Inhibitory Effect Of PGE2 Research Articles

Inhibition of nNOS expression in the macula densa by COX-2-derived prostaglandin E(2).

It is well established that cyclooxygenase-2 (COX-2) and the neuronal form of nitric oxide synthase (nNOS) are coexpressed in macula densa cells and that the expression of both enzymes is stimulated in a number of high-renin states. To further explore the role of nNOS and COX-2 in renin secretion, we determined plasma renin activity in mice deficient in nNOS or COX-2. Plasma renin activity was significantly reduced in nNOS -/- mice on a mixed genetic background and in COX-2 -/- mice on either BALB/c or C57/BL6 congenic backgrounds. In additional studies, we accumulated evidence to show an inhibitory influence of PGE(2) on nNOS expression. In a cultured macula densa cell line, PGE(2) significantly reduced nNOS mRNA expression, as quantified by real-time RT-PCR. In COX-2 -/- mice, nNOS mRNA expression in the kidney, determined by real-time RT-PCR, was upregulated throughout the postnatal periods, ranging from postnatal day (PND) 3 to PND 60. The induction of nNOS protein expression and NOS activity in COX-2 -/- mice was localized to macula densa cells using immunohistochemistry and NADPH-diaphorase staining methods, respectively. Therefore, these findings reveal that the absence of either COX-2 or nNOS is associated with suppressed renin secretion. Furthermore, the inhibitory effect of PGE(2) on nNOS mRNA expression indicates a novel interaction between NO and prostaglandin-mediated pathways of renin regulation.

PLA 2/PGE 2 are involved in the inhibitory effect of bradykinin on the angiotensin-(1–7)-stimulated Na +-ATPase activity of the proximal tubule

Recently, we demonstrated that bradykinin (BK) counteracts the stimulatory effect of Ang-(1–7) on the Na +-ATPase activity from basolateral membrane of the proximal tubule through B 2 receptor. In the present paper, the signaling pathway involved in the inhibitory response of the Na +-ATPase activity to BK was investigated. The following results indicate that the phospholipase A 2 (PLA 2)/COX/prostaglandin E (PGE 2) pathway is implicated in this process: (1) The inhibitory effect of BK on Ang-(1–7)-stimulated enzyme is abolished in a dose-dependent manner by quinacrine (10 −9;-10 −6M), a nonspecific PLA 2 inhibitor, and by PACOCF 3 (10 −7M), an inhibitor of a Ca 2+-independent PLA 2. However, AACOCF 3 (2×10 −4 M), an inhibitor of the cytosolic PLA 2, does not modify the inhibitory effect of BK. (2) The inhibitory effect of BK on the Ang-(1–7)-stimulated enzyme is reversed by cyclooxygenase (COX) inhibitors diclofenac (10 −12 M) and indomethacin (10 −12 M). (3) PGE 2 (10 −12–10 −5 M) inhibits the Na +-ATPase activity in a dose dependent manner. (4)The inhibitory effects of PGE 2 and BK on the Na +-ATPase activity are not cumulative. (5) PGE 2 (10 −12–10 −8 M) counteracts the stimulatory effect of Ang-(1–7) on the enzyme activity in a dose-dependent manner.

Effect of prostaglandin E2 on intercellular adhesion molecule-1 and B7 expression in mixed lymphocyte reaction.

The elevation of plasma interleukin (IL)-18 levels and the expression of intercellular adhesion molecule (ICAM)-1 and B7 on monocytes are involved in acute rejection. Prostaglandin (PG) E2 suppresses the rejection in animal transplantation models; however, little is known about its action mechanism. We examined the effect of PGE2 on the expression of ICAM-1 and B7 in the human mixed leukocyte reaction (MLR) in the presence or absence of IL-18. We measured the expression of ICAM-1, B7.1, and B7.2 on human monocytes by flow cytometry and determined the associated production of interferon-gamma and IL-12 by enzyme-linked immunosorbent assay. The modulatory effects of PGE2 and the relevant PGE2 receptor subtypes were characterized pharmacologically. PGE2 inhibited the expression of ICAM-1, B7.1, and B7.2 on monocytes in MLR in a concentration-dependent manner. Whereas IL-18 significantly induced the expression of ICAM-1, B7.1, and B7.2 on monocytes in MLR and the production of interferon-gamma and IL-12, PGE2 inhibited these IL-18-initiated enhancements. The effects of PGE2 were mimicked by selective EP2 and EP4 agonists, but not by EP1 and EP3 agonists. PGE2 strongly inhibited MLR with respect to the expression of ICAM-1, B7.1, and B7.2 via the EP2 and EP4 receptors, irrespective of the presence or absence of IL-18. In the previous study, histamine inhibited ICAM-1 expression in the presence of IL-18 but had no effect in the absence of IL-18. These results indicate that the inhibitory effect of PGE2 may be more general and stronger than that of histamine and may play an important role in future immunosuppressive strategies.

