E-prostanoid 3 receptor deletion improves pulmonary host defense and protects mice from death in severe Streptococcus pneumoniae infection.

Prostaglandins (PGs) are potent lipid mediators that are produced during infections and whose synthesis and signaling networks present potential pharmacologic targets for immunomodulation. PGE(2) acts through the ligation of four distinct G protein-coupled receptors, E-prostanoid (EP) 1-4. Previous in vitro and in vivo studies demonstrated that the activation of the G(alphas)-coupled EP2 and EP4 receptors suppresses inflammatory responses to microbial pathogens through cAMP-dependent signaling cascades. Although it is speculated that PGE(2) signaling via the G(alphai)-coupled EP3 receptor might counteract EP2/EP4 immunosuppression in the context of bacterial infection (or severe inflammation), this has not previously been tested in vivo. To address this, we infected wild-type (EP3(+/+)) and EP3(-/-) mice with the important respiratory pathogen Streptococcus pneumoniae or injected mice i.p. with LPS. Unexpectedly, we observed that EP3(-/-) mice were protected from mortality after infection or LPS. The enhanced survival observed in the infected EP3(-/-) mice correlated with enhanced pulmonary clearance of bacteria; reduced accumulation of lung neutrophils; lower numbers of circulating blood leukocytes; and an impaired febrile response to infection. In vitro studies revealed improved alveolar macrophage phagocytic and bactericidal capacities in EP3(-/-) cells that were associated with an increased capacity to generate NO in response to immune stimulation. Our studies underscore the complex nature of PGE(2) immunomodulation in the context of host-microbial interactions in the lung. Pharmacological targeting of the PGE(2)-EP3 axis represents a novel area warranting greater investigative interest in the prevention and/or treatment of infectious diseases.

Evidence for post-transcriptional regulation of Na,K-ATPase by prostaglandin E1.

The stimulatory effect of PGE1 on the activity of the Na,K-ATPase in MDCK cells is associated with an increase in the rate of transcription of the Na,K-ATPase beta1 subunit gene and an increase in the rate of biosynthesis of the Na,K-ATPase [M.L. Taub, Y. Wang, I.S. Yang, P. Fiorella, S.M. Lee, Regulation of the Na,K-ATPase activity of Madin-Darby canine kidney cells in defined medium by prostaglandin E1 and 8-bromocyclic AMP, J. Cell. Physiol. 151 (1992) 337-346]. In order to further define the molecular mechanisms, transient transfection and biosynthesis studies were conducted with dibutyryl cAMP resistant (DBr) MDCK cells, defective in cAMP dependent protein kinase, and PGE1 independent (PGE1 Ind) MDCK cells with elevated intracellular cAMP. Transient transfection studies with the human Na,K-ATPase beta1 promoter/luciferase construct, pHbeta1-1141 Luc [J. Feng, J. Orlowski, J.B. Lingrel, Identification of a functional thyroid hormone response element in the upstream flanking region of the human Na,K-ATPase beta 1 gene, Nucleic Acids Res. 21 (1993) 2619-2626], showed that the stimulatory effect of PGE1 and 8Br-cAMP on beta1 subunit gene transcription is retained in the DBr and PGE1 independent variants. However, the stimulatory effect of PGE1 and 8Br-cAMP on Na,K-ATPase biosynthesis was lost in DBr (unlike PGE1 Ind) variants. These results can be explained by a defect in post-transcriptional regulation.

PGE1 abolishes the mitochondrial-independent cell death pathway induced by D-galactosamine in primary culture of rat hepatocytes.

