The role of platelets in hemostasis and thrombosis has long been recognized, recently their contribution to immunological and inflammatory processes is emerging. Platelets could be the missing link ...between cardiovascular disease, chronic stress and depressive symptoms. Both physical and mental stressors cause platelet activation reflected by changes in platelet bioactivity and aggregation. Here we evaluate the proinflammatory platelet response to acute and chronic mental stress. In a prospective study design an acute mental stress test was administered to 55 healthy male participants once without and once in the presence of chronic mental stress. Blood was collected prior to and at three time points following an acute mental stress test (0, 30, 60 min). Platelet proinflammatory activation markers, were assessed using FACS analysis and aggregability was measured in response to ADP or epinephrine using PFA-100. A linear mixed model was used for analysis. Chronic mental stress lead to a significant increase in state anxiety (
p
< 0.001), depressive symptoms (
p
= 0.045) and perceived stress (
p
= 0.001). The factor “chronic mental stress” was significantly associated with increased numbers of CD63+ platelets (
p
= 0.009). The factor “acute mental stress” was associated with alterations in CD62P+ platelets (
p
< 0.001), CD63+ platelets (
p
= 0.011), PAC-1+ platelets (p < 0.001) as well as platelet leucocyte aggregates (
p
= 0.019). The recovery of CD62P function following the acute mental stress exposure was significantly impaired by chronic stress (
p
= 0.023). Aggregation was affected by chronic and acute mental stress. In conclusion, mental stress is linked to an increased and prolonged proinflammatory platelet bioactivity. This proinflammatory and immunomodulatory stimuli could help to explain the link between mental and somatic disorders.
Graphical Abstract
The immunomodulatory capacity of mental stress is one of the basic concepts of psychoneuroimmunology. The current prospective longitudinal study was designed to evaluate the effect of acute mental ...stress on neurotransmitter precursor amino acid levels in individuals with depression at 2 time points. Ten physically healthy patients with a diagnosis of major depressive episode and Montgomery–Åsberg Depression Rating Scale scores (MADRAS) ⩾20 points at inclusion were assessed on 2 study days (once with higher MADRAS scores, once with lower MADRAS scores; median 34.5 days apart) and subjected to a standardized acute mental stress test on each study day. Blood was collected at 4 time points: once prior to and at 3 time points (0, 30 minutes, 60 minutes) following mental stress. Neurotransmitter precursor amino acid levels, that is kynurenine/tryptophan (KYN/TRP) and phenylalanine/tyrosine (PHE/TYR), as well as neopterin and nitrite were analyzed in a total of 80 individual blood samples. Regression and correlation analyses were performed. Regression analyses of PHE/TYR (R2 = .547) and KYN/TRP (R2 = .440) in relation to MADRAS depression severity showed a quadratic curve fit. This was reflected by a negative linear correlation between MADRAS scores and PHE/TYR as well as KYN/TRP in the lower score range (r = −.805, P < .001 and r = −.586, P < .001 respectively) and a positive correlation in the higher MADRAS score range (r = .713, P < .001 and r = .379, P = .016 respectively). No effect of acute mental stress was found. This analysis exemplifies the implications of sampling as well as data distributions on results. The crosstalk of biological mechanisms that orchestrate metabolic and immunological signaling may vary depending on depression severity resulting in non-linear associations that may explain the heterogeneity of results found in the literature.
Neutralizing antibodies against interferon-beta are associated with a reduction of the efficacy of this drug. Continuing treatment leads to a decline or even loss of neutralizing antibodies over ...years. No strategies are currently available to shorten the period of neutralizing antibody positivity. The objective of this study was to investigate the effect of switching between high and low immunogenic interferon-beta products on neutralising antibody titres. Twenty-four patients treated with the subcutaneously administered interferon-beta 1b or 1a and high titres of neutralizing antibodies were included. At baseline interferon-beta therapy was interrupted for 3 months and two pulses of high dose methylprednisolone were applied. Patients were then randomized to receive either the previous interferon-beta preparation or the low immunogenic intramuscular interferon-beta 1a. The primary end-point was the change of neutralizing antibody titres 12 months after randomization. Twelve patients were switched to interferon-beta 1a intramuscularly and 12 patients remained on previous treatment. Median neutralizing antibody titres were 846 NU at baseline and 196 NU at the end of the study. The median change of neutralizing antibody titres did not differ significantly between therapy switchers and non-switchers. Baseline and final neutralizing antibody titres correlated significantly. In conclusion, neither switching nor continuous therapy with any subcutaneous interferon-beta preparation significantly changed neutralizing antibody titres.
