Effects of a platelet-activating factor antagonist,CV-6209, on Gastric mucosal lesions induced by ischemia-reperfusion

Recent research was shown that oxygen-derived free radicals are involved in the pathogenesis of various diseases, including ischemia-reperfusion injury. We have also reported that oxygen-derived free radicals and lipid peroxidation may play an important role in gastric mucosal injury induced by ischemia-reperfusion. The hypoxanthinexanthine oxidase system and neutrophils are considered important sources of oxygen-derived free radicals in this process. In recent years, it also has been shown that serum platelet-activating factor (PAF) levels increased during ischemia-reperfusion, and that induction of superoxide generation by neutrophils is one of the important biological effects of PAF. In the present study, we examined the effect of CV-6209, a specific PAF receptor antagonist, on gastric mucosal injury induced by ischemia-reperfusion, to shed some light on the possible involvement of PAF in such lesions. CV-6209 significantly attenuated the gastric mucosal injury induced by ischemia-reperfusion, and inhibited both an increase of thiobarbituric acid reactive substances and a decrease of α-tocopherol in gastric mucosa after ischemia-reperfusion. However, CV-6209 had no effect on gastric mucosal blood flow during ischemiano effect on gastric mucosal blood flow during ischemia-reperfusion. These results suggest that endogenous PAF may play an important role in gastric mucosal injury induced by ischemia-reperfusion, and that CV-6209 exerts its beneficial effect mainly by inhibiting neutrophil superoxide production induced by PAF. Based in part on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Role of platelet-activating factor (PAF) in superoxide production by human polymorphonuclear leukocytes

The effect of platelet-activating factor (PAF) in superoxide production by human polymorphonuclear leukocytes (PMN) was studied. Cypridina luciferin analog (CLA) dependent chemiluminescence was used to detect superoxide anion radicals. PAF induced superoxide generation in human PMN in a dose-dependent manner. Preincubation with a small amount of PAF (5 x 10⁻⁹ M) enhanced PMN superoxide release induced by various stimuli, such as phorbol myristate acetate (PMA), opsonized zymosan (OZ), calcium ionophore (A23187) andN-formyl-methionyl-leucyl-phenylalanine (FMLP). The PAF antagonist, CV-6209, inhibited superoxide production induced by PAF, but not that induced by other stimuli. These findings would indicate that PAF may play an important role at inflammatory reaction sites and that CV-6209 may inhibit excessive inflammatory reaction.     

Calcium ion mobilization in neuronal cells induced by PAF

We have reported previously that platelet-activating factor (PAF) interacts with the neuronal cell line NG108-15 (neuroblastoma X glioma hybrid) and the pheochromocytoma cell line, PC12. PAF acts on these cells by raising levels of intracellular free calcium ions. In the present report, we extend these studies. PAF induced the vesicular release of adenosine 5′-triphosphate (ATP) from PC12 cells in a dose-dependent manner. The PAF-induced ATP release was inhibited by the PAF antagonists, CV-3988 and CV-6209, and the calcium antagonist prenylamine. The relevance of the interaction of PAF with neuronal cells was investigated further by using brain synaptosomal preparations and primary cortical and neostriatal cells. Nanomolar concentrations of PAF induced calcium transients in aequorin-loaded synaptosomal preparations, and cortical and neostriatal cells were sensitive to the action of PAF. The possible physiological and pathophysiological roles of PAF in brain function are discussed. Based in part on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Guinea pig bone marrow cells treated with platelet-activating factor generate factor(s) which affects their DNA synthesis and microbicidal activity