BACKGROUND AND AIM: PGE1 reduces in vivo and in vitro D-galactosamine (D-GalN)-induced cell death in hepatocytes. The present study was undertaken to elucidate the intracellular pathway by which D-GalN induces cell death in cultured hepatocytes. In addition, we evaluated if PGE1 was able to modulate different parameters related to D-GalN-induced apoptosis in cultured rat hepatocytes. METHODS: Hepatocytes were isolated from male Wistar rats (225-275 g) by the classical collagenase procedure. PGE1 (1 microM) was administered 2 h before D-GalN (5 mM) in primary culture of rat hepatocytes. Apoptosis was determined by DNA fragmentation and caspase-3, -6, -8 and -9 activation in hepatocytes. Caspase activation was evaluated by the detection of the related cleaved product and its associated activity. Cell necrosis was determined by the measurement of lactate dehydrogenase (LDH) activity in culture medium. To elucidate the role of mitochondria, we measured neutral (nSMase) and acid (aSMase) sphingomyelinase, as well as the expression of cytochrome c in mitochondria and cytoplasm fractions from D-GalN treated hepatocytes. RESULTS: D-GalN induced caspase-3 activation and DNA fragmentation in hepatocytes. This apoptotic response was not associated with the activation of caspase-6, -8 or -9. The use of specific inhibitors confirmed that only caspase-3 was involved in D-GalN-induced apoptosis. D-GalN did not modify nSMase and aSMase activities, nor mitochondrial cytochrome c release in hepatocytes. CONCLUSIONS: D-GalN induced apoptosis through caspase-3 activation but without modification of the activity of caspase-6, -8, -9, SMases or cytochrome c release. PGE1 appears to prevent D-GalN-induced apoptosis by a mitochondria-independent mechanism.

CCK-8 and PGE1: central effects on circadian body temperature and activity rhythms in rats.

Cholecystokinin-octapeptide (CCK-8) has been shown to possess an acute thermogenic and hyperthermic action when given intracerebroventricularly in slightly restrained rats. To substantiate the febrile nature of that hyperthermia freely moving animals should be used and together with body core temperature, at least one behavioral parameter, such as general activity, should also be recorded. In the present studies, Wistar rats (N=34) exposed to thermoneutral (26-28 degrees C) or cold (4 degrees C) ambient temperature and to a 12:12-h light/darkness schedule were infused intracerebroventricularly with CCK-8 or prostaglandin E1 (PGE1) for several days using ALZET minipump and changes in body core temperature and general activity were recorded by biotelemetry (Minimitter). In rats exposed to a thermoneutral ambient temperature, low doses of CCK-8 induced slight but significant rises of day minima of circadian body temperature rhythm (CBTR) and with a high dose (1 microg/h) of the peptide--infused either at thermoneutrality or during cold exposure--an increase of acrometron could also be recorded. All of these changes were observed only during the first 2-4 days of 7-day-long infusions. Intracerebroventricular infusion of PGE1 administered at thermoneutrality in a dose of 1 microg/h for 7 days induced a marked rise in body core temperature with a disappearance of CBTR in some rats for 2-3 days or with rises of day minima/acrometron in others. General activity--running parallel with CBTR in periods without infusions--tended to be decreased when core temperature rose during the first couple of days of intracerebroventricular infusion of higher doses of CCK-8 or of PGE1. The decreased general activity--one component of sickness behavior--together with an increased body core temperature found in the present study, supports the view that they are components of a genuine fever induced by the central effect of the two mediators used.

Prostaglandin E1 induces vascular endothelial growth factor-1 in human adult cardiac myocytes but not in human adult cardiac fibroblasts via a cAMP-dependent mechanism.

Prostaglandin E(1) (PGE(1)) has been used to treat pulmonary hypertension and peripheral artery occlusive disease and has been successfully employed for pharmacological bridging to transplantation in patients with chronic end-stage heart failure. In addition to its vasoactive effects PGE(1) was shown to stimulate angiogenesis in animal models. Recently we showed that PGE(1)-induced angiogenesis in hearts of patients with ischemic heart disease. We proposed that the angiogenic action of PGE(1) is mediated by vascular endothelial growth factor (VEGF). In the present paper we studied a possible effect of PGE(1) on the expression of VEGF-1 in cultured human adult cardiac myocytes (HACM) and cultured human adult cardiac fibroblasts (HACFB), respectively, to identify a cellular source of VEGF-1 in patients treated with PGE(1). We also aimed to delineate mechanisms involved in a possible regulation of VEGF-1 by PGE(1) in these cells. When HACM, isolated from human myocardial tissue, were treated with PGE(1), a significant up to 3-fold increase in VEGF-1 production could be observed. These results could be confirmed on the level of specific mRNA expression as determined by real-time polymerase chain reaction. The effect of PGE(1) on VEGF-1 expression could be blocked by H089, an inhibitor of cAMP-dependent protein kinase A. In HACFB, also isolated from human myocardial tissue, no effect of PGE(1) on VEGF-1 production was seen. If this effect of PGE(1) is also operative in the in vivo situation, one could speculate that cardiac myocytes could be a cellular source of PGE(1)-induced VEGF-1 expression in patients treated with this drug.