Transforming growth factor-ß2 inhibition of corneal endothelial proliferation mediated by prostaglandin

Purpose. To determine the influence of Prostaglandin (PG) E2 on transforming growth factor (TGF)-ß2-mediated inhibitory effects on the proliferation of corneal endothelial cells (CE). Methods. The PGE2 and cell proliferation assays were performed using cultured rabbit corneal endothelium. A PGE2-specific enzyme immunoassay was used to check PGE2 synthesis in supernatants of cells cultured with and without added TGF-ß2 and/or indomethacin. To evaluate the inhibitory effects of PGE2 and TGF-ß2 on CE proliferation, the number of cells grown with exogenous PGE2, or TGF-ß2 with or without indomethacin pretreatment was determined. Results. TGF-ß2, 0.5 to 50 ng/ml, increased the PGE2 secretion of CE dose-dependently in a time-dependent manner. Indomethacin (=0.1mg/ml) inhibited this PGE2 secretion to a low level (around 5-10 ng/ml) in the presence or absence of exogenous TGF-ß2. Both exogenous TGF-ß2 and PGE2 inhibited CE proliferation dose-dependently over a wide range of concentrations. Indomethacin reversed the inhibitory effects of TGF-ß2 but not those of exogenous PGE2. In the medium supplemented with indomethacin, even in the presence of 50 ng/ml of TGF-ß2, CE growth did not differ from control cultures. Conclusions. TGF-ß2 stimulates PGE2 synthesis in CE and inhibits CE proliferation in a dose-dependent manner. Indomethacin extinguishes the inhibitory effects of TGF-ß2 on CE proliferation but not the effect of exogenous PGE2. These data suggest that the antiproliferative effects of TGF-ß2 on CE may be possibly due to TGF-ß2-induced synthesis of PG, most likely PGE2.

Inhibitory effects of PGE(2) on K(+) currents and Ca(2+) oscillations in rat pancreatic acinar cells.

Prostaglandin E(2) (PGE(2)) inhibits pancreatic enzyme secretion and shows a protective action against pancreatitis. In this study, we tested the effects of PGE(2) on the slowly activating voltage-dependent K(+) channel current ( I(Ks)) and cholecystokinin (CCK)-induced oscillations of cytosolic [Ca(2+)] ([Ca(2+)](i)) in rat pancreatic acini (RPA). I(Ks) in RPA is reportedly augmented by both Ca(2+)- and cAMP-mediated secretagogues. PGE(2) (10(-7) M) decreased the amplitude of I(Ks), an effect that was more prominent following prior stimulation with secretin. The application of the membrane-permeable cAMP analogue 8-Br-cAMP prevented the effect of PGE(2) on I(Ks). The Ca(2+)-mediated augmentation of I(Ks) by ACh was unaffected by pretreatment with PGE(2). Using fura-2 fluorescence ratiometry to assess [Ca(2+)](i), CCK (<or=10(-10) M)-induced Ca(2+) oscillations were observed in RPAs. The amplitude of the Ca(2+) oscillations was decreased by PGE(2), irrespective of the presence of 8-Br-cAMP. RT-PCR analysis showed that RPAs express predominantly the EP3 subtype of the PGE(2) receptor and its splice variants. Enzyme-immunoassay showed that the secretin-induced production of cAMP in RPAs was inhibited by treatment with PGE(2). In summary, PGE(2) acts on the EP3 receptors to antagonize the cAMP-generating effect of secretin, resulting in the decrease of I(Ks). In addition, PGE(2) suppresses CCK-induced Ca(2+) oscillations in a cAMP-independent manner. These effects of PGE(2) may explain the inhibitory action mechanism of PGE(2) in the exocrine pancreas.

