Accumulation Of Prostaglandins Research Articles

15-Deoxy-Δ12,14-prostaglandin J2 Induces Epithelial-to-mesenchymal Transition in Human Breast Cancer Cells and Promotes Fibroblast Activation.

In inflammation-associated carcinogenesis, COX-2 is markedly overexpressed, resulting in accumulation of various prostaglandins. 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) is one of the terminal products of COX-2-catalyzed arachidonic acid catabolism with oncogenic potential. Epithelial-to-mesenchymal transition (EMT) is a process by which epithelial cells lose their polarity and adhesiveness, and thereby gain migratory and invasive properties. Treatment of human breast cancer MCF-7 cells with 15d-PGJ2 induced EMT as evidenced by increased expression of Snail and ZEB1, with concurrent down-regulation of E-cadherin. Nuclear extract from 15d-PGJ2-treated MCF-7 cells showed the binding of Snail and ZEB1 to E-box sequences present in the E-cadherin promoter, which accounts for repression of E-catherin expression. Unlike 15d-PGJ2, its non-electrophilic analogue 9,10-dihydro-15d-PGJ2 failed to induce EMT, suggesting that the α,β-unsaturated carbonyl group located in the cyclopentenone ring of 15d-PGJ2 is essential for its oncogenic function. Notably, the mRNA level of interleukin-8 (IL-8)/CXCL8 was highly elevated in 15d-PGJ2-stimulated MCF-7 cells. 15d-PGJ2-induced up-regulation of IL-8/CXCL8 expression was abrogated by silencing of Snail short interfering RNA. Treatment of normal fibroblast with conditioned medium obtained from cultures of MCF-7 cells undergoing EMT induced the expression of activated fibroblast marker proteins, α-smooth muscle actin and fibroblasts activation protein-α. Co-culture of normal fibroblasts with 15d-PGJ2-stimulated MCF-7 cells also activated normal fibroblast cells to cancer associated fibroblasts. Taken together, above findings suggest that 15d-PGJ2 induces EMT through up-regulation of Snail expression and subsequent production of CXCL8 as a putative activator of fibroblasts, which may contribute to tumor-stroma interaction in inflammatory breast cancer microenvironment.

Mechanisms and Treatment of Light-Induced Retinal Degeneration-Associated Inflammation: Insights from Biochemical Profiling of the Aqueous Humor.

Ocular inflammation contributes to the pathogenesis of blind-causing retinal degenerative diseases, such as age-related macular degeneration (AMD) or photic maculopathy. Here, we report on inflammatory mechanisms that are associated with retinal degeneration induced by bright visible light, which were revealed while using a rabbit model. Histologically and electrophysiologically noticeable degeneration of the retina is preceded and accompanied by oxidative stress and inflammation, as evidenced by granulocyte infiltration and edema in this tissue, as well as the upregulation of total protein, pro-inflammatory cytokines, and oxidative stress markers in aqueous humor (AH). Consistently, quantitative lipidomic studies of AH elucidated increase in the concentration of arachidonic (AA) and docosahexaenoic (DHA) acids and lyso-platelet activating factor (lyso-PAF), together with pronounced oxidative and inflammatory alterations in content of lipid mediators oxylipins. These alterations include long-term elevation of prostaglandins, which are synthesized from AA via cyclooxygenase-dependent pathways, as well as a short burst of linoleic acid derivatives that can be produced by both enzymatic and non-enzymatic free radical-dependent mechanisms. The upregulation of all oxylipins is inhibited by the premedication of the eyes while using mitochondria-targeted antioxidant SkQ1, whereas the accumulation of prostaglandins and lyso-PAF can be specifically suppressed by topical treatment with cyclooxygenase inhibitor Nepafenac. Interestingly, the most prominent antioxidant and anti-inflammatory benefits and overall retinal protective effects are achieved by simultaneous administrating of both drugs indicating their synergistic action. Taken together, these findings provide a rationale for using a combination of mitochondria-targeted antioxidant and cyclooxygenase inhibitor for the treatment of inflammatory components of retinal degenerative diseases.