Erectile dysfunction.

Erectile dysfunction (ED) is a highly prevalent and often undertreated condition. It may be a symptom of underlying, chronic illness and can have a negative impact on quality of life, psychosocial health, and relationships. The aging of the population, as well as the introduction of new treatment options, such as sildenafil, has led to increased public awareness of this disorder. New oral therapeutic agents are on the horizon. This article provides an overview of the physiology of erection, the pathophysiology of ED, and modern patient evaluation. Management options, including traditional therapeutic approaches as well as the new generation of oral agents, are also presented.

An hypothesis on the consolidation and PGE1-induced deconsolidation of a platelet plug.

UNLABELLED: Consolidation is the final stage in haemostasis in which a platelet plug blocking a bleeding area of a vessel: (a) becomes impermeable to circulating plasma proteins and (b) contracts to resist blood pressure. HYPOTHESIS: The impermeabilization step of consolidation is accomplished through fluid uptake by the platelets from a hydrated intercellular glue formed during thrombin activation. Dehydration occurs through inhibition of the Na+,K+-ATPase of platelets with sodium and water uptake. However, and uniquely, due to the high cellular density of the platelet plug, access of peripheral plasma fluids to the plug is limited forcing the platelets to take up preferentially the fluid of interplatelet space. The increased adhesion properties of the dehydrated glue simultaneously furthers a decreased hydraulic permeability and an improved coupling of the contractile forces among platelets. In 'Deconsolidation', the fluid uptake process can be reversed and amplified by agents that increase cAMP, reactivating the Na+,K+-ATPase and expressing CFTR or equivalent Cl- secretory channels that force the extrusion of fluid from the platelets, with rehydration of the intercellular polymer and a large increase in the interplatelet space.

EP receptor-mediated inhibition by prostaglandin E(1) of cardiac L-type Ca(2+) current of rabbits.

Prostaglandin E(1) (PGE(1)) has cardioprotective effects on the ischemic-reperfused heart. To clarify the mechanisms underlying the protective action of PGE(1) on myocardium, we examined the effect of PGE(1) on the L-type Ca(2+) current (I(Ca)) using single atrial cells from rabbits. PGE(1) did not show a significant effect on basal I(Ca) but inhibited the I(Ca) prestimulated by isoproterenol (Iso, 30 nM). This inhibition was concentration dependent (EC(50) = 0.027 microM). Both sulprostone, a specific PGE receptor subtype (EP(1) and EP(3)) agonist, and 11-deoxy-PGE(1), an EP(3) agonist, inhibited the Iso-stimulated I(Ca), similar to PGE(1). Pretreatment with pertussis toxin (PTX) abolished the PGE(1) inhibition of I(Ca). Both the application of forskolin plus IBMX and intracellular dialysis with 8-bromoadenosine 3',5'-cyclic monophosphate eliminated the effect of PGE(1). PGE(1) did not show any further inhibition of I(Ca) when the effect of Iso was almost fully antagonized by acetylcholine. Methylene blue (guanylate cyclase inhibitor), KT-5823 (cGMP-dependent protein kinase inhibitor), and erythro-9-(2-hydroxy-3-nonyl)adenine (type II phosphodiesterase inhibitor) did not significantly change the inhibitory effect of PGE(1). These findings suggest that 1) PGE(1) inhibits Iso-stimulated I(Ca) by binding to the EP(3) receptor and 2) the PTX-sensitive and cAMP-dependent pathway is involved in the PGE(1) inhibition of I(Ca), but the nitric oxide-cGMP-dependent pathway is not. The PGE(1)-induced antiadrenergic effect shown in this study may contribute to the PGE(1) protection of myocardium against ischemia.

