Effect of behavioral stress on platelet reactivity on polymeric surfaces

Hemocompatibility of stent materials: alterations in electrical parameters of erythrocyte membranes

Background

It is presently unknown if stents used in the correction of artery stenosis are fully hemocompatible or if their implantation causes alterations at the level of the plasma membrane in red blood cells.

Methods

We addressed this important issue by measuring the passive electrical properties of the erythrocyte membrane before and after stent insertion by means of dielectric relaxation spectroscopy in the radiowave frequency range in a series of patients who were undergoing standard surgical treatment of arterial disease.

Results

Our findings provide evidence that full hemocompatibility of stents has not yet been reached, and that there are some measurable alterations in the passive electrical behavior of the red blood cell membrane induced by the presence of the stent.

Conclusion

It is possible that these changes do not have any physiological significance and simply reflect the intrinsic variability of biological samples. However, caution is urged, and the technique we describe here should be considered when investigating the hemocompatibility of a medical device at a cell membrane level.

Hemocompatibility of carotid artery stents: alterations of the electrical parameters of erythrocyte cell membrane--a word of caution

The hemocompatibility of standard surgical treatment of carotid artery disease through the insertion of metallic stents is investigated by means of radio wave dielectric spectroscopy technique that allows the measurements of the electrical parameters of the red blood cell membrane. Our measurements suggest that both the membrane permittivity and the membrane conductivity, which characterize the overall electrical behavior of the cell membrane, undergo an appreciable alteration of their standard values as a consequence of the stent insertion. These alterations persist over long period of time, up to 4 weeks. Even if these effects could not cause any evident damage at physiological or clinical level to the patient, the presence of a host response to the stent implant suggests that a full hemocompatibility has not yet reached, and a word of caution is necessary.

Dietary supplements: altered coagulation and effects on bruising

BACKGROUND

Patient use of dietary supplements that alter coagulation or have an effect on bruising is becoming increasingly common.

OBJECTIVE

To identify and describe dietary supplements that alter coagulation or are reported to alter bruising during and after surgical procedures.

METHODS

The MEDLINE, Cochrane Collaboration, and International Bibliographic Information on Dietary Supplements databases were searched for articles using the search words "bruising," "bleeding," "coagulation," "hemostasis," "herbal medicine," "alternative medicine," and "dietary supplement." Additional sources were obtained from manual searches of recent journal articles.

RESULTS

In vivo and in vitro evidence supports the notion that many dietary supplements alter coagulation. Limited evidence is available to support anecdotal claims of diminished postoperative bruising after the use of dietary supplements.

CONCLUSION

Surgeons should be aware that many of their patients are taking dietary supplements that may alter coagulation. Because most patients will not readily volunteer this information, specific steps should be taken to obtain it prior to more extensive surgical procedures.

Fibrinogen Conformation and Platelet Reactivity in Relation to Material−Blood Interaction: Effect of Stress Hormones

The performance of many biomaterials in hemocompatibility tests is altered when blood is drawn from stressed subjects. A salient physiological response during stress is one in which hormones are released into plasma by the hypothalamo-pituitary-adrenal axis. We investigated the influence of basal and stress levels of epinephrine and beta-endorphin on the conformation of fibrinogen (Fbg), both in saline solution (under physiological conditions) and after its adsorption to polyethylene (PE), by FT-IR spectroscopy. Moreover, as Fbg is one of the major mediators of platelet adhesion, the behavior of platelets in contact with PE was also evaluated as a function of the two different hormone concentrations. Epinephrine was found to affect Fbg conformation and to increase platelet adhesion to PE at stress level. Basal and stress levels of beta-endorphin did not significantly affect the Fbg conformation and only induced adhesion of isolated platelets to the PE surface. A direct relationship was therefore found between Fbg conformation and platelet behavior. The response of platelets was affected by the stress status of donors through the influence of epinephrine on Fbg conformation.

