Interleukin-10 and pentoxifylline inhibit C-reactive protein-induced tissue factor gene expression in peripheral human blood monocytes

The Potential Role of C-Reactive Protein in Metabolic-Dysfunction-Associated Fatty Liver Disease and Aging

Nonalcoholic fatty liver disease (NAFLD), recently redefined as metabolic-dysfunction-associated fatty liver disease (MASLD), is liver-metabolism-associated steatohepatitis caused by nonalcoholic factors. NAFLD/MASLD is currently the most prevalent liver disease in the world, affecting one-fourth of the global population, and its prevalence increases with age. Current treatments are limited; one important reason hindering drug development is the insufficient understanding of the onset and pathogenesis of NAFLD/MASLD. C-reactive protein (CRP), a marker of inflammation, has been linked to NAFLD and aging in recent studies. As a conserved acute-phase protein, CRP is widely characterized for its host defense functions, but the link between CRP and NAFLD/MASLD remains unclear. Herein, we discuss the currently available evidence for the involvement of CRP in MASLD to identify areas where further research is needed. We hope this review can provide new insights into the development of aging-associated NAFLD biomarkers and suggest that modulation of CRP signaling is a potential therapeutic target.

Effectiveness of pentoxifylline in severe early-onset fetal growth restriction: A randomized double-blinded clinical trial

OBJECTIVE

Management of pregnancy complicated by severe early-onset fetal growth restriction (FGR) is one of the most challenging obstetrical issues. So far, there has not been a proven option for the treatment or improvement of this condition. Improper immune response during placentation leads to inadequate trophoblast invasion and impaired utero-placental perfusion. Pentoxifylline improves the endothelial function and induces vasodilation by reducing the inflammatory-mediated cytokines. We have evaluated the effect of Pentoxifylline on fetal-placental perfusion, neonatal outcome, and the level of oxidative stress markers before and after the intervention in the setting of severe early-onset FGR.

MATERIALS AND METHODS

This study is a pilot randomized clinical trial on 40 pregnant women who had developed early-onset growth restricted fetus. Pentoxifylline and placebo were given with a dose of 400 mg per os two times daily until delivery. Serial ultrasound examination regarding fetal weight, amniotic fluid and also utero-placenta-fetal Doppler's were done. For the assessment of serum Antioxidant level, blood sampling was done once at the beginning of the study and again, at least, three weeks after the investigation. After delivery, umbilical-cord blood gas analysis, APGAR score at 1 and 5 min, NICU admission, and neonatal death were recorded and compared between the two groups.

RESULTS

Utero-placenta-fetal Doppler's in the Pentoxifylline group did not significantly change compared to the control group. Fetal weight gain was significantly higher in the Pentoxifylline group before (996.33 ± 317.41) and after (1616.89 ± 527.90) treatment (P = 0.002). Total serum antioxidant capacity significantly increased in the Pentoxifylline group (p < 0.036). Average 5 min Apgar score was significantly higher (P < 0.036) and the percentage of babies admitted to NICU was significantly lower (P < 0.030) in the treated group.

CONCLUSION

Using Pentoxifylline in pregnancy affected by FGR might show promising effects. In this study, Pentoxifylline improved the neonatal outcome, increased fetal weight gain, and reduced neonatal mortality by decreasing the level of oxidative stress markers and cutting down the inflammatory cascade.

Novel therapeutic targets in mood disorders: Pentoxifylline (PTX) as a candidate treatment

Numerous pharmacological treatments for mood disorders are currently available; however, rates of treatment resistance, relapse and recurrence remain high. Therefore, novel treatments acting outside of the conventionally targeted monoamine system are urgently needed to improve patient outcomes. Emerging and converging evidence suggests that immune dysfunction, oxidative stress, impaired cerebral blood flow (CBF) and decreased neurotrophic factors all contribute to mood disorder pathophysiology and are therefore treatment targets of interest. Pentoxifylline (PTX) is a phosphodiesterase inhibitor with potent anti-inflammatory and antioxidant effects, with additional pleiotropic effects that lead to improved CBF and increases in brain derived neurotrophic factor (BDNF) levels. The direct effect of non-specific phosphodiesterase inhibition may also improve alertness and cognitive function through enhancing second messenger systems. Replicated preclinical studies have demonstrated antidepressant-like effects in animal models. Small preliminary clinical trials have demonstrated promising results for antidepressant and procognitive effects, however, have yet to be replicated in larger mood disorder samples. Only one randomized clinical trial (RCT) specifically assessed the effects of adjunctive PTX in major depressive disorder (MDD), showing clinically and statistically significant antidepressant effects compared to placebo. No studies have assessed PTX in bipolar disorder (BD), where inflammation and altered CBF have also been strongly implicated. Taken together, PTX presents as a promising pleiotropic agent with several potential novel mechanisms of action meriting further evaluation in clinical trials to evaluate target engagement, antidepressant, procognitive and mood stabilizing effects.

