In vitro norepinephrine significantly activates isolated platelets from healthy volunteers and critically ill patients following severe traumatic brain injury

Age and mean platelet volume-based nomogram for predicting the therapeutic efficacy of metoprolol in Chinese pediatric patients with vasovagal syncope

BACKGROUND

Vasovagal syncope (VVS) is the most common type of orthostatic intolerance in children. We investigated whether platelet-related factors related to treatment efficacy in children suffering from VVS treated with metoprolol.

METHODS

Metoprolol-treated VVS patients were recruited. The median duration of therapy was three months. Patients were followed and divided into two groups, treament-effective group and treatment-ineffective group. Logistic and least absolute shrinkage selection operator regressions were used to examine treatment outcome variables. Receiver-operating characteristic (ROC) curves, precision-recall (PR) curves, calibration plots, and decision curve analyses were used to evaluate the nomogram model.

RESULTS

Among the 72 patients who complete the follow-up, treatment-effective group and treatment-ineffective group included 42 (58.3%) and 30 (41.7%) cases, respectively. The patients in the treatment-effective group exhibited higher mean platelet volume (MPV) [(11.0 ± 1.0) fl vs. (9.8 ± 1.0) fl, P < 0.01] and platelet distribution width [12.7% (12.3%, 14.3%) vs. 11.3% (10.2%, 12.2%), P < 0.01] than those in the treatment-ineffective group. The sex ratio was significantly different (P = 0.046). A fit model comprising age [odds ratio (OR) = 0.766, 95% confidence interval (CI) = 0.594-0.987] and MPV (OR = 5.613, 95% CI = 2.297-13.711) might predict therapeutic efficacy. The area under the curve of the ROC and PR curves was computed to be 0.85 and 0.9, respectively. The P value of the Hosmer-Lemeshow test was 0.27. The decision curve analysis confirmed that managing children with VVS based on the predictive model led to a net advantage ranging from 0.01 to 0.58. The nomogram is convenient for clinical applications.

CONCLUSION

A novel nomogram based on age and MPV can predict the therapeutic benefits of metoprolol in children with VVS.

Cytokine Release by Microglia Exposed to Neurologic Injury Is Amplified by Lipopolysaccharide

INTRODUCTION

Traumatic brain injury (TBI) is a leading cause of death and morbidity in the trauma population. Microglia drive the secondary neuroinflammatory response after TBI. We sought to determine if the microglial response to neurologic injury was exacerbated by a second stimulus after exposure to neurologic injury.

METHODS

Sprague-Dawley rats (age 2-3 wk) were divided into injured and noninjured groups. Injured rats underwent a controlled cortical impact injury; noninjured rats remained naïve to any injury and served as the control group. Primary rat microglia were isolated and applied to in vitro cultures. After incubation for 24 h, the microglia were stimulated with lipopolysaccharide (LPS) or norepinephrine. Twenty-four hours after stimulation, cell culture supernatant was collected. Tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) production were measured by standard enzyme-linked immunosorbent assays. GraphPad Prism was used for statistical analysis.

RESULTS

When compared to noninjured microglia, LPS induced a significantly greater production of TNF-α in microglia isolated from the injured ipsilateral (versus noninjured = 938.8 ± 155.1, P < 0.0001) and injured contralateral hemispheres (versus noninjured = 426.6 ± 155.1, P < 0.0001). When compared to microglia from noninjured cerebral tissue, IL-6 production was significantly greater after LPS stimulation in the injured ipsilateral hemisphere (mean difference versus noninjured = 9540 ± 3016, P = 0.0101) and the contralateral hemisphere (16,700 ± 3016, P < 0.0001). Norepinephrine did not have a significant effect on IL-6 or TNF-α production.

CONCLUSIONS

LPS stimulation may amplify the release of proinflammatory cytokines from postinjury microglia. These data suggest that post-TBI complications, like sepsis, may propagate neuroinflammation by augmenting the proinflammatory response of microglia.

Long-Term Impact of Diffuse Traumatic Brain Injury on Neuroinflammation and Catecholaminergic Signaling: Potential Relevance for Parkinson's Disease Risk

Traumatic brain injury (TBI) is associated with an increased risk of developing Parkinson's disease (PD), though the exact mechanisms remain unclear. TBI triggers acute neuroinflammation and catecholamine dysfunction post-injury, both implicated in PD pathophysiology. The long-term impact on these pathways following TBI, however, remains uncertain. In this study, male Sprague-Dawley rats underwent sham surgery or Marmarou's impact acceleration model to induce varying TBI severities: single mild TBI (mTBI), repetitive mild TBI (rmTBI), or moderate-severe TBI (msTBI). At 12 months post-injury, astrocyte reactivity (GFAP) and microglial levels (IBA1) were assessed in the striatum (STR), substantia nigra (SN), and prefrontal cortex (PFC) using immunohistochemistry. Key enzymes and receptors involved in catecholaminergic transmission were measured via Western blot within the same regions. Minimal changes in these markers were observed, regardless of initial injury severity. Following mTBI, elevated protein levels of dopamine D1 receptors (DRD1) were noted in the PFC, while msTBI resulted in increased alpha-2A adrenoceptors (ADRA2A) in the STR and decreased dopamine beta-hydroxylase (DβH) in the SN. Neuroinflammatory changes were subtle, with a reduced number of GFAP+ cells in the SN following msTBI. However, considering the potential for neurodegenerative outcomes to manifest decades after injury, longer post-injury intervals may be necessary to observe PD-relevant alterations within these systems.

