated the role of AT1a receptors on the vasopressin-producing cell in cardiometabolic control.

The Western diet is high in fats and sugar and can lead to an increase in metabolic diseases, which cause a chronic state of peripheral inflammation (1). My project this summer aims to observe the effect of diet on brain inflammation. We used a mouse model of tagged peripheral monocytes (3). Monocytes turn into macrophages, which target inflammation in the body and brain (2). These mice were fed either a diet high in fat and fructose or a normal diet for 5 weeks. Then the blood from their brain was washed out, and the brain was sliced. The slices were stained for the genetic tag for the peripheral macrophages. Peripheral macrophages found in the brain suggest that chronic inflammation weakens the blood-brain barrier, allowing peripheral macrophages to cross where they increase brain inflammation. This may cause damage and may have links to diseases such as Alzheimer’s Disease and Parkinson’s Disease, which show increased inflammation in the brain (4). This project would further support the idea that a healthy diet could be a key factor in prevention of brain diseases.

This project, as well as science in general, had many obstacles that I had to overcome. Originally, I planned to analyze a different genetic mouse that modeled Alzheimer’s disease. Those mice were also going to be fed a high fat high fructose or control diet, and were going to be compared to see if there was an increase in peripheral macrophages in the brain in diet treated mice. However, those brains didn’t have the blood cleared from the brain, which limited our ability to see the stain. To overcome that problem, we used the new mouse type that had peripheral monocytes tagged, which had the blood removed from it. With this new mouse model, I would have a smaller number of animals, but I could better test my hypothesis.

I enjoy the day-to-day life in research. I was expecting it to be somewhat repetitive, but that was far from the case. I had many problems that I had to solve and was constantly learning, which made the time fly by. My day was broken up by working on different parts of my experiment, writing and reading literature, and meeting and talking with my lab members. The best part for me was that I constantly learned new things. There were many hiccups in my summer experience, which were disheartening at times. However, solving these problems and further learning more made it rewarding as well. The Tansey lab has many members who have been very helpful in solving these problems. I enjoyed being a part of a larger team, as there were so many projects going on that I could learn from.

References

De Sousa Rodrigues, M. E., Bekhbat, M., Houser, M., Chang, J., Walker, D., Jones, D. P., Oller do Nascimento,C., Barnum, C. J. & Tansey, M. Chronic psychological stress and high-fat high-fructose diet disrupt metabolic and inflammatory gene networks in the brain, liver, and gut and promote behavioral deficits in mice. Brain, Behavior, and Immunity 59: 158-172, 2017.
Khoury, J. E., Toft, M., Hickman, S.E., Means, T. K., Terada, K., Geula, G., & Luster, A. D. Ccr2 deficiency impairs microglial accumulation and accelerates progression of Alzheimer-like disease. Nature Medicine 13: 432-438, 2007.
Saederup, N., Cardona, A. E., Croft, K., Mizutani, M., Cotleur, A. C., Tsou, C.-L., Ransohoff, R. M., & Charo, I. F. Selective chemokine receptor usage by central nervous system myeloid cells in CCR2-red fluorescent protein knock-in mice. PLoS ONE 5: e13693, 2010.
Selkoe, D. J. The therapeutics of Alzheimer’s disease: where we stand and where we are heading. Annals of Neurology 74: 328-336, 2013.

Lindsey Sniffen is a senior majoring in Neuroscience and Behavioral Biology at Emory University in Atlanta, GA. She is a 2017 Integrative Organismal Systems Physiology (IOSP) Fellow in Dr. Malu Tansey in the Department of Physiology at Emory University in Atlanta, GA. Her fellowship is funded by the APS and a grant from the National Science Foundation Integrative Organismal Systems (IOS) (Grant #IOS-1238831). After graduation, she plans to pursue a Ph.D. in pharmacology, and then work in the pharmaceutical industry.