Epigenetic Engineering in Immune Cells Prevents Disease Mechanisms in Atherosclerosis

AJAS · 2022 Cellular Science

Anvitha Boosani

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Overview

Atherosclerosis is an immunoinflammatory disease characterized by low-density lipoprotein (LDL) accumulations within arterial walls. These buildups can cause ischemic conditions within the circulatory system, later leading to diseases such as stroke and heart failure. In atherosclerosis, monocytes (immune cells) migrate across blood vessel walls and differentiate into macrophages to consume oxidized low-density lipoprotein (LDL; cholesterol) buildups in arteries. These LDL-engulfing macrophages become foam-cells, which are enlarged cells that accumulate within arterial walls and promote plaque progression. The purpose of this study was to determine if monocytes can be engineered to alter newly initiated disease-promoting epigenetic mechanisms in order to prevent such foam-cell formation, and thus plaque development. Previously, the epigenetic protein histone deacetylase 10 (HDAC10) was reported to induce autophagy, a protective mechanism that aids in cell survival by recycling cellular components. However, it was reported that in cancer cells, overexpression of HDAC10 caused cell death induced by the autophagy mechanism (autophagy-induced cell death). In this study, the effects of autophagy-induced cell death on the prevention of atherosclerotic plaque growth were explored. We found that HDAC10 overexpression causes autophagy-induced cell death in engineered monocyte-derived macrophages. There are two types of macrophages: M1 (inflammatory; associated with the CD86 marker) and M2 (non-inflammatory; associated with the CD206 marker). In the study, macrophages were cultured and stained, and their macrophage types were identified and quantified through immunofluorescence staining methods. Under normal HDAC10 expression conditions, higher CD206 expression levels were observed, indicating a higher number of the M2 non-inflammatory type. Under HDAC10 inhibition conditions, higher CD86 expression levels were observed, indicating a higher number of the M1 inflammatory type, the type that promotes atherosclerosis. Further, to understand the molecular functions of HDAC10, we used protein docking methods and molecular visualizations. We identified that HDAC10 structurally interacts with histone deacetylase 2 (HDAC2), suggesting HDAC2’s role as an upstream regulator. However, HDAC2 cannot be targeted due to its essential roles in many cellular functions (through siRNA inhibition, we found that inhibition of HDAC2 leads to cell death). Thus, the present findings suggest that epigenetic engineering of immune cells through enhancing HDAC10 expression can prevent atherosclerotic plaque development.

Acknowledgements

I would like to thank Professor Jonathan Green and Dr. Chandra Boosani at the University of Missouri-Columbia’s Somatic Cell and Gene Editing Center for providing me with the

opportunity to conduct my work in Dr. Green's lab. I would also like to thank Dr. Green's graduate student Ben Nelson for his supervision throughout the project.

Additionally, I would like to thank AJAS for giving me the opportunity to present my work here, and the Nebraska Junior Academy of Sciences and Metropolitan Science and Engineering Fair for their continued support.

The work presented here relating to HDAC10 protein interactions has been accepted for

publication in the Elsevier publication titled Epigenetics in Organ Specific Disorders.

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From the student

I’ve always had a passion for the sciences, growing up in a household where I’d partake in science-related discussions every night with my parents. However, it wasn’t until around eighth grade when I really started to get interested in research. CAR T-cell therapy was a topic that had been gaining traction at that time, and after reading about it I became fascinated with the idea that we can alter our own immune systems to target disease, essentially “programming” cells to follow a different behavior than what was naturally self-destructive.

A couple years later, I chose to pursue that same line of research, applying the key concept of immune engineering to atherosclerosis rather than cancer (which was treated using the CAR T-cell therapy I had read about prior). After initial research I found that HDAC10 was a key gene in the formation and development of atherosclerotic plaques, and I chose to investigate it further, along with other proteins that regulate its expression. I’ve always strived to center my work around the concept of immune cell engineering; it’s a topic that is rapidly growing, but there’s still so much we don’t know about it. Over the years, I’ve learned that what I enjoy most is working on the frontlines, researching what hasn’t been researched before and being edged on by the prospect of discovering something new. The work I am presenting here is a project I've been working on for the past four years, and I plan on continuing it in the future. I received a national STEM grant in June 2021 and, under the supervision of Dr. Jonathan Green and his graduate student Ben Nelson at the University of Missouri, I’m currently conducting the next phase of my research under grant funding. The research presented here on structural interactions of HDAC10 with other proteins has been accepted for publication as a chapter in Epigenetics in Organ Specific Disorders, an Elsevier publication.