Potentiating glymphatic drainage minimizes post-traumatic cerebral oedema

Cerebral oedema is associated with morbidity and mortality after traumatic brain injury (TBI)1. Noradrenaline levels are increased after TBI2-4, and the amplitude of the increase in noradrenaline predicts both the extent of injury5 and the likelihood of mortality6. Glymphatic impairment is both a feature of and a contributor to brain injury7,8, but its relationship with the injury-associated surge in noradrenaline is unclear. Here we report that acute post-traumatic oedema results from a suppression of glymphatic and lymphatic fluid flow that occurs in response to excessive systemic release of noradrenaline. This post-TBI adrenergic storm was associated with reduced contractility of cervical lymphatic vessels, consistent with diminished return of glymphatic and lymphatic fluid to the systemic circulation. Accordingly, pan-adrenergic receptor inhibition normalized central venous pressure and partly restored glymphatic and cervical lymphatic flow in a mouse model of TBI, and these actions led to substantially reduced brain oedema and improved functional outcomes. Furthermore, post-traumatic inhibition of adrenergic signalling boosted lymphatic export of cellular debris from the traumatic lesion, substantially reducing secondary inflammation and accumulation of phosphorylated tau. These observations suggest that targeting the noradrenergic control of central glymphatic flow may offer a therapeutic approach for treating acute TBI.

Pheochromocytoma/paraganglioma-associated cardiomyopathy

Pheochromocytoma/paraganglioma (PPGL) are neuroendocrine tumors that frequently produce and release catecholamines. Catecholamine excess can manifest in several cardiovascular syndromes, including cardiomyopathy. PPGL-induced cardiomyopathies occur in up to 11% of cases and are most often associated with an adrenal pheochromocytoma (90%) and rarely with a paraganglioma derived from the sympathetic ganglia (10%). PPGL-associated cardiomyopathies can be chronic or acute, with takotsubo cardiomyopathy being the most often reported. These two types of PPGL-induced cardiomyopathy seem to have different pathophysiological backgrounds. Acute catecholaminergic stress inundates myocardial β-adrenoceptors and leads to left ventricle stunning and slight histological apoptosis. In chronic cardiomyopathy, prolonged catecholamine exposure leads to extended myocardial fibrosis, inflammation, and necrosis, and ultimately it causes dilated cardiomyopathy with a low ejection fraction. Sometimes, especially in cases associated with hypertension, hypertrophic cardiomyopathy can develop. The prognosis appears to be worse in chronic cases with a higher hospital mortality rate, higher cardiogenic shock rate at initial presentation, and lower left ventricular recovery rate after surgery. Therefore, establishing the correct diagnosis at an early stage of a PPGL is essential. This mini-review summarizes current data on pathophysiological pathways of cardiac damage caused by catecholamines, the clinical presentation of PPGL-induced cardiomyopathies, and discusses treatment options.

The levels of TGFβ1, VEGF, PDGF-BB, and PF4 in platelet-rich plasma of professional soccer players: a cross-sectional pilot study

Background

Regenerative therapy using platelet-rich plasma (PRP), a rich source of growth factors, has become popular in orthopedic sports medicine. Elite athletes prefer PRP therapy for their injured muscles and tendons primarily to avoid the possible risks of surgical treatment. However, the clinical effectiveness of PRP therapy in elite athletes compared to that in non-athletes remains unknown. Therefore, to investigate the effectiveness of PRP therapy in professional athletes (pro-athletes), we focused on the quality of PRP preparations and compared the levels of bioactive molecules between pro-athletes and non-athletes.

Methods

PRP was prepared from healthy, non-smoking male professional soccer players (pro-athletes) (n = 22) and non-athletes (VEGF: n = 34, others: n = 38). The levels of TGFβ1, PDGF-BB, VEGF, and PF4 were determined using ELISA kits. Polyphosphate was probed with 4’,6-diamidino-2-phenylindole and monitored using a fluorometer. The body composition of the donors was determined using a bathroom weighing scale.

Results

The levels of TGFβ1 and VEGF were significantly lower in pro-athletes than in non-athletes, whereas PF4 levels were significantly higher in pro-athletes. No significant difference was found in PDGF-BB levels between these groups. Biomolecule levels were not correlated with polyphosphate levels.

Conclusion

TGFβ1, VEGF, and PDGF-BB levels in pro-athletes were not higher than those in non-athletes. These findings suggest that growth factor levels in PRP may not be a predominant determinant of the clinical effectiveness of PRP therapy in pro-athletes. Increased PF4 levels in pro-athletes suggest an immunological function of PRP that may positively influence tissue regeneration.

