scholarly journals Heparin Re-Exposure in Patients with Heparin-Induced Thrombocytopenia (HIT)

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4265-4265 ◽  
Author(s):  
Prajwal Dhakal ◽  
Vijaya R. Bhatt
Keyword(s):  
Conflicts Of Interest ◽  
Small Sample Size ◽  
Small Sample ◽  
Platelet Factor 4 ◽  
Systemic Review ◽  
Enzyme Linked Immunosorbent Assay ◽  
Platelet Factor ◽  
Platelet Recovery ◽  
Risk Of Recurrence ◽  
History Of

Abstract Introduction Patients with a history of HIT, who require cardiopulmonary bypass (CPB), have limited anticoagulation options. Unfractionated heparin (UFH) is preferred by surgeons during CPB because of their extensive experience, short half-life of the drug, and the availability of protamine sulfate to reverse its effect. However, heparin re-challenge may be associated with a risk of recurrence of HIT. A number of instances of successful heparin re-exposure during CPB have been reported in HIT patients. However, small sample size of these reports and a lack of systemic review have prevented better understanding of the potential complications. The objective of this study was to determine the safety of heparin re-exposure in HIT patients and various strategies utilized to reduce the recurrence of HIT. Methods Using several search terms, all cases of heparin re-exposure in HIT patients published and indexed in English language in Pubmed by June 2014 were reviewed. The bibliography of each relevant article was searched for additional related reports. The diagnosis of HIT was based on the clinical probability or 4T scoring system and laboratory tests. The exposure to either UFH or low molecular weight heparin (LMWH) in patients with a history of HIT was considered a re-exposure. In two cases, heparin was used multiple times for repeated cardiovascular surgeries after an initial diagnosis of HIT. Each re-exposure was determined as a different instance of re-exposure during analysis. Results A total of 136 patients with a history of HIT had 141 instances of heparin re-exposure. Median age was 56 years (6 weeks -87 yrs) and 67% were males. Regarding the original HIT diagnosis, UFH (98%) and nadroparin (2%) were the causative agents. Thrombotic complications occurred in 23%. The pretest probability score was high in 79% and moderate in 21%. Platelet aggregation studies (66%), enzyme linked immunosorbent assay (ELISA)/enzyme immunoassay (EIA) (20%), serotonin release assay (SRA) (2%), and both SRA and EIA (12%) were performed for diagnosis. Cardiac (76%) and vascular surgeries (11%) were the most common indications for heparin re-exposure. Although 67% were re-exposed to heparin after 3 months of HIT diagnosis, 11%, 8% and 15% were re-exposed within 1 week, between 1 week to 1 month, and 1 month to 3 months of HIT diagnosis respectively. Anti-platelet factor 4/heparin antibodies were positive in 63% before re-exposure. UFH (93%) or LMWH (7%) were the utilized agents during re-exposure. Sixteen patients (11%) underwent plasmapheresis to lower the level of anti-platelet factor 4/heparin antibodies before the re-exposure. Non-heparin anticoagulants such as bivalirudin, fondaparinux, danaparoid, r-hirudin, argatroban, lepirudin, and warfarin were used singly or in combination after the exposure in 63% of patients. With heparin re-exposure, 4.2% had complications, which included recurrence of HIT (2.1%), and bleeding (2.1%). Among the patients with HIT recurrence (n=3), one patient was re-exposed to UFH within a week of HIT diagnosis and shortly after platelet recovery with LMWH (Intensive Care Med. 1991;17(3):185-6.). The other two patients were initially diagnosed with HIT more than 5 years back and tested negative for anti-platelet factor 4/heparin antibody prior to heparin re-exposure. Conclusion A review of the published reports indicates that intra-operative heparin re-exposure in patients with HIT has a small risk of developing thrombocytopenia or recurrence of HIT. The use of pre-exposure plasmapheresis in patients with positive anti-platelet factor 4/heparin antibody and post-exposure non-heparin anticoagulants may have reduced the risk of recurrence of HIT. Given several limitations of such retrospective review, prospective studies are needed to validate these results. Disclosures No relevant conflicts of interest to declare.