Platelet adhesion and aggregation on polyethylene: Effect of exhaustive exercise

The aim of the present study was to evaluate the effect of an exhaustive exercise on platelet adhesion and aggregation on polyethylene (PE) in relation to changes in plasma cortisol concentration in order to ascertain the effect of physical stress response in the blood-contacting properties of polymeric materials. Twelve healthy sedentary subjects, six males and six females, were studied. Each subject performed an exercise test on a bicycle ergometer at intensity corresponding to 70% VO2 max until exhaustion. One month after the exercise session, each subject participated in a control rest session. In both sessions, blood samples were drawn every 5 min for cortisol, lactate, hemoglobin, and hematocrit determinations and every 15 min for evaluation of platelet adhesion and aggregation. Individual comparisons between the rest and exercise cortisol patterns identified three categories of cortisol responders to exercise: positive responders (C +, showing higher concentrations during exercise than during rest), negative responders (C -, showing lower concentrations during exercise than during rest), and nonresponders (NR, showing similar concentrations during exercise and rest). The results revealed that C + had lower platelet adhesion and aggregation scores during exercise than during rest; moreover C - had higher scores than C + and NR during exercise. The results obtained demonstrated no effects of sex or exercise on either cortisol plasma levels or platelet adhesion and aggregation on PE surface. With regard to cardiovascular risk, the results suggest that exercise favorably affects platelet functions when mechanisms of metabolic adaptation to prolonged muscular work, expressed by a cortisol increase, are activated during exercise.

Depression is associated with an increase in the expression of the platelet adhesion receptor glycoprotein Ib

There is a significant association between cardiovascular disease and depression. Previous studies have documented changes in platelets in depression. It is unknown if depression causes functional changes in platelet surface receptors. Therefore, we analyzed (1) the surface expression of glycoprotein (GP)Ib and the integrin receptor alpha(IIb)beta(IIIa), receptors involved in platelet adhesion and aggregation, (2) CD62 (P-selectin) and CD63, integral granule proteins translocated during platelet activation, (3) platelet aggregation in response to ADP and (4) plasma levels of glycocalicin and von Willebrand factor (vWF), in depressed patients compared to healthy volunteers. Fifteen depressed patients with a Hamilton depression score of at least 22 and fifteen control subjects were studied. Platelets were assessed for surface expression levels of GPIb, alpha(IIb)beta(IIIa), CD62 and CD63 by flow cytometry. Genomic DNA was isolated to investigate a recently described polymorphism in the 5' untranslated region of the GPIbalpha gene. The number of GPIb receptors was significantly increased on the surface of platelets from patients with depression compared to control subjects. Surface expression of CD62 was also significantly increased in the depressed patients versus control subjects. There was no significant difference between depressed patients and healthy volunteers in the surface expression of alpha(IIb)beta(IIIa) or CD63, or in glycocalicin or vWF plasma concentration, or ADP-induced aggregation. There was no difference in allele frequency of the Kozak region polymorphism of the GPIbalpha gene, which can affect GPIb expression. The results of this study demonstrate that the number of GPIb receptors on platelets are increased in depression and suggest a novel risk factor for thrombosis in patients with depression.

Platelet adhesion to commercial and modified polymer materials in animals under psychological stress and in a no-stress condition

It is well known that stressful stimuli change blood functions and that protein and platelet parameters are altered in humans and animals subjected to stress. We have examined the influence of psychological stress on the morphological responses of platelets on commercially available materials [polyester (VP), fluoropassivated polyester (VPF), non-woven benzylic ester of hyaluronic acid (Hyaff11)] and on materials synthesised (PUPA) and/or surface modified by sulphation (Hyaff11S) or by immobilisation of the anticoagulant molecules heparin and sulphated hyaluronic acid (PUPA-Heparin, PUPA-HyalS, HyalS-PET). Moreover, the anticoagulant activity (i.e. thrombin inactivation) of the materials was analysed. In the no-stress condition, the surfaces with a low degree of platelet adhesion were Hyaff11S, HyalS-PET, PUPA-Heparin and PUPA-HyalS. Hyaff11, PET and PUPA had the highest number of adherent platelets within the series. VP and VPF exhibited an intermediate behaviour. The exposure of animals to stress induced a dramatic change in platelet number and morphology on PET, HyalS-PET, PUPA, PUPA-HyalS and Hyaff11: there was a higher degree of platelet adhesion, increased platelet spreading and the appearance of pseudopodia. In VP, VPF, Hyaff11S and PUPA-Heparin, there were no changes in platelet adhesion in stress conditions with respect to the no-stress condition; the latter two materials, the only ones able to prolong thrombin time, had a very low number of adherent platelets.

