The search for reliable early indicators of age-related cognitive decline represents an important avenue in aging research. Most research on late-life development charts cognitive change as a function of chronological age (CA), however, although CA is a commonly used developmental index, it offers little insight into the mechanisms underlying cognitive decline. In contrast, biological age (BioAge), reflecting the vitality of essential biological processes, represents a promising operationalization of developmental time. My overall programmatic doctoral research interests involve the identification of biological risk factors that predict age-related cognitive decline, impairment and dementia. In this dissertation document, I present: an overview of my empirical contributions to the BioAge and cognitive aging literature throughout my doctoral training; the dissertation project which uses preliminary data from the PREVENT study and provides evidence that elevated plasma pro-inflammatory proteins are associated with cognitive status (healthy controls (HC) vs Alzheimer’s disease dementia (AD)), cognitive performance and are related to poorer cognitive performance in amnestic mild cognitive impairment (a-MCI); and a discussion on the broad implications of the project results and future directions in BioAge research. / Graduate

Hypercholesterolemia is a significant risk factor in the development of cardiovascular disease and is associated with chronic leukocyte adhesion in the microvasculature. While the underlying mechanisms behind this have yet to be determined, it may be possible that hypercholesterolemia impairs the fluid shear stress (FSS) inactivation of neutrophils through the rigidifying effect of cholesterol on membrane fluidity. FSS restricts surface expression of CD18 integrins through cathepsin B (ctsB) proteolysis, which minimizes neutrophil adhesivity. If hypercholesterolemia blocks FSS mechanotransduction, then the inhibition of CD18 cleavage may link pathologic blood cholesterol elevations with dysregulated neutrophil adhesion. We hypothesized that elevated cholesterol contributes to dysregulated neutrophil adhesion by impairing ctsB FSS-induced CD18 cleavage through membrane fluidity changes. In the first part of this study, we demonstrated that FSS-induced CD18 cleavage is a robust response of neutrophils and involves selective cleavage of macrophage 1-antigen (Mac1) through ctsB proteolysis. The second part of this study confirmed that ctsB regulates neutrophil adhesion through its proteolytic actions on Mac1, an important integrin involved in adhesion and chemotaxis. Specifically, ctsB accelerated neutrophil motility through an effect on Mac1 integrins during pseudopod retraction. Furthermore, by using a flow-based assay to quantify the mechanoregulation of neutrophil adhesivity, we demonstrated that FSS-induced ctsB release promoted neutrophil detachment from platelet-coated substrates and unstimulated endothelium. For the third part of this study, we linked cholesterol-related membrane fluidity changes with the ability of FSS to restrict neutrophil adhesion through Mac1. We also determined that pathologic cholesterol elevations associated with hypercholesterolemia could block FSS-induced Mac1 cleavage and were linked to disrupted tissue blood flow. This was accomplished using low-density lipoprotein receptor deficient (LDLR-/-) mice fed a high-fat diet. Ultimately, the results provided in the present study confirmed that cholesterol-related changes in membrane fluidity blocked the ability of ctsB to regulate neutrophil adhesion through FSS-induced Mac1 cleavage. This implicates an impaired neutrophil FSS mechanotransduction response in the dysregulation of neutrophil adhesion associated with hypercholesterolemia. Since dysregulated adhesion may be one of the earliest upstream features of cardiovascular disease associated with hypercholesterolemia, the present study provides a foundation for identifying a new mechanobiological factor in the pathobiology of microcirculatory dysfunction.

