A Prostacyclin-sparing Effect of Indobufen vs. Aspirin

Indobufen ((±)-2-[p-(l-oxo-2-insoindolinyl)-phenyI]-butyric acid, indo) is a drug inhibiting platelet function by a reversible block of the arachidonic acid metabolism at the level of cyclooxygenase. Since tolerability profile of such drugs is mostly linked to extra-platelet cyclooxygenase inhibition, we prospectively evaluated the extent of platelet and extra-platelet cyclooxygenase inhibition by in vivo administration of indo in comparison with ASA. We assessed the effects of the two drugs on the ex vivo generation of TXB2 and 6-keto-PGFlΑ in whole blood, as indices of the production of TXA2 and PGI2 (prostacyclin), respectively, either after spontaneous clotting at 37° C for 1 h (Study 1) or after the addition of 2 Μg/ml collagen (Study 2). Generation of 6-keto-PGFlΑ in whole blood is a mixed index of platelet and extra-platelet cyclooxygenase activity, deriving from both platelet and white blood cell arachidonic acid metabolization. Fifteen patients with ischemic heart disease and baseline serum TXB2 levels > 300 ng/ml were allocated to receiving one single administration of either indobufen 200 mg (n = 6) or aspirin 500 mg (n = 9). Whole blood prostanoid generation was assessed at 0,1,2,4,6, 8,12 and 24 h after drug administration (Study 1). Ten healthy male volunteers were allocated to a double-blind, randomized crossover comparison of indo 200 mg b.i.d. vs. ASA 300 mg/d for 7 days (Study 2). Prostanoid generation and whole blood platelet aggregation were performed before and at the end of each study period (Day 0 and Day 7). At each time-point after single dose administration (Study 1), indobufen caused less % inhibition of whole blood 6-keto-PGFlΑ than of TXB2. At 2 h, TXB2 was reduced to a similar extent after ASA (98 ± 4%) and indo (97 ± 6%) (p = N.S.), while inhibition of 6-keto-PGFla was clearly different (> 98% after ASA, 81 ± 2.5% after indo, p < 0.01). After one week of ASA or indo (Study 2) the maximum extent of whole blood platelet aggregation was similarly inhibited (from 17.2 ± 1.4 ohms to 3.6 ± 1.3 ohms with ASA; from 18.3 ± 1.0 ohms to 1.6 ± 0.7 ohms with indo (p ASA vs. indo = N. S.). Despite equal inhibition of whole blood TX production after collagen (from 49.0 ± 4.3 ng/ml to 1.1 ± 0.6 ng/ml with ASA, from 49.8 ± 1.3 ng/ml to 1.4 ± 0.6 ng/ml with indo), again, however, 6-keto-PGFlΑ production was less affected by indo than by ASA (from 409 ± 30 pg/ml to 37 ± 13 pg/ml with ASA, inhibition = 91%; from 396 ± 35 to 318 ± 40 with indo, inhibition = 20%). These differential effects of indo and ASA might lead to a better platelet selectivity, tolerability and benefit/risk profile of indo vs. ASA, which are worthy of further assessment.

Persistent impairment of platelet aggregation following cessation of a short-course dietary supplementation of moderate amounts of N-3 fatty acid ethyl esters

The duration of the effect of a short-course (1-mo twice-daily) supplementation of moderate amounts (2.28 g) of n-3 fatty acid ethyl esters (FA) on platelet lipid composition and aggregation was compared with that of olive oil (3 g/d) supplementation in 14 healthy volunteers. The FA preparation employed contained eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA) in a ratio of 1:1.4. A marked rise (p <0.05) in the plasma and platelet content of EPA and DHA, and minimal changes in the content of arachidonic acid (AA) were documented at withdrawal of the n-3 FA supplementation. EPA/AA and DHA/AA ratios in platelet phospholipids showed that the FA accumulation persisted 8-12 wks after stopping the supplementation (p <0.05). The aggregation of platelets in response to collagen or ADP, and thromboxane B2 (TXB2) formation were impaired at withdrawal. The impaired aggregation lasted 8-12 weeks (p always <0.05), whereas TXB2 formation returned to basal values 4 weeks after stopping the n-3 supplementation. No correlation was found between impaired aggregation and TXB2 formation. In contrast, the impaired sensitivity to ADP (p = 0.036) and, to a lesser extent, to collagen (p = 0.068) were related to changes in the intracellular pH (pHi) of the Na+/H+ reverse transport. No changes in platelet composition or function were observed either during or following olive oil supplementation. These results document a long-lasting impairment of platelet sensitivity to ADP and collagen; changes in the pHi values of the Na+/H+ reverse transport, and a simultaneous persistent accumulation of EPA and DHA in platelet phospholipids, after stopping a short-course dietary supplementation of moderate amounts of n-3 fatty acid ethyl esters.