Hypothesis: Pentoxifylline explores new horizons in treatment of preeclampsia

Preeclampsia, the leading cause of maternal morbidity and perinatal mortality, initiates as inappropriate immune response to trophoblastic invasion impairs placentation and placental circulation. A poorly perfused placenta generates superoxide anions as well as anti-angiogenic factors and this series of events result in impairment of endothelial function, followed by maternal morbidities such as hypertension, kidney injury and proteinuria. Renal loss of anti-coagulant proteins and subsequent hyper-coagulable state along with endothelial dysfunction accelerates progression of the disease toward eclampsia. Since Pentoxifylline, a methyl-xanthine derivative known for enhancement of vascular endothelial function, down-regulation of many inflammatory cytokines increased during preeclampsia, improvement of placental circulation, reduction of ischemia-reperfusion injury, enhancement of vasodilatation and endothelial function, ameliorating proteinuria, inhibition of platelet aggregation and decreasing risk of preterm labor, which are all amongst morbidities of preeclampsia, here it is hypothesized that Pentoxifylline prevents development of preeclampsia and/or decelerate progression of the disease.

Preoperative oral pentoxifylline in case of coronary artery bypass grafting with left ventricular dysfunction (ejection fraction equal to/less than 30%)

OBJECTIVE

Most coronary artery bypass grafts are done by applying cardiopulmonary bypass, which usually induces unwanted inflammatory reactions and impairs the outcomes. In order to minimize the perilous response of cardiopulmonary bypass, pentoxifylline was getting used orally.

METHODS

In a prospective, placebo-controlled, randomized clinical trial, 178 coronary artery bypass graft candidates with ejection fraction lower/equal to 30%, divided into two equal groups (pentoxifylline and control), participated in the study. Pentoxifylline patients received 400 mg pentoxifylline 3 times a day for 3 days before operation. The outcomes were compared between groups using student's t-test, Mann-Whitney U-test, Pearson chi-square, or Fisher's exact test.

RESULTS

Pentoxifylline administration did not significantly affect troponin-T (p=0.68), but it reduced tumor necrosis factor-α (p=0.01) and interleukin-6 (p=0.01). It improved left ventricular ejection fraction significantly (p=0.01). White blood cell and platelet counts, hemoglobin, and hematocrit were not influenced by pentoxifylline. The drug did not affect blood urea nitrogen and creatinine, occurrence of renal failure, cerebrovascular accidents, and in-hospital mortality rate. The need for an intra-aortic balloon pump, cardiopulmonary bypass, and aortic cross-clamp times were not affected, either. Pentoxifylline decreased the intensive care unit stay (p<0.001), ventilation time, 10.4 hours in the pentoxifylline group against 14.7 hours in the control group (p=0.01), and the requirement of inotropic agents (p=0.02) and blood transfusion (p=0.01).

CONCLUSION

Pentoxifylline has more beneficial potencies in reducing adverse events after coronary artery bypass graft using cardiopulmonary bypass, than what are known.

The grade-response relation between severity of peritonitis and serum cytokine concentrations explains Mannheim Peritonitis Index threshold

AIM

To explore the gradient between the acute-phase response (APR) and peritonitis of differing severity.

METHODS

In 202 patients with peritonitis, we determined serum concentrations of interleukin (IL)-6, IL-10, IL-13, tumor necrosis factor (TNF)-alpha, and C-reactive protein (CRP). The severity of peritonitis was graded in accordance with the Mannheim Peritonitis Index (MPI). The grade-response relation between the severity of peritonitis and each analyte was explored.