Atf3 negatively regulates Ptgs2/Cox2 expression during acute inflammation

By generating prostaglandins, cyclooxygenase-2 (Cox-2/Ptgs2) plays a critical role in regulating inflammatory responses. While several inflammatory stimuli have been shown to increase Ptgs2 expression, less is known about how the transcription of this gene is terminated. Here we show that stimulation of macrophages with yeast zymosan, a TLR2/6 and dectin-1 agonist, causes a transient increase in the expression of Ptgs2 accompanied by a simultaneous increase in the expression of the transcriptional repressor, activating transcription factor-3 (Atf3). The expression of Ptgs2 was significantly higher in resident peritoneal macrophages isolated from Atf3−/− mice than that from Atf3+/+ mice and was associated with higher prostaglandin production upon stimulation with zymosan. In activated macrophages, Atf3 accumulated in the nucleus and chromatin-immunoprecipitation analysis showed that Atf3 is recruited to the Ptgs2 promoter region. In acute peritonitis and in cutaneous wounds, there was increased leukocyte accumulation and higher levels of prostaglandins (PGE2/PGD2) in inflammatory exudates of Atf3−/− mice compared with WT mice. Collectively, these results demonstrate that during acute inflammation Atf3 negatively regulates Ptgs2 and therefore dysregulation of this axis could potentially contribute to aberrant Ptgs2 expression in chronic inflammatory diseases. Moreover, this axis could be a new therapeutic target for suppressing Ptgs2 expression and the resultant inflammatory responses.

Abstract 3591: 15-Deoxy-Δ12,14-prostaglandin J2-induced epithelial-to-mesenchymal transition in human breast cancer cells promotes fibroblast activation

Abstract In inflammation-associated carcinogenesis, cyclooxygenase-2 (COX-2) is markedly overexpressed, resulting in accumulation of various prostaglandins. 15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) and prostahlandin E2 (PGE2) are the predominant COX-2-derived prostaglandins (PGs) with oncogenic potential. In the present study, we examined the effects of these to PGs on epithelial-to-mesenchymal transition (EMT), a process by which epithelial cells lose their cell polarity and cell-cell adhesion, and gain migratory and invasive properties. 15d-PGJ2 induced EMT to a greater than PGE2 in human breast cancer (MCF-7) cells. Snail and ZEB1 are known to bind to the E-boxes present in the E-cadherin promoter, thereby repressing E-cadherin transcription. Treatment of MCF-7 cells with 30 μM of 15d-PGJ2 increased the expression of Snail and ZEB1, followed by the down-regulation of E-cadherin. Nuclear extract from 15d-PGJ2-treated MCF-7 cells showed the binding of Snail and ZEB1 to E-box sequences in the E-cadherin promoter. In addition, among various cytokines/chemokines examined, the mRNA level of interleukin-8 (CXCL8) was highly elevated in 15d-PGJ2-stimulated MCF-7 cells. 15d-PGJ2-induced up-regulation of CXCL8 expression was abrogated by the introduction of Snail short interfering RNA. These findings suggest that CXCL8 may function as a positive regulator of EMT in 15d-PGJ2-treated MCF-7 cells. Moreover, the addition of conditioned medium of MCF-7 cells undergoing EMT activates normal fibroblast cells to cancer-associated fibroblasts (CAFs). Co-culture of normal fibroblasts with 15d-PGJ2-treaed-MCF-7 cells also induced the expression of α-SMA and FAPα, representative markers of CAFs. As a corresponding receptor of CXCL8, CXCR2 was overexpressed in activated fibroblasts co-cultured with 15d-PGJ2-treated MCF-7 cells. Unlike 15d-PGJ2, its non-electrophilic analogue 9,10-dihydro-15d-PGJ2 failed to induce EMT, suggesting that the α,β-unsaturated carbonyl group located in the cyclopentenone ring of 15d-PGJ2 is essential for EMT induction. Notably, activation of Rho kinase through direct binding of ArhGEF5, a guanine nucleotide exchange factor, with 15d-PGJ2 seems to contribute to the EMT induction. Taken together, above findings suggest that 15d-PGJ2 induces EMT through up-regulation of Snail expression and subsequent production of CXCL8 which may contribute to increased EMT of human breast cancer cells. Citation Format: Do-Hee Kim, Jeehye Choi, Jin-Young Suh, Hye-Kyung Na, Young-Joon Surh. 15-Deoxy-Δ12,14-prostaglandin J2-induced epithelial-to-mesenchymal transition in human breast cancer cells promotes fibroblast activation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3591. doi:10.1158/1538-7445.AM2014-3591