One-year treatment with ethyl esters of n-3 fatty acids in patients with hypertriglyceridemia and glucose intolerance: reduced triglyceridemia, total cholesterol and increased HDL-C without glycemic alterations

n-3 Fatty acids in the form of ethyl esters (EE) allow lower daily doses and improved compliance. Administration of n-3 fatty acids to patients with glucose intolerance has led to controversial findings, some studies indicating worsening of the disorder, others no effect, or an improvement. A total of 935 patients with hypertriglyceridemia, associated with additional cardiovascular risk factors, i.e. glucose intolerance, NIDDM and/or arterial hypertension were entered a double blind (DB) protocol lasting 6 months with n-3 EE versus placebo, followed by a further 6 months of open study (n = 868) on 2 g a day of n-3 EE. At the end of the DB period, triglyceridemia in the total group was reduced significantly more by n-3 EE, without alterations in glycemic parameters. In the 6 months open follow up, patients on n-3 EE with type IIB hyperlipoproteinemia showed a significant reduction of total cholesterol, both in cases with (-4.15% vs. the 6 month levels) and without NIDDM (-3.8%). HDL-cholesterol had an overall mean rise of 7.4%, maximal in type IV patients with (+9.1%) and without (+10.1%) NIDDM. No alterations in glycemic parameters were detected in treated patients. Administration of n-3 EE to patients with hypertriglyceridemia associated with NIDDM or impaired glucose tolerance appears safe and effective.

Effect of n-3 polyunsaturated fatty acids on cyclosporine pharmacokinetics in kidney graft recipients: a randomized placebo-controlled study

Highly concentrated marine polyunsaturated fatty acids (n-3 PUFA), affecting the lipids and lipophilic drugs metabolism, can interfere with cyclosporine (CyA) pharmacokinetics. This prospective, randomized and placebo-controlled, double-blind study involved 42 kidney graft recipients. From day +1, 21 pts (E) received 6 g n-3 PUFA (85% EPA + DHA, Esapent, Pharmacia) and 21 pts (P) received placebo (olive oil), both reduced to 3 g from day +30 on. A quadruple immunosuppressive regimen was employed. Plasma creatinine, lipids and CyA pharmacokinetics were investigated 1, 3, 6, 9 and 12 months after graft. The two groups were comparable for age, weight, M/F ratio, hypertension prevalence and baseline lipids. Active treatment did not affect total and HDL-cholesterol, but significantly lowered triglycerides (E:120 +/- 12 vs P:166 +/- 21 mg/dl, p < 0.0001). At one year, E pts had lower creatinine than P (1.26 +/- 0.06 vs. 1.88 +/- 0.2 mg/dl, p < 0.05), comparable CyA dosage, and a larger CyA area under the curve (AUC) (n.s.), with a higher blood peak level (Cmax) (p < 0.04) and less variance in time to peak (n.s.). The larger AUC in the E group at all intervals and the better pattern of plasma creatinine, with no rise in blood pressure, provided evidence of better CyA absorption and metabolism in n-3 PUFA supplemented kidney graft recipients.

