京都大学 / 新制・課程博士 / 博士(医学) / 甲第23468号 / 医博第4775号 / 新制||医||1053(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 竹内 理, 教授 山下 潤, 教授 戸口田 淳也 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Aims: The ability of lipopolysaccharide (LPS) pre-treatment to induce cardioprotection following ischaemia/reperfusion (I/R) has been well documented; however, the mechanisms have not been fully elucidated. LPS is a Toll-like receptor 4 (TLR4) ligand. Recent evidence indicates that there is cross-talk between the TLR and phosphoinositide 3-kinase/Akt (PI3K/Akt) signalling pathways. We hypothesized that activation of PI3K/Akt signalling plays a critical role in LPS-induced cardioprotection. Methods and results: To evaluate this hypothesis, we pre-treated mice with LPS 24 h before the hearts were subjected to ischaemia (45 min) and reperfusion (4 h). We examined activation of the PI3K/Akt/GSK-3β signalling pathway. The effect of PI3K/Akt inhibition on LPS-induced cardioprotection was also evaluated. LPS pre-treatment significantly reduced infarct size (71.25%) compared with the untreated group (9.3 ± 1.58 vs. 32.3 ± 2.92%, P < 0.01). Cardiac myocyte apoptosis and caspase-3 activity in LPS-pre-treated mice were significantly reduced following I/R. LPS pre-treatment significantly increased the levels of phospho-Akt, phospho-GSK-3β, and heat shock protein 27 in the myocardium. Pharmacological inhibition of PI3K by LY294002 or genetic modulation employing kinase-defective Akt transgenic mice abolished the cardioprotection induced by LPS. Conclusion: These results indicate that LPS-induced cardioprotection in I/R injury is mediated through a PI3K/Akt-dependent mechanism.

The Shigella species are Gram-negative enteropathogens that produce severe diarrhea, cramping, and dehydration in millions of people annually. The pathogens most commonly infect children under the age of 5 years in developing nations, where the rise of multidrug-resistant species is increasingly problematic. Despite several attempts to develop a vaccine against these pathogens, no successful vaccine has been produced. In order to achieve this goal, several characteristics of Shigella must be further elucidated. Namely, we must better understand the mechanisms Shigella employs in order to circumvent the immune response. A key way in which Shigella circumvents the innate defenses of the host is through resistance to bile salts, the principal component of bile, a substance found in the small intestine that is required for digestion. One such bile salt resistance mechanism of Shigella involves lipopolysaccharide (LPS), an extracellular structure composed of three regions: a transmembrane lipid, a polysaccharide core, and an O-antigen. LPS and LPS modifications have been implicated in bile salts resistance in other enteropathogens. Thus, the goal of this study was to build from preliminary findings to understand the role of LPS in conferring bile salts resistance in Shigella. Two Shigella flexneri mutants were studied to understand the roles of the polysaccharide core and O-antigen on bacterial growth and LPS modifications during exposure to bile salts. Growth comparisons of the mutants relative to wild type bacteria in the presence of bile salts were performed, including analysis of growth with exposure to bile salts and with varying levels of environmental glucose. Additionally, LPS was extracted from wild type and mutant bacteria grown in these conditions for analysis by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE). The growth curves demonstrated that both the O-antigen and polysaccharide core mutants exhibited slow growth with exposure to bile salts, while the SDS-PAGE analyses revealed changes in the LPS profile of wild type and both LPS mutants when grown in bile salts. These data indicate that the O-antigen likely has an important role in conferring bile salts resistance and that the polysaccharide core may also facilitate resistance. This study allows us to better understand how LPS contributes to bile salts resistance in S. flexneri, which may enhance efforts to develop an effective vaccine against this pathogen. / 2023-12-10T00:00:00Z

No description available.