Inhibition by Prostaglandin E2 of Anaphylatoxin C5a- but Not Zymosan-Induced Prostanoid Release from Rat Kupffer Cells

The proinflammatory anaphylatoxin C5a induces the release of prostanoids, ie, prostaglandins (PG) and thromboxane (TX), from the resident liver macrophages (Kupffer cells [KC]). Because KC themselves express prostanoid receptors, prostanoids—besides having paracrine functions—might regulate their own release in an autocrine loop. So far, such a possible feedback regulation has not been investigated systematically, probably because of methodological difficulties to measure newly synthesized prostanoids in the presence of added prostanoids. Here, after prelabeling of phospholipids with [14C]arachidonate, cellularly formed [14C]prostanoids were determined in the presence of added unlabelled prostanoids by thin layer chromatography. In cultured KC, recombinant rat C5a (rrC5a) rapidly increased PGD2, PGE2, and TXA2 release, which was strongly reduced by PGE2, but neither by PGD2 nor by the TXA2 analog U46619. The inhibitory effect of PGE2 was mimicked by cAMP, indicating that the Gs-coupled PGE2 receptors type 2 or 4 were involved. Zymosan also enhanced prostanoid release from KC, but with slightly slower kinetics; this action was neither inhibited by PGE2 nor by cAMP. Also in perfused rat livers, rrC5a enhanced prostanoid release from KC as shown by prostanoid overflow and thereby indirectly increased glucose output from hepatocytes. Again, PGE2, but not PGD2, inhibited rrC5a-elicited prostanoid overflow. This resulted in a complete inhibition of rrC5a-induced, prostanoid-mediated glucose output. Thus, PGE2 can inhibit specifically the C5a-induced prostanoid release from KC via a feedback mechanism and thereby limit prostanoid-mediated hepatocellular defense reactions, eg, glucose release.

A direct inhibitory action of prostaglandins upon ACTH secretion at the late stages of the secretory pathway of AtT-20 cells.

1. The mouse AtT-20/D16-16 anterior pituitary tumour cell line was used as a model system for the study of the effects of prostaglandins upon the late stages of the adrenocorticotrophin (ACTH) secretory pathway. 2. Calcium (1 nM - 100 microM), guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma-S) (1 - 100 microM) and mastoparan (1 and 10 microM) all stimulated ACTH secretion from permeabilized AtT-20 cells in a concentration-dependent manner. GTP-gamma-S and mastoparan stimulated ACTH secretion from permeabilized cells in the absence of calcium. Co-incubation with prostaglandins E(1) and E(2) (PGE(1), PGE(2)) (10 microM) but not prostaglandin F(2 alpha) (PGF(2 alpha)) (10 microM) significantly inhibited calcium-, GTP-gamma-S and mastoparan-evoked secretion by 30 - 50%. 3. The effects of PGE(1) and PGE(2) upon GTP-gamma-S (100 microM)-, calcium (10 microM)- and mastoparan (10 microM)-evoked secretion were concentration-dependent. PGE(1) significantly inhibited GTP-gamma-S- and calcium-evoked secretion at concentrations of PGE(1) above 1 microM but mastoparan-evoked secretion only at the highest concentration of PGE(1) investigated (10 microM). PGE(2) was much more potent than PGE(1) and significantly inhibited GTP-gamma-S- and calcium-evoked secretion at 10 nM and above and mastoparan-evoked secretion above 1 microM. 4. The inhibitory effects of PGE(1) and PGE(2) upon calcium-, GTP-gamma-S- and mastoparan-stimulated ACTH secretion from permeabilized cells were pertussis toxin (PTX) sensitive. 5. In intact cells PGE(1), PGE(2) and PGF(2 alpha) (1 nM - 10 microM) acting singly had little or no effect upon ACTH secretion. However, only PGE(2) (1 nM - 10 microM) significantly inhibited corticotrophin-releasing factor-41 (CRF-41) (100 nM)-evoked secretion in a concentration dependent manner. 6. The present study finds that prostaglandins of the E series exert an inhibitory action, via a pertussis toxin-sensitive GTP-binding (G)-protein, in the late stages of the ACTH secretory pathway distal to the G-exocytosis (Ge)/calcium point of control.

