The effect of olive leaf extract on platelet function

Background Epidemiological studies have shown a reduced incidence of cardiovascular disease in the Mediterranean population attributed to the consumption of dietary olive oil rich in antioxidants. This has lead to increased interest in the antioxidant properties of other phenolic compounds of olive tree products. It has been suggested that olive leaf extract may also have health benefits due to its antioxidant and anti-inflammatory activities. Antioxidants can prevent the effects of oxidative metabolism by scavenging free radicals and decreasing the hyperactivity of platelets associated with the development of occlusive thrombosis. No studies to date have investigated the effects of olive leaf extract on platelet function to our knowledge. Improved understanding of the antioxidant properties of olive leaf extract and its effect on platelet function could lead to improved cardiovascular health. Objective The current study used an olive leaf extract prepared from the Olea europaea L. tree. The aim was to determine if polyphenols in olive leaf extract would reduce platelet activity and, to establish an optimal dose in vitro that would reduce platelet aggregation and ATP release. Design Eleven subjects with normal platelet counts (150–400 x 109/L) were recruited for the current in vitro study. Olive leaf extract was added to citrated whole blood to obtain five concentrations ranging from 5.4 ug/mL to 54.0 ug/mL for a dose response curve. Baseline samples, without olive leaf extract were used as a negative control for each subject. After 2 hours incubation with olive leaf extract samples were analyzed for platelet aggregation and ATP release from platelets stimulated by the addition of collagen. Results Whole blood analysis (n=11) showed a clear dose-dependant reduction in platelet aggregation with the increasing olive leaf extract concentrations (p<0.0001). There was also a similar decrease in ATP release from collagen stimulated platelets (p=0.02). Conclusion In the current study the olive leaf extract obtained from Olea europaea L. inhibited platelet aggregation and ATP release from collagen stimulated platelets in vitro. This study suggests olive leaf extract may prevent occlusive thrombosis by reducing platelet hyperactivity.

Effect of aerobic interval training and caffeine on blood platelet function

Purpose: Hyperactive platelets contribute to the thrombotic response in humans, and exercise transiently increases platelet function. Caffeine is routinely used by athletes as an ergogenic aid, but the combined effect of exercise and caffeine on platelet function has not been investigated. Methods: Twelve healthy males were randomly assigned to one of four groups and undertook four experimental trials of a high-intensity aerobic interval training (AIT) bout or rest with ingestion of caffeine (3 mg·kg-1) or placebo. AIT was 8 × 5 min at approximately 75% peak power output (approximately 80% V?O2peak) and 1-min recovery (approximately 40% peak power output, approximately 50% V?O2peak) intervals. Blood/urine was collected before, 60, and 90 min after capsule ingestion and analyzed for platelet aggregation/activation. Results: AIT increased platelet reactivity to adenosine diphosphate (placebo 30.3%, caffeine 13.4%, P < 0.05) and collagen (placebo 10.8%, caffeine 5.1%, P < 0.05) compared with rest. Exercise placebo increased adenosine diphosphate-induced aggregation 90 min postingestion compared with baseline (40.5%, P < 0.05), but the increase when exercise was combined with caffeine was small (6.6%). During the resting caffeine protocol, collagen-induced aggregation was reduced (-4.3%, P < 0.05). AIT increased expression of platelet activation marker PAC-1 with exercise placebo (P < 0.05) but not when combined with caffeine. Conclusion: A single bout of AIT increases platelet function, but caffeine ingestion (3 mg·kg) does not exacerbate platelet function at rest or in response to AIT. Our results provide new information showing caffeine at a dose that can elicit ergogenic effects on performance has no detrimental effect on platelet function and may have the potential to attenuate increases in platelet activation and aggregation when undertaking strenuous exercise.

Inhibition of platelet aggregation and 5-HT release by extracts of Australian plants used traditionally as headache treatments

To identify potential migraine therapeutics, extracts of eighteen plants were screened to detect plant constituents affecting ADP induced platelet aggregation and [14C]5-hydroxytryptamine (5-HT) release. Extracts of the seven plants exhibiting significant inhibition of platelet function were reanalysed in the presence of polyvinyl pyrrolidone (PVP) to remove polyphenolic tannins that precipitate proteins. Two of these extracts no longer exhibited inhibition of platelet activity after removal of tannins. However, extracts of Crataegus monogyna, Ipomoea pes-caprae, Eremophila freelingii, Eremophila longifolia, and Asteromyrtus symphyocarpa still potently inhibited ADP induced human platelet [14C]5-HT release in vitro, with levels ranging from 62 to 95% inhibition. I. pes-caprae, and C. monogyna also caused significant inhibition of ADP induced platelet aggregation. All of these plants have been previously used as traditional headache treatments, except for C. monogyna which is used primarily for protective effects on the cardiovascular system. Further studies elucidating the compounds that are responsible for these anti-platelet effects are needed to determine their exact mechanism of action.