Abstract Background Changes in platelet bioactivity and aggregation are of interest when studying patients with depression as this could help to explain the statistically observed association of ...depression and chronic somatic, especially cardiovascular disease. This link could potentially be mediated through serotonergic signaling or immunological changes. Methods 38 medicated patients with major depressive disorder (MDD) and 30 mentally healthy controls, both without a diagnosis of cardiovascular disease, were included in this naturalistic study. Demographic and psychometric data were obtained. Platelet aggregability was measured by PFA-100 and bioactive compounds and serotonin levels were quantified in platelet sonicate. Results The comparison of patients with controls revealed no changes in platelet aggregability, but significant differences in platelet content of several bioactive compounds. In a second analysis, patients were grouped according to the receptors and transporters influenced by their medication and again compared to controls. A significant effect of MDD was found for platelet content of serotonin, CD40L, interleukin-1β, and platelet factor-4, independent of medication. These markers can thus be classified as sensitive to MDD. The effect of medication on platelet parameters was also evaluated. Platelet content of matrix metalloproteinase-2 and β-thromboglobulin was normalized in MDD patients by medication acting on the serotonin transporter. Limitations Owing to the naturalistic study design, patients were on a variety of different medications and combination therapies. This was accounted for by a novel analysis method. Conclusion Platelet serotonin levels and content of immunomodulatory compounds are significantly altered in patients with MDD, even if treatment effects are taken into account.
ABSTRACT Platelets are important in hemostasis, but also contain adhesion molecules, pro-inflammatory and immune-modulatory compounds, as well as most of the serotonin outside the central nervous ...system. Dysbalance in the serotonin pathways is involved in the pathogenesis of depressive symptoms. Thus, changes in platelet aggregation and content of bioactive compounds are of interest when investigating physiological stress-related mental processes as well as stress-related psychiatric diseases such as depression. In the present study, a characterization of platelet reactivity in acute physical and persistent mental stress was performed (aggregation, serotonin and serotonin 2A-receptor, P-selectin, CD40 ligand, matrix metalloproteinase-2 and -9 (MMP-2 and -9), platelet/endothelial adhesion molecule-1 (PECAM-1), intercellular adhesion molecule-1 (ICAM-1), β-thromboglobulin (β-TG) and platelet factor 4 (PF-4). Acute physical stress increased platelet aggregability while leaving platelet content of bioactive compounds unchanged. Persistent mental stress led to changes in platelet content of bioactive compounds and serotonin 2A-receptor only. The values of most bioactive compounds correlated with each other. Acute physical and persistent mental stress influences platelets through distinct pathways, leading to differential changes in aggregability and content of bioactive compounds.
It is well established that various mental stress conditions contribute, or at least influence, underlying pathophysiological mechanisms in somatic, as well as in psychiatric disorders; blood ...platelets are supposed to represent a possible link in this respect. The anculeated platelets are the smallest corpuscular elements circulating in the human blood. They display different serotonergic markers which seem to reflect the central nervous serotonin metabolism. They are known as main effectors in haematological processes but recent research highlights their role in the innate and adaptive immune system. Platelets are containing a multitude of pro-inflammatory and immune-modulatory bioactive compounds in their granules and are expressing immune-competent surface markers. Research gives hint that platelets activation and reactivity is increased by mental stress. This leads to enhanced cross talk with the immune system via paracrine secretion, receptor interaction and formation of platelet leucocyte-aggregates. Recently it has been demonstrated that the immune system can have a remarkable impact in the development of psychiatric disorders. Therefore platelets represent an interesting research area in psychiatry and their role as a possible biomarker has been investigated. We review the influence of mental stress on what is termed platelet bioactivity in this article, which subsumes the mainly immune-modulatory activity of platelets in healthy volunteers, elderly persons with chronic care-giving strain, patients with cardiovascular diseases who are prone to psychosocial stress, as well as in patients with posttraumatic stress disorder. Research data suggest that stress enhances platelet activity, reactivity and immune-modulatory capacities.
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