Role of renal prostaglandins in circulatory homeostasis

The evidence is reviewed that prostaglandins of renal origin through (i) their local actions on renal blood vessels, and (ii) complex interactions with the nervous adrenergic and the endocrine vasoactive renin-angiotensin-aldosterone and kallikrein-kinin systems, may participate in the regulation of excretory functions of the kidney and thereby contribute to circulatory homeostatic mechanisms.

An investigation into the role of prostaglandins in zebrafish oocyte maturation and ovulation

This study explored the potential for ovarian-derived prostaglandins (PGs) to be involved in the regulation of oocyte maturation and ovulation in zebrafish. It was demonstrated that cultured vitellogenic follicles have the capacity to produce prostaglandin E(2) (PGE(2)) and PGF(2alpha) in response to arachidonic acid (AA) in a concentration-dependent manner, and that AA stimulates the in vitro production of 17beta-estradiol (E(2)). The production of AA-stimulated PGF(2alpha) was significantly reduced by treatment with the non-selective cyclooxygenase (COX) inhibitor, indomethacin (INDO). Treatment of full-grown follicles with AA did not induce oocyte maturation as assessed by germinal vesicle breakdown, but INDO significantly decreased the rate of spontaneous maturation. Using Real-Time PCR, it was shown that follicles of different developmental size classes (primary growth and pre-vitellogenic, early-vitellogenic, and mid- to full-grown vitellogenic) express enzymes that release (cytosolic phospholipase A(2) (cPLA(2)); phospholipase Cgamma1) or metabolize (COX-1, COX-2, and prostaglandin synthase-2) AA to PG metabolites. The expression of cPLA(2) was found to be significantly greater in full-grown follicles compared to follicles of the pre- and early-vitellogenic stages. In vivo studies demonstrated that breeding groups of zebrafish exposed to 100 microg/L INDO exhibited reduced spawning rates and clutch sizes compared with control and 1 microg/L INDO exposed fish. In other studies, it was shown that naturally spawning groups of females exhibit increased ovarian levels of PGF(2alpha), E(2), and 17alpha,20beta-dihydroxy-4-pregnen-3-one (a maturation-inducing hormone in zebrafish) near the time of ovulation compared with non-breeding females. Collectively, these experiments indicate that the AA pathway in zebrafish ovaries is involved in the regulation of oocyte maturation and ovulation and a non-selective inhibitor of COX disrupts these processes.

Antiluteolytic effect of the embryo

In several mammalian species, prostaglandin F2 alpha (PGF2 alpha) released from the uterus causes corpus luteum regression, and thereby regulates the length of the oestrous cycle or pseudopregnancy. If the animal becomes pregnant, luteal regression must be prevented since ovarian progesterone is necessary for pregnancy maintenance during at least the first one-third of pregnancy. Evidence is presented that the guinea-pig conceptus produces an antiluteolytic factor which suppresses PGF2 alpha output from the uterus by preventing the increase in uterine PGF2 alpha-synthesizing capacity which occurs around the time of luteolysis. Experiments in unilaterally pregnant guinea-pigs, with either an intact or a transected sterile horn, indicate that this factor acts both locally systemically, though separation of the two uterine horns does greatly reduce its effect on the sterile side. Oestradiol administered during early pregnancy induces abortion, which is associated with a high PGF2 alpha-synthesizing capacity of the uterus. However, luteal regression does not take place while the conceptuses are in the uterus. Spontaneously aborting guinea-pigs behave similarly. The conceptus may therefore secrete a luteotrophic hormone as well. Luteal maintenance during early pregnancy in other species is discussed, since experiments on sheep indicate that the sheep embryo may also secrete an antiluteolytic factor.

Components in seminal plasma regulating sperm transport and elimination

Seminal plasma has been suggested to be involved in sperm transport, and as a modulator of sperm-induced inflammation, which is thought to be an important part of sperm elimination from the female reproductive tract. This article reports on recent experiments on the importance of seminal plasma components in sperm transport and elimination. In Experiment 1, hysteroscopic insemination in the presence (n = 3) or absence (n = 3) of 2 ng/mL PGE showed an increased portion of spermatozoa crossing the utero-tubal junction in the presence of PGE in two mares, while no difference was observed between treatments in a third mare. In Experiment 2, whole seminal plasma, heat-treated seminal plasma (90 degrees C for 45 min), and charcoal-treated seminal plasma were added to: (1) sperm samples during opsonization prior to polymorphonuclear neutrophil(s) (PMN)-phagocytosis assays (n = 5); or to (2) phagocytosis assays (n = 5). Opsonization of spermatozoa was suppressed in the presence of whole seminal plasma, compared with samples without seminal plasma (p < 0.05). Charcoal treatment did not remove the suppressive effect of seminal plasma on opsonization, but heat treatment of seminal plasma reduced its suppressive properties (p < 0.05). The addition of whole seminal plasma to opsonized spermatozoa almost completely blocked phagocytosis (p < 0.05). Charcoal treatment did not remove the suppressive effect of seminal plasma. However, heat-treated fractions of seminal plasma removed the suppressive effect of seminal plasma on phagocytosis (p < 0.05). In Experiment 3, viable and non-viable (snap-frozen/thawed) spermatozoa were subjected to in vitro assays for PMN binding and phagocytosis with the following treatments (n = 3): (1) seminal plasma (SP), (2) extender; (3) ammonium sulfate precipitated seminal plasma proteins with protease inhibitor (SPP+); or (4) ammonium sulfate precipitated seminal plasma proteins without protease inhibitor (SPP-). Treatment was observed to impact binding and phagocytosis of viable and non-viable spermatozoa (p < 0.05). SP and SPP+ suppressed PMN-binding and phagocytosis of viable sperm. This effect was also seen, but to a lesser degree, in SPP- treated samples. Non-viable spermatozoa showed less PMN-binding and phagocytosis than live sperm in the absence of SP. The addition of SP promoted PMN-binding and phagocytosis of non-viable spermatozoa. SPP- treated samples also restored PMN-binding of non-viable spermatozoa. The addition of protease inhibitors removed this effect. In Experiment 4, seminal plasma proteins were fractionated based on MW by Sephacryl S200 HR columns (range 5000-250,000 kDa). Fractionated proteins were submitted to sperm-PMN binding assays. A protein fraction <35 kDa suppressed PMN-binding to live and snap-frozen spermatozoa. A greater MW protein fraction appeared to promote binding between PMNs and snap-frozen spermatozoa. While the addition of protease inhibitors was necessary to maintain the protective effect of seminal plasma proteins on viable spermatozoa, the promotive effect of seminal plasma on non-viable spermatozoa appeared to require some protease activity. It was concluded from these experiments that components of seminal plasma play active roles in transportation and survival of viable spermatozoa in the female reproductive tract and in the elimination of non-viable spermatozoa from the uterus.

[Regulation of prostaglandin E molecular network in mammalian reproduction]

Prostaglandin E molecular network includes cyclooxygenase, phospholipase A2, prostaglandin E, prostaglandin E receptors, and prostaglandin E synthase. Recently, it was found that PGE2 receptors localized not only on the cell membrane but also on the envelope of nucleus. They are different in the signaling pathways and in regulation mechanism between nuclear receptors and membrane receptors. They compose a delicate network, which plays important roles in mammalian reproduction, especially in most processes of female reproduction.

