Bradykinin-stimulated prostaglandin E2 production by endothelial cells and its modulation by antiinflammatory compounds

Tick bite-induced alpha-gal syndrome and immunologic responses in an alpha-gal deficient murine model

Introduction

Alpha-Gal Syndrome (AGS) is a delayed allergic reaction due to specific IgE antibodies targeting galactose-α-1,3-galactose (α-gal), a carbohydrate found in red meat. This condition has gained significant attention globally due to its increasing prevalence, with more than 450,000 cases estimated just in the United States alone. Previous research has established a connection between AGS and tick bites, which sensitize individuals to α-gal antigens and elevate the levels of specific IgE. However, the precise mechanism by which tick bites influence the host's immune system and contribute to the development of AGS remains poorly understood. This study investigates various factors related to ticks and the host associated with the development of AGS following a tick bite, using mice with a targeted disruption of alpha-1,3-galactosyltransferase (AGKO) as a model organism.

Methods

Lone-star tick (Amblyomma americanum) and gulf-coast tick (Amblyomma maculatum) nymphs were used to sensitize AGKO mice, followed by pork meat challenge. Tick bite site biopsies from sensitized and non-sensitized mice were subjected to mRNA gene expression analysis to assess the host immune response. Antibody responses in sensitized mice were also determined.

Results

Our results showed a significant increase in the total IgE, IgG1, and α-gal IgG1 antibodies titers in the lone-star tick-sensitized AGKO mice compared to the gulf-coast tick-sensitized mice. Pork challenge in Am. americanum -sensitized mice led to a decline in body temperature after the meat challenge. Gene expression analysis revealed that Am. americanum bites direct mouse immunity toward Th2 and facilitate host sensitization to the α-gal antigen.

Conclusion

This study supports the hypothesis that specific tick species may increase the risk of developing α-gal-specific IgE and hypersensitivity reactions or AGS, thereby providing opportunities for future research on the mechanistic role of tick and host-related factors in AGS development.

Tick bite-induced Alpha-Gal Syndrome and Immunologic Responses in an Alpha-Gal Deficient Murine Model

Introduction

Alpha-Gal Syndrome (AGS) is a delayed allergic reaction due to specific IgE antibodies targeting galactose-α-1,3-galactose (α-gal), a carbohydrate found in red meat. This condition has gained significant attention globally due to its increasing prevalence, with more than 450,000 cases estimated in the United States alone. Previous research has established a connection between AGS and tick bites, which sensitize individuals to α-gal antigens and elevate the levels of α-gal specific IgE. However, the precise mechanism by which tick bites influence the hosťs immune system and contribute to the development of AGS remains poorly understood. This study investigates various factors related to ticks and the host associated with the development of AGS following a tick bite, using mice with a targeted disruption of alpha-1,3-galactosyltransferase (AGKO) as a model organism.

Methods

Lone-star tick (Amblyomma americanum) and gulf-coast tick (Amblyomma maculatum) nymphs were used to sensitize AGKO mice, followed by pork meat challenge. Tick bite site biopsies from sensitized and non-sensitized mice were subjected to mRNA gene expression analysis to assess the host immune response. Antibody responses in sensitized mice were also determined.

Results

Our results showed a significant increase in the titer of total IgE, IgG1, and α-gal IgG1 antibodies in the lone-star tick-sensitized AGKO mice compared to the gulf-coast tick-sensitized mice. Pork challenge in Am. americanum -sensitized mice led to a decline in body temperature after the meat challenge. Gene expression analysis revealed that Am. americanum bites direct mouse immunity toward Th2 and facilitate host sensitization to the α-gal antigen, while Am. maculatum did not.

Conclusion

This study supports the hypothesis that specific tick species may increase the risk of developing α-gal-specific IgE and hypersensitivity reactions or AGS, thereby providing opportunities for future research on the mechanistic role of tick and host-related factors in AGS development.

