• T Cell Immune Response in Persistent Infection of Lymphocytic Choriomeningitis Virus (LCMV)

      Ou, Rong; Georgia Cancer Center (2004-07)
      The m urine LCMV system provides a ciassic model to study the mechanism of immunological tolerance, an efficient strategy used by virus to establish a persistent infection by selective down-regulation of virus-specific T lymphocytes. High viral burden in the onset o f infection drives responding cells into functional unresposiveness (anergy) that can, be followed by their physical elimination. In this study, the downregulation o f the virus-specific CD8^-T-ceil response was studied during a persistent infection o f adult mice, with particular emphasis on the contribution of the interferon response in promoting host defense, or perforin-, Fas/FasL-, or TN FR l-m ediated cytolysis in regulating T-cell homeostasis. Since LCMV infects a broad range o f host tissues, the functional properties o f virus-specific CD8'^ T cells in different tissues during LCMV infection were also evaluated. Infection of mice deficient in receptor for type I (IFN-a/p), type II (IFN-y), or both type I and II IFNs with LCMV isolates that vary in their capacity to induce T-celi exhaustion, revealed a critical role for IFN -a/p in restricting LCMV spread at the onset o f infection while IFN-y has impact on effector cells. The production o f IF N -a/p and/or IFN-y critically regulates the virus-host balance during the acute phase o f infection, such that a high viral burden drives responding cells into different programs o f exhaustion. Infection o f mice deficient in perferin, FasL or TNFRl with the Docile or Aggressive strains of LCMV revealed comparable kinetics of expansion and functional inactivation o f virusspecific C D ^ T cells in the early phase o f Infection in C57BL/6 controls. However, the data underscore a critical role for these molecules in the persistence o f the virus-specific CD8"‘-T-ceil population once it has become anergic. Study o f the functional properties of virus-specific CD8'^ T cells in different tissues during LCMV infections showed that a centra! role for the viral load in lymphoid tissue in the induction and maintenance of clonal exhaustion. The data strongly suggest that CD8^ T ceils may be differentially regulated in the environments o f lymphoid versus nonlymphoid tissues, and the pattern of T cell exhaustion observed with mice is likely a common feature o f the immune response during chronic infections in humans.
    • T-Type Calcium Current and Calcium-Induced Calcium-Release in Developing Chick Myocardium

      Kitchens, Susan A.; Department of Cellular Biology and Anatomy (2002-02)
      HYPOTHESES 1. The contribution of T-type calcium currents to the calcium transient are greater at young developmental ages, but decline with chick heart development. The decrease in contribution of T-type calcium current to the calcium transient mirrors the normal developmental reduction in magnitude of T-type current in the chick heart. 2. T-type calcium current plays a role in calcium-induced calcium-release during chick heart development. T-type current plays a significant role in the calcium-induced calcium-release process in younger embryos due to the greater magnitude of the current at earlier developmental stages. 3. More than one isoform of the T-type calcium channel is present in developing chick myocardium. The multiple isoforms will function concomitantly to provide sufficient T-type calcium current for proper development. 4. The expression of the T-type calcium channel in ventricle decreases with development. There is a concomitant decrease in T-type Ca2* current stimulation of CICR. SPECIFIC AIMS 1. To determine the contribution of T-type calcium current to the calcium transient during development in chick ventricular myocytes. The approach is to use a fluorescent calcium indicator to measure the transients from myocytes at embryonic day (ED) 5, EDI 1 andED15. 2. To determine the contribution of T-type calcium current to calcium-induced calciumrelease during chick heart development. The approach is to use pharmacological agents to quantify the contribution to the Ca3* transient from T-type Ca3* current stimulated CICR. 3. To determine which isoforms of the T-type calcium channel are likely to be present in chick myocardium. The approach is to use PCR methods to identify any T-type channel isoform mRNA expressed in chick ventricle. 4. To determine the level of expression of T-type calcium channel isoforms during the development of chick ventricle. The approach is to use molecular quantitation methods to examine the expression pattern of T-type channel isoforms in chick ventricle during development.
    • T-type calcium current and calcium-induced calcium-release in developing chick myocardium

      Kitchens, Susan A.; Medical College of Georgia (Augusta University, 2002-02)
    • A Tailored intervention program for overweight and obese veterans: who benefits and when

