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Biomedical subjects

A M Mayer

Publications and source records attributed to A M Mayer.

At least 37 records · Page 2Linked to original sources
PubMed1996

Pharmacological targeting of signaling pathways in protein kinase C-stimulated superoxide generation in neutrophil-like HL-60 cells: effect of phorbol ester, arachidonic acid and inhibitors of kinase(s), phosphatase(s) and phospholipase A2.

The purpose of this investigation was to pharmacologically probe the signaling pathways thought to be involved in protein kinase C (PKC)-stimulated superoxide anion (O2-) generation in all-trans retinoic acid-treated human promyelocytic HL-60 cell line (HL-60), targeting PKC, mitogen-activated protein kinase (MAPK), MAPK kinase (MEK), protein serine-threonine phosphatase(s) (PSP), protein tyrosine kinase(s) (PTK) and phosphatase(s) (PTP), secretory phospholipase A2, cyclooxygenase (CO) and 5-lipoxygenase with selected inhibitors. The following agents inhibited phorbol 12-myristate 13-acetate-stimulated O2- generation significantly in the all-trans retinoic acid-treated HL-60 cells (expressed as percentage of control, P < .05): 1) PKC inhibitors: staurosporine (100 nM, 3 +/- 1%); Ro 31-8220 (1 microM, 3 +/- 2%); sphingosine (100 microM, 15 +/- 7%); 2) PSP 1 and 2a inhibitors, okadaic acid (10 microM, 35 +/- 1%); calyculin A (10 microM, 73 +/- 1%); 3) MAPK inhibitor: SB-203580 (100 microM, 62 +/- 1%); 4) PTP inhibitors: phenylarsine oxide (1 microM, 12 +/- 9%); diamide (1 mM, 21 +/- 11%); and 5) secretory phospholipase A2 inhibitors: manoalide (1 microM, 24 +/- 10%); scalaradial (1 microM, 11 +/- 4%). Exogenously added arachidonic acid-stimulated O2- generation in a time- and dose-dependent manner. The following inhibitors enhanced or did not significantly affect phorbol 12-myristate 13-acetate-stimulated O2- generation (expressed as percentage of control): 1) PTK inhibitors: genistein (100 microM, 69 +/- 12%); CGP 53716 (100 microM, 67 +/- 10%); herbimycin A (10 microM, 67.4 +/- 1%); 2) PSP 2b inhibitors: cyclosporin A (30 microM, 71 +/- 5%); FK506 (30 microM, 88 +/- 7%); 3) CO inhibitor: indomethacin (100 microM, 111 +/- 12%); 4) 5-lipoxygenase inhibitor: WY 50,295 (100 microM, 140 +/- 23%); 5) MEK inhibitor: PD98059 (100 microM, 94 +/- 6.7%); and 6) the PTP inhibitor: orthovanadate (100 microM, 131 +/- 25%). Our pharmacological study suggests that, in neutrophil-like HL-60 cells, the signaling pathways leading to PMA-stimulated O2- generation appear to involve PKC, MAPK, phospholipase A2, arachidonic acid, PSP 1 and 2a and PTP. Furthermore, PTK, MEK, CO, 5-lipoxygenase and PSP 2b do not appear to participate in the modulation of PKC-stimulated O2- generation.

Arachidonic Acid↗
PubMed1995

Modulation of superoxide generation in in vivo lipopolysaccharide-primed rat alveolar macrophages by arachidonic acid and inhibitors of protein kinase C, phospholipase A2, protein serine-threonine phosphatase(s), protein tyrosine kinase(s) and phosphatase(s).