Lipopolysaccharide (LPS), a Gram-negative endotoxin, has been well-established as the trigger for the effects of sepsis and septic shock through its binding with the innate immune receptor, Toll-like receptor 4 (TLR4). High doses of LPS signal through TLR4 to produce a massive release of pro-inflammatory cytokines including IL-6, TNFα, and other. Additionally, several recent publications have demonstrated severe metabolic alterations after LPS challenge, suppressing lipid oxidation and concurrently up-regulating glucose oxidation. Unfortunately, this switch in metabolism is inefficient for the great energy demands of the host during a systemic microbial infection which can result in vital organ failure. Meanwhile, a novel concept in several chronic disease pathologies also implicates LPS, although at very low doses. The presence of subclinically elevated circulating endotoxin levels has been termed metabolic endotoxemia and is beginning to be investigated in disease pathologies including insulin resistance and type II diabetes, atherosclerosis, cancer metastasis and Parkinson's disease. These disease phenotypes all possess a component of chronic inflammation whose source has not largely been understood, but examining the effects of very low doses of LPS may provide vital information in understanding their etiologies. However, most information on LPS signaling has been obtained using high doses of LPS (10-200ng/ml) while little to no studies have been published regarding the effects of very low doses of LPS (1pg-100pg/ml) on inflammatory and metabolic alterations. Thus, we use in vivo and in vitro models to determine that both IRAK1 and JNK are critical points of crosstalk downstream of TLR4 for the metabolic and inflammatory alterations associated with metabolic endotoxemia. Additionally, we observed significant down-regulation of nuclear receptors responsible for fatty acid metabolism, including PGC1α, PPARα, and PPARγ after very low dose LPS challenge. Further, we observe phenotypic changes in fatty acid oxidation and glucose oxidation, as well as subsequent changes in cytosolic acetyl-CoA levels and acetylation of pro-inflammatory transcription factor ATF2. Overall our studies point to several mechanisms of cross-talk between metabolism and inflammation and offer significant support to the concept of metabolic endotoxemia in the development of chronic disease. / Ph. D.

The gram-negative endotoxin, lipopolysaccharide (LPS), has been extensively researched in high doses (10-200ng/ml) and is well-documented in the literature for its ability to result in devastating effects such as multi-organ failure, sepsis, and septic shock. In high doses, LPS signals through Toll-like-receptor 4 (TLR4) and triggers a cascade of events culminating in the release of pro- and anti-inflammatory cytokines and the activation of NF-κB. In contrast, super-low doses of LPS (1-100pg/ml) are able to trigger the persistent release of pro-inflammatory mediators while evading the compensatory activation of NF-κB. This mild yet persistent induction of inflammation may lie at the heart of numerous inflammatory diseases and disorders and warrants studies such as this to elucidate the novel mechanisms. In this study, we explored the novel mechanisms utilized by super-low dose LPS in cellular stress and low-grade inflammation. In the first study, the molecular mechanisms governing the role of super-low dose LPS on cellular stress and necroptosis were examined. We show that in the presence of super-low dose LPS (50pg/ml), the key regulators of mitochondrial fission and fusion, Drp1 and Mfn1 respectively, are inversely regulated. An increase in mitochondrial fragmentation and cell death which was not dependent on caspase activation was observed. In addition, super-low dose LPS was able to activate RIP3, a kinase responsible for inducing the inflammatory cell death, necroptosis. These mechanisms were regulated in an Interleukin-1 receptor-associated kinase 1 (IRAK-1) dependent manner. In the second study, the molecular mechanisms governing the role of super-low dose LPS on cellular stress and endosome/lysosome fusion were examined. In the presence of low-dose LPS (50pg/ml), endosomal-lysosomal fusion is inhibited and a loss of endosomal acidification required for the successful clearance of cellular debris and resolution of inflammation was observed. Additionally, super-low dose LPS induced the accumulation of p62 indicative of the suppression of autophagy. Tollip and Interleukin-1 receptor-associated kinase 3 (IRAK-M) appear to be critical regulators in this process. Collectively, these studies show that low-dose endotoxemia is capable of causing persistent cellular stress, not observed in the presence of high-dose LPS (10-200ng/ml), and that it promotes necroptotic cell death while suppressing mechanisms necessary for the resolution of inflammation such as endosome-lysosome fusion. This research reveals novel mechanisms utilized by low-dose endotoxemia which could aid future efforts to develop prevention and treatment for various debilitating inflammatory diseases. / Ph. D.