The enhanced permeability retention effect: a new paradigm for drug targeting in infection

Multidrug-resistant, Gram-negative infection is a major global determinant of morbidity, mortality and cost of care. The advent of nanomedicine has enabled tailored engineering of macromolecular constructs, permitting increasingly selective targeting, alteration of volume of distribution and activity/toxicity. Macromolecules tend to passively and preferentially accumulate at sites of enhanced vascular permeability and are then retained. This enhanced permeability and retention (EPR) effect, whilst recognized as a major breakthrough in anti-tumoral targeting, has not yet been fully exploited in infection. Shared pathophysiological pathways in both cancer and infection are evident and a number of novel nanomedicines have shown promise in selective, passive, size-mediated targeting to infection. This review describes the similarities and parallels in pathophysiological pathways at molecular, cellular and circulatory levels between inflammation/infection and cancer therapy, where use of this principle has been established.

Angiotensin, bradykinin and the endothelium

Angiotensins and kinins are endogenous peptides with diverse biological actions; as such, they represent current and future targets of therapeutic intervention. The field of angiotensin biology has changed significantly over the last 50 years. Our original understanding of the crucial role of angiotensin II in the regulation of vascular tone and electrolyte homeostasis has been expanded to include the discovery of new angiotensins, their important role in cardiovascular inflammation and the development of clinically useful synthesis inhibitors and receptor antagonists. While less applied progress has been achieved in the kinin field, there are continuous discoveries in bradykinin physiology and in the complexity of kinin interactions with other proteins. The present review focuses on mechanisms and interactions of angiotensins and kinins that deal specifically with vascular endothelium.

Bradykinin-induced plasma exudation in guinea-pig airways: involvement of platelet activating factor

1. We studied the effect of bradykinin on plasma exudation in the airways of the anaesthetized guinea-pig in vivo. Tissue content of extravasated Evans blue dye was used as an index of protein exudation in the larynx, trachea, main bronchi and intrapulmonary airways (i.p.a.). 2. Bradykinin increased the content of Evans blue in all tissues studied in a dose-related manner. The response was greatest in the main bronchi and i.p.a., less in the trachea and least in the larynx. A dose of 47 nmol kg-1 was the lowest tested which caused significant (P less than 0.001) plasma exudation with increases in leakage above control values of 256% in the larynx, 405% in the trachea, 394% in the main bronchi and 485% in intrapulmonary airways. 3. Leakage was significantly (P less than 0.05) increased above control values by 1 min after bradykinin (47 nmol kg-1) in the main bronchi and intrapulmonary airways and was maximal in all airways 5 min after bradykinin. Although reduced by 15 min, the tissue content of dye was still significantly (P less than 0.05) increased 2 h after bradykinin. 4. The prolonged tissue dye retention was due to a later phase of slow and maintained exudation preventing full clearance of dye after the initial response. 5. The initial phase of leakage was partially attenuated by the platelet activating factor (PAF) receptor antagonists WEB 2086 or BN 52021, by indomethacin or by inhibiting sensory nerve activation by opioid anaesthesia: it was not affected by mepyramine and cimetidine nor by the sulphidopeptide leukotriene receptor antagonists FPL 55712 or ICI 198,615. Adrenoceptor blockade of the anti-leakage effects of endogenously-released catecholamines significantly (P < 0.05) enhanced leakage. 6. The later phase of plasma leakage was completely inhibited by the PAF antagonists. 7. We conclude that, in guinea-pig airways in vivo, the initial phase of bradykinin-induced plasma exudation is mediated in part by PAF, sensory nerves and prostaglandins, whereas the later, prolonged phase of leakage is mediated exclusively by PAF. If bradykinin is generated in asthma, its potent and prolonged effects on plasma leakage may contribute significantly to airway oedema and may be involved in the development of bronchial hyperresponsiveness.