RESULTS

A statistically significant association was found between the medians of severity of peritonitis and IL-6 (p < 0.025), TNF-alpha (p < 0.01), CRP (p < 0.033), IL-10 (p < 0.0001), and IL-13 (p < 0.004). Both TNF-alpha and IL-10 had a direct, and IL-13 an indirect, relation to severity, whereas CRP and IL-6 tended toward linear behavior in equilibrium. A significant association persisted between individual MPI scores and IL-6 (p < 0.002), TNF-alpha (p < 0.002), CRP (p < 0.002), and IL-10 (p < 0.001), but not IL-13 (p = 0.646).

CONCLUSION

Around the mean value of grade II peritonitis, the equilibrium between pro-inflammatory and anti-inflammatory cytokines is lost. This change coincides with the 26-point threshold for the MPI.

Pentoxifylline reduces pro-inflammatory and increases anti-inflammatory activity in patients with coronary artery disease—A randomized placebo-controlled study

The balance between different immunological stimuli is essential in the progression and stabilization of atherosclerotic plaques. Immune regulation has been suggested as potential target for the treatment of atherosclerotic disease. We sought to determine whether treatment with pentoxifylline, a phosphodiesterase inhibitor with immunomodulating properties, could reduce the pro-inflammatory response observed in patients with acute coronary syndromes (ACS) and increase anti-inflammatory activity. In a double-blind, prospective, placebo-controlled study, 64 patients with ACS were randomized to receive pentoxifylline 400mg TID or placebo for 6 months. Analysis of the pro-inflammatory markers, C-reactive protein (CRP), interleukin (IL)-6, IL-12, interferon-gamma and tumor necrosis factor (TNF)-alpha and the anti-inflammatory cytokines, transforming growth factor (TGF)-beta1 and IL-10 were done at baseline, 1 and 6 months. Pentoxifylline treatment significantly reduced the adjusted levels of CRP and TNF-alpha compared to placebo after 6 months (P=0.04 and P<0.01, respectively). IL-12 increase was significantly less pronounced with pentoxifylline (P=0.04). The levels of the anti-inflammatory cytokine, IL-10, also declined significantly less in the pentoxifylline group compared to placebo (P<0.01) with a trend towards a higher increase of TGF-beta1 in the former group (P=0.16). Pentoxifylline reduces pro-inflammatory and increases anti-inflammatory response in patients with ACS and may have beneficial clinical effects on cardiovascular events.

C-reactive protein is expressed and secreted by peripheral blood mononuclear cells

C-reactive protein (CRP) protects against bacterial pathogens and is a predictor of cardiovascular events. CRP is produced by vascular and organ-specific cells but the generation of CRP from peripheral blood mononuclear cells (PBMC) is poorly established. In a randomized, double-blind, placebo-controlled, two-way cross-over trial six healthy volunteers received a bolus infusion of 20 IU/kg Escherichia coli endotoxin [lipopolysaccharide (LPS)] or placebo. Intracellular CRP protein and CRP secretion of peripheral blood mononuclear cells (PBMC) was measured at baseline and 6 h after LPS by flow cytometry and enzyme-linked immubosorbent assay (ELISA), respectively. CRP mRNA expression was determined by real-time polymerase chain reaction (PCR). Regulation of the expression pathway was assessed using specific inhibitors in vitro. Small amounts of CRP protein and mRNA were detectable in PBMC, which were up-regulated between two- and eightfold by endotoxaemia in vivo. Augmented expression and release of CRP by LPS was consistent in PBMC cell culture experiments. LPS, interleukin (IL)-1, IL-6 and tumour necrosis factor (TNF)-alpha increased and IL-10 reduced CRP expression in PBMC. Toll-like receptor (TLR)-4, nuclear factor (NF)-kappaB and protein kinase C (PKC) activation were identified as intracellular signal transduction pathways of LPS-induced CRP expression. Constitutive CRP expression and release in PBMC is enhanced by inflammatory stimuli in vivo and in vitro. LPS might induce CRP generation via activation of TLR-4, NF-kappaB and PKC.

C-reactive protein decreases expression of thrombomodulin and endothelial protein C receptor in human endothelial cells

BACKGROUND

C-reactive protein (CRP) is associated with atherosclerosis and thrombosis. However, it is unclear whether CRP has direct effects on the antithrombogenic properties of endothelial cells. The objective of the present study was to determine the effect of CRP on the expression of thrombomodulin (TM) and the endothelial protein C receptor (EPCR) in human endothelial cells.