Levuglandins and isolevuglandins: stealthy toxins of oxidative injury

Inspired by a reaction discovered through basic research on the chemistry of the bicyclic peroxide nucleus of the prostaglandin endoperoxide PGH2, we postulated that levulinaldehyde derivatives with prostaglandin side chains, levuglandins (LGs), and structurally isomeric analogues, isolevuglandins (iso[n]LGs), would be generated by nonenzymatic rearrangements of prostanoid and isoprostanoid endoperoxides. Two decades of subsequent studies culminated in our discoveries of the LG and isoLG pathways, branches of the cyclooxygenase and isoprostane pathways, respectively. In cells, PGH2 rearranges nonenzymatically to LGs even in the presence of enzymes that use PGH2 as a substrate. IsoLGs, also known as isoketals or neuroketals, are generated in vivo through free radical-induced autoxidation of polyunsaturated phospholipid esters. Hydrolysis occurs after rapid adduction of isoLG phospholipids to proteins. The proclivity of these reactive species to avidly bind covalently with and cross-link proteins and nucleic acids complicated the hunt for LGs and isoLGs in vivo. The extraordinary reactivity of these "stealthy toxins" underlies much, if not all, of the biological consequences of LG and isoLG generation. They interfere with protein function and are among the most potent neurotoxic products of lipid oxidation known. Because they can accumulate over the lifetimes of proteins, iso[n]LG-protein adducts represent a convenient dosimeter of oxidative stress.

Cyclooxygenase-2-derived E prostaglandins down-regulate matrix metalloproteinase-1 expression in fibroblast-like synoviocytes via inhibition of extracellular signal-regulated kinase activation

We examined the regulation of matrix metalloproteinase (MMP) production by mitogen-activated protein kinases and cyclooxygenases (COXs) in fibroblast-like synoviocytes (FLSCs). IL-1beta and TNF-alpha stimulated FLSC extracellular signal-regulated kinase (ERK) activation as well as MMP-1 and -13 release. Pharmacologic inhibitors of ERK inhibited MMP-1, but not MMP-13 expression. Whereas millimolar salicylates inhibited both ERK and MMP-1, nonsalicylate COX and selective COX-2 inhibitors enhanced stimulated MMP-1 release. Addition of exogenous PGE(1) or PGE(2) inhibited MMP-1, reversed the effects of COX inhibitors, and inhibited ERK activation, suggesting that COX-2 activity tonically inhibits MMP-1 production via ERK inhibition by E PGs. Exposure of FLSCs to nonselective COX and selective COX-2 inhibitors in the absence of stimulation resulted in up-regulation of MMP-1 expression in an ERK-dependent manner. Moreover, COX inhibition sufficient to reduce PGE levels increased ERK activity. Our data indicate that: 1) ERK activation mediates MMP-1 but not MMP-13 release from FLSCs, 2) COX-2-derived E PGs inhibit MMP-1 release from FLSCs via inhibition of ERK, and 3) COX inhibitors, by attenuating PGE inhibition of ERK, enhance the release of MMP-1 by FLSC.

[Comparative morpho-functional assessment of the impact produced by prolonged infusions of prostaglandins E and F on the course of genetically preconditioned arterial hypertension]

The administration of prolonged intravenous infusions of prostaglandins is defined; the method provided for specifying a long-term impact produced by prostaglandins on a nature of the course of genetically preconditioned arterial hypertension (AHT) in rats. Infusions of PGE-2 bring about a prolonged and stable reduction of mean arterial presser (AP) by 10% versus its original value; they intensify 2-fold the depressor baroreflectory regulation and stimulate the urinary excretion of endogenous renal PGF-2 alpha; besides, they contribute to a better blood supply to organs, i.e. an increased perfusion of the cortical and medullary layers of the kidneys and of the brain substances; and dilatation of the intramural branches of the coronary arteries, due to which the AP becomes milder. Infusions of PGF-2 alpha contribute to a prolonged and stable elevation of mean AP by 12% versus the original value; they inhibit the depressor baroreflectory regulation and intensify the pressor baroreflectory regulation; they, additionally, induce the urinary excretion of endogenous renal PGF-2 alpha and correct the lesions in the blood supply to organs, i.e. pathological microcirculation, anemia and spasm of the renal parenchyma, ischemic foci in the myocardium, spastic contraction of small cerebral arteries, edema and destructive changes (of the local necrosis variation) in the cerebral substance microvessels concomitant with a commencing diapedetic hemorrhages. Finally, all above listed lesions are signs of the malignant AP course.

[Inhibitory effect of alveolar macrophages on the proliferation of pulmonary fibroblasts]

The effect of alveolar macrophages (AM) harvested from Wistar rats by lung lavage on proliferation of human embryo pulmonary fibroblasts in culture was investigated. It was observed that supernatants of AM decreased the uptake of (3)H TdR by the pulmonary fibroblasts. The AM activated with opsonized zymosan (OPZ) showed a stronger inhibitory effect on fibroblast proliferation compared with inactivated AM. Following pretreatment with indomethacin, the inhibitory effect of AM was abolished and reversed to stimulatory effect on pulmonary fibroblast proliferation. The PGE content in AM supernatant was measured with radioimmunoassay. It was observed that the inhibitory effect of AM was highly correlated to prostaglandin (PGE) content in the supernatant of AM. The results suggest that AM has both inhibitory and stimulatory effects on the proliferation of pulmonary fibroblast; the inhibitory effect is primary under normal conditions. This inhibitory action is mainly due to PGE secreted from AM. It is, therefore, suggested that AM plays an important role in suppressing pulmonary fibrosis under normal conditions.

Adenylate cyclase/protein kinase A signaling pathway enhances angiogenesis through induction of vascular endothelial growth factor in vivo

We previously reported that endogenous prostaglandins (PGs) may increase cAMP facilitated angiogenesis through the induction of vascular endothelial growth factor (VEGF) in rat sponge implantation models. In the present experiment, we tested whether or not adenylate cyclase / protein kinase A (AC/PKA)-dependent VEGF induction enhanced angiogenesis in this model. Topical daily injections of 8-bromo-cAMP enhanced angiogenesis in a dose-dependent manner. Forskolin, an activator of AC, also facilitated angiogenesis as did amrinone, an inhibitor of phosphodiesterase. VEGF induction was confirmed by the increased levels in the fluids in the sponge matrix after topical injection of 8-bromo-cAMP. Immunohistochemical investigation further revealed the VEGF-expressed cells in the sponge granulation tissues to be fibroblasts, and the intensity of positive reactions was enhanced by 8-bromo-cAMP, forskolin and amrinone. Angiogenesis without topical injections of the above compounds was suppressed by SQ22,536, an inhibitor for AC, or H-89, an inhibitor for PKA, with concomitant reductions in VEGF levels. Daily topical injections of neutralizing antibody or anti-sense oligonucleotide against VEGF significantly suppressed angiogenesis. PGE2-induced angiogenesis was suppressed with SQ22,536 or H-89. These results suggested that AC/PKA-dependent induction of VEGF certainly enhanced angiogenesis and that pharmacological tools for controlling this signaling pathway may be able to facilitate the management of conditions involving angiogenesis.

