Platelet hyperactivity and risk of recurrent thrombosis

Anti-anger Effects of Herbal Medicine: A Mini-Review of Rat Studies

OBJECTIVE

To analyze the available data on the anti-anger effects of herbal medicines (HMs) as well as their underlying mechanisms in rat models.

METHODS

From 6 electronic databases [PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), Wanfang, Oriental Medicine Advanced Searching Integrated System (OASIS), and Research Information Sharing Service (RISS)], relevant animal experiments were searched by using "anger," "rats," and "animal" as search keywords. The last search was conducted on November 22, 2019, and all experiments involving rat models of anger and treatment using HMs published until the date of the search were considered.

RESULTS

A total of 24 studies with 16 kinds of HMs were included. Most studies have used the "tail irritating method" and "social isolation and resident intruder" method to establish anger models. According to the included studies, the therapeutic mechanisms of HMs for anger regulation and important herbs by their frequency and/or preclinical evidence mainly incladed regulation of hemorheology (Bupleuri Radix, Paeoniae Radix Alba, and Glycyrrhizae Radix), regulation of sex hormones (Bupleuri Radix, Cyperi Rhizoma, and Paeoniae Radix Alba), regulation of neurotransmitters (Cyperi Rhizoma), regulation of anger-related genes (Bupleuri Radix, Glycyrrhizae Radix, and Paeoniae Radix Alba), and other effects. Overall, Liver (Gan) qi-smoothing herbs including Bupleuri Radix and Cyperi Rhizoma were the most frequently used.

CONCLUSIONS

This review found the frequent methods to establish an anger model, and major mechanisms of anti-anger effects of HMs. Interestingly, some Liver qi-smoothing herbs have been frequently used to investigate the anti-anger effects of HM. These findings provide insight into the role and relevance of HMs in the field of anger management.

Reduced platelet hyperreactivity and platelet-monocyte aggregation in HIV-infected individuals receiving a raltegravir-based regimen

OBJECTIVE

Platelets are key cells in atherosclerosis and acute cardiovascular events. Platelet hyperreactivity and increased platelet-monocyte aggregation (PMA) are found in HIV-infected patients and may contribute to the excess cardiovascular risk. The integrase inhibitor raltegravir (RAL) has been associated with better residual viral suppression and reduction in inflammatory and coagulation biomarkers. The aim of our study was to investigate whether RAL-treated patients have reduced platelet reactivity and PMA.

DESIGN AND METHODS

We performed a cross-sectional study involving 80 virologically suppressed adult HIV1-infected patients on a RAL-based (n = 25), nonnucleoside reverse transcriptase inhibitor (NNRTI)-based (n = 30) or a protease inhibitor based (n = 25) regimen and 30 healthy controls. Platelet reactivity was determined by measuring platelet P-selectin expression and the binding of fibrinogen to platelets to stimulation with two concentrations of ADP. PMA was determined by measuring the expression of the platelet marker CD42b on CD14 positive cells.

RESULTS

HIV-infected individuals had higher platelet reactivity and PMA than controls. RAL-treated individuals showed significantly lower P-selectin expression to stimulation with low (P = 0.026 vs. NNRTI and P = 0.005 vs. protease inhibitor group) and high-dose ADP (P = 0.009 vs. NNRTI and P = 0.003 vs. protease inhibitor group). A similar trend for was found for fibrinogen binding, although only the difference in P-selectin expression between RAL and protease inhibitor treated patients reached statistical significance (P = 0.038). PMA was also lower in the RAL group than in the NNRTI (P = 0.037) and protease inhibitor (P = 0.034) groups.

CONCLUSION

Use of a RAL-based regimen was associated with a reduction in persistent HIV-induced platelet hyperreactivity and PMA compared with NNRTI and protease inhibitor based regimen.

Effects of acute and chronic psychological stress on platelet aggregation in mice

Although psychological stress has long been known to alter cardiovascular function, there have been few studies on the effect of psychological stress on platelets, which play a pivotal role in cardiovascular disease. In the present study, we investigated the effects of acute and chronic psychological stress on the aggregation of platelets and platelet cytosolic free calcium concentration ([Ca(2+)]i). Mice were subjected to both transportation stress (exposure to novel environment, psychological stress) and restraint stress (psychological stress) for 2 h (acute stress) or 3 weeks (2 h/day) (chronic stress). In addition, adrenalectomized mice were subjected to similar chronic stress (both transportation and restraint stress for 3 weeks). The aggregation of platelets from mice and [Ca(2+)]i was determined by light transmission assay and fura-2 fluorescence assay, respectively. Although acute stress had no effect on agonist-induced platelet aggregation, chronic stress enhanced the ability of the platelet agonists thrombin and ADP to stimulate platelet aggregation. However, chronic stress failed to enhance agonist-induced increase in [Ca(2+)]i. Adrenalectomy blocked chronic stress-induced enhancement of platelet aggregation. These results suggest that chronic, but not acute, psychological stress enhances agonist-stimulated platelet aggregation independently of [Ca(2+)]i increase, and the enhancement may be mediated by stress hormones secreted from the adrenal glands.

