Platelet-derived growth factor release and antiplatelet treatment with low-dose acetylsalicylic acid

Pleiotropic Effects of Acetylsalicylic Acid after Coronary Artery Bypass Grafting-Beyond Platelet Inhibition

Acetylsalicylic acid (ASA) is one of the most frequently used medications worldwide. Yet, the main indications for ASA are the atherosclerosis-based cardiovascular diseases, including coronary artery disease (CAD). Despite the increasing number of percutaneous procedures to treat CAD, coronary artery bypass grafting (CABG) remains the treatment of choice in patients with multivessel CAD and intermediate or high anatomical lesion complexity. Taking into account that CABG is a potent activator of inflammation, ASA is an important part in the postoperative therapy, not only due to ASA antiplatelet action, but also as an anti-inflammatory agent. Additional benefits of ASA after CABG include anticancerogenic, hypotensive, antiproliferative, anti-osteoporotic, and neuroprotective effects, which are especially important in patients after CABG, prone to hypertension, graft occlusion, atherosclerosis progression, and cognitive impairment. Here, we discuss the pleiotropic effects of ASA after CABG and provide insights into the mechanisms underlying the benefits of treatment with ASA, beyond platelet inhibition. Since some of ASA pleiotropic effects seem to increase the risk of bleeding, it could be considered a starting point to investigate whether the increase of the intensity of the treatment with ASA after CABG is beneficial for the CABG group of patients.

Effects of Antiplatelet and Nonsteroidal Anti-inflammatory Medications on Platelet-Rich Plasma: A Systematic Review

Background:

Platelet-rich plasma (PRP) has wide applications in orthopaedic care. Its beneficial effects are attributed to the growth factor profile from the platelet secretome. In theory, these effects would be diminished by medications that inhibit platelet activation and/or the subsequent release of growth factors.

Purpose:

To determine whether commonly used antiplatelets, nonsteroidal anti-inflammatory drugs (NSAIDs), or anticoagulant medications affect platelet growth factor release in PRP.

Study Design:

Systematic review; Level of evidence, 2.

Method:

A systematic review of the literature related to antiplatelet, anti-inflammatory, and anticoagulant drugs was performed following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. We used the Downs and Black objective quality scoring system. The literature search consisted of PubMed and Cochrane Library databases. Search terms consisted of 1 item selected from “platelet-rich plasma,” “platelet-derived growth factor,” and “platelet-rich plasma AND growth factor” combined with 1 item from “antiplatelet,” “aspirin,” “anticoagulant,” and “NSAID.” Only studies published within the past 25 years were included.

Results:

A total of 15 studies met the inclusion criteria: 7 studies detected no significant decrease in growth factors or mitogenesis, whereas 6 detected a decrease with antiplatelet agents, 1 detected mixed results with an antiplatelet agent, and 1 had mixed results with an antiplatelet agent/vasodilator. In terms of PRP activation, all 3 studies assessing collagen, the 2 studies analyzing adenosine diphosphate alone, and the 1 study investigating arachidonic acid found a decrease in growth factor concentration.

Conclusion:

Antiplatelet medications may decrease the growth factor release profile in a cyclooxygenase 1– and cyclooxygenase 2–dependent manner. Eight of 15 studies found a decrease in growth factors or mitogenesis. However, more studies are needed to comprehensively understand antiplatelet effects on the PRP secretome.

Outcomes after Percutaneous Angioplasty of Arteriovenous Fistulas and Grafts in African American Patients

Purpose

Arteriovenous fistulas and grafts, necessary for hemodialysis, may develop stenoses due to neointimal hyperplasia, which often require percutaneous transluminal angioplasty. Patient and lesion characteristics were evaluated prior to angioplasty and were correlated with 1- and 6-month outcomes.

Materials and Methods

This was an observational study of African American hemodialysis patients who presented for angioplasty of a dysfunctional fistula or graft. Clinical outcomes were ascertained from dialysis facilities 1 month and 6 months after angioplasty. One-month clinical success was defined as dialyzer blood flows of 450 mL/min without complications or interval shunt thrombosis, interventions, or loss of access, which was rarely achieved at 6 months. Logistic regression models were used to evaluate associations of clinical variables with outcomes.