METHODS

Human coronary artery endothelial cells (HCAECs) were treated with CRP in a dose- and time-dependent manner. The messenger RNA levels of TM and EPCR were determined by real-time polymerase chain reaction. Anti-CD32 antibody and curcumin were used to block the potential effects of CRP.

RESULTS

In HCAECs, CRP (10 and 25 microg/mL) significantly reduced TM messenger RNA levels by 18 and 30%, respectively, compared with controls (P < .05). This effect was also confirmed in other types of human endothelial cells from umbilical veins and skin microvessels. The cells treated with CRP (10 and 25 microg/mL) showed significant reductions of EPCR mRNA levels by 34% and 33%, respectively (P < .05). Anti-CD32 antibody partially blocked CRP-induced downregulation of TM and EPCR in HCAECs. Furthermore, curcumin (5 and 10 microM) in combination with CRP (10 microg/mL) significantly increased TM mRNA levels by 45 and 100%, respectively, and increased EPCR mRNA levels by 24 and 45%, respectively, compared with those in CRP-treated cells (P < .05).

CONCLUSIONS

CRP significantly decreases the expression of TM and EPCR in human endothelial cells, thereby promoting thrombogenic conditions. This effect is partially mediated by CD32. Curcumin completely blocks CRP-induced downregulation of TM and EPCR in HCAECs.

Angiotensin II induces the expression of tissue factor and its mechanism in human monocytes

The renin-angiotensin system (RAS) is linked with the vascular motion and the secretion of aldosterone. The purpose of the present study was to elucidate whether angiotensin II (Ang II) induces monocytes (Mo) to express tissue factor (TF) and if Ang II subtype 1 receptor (AT1R) antagonists inhibit the effect of Ang II. The roles of different intracellular signal transduction pathways and IkappaB/NF-kappaB in Ang II-induced TF expression of Mo were also studied to explore the mechanisms involved. Mo were isolated from heparinized human blood by a two-step gradient centrifugation, cultured in RPMI-1640 and exposed to Ang II and other test reagents. Mo TF activity and TF antigen were determined with a one-stage clotting method and ELISA, respectively, after the culture. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the TF mRNA levels in Mo. The level of IkappaBalpha in Mo was detected by Western blot analysis. Electrophoresis mobility shift assay (EMSA) was performed to evaluate the binding activity of NF-kappaB in Mo. The experiment results are as follows: (1) Ang II (10(-10)-10(-7) M) induced Mo to express TF activity but had no marked effect on other mononuclear cells. Ang II 10(-10)-10(-7) M) also caused increased TF mRNA expression and TF antigen from Mo in a dose-dependent manner. The TF antigen of Mo was elevated at 4 h after Mo was exposed to Ang II (10(-7) M) in culture, reached the peak at 6 h, and then declined from 12 h. The changes of TF activity were positively correlated with those of TF antigen. TF mRNA expression was elevated at 1 h, peaked at 3 h, and declined after 8 h. (2) Losartan (10(-6)-10(-5) M) significantly inhibited the stimulative effects of Ang II on TF activity, TF antigen and TF mRNA in Mo in a dose-dependent manner. (3) The protein kinase C (PKC) inhibitor, staurosporine, and the protein tyrosine kinase (PTK) inhibitor, genistein, both lowered TF levels in Mo, but the inhibitory effect of staurosporine was stronger than that of genistein. The effect of mitogen-activated protein kinase (MAPK) inhibitor, U0126, on monocytic TF expression was not significant. (4) Western blot analysis revealed that after Ang II (10(-7) M)exposure, levels of IkappaBalpha began to decrease at 15 min, reached a nadir at 60 min (P<.01), and recovered at 180 min. (5) EMSA showed that NF-kappaB binding activity started to increase at 15 min, reached a peak at 60 min, and returned to baseline at 180 min. The present data suggest that Ang II can directly induce TF expression in human Mo and this effect is mediated by AT1R. PKC may play the most important role in Ang II-induced TF expression among the three signal pathways detected. In addition, activation of NF-kappaB is also involved in the TF expression of Mo induced by Ang II.

C-Reactive Protein Does Not Directly Induce Tissue Factor in Human Monocytes

OBJECTIVE

It is generally assumed that C-reactive protein (CRP) induces synthesis of tissue factor (TF) in monocytic cells, thereby potentially initiating intravascular blood coagulation. We aimed to elucidate the mechanism of CRP-induced TF expression in monocytes and monocyte-derived macrophages (MDMs) in vitro.

