The EP3 Agonist Sulprostone Enhances Platelet Adhesion But Not Thrombus Formation Under Flow Conditions

Thromboelastometry-guided treatment algorithm in postpartum haemorrhage: a randomised, controlled pilot trial

BACKGROUND

Postpartum haemorrhage causes significant mortality among parturients. Early transfusion of blood products based on clinical judgement and conventional coagulation testing has been adapted to the treatment of postpartum haemorrhage, but rotational thromboelastometry (ROTEM) may provide clinicians means for a goal-directed therapy to control coagulation. We conducted a parallel design, randomised, controlled trial comparing these two approaches. We hypothesised that a ROTEM-guided protocol would decrease the need for red blood cell transfusion.

METHODS

We randomised 