The Multidrug Resistance-Associated Protein 4 (MRP4) Appears as a Functional Carrier of Prostaglandins Regulated by Oxytocin in the Bovine Endometrium

Prostaglandins (PG) are involved in several female reproductive processes, and their action is regulated at the levels of biosynthesis, catabolism, and signal transduction. Facilitated transport across cell membranes emerges as an additional checkpoint regulating PG action. We have already reported on the influx transporter solute carrier organic anion transporting polypeptide (SLCO2A1) [PG transporter (PGT)] in relation to PG action in the bovine endometrium. In the present study, we report on the functional expression and regulation of multidrug resistance-associated protein 4 (MRP4)/ATP-binding cassette carrier 4, an alternate PG transporter belonging to the ATP-binding cassette carrier (ABC) family. We have found that MRP4 protein was present throughout the estrous cycle and exhibited a pattern of expression similar to that of PGT with maximal expression during early-mid luteal phase in the bovine endometrium. Functional expression and regulation of MRP4 was studied in vitro using the newly developed bovine endometrial epithelial bEEL and stromal CSC cell lines. Oxytocin (OT) stimulated PGF2α production and MRP4 mRNA and protein in a time- and dose-dependent manner but had no effect on PGT. OT induced preferred accumulation of PG outside the cells and secretion toward the basolateral side of polarized bEEL cells grown on membrane inserts. MK-571 and indomethacin, two documented inhibitors of MRP4 activity, blocked preferred accumulation of PG, but interferon-τ and NS-398 had no effect on MRP4 expression or the direction of PG transport. Our results suggest that MRP4 is a functional PG carrier under the regulation of OT in the bovine endometrium.

Non-targeted metabolite profiling in activated macrophage secretion

Periodontal diseases are inflammatory infectious diseases that affect the periodontal tissue. Macrophages play a central role in inflammatory conditions, leading to the destruction of tissues. Identifying the signaling molecules secreted by macrophages would be valuable to the study of these diseases. Here, we present non-targeted analysis using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) for the profiling of extracellular metabolites released during macrophage activation. Lipopolysaccharide (LPS)-induced activation of a mouse macrophage-like cell line RAW264.7 was used as a model system. Cells were treated without (control) or with LPS for 22 h and, after washing, were incubated for 1 h in phosphate-buffered saline. The accumulation of metabolites in the culture supernatant was monitored. LPS treatment significantly enhanced the accumulation of prostaglandins, tumor necrosis factor-α, nitric oxide and citrulline in the culture medium. RAW264.7 cells produced 46 metabolites and 66% of these showed significant changes (P < 0.05) following cell activation. In particular, the production of leucine, hypoxanthine, choline, putrecine, N 8-acetylspermidine, succinate, itaconate, and 4-methyl-2-oxopentanoate was significantly increased by cell activation (P < 0.001). Significantly elevated production of lactate and glycine was also observed. Here, we present the first catalog of the up and down-regulation of the various metabolites secreted by macrophages following inflammatory activation.

Identification of genetic factors associated with susceptibility to angiotensin-converting enzyme inhibitors-induced cough

Angiotensin-converting enzyme inhibitors (ACEi) are the first selected drugs for hypertensive patients because of its protective properties against heart and kidney diseases. Persistent cough is a common adverse reaction associated with ACEi, which can bind to the treatment cessation, but its etiology remains an unresolved issue. The most accepted mechanism is that the inhibition of ACEi increases kinins levels, resulting in the activation of proinflammatory mechanisms and nitric oxide generation. However, relatively little is known about the genetic susceptibility to ACEi-induced cough in hypertensive patients. We carried out a monogenic association analysis of 39 polymorphisms and haplotypes in genes encoding key proteins related to ACEi activity with the occurrence of ACEi-induced cough. We also carried out a digenic association analysis and investigated the existence of epistatic interactions between the analyzed polymorphisms using a logistic regression procedure. Finally, we investigated the predictive value of the identified associations for ACEi-induced cough. We found that genetic polymorphisms in MME [rs2016848, P=0.002, odds ratio (OR)=1.795], BDKRB2 (rs8012552, P=0.012, OR=1.609), PTGER3 (rs11209716, P=0.002, OR=0.565), and ACE (rs4344) genes are associated with ACEi-related cough. For the latter, the effect is sex specific, having a protective effect in males (P=0.027, OR=0.560) and increasing the risk in females (P=0.031, OR=1.847). In addition, genetic interactions between peptidases involved in kinins levels (CPN1 and XPNPEP1) and proteins related to prostaglandin metabolism (PTGIS and PTGIR) strongly modify the risk of ACEi-induced cough presentation (0.102≤OR≤0.384 for protective combinations and 2.732≤OR≤7.216 for risk combinations). These results are consistent with the hypothesis that the mechanism of cough is related to the accumulation of bradykinin, substance P, and prostaglandins.