Production of prostaglandin E2 by human amnion in vitro in response to addition of media conditioned by microorganisms associated with chorioamnionitis and preterm labor

To examine the potential role of bacterial infection in the cause of spontaneous preterm labor, human amnion cells in tissue culture were exposed to medium conditioned by culturing each of 21 microorganisms previously found in association with chorioamnionitis and preterm labor. At a final concentration of 0.1% bacterial conditioned medium, a significant stimulation of prostaglandin E2 production from amnion cells was observed for this range of microorganisms. Conditioned medium obtained from culturing Bacteroides fragilis caused a dose-related increase in prostaglandin production, final concentrations of 0.02% to 0.1% being stimulatory but greater concentrations (0.1% to 10%) causing a progressive inhibition of prostaglandin synthesis. A similar concentration-related response in which stimulation was followed by inhibition occurred on addition of increasing concentrations of phospholipase A2 to amnion cells. These data suggest that bacterial phospholipase may release arachidonic acid from amnion leading to prostaglandin E2 synthesis, but excessive addition of phospholipase and consequent increased arachidonic acid availability may give rise to substrate inhibition of cyclooxygenase enzyme and inhibit prostaglandin E2 synthesis. Overall it appears that a wide variety of microorganisms associated with preterm labor may secrete phospholipase, which liberates amnion arachidonic acid for conversion to the oxytocic agent prostaglandin E2.

Inhibitory effects of diclofenac and indomethacin on interleukin-1-induced changes in PGE2 release. A novel effect on free arachidonic acid levels in human synovial cells

The inhibitory effects of two non-steroidal anti-inflammatory drugs (NSAIDS), diclofenac and indomethacin, on interleukin-1 (IL-1)-induced changes in arachidonic acid (AA) release and prostaglandin E2(PGE2) production by human synovial cells was investigated. Both diclofenac and indomethacin potently inhibited IL-1 alpha-induced PGE2 release, with IC50 values of 1.6 +/- 0.02 nM and 5.5 +/- 0.1 nM, respectively. A novel effect on IL-1 alpha-mediated changes in AA levels was observed using cells labelled with radioactive AA. Both drugs at micromolar concentrations (10-30 microM) showed an apparent inhibition of IL-1 alpha-induced increases in radioactivity associated with free AA. Concomitant with this inhibition, there was an increase in radioactivity associated with phosphatidylethanolamine (PE) and triglyceride (TG). As the drugs had no effect on IL-1 alpha-induced decreases in radioactivity associated with phosphatidylcholine (PC), this result was interpreted as being due to an enhanced acylation of AA into PE and TG. These results suggest that whilst at nanomolar concentrations, diclofenac and indomethacin can inhibit IL-1 alpha-induced PGE2 output, at micromolar concentrations an effect on free AA levels is also evident. This may have consequences for the release of other mediators such as leukotrienes, whose synthesis also involves the level of free AA.

Prostanoid production by rat aortic endothelial cells by bradykinin and histamine

The present studies demonstrate that rat aortic endothelial cells, when stimulated with either bradykinin or histamine, caused the release of both PGI2 and PGE2. The method has also been used to characterize the histamine receptor involved which is H1-subtype. The findings suggest that prostanoid production by bradykinin and histamine constitutes an alternative mechanism to endothelium-derived relaxing factor in mediating vasodilatation.

Interleukin-1 potentiates bradykinin- and TNF alpha-induced PGE2 release

The ability of interleukin-1 (IL-1 alpha), IL-1 beta, tumour necrosis factor alpha (TNF alpha) and bradykinin to cause prostaglandin E2 (PGE2) release from human synovial cells was examined. IL-1 alpha and IL-beta proved equipotent in their effect, and were up to four orders of magnitude more potent than TNF alpha after incubation for 24 h. Bradykinin proved the weakest of all the agonists examined. When the cells were pretreated with IL-1 alpha or IL-1 beta for 24 h, their ability to release PGE2 in response to a short incubation (1 h) with bradykinin, TNF alpha or a second dose of IL-1 was potentiated. In addition, TNF alpha and bradykinin were shown to increase the level of free arachidonic acid (AA) in the cells. Furthermore, a similar potentiation in the response of pretreated cells was observed with exogenous AA. It is already known that pretreatment with IL-1 for 24 h results in an induction of cyclo-oxygenase (CO). It seems likely, therefore, that activation of phospholipase A2 which occurs during a short incubation with IL-1, TNF alpha or bradykinin releases substrate, AA, which is more rapidly converted to PGE2 by cells in which CO has been induced. The result of these events might indicate a sustained release of PGE2 at sites of inflammation where such mediators are released.