Small cell lung cancer (SCLC) is characterised by rapid growth, early metastatic spread and poor long-term survival. The tumour is initially sensitive to chemotherapy and thus objective response rates are high. Unfortunately, this response is often short-lived and SCLC recurs with acquired drug resistance, resulting in early patient death. Despite intensive chemo- and radiotherapy regimes survival has not improved significantly in 20 years. Prior research suggests a critical role for the tumour microenvironment in the pathogenesis of other cancers. Therefore, investigating interactions between SCLC cells and components of the tumour stroma may identify novel therapeutic targets. This thesis demonstrates that extracellular matrix (ECM) proteins present in the tumour microenvironment protect SCLC cells in vitro from chemo- and radiotherapy induced cell cycle arrest and apoptosis via cell surface β1 integrins. Pharmacological and genetic inhibition of phosphoinositol-3 kinase signalling abrogates this effect, defining a central role for this pathway in SCLC de novo drug resistance. Furthermore, the protective effect of ECM occurs without alteration in chemotherapy-induced DNA damage allowing SCLC cells to survive with new genetic defects. Integrin-mediated drug resistance has been shown to be important in other tumours and thus development of strategies to inhibit this pathway may yield new anti-cancer treatments. The design of targeted agents to down-regulate integrin-ECM interaction requires an in depth understanding of the intracellular signals that modulate integrin affinity. Two such pathways are investigated in this thesis. 1) H-Ras, a dominant suppressor of integrin affinity, acts in part through phosphorylation of Erk. Data presented here demonstrate that H-Ras also suppresses integrins through a phospholipase-C epsilon (PLCε)-dependent pathway, thus explaining discrepancies in prior data and confirming a physiological role for this recently identified phospholipase. 2) The Notch signalling pathway has been shown to have important roles in both development and cancer. It is shown here that activation of Notch signalling increases β1 integrin affinity and can protect SCLC cells from chemotherapyinduced apoptosis. However the mechanisms appear to be different; Notch-1 modulates integrin activation through the small GTPase R-Ras and Notch-2 promotes SCLC cell survival. These results define a new Notch pathway, a novel integrin modulator and a potential therapeutic target in SCLC cells. In addition to ECM proteins, the tumour microenvironment contains immune cells that may contribute to cancer growth. The cellular composition of the SCLC stroma is poorly understood. The data presented here indicate that the microenvironment of SCLC is infiltrated by lymphocytes and macrophages, the degree of which independently predicts patient survival. This suggests that the host immune system may be able to suppress SCLC growth. It is well recognised that patients with SCLC have defects in cellular immunity which correlate with survival. An in vitro coculture model was used to investigate the underpinning mechanisms, showing SCLC cells can suppress CD4+ T-cell proliferation and macrophage CD86 expression. Furthermore, preliminary data suggest a role for a soluble factor released by SCLC cells that up-regulates CD4+ T-cell production of IL-10. The work in this thesis implies a complex interaction between SCLC cells, ECM and immune cells in the tumour microenvironment. Manipulation of these pathways may have important therapeutic implications. Further investigation is required to understand the mechanisms of this interplay, which may in part be aided by prospective analysis of patient tumour samples and an in vivo model of SCLC.

With increasing problem of resistance development in bacteria against conventional antibiotics, as well as problems associated with diseases either triggered or enhanced by infection, there is an urgent need to identify new types of effective therapeutics for the treatment of infectious diseases and its consequences. Antimicrobial and anti-inflammatory peptides have attracted considerable interest as potential new antibiotics in this context. While antimicrobial function of such peptides is being increasingly understood demonstrated to be due to bacterial membrane disruption, the mechanisms of their anti-inflammatory function are poorly understood. Since bacterial membrane component lipopolysaccharide triggers inflammation, this thesis aims at clarifying importance of lipopolysaccharide (LPS)-peptide interactions while investigating possible modes of action of peptides exhibiting anti-inflammatory effect. Furthermore, effect of poly(ethylene)glycol (PEG)-conjugation was investigated to increase performance of such peptides. Results presented in this thesis demonstrate that peptide-induced LPS- and lipid A binding/scavenging is necessary but not sufficient criterium for anti-inflammatory effects of peptides. Furthermore, preferential binding to LPS over lipid membrane, as well as higher binding affinity to the lipid A moiety within LPS, are seen for these peptides. In addition, results demonstrate that apart from direct LPS scavenging, membrane-localized peptide-induced LPS scavenging seem to contribute partially to anti-inflammatory effect. Furthermore, fragmentation and densification of LPS aggregates, in turn dependent on the peptide secondary structure on LPS binding, as well as aromatic packing interactions, correlate to the anti-inflammatory effect, thus promoting peptide-induced packing transition in LPS aggregates as key for anti-inflammatory functionality. Thus, peptide-induced LPS aggregate disruption together with reduction of the negative charge of LPS suggests the importance of phagocytosis as an alternative to the inflammatory pathway, which needs to be further investigated. Furthermore, PEG conjugation of peptide results in strongly reduced toxicity at a cost of reduced antimicrobial activity but markedly retained anti-inflammatory effect. Taken together, the results obtained in this work have demonstrated several key issues which need to be taken into consideration in the development of effective and selective anti-inflammatory peptide therapeutics for the treatment of severe Gram-negative bacterial infections.