Cyclooxygenase-2-issued prostaglandin e(2) enhances the production of endogenous IL-10, which down-regulates dendritic cell functions.

PGE(2) is a well-known immunomodulator produced in the immune response by APCs, such as dendritic cells (DCs), the most potent APC of the immune system. We investigated the PGE(2) biosynthetic capacity of bone marrow-derived DC (BM-DC) and the effects of PG on the APC. We observed that BM-DC produce PGE(2) and other proinflammatory mediators, such as leukotriene B(4) and NO, after LPS exposure. Constitutively present in BM-DC, cyclooxygenase (COX)-1 did not contribute significantly to the total pool of PGE(2) compared with the LPS-induced COX-2-produced PGE(2). Treatment of BM-DC with exogenous PGE(2) induced the production of large amounts of IL-10 and less IL-12p70. In addition, selective inhibition of COX-2, but not COX-1, was followed by significant decrements in PGE(2) and IL-10, a concomitant restoration of IL-12 production, and an enhancement of DC stimulatory potential. In contrast, we found no demonstrable role for leukotriene B(4) or NO. In view of the potential of PGE(2) to stimulate IL-10, we examined the possibility that the suppressive effect of PGE(2) is mediated via IL-10. We found that exogenous IL-10 inhibits IL-12p70 production in the presence of NS-398, a COX-2 selective inhibitor, while the inhibitory effects of PGE(2) were totally reversed by anti-IL-10. We conclude that COX-2-mediated PGE(2) up-regulates IL-10, which down-regulates IL-12 production and the APC function of BM-DC.

Permeability of endothelial monolayers to albumin is increased by bradykinin and inhibited by prostaglandins.

Using monolayers of bovine aortic endothelial cells (BAEC) in modified Boyden chambers, we examined the role of prostaglandins (PGs) in the bradykinin (BK)-induced increase of albumin permeability. BK induced a concentration-dependent increase of the permeability of BAEC, which reached 49.9 +/- 1% at the concentration of 10(-8) M. Two inhibitors of the prostaglandin G/H synthase, indomethacin (2.88 microM) and ibuprofen (10 microM), potentiated BK-induced permeability 1.8- and 3.9-fold, respectively. Exogenously administered PGE2 and iloprost, a stable analog of prostacyclin, attenuated the effect of BK in a concentration-dependent manner. Butaprost equally reduced the effect of BK, suggesting the participation of the EP2 receptor in this phenomenon. However, the EP4-selective antagonist AH-23848 did not significantly inhibit the protective effect of PGE2. The inhibitory effect of PGE2 was reversed by the adenylate cyclase inhibitor MDL-12330A (10 microM). These results suggest that BK-induced increase of permeability of BAEC monolayer to (125)I-labeled albumin is negatively regulated by PGs. This postulated autocrine activity of PGs may involve an increase in the intracellular level of cAMP.

Regulation of TCR-induced IFN-gamma release from islet-reactive non-obese diabetic CD8(+) T cells by prostaglandin E(2) receptor signaling.

Prostaglandins (PG) are released during tissue injury and inflammation, and inhibit immune responses at many points. PG may be one of several factors that protect not only against injury-induced, but also spontaneous, organ-specific autoimmune disease. Here we show that the production of PGE(2), normally produced at a very low rate in islets of Langerhans, is significantly increased in inflamed islets of non-obese diabetic (NOD) mice. We investigated a possible role of PGE(2) in controlling TCR-dependent release of IFN-gamma from islet-reactive NOD CD8(+) T cells. PGE(2) inhibited anti-TCR antibody-triggered release of IFN-gamma from CD8(+) T cell clone 8D8 and from polyclonal cytotoxic T lymphocytes (CTL). Using receptor subtype selective agonists, we present evidence that the effect of PGE(2) is mediated by EP(2) and EP(4) receptors, both of which are coupled to an increase in intracellular cAMP production. The cAMP analogs 8-Br-cAMP and Sp-cAMPS mimic the effect of EP(2)/EP(4) receptor agonists, inhibiting TCR-triggered IFN-gamma release from NOD CD8(+) T cells in a dose-dependent manner. The inhibitory effect of PGE(2) was largely reversed by IL-2 added at the time of culture initiation and decreased with increasing strength of stimulation through the TCR. Resting CTL were more sensitive to PGE(2) than recently expanded CTL and NOD CD8(+) T cells remained insensitive to PGE(2) for a longer time than BALB/c cells. Our study suggests that PGE(2) may be part of a regulatory network that controls local activation of T cells and may play a role in the balance between the development of islet autoimmunity or maintenance of tolerance.