Fatty acid dietary intake and the risk of ischaemic stroke: a multicentre case-control study. UFA Study Group

A low dietary intake of unsaturated fatty acids has been found in male patients with stroke as compared with controls in Italy, and a high consumption of meat has been associated with an increased risk of stroke in Australia. We present a case-control study, comparing the unsaturated and saturated fatty acids content of red cell membranes (which reflects the dietary intake of saturated and unsaturated fats) in 89 patients with ischaemic stroke and 89 controls matched for age and sex. In univariate analysis, besides hypertension, atrial fibrillation, ischaemic changes in ECG and hypercholesterolaemia, stroke patients showed a lower level of oleic acid (P = 0.000), but a higher level of eicosatrienoic acid (P = 0.009). Conditional logistic regression (dependent variable; being a case) showed that the best model included atrial fibrillation, hypertension, oleic acid and eicosatrienoic acids. These results confirm a possible protective role of unsaturated fatty acids against vascular diseases; however, we did not find any difference in the content of omega3 acids, which have been considered in the past to protect against coronary heart disease. We conclude that the preceding diet of patients with ischaemic stroke may be poor in unsaturated fatty acids (namely, oleic acid), and this defect is independent of other vascular risk factors. Only further studies will show whether changes in diet and/or supplement of unsaturated fatty acids might reduce the incidence of ischaemic stroke.

N-3 fatty acids do not lead to an increased diabetic risk in patients with hyperlipidemia and abnormal glucose tolerance. Italian Fish Oil Multicenter Study

A multicenter, randomized, double-blind, place-bo-controlled study evaluated the possible worsening of glycemic control after a moderate daily intake of n-3 fatty acid ethyl esters in patients with hypertriglyceridemia with and without glucose intolerance or diabetes. A total of 935 patients of both sexes in 63 Italian clinical centers were selected; 55% had either impaired glucose tolerance or non-insulin-dependent diabetes mellitus (NIDDM). They received for 2 mo either 1 g n-3 ethyl esters three times a day or a corresponding placebo, followed by 4 mo of either 1 g n-3 ethyl esters twice a day or placebo. In addition to the complete lipid and lipoprotein evaluation, patients with impaired glucose tolerance also underwent an oral-glucose-tolerance test; in patients with NIDDM, serum insulin and glycated hemoglobin (Hb A1c) concentrations were determined. Plasma triacylglycerol concentrations decreased significantly, up to 21.53% at 6 mo compared with baseline (decreased 15% compared with placebo), with a tendency toward a progressive reduction with time. There was no evidence for a different response in patients with either NIDDM or impaired glucose tolerance. Among NIDDM patients, the triacylglycerol reduction was greater in those with high-density-lipoprotein cholesterol < or = 0.91 mmol/L. There was no alteration in the major glycemic indexes: fasting glucose, Hb A1c, insulinemia, and oral glucose tolerance in patients with impaired glucose tolerance or NIDDM after treatment with n-3 ethyl esters. Treatment with a moderate daily dose of n-3 ethyl esters over a prolonged period of time significantly reduced triacylglycerol concentrations without any worsening of glucose tolerance in patients with hypertriglyceridemia with and without impaired glycemic regulation.