Results

There were 150 stenoses treated during 99 procedures performed on 82 patients. The clinical success rate at one month was 67% with no complications as a result of the percutaneous transluminal angioplasty. Success at 1 month was positively associated with use of aspirin ( P = .005) and with referral for high venous pressures ( P = .004). Six-month data were available for 81 procedures, with 45.7% requiring repeat angioplasty and 12.3% suffering major complications (thrombectomy, revision surgery, or access abandonment). Major complications were seen predominantly in patients who were not receiving aspirin.

Conclusions

Aspirin use and high venous pressure were associated with 1-month clinical success and fewer major complications at 6 months. Future work should investigate biologic mechanisms of action of aspirin and long-term effects of use to maintain vascular access.

Aspirin inhibits oxidant stress, reduces age-associated functional declines, and extends lifespan of Caenorhabditis elegans

AIMS

Oxidative stress and inflammation are leading risk factors for age-associated functional declines. We assessed aspirin effects on endogenous oxidative-stress levels, lifespan, and age-related functional declines, in the nematode Caenorhabditis elegans.

RESULTS

Both aspirin and its salicylate moiety, at nontoxic concentrations (0.5-1 mM), attenuated endogenous levels of reactive oxygen species (p<0.001), and upregulated antioxidant genes encoding superoxide dismutases (especially sod-3, p<0.001), catalases (especially ctl-2, p<0.0001), and two glutathione-S-transferases (gst-4 and gst-10; each p<0.005). Aspirin, and to a lesser degree salicylate, improved survival of hydrogen peroxide, and in the absence of exogenous stress aspirin extended lifespan by 21%-23% (each p<10(-9)), while salicylate added 14% (p<10(-6)). Aspirin and salicylate delayed age-dependent declines in motility and pharyngeal pumping (each p<0.005), and decreased intracellular protein aggregation (p<0.0001)-all established markers of physiological aging-consistent with slowing of the aging process. Aspirin fails to improve stress resistance or lifespan in nematodes lacking DAF-16, implying that it acts through this FOXO transcription factor.

INNOVATION

Studies in mice and humans suggest that aspirin may protect against multiple age-associated diseases by reducing all-cause mortality. We now demonstrate that aspirin markedly slows many measures of aging in the nematode.

CONCLUSIONS

Aspirin treatment is associated with diminished endogenous oxidant stress and enhanced resistance to exogenous peroxide, both likely mediated by activation of antioxidant defenses. Our evidence indicates that aspirin attenuates insulin-like signaling, thus protecting against oxidative stress, postponing age-associated functional declines and extending C. elegans lifespan under benign conditions.

Collagen density significantly affects the functional properties of an engineered provisional scaffold

The formation of a provisional scaffold is essential in wound healing. However, for tissues inside of joints, this process is impeded by the synovial fluid environment and wound healing is significantly impaired as a result. Therefore, development of substitute provisional scaffolds which are effective in the intra-articular environment is of great interest. Collagen-platelet hydrogels have recently been found useful as substitute provisional scaffolding materials. In this study, our hypothesis was that increasing the collagen density in the hydrogel would result in physiologic changes that would be likely to affect their function as provisional scaffold substitutes. The primary functional outcome measures were modulus of the hydrogel, platelet activation, fibroblast proliferation, and scaffold retraction. Increased collagen density resulted in collagen-platelet hydrogels with a higher storage modulus. Platelet activation was not found to be dependent on the collagen density within the range tested. Increasing the collagen density had a suppressive effect on both fibroblast proliferation and scaffold retraction. These studies suggest that the collagen density may be able to significantly influence the function of collagen-platelet hydrogels used as substitute provisional scaffolds.

Gene expression profiling of non-alcoholic steatohepatitis using gene set enrichment analysis

AIM

Non-alcoholic steatohepatitis (NASH) is a subset of non-alcoholic fatty liver disease (NAFLD) and sometimes progresses to cirrhosis and liver failure. In this study we analyzed the expression profile of genes and biological pathways involved in NASH in comparison with non-NASH by gene set enrichment analysis (GSEA) employing a DNA microarray technique.

METHODS

mRNA from liver biopsy specimens was collected from a group of NASH patients and a group of non-NASH patients. We analyzed the relative abundance of mRNA using high-density oligonucleotide microarrays containing probes for 54 675 known genes, and investigated the pathogenetic mechanisms of NASH by means of a powerful technique for analyzing molecular profiling data, GSEA.

