Cellular & Integrative Physiology Department Theses and Dissertations

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    Multiplexed High-Resolution Imaging Approach to Decipher the Cellular Heterogeneity of the Kidney and its Alteration in Kidney Disease and Nephrolithiasis
    (2023-01) Sabo, Angela Renae; Williams, James C., Jr.; El-Achkar, Tarek M.; Moe, Sharon M.; Dunn, Kenneth W.
    Kidney disease and nephrolithiasis both present a major burden on the health care system in the US and worldwide. The cellular and molecular events governing the pathogenesis of these diseases are not fully understood. We propose that defining the cellular heterogeneity and niches in human and mouse kidney tissue specimens from controls and various models of renal disease could provide unique insights into the molecular pathogenesis. For that purpose, a multiplexed fluorescence imaging approach using co-detection by Indexing (CODEX) was used, using a panel of 33 and 38 markers for mouse and human kidney tissues, respectively. A customized computational analytical pipeline was developed and applied to the imaging data using unsupervised and/or semi-supervised machine learning and statistical approaches. The goal was to identify various cell populations present within the tissues, as well as identify unique cellular niches that may be altered with disease and/or injury. In mice, we examined disease models of acute kidney injury (AKI) and in human tissues we analyzed specimens from patients with AKI, IgA nephropathy, chronic kidney disease, systemic lupus erythematosus, and nephrolithiasis. In both mice and humans, the disease and reference samples show similar broad cell populations for the main segments of the nephron, endothelium, as well as similar groups of immune cells, such as resident macrophages and neutrophils. When comparing between health and disease, however, a change in the distribution of few sub-populations occurred. For example, in human kidney tissues, the abundance and distribution of a subpopulation of proximal tubules positive for THY1 (a marker of differentiation and repair), was markedly reduced with disease. Changes observed in mouse tissues included shifts in the immune cell population types and niches with disease. We propose that our analytical workflow and the observed changes in situ will play an important role in deciphering the pathogenesis of kidney disease.
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    Generation and Exploration of a Novel Low Oxygen Landscape for Hematopoietic Stem and Progenitor Cells
    (2022-10) Dausinas, Paige Burke; Elmendorf, Jeffrey; O'Leary, Heather; Bidwell, Joseph; Wan, Jun; Zhang, Ji
    Hematopoietic stem (HSC) and progenitor (HSPC) cells reside in low oxygen (~1- 4%, low O2) bone marrow niches which provide critical signals for maintenance, selfrenewal, and differentiation. Exposure of HSC/HSPCs to air (~21%) for less than 10 minutes irreversibly diminishes numbers of phenotypic and functional stem cells, a phenomenon termed extra physiologic oxygen stress/shock. Yet, most studies harvest and analyze HSC/HSPCs in air and often in fixed cells, leaving endogenous signaling mechanisms unidentified. To better understand the endogenous mechanisms regulating HSCs and HSPCs, we generated the first low O2 landscape of phenotypic/functional/signaling alterations in live, low O2 harvested/sorted HSC/HSPCs utilizing novel technology. HSC (LSKCD150+) and HSC/HSPC (LSK) expression, frequency, and stem cell maintenance retention were enhanced in low O2 relative to historic data and our air data. Transcriptomics uncovered low O2 differential pathway regulation of HSC/HSPCs and HSCs with analysis identifying low O2 enrichment of genes/pathways including Ca2+ ion binding, altered sodium hydrogen (Na+/H+) activity, viral entry, and transmembrane receptor activity in both HSCs and HSPCs. In exploring the low O2 landscape, we investigated differential low O2 regulation of Ca2+ and SARS-CoV-2 related pathways/mechanisms in HSCs and HSPCs. Differential Ca2+ regulation was observed in our transcriptional/proteomic analysis corroborated by phenotypic/functional data demonstrating increases in low O2 of cytosolic and mitochondrial Ca2+ flux, ABC Transporter (ABCG2) and Na+/H+ (NHE1) expression, discovery of a novel low O2 Ca2+ high HSPC population that enhances HSC maintenance compared to Ca2+ low populations and blunting of this population and subsequent enhanced stem cell maintenance upon NHE1 inhibition (Cariporide). Multi-omics analyses also identified enhancements in COVID19-related pathways in low O2 that corresponded with enhanced expression of SARS-CoV-2 receptors/co-receptors, SARS-CoV-2 spike protein (SP) binding, and expansion of SP-bound HSC/HSPCs in low O2 compared to air, as well as enhanced stem cell maintenance of SP-bound, versus unbound, cells in low O2. Together, these data presented show low O2 harvest/retention of HSC/HSPCs enhances stem cell maintenance, which could be utilized to improve HSC expansion, and leads to differential pathway/signaling regulation of various biological pathways in HSC/HSPCs including Ca2+ and SARS-CoV-2/viral infection that results in phenotypic and functional consequences.