In vivo platelet activation and platelet hyperreactivity in abacavir-treated HIV-infected patients

Abacavir (ABC) has been associated with ischaemic cardiovascular events in HIV-infected patients, but the pathogenic mechanisms are unknown. Aim of our study was to assess whether ABC induces in vivo platelet activation and ex vivo platelet hyper-reactivity. In a retrospective, case-control study, in vivo platelet activation markers were measured in 69 HIV-infected patients, before starting therapy and after 6-12 months of either ABC (n=35) or tenofovir (TDF) (n=34), and compared with those from 20 untreated HIV-infected patients. A subgroup of patients was restudied after 28-34 months for ex vivo platelet reactivity. In vivo platelet activation markers were assessed by ELISA or flow cytometry, ex vivo platelet reactivity by light transmission aggregometry (LTA) and PFA-100®. Thein vitro effects of the ABC metabolite, carbovir triphosphate, on aggregation and intra-platelet cGMP were also studied. sPLA2, sPsel and sGPV increased significantly 6-12 months after the beginning of ABC, but not of TDF or of no treatment. Ex vivo platelet function studies showed enhanced LTA, shorter PFA-100® C/ADP closure time and enhanced platelet expression of P-sel and CD40L in the ABC group. The intake of ABC blunted the increase of intraplatelet cGMP induced by nitric oxide (NO) and acutely enhanced collagen-induced aggregation. Preincubation of control platelets with carbovir triphosphate in vitro enhanced platelet aggregation and blunted NO-induced cGMP elevation. In conclusion, treatment with ABC enhances in vivo platelet activation and induces platelet hyperreactivity by blunting the inhibitory effects of NO on platelets. These effects may lead to an increase of ischaemic cardiovascular events.

Increased platelet reactivity in HIV-1-infected patients receiving abacavir-containing antiretroviral therapy

BACKGROUND

Current or recent use of abacavir for treating human immunodeficiency virus type 1 (HIV-1) infection has been associated with increased rates of myocardial infarction (MI). Given the role of platelet aggregation in thrombus formation in MI and the reversible nature of the abacavir association, we hypothesized that patients treated with abacavir would have increased platelet reactivity.

METHODS

In a prospective study in adult HIV-infected patients, we determined associations between antiretrovirals (ARVs), and in particular the nucleoside reverse transcriptase inhibitor abacavir, and platelet reactivity by measuring time-dependent platelet aggregation in response to agonists: adenosine diphosphate (ADP), thrombin receptor-activating peptide (TRAP), collagen, and epinephrine.

RESULTS

Of 120 subjects, 40 were ARV-naive and 80 ARV-treated, 40 of whom were receiving abacavir. No consistent differences in platelet reactivity were observed between the ARV-naive and ARV-treated groups. In contrast, within the ARV-treated group, abacavir-treated subjects had consistently higher percentages of platelet aggregation upon exposure to ADP, collagen, and epinephrine (P = .037, P = .022, and P = .032, respectively) and had platelets that were more sensitive to aggregation upon exposure to TRAP (P = .025).

CONCLUSIONS

The consistent increases in platelet reactivity observed in response to a range of agonists provides a plausible underlying mechanism to explain the reversible increased rates of MI observed in abacavir-treated patients.