Ninety minutes after i.v. injection of Escherichia coli lipopolysaccharide (LPS) (1 mg/kg) into rats, phorbol 12-myristate 13-acetate (PMA)-stimulated superoxide anion (O2-) secretion was enhanced in suspensions of in vivo LPS-treated alveolar macrophages (AM phi) when compared with saline (SAL)-treated AM phi. The purpose of this investigation was to dissect the in vitro mechanism of PMA-stimulated O2- generation in both LPS and SAL-treated rat AM phi, with a panel of inhibitors of protein kinase C (PKC), protein serine-threonine phosphatase(s) (PSP), protein tyrosine kinase(s) (PTK) and phosphatase(s) (PTP), phospholipase A2 (PLA2), cyclooxygenase (CO) and 5-lipoxygenase (5-LO). The following agents blocked PMA-stimulated O2- generation in both LPS- and SAL-treated AM phi (expressed as percentage of control): 1) PKC inhibitors: staurosporine: 100 nM, 7.0% (LPS) and 5.6% (SAL); sphingosine: 10 microM, 21% (LPS) and 10.5% (SAL); 2) PTK inhibitor: genistein: 100 microM, 44% (LPS) and 31% (SAL); 3) PTP inhibitors: phenylarsine oxide, 10 microM, 12.1% (LPS) and 18% (SAL); diamide, 1000 microM, 10.1% (LPS) and 10.5% (SAL); and 4) PLA2 inhibitors: manoalide: 1 microM, 29.3% (LPS) and 5.2% (SAL); scalaradial: 1 microM, 7.7% (LPS) and 7.1% (SAL); and WAY 125,984: 10 microM, 17.1% (LPS) and 14.5% (SAL). In addition, it was observed that exogenously added arachidonic acid (AA)-stimulated O2- generation in a time- and dose-dependent manner in both LPS and SAL-treated AM phi. The following inhibitors enhanced or did not affect PMA-stimulated O2- generation in LPS- and SAL-treated AM phi (expressed as percentage of of control): 1) PSP inhibitors: okadaic acid: 0.5 microM, 117% (LPS) and 153% (SAL); calyculin A: 1 microM, 112% (LPS) and 101% (SAL); 2) CO and 5-LO inhibitors: indomethacin: 10 microM, 107% (LPS) and 90% (SAL); WY 50, 295: 1 microM, 99% (LPS) and 103% (SAL); and 3) the PTP inhibitor orthovanadate upon prolonged preincubation. In both in vivo LPS- or SAL-primed AM phi, PMA-stimulated O2- generation appears to be modulated by PKC, PLA2, AA, PTK, PTP and PSP. No modulatory role was evident for either CO or 5-LO metabolites. These findings might bear on the design of therapeutic approaches for the modulation of O2- release by AM phi in the early stages of sepsis and adult respiratory distress syndrome.

Animals↗
PubMed1994

Functional characterization of peripheral circulating and liver recruited neutrophils in endotoxic rats.

Neutrophil accumulation in tissue is a hallmark of inflammation and is associated with a variety of pathological conditions. In bacterial infection neutrophils are selectively attracted in large numbers to phagocytose and kill invading microorganisms. However, activated neutrophils can also cause injury to tissues. To investigate functional alterations in liver recruited neutrophils (PMNs), we studied the functional characteristics of circulating blood and liver sequestered PMNs in terms of host defense mechanisms, such as nitric oxide (NO) and superoxide (SO) generation, beta 2 integrin expression, phagocytosis, and eicosanoid profile. Cells were isolated from rats infused with a nonlethal dose (320 micrograms/kg) of E. coli endotoxin (ET) or pyrogen-free saline for 90 min. Liver PMNs produced significantly more NO both in the absence and in the presence of an in vitro endotoxin challenge than did blood PMNs. No significant difference was observed in phorbol myristate acetate-stimulated SO generation. Endotoxin infusion significantly up-regulated the expression of CD11b/c in circulating and even more so in liver PMNs. Phagocytosis was significantly enhanced by in vivo ET treatment in blood PMNs, and liver PMNs showed even greater phagocytic activity than blood PMNs or Kupffer cells. The percent distribution of prostaglandins D2 and E2 of total 14C-eicosanoids was significantly higher and that of thromboxane B2 and 5-, 12-, and 15-HETEs was significantly lower in liver than in blood PMNs. Our study demonstrates several functional differences between liver-recruited and circulating PMNs in an acute endotoxic model. The implications of altered neutrophil function may extend to mechanisms of host defense and hepatotoxicity associated with sepsis and endotoxemia.