scholarly journals Heparin Induced Thrombocytopenia in Patients with COVID-19

2021 ◽  
Author(s):  
Surbhi Warrior ◽  
Elizabeth Behrens ◽  
Sefer Gezer ◽  
Parameswaran Venugopal ◽  
Shivi Jain
Keyword(s):  
Mortality Rate ◽  
General Population ◽  
Small Sample Size ◽  
Small Sample ◽  
Platelet Factor 4 ◽  
Thromboembolic Events ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Confirmatory Testing ◽  
Increased Risk

Abstract Background Acute respiratory and renal failure as well as systemic coagulopathy are critical aspects of the morbidity and mortality in patients with COVID-19. Heparin Induced Thrombocytopenia (HIT) occurs when IgG antibodies form against platelet factor 4-Heparin complex, resulting in platelet activation and removal, leading to a prothrombotic state. Studies have shown that only 6% who are investigated serologically for HIT actually have the diagnosis. Methods A retrospective analysis was performed on all COVID-19 positive patients hospitalized between March and June 2020. Patients with suspicion for HIT were tested for HIT antibodies with IgG-specific platelet factor 4(PF4)-dependent enzyme immunoassay (EIA). Confirmatory testing with serotonin release assay (SRA) and heparin-induced platelet aggregation were used in cases with intermediate or low optical density (OD) with EIA positivity (EIA+). Due to rarity of disease, a through literature review on HIT in COVID-19 patients was also analyzed. Results Incidence of EIA + in COVID-19 patients was 0.6%, significantly higher than in the general population 0.2% (p < 0.0001). The incidence of thromboembolic events in EIA + patients was 87.5%, significantly higher than the rate of 10.90% in all COVID-19 patients (p < 0.0001). The mortality rate in EIA + patients was 50%, significantly greater than the mortality rate of 12% in all hospitalized COVID-19 patients (p = 0.0011). Serological confirmation of HIT diagnosis was 37.5% which is significantly higher than confirmation of HIT in nonCOVID-19 patients 6% (p < 0.0001). Of 39 HIT antibody positive patients in the literature, 23.07% had positive confirmatory testing (6 SRA, 3 HIPAA) which is significantly higher than 5.6% in the general population (p = 0.00001). The incidence of thrombosis in EIA + COVID-19 patients in the literature was 56.4% which is significantly higher than reported rates of thrombotic events in in all COVID-19 patients in the literature at 4.8%1 (p = 0.00001). Conclusion Our study indicates incidence of HIT is higher in the COVID-19 population. This can be attributed to the cytokine storm and severe sepsis seen in critically ill COVID-19 patients. Our study also suggests that development of HIT can contribute to increased risk for thromboembolic events as well as mortality of COVID-19 patients, however, our study is limited due to small sample size.

scholarly journals Hysterosalpingography Findings In Infertile Women: A Systematic Review

2020 ◽  
Vol 34 (1) ◽  
pp. 24-28
Author(s):  
Mohammed S ◽  
Abdurrahaman A A
Keyword(s):  
English Language ◽  
Small Sample Size ◽  
Clinical History ◽  
Small Sample ◽  
Female Reproductive Tract ◽  
Systemic Review ◽  
Demographic Information ◽  
Infertile Women ◽  
Frequent Finding ◽  
History Of