Prostaglandin dehydrogenase (PGDH) in granulosa cells of primate periovulatory follicles is regulated by the ovulatory gonadotropin surge via multiple G proteins

The ovulatory gonadotropin surge increases granulosa cell prostaglandin synthesis as well as prostaglandin dehydrogenase (PGDH), the key enzyme responsible for prostaglandin metabolism. To investigate gonadotropin regulation of PGDH in the primate follicle, monkey granulosa cells were obtained across the 40-h periovulatory interval. PGDH activity was low before the ovulatory hCG stimulus, peaked 12–24 h after hCG, and was low again 36 h after hCG administration. Granulosa cells maintained in vitro with hCG showed a similar temporal pattern of PGDH. The LH/CG receptor can utilize multiple signaling pathways to regulate intracellular events. Gonadotropin-stimulated cAMP appears to act primarily via the Epacs to increase PGDH mRNA, protein, and activity. In contrast, PLC activation of PKC likely decreases PGDH mRNA, protein, and activity late in the periovulatory interval. Increased, then decreased PGDH activity may delay accumulation of prostaglandins in the follicle until late in the periovulatory interval, contributing to timely ovulation in primates.

Effects of Zofenopril and Ramipril on Cough Reflex Responses in Anesthetized and Awake Rabbits

Cough is the most common symptom reported by patients in a primary care setting and is one of the most frequent secondary effects recorded during treatment with angiotensin-converting enzyme (ACE) inhibitors. The aim of the current study was to analyze potential differences in cough induction between 2 structurally different ACE inhibitors, namely zofenopril, which has a sulphydryl moiety, and ramipril, which has a carboxyl moiety. The cough reflex was induced by chemical (citric acid) and/or mechanical stimulation of the tracheobronchial tree in awake and anesthetized rabbits. Intravenous injection of the active compounds of the 2 ACE inhibitors, zofenoprilat (288 nmol/kg) and ramiprilat (129 nmol/kg), caused similar hypotensive effects in anesthetized rabbits. None of the studied cough-related variables changed in response to ACE inhibitor administration, with the exception of the number of coughs. Ramiprilat, but not zofenoprilat, increased the cough response induced by both mechanical and chemical stimulation (1 mol/L citric acid aerosol) of the tracheobronchial tree. In awake animals, zofenoprilat- or vehicle-treated rabbits did not show any significant changes in the number of coughs induced by 1 mol/L citric acid aerosol compared to their respective basal values (from 15.2 ± 2.3 to 13.1 ± 1.3 and from 16.1 ± 4.9 to 15.8 ± 4.3, respectively). Conversely, ramiprilat resulted in a significant increase in the number of coughs (from 21.1 ± 2.6 to 34.9 ± 3.5; P < .01). These findings confirm that there are differences in the cough potentiation effect induced by different ACE inhibitors. The low rate of cough seen with zofenoprilat may be related to its ability to induce a lower accumulation of bradykinin and prostaglandins at the lung level.

Lipid mediator interplay: resolvin D1 attenuates inflammation evoked by glutathione‐conjugated lipid peroxidation products

Non-enzymatic oxidation of cellular lipids, one of the characteristic features of inflammation, leads to formation of highly reactive and toxic alpha,beta-unsaturated aldehydes, such as 4-hydroxy-trans-2-nonenal (HNE). Conjugation of HNE with reduced glutathione (GS-HNE) is widely believed to represent a form of detoxification. The study by Spite et al. in the current issue of the British Journal of Pharmacology shows that glutathiolation of HNE confers potent pro-inflammatory properties on this alpha,beta-unsaturated aldehyde. They find that GS-HNE directly activates human neutrophil granulocytes in vitro and evokes peritonitis in mice. Pre-treatment with resolvin D1, which is derived from omega-3 fatty acids, markedly attenuated the peritoneal leukocyte accumulation and production of prostaglandins and leukotrienes induced by GS-HNE. Their findings have profound implications for the analysis of inflammation in describing the generation of a novel class of pro-inflammatory mediators, through glutathione-dependent metabolism of lipid-peroxidation products, and emphasize the therapeutic potential of resolvin D1 in inflammatory diseases.