Extracorporeal lessons from sheep

Background: Extracorporeal circulation (ECC), the diversion of blood flow through a circuit located outside of the body, has been one of the major advances in modern medicine. Cardio-pulmonary bypass (CPB), renal dialysis, apheresis and extracorporeal membrane oxygenation (ECMO) are all different forms of ECC. Despite its major benefits, when blood comes into contact with foreign material, both the coagulation and inflammation cascades are activated simultaneously. Short periods of exposure to ECC e.g. CPB (�2 h duration), are known to be associated with haemolysis, coagulopathies, bleeding and inflammation which demand blood product support. Therefore, it is not unexpected that these complications would be exaggerated with prolonged periods of ECC such as in ECMO (days to weeks duration). The variability and complexities of the underlying pathologies of patients requiring ECC makes it difficult to study the cause and effect of these complications. To overcome this problem we developed an ovine (sheep) model of ECC. Method: Healthy female sheep (1–3 y.o.) weighing 40–50 kg were fasted overnight, anaesthetised, intubated and ventilated [1]. Half the group received smoke induced acute lung injury (S-ALI group) (n = 8) and the other half did not (healthy group) (n = 8). Sheep were subsequently cannulated (Medtronic Inc, Minneapolis, MN, USA) and veno-venous ECMO commenced using PLS ECMO circuit and Quadrox D oxygenator (Maquet Cardiopulmonary AG, Hechinger Straße, Germany). There was continuous physiological monitoring and blood was collected at specified time intervals for full blood counts, platelet function analysis (by Multiplate®), routine coagulation and assessment of clot formation and lysis (by ROTEM®). Preliminary results Full blood counts and routine coagulation results from normal healthy sheep were comparable to those of normal human adults. Within 15 min of initiating of ECMO, PT, PTT and EXTEM clot formation time increased, whilst EXTEM maximum clot firmness decreased in both cohorts. Discussion & Conclusions: Preliminary results of sheep from both 2 h ECMO cohorts showed that the anatomy, haematology and coagulation parameters of an adult sheep are comparable to that a human adult. Experiments are currently underway with healthy (n = 8) and S-ALI (n = 8) sheep on ECMO for 24 h. In addition to characterising how ECMO alters haematology and coagulation parameters, we hope that it will also define which blood components will be most effective to correct bleeding or clotting complications during ECMO support.

The acute effects of eccentrically-biased versus conventional weight training in older adults : a randomised controlled cross-over study

Background Whilst resistance training has been proven to convey considerable benefits to older people; immediately post-exercise there may be elevated transient risks for cardiac events and falls. Objectives and Measurements We assessed the acute effects of eccentrically-biased (EB) and conventional (CONV) resistance exercise on: platelet number, activation and granule exocytsosis; and mean velocity of centre of pressure displacement (Vm). Design, Setting, Participants and Intervention Ten older adults (7 males, 3 females; 69 ± 4 years) participated in this randomised controlled cross-over study in which they performed EB and CONV training sessions that were matched for total work and a control condition. Results Immediately post-exercise there was a statistically significant difference in platelet count between the control condition, in which it fell (pre 224 ± 35 109/L; post 211 ± 30 109/L: P < 0.05) and CONV in which it increased (pre 236 ± 55 109/L; post 242 ± 51 109/L: P > 0.05). There was no change in platelet activation and granule exocytsosis or Vm following EB and CONV. Conclusions Overall, while minor differences between regimens were observed, no major adverse effect on parameters of platelet function or centre of pressure displacement were observed acutely following either regimen. Eccentrically-biased and conventional resistance exercise training regimens do not appear to present an elevated acute risk in the context of changes to platelet function contributing to a cardiac event or postural stability increasing falls risk for apparently healthy older adults.

Biomimetic tubular nanofiber mesh and platelet rich plasma-mediated delivery of BMP-7 for large bone defect regeneration.

There is a growing need for successful bone tissue engineering strategies and advanced biomaterials that mimic the structure and function of native tissues carry great promise. Successful bone repair approaches may include an osteoconductive scaffold, osteoinductive growth factors, cells with an osteogenic potential and capacity for graft vascularisation. To increase osteoinductivity of biomaterials, the local combination and delivery of growth factors has been developed. In the present study we investigated the osteogenic effects of calcium phosphate (CaP)-coated nanofiber mesh tube-mediated delivery of BMP-7 from a PRP matrix for the regeneration of critical sized segmental bone defects in a small animal model. Bilateral full-thickness diaphyseal segmental defects were created in twelve male Lewis rats and nanofiber mesh tubes were placed around the defect. Defects received either treatment with a CaP-coated nanofiber mesh tube (n = 6), an un-coated nanofiber mesh tube (n=6) a CaP-coated nanofiber mesh tube with PRP (n=6) or a CaP-coated nanofiber mesh tube in combination with 5 μg BMP-7 and PRP (n = 6). After 12 weeks, bone volume and biomechanical properties were evaluated using radiography, microCT, biomechanical testing and histology. The results demonstrated significantly higher biomechanical properties and bone volume for the BMP group compared to the control groups. These results were supported by the histological evaluations, where BMP group showed the highest rate of bone regeneration within the defect. In conclusion, BMP-7 delivery via PRP enhanced functional bone defect regeneration, and together these data support the use of BMP-7 in the treatment of critical sized defects.