Thesis (MSc (Biochemistry))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Crosstalk exists between the stress- and immune-system and this crosstalk has pharmacological importance in the use of glucocorticoids (GCs) as anti-inflammatory drugs for diseases such as asthma and arthritis. The focus of studies on this crosstalk has mainly been on the effects of GCs on immune function. The effect of the immune system on GC action, especially in the periphery, is not as well studied. The liver plays an important role in inflammation and stress in producing the acute phase proteins (APPs) required for the resolution of inflammation as well as in producing systemic glucose, through gluconeogenesis, required to fuel the stress responses. Understanding effects of stress and inflammation and their interplay in the liver is thus not only useful to expand our understanding of these systems but could also have clinical applications in understanding the side-effects associated with pharmacological use of GCs. CpdA has been identified as a selective glucocorticoid receptor (GR) modulator (SEGRM) in that it is able to repress genes but is not capable of activating genes via the GR. This attribute suggests that CpdA has the potential to be developed as an anti-inflammatory drug that displays fewer side effects. The current study investigated and compared effects of dexamethasone, a potent GR agonist, and CpdA, in the presence and absence of interleukin 6 (IL6), on the glucocorticoid receptor, three metabolic enzyme genes, involved in gluconeogenesis, and three APP genes. The metabolic enzyme genes investigated were tyrosine amintotransferase (TAT), phosphoenolpyruvate carboxykinase (PEPCK), and gamma glutmayltransferase (GGT), while the APP genes were serum amyloid A (SAA), Creactive protein (CRP), and corticosteroid-binding globulin (CBG). The study investigated effects at the protein level, using Western blotting and ELISA assays, the protein activity level, using enzyme activity assays and whole cell binding, and at the mRNA level, using quantitive polymerase chain reactions (qPCR), in a mouse hepatoma cell line (BWTG3). The study showed that dexamethasone (Dex) and IL6 generally have divergent effects on the GR and metabolic enzymes Crosstalk exists between the stress- and immune-system and this crosstalk has pharmacological importance in the use of glucocorticoids (GCs) as anti-inflammatory drugs for diseases such as asthma and arthritis. The focus of studies on this crosstalk has mainly been on the effects of GCs on immune function. The effect of the immune system on GC action, especially in the periphery, is not as well studied. The liver plays an important role in inflammation and stress in producing the acute phase proteins (APPs) required for the resolution of inflammation as well as in producing systemic glucose, through gluconeogenesis, required to fuel the stress responses. Understanding effects of stress and inflammation and their interplay in the liver is thus not only useful to expand our understanding of these systems but could also have clinical applications in understanding the side-effects associated with pharmacological use of GCs. CpdA has been identified as a selective glucocorticoid receptor (GR) modulator (SEGRM) in that it is able to repress genes but is not capable of activating genes via the GR. This attribute suggests that CpdA has the potential to be developed as an anti-inflammatory drug that displays fewer side effects. The current study investigated and compared effects of dexamethasone, a potent GR agonist, and CpdA, in the presence and absence of interleukin 6 (IL6), on the glucocorticoid receptor, three metabolic enzyme genes, involved in gluconeogenesis, and three APP genes. The metabolic enzyme genes investigated were tyrosine amintotransferase (TAT), phosphoenolpyruvate carboxykinase (PEPCK), and gamma glutmayltransferase (GGT), while the APP genes were serum amyloid A (SAA), Creactive protein (CRP), and corticosteroid-binding globulin (CBG). The study investigated effects at the protein level, using Western blotting and ELISA assays, the protein activity level, using enzyme activity assays and whole cell binding, and at the mRNA level, using quantitive polymerase chain reactions (qPCR), in a mouse hepatoma cell line (BWTG3). The study showed that dexamethasone (Dex) and IL6 generally have divergent effects on the GR and metabolic enzymes / AFRIKAANSE OPSOMMING: Kruiskommunikasie bestaan tussen die stres– en die immuunsisteem en hierdie kruiskommunikasie is van farmakologiese belang vir die gebruik van glukokortikoïede (GKe) as anti-inflammatoriese medikasie vir siektes soos asma en artritis. Tot dusver was die fokus van studies oor hierdie kruiskommunikasie hoofsaaklik op die effek van GKe op immuunfunksie. Die effek van die immuunsisteem op GK werking, veral in die periferie, is nie so goed bestudeer nie. Die lewer speel ʼn belangrike rol in inflammasie en stres deurdat dit die akute fase proteïene (AFPs) produseer wat benodig word vir die resolusie van inflammasie en omdat dit ook sistemiese glukose produseer, d.m.v. glukoneogenese, wat benodig word om die stres reaksie te dryf. ’n Beter insig in die effek van stres en inflammasie sowel as hul interaksie in die lewer is dus handig, nie net om ons begrip van hierdie sisteme te verbeter nie, maar ook omdat dit kliniese toepassing kan hê deurdat dit ons begrip van die newe-effekte wat gepaard gaan met die farmakologiese gebruik van GKe verbeter. Verbinding A (CpdA) is geïdentifiseer as ʼn selektiewe glukokortikoïed reseptor (GR) moderator (SERGM) omdat dit die vermoë het om gene te onderdruk maar nie te aktiveer d.m.v. die GR. Hierdie eienskap dui op die potensiaal van CpdA om ontwikkel te word as ʼn anti-inflammatoriese middel met minder newe-effekte. Die huidige studie het die effekte van dexamethasone, ʼn sterk GR agonis, en CpdA, beide in die teenwoordigheid en afwesigheid van interleukin 6 (IL6), op die GR, drie metaboliese ensiem gene wat betrokke is by glukoneogenese, sowel as drie APP gene, ondersoek en vergelyk. Die metaboliese ensiem gene wat ondersoek is, is tirosien aminotransferase (TAT), fosfoenolpirovaat karboksikinase (PEPCK), en gamma glutamieltransferase (GGT), terwyl die APP gene serum amiloïede A (SAA), C-reaktiewe proteïen (CRP), en kortikosteroïed bindings globien (CBG) was. Die studie het die effekte in ʼn muis hepatoma sellyn (BWTG3) op die proteïen vlak, deur van Western blotting en ELISA essays gebruik te maak, die proteïen aktiwiteits vlak, deur van ensiem aktiwiteits essays en vol-sel binding gebruik te maak, sowel as op die mRNA vlak, deur van kwantitatiewe polimerase ketting reaksie (qPCR) gebruik te maak, ondersoek. Die studie toon dat dexamethasone (Dex) en IL6 in die algemeen divergente effekte het op die GR en metaboliese ensieme deurdat Dex GR af-reguleer en die metaboliese ensieme op-reguleer, terwyl IL6 die GR op-reguleer en die metaboliese ensieme af-reguleer, en dat hulle funksies konvergerend is vir die APPs deurdat beide positiewe APPs opreguleer en negatiewe APPs afreguleer. In teenstelling met Dex het CpdA die GR op-gereguleer en die metaboliese ensieme af-gereguleer terwyl dit, soos Dex, die positiewe APPs op-gereguleer en die negatiewe APPs af-gereguleer het. Ons resultate vir Dex en IL6 word ondersteun deur vorige werk in die literatuur. Ons studie is wel uniek omdat dit die ondersoek van drie metaboliese ensieme kombineer met die ondersoek van drie APPs, sowel as GR vlakke in ʼn enkele sisteem onder dieselfde eksperimentele kondisies. Verder het ons resultate met CpdA verskeie nuwe aspekte, soos die af-regulering van metaboliese gene, opgelewer wat bydra tot die groeiende poel van kennis oor hierdie ongewone GR ligand en die moontlike farmakologiese gebruik daarvan.

