Inhibition Of Prostaglandin E2 Formation Research Articles

Rotavirus-Mediated Prostaglandin E2 Production in MA104 Cells Promotes Virus Attachment and Internalisation, Resulting in an Increased Viral Load.

Rotaviruses are one of the leading causes of severe dehydrating diarrhoea in infants and children under the age of five. Despite the introduction of vaccines, disease burden remains high in sub-Saharan Africa, with no known anti-viral treatments available. During early infection rotavirus attaches to several cellular receptors and enters the cells by either clathrin-dependent or -independent endocytosis. Prostaglandin E2, an abundant eicosanoid, is produced from arachidonic acid during rotavirus infection and inhibition of prostaglandin E2 formation have a deleterious effect on rotavirus infection. In this study, MA104 cells were supplemented with γ-linolenic acid (GLA), a precursor of arachidonic acid. Infection of supplemented cells with rotavirus SA11 led to a depletion in the relative percentages of GLA and arachidonic acid which coincided with an increased production of prostaglandin E2 as monitored by ELISA. Confocal microscopy demonstrated that prostaglandin E2 co-localises with the viroplasm-forming proteins, NSP5 and NSP2. Due to the known association of viroplasms with lipid droplets and the fact that lipid droplets are sites for prostaglandin E2 production, our results indicate a possible role for viroplasms in the production of rotavirus-induced prostaglandin E2. Replication kinetics showed that inhibitors, targeting the biosynthesis of prostaglandin E2, had negative effects on rotavirus yield, especially during the early stages of infection. Using flow cytometry and prostaglandin E2 addback experiments, we show that prostaglandin E2 enhances the attachment and internalisation of rotavirus in MA104 cells indicating a possible role for prostaglandin E2 during clathrin-mediated rotavirus entry. The production of prostaglandin E2 during rotavirus infection could serve as a possible target for anti-viral treatment.

COX2/mPGES1/PGE2 pathway regulates PD-L1 expression in tumor-associated macrophages and myeloid-derived suppressor cells

In recent years, it has been established that programmed cell death protein ligand 1 (PD-L1)-mediated inhibition of activated PD-1+ T lymphocytes plays a major role in tumor escape from immune system during cancer progression. Lately, the anti-PD-L1 and -PD-1 immune therapies have become an important tool for treatment of advanced human cancers, including bladder cancer. However, the underlying mechanisms of PD-L1 expression in cancer are not fully understood. We found that coculture of murine bone marrow cells with bladder tumor cells promoted strong expression of PD-L1 in bone marrow-derived myeloid cells. Tumor-induced expression of PD-L1 was limited to F4/80+ macrophages and Ly-6C+ myeloid-derived suppressor cells. These PD-L1-expressing cells were immunosuppressive and were capable of eliminating CD8 T cells in vitro. Tumor-infiltrating PD-L1+ cells isolated from tumor-bearing mice also exerted morphology of tumor-associated macrophages and expressed high levels of prostaglandin E2 (PGE2)-forming enzymes microsomal PGE2 synthase 1 (mPGES1) and COX2. Inhibition of PGE2 formation, using pharmacologic mPGES1 and COX2 inhibitors or genetic overexpression of PGE2-degrading enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH), resulted in reduced PD-L1 expression. Together, our study demonstrates that the COX2/mPGES1/PGE2 pathway involved in the regulation of PD-L1 expression in tumor-infiltrating myeloid cells and, therefore, reprogramming of PGE2 metabolism in tumor microenvironment provides an opportunity to reduce immune suppression in tumor host.

Influence of Navisporus floccosus (Higher Basidiomycetes) n-Hexane Extract on Arachidonate Metabolism in Vitro.