      Garvin, Jane Threatt; Medical College of Geotgia (Augusta University, 2012-06)
      This descriptive, exploratory study examined longitudinal clinical data for variables associated with weight reduction among veterans enrolled in a weight reduction intervention, the MOVE! Program. Variables of interest included background characteristics and exposure to components of the intervention. Background, intervention, and outcome variables were organized around the Interaction Model of. Client Health Behavior. In addition to the outcomes related to weight, hemoglobin A1C, blood pressure, and serum lipid levels were examined. Thirteen percent of participants (N = 53 of 404) achieved a 5°/o weight reduction. Overall, .the sample was primarily non-Hispanic (96% ), urban (83o/o ), Black (58.4%)), married (58.4o/o) and male (-80%). The mean age was 56 years. Common comorbidities associated with obesity were evident including diabetes (30.2o/o), hypertension (60.9%), and hyperlipidemia (54.0o/o). The average body mass index was -35. All available data were collected from program entry to a designated stop date; therefore, participants had unequal and irregular data points. Participants were observed repeatedly over time with 51 °/o having 10 or more observations. A little more than half of the participants were group attendees (-56o/o) rather than self-managed. The majority of the intervention exposures were group rather than· individual or telephone visits with providers. Achieving a 5°/o weight reduction was significantly associated with age in years (OR 1.04), group attendance beyond the day of orientation (OR 6.61 ), · attendance at the holiday eating class (OR 3.67), exposure over time (measured ·in weeks, OR 1.02), and the interaction between time and group (OR .97). Weight reduction in pounds was significantly associated with age, baseline body mass index, total number of group classes attend.ed, and telephone contact with the registered nurse. Using repeated measures of weight, the trajectory of weight was significantly associated with gender, baseline body mass index, and exposure to the intervention over time. Examination of additional outcomes revealed that components of the intervention were associated with beneficial changes in hemoglobin A1C, blood pressure, and serum lipid levels. Further research is needed to more fully describe successful weight reducers and the identify best practices to convert unsuccessful weight reducers to successful ones.
    • A Tailored Intervention Program for Overweight and Obese Vetrans: Who Benefits and When

      Garvin, Jane; Department of Physiological & Technological Nursing (2012-06)
      This descriptive, exploratory study examined longitudinal clinical data for variables associated with weight reduction among veterans enrolled in a weight reduction intervention, the MOVE! Program. Variables of interest included background characteristics and exposure to components of the intervention. Background, intervention, and outcome variables were organized around the Interaction Model of Client Health Behavior. In addition to the outcomes related to weight, hemoglobin A1 Thirteen percent of participants (N = 53 of 404) achieved a 5% weight reduction. Overall, the sample was primarily non-Hispanic (96%), urban (83%), Black (58.4%), married (58.4%) and male (~80%). The mean age was 56 years. Common comorbidities associated with obesity were evident including diabetes (30.2%), hypertension (60.9%), and hyperlipidemia (54.0%). The average body mass index was ~35. All available data were collected from program entry to a designated stop date; therefore, participants had unequal and irregular data points. Participants were observed repeatedly over time with 51% having 10 or more observations. A little more than half of the participants were group attendees (~56%) rather than self-managed. The majority of the intervention exposures were group rather than individual or telephone visits with providers. C, blood pressure, and serum lipid levels were examined. Achieving a 5% weight reduction was significantly associated with age in years (OR 1.04), group attendance beyond the day of orientation (OR 6.61), attendance at the holiday eating class (OR 3.67), exposure over time (measured in weeks, OR 1.02), and the interaction between time and group (OR .97). Weight reduction in pounds was significantly associated with age, baseline body mass index, total number of group classes attended, and telephone contact with the registered nurse. Using repeated measures of weight, the trajectory of weight was significantly associated with gender, baseline body mass index, and exposure to the intervention over time. Examination of additional outcomes revealed that components of the intervention were associated with beneficial changes in hemoglobin A1C, blood pressure, and serum lipid levels. Further research is needed to more fully describe successful weight reducers and the identify best practices to convert unsuccessful weight reducers to successful ones.
    • Targeting cyclic GMP signaling for the treatment of gastrointestinal diseases

