Mucositis refers to the widespread damage of mucosal surfaces throughout the length of the alimentary tract (AT) that can occur during cancer treatment. Its development is an important clinical problem that complicates and limits treatment options as well as adversely affecting the quality of life and treatment outcomes for patients. Recent studies directed at determining the pathobiology of mucositis have indicated increasing evidence for the role of transcription factors, such as nuclear factor-κB (NF-κB), and certain pro-inflammatory cytokines, for example tumour necrosis factor (TNF), interleukin-1β (IL-1β) and interleukin- 6 (IL-6), in its development. This thesis developed from an initial clinical investigation in which the expression of NF-κB and COX-2 in oral mucosa was investigated in patients undergoing chemotherapy. Increased levels of NF-κB were demonstrated in the buccal mucosa following chemotherapy. It is well established that mucositis occurs in different sites of the AT. The aims of this research, therefore, were to compare and contrast the changes that do occur at different sites of the AT following chemotherapy in an established animal model (Dark Agouti (DA) rat). Furthermore, the studies were conducted to determine whether changes in tissue and serum levels of NF-κB and pro-inflammatory cytokines occurred following chemotherapy and, with respect to tissue levels, identify whether there were differences in expression at different sites throughout the AT. The final aim was to examine whether the histological changes and changes in pro-inflammatory cytokines were affected by the type of chemotherapy drug used. The effects of three chemotherapy drugs with different mechanisms of action (irinotecan, methotrexate and 5-fluorouracil) were investigated, all of which can cause mucositis in the clinical setting. The thesis is divided into a Literature Review (Chapter 1) followed by 4 research papers: Chapter 2 – “Nuclear factor- κB (NF- κB) and cyclooxygenase-2 (COX-2) expression in the oral mucosa following cancer chemotherapy” Chapter 3 -“Characterisation of mucosal changes in the alimentary tract following administration of irinotecan: Implications for the pathobiology of mucositis” Chapter 4 – “Is the pathobiology of chemotherapy-induced alimentary tract mucositis influenced by the type of mucotoxic drug administered?”, Chapter 5 – “Serum levels of NF-κB and pro-inflammatory cytokines following administration of mucotoxic drugs”. Chapter 6 provides an overall summary and discussion of the results. Previous research has indicated that following administration of chemotherapeutic agents there may be subclinical changes occurring in the mucosa prior to obvious clinical manifestations. The results presented in this thesis also demonstrate this in both humans and animals following administration of chemotherapy. Immunohistochemical analysis of tissue taken from the oral cavity, jejunum and colon from the DA rats following chemotherapy demonstrated that changes in NF-κB and the pro-inflammatory cytokines, TNF, IL-1β and IL- 6, occurred at all sites over a 72 hour time period. This was evident before severe histological evidence of mucositis were observed such as epithelial atrophy in the oral mucosa, atrophy, blunting and fusion of the villi in the jejunum and crypt ablation in the jejunum and colon. Furthermore, each of the three drugs caused different patterns of NF-κB and pro-inflammatory cytokine expression in the tissues; in spite of this, however, histological features of damage were similar. With respect to serum levels of NF-κB and pro-inflammatory cytokines, differences were observed between the serum and tissue levels. Generally, serum changes followed initial histological changes in the tissues, or occurred simultaneously with histological changes. The mechanisms behind this are unclear; however it may be that elevated cytokines in the tissues “overflow” into the serum as tissue damage increases. Furthermore, the use of serum cytokine level measurement to predict mucosal damage is limited because of the differences in timing and short time intervals between changes in the serum and tissues. This thesis has provided additional important information on mucositis pathobiology and highlights its complexity. In particular, it has provided new evidence supporting the notion that mucositis is not restricted to the oral cavity and that other sites of the AT are also affected. Furthermore, these results confirm previous data indicating that subclinical changes occur in the mucosa prior to the development of obvious histological damage or clinical manifestations of