In vitro anti-inflammatory activity of 4 extracts with different polarity from the basidiomycete Navisporus floccosus was evaluated by determination of the inhibition of prostaglandin E2 formation catalyzed by purified cyclooxygenase (COX)-1 and COX-2 enzymes, and of the inhibition of leukotriene (LT) B4 formation in human polymorphonuclear leukocytes. The n-hexane extract showed the highest activity in all 3 assays. Through analysis by gas chromatography coupled with mass spectrometry (GC-MS), 9 fatty acids and fatty acid esters were identified as the major constituents of this extract. As several of them also showed inhibitory activity in the COX and LTB4 formation assays, it can be assumed that the unsaturated as well as the saturated fatty acids, and maybe also the fatty acid esters, present in the extract synergistically contribute to its in vitro anti-inflammatory activity.

Inhibition of prostanoid formation in intact cells by 2,5-di-(tert-butyl)-1,4-benzohydroquinone, a blocker of Ca(2+)-ATPases.

1 The blocker of endoplasmic reticulum Ca(2+)-ATPase, 2,5-di-(tert-butyl)-1,4-benzohydroquinone (BHQ) was shown to inhibit formation of prostaglandin E2 and prostacyclin in the osteoblast-like cell lines, MC3T3-E1 and ROS 17/2.8, respectively, in a dose-dependent manner with an IC50 of 0.5-1 microM. Inhibition was observed with various stimuli (arachidonic acid, bradykinin, melittin and calcium ionophore, A23187). 2 This effect was also observed in human platelets, where BHQ dose-dependently blocked thromboxane biosynthesis and formation of 12-hydroxy-heptadecatrienoic acid after stimulation with arachidonic acid, but not formation of 12-hydroxy-eicosatetraenoic acid. 3 Inhibition of prostaglandin E2 formation in MC3T3-E1 cells was not observed with thapsigargin after stimulation with arachidonic acid, A23187 or melittin, whereas bradykinin-induced prostaglandin E2 biosynthesis was blocked. 4 Taken together, the results suggest a direct inhibitory action of BHQ on the cyclo-oxygenase in these three cell systems.

Inhibition of prostaglandin E2 formation and histamine action in cancer immunotherapy.

The activity of cell-mediated defense systems is stimulated by consecutive formation of interleukin-1 beta (IL-1 beta), interleukin-2 (IL-2) and interferon gamma (IFN gamma). The system is inhibited by interleukin-4 (IL-4) and also by prostaglandin E2 (PGE2) and histamine, which are released when the immune system is activated. The inhibition is strong in cancer patients, because PGE2 is formed in many cancer cells and its formation is stimulated by IL-1 beta. The release of histamine is also stimulated by IL-1 beta. Thus PGE2 and histamine are feedback inhibitors of cell-mediated immunity. This inhibition can be abolished by inhibitors of the cyclo-oxygenase (e.g. indomethacin) and H-2 receptor antagonists (e.g. cimetidine). This may offer a new option to stimulate the immune system to kill cancer cells.

Effect of TEI-2117, a new antithrombotic agent: A fundamental study on platelet aggregation

TEI-2117 (I), 2-(3-benzoyl-2, 5-dimethylpyrrole) propanol, is a novel compound synthesized by our laboratories. The effect of I was studied on human platelet aggregation and on prostaglandin biosynthesis in vitro comparing with indomethacin (IM). The compound (I) was more potent inhibitor than IM in arachidonic acid-induced platelet aggregation. I had similar inhibitory activity to that of IM in aggregation by collagen. It also inhibited the secondary phase of aggregation induced by epinephrine. Inhibition of the release of rabbit aorta contracting substances was also observed by preincubation of PRP with I. However, I was less active in inhibition of prostaglandin E2 formation when bovine seminale vesicles were used as an enzyme source. In the study of prostaglandin biosynthesis using human platelet microsome and 14C-arachidonic acid, the regulatory pattern of prostaglandin biosynthesis by I was different from that by IM. The effect of I on platelet aggregation was further studied in extra vivo. When I was administered subcutaneously (10mg/kg) or orally (100mg/kg) to guinea pig, 98 percent and 70 percent inhibition of platelet aggregation induced by arachidonic acid, was observed, whereas aspirin was nearly equipotent to I at the same dose. These result suggest that I may play in vivo effect on prevention of thrombus formation through antagonizing arachidonic acid metabolism in platelets.