Viewpoint: A Potential Role for Platelet Derived Cytokines in the Inflammatory Response

Transforming growth factor beta 1 (TGF-β1) in COVID-19 patients: relation to platelets and association with the disease outcome

Transforming growth factor beta (TGF-β) is a ubiquitously distributed cytokine known to contribute to the pathogenesis of numerous pathological processes. The aim of this study was to measure serum concentrations of TGF-β1 in severely ill COVID-19 patients and to analyze its relationship with selected hematological and biochemical parameters and with the disease outcome. The study population included 53 COVID-19 patients with severe clinical expression of the disease and 15 control subjects. TGF-β1 was determined in serum samples and supernatants from PHA-stimulated whole blood cultures using ELISA assay. Biochemical and hematological parameters were analyzed using standard accepted methods. Our results showed that serum levels of TGF-β1 in COVID-19 patients and controls correlate with the platelet counts. Also, positive correlations of TGF-β1 with white blood cell and lymphocyte counts, platelet-to-lymphocyte (PLR) ratio, and fibrinogen level were shown, while negative correlations of this cytokine with platelet distribution width (PDW), D-dimer and activated partial thromboplastin time (a-PTT) values in COVID-19 patients were observed. The lower serum values of TGF-β1 were associated with the unfavorable outcome of COVID-19. In conclusion, TGF-β1 levels were strongly associated with platelet counts and unfavorable disease outcome of severely ill COVID-19 patients.

Fish Oil Supplementation Inhibits Platelet Aggregation and ATP Release Induced by Platelet-activating Factor and Other Agonists

The anti-inflammatory effects of fish oil may partly be due to the inhibition of platelet activation induced by platelet-activating factor (PAF) and other agonists. To investigate this hypothesis, the diets of 12 healthy volunteers were supplemented with 12 fish oil capsules or 12 olive oil capsules daily for 4 weeks in a double blind crossover study. Aggregation induced by PAF (18 and 12.5 nM) and collagen (20 μg/ml)tended to be reduced after fish oil but the effect was statistically significant only in subjects receiving fish oil in the 6rst 4 weeks of the study (P 0.05, n=6). The effect of fish oil supplementation on platelet ATP release was more marked with significant inhibition of ATP release induced by PAF (1200 and 36 nM, P 0.01, n = 12), collagen (20 μg/ml, P 0.005, n = 12) and ADP (15,10 and 5 μM, P 0.05, n = 12). Olive oil supplementation appeared to inhibit ATP release induced by collagen (45 and 30 μg/ml, P> 0.025, n = 12), while aggregation and ATP release induced by arachidonic acid and adrenaline were unaffected by the supplements. Plasma fibrinogen was significantly reduced after olive oil (P 0.01, n = 12) while prothrombin time was reduced after fish oil (P 0.001, n = 12) and olive oil (P 0.0025). Reduced platelet aggregation and more importantly, inhibition of platelet release induced by PAF and other agonists may contribute to the anti-inflammatory effects of fish oil supplementation in a number of disease states but olive oil may also independently affect platelet function and influence the effect offish oil.

Serum adenosine deaminase enzyme and plasma platelet factor 4 activities in active pulmonary tuberculosis, HIV-seropositive subjects and cancer patients

The aim of this study was to determine the serum adenosine deaminase (ADA) and plasma platelet factor (PF-4) activities in patients with active pulmonary tuberculosis, HIV seropositive subjects, cancer patients (acute and chronic type lymphoblastic leukaemia) and to compare them with the results of healthy individuals. Eighty-eight subjects were enrolled in this study, 24 patients with active pulmonary tuberculosis, 20 patients with HIV seropositive subjects, 24 patients with cancer, 12 patients with acute type lymphoblastic leukaemia, 12 patients with chronic type lymphoblastic leukaemia) patients and 20 healthy individuals. ADA activity was determined in serum samples using colorimetric method and plasma PF4 activity was measured by using a sandwich-type enzyme immunoassay. When all study groups were compared with the control group, mean serum ADA activities were found to be significantly (p<0.01) higher in the sera of patients with active pulmonary tuberculosis (median, range: 39 IU/l), HIV seropositive subjects (median, range: 31 IU/l) than in the sera of cancer patients (median, range: 15) and healthy controls (median, range: 32 IU/l). Plasma PF-4 activities in active pulmonary tuberculosis patients (median, range: 84 IU/ml) were found to be significantly elevated when compared to HIV seropositive subjects (median, range: 59 IU/ml), cancer patients (median, range 55 IU/ml) and healthy individuals (median, range: 56 IU/ml) (p<0.01). Serum ADA and plasma PF-4 activities showed significant alteration in patients with active pulmonary tuberculosis compared to patients with HIV seropositive subjects, cancer patients and healthy individuals. In conclusion, we suggest that serum ADA and PF-4 activities can be used in the diagnosis of tuberculosis as an supplementary laboratory test in combination with clinical and laboratory findings. Further controlled studies are necessary to determine the importance of the PF-4 and ADA activities in patients with active pulmonary tuberculosis, HIV seropositive subjects and cancer patients.