mucositis. Contrary to previous reports, these studies have indicated that, although the clinical and histological changes may be similar, the alterations in NF-κB and pro-inflammatory cytokines in the tissues are affected by the type of drug used. This has important implications in the management and prevention of mucositis in the clinical setting particularly when multi-drug or chemotherapy-radiotherapy regimens are used. A common pathway that leads to mucosal damage is yet to be determined. The fact that serum levels appear to reflect the “global” nature of the effects of chemotherapy, highlights the fact that ongoing research needs to be directed, not necessarily at specific side effects, but rather how side effects of chemotherapy are interrelated so that better patient management can be achieved and ultimately provide optimum treatment and better survival for patients with cancer. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1321557 / Thesis (Ph.D.) -- University of Adelaide, School of Dentistry, 2008

<p>The novel cyanoguanidine CHS 828 has shown promising antitumor activity in many in vitro and in vivo studies. </p><p>The long-term 14 days in vitro hollow fiber cultures, where tumor cells from different tumor cell lines were cultured inside semipermeable fibers, were more resistant to CHS 828 and other cytotoxic drugs than the shorter-term 3 days cultures. CHS 828 was generally more effective against haematological than solid tumor cells from both cell lines and patients samples. </p><p>In vivo, the hollow fibers were implanted into immunocompetent rats and the pharmacokinetics, tumor response and/or toxicity (pharmacodynamics) of CHS 828 were successfully assayed. CHS 828 showed higher activity in this model when a more protracted schedule was used. The quantitative relationships between dose, plasma concentration and response (PK/PD model) developed for CHS 828 explained this phenomenon partly by dose-dependent fraction absorbed and partly by a schedule-dependent pharmacodynamic effect.</p><p>Modelling of the in vitro CHS 828 and standard cytotoxic drugs concentration-time effect data in different tumor cell types and characterization of pattern of change of the potency and the slope of the concentration-time effect curves were performed. The results suggest two different mechanisms of action for CHS 828 and that CHS 828 cytotoxicity may depend on the schedule used.</p><p>The NF-kB pathway that regulates the transcription of anti-apoptotic genes proved to be inhibited by CHS 828 in different tumor cell lines and the inhibition was correlated to the cell death induced by this agent. CHS 828 did not seem to induce the NF-kB inhibition by affecting the proteasome activity. </p><p>The in vitro and in vivo hollow fiber methods were also used successfully to evaluate the new paclitaxel formulation, Pacliex. Pacliex had a similar activity to that of the clinically used formulation Taxol®.</p>

Early innate response of intestinal epithelial cells is the first line defense against enteric pathogens. Toxoplasma gondii infections acquired naturally via the peroral route, encounter intestinal epithelial cells early post-infection. Although the population structure of T. gondii is known to be highly clonal, clinical strains of T. gondii have been classified into three genotypes based on their virulence. In this study we investigated whether human intestinal epithelial cell immune response to T. gondii is virulence dependent. We demonstrated distinct virulence of the three T. gondii genotype strains evaluated in human intestinal epithelial cells by their capacity to replicate and induce host cell cytotoxicity. The early host innate mechanisms such as activation of signaling pathways and induction of innate effectors were likewise differentially elicited by the three T. gondii strains. Low levels of TLR dependent NF-kB activation and a failure to rapidly up-regulate innate cytokine and chemokine genes was observed after virulent Type I strain infection. In contrast, early innate response to the less virulent Type II strain was rapid, efficient and led to high levels of IL-8 and IL-6 secretion, whereas response to Type III parasites was intermediate. Early expression of b-defensin 2 gene was suppressed specifically by virulent Type I strain and its activation prior to infection in intestinal epithelial cells led to decreased parasite viability. These findings provide evidence for T. gondii strain virulence dependent down-modulation of early human intestinal epithelial cell innate responses and highlight the importance of these cells in host defense against this infection.