Cough induced by losartan with resolution after substitution with enalapril

Introduction: Cough is an adverse event associated with the angiotensin-converting enzyme (AA inhibitor drugs. ACE inhibitor-induced cough is believed to be related to the accumulation of bradykinin,substance P,and prostaglandins resulting from the inhibition of ACE.Angiotensin-receptor blockers (AARBs) do not have any effect on ACE and theoretically might not cause cough. Therefore, a proposed option in patients suffering with ACE inhibitor -induced cough is to try an ARB.However,this report describes the reverse: a case of lo osarta an-iin nduced cough th hat co om mple etely resolved after it was substituted with an ACE inhibitor, enalapril. Case summary: A 23-yyear-oold, nonsmoking white woman, weighing 73.55 kg,ACE inhibitor naive (before admission),presented to the emergency department at Imam Referral Hospital,Tehran, Iran,with hypertension,proteinuria, and hyperlipidemia.The patient was admitted to the nephrology ward.She was prescribed hydrochlorothiazide 12.55 mg/dd, furosemide 20 mg BID,and simvasta atin 20 mg/dd. The patient had no respiratory illnesses. The patient experienced cough 3 days following the initiation of losartan treatment.The cough continued in this patient for the 2-week dura atio on of lo osarta an treatm ment; however, 1 week after substitution of losartan with enalapril (22.5 mg/dd),the cough resolved completely. Conclusion: This report describes a young woman who developed cough while receiving losartan treatment,which resolved after substitution with the ACE inhibitor enalapril.

Peroxisome proliferator-activated receptor (PPAR) expression in cultured bovine endometrial cells and response to omega-3 fatty acid, growth hormone and agonist stimulation in relation to series 2 prostaglandin production

The peroxisome proliferator-activated receptors (PPARs) are a family of nuclear transcription factors thought to act as receptors for polyunsaturated fatty acids and to reduce production of series 2 prostaglandins (PG). The objectives of the current study were to characterize PPAR expression and the prostaglandin synthetic activity of cultured bovine endometrial cells in response to known PPAR ligands, as well as to key stimulators and inhibitors of series 2 prostaglandin secretion. PPARα and PPARδ, but not PPARγ, mRNAs are expressed in the BEND cell line regardless of treatment. Under resting conditions, PPARα mRNA levels increase in response to growth hormone ( P < 0.05). In cells stimulated with PdBu, growth hormone depresses PPARα mRNA levels, regardless of whether cells also are treated with IFNτ. In contrast, PPARδ mRNA levels are increased by exposure to PdBu, eicosapentanoic acid and IFNτ, and these effects are additive. PPAR mRNA levels are not predictive of prostaglandin accumulation. Agonist activation of PPARα, PPARδ or PPARγ augments PdBu-induced increases in prostaglandin H synthase-2 mRNA and media accumulation of prostaglandins F 2α and E 2. Treatment with the PPARα/δ agonist carbaprostacyclin, but not the PPARα agonist Wy14643 or PPARγ agonist ciglitazone, completely reverses the IFNτ suppression of prostaglandin synthesis. In conclusion, PPARα and PPARδ function in the response of bovine endometrium to growth hormone and long chain omega-3 polyunsaturated fatty acids.

In vitro evaluation of Bacopa monniera on anti-Helicobacter pylori activity and accumulation of prostaglandins.

Bacopa monniera is an Indian tratidional medicine widely used to improve intellectual functions. Earlier, we had reported the prophylactic and curative effects of standardized extract of Bacopa monniera (BME) in various gastric ulcer models. The effect was due to augmentation of the defensive mucosal factors like increase in mucin secretion, life span of mucosal cells and gastric antioxidant effect rather than on the offensive acid-pepsin secretion. The present study includes evaluation of standardized BME (bacoside A content--35.5 +/- 0.9) on other contributing factors towards ulcerogenesis. BME in the dose of 1000 microg/ml showed anti-Helicobacter pylori activity in vitrol and in the dose of 10 microg/ml increased in vitro of prostanoids (PGE and PGI2) in human colonic mucosal incubates. It may be concluded that these factors may contribute to antiulcerogenic activity of BME.