A prostacyclin-sparing effect of indobufen vs. aspirin

Indobufen ((+/-)-2-[p-(1-oxo-2-insoindolinyl)-phenyl]-butyric acid, indo) is a drug inhibiting platelet function by a reversible block of the arachidonic acid metabolism at the level of cyclooxygenase. Since tolerability profile of such drugs is mostly linked to extra-platelet cyclooxygenase inhibition, we prospectively evaluated the extent of platelet and extra-platelet cyclooxygenase inhibition by in vivo administration of indo in comparison with ASA. We assessed the effects of the two drugs on the ex vivo generation of TXB2 and 6-keto-PGF1 alpha in whole blood, as indices of the production of TXA2 and PGI2 (prostacyclin), respectively, either after spontaneous clotting at 37 degrees C for 1 h (Study 1) or after the addition of 2 micrograms/ml collagen (Study 2). Generation of 6-keto-PGF1 alpha in whole blood is a mixed index of platelet and extra-platelet cyclooxygenase activity, deriving from both platelet and white blood cell arachidonic acid metabolization. Fifteen patients with ischemic heart disease and baseline serum TXB2 levels > 300 ng/ml were allocated to receiving one single administration of either indobufen 200 mg (n = 6) or aspirin 500 mg (n = 9). Whole blood prostanoid generation was assessed at 0, 1, 2, 4, 6, 8, 12 and 24 h after drug administration (Study I). Ten healthy male volunteers were allocated to a double-blind, randomized crossover comparison of indo 200 mg b.i.d. vs. ASA 300 mg/d for 7 days (Study 2). Prostanoid generation and whole blood platelet aggregation were performed before and at the end of each study period (Day 0 and Day 7). At each time-point after single dose administration (Study 1), indobufen caused less % inhibition of whole blood 6-keto-PGF1 alpha than of TXB2. At 2 h, TXB2 was reduced to a similar extent after ASA (98 +/- 4%) and indo (97 +/- 6%) (p = N.S.), while inhibition of 6-keto-PGF1 alpha was clearly different ( > 98% after ASA, 81 +/- 2.5% after indo, p < 0.01). After one week of ASA or indo (Study 2) the maximum extent of whole blood platelet aggregation was similarly inhibited (from 17.2 +/- 1.4 ohms to 3.6 +/- 1.3 ohms with ASA; from 18.3 +/- 1.0 ohms to 1.6 +/- 0.7 ohms with indo (p ASA vs. indo = N.S.). Despite equal inhibition of whole blood TX production after collagen (from 49.0 +/- 4.3 ng/ml to 1.1 +/- 0.6 ng/ml with ASA, from 49.8 +/- 1.3 ng/ml to 1.4 +/- 0.6 ng/ml with indo), again, however, 6-keto-PGF1 alpha production was less affected by indo than by ASA (from 409 +/- 30 pg/ml to 37 +/- 13 pg/ml with ASA, inhibition = 91%; from 396 +/- 35 to 318 +/- 40 with indo, inhibition = 20%). These differential effects of indo and ASA might lead to a better platelet selectivity, tolerability and benefit/risk profile of indo vs. ASA, which are worthy of further assessment.

Cytokine secretion and eicosanoid production in the peripheral blood mononuclear cells of MS patients undergoing dietary supplementation with n-3 polyunsaturated fatty acids

To demonstrate the influence of n-3 PUFA supplementation on cytokine and eicosanoid production in peripheral blood mononuclear cells (PBMCs) of MS patients (MSP), we investigated the impact of a 6-month dietary supplementation with these fatty acids on the levels of interleukin-1 beta (IL-1 beta), IL-2, interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) in the supernatants of stimulated PBMCs and serum soluble IL-2 receptors in a group of 20 relapsing-remitting (R-R) MSP and a group of 15 age-matched control individuals (CI). The production of PGE2 and LTB4 in the stimulated PBMCs was also assessed in patient and control groups supplemented with n-3 PUFAs. In both groups, n-3 PUFA supplementation led to a significant decrease in the levels of IL-1 beta and TNF-alpha, and this reduction was more pronounced in the 3rd and 6th month of supplementation. An analogous decrease was observed in the levels of IL-2 and IFN-gamma produced by stimulated PBMCs, and in the levels of serum soluble IL-2 receptors. n-3 PUFA supplementation also appeared to significantly affect prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) production in PBMCs, both in MSP and the control group. The reduced production of these proinflammatory eicosanoids, and the decrease of some cytokines with an immunohenancing effect as a consequence of n-3 PUFA supplementation, could modulate some immune functions which have been demonstrated to be altered in MSP.