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    Pancreatic Beta Cell Identity Regulated by the Endoplasmic Reticulum Calcium Sensor Stromal Interaction Molecule 1
    (2021-12) Sohn, Paul; Evans-Molina, Carmella; Elmendorf, Jeffrey; Linnemann, Amelia; Sankar, Uma
    Type 2 diabetes mellitus is a chronic disorder characterized by hyperglycemia, insulin resistance, and insufficient insulin secretion from the pancreatic β cells. To maintain adequate levels of insulin secretion, β cells rely on highly coordinated control of luminal ER Ca2+. Stromal Interaction Molecule 1 (STIM1) is an ER Ca2+ sensor that serves to replenish ER Ca2+ stores in response to depletion by gating plasmalemmal Orai1 channels in a process known as store-operated calcium entry (SOCE). We developed a method for the direct measurement of SOCE in pancreatic β cells and found that deletion of STIM1 in INS-1 cells (STIM1KO) is sufficient to block Ca2+ influx in response to store-depletion. To determine the physiological importance of β cell STIM1, we created mice with pancreatic β cell specific deletion of STIM1 (STIM1Δβ) and placed them on a high fat diet (HFD) with 60% of kilocalories derived from fat. After 8 weeks of HFD, female, but not male, STIM1Δβ mice exhibited increased body weight and fat mass as well as significant glucose intolerance and impaired insulin secretion without observable differences in insulin tolerance. Immunohistochemical analysis revealed a reduction of β cell mass and an increase of α cell mass; ELISA of islet lysates revealed a similar significant reduction in insulin content and increased glucagon content. RNA-sequencing performed on STIM1Δβ islets revealed differentially expressed genes for functions related to apoptosis, lipid metabolism, and epithelial cell differentiation, as well as loss of β cell identity. Proteomics analysis of STIM1KO cells phenocopied the metabolic findings, revealing significantly increased glucagon expression. Analysis of islet RNA-sequencing results showed modulation of pathways related to 17-β estradiol (E2) signaling, with notable downregulation of G-protein coupled estrogen receptor 1 (GPER1) expression. Consistently, treatment of female wild-type islets with pharmacological SOCE inhibitors led to reduced expression GPER1, while STIM1KO cells showed lower mobilization of intracellular cAMP levels in response to GPER agonist treatment. Taken together, these findings identify a novel interaction between SOCE and E2 signaling in the female islet and suggest that loss of STIM1 and impairments in SOCE may contribute to diabetes pathophysiology through loss of β cell identity.
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    Neutrophil Diversity in the Pathogenesis of Ischemic Acute Kidney Injury
    (2020-09) Winfree, Seth; El-Achkar, Tarek M.; Dagher, Pierre C.; Day, Richard N.; Williams, James C., Jr.