Histamine and prostaglandins in schizophrenia: revisited.

It has long been accepted that schizophrenia is primarily a physical illness resulting from a chemical imbalance in the brain. This paper will review evidence supporting the hypothesis that histamine and prostaglandins are both linked and primary in the etiology of schizophrenia. Furthermore, their etiological significance supersedes the role of dopamine as a primary causative factor.

Regulation of tumour cell fatty acid oxidation by n-6 polyunsaturated fatty acids.

Fatty acids have been shown to regulate the expression of mRNA for both lipogenic and glycolytic enzymes in rat liver. The role of fatty acids in the regulation of carnitine palmitoyltransferase (CPT) I and II activity in tumour cells was investigated. The polyunsaturated fatty acids, gamma-linolenic and arachidonic acid, caused 60-70% inhibition of tumour cell CPT I activity and 45-50% inhibition of [14C]-palmitic acid oxidation to 14CO2. These effects were blocked by the cyclooxygenase inhibitor, indomethacin. Prostaglandins E1 and E2 caused marked inhibition of both CPT I and CPT II activity and inhibition of cell proliferation. Prostaglandin E2 production by tumour cells was increased in the presence of arachidonic acid and inhibited when indomethacin was present. The proliferation of the HT29 cell line was unaffected as was its CPT I and II activity by both fatty acids and prostaglandins. CPT I mRNA expression was not inhibited by fatty acids, indeed it increased-in the presence of arachidonic acid and prostaglandin E1. These results strongly suggest that polyunsaturated n-6 fatty acids are able, via prostaglandin products, to regulate the CPT activity of certain tumour cells. This may have a considerable impact on mitochondrial beta-oxidation and cellular metabolism of fatty acids, reflected in the marked inhibition of cell proliferation by these fatty acids.

Acute lesions of the ventromedial hypothalamus reduce sympathetic activation and thermogenic changes induced by PGE1.

The aim of this experiment was to evaluate the effects of an intracerebroventricular (icv) injection of prostaglandin E1 (PGE1) on the sympathetic activation and the thermogenic changes in rats with acute lesions of the ventromedial hypothalamus (VMH). Four groups of six Sprague-Dawley male rats were anesthetized with ethyl-urethane. The firing rate of the sympathetic nerves innervating the interscapular brown adipose tissue (IBAT) and the colonic and IBAT temperatures were monitored both before and after one of the following treatments: 1) VMH lesion plus icv injection of PGE1 (500 ng); 2) VMH lesion plus icv injection of saline: 3) sham lesion plus icv injection of PGE1; and 4) sham lesion plus icv injection of saline. PGE1 induced an increase in the firing rate of IBAT nerves and the colonic and IBAT temperatures. These effects were reduced by VMH lesion. The findings indicate that acute lesions of the VMH reduce the effects of PGE1 and seem to suggest a possible role played by the VMH in the control of the sympathetic activation and the thermogenic changes during PGE1 hyperthermia.

Endogenous ADP prevents PGE1-induced tyrosine dephosphorylation of focal adhesion kinase in thrombin-activated platelets.

Prostaglandin E1(PGE1) inhibits tyrosine phosphorylation induced by low thrombin concentration (0.05 U/ml), but this is overcome by a high thrombin (2.0 U/ml) concentration. Thromboxane A2 and ADP are endogenous platelet agonists released during platelet activation which potentiate platelet responses. We investigated how these endogenous agonists influenced the effects of PGE1 on thrombin (2.0 U/ml)-induced tyrosine phosphorylation by removing released ADP with apyrase (2.0 U/ml) and by inhibiting thromboxane A2 synthesis with indomethacin (1 microM). Adding PGE1 (1 microM) before thrombin in apyrase/indomethacin(A/I)-treated platelets selectively prevented thrombin-induced tyrosine phosphorylation of a 117 kDa protein while other substrates were not affected. This selective effect was evident only in the presence of apyrase and was not dependent on indomethacin. Addition of PGE1 to A/I-treated platelets after thrombin also caused selective tyrosine dephosphorylation of the 117 kDa protein. Conditions which prevented thrombin-induced 117 kDa protein tyrosine phosphorylation also decreased fibrinogen binding to platelets. The 117 kDa protein was identified as the focal adhesion kinase (FAK) by immunoprecipitation with a monoclonal antibody to FAK and by absence of its tyrosine phosphorylation in the presence of RGDS peptide which inhibits fibrinogen binding and platelet aggregation. Thus, released endogenous ADP selectively prevents PGE1-mediated tyrosine dephosphorylation of platelet FAK most likely by stabilizing fibrinogen binding to platelets.