Antipyretics: mechanisms of action and clinical use in fever suppression

Fever is a complex physiologic response triggered by infectious or aseptic stimuli. Elevations in body temperature occur when concentrations of prostaglandin E(2) (PGE(2)) increase within certain areas of the brain. These elevations alter the firing rate of neurons that control thermoregulation in the hypothalamus. Although fever benefits the nonspecific immune response to invading microorganisms, it is also viewed as a source of discomfort and is commonly suppressed with antipyretic medication. Antipyretics such as aspirin have been widely used since the late 19th century, but the mechanisms by which they relieve fever have only been characterized in the last few decades. It is now clear that most antipyretics work by inhibiting the enzyme cyclooxygenase and reducing the levels of PGE(2) within the hypothalamus. Recently, other mechanisms of action for antipyretic drugs have been suggested, including their ability to reduce proinflammatory mediators, enhance anti-inflammatory signals at sites of injury, or boost antipyretic messages within the brain. Although the complex biologic actions of antipyretic agents are better understood, the indications for their clinical use are less clear. They may not be indicated for all febrile conditions because some paradoxically contribute to patient discomfort, interfere with accurately assessing patients receiving antimicrobials, or predispose patients to adverse effects from other medications. The development of more selective fever-relieving agents and their prudent use with attention to possible untoward consequences are important to the future quality of clinical medicine.

[Role of EP4 receptor in bone resorption induced by PGE]

Prostaglandin E2 (PGE2) acts as a potent stimulator of bone resorption. We examined PGE2-induced bone resorption using mice lacking each subtype (EP1, EP2, EP3 and EP4) of PGE receptor and identified the PGE receptor subtype(s) mediating PGE2 action. In calvarial culture from EP1-, EP2-, and EP3- knockout mice, PGE2 stimulated bone resorption to a similar extent to that found in calvaria from the wild-type mice. On the other hand, a marked reduction in bone resorption in response to PGE2 was found in the calvarial culture from EP4-knockout/mice. DbcAMP greatly stimulated bone resorption similarly in both wild-type and EP4-knockout mice. In mouse calvarial cultures, EP4-agonist markedly stimulated bone resorption, but its maximal stimulation was less than that induced by PGE2. EP2-agonist also stimulated bone resorption, but only slightly, EP1- and EP3-agonists did not stimulate it at all. These findings suggest that PGE2 stimulates bone resorption by a mechanism involving cAMP, which is mediated mainly by EP4 and partially by EP2.

The role of nitric oxide in dilating the fetal ductus arteriosus in rats

Prostaglandin E is a major dilator of the fetal ductus arteriosus (DA), but the role of nitric oxide in fetal ductal dilation has not been established. We studied the effects of a potent nitric oxide synthase inhibitor, Nomega-nitro-L-arginine methyl ester (L-NAME), on the fetal DA in rats. L-NAME was injected into the dorsum of pregnant rats, and fetal DA was studied 4 h later with a rapid whole body freezing method. The inner diameters of the DA and the main pulmonary artery were measured on a freezing microtome. The inner diameter ratio of DA to main pulmonary artery (DA/PA) was 1.02+/-0.03 (mean +/- SEM; number of fetuses [n], 21) in normal near-term fetuses. The effect of prostaglandin synthesis inhibition was studied after orogastric administration of indomethacin to pregnant rats. In near-term rats on the 21st day of gestation (term, 21.5 d), a large dose of L-NAME (100 mg/kg) caused only mild ductal constriction, with DA/PA reduced to 0.83+/-0.05 (n = 20). Indomethacin (1 mg/kg) caused moderate ductal constriction, and DA/PA was decreased to 0.65+/-0.05 (n = 21). Combined administration of L-NAME (10 mg/kg) and indomethacin (1 mg/kg) caused severe ductal constriction, with DA/PA of 0.26+/-0.03 (n = 16). In preterm rats on the 19th day of gestation, a moderate dose of L-NAME (10 mg/kg) caused severe ductal constriction, with a DA/PA of 0.32+/-0.05 (n = 24). Indomethacin (1 mg/kg) alone caused only mild ductal constriction, with DA/PA 0.86+/-0.02 (n = 16). In conclusion, prostaglandin has a major role and nitric oxide has a minor role in dilating the DA in the near-term fetal rat. In contrast, nitric oxide has a major role and prostaglandin has a minor role in dilating the DA in preterm fetal rats.

Interaction between nitric oxide and prostaglandin E pathways in rat smooth muscle myometrial cells

Previously, we demonstrated the presence of a nitric oxide (NO) prostaglandin (PG) pathway in myometrial cells obtained from uterine rat tissue. This pathway was modulated by estrogen and one possible function could be to modulate uterine relaxation. In the present study, we investigated the role of progesterone in the regulation of NO synthesis and the uterotonic PGE production by myometrial cells from uterine rat tissue. We worked with two groups of rats: (i) ovariectomizcd (OV) rats, without influence of sex hormones and (ii) OV rats injected with progesterone (4 mg) s.c. Myometrial uterine cells were obtained by a selective enzymatic digestion. In the incubation medium of these cells, nitrite concentration (as a measure of NO production) and PGE production were evaluated. To ensure a specific response, a competitive NOs inhibitor, N(G)-monomethyl-L-arginine; L-NMMA (300 microM) was used. We found that at 48 h of the incubation period, cells obtained from progesterone-primed uterine tissue presented an increase in the nitrite concentration concomitant with a decrease in the PGE production. When L-NMMA was added to the cells, nitrite production and PGE synthesis returned to control values. The fact that this effect had not been observed in the group of cells obtained from OV rats suggests that progesterone was responsible for it. These data provide strong evidence that in spite of the fact that estrogen and progesterone modulate the NO-PG pathway in the uterine rat tissue, the two hormones have opposite effects.

Brown adipose tissue. More than an effector of thermogenesis?

Brown adipose tissue (BAT) produces heat by oxidation of fatty acids. This takes place when the tissue is stimulated by norepinephrine; the molecular background for the ability of BAT to produce heat is the tissue-specific mitochondrial protein UCP1. In the classic view of BAT with respect to fever, BAT is an effector organ, producing heat especially during the onset phase of the fever. There is good evidence that BAT thermogenesis is stimulated via a lipopolysaccharide (LPS), interleukin (IL)-1 beta, IL-6, prostaglandin E cascade. Under physiologic conditions of constantly stimulated activity, BAT is expected to be recruited, but in fevers this is only evident in thyroxine fever. However, BAT may be more than merely an effector. There are indications of a correlation between the amount of BAT and the intensity of fevers, and brown adipocytes can indeed produce IL-1 alpha and IL-6. Furthermore, brown adipocytes are directly sensitive to LPS; this LPS sensitivity is augmented in brown adipocytes from IL-1 beta-deficient mice. Thus, BAT may also have a controlling role in thermoregulation. The existence of transgenic mice with ablations of proteins central in fever and in BAT thermogenesis opens up possibilities for identification and elucidation of this putative new role for brown adipose tissue as an endocrine organ involved in the control of fever.