Induction of cyclo-oxygenase by interleukin-1 in rheumatoid synovial cells

The ability of interleukin-1 (IL-1) to stimulate prostaglandin E2 (PGE2) production by human rheumatoid adherent synovial cells was found to be time-dependent and sensitive to protein synthesis inhibitors. Cells incubated with exogenous arachidonic acid (10 microM) showed no increase in PGE2 production. However, with IL-1 (2.5 U/ml) and exogenous arachidonic acid there was a marked increase, with levels reaching twice that for cells incubated with IL-1 alone. Aspirin pre-treatment studies and the use of [acetyl-14C]aspirin showed that IL-1 increased PGE2 production through the induction of cyclo-oxygenase.

Kinetics of the generation and action of chemical mediators in zymosan-induced inflammation of the rabbit peritoneal cavity

Acute inflammation was induced by intraperitoneal injection of zymosan (yeast cell walls) in the rabbit. Peritoneal inflammation was monitored by the local accumulation of intravenously-injected Evans blue dye (which binds to plasma albumin) and of polymorphonuclear leukocytes (PMNLs). The zymosan-induced exudate fluid contained a microvascular permeability-increasing factor or factors which, unlike histamine and bradykinin, had a long duration of action when tested in rabbit skin and was dependent on circulating PMNLs. Using radioimmunoassay, high levels of rabbit C5a, or C5a des Arg, were detected in the exudate fluid and accounted for much of the permeability-increasing activity, as judged by skin bioassay after separation on Sephadex G-100. The vasodilator prostaglandin, prostaglandin I2 (PGI2), was generated in the inflammatory reaction, as judged by the presence of high levels of 6-oxo-PGF1 alpha detected in the exudate by radioimmunoassay. However, in contrast to observations in rabbit skin, inhibition of prostaglandin generation had a relatively small effect on peritoneal oedema formation. C5a and C5a des Arg increase microvascular permeability by a PMNL-dependent mechanism in the rabbit. However, in response to zymosan, protein leakage was detected considerably earlier than PMNL accumulation. A hypothesis to account for this difference is proposed.

Immunosuppressive actions of prostaglandins and the possible increase in chronic inflammation after cyclo-oxygenase inhibitors

A method is described to examine the activity of potential antirheumatic drugs on the release and activity of lymphokines and interleukins in vitro, using human peripheral blood mononuclear cells and synovial cells. The enhancement of lymphocyte-mediated effects brought about by non-steroid anti-inflammatory drugs has been shown to be the result of inhibition of a prostaglandin negative-feedback mechanism. Since the underlying features of rheumatoid arthritis and related diseases are almost certainly brought about by mononuclear cell activation, their enhancement by non-steroid anti-inflammatory drugs might well have serious clinical implications. The possibility is discussed that aspirin-like drugs, administered in large doses to patients suffering slight joint pain, might well exacerbate, perpetuate or even initiate a chronic arthritic condition. We suggest that, as soon as the disease has been diagnosed, patients should be treated with a disease-modifying drug and, if necessary, an analgesic which does not inhibit cyclo-oxygenase.