Light transmittance aggregometry induced by different concentrations of adenosine diphosphate to monitor clopidogrel therapy: a methodological study

Light transmission aggregation (LTA) is considered the reference method to identify residual platelet reactivity (RPR) in high-risk patients with coronary artery disease on clopidogrel treatment. An international standardization of this technique is still ongoing and different concentrations of adenosine diphosphate (ADP) as the agonist for LTA have been used to evaluate the inhibitory effect of clopidogrel treatment. To evaluate RPR, LTA was performed using different ADP concentrations (2, 5, 10, and 20 μmol/L) in 466 high-risk patients with coronary artery disease on dual antiplatelet therapy who underwent percutaneous coronary intervention and in 46 healthy subjects. A VerifyNow P2Y12 assay was assessed as a point-of care system. Imprecision studies showed higher coefficients of variation for LTA by 2 and 5 μmol/L ADP (healthy subjects: 4.7% and 3.9%; patients: 6.8% and 5.2%, respectively) in comparison with those obtained determining LTA using 10 and 20 μmol/L ADP (healthy subjects: 2.2% and 2.3%; patients: 2.7% and 3.1%, respectively). In patients, a significant difference (P < 0.0001) between mean values of LTA obtained with all ADP concentrations was found, even if LTA data were significantly correlated (at least: rho = 0.88, P < 0.0001). However, data from 10 and 20 μmol/L ADP LTA were very similar and highly concordant (k = 95.9%). All agreements were significant (for all P < 0.0001), in particular the agreement between 10 and 20 μmol/L ADP LTA was very good (k = 0.86, P < 0.0001). A moderate agreement between VerifyNow and both 10 and 20 μmol/L ADP LTA was observed. LTA by 10 and 20 μmol/L ADP gave equivalent percentages of aggregation and highly concordant results in terms of RPR in patients with coronary artery disease on clopidogrel. Significant concordant results were observed between both 10 and 20 μM ADP LTA and VerifyNow. This suggests that a concentration of 10 μmol/L ADP may be considered adequate for the identification of RPR of patients on clopidogrel and should be preferred for standardization LTA.

Platelet function and HIV: a case-control study

OBJECTIVE

Cardiovascular disease and myocardial infarction are of increasing concern in HIV-infected populations. Although platelets mediate arterial thrombosis, central to myocardial infarction, data on platelet function in HIV infection are lacking. We hypothesized that HIV-infected patients would have altered platelet reactivity.

DESIGN

A case-control study of platelet reactivity in 20 HIV-infected (HIVpos) and 20 age and sex-matched HIV-negative (HIVneg) individuals.

METHODS

Time-dependent platelet aggregation was measured in response to increasing concentrations of platelet agonists: epinephrine, collagen, thrombin receptor-activating peptide and ADP using light absorbance.

RESULTS

In both groups, mean age was 34 years, and 65% were men. Sixteen out of 20 (80%) of the HIVpos patients were on antiretroviral therapy with 12 out of 20 (60%) patients having HIV RNA less than 50 copies/ml. There were significant between-group differences in platelet reactivity across all four agonists. Platelets from HIVpos patients were more reactive to epinephrine [mean (SD) log concentration required to induce 50% maximal aggregation, 1.9 (1.2) versus 3.0 (1.7) mumol/l in HIVneg individuals, P = 0.028], whereas less platelet aggregation was observed in response to submaximal concentrations of the other agonists [thrombin receptor-activating peptide 72.5 (14.5)% versus 82.2 (7.6)% at 10 mumol/l, P = 0.011; ADP 67.3 (12.1)% versus 75.2 (8.8)% at 10 mumol/l, P = 0.035; collagen 16.6 (25.1)% versus 35.4 (31.5)% at 71.25 microg/ml, P = 0.007].

CONCLUSION

Between-group differences in platelet responses to all agonists suggest multiple underlying defects in platelet function in HIV infection. Further research is required to determine the contribution of antiretroviral therapy and relationships between platelet function and the increased cardiovascular disease observed in HIV-infected populations.

Platelet hyper-reactivity in active inflammatory arthritis is unique to the adenosine diphosphate pathway: a novel finding and potential therapeutic target

OBJECTIVE

To assess the influence of disease activity on platelet function in patients with inflammatory arthritis (IA).

METHODS

Ninety-six patients with an established diagnosis of IA (RA, PsA, seronegative SpA) were recruited. Patients with a history of cardiovascular disease (CVD), diabetes mellitus or receiving anti-platelet therapy were excluded. Demographic data, traditional CVD risk factors and medication use were recorded. Patients were characterized as active disease (n = 38) or control disease (n = 58) groups, respectively, based on internationally validated measures of disease activity [comprising serological markers (ESR, CRP, fibrinogen), patient measures (visual analogue scale of disease activity), evaluator global assessment and the 28-joint disease activity score]. Platelet function was assessed using a novel assay of platelet reactivity. Platelet aggregation to multiple concentrations of arachidonic acid, collagen, epinephrine, thrombin receptor activating peptide and adenosine diphosphate (ADP) were measured simultaneously using a modification of light transmission aggregometry.