Abnormal Uterus with Polycysts, Accumulation of Uterine Prostaglandins, and Reduced Fertility in Mice Heterozygous for Acyl-CoA Synthetase 4 Deficiency

Arachidonate released by various stimuli is rapidly reesterified into membrane phospholipids initiated by acyl-CoA synthetase (ACS) and subsequent acyl-transfer reactions. ACS4 is an arachidonate-preferring enzyme abundant in steroidogenic tissues and postulated to modulate eicosanoid production. Female mice heterozygous for ACS4 deficiency become pregnant less frequently and produce small litters with extremely low transmission of the disrupted alleles. Striking morphological changes, including extremely enlarged uteri and lumina filled with numerous proliferative cysts of various sizes, were detected in ACS4+/− females. Furthermore, marked accumulation of prostaglandins was seen in the uterus of the heterozygous females. These results indicate that ACS4 modulates female fertility and uterine prostaglandin production.

Molecular basis for treating endometriosis with aromatase inhibitors.

Although treatment of one unusually aggressive case of postmenopausal endometriosis with an aromatase inhibitor has been strikingly successful, large clinical trials are required to establish whether aromatase inhibitors will have a significant role in the medical management of endometriosis. Introduction of aromatase inhibitors into the treatment of endometriosis underscores the importance of basic research leading to the development of novel strategies in reproductive disorders. It was shown earlier that aromatase activity was not detectable in normal endometrium. Aromatase, however, is expressed inappropriately in endometriosis and stimulated by prostaglandin E2. Aromatase activity gives rise to local biosynthesis of oestrogen, which, in turn, stimulates prostaglandin E2 production, thus establishing a positive feedback cycle. This favours accumulation of oestrogen and prostaglandins in endometriosis, which is an inflammatory disorder dependent on oestrogen for growth.

Renin Angiotensin System Antagonists and Anesthesia

R enin angiotensin system (RAS) antagonists, angiotensin-converting enzyme (ACE) inhibitors, and angiotensin II receptor antagonists are increasingly used to treat cardiovascular and other diseases (1–6). These treatments induce a blockade of the RAS that may affect hemodynamics during anesthesia and surgery. In 1978, Miller et al. (7) reported that the RAS is involved in maintaining normal blood pressure during anesthesia. Although anesthesia is not invariably associated with a deleterious hemodynamic event in RAS-blocked patients (8–10), hemodynamic instability, described as unexpected episodes of hypotension, have been reported (11–13). Otherwise, stresses such as surgery or hypotension stimulate the generation of angiotensin II, which induces vasoconstriction (14) to maintain blood pressure but reduces blood flow to organs such as the kidneys and bowels. Accordingly, an angiotensin II-induced reduction in blood flow may contribute to acute renal failure (15) and splanchnic ischemia (16), which are obvious factors in postoperative morbidity (17). RAS blockade with ACE inhibitors decreases some consequences of the stress response on the regional circulation (9,18,19), which may then contribute to body protection. Much of the information regarding the physiology and pathophysiology of the RAS during anesthesia and surgery is based on the effects of ACE inhibitors. Because ACE inhibitors probably act mostly by blocking the RAS, similar effects should be obtained from angiotensin (AT) receptor antagonists. RAS antagonist pharmacology may help us to understand the hemodynamic risk of anesthesia in RAS-blocked patients, to identify predisposing factors, and to determine the potential benefit of RAS antagonists during anesthesia and surgery. Physiology of the RAS Generation of Angiotensin II

Activation and inactivation of cyclo-oxygenase in rat alveolar macrophages by aqueous cigarette tar extracts

Cyclo-oxygenase (COX) activity and its level of expression, the release of arachidonic acid (AA), and the accumulation of prostaglandins (PGs) were determined in isolated rat pulmonary alveolar macrophages (PAM) exposed to aqueous cigarette tar (ACT) extracts. COX activity increased 3-fold above the initial activity within 2 h of incubation with ACT extracts and gradually decreased below the initial activity after 8 h of incubation. The increased COX activity after 2 h of incubation did not lead to increased accumulation of PGE 2. Accumulated levels of PGE 2 increased dramatically after 12 h of incubation despite decreased COX activity in cells incubated with ACT extracts. This increased accumulation of PGE 2 was greater in cells derived from vitamin E deficient rats compared with control rats. Release of AA from cells was dramatically increased in cells incubated with ACT extracts in parallel to PG accumulation. Thus increased accumulation of PGE 2 despite decreased COX activity after 12 h of incubation is likely the result of increased substrate availability. These results suggest that, contrary to earlier reports, cigarette smoke stimulates the formation of PGs in alveolar macrophages. Increased PG production may lead to suppressed immune response and enhanced risk of tumorigenesis in smokers’ lungs.