Ovarian increase in kinin-generating capacity in PMSG/hCG-primed immature rat

Ovarian kinin-generating capacity was determined during induced ovulation in immature Wistar rats. The onset of ovulation was monitored by counting the number of ova in the oviducts at 2-h intervals after the administration of human chorionic gonadotropin (hCG). Ova began to appear in significant numbers at 14 h after hCG, with an average of 7.6 +/- 2.3 ova/rat. By 16 h after hCG, the oviducts contained 32.7 +/- 4.1 ova/rat. The ovaries from each group of animals were homogenized in phosphate-buffered saline, and extracts of this tissue were incubated for 200 min to allow the generation of kinins from endogenous kininogen. The amount of kinin generated by this procedure was measured by radioimmunoassay. At 0 h (i.e., just before the administration of hCG), the ovaries contained 5.90 +/- 0.60 pg kinin/micrograms protein per 200 min in the ovarian extract. By 4 h after hCG, the kinins increased significantly (P less than 0.05) to 13.16 +/- 3.61 pg kinin/micrograms protein. The kinins progressively increased (P less than 0.001) to 67.88 +/- 23.26 pg kinin/micrograms protein by 16 h after hCG. Indomethacin and cycloheximide significantly inhibited both kinin-generating activity and ovulation. These data suggest that kinin-forming activity and kinins may have a role in the ovulatory process of mammals.

The production of prostaglandin and the regulation of cell division in neonate rat primary mixed glial cultures

The production of prostaglandins has been studied in neonate rat primary mixed glial cultures. A correlation was found between inhibition of [3H]thymidine incorporation in the cultures and production of prostaglandin, which was stimulated by the addition of supernatant from Con A-activated rat splenocytes. Inhibition of prostaglandin synthesis in the cultures by indomethacin results in a striking increase in incorporation of [3H]thymidine into the cultures, an effect which was reversed by the addition of exogenous PGE2, but not PGF2 alpha. PGE was the principal prostaglandin detected, with both macrophages/microglia and astrocytes contributing to the output. A possible role for prostaglandins in the modulation of inflammatory responses in the central nervous system is discussed.

Histamine stimulates prostaglandin E production by rheumatoid synovial cells and human articular chondrocytes in culture

Histamine stimulates prostaglandin E (PGE) production by cultures of adherent rheumatoid synovial cells and human articular chondrocytes. When subcultured synovial fibroblasts or human articular chondrocytes were "primed" by preincubation with conditioned media from primary adherent rheumatoid synovial cell cultures (synovial factor), each produced even higher PGE levels upon histamine exposure. This histamine stimulation was prevented by histamine H1, but not H2, antagonists and was more marked if serum was absent from the culture media. Thus, histamine-induced PGE production by these cells is mediated via H1 receptor activation and subsequent arachidonic acid liberation.

A study of the prostaglandin and thromboxane content of the central nervous tissues with the development of chronic relapsing allergic encephalomyelitis

Levels of PGE, PGF2 alpha, 6-oxo-PGF1 alpha and thromboxane (TXB2) in spinal cords and cerebellums of guinea pigs at different stages of chronic relapsing allergic encephalomyelitis (CREAE) were compared with those in Freund's adjuvant-treated, age-matched controls. PGE and TXB2 levels were found to be increased in spinal cords during acute and relapse phases of the disease. The number of lesions in the spinal cord was similarly increased in acute and relapse stages. There was, however, no similar correlation between number of lesions and eicosanoid levels in the cerebellum with the clinical stages of the disease based on hind limb paralysis. In the acute phase and remission lesion numbers were low, and high levels, similar to those found in the spinal cord, were only found in the relapse phase. Eicosanoid levels were high in the acute phase and remission, and generally low in relapse. The spinal cord levels of eicosanoids in remission and relapse correlated well with previous data obtained from the CSF of patients with multiple sclerosis.

