Cyclooxygenase (COX) is the rate limiting enzyme that catalyses the production of prostanoids, which are crucial to vascular homeostasis. Evidence suggests that endothelial dysfunction and inflammation play a role in vascular complications in aging and diabetes. Previous animal studies by our laboratory at RMIT University reported enhanced COX expression with aging in rat aortas, platelets and monocytes. Potentially, alteration in COX expression may result in an imbalanced prostanoid production favoring the synthesis of vasoconstrictors and hence increase the risk of cardiovascular events in the aging population. The regulation of altered COX expression in aging, however, is not clear. It has been suggested that histone hyperacetylation may be an important mechanism that regulates COX levels during the aging process as increased histone acetylation has been shown to occur with aging. Thus, we hypothesized that COX expression is modulated by histone hyperacetylati on. This was investigated by measuring COX expression in histone hyperacetylated cultured endothelial cells. In the case of diabetes, studies have reported that the development of diabetes and its complications is associated with persistent inflammatory activity, evident with increased inflammatory markers in the circulation. COX-mediated pathways may be involved in this inflammatory process in diabetes. Furthermore, the formation of advanced glycation end products (AGEs) is accelerated in diabetes. AGEs can bind to receptors for AGEs (RAGE), which has also been suggested to play a role in inflammation in diabetes. We hypothesized that COX- and RAGE-mediated pathways contribute to increased inflammation in diabetes and potentiate the development of diabetic vascular complications. This was investigated by measuring changes in COX-mediated pathways in both rat and human diabetic models. The current thesis reports: 1) in cultured endothelial cells, histone hyperacetylation was associated with increased COX expression; 2) an overall increase in inflammation was observed in diabetes involving COX- and RAGE-mediated pathways. This was supported by increased platelet COX-1 and monocyte COX-2 levels in Zucker rats, increased monocyte COX-2 in human Type 1 diabetes and elevated plasma TXB2 and PGE2 levels in both human Type 1 and Type 2 diabetic subjects. Up-regulation of RAGE expression was further found in platelets and monocytes in both human diabetes types. When treated with NSAIDs, plasma prostanoid levels, COX and RAGE expression were reduced significantly in both platelets and monocytes in human diabetic subjects. 3) It is unclear how COX and RAGE expression was regulated, but histone modifications may be one of the mechanisms. Data from cultured cells indicated that increased COX expression was associated with increased histone acetylation levels induced by TSA. Concurrent increases in histone acetylation and COX-2 levels were also observed in human Type 1 diabetes, but similar findings were not observed in human Type 2 diabetes. In addition, we failed to find an age-dependent increase in monocyte histone H4 acetylation in human Type 2 diabetes despite an age-dependent increase in monocyte COX-2 expression. Thus, whether histone hyperacetylation modulates COX expression and in what conditions require further investigation.

<p>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.</p><p>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.</p><p>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.</p>

<p>After drinking water, the fluid quickly leaves the stomach thereby creating a hypotonic luminal environment in the duodenum. This in turn constitutes a potential threat to the integrity of the duodenal epithelium. It therefore seems highly likely that luminal hypotonicity activates physiological mechanisms that aim to increase luminal osmolality. One such physiological mechanism may be to increase mucosal permeability thereby facilitating the transport of osmolytes into the lumen.</p><p>A draw-back of performing experiments in anesthetized animals is that surgery <i>per se</i> depresses gut functions, such as peristalsis, by mechanisms involving endogenous prostaglandins. In this thesis it is shown that inhibition of cyclooxygenase-2 (COX-2), in animals subjected to an abdominal operation, restore and/or improve duodenal functions such as motility, mucosal bicarbonate secretion, hypotonicity-induced increase in mucosal permeability and the osmolality-adjusting capability.</p><p>Experiments revealed that the stomach is resistant to hypotonic challenge while the jejunum is more sensitive to hypotonicity-induced increase in mucosal permeability than the duodenum. The hypotonicity-induced increase in duodenal mucosal permeability is not due to injury but possibly reflects physiological dilatation of paracellular shunts.</p><p>Luminal perfusion of the duodenum with an isotonic solution lacking Cl^- decreased bicarbonate secretion while the lack of luminal Na⁺ increased mucosal permeability. Stimulation of bicarbonate secretion by COX-2 inhibition is to a large extent dependent on luminal Cl^- while that induced by vasoactive intestinal peptide is not.</p><p>The hypotonicity-induced increase in mucosal permeability involves the release and action of serotonin (5-HT) on 5-HT₃ and 5-HT₄ receptors and stimulation of enteric nerves strongly implicating physiological regulation of this process.</p>