Background: Hysterosalpingography (HSG) is a valuable radiological procedure for imaging the female reproductive tract. Structural abnormalities on hysterosalpingography (HSG) are among the important factors in the evaluation of female infertility. Objectives: The study was aimed at reviewing the available literature on hysterosalpingography findings in infertile women, identifying the missing gap in the subject area, coming up which area of further that will further enhance the role of HSG in the diagnosis of infertility. Methods: The study was a systemic review that focused on the literature on the topic and keywords of research. The references were obtained using a database; IEEE Xplore, EBSCO, Cochrane and MEDLINE. The search terms used were; hysterosalpingography findings, HSG, detection of infertility, fluoroscopic examinations. The inclusion criteria are articles published in the English language, non-duplicated and those that full text is available online. Result: Eleven articles were considered for the review. Four of the articles were prospective, whereas the other seven were retrospective studies. Ten of the reviewed articles are from Africa and only one is from Asia. The most frequent finding in the reviewed articles on the two continents was bilateral tubal blockage whereas the least frequent finding is associated with the cervix. The majority of the reviewed articles used short study duration, retrospective, or small sample size. None of the reviewed articles established a relationship between the HSG findings with demographic information or clinical history of the selected subjects. Conclusion: The findings of the published articles have proven the potentiality of HSG in detecting uterine abnormalities related to infertility. None of the reviewed articles established a relationship between the HSG findings with demographic information or clinical history of the selected subjects.

Investigating the Dynamics of Suicidal Ideation

Crisis ◽  
2018 ◽  
Vol 39 (1) ◽  
pp. 65-69 ◽  
Author(s):  
Nina Hallensleben ◽  
Lena Spangenberg ◽  
Thomas Forkmann ◽  
Dajana Rath ◽  
Ulrich Hegerl ◽  
...  
Keyword(s):  
Suicidal Ideation ◽  
Small Sample Size ◽  
Unipolar Depression ◽  
Small Sample ◽  
History Of ◽  
Severity Of Depression ◽  
Ecological Momentary ◽  
Depressive Episodes ◽  
Ema Method ◽  
Shed Light

Abstract. Background: Although the fluctuating nature of suicidal ideation (SI) has been described previously, longitudinal studies investigating the dynamics of SI are scarce. Aim: To demonstrate the fluctuation of SI across 6 days and up to 60 measurement points using smartphone-based ecological momentary assessments (EMA). Method: Twenty inpatients with unipolar depression and current and/or lifetime suicidal ideation rated their momentary SI 10 times per day over a 6-day period. Mean squared successive difference (MSSD) was calculated as a measure of variability. Correlations of MSSD with severity of depression, number of previous depressive episodes, and history of suicidal behavior were examined. Results: Individual trajectories of SI are shown to illustrate fluctuation. MSSD values ranged from 0.2 to 21.7. No significant correlations of MSSD with several clinical parameters were found, but there are hints of associations between fluctuation of SI and severity of depression and suicidality. Limitations: Main limitation of this study is the small sample size leading to low power and probably missing potential effects. Further research with larger samples is necessary to shed light on the dynamics of SI. Conclusion: The results illustrate the dynamic nature and the diversity of trajectories of SI across 6 days in psychiatric inpatients with unipolar depression. Prediction of the fluctuation of SI might be of high clinical relevance. Further research using EMA and sophisticated analyses with larger samples is necessary to shed light on the dynamics of SI.

Case series: COVID-19 infection causing new-onset diabetes mellitus?

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Rujuta Katkar ◽  
Narasa Raju Madam
Keyword(s):  
Diabetes Mellitus ◽  
Severe Acute Respiratory Syndrome ◽  
Cell Damage ◽  
Small Sample Size ◽  
Case Series ◽  
Small Sample ◽  
Onset Diabetes ◽  
History Of ◽  
New Onset Diabetes Mellitus ◽  
New Onset