We have previously reported that platelet-activating factor (PAF) induces proliferation and microbicidal activity of guinea pig bone marrow cells. In the present study, we have found that the conditioned medium of PAF- or nonmetabolizable PAF agonist-treated guinea pig bone marrow cells augmented DNA synthesis and induced microbicial activity of bone marrow cells. A PAF specific antagonist, CV-6209, inhibited generation of the active conditioned medium by PAF. Addition of the PAF antagonist only partially suppressed the augmentative effect of the active conditioned medium on DNA synthesis; this is consistent with the fact that, because of the rapid breakdown, no appreciable amount of PAF remained in the conditioned medium of PAF-treated cells. Although mouse bone marrow cells did not respond to PAF unlike guinea pig cells, their DNA synthesis was significantly enhanced by the conditioned medium of PAF-treated guinea pig bone marrow cells. Thus, some newly generated factor(s) distinct from the originally inoculated PAF seemed to modulate the bioactions of PAF on bone marrow cells. An appreciable amount of PAF was produced by calcium ionophore-treated guinea pig bone marrow cells. These findings indicate that PAF synthesized in guinea pig bone marrow cells induces generation in the cells of some factor(s) which affects proliferation or microbicidal activity. Presented at The Third International Conference on Platelet-Activating Factor and Structurally Related Ether Lipids, Tokyo, Japan, May 1989.     

Involvement of platelet-activating factor in zymosan-induced rat pleurisy

The role of platelet-activating factor (PAF) in inflammatory reactions was studied in zymosan-induced rat pleurisy. Pleurisy was induced by injection of a 2% zymosan suspension into the pleural cavity of rats. The time course of pleural exudate accumulation, the exudation rate, and exudate leukocyte numbers were followed then for 96 hr. Peak pleural exudate accumulation was about 3 mL at 24 hr, whereas the exudation rate increased biphasically with peaks at 0.5 hr and 5 hr. The migration of leukocytes into the pleural cavity increased with time up to 48 hr. The polymorphonuclear leukocytes were the dominant white cells in the exudate between 5 and 16 hr, but mononuclear leukocytes started to outnumber them around 24 hr. Pretreatment with cyproheptadine (5 mg/kg), an inhibitor of both histamine and seotonin, significantly suppressed pleural fluid accumulation and the exudation rate at 0.5 hr. The PAF antagonist CV-6209 (1 mg/kg) significantly suppressed pleural fluid accumulation and the exudation rate at both 0.5 and 5 hr. At either time point, the parameters were not suppressed by indomethacin. We detected PAF activity in the high-performance liquid chromatography (HPLC) fraction (with a retention time corresponding to that of authentic PAF) of the exudates at 0.5 hr, 5 hr, and 16 hr using an aggregation bioassay with washed rabbit platelets. The results suggest that in zymosan-induced rat pleurisy, histamine and/or serotonin are the main mediators of exudation at 0.5 hr and that PAF may be partly responsible for exudation at 0.5 hr and later at 5 hr to 16 hr. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Differential effect of a PAF antagonist CV-3988 on active and passive anaphylactic shock in various mouse strains

To define the role of platelet-activating factor (PAF) in anaphylactic shock in the mouse, the suppressive effect of CV-3988, a PAF antagonist, on active and passive anaphylactic shock was studied. Various mouse strains treated or not treated withBordetella pertussis (B. pertussis) were used. We found that the effect of CV-3988 on anaphylactic shock in the mice that were actively sensitized with bovine serum albumin plusB. pertussis differed markedly according to mouse strain. CV-3988 suppressed the anaphylactic shock in C3H/He and CBA/JN mice at a low dose of 3 mg/kg, whereas antagonists to other mediators such as histamine, serotonin, thromboxane A₂ and leukotrienes did not show a suppressive effect. This suggests that PAF plays a major role in anaphylactic shock in these strains. On the other hand, CV-3988 did not suppress active anaphylactic shock in cataract Shionogi (CTS), NOD and DS strains even at a high dose of 30 mg/kg, which could be interpreted to suggest that PAF is not active in these strains. However, this possibility was ruled out based on the similar results obtained in passive anaphylactic shock and PAF-induced shock in these mice. Passive anaphylactic shock in CTS mice mediated by IgG₁ antibody was markedly suppressed by CV-3988 but not at all by antagonists to other mediators. Furthermore, the suppressive action of CV-3988 against passive anaphylactic shock, and PAF-induced shock was greatly attenuated when the mice were pretreated withB. pertussis. From these results, the conclusion can be drawn that PAF is the main mediator of active and passive anaphylactic shock in the mouse in general, even though the effect of CV-3988 differs depending on the mouse strain and on whether or notB. pertussis treatment is used. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Inhibition of myocardial lipoprotein lipase by U-57,908 (RHC 80267)