After drinking water, the fluid quickly leaves the stomach thereby creating a hypotonic luminal environment in the duodenum. This in turn constitutes a potential threat to the integrity of the duodenal epithelium. It therefore seems highly likely that luminal hypotonicity activates physiological mechanisms that aim to increase luminal osmolality. One such physiological mechanism may be to increase mucosal permeability thereby facilitating the transport of osmolytes into the lumen. A draw-back of performing experiments in anesthetized animals is that surgery per se depresses gut functions, such as peristalsis, by mechanisms involving endogenous prostaglandins. In this thesis it is shown that inhibition of cyclooxygenase-2 (COX-2), in animals subjected to an abdominal operation, restore and/or improve duodenal functions such as motility, mucosal bicarbonate secretion, hypotonicity-induced increase in mucosal permeability and the osmolality-adjusting capability. Experiments revealed that the stomach is resistant to hypotonic challenge while the jejunum is more sensitive to hypotonicity-induced increase in mucosal permeability than the duodenum. The hypotonicity-induced increase in duodenal mucosal permeability is not due to injury but possibly reflects physiological dilatation of paracellular shunts. Luminal perfusion of the duodenum with an isotonic solution lacking Cl- decreased bicarbonate secretion while the lack of luminal Na+ increased mucosal permeability. Stimulation of bicarbonate secretion by COX-2 inhibition is to a large extent dependent on luminal Cl- while that induced by vasoactive intestinal peptide is not. The hypotonicity-induced increase in mucosal permeability involves the release and action of serotonin (5-HT) on 5-HT3 and 5-HT4 receptors and stimulation of enteric nerves strongly implicating physiological regulation of this process.

Pharmaceuticals and personal care products are a growing concern in the aquatic environment. Compounds from the class of non-steroidal anti-inflammatory drugs are commonly detected in surface waters and have the potential to negatively affect aquatic organisms. The purpose of this experiment was to determine the acute and chronic effects of ibuprofen on rainbow trout (Oncorhynchus mykiss). Cyclooxygenase (COX) activity, vitellogenin (VTG) concentration and ethoxyresorufin-O-deethylase (EROD) activity were evaluated following waterborne ibuprofen exposure of trout to 1 and 10 mg/L in the acute exposure and 1, 32 and 1000 μg/L in the chronic exposure, along with an experimental control, E2 control of 1000 μg/L and an E2-ibuprofen mixed treatment. Ibuprofen did not inhibit COX enzyme activity in either gill or kidney tissue. To evaluate the estrogenic effects of ibuprofen, VTG concentrations were measured; by the end of the 56 day chronic exposure VTG concentrations significantly increased in all of the ibuprofen treatments relative to the controls. EROD activity may have been inhibited by ibuprofen but definitive conclusions could not be made. These findings indicate that more research needs to be done studying ibuprofen in aquatic systems. / UOIT

In clinical situations, most of the patients suffer from inflammation and acute postoperative pain after surgery. Postoperative pain has been emphasized as a very crucial issue in improving the quality of medical care in each medical center. Therefore, management of the postoperative pain is an effective approach to reduce the painful unpleasant feeling, complications, and death rate after surgery. Surgical trauma results in the induction of COX-2, leading to the release of prostaglandins, which sensitize peripheral nociceptors and increase the excitability of spinal neurons, producing pain hypersensitivity in the surrounding uninjured tissue.The purpose of this study is to test the preventive effect of COX-2 inhibitor SC-236 for post-operative pain by rat plantar incision model.Then, we explored whether SC-236 is more effective in reducing the hyperalgesia and inflammation response administered before incision than after incision. Furthermore, we used male Sprague-Dawley rats received plantar incision were used in this study, the rats received subcutaneous injection of SC-236 before or after plantar incision. Behavior teste of mechanical allodynia¡Bthermal hyperalgesia and COX-2 expression level was determined at 4 h and 1, 2, and 3 days after surgery. Mechanical allodynia was measured by mechanical withdrawal threshold that was determined by stimulating with von Frey filaments stimulation. Thermal hyperalgesia was measured by thermal withdrawal thermal tested by radioactive thermal assay. Mechanical allodynia¡Bthermal hyperalgesia and COX-2 expression level were measured at various time points by behavior teste¡Breal-time polymerase chain reaction¡Bwestern blot and immunohistochemistry. The data from pre-incisional injection of SC-236 was compared with that from post-incisional injection of SC-236.The results revealed pre-incisional injection of COX-2 inhibitor significantly inhibited thermal hyperalgesia but not mechanical allodynia then post-incisional injection of COX-2 inhibitor group. Skin of pre-incisional injection of SC-236 show significant decreased mRNA expression of COX-2 at 1 day and 2 day after incision evidenced by real-time polymerase chain reaction. Western blot and immunohistochemistry also show significant decreased protein expression of COX-2 at 4 hours and 1 day after incision. Therefore, pre-incisional administration of SC-236 could prevent the surgical wound induced thermal hyperalgesia and decrease mRNA and protein expression level of cutaneous COX-2 at 4 hours and one day after surgical incision compared to post-incisional administration of SC-236 .