Early onset of parturition induced by acute alcohol exposure in C57BL/6J mice: role of uterine PGE and PGF2alpha

These studies were designed to determine the effect of acute alcohol treatment on gestational length and to probe for a mechanism underlying alcohol-induced early onset of parturition (EOP) in mice. Experiment 1: alcohol increases the incidence of EOP. Pregnant C57BL/6J mice were given alcohol (0, 4, 5 or 6 g kg(-1), i.g.) on Gestational Day (GD) 10, 15, 16, 17 or 18. Deliveries were monitored every 6 h from GD 18. Results indicated that 6 g kg(-1) alcohol treatment on GD 17 or 18 increased the incidence of EOP. Experiment 2: prostaglandins (PGs) play roles in parturition. The purpose of Experiment 2 was to determine whether PGs mediate alcohol-induced EOP in mice. The results indicated that pretreatment on GD 17 with aspirin, a prostaglandin synthesis inhibitor, prevented alcohol-induced EOP. These data suggest that alcohol-induced EOP in mice may be mediated by PGs. Experiment 3: PGs are influenced by alcohol and are triggers of labour. Experiment 3 measured uterine PGs associated with the onset of alcohol-induced EOP in mice. Alcohol increased uterine PGE and PGF2alpha, with PGE levels higher than control before labour, and elevated PGF2alpha levels correlating with labour. Changes in gestational length have important implications for pregnancy outcome, as well as for normal fetal growth and development.

Is there a role of hypoxemia in penile fibrosis: a viewpoint presented to the Society for the Study of Impotence

During erection, oxygen tension changes in the corpus cavernosum penis from 25-40 mm Hg in the flaccid state to 90-100 mm Hg in the erect state. The relationship between corpus cavernosum trabecular structure and erectile function is dependent on a critical balance of smooth muscle to connective tissue for successful veno-occlusion. In this article, the potential role for transforming growth factor beta(1) (TGF-beta(1)) and prostaglandin E (PGE) in maintaining a functional smooth muscle/connective tissue balance are discussed as well as the importance of oxygen tension in the synthesis of these factors. Correlations between animal models of disease as well as clinical reports are presented in support of a role for hypoxemia in penile fibrosis. A case is presented for a biological basis of nocturnal penile tumescence in the preservation of potency and an overall hypothesis for the molecular pathology of erectile dysfunction is proposed.

Gastric cytoprotective activity of dehydroleucodine in rats. Role of prostaglandins

Previously, we reported that dehydroleucodine (DhL), a sesquiterpene lactone, protected the gastric mucosa of rats from absolute ethanol-induced lesions in a dose-dependent fashion. The mechanism is not mediated by an antiacid secretory action and DhL stimulated mucous production. In the present study, we report the effect of DhL on the mucosal production of prostaglandin E (PGE) and the mucosal release of PGE2 in rats stomach. DhL in acute treatment does not modify these values decreased by previous treatment with indomethacin or absolute ethanol. However, DhL in subchronic treatment significantly enhanced the mucosal production of PGE and the mucosal release of PGE2. Also, indomethacin pretreatment resulted in a significant reduction of the cytoprotective action of DhL. These results indicate the participation of endogenous prostaglandins in DhL protection against ethanol damage. Moreover, we suggest that the gastric protective activity of DhL against ethanol induced gastric mucosal damage is mediated, at least in part, through PGE and PGE2 in subchronic treatment.

Priming with IL-4 and IL-13 during HIV-1 infection restores in vitro IL-12 production by mononuclear cells of HIV-infected patients

The production of proinflammatory cytokines can be regulated by several factors that exert activating or inhibitory effects. IL-4, IL-10, IL-13, TGF-beta, and PGE2 have demonstrated a very wide range of potent macrophage-deactivating activities and, specifically, down-regulation of the production of many proinflammatory monokines. IL-12 plays a key role during immune response by providing a link between natural resistance and adaptive immunity. We and others have previously shown an impairment in IL-12 production by PBMC from HIV-1-infected individuals in response to various stimuli, but defining the mechanism responsible remains elusive. In this study, we observed that pretreatment of PBMC from patients with IL-4 or IL-13 for 24 h primes the cells for enhanced production of IL-12 in response to Staphylococcus aureus, and almost completely restores their deficient IL-12 production when compared with healthy controls. Although this priming effect was completely abrogated by IL-10 and PGE2, IL-10 was produced equivalently by untreated and IL-4- or IL-13-pretreated PBMC from both patients and controls. Additionally, indomethacin, which shuts off PGE2 synthesis, and cAMP-blocking reagents failed to restore or enhance IL-12 production. The priming effect of IL-4 and IL-13 is at the transcription level for both p40 and p35 genes. This complete restoration of IL-12 production by Th2-associated cytokines was unexpected in light of the mutually antagonistic roles of IL-12 and IL-4 in promoting Th1 or Th2 immune responses.

Effects of chronic indomethacin therapy on the development and progression of spontaneous mammary tumors in C3H/HEJ mice

The present study was designed to test the hypothesis that endogenous prostaglandin E (PGE) promotes the development, growth and metastasis of spontaneous mammary tumors in C3H/HeJ female retired breeder mice. The effect of chronic oral indomethacin (indo) therapy starting at 6 months of age was tested on these parameters as well as on animal survival, in comparison with control mice placed on 0.2% ethanol in drinking water for up to 25 months of age. Indo treatment delayed the initial (up to 27 weeks) development of primary tumors by 11-12 weeks; however, the subsequent rate of tumor appearance was unaffected (totaling 82% in indo-treated vs. 90% in controls by 25 months of age). Spontaneous regression of primary tumors (26% in controls) increased 2-fold (53%) with indo therapy. While the apparent reduction in the growth rate of primary tumors and the overall prolongation of animal survival were not significant, the lifespan of mice bearing multiple tumors was significantly prolonged by therapy. There was also a 2-fold reduction in the incidence of lung metastases in mice bearing detectable primary tumors, and this was more pronounced during the earlier phase of tumor development. Positive immunostaining for cyclooxygenase-2 enzyme (indicative of the cellular source of PGE) was exhibited by tumor cells, stromal cells and macrophages within the primary tumors. Tumors in indo-treated mice exhibited histological evidence of increased differentiation (acinar architecture), significant tumor cell death, mononuclear cell infiltration and reduction in vascularity, indicating that the beneficial effects of indo were due to multiple mechanisms, including improved immune response and reduced angiogenesis.

Immunomodulation by human seminal plasma: a benefit for spermatozoon and pathogen?

The immunosuppressive effect of human seminal plasma and its implications for sperm survival are reviewed. Human semen contains high concentrations of prostaglandins that can effect a cytokine-mediated switch away from a cell-mediated immune response. This effect on antigen presenting cells would induce a state of non-responsiveness to sperm antigens in the female reproductive tract. It is postulated that the induction of anergy to sperm antigen may be fundamental to the continuing fecundity of the individual. However, although this immune system modulation will benefit the spermatozoa, the response to infective agents present in semen will also be affected, which may play a critical role in the aetiology and progress of sexually transmitted disease.