Amino Acid Oxidoreductases↗
PubMed1994

Prohormone convertases PC2 and PC3 in rat neutrophils and macrophages. Parallel changes with proenkephalin-derived peptides induced by LPS in vivo.

Prohormone- or proneuropeptide-converting enzymes PC2 and PC3 have been observed exclusively in nervous and endocrine tissues. In this work the presence of these enzymes in cells of the immune system was demonstrated. PC2 was detected in peripheral and liver-infiltrating polymorphonuclear leukocytes (PMN) but not in alveolar macrophages (AM) or spleen mononuclear cells (SMC). PC2 proteins corresponded to 75, 71 and 56 kDa forms. PC3 appeared in AM and SMC but not in PMN, and a 66 kDa protein was the only PC3 form detected. Proenkephalin-derived peptides (PENKp) were observed in PMN and AM, showing peptides of 35, 28, 21, 18 and 14 kDa in the former cells and a doublet of 35 and 32 kDa in the latter. PC2 proteins and PENKp decreased in liver PMN and peripheral PMN 90 min after intravenous (i.v.) infusion of LPS, suggesting an increased release. However, in vitro assays showed that the chemotactic peptide FMLP but not LPS increased the basal secretion of PC2 proteins and PENKp in PMN. These results indicate that PC2 proteins are released from PMN, together with PENKp, and suggest that LPS in vivo may act through an indirect mechanism. Low levels of PC3 and PENK were detected in the AM of rats treated for 90 min with SAL or LPS. However, a significant increase of PC3 and PENKp appeared 30 h after LPS infusion. These results show for the first time that PC2 and PC3 are differentially expressed in PMN and AM, respectively, which were paralleled by the presence of different post-translational products of PENK. In addition, the in vivo effect of LPS on PC2, PC3 and PENKp levels in PMN and AM resembles the effect of LPS on prohormone levels in endocrine tissues, suggesting that similar mechanisms may control the turnover of PENK in endocrine and in these immune cells.

Animals↗
PubMed1994

Antitumor and cytotoxic screen of 5,6,7-trisubstituted flavones from Gomphrena martiana.

An in vivo antitumor screening of extracts of Gomphrena martiana indicated positive activity in the petroleum ether extract, and its further bioactivity-directed fractionation resulted in a lipophilic flavonoid fraction. Upon inoculation of various doses of 5,6,7-trisubstituted flavones on two murine tumor lines, Sarcoma 180 and Ehrlich's carcinoma, a decrease of tumor growth was observed. An in vitro KB cultured cell screen indicated cytotoxicity.

Animals↗
PubMed1994

Recycling unused medical supplies: a surgeon's response.

In Third World countries, there is a desperate need for basic medical supplies. Surgeons are responsible for a significant amount of medical waste in operating rooms, and much of that waste comes from partially used prepackaged sterile operative sets. In October 1992, InterVol established a regional pilot program in Rochester, N.Y., to test the feasibility of collecting unused medical supplies from area health-care facilities and shipping them to countries that need them. This project was designed to help hospitals dispose of reusable medical supplies while providing direct support to Third World hospitals and to medical teams that volunteer in Third World countries. In the process, a data base was created, which could be analyzed to find new ways of limiting unused materials that needed to be discarded. This project operated in four phases: (1) setup and education, (2) collection, (3) sorting and inventory, and (4) distribution. The program was proved to be effective and may serve as a model to help other communities establish similar programs.

