Prostaglandin (PG) E2 is an eicosanoid derived from the polyunsaturated twenty carbon fatty acid arachidonic acid (AA). PGE2 has physiological as well as pathophysiological functions and is known to be a key mediator of inflammatory responses. Formation of PGE2 is dependent upon the activities of three specific enzymes involved in the AA cascade; phospholipase A2 (PLA2), cyclooxygenase (COX) and PGE synthase (PGEs). Although the research within this field has been intense for decades, the regulatory mechanisms concerning the PGE2 synthesising enzymes are not completely established. PGE2 was investigated in human monocytes with or without lipopolysaccharide (LPS) pre-treatment followed by stimulation with calcium ionophore, opsonised zymosan or phorbol myristate acetate (PMA). Cytosolic PLA2a (cPLA2a) was shown to be pivotal for the mobilization of AA and subsequent formation of PGE2. Although COX-1 was constitutively expressed, monocytes required expression of COX-2 protein in order to convert the mobilized AA into PGH2. The conversion of PGH2 to the final product PGE2 was to a large extent due to the action of microsomal PGEs-1 (mPGEs-1). In addition, experiments with inhibitors of extracellular signal regulated kinase and p38 activation, indicated that phosphorylation of cPLA2α was markedly advantageous for the formation of PGE2. Ellagic acid, a natural polyphenolic compound found in fruits and nuts, was shown to inhibit stimuli induced release of PGE2 in human monocytes. The effect of ellagic acid was not due to a direct effect on the activities of the enzymes but rather to inhibition of the LPS-induced protein expression of COX-2, mPGEs-1 and cPLA2a.

Although the etiology of diabetic nephropathy is still uncertain, proteinuria due to podocyte injury and loss (podocytopenia) are early features of the disease. Significant increases in thromboxane A2 (TXA2) production as well as expression of its receptor in animal models of diabetic nephropathy led to the hypothesis that TXA2 acting via its thromboxane-prostanoid (TP) receptor induces podocytopenia resulting in proteinuria. Systemic infusion of a TP antagonist demonstrated an important role of TXA2/TP signalling in our model of streptozotocin induced type-1 diabetic nephropathy by reducing kidney damage including proteinuria. Podocyte specific TP overexpressing mice did not demonstrate more pathologic or dynamic kidney damage than non-transgenic mice in STZ-induced diabetic nephropathy. Further assessment of the TP transgene functionality in this mice line is necessary to validate those results. Whereas the importance of TXA2/TP signalling is undeniable in diabetic nephropathy, it appears that podocyte TP receptors might not be directly targeted.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22329号 / 医博第4570号 / 新制||医||1041(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 坂井 義治, 教授 斎藤 通紀, 教授 岩田 想 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Candida albicans is an increasingly important pulmonary fungal pathogen. Resident alveolar macrophages are important in host defense against opportunistic fungal infections. Activation of Group IVA cytosolic phospholipase A2α (cPLA2α) in macrophages initiates arachidonic acid (AA) release for production of eicosanoids, which regulate inflammation and immune responses. We investigated the ability of C. albicans to activate cPLA2α in unprimed alveolar macrophages and after priming with granulocyte macrophage colony-stimulating factor (GM-CSF), which regulates alveolar macrophage maturation. AA was released within minutes by GM-CSF-primed but not unprimed alveolar macrophages in response to C. albicans, and was blocked by soluble glucan phosphate (S-GP). The expression of the β-glucan receptor dectin-1 was increased in GM-CSF-primed macrophages, and AA release from GM-CSF-primed dectin-1-/- alveolar macrophages was reduced to basal levels. The enhanced activation of extracellular signal-regulated kinases and phosphorylation of cPLA2α on Ser-505 that occurred in GM-CSF-primed macrophages were reduced by MEK1 and Syk inhibitors, which also suppressed AA release. At later times after C. albicans infection (6 h), unprimed and GM-CSF-primed macrophages released similar levels of AA. The expression of cyclooxygenase 2 and prostanoid production at 6 hours was higher in GM-CSF-primed macrophages, but the responses were not dependent on dectin-1. However, dectin-1 contributed to the C. albicans-stimulated increase in TNF-α production that occurred in GM-CSF-primed macrophages. The results demonstrate that dectin-1 mediates the acute activation of cPLA 2α in GM-CSF-primed alveolar macrophages, but not in the more delayed phase of AA release and GM-CSF-dependent prostanoid production.