    Acute kidney injury (AKI) affects millions of patients worldwide yet has few treatment options. There is a critical need to identify novel interventions for AKI, especially approaches targeting cell types that are central to the disease, such as neutrophils. Neutrophils are professional phagocytic cells that respond early to tissue injury. In rodent models of severe ischemic-reperfusion-injury AKI, neutrophils transiently infiltrate the injured kidney, appearing within 6 hours, and are gone by 72 hours. These infiltrating neutrophils are considered proinflammatory and harmful to tissue repair and recovery of kidney function. However, neutrophils can exhibit atypical activity such as antigen presentation and have a central role in recovery from myocardial ischemic injury. Furthermore, little is known of neutrophil polarization, atypical activity, or neutrophil diversity in AKI. Lastly, the kidney generated and renal-protective immunomodulatory protein uromodulin (Tamm-Horsfall Protein, THP) regulates granulopoiesis. In the absence of uromodulin, there is a systemic increase in neutrophils and mouse kidneys are sensitive to injury in AKI. To elucidate neutrophil diversity in AKI and their sensitivity to uromodulin, I performed a series of single-cell sequencing experiments to generate transcriptional profiles of neutrophils from the blood and kidneys of wild-type and THPknockout mice after renal ischemic-reperfusion-injury (IRI). Neutrophil diversity was detected following IRI of the mouse kidney in the blood and kidney. The distribution of subpopulations was sensitive to the kidney milieu. Within the kidney, this diversity and the transcriptional programs of neutrophil subpopulations was sensitive to the severity of ischemic injury. Lastly, Cxcl3 was uniquely upregulated in specific neutrophils after severe ischemic injury. Using single-cell sequencing of uromodulin knock-out mice, I detected the upregulation of toll-like receptor pathways and complement cascades across neutrophil subpopulations in a THP sensitive manner. Furthermore, CXCR2 ligand expression was a combination of moderate and severe injury in wild-type mice. This confirmed previously reported cytokine dysregulation in the uromodulin knock-out mouse after IRI and uncovers a novel role for Cxcl3. Thus, upon revisiting the well-studied neutrophil, I have uncovered novel neutrophil diversity that correlates with recovery of kidney function in AKI and suggests new roles for an old player.
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    The Exploration of an Effective Medical Countermeasure Enhancing Survival and Hematopoietic Recovery and Preventing Immune Insufficiency in Lethally-Irradiated Mice
    (2020-08) Wu, Tong; Orschell, Christie M.; Basile, David P.; Unthank, Joseph L.; Haneline, Laura S.; Pelus, Louis M.; MacVittie, Thomas J.
    There is an urgent demand for effective medical countermeasures (MCM) in the event of high-dose radiation exposure ranging from nuclear plant disasters to potential nuclear warfare. Victims of lethal-dose radiation exposure face multi-organ injuries including the hematopoietic acute radiation syndrome (H-ARS) and the delayed effects of acute radiation exposure (DEARE) years after irradiation. Defective lymphocyte reconstitution and its subsequent immune insufficiency are some of the most serious consequences of H-ARS and DEARE. In order to investigate potential MCMs to protect or mitigate these radiation injuries, the prolonged tissue-specific immunosuppression at all levels of lymphocyte development in established murine H-ARS and DEARE models was defined, along with unique sex-related and age-related changes present in some tissues but not others. The “double hits” of irradiation and age-related stress on lymphopoiesis led to significant myeloid skew and long-term immune involution. Different kinds and different combinations of hematopoietic growth factors, some in combination with angiotensin converting enzyme inhibitor, were administered to lethally irradiated mice. These radiomitigators were found to significantly increase survival and enhance hematopoiesis in H-ARS, but they did little to alleviate the severity of DEARE including immune insufficiency. 16,16 dimethyl-prostaglandin E2 (dmPGE2), a long-acting formulation of PGE2 with similar biological effects as PGE2, was found to enhance survival and hematopoiesis in lethal-irradiated mice when used as radiomitigator or radioprotectant. The optimum time window for administration of radioprotectant and radiomitigator dmPGE2 was defined, which is -3hr to -15min prior to irradiation and +6hr to +30hr post irradiation. Significant survival efficacy of radioprotectant dmPGE2 was also demonstrated in pediatric and geriatric mice. Using specific PGE2 receptor (EP) agonists, the EP4 receptor was defined as the PGE2 receptor potentially responsible for dmPGE2 radioprotection. Radioprotectant dmPGE2 was also found to prevent radiation-induced thymic involution and to ameliorate the long-term immune suppression in radiation survivors in the DEARE phase via promoting hematopoietic stem cell differentiation towards to the lymphoid lineage. This is the first report of an effective MCM for H-ARS which also targets long-term thymic involution and lymphoid lineage reconstitution.