METHODS AND RESULTS

Monocytes were isolated from the blood of healthy donors and cultured with or without CRP or lipopolysaccharide (LPS) to study the time course of TF antigen and TF mRNA expression. Addition of 100 microg/mL CRP did not result in a significant increase in TF antigen (range: 9 to 163 pg/10(6) cells, n=11) and TF mRNA (relative number of TF transcripts; N(TF)=0.01 to 0.33), when compared with nonstimulated cells (TF antigen 7 to 46 pg/10(6) cells, N(TF)=0.01 to 0.13). Variation of CRP concentration and exposure time did not affect the TF response. Similar results were obtained in monocytes cultured in suspension and in MDMs. In contrast, TF was strongly induced by 10 microg/mL LPS (TF antigen 1125 to 6120 pg/10(6) cells, N(TF)=5.94 to 23.43). Cultured monocytes did express FcRgammaII, a putative CRP receptor, and addition of CRP induced a 7-fold increase in the production of monocyte chemoattractant protein-1 (MCP-1). Interestingly, CRP addition to peripheral blood mononuclear cells (PBMCs) did result in TF expression on monocytic cells.

CONCLUSIONS

The absence of TF induction after incubation of purified monocytes with CRP indicates that CRP is unable to induce TF expression in monocytes and MDMs directly. The presence of CRP-induced TF expression in PBMCs suggests that CRP can induce TF indirectly, probably through cross-talk between cells.

Increased resistance of LFA-1-deficient mice to lipopolysaccharide-induced shock/liver injury in the presence of TNF-alpha and IL-12 is mediated by IL-10: a novel role for LFA-1 in the regulation of the proinflammatory and anti-inflammatory cytokine balance

Challenge with low doses of LPS together with D-galactosamine causes severe liver injury, resulting in lethal shock (low dose LPS-induced shock). We examined the role of LFA-1 in low dose LPS-induced shock. LFA-1(-/-) mice were more resistant to low dose LPS-induced shock/liver injury than their heterozygous littermates, although serum levels of TNF-alpha and IL-12 were higher in these mice. C57BL/6 mice were not rescued from lethal effects of LPS by depletion of NK1(+) cells, granulocytes, or macrophages, and susceptibility of NKT cell-deficient mice was comparable to that of controls. High numbers of platelets were detected in the liver of LFA-1(+/-) mice after low dose LPS challenge, whereas liver accumulation of platelets was only marginal in LFA-1(-/-) mice. Following low dose LPS challenge, serum levels of IL-10 were higher in LFA-1(-/-) mice than in LFA-1(+/-) mice, and susceptibility to low dose LPS-induced shock as well as platelet accumulation in the liver of LFA-1(-/-) mice were markedly increased by IL-10 neutralization. Serum levels of IL-10 in LFA-1(+/-) mice were only marginally affected by macrophage depletion. However, in LFA-1(-/-) mice macrophage depletion markedly reduced serum levels of IL-10, and as a corollary, susceptibility of LFA-1(-/-) mice to low dose LPS-induced shock was markedly elevated despite the fact that TNF-alpha levels were also diminished. We conclude that LFA-1 participates in LPS-induced lethal shock/liver injury by regulating IL-10 secretion from macrophages and that IL-10 plays a decisive role in resistance to shock/liver injury. Our data point to a novel role of LFA-1 in control of the proinflammatory/anti-inflammatory cytokine network.

Reduction of serum C-reactive protein by statin therapy may reflect decreased isoprenylation of Rac-1, a mediator of the IL-6 signal transduction pathway

Recent studies demonstrate that statin therapy decreases plasma levels of C-reactive protein (CRP), a potent risk factor for thrombotic vascular events. CRP is an acute phase reactant, and most circulating CRP is synthesized by hepatocytes in response to IL-6. Since statins do not appear to have a consistent impact on serum levels of IL-6, their impact on plasma CRP very likely reflects down-regulation of hepatocyte responsiveness to this cytokine. The ability of IL-6 to promote transcription of CRP is mediated, in large part, by activation of the transcription factor STAT3; this activation requires both a tyrosine phosphorylation (mediated by the IL-6 receptor complex) and a serine phosphorylation (Ser-727), the origin of which has been more obscure. There is new evidence that, when hepatocytes are exposed to IL-6, the consequent serine phosphorylation of STATS is mediated by a signal transduction pathway in which the G-protein Rac-1 plays an obligate role. Inasmuch as the proper function of Rac-1 is contingent on isoprenylation that anchors it to the plasma membrane, it is reasonable to hypothesize that statin therapy interferes with IL-6 signaling in hepatocytes by suppressing the isoprenylation of Rac-1; a decrease in the transcription of CRP would be a likely consequence of this effect. Whether or not a reduction in elevated CRP is directly beneficial to vascular health, statins can exert direct effects on vascular endothelial function that should help prevent vascular inflammation and thrombosis, and thus should be of particular benefit to subjects - such as those with high CRP levels - who are at high risk for vascular events.