The novel cyanoguanidine CHS 828 has shown promising antitumor activity in many in vitro and in vivo studies. The long-term 14 days in vitro hollow fiber cultures, where tumor cells from different tumor cell lines were cultured inside semipermeable fibers, were more resistant to CHS 828 and other cytotoxic drugs than the shorter-term 3 days cultures. CHS 828 was generally more effective against haematological than solid tumor cells from both cell lines and patients samples. In vivo, the hollow fibers were implanted into immunocompetent rats and the pharmacokinetics, tumor response and/or toxicity (pharmacodynamics) of CHS 828 were successfully assayed. CHS 828 showed higher activity in this model when a more protracted schedule was used. The quantitative relationships between dose, plasma concentration and response (PK/PD model) developed for CHS 828 explained this phenomenon partly by dose-dependent fraction absorbed and partly by a schedule-dependent pharmacodynamic effect. Modelling of the in vitro CHS 828 and standard cytotoxic drugs concentration-time effect data in different tumor cell types and characterization of pattern of change of the potency and the slope of the concentration-time effect curves were performed. The results suggest two different mechanisms of action for CHS 828 and that CHS 828 cytotoxicity may depend on the schedule used. The NF-kB pathway that regulates the transcription of anti-apoptotic genes proved to be inhibited by CHS 828 in different tumor cell lines and the inhibition was correlated to the cell death induced by this agent. CHS 828 did not seem to induce the NF-kB inhibition by affecting the proteasome activity. The in vitro and in vivo hollow fiber methods were also used successfully to evaluate the new paclitaxel formulation, Pacliex. Pacliex had a similar activity to that of the clinically used formulation Taxol®.

Colon cancer and obesity are two significant and related pathological states with multiple etiological factors. In this dissertation, it was hypothesized that tumor growth is accelerated in the altered state of obesity due to their resistance towards tumor necrosis factor-alpha (TNF-alpha) mediated cytotoxicity. Physiologically elevated TNF-alpha in an obese state induces increased nuclear transcription factor-kB (NF-kB) activity, known to transcribe genes crucial to cell survival. Insulin resistance, oxidative stress, and a pro-inflammatory environment are few of the biological consequences of TNF-alpha and NF-kB pathway activation, and further contribute to disease progression. <br /><br /> Three major studies were conducted to investigate phenotypical changes in obesity associated tumors. Firstly, characteristics of the TNF-alpha resistant phenotype were preliminarily assessed by evaluating the effects of exogenous TNF-alpha treatment to HT-29 cells. Elevated levels of NF-kB in response to exogenous TNF-alpha gave an indication that this pathway is critical for cell survival. Furthermore, upregulation of TNF-alpha receptor 2 (TNFR2) suggested another strategy by which the cells were utilizing exogenous TNF-alpha for a survival advantage. Inhibition of NF-kB via St. John?s Wort treatment demonstrated that HT-29 cells may be sensitized towards TNF-alpha mediated cytotoxicity. <br /><br /> Zucker obese (Zk-Ob), Zucker lean (Zk-Ln), and Sprague Dawley (SD) animal models were used to assess tumor phenotype <em>in vivo</em>. Remarkable physiological differences between genotypes were observed. Zk-Ob rats had significantly higher body and organ weights as well as plasma TNF- alpha, insulin, leptin, and oxidative markers than Zk-Ln and SD animals. Tumor incidence and multiplicity were also notably higher in Zk-Ob rats. Protein analyses demonstrated increased levels of TNF-alpha, TNFR2, NF-kB, IkB kinase beta (IKKbeta), insulin receptor (IR), insulin like growth factor-I-receptor (IGF-IR), and mitogen activated protein kinase (MAPK) in Zk-Ob tumors than Zk-Ln counterparts. In all groups, tumors generally had higher protein expression than surrounding, normal appearing colonic mucosa. It is well known that these molecules are involved in signaling pathways that influence and co-operate with each other in rendering growth autonomy to tumor tissue. <br /><br /> A higher number of lesions in the distal than proximal colon in Zk-Ob rats was observed, supporting the emerging concept that genotype/physiological state of the host affects development and distribution of tumors. Thus, a third study was conducted to explore differences between distal and proximal tumor phenotype. Results demonstrated that expression of TNFR2, NF-kB, IR, IGF-IR, and MAPK p44 were significantly higher in distal than proximal tumors. This observation suggested that development of tumors in different regions of the colon varied under the same physiological conditions. Moreover, phenotype of distal tumors appeared to be upregulating survival pathways in comparison to proximal lesions, possibly explaining the higher tumor incidence in the distal colon. <br /><br /> Research documented in this thesis supported the hypothesis that the physiological status of the host intricately affects tumor phenotype. In particular, the TNF-alpha resistant phenotype was most prominent in Zk-Ob tumors, and appeared to be associated with upregulation of multiple signaling pathways cooperating towards tumorigenesis.