Objectives: This paper seeks to explore the hypothesis of the potential diabetogenic effect of SARS-COV-2 (Severe Acute respiratory syndrome coronavirus). Case series presentation: We present a case series of observation among 8 patients of age group ranging from 34 to 74 years with a BMI range of 26.61 to 53.21 Kilogram/square meters that developed new-onset diabetes after COVID-19 infection. Severe Acute Respiratory Syndrome Coronavirus (SARS-COV-2), commonly known as Coronavirus or COVID-19(Coronavirus infectious disease), gains entry into the cells by binding to the Angiotensin-converting enzyme-2(ACE-2) receptors located in essential metabolic tissues including the pancreas, adipose tissue, small intestine, and kidneys. The evidence reviewed from the scientific literature describes how ACE 2 receptors play a role in the pathogenesis of diabetes and the plausible interaction of SARS-COV-2 with ACE 2 receptors in metabolic organs and tissues. Conclusion: The 8 patients without a past medical history of diabetes admitted with COVID-19 infection developed new-onset diabetes mellitus due to plausible interaction of SARS-COV-2 with ACE 2 receptors. The resulting downregulation of ACE-2 and ACE-2 receptors expression caused islet-cell damage resulting into diabetes. The resulting observation has the potential to adversely impact significant number of the globally affected population. Screening patients with COVID-19 for diabetes routinely can help in early detection, significantly reducing morbidity and mortality associated with diabetes. Due to limitations of observational study with a small sample size will require further investigation in the form of Clinical trial.

scholarly journals Heparin-induced thrombocytopenia: in vitro studies on the interaction of dabigatran, rivaroxaban, and low-sulfated heparin, with platelet factor 4 and anti-PF4/heparin antibodies

Blood ◽  
2012 ◽  
Vol 119 (5) ◽  
pp. 1248-1255 ◽  
Author(s):  
Krystin Krauel ◽  
Christine Hackbarth ◽  
Birgitt Fürll ◽  
Andreas Greinacher
Keyword(s):  
Factor Xa ◽  
Platelet Factor 4 ◽  
Thrombin Inhibitors ◽  
Direct Thrombin Inhibitors ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Alternative Anticoagulation ◽  
Heparin Complexes ◽  
History Of

Abstract Heparin is a widely used anticoagulant. Because of its negative charge, it forms complexes with positively charged platelet factor 4 (PF4). This can induce anti-PF4/heparin IgG Abs. Resulting immune complexes activate platelets, leading to the prothrombotic adverse drug reaction heparin-induced thrombocytopenia (HIT). HIT requires treatment with alternative anticoagulants. Approved for HIT are 2 direct thrombin inhibitors (DTI; lepirudin, argatroban) and danaparoid. They are niche products with limitations. We assessed the effects of the DTI dabigatran, the direct factor Xa-inhibitor rivaroxaban, and of 2-O, 3-O desulfated heparin (ODSH; a partially desulfated heparin with minimal anticoagulant effects) on PF4/heparin complexes and the interaction of anti-PF4/heparin Abs with platelets. Neither dabigatran nor rivaroxaban had any effect on the interaction of PF4 or anti-PF4/heparin Abs with platelets. In contrast, ODSH inhibited PF4 binding to gel-filtered platelets, displaced PF4 from a PF4-transfected cell line, displaced PF4/heparin complexes from platelet surfaces, and inhibited anti-PF4/heparin Ab binding to PF4/heparin complexes and subsequent platelet activation. Dabigatran and rivaroxaban seem to be options for alternative anticoagulation in patients with a history of HIT. ODSH prevents formation of immunogenic PF4/heparin complexes, and, when given together with heparin, may have the potential to reduce the risk for HIT during treatment with heparin.