Developing Countries↗
PubMed1994

Increased surface expression of CD11b/c and CD18 appears to be dissociated from anti-CD11b/c monoclonal antibody stimulated O2- anion generation in in vivo Escherichia coli lipopolysaccharide and tumor necrosis factor-alpha-treated rat neutrophils.

The purpose of this investigation was to determine the effect of anti-rat CD11b/c monoclonal antibody (MAb) on in vitro superoxide anion (O2-) generation in in vivo Escherichia coli lipopolysaccharide (LPS) and tumor necrosis-alpha (TNF)-treated rat polymorphonuclear leukocytes (PMN). After a continuous infusion of a nonlethal dose of E. coli LPS (.5 mg/kg) or TNF (6.0 x 10(5) units) into rats, PMN were recovered by centrifugal elutriation and discontinuous density gradient centrifugation from the liver (LPS-treated) and whole blood (LPS- and TNF-treated) and compared for CD11b/c, CD11a, and CD18 upregulation and their capacity for basal and agonist-stimulated O2- production. Immunofluorescence flow cytometry studies of rat whole blood PMN demonstrated that, upon LPS infusion, there was a time-dependent upregulation of CD11b/c and CD18, but not of CD11a. Similarly, TNF infusion upregulated CD11b/c although to a lesser degree. Stimulation of LPS- and TNF-treated PMN with phorbol 12-myristate 13-acetate (PMA), opsonized zymosan (OPZ), and anti-rat CD11b/c MAb triggered O2- generation. Although total O2- generated by OPZ and anti-rat CD11b/c MAb was less than that generated by PMA stimulation, the in vivo LPS- and TNF-induced beta 2 integrin upregulation did not result in a statistically significant enhancement of O2- generation with respect to normal saline-treated PMN. Our results do not appear to support the hypothesis that enhanced expression of CD11b/c or CD18 might be associated with enhanced in vitro anti-CD11b/c MAb-triggered O2- generation in LPS- and TNF-treated PMN in vivo.

Animals↗
PubMed1994

Import, targeting, and processing of a plant polyphenol oxidase.

A tomato (Lycopersicon esculentum L.) gene encoding a precursor of polyphenol oxidase (PPO) was transcribed and translated in vitro. The import, targeting, and processing of the [35S]methionine-labeled precursor protein (pPPO) were studied in isolated chloroplasts. The protein was routed to the thylakoid lumen in two steps. The 67-kD precursor was first imported into the stroma in an ATP-dependent step. It was processed to a 62-kD intermediate by a stromal peptidase. Translocation into the lumen was light dependent and involved processing of the 62-kD to the 59-kD mature form. The mature polypeptide was soluble in the lumen and not bound to thylakoids. This two-step targeting pattern was observed in plastids from a variety of plants including pea (Pisum sativum L.), tomato, and maize (Zea mays L.). The ratio between the intermediate and mature forms observed depended on the plant species, leaf age, growth conditions, and illumination regime to which the plants had been subjected. Cu2+ was not required for pPPO import or processing. Furthermore, low concentrations of Cu2+ (1-5 microM) markedly inhibited the first import step. Tentoxin specifically inhibited pPPO import, leaving the precursor bound to the envelope membrane. The two-step routing of pPPO into chloroplasts, typical of thylakoid lumen proteins, is consistent with the two-domain structure of the transit peptide and appears to be a feature of all plant PPO genes isolated so far. No evidence was found for unorthodox routing mechanisms, which have been suggested to be involved in the import of plant PPOs. The two-step routing may account for some of the multiplicity of PPO observed in vivo.

Amino Acid Sequence↗
PubMed1994

Modulation of superoxide generation in in vivo lipopolysaccharide-primed Kupffer cells by staurosporine, okadaic acid, manoalide, arachidonic acid, genistein and sodium orthovanadate.