Functionally abnormal monocytes in hypercholesterolemia

We investigated some functions of monocytes from 20 type IIa hypercholesterolemic (HC) and five homozygous familial hypercholesterolemic (FH) patients. Monocytes from the HC patients contained as much cholesterol and formed as much thromboxane B2 in response to N-formyl-methionyl-leucyl-phenylalanine (fMLP) or calcium ionophore A23187 as those from normal individuals. In contrast, the generation of prostaglandin E2 and 6-ketoprostaglandin F1 alpha in response to these agonists was 1.5-3 times normal, and that of leukotriene B4 was 40-60% of the normal value (p < 0.05 for all). Studies in which the combination of fMLP or A23187 with sodium arachidonate were employed suggested that these abnormalities were independent of the availability of the endogenous substrate for the lipoxygenase or cyclooxygenase enzymes. Quantitatively and qualitatively comparable abnormalities were found in monocytes from the five FH patients, and these were little affected when the patients' plasma cholesterol levels were almost normalized by low density lipoprotein apheresis. In keeping with the abnormalities in the eicosanoid metabolism, monocytes from HC patients exhibited a defective ability (p < 0.05) to generate O2-, the extent of which was correlated with the impaired formation of leukotriene B4. On the other hand, adhesion studies indicated that patients' cells exhibited an abnormally high ability to adhere to glass (p < 0.01). These data indicate the presence of functionally abnormal monocytes in hypercholesterolemia and suggest a direction to be followed to understand the importance of such cells in the premature atherosclerosis that occurs in these patients.

In human monocytes interleukin-1 stimulates a phospholipase C active on phosphatidylcholine and inactive on phosphatidylinositol

Interleukin-1 (IL-1) can initiate the synthesis of prostaglandins which in turn act as endogenous modulators of IL-1 production. The human monocyte/macrophage synthesizes various eicosanoids through the activation of the cellular phospholipase system. Cell stimulation results in the activation of phospholipase A2 (PLA2) whose major substrate is phosphatidylcholine (PC) and the release of the eicosanoid precursor arachidonic acid (AA) from PC. Another pathway is the stimulation of a phospholipase C (PLC) mainly active on phosphoinositides and the resulting formation of inositol phosphates (IPs) and diacylglycerol (DAG). Phospholipids other than phosphoinositides can also be hydrolysed by PLC to give rise to DAG. Studies have shown that IL-1 does not activate the IP pathway, but it primarily stimulates a PLC linked to phosphatidylethanolamine in cultured rat mesangial cells, and a PLC linked to PC in Jurkart cells. We have stimulated human monocytes with IL-1 and calcium ionophore A23187 and we have observed their effect on the phospholipase system. The results indicate that IL-1 does not activate the formation of IPs in cells labeled with [3H]myo-inositol. In contrast, in cells labeled with [3H]AA, IL-1 causes the formation of DAG associated with the hydrolysis of PC. Moreover, after stimulation with IL-1 there is no accumulation of free AA which would indicate that there has been no activation of PLA2, which occurs instead with A23187 stimulation. These data suggest that, in monocytes, IL-1 does not directly stimulate a PLA2 or a PLC active on phosphatidylinositol; instead it primarily stimulates a PLC active on PC.

Effects of tenoxicam on superoxide anion formation, beta-glucuronidase release and fMLP binding in human neutrophils: comparison with other NSAIDs

Non-steroidal anti-inflammatory drugs (NSAIDs) are considered to exert their activity by interfering with the generation of arachidonate metabolites in various cells, mainly in neutrophils and monocytes. The inhibition of cellular cyclooxygenase enzyme, however, does not always correlate with the in vivo activity of these drugs. Recent evidence indicates that several NSAIDs may interfere with the stimulus-response coupling of inflammatory cells. In this study, the effects of tenoxicam, an oxicam derivative with a thienothiazine structure, on neutrophil activation were evaluated by the assessment of the following parameters: (1) superoxide anion generation by neutrophils and whole blood stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP), the calcium ionophore A23187 and serum treated zymosan (STZ); (2) beta-glucuronidase release from neutrophils stimulated with fMLP, A23187 and STZ; (3) binding of [3H]fMLP to intact neutrophils. The results were compared to those obtained using piroxicam and diclofenac. Tenoxicam, added in vitro to whole blood, at concentrations ranging between 10(-5) and 3 x 10(-4) M, significantly inhibited the generation of superoxide anion induced by fMLP, A23187 and STZ. The activity of tenoxicam on whole blood was similar to that of piroxicam, whereas diclofenac had only minimal effects on this experimental system. In isolated cells tenoxicam inhibited the generation of superoxide anion induced by A23187 and STZ. In addition, at the 3 x 10(-4) M concentration, tenoxicam and diclofenac similarly inhibited O2- generation by neutrophils stimulated with fMLP, whereas piroxicam only minimally affected this parameter. Tenoxicam also slightly, but not significantly, inhibited beta-glucuronidase release by isolated neutrophils induced by all the agonists used. Specific binding of [3H]fMLP to neutrophils was inhibited by the three NSAIDs tested in a dose-dependent fashion and tenoxicam was the most potent. The affinities (Kd) of tenoxicam, piroxicam and diclofenac were 1.11, 1.80 and 2.70 x 10(-5) M, respectively. The mechanism of inhibition of [3H]fMLP binding by tenoxicam was non-competitive. It is concluded that tenoxicam, at concentrations achievable in plasma at steady state, effectively inhibits some of the processes involved in neutrophil activation, which bear some relevance in the inflammatory disease.