Risk Factors for Cardiac Complications in Patients With Pheochromocytoma and Paraganglioma: A Retrospective Single-Center Study

BACKGROUND

Catecholamine excess arising from pheochromocytomas and paragangliomas (PPGLs) can cause a wide spectrum of cardiac manifestations. Although there are reviews of reported cases, these reviews lack detailed data, which makes it impossible to perform an accurate analysis. In this study, we conducted a comprehensive analysis of cardiovascular complications (CCs), including PPGL-related myocardial injury, cardiogenic shock, and arrhythmias requiring antiarrhythmic therapy, in a large cohort of patients with PPGL.

METHODS

We retrospectively analyzed the clinical data of consecutive patients with PPGL admitted between January 2018 and June 2020. The prevalence and the characteristics of patients with CCs were investigated. Moreover, comparisons were made between patients with and without CCs.

RESULTS

Compared with the non-CC group, the percentage of men was significantly lower (14/41 vs.92/175, 34.1% vs. 52.6%, p = 0.034) and the proportion of patients with paroxysmal hypertension was significantly higher (13/41 vs.29/173, 31.7% vs.16.8%, p = 0.03) in the CC group. More patients showed excessive sweating (19/41 vs 64/175, 46.3% vs. 24.0%, p = 0.004) and PPGL crisis (7/41 vs. 10/175, 17.1% vs.5.7%, p=0.035) in the CC group. In terms of laboratory findings, higher white blood cell [7.36 (6.49, 20.23) vs. 5.95 (5.1, 6.97)×10⁹/L, p<0.001] and platelet [339.28 ± 108.54 vs. 250.66 ± 70.83(×10⁹/L), p = 0.021] counts were more common in the CC group. There was also a higher prevalence of combination-producing PPGL in the CC group (13/24 vs.20/149, 54.2% vs.13.4%, p<0.001). However, the tumor size, invasive behavior on histology, and hemorrhage or necrosis on histology did not differ between the two groups. Platelet count [odds ratio (OR): 1.009; 95% confidence interval (CI) 1.001-1.016; p=0.023] and combination-secreting PPGL (OR: 5.009; 95% CI 1.365-18.38; p=0.015) are independent risk factors for CCs in patients with PPGL.

CONCLUSIONS

In patients with PPGL, even in the absence of signs and symptoms of CCs, a work up of cardiology should be strongly considered. Importantly, if patients with PPGLs have higher platelet counts and the combination-secreting pattern, they are more likely to have CCs. Thus, a careful cardiac evaluation should be performed.

Norepinephrine exhibits thermo-optical nonlinearity under physiological conditions

Norepinephrine (NE), a crucial modulatory neurotransmitter, plays a significant role in human physiology. Here, we use the Z-scan technique to investigate the nonlinear properties of NE at physiological conditions. Results reveal that NE exhibits thermo-optical nonlinearity. Outcomes can be utilized to investigate noradrenergic processes in correlation with various diseases.

Neurologic Assessment of the Neurocritical Care Patient

Sedation is a ubiquitous practice in ICUs and NCCUs. It has the benefit of reducing cerebral energy demands, but also precludes an accurate neurologic assessment. Because of this, sedation is intermittently stopped for the purposes of a neurologic assessment, which is termed a neurologic wake-up test (NWT). NWTs are considered to be the gold-standard in continued assessment of brain-injured patients under sedation. NWTs also produce an acute stress response that is accompanied by elevations in blood pressure, respiratory rate, heart rate, and ICP. Utilization of cerebral microdialysis and brain tissue oxygen monitoring in small cohorts of brain-injured patients suggests that this is not mirrored by alterations in cerebral metabolism, and seldom affects oxygenation. The hard contraindications for the NWT are preexisting intracranial hypertension, barbiturate treatment, status epilepticus, and hyperthermia. However, hemodynamic instability, sedative use for primary ICP control, and sedative use for severe agitation or respiratory distress are considered significant safety concerns. Despite ubiquitous recommendation, it is not clear if additional clinically relevant information is gleaned through its use, especially with the contemporaneous utilization of multimodality monitoring. Various monitoring modalities provide unique and pertinent information about neurologic function, however, their role in improving patient outcomes and guiding treatment plans has not been fully elucidated. There is a paucity of information pertaining to the optimal frequency of NWTs, and if it differs based on type of injury. Only one concrete recommendation was found in the literature, exemplifying the uncertainty surrounding its utility. The most common sedative used and recommended is propofol because of its rapid onset, short duration, and reduction of cerebral energy requirements. Dexmedetomidine may be employed to facilitate serial NWTs, and should always be used in the non-intubated patient or if propofol infusion syndrome (PRIS) develops. Midazolam is not recommended due to tissue accumulation and residual sedation confounding a reliable NWT. Thus, NWTs are well-tolerated in selected patients and remain recommended as the gold-standard for continued neuromonitoring. Predicated upon one expert panel, they should be performed at least one time per day. Propofol or dexmedetomidine are the main sedative choices, both enabling a rapid awakening and consistent NWT.