The prostaglandin E series modulates high-voltage-activated calcium channels probably through the EP 3 receptor in rat paratracheal ganglia

The modulation of high-voltage-activated (HVA) Ca 2+ channels by the prostaglandin E series (PGE 1 and PGE 2) was studied in the paratracheal ganglion cells. Prostaglandin E 1, E 2, STA 2 (a stable analogue of thromboxane A 2), 17-phenyl-trinor-PGE 2 (an EP 1-selective agonist) and sulprostone (an EP 3-selective agonist) inhibited the HVA Ca 2+ current (HVA I Ca) dose-dependently, and the rank order of potency to inhibit HVA Ca 2+ channels was sulprostone>PGE 2, PGE 1>STA 2≫17-phenyl-trinor-PGE 2. SC-51089 (10 −5 M), a selective EP 1-receptor antagonist, showed no effect on the PGE 1- or PGE 2-induced inhibition of the HVA I Ca, thereby indicating that PGE 1- and PGE 2-induced inhibition of the HVA Ca 2+ channels is possibly mediated by the EP 3 receptor. The PGE 1-sensitive component of the current was markedly reduced in the presence of ω-conotoxin-GVIA (3×10 −6 M), but not with nifedipine (3×10 −6 M). PGE 1 and PGE 2 also inhibited the remaining I Ca in a saturating concentration of nifedipine, ω-conotoxin-GVIA and ω-conotoxin-MVIIC, suggesting that R-type Ca 2+ channels are involved. The inhibitory effect of PGE 1 or sulprostone was prevented by pretreatment with pertussis toxin [islet activating protein (IAP)] or phorbol-12-myristate-13-acetate (PMA), and the protein kinase C (PKC) inhibitor chelerythrine blocked the action of PMA. It was concluded that PGE 1 selectively reduces both N- and R-type Ca 2+ currents by activating a G-protein probably through the EP 3 receptor in paratracheal ganglion cells.

Prostaglandin E receptor subtypes in cultured rat microglia and their role in reducing lipopolysaccharide-induced interleukin-1beta production.

Prostaglandins (PGs) are potent modulators of brain function under normal and pathological conditions. The diverse effects of PGs are due to the various actions of specific receptor subtypes for these prostanoids. Recent work has shown that PGE2, while generally considered a proinflammatory molecule, reduces microglial activation and thus has an antiinflammatory effect on these cells. To gain further insight to the mechanisms by which PGE2 influences the activation of microglia, we investigated PGE receptor subtype, i.e., EP1, EP2, EP3, and EP4, expression and function in cultured rat microglia. RT-PCR showed the presence of the EP1 and EP2 but not EP3 and EP4 receptor subtypes. Sequencing confirmed their identity with previously published receptor subtypes. PGE2 and the EP1 agonist 17-phenyl trinor PGE2 but not the EP3 agonist sulprostone elicited reversible intracellular [Ca2+] increases in microglia as measured by fura-2. PGE2 and the EP2/EP4-specific agonists 11-deoxy-PGE1 and 19-hydroxy-PGE2 but not the EP4-selective agonist 1-hydroxy-PGE1 induced dose-dependent production of cyclic AMP (cAMP). Interleukin (IL)-1beta production, a marker of activated microglia, was also measured following lipopolysaccharide exposure in the presence or absence of the receptor subtype agonists. PGE2 and the EP2 agonists reduced IL-1beta production. IL-1beta production was unchanged by EP1, EP3, and EP4 agonists. The adenylyl cyclase activator forskolin and the cAMP analogue dibutyryl cAMP also reduced IL-1beta production. Thus, the inhibitory effects of PGE2 on microglia are mediated by the EP2 receptor subtype, and the signaling mechanism of this effect is likely via cAMP. These results show that the effects of PGE2 on microglia are receptor subtype-specific. Furthermore, they suggest that specific and selective manipulation of the effects of PGs on microglia and, as a result, brain function may be possible.