Colon cancer and obesity are two significant and related pathological states with multiple etiological factors. In this dissertation, it was hypothesized that tumor growth is accelerated in the altered state of obesity due to their resistance towards tumor necrosis factor-alpha (TNF-alpha) mediated cytotoxicity. Physiologically elevated TNF-alpha in an obese state induces increased nuclear transcription factor-kB (NF-kB) activity, known to transcribe genes crucial to cell survival. Insulin resistance, oxidative stress, and a pro-inflammatory environment are few of the biological consequences of TNF-alpha and NF-kB pathway activation, and further contribute to disease progression. <br /><br /> Three major studies were conducted to investigate phenotypical changes in obesity associated tumors. Firstly, characteristics of the TNF-alpha resistant phenotype were preliminarily assessed by evaluating the effects of exogenous TNF-alpha treatment to HT-29 cells. Elevated levels of NF-kB in response to exogenous TNF-alpha gave an indication that this pathway is critical for cell survival. Furthermore, upregulation of TNF-alpha receptor 2 (TNFR2) suggested another strategy by which the cells were utilizing exogenous TNF-alpha for a survival advantage. Inhibition of NF-kB via St. John?s Wort treatment demonstrated that HT-29 cells may be sensitized towards TNF-alpha mediated cytotoxicity. <br /><br /> Zucker obese (Zk-Ob), Zucker lean (Zk-Ln), and Sprague Dawley (SD) animal models were used to assess tumor phenotype <em>in vivo</em>. Remarkable physiological differences between genotypes were observed. Zk-Ob rats had significantly higher body and organ weights as well as plasma TNF- alpha, insulin, leptin, and oxidative markers than Zk-Ln and SD animals. Tumor incidence and multiplicity were also notably higher in Zk-Ob rats. Protein analyses demonstrated increased levels of TNF-alpha, TNFR2, NF-kB, IkB kinase beta (IKKbeta), insulin receptor (IR), insulin like growth factor-I-receptor (IGF-IR), and mitogen activated protein kinase (MAPK) in Zk-Ob tumors than Zk-Ln counterparts. In all groups, tumors generally had higher protein expression than surrounding, normal appearing colonic mucosa. It is well known that these molecules are involved in signaling pathways that influence and co-operate with each other in rendering growth autonomy to tumor tissue. <br /><br /> A higher number of lesions in the distal than proximal colon in Zk-Ob rats was observed, supporting the emerging concept that genotype/physiological state of the host affects development and distribution of tumors. Thus, a third study was conducted to explore differences between distal and proximal tumor phenotype. Results demonstrated that expression of TNFR2, NF-kB, IR, IGF-IR, and MAPK p44 were significantly higher in distal than proximal tumors. This observation suggested that development of tumors in different regions of the colon varied under the same physiological conditions. Moreover, phenotype of distal tumors appeared to be upregulating survival pathways in comparison to proximal lesions, possibly explaining the higher tumor incidence in the distal colon. <br /><br /> Research documented in this thesis supported the hypothesis that the physiological status of the host intricately affects tumor phenotype. In particular, the TNF-alpha resistant phenotype was most prominent in Zk-Ob tumors, and appeared to be associated with upregulation of multiple signaling pathways cooperating towards tumorigenesis.