The roles of prostaglandin endoperoxides, thromboxane A2 and adenosine diphosphate in collagen-induced aggregation in man and the rat

The effects of aspirin, carboxyheptylimidazole (CHI) and creatine phosphate/creatine phosphokinase (CP/CPK) on platelet aggregation and thromboxane B2 (TxB2) formation induced by collagen have been examined in vitro. Platelets from two species, man and the rat, have been used. In man, aspirin and CHI abolished TxB2 production but only partially inhibited aggregation. CP/CPK partially inhibited aggregation and TxB2 formation. In the rat, aspirin and CHI abolished TxB2 formation but had no effect on aggregation. CP/CPK completely inhibited aggregation and partially inhibited TxB2 generation. In man, collagen-induced aggregation is largely dependent on ADP and to a lesser extent on arachidonate metabolites whereas, in the rat, ADP alone mediates aggregation induced by this agonist. The results with CP/CPK suggest that TxB2 formation is dependent either on the prior release of platelet ADP or on aggregation itself rather than being responsible for the aggregation response.

Intrarenal prostaglandin release: effects of arachidonic acid and hyperchloremia

We measured the release of PGE2, 6kPGF1 alpha, PGF2 alpha, and TXB2 into urine (U) and renal hilar lymph (L) to assess the possible roles of intrarenal prostaglandins (PGs) in arachidonic acid (AA)-induced renal vasodilation and Cl-induced renal vasoconstriction, (a model of tubuloglomerular feedback, TG). AA caused an ipsilateral fall in renal vascular resistance (RVR) and diuresis and increased release of all PGs into U; release of 6kPGF1 alpha into L increased ninefold. Hypertonic NaCl infusion caused ipsilateral vasoconstriction and decreased GFR; the release of TXB2 into U and L increased, but other PGs were not altered consistently. During a background infusion of AA, hypertonic NaCl infusion again evoked TXB2 release into U and L without significant changes in other PGs. AA attenuated the NaCl-induced renal vasoconstriction in dogs with the highest rates of PGE2 release into L. Changes in RVR correlated with the ratio of excretion of vasodilator PG (PGE2 + 6kPGF1 alpha) to TXB2 (r = -0.74). Indomethacin administration blunted, but did not abolish, the Cl-induced increase in RVR. In conclusion, (1) AA evokes the release of PGs, especially prostacyclin, into renal cortex; (2) hypercholoremia increases RVR and evokes a rather selective release of renal TX; (3) the production of vasodilator PGs by AA may attenuate Cl-induced renal vasoconstriction; (4) renal vasodilator and vasoconstrictor PGs can be released relatively independently--their balance could modulate RVR during activation of the TG response.

Correlation between prostaglandin and thromboxane levels and clinical signs in cyclosporine A-treated guinea pigs with acute experimental allergic encephalomyelitis

Prostaglandin E, prostaglandin F2 alpha and thromboxane B2 levels were measured in the spinal cord and cerebellum of guinea pigs with acute experimental allergic encephalomyelitis treated with Cyclosporine A in a schedule which delayed the onset of the disease and completely suppressed it in 40% of the animals. A correlation was found between the eicosanoid levels in the central nervous system and clinical signs of the disease. Where lesions were completely suppressed the levels of eicosanoids were normal. The number of lesions found correlated well with the clinical state of the animals.

Isolation from Cannabis sativa L. of cannflavin--a novel inhibitor of prostaglandin production

The isolation from Cannabis sativa L. of an inhibitor of prostaglandin (PG) E2 production by cultured rheumatoid synovial cells is described. This agent, for which the name Cannflavin has been coined, is distinct from cannabinoids on the basis of isolation procedure, preliminary structural analysis and biological properties. The activity of Cannflavin has been compared with several established anti-inflammatory drugs and the major cannabinoids.

Structural correlations of phorbol-ester-induced stimulation of PGE2 production by human rheumatoid synovial cells

Eight phorbol esters were studied for their ability to stimulate prostaglandin production in human rheumatoid synovial cells over the dose range 0.1 ng to 1.0 micrograms. These derivatives were based upon phorbol, 4-deoxyphorbol, and 12-deoxyphorbol nuclei. This activity was structurally dependent and, although it did not correlate with the actions of the same compounds to induce erythema in vivo, it did correlate with their ability to stimulate human lymphocyte mitogenesis. Stimulation of PGE2 production by a phorbol and a 12-deoxyphorbol analog was inhibited in this system by both indomethacin and dexamethasone.