U-57,908 (RHC 80267) was shown to inhibit lipoprotein lipase (LPL) activity in cardiac myocytes from rat hearts; the concentrations required for inhibition to 50% of control activity were 1.1 μM and 2.5 μM for myocyte homogenates and a post-heparin medium preparation, respectively. The inhibition of LPL activity by U-57,908 was not changed when the concentration of the triolein substrate and apolipoprotein CII activator in the assay was reduced. The availability of U-57,908 as a potent and selective LPL inhibitor may provide a useful experimental approach in studies on lipoprotein metabolism.     

Release of lipoprotein lipase from cardiac myocytes by low-molecular weight heparin

Incubation of cardiac myocytes from rat heart with low-molecular weight heparin (LMWH; Mr approx. 3 kDa) for 30 min resulted in a concentration-dependent release of lipoprotein lipase (LPL) activity into the incubation medium. The release of lipoprotein lipase from cardiac myocytes isolated from both control and diabetic rat hearts induced by LMWH (10 μg/mL) following incubation times of 10 or 30 min was significantly greater than that produced by unfractionated heparin (10 and 30 μg/mL) or decavanadate (1 mM). Since LMWH released more LPL activity into the incubation medium than unfractionated heparin following a short (10 min) incubation time, LMWH is probably more effective in displacing LPL bound to heparan sulfate proteoglycan binding sites on the cell surface of cardiac myocytes.     

Induction of platelet-activating factor in mice by intravenous administration of a neutral fraction of bakers' yeast mannan

A neutral subfraction of mannan of bakers' yeast (WNM) was found to show a lethal effect in mice when administered intravenously. Symptoms caused by intravenous (i.v.) administration of WNM resembled those resulting from the administration of platelet-activating factor (PAF). CV-3988 and ONO-6240, selective PAF antagonists, prevented hypotension and death caused by the administration of WNM or PAF. A β-adrenoceptor agonist was shown to prevent death caused by WNM, whereas propranolol increased the lethal activity of WNM. Intravenous administration of WNM into mice produced PAF in gall bladder fluid which was determined by platelet aggregation assay. The findings indicate that WNM is able to induce PAF in mice and that the resultant PAF may participate in the WNM-induced lethal activity observed in mice.     

Intravascular release of a platelet-activating factor-like lipid (PAF-LL) induced by cigarette smoking

To assess the role of platelet-activating factor (PAF) in smoking-induced vascular injury, the effect of cigarette smoking on PAF-like lipid (PAF-LL) in plasma was studied. The subjects were 12 young smokers (22±1.3 years old), 13 young non-smokers (22±2.1 years old), 14 older smokers (59±9.6 years old), and 11 older non-smokers (60±8.7 years old). Lipids were extracted from 5 mL of plasma and then were separated by thin-layer chromatography. The fraction with the same migration as authentic PAF was recovered and tested for the ability to aggregate human polymorphonuclear neutrophils (PMN). The activity was identified as PAF-LL because it was inactivated by phospholipase A₂, and because the effects on PMN were blocked by CV-3988, a competitive antagonist of the PAF receptor. PAF-LL was detected in plasma from 3 young non-smokers (23%), 5 young smokers (42%), 3 older non-smokers (27%) and 11 older smokers (79%). The incidence of the detection of plasma PAF-LL in older smokers was significantly higher than those in young non-smokers (p<0.01) or in older non-smokers (p<0.05). In young smokers, the acute effect of smoking was also studied. Plasma PAF-LL was detected in all of the 12 subjects immediately after smoking a cigarette, in sharp contrast to the incidence of 42% before smoking. Plasma β-thromboglobulin was highest in older smokers, and it increased significantly after smoking a cigarette in young smokers. Smoking is associated with increased production of PAF or a similar lipid, which may play an important role in the pathogenesis of smoking-induced vascular diseases. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Effect of the hetrazepinoic platelet-activating factor antagonist bepafant (WEB 2170) in models of active and passive anaphylaxis in mice and guinea pigs