      Sharman, Sarah Kristen; Department of Biochemistry and Molecular Biology / Cancer Center (2017)
      Continual renewal of the luminal epithelium in the gut is essential for the maintenance of a healthy intestine as it sustains the barrier that protects underlying tissue from infiltration of material passing through the lumen. Dysregulation of homeostatic processes involved in maintenance of the barrier have been implicated in numerous gastrointestinal diseases. The cGMP signaling axis has emerged as an important regulator of homeostasis in the intestinal mucosa, and has been implicated in the suppression of visceral pain, colitis, and colon cancer. While there is considerable interest in exploiting this pathway, until recently the approaches used to increase cGMP have been limited. The present study sought to test the hypothesis that elevation of cGMP in the intestinal epithelium using PDE5 inhibitors will alter epithelial homeostasis and be therapeutic for constipation and preventative for colon cancer. Healthy mice treated with the PDE5 inhibitor sildenafil or the GC-C agonist linaclotide exhibited reduced proliferation and apoptosis, and increased numbers of differentiated secretory cells in the intestinal epithelium. In addition to these homeostatic effects, both drugs normalized intestinal transit and fecal water content in two mouse models of constipation. Furthermore, administration of sildenafil to mice treated with dextran sulfate sodium tightened the disrupted epithelial barrier. Treatment of ApcMin/+ mice with sildenafil or linaclotide significantly reduced the number of polyps per mouse (67% and 50%, respectively). The effect of these cGMP-elevating agents was not on the polyps themselves but was rather on the pre-neoplastic tissue, which was less proliferative and more apoptotic in the presence of the drugs. Taken together, the results of this study demonstrate that increasing cGMP with a pediatric dose of PDE5 inhibitors could be a potential alternative to GC-C agonists for the treatment of gastrointestinal diseases.
    • Temperament, childrearing practices and unintentional childhood injury

      Markowitz, Monika S.; School of Nursing (1987-04)
      ~his study examined the rel.at~onsh.~p. a~()ng parents' . . . - ··- . . . . perceptions-of the~r c::hildren's temperament, self-reported ~hildrear:in~ practices and urililt·en_tional injury in children. ~he sample consisted of 23 injured children· • • ~ ' • • + between the ages of 1· an.d 7 Y~.CJ.rs who, wer~ _recr'lli~ed from the emergency rqoms, hospital·f~~ors and pedia~ric intensiv~ car~·units of two meiropolitan hospitals. . . . ' '. '. ' -. ~ ' ' . . . . . Parents completed·a temperament. questionnaire, a . . childrearing ~ractices questi6~naire and a demographic data . form. Inform·ation related to th~ injury was r~corded· and· the Physiologic Stability Index, which measured injury ' - ' ' ' . ' . . . . . . severity, was deter~ined by tne investigp.t_or afte:r a c}lar~ review. In this study, a.greater frequency of injury was rel.ated to a pa·re_nting style .of low warmth and a .greater injury severity was related to a childrearing practice of. low control, r=. 57 and ··51 respectiv.ely (p< ·• 01). Parents· of inj~red children reported themselves as practicing ' ' . ' . significantly more control and ·prot~ctiveness ·.than a sample ·of parents of non-injured children (n=20). The injured ·children were perceived l:?Y t~eir mothers as b.ein_g.slow in ·.adaptability, demonstrating low-rhythmicity, high withdrawal; and negative mood when compared to normative data bn other child subjects~
    • Temperamental Differences and Preschool Adjustment to Day Care

      Hatmaker, Debra; School of Nursing (1986-05)
      Adjustment of preschool children to group day care was studied in relation to their temperament characteristics. Temperament measurement, by means of the Toddler Temperament scale by Fullard, McDevitt, and carey, was completed at the beginning of group care on a sample of 18 children ages 23-42 months. Adjustment-to day care was measured at the.beginning of group care, at one week, and at four weeks after enrollment using the Preschool Behavior Questionnaiie by Behar and Stringfield. Three hypotheses were tested. The first hypothesis suggesting a positive correlation between children's average temperament scores and their negative behavior ratings was rejected after statistical testing by Pearson's Product Moment Correlation. Hypothesis II predicted a significant decline in negative behavior ratings from the first to the fourth week of day care enrollment. This second hypothesis was rejected after-results from paired t-tests failed to reach significance. Hypothesis III stated that there would be a positive-relationship between parents' and caregivers' ratings of ~hildren~ negative behaviors. Ratings from the first and fourth week were compared using the Pearson's Product Moment Correlation resulting in correlations of .61 and·.39, respedtiVely. These correlations were statistically signi~icant and the third hypothesis was accepted. These findings do suggest that parents and caregivers have similar perceptions in identifying certain negative behaviors for preschool children. As providers of anticipatory guidance, nurses must be well versed in the aspects of quality day care and be able to impart this imformation to families based
    • TEMPERATURE. AND P~2.TRANSIENTS IN KINDLED EPILEPTIC FOCI OF THE RAT