Impact of race on biomarker testing among HER2- advanced breast cancer (ABC) patients (pts) in the United States: Results from a real-world study.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 10598-10598
Author(s):  
Reshma L. Mahtani ◽  
Alexander Niyazov ◽  
Katie Lewis ◽  
Lucy Massey ◽  
Alex Rider ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Targeted Therapies ◽  
Small Sample Size ◽  
The United States ◽  
Small Sample ◽  
Access To Treatment ◽  
History Of ◽  
Biomarker Testing ◽  
Abstract Data ◽  
The Impact

10598 Background: African Americans (AA) have the highest breast cancer (BC) mortality rate. Access to treatment is a known contributing factor. In the past 4 years, several targeted therapies for HER2- BC have become available which require testing for specific biomarkers. This study assessed the impact of race on biomarker testing rates in HER2- ABC pts receiving treatment in the US. Methods: Oncologists were recruited to abstract data from medical charts for the next 8-10 pts receiving treatment with HER2- ABC during Sept 2019-Apr 2020. Pts records were stratified by race and categorized into 3 mutually exclusive cohorts [White/Caucasian (White), AA, Other]. The other race cohort was excluded from this analysis due to small sample size. Differences in pt demographics/clinical characteristics were analyzed via Fisher’s exact tests. Testing rates for actionable biomarkers (i.e. BRCA1/2, PIK3CA, PD-L1) were compared between White and AA pts utilizing logistic regressions controlling for age, known family history of a BRCA-related cancer, hormone receptor (HR) status and practice setting (academic vs. community). Further analyses by age will be presented. Results: This analysis included 378 pts records, provided by 40 oncologists. Mean age was 64 years; 77% had HR+/HER2- ABC; 20% had advanced triple negative breast cancer (TNBC), 3% had ABC with an unknown HR status. Compared to White pts, AA pts were significantly more likely to have advanced TNBC (27% vs. 18%, p<0.05). Compared to White pts, AA pts had significantly lower BRCA1/2 mutation (mut) testing rates (Table). Numerically lower rates of PIK3CAmut and PD-L1 testing were observed among AA pts (Table). BRCA1/2mut positivity rate (germline [g] and/or somatic [s]) was higher among AA vs. White pts (30% vs. 22%). Positivity rate for PIK3CAmut was lower for AA vs. White pts (8% vs. 11%). Conclusions: A higher than expected BRCA1/2mut positivity rate was observed than previously reported in the literature. This is likely because this analysis included s BRCA1/2mut and represented a high risk pt population. Across all biomarkers assessed, AA pts had lower testing rates than White pts. This suggests racial disparities in testing rates of actionable biomarkers. Consistent with guidelines, and with the increased availability of targeted therapies, focused efforts should be developed to increase biomarker testing in AA pts. Funding: Pfizer Biomarker Testing Rates by Race.[Table: see text]

Investigations of the Immunoglobulin Subtype Transformation of Anti–Heparin-Platelet Factor 4 Antibodies During Treatment With a Low-Molecular-Weight Heparin (Clivarin) in Orthopedic Patients

2003 ◽  
Vol 127 (5) ◽  
pp. 584-588
Author(s):  
Sarfraz Ahmad ◽  
H. Peter Bacher ◽  
Michael R. Lassen ◽  
Debra A. Hoppensteadt ◽  
Helen Leitz ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Serotonin Release ◽  
Platelet Factor 4 ◽  
Enzyme Linked Immunosorbent Assay ◽  
Low Molecular Weight ◽  
Platelet Factor ◽  
Significant Difference ◽  
Antibody Titers ◽  
Orthopedic Patients