Cytotoxicity of Anti-Cancer Drugs to Vascular Endothelial Cells and Inhibitory Effect of PGE.

In this study, the degree of in vitro cytotoxicity of anticancer drugs, including 5-fluorouracil, doxorubicin, cis-diamminedi-chloroplatinum, and mitomycin C, to vascular endothelial cells collected from the carotid artery of cows was evaluated by the MTT (3-(4, 5-dimeth-ylthiazol-2-yl)-3, 5-Biphenyl tetrazolium bromide) assay. The results indicated that the viability of vascular endothelial cells decreased with the addition of all of the above anti-cancer drugs, and a positive correlation was found between cytotoxicity and the drug concentration, as well as between cytotoxicity and the length of incubation with the anti-cancer drugs. The cytotoxicity of doxorubicin, cis-diamminedichloroplatinum, and mitomycin C became evident very rapidly and was stronger than that of 5-fluorouracil. The protective effect of prostaglandin E1 on the cytotoxicity caused by anti-cancer drugs was examined. The results also indicated that the addition of prostaglandin E1 inhibited the decrease in the viability of vascular endothelial cells which had been induced by 5-fluorouracil. These findings suggested that anti-cancer drugs cause endothelial cell injury and that prostaglandin E1 can protect this type of injury at least when induced by 5-fluorouracil.

Effects of agents which elevate cyclic AMP on guinea-pig eosinophil homotypic aggregation.

1. Eosinophil recruitment and activation in inflamed tissue is thought to play an important role in the pathophysiology of allergic diseases. Experimental evidence suggests that elevating cyclic AMP is an effective means of reducing eosinophil recruitment in vivo and may therefore have therapeutic benefit. In the present study, we have assessed the capacity of cyclic AMP-elevating agents to modulate guinea-pig eosinophil homotypic aggregation, a CD18-dependent process, which may be an important component of eosinophil function in vivo. 2. Prostaglandin E1 (PGE1, 10(-16) to 10(-6) M) inhibited platelet activating-factor (PAF)- and C5a-induced eosinophil aggregation in a concentration-dependent manner. However, PAF-induced responses were more potently and more effectively inhibited by PGE1. The inhibitory effects of PGE1 on PAF-induced aggregation were reversed by pretreatment of eosinophils with the protein kinase A inhibitors H89 and KT5720. 3. The beta 2-adrenoceptor agonists, salbutamol and salmeterol, concentration-dependently inhibited eosinophil aggregation induced by C5a and PAF and, again. PAF-induced responses were more effectively reduced. The inhibitory effect of salmeterol was mediated by beta-adrenoceptors, as assessed by the reversal after pretreatment with propranolol. 4. Rolipram, a selective phosphodiesterase 4 (PDE4) inhibitor, also attenuated PAF- and C5a-induced aggregation and at a low concentration which did not affect aggregation per se, had a synergistic effect with PGE1 and salbutamol to suppress this response. 5. Activation of eosinophils with PAF or C5a induced a small but significant increase in the level of CD18 expression on the eosinophil surface. PGE1 (10(-7) M) decreased PAF- and C5a-induced upregulation of CD18 by 93% and 62%, respectively. 6. These results demonstrate that cyclic AMP-elevating agents effectively inhibit eosinophil aggregation, a CD18-dependent functional response. Because CD18 has been shown to be important for eosinophil recruitment to inflamed tissue in vivo, our findings may be of relevance to the efficacy of cyclic AMP-elevating agents at inhibiting eosinophil trafficking.

Activation of elements of the phosphatidylinositol pathway in the primate corpus luteum by prostaglandin E2.