      Lynch, Thomas Joseph; Department of Physiology (1983-02)
      A finite epileptic focus was created in the brains of 25 Sprague-Dawley rats by kindling electrical stimuli delivered to the left amygdala. With the left amygdala thus defined to be the focus of epileptogenesis, changes in focal site temperature and p02 were monitored during progressively worsening convulsions. Convulsions were evoked by the daily administration of a kindling stimulus composed of a 3 second long, 60Hz, sinusoidal current of 150 microamperes. Two separate studies were conducted in which only those ictal temperature or ictal po2 transients occur~ing at the focus were monitored. In the main temperature study, the range of kindled seizure activity from simple electrographic afterdischarge (AD) through generalized convulsion caused a mean focal heating transient of .028°F with a range of from 0 to .738°F. Focal heating transients generally increased as the animals' convulsions progressed in severity from focal to generalized. In one supplementary temperature study using two rats, the contralateral unstimulated amygdala was found to undergo much the same progression of ictal heating transients as the stimulated amygdala. In a second supplementary study of four rats under neuromuscular block, the lack of convulsive motor activity seemed to be the cause of a significant reduction of the total, focal, ictal heating. In a third measurement between left and right amygdalae showed that their relative rates and directions of temperature change were different despite the gross similarity observed when left and right amygdala temperatures were recorded simultaneously. In the main po2 study, the standard ictal response was a 20- 50% increase in po2 over the baseline level. This increase occurred regardless of the severity of convulsion but- tended to become slightly enhanced as convulsions generalized. When p02 increased and peaked during a seizure, the p02 peak consistently occurred at the moment when the AD in the electroencephalogram ended. Among singly evoked kindled convulsions, significant decreases in focal p02 were rarely observed. Furthermore, in one rat evocation of 17 generalized convulsions, one every ten minutes, still caused a focal po2 increase during each convulsion. In another rat, six spontaneous seizures spaced about 2 minutes apart also caused only increased focal po2• These records are the first such reported for the kindling model of epilepsy and though the findings regarding temperature are similar to those in the available epilepsy literature, the findings regarding p02 are different in that no trend toward ictal reduction in brain po2 was found. That the overwhelming majority of kindled seizures cause focal brain p02 to increase is indication of a fundamental difference between kindled epileptic foci and epileptic tissue created by other models.
    • Temporal and spatial angiogenesis-associated gene expression in rat ischemic skin flaps

