The effects of signal transducer and activator of transcription three mutations on human platelets

Involvement of signal transducer and activator of transcription 3 (STAT3) in inflammation is well known. Recently, a role for STAT3 in platelet activation and platelet production has been suggested. Platelets exhibit important immune functions and engagement of STAT3 in platelet physiology may link inflammation and hemostasis. This study investigated the effects of STAT3 loss-of-function mutations and single nucleotide polymorphisms (SNPs) in STAT3 on glycoprotein VI (GPVI)-mediated platelet activation and platelet numbers in humans. Two cohorts were studied. The first cohort concerned patients with STAT3 loss-of-function mutations. Platelet numbers were investigated in eight patients and GPVI-mediated platelet activation was functionally tested in four patients. Additional experiments were performed to investigate underlying mechanisms. The second cohort concerned 334 healthy volunteers and investigated the consequences of SNPs in STAT3 on GPVI-mediated platelet activation and platelet numbers. Platelet activation was lower in STAT3 loss-of-function patients at baseline and after stimulation of the GPVI receptor, reflected by decreased P-selectin expression. This was independent of gene transcription. Blockade of the adenosine di-phosphate (ADP) pathway resulted in a further decrease of P-selectin expression, particularly in STAT3 loss-of-function patients. In contrast, the SNPs in STAT3 did not influence GPVI-mediated platelet activation. Also, platelet numbers were not affected by STAT3 loss-of-function mutations, nor was there an association with the SNPs. In conclusion, STAT3 signaling does not seem to play a major role in thrombopoiesis. We confirm that STAT3 is involved in GPVI-mediated platelet activation in humans, independent of gene transcription. GPVI-mediated platelet activation is highly dependent on secondary ADP release. Our findings suggest that STAT3 modulation may affect inflammation, hemostasis, and their interaction.</p

Evaluation of a continuous monitoring and feedback initiative to improve quality of anaesthetic care: a mixed-methods quasi-experimental study

Background: This study evaluated the impact of a continuous quality monitoring and feedback initiative in anaesthesia. Objectives: To conduct a quasi-experimental evaluation of the feedback initiative and its effect on quality of anaesthetic care and perioperative efficiency. To understand the longitudinal effects of passive and active feedback and investigate the mechanisms and interactions underpinning those effects. Design: Mixed-methods evaluation with analysis and synthesis of data from longitudinal qualitative interviews, longitudinal evaluative surveys and an interrupted time series study. Intervention: Continuous measurement of a range of anaesthetic quality indicators was undertaken in a London teaching hospital alongside monthly personal feedback from case summary data to a cohort of anaesthetists, with follow-up roll-out to the whole NHS trust. Basic feedback consisted of the provision of passive monthly personalised feedback reports containing summary case data. In the enhanced phase, data feedback consisted of more sophisticated statistical breakdown of data, comparative and longitudinal views, and was paired with an active programme of dissemination and professional engagement. Methods: Baseline data collection began in March 2010. Implementation of basic feedback took place in October 2010, followed by implementation of the enhanced feedback protocol in July 2012. Weekly aggregated quality indicator data, coupled with surgical site infection and mortality rates, was modelled using interrupted time series analyses. The study anaesthetist cohort comprised 50,235 cases, performed by 44 anaesthetists over the course of the study, with 22,670 cases performed at the primary site. Anaesthetist responses to the surveys were collected pre and post implementation of feedback at all three sites in parallel with qualitative investigation. Seventy anaesthetists completed the survey at one or more time points and 35 health-care professionals, including 24 anaesthetists, were interviewed across two time points. Results: Results from the time series analysis of longitudinal variation in perioperative indicators did not support the hypothesis that implementation of basic feedback improved quality of anaesthetic care. The implementation of enhanced feedback was found to have a significant positive impact on two postoperative pain measures, nurse-recorded freedom from nausea, mean patient temperature on arrival in recovery and Quality of Recovery Scale scores. Analysis of survey data demonstrated that anaesthetists value perceived credibility of data and local relevance of quality indicators above other criteria when assessing utility of feedback. A significant improvement in the perceived value of quality indicators, feedback, data use and overall effectiveness was observed between baseline and implementation of feedback at the primary site, a finding replicated at the two secondary sites. Findings from the qualitative research elucidated processes of interaction between context, intervention and user, demonstrating a positive response by clinicians to this type of initiative and willingness to interact with a sustained and comprehensive feedback protocol to understand variations in care. Conclusions: The results support the potential of quality monitoring and feedback interventions as quality improvement mechanisms and provide insight into the positive response of clinicians to this type of initiative, including documentation of the experiences of anaesthetists that participated as users and codesigners of the feedback. Future work in this area might usefully investigate how this type of intervention may be transferred to other areas of clinical practice and further explore interactions between local context and the successful implementation of quality monitoring and feedback systems. Funding: The National Institute for Health Research Health Services and Delivery Research programme