The current study was designed to examine the effects of prostaglandin (PG) E2 on progesterone production by primate luteal cells collected during the late luteal phase. PGE2 inhibited basal and human chorionic gonadotrophin (HCG)-stimulated progesterone production (P < 0.01) in late luteal phase corpora lutea. The ability of PGE2 to activate a second messenger system (phosphatidylinositol pathway) in corpora lutea of rhesus monkeys was also assessed. PGE2 significantly increased the accumulation of inositol phosphates (P < 0.05). This stimulation was not apparent in the early luteal phase but was manifested in the mid-late luteal phase. PGE2 also caused a rapid, yet transient, increase (P < 0.01) in intracellular free calcium ion concentrations ([Ca2+]i) in a large proportion of primate luteal cells. The proportion of luteal cells that responded to PGE2 with an increase in [Ca2+]i was smaller (P < 0.05) in corpora lutea collected during the early luteal phase (12%) in comparison with those collected during the latter half of the luteal phase (63-66%). Changes in [Ca2+]i in response to PGE2 were similar in small and large luteal cells. This study demonstrates that PGE2 activates elements of the phosphatidylinositol pathway in primate corpora lutea. This activation is augmented as the luteal phase progresses. Thus, the inhibitory effects of PGE2 on luteal progesterone production observed in the late luteal phase are associated with activation of elements of the phosphatidylinositol pathway.

INHIBITORY EFFECTS OF PGE2, and TGF-β ON LYMPHOCYTE Ca2+ SIGNALING, and PROLIFERATIVE RESPONSES

SHOCK®: Injury, Inflammation, and Sepsis: Laboratory and Clinical Approaches includes studies of novel therapeutic approaches, such as immunomodulation, gene therapy, nutrition, and others. The mission of the Journal is to foster and promote multidisciplinary studies, both experimental and clinical in nature, that critically examine the etiology, mechanisms and novel therapeutics of shock-related pathophysiological conditions. Its purpose is to excel as a vehicle for timely publication in the areas of basic and clinical studies of shock, trauma, sepsis, inflammation, ischemia, and related pathobiological states, with particular emphasis on the biologic mechanisms that determine the response to such injury. Making such information available will ultimately facilitate improved care of the traumatized or septic individual. SHOCK® is also privileged to have fourteen distinguished Associate Editors, as well as a diverse group of editorial board members from various parts of the world, who enjoy the respect and admiration of their colleagues in their areas of investigation. The Official Journal of the Shock Society, the European Shock Society, the Indonesian Shock Society, the International Federation of Shock Societies, and the Official and International Journal of the Japan Shock Society

Cross-talk between cyclooxygenase and nitric oxide pathways: prostaglandin E2 negatively modulates induction of nitric oxide synthase by interleukin 1.

The inflammatory cytokine interleukin 1 beta (IL-1 beta) induces both cyclooxygenase (COX) and nitric oxide synthase (NOS) with increases in the release of prostaglandin (PG) and nitric oxide (NO) by mesangial cells. Recently, activation of the COX enzyme by NO has been described. However, the effects of COX products (PGs) on the NO pathway have not been fully clarified. Thus we determined the effect of COX inhibition and exogenous PGs on NO production and NOS induction in rat mesangial cells. A COX inhibitor, indomethacin, enhanced IL-1 beta-induced steady-state level of the inducible NOS (iNOS) mRNA and nitrite production. The effect of indomethacin was dose dependently reversed by the replacement of endogenous PGE2 with exogenous PGE2, which is the predominant product of the COX pathway in rat mesangial cells. In contrast to PGE2, a stable analog of PGI2, carba prostacyclin, enhanced IL-1 beta-induced iNOS mRNA levels and nitrite production. Forskolin, an activator of the adenylate cyclase, mimicked the effect of carba prostacyclin but not PGE2. These data suggest that (i) endogenous PGE2 downregulates iNOS induction, (ii) this inhibitory effect of PGE2 on iNOS induction is not mediated by activation of adenylate cyclase, and (iii) exogenous PGI2 stimulates COX induction possibly by activation of adenylate cyclase.

CAMP inhibition of interleukin-1-induced interleukin-6 production by human lung fibroblasts.