RESULTS

The results showed that the level of expression of 27 gene sets was significantly higher and the level of expression of 25 gene sets was significantly lower in the NASH samples than in the non-NASH samples. Based on these results we created an online, publicly available, searchable database containing the data for the gene expression profiles of the NASH patients (http://www2.genome.rcast.u-tokyo.ac.jp/___/NASH/NASH_GSEA2/).

CONCLUSION

Our data revealed differences in expression of many gene sets that are involved in the pathogenesis of NASH.

Platelet-derived growth factor and platelet profiles in childhood nephrotic syndrome

The aim of the study was to investigate (1) whether there are any changes in release of platelet-derived growth factor AA (PDGF AA) in children with nephrotic syndrome without clinical thromboembolic symptoms 2; (2) whether serum PDGF AA correlates with the platelet count (PLT) and platelet indices; (3) whether prednisone therapy affects the serum PDGF AA and the PLT; (4) whether PDGF AA is a useful predictor of disease activity. The study involved two groups of children: 33 with nephrotic syndrome (I) who were evaluated twice (A during relapse and B after 2 weeks of prednisone treatment) and 34 healthy children (II). The serum concentration of PDGF was measured by ELISA. In group I/A the PLT (P<0.01) and platelet distribution width (P<0.05) were elevated, the mean platelet volume (MPV) (P<0.05) was decreased and the plateletcrit (P>0.05) was normal. In group I/B, the PLT was decreased and MPV increased. The concentration of PDGF AA was still increased and correlated negatively with the albumin concentration. Hence in children with nephrotic syndrome an increase in PLT, a decrease in MPV, and a higher concentration of PDGF were observed. Treatment of nephrotic syndrome with prednisone for 2 weeks is not sufficient to normalize platelet parameters. Further studies are necessary to confirm the role of PDGF AA in the hypercoagulation state in children with nephrotic syndrome.

Acetylsalicylic acid inhibits cell proliferation by involving transforming growth factor-beta

BACKGROUND

Acetylsalicylic acid (ASA) inhibits cell proliferation. This may be mediated by transforming growth factor-beta (TGF-beta). TGF-beta directly stops cell proliferation, restrains cells in G(0), and inhibits the uptake of platelet-derived growth factor and insulin-like growth factor. These effects are identical to those observed with ASA treatment.

METHODS AND RESULTS

We cultured rat thoracic aorta vascular smooth muscle cells and measured cytotoxicity, cell proliferation, cell cycle, transcription of TGF-beta1, and concentration of TGF-beta1 in supernatant medium. ASA dose-dependently restrained cells in G(0) phase with no cytotoxic effect and inhibited cell proliferation by 30.86%. Anti-TGF-beta1 reversed this inhibition by 30.21%. However, ASA treatment decreased TGF-beta1 transcription and had no significant effect on TGF-beta1 concentration.

CONCLUSIONS

TGF-beta seems to play an important role in ASA-mediated inhibition of cell proliferation. Therefore, treatment with ASA prevents coronary disease not only by means of its antiplatelet properties but also by an important inhibition of plaque growth. This relationship between ASA and TGF-beta explains many other effects, such as cancer chemoprevention, immunomodulation, and wound healing. The aim of this study was to demonstrate this link.

Platelet CD62 expression and PDGFAB secretion in patients undergoing PTCA and treatment with abciximab

AIMS

To investigate a correlation of the platelet activation marker CD62 and secretion of the growth factor PDGF from platelets in coronary patients under therapy with the GPIIb/IIIa-inhibitor abciximab.

METHODS

Flow cytometric assessment of fibrinogen binding (GPIIb/IIIa-binding site) and CD62 expression, as well as PDGF release of human platelets (immunoassay) and platelet aggregation with 20 microM ADP and 2 microg ml(-1) collagen were evaluated in nine patients with stable coronary artery disease. Patients were undergoing elective balloon angioplasty and were treated with aspirin (100 mg day(-1)), heparin (ACT < 220 s) and abciximab (bolus and infusion over 12 h). Blood samples were obtained before initiation of abciximab therapy (under aspirin and heparin) (I), 3 h after angioplasty under abciximab (II) and 12 h after termination of abciximab infusion (III).