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    Mechanisms Underlying Cardiovascular Benefits of Sodium Glucose Co-Transporter-2 Inhibitors: Myocardial Substrate or Sodium/Hydrogen Exchanger?
    (2020-01) Baker, Hana Elisabeth; Tune, Johnathan D.; Basile, David; Goodwill, Adam; Kowala, Mark; Mather, Kieren; Michael, Mervyn (Dod)
    Recent clinical outcome studies demonstrate that Sodium glucose cotransporter 2 inhibitors (SGLT2i) significantly reduce major adverse cardiovascular events and heart failure outcomes in subjects with type 2 diabetes mellitus. At present, several hypotheses have been proposed to explain the observed cardiovascular benefit of SGLT2i, however, the mechanisms responsible remain to be elucidated. This investigation tested the hypothesis that SGLT2i improves cardiac function and efficiency during acute, regional ischemia/reperfusion injury via preferential shifts in myocardial substrate selection and/or inhibition of cardiac sodium/hydrogen exchanger-1 (NHE-1). Our initial investigation evaluated the effects of 24 hour pretreatment of the SGLT2i canagliflozin on cardiac contractile function, substrate utilization, and efficiency before and during regional myocardial ischemia/reperfusion injury in healthy swine. At the onset of ischemia, canagliflozin increased left ventricular end diastolic and systolic volumes which returned to baseline with reperfusion. This increased end diastolic volume was directly associated with increased stroke volume and stroke work relative to controls during ischemia. Canagliflozin also increased cardiac work efficiency during ischemia relative to control swine. No differences in myocardial substrate uptake of glucose, lactate, fatty acids or ketones were detected between groups. In separate experiments using a longer 60 min coronary occlusion, canagliflozin significantly diminished myocardial infarct size. Subsequent studies investigated the effect of an acute administration (15-30 min pre-treatment) of canagliflozin and the NHE-1i cariporide on cardiac contractile function efficiency in response to myocardial ischemia/reperfusion injury. Similar to our initial studies, canagliflozin increased diastolic filling, stroke work and improved cardiac work efficiency relative to untreated control hearts during the ischemic period. In contrast, cariporide did not alter ventricular filling volume, cardiac output or work efficiency at any time point. Additional examination of AP-1 cells transfected with wild-type NHE-1 showed dose-dependent inhibition of NHE-1 activity by cariporide, while canagliflozin had minimal effect on overall activity. This investigation demonstrates that SGLT2i improves cardiac function and efficiency during acute, regional ischemia in healthy swine. However, the present data fail to support the hypothesis that these SGLT2i-mediated improvements involve either preferential alterations in myocardial substrate utilization or the inhibition of NHE-1 activity.
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    Cellular & Molecular Mechanisms That Contribute to the Early Development of Skeletal Muscle & Systemic Insulin Resistance
    (2019-10) Grice, Brian A.; Elmendorf, Jeffrey; Considine, Robert; Herring, Paul; Mather, Kieren; Mirmira, Raghu
    Insulin resistance starts years before type 2 diabetes (T2D) diagnosis, even before recognition of prediabetes. Mice on a high fat diet have a similar early onset of insulin resistance, yet the mechanism remains unknown. Several studies have demonstrated that skeletal muscle insulin resistance resulting from obesity or high fat feeding does not stem from defects in proximal insulin signaling. Our lab discovered that excess plasma membrane cholesterol impairs insulin action. Excess cholesterol in the plasma membrane causes a loss of cortical actin filaments that are essential for glucose transporter GLUT4 regulation by insulin. Our cell studies further revealed that increased hexosamine biosynthesis pathway (HBP) activity increases O-linked N-acetylglucosamine modification of the transcription factor Sp1, leading to transcription of HMG-CoA reductase (HMGR), the rate-limiting enzyme in cholesterol biosynthesis. Our central hypothesis is that cholesterol accumulation mediated by HBP activity is an early reversible mechanism of high-fat diet-induced insulin resistance. We performed a series of studies and found that early high-fat feeding-induced insulin resistance is associated with a buildup of cholesterol in skeletal muscle membranes (SMM). Akin to the antidiabetic effect of caloric restriction, we found that high-fat diet removal fully mitigated SMM cholesterol accumulation and insulin resistance. Furthermore, using the cholesterol-binding agent methyl-β-cyclodextrin (MβCD), studies established causality between excess SMM cholesterol and insulin resistance. To begin to assess the role of the HBP/Sp1 in contributing to de novo cholesterol biosynthesis, SMM accumulation, and insulin resistance we treated high-fat fed mice with an Sp1 inhibitor, mithramycin. We found that mithramycin prevented SMM cholesterol accumulation and insulin resistance. This series of studies provide evidence that HBP/Sp1-mediated cholesterol accumulation in SMM is a causal, early and reversible mechanism of whole body insulin resistance.