Francisella tularensis is a Gram-negative, zoonotic bacterium that causes tularemia in animals and humans. The two subspecies tularensis (Type A) and holarctica (Type B) are considered Tier I Select Agents due to the bioweapon potential of these subspecies. Type A strains, considered the more virulent of the subspecies, are highly infective producing respiratory tularemia with inhalation of as few as 10 cells. Due to classification as a Select Agent, a vast amount of F. tularensis research has occurred in the last two decades after the September 11th terrorism attack and the use of Bacillus anthracis spores in a biological attack on the United States Postal Services in 2001. This research has uncovered many of the various virulence factors of F. tularensis including an intracellular nature, the unique lipopolysaccharide produced, and a genetic pathogenicity island. This dissertation aims to further characterize outer surface antigens of F. tularensis subspecies in regards to virulence, biofilm formation, and role in vaccine development. In addition, this dissertation will also investigate the use of a novel vaccine delivery vehicle, alginate microencapsulation, in increasing the efficacy of these mutant strains. F. novicida is a subspecies of F. tularensis and usually classified as being non-encapsulated. However, F. novicida has a similar capsule glycosylation locus as F. tularensis and could produce a similar capsule-like complex that has previously been described for the F. tularensis LVS strain. I was able to isolate and characterize this CLC of F. novicida, which contained a heterogenous mixture of proteins and possible glycosylated proteins. A mutant with a multi-gene interruption within the glycosylation locus (F. novicidaΔ1212-1218) produced significantly less carbohydrate than the parent strain, was attenuated in the mouse model, and was partially protective when used to immunize mice against a virulent challenge. Biofilms of F. novicida were also characterized in regards to biofilm formation in various growth media and biofilm formation of strains lacking the O-antigen of the lipopolysaccharide (LPS). In general, F. novicida produced the greatest amount of biofilm in a brain heart infusion (BHI) broth, compared to other media. Loss of the O-antigen led to increased biofilm production when grown in BHI and decreased or similar biofilm production as the wildtype when grown in other media. This highlights the need to carefully select the growth medium when assessing biofilm formation of Francisella strains in the future. A final study of this dissertation characterized the use of alginate microspheres as a vaccine vehicle for an attenuated F. tularensis type A O-antigen deficient strain. O-antigen deficient strains of F. tularensis are highly attenuated in vivo and would be a safe choice for a vaccine candidate. However, these strains produce less than ideal protection against virulent challenge when used to immunize mice, possibly due to a lack of persistence in the host. In an attempt to increase persistence, we encapsulated an O-antigen deficient strain within sodium alginate microspheres and used those microspheres to immunize mice. The immunized mice produced a higher level of antibody response than mice immunized with a non-encapsulated version. However, this immunization only partially protected mice from a virulent challenge and did not match the protection afforded by the former Live Vaccine Strain (LVS). In part the deficiency in protection appears to be due to a lack of a robust cellular immune response in mice immunized with the alginate microspheres. In summary, this dissertation focuses on the various extracellular polysaccharides of F. tularensis: the glycosylation of CLC, the O-antigen, and the biofilm. Each polysaccharide plays a role in the virulence and pathogenesis of F. tularensis. Glycosylation of the CLC and the O-antigen are important virulence factors in mammalian disease, and mutants lacking either (not type A strains) are attenuated in the mouse model. Both also appear to play a role in the formation of the F. tularensis biofilm in a manner dependent on the environment or culture medium used. Each of these extracellular polysaccharides contribute to the lifecycle of Francisella. / Ph.D. / Francisella tularensis is a highly infectious bacterial pathogen that can cause disease in a wide array of animals and in humans. F. tularensis is also considered a potential weapon of bioterrorism and the development of an effective vaccine is a critical area of research. One strategy of developing a tularemia vaccine includes mutating a strain of F. tularensis to reduce expression of extracellular components that include polysaccharides. Strains that cannot express these components are usually unable to produce clinical signs in the host and may provide protection against fully virulent F. tularensis strains. The work presented in this dissertation will focus on characterizing the polysaccharide extracellular components of F. tularensis and developing a novel vaccine vehicle to increase protection from strains that do not cause disease.