RESULTS

Compared with sample I before abciximab therapy, fibrinogen binding was reduced to 37% (+/- 34 s.d., P < 0.05) (II) and 55% (+/- 40 s.d., P < 0.05) (III). Reduced fibrinogen binding also led to a significant reduction of the aggregation response to ADP (down to 37% +/- 20) and collagen (down to 0%). Mean fluorescence intensity of CD62-expression was 78 units (+/- 20 s.d.) (I), 72 units (+/- 14 s.d.) (II) and 64 units (+/- 12 s.d., P < 0.05) (III). PDGF release from isolated, washed platelets was 99 (+/- 33 s.d.) ng/10(9) platelets at (I), 82 (+/- 31 s.d.) ng/10(9) platelets and 96 (+/- 30 s.d.) ng/10(9) platelets.

CONCLUSIONS

The results indicate that despite a strong reduction of GPIIb/IIIa-binding and platelet aggregation, CD62 as a marker of platelet secretion and the secretion product PDGF were only slightly reduced under abciximab treatment. No direct correlation between CD62 expression and PDGF release could be demonstrated.

Effect of i.v. tenoxicam during caesarean delivery on platelet activity

BACKGROUND

Non-steroidal anti-inflammatory drugs inhibit platelet aggregation and prolong bleeding time in healthy subjects. We have studied the effect of i.v. tenoxicam during caesarean delivery on skin bleeding time, operative, and postoperative blood loss, and beta-thromboglobulin and platelet factor 4 as specific molecular markers for platelet activity.

METHODS

Fifty women were studied. Twenty-five were given tenoxicam 20 mg i.v. 10 min before induction of general anaesthesia, and 25 formed a control group. Skin bleeding time and platelet markers were determined the day before and 1 h after induction of anaesthesia.

RESULTS

In the tenoxicam group, there was an slight increase in skin bleeding time with no statistically significant changes in platelet marker levels. In the control group, platelet markers increased 1 h after surgery. The surgeon's assessment of uterine relaxation, using a visual analogue score, operating theatre blood loss, and the frequency of bleeding over 24 h after operation, showed no significant difference between the two groups.

CONCLUSION

During caesarean delivery i.v. tenoxicam causes a slight increase in bleeding time with no significant changes in platelet marker levels.

Platelets and restenosis

Restenosis is currently the major limitation of percutaneous transluminal coronary angioplasty (PTCA). Factors such as elastic recoil, migration of vascular smooth muscle cells from media to intima, neointimal proliferation and vascular remodeling underly the restenotic process. Presently there is no effective therapy available for restenosis. The role of platelets in the development of thrombosis and abrupt closure after PTCA is well recognized. However, the effects of platelets in PTCA extend well beyond the early phase. Although antiplatelet agents such as glycoprotein IIb/IIIa antagonists have been reported to reduce target vessel revascularization, major unresolved controversies still exist. This report reviews the potential role of platelets in restenosis. Various drugs, successfully tested in experimental studies and in a small number of human studies, that inhibit the effect of platelets on the restenotic process are also reviewed.

Dipyridamole and Platelet Release of Platelet-derived Growth Factor

Platelet-derived growth factor (PDGF) and β-thromboglobulin (β-TG) are released from platelet alpha-granules during platelet activation. PDGF is a potent chemoattractant and mitogen for human vascular smooth muscle cells, and may be important in the development of late restenosis following angioplasty and in atherogenesis. In recent studies, where PDGF release into serum was evaluated indirectly by measuring (3)H-thymidine incorporation into fibroblasts, it was reported that the antiplatelet drug dipyridamole (DPM) decreased serum levels of PDGF. Such selective inhibition of the PDGF-release would have potential important implications for patients with atherosclerosis and for patients undergoing angioplasty. We therefore measured platelet content of PDGF and β-TG as well as platelet release of PDGF using a newly developed radioimmunoassay in healthy volunteers before and immediately after ingestion of DPM 100 mg t.i.d. for 3 days. We found no significant differences in platelet content of PDGF or β-TG before and after DPM. PDGF release from platelets isolated from plasma by gel filtration and stimulated with thrombin as well as platelet release of PDGF into serum was also unaffected by DPM. In conclusion, treatment with DPM does not affect platelet content of PDGF or β-TG. The treatment did not inhibit the platelet-release of PDGF as previously reported, neither via direct effects on platelets nor on inhibitory plasma components. DPM may, however, inhibit (3)H-thymidine incorporation into fibroblasts.