Acute platelet response to aneurysmal subarachnoid hemorrhage depends on severity and distribution of bleeding: an observational cohort study

Microthrombosis after aneurysmal subarachnoid hemorrhage (aSAH) is considered to initiate neuroinflammation, vessel remodeling, and blood-brain barrier leakage. We aimed to verify the hypothesis that the intensity of thrombogenicity immediately after aSAH depends on the amount and distribution of extravasated blood. This observational cohort study included 37 consecutive aSAH patients admitted no longer than 24 h after ictus. Volumes of subarachnoid and intraventricular hemorrhages as well as the Subarachnoid Hemorrhage Early Brain Edema Scale (SEBES) score were calculated in each case. Platelet system status was described by platelet count (PLT), mean platelet volume (MPV), MPV to PLT ratio, and platelet-large cell ratio (P-LCR). Median hemorrhage volume amounted to 11.4 ml (interquartile range 2.8-26.8 ml). Patients with more severe hemorrhage had lower PLT and higher MPV to PLT ratio (ρ =  - 0.49, p < .002; ρ = 0.50, p < .002, respectively). PLT decreased by 2.80 G/l per 1 ml of hemorrhage volume (95% CL 1.30-4.30, p < .001). Further analysis revealed that intraventricular hemorrhage volume was associated with P-LCR and MPV (ρ = 0.34, p < .039; ρ = 0.33, p < .048, respectively), whereas SAH volume with PLT and MPV:PLT ratio (ρ =  - 0.40, p < .013; ρ = 0.41, p < .013, respectively). The odds of unfavorable neurological outcome increased 3.95 times per 1 fl of MPV (95% CI 1.19-13.12, p < .025). MPV was independently correlated with SEBES (ρ = 0.44, p < .006). This study demonstrated that the extent and distribution of aneurysmal subarachnoid hemorrhage are related to different types of acute platelet response, which may be interpreted as local and systemic thrombogenicity. Increased mean platelet volume measured in the acute phase of aSAH may identify patients at risk for unfavorable neurological outcomes and may serve as a marker of early brain injury.

Platelet-Derived Microparticles (MPs) and Thrombin Generation Velocity in Deep Vein Thrombosis (DVT): Results of a Case-Control Study

Introduction

The role of platelets (Ps) and platelet-derived microparticles (MPs) in venous thromboembolism (VTE) is still being debated.

Methods

We measured MPs, velocity of thrombin formation (PiCT) and phospholipid generation (PLPs) in 40 patients with unprovoked deep vein thrombosis (DVT), who were compared with 40 healthy controls.

Results

MPs were higher in DVT (7.12 nM; 25th–75th percentile 5.26–9.12) than in controls (5.45 nM; 25th–75th percentile 1.67–8.96) (p = 0.19). PiCT velocity was lower in DVT (1.87 sec; 25th–75th percentile 1.75–1.93 sec) compared with controls (1.95 sec; 25th–75th percentile 1.84–2.24 sec) (p = 0.04). PLPs were higher in DVT (77.03 µg/mL; 25th–75th percentile 72.12–103.59 µg/mL) compared with controls (68.65 µg/mL, 25th–75th percentile 55.31–78.20 µg/mL) (p = 0.02).

Discussion

We hypothesize that MPs could be integrated with the lab network assay in evaluating Ps’ role as an activated procoagulative condition. We encourage research on Ps and P-derived microvesicle pathways in patients with unprovoked DVT and not only in patients with cancer-induced DVT.

Depression and Cardiovascular Disease: The Viewpoint of Platelets

Depression is a major cause of morbidity and low quality of life among patients with cardiovascular disease (CVD), and it is now considered as an independent risk factor for major adverse cardiovascular events. Increasing evidence indicates not only that depression worsens the prognosis of cardiac events, but also that a cross-vulnerability between the two conditions occurs. Among the several mechanisms proposed to explain this interplay, platelet activation is the more attractive, seeing platelets as potential mirror of the brain function. In this review, we dissected the mechanisms linking depression and CVD highlighting the critical role of platelet behavior during depression as trigger of cardiovascular complication. In particular, we will discuss the relationship between depression and molecules involved in the CVD (e.g., catecholamines, adipokines, lipids, reactive oxygen species, and chemokines), emphasizing their impact on platelet activation and related mechanisms.

Effect of Physical Exercise on the Release of Microparticles with Angiogenic Potential

Cellular communication has a fundamental role in both human physiological and pathological states and various mechanisms are involved in the crosstalk between organs. Among these, microparticles (MPs) have an important involvement. MPs are a subtype of extracellular vesicles produced by a variety of cells following activation or apoptosis. They are normally present in physiological conditions, but their concentration varies in pathological states such as cardiovascular disease, diabetes mellitus, or cancer. Acute and chronic physical exercise are able to modify MPs amounts as well. Among various actions, exercise-responsive MPs affect angiogenesis, the process through which new blood vessels grow from pre-existing vessels. Usually, the neo vascular growth has functional role; but an aberrant neovascularization accompanies several oncogenic, ischemic, or inflammatory diseases. In addition, angiogenesis is one of the key adaptations to physical exercise and training. In the present review, we report evidence regarding the effect of various typologies of exercise on circulating MPs that are able to affect angiogenesis.