The selective hetrazepinoic platelet-activating factor (PAF) antagonist WEB 2170 (Bepafant) was used to study the pathophysiological role of PAF in several models of anaphylaxis in mice and guinea pigs. In actively sensitized mice, the PAF antagonist WEB 2170 (1.0–10 mg/kgp.o.) protected mice from anaphylactic death in a dosedependent manner when the anaphylactic response was potentiated by the beta-receptor antagonist propranolol. When active anaphylaxis in guinea pigs was induced intravenously by 100 mg/kg ovalbumin (OA) in the presence of small doses of the antihistamine mepyramine, additional treatment with oral or intravenous WEB 2170 protected the guinea pigs from anaphylactic death. Also, the remaining anaphylactic bronchoconstriction and blood pressure changes (including anaphylactic hypotension) were attenuated. When guinea pigs were passively sensitized with a heterologous antibodyvia the tracheal route and then challenged by ovalbumin (100 mg/kgi.v.) 24 hr after sensitization in the presence of 0.003 mg/kgi.v. mepyramine, additional treatment with tracheal WEB 2170 at 0.1–1 mg/kg protected the guinea pigs dosedependently not only from anaphylactic death but also from a further decrease of respiratory flow and changes of blood pressure. Increased levels of PAF-like activity (20–50 ng PAF/whole lung) were detected in lungs removed from antigen-challenged animals. The results suggest a causative role for PAF in active and passive anaphylaxis. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Myoelectric intestinal disturbances inEscherichia coli endotoxic shock in rats. Involvement of platelet-activating factor

Administration of BN 52021 (50 mg/kgi.v.), a specific antagonist of platelet-activating factor (PAF), significantly reduced the intestinal myoelectric disturbances induced byE. coli endotoxin injection (50 μg/kgi.v.) by 62%. Thus, PAF may be involved in the intestinal motor alterations observed in endotoxic shock. When given in combination with indomethacin (10 mg/kgi.p.), BN 52021 inhibited endotoxic shock intestinal disturbances. Indomethacin alone also reduced PAF induced (25 μg/kgi.p.) disruption of migrating myoelectric complexes. Endotoxins may act on intestinal motilityvia release of endogenous PAF and prostaglandins, the effects of PAF being mediated through the release of prostaglandins. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

The hormonal regulation of platelet-activating factor acetylhydrolase activity in plasma

We have previously reported that certain fetal tissues including the lung and kidney have an increased platelet-activating factor (PAF) content and enzymatic mechanism for its elevated biosynthesis during the latter stages of pregnancy. In contrast, in the maternal plasma compartment of both the rabbit and human, a decreased capacity to inactivate PAF has been demonstrated. The PAF acetylhydrolase in the fetal plasma is also suppressed. The present study was undertaken to determine the mechanism(s) involved in the regulation of PAF acetylhydrolase. The 17α-ethynylestradiol was administered (intraperitoneal [i.p.] 2.5 mg/kg body wt 5 days) to female and male rats. The plasma PAF acetylhydrolase activity decreased 5-fold. A decrease was observed when a concentration of the estrogen as low as 50 μg/kg was employed. The injection of dexamethasone (i.p., 1.3 mg/kg body wt, 5 days) to male and female rats resulted in a 3-fold increase in the plasma PAF acetylhydrolase activity. The activity returned to the values prior to hormone treatment 4 days after cessation of treatment. Testosterone and progesterone were without effect on plasma acetylhydrolase activity. The change in PAF acetylhydrolase activity caused by estrogen and the glucocorticoid was reflected by a change in the activity in the HDL fraction and not due to the presence of an inhibitor or activator in the plasma of the hormone-treated animals. Human serum obtained from a group of women, in which the 17β-estradiol concentration was elevated in preparation for anin vitro fertilization procedure, showed an inverse relationship between the plasma estrogen concentration and the PAF acetylhydrolase activity. It is suggested that estrogen is responsible for the regulation of PAF acetylhydrolase and the decrease in the plasma PAF acetylhydrolase during the latter stages of pregnancy in both the maternal and fetal plasma caused by the hyperestrogenic state that occurs during this period. The observed increase in PAF acetylhydrolase by dexamethasone may account for, in part, the known anti-inflammatory properties of this steroid by decreasing the concentration of this potent autacoid. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Platelet-activating factor may participate in signal transduction processes in rabbit leukocytes

