Prostaglandin and thromboxane biosynthesis in isolated platelet-free human monocytes. III. The induction of cycloxygenase by colony stimulating factor-1

Soluble factors differ in platelets derived from separate niches: a pilot study comparing the secretome of peripheral blood and bone marrow platelets

BACKGROUND AIMS

Platelet-rich plasma (PRP) and bone marrow aspirate are commonly used in orthobiologics for their anti-inflammatory, anabolic/regenerative and immunomodulatory characteristics via platelet degranulation and cell secretions. Although platelets are derived from megakaryocytes in the bone marrow, no attention has been paid to the potential benefits of bone marrow platelets and whether their contents differ from aging platelets in peripheral blood.

METHODS

In the present study, leukocyte-poor peripheral blood-derived platelets in plasma (LPP) and leukocyte-poor bone marrow platelets in plasma (BMP) were prepared from six donors, activated with calcium chloride, incubated and sampled at day 0, day 3 and day 6. LPP and BMP are platelet preparations intended to evaluate the respective platelet secretomes but are not classified as conventional PRPs, as they are not concentrated to the extent necessary to meet the qualifying criteria. At each time point, 15 growth and immunomodulatory factors were quantitated in LPP and BMP: platelet-derived growth factor AA, basic fibroblast growth factor/fibroblast growth factor 2, granulocyte-macrophage colony-stimulating factor, hepatocyte growth factor, macrophage colony-stimulating factor, stem cell factor, vascular endothelial growth factor, tumor necrosis factor alpha, IL-1β, interferon gamma, IL-4, IL-10, IL-1 receptor antagonist protein, IL-12p40 and arginase-1.

RESULTS

The results illustrate that platelets derived from bone marrow have a unique secretome profile compared with those derived from peripheral blood, with significant differences in anti-inflammatory cytokines, which are associated with monocyte polarization.

CONCLUSIONS

Ultimately, bone marrow-derived platelets may be useful as a stand-alone orthobiologic or as an effective adjuvant to autologous cell therapies where anti-inflammatory and anabolic processes are desired, especially with respect to monocyte function.

Cigarette smoking is associated with increased circulating proinflammatory and procoagulant markers in patients with chronic coronary artery disease: effects of aspirin treatment

BACKGROUND

Smoking is associated with endothelial dysfunction. Cytokines released by injured endothelium promote vascular interactions with leukocytes and platelets. We investigated whether (a) cigarette smoking is linked to increased cytokine production, which may mediate platelet activation and thrombin generation in chronic coronary artery disease (CAD), and (b) aspirin treatment inhibits smoking-related changes on cytokines, platelets, and thrombin.

METHODS AND RESULTS

Plasma macrophage-colony-stimulating factor (M-CSF) and C-reactive protein (CRP) were measured in 100 patients with chronic CAD, 60 of whom were chronic smokers. Prothrombin fragments 1+2 and urinary 11-dehydro-thromboxane B2 (TXB2) were additionally measured in 60 of 100 patients (30 of whom were smokers) and in 24 healthy controls. Smokers (n = 20) matched for age, myocardial ischemia, and other risk factors with 20 nonsmokers entered a double-blind crossover trial of aspirin (300 mg/d for 3 weeks) versus placebo. Blood and urine measurements were repeated after each treatment. Compared with nonsmokers, smokers had 3-fold median M-CSF (1499 vs 476 pg/mL), 2-fold CRP (1.5 vs 0.8 mg/L), and higher 11-dehydro-TXB 2 (3.6 vs 2.1 ng/mg creatinine, P < .01 for all comparisons). After aspirin treatment, M-CSF, CRP, 11-dehydro-TXB 2 , and prothrombin fragments 1+2 remained higher in smokers compared with nonsmokers despite a significant reduction of these markers by aspirin (P < .05). M-CSF remained related to 11-dehydro-TXB 2 excretion during both treatment phases (P < .01) suggesting that cytokine-mediated thromboxane A 2 production was not altered by aspirin.

CONCLUSIONS

Smoking is associated with increased M-CSF, CRP, and platelet activity. Although aspirin treatment reduces the proinflammatory and procoagulant markers in smokers, it does not abolish the proinflammatory effects of smoking in patients with chronic CAD.

Increased circulating C-reactive protein and macrophage-colony stimulating factor are complementary predictors of long-term outcome in patients with chronic coronary artery disease

AIMS

We investigated, in a 6 year follow-up study, whether circulating levels of C-reactive protein (CRP) and macrophage colony stimulating factor (MCSF) have an independent or complementary prognostic value in patients with chronic coronary artery disease (CAD).

METHODS AND RESULTS

MCSF and CRP were measured in 100 patients with chronic CAD. Of 95 (33%) patients, 31 who completed the 6 year follow-up presented adverse events (death, myocardial infarction, and unstable angina). In multivariable analysis (including traditional risk factors and medications), the upper tertiles of MCSF (> or =814 pg/mL) and CRP (> or =2.5 mg/L) levels were independently associated with a 13- and 6-fold increase in risk of events, respectively (P<0.01). Patients with combined high CRP and MCSF had a higher absolute risk of events than patients with elevated MCSF or CRP alone (75 vs. 59 vs. 32%, respectively, P<0.01). The mean event-free time was 39, 64, and 52 months in patients with elevated MCSF, elevated CRP, and their combination, respectively.