Continuous infusion of a nonlethal dose of Escherichia coli lipopolysaccharide (LPS) into rats induced extravasation of mononuclear phagocytes into the liver and the priming of Kupffer cells for in vitro phorbol myristate acetate (PMA)-stimulated superoxide anion (O2-) release. The purpose of this investigation was to determine the role of protein kinase C (PKC), protein serine-threonine phosphatase(s) 1 and 2a, protein tyrosine kinase(s) and phosphatase(s), phospholipase A2 (PLA2), arachidonic acid (AA) and its cyclooxygenase (CO) and 5-lipoxygenase (5-LO) metabolites in the modulation of PMA-stimulated O2-generation in in vivo LPS-primed rat Kupffer cells. The following inhibitors blocked PMA-stimulated O2- generation in the absence (-AA) or presence of AA (+AA) (50 microM): 1) staurosporine, a putative PKC inhibitor (150 nM, 95% inhibition without AA, 88% inhibition with AA); 2) okadaic acid, a protein serine-threonine phosphatase inhibitor (2 microM, 65% inhibition with or without AA); 3) the marine PLA2 inhibitor manoalide (1 microM, 97.5% inhibition without AA, 75% with AA). In addition, it was observed that exogenously added AA enhanced PMA-stimulated O2- generation in a time- and dose-dependent manner (5-50 microM) and partially reversed the inhibitory effect of manoalide. The following inhibitors did not block PMA-stimulated O2- generation in the absence or presence of AA: 1) indomethacin, a CO inhibitor (1-100 microM) and WY-50,295M tromethamine, a novel 5-LO inhibitor (1-100 microM); 2) genistein, a protein tyrosine kinase inhibitor (1-100 microM); and 3) sodium orthovanadate (1-300 microM), a protein tyrosine phosphatase inhibitor. It was concluded that, in in vivo LPS-primed Kupffer cells, PMA-stimulated O2- generation is modulated by PKC, protein serine-threonine phosphatase(s), PLA2 and AA but not by protein tyrosine kinase(s) and phosphatase(s) and CO and 5-LO products. These findings could have implications on the design of novel therapeutic approaches for the modulation of enhanced O2- release by Kupffer cells in endotoxemia.

Alkaloids↗
PubMed1993

Hepatic neutrophil influx: eicosanoid and superoxide formation in endotoxemia.

We examined early changes, at 0.5, 1.5, and 3 hr of infusion of a nonlethal dose of Escherichia coli endotoxin (ET) in neutrophil (PMN) sequestration in the liver and accompanying alterations in [1-14C]arachidonic acid metabolism and superoxide anion release by Kupffer and endothelial cells and PMNs. One hundred fifty micrograms ET (268 micrograms/kg) was infused over 3 hr. Shorter infusions delivered proportionally less ET. By 30 min of ET infusion the number of PMNs in the 45 ml/min fraction was 2.41 x 10(7), eightfold higher than that in the NaCl-infused rats, representing 35.90 +/- 3.49% (n = 7) of the total cell yield vs 8.20 +/- 0.20% (n = 4) in NaCl controls. By 90 and 180 min of ET infusion the number of PMNs and their share of the total cell yield increased significantly further. Cells were separated by elutriation, followed by application of a Ficoll-Hypaque gradient, when appropriate. Kupffer cells and PMNs were recovered in the 45 ml/min fraction, endothelial cells in the 23 ml/min fraction. At 30 min of ET infusion the profile of arachidonic acid metabolites released from [1-14C]arachidonic acid-prelabeled nonparenchymal cells upon A23187 stimulation was not different from that of cells of NaCl-infused rats. Infusion of ET for 90 min accentuated PMN infiltration, and resulted in significant modulation of the eicosanoid profile, consisting of a major shift in PGD2/PGE2 to PGE2, and LTB4 and 12-HETE accounting for 34% of the total eicosanoids, compared to 12.9% in time-matched NaCL controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of in vivo TNF administration on superoxide production and PKC activity of rat alveolar macrophages.