STAT3 phosphorylation mediates the stimulatory effects of interferon alpha on B cell differentiation and activation in SLE.

OBJECTIVE: Type I IFNs play a well-known role in the pathogenesis of SLE, through activation of CD4 T and antigen-presenting cells. Here, we investigated the effects of IFN alpha (IFNα) on SLE B cell activation and differentiation. METHODS: Peripheral blood mononuclear cells (PBMCs) and purified total or naïve B cells were obtained from healthy controls and SLE patients. The effects of IFNα on B cell differentiation were studied by flow cytometry. The role of STAT3 in B cell responses to IFNα was studied using pharmacological inhibitors and PBMCs from STAT3-deficient individuals. RESULTS: Incubation of normal PBMCs with IFNα induces a B cell differentiation pattern as observed spontaneously in SLE PBMCs. IFNα displays direct stimulatory effects on purified naïve B cells from healthy individuals, as evidenced by a significant induction of cell surface CD38 and CD95 in the presence of the cytokine. In purified naïve B cells, IFNα also induces STAT3 phosphorylation. IFNα-induced naïve B cell differentiation in total PBMCs is significantly inhibited in the presence of STAT3 inhibitors, or in PBMCs from individuals with STAT3 loss of function mutations. Spontaneous levels of STAT3, but not STAT1, phosphorylation are significantly higher in total B cells from SLE patients compared with controls. Pharmacological STAT3 inhibition in SLE PBMCs inhibits naïve B cell activation and differentiation. CONCLUSION: IFNα displays direct stimulatory effects on B cell differentiation and activation in SLE. STAT3 phosphorylation mediates the effects of IFNα stimulation in naïve B cells, an observation that opens new therapeutic perspectives in SLE

Platelet Integrin alpha IIb beta 3 Activation is Associated with 25-Hydroxyvitamin D Concentrations in Healthy Adults

Item does not contain fulltextBACKGROUND:  Cardiovascular events are associated with low circulating vitamin D concentrations, although the underlying mechanisms are poorly understood. This study investigated associations between 25-hydroxyvitamin D concentrations, platelet function, and single-nucleotide polymorphisms (SNPs) in genes influencing vitamin D biology in the 500 Functional Genomics (500FG) cohort. METHODS:  In this observational study, platelet activation and function were measured by flow cytometry by binding of fibrinogen to the activated fibrinogen receptor integrin αIIbβ3 and expression of P-selectin, markers of platelet aggregation and degranulation, respectively. These parameters were correlated to serum 25-hydroxyvitamin D and genotyping was performed to investigate SNPs in genes important for vitamin D biology. RESULTS:  Circulating 25-hydroxyvitamin D concentrations correlated inversely with baseline platelet binding of fibrinogen to integrin αIIbβ3 (Pearson's r= -0.172, p = 0.002) and platelet responses to platelet agonist cross-linked collagen-related peptide (CRP-XL) (Pearson's r= -0.196,p = 0.002). This effect was due to circulating vitamin D levels ≤50nmol/L, since no differences in platelet fibrinogen binding were observed between subjects with normal 25-hydroxyvitamin D concentrations (>75nmol/L) and a 25-hydroxyvitamin D insufficiency (50-75 nmol/L). No correlations between 25-hydroxyvitamin D concentrations and platelet P-selectin expression were found. Several SNPs in the GC region of the vitamin D binding proteingene were associated with platelet responses to CRP-XL. CONCLUSION:  Low circulating vitamin D concentrations are associated with increased platelet fibrinogen binding to integrin αIIbβ3 in unstimulated samples and after stimulation with CRP-XL. These findings may contribute to the increased incidence of cardiovascular events in vitamin D deficient adults and its seasonal variation. Further studies are needed to investigate causality