Pro-inflammatory effects of oestrogens during use of oral contraceptives and hormone replacement treatment

The effects of two third-generation monophasic combined oral contraceptives (COC) and a postmenopausal hormone replacement therapy (HRT) consisting of 2 mg 17 beta-oestradiol on the plasma level of the acute-phase indicator C-reactive protein (CRP) and other acute-phase reactants were analysed. Two studies were conducted: (1) a randomised, open-label study with two different oral contraceptive preparations with an equal dose of ethinylestradiol (30 micrograms) and a different progestogen, either 75 micrograms gestodene (GSD-EE) or 150 micrograms desogestrel (DSG-EE); blood samples of 39 young women were analysed before and after 3, 6, 12 treatment cycles; (2) a randomised, blinded placebo-controlled study with 2 mg 17 beta-oestradiol in postmenopausal women with non-insulin-dependent diabetes mellitus without signs of cardiac involvement; blood samples of 38 women were analysed before and after 6 weeks of treatment. The plasma concentration of CRP increased strongly during oral contraceptive use for both preparations; the increase persisted over 12 cycles. The already elevated CRP in postmenopausal diabetic women showed a moderate increase after 6 weeks of treatment with 17 beta-oestradiol. CRP increases during oral contraceptive use were associated with changes in some other acute-phase proteins (fibrinogen, ceruloplasmin, von Willebrand factor [vWF]) originating from the liver and vessel wall, but not in others (interleukin-6 [IL-6], serum amyloid A [SAA]). The results demonstrate an increase in a specific set of acute-phase reactants caused by oestrogen-containing preparations. It is proposed that the pro-inflammatory effect of oestrogens should be checked for a relationship with the increased risk of thromboembolism for both oral contraceptive and HRT.

Interleukin-10 regulates the tissue factor activity of monocytes in an in vitro model of bacterial endocarditis

Monocytes are important effector cells in the pathogenesis of bacterial endocarditis since they provide the tissue factor that activates the coagulation system and maintains established vegetations. Monocytes secrete cytokines that can modulate monocyte tissue factor activity (TFA), thereby affecting the formation and maintenance of vegetations. In this study, we show that monocytes cultured for 4 h on a Streptococcus sanguis-infected fibrin matrix mimicking the in vivo vegetational surface express high levels of TFA. This was accompanied by secretion of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and IL-1 beta. After a 24-h incubation period the anti-inflammatory cytokine IL-10 could also be detected. Our data show that, whereas TNF-alpha and IL-1 have a minor role in the induction of TFA by monocytes cultured on a fibrin matrix, TNF-alpha but not IL-1 plays an important role in the induction of IL-10 by these cells. In turn, our data show that IL-10 is an important factor in the downregulation of monocyte TFA. In summary, we conclude that IL-10 is an important factor in the control of monocyte TFA in endocardial vegetations.

Tissue factor in atherosclerosis

Thrombosis is a key feature of the initiation and progression of atherosclerosis and its clinical sequelae. Acute thrombosis can lead to arterial occlusion and consequently provoke myocardial infarction, unstable angina, stroke and sudden death. Acute thrombosis can also be a complication of arterial bypass surgery, balloon angioplasty, atherectomy, or coronary artery stenting. The thrombotic response is influenced by several factors, among them the thrombogenicity of the vessel wall and of certain blood components as well as their interaction with the lipid pool. Tissue factor (TF) is considered to be the primary cofactor of cellular origin that is involved in activation of the coagulation pathway. The active form of TF has been shown to be present in specimens of human coronary artery in association both with acellular lipid areas and with macrophages and smooth muscle cells, which suggests that TF plays a major role in determining plaque thrombogenicity. We discuss here what is currently known about the role of tissue factor in atherogenesis, and focus attention on pharmacological approaches in this area.

