Changes in macrophage membrane proteins in relation to protein deficiency in rats

Resident and thioglycollate (TG) macrophages were isolated from rats fed 20 and 4% protein diets. These cells were cultured for 2 and 18 hr; further the membrane proteins were separated by SDSPAGE. Though basically all the samples had a similar banding pattern, the protein profile was very complex in nature. TG elicited macrophages from the protein fed group had increased contents of high molecular weight proteins compared to the resident cells from both the groups as well as TG cells from the protein deficient group. The difference increased with prolonged incubation. Polypeptides at 56.5 and 46 kd which were prominently present in the control samples, was very low in the protein deficient ones. Bands at 34, 32, 27 to 19.5 kd were reduced in the TG cells from the protein fed group. The protein deficient samples exhibited a strong band at 43 kd (presumably actin) while it was present in very small amounts in the cells from the protein fed groups. These observations indicate that the protein restriction had down regulated TG induced modulation of macrophage membrane proteins to the level of resident cells which are physiologically in a lower state of activation. These changes could reflect on their reduced functional properties.     

Human alveolar macrophages and granulocyte-macrophage colony-stimulating factor-induced monocyte-derived macrophages are resistant to H2O2 via their high basal and inducible levels of catalase activity

Human alveolar macrophages (A-MPhi) and macrophages (MPhi) generated from human monocytes under the influence of granulocyte-macrophage colony-stimulating factors (GM-MPhi) express high levels of catalase activity and are highly resistant to H(2)O(2). In contrast, MPhi generated from monocytes by macrophage colony-stimulating factors (M-MPhi) express low catalase activity and are about 50-fold more sensitive to H(2)O(2) than GM-MPhi or A-MPhi. Both A-MPhi and GM-MPhi but not M-MPhi can induce catalase expression in both protein and mRNA levels when stimulated with H(2)O(2) or zymosan. M-MPhi but not GM-MPhi produce a large amount of H(2)O(2) in response to zymosan or heat-killed Staphylococcus aureus. These findings indicate that GM-MPhi and A-MPhi but not M-MPhi are strong scavengers of H(2)O(2) via the high basal level of catalase activity and a marked ability of catalase induction and that catalase activity of MPhi is regulated by colony-stimulating factors during differentiation.     

Activation of lysosomal enzymes in chemotactically elicited rat peritoneal macrophages

Activation profile of lysosomal enzymes in rat peritoneal macrophages elicited in response to three stimulants, thioglycollate (TG), protease peptone (PP) and lipopolysaccharide (LPS) was studied from 0 to 6 days. Macrophages elicited in response to LPS were larger in number and heterogeneous in nature while TG and PP induced cells were comparatively more homogeneous. Maximum elicitation of macrophages in response to the three stimulants, though at different degrees, was observed around 3 days. This could be correlated to increased blood monocytes. The progressive activation of macrophages reflected in corresponding decrease in total cellular protein content and increase in the activities of their lysosomal enzymes. The catalytic activities of aryl sulphatase, beta-glucuronidase and cathepsin D increased several fold (2-8 fold) over the resident values. TG elicited cells possessed the highest enzyme activities, followed by PP and LPS elicited ones. Beta-Glucuronidase was the most stimulated (4-8 fold) of the enzymes studied. The cellular catalytic activities of these enzymes were also enhanced 2- to 4-fold compared to the resident levels in the TG and PP elicited macrophages. Though the enzyme catalytic activities were increased in the LPS treated cells, their cellular levels remained below the resident activities in all the three enzymes studied. The results indicate that the events related to the elaboration of these macrophage lysosomal enzymes in vivo are subject to selective modulation and are stimulus specific.     

Time-dependent alterations of leukotriene production and catabolism in rat peritoneal macrophages following intraperitoneal injection of thioglycollate broth.

Alterations of leukotriene (LT) productivity in peritoneal macrophages (PM) from untreated rats (control) as well as from rats treated i.p. with thioglycollate broth (TG) were investigated on days 3, 7 and 14 after TG administration. The resident PM from the untreated rats produced mainly LTB4 and 5-HETE with small amounts of 12-HETE and LTD4 with only a trace of LTC4 when stimulated with the calcium ionophore A23187. The PM elicited from rats on days 3 and 7 produced more LTC4 than did the resident PM but fewer other lipoxygenase metabolites. On day 14, however, the elicited PM resembled the resident PM in terms of lipoxygenase metabolite production. Similar results were achieved in the presence of arachidonic acid and A23187. A decrease in lipoxygenase metabolism in the elicited PM was also suggested by using opsonized zymosan. Catabolism studies indicated a reduction in r-glutamyl transpeptidase activity in the elicited PM and suggested a reduction in catabolism for LTB4 in the former cells. The authors conclude that the TG-elicited PM generate fewer lipoxygenase metabolites than the resident PM following stimulation, but show a preferential conversion of LTA4 to sulfidopeptide LTs rather than to LTB4. The elicited PM also show a reduced catabolism for LTC4 and LTB4.     