Chaque année, la grippe provoque des centaines de milliers de décès dans le monde. Dans le cas d’infections sévères, il a été démontré que la génération excessive de molécules inflammatoires telles que les cytokines et les chimiokines, la sécrétion d’espèces réactives dérivées de l'oxygène ainsi que l’afflux massif de cellules immunitaires innées et adaptatives dans les voies respiratoires contribuent à la génération de dommages pulmonaires aigus et contribuent à l'immunopathologie reliée à l’infection. Tenant compte de ce fait, le défi actuel dans le traitement de la grippe est de contrôler la réponse inflammatoire tout en inhibant la réplication virale afin de permettre à l'organisme de se défendre contre les infections sévères à l'influenza. Des études récentes ont montré que l’activation du récepteur nucléaire PPARγ par ses ligands, tel que la 15d-PGJ[indice inférieur 2], diminuait l’inflammation pulmonaire et améliorait la survie des souris infectées avec des doses létales du virus influenza. Mis à part ses effets sur PPARγ, le ligand 15d-PGJ[indice inférieur 2] est aussi connu pour activer le facteur nucléaire antioxydant Nrf2. Il a été montré que Nrf2 réduit la réplication du virus influenza. Cependant, son mode d'action dans cette fonction nécessite une clarification. De manière intéressante, une étude a montré que Nrf2 réduit l’inflammation pulmonaire en régulant l’expression de PPARγ et ceci dans un modèle murin du syndrome de détresse respiratoire aigu. Les résultats de ces études précédentes mènent à l’hypothèse que les voies de PPARγ et Nrf2 interagissent fonctionnellement et qu'elles sont impliquées dans la réduction de l’inflammation induite lors d'infections sévères causées par l'influenza. L’objectif général de cette étude est donc de mieux comprendre les mécanismes protecteurs de PPARγ et Nrf2 dans la régulation de l’inflammation et la réplication virale suite à une infection par le virus influenza. Nos résultats ont démontré premièrement que le fait de cibler les deux voies moléculaires PPARγ et Nrf2, permet une inhibition significative de l’inflammation et de la morbidité liée à l’infection. Dans un deuxième temps, nos résultats dévoilent le mécanisme antiviral de Nrf2 et démontrent que l’activation de cette voie réduit la réplication du virus influenza d’une façon dépendante de l’expression de l’antiprotéase SLPI.