CONCLUSION

In patients with chronic CAD, the prognostic value of MCSF is independent and complementary to that of CRP. MCSF is a particularly useful prognostic marker when CRP levels are low, but also provides additional information concerning risk and time-course of events in patients with elevated CRP.

Reduction of daily life ischaemia by aspirin in patients with angina: underlying link between thromboxane A2 and macrophage colony stimulating factor

OBJECTIVES

To evaluate whether aspirin reduces the incidence and frequency of daily life myocardial ischaemia in a cohort of patients with chronic stable coronary artery disease.

SETTING

Tertiary referral centre.

METHODS

60 patients with chronic stable coronary artery disease underwent 48 hour Holter monitoring to assess the incidence and frequency of daily life myocardial ischaemia. Those with myocardial ischaemia (40/60) entered a double blind, crossover trial of aspirin (300 mg/day for three weeks) versus placebo. After each treatment arm, 48 hour Holter monitoring was repeated and urinary thromboxane (Tx) B2, 11-dehydro-TxB2, plasma prothrombin fragment F1+2, macrophage colony stimulating factor (MCSF), and interleukin (IL)-6 were measured.

RESULTS

Aspirin reduced the total number and duration of ischaemic episodes from 339 to 251 and from 1765 to 1365 minutes, respectively (p < 0.01 for both). TxB2 was also reduced from 0.2 to 0.1 ng/mg creatinine, 11-dehydro-TxB2 from 3.3 to 1.3 ng/mg creatinine, F1+2 from 1.5 to 1.2 nmol/l, MCSF from 991 to 843 pg/ml, and IL-6 from 3.5 to 2.9 pg/ml (p < 0.05 for all). 11-dehydro-TxB2 excretion with and without aspirin was related to MCSF concentrations (p < 0.01), and the percentage reduction of MCSF by aspirin was related to the reduction of 11-dehydro-TxB2 (p < 0.05) and the reduction of the ischaemic burden compared with placebo (p < 0.05).

CONCLUSIONS

In patients with daily life ischaemia, aspirin reduces the incidence and frequency of ischaemic episodes as well as the systemic concentrations of haemostatic/inflammatory markers. Aspirin may prevent transient coronary flow reductions through platelet, thrombin, and cytokine inhibition.

Comparison of mononuclear cell proteins and plasma proteins before and during parturition by two dimensional electrophoresis

Two dimensional electrophoresis is a technique whereby protein sources are organized by molecular weight and electrical charge on a polyacrylamide gel. To detect changes that may be associated with the onset of parturition, we compared electrophoresis patterns of mononuclear cell proteins and plasma proteins before and during active labor. Mononuclear cells and plasma were obtained from 5 pregnant volunteers. It appears that A-1 apolipoprotein, identified by Western Blot analysis, is increased in mononuclear cells during active labor. Conversely, a decrease in the concentration of A-1 apolipoprotein was seen in plasma during parturition. These "normal" protein patterns can now be compared with those observed in pathologic conditions including preterm labor and may allow early detection of disease by protein abnormalities before clinical signs and symptoms develop.

Increased proinflammatory cytokines in patients with chronic stable angina and their reduction by aspirin

BACKGROUND

Proinflammatory cytokines released by injured endothelium facilitate interaction of endothelial cells with circulating leukocytes and thus may contribute to development and progression of atherosclerosis. We investigated whether cytokines and C-reactive protein (CRP) are indicative of myocardial ischemia or of diseased vessels and whether they are influenced by aspirin treatment in patients with chronic stable angina.

METHODS AND RESULTS

Plasma macrophage colony stimulating factor (MCSF), IL-1b, IL-6, and CRP were measured in 60 stable patients after 48-hour Holter monitoring and in 24 matched controls. All patients had angiographic documentation of disease and positive exercise ECGs. Patients with ischemia on Holter monitoring (n=40) received aspirin or placebo in a 6-week, randomized, double blind, crossover trial. Blood sampling was repeated at the end of each treatment phase (3 weeks). Compared to controls, patients had more than twice median MCSF (800 versus 372 pg/mL), IL-6 (3.9 versus 1.7 pg/mL), and CRP (1.25 versus 0.23 mg/L) levels (P<0.01 for all comparisons). MCSF was related to ischemia on Holter monitoring (P<0.01), to low ischemic threshold during exercise (P<0.01), and together with IL-1b to number of diseased vessels (P<0.05). MCSF, IL-6, and CRP were all reduced after 6 weeks of aspirin treatment (P<0.05).

CONCLUSIONS

These findings suggest that cytokines are associated with both ischemia and anatomic extent of disease in patients with stable angina. Reduced cytokine and CRP levels by aspirin may explain part of aspirin's therapeutic action.