Linkage between inflammation and coagulation: an update on the molecular basis of the crosstalk

Inflammation and coagulation cannot be considered as two separate processes, since there are several connecting points making them part of unique, defensive host response. The endothelium can be considered as the first link between inflammation and coagulation, since damaged endothelium during inflammation represents a surface where proteins involved in both coagulation and the development of inflammation are expressed. During inflammation, cytokines modulate the coagulation system by downregulating the expression of thrombomodulin and the activation of protein C pattern but, at the same time, they induce the expression of tissue factor, modifying, in this way, the balance between procoagulant and anticoagulant activities. At the same time, at the site of tissue injury, platelets become activated and release several mediators that modify tissue integrity. Thrombin, formed following activation of the coagulation cascade, is essential to promote haemostasis but also stimulates several cell functions, including chemotaxis and mitogenesis, which are responsible for the spreading of the lesion and the tissue repair process. Therefore, in the study of inflammation the involvement of the coagulation pathway has to be taken into account, since the interaction between coagulation and inflammation pathways is a critical issue.

Platelet serotonin and interleukin-1 beta after sleep deprivation and recovery sleep in humans

Sleep deprivation (SD) represents a well-established therapy for major depression. Recent findings suggest that the antidepressive effects of sleep deprivation are mediated at least in part by pro-serotoninergic mechanisms. Furthermore, SD has been demonstrated to modify different host defense activities. We therefore investigated the serotonin (5-HT) content in platelets, platelet density distribution and 5-HT-induced IL-1 beta release from platelets in 10 healthy men before and after total SD (TSD) as well as after recovery sleep. Blood samples were drawn on 3 consecutive days at 7.00 h, 13.00 h, and 19.00 h, respectively. In addition, the psychophysiological parameters tiredness and wakefulness were assessed. After TSD the normal daily variation of IL-1 beta release with high morning levels and low evening levels was found to be significantly inverted. The release of IL-1 beta corresponded positively to the subjectively experienced tiredness of the probands. Analysis of platelet density distribution indicated a significant daily variation of low density platelets with low levels in the morning and high levels in the evening, which was absent after TSD. Our findings favour an increased pro-serotoninergic effect after TSD, which comprises respective variations of the host defense system, but is abolished by consecutive recovery sleep.

Inhibitory effects of pentoxifylline on LPS-induced leukocyte adhesion and macromolecular extravasation in the microcirculation

Pentoxifylline (PTX) has been shown to combat effectively endotoxin induced symptoms of shock or inflammation by reducing both leukocyte activation and endogenous cytokine formation. With regard to blood perfusion, inflammation is defined as a local reaction to injury of the living microvasculature and its content. Leukocyte margination, rolling, adhesion, and emigration is mediated by adhesion molecules along the endothelium of postcapillary venules and is considered to be an important step in the inflammatory response. Changes in the vascular integrity can be estimated in terms of increased extravasation of macromolecules. Using intravital microscopy with the help of an analogous video image processing system we measured the effect of PTX on lipopolysaccharide (LPS, 15 mg/kg i.v.) induced leukocyte adhesion and extravasation of FITC-rat serum albumin (FITC-RSA) in rat mesenteric venules. The changes in vascular permeability correlates significantly (r = 0.75) with a locally increased number of adherent leukocytes. PTX significantly inhibits both leukocyte adhesion and extravasation of FITC-RSA dose dependently. Our results indicate that PTX effectively preserves vascular integrity in the microcirculation by acting primarily on LPS-induced leukocyte adhesion.

Hyperaggregation of platelets in intestinal tuberculosis: role of platelets in chronic inflammation

Eighty-eight percent (38/43) patients of intestinal tuberculosis showed significant hyperaggregation of platelets (P < 0.001). Serum and plasma from 15 patients when incubated with normal platelets caused hyperaggregation. Gel filtered platelets from 2 patients suspended in normal plasma showed hyperaggregation of platelets with arachidonic acid. Tubercular protein had no effect on platelet aggregation. A role of hyperactive platelets in chronic inflammatory response is discussed.