Procoagulant inflammatory responses of monocytes after direct balloon angioplasty in acute myocardial infarction

This study sought to investigate monocyte procoagulant activity and Mac-1 expression after successful percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI). An increased leukocyte count is an important risk factor for subsequent adverse cardiac events in AMI. Cellular procoagulant responses may contribute to the risk of thrombotic events after AMI. In 20 patients with AMI serial venous blood samples were obtained before, 4, 8 hours, and daily after direct PTCA. Twenty patients with elective PTCA served as a control group. We measured leukocyte procoagulant activity with a 1-stage clotting assay, Mac-1 expression of monocytes by flow cytometry, concentrations of tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, and IL-8 using immunoassays. Forty-eight hours after PTCA in patients with AMI, an increase in systemic IL-6 and C-reactive concentrations was found (p = 0.001, p = 0.008) associated with an increase in monocyte Mac-1 expression by 49 +/- 18% (p = 0.04) and followed by an increase in monocyte procoagulant activity by 140 +/- 63% 72 hours after PTCA (p = 0.01). None of these changes were detectable in the control group. No changes in the concentrations of the cytokines IL-1beta, tumor necrosis factor-alpha, or IL-8 were found. The present study demonstrates an increase in procoagulant activity along with an increase in Mac-1 expression on circulating monocytes after successful PTCA in AMI associated with an increase in systemic IL-6. These cellular procoagulant responses may limit the clinical benefit from timely reperfusion.

Interleukin-10 Inhibits Activation of Coagulation and Fibrinolysis During Human Endotoxemia

Interleukin-10 (IL-10) has been found to inhibit lipopolysaccharide (LPS)-induced tissue factor expression by monocytes in vitro. To determine the effects of IL-10 on LPS-induced activation of the hemostatic mechanisms in vivo, we performed a placebo-controlled, cross-over study of human endotoxemia. Two groups of eight volunteers were challenged with LPS (4 ng/kg) on two occasions: once in conjunction with placebo, and once with recombinant human IL-10 (rhIL-10; 25 μg/kg). In group 1, placebo or rhIL-10 was given 2 minutes before LPS challenge, group 2 received placebo or rhIL-10 1 hour after LPS administration. Pretreatment with rhIL-10 reduced both LPS-induced activation of the fibrinolytic system (plasma concentrations of tissue type plasminogen activator, plasmin-α2–antiplasmin complexes, and D-dimer), and inhibition of fibrinolysis (plasma levels of plasminogen activator inhibitor 1), whereas posttreatment only inhibited the latter response. Both IL-10 pre- and posttreatment attenuated activation of the coagulation system (plasma levels of prothrombin fragment F1 + 2 and thrombin–antithrombin complexes). These results indicate that rhIL-10, besides its well-described inhibitory effects on cytokine release, potently modulates the fibrinolytic system and inhibits the coagulant responses during endotoxemia.

Effects of alpha 1-acid glycoprotein on tissue factor expression and tumor necrosis factor secretion in human monocytes

Activated monocytes express tissue factor (TF) and secrete tumor necrosis factor alpha (TNF alpha), which are important in the initiation of blood coagulation and inflammation. We investigated the effect of alpha 1-acid glycoprotein (alpha 1-AGP), an acute phase protein, on the induction of the expression of TF and the secretion of TNF alpha in human monocytes in vitro. The TF activity of both fresh human monocytes and human monocytic cell line U937 significantly increased in a dose-dependent manner after a 6 h incubation with human or bovine alpha 1-AGP. The activity of TF gradually tailed off after 24 h. RT-PCR and Southern blot analysis revealed that TF mRNA synthesis was induced in monocytes. Inhibition of alpha 1-AGP induced TF expression by actinomycin D (ActD) further support that de novo TF mRNA synthesis was required. The specificity of the alpha 1-AGP-induced TF activity was demonstrated by anti-alpha 1-AGP antibody inhibition. TNF alpha secretion in alpha 1-AGP stimulated monocytes was also increased; this could be blocked by pentoxifylline (PTX). The possible contamination of lipopolysaccharide (LPS) in the alpha 1-AGP was excluded by limulus amoebocyte lysate. Therefore, these results indicate that alpha 1-AGP may contribute to the cellular initiation of coagulation and inflammation by increasing TF expression and TNF alpha secretion of monocytes.