      Johnson, Thomas; Medical College of Georgia (Augusta University, 2008-04)
      Background: Emerging therapies designed to improve ischemic soft tissue flap survival include the use of angiogenic factors. However, endogenous expression patterns for these factors have not been characterized. The purpose of this study was to identify variations in gene expression patterns for angiogenesis-associated genes in ischemic rat skin flaps with respect to post operative time and distance from flap base. Methods: Caudally based dorsal random pattern skin flaps measuring 3x10 cm were created on fifteen male Sprague-Dawley rats. The rats were sacrificed at one, three, or seven days post surgery. Following euthanasia, flaps were harvested and sectioned into four 3x2.5 cm zones, with zone I located furthest from the flap base. Total RNA was isolated from each zone, amplified, labeled with biotin, and hybridized with oligoDNA microarrays containing probes for 113 angiogenesis-associated genes. Microarrays were imaged using chemiluminescence, and signal intensities were analyzed using web based software. In a previously published report, flap survival was assessed using orthogonal polarization spectral imaging, and the areas of the flap characterized by blood flow versus stasis ( absent capillary blood flow) were identified. Results: Orthogonal polarization spectral imaging results showed the transition of tissue from stasis to necrosis over time. The area of necrosis increased from day one to day seven as necrotic tissue replaced viable tissue in the stasis zone. Rat angiogenesis microarray analysis revealed significant modulation in the expression of multiple genes (p<0.05) in the areas of the skin flap characterized by advancing necrosis and stasis. A burst of gene modulation occurred from day one to day three in the most distal portion of the flap, and a similar burst occurred in the area characterized by stasis from day three to day seven. Six patterns of gene expression were defined. Patterns of angiogenesisassociated gene expression were different in the areas of blood flow compared to the areas of necrosis and stl!5is. Modulation of various gene functional groups also varied temporally and spatially. Conclusions: This study represents the first attempt to characterize endogenous spatial and temporal angiogenesis-associated gene expression patterns in ischemic skin flaps. The molecular analysis performed in this study correlates with the hemodynamic profile previously published. The gene expression patterns observed in this study may represent responses to hypoxia and necrosis as these processes proceeded proximally from the distal flap margin. In the future, molecular analysis of ischemic tissue may allow clinicians to distinguish hopeless tissue from a flap that may be rescued via pharmacological or surgical intervention. Additionally, molecular analysis in treated and untreated tissue may offer insight into the mechanisms by which pharmacological agents enhance flap survival.
    • Teratogenic activity of trypan blue in rats

      Ferris, Virginia W.; Department of Anatomy (1962-06)
    • Terminal competencies of the baccalaureate nursing graduate

      Eberhart, Aeris Dee; School of Nursing (1974-05)
    • The E2F1 corepressor BIN1 is a novel tumor suppressor RB1-binding cofactor for cell-cycle arrest and genomic instability

      Folk, Watson; Biomedical Sciences (Augusta University, 2020-04)
      The bridging integrator 1 protein (BIN1) exhibits tumor suppressor activities through multiple mechanisms, including by acting as a corepressor of the adenovirus E2-promoter binding cellular factor 1 (E2F1) transcription factor and sensitizing cells to genotoxic stress. By inhibiting E2F1-dependent cell-cycle progression, BIN1 displays an overlapping function with the well-known E2F1 corepressor retinoblastoma protein 1 (RB1). However, whether RB1 and BIN1 collaborate to inhibit E2F1 activity and whether E2F1 is involved in BIN1-dependent sensitization to DNA-damaging agents remain unresolved. Here, I report that BIN1 physically interacts with RB1 to cooperatively repress E2F1-mediated transactivation and that BIN1 interferes with the early stages of DNA damage responses in a manner dependent on BIN1/E2F1 interaction. BIN1 efficiently bound hypophosphorylated RB1, particularly when BIN1 contained exon 10. This was functionally meaningful because BIN1 inhibited serum-induced RB1 phosphorylation by blocking the physical binding of cyclin D1 to RB1 and stabilized hypophosphorylated RB1 on an E2F-sensitive gene promoter. BIN1 and RB1 cooperatively suppressed the transcription of a number of E2F1-sensitive genes, including ATM Ser/Thr kinase (ATM) and BRCA1, and reduced cellular DNA-end joining. Because BIN1 inhibits cellular poly(ADP-ribosyl)ation, simultaneous activation of RB1 and BIN1 induced ‘synthetic lethality’ in multiple cancer cell lines regardless of ‘BRCAness’. Furthermore, even in the absence of DNA damage, depletion of BIN1 enhanced E2F1-dependent ATM autophosphorylation, formation of the MRE11A/RAD50/NBS1 DNA-repair–promoting complex, and phosphorylation of histone H2AX (forming γH2AX, a biomarker of double-stranded DNA breaks). Similar to BIN1 reduction, RB1 deficit increased cancer-cell resistance to cisplatin. Our study reveals that by physically binding to RB1, BIN1 acts as a novel RB1 cofactor and stabilizes RB1 on an E2F-sensitive promoter. Additionally, we unveil that one of the likely mechanisms by which the tumor suppressors BIN1 and RB1 induce growth arrest is attributable to facilitating accumulation of genomic instability via inhibition of E2F1-dependent DNA-repair–promoting activities.
    • The Influence of Instructional Rounds on Teacher Metacognition in a Middle School Context: A Mixed Methods Study