Involvement of the beta gamma subunits of inhibitory GTP-binding protein in chemoattractant receptor-mediated potentiation of cyclic AMP formation in guinea pig neutrophils.

Cellular cyclic AMP formation in response to prostaglandin (PG) E1 was markedly potentiated by the chemoattractant formyl-Met-Leu-Phe (fMLP) in guinea pig neutrophils. This potentiation by fMLP was abolished by prior treatment of the cells with pertussis toxin, but not by the prevention of an fMLP-induced intracellular Ca2+ increase in the cells, indicating the direct involvement of the inhibitory GTP-binding protein (Gj), but not Ca2+, in the fMLP-induced potentiation of cyclic AMP formation. Cyclic AMP formation in the neutrophils was also unique in response to forskolin; the diterpene inhibited cyclic AMP formation stimulated by PGE1 plus fMLP at low concentrations, but it slightly stimulated the basal and fMLP-induced cyclic AMP formation at high concentrations. Such a forskolin-induced inhibition was also observed in the adenylyl cyclase of the cell membranes and detergent extract therefrom only when the cyclase was activated by GTP or its nonhydrolyzable analogue (GTP gamma S). The forskolin-inhibitable activity could be affinity-purified from the GTP gamma S-treated cell membranes with a forskolin-agarose column. The cyclase appeared to be purified as a complex with the GTP gamma S-bound alpha subunit of the stimulatory GTP-binding protein (Gs alpha), but not with the beta gamma subunits, as judged from immunoblot analysis with specific antisera. The GTP gamma S-bound Gs alpha-stimulated cyclase activity was further enhanced by beta gamma, and this enhancement was again inhibited by forskolin. These results suggest that the GTP-bound Gs alpha produced by PGE1 receptor stimulation and the beta gamma subunits released from Gj by fMLP receptor stimulation were acting synergistically in the cyclic AMP formation of intact neutrophils.

The rationale for prostaglandin E1 in erectile failure: a survey of worldwide experience.

PURPOSE: Prostaglandin E1 (PGE1, alprostadil) is used worldwide for self-injection therapy in erectile failure and was recently officially approved for this purpose in the United States and most European countries. Therefore a comprehensive overview on biochemistry, pharmacology and therapeutic results of PGE1 is provided. MATERIALS AND METHODS: The relevant literature on PGE1 was reviewed along with personal experience with 4,577 patients during a 7-year period. PGE1 was compared to other vasoactive drugs, such as papaverine, the mixture of papaverine and phentolamine or linsidomine alone. RESULTS: In Europe PGE1 was officially approved for the therapy of peripheral arterial occlusive disease of the lower limbs in 1984. The drug has direct relaxing effects on smooth muscle cells of vessels and cavernous bodies, shows inhibitory effects on platelet aggregation, on low-density lipoprotein entry into the vascular wall and on presynaptic noradrenaline release and, therefore, it prevents the progress of atherosclerosis. In erectile failure PGE1 shows a response rate of more than 70% and, compared to papaverine with phentolamine, a considerably lower risk of priapism (0.35% versus 6%, respectively) as well as of local fibrotic complications. Except for rare cases of blood pressure decrease, no systemic side effects were observed after intracavernous injection of PGE1. CONCLUSIONS: For self-injection therapy, PGE1 presently represents the most efficacious and safest drug. Ongoing trials with topical and especially intraurethral PGE1 are promising and may offer less invasive therapies in the near future.