Abstract Context.—It is now widely accepted that the pathophysiology of heparin-induced thrombocytopenia (HIT) syndrome is mediated by the generation of a wide array of functional and molecularly heterogeneous anti–heparin-platelet factor 4 (AHPF4) antibodies that may mediate platelet and/or endothelial cell activation/destruction. Objective.—We investigated the differential prevalence and functionality of AHPF4 immunoglobulin subtypes (IgA, IgG, and IgM) in plasmas obtained from orthopedic patients immobilized with Plaster-Cast and treated with clivarin (a low-molecular-weight heparin) in comparison to a placebo for the prophylaxis of deep-vein thrombosis. Design and Methods.—Clivarin was administered subcutaneously at a fixed daily dosage of 1750 U without any adjustment or loading dosage. Citrated plasmas were obtained at baseline, at 10 to 14 days, and at postbrace procedure (5–12 weeks). An enzyme-linked immunosorbent assay (ELISA) was used to quantitate the AHPF4 antibody titers. The functionality of the ELISA-positive samples was determined by a 14C-serotonin release assay (SRA). Results.—In the ELISA test, 16 of 1073 samples (1.5%; 6 in clivarin and 10 in placebo groups) were positive for AHPF4 antibodies (mean optical density [OD] = 0.46 ± 0.02). None of the ELISA-positive samples for AHPF4 antibodies could mediate platelet activation responses as determined by the SRA (0%–3% serotonin release, P &gt; .10, n = 16). Through differential immunoglobulin subtype analysis of the samples positive for (cumulative) AHPF4 antibodies, we determined that their relative prevalence in plasma were as follows: IgM (mean OD = 0.71 ± 0.13) &gt; IgG (0.31 ± 0.08) &gt; IgA (0.14 ± 0.02). Although there was no significant difference in the total antibody titers between clivarin and placebo groups, the antibody subtyping data showed conversion trends (ie, IgA [clivarin to placebo], IgG [placebo to clivarin], and IgM [clivarin to placebo]). Conclusion.—These observations indicate that even at reduced dosages, clivarin can shift the immunogenic up-regulation toward the IgG subpopulation; however, the IgG subtype is of a nonfunctional type of AHPF4 antibody and thus may not cause any HIT-related pathogenic responses.

scholarly journals Dengue Fever and Severe Dengue in Barbados, 2008–2016

2020 ◽  
Vol 5 (2) ◽  
pp. 68
Author(s):  
Kirk Osmond Douglas ◽  
Sudip Kumar Dutta ◽  
Byron Martina ◽  
Fatih Anfasa ◽  
T. Alafia Samuels ◽  
...  
Keyword(s):  
Dengue Virus ◽  
Dengue Fever ◽  
Small Sample Size ◽  
Health Planning ◽  
Case Fatality ◽  
Small Sample ◽  
Severe Dengue ◽  
Medical Attention ◽  
Enzyme Linked Immunosorbent Assay ◽  
Virus Serotype

Analysis of the temporal, seasonal and demographic distribution of dengue virus (DENV) infections in Barbados was conducted using national surveillance data from a total of 3994 confirmed dengue cases. Diagnosis was confirmed either by DENV–specific real time reverse transcriptase polymerase chain reaction (rRT–PCR), or non–structural protein 1 (NS1) antigen or enzyme linked immunosorbent assay (ELISA) tests; a case fatality rate of 0.4% (10/3994) was observed. The dengue fever (DF) prevalence varied from 27.5 to 453.9 cases per 100,000 population among febrile patients who sought medical attention annually. DF cases occurred throughout the year with low level of transmission observed during the dry season (December to June), then increased transmission during rainy season (July to November) peaking in October. Three major dengue epidemics occurred in Barbados during 2010, 2013 and possibly 2016 with an emerging three–year interval. DF prevalence among febrile patients who sought medical attention overall was highest among the 10–19 years old age group. The highest DF hospitalisation prevalence was observed in 2013. Multiple serotypes circulated during the study period and Dengue virus serotype 2 (DENV–2) was the most prevalent serotype during 2010, whilst DENV–1 was the most prevalent serotype in 2013. Two DENV–1 strains from the 2013 DENV epidemic were genetically more closely related to South East Asian strains, than Caribbean or South American strains, and represent the first ever sequencing of DENV strains in Barbados. However, the small sample size (n = 2) limits any meaningful conclusions. DF prevalence was not significantly different between females and males. Public health planning should consider DENV inter–epidemic periodicity, the current COVID–19 pandemic and similar clinical symptomology between DF and COVID–19. The implementation of routine sequencing of DENV strains to obtain critical data can aid in battling DENV epidemics in Barbados.