Prostaglandin levels in cerebrospinal fluid from multiple sclerosis patients in remission and relapse

Radioimmunoassay (RIA) techniques have been employed to determine prostaglandin (PG) levels in the cerebrospinal fluid (CSF) from multiple sclerosis (MS) patients in remission and relapse and in subjects with other neurological diseases (OND). PGE and PGF2 alpha concentrations in spinal fluid from MS patients in relapse were significantly lower than values estimated during remission and in individuals with OND of the central nervous system (CNS). These observations are discussed in relation to the clinical state of patients with demyelinating disease together with a consideration of the concept that disordered immune mechanisms contribute a central role in the pathogenesis of MS.

Effects of piroxicam on mononuclear cells. Comparison with other antiarthritic drugs

Piroxicam and other antiarthritic drugs were compared with respect to their effects on T-lymphocyte/monocyte/rheumatoid synovial cell interactions leading to inflammatory mediator production. Piroxicam inhibited PGE2 formation by blood mononuclear cells, but was less potent than indomethacin. Both drugs enhanced suboptimal phytohemagglutinin (PHA)-stimulated tritiated thymidine (3H-TdR) incorporation by mononuclear cells, although optimal responses were less affected. Exogenous interleukin-2 (IL-2) enhanced suboptimal but not optimal PHA responses, and the effects of the cyclo-oxygenase inhibitors were overcome by exogenous PGE2. Thus piroxicam and indomethacin prevented the inhibition by endogenous monocyte-derived PGE2 of IL-2 secretion and activity. Other antiarthritic drugs, including antimalarials, immunosuppressive agents and gold salts, inhibited PHA-induced lymphocyte proliferation regardless of the level of stimulation. Mepacrine and chloroquine were more effective in inhibiting the release of mononuclear cell factor (MCF) that stimulated PGE2 synthesis by synovial cells. Cyclosporin-A, azathioprine and 6-mercaptopurine were more potent as antiproliferative agents than as inhibitors of mediator release. Sodium aurothiomalate and aurothioglucose selectively interfered with lymphocyte-mediated amplification of MCF release, whereas auranofin inhibited spontaneous production of monocytes and the action of MCF on synovial cells. In rheumatoid synovial cells, piroxicam and indomethacin inhibited PGE2 production but not collagenase release. Suppression of MCF release could lead indirectly to reduction of IL-2 and collagenase as well as PGE2 production and consequently to more profound inhibition of immunologically-mediated inflammation.

Phosphatidylcholine is the major phospholipid providing arachidonic acid for prostacyclin synthesis in thrombin-stimulated human endothelial cells

Upon incubation for 24 hours with [3H]arachidonic acid (AA, 1 mu Ci/ml), cultured endothelial cells from human umbilical vein incorporated one half of the added radioactivity, mostly into phospholipids (83% of the total cell radioactivity). Distribution of the label between the various phospholipid classes was found to reflect the distribution of endogenous AA. Stimulation with human thrombin (2 U/ml) promoted a rapid release of radioactive material into supernatants, which contained essentially 6-keto-prostaglandin F1 alpha and non-converted AA. This process levelled off at 10 min, at which time phosphatidylcholine displayed a decrease accounting for 3.7% of the total cell radioactivity. Phosphatidylinositol also appeared significantly diminished, but this decrease was almost 2.5 fold less than that observed in phosphatidylcholine. It is concluded that AA availability for prostacyclin biosynthesis is mostly regulated by a phospholipase A2.