An acute growth factor treatment that preserves function after spinal cord contusion injury

Inflammation of the spinal cord after traumatic spinal cord injury leads to destruction of healthy tissue. This “secondary degeneration” is more damaging than the initial physical damage and is the major contributor to permanent loss of functions. In our previous study we showed that combined delivery of two growth factors, vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF), significantly reduced secondary degeneration after hemi-section injury of the spinal cord in the rat. Growth factor treatment reduced the size of the lesion cavity at 30d compared to control animals and further reduced the cavity at 90d in treated animals while in control animals the lesion cavity continued to increase in size. Growth factor treatment also reduced astrogliosis and reduced macroglia/macrophage activation around the injury site. Treatment with individual growth factors alone had similar effects to control treatments. The present study investigated whether growth factor treatment would improve locomotor behaviour after spinal contusion injury, a more relevant preclinical model of spinal cord injury. The growth factors were delivered for the first 7d to the injury site via osmotic minipump. Locomotor behaviour was monitored at 1-28d after injury using the BBB score and at 30d using automated gait analysis. Treated animals had BBB scores of 18; Control animals scored 10. Treated animals had significantly reduced lesion cavities and reduced macroglia/macrophage activation around the injury site. We conclude that growth factor treatment preserved spinal cord tissues after contusion injury, thereby allowing functional recovery. This treatment has the potential to significantly reduce the severity of human spinal cord injuries.

Soluble mediators in platelet concentrates modulate dendritic cell inflammatory responses in an experimental model of transfusion

The transfusion of platelet concentrates (PCs) is widely used to treat thrombocytopenia and severe trauma. Ex vivo storage of PCs is associated with a storage lesion characterized by partial platelet activation and the release of soluble mediators, such as soluble CD40 ligand (sCD40L), RANTES, and interleukin (IL)-8. An in vitro whole blood culture transfusion model was employed to assess whether mediators present in PC supernatants (PC-SNs) modulated dendritic cell (DC)-specific inflammatory responses (intracellular staining) and the overall inflammatory response (cytometric bead array). Lipopolysaccharide (LPS) was included in parallel cultures to model the impact of PC-SNs on cell responses following toll-like receptor-mediated pathogen recognition. The impact of both the PC dose (10%, 25%) and ex vivo storage period was investigated [day 2 (D2), day 5 (D5), day 7 (D7)]. PC-SNs alone had minimal impact on DC-specific inflammatory responses and the overall inflammatory response. However, in the presence of LPS, exposure to PC-SNs resulted in a significant dose associated suppression of the production of DC IL-12, IL-6, IL-1a, tumor necrosis factor-a (TNF-a), and macrophage inflammatory protein (MIP)-1b and storage-associated suppression of the production of DC IL-10, TNF-a, and IL-8. For the overall inflammatory response, IL-6, TNF-a, MIP-1a, MIP-1b, and inflammatory protein (IP)-10 were significantly suppressed and IL-8, IL-10, and IL-1b significantly increased following exposure to PC-SNs in the presence of LPS. These data suggest that soluble mediators present in PCs significantly suppress DC function and modulate the overall inflammatory response, particularly in the presence of an infectious stimulus. Given the central role of DCs in the initiation and regulation of the immune response, these results suggest that modulation of the DC inflammatory profile is a probable mechanism contributing to transfusion-related complications.

An approximate method for the solution of an influence function foil rolling model

Fleck and Johnson (Int. J. Mech. Sci. 29 (1987) 507) and Fleck et al. (Proc. Inst. Mech. Eng. 206 (1992) 119) have developed foil rolling models which allow for large deformations in the roll profile, including the possibility that the rolls flatten completely. However, these models require computationally expensive iterative solution techniques. A new approach to the approximate solution of the Fleck et al. (1992) Influence Function Model has been developed using both analytic and approximation techniques. The numerical difficulties arising from solving an integral equation in the flattened region have been reduced by applying an Inverse Hilbert Transform to get an analytic expression for the pressure. The method described in this paper is applicable to cases where there is or there is not a flat region.