The molecular mechanisms of putative anti-inflammatory nutrients, i.e., fish oil, curcumin and limonin, were investgated with respect to CD4+ T cell function. Initially, using a DO11.10 mouse model which exhibits a transgenic T cell receptor specific to OVA 323-339 peptide, we demonstrated that dietary fish oil suppresses antigen-specific Th1 clonal expansion in vivo. Following immunization, the accumulation of adoptively transferred transgenic cells in wild type recipient mouse lymph nodes was suppressed. In addition, cell division analysis by carboxyfluorescein succinimidyl ester (CFSE) revealed that both total cell number in lymph nodes as well as cell division were decreased by fish oil. Since n-3 polyunsaturated fatty acids (PUFA), active long chain fatty acids in fish oil, elicit favorable effects on a variety of cell types, e.g., anti-tumor effect on colonocytes, amelioration of coronary heart disease and anti-inflammatory effects involving T cells, B cells, dendritic cells and macrophages, we postulated that a fundamental mechanism of action may explain the multiple effects observed. In a series of experiments described herein, we demonstrated that n-3 PUFA alters the formation/location of membrane subdomains, referenced to as lipid rafts. Specifically, lipid raft formation at the immunological synapse (IS) in CD4+ T cells was suppressed following membrane enrichment with n-3 PUFA. The alteration of lipid rafts down-regulated the localization of select signaling proteins, including F-actin, PKC and PLC-1, and phosphorylation of PLC-1 at the IS. Consequently, CD4+ T cell proliferation was suppressed as assessed by CFSE analysis and radioactive thymidine incorporation. Phytochemicals have been used for chemopreventive and chemotherapeutic purposes. We examined the putative anti-inflammatory effects of curcumin (1%) and limonin (0.02%) with respect to CD4+ T cell function. Dietary curcumin and limonin suppressed NF-B activation in CD4+ T cells. In addition, CD4+ T cell proliferation was modulated by 2% curcumin. We further investigated the combined therapeutic potential of phytochemicals and fish oil, containing n-3 PUFA. Interestingly, fish oil and limonin together significantly (P<0.05) suppressed T cell proliferation, whereas feeding either fish oil or limonin alone showed little effect. In summary, our data indicated that dietary fish oil alters proximal signaling of T cells by perturbing lipid raft formation. Curcumin and limoin are capable of suppressing NF-B in T cells, thereby exhibiting a synergistic effect when combined with fish oil. Further studies are required to elucidate the relationship of dietary dose of active compoments with respect to mechanism of actions.

L’infection par le Virus Respiratoire Syncytial cause des affections pulmonaires aiguës en pédiatrie caractérisée par une réponse inflammatoire excessive médiée par la production de cytokines par les cellules épithéliales des voies aériennes. Les gènes codant pour ces cytokines sont régulés par le facteur de transcription NF-κB (p50/p65) dont l’activation est classiquement induite par la phosphorylation de son inhibiteur IκBα, ce qui permet l’accumulation de l’hétérodimère au noyau. Par contre, nous avons récemment identifié la phosphorylation en sérine 536 de la sous-unité p65 comme une autre étape essentielle à son activation lors de l’infection des AEC par RSV. Le travail présenté dans ce mémoire a permis de démontrer que l’inhibition de l’expression de RIG-I, de Cardif ou de TRAF6, 3 protéines impliquées dans la reconnaissance cellulaire des virus, conduit à l’inhibition de cette phosphorylation en réponse à RSV. Nous avons également établi à l’aide d’inhibiteurs pharmacologiques et d’ARNi que, parmi les diverses kinases connues pour phosphoryler p65 en réponse à divers stimulus, IKKα/β sont essentielles à cette phosphorylation lors d’une stimulation par RSV. Puisque TRAF6 est bien connu dans la littérature pour activer le complexe IKK, nous proposons que TRAF6, après reconnaissance de l’ARN viral de RSV par RIG-I, active le complexe IKK qui induit la phosphorylation de la sousunité p65 de NF-κB, permettant l’expression de gènes cibles. D’autre part, nous avions précédemment démontré que Nox2, un isoforme de NADPH oxydase, contrôle l’activation de