      Hamilton, William B; Department of Advanced Studies and Innovation (Augusta University, 2020-05)
      This study investigated, quantified, and observed metacognitive transformation in middle school ELA and math teachers through the implementation of instructional rounds as a change agent in comparison to the traditional, one-stop workshop format of professional development. A mixed method design was utilized that addressed two research questions: How is teacher metacognition impacted through professional development, and what is the difference in teacher metacognition scores after receiving traditional professional development versus instructional rounds? The results of the study suggested that teacher metacognition is positively impacted by instructional rounds and there were positive attitudes towards instructional rounds as an alternative to traditional professional development. Additionally, the qualitative data indicated that instructional rounds did have a positive impact on instructional practices and supported a progressive maturation of teacher metacognition that could be ultimately transferred to the learner. First, the results elucidated that normal teaching practice is inherently metacognitive and embodies the metacognitive knowledge tenets: person, task, and strategy. Next, teacher collaboration supports the perpetuation of a metacognitive experience, which innately lends itself to reflection. Thirdly, teacher reflection fosters metacognitive goals, thereby resulting in regulation of actions or strategies. Finally, teacher action derived from goal setting is, by definition, metacognitive action. In summary, instructional rounds appeared to be an effective form of professional development that increased and matured teacher metacognition. Keywords: Instructional rounds, metacognition, professional development, teaching practice
    • The Influence of Instructional Rounds on Teacher Metacognition in a Middle School Context: A Mixed Methods Study

      Scoggins, Katherine; Department of Advanced Studies and Innovation (Augusta University, 2020-05)
      This study investigated, quantified, and observed metacognitive transformation in middle school ELA and math teachers through the implementation of instructional rounds as a change agent in comparison to the traditional, one-stop workshop format of professional development. A mixed method design was utilized that addressed two research questions: How is teacher metacognition impacted through professional development, and what is the difference in teacher metacognition scores after receiving traditional professional development versus instructional rounds? The results of the study suggested that teacher metacognition is positively impacted by instructional rounds and there were positive attitudes towards instructional rounds as an alternative to traditional professional development. Additionally, the qualitative data indicated that instructional rounds did have a positive impact on instructional practices and supported a progressive maturation of teacher metacognition that could be ultimately transferred to the learner. First, the results elucidated that normal teaching practice is inherently metacognitive and embodies the metacognitive knowledge tenets: person, task, and strategy. Next, teacher collaboration supports the perpetuation of a metacognitive experience, which innately lends itself to reflection. Thirdly, teacher reflection fosters metacognitive goals, thereby resulting in regulation of actions or strategies. Finally, teacher action derived from goal setting is, by definition, metacognitive action. In summary, instructional rounds appeared to be an effective form of professional development that increased and matured teacher metacognition.
    • The Influence of Instructional Rounds on Teacher Metacognition in a Middle School Context: A Mixed Methods Study

      Townsend, Holly; Department of Advanced Studies and Innovation (Augusta University, 2020-05)
      This study investigated, quantified, and observed metacognitive transformation in middle school ELA and math teachers through the implementation of instructional rounds as a change agent in comparison to the traditional, one-stop workshop format of professional development. A mixed method design was utilized that addressed two research questions: How is teacher metacognition impacted through professional development, and what is the difference in teacher metacognition scores after receiving traditional professional development versus instructional rounds? The results of the study suggested that teacher metacognition is positively impacted by instructional rounds and there were positive attitudes towards instructional rounds as an alternative to traditional professional development. Additionally, the qualitative data indicated that instructional rounds did have a positive impact on instructional practices and supported a progressive maturation of teacher metacognition that could be ultimately transferred to the learner. First, the results elucidated that normal teaching practice is inherently metacognitive and embodies the metacognitive knowledge tenets: person, task, and strategy. Next, teacher collaboration supports the perpetuation of a metacognitive experience, which innately lends itself to reflection. Thirdly, teacher reflection fosters metacognitive goals, thereby resulting in regulation of actions or strategies. Finally, teacher action derived from goal setting is, by definition, metacognitive action. In summary, instructional rounds appeared to be an effective form of professional development that increased and matured teacher metacognition.
    • THE ROLE OF GPR109A IN REGULATION OF RETINAL ANGIOGENESIS AND BLOOD-RETINAL BARRIER AS A POTENTIAL THERAPEUTIC TARGET IN DIABETIC RETINOPATHY