RESULTS

The two groups (active vs control) were similar in terms of demographics and CVD risk factors. Anti-TNF-alpha therapy use was higher in the control group (P = 0.004), whereas NSAID use was higher in the active group (P = 0.001). There was a significant difference between the two groups in platelet response to ADP (P < 0.001). Platelet aggregation, in response to submaximal concentrations of ADP, was increased in the active disease group compared with the control group. There was no difference in platelet reactivity between the groups in response to any of the other agonists.

CONCLUSION

Patients with active IA demonstrate enhanced platelet reactivity, unique to the ADP pathway. This potential pro-thrombotic bias may contribute to their increased cardiovascular risk.

Dual antiplatelet therapy unmasks distinct platelet reactivity in patients with coronary artery disease

BACKGROUND

Platelet-induced thrombosis is a major risk factor for recurrent ischemic events, although platelet function in patients with cardiovascular disease taking aspirin and clopidogrel is very poorly characterized. The aim of this study was to assess platelet reactivity in patients with cardiovascular disease taking aspirin and clopidogrel.

METHODS

We developed a rapid assay to measure platelet aggregation in response to arachidonic acid, collagen, adenosine diphosphate (ADP), epinephrine and thrombin receptor activating peptide (TRAP) in 80 healthy volunteers. We then recruited 200 consecutive patients from outpatient clinics and the cardiac catheterization laboratory and tested platelet function. Platelet aggregation induced by epinephrine is a marker of global platelet reactivity. We tested platelet function in 146 patients compliant with antiplatelet therapy. Platelet aggregation to epinephrine was divided into quartiles. The platelet response to the other agonists was analysed based on the response to epinephrine.

RESULTS

Platelet reactivity increased significantly across the quartiles in response to epinephrine in healthy volunteers and patients (P < 0.0001). A significant increase in response across quartiles was seen with all agonists in healthy volunteers (P < 0.001). In contrast, a significant increase in response across quartiles was only seen with ADP in patients (P < 0.0001). Hypertension, smoking and diabetes were significantly associated with increasing platelet reactivity to epinephrine (P < 0.05).

CONCLUSION

This study shows that platelet response differs between healthy volunteers and patients on dual antiplatelet therapy. In patients with cardiovascular disease, dual antiplatelet therapy unmasks a distinct type of platelet reactivity in response to epinephrine and ADP but not other agonists.

Different methodologies for evaluating the effect of clopidogrel on platelet function in high-risk coronary artery disease patients

BACKGROUND

Two point-of-care (POC) systems have been recently proposed as rapid tools with which to evaluate residual platelet reactivity (RPR) in coronary artery disease (CAD) patients.

OBJECTIVES AND METHODS

We compared Platelet Function Analyzer-100 (PFA-100) closure times (CTs) by collagen/adenosine 5'-diphosphate (ADP) (C/ADP CT) cartridge and the VerifyNow P2Y12 Assay (VerifyNow) with light transmission aggregation (LTA) induced by 2 and 10 micromol L(-1) ADP in 1267 CAD patients on dual antiplatelet therapy who underwent percutaneous coronary intervention. We also performed the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay by cytofluorimetric analysis in a subgroup of 115 patients.

RESULTS

Cut-off values for identifying RPR were: > or = 54% and > or = 66% for LTA induced by 2 and 10 micromol L(-1) ADP respectively, and > or = 264 P2Y12 Reaction Units (PRU) for VerifyNow. The cut-off for PFA-100 C/ADP CT was > or = 68 s. RPR was detected in 25.1% of patients by 2 mumol L(-1) ADP-induced LTA (ADP-LTA), in 23.2% by 10 micromol L(-1) ADP-LTA, in 24.4% by PFA-100, and in 24.7% by VerifyNow. PFA-100 results did not parallel those obtained with LTA. VerifyNow showed a significant correlation (rho = 0.62, P < 0.001) and significant agreement (k = 0.34, P < 0.001) with LTA induced by 2 micromol L(-1) ADP. The correlation was similar but the agreement was better between VerifyNow and 10 micromol L(-1) ADP-LTA (rho = 0.64, P < 0.0001; k = 0.43, P < 0.001). Significant relationships were found between VASP platelet reactivity index and both ADP-LTA and VerifyNow. PFA-100 C/ADP CT did not significantly correlate with any of the other assays.

CONCLUSIONS

Our results show a significant correlation between LTA and VerifyNow but not the PFA-100 C/ADP assay. Clinical validation studies for POC systems are necessary.