After the intravenous injection of recombinant human tumor necrosis factor (TNF)-alpha (6.0 x 10(5) U) into rats, phorbol 12-myristate 13-acetate (PMA)-stimulated superoxide anion (O2-) secretion was enhanced in suspensions of alveolar macrophages (AM phi) compared with saline-treated controls. No enhancement of spontaneous, A23187-stimulated, or opsonized zymosan (OPZ)-stimulated O2- release was observed. Intratracheal injection of TNF-alpha (6.0 x 10(5) U) did not result in enhancement of spontaneous or A23187-, OPZ-, or PMA-stimulated O2- release. Although no TNF-alpha was detected in the bronchoalveolar lavage fluid, small quantities of TNF-alpha and/or other mediators secreted by polymorphonuclear leukocytes present in the lung capillaries, veins, and arteries may have leaked into the alveolar compartment and primed AM phi for enhanced PMA-stimulated O2- release. The respiratory burst in macrophages and neutrophils appears to be dependent on the translocation of protein kinase C. We have demonstrated protein kinase C translocation in both TNF-alpha- and saline-treated AM phi on PMA stimulation, although no differences were observed due to TNF-alpha treatment.

Animals↗
PubMed1993

Modulation of superoxide anion generation by manoalide, arachidonic acid and staurosporine in liver infiltrated neutrophils in a rat model of endotoxemia.

Early accumulation of polymorphonuclear leukocytes (PMN) in the liver after in vivo exposure to Escherichia coli lipopolysaccharide (LPS) and concomitant in vitro phorbol myristate acetate (PMA)-stimulated superoxide anion (O2-) generation has recently been described in a rat model of endotoxemia. The purpose of this investigation was to study the role of phospholipase A2 (PLA2), arachidonic acid (AA), its metabolites, and protein kinase C (PKC) in the mechanism of PMA-stimulated O2- generation of liver infiltrated PMN as compared to circulating blood PMN. Rat PMN were isolated after a 1.5-h infusion of saline or LPS from the blood (SAL-PMN) or the liver (LPS-PMN), respectively. The following results were observed in both SAL-PMN and LPS-PMN: 1) Inhibitors of cyclooxygenase (indomethacin) and 5-lipoxygenase [eicosatetraynoic acid, WY 50,295 tromethamine and VZ 65, 4-(11-hydroxy-1,9-undecadiin)-brenzcatechin] pathways did not inhibit O2- generation; 2) the potent marine PLA2 inhibitor Manoalide inhibited O2- generation in a dose-dependent manner (IC50 = 0.5 microM); 3) exogenously added AA enhanced PMA-stimulated O2- generation in a time- and dose-dependent manner and partially reversed the effect of Manoalide in LPS-PMN; 4) staurosporine, a putative PKC inhibitor, blocked PMA-stimulated O2- generation completely in the absence of AA and 79% in the presence of AA. It was concluded that LPS-induced liver sequestration of PMN does not alter the role PLA2, AA and PKC play in PMA-stimulated O2- generation. These findings should have implications on the design of novel therapeutic approaches for the modulation of O2- release in the pathogenesis of LPS hepatotoxicity.

Alkaloids↗
PubMed1991

Continuous infusion of Escherichia coli endotoxin in vivo primes in vitro superoxide anion release in rat polymorphonuclear leukocytes and Kupffer cells in a time-dependent manner.