NF-κB en régulant les phosphorylations de IκBα et p65. Nous montrons ici que l’inhibition de Nox2 réduit fortement l’activité du complexe kinase IKK. De plus, la présence au niveau basal de Nox2 est critique pour le niveau d’ARN messager de Cardif. Nous proposons donc que la régulation de la phosphorylation de p65 en ser536 par Nox2 soit via son effet sur Cardif en permettant la fonctionnalité de la voie RIG-I. / The infection by the Respiratory Syncytial Virus causes acute respiratory tract affections among children characterized by an excessive inflammatory response mediated by airway epithelial cells production of cytokines. The genes coding for theses cytokines are regulated by the transcription factor NF-κB (p50/p65) which is classically activated by phosphorylation of its inhibitor IκBα, permitting the nuclear accumulation of the heterodimer. The work presented in this master’s thesis allowed demonstrating that the inhibition of either RIG-I, Cardif or TRAF6, 3 proteins implicated in the cellular recognition of virus, leads to the inhibition of this phosphorylation in response to RSV. Moreover, we established with pharmacological inhibitors and siRNA that, among all kinases known to phosphorylate p65 in response to various stimulus, IKKα/β are essential to this phosphorylation in RSV stimulation. Since TRAF6 is a well-known IKK complex activator in the literature, we propose that TRAF6, after the recognition of the RSV viral RNA by RIG-I, activates the IKK complex witch induces the phosphorylation of the NF-κB subunit p65, allowing the expression of targets genes. Furthermore, we had previously demonstrated that Nox2, a NADPH oxydase isoform, controls the activation of NF-κB by regulating the phosphorylation of IκBα and p65. We show here that the inhibition of Nox2 by siRNA reduces strongly the activity of the IKK complex. Moreover, the basal level presence of Nox2 is critic for the messenger RNA level of Cardif. Thus, we propose that the Nox2 regulation of p65 ser536 is done by its effect on Cardif, which allows the integrity of the RIG-I pathway.

Memory is subdivided into short- and long-term memory. The interaction between transcription factors (TF) and expressed genes are essential steps in memory formation. Some TFs that might be involved in memory formation include CREB, NF-kB and Egr-2. We hypothesized that there would be a difference in the expression levels of these TFs following learning in the Morris Water Maze (MWM). In study one, CD1 mice were categorized into two groups. Group 1 assigned as non-trained control group. Group 2 (experimental group) underwent 9 consecutive days of MWM training. In the second study, male C57BL/6 mice were categorized into four groups. Group 1 was a non-trained control group (allowed to swim randomly). Groups 2, 3, and 4 (experimental groups) had variations in their MWM training. Search strategies, escape latency, time spending in the target quadrant and number of attempts passing the missing platform, were measured. To evaluate the expression levels of TFs pre- versus post-learning, mice were sacrificed at the end of MWM. Hippocampi were separated and Western blot and immunohistochemical procedures were done. In study one, the escape latency decreased progressively toward the end of the acquisition phase in the trained group. The search pattern showed that the mice used primarily spatial strategies. Mice spent more time in the target quadrant during the retention phase. The number of passes over the missing platform peaked on the first day of the retention phase. NF-kB and CREB were expressed significantly higher in the control group versus the MWM trained mice (p = 0.0031 and p < 0.0001 respectively). There was no statistically significant difference in expression of Egr-2 between the two groups (p = 0.3092). In study two, Group 4 showed the highest and Group 1 the lowest levels of CREB expression. CREB and NF-kB were decreased following MWM training in study one. In study two CREB levels were highest in the Group 4 which had interval between the acquisition and retention phases. These differences could be due to multiphasic expression patterns and/or other experimental design issues. Further studies are warranted to examine time dependent differential expression of TFs in memory.