Thromboxane A2 synthase activity in platelet free human monocytes

Soon after platelets, the highest amounts of thromboxane A2 (TXA2) can be detected in human monocytes activated by serum. Using platelet-free human monocytes, we have shown that foetal calf serum (FCS) induces prostaglandin H synthase (PGH synthase) after 16 h of incubation, as shown by the use of transcriptional inhibitors and Western blotting. The effect of serum can be in part mimicked by recombinant colony stimulating factor-1 (hr CSF-1). It is not known whether the limiting step leading from arachidonate to TXA2 is represented solely by the level of PGH synthase or also by the level of TXA2 synthase. We approached this problem by using a Western blot specific for the enzyme, as well as by using PGH2 as substrate. The results show that TXA2 synthase is constitutively expressed in monocytes, i.e., its levels were high soon after their isolation, and similar to those observed after 24 h of incubation with serum. However TXA2 failed to be synthesized until at least 3 h of incubation, and the pattern of synthesis was dependent on the kinetics of PGH synthase induction. In any condition in which TXA2 synthase was immunodetectable, using PGH2 as substrate a high rate of conversion to TXB2 could be detected. Experiments with actinomycin D and cycloheximide indicate that the half-life of TXA2 synthase was longer than 16 h, therefore much longer than that of PGH synthase, that the gene coding for it is fully active in resting monocytes, and that the conversion of arachidonate to TXA2 induced by serum or CSF-1 is dependent solely on the de novo synthesis of PGH synthase.

Differential turnover of enzymes involved in human monocyte eicosanoid metabolism. Selective inhibition of cyclooxygenase product formation by cycloheximide in the absence of effects on 5-lipoxygenase or phospholipase A2

Human monocytes treated with cycloheximide (CHX) demonstrated a concentration- and time-dependent inhibition of prostaglandin E2 (PGE2) synthesis and release in response to stimulation with phorbol myristate acetate, ionomycin, serum-treated zymosan, or concanavalin A. The effect of CHX required preincubation and was largely reversible within 2 hr. Thromboxane A2 release was affected similarly but no comparable effects were observed on labeled arachidonic acid release or leukotriene B4 generation. The PGE2 response was also inhibited by CHX when monocytes were given exogenous arachidonic acid with or without stimulation. CHX pretreatment also comparably decreased the amount of immunoreactive cyclooxygenase in resting and stimulated monocytes. These data indicate that monocyte cyclooxygenase, in contrast to phospholipase A2 or 5-lipoxygenase and their regulatory proteins, turns over rapidly and may be a target for up- or down-regulation by pharmacologic or (potentially) physiologic agents which affect protein synthesis or degradation.

Transduction of a signal for arachidonic acid metabolism by untriggered CSF-1 receptor induces an opposite effect to that induced by CSF-1 receptor and its ligand: separate regulation of phospholipase A2 and cyclooxygenase by CSF-1 receptor/CSF-1

The mouse hematopoietic cell line, 32D, was transfected with c-fms, which encodes for the CSF-1 receptor, a tyrosine kinase (TK). In the absence of CSF-1, transfected cells show moderate levels of arachidonic acid (AA) release and produce a substantial amount of prostaglandin E2 (PGE2) in comparison with the original cell line. Exposure of transfected cells to CSF-1, while inducing a substantial increase in arachidonate release, nevertheless resulted in inhibition of PGE2 production. Addition of ST638, a tyrosine kinase inhibitor, to cells transfected with c-fms in the absence of CSF-1 inhibited PGE2 production within 10-60 min. Its addition to the same cells in the presence of CSF-1 induced an opposite effect, but required longer treatment (24 h). In either cell type, AA release was not affected by this agent. These data indicate that CSF-1 may regulate cyclooxygenase activity. The different effect of CSF-1 receptor on PGE2 production in the presence or absence of CSF-1 and the opposite effect of a tyrosine kinase inhibitor on PGE2 suggest that both the receptor alone or the receptor-ligand complex may transduce an active, but different, signal through tyrosine phosphorylation. CSF-1 receptor and CSF-1 may exert separate, but related, effects on phospholipase A2 and cyclooxygenase activity which, in concert, or along with other tyrosine kinases, regulate prostaglandin production.

Prostanoids as second messengers of polypeptide growth factors

Prostaglandin H synthase (PGHs), also known as cyclooxygenase, is an unstable enzyme whose mRNA has an half life of 10 minutes. Some polypeptide factors have been reported to induce the enzyme in target cells. We have purified and characterized a component of animal sera which behaves as a potent inducer of human monocyte PGHs. This factor, called serum monocytotropic factor, has been identified in human platelets and it appears to be structurally and biochemically different from identified platelet factors, such as platelet derived growth factor (PDGF) and transforming growth factor beta (TGF-beta), while showing strong similarities to colony stimulating factor 1 (CSF-1), so far undetected in platelets. Moreover, we have shown, by immunoblot analysis, that CSF-1 behaves as a potent and specific inducer of monocyte PGHs. The hypothesis that prostanoids may be considered as second messengers of platelet CSF-1 like factor, as well as of other growth factors and that PGHs induction plays a pivotal role in this process, will be illustrated.