Both plasma glucose concentration and glucose uptake are deranged in insulin resistance. A high free fatty acid plasma level is a potential cause of insulin resistance, and therefore of type 2 diabetes mellitus animals and humans. The mechanism behind this is still unclear. The objectives of the present study were: (i) to research the effect of arachidonic acid (AA) as fatty acid representative, on glucose uptake into human isolated adipocytes, (ii) to investigate the uptake of AA into adipocyte membranes and nuclei, as a step to identify the mechanism whereby AA affects glucose uptake, and (iii) to verify the influence of insulin on AA uptake in adipocytes. The first objective was achieved by exposing adipocytes to AA and measuring the effect on deoxyglucose uptakt. To achieve the second objective, adipocytes were exposed to 14C-AA; radioactive uptake in membranes and nuclei was determined. The AA uptake into membranes was also determinate by membranes fatty acid profile using gas chromatography; the results of the two methods were compared. Finally, the third objective was achieved by exposing adipocytes to different concentrations of insulin and testing the effect by measuring arachidonic acid uptake by the entire cell. The results of this study shown that, acute (30 min) exposure of AA significantly stimulates glucose uptake by adipocytes (4.56 ± 0.6 nmole glucose /mg protein /min) compared to the control (3.12 ± 0.25 nmole glucose /mg protein /min). Secondly, 14C-AA was significantly taken up by the membranes between 20 and 30 minutes of exposure. The uptake into membranes was increased by 49.57 ± 29% and 123 ± 73% compared to the control 100% (1.77 ± 0.06 nmole AA /mg protein) respectively for 20 and 30 min exposure). AA significantly rose in the nuclei after 30 minutes (147 ± 19% increase) compared to the control 100% (2.25 ± 0.10 nmole AA /mg protein). The determination of AA uptake by gas chromatography analysis of the membrane fatty acid profile showed that the content of AA increased after 30 min exposure (0.57% AA of total membrane fatty acids) compared to the 10 min exposure (0.29% AA of total membrane fatty acid). Insulin was shown to stimulate 10 and 30 min AA uptake by adipocytes from a non-obese subject. The increases of AA uptake measured for 30 minutes were 20 ±8%, 21 ± 25% and 31 ± 4% compared to the control (0.58nmole AA / mg protein / min) respectively for the actions of 10nM, 20nM and 40 nM insulin. A similar tendency was observed when the AA uptake was measured for 10 min (81 ± 31% and 208 ± 36% respectively for the action of 10nM and 40nM insulin compared to the control 100% (0.06nmole AA/mg protein/min). In contrast to this finding, insulin depressed AA uptake by adipocytes from an obese subject (depression of 15 ± 5%, 14 ± 8% and 21 ± 5% respectively for 10nM, 20nM and 40nM insulin, compared to the control 100% (0.74 nmole AA/mg protein/min). In both situations the effect of insulin seemed dose dependent. The study demonstrated that AA acid positively modulates glucose uptake into adipocytes exposed for short periods (< 30 min). This was attributed to the probable this FA in the cell membrane, rather than its eventual effect on the DNA. The best method to measure membranes AA over short period of exposure when small amounts of adipocytes (2- 6 ml) are used was by radioactive means. It also suggested that insulin effect’s on AA acid uptake into adipocytes was dose dependent. This varies with the body mass index (BMI) of the patient, probably as a result of their cell’s insulin resistant state. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2007. / Anatomy and Physiology / MSc / unrestricted

Indiana University-Purdue University Indianapolis (IUPUI) / Hydrocephalus is a debilitating disease characterized by an increase in cerebrospinal fluid (CSF) in the brain, leading to increases in pressure that can ultimately result in death. Current treatments for hydrocephalus include only invasive brain surgery. Therefore, the need for a pharmaceutical therapy is great. In order to develop a suitable treatment, we first must be able to study the disease and the mechanisms by which it develops. By characterizing appropriate in vivo and in vitro models, we are better able to study this disease. In this thesis, the Wpk rat model and the PCP-R cell line are described as such appropriate models. In addition to suitable models, we also require a target for drug treatment. Transient Receptor Potential Vanilloid 4 (TRPV4) is a non-selective cation ion channel present in the main CSF-producing organ in the brain, the choroid plexus (CP). Preliminary data suggest this channel plays a role in the development of hydrocephalus. In the following work, some of the mechanisms by which TRPV4 functions in the brain are also described, including through calcium-sensitive potassium channels and inflammation. From this research, we are able to achieve a better understanding of the function of TRPV4 and how it can affect the development and progression of hydrocephalus.

No description available.

Although synthetic analogs of alkylglycerol (AG), such as dodecylglycerol, possess potent biological activities, their mechanism of action has not been determined. We recently detected substantial amounts of AG in unstimulated MDCK cells (Warne, T.R. and Robinson, M. (1991) Anal. Biochem. 198, 302-307) raising the possibility mediator. In this study, we examined the effects of synthetic AG on the release of arachidonic acid and arachidonate metabolites (AA) from Madin Darby canine kidney (MDCK) cells in response to 12-O-tetradecanoylphorbol-13-acetate (TPA) in order to characterize its effects on this signalling pathway. Treatment of MDCK with AG potently inhibited the release of AA during subsequent stimulation with TPA. Dodecylglycerol, the most effective of a series of alkylgycerols tested, was active at concentrations as low as 3 μM. The sn-1 and sn-3 forms of AG were found to be equally potent inhibitors. The effects of AG on AA release were not the result of arachidonic acid redistribution among cellular lipids and were independent of the phospholipid source of the released AA. AG did not inhibit the release of AA from MDCK cells when bradykinin was used as a stimulus, indicating selectivity for the effects produced by phorbol esters. These results show that AG can function as a potent and specific inhibitor of TPA-mediated AA release. The ability of AG to regulate this signalling pathway in intact MDCK cells, together with its natural occurrence, suggests a potential bioregulatory role for the endogenous compound as an inhibitor of protein kinase C.

No description available.

No description available.