Inhibition of human neutrophil aggregation by albumin. Relationship with cytoskeleton reorganization

Albumin, at concentration normally present in plasma (approximately 600 microM), significantly inhibited leukotriene B4 formation induced by a receptor mediated (fMet-Leu-Phe) and a receptor independent (calcium ionophore A23187) stimuli in human neutrophils. The inhibition of leukotriene B4 synthesis was accompanied by a concomitant reduction of neutrophil aggregation. In addition, this plasma protein prevented the increase in F-actin content of neutrophils stimulated with fMet-Leu-Phe and A23187, thus suppressing actin polymerization. These data indicate that albumin profoundly affects biochemical and functional aspects of neutrophils suggesting, for this plasma protein, a regulatory role in the overall pattern of the inflammatory reaction.

Effect of single oral administrations of non steroidal antiinflammatory drugs to healthy volunteers on arachidonic acid metabolism in peripheral polymorphonuclear and mononuclear leukocytes

The effects of a single oral administration of acetylsalicylic acid (500 mg), indomethacin (50 mg) and piroxicam (40 mg) to healthy volunteers on functional and biochemical parameters of platelets, polymorphonuclear (PMN) and mononuclear (MNL) leukocytes were evaluated. Blood was collected before and two hours after the drug intake and blood cells separated according to conventional techniques. The considered drugs almost completely suppressed the aggregation of platelets, whereas they did not affect either PMN and MNL aggregation. Superoxide anion generation by leukocytes was (PMN), or no effect (MNL) was observed after piroxicam and indomethacin respectively. The formation of arachidonate metabolites via the 5-lipoxygenase pathway by PMN and MNL challenged with 10 microM A23187 was unchanged following aspirin and indomethacin. In this respect a selective increase of 5-HETE and LTC4 synthesis by MNL only was detected after piroxicam administration. The three drugs similarly reduced TXB2 synthesis by platelets and PMN (-80% for aspirin and indomethacin, and -40% for piroxicam). As far as MNL is concerned, aspirin inhibited this metabolite by 80%, while indomethacin reduced it by 40% only. In contrast piroxicam increased TXB2 synthesis by stimulated MNL. It can be concluded that the considered antiinflammatory drugs 1) differently affect the cyclooxygenase enzyme in platelets and leukocytes; 2) at variance with the situation in platelets, the inhibition of thromboxane formation by leukocytes is not related to modifications of cellular function; 3) the formation of arachidonate metabolites via the 5-lipoxygenase pathway is affected by piroxicam only.

Vitamin E influences the effects of fish oil on fatty acids and eicosanoid production in plasma and circulating cells in the rat