The role of endotoxin and cytokines in the pathogenesis of odontogenic cysts

Odontogenic cysts arise from tooth-forming epithelial residues. The stimulus for the formation of radicular cysts is thought to be endotoxin released from the infected necrotic tooth pulp. However, in keratocysts and follicular cysts, such a stimulus is not present. In order to investigate what drives the cyst epithelium to proliferate, explant media and fluids from 16 radicular cysts, eight keratocysts and seven follicular cysts and explant media from four specimens of non-inflamed gingival tissue were examined for the presence of endotoxin and cytokines. Cyst fluids were also cultured for 72 h in anaerobic and aerobic conditions to detect micro-organisms. Endotoxin from three different bacteria, cytokines [interleukin-(IL) 1 alpha, IL-1 beta and IL-6] as well as prostaglandin E2 (PGE2) were tested in an epithelial cell-proliferation assay. As the cyst epithelium is supported by a connective tissue capsule, the effect of fibroblast culture media on epithelial cell proliferation was also investigated. The results showed significantly higher concentrations of endotoxin in radicular cyst fluid than in the keratocyst or the follicular cyst. None of the cyst fluids contained micro-organisms. Immunoassays demonstrated the presence of IL-1 alpha and -6 in all fluids and explants tested; IL-1 beta was only found in the inflammatory radicular cysts. However, reverse transcriptase-polymerase chain reaction showed that mRNAs for IL-1 alpha, -1 beta and -6 were present in all cyst types. Proliferation studies indicated that endotoxin and the cytokines had a mitogenic effect on epithelia at low concentrations; PGE2 had very little effect at low concentrations, and had an inhibitory effect at high concentrations. Cyst fibroblast culture media had a mitogenic effect on the epithelia that was enhanced by the presence of endotoxin.

Role of prostaglandin in the formation of osteoclasts induced by capsular-like polysaccharide antigen of Actinobacillus actinomycetemcomitans strain Y4

We found no reports that capsular-like polysaccharide antigen purified from Actinobacillus actinomycetemcomitans either induces osteoclastic bone resorption in mouse organ cultures or promotes osteoclast formation in mouse marrow cultures. In contrast, capsular-like polysaccharide antigen purified from A. actinomycetemcomitans strain Y4 induced bone resorption in mouse organ culture. To examine the mechanism of bone resorption induced by A. actinomycetemcomitans, mouse bone marrow cells were cultured with A. actinomycetemcomitans strain Y4 capsular-like polysaccharide antigen. A. actinomycetemcomitans strain Y4 capsular-like polysaccharide antigen stimulated osteoclast-like cell formation in mouse bone marrow cultures. However, the polysaccharide of A. actinomycetemcomitans lipopolysaccharide did not induce the formation of osteoclast-like cells. Indomethacin inhibited osteoclast-like cell formation mediated by A. actinomycetemcomitans strain Y4 capsular-like polysaccharide antigen in a dose-dependent manner. There was a good correlation between the number of osteoclast-like cells formed in the marrow culture and the amount of prostaglandin E2 released into the culture media. When mouse bone marrow cells were cultured with prostaglandin E2 during the culture periods, many osteoclast-like cells were formed. These results indicate that prostaglandin E2 is involved in the mechanism of the formation of osteoclast-like cells mediated by A. actinomycetemcomitans strain Y4 capsular-like polysaccharide antigen. A. actinomycetemcomitans strain Y4 capsular-like polysaccharide antigen may play an important role in inflammatory bone resorption by promoting osteoclast formation in periodontal disease.

[Role of prostaglandins F and E in regulation of bronchial activity]

Prostaglandins (PGs) belong to the family of eicosanoids. A main substrate in their biosynthesis is arachidonic acid. Involvement of PGs in regulation of bronchial activity is a complex process and far from being fully understood. In 1968 it was shown that prostaglandins E1 and E2 cause bronchodilation, while prostaglandin F2a constricts an isolated human smooth muscle. The recent studies which revealed protective effects of PGE2 on bronchial reaction induced in patients by ultrasonically nebulized distilled water, allergen, metabisulfite, or exercise, revitalized interest among clinicians. Reports that PGE2 inhibits airways response in bronchial provocation with lysine aspirin, allow to believe that PGE2 plays a role in pathogenesis of aspirin induced asthma.

[Physiopathology of pruritus]

Itching is the predominant symptom of inflammatory skin diseases. Present evidence indicates that histamine and unidentified peptides mediate itching. No evidence is available that lymphokines or cytokines play a direct role as itch mediators. Prostaglandins serve an important synergistic function in itching. Evidence points to a role for opioid peptides of the central nervous system in the perception of itch and as direct mediators. Pruritus may be a prominent symptom in uraemia, biliary obstruction, atopic dermatitis and neoplasia.

Osteoporosis in rheumatoid arthritis: a molecular biological aspect of connective tissue gene activation

Osteoporosis, especially the juxtaarticular osteoporosis of involved joints, is a characteristic manifestation of rheumatoid arthritis (RA). Histomorphometric studies suggest the existence of increased bone turnover in RA: impaired bone formation and hightened osteoclasic bone resorption. Recent studies show that important mediators in the pathogenesis of RA such as prostaglandin E, interleukin 1 (IL1) or tumor necrosis factor (TNF) alpha also play important roles in bone remodelling. Prostaglandin E2 promotes maturation of osteoclasts from hematopoietic precursor cells. IL1 inhibits collagen synthesis in osteoblasts. IL1 enhances collagenase and stromelysin gene expression and stimulates osteoclastic bone resorption. TNF alpha inhibits bone collagen synthesis and causes osteoclastic bone resorption. TNF alpha, and possibly IL1, enhances collagenase and stromelysin gene expression by stimulating the AP-1 promoter sites of the genes. Constitutive expression of c-fos induces joint destruction without lymphocyte infiltration in antigen-induced arthritis in mice, and supports cell growth of human rheumatoid synovial cells, possibly acting on the AP-1 sites. Furthermore, constitutive c-fos expression decreases collagen synthesis in osteoblasts and increases the mediator secretion from osteoblasts thereby stimulating osteoclastic bone resorption. These findings suggest that signal transduction through AP-1 transcriptional regulation sites may play an important role in the pathogenesis of joint destruction and osteoporosis in RA.

Molecular mediators formed in the small intestine in response to cholera toxin

The molecular mechanism of experimental cholera, leading to increased water and electrolyte secretion, was evaluated with the rabbit intestinal loop model. The levels of cyclic adenosine monophosphate (cAMP), prostaglandin E2 (PGE2), and 5-hydroxytryptamine (5-HT) were measured in mucosal tissue or luminal fluids from intestinal segments exposed to cholera toxin (CT). Each mediator increased in a dose-dependent manner coinciding with the amount of fluid accumulating in the CT-treated loops within the 16 h observation period. Interestingly, a substantial amount of the cAMP in the CT loops was released into the intestinal lumen, along with the fluid. Fluid accumulation was evoked by instillation of PGE2 and CT into the intestinal segments, but not by 5-HT. Large doses of dibutyryl cAMP at 50 mg/ml, but not at 25 mg/ml, also evoked fluid accumulation when injected into the intestine. Further, CT evoked the release of 5-HT from the mucosa, although the high doses of cAMP caused a massive release of 5-HT. PGE2 injection was without effect on 5-HT release. Although CT increased the amount of PGE2 into the luminal fluid, no effect on PGE2 levels was observed by injecting any dose of dibutyryl cAMP or 5-HT into the intestinal lumen. Our interpretation of these data is that CT stimulates the independent synthesis and release of both cAMP and PGE2. The cAMP appears to cause the release of 5-HT from the enterochromaffin cells. Since dibutyryl cAMP did not evoke a PGE2 response, it was concluded that cAMP could elicit secretion of fluid without the participation of PGE2; however, the cAMP doses were not physiological.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of cytokines and inflammatory mediators in tissue destruction