Exercise-Derived Microvesicles: A Review of the Literature

Initially suggested as simple cell debris, cell-derived microvesicles (MVs) have now gained acceptance as recognized players in cellular communication and physiology. Shed by most, and perhaps all, human cells, these tiny lipid-membrane vesicles carry bioactive agents, such as proteins, lipids and microRNA from their cell source, and are produced under orchestrated events in response to a myriad of stimuli. Physical exercise introduces systemic physiological challenges capable of acutely disrupting cell homeostasis and stimulating the release of MVs into the circulation. The novel and promising field of exercise-derived MVs is expanding quickly, and the following work provides a review of the influence of exercise on circulating MVs, considering both acute and chronic aspects of exercise and training. Potential effects of the MV response to exercise are highlighted and future directions suggested as exercise and sports sciences extend the realm of extracellular vesicles.

Whole-body heat stress and exercise stimulate the appearance of platelet microvesicles in plasma with limited influence of vascular shear stress

Intense, large muscle mass exercise increases circulating microvesicles, but our understanding of microvesicle dynamics and mechanisms inducing their release remains limited. However, increased vascular shear stress is generally thought to be involved. Here, we manipulated exercise‐independent and exercise‐dependent shear stress using systemic heat stress with localized single‐leg cooling (low shear) followed by single‐leg knee extensor exercise with the cooled or heated leg (Study 1, n = 8) and whole‐body passive heat stress followed by cycling (Study 2, n = 8). We quantified femoral artery shear rates (SRs) and arterial and venous platelet microvesicles (PMV–CD41⁺) and endothelial microvesicles (EMV–CD62E⁺). In Study 1, mild passive heat stress while one leg remained cooled did not affect [microvesicle] (P ≥ 0.05). Single‐leg knee extensor exercise increased active leg SRs by ~12‐fold and increased arterial and venous [PMVs] by two‐ to threefold, even in the nonexercising contralateral leg (P < 0.05). In Study 2, moderate whole‐body passive heat stress increased arterial [PMV] compared with baseline (mean±SE, from 19.9 ± 1.5 to 35.5 ± 5.4 PMV^.μL^−1.10³, P < 0.05), and cycling with heat stress increased [PMV] further in the venous circulation (from 27.5 ± 2.2 at baseline to 57.5 ± 7.2 PMV^.μL^−1.10³ during cycling with heat stress, P < 0.05), with a tendency for increased appearance of PMV across exercising limbs. Taken together, these findings demonstrate that whole‐body heat stress may increase arterial [PMV], and intense exercise engaging either large or small muscle mass promote PMV formation locally and systemically, with no influence upon [EMV]. Local shear stress, however, does not appear to be the major stimulus modulating PMV formation in healthy humans.

Physiologic Impact of Circulating RBC Microparticles upon Blood-Vascular Interactions

Here, we review current data elucidating the role of red blood cell derived microparticles (RMPs) in normal vascular physiology and disease progression. Microparticles (MPs) are submicron-size, membrane-encapsulated vesicles derived from various parent cell types. MPs are produced in response to numerous stimuli that promote a sequence of cytoskeletal and membrane phospholipid changes and resulting MP genesis. MPs were originally considered as potential biomarkers for multiple disease processes and more recently are recognized to have pleiotropic biological effects, most notably in: promotion of coagulation, production and handling of reactive oxygen species, immune modulation, angiogenesis, and in initiating apoptosis. RMPs, specifically, form normally during RBC maturation in response to injury during circulation, and are copiously produced during processing and storage for transfusion. Notably, several factors during RBC storage are known to trigger RMP production, including: increased intracellular calcium, increased potassium leakage, and energy failure with ATP depletion. Of note, RMP composition differs markedly from that of intact RBCs and the nature/composition of RMP components are affected by the specific circumstances of RMP genesis. Described RMP bioactivities include: promotion of coagulation, immune modulation, and promotion of endothelial adhesion as well as influence upon vasoregulation via influence upon nitric oxide (NO) bioavailability. Of particular relevance, RMPs scavenge NO more avidly than do intact RBCs; this physiology has been proposed to contribute to the impaired oxygen delivery homeostasis that may be observed following transfusion. In summary, RMPs are submicron particles released from RBCs, with demonstrated vasoactive properties that appear to disturb oxygen delivery homeostasis. The clinical impact of RMPs in normal and patho-physiology and in transfusion recipients is an area of continued investigation.