Mechanism of Prostaglandin E2 Transport across the Plasma Membrane of HeLa Cells and Xenopus Oocytes Expressing the Prostaglandin Transporter “PGT”

We recently identified a novel prostaglandin transporter called PGT (Kanai, N., Lu, R., Satriano, J. A., Bao, Y., Wolkoff, A. W., and Schuster, V. L. (1995) Science 268, 866-869). Based on initial functional studies, we have hypothesized that PGT might mediate the release of newly synthesized prostaglandins (PG), epithelial transport of PGs, or metabolic clearance of PGs. Here we examined the mechanism of PGT transport as expressed in HeLa cells and Xenopus oocytes, using isotopic PG influx and efflux studies. In both native HeLa cells and oocytes, cell membranes were poorly permeable to PGs. In contrast, in oocytes injected with PGT mRNA, the PG influx permeability coefficient was 90-157 times that of oocytes injected with water. The rank order substrate profile was PGF2alpha approximately PGE2 > TXB2 >> 6 keto-PGF1alpha. PG influx displayed an overshoot with rapid accumulation of tracer PGE2, followed by a gradual return to baseline. Based on estimated oocyte volumes, the PGT-mediated accumulation of PGE2 reached steady state at intra-oocyte concentrations 25-fold higher than the external media. The accumulation of PG was not due to intracellular binding or metabolism. PGT-mediated uptake was ATP- and temperature-dependent, but not sodium-dependent, and was inhibited by disulfonic stilbenes, niflumic acid, and the thiol reactive anion MTSES (Na(2-sulfonatoethyl)methanethiosulfonate). [3H]PGE2 efflux from PGT-transfected HeLa cells was stimulated by external (trans) PGE2 in a dose-dependent fashion and was inhibited by bromcresol green and 4,4'-diisothiocyanatostilbene-2,2'-disulfonate. Membrane depolarization inhibited uptake of [3H]PGE2, consistent with a model of net outward movement of negative charge during the translocation event. These findings suggest that PGT mediates [3H]PGE2 accumulation via obligatory, electrogenic anion exchange.

Membrane phospholipid alterations in Alzheimer's disease: deficiency of ethanolamine plasmalogens.

The ethanolamine plasmalogens are decreased whereas serine glycerophospholipids are significantly increased in plasma membrane phospholipid in affected regions of brain in Alzheimer's disease. This may be due to stimulation of Ca(2+)-independent plasmalogen-selective phospholipase A2 which was recently discovered in brain. This phospholipase A2 differs from other Ca(2+)-independent phospholipases A2 in response to ATP and various inhibitors. It may be responsible for excess release of arachidonic acid and accumulation of prostaglandins and lipid peroxides in AD. Accumulation of the above lipid metabolites due to abnormal receptor function and signal transduction may contribute to neurodegeneration in AD.

ACE inhibitor-induced cough and bronchospasm. Incidence, mechanisms and management.

A dry, tickly and often bothersome cough is the most common adverse effect of ACE inhibitors. Recent studies indicate that cough may develop in around 10% of the patients treated with ACE inhibitors. In half of these patients, the ACE inhibitor has to be discontinued. Cough has emerged as a class effect occurring with all ACE inhibitors with no clear difference between the single substances. While ACE inhibition is safe in the vast majority of patients with obstructive airways disease, asthmatic symptoms or exacerbation of asthma as well as a rise in bronchial reactivity have been occasionally reported. ACE inhibition increases the cough reflex. The mechanisms underlying ACE inhibitor-induced cough are probably linked to suppression of kininase II activity, which may be followed by an accumulation of kinins, substance P and prostaglandins. Physicians should be aware that a dry cough is the most common adverse effect of ACE inhibitors and that this symptom may occur not necessarily shortly after institution of therapy but months or even a year later. Replacement by another ACE inhibitor should not be tried, since the cough will almost always recur on rechallenge with the same or another ACE inhibitor. After withdrawal of the ACE inhibitor, which is the treatment of choice, cough will resolve usually within a few days.