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    Understanding the Integrated Pathophysiological Role of a Moonlighting Protein in Lung Development
    (2019-08) Lee, Dong Il; Schwarz, Margaret; Tune, Johnathan; Kaplan, Mark; Basile, David
    Sensing, integrating, and relaying signals from the environment through proteins, metabolites, and lipids to the lung are critical for proper development. Moonlighting proteins, such as AIMP1, are a unique subset that serves at least two independent physiological functions. Encoded by gene AIMP1, AIMP1 has two known functions: (1) C-terminus EMAP II domain of full-length AIMP1 can be secreted out of the cell to chemoattract myeloid cells; (2) intracellular full-length protein interacts with tRNA synthetases in protein translation. However, despite the linkage of protein expression levels of with several lung pathologies such as bronchopulmonary dysplasia (BPD), effectively targeting the protein encoded by AIMP1 has been a challenge due to poorly understood mechanisms. This thesis explores physiological, signaling, and immunological moonlighting mechanisms of first, the extracellular EMAP II then the intracellular AIMP1. Experiments utilize both in vitro and in vivo models, including a murine model of BPD and Cre-mediated exon-deletion knockout. Experimental results provide evidence that in the BPD model, EMAP II levels are elevated and sustained – first in bronchial epithelial cells then in macrophages. Mice exposed to sustained and elevated EMAP II protein levels resemble the BPD phenotype while neutralization partially rescued the phenotype, implying EMAP II as a potential therapeutic target against BPD. Results from studies exploring EMAP II’s signaling mechanism identify transient stimulation of JAK-STAT3 phosphorylation, commonly found in inflammation-resolving macrophages. In contrast, it induces unique transcriptional changes that are reversible both by JAK-STAT inhibitor and siRNA-mediated knockdown of Stat3. Studies using AIMP1 knockout mouse reveal a novel function for the intracellular AIMP1. AIMP1 knockout mice exhibited neonatal lethality with a respiratory distress phenotype, decreased type I alveolar cell expression, and disorganized bronchial epithelium, suggesting a role in lung maturation. In vitro experiments suggest that a portion of AIMP1 residing in the cell’s membrane interacts with various phosphatidylinositols and contributes toward F-actin deposition and assembly. Data from these experimental studies provide insight into how the various functions of the promiscuous AIMP1 gene affect lung development. These studies exemplify not only characterize novel moonlighting mechanisms of AIMP1, but also highlight the importance of characterizing moonlighting proteins to promote therapeutic preventions.
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    Coronary Smooth Muscle Cell Cytodifferentiation and Intracellular Ca2+ Handling in Coronary Artery Disease
    (2019-08) Badin, Jill Kimberly; Sturek, Michael S.; Evans-Molina, Carmella; Moe, Sharon; Tune, Jonathan D.