Influence of red blood cell-derived microparticles upon vasoregulation

Here we review recent data and the evolving understanding of the role of red blood cell-derived microparticles (RMPs) in normal physiology and in disease progression. Microparticles (MPs) are small membrane vesicles derived from various parent cell types. MPs are produced in response to a variety of stimuli through several cytoskeletal and membrane phospholipid changes. MPs have been investigated as potential biomarkers for multiple disease processes and are thought to have biological effects, most notably in: promotion of coagulation, production and handling of reactive oxygen species, immune modulation, angiogenesis, and in apoptosis. Specifically, RMPs are produced normally during RBC maturation and their production is accelerated during processing and storage for transfusion. Several factors during RBC storage are known to trigger RMP production, including: increased intracellular calcium, increased potassium leakage, and energy failure with ATP depletion. Of note, RMP composition differs from that of intact RBCs, and the nature and composition of RMP components are affected by both storage duration and the character of storage solutions. Recognised RMP bioactivities include: promotion of coagulation, immune modulation, and promotion of endothelial adhesion, as well as influence upon vasoregulation via nitric oxide (NO) scavenging. Of particular relevance, RMPs are more avid NO scavengers than intact RBCs and this feature has been proposed as a mechanism for the impaired oxygen delivery homeostasis that has been observed following transfusion. Preliminary human studies demonstrate that circulating RMP abundance increases with RBC transfusion and is associated with altered plasma vasoactivity and abnormal vasoregulation. In summary, RMPs are submicron particles released from stored RBCs, with demonstrated vasoactive properties that appear to disturb oxygen delivery homeostasis. The clinical impact of RMPs in transfusion recipients is an area of continued investigation.

Cellular microparticles and pathophysiology of traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. The finding that cellular microparticles (MPs) generated by injured cells profoundly impact on pathological courses of TBI has paved the way for new diagnostic and therapeutic strategies. MPs are subcellular fragments or organelles that serve as carriers of lipids, adhesive receptors, cytokines, nucleic acids, and tissue-degrading enzymes that are unique to the parental cells. Their sub-micron sizes allow MPs to travel to areas that parental cells are unable to reach to exercise diverse biological functions. In this review, we summarize recent developments in identifying a casual role of MPs in the pathologies of TBI and suggest that MPs serve as a new class of therapeutic targets for the prevention and treatment of TBI and associated systemic complications.

Exercise intensity modulates the appearance of circulating microvesicles with proangiogenic potential upon endothelial cells

The effect of endurance exercise on circulating microvesicle dynamics and their impact on surrounding endothelial cells is unclear. Here we tested the hypothesis that exercise intensity modulates the time course of platelet (PMV) and endothelial-derived (EMV) microvesicle appearance in the circulation through hemodynamic and biochemical-related mechanisms, and that microvesicles formed during exercise would stimulate endothelial angiogenesis in vitro. Nine healthy young men had venous blood samples taken before, during, and throughout the recovery period after 1 h of moderate [46 ± 2% maximal oxygen uptake (V̇o_2max)] or heavy (67 ± 2% V̇o_2max) intensity semirecumbent cycling and a time-matched resting control trial. In vitro experiments were performed by incubating endothelial cells with rest and exercise-derived microvesicles to examine their effects on cell angiogenic capacities. PMVs (CD41⁺) increased from baseline only during heavy exercise (from 21 ± 1 × 10³ to 55 ± 8 × 10³ and 48 ± 6 × 10³ PMV/μl at 30 and 60 min, respectively; P < 0.05), returning to baseline early in postexercise recovery (P > 0.05), whereas EMVs (CD62E⁺) were unchanged (P > 0.05). PMVs were related to brachial artery shear rate (r² = 0.43) and plasma norepinephrine concentrations (r² = 0.21) during exercise (P < 0.05). Exercise-derived microvesicles enhanced endothelial proliferation, migration, and tubule formation compared with rest microvesicles (P < 0.05). These results demonstrate substantial increases in circulating PMVs during heavy exercise and that exercise-derived microvesicles stimulate human endothelial cells by enhancing angiogenesis and proliferation. This involvement of microvesicles may be considered a novel mechanism through which exercise mediates vascular healing and adaptation.

Role of Platelet-Derived Microvesicles As Crosstalk Mediators in Atherothrombosis and Future Pharmacology Targets: A Link between Inflammation, Atherosclerosis, and Thrombosis

Reports in the last decade have suggested that the role of platelets in atherosclerosis and its thrombotic complications may be mediated, in part, by local secretion of platelet-derived microvesicles (pMVs), small cell blebs released during the platelet activation process. MVs are the most abundant cell-derived microvesicle subtype in the circulation. High concentrations of circulating MVs have been reported in patients with atherosclerosis, acute vascular syndromes, and/or diabetes mellitus, suggesting a potential correlation between the quantity of microvesicles and the clinical severity of the atherosclerotic disease. pMVs are considered to be biomarkers of disease but new information indicates that pMVs are also involved in signaling functions. pMVs evoke or promote haemostatic and inflammatory responses, neovascularization, cell survival, and apoptosis, processes involved in the pathophysiology of cardiovascular disease. This review is focused on the complex cross-talk between platelet-derived microvesicles, inflammatory cells and vascular elements and their relevance in the development of the atherosclerotic disease and its clinical outcomes, providing an updated state-of-the art of pMV involvement in atherothrombosis and pMV potential use as therapeutic agent influencing cardiovascular biomedicine in the future.