Stimulation of macrophage H2O2 release by resident thymocytes: effect of a soluble factor distinct from interferon-gamma

Activated T cells are known to stimulate macrophage oxidative metabolism and antimicrobial activity through release of interferon-gamma (IFN-gamma). In contrast, the role of nonactivated T cells in regulating macrophage effector functions is less well defined. We have previously reported that a low molecular weight soluble factor derived from resident (nonactivated) thymocytes enhances macrophage receptor-mediated phagocytosis. In the present study, we examined the capacity of resident murine thymocytes to stimulate the respiratory burst and microbicidal activity of peritoneal macrophages. Macrophages cultured for 1-2 days with cell-free thymocyte supernatant (TS) released two to three times more H2O2 in response to PMA or opsonized zymosan than did control macrophages. The H2O2-stimulating factor in TS was distinguished from IFN-gamma by its heat stability (100 degrees C, 20 min), approximate MW of 2400 Da (gel filtration high-pressure liquid chromatography), and absence of interferon activity in both antiviral and enzyme-linked immunosorbent assays. TS-treated macrophages, however, did not exhibit a greater capacity to kill or inhibit the intracellular growth of Toxoplasma gondii, indicating that the thymocyte factor did not fully activate macrophage microbicidal mechanisms. These data suggest that thymocytes can increase the respiratory burst capacity of macrophages in the absence of antigen-specific immune responses.     

Cyclosporin A inhibits phorbol ester-induced activation of superoxide production in resident mouse peritoneal macrophages.

Peritoneal resident macrophages from mice are sensitive to inhibition by cyclosporin A (CsA) of phorbol 12-myristate 13-acetate (PMA)-stimulated oxidative burst. Inhibition was assessed in terms of superoxide anion (O2.-) and H2O2 production. Key findings were as follows. (a) CsA inhibited in a dose-dependent manner the production of O2.- when cells were stimulated with PMA. CsA did not alter the respiratory burst induced by other stimuli (zymosan, concanavalin A and fMet-Leu-Phe). It was verified that CsA itself had no scavenger effect. (b) A concomitant decrease in H2O2 liberation following CsA exposure was found. This inhibition was observed both in the initial rate of synthesis and in the accumulation after 15 min of incubation. (c) NADPH oxidase activity in the crude supernatant was unaffected by the previous incubation of macrophages with CsA. CsA does not inhibit glucose transport measured as 14CO2 production. (d) The production of O2.- was strongly dependent on the glucose concentration. Sodium oleate also stimulated O2.- production in resident macrophages. These data might be correlated with the inhibitory effect of CsA upon other functions of macrophages.     

Redox interactions between catalase and alcohol dehydrogenase pathways of ethanol metabolism in the perfused rat liver

Alcohol metabolism via alcohol dehydrogenase (ADH) and catalase was studied in perfused rat livers by measuring the oxidation of methanol and butanol, selective substrates for catalase and ADH, respectively. In livers from fasted rats, basal rates of methanol uptake of 15 +/- 1 mumol/g/h were decreased significantly to 8 +/- 2 mumol/g/h by addition of butanol. Concomitantly, pyridine nucleotide fluorescence detected from the liver surface was increased by butanol but not methanol. Both effects of butanol were blocked by an inhibitor of ADH, 4-methylpyrazole, consistent with the hypothesis that elevation of the NADH redox state by butanol inhibited H2O2 production via NAD+-requiring peroxisomal beta-oxidation, leading indirectly to diminished rates of catalase-dependent methanol uptake. In support of this idea, both butanol and butyraldehyde inhibited H2O2 generation. The NADH redox state was also elevated by xylitol, causing a 75% decrease in rates of methanol uptake by livers from fasted rats. This effect was not observed in livers from fed rats unless malate-aspartate shuttle activity was reduced by infusion of the transaminase inhibitor aminooxyacetate. Taken together, these data indicate that generation of reducing equivalents from ADH in the cytosol inhibits H2O2 generation leading to significantly diminished rates of peroxidation of alcohols via catalase. This phenomenon may represent an important physiological mechanism of regulation of ethanol oxidation in intact cells.     

Effect of Muramyldipeptide,a Synthetic Bacterial Adjuvant,on Enzyme Release from Cultured Mouse Macrophages

Monolayer cultures of macrophages obtained by peritoneal lavage of normal or thioglycollate-stimulated mice spontaneously secreted lysosomal enzymes into the culture medium. When the elicited macrophages were cultured in the presence of muramyldipeptide (MDP), a 20–30% increase in the release of β-glucuro-nidase was consistently observed and the intracellular activity decreased to about 45% of that of control cells after 6–8 days' culture. A stimulatory effect of MDP on lysozyme secretion, though less profound, was also observed. In contrast, release of neither enzyme was stimulated in resident macrophages by the addition of MDP. A neutral α-glucosidase, which has recently been found to localize also in granules of macrophages, remained inside the cells and neither its activity nor its release was affected by the addition of MDP to either type of macrophages. A large amount of lactic dehydrogenase was released only when the resident, not the elicited, macrophages were cultured for 3–4 days and then phagocytosed zymosan.     

Glutathione metabolism in resting and phagocytizing peritoneal macrophages

The steady state GSH content of cultured mouse resident peritoneal macrophages was 34 +/- 5 pmol/microgram of cell protein. Intracellular GSH content decreased concomitantly with zymosan ingestion. The half-life of GSH decreased from 1.9 h in resting cells to 0.58 h during phagocytosis as determined by inhibition of GSH synthesis with buthionine sulfoximine. The decrease in GSH half-life was directly related to the extent of particle uptake. In cytochalasin D-treated cells, attachment of zymosan to the macrophage plasma membrane in the absence of particle interiorization was sufficient to stimulate GSH turnover. Efflux was the major route of GSH loss in [35S]cystine-labeled macrophages, and was enhanced 3-fold by a zymosan challenge. GSH was lost intact since resident macrophages lack gamma-glutamyl transpeptidase (less than 1 pmol of L-gamma-glutamyl-p-nitroanilide/microgram of protein . h). Macrophages obtained from mice challenged in vivo with Corynebacterium parvum maintained higher intracellular GSH levels (50 +/- 5 pmol/microgram of cell protein) than did resident cells. The half-life of GSH in buthionine sulfoximine-treated C. parvum-elicited macrophages was 3.8 +/- 0.2 h while resting and 1.3 +/- 0.2 h during phagocytosis. C. parvum-elicited macrophages, in contrast to resident cells, contained sufficient levels of gamma-glutamyl transpeptidase activity to hydrolyze 55 pmol of L-gamma-glutamyl-p-nitroanilide/microgram of cell protein . h. These studies indicate that phagocytosis and cellular activation have profound effects on GSH metabolism in macrophages.     

Antioxidant enzymes suppress nitric oxide production through the inhibition of NF-kappa B activation: role of H(2)O(2) and nitric oxide in inducible nitric oxide synthase expression in macrophages.

Reactive molecules O(-)(2), H(2)O(2), and nitrogen monoxide (NO) are produced from macrophages following exposure to lipopolysaccharide (LPS) and involved in cellular signaling for gene expression. Experiments were carried out to determine whether these molecules regulate inducible nitric oxide synthase (iNOS) gene expression in RAW264.7 macrophages exposed to LPS. NO production was inhibited by the antioxidative enzymes catalase, horseradish peroxidase, and myeloperoxidase but not by superoxide dismutase (SOD). In contrast, the NO-producing activity of LPS-stimulated RAW264.7 cells was enhanced by the NO scavengers hemoglobin (Hb) and myoglobin. The antioxidant enzymes decreased levels of iNOS mRNA and protein in LPS-stimulated RAW264.7 cells, whereas the NOS inhibitor N(G)-monomethyl-L-arginine as well as Hb increased the level of iNOS protein but not mRNA, indicating that NO inhibits iNOS protein expression. NF-kappa B was activated in LPS-stimulated RAW264.7 cells and the activation was significantly inhibited by antioxidant enzymes, but not by Hb. Similar results were obtained using LPS-stimulated rodent peritoneal macrophages. Extracellular O(-)(2) generation by LPS-stimulated macrophages was suppressed by SOD, but not by antioxidative enzymes, while accumulation of intracellular reactive oxygen species was inhibited by antioxidative enzymes, but not by SOD. Exogenous H(2)O(2) induced NF-kappa B activation in macrophages, which was inhibited by catalase and pyrroline dithiocarbamate (PDTC). H(2)O(2) enhanced iNOS expression and NO production in peritoneal macrophages when added with interferon-gamma, and the effect of H(2)O(2) was inhibited by catalase and PDTC. These findings suggest that H(2)O(2) production from LPS-stimulated macrophages participates in the upregulation of iNOS expression via NF-kappa B activation and that NO is a negative feedback inhibitor of iNOS protein expression.     

Effect of RNA and protein synthesis inhibitors on the release of inflammatory mediators by macrophages responding to phorbol myristate acetate

The interaction of phorbol myristate acetate with resident populations of mouse peritoneal macrophages causes an increased release of arachidonic acid followed by increased synthesis and secretion of prostaglandin E2 and 6-keto-prostaglandin F1 alpha. In addition, phorbol myristate acetate causes the selective release of lysosomal acid hydrolases from resident and elicited macrophages. These effects of phorbol myristate acetate on macrophages do not cause lactate dehydrogenase to leak into the culture media. The phorbol myristate acetate-induced release of arachidonic acid and increased synthesis and secretion of prostaglandins by macrophages can be inhibited by RNA and protein synthesis inhibitors, whereas the release of lysosomal hydrolases is unaffected. 0.1 microgram/ml actinomycin D blocked the increased prostaglandin production due to this inflammatory agent by more than 80%, and 3 microgram/ml cycloheximide blocked prostaglandin production by 78%. Similar results with these metabolic inhibitors were found with another stimulator of prostaglandin production, zymosan. However, these inhibitors do not interfere with lysosomal hydrolase releases caused by zymosan or phorbol myristate acetate. It appears that one of the results of the interaction of macrophages with inflammatory stimuli is the synthesis of a rapidly turning-over protein which regulates the production of prostaglandins. It is also clear that the secretion of prostaglandins and lysosomal hydrolases are independently regulated.     

Effect of heme on Bacteroides distasonis catalase and aerotolerance

Parallel increases in intracellular catalase activity and resistance to extracellular H2O2 and to hyperbaric O2 toxicity were observed when Bacteroides distasonis VPI 4243 (ATCC 8503, type strain) was grown in either complex or defined medium containing graded amounts of hemin. Virtually all of the cells with high catalase activity (greater than 200 U/mg) remained viable upon exposure at 37 degrees C to 100-lb/in2 O2 on agar surfaces for 1 h, whereas low-catalase cells (less than 10 U/mg) lost 1.2 log units of viable cells during that treatment. Upon exposure to 500 microM H2O2, high-catalase cells lost 0.4 log units of the initial viable colonies during the same period in which low-catalase cells lost 3 log units of viable cells. The superoxide dismutase activity was the same in each test culture. These data support the role of intracellular catalase in protecting B. distasonis from oxidative damage resulting from hyperbaric oxygenation or H2O2 exposure. Catalase activity elicited by adding hemin to cells grown previously in medium lacking hemin was inhibited only 40% by prior incubation of the cells with chloramphenicol (30 micrograms/ml) and only 22% with rifampin (5 micrograms/ml). A model which is consistent with these data involves the production of an apocatalase in cells grown in low-hemin medium. Addition of hemin to the cells would result in a rapid chloramphenicolor rifampin-insensitive stimulation of catalase activity followed by further de novo biosynthesis of catalase.     

Biosynthesis of C4 by mouse peritoneal macrophages. II. Comparison of C4 synthesis by resident and elicited cell populations

Five elicited macrophage populations synthesized one-third to one-tenth as much hemolytically active C4 when compared with resident peritoneal macrophages. This decrease in functional C4 activity was not caused by inhibitors or protease activity in the elicited macrophage supernatants. Analysis of C4 antigen indicated a similar reduction in the elicited cells compared with the resident macrophages. A defect in precursor processing or secretion was deemed unlikely because the intracellular C4 precursor was appropriately reduced in the elicited cells. We postulate that mouse resident peritoneal macrophages are a pluripotent cell population with broad capabilities in regard to the initiation of the inflammatory response. In contrast, elicited or activated macrophages may be more specialized cells, with one manifestation of this being the "down" regulation of C4 synthesis.     

Some biochemical and functional characteristics of macrophages activated by Tetrahymena pyriformis

Phagocytosis, enzyme activities and capacity to release hydrogen peroxide (H2O2) and superoxide anion (O2-) of peritoneal macrophages from mice inoculated with Tetrahymena pyriformis, a free-living ciliate, were examined in comparison with resident and BCG-activated macrophages. Fc receptor-mediated phagocytosis of sheep erythrocytes was markedly increased in Tetrahymena-activated macrophages to the same level as that seen in BCG-activated ones. Tetrahymena-activated macrophages showed an increased level of acid phosphatase (lysosomal enzyme) and a reduced level of alkaline phosphodiesterase I (plasma membrane ectoenzyme) as compared with resident macrophages. Similar changes in the activities of the two enzymes were also observed in BCG-activated macrophages. Both Tetrahymena- and BCG-activated macrophages exhibited more enhanced capacity to release H2O2 and O2- than resident macrophages when stimulated with phorbol myristate acetate. In the macrophages from mice inoculated with varying doses of Tetrahymena, a significant correlation was observed between the increased capacity of H2O2 and O2- release as observed in the present study, and the enhanced toxoplasmacidal activity as observed in a previous study, in a dose-dependent fashion.     

Protection of human endothelial cells from oxidant injury by adenovirus-mediated transfer of the human catalase cDNA.

In a variety of disorders, endothelial cells are exposed to high levels of oxidants, generated within the cells and/or consequent to local inflammation. In the context of the sensitivity of endothelial cells to oxidant stress, particularly related to H2O2, we have designed a replication deficient recombinant adenovirus containing the human catalase cDNA (AdCL) to transfer the catalase cDNA to the endothelial cells, in order to augment intracellular anti-H2O2 protection. Human umbilical vein endothelial cells that were not infected or infected with control adenovirus maintained low levels of catalase mRNA. Endothelial cells infected with AdCL expressed AdCL-driven exogenous catalase mRNA, as early as 24 hr and at least for 7 days. Catalase protein levels were increased significantly over controls in cells infected with AdCL, as were catalase activity levels, with catalase activity correlated closely with levels of catalase protein. Importantly, when the endothelial cells were exposed to 500 microM H2O2, all the AdCL infected endothelial cells survived, compared to only 37% of the control cells. Thus, a recombinant adenovirus containing the human catalase cDNA is able to infect human endothelial cells in vitro and express high levels of functional intracellular catalase, protecting the cells against H2O2-mediated oxidant stress. These observations support the feasibility of the transfer of catalase cDNA to human endothelium to protect against oxidant injury.     

Alteration with dietary state of the activity and zonal distribution of adenylate cyclase stimulated by glucagon, fluoride and forskolin in microdissected rat liver tissue

Adenylate cyclase activated by glucagon, fluoride and forskolin was measured in liver homogenates and microdissected periportal and perivenous tissue of fed and fasted rats. A radiochemical microtest, more sensitive by 2-3 orders of magnitude as compared with the usual assay, was established for the determination of the activity in liver samples corresponding to 200-600 ng dry weight. In liver homogenates from fasted as compared to fed animals the glucagon-stimulated and fluoride-stimulated activity was increased by 1.65-fold, while the basal and the forskolin-stimulated activity remained the same. In microdissected tissue of both fed and fasted animals the activity was stimulated in about 60% of the samples by glucagon, fluoride and forskolin (responsive samples). However, in about 40% of the microdissected tissue samples the activity could not be stimulated by any of the above activators (non-responsive samples). In responsive microdissected tissue of fasted as compared to fed animals, the glucagon-stimulated and fluoride stimulated activity but not the basal and the forskolin-activated activity was increased by 2-3-fold. In responsive microdissected samples of fed animals neither the basal nor the stimulated activities showed a significant periportal to perivenous gradient. In samples of fasted animals, however, a zonal gradient was observed for the glucagon-stimulated activity exhibiting a 1.5-fold higher rate in the perivenous zone.     

Parallel inheritance of tissue catalase activity and immunostimulatory action of amphotericin B in inbred mouse strains