No / 1 In this study we examined the signalling events that regulate lipopolysaccharide (LPS)-stimulated induction of interferon regulatory factor (IRF)-1 in human umbilical vein endothelial cells (HUVECS). 2 LPS stimulated a time- and concentration-dependent increase in IRF-1 protein expression, an effect that was mimicked by the cytokine, tumour necrosis factor (TNF)-¿. 3 LPS stimulated a rapid increase in nuclear factor kappa B (NFKB) DNA-binding activity. Preincubation with the NFKB pathway inhibitors, N-¿-tosyl-L-lysine chloromethyl ketone (TLCK) or pyrrolidine dithiocarbamate (PDTC), or infection with adenovirus encoding IKB¿, blocked both IRF-1 induction and NFKB DNA-binding activity. 4 LPS and TNF¿ also stimulated a rapid activation of gamma interferon activation site/gamma interferon activation factor (GAS/GAF) DNA-binding in HUVECs. Preincubation with the Janus kinase (JAK)-2 inhibitor, AG490 blocked LPS-stimulated IRF-I induction but did not affect GAS/ GAF DNA-binding. 5 Preincubation with TLCK, PDTC or infection with I¿Ba adenovirus abolished LPS-stimulated GAS/GAF DNA-binding. 6 Incubation of nuclear extracts with antibodies to RelA/p50 supershifted GAS/GAF DNA-binding demonstrating the involvement of NF¿B isoforms in the formation of the GAS/GAF complex. 7 These studies show that NF¿B plays an important role in the regulation of IRF-1 induction in HUVECs. This is in part due to the interaction of NF¿B isoforms with the GAS/GAF complex either directly or via an intermediate protein.

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Lorsque l’anesthésie par inhalation ne peut être utilisée chez le rat, la combinaison de kétamine et de xylazine est l’alternative la plus fréquemment utilisée. Les doses administrées peuvent varier selon le protocole expérimental. En présence de fièvre, d’infections ou de processus tumoral accompagné de fièvre, la pharmacocinétique de ces drogues peut être modifiée. Ce projet porte sur l’évaluation des changements physiologiques, hématologiques, biochimiques et pharmacocinétiques chez le rat Sprague Dawley lors d’anesthésie avec le mélange kétamine-xylazine suite à l’administration de trois doses différentes de lipopolysaccharide (LPS). Après l’administration de LPS, une anesthésie à la kétamine-xylazine fut induite chez des rats Sprague Dawley. Des prélèvements sanguins périodiques ainsi que des mesures des paramètres physiologiques furent effectués afin d’évaluer l’effet du LPS sur la pharmacocinétique des deux drogues ainsi que sur les paramètres biochimiques et hématologiques. Les différentes doses de LPS ont causé certaines modifications notamment en produisant une baisse marquée de la saturation en oxygène et de l’albumine sérique, une augmentation de la durée d’anesthésie ainsi que des lésions hépatiques mineures. Les paramètres pharmacocinétiques de la kétamine furent peu altérés par l’administration de LPS tandis qu’une diminution de la clairance et une augmentation de l’aire sous la courbe (AUC) furent observées pour la xylazine dans les groupes ayant reçu les doses moyenne et élevée de LPS. Ces résultats montrent que les doses de xylazine doivent être adaptées en présence de LPS pour permettre une anesthésie de courte durée et des changements physiologiques et biochimiques moindres lorsqu’elle est administrée avec de la kétamine. / When inhalation anesthesia cannot be used in laboratory rats, ketamine-xylazine combination is the most frequent alternate regimen. The administrated doses can vary according to the experimental protocol. During fever episodes, infections or tumoral process, the pharmacokinetics of these drugs can be modified. This project focuses on the evaluation of the physiological, hematological, biochemical and pharmacokinetics changes in Sprague Dawley rats during ketamine-xylazine anesthesia, after administration of three different doses of lipopolysaccharide (LPS). After administration of LPS to Sprague Dawley rats, ketamine-xylazine anesthesia was induced. Periodic blood samplings and monitoring of physiologic parameters were made in order to evaluate the effect of LPS on ketamine-xylazine pharmacokinetics and hematological and biochemical parameters. The different LPS doses caused specific parameter modifications including a marked decrease of oxygen blood saturation and serum albumin, a longer anesthesia duration and minor hepatic lesions. No significant modifications of pharmacokinetics parameters of ketamine were observed. An increase of area under curve (AUC) and a decrease of xylazine clearance were noted in groups who received medium and large doses of LPS. These results show that that xylazine doses need to be adapted in the presence of LPS, to allow a shorter duration anaesthesia and lesser physiological and biochemical changes when administered with ketamine.