Colorectal cancer, among other tumors, is characterized by elevated levels of prostaglandins due to the up-regulation of cyclooxygenase -2 (COX-2), a key enzyme in the eicosanoid biosynthesis pathway. Prostaglandin E2 (PGE2) is an important prostaglandin that exerts its biological function via four transmembrane G protein coupled receptors (EP1-4), among which the EP4 receptor is the most important. The relevance of EP4 receptor to the carcinogenic process and the consequences of its interaction with PGE2 were explored in this dissertation.Despite the importance of the EP4 receptor in colon carcinogenesis, studies looking at the receptor expression during cancer progression have not been extensive. One study showed that the protein levels of EP4 receptor were elevated in colon cancer whereas another study indicated that mRNA levels were decreased in tumor compared to normal. We expanded these observations and now report that the elevated protein levels of EP4 receptor in cancer are due to increased translation of proteins.In addition, we identified S100P as a novel downstream target of the PGE2/EP4 receptor signaling pathway. S100P has been previously implicated in a number of gastro-intestinal cancers such as pancreatic, gastric and colon cancers. However, its regulation via the PGE2/EP4 receptor signaling pathway has never been investigated. Here, we show that PGE2 via the EP4 receptor signaling leads to the transcriptional activation of S100P and that this activation happens exclusively in the presence of CREB. In summary, this dissertation brings to light novel therapeutic targets which could be used as potential markers to stratify colon cancer patients as well as avenues for clinical intervention for the management of colon carcinogenesis.

High output of prostaglandins (PGs) are the hallmark of inflammatory and immune reactions. A rate-limiting step in the production of PGs is the presence of the enzyme cyclooxygenase (COX). COX exists as two isoforms: COX-1 which is constitutively expressed in most cells and COX-2 which is inducible by LPS, proinflammatory cytokines and other stimuli in cells involved in inflammation. The objective of this study was to determine the effect of nonsteroidal antiinflammatory drugs and proinflammatory cytokines on COX-2 expression in human macrophages. COX-2 specific (NS-398) and non-specific (aspirin, indomethacin and naproxen) inhibitors showed no effect on COX mRNA and protein expression induced by LPS. In contrast, the drugs markedly inhibited COX activity as measured by the accumulation of PGE2. The induction of COX-2 mRNA expression by LPS was rapid and sustained. However, LPS only transiently stimulated the transcription of COX-2 gene and activation of the transcription factor NF-kappaB. LPS stimulated the release of IL-1beta and TNF-alpha but these cytokines had no autocrine effect on the transcriptional or post-transcriptional regulation of COX-2. The presence of LPS was essential for the maintenance of high levels of long-lived COX-2 mRNA. As IFN-gamma is a major macrophage activating factor, we determined the role of this cytokine on COX-2 expression induced by exogenous IL-1beta. IFN-gamma-primed macrophages showed significantly lower levels of COX-2 mRNA, protein and PGE2 production compared to non-primed cells. IFN-gamma specifically decreased the transcriptional activation of COX-2 gene by IL-1beta but not by LPS without affecting the rate of mRNA decay. These results demonstrate that sustained production of PGE2 by macrophages in an inflammatory milieu can occur through the stabilization of COX-2 mRNA and revealed a role for IFN-gamma as an anti-inflammatory cytokine counteracting the expression of COX-2. A better understanding of COX-2 regulation will

The role of 2-arachidonoylglycerol (2-AG) in nausea and vomiting was evaluated using a shrew (Suncus murinus) model of emesis and nausea-like behavior in rats, conditioned gaping. Shrews received JZL184, a selective MAGL inhibitor, prior to treatment with emetogenic lithium chloride (LiCl). The potential of exogenously administered 2-AG and arachidonic acid (AA) to regulate conditioned gaping was assessed in rats. The role of cannabinoid receptors and cyclooxygenase (COX) inhibition in suppression of vomiting and conditioned gaping was also evaluated. JZL184 dose-dependently suppressed vomiting in shrews, and was shown to inhibit MAGL in shrew brain tissue. The anti-emetic effects of JZL184 were prevented by the CB1 antagonist, AM251. Exogenous 2-AG suppressed LiCl-induced conditioned gaping, but was not prevented by AM251 or the CB2 antagonist, AM630. Instead, the COX inhibitor, indomethacin, prevented the suppressive effects of 2-AG, as well as AA. These results suggest that manipulations that elevate 2-AG may have anti-emetic/anti-nausea potential. / This research was supported by research grants from the Natural Sciences and Engineering Research Council of Canada (NSERC 92057) to Linda Parker, the Israel Science Foundation (DA009789) to Raphael Mechoulam, and the National Institutes of Health (DA009789, DA017259) to Benjamin Cravatt.

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly worldwide. Due to the inadequacy of current pharmacotherapies, novel molecular targets must be sought as potential therapeutic candidates. Furthermore, there is a need for more efficient and cost-effective animal models of this pathology in order to accelerate in vivo investigations. / Our laboratory is in possession of human choroidal neovascular membranes which we examined for expression of cyclooxygenase (COX)-2. This expression was characterized in retinal pigment epithelial, vascular endothelial, and fibroblast cells and correlated with patient age. We also looked at the feasibility of creating a rabbit laser-injury model to adequately mimic human neovascular AMD. / Our results suggest that anti-COX-2 therapies may be beneficial to some patients with neovascular AMD. Moreover, there is strong potential for the development of clinically relevant choroidal neovascularization in rabbits using the laser-injury technique. This approach may yield a novel, cost-effective AMD model.