Platelet Factor 4 Regulates Platelet Count In Vivo: Implications for Platelet Recovery after Cytotoxic Therapy.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3144-3144
Author(s):  
Michele P. Lambert ◽  
M. Anna Kowalska ◽  
Mortimer Poncz
Keyword(s):  
Bone Marrow ◽  
Platelet Count ◽  
Mononuclear Cells ◽  
Physiological Role ◽  
Platelet Factor 4 ◽  
Cytotoxic Therapy ◽  
Platelet Factor ◽  
Platelet Recovery ◽  
Platelet Counts

Abstract Platelet factor 4 (PF4), a platelet-specific CXC chemokine, was the first reported negative autocrine regulator of megakaryopoiesis in vitro. To define the physiological role(s) of PF4, we established mice that either were deficient in murine (m) PF4 (mPF4−/−) or that over-expressed human (h) PF4 (hPF4+/+). These mice had a level of PF4 ~6-fold greater than that present in human platelet controls. All lines studied had been backcrossed onto a C57Bl/6J background for &gt;10 generations. Platelet counts in these animals correlated inversely with PF4 determined expression, beginning with a low platelet count of 702 ± 57 x 103/μL in the hPF4+/+ mice &lt; hPF4+ &lt; wildtype (WT) &lt; mPF4+/− &lt; mPF4−/− mice in which the platelet count was 1,404 ± 117 x 103/μL. The half-life of the platelets from the hPF4+/+ was identical to that of WT mice. Cultured bone marrow mononuclear cells (BMMNC) in serum-free media showed that each line had identical efficiency in growing megakaryocyte colonies, suggesting that megakaryocyte progenitor cells in these different genetic lines were intrinsically normal. Megakaryocyte colony numbers derived from WT BMMNC were reduced by the addition of recombinant PF4 or supernatant from irradiated bone marrow of hPF4+ mice, but not from mPF4−/− mice, suggesting that megakaryocyte lysis in vivo during cytoreductive therapy may contribute to the subsequent thrombocytopenia by releasing PF4. Additionally, a rabbit polyclonal anti-mPF4 antibody (Ab) was able in culture to significantly reverse this inhibitory effect of PF4 on megakaryopoiesis. Preliminary cytoreductive studies using either 600 cGy or 150 mg/kg of 5-fluorouracil (5-FU) intraperitoneally (IP) were performed. In irradiation studies, mPF4−/− mice began to recover on the same day as WT littermates, but they clearly had higher platelet counts at their nadir, with a drop to only 42 ± 7% of baseline vs. 32 ± 6% in the WT mice (n =12 in each arm, p = 0.06). By Day 13, 9 of 12 mPF4−/− mice had recovered to &gt;75% of baseline, while only 3 of 12 WT mice had recovered (p &lt;0.001). hPF4+ mice (n = 7) were studied after 5-FU treatment. Compared to WT littermates (n = 9), the hPF4+ recovered later (15.6 ± 2.2 vs. 11.2 ± 1.5 days, p &lt; 0.0003), and clearly had significantly greater drop to 30 ± 6% vs. 56 ± 9% of baseline (p &lt; 0.00001). By day 15, all of the WT mice had recovered, but only 43% of hPF4+ mice had returned to &gt;75% of baseline platelet count (p = 0.009). To examine if anti-mPF4 Ab was protective of cytotoxic therapy-induced thrombocytopenia, WT mice were treated with 180 mg/kg of 5-FU and were given either anti-mPF4 Ab (25 mg/kg, IV, x 2) or an equal volume of vehicle. By day 5, the Ab-treated group had a platelet count of 45 ± 6% vs. 32 ± 4% in the untreated (n &gt; 13 per arm, p = 0.015). Platelet counts remained higher in the Ab-treated arm throughout the study. By day 10 after intervention, 9 of 16 mice of the Ab-treated arm had platelet counts over 75% of the baseline, while only 3 of 13 control mice did (p &lt; 0.001). Thus, it appears that PF4 is an important negative autocrine regulator of platelet count in vivo. Excessive release of PF4 following cytotoxic therapy may be a mediator of treatment-related thrombocytopenia. Strategies directed to alleviate the consequence of released PF4 may have clinical benefit in ameliorating this thrombocytopenia.