    Metabolic syndrome (MetS) affects 1/3 of all Americans and is the clustering of three or more of the following cardiometabolic risk factors: obesity, hypertension, dyslipidemia, glucose intolerance, and insulin resistance. MetS drastically increases the incidence of coronary artery disease (CAD), which is the leading cause of mortality globally. A cornerstone of CAD is arterial remodeling associated with coronary smooth muscle (CSM) cytodifferentiation from a contractile phenotype to proliferative and osteogenic phenotypes. This cytodifferentiation is tightly coupled to changes in intracellular Ca2+ handling that regulate several key cellular functions, including contraction, transcription, proliferation, and migration. Our group has recently elucidated the time course of Ca2+ dysregulation during MetS-induced CAD development. Ca2+ transport mechanisms, including voltage-gated calcium channels, sarcoplasmic reticulum (SR) Ca2+ store, and sarco-endoplasmic reticulum Ca2+ ATPase (SERCA), are enhanced in early, mild disease and diminished in late, severe disease in the Ossabaw miniature swine. Using this well-characterized large animal model, I tested the hypothesis that this Ca2+ dysregulation pattern occurs in multiple etiologies of CAD, including diabetes and aging. The fluorescent intracellular Ca2+ ([Ca2+]i) indicator fura-2 was utilized to measure [Ca2+]i handling in CSM from lean and diseased swine. I found that [Ca2+]i handling is enhanced in mild disease with minimal CSM phenotypic switching and diminished in severe disease with greater phenotypic switching, regardless of CAD etiology. We are confident of the translatability of this research, as the Ca2+ influx, SR Ca2+ store, and SERCA functional changes in CSM of humans with CAD are similar to those found in Ossabaw swine with MetS. Single-cell RNA sequencing revealed that CSM cells from an organ culture model of CAD exhibited many different phenotypes, indicating that phenotypic modulation is not a discreet event, but a continuum. Transcriptomic analysis revealed differential expression of many genes that are involved in the osteogenic signaling pathway and in cellular inflammatory responses across phenotypes. These genes may be another regulatory mechanism common to the different CAD etiologies. This study is the first to show that CSM Ca2+ dysregulation is common among different CAD etiologies in a clinically relevant animal model.
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    Mechanisms of HIV-Nef Induced Endothelial Cell Stress: Implications of HIV-Nef Protein Persistence in Aviremic HIV Patients
    (2019-05) Chelvanambi, Sarvesh; Clauss, Matthias; Basile, David; Day, Richard; Yu, Andy
    HIV-associated cardio-pulmonary vascular pathologies such as coronary artery disease, pulmonary hypertension and emphysema remain a major issue in the HIVinfected population even in the era of antiretroviral therapy (ART). The continued production of HIV encoded pro-apoptotic protein, such as Nef in latently HIV-infected cells is a possible mechanism for vascular dysfunction underlying these diseases. HIVNef persists in two compartments in these patients: (i) extracellular vesicles (EV) of plasma and bronchoalveolar lavage (BAL) fluid and (ii) PBMC and BAL derived cells. Here I demonstrate that the presence of HIV-Nef protein in cells and EV is capable of stressing endothelial cells by inducing ROS production leading to endothelial cell apoptosis. HIV-Nef protein hijacks host cell signaling by interacting with small GTP binding protein Rac1 which activates PAK2 to promote the release of pro-apoptotic cargo containing EV and surface expression of pro-apoptotic protein Endothelial Monocyte Activating Polypeptide II (EMAPII). Using this mechanism, Nef protein robustly induces apoptosis in Human Coronary Artery Endothelial Cells and Human Lung microvascular endothelial cells. Endothelial specific expression of HIV-Nef protein in transgenic mice was sufficient to induce vascular pathologies as evidenced by impaired endothelium mediated vasodilation of the aorta and vascular remodeling and emphysema like alveolar rarefaction in the lung. Furthermore, EV isolated from HIV patients on ART was capable of inducing endothelial apoptosis in a Nef dependent fashion. Of therapeutic interest, EMAPII neutralizing antibodies to block EMAPII mediated apoptosis and statin treatment to ameliorate Nef induced Rac1 signaling was capable of blocking Nef induced endothelial stress in both in vivo and in vitro. In conclusion, HIV-Nef protein uses a Rac1-Pak2 signaling axis to promote its dissemination in EV, which in turn induces endothelial cell stress after its uptake.