published_or_final_version / Community Medicine / Doctoral / Doctor of Philosophy

published_or_final_version / Surgery / Master / Master of Medical Sciences

Skeletal muscle protein synthesis is regulated by the mammalian target of rapamycin (mTOR) signaling pathway. The first objective was to optimize the methodological procedures for assessing mTOR signaling in horses. The response of mTOR signaling (P-Akt Ser473, P-S6K1 Thr389, P-rpS6 Ser235/26 & 240/244, and P-4EBP1 Thr37/46 by Western blotting techniques) to meal consumption was determined at three gluteal muscle biopsy depths (6, 8, and 10 cm), and the repeatability of the contralateral side at 8 cm during 5 days of repeated biopsies. There was no effect (P > 0.05) of sampling side or biopsy depth on mTOR signaling in mature horses. During repeated biopsies there was an increase (P < 0.05) in downstream (P-S6K1 Thr389, P-rpS6 Ser235/236 & 240/244 and P-4EBP1 Thr389) mTOR signaling in response to feeding. The second objective was to characterize alterations in mTOR signaling throughout the equid lifespan. Adolescent horses (yearlings and two year olds) studied in the postprandial had a lowered (P < 0.05) activation of downstream mTOR signaling with aging. There was a lower (P < 0.05) abundance of P-S6K1 Thr389 in aged horses (23.5 years old) than in mature horses (11 years old) during the post-absorptive state. The final objective was to assess mTOR signaling during acute and chronic inflammation. Acute inflammation occurred during 5 days of repeated biopsies, and chronic inflammation is characteristic of the aged. During acute inflammation, characterized by increased muscle mRNA expression of inflammatory cytokines, there was an increase (P < 0.05) in downstream mTOR signaling. Chronic inflammation resulted in a decrease (P < 0.05) in the abundance of P-S6K1 Thr389. Phenylbutazone was administered to reduce (P < 0.05) acute and chronic inflammation in muscle. Phenylbutazone administration during acute inflammation reduced (P < 0.05) the activation of downstream mTOR signaling and trended to increase (P = 0.09) P-S6K1 Thr389 abundance during chronic inflammation. Whole-body protein synthesis determined using isotope infusion techniques increased (P < 0.05) when chronic inflammation was reduced due to phenylbutazone administration. This research provides new standards for muscle biopsy collection when examining mTOR signaling, and insight into management and feeding practices for adolescent and aging horses.

Blackberries are rich in polyphenols including anthocyanins. Polyphenols are hypothesized to have biological activities that impact positively on human health. The purpose of these studies was to develop phenolic extracts from selected cultivars of blackberries currently grown in Kentucky as potential Botanical Drug Products for the treatment and prevention of cancer and inflammatory diseases. An ultrasound-assisted ethanol extraction method was employed to obtain anthocyanin-containing extracts (ACEs) from puree or powder (lyophilized puree) of blackberries. ACEs were analyzed for total anthocyanin and phenolics content, polymeric color, and total antioxidant capacity (TAC). The influence of water content in the extraction system was evaluated. A 90 day stability study of the extract and a 48 h stability study of the extract in biologically relevant buffers were completed. HPLC-MS results showed the anthocyanins in ACE were mainly cyanidin-based. As compared to powder-derived ACEs, puree-derived ACEs contained similar amounts of anthocyanins, but greater levels of phenolics and increased TAC. The in vitro antiproliferative effects of ACEs were evaluated in human leukemia (HL- 60), colon (HT-29), and breast (MCF-7) cancer cells. The anticancer mechanism involving reactive oxygen species (ROS) generation was investigated. It was found puree-derived ACEs significantly enhanced production of H2O2 and cytotoxicity in all cell lines as compared to powder-derived ACEs. Cyanidin 3-glucoside exerted anticancer effect by acting synergistically or additively with other active components in the extracts. Furthermore, the phenolic-enriched fractions were separated from non-phenolic fractions in ACEs and found to have potent antioxidant and antiproliferative activities. Pureederived ACE and corresponding phenolic-enriched methanol fraction (MF) induced cell death through ROS-independent caspase 3 pathway whereas the cytotoxicity induced by powder-derived ACE and corresponding MF is related to ROS mechanisms. The in vitro anti-inflammatory studies showed ACEs inhibited Lipid A-induced Interleukin-12 (IL-12) release from mouse dendritic cells, and modulated lipopolysaccharide (LPS)-induced secretion of tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6) from murine macrophages. These studies have important implications for the potential use of blackberry extracts for the treatment and prevention of cancer and inflammation diseases and provide essential information for the development of Botanical Drug Products from extracts derived from blackberries and other fruits.