Continuous infusion of a nonlethal dose of Escherichia coli lipopolysaccharide (LPS) (0.5 mg/kg) induced early (3 h) accumulation of polymorphonuclear leukocytes (PMNL) in rat liver followed by later (30 h) greater extravasation of mononuclear phagocytes (MNP) (E. B. Rodriguez de Turco and J. A. Spitzer, J. Leukocyte Biol. 48:488-494, 1990). Nonparenchymal liver cells from rats treated for 3 and 30 h with LPS were recovered by centrifugal elutriation, yielding a 23-ml/min fraction (endothelial cells) and a 45-ml/min fraction (PMNL, Kupffer cells, and MNP), and compared for their capacity for basal and agonist-stimulated superoxide (O2-) production. Stimulation with phorbol myristate acetate and opsonized zymosan caused a dose-dependent release of O2- from the 45-ml/min fraction derived from rats treated for 3 h with saline, but not from the 23-ml/min fraction. Further purification of the 45-ml/min fraction by discontinuous density gradient centrifugation into a Kupffer and a PMNL fraction revealed that most of the agonist-induced O2- release was generated by infiltrating PMNL at this early time point of LPS infusion. By 30 h of LPS infusion, although enhancement of the phorbol-12-myristate-13-acetate- and opsonized zymosan-stimulated release of O2- was observed in the 45-ml/min fraction, but not in the 23-ml/min fraction, the maximum release of O2- was smaller than that observed in the rats treated for 3 h. Our results support the following conclusions: (i) after a 3-h LPS infusion, PMNL found in the liver in increased numbers are also highly primed for agonist-stimulated release of O2-, while Kupffer cell priming is of a lesser extent; (ii) after a 30-h infusion of LPS, infiltrating MNP found in the liver in increased numbers are primed for agonist-induced O2- release, while priming of PMNL has diminished; (iii) at both 3 and 30 h of LPS infusion, liver endothelial cells are not significantly primed for agonist-stimulated O2- release; and (iv) in vivo priming by LPS infusion at both 3 and 30 h was not reversed by the experimental method used for cell recovery (ca. 3 h), thus suggesting that in vivo LPS priming of O2- release may ultimately lead to severe impairment of liver function and metabolism observed during endotoxemia and sepsis if not therapeutically blocked at an early time point.

Animals↗
PubMed1989

[Manoalide: a new phospholipase A2 inhibitor of marine origin with potential immunoregulatory effect].

Manoalide, a non-steroidal sesterterpenoid isolated from a marine sponge, is a potent analgesic and antiinflammatory compound. Manoalide inhibits phospholipase A2 from extracellular sources (snake venoms, bee, etc.), the release of arachidonic acid from rabbit polymorphonuclear leukocytes as well as calcium mobilization. This suggests that the anti-inflamatory effect might be caused by the regulation of eicosanoid biosynthesis. The macrophage plays a major role in the immune response and the inflammatory process, it has the capacity to synthesize and secrete arachidonic acid oxygenation products derived from both cyclooxygenase and lipoxygenase catalyzed pathways, and has been used extensively to study the effect of inhibitors of phospholipases, cyclooxygenase and lipoxygenase enzymes. Our results demonstrate that Manoalide modified the release of arachidonic acid and its further metabolism into prostaglandins and leukotrienes in mouse cultured peritoneal macrophages stimulated by phorbol myristate acetate, calcium ionophore A23187 and zymosan. Since eicosanoids have been shown to cause pain, we studied the possibility that the analgesic effect of Manoalide might be correlated with a decrease of eicosanoid release in vivo. The fact that Manoalide reduced both zymosan-induced peritoneal writhing in the mouse and the synthesis of both 6-keto-prostaglandin F1 alfa and leukotriene C4 suggests that the analgesic effect of Manoalide is at least in part linked to the inhibition of eicosanoid production in vivo. Since it has been shown that eicosanoids have immunoregulatory functions, a future possibility is that a phospholipase A2 inhibitor such as Manoalide may prove useful to investigate the biological role of eicosanoid metabolites on the immune function.

Animals↗
PubMed1988

Regulation of eicosanoid biosynthesis in vitro and in vivo by the marine natural product manoalide: a potent inactivator of venom phospholipases.