Prostaglandin and thromboxane levels in central nervous system tissues from rats during the induction and development of experimental allergic encephalomyelitis (EAE)

Prostaglandin (PG) and thromboxane levels were measured in the spinal cords and cerebellums of rats during the induction, disease and recovery periods of experimental allergic encephalomyelitis (EAE). In spinal cords PGE and 6-oxo-PGF1 alpha increased to maximum with the onset of neurological symptoms, 11-12 days after inoculation. However, the levels returned to normal at the height of clinical disease, despite the persistence of inflammatory lesions. After an initial fall, PGF2 alpha increased to normal limits, 11-12 days after inoculation, and remained at this level throughout the experiment. In contrast, the cerebellum content of all the eicosanoids decreased prior to the appearance of clinical EAE. PGF2 alpha and 6-oxo-PGF1 alpha concentrations subsequently increased but the PGE and thromboxane levels remained depressed for the duration of the study. The role of the eicosanoids in modulating the immune response to neuroantigen is discussed together with our recent findings in guinea pigs with acute EAE.

A longitudinal study of the prostaglandin content of central nervous system tissues from guinea pigs with acute experimental allergic encephalomyelitis (EAE)

The levels of prostaglandins (PGs) E, F2 alpha and 6-oxo-PGF1 alpha, in spinal cords and cerebellums of guinea pigs were measured during the development of experimental allergic encephalomyelitis (EAE). The earliest change observed was an elevation of PGE in spinal cords, but not cerebellums , 5-7 days post-inoculation (PI) and prior to the appearance of clinical symptoms. PGE content of spinal cords continued to rise until days 12-14 PI when the animals displayed paralytic EAE. In contrast, PGF2 alpha and 6-oxo-PGF1 alpha levels in spinal cords peaked on days 9-11, when the animals exhibited initial clinical signs, but fell to lower values by days 12-14 PI. In cerebellums , the PGE content increased more slowly than in spinal cords, consistent with the lower numbers of mononuclear cell infiltrates, whereas PGF2 alpha and 6-oxo-PGF1 alpha levels remained unaltered. The relationships between the observed changes in prostanoid levels, lesion development and the appearance of clinical symptoms are discussed.

Evidence for fibroblasts as the major source of prostacyclin and prostaglandin synthesis in dental cyst in man

Periodontal cysts synthesize large amounts of prostaglandins and collagenase which probably cause the localized bone destruction essential for intraosseous cyst growth. Fragments of cyst wall, and fibroblasts cultured from them, synthesized prostacyclin (PGI2) in addition to prostaglandin E2 (PGE2), PGF2 alpha and collagenase in vitro. Soluble products from cultures of unstimulated and phytohaemagglutinin-stimulated blood mononuclear cells enhanced the synthesis of these prostaglandins in monolayer cultures of cyst-wall fibroblasts. It is therefore proposed that cyst capsule fibroblasts are the major source of these bone-resorbing factors, acting under the stimulus of lymphocytes and monocytes in chronically inflamed cysts. Cysts which were not infiltrated by chronic inflammatory cells (follicular cysts, a keratocyst, an ameloblastoma, and an aneurysmal bone cyst) also produced prostaglandins and collagenase, indicating that the stimulatory mechanism for the production of bone-resorbing factors in these cysts may differ from that in periodontal cysts.

Altered prostaglandin synthesis in isolated lungs of rats with streptozotocin-induced diabetes

Metabolism of exogenous and endogenous arachidonic acid (AA) to several cyclo-oxygenase products has been studied by bioassay, radioimmunoassay and radiochemical assay in isolated lungs from rats made diabetic with streptozotocin and compared with that occurring in lungs from untreated rats. From exogenous AA, more PGE2, PGF2 alpha and PGD2 were formed in diabetic lungs than in control lungs, although amounts of PGI2 and TxA2 formed did not differ between the two sets of lungs. From endogenous AA, the synthesis of PGI2 in diabetic lungs was nearly half that in controls lungs. Such a deficiency in the unstimulated synthesis of a potent anti-aggregatory substance would contribute to the hyperaggregable state observed in diabetes.