Sympathetic stimulation facilitates thrombopoiesis by promoting megakaryocyte adhesion, migration, and proplatelet formation

NE and EPI promote megakaryocyte adhesion, migration, and proplatelet formation via α2-adrenoceptor-ERK1/2 signaling. Sympathetic stimulation enhances platelet production, which may facilitate recovery of thrombocytopenia or aggravate atherosclerosis.

Catecholaminergic based therapies for functional recovery after TBI

Among the many pathophysiologic consequences of traumatic brain injury are changes in catecholamines, including dopamine, epinephrine, and norepinephrine. In the context of TBI, dopamine is the one most extensively studied, though some research exploring epinephrine and norepinephrine have also been published. The purpose of this review is to summarize the evidence surrounding use of drugs that target the catecholaminergic system on pathophysiological and functional outcomes of TBI using published evidence from pre-clinical and clinical brain injury studies. Evidence of the effects of specific drugs that target catecholamines as agonists or antagonists will be discussed. Taken together, available evidence suggests that therapies targeting the catecholaminergic system may attenuate functional deficits after TBI. Notably, it is fairly common for TBI patients to be treated with catecholamine agonists for either physiological symptoms of TBI (e.g. altered cerebral perfusion pressures) or a co-occuring condition (e.g. shock), or cognitive symptoms (e.g. attentional and arousal deficits). Previous clinical trials are limited by methodological limitations, failure to replicate findings, challenges translating therapies to clinical practice, the complexity or lack of specificity of catecholamine receptors, as well as potentially counfounding effects of personal and genetic factors. Overall, there is a need for additional research evidence, along with a need for systematic dissemination of important study details and results as outlined in the common data elements published by the National Institute of Neurological Diseases and Stroke. Ultimately, a better understanding of catecholamines in the context of TBI may lead to therapeutic advancements. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Hematuria following Botox treatment for upper limb spasticity: a case report

Hematuria is a documented side effect of botulinum toxin injection and has only been reported when it is used for overactive bladder. Here we report a rare case of hematuria following onabotulinumtoxin A (Botox) injection for upper limb spasticity in a 29-year-old male with a history of traumatic brain injury and hemophilia. Hematuria resolved without further complication after self-injection of factor VIII as recommended by his hematologist. Botulinum toxin binds peripheral cholinergic nerve endings to prevent acetylcholine and norepinephrine exocytosis. Studies have shown that both of these compounds are involved in antifibrinolytic activation, suggesting botulinum toxin may play a role in the coagulation cascade by preventing formation of fibrin. This is further supported by resolution of hematuria in our patient after self-injection of factor VIII. As such, botulinum toxin injection may result in mild spontaneous hemorrhage in patients with underlying hematological deficiencies. Further studies are needed to elucidate its effects in coagulation.

Effects of analgesic use on inflammation and hematology in a murine model of venous thrombosis

Venous thrombosis (VT) is a significant cause of morbidity and mortality in humans. Surgical animal models are crucial in studies investigating the pathogenesis of this disease and evaluating VT therapies. Because inflammation is critical to both the development and resolution of VT, analgesic medications have the potential to adversely affect multiple parameters of interest in VT research. The objective of this study was to determine how several common analgesics affect key variables in a murine ligation model of deep vein thrombosis. Male C57BL/6 mice were randomly assigned to receive either local (bupivacaine) or systemic parenteral analgesia (buprenorphine, tramadol, or carprofen) or 0.9% NaCl (control). All mice underwent laparotomy and ligation of the inferior vena cava, and treatment was continued until euthanasia at 6 or 48 h after surgery. Analysis of harvested tissues and blood included: hematology, thrombus weight, serum and vein-wall cytokines (IL1β, IL6, IL10, TNFα), soluble P-selectin, and vein-wall leukocyte infiltration. Compared with 0.9% NaCl, all of the analgesics affected multiple parameters important to VT research. Carprofen and tramadol affected the most parameters and should not be used in murine models of VT. Although they affected fewer parameters, a single dose of bupivacaine increased thrombus weight at 6 h, and buprenorphine was associated with reduced vein wall macrophages at 48 h. Although we cannot recommend the use of any of the evaluated analgesic dosages in this mouse model of VT, buprenorphine merits additional investigation to ensure the highest level of laboratory animal care and welfare.