The marine natural produce manoalide has been reported to inactivate venom phospholipase A2 from several sources and phospholipase A2 from polymorphonuclear leukocytes. In this investigation, the regulation of eicosanoid production was studied both in an in vitro and in an in vivo model. The release of arachidonic acid and prostaglandin E2 was inhibited by manoalide when cultured mouse peritoneal macrophages were stimulated with phorbol myristate acetate (apparent IC50 = 0.23 microM), calcium ionophore A23187 (apparent IC50 = 0.23 microM) and zymosan (apparent IC50 = 0.18 microM). Leukotriene C4 production was inhibited by manoalide when macrophages were stimulated by A23187 (IC50 = 0.35 microM) but was enhanced when the cells were stimulated with zymosan. In an in vivo model, manoalide antagonized zymosan-induced peritoneal writhing in the mouse (ED50 = 0.71 mg/kg) and inhibited the i.p. release of 6-keto-prostaglandin F1 alpha (ED50 = 0.2 mg/kg) and leukotriene C4 (ED50 = 0.24 mg/kg). Our results suggest that: 1) manoalide modifies arachidonic acid release and metabolism to prostaglandins and leukotrienes in mouse cultured peritoneal macrophages stimulated by phorbol myristate acetate, calcium ionophore A23187 and zymosan and 2) the analgesic properties of manoalide seem to be partially correlated with reduced eicosanoid production in zymosan-stimulated mouse peritoneal exudates.

6-Ketoprostaglandin F1 alpha↗
PubMed1980

Immunization against primary, transplanted and spontaneous murine leukaemia using a live Moloney sarcoma virus vaccine.

The purpose of this study was to use an immunization protocol with Moloney sarcoma virus (MSV-M) as active immunogen against exogenous and endogenous leukaemia. The s.c. route was chosen since it offered advantages over the i.m. route: the primary sarcomas were smaller, the regression faster, there were fewer recurrences and there was good persistent immunity. Strong protection was obtained against primary leukaemias induced by Friend leukaemia virus (FLV), Moloney leukaemia virus (MLV), Rauscher leukaemia virus (RLV), Precerutti-Law leukaemia virus (PLLV/T2), and H179A leukaemia virus. It was not possible to protect against leukaemia induced by Gross leukaemia virus (GLV). With transplantable leukaemias the results varied: partial protection was observed against H110 leukaemia (induced with human material) and R14 leukaemia (induced by X-irradiation) whilst no protection was obtained against P277 leukaemia (induced by Moloney leukaemia virus). As for spontaneous leukaemias, immunized BALB/c mice showed an increased incidence over the controls, while in F1 (Swiss x AKR) mice the incidence was similar but the latent period was shorter. Furthermore, in long-term observations the MSV-M-immunized mice showed an increased mortaltiy, which could be related to (1) new phenotypic mixtures between MSV-M and leukaemia viruses; (2) reactivation of MSV-M sarcoma-genesis with age, and (3) genotype susceptibility to MSV-M.

Animals↗
PubMed1977

Enhanced growth of syngeneic Moloney sarcoma with decreased immunity in the regressors.

S.c. cellular transplants of MS tumours have a high incidence of rejection in adult BALB/c mice, which can then be used as syngeneic regressors. When these tumours were inoculated within a glass cylinder which had been implanted s.c. in BALB/c mice 2 days earlier, 51% of the animals died with progressively growing tumours, compared with 2% in animals which had received the same inoculum directly s.c. This experimental model demonstrates tumour enhancement in a syngeneic system, and duplicates what has been previously reported in two different allogeneic tumour-host combinations, where it was demonstrated that immunological enhancement was operating, since the addition of either progressor serum or soluble tumour antigen significantly increased tumour incidence. For the purpose of investigating whether the glass cylinder model could also modify the immune response of the host to a second tumour challenge, a leukaemia virus known to crossreact with MS was used. Regressors were challenged i.p. with a lethal dose of a leukaemia virus, PLLV. Regressors bearing a glass cylinder showed a 22% survival rate which was significantly lower than that of the s.c. inoculated regressors (71%). This decrease in cross-immunity suggests that the artificially constructed privileged site created by the glass cylinder, by conditioning for tumour enhancement, also decreases immunological memory.

Animals↗