      Abdelrahman, Ammar; Department of Biochemistry and Molecular Biology (Augusta University, 2020-12)
      Currently, treatments of diabetic retinopathy (DR) have limited therapeutic benefits and limited accessibility to the growing diabetic population at risk because of the high expenses and complicated procedures. Inflammation, endothelial dysfunction, and microvascular damage are common features of diabetic complications including DR. GPR109A is the metabolite sensing receptor of beta-hydroxybutyrate (BHB) the principal ketone body in humans. Our previous studies have shown the role of GPR109A expression in promoting anti-inflammatory response in retinal pigmented epithelial (RPE) cells and the relevance of the receptor in DR. Expression of the GPR109A in microvascular endothelial cells (ECs) has been reported recently. However, the relevance of GPR109A expression and activation to retinal EC functions are yet to be studied. Our goal in this study was to identify the role of GPR109A expression and activation in barrier and angiogenic functions of retinal ECs in context of diabetic retinopathy. We used electrical cell impedance sensing (ECIS) technology to evaluate barrier functions in primary human retinal endothelial cells (HRECs) which constitute the inner BRB. Knocking down GPR109A in HRECs with siRNA decreased the transendothelial electrical resistance (TEER) compared to scrambled siRNA. Treating HRECs with BHB increased their TEER and counteracted VEGF-induced barrier disruption through activation of GPR109A and increasing zonula occludens-1 (ZO-1) expression. Treatment of STZ-diabetic mice with exogenous BHB for one month protected against the pathologic albumin leakage induced by diabetes and improved the visual acuity of this animal model of diabetes. Using the mouse model of oxygen induced retinopathy (OIR), we showed that Gpr109a-/- mice had slower vascular recovery from pathologic angiogenesis compared to age matched wild type mice. Moreover, physiologic revascularization of vaso-oblitrated retinas was impaired by loss of GPR109a and associated with dysregulated inflammatory and angiogenic signaling. Collectively, these data point to a role for GPR109A in the regulation of barrier and angiogenic mechanisms in retinal ECs and, promote the receptor as a potential druggable target for impacting these mechanisms in microvascular retinal diseases such as DR.
    • THE ROLE OF KYNURENINE, A TRYPTOPHAN METABOLITE THAT INCREASES WITH AGE, IN MUSCLE ATROPHY AND LIPID PEROXIDATION)

      Kaiser, Helen E.; Department of Cellular Biology and Anatomy (Augusta University, 2020-05)
      Loss of mobility and independence are risk factors for falls and mortality, and drastically reduce the quality of life among older adults. The cellular and molecular mechanisms underlying loss of muscle mass and strength with age (sarcopenia) are not well-understood; however, heterochronic parabiosis experiments show that circulating factors are likely to play a role. Kynurenine (KYN) is a circulating tryptophan metabolite that is known to increase with age and is implicated in several age-related pathologies. Here I tested the hypothesis that KYN contributes directly to muscle loss with aging. Results indicate that that KYN treatment of mouse and human myoblasts increased levels of reactive oxygen species (ROS) two-fold, and significantly increased lipid peroxidation enzymes. Small-molecule inhibition of the Aryl hydrocarbon receptor (Ahr), an endogenous KYN receptor, in vitro did not prevent KYN-induced increases in ROS, and homozygous Ahr knockout in vivo did not protect mice from KYN-induced stress, suggesting that KYN can directly increase ROS independent of Ahr activation. In vivo, wild-type mice treated with KYN had reduced skeletal muscle strength, size, and increased oxidative stress and lipid peroxidation. Old wild-type mice treated with 1MT, a small molecule that suppresses KYN production by IDO1, showed an increase in muscle fiber size, peak muscle strength, and oxidative stress. Protein analysis identified mitochondrial lipid peroxidation as a downstream mechanism that is increased upon KYN treatment. Lipid peroxidation enzymes increased with KYN have been shown to produce H2O2 outside of the electron transport chain. Our data suggest that IDO inhibition may represent a novel therapeutic approach for the attenuation of sarcopenia and possibly other age-associated conditions associated with KYN accumulation such as bone loss and neurodegeneration.