Blood tubing and cytokine production: effect of sterilization

Blood tubings commonly represent an integral component of hemodialysis circuits. Different factors may influence their biocompatibility, such as the type of material, the sterilization mode and the geometry. In vivo the final biocompatibility may be further complicated by the individual host response, the flow parameters, and the impact of mechanical trauma on blood's cellular components (i.e. erythrocytes). In this in vitro study we evaluated some commercially available blood tubings sterilized by different methods as to their interaction with normal leukocyte population and tested the response of these cells in terms of cytokines (IL-1beta, IL-1Ra, TNF-alpha). As a positive control, leukocytes were incubated with 0.5 ng/mL of bacterial lipopolysaccharide (LPS) or with Cuprophan of comparable surface. The results showed that cytokine production was markedly reduced, particularly in the case of gamma-ray-sterilized tubings. Of interest, it was not always related to the adherence. However in some cases, particularly of gamma-ray sterilization, adherence was none, despite the cytokine production.

The role of Fbg in platelet adhesion to polymeric materials in conditions of psychological stress

The effect of psychological stress on platelet adhesion to five polymeric materials (polyurethane, polyurethane filled with BaSO4, polyethyleneterephthalate, silicone and low-density polyethylene) was studied. The platelets were obtained from non-stressed and stressed rabbits as platelet-rich plasma (PRP) and, once washed (Pw), were suspended in different media, i.e. in platelet poor plasma (Pw-PPP), in serum (Pw-S) and in Krebs-Ringer solution (Pw-KR). Scanning electron microscopy of platelet adhesion and morphology revealed differences in the platelet activating power of the various materials. The washing procedure and resuspension in PPP generally resulted in an increased number of adherent platelets, compared with the number of platelets adherent to the same material in PRP. However, platelets washed and suspended in Pw-KR or Pw-S showed the same shape distribution as in PRP. When platelets from stressed rabbits were used, there was very strong aggregation and activation of the platelets in both PRP and Pw-PPP, independent of the chemical nature and surface structure of the material. In contrast, in Pw-KR and Pw-S (in which Fbg is absent) a general picture of single, not very modified platelets was observed. Their number and shapes changed according to the nature of the different materials. On the whole, the present results confirm our original hypothesis of a key role of the psychological condition of the blood donor and strongly indicate Fbg as the determinant factor in the pattern of platelet adhesion.

The role of plasma proteins and stress in the assessment of hemocompatibility

The physiological and psychological conditions of subjects supplying blood for hemocompatibility tests significantly affect the behavior of platelets in terms of both adhesion and activation. The responses of platelets to a standard biomaterial, polyethylene (PE), were examined with blood collected from male rabbits both in basal conditions and after stress. Different media were utilized. First, platelet-rich plasma (PRP) was used to obtain a PE response to contact with platelets. Then platelets drawn from PRP were isolated and washed with Krebs-Ringer solution. One aliquot was suspended in serum (Pw-S) where fibrinogen was absent, another aliquot in Krebs-Ringer solution (Pw-KR) (in order to avoid the influence of the plasma proteins on platelets), and a third aliquot in the original plasma from which the platelets were drawn (Pw-PPP) (in order to restore the initial condition of the plasma but with washed platelets). The analysis of platelet adhesion and morphology was performed by Scanning Electron Microscopy (SEM). Differences in platelet adhesion and morphology were observed with four different media in nonstressed animals, with Pw-PPP showing a higher number and Pw-S and PW-KR lower numbers. Platelet morphology indicated low levels of activation. The platelets drawn from stressed subjects could not be counted in either PRP or PPP medium because they were fully aggregated and adhered; in contrast, in Pw-KR and Pw-S, no significant differences were found with respect to nonstressed conditions, and there was little difference in platelet morphology. All of these factors underline the role of plasma proteins, in particular fibrinogen, in the stress-induced activation of platelets.