Colonization or emergence of microbial pathogens may result in tissue destruction by activation of one or more of five distinct host degradative pathways (matrix metalloproteinase pathway, plasminogen-dependent pathway, phagocytic pathway, PMN-serine proteinase pathway and osteoclastic bone resorption) or by direct cleavage of extracellular matrix constituents by microbial proteinases. Activation of endogenous destructive pathways may be mediated by immune responses resulting in expression of degradative cellular phenotypes among both immigrant and resident cell populations. In addition, expression of degradative phenotypes may be triggered by direct influences on host cells of microbial products (LPS, enzymes, toxins). A body of evidence suggests that each of these mechanisms involves local production of proinflammatory cytokines and growth factors. The matrix metalloproteinase pathway is centrally involved in dissolution of all unmineralized connective tissues and perhaps in resorption of bone as well. The matrix metalloproteinase family consists of nine or more genetically distinct Zn++ endopeptidases which collectively cleave all of the constituents of the extracellular matrix. Recent studies have uncovered many essential elements of a complex, but still incomplete, regulatory network that governs tissue destruction. Proinflammatory cytokines and growth factors induce signalling pathways several of which are dependent on protein kinase C and result in transient expression of the transcription factors c-jun and c-fos. Initiation of transcription of most matrix metalloproteinase genes requires binding of the transcription factor AP-1 (c-jun/c-fos) to a specific promoter sequence but attainment of maximal transcription rates is dependent on interaction with other promoter elements as well. Several matrix metalloproteinases have been detected in crevicular fluids and tissues of inflamed human gingiva as have the proinflammatory cytokines (IL-1 and TNF-alpha) which regulate their transcription. Although the mere presence of enzymes and cytokines does not necessarily impart function per se, these observations suggest that some level of spatial or temporal linkage exists between metalloproteinase/cytokine expression and gingival inflammation.

Vasoactive substances as regulators of renal growth

The influential studies by Hostetter and associates [103] as well as by others in the last decade have firmly established the association between adaptive increases in renal hemodynamics as well as tubular reabsorption and the progression of renal disease. Many different vasoactive hormones may be involved in such regulatory processes. On the other hand, many investigators have observed that compensatory renal growth, although initially helping to restore functional renal tissue, may be rather harmful in the long-term for renal function, even in the absence of concomitant hemodynamic changes. These apparently separate areas of renal pathophysiology have become united by the identification of the growth regulatory properties of many vasoactive substances. Thus, a perturbation of vasoconstrictors and vasodilatory substances may not only influence vascular tone, glomerular filtration rate and renal plasma flow but also the growth regulation of distinct populations of cells along the nephron. As a generalization, it appears that vasoconstrictors stimulate growth of renal cells (mitogenesis and hypertrophy), whereas vasodilators inhibit the growth response. It can be speculated that similar effects of different hormones may depend on the activation of common second messenger pathway, e.g. the ANG-II-, AVP-, ET-induced mesangial proliferation through the phosphorylation of a common set of target proteins, or the antimitogenic effects of ANP, EDRF and PGE2 through an increase in intracellular cGMP. However, the majority of the growth regulatory effects of vasoactive substances have been studied in relatively artificial cell culture systems. Nevertheless, the well-documented protective effects of ACE inhibitors on renal function in several models include effects on renal growth. The rapid development of new vasoactive drugs like the recently introduced nonpeptide ANG II receptor antagonists may also offer an opportunity to influence renal growth [104]. The mechanisms of the progression of renal disease have become fascinatingly complex, and the next years will most likely witness major achievements in the elucidation of chronic renal pathophysiology on both cellular and molecular levels.

Pancreas-specific venular labeling by monastral blue B in the BB rat: modulation by prostaglandins and their inhibitors

Leaky blood vessels in the microcirculation can be detected in vivo by injecting an animal with colloidal pigments like Monastral blue B (MbB). We have previously used this labeling method in the BB rat, an animal model of spontaneous autoimmune diabetes, and detected increased vascular permeability restricted to the venules of the pancreas. The earlier data suggested that pancreata of animals susceptible to labeling contain trapped intravascular monocytes that are activated to release vasoactive mediators after phagocytosis of MbB. To explore these observations further, we investigated the effects of prostaglandins on this system. Prostaglandins are known to be important mediators of inflammatory responses and to modulate the expression of disease in other animal models of autoimmunity. We now report that MbB-induced pancreatic labeling is modulated by misoprostol (an analogue of prostaglandin E1), prostaglandins of the E series, and inhibitors of prostaglandin synthesis. The nonsteroidal anti-inflammatory drugs ibuprofen and ketorolac both reduced the intensity of labeling in susceptible BB rats in a dose dependent manner. In contrast, both misoprostol and prostaglandin E2 given at low doses induced pancreatic permeability in the labeling-resistant Wistar Furth rat. To extend this finding, we also tested much higher drug doses, since at high concentrations, E series prostanoids exert anti-inflammatory effects. We observed that large doses of prostaglandin E1, prostaglandin E2, and misoprostol all suppressed labeling in the BB rat. We conclude that presence of MbB in the pancreatic circulation of the rat induces organ specific venular leakage by an inflammatory process involving prostaglandins.

Salt and hypertension: water-sodium handling in essential hypertension

This paper describes sodium handling in the kidney and the significance and mechanisms of its effects upon essential hypertension. In patients with low renin essential hypertension, plasma and urinary norepinephrine levels, plasma renin activity and fractional excretion of sodium were significantly lower, while plasma volume, extracellular fluid volume and exchangeable sodium were higher than in normal renin essential hypertension. The suppression of some renal depressor-natriuretic systems, the dopaminergic, kallikrein-kinin and prostaglandin E2 systems may contribute to the retention of sodium-water in these patients, because these depressor systems were observed to be greatly suppressed in essential hypertension, especially in the low renin group. The reduction of conversion from L-dopa to dopamine by dopa-decarboxylase in the proximal tubules was suggested from our clearance studies as the mechanism of the suppression of renal dopaminergic activity. Moreover, renal dopaminergic activity was already suppressed at the prehypertensive stage, possibly through the inhibition of renal dopa-decarboxylase activity. Thus, it appears that the suppression of renal depressor-natriuretic systems play an important role in the pathogenesis of essential hypertension through the retention of sodium and body fluid volume.

Effect of prostaglandin E on immune function in normal healthy volunteers

Prostaglandin E (PGE) has been hypothesized to be the endogenous metabolite that results in the immunosuppression seen in patients with tumor and trauma. This has resulted in multiple investigators proposing that administration of PGE inhibitors, such as aspirin and indomethacin, might improve immune function in such patients. We administered a long acting PGE analog, misoprostol, to nine normal healthy volunteers for five days and assayed immune function before and after therapy. The PGE analog improved lymphocyte blastogenesis and increased tumor necrosis factor production. The PGE analog also resulted in the volunteers having symptoms similar to those seen in patients with sepsis. The results of these studies indicate that elevated levels of PGE do not seem to result in impairment of immune function, but may be the endogenous metabolite responsible for the symptologic factors seen in infected patients.