Methylglyoxal (MG) is a reactive dicarbonyl metabolite formed during glucose, protein and fatty acid metabolism. In hyperglycemic conditions, an increased MG level has been linked to the development of diabetes and the accompanying vascular inflammation encountered at both macro- and microvascular levels. The present study explores the mechanisms of MG-induced leukocyte recruitment in mouse cremasteric microvasculature. Biochemical and intravital microscopy studies performed suggest that administration of MG (25 and 50 mg/kg) to mouse cremaster muscle tissue induces dose-dependent leukocyte recruitment in cremasteric vasculature with 84-92% recruited cells being neutrophils. MG treatment up-regulated the expression of endothelial cell (EC) adhesion molecules P-selectin, E-selectin and intercellular adhesion molecule-1 (ICAM-1) via the activation of nuclear factor-κB (NF-κB) signalling pathway and contributed to the increased leukocyte rolling flux, reduced leukocyte rolling velocity, and increased leukocyte adhesion, respectively. The inhibition of NF-κB blunted MG-induced endothelial adhesion molecule expression and thus attenuated leukocyte recruitment. Further study of signalling pathways revealed that MG induced Akt-regulated transient glycogen synthase kinase 3 (GSK3) activation in ECs, which was responsible for NF-κB activation at early time-points (< 1 h). After MG activation for 1 h, the endothelial GSK3 activity was decreased due to the up-regulation of serum- and glucocorticoid-regulated kinase 1 (SGK1), which was responsible for maintaining NF-κB activity at later time-points. Silencing GSK3 or SGK1 attenuated P-selectin, E-selectin and ICAM-1 expression in ECs, and abated MG-induced leukocyte recruitment. SGK1 also promoted cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) activity which was partially involved in ICAM-1 expression. Silencing CREB blunted ICAM-1 expression while P-selectin and E-selectin levels remained unaffected. MG also induced GSK3 activation in isolated neutrophils after 30 min treatment, an effect that was not responsible for MG-elicited Mac-1 expression. These data suggest the sequential activation of GSK3 and SGK1 in ECs as the pivotal signalling mechanism in MG-elicited leukocyte recruitment. Additionally, MG-treatment led to uncoupling of endothelial nitric oxide synthase (eNOS) following MG-induced superoxide generation in ECs. MG triggered eNOS uncoupling and hypophosphorylation associated with superoxide generation and biopterin depletion in EA.hy926 ECs. In cremaster muscle, as well as in cultured murine and human primary ECs, MG increased eNOS monomerization and decreased 5,6,7,8-tetrahydroboipterin (BH4)/total biopterin ratio, effects that were significantly mitigated by supplementation of BH4 or its precursor sepiapterin but not by NG-nitro-L-arginine methyl ester (L-NAME) or 5,6,7,8-tetrahydroneopterin (NH4). These observations confirm that MG administration triggers eNOS uncoupling. In murine cremaster muscle, MG triggered the reduction of leukocyte rolling velocity and the increases in rolling flux, adhesion, emigration and microvascular permeability. MG-induced leukocyte recruitment was significantly attenuated by supplementation of BH4 or sepiapterin or suppression of superoxide by L-NAME confirming the role of eNOS uncoupling in MG-elicited leukocyte recruitment. MG treatment further decreased the expression of guanosine triphosphate cyclohydrolase I in murine primary ECs, suggesting the impaired BH4 biosynthesis caused by MG. Taken together, these data suggest that vascular inflammation and endothelial dysfunction occurring in diabetes may be linked to GSK3/SGK1 regulated adhesion molecule expression, as well as the uncoupling of eNOS evoked by elevated levels of MG. These findings not only provide a better understanding of the role of MG in the development of diabetic vascular inflammation, but also suggest the potential therapeutic targets for MG-sensitive endothelial dysfunction in diabetes.