An EPA enriched oil (MaxEPA, Seven Seas, U.K. containing 18% EPA and 12% DHA) alone or supplemented with 10 mg/ml/alpha tocopherol, was administered by gastric intubation at the dose of 3.2 ml/kg/day for a period of eight weeks to male rats fed a standard diet. An additional group of animals was treated with the same amount of olive oil. The administration of MaxEPA alone resulted, as expected, in accumulation of EPA and reduction of AA levels in plasma, platelet, red blood cell and PMNL phospholipids, when compared to values in the olive oil group. In addition, levels of linoleic acid were elevated, suggesting inhibition of the conversion of linoleic to arachidonic acid. Formation of i.r. TxB2 by stimulated PRP, of i.r. 6-keto-PGF1 alpha by perfused aortas, and of IR LTB4 and C4 by stimulated PMNL were reduced, but production of superoxide anion by PMNL was enhanced by MaxEPA treatment vs the olive oil treatment. Supplementation of MaxEPA with vitamin E caused a smaller reduction of 20:4 levels and a smaller increase of 20:5 levels in plasma and cell phospholipids and modified the effects of MaxEPA on eicosanoid and superoxide anion production, suggesting that lipid peroxidation may mediate some of the biological effects of omega 3 fatty acids.

Proinflammatory lipoxygenase products from peripheral mononuclear cells in patients with rheumatoid arthritis

The formation of 5-lipoxygenase products (5-hydroxyeicosatetraenoic acid [5-HETE], leukotriene B4 [LTB4], and leukotriene C4 [LTC4]) by polymorphonuclear and mononuclear leukocytes isolated from peripheral blood of patients with rheumatoid arthritis was evaluated and compared with the data obtained from a group of control subjects. Although the levels of arachidonic acid metabolites via 5-lipoxygenase pathway by stimulated polymorphonuclear cells were comparable between patients and controls, mononuclear leukocytes from patients synthesized, when stimulated, significantly greater amounts of 5-HETE, LTB4, and LTC4 than did cells isolated from normal subjects. In addition, the release of superoxide anion, stimulated by either a particulate or a soluble stimulus, was increased in mononuclear cells from patients. The enhanced capacity of peripheral mononuclear leukocytes isolated from patients with rheumatoid arthritis to generate proinflammatory metabolites of arachidonic acid and oxygenated species with bactericidal and tissue-damaging properties may contribute to the pathogenesis of this complex disease.

In vitro assessment of mononuclear leukocyte aggregation in response to sodium arachidonate and calcium ionophore A23187: comparison with polymorphonuclear leukocytes

The effects of ionophore A23187 and sodium arachidonate (AASS) on mononuclear leukocyte (MNL) aggregation were evaluated and the results compared to those obtained with similarly challenged polymorphonuclear leukocytes (PMN). MNL aggregated in response to both ionophore A23187 (8-40 microM f.c.) and AASS (0.05-0.5 mM f.c.) and the response was comparable to that of similarly challenged PMN. The AASS induced aggregation of the two leukocyte subpopulations was inhibited by the presence of bovine serum albumin (BSA) in the incubation media and by calcium exogenously added. In contrast, this cation stimulated ionophore induced aggregation. When PMN and MNL aggregation was induced by AASS, a marked release of lactic dehydrogenase (LDH) was detected. The thromboxane-synthetase inhibitor UK 37248, inhibited both leukocyte aggregation and LDH release. When the response of leukocytes from male and female subjects was compared, in terms of aggregation, it appeared that the response of PMN from female volunteers was higher than that of PMN isolated from male donors, whereas no sex-related difference was detected when MNL aggregation was evaluated.

Differential effects of aspirin and indomethacin on platelet and leukocyte thromboxane A2 formation

In this study, the in vitro inhibitory effects of aspirin and indomethacin on the arachidonic acid induced thromboxane B2 formation by human leukocytes, are evaluated. The results are compared to those obtained using similarly challenged human washed platelets. Acetylsalicylic acid inhibition, calculated as IC50 by a dose-response curve, is more than ten fold higher for leukocytes vs platelets. In fact, a concentration of aspirin as low as 5 microM almost completely suppresses thromboxane B2 formation by washed platelets, whereas a concentration of 50 microM is necessary to achieve the same inhibition with leukocytes. Indomethacin (0.001-100 microM), incubated with platelet and leukocyte suspensions acts similarly to aspirin. Leukocyte and platelet cyclooxygenases are, therefore, differently affected by both aspirin and indomethacin. These differences may be relevant in the understanding of the wide divergence between the aspirin doses used in thrombosis prevention and in the treatment of inflammatory disease.