Soybean agglutinin-positive natural suppressor cells in mouse bone marrow inhibit interleukin 2 production and utilization in mixed lymphocyte reactions

Although natural suppressor (NS) cells resident in bone marrow (BM) have been the subject of intensive study, the exact nature and mode of action of these potentially important immunoregulatory cells are still uncertain. Here we show that NS cells with potent inhibitory effects on mixed lymphocyte reactions (MLRs) can be isolated from BM of normal adult mice by agglutination with the plant lectin soybean agglutinin (SBA). Complement-dependent lysis of SBA receptor-bearing BM cells with antibodies to asialoGM1, Mac-1, Thy-1.2, J11d.2, and 2C1 phenotypic markers reveals the presence of at least two distinct populations of BM NS cells. Most of the SBA-binding BM cells with NS capacity have the null phenotype and resemble hematopoietic stem cells, and some inhibitory SBA+ BM cells express the 2C1 marker found on pregnancy-associated splenic NS cells and the J11d.2 antigen characteristic of B cells and immature T cells. Results of positive selective experiments confirmed these findings. The mechanism of natural suppression was also studied. Evidence is presented that SBA+ BM cells exert NS activity in MLRs by interfering with the production and utilization of interleukin 2. Indomethacin does not relieve natural suppression associated with SBA+ BM cells, indicating that prostaglandin synthesis is not a requirement for inhibitory function. However, neutralizing antibodies to transforming growth factor beta (TGF-beta) partially reverse the suppression mediated by SBA+ BM cells, suggesting that some BM NS cells may act through the release of an immunosuppressive molecule related to TGF beta.

Physiological evidence for the possible existence of anhydrolevuglandin E2-like activity in extracts and media from uteri of rats

Physiological evidence is presented for the possible existence of anhydrolevuglandin E2-like activity in extracts of uteri from diestrous rats and after treatment of adult rats with estradiol and progesterone. The extracts were able to inhibit contractions in rat uterine preparations stimulated by PGE2. Uteri of vaginal Stage 3 (metestrus) were quiescent and showed decreased responsiveness to PGE2 and PGF2 alpha. These uteri showed some contractility when incubation medium from diestrous uteri (Stage 5) were transferred to them and incubation medium from them inhibited the contractility of Stage 5 uteri. When incubation media were exchanged between contractile uteri from of stages other than Stage 3, there was no change in the contraction patterns. Taken together, we believe these data indicate that AnLGE2 may be a normal constituent of the rat uterus and is physiologically increased during Stage 3 (metestrus) of the estrous cycle.

The inhibition of T-lymphocyte proliferation by fatty acids is via an eicosanoid-independent mechanism

Eicosanoids, in particular prostaglandin E2 (PGE2), are potent inhibitors of a number of immune responses, including lymphocyte proliferation. We have previously shown that fatty acids, especially polyunsaturated fatty acids (PUFA), inhibit mitogen-stimulated proliferation of lymphocytes. One mechanism by which fatty acids could exert their inhibitory effect is via modulation of eicosanoid synthesis. This possibility was investigated in the present study. PGE2 concentrations in the medium taken from lymphocytes cultured in the presence of a range of different fatty acids did not correlate with the inhibitory effects of the fatty acids upon lymphocyte proliferation. Although PGE2 at concentrations above 10 nM caused inhibition of lymphocyte proliferation, PGE2 at the concentration measured in lymphocyte culture medium (0.3-4 nM) was not inhibitory. PGE3 did not inhibit lymphocyte proliferation, except at high concentrations (greater than 250 nM). The maximal inhibition of proliferation caused by PGE2 or PGE3 was less than the inhibition caused by each of the fatty acids except myristic or palmitic acids. Inclusion of inhibitors of phospholipase A2, cyclo-oxygenase or lipoxygenase in the culture medium did not prevent the fatty acids from exerting their inhibitory effect on lymphocyte proliferation. The eicosanoids present in lymph node cell cultures originate from macrophages rather than lymphocytes. Depletion of macrophages from the cell preparation by adherence did not prevent fatty acids from inhibiting proliferation. Proliferation of thoracic duct lymphocytes, which are devoid of macrophages, is inhibited by fatty acids to a similar extent as proliferation of lymph node lymphocytes. These observations provide convincing evidence that the inhibition of lymphocyte proliferation by fatty acids is independent of the production of eicosanoids. Therefore, other mechanisms must be investigated if the effect of fatty acids upon lymphocyte proliferation is to be understood at a biochemical level.

Suppressor Cytokines and Regulation of Myelopoiesis; Biology and Possible Clinical Uses

A number of biologically active and biochemically well-characterized cytokines have been shown to have either direct or indirect suppressive activities on the proliferation/differentiation of myeloid stem/progenitor cells. This article is a brief review of the actions of some of these molecules. These molecules include H-subunit ferritin, macrophage inflammatory protein-1 alpha, the interferons-alpha, -beta, and -gamma, the tumor necrosis factors-alpha and -beta (lymphotoxin), prostaglandins, E1 and E2, inhibin, transforming growth factor-beta, and lactoferrin. I will also review the actions of other suppressor molecules, including a newly identified 8-kd molecule that has not yet been sequenced and a synthetic pentapeptide. Current information is given on the in vitro actions of these molecules together with their activity in vivo in animal models. Possibilities for their clinical use are discussed.

[Uterine collagens. General review]

Several collagen types (mainly types I, III, V and VI), elastin, fibronectin and some proteoglycans are active constituents of uterine myometer. They surround and associate smooth muscle cells. The type I collagen biosynthesis in the uterus is under the positive control of estrogens that in addition repress the collagenase secretion and in this way prevent collagen from degradation. The cervical softening and dilation are caused by a progressive degradation of collagen and by the synthesis of an additional proteoglycan that separates and disorganizes the collagen fibres. Prostaglandin E2 and relaxin participate in the activation of collagenases. After delivery, the drop in estrogens and progesterone permits collagenases to rapidly degrade uterine collagen in excess.

Psychoneuroimmunology: where are we, where are we going?

We have reviewed briefly the current status of research on central nervous system-immune system interactions, focusing attention on the neural and humoral pathways by which CNS and IS communicate and interact and on the effects of stress and psychiatric illness on immune function. It is evident that CNS-IS communication occurs by direct innervation of lymphoid organs and by means of hormones, neuropeptides and cytokines. There is also clear evidence that humoral substances each of which were thought to be the product of one specific cell type are elaborated and secreted by a variety of cell types. This observation suggests a new unified concept of CNS-IS interactions with mediators of these interactions being produced ubiquitously and acting on cells of the two systems. In examining the effects of stress on IS it has become apparent that stress of various types can have a depressive effect on immune functions, primarily at the level of T lymphocytes and NK cells. This suggests that the defense mechanisms affected by stress are those which are responsible for cytotoxic effector responses. These findings are interesting in that they support older studies implicating stress in the pathogenesis and/or the clinical course of neoplastic diseases. Further support for a role of stress-induced immunodepression in morbidity comes from a very interesting, recent prospective study showing that stress will affect susceptibility to viruses. Finally, exploration of the mechanisms of stress-induced immunodepression, suggests that a variety of mediators which regulate lymphocyte interactions and activation may be affected, perhaps at the level of gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)