Therapeutic drug-induced platelet apoptosis: an overlooked issue in pharmacotoxicology

The surfacing of the applied fields of biology such as, biotechnology, pharmacology and drug discovery was a boon to the modern man. However, it had its share of disadvantages too. The indiscriminate use of antibiotics and other biological drugs resulted in numerous adverse reactions including thrombocytopenia. One of the reasons for drug-induced thrombocytopenia could be attributed to an enhanced rate of platelet apoptosis, which is a less investigated aspect. The present essay sheds light on the adverse (pro-apoptotic) effects of some of the commonly used drugs and antibiotics on platelets viz. cisplatin, aspirin, vancomycin and balhimycin. Furthermore, the undesirable reactions resulting from chemotherapy could be attributed at least to some extent to the systemic stress induced by microparticles, which in turn are the byproducts of platelet apoptosis. Thereby, the essay aims to highlight the challenges in the emerging trend of cross-disciplinary implications, i.e., drug-induced platelet apoptosis, which is a nascent field. Thus, the different mechanisms through which drugs induce platelet apoptosis are discussed, which also opens up a new perspective through which the adverse effects of commonly used drugs could be dealt. The drug-associated platelet toxicity is of grave concern and demands immediate attention. Besides, it would also be appealing to examine the platelet pro-apoptotic effects of other commonly used therapeutic drugs.

Neurological soft signs in individuals with pathological gambling

Increased neurological soft signs (NSSs) have been found in a number of neuropsychiatric syndromes, including chemical addiction. The present study examined NSSs related to perceptual-motor and visuospatial processing in a behavioral addiction viz., pathological gambling (PG). As compared to mentally healthy individuals, pathological gamblers displayed significantly poorer ability to copy two- and three-dimensional figures, to recognize objects against a background noise, and to orient in space on a road-map test. Results indicated that PG is associated with subtle cerebral cortical abnormalities. Further prospective clinical research is needed to address the NSSs' origin and chronology (e.g., predate or follow the development of PG) as well as their response to therapeutic interventions and/or their ability to predict such a response.

Microparticles: biomarkers and beyond

Membrane microparticles are submicron fragments of membrane shed into extracellular space from cells under conditions of stress/injury. They may be distinguished from other classes of extracellular vesicles (i.e. exosomes) on the basis of size, content and mechanism of formation. Microparticles are found in plasma and other biological fluids from healthy individuals and their levels are altered in various diseases, including diabetes, chronic kidney disease, pre-eclampsia and hypertension among others. Accordingly, they have been considered biomarkers of vascular injury and pro-thrombotic or pro-inflammatory conditions. In addition to this, emerging evidence suggests that microparticles are not simply a consequence of disease, but that they themselves may contribute to pathological processes. Thus microparticles appear to serve as both markers and mediators of pathology. The present review examines the evidence for microparticles as both biomarkers of, and contributors to, the progression of disease. Approaches for the detection of microparticles are summarized and novel concepts relating to the formation of microparticles and their biological effects are examined.

Increasing hematocrit above 28% during early resuscitative phase is not associated with decreased mortality following severe traumatic brain injury

BACKGROUND

To prevent iatrogenic damage, transfusions of red blood cells should be avoided. For this, specific and reliable transfusion triggers must be defined. To date, the optimal hematocrit during the initial operating room (OR) phase is still unclear in patients with severe traumatic brain injury (TBI). We hypothesized that hematocrit values exceeding 28%, the local hematocrit target reached by the end of the initial OR phase, resulted in more complications, increased mortality, and impaired recovery compared to patients in whom hematocrit levels did not exceed 28%.

METHODS

Impact of hematocrit (independent variable) reached by the end of the OR phase on mortality and morbidity determined by the extended Glasgow outcome scale (eGOS; dependent variables) was investigated retrospectively in 139 TBI patients. In addition, multiple logistic regression analysis was performed to identify additional important variables.

FINDINGS

Following severe TBI, mortality and morbidity were neither aggravated by hematocrit above 28% reached by the end of the OR phase nor worsened by the required transfusions. Upon multiple logistic regression analysis, eGOS was significantly influenced by the highest intracranial pressure and the lowest cerebral perfusion pressure values during the initial OR phase.

CONCLUSIONS

Based on this retrospective observational analysis, increasing hematocrit above 28% during the initial OR phase following severe TBI was not associated with improved or worsened outcome. This questions the need for aggressive transfusion management. Prospective analysis is required to determine the lowest acceptable hematocrit value during the OR phase which neither increases mortality nor impairs recovery. For this, a larger caseload and early monitoring of cerebral metabolism and oxygenation are indispensable.

Does tirofiban prevent platelet loss in patients after cardiogenic shock during continuous renal replacement therapy?

Link and colleagues present a pilot study investigating platelet function and platelet numbers in patients with cardiogenic shock and acute kidney failure undergoing continuous venovenous haemodialysis. Their data indicate a significantly reduced platelet loss with combined therapy of unfractionated heparin plus tirofiban, the glycoprotein IIb/IIIa antagonist, compared with unfractionated heparin therapy alone. Owing to the small sample size, however, the potential impact of additional treatment variables (antiplatelet agents, intraaortic counterpulsation) could not be clarified. A substantially larger, adequately powered study is therefore called for to establish the potential clinical relevance of these findings.