The bacterial chemotactic peptide, formyl-methionyl-leucyl-phenylalanine (fMLP), induces the generation of platelet-activating factor (PAF), the mobilization of arachidonic acid and generation of superoxide anion (O₂ ⁻) in rabbit polymorphonuclear leukocytes (PMNs). The PAF receptor antagonists, WEB 2086 (10–100 μM) and CV 6209 (1–10 μM), reduced the mobilization of arachidonic acid and the O₂ ⁻ generation in response to fMLP but not that in response to A23187. Pretreatment of PMNs with the phospholipase A₂ inhibitor, chloroquine, or the serine protease inhibitor, tosyl-phenylalanine chloromethyl ketone, reduced the fMLP-stimulated generation of PAF and also reduced the generation of O₂ ⁻. The respiratory burst induced by a submaximal concentration of phorbol myristate acetate was not affected by these compounds. These data are consistent with the suggestion that endogenous PAF may contribute to the signal transduction cascade initiated by fMLP. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May, 1989.     

The effect of CV-3988 and CV-6209 on the acute gastric erosions of rats due to water-immersion and restraint stress

CV-3988 and CV-6209 inhibited gastric erosions in rats due to water-immersion and restraint stress in a dose-dependent manner. The above inhibitory effects of CV-3988 were observed in the presence of indomethacin, which may indicate that the inhibition is not prostaglandin dependent. The studies indicate that platelet-activating factor may be involved in the formation of erosions in rats under water-immersion and restraint stress. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989. The data on CV-3988 were originally reported inNippon Shokakibyo Gakkai Zasshi (Jap. J. Gastroenterol.) 85, 2149–2154 (1988).     

A novel bioaction of PAF: Induction of microbicidal activity in guinea pig bone marrow cells

When guinea pig bone marrow cells were incubated in the presence of 10⁻⁸ to 10⁻⁶ M platelet activating factor (PAF) for 24 to 72 hr, microbicidal activity againstCandida parapsilosis of cells was augmented. This augmentation was inhibited by PAF-specific antagonists, CV6209 or FR900452. PAF-specific binding sites with a high affinity were found on guinea pig bone marrow cells. Carrageenan or 2-chloroadenosine, reagents known to be preferentially cytotoxic to macrophages, abolished the microbicidal activity of PAF-treated bone marrow cells. Macrophages prepared from the peritoneal cavity, however, acquired no appreciable microbicidal action by treatment with PAF. These observations suggest that PAF may affect a class of guinea pig bone marrow cells through binding to receptors specific to PAF, resulting in activation and/or induction of differentiation of monocyte-macrophage lineage cells.     

Antagonism of platelet-activating factor in isolated rat colon: Possible mechanism

The contractions of three different regions of rat colon in response to platelet-activating factor (PAF) were compared. The ascending colon was found to be the most responsive. The slow contraction of the ascending colon induced by PAF was dependent on external Ca²⁺. CV-3988, a structural analog of PAF, slowly induced irreversible inhibition of PAF-induced contraction, whereas FR-900452, which is structurally unrelated to PAF, caused rapid reversible inhibition of PAF-induced contraction. No inhibitory effects of CV-3988 were observed when the strip was washed with Tyrode's solution containing 1% bovine serum albumin (BSA). The results suggest that PAF and CV-3988 penetrate slowly into the outer half of the lipid bilayer of plasma membranes of cells in isolated rat colon, and then rapidly diffuse laterally to associate firmly with specific binding sites. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Inhibition by the PAF antagonist WEB 2086 of PAF induced inositol-1,4,5-trisphosphate production in human platelets