Histones, Like Platelet Factor 4 (PF4), Affect Generation of Activated Protein C: Implications for the Pathogenesis of Severe Sepsis

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 530-530
Author(s):  
M. Anna Kowalska ◽  
Guohua Zhao ◽  
George David ◽  
Mortimer Poncz
Keyword(s):  
Severe Sepsis ◽  
Protein C ◽  
Conflicts Of Interest ◽  
Platelet Factor 4 ◽  
Endothelial Protein C Receptor ◽  
Maximal Increase ◽  
Platelet Factor ◽  
Positively Charged ◽  
Formation Of Complexes

Abstract Abstract 530 Platelet factor 4 (PF4) increases aPC generation by the thrombin (IIa)/thrombomodulin (TM) complex and may impact outcome in sepsis. PF4's effect on aPC generation follows a biphasic curve when tested in solution, on human TM expressing HEK293, and on primary endothelial cells (ECs) with a peak concentration at around 25 μg/ml. Formation of complexes at a specific molar ratio between positively-charged tetramers of PF4 and negatively-charged chondroitin sulfate (CS) on the TM glycosaminoglycan (GAG) is crucial for the increase in aPC generation. Other positively-charged molecules like protamine sulfate (PRT) affect aPC generation in a similar manner, and heparin, which is known to bind PF4 and PRT more avidly than CS, lowers effective PF4 or PRT concentrations. Here we examined whether histones, that are also small positively-charged molecules, affect aPC generation. Histones released from cells in sepsis are cytotoxic toward ECs and lethal when injected into mice, and aPC reverses this lethality. May histones affect aPC generation by the same mechanism as other positively-charged molecules, and how does the presence of PF4 or heparin influence this effect? We have addressed these questions both in solution and with TM-expressing cells, in the absence or presence of endothelial protein C receptor. We found that individual, or mixed histones affect aPC formation following a similar biphasic curve seen with PF4 with a peak effect at around 10 μg/ml but to lesser extent (2-fold maximal increase compared to 6-fold for PF4). Histones and PF4 are additive at low concentrations; however, more importantly, histones only decreased aPC generation when tested in the presence of optimal or higher PF4 concentration (>25 μg/ml). Just as with PF4, added heparin decreased effective histone concentration and shifted the curve for aPC generation to the right, both in the absence or presence of PF4. We hypothesize that normally PF4 released from platelets augments aPC generation and low concentration of histones have similar effect. But when histones are released in sepsis in high concentrations, their interaction with CS on TM blocks formation of complexes between PF4 and TM's CS that are optimal for maximal increase of aPC generation. Further we tested the effect of histones on aPC generation in vivo. Injection of histones in mice increased IIa-induced (2U/kg) aPC generation in plasma. This increase was concentration dependent (at 1 to 20 mg/kg increasing aPC generation up to 10-fold), but injection of higher amount of histones (40 mg/kg) became lethal. Mice that were overexpressing human PF4 had an increased lethality when histones at 40 mg/kg were co-injected with thrombin (2U/kg) over the littermate mice deficient in murine PF4 (60% vs. 0% mortality, respectively, n=5 for each group) suggesting that in vivo histones may also act additively with PF4 on aPC generation. We propose that in severe septic patients, especially those with high levels of released PF4, concurrently available histones suppress aPC generation. By binding to the excess of PF4 and/or histones, heparin may be beneficial in severe sepsis by allowing improved aPC generation. Disclosures: No relevant conflicts of interest to declare.

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