[Roles of prostaglandin on rabbit vesicourethral smooth muscle contraction]

The effects of prostaglandin (PG) E1, E2 and F2 alpha on isolated smooth muscles of rabbit bladder and urethra were studied by in vitro techniques for recording contractile activities. To examine the mechanism of PGs' effect, intracellular cyclic AMP content was also measured by radioimmunoassay. Spontaneous contractile force of muscle strips isolated from rabbit urinary bladder dome and base was increased dose-dependently by administration of PGE1, E2 or F2 alpha. Isolated muscle strips from bladder dome responded to PG more markedly than those from bladder base. The rank order of potency to induce contractile responses was PGF2 alpha greater than PGE2 greater than PGE1 in both dome and base muscles. Spontaneous contractile force of muscle strips isolated from rabbit urethra was increased dose-dependently by administration of PGF2 alpha, and, in contrast, was decreased dose-dependently by PGE1 or E2. These effects were not affected by pretreatment with atropine, phentolamine, propranolol and tetrodotoxin, but were significantly inhibited by pretreatment with verapamil, a Ca-antagonist. Cyclic AMP accumulation in urethral muscle strips significantly increased after administration of PGE1. These results demonstrated that contractile response of rabbit bladder smooth muscle to PG was mainly induced by Ca2+ influx and that cyclic AMP was related to the relaxation of rabbit urethral smooth muscle by PGE1.

Role of interleukin-1 and prostaglandin in in vitro bone resorption induced by Actinobacillus actinomycetemcomitans lipopolysaccharide

Lipopolysaccharide (Y4 LPS) isolated from Actinobacillus actinomycetemcomitans strain Y4 induced bone resorption in BALB/c mouse calvaria organ culture. The calcium release from LPS-low responsive C3H/HeJ mouse calvaria by Y4 LPS was very low. Indomethacin almost completely inhibited prostaglandin E2 (PGE2) production by Y4 LPS-stimulated BALB/c mouse calvaria, but did not suppress interleukin-1 (IL-1) release from the calvaria, and partially suppressed the bone resorption. Dexamethasone strongly inhibited the PGE2 and IL-1 production by Y4 LPS-stimulated BALB/c mouse calvaria, as well as Y4 LPS-induced bone resorption. Dexamethasone inhibited expression of membrane IL-1 on osteoblastic cells stimulated with Y4 LPS, but indomethacin did not. Furthermore, anti-IL-1 serum partially suppressed the calcium release from Y4 LPS-stimulated BALB/c mouse calvaria. These results suggest that both PGE2 and IL-1 participate in Y4 LPS-induced bone resorption in vitro.

Receptor-mediated supra-additive activation of guinea pig superior cervical ganglion adenylate cyclase: role of Mn2+ ions and calmodulin

The effects of Mn2+ and calmodulin were studied on the basal and agonist-modulated adenylate cyclase activity of the guinea pig superior cervical ganglion. The divalent cation strongly stimulates the basal and agonist-modulated enzyme in a concentration-dependent manner. Moreover, in the presence of Mn2+ the inhibitory effects of "high" GTP concentrations and of D-Ala2-Met-enkephalinamide on adenylate cyclase are eliminated, while the stimulation exerted by prostaglandin E2 and the supra-additive activation of the enzyme by the combination of the two drugs are unaffected. In EGTA-washed, calmodulin-depleted membrane preparations, Mn2+ still activates the cyclase but the enkephalin inhibition and the superactivation of the enzyme induced by the combination of opiate and prostaglandin are lost, both in the absence and in the presence of the cation. Reconstituting the depleted membranes with exogenous Ca2+/calmodulin fully restored the enzyme responsivity to the combination and, partially, to the enkephalin. The findings suggest the existence in the guinea pig superior cervical ganglion of both the calmodulin-sensitive and differently regulated calmodulin-insensitive adenylate cyclase.

Effects of parathyroid hormone, 1,25-dihydroxyvitamin D3, and prostaglandin E2 on alkaline phosphatase activity in cultured dental pulp and gingiva cells of bovine calf

The effects of parathyroid hormone (PTH), 1,25-dihydroxyvitamin D3, and prostaglandin E2 (PGE2) on alkaline phosphatase activity on cultured dental pulp and gingiva cells of bovine calf were compared. In pulp cells, PTH, 1,25-dihydroxyvitamin D3, and PGE2 significantly increased alkaline phosphatase activity, but no increase in the enzyme activity by these factors was observed in gingiva cells. Dibutyryl cAMP also increased alkaline phosphatase activity in both types of cell, but the increase in pulp cells was greater than that in gingiva cells. Treatment of the cultured pulp cells with PTH or PGE2 significantly increased the intracellular cAMP content. These results suggest that calciotropic factors such as PTH, 1,25-dihydroxyvitamin D3, and PGE2 may be involved in the differentiation of dental pulp cells and that some of these effects (those of PTH and PGE2) are mediated by cAMP.

[Immune regulatory importance of prostaglandins E in atopy]

The concept proposed for the pathogenesis and prevention of atopy [Hautarzt (1989) 40:685-692] is refined by further insights into the immunoregulatory role of E-prostaglandins. It is demonstrated that in vitro IgE synthesis of peripheral blood mononuclear cell cultures of patients with atopic dermatitis is suppressed by the addition of PGE1 or PGE2. The enhanced IgE production in atopy is explained by insufficient PGE-mediated down-regulation of interleukin-4-induced IgE synthesis.

Interleukin 1 beta and prostaglandin E are involved in the response of periodontal cells to mechanical stress in vivo and in vitro

Cytokines are local mediators released by cells of the immune system in response to stimulation by a variety of agents. These polypeptides may interact directly or indirectly with bone cells. The objectives of this study were (1) to localize prostaglandin E (PGE) and the cytokine interleukin-1 beta (IL-1 beta) in the periodontal ligament after the application of mechanical force to teeth in vivo and (2) to determine the effects of mechanical stress or IL-1 beta (or the two in combination) on PGE synthesis and bone resorption by fibroblasts in the human periodontal ligament (PDL). In 24 female cats, one maxillary canine was tipped distally by 80 gm force for 12 hours, 24 hours, or 7 days. PGE and IL-1 beta were localized immunohistochemically in serial jaw sections, and semiquantitation of cellular-staining intensity was done by microphotometry. Unstressed periodontal ligament cells stained mildly for PGE and IL-1 beta, but the staining intensity increased significantly in sites of tension. Human periodontal ligament fibroblasts were preincubated with mechanical stress and/or IL-1 beta in the presence or absence of indomethacin for 1 hour. Then the media were replaced by BGJb (Fitton-Jackson modification) medium (GIBCO), and incubation was continued for 4, 8, or 24 hours in conditioned media. PGE concentrations in conditioned media were determined by radioimmunoassay, and bone-resorbing activity in conditioned media was assessed by 45Ca release from prelabeled neonatal mouse calvaria. The conditioned media derived from cells stimulated by mechanical stress plus IL-1 beta caused significantly more bone resorption than the conditioned media obtained from cells that had been treated by each factor alone. The addition of indomethacin did not inhibit bone resorption completely. These results demonstrate that periodontal ligament cells respond to mechanical stress by increased production of PGE, and that IL-1 beta enhances this response.