Prostaglandin synthesis by cumulus-oocyte complexes: effects on in vitro fertilization in mice.

Cumulus-oocyte complexes, obtained from superovulated Balb/C virgin female mice, released to the incubation media significant amounts of PGE1, PGE2 and PGF2 alpha, as estimated by bioassay. Fertilization rates in vitro decreased sharply when cumulus-oocyte complexes were treated with indomethacin (10(-6) M) and then inseminated with 5000 sperm per oocyte. In order to explore if the reduced prostaglandin (PG) concentration was responsible for diminished fertilization rates, PGE1, PGE2 and PGF2 alpha (10(-9) M) were added to the fertilization media of treated oocytes. PGE1 and PGE2 but not PGF2 alpha returned fertilization rates to control levels. Besides, PGE1 (10(-9) M) enhanced fertilization rates with reduced sperm numbers (1000 sperm per oocyte) of untreated cumulus-oocyte complexes. In conclusion, PG synthesis and release of mouse cumulus-oocyte complexes affects fertilization in vitro, and it is suggested that PGs of the E series modulate sperm function at the moment of fertilization.

Role of prostaglandins E1, E2 and F2 alpha in the brain in interleukin 1 beta-induced adrenocorticotropin secretion in the rat.

It is well known that interleukin (IL)-1 is a potent activator of the hypothalamo-pituitary-adrenal axis in the rat. Many studies have reported that prostaglandins (PGs), especially PGE2, in the brain may mediate the IL-1 stimulation of corticotropin-releasing hormone release, which then leads to adrenocorticotropin (ACTH) secretion. However, a general consensus has yet to emerge regarding whether PGE2 is the only or the most important PG in the brain mediating IL-1-induced ACTH secretion in the rat. To address this question, we examined the effect of intracerebroventricular (icv) administration of antisera against PGE1, PGE2 or PGF2 alpha, or normal rabbit serum on the ACTH response induced by an icv injection of IL-1 beta in the rat. Each antibody or normal rabbit serum (as the control) was given icv 15 min before an icv administration of human recombinant IL-1 beta (50 ng). IL-1 beta produced a significant rise in plasma ACTH levels, and this response was significantly suppressed by either of the three PG antibodies. Interestingly, the inhibitory effect of anti-PGE2 antibody seemed to be somewhat weaker than those of the other two antibodies. We conclude that not only PGE2 but also PGE1 and PGF2 alpha in the brain may mediate the IL-1 beta stimulation of ACTH secretion in the rat.

Prostanoid enhancement of interleukin-6 production by rat peritoneal mast cells.

Mast cells are traditionally associated with an acute response involving the short-term release of mediators such as histamine. We have shown previously that mast cells can produce IL-6 without prior histamine release. In this study we examined the hypothesis that mast cell IL-6 production can be selectively regulated by PGs. Highly purified rat peritoneal mast cells were cultured in the presence of PGE1, PGE2, or PGD2 alone or in combination with anti-IgE or bacterial LPS. Histamine release was assessed after 10 min; IL-6 and TNF-alpha production was measured in supernatants after 18 h. Mast cell IL-6 production was induced by PGE1 and PGE2 to a similar level to that observed in anti-IgE-activated cells. In contrast, constitutive production of TNF-alpha was inhibited by PGE1 and PGE2, but not by PGD2. PGE2 had a synergistic effect, inducing IL-6 in the presence of LPS, whereas an additive effect was observed in the presence of anti-IgE. None of the prostanoids alone induced significant histamine release at the 10-min time point. However, PGE2 significantly increased histamine release when added concurrently with anti-IgE. Flurbiprofen in the context of anti-IgE or LPS activation did not alter mast cell IL-6 or TNF-alpha production. IL-6 production in response to each of the stimuli was significantly inhibited by the corticosteroid dexamethasone. These observations of selective modulation of mast cell cytokine production are important to understand the mechanisms by which mast cells interact with other cells during an inflammatory process involving prostanoid synthesis.