We characterized the effects of agents that alter intracellular adenosine 3',5'-cyclic monophosphate (cAMP) on the interleukin (IL)-6 production of human lung fibroblasts. Unstimulated fibroblasts did not produce significant amounts of IL-6. Recombinant (r) tumor necrosis factor (TNF) weakly stimulated, recombinant interleukin-1-alpha (rIL-1 alpha) strongly stimulated, and rIL-1 alpha and rTNF in combination synergistically augmented fibroblast IL-6 production. Prostaglandin (PG)E1, forskolin, dibutyryl cAMP (DBcAMP), 3-isobutyl-1-methylxanthine (IBMX), and cholera toxin did not cause a detectable alteration in the IL-6 production of unstimulated fibroblasts. However, these agents inhibited the IL-6 production of rIL-1 and rIL-1 plus rTNF-stimulated cells. These effects were dose dependent with a concentration of 2 x 10(-9) M PGE1, 5 x 10(-6) M forskolin, 5 x 10(-4) M DBcAMP, and 1 x 10(-3) M IBMX decreasing rIL-1 alpha (2.5 ng/ml)-induced IL-6 production by approximately 50%. The inhibitory effects of these agents, correlated with their ability to induce fibroblast cAMP accumulation, could not be explained by alterations in cell number or viability and were appreciable even when cAMP modifiers were added to fibroblast culture, 1 h after rIL-1. They were also at least partly specific for rIL-1, since these agents increased the IL-6 production of rTNF-stimulated cells. These cAMP-induced alterations in IL-6 production were associated with corresponding alterations in IL-6 mRNA accumulation. Nuclear run-on analysis demonstrated that the inhibitory effects of PGE1 were associated with a comparable decrease in IL-6 transcription. Agents that increase the levels of intracellular cAMP inhibit rIL-1-induced IL-6 by human lung fibroblasts.

Comparative effects of cytosine arabinoside and a prostaglandin E 2 antagonist, AH6809, on chondrogenesis in serum-free cultures of chick limb mesenchyme

The present study was designed to compare effects of an established inhibitor of cell proliferation and growth, cytosine arabinoside (Ara C), with that of a prostaglandin E 2 (PGE 2) antagonist, AH6809, on chondrogenesis in cultured mesenchyme derived from stage 25 chick limb buds. Continuous treatment of cell cultures with 10 −4 M AH6809 prevented completely the twofold increases in DNA content of control cultures which occurred between Day 1 and Day 5 of culture and also produced 90% inhibition of chondrogenesis occurring in control cultures during this same period. Treatment of cells with Ara C (0.1–0.5 μg/ml) produced equivalent inhibition of DNA content during the same time period; however, chondrogenesis, as evaluated on Day 5 of cell culture, remained at approximately 90% of control cultures. These results indicate that the inhibitory effect of PGE 2 receptor blockade on cell growth in these cultures cannot account for the potent inhibitory effects observed on differentiation of cartilage and provide further evidence in support of the notion that PGE 2 plays an important initiating role in the process of chondrocyte differentiation within limb mesenchyme.

Prostaglandin E 1 suppression of platelet aggregation response in schizophrenia

The inhibitory effects of prostaglandin E 1 (PGE 1) on the platelet aggregation response (PAR) to adenosine diphosphate (ADP) in 103 schizophrenics, 55 patients with other mental disorders, and 71 controls were examined. The three groups did not differ in PAR to ADP. However, schizophrenic patients, especially in the acute state, showed a significant reduction in the inhibitory effects of PGE 1 on PAR compared to the other two groups. These results suggest PGE 1 hyposensitivity exists in some schizophrenic patients, which may result from PGE 1 deficiency. As clinical characteristics of the subgroup showing platelet PGE 1 subsensitivity, relatively successful heterosexual relations, less anergia, and a more severe activation factor on BPRS were identified. Furthermore, the relationship between platelet sensitivity to PGE 1 and brain morphology, using magnetic resonance imaging on 39 male schizophrenics was examined. Of 11 parameters obtained from MRI measurements, only callosum: brain ratio showed a significant negative correlation with a platelet sensitivity to PGE 1. The current study suggested existence of a subgroup of schizophrenia having platelet hyposensitivity and a definite clinical feature as state markers and small corpus callosum as a trait marker.