Both amphotericin B (AmB) and its methyl ester derivative are potent immunoadjuvants that also stimulate murine B lymphocytes and macrophages in vitro. Most of the common inbred mouse strains show AmB-induced immunostimulation (AmB-high responders) but mice from the C57BL strains, regardless of H-2 genotype, are AmB-low responders. Lymphoid cells from AmB-high responder strains also exhibit greater resistance to H2O2 toxicity in vitro compared with cells from AmB-low responders. This result led to an evaluation of differences in the tissue catalase levels of AmB-high and -low responder strains. Results from several laboratories, including ours, indicate that C57BL mouse strains express low levels of tissue catalase activity in addition to low or absent immunostimulant effects of AmB. Several AmB-high responder strains have high spleen cell, macrophage, and liver catalase, and the mouse strain distribution of enzyme activity as well as the dominant inheritance of the low catalase phenotype is compatible with regulation by the Ce-1 locus in lymphoid organs as well as liver. Other evidence also suggests that H2O2 metabolism is important in lymphoid cell responses to AmB. For example, AmB stimulates a stronger respiratory burst in macrophages from AmB-high responder strains under the same conditions that inhibit burst activity in macrophages from low responders. Selective immune enhancement by AmB in high catalase mouse strains along with enhanced susceptibility to AmB toxicity in low responder C57BL mice with low tissue catalase activity suggests that cellular peroxidation is a major determinant of the genetic regulation of amphotericin-induced immunostimulation.     

Analysis of glucose metabolism in farmed European sea bass (Dicentrarchus labrax L.) using deuterated water

Glucose metabolism in free-swimming fasted and fed seabass was studied using deuterated water ((2)H(2)O). After transfer to seawater enriched with 4.9% (2)H(2)O for 6-h or for 72-h, positional and mole percent enrichment (MPE) of plasma glucose and water were quantified by (2)H NMR and ESI-MS/MS. Plasma water (2)H-enrichment reached that of seawater within 6h. In both fasted and fed fish, plasma glucose MPE increased asymptotically attaining ~55% of plasma water enrichment by 72 h. The distribution of (2)H-enrichment between the different glucose positions was relatively uniform. The gluconeogenic contribution to glucose that was synthesized during (2)H(2)O administration was estimated from the ratio of position 5 and 2 glucose enrichments. For both fed and fasted fish, gluconeogenesis accounted for 98±1% of the glucose that was produced during the 72-h (2)H(2)O administration period. For fasted fish, gluconeogenic contributions measured after 6h were identical to 72-h values (94±3%). For fed fish, the apparent gluconeogenic contribution at 6-h was significantly lower compared to 72-h (79±5% versus 98±1%, p<0.05). This may reflect a brief augmentation of gluconeogenic flux by glycogenolysis after feeding and/or selective enrichment of plasma glucose position 2 via futile glucose-glucose-6-phosphate cycling.     

Effect of RNA and protein synthesis inhibitors on the release of inflammatory mediators by macrophages responding to phorbol myristate acetate

The interaction of phorbol myristate acetate with resident populations of mouse peritoneal macrophages causes an increased release of arachidonic acid followed by increased synthesis and secretion of prostaglandin E₂ and 6-keto-prostaglandin F_1α. In addition, phorbol myristate acetate causes the selective release of lysosomal acid hydrolases from resident and elicited macrophages. These effects of phorbol myristate acetate on macrophages do not cause lactate dehydrogenase to leak into the culture media. The phorbol myristate acetate-induced release of arachidonic acid and increased synthesis and secretion of prostaglandins by macrophages can be inhibited by RNA and protein synthesis inhibitors, whereas the release of lysosomal hydrolases is unaffected. 0.1 μg/ml actinomycin D blocked the increased prostaglandin production due to this inflammatory agent by more than 80%, and 3 μg/ml cycloheximide blocked prostaglandin production by 78%. Similar results with these metabolic inhibitors were found with another stimulator of prostaglandin production, zymosan. However, these inhibitors do not interfere with lysosomal hydrolase releases caused by zymosan or phorbol myristate acetate. It appears that one of the results of the interaction of macrophages with inflammatory stimuli is the synthesis of a rapidly turning-over protein which regulates the production of prostaglandins. It is also clear that the secretion of prostaglandins and lysosomal hydrolyses are independently regulated.     

Production of arachidonic acid metabolites by operationally defined macrophage subsets

The antitumor activity and arachidonic acid metabolism of operationally defined macrophage populations was examined. Macrophages from mice injected with Mycobacterium bovis (strain BCG) or with pyran-copolymer were cytotoxic for tumor cells. The major arachidonic acid metabolite of these cells was PGE2. Neither resident nor elicited macrophages were cytotoxic. However, elicited macrophages as well as macrophages from BCG injected mice inhibited tumor cell growth. The production of arachidonic acid metabolites by elicited cells, while low initially, was followed by a rapid increase in PGE2. The major metabolites of resident cells were PGE2 and prostacyclin. The cAMP:cGMP ratio correlated with the metabolic activity of the cells.