Platelet-activating factor (PAF) activates human platelets by binding to a putative PAF receptor which evokes the rapid formation of inositol-1,4,5-trisphosphate (IP₃) by phospholipase C mediated phosphatidylinositol-4,5-bisphosphate (PIP₂) hydrolysis. Stimulation of [³H]inositol-labeled human platelets by PAF (1 nM-1μM) resulted in a concentration-dependent increase of intracellular IP₃, IP₂ and inositolmonophosphate (IP₁). IP₁ levels increased up to three-fold upon maximum stimulation by 100 nM PAF. The EC₅₀ concentration for PAF was 1.2±0.3 nM. Addition of the hetrazepinoic PAF antagonist, WEB 2086, inhibited PAF stimulated hydrolysis of PIP₂ in a dose-dependent manner. WEB 2086 (100 μM) blocked inositol-1,4,5-trisphosphate formation down to baseline levels (IC₅₀=33±12 μM WEB 2086). In thrombin and ADP stimulated platelets, inositol phosphate (IP) generation was not influenced by WEB 2086. It is concluded that WEB 2086 selectively antagonizes PAF-induced increases in IP and does not interfere directly with intracellular signal transduction. Instead, WEB 2086, which has been shown to bind specifically and with high affinity (K_i 15 nM) to human platelets, acts as a competitive antagonist at the PAF receptor level. Based on a paper presented at the Third International Confrence on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

A novel type hypertriglyceridemia observed in FLS mice

The unique inborn hypertriglyceridemia seen in FLS (fatty liver Shionogi) mice was relieved by the administration of purified apolipoprotein (apo) C-II. Lipoprotein lipase (LPL) and its cofactor, apoC-II, play a pivotal role in VLDL metabolism. Therefore, we investigated the genetic background involved in this hypertriglyceridemia. Plasma levels of TG and total cholesterol as well as LPL activity were measured in male FLS mice and C57/BL6J mice. Agarose gel electrophoresis and fast protein liquid chromatography were used to analyze the lipoprotein profile. A cross experiment was done to determine the genetic background of hypertriglyceridemia observed in FLS mice. cDNA sequences of apoC-II and apoC-III of FLS mice were determined. Preα-lipoprotein was the predominant lipoprotein class in FLS mouse plasma. LPL activity remained in the range observed in C57/BL6J mice, and purified apoC-II transiently relieved FLS mice from hypertriglyceridemia. Preα-lipoproteinemia was inherited in an autosomal recessive manner. ApoC-III appeared to be a causal factor for this unique hypertriglyceridemia. Microsatellite analysis, however, revealed that the responsible chromosome was not 7; rather, apoC-III mapped onto chromosome 9. Therefore, we suggest apoC-III as a candidate causative factor for the hypertriglyceridemia observed in FLS mice because an excessive amount of apoC-III attenuates LPL activity in vivo and in vitro.     

Combined effects of EFA deficiency and tumor necrosis factor-α on circulating lipoproteins in rats

Both tumor necrosis factor-α (TNF-α) and EFA deficiency (EFAD) have been established as causes of marked perturbations in lipid and lipoprotein metabolism. Excessive levels of circulating TNF-α can coexist with EFAD in various clinical disorders such as cystic fibrosis and type I diabetes. The present study therefore aimed to investigate their combined effects on lipid profile and lipoprotein composition by administering TNF-α to EFAD rats. Lipoprotein lipase (LPL), the ratelimiting enzyme in TG catabolism, was also measured in epididymal adipose tissue. EFAD, after a 4-wk period, induced significant increases in plasma TG (80%, P<0.001), total cholesterol (TC, 27%, P<0.025), and HDL-cholesterol (HDL-C, 62%). Two hours after the administration of TNF-α, a further rise in TG (43%, P<0.05) was noted in controls, but not EFAD animals. TC and HDL-C were unaffected by TNF-α treatment. In addition, TNF-α modified lipoprotein-lipid composition. VLDL and HDL₂ derived from EFAD rats were depleted in apolipoprotein (apo) E and apo A-II, and enriched in apo A-12 h after TNF-α administration. Finally, TNF-α decreased adipose tissue LPL activity in both control and EFAD animals. The TNF-α-induced inhibition was more marked in EFAD rats. The present results demonstrated that TNF-α can amplify or antagonize the effects of EFAD on lipid profile, lipoprotein composition, and LPL activity. These data also suggest that the host's nutritional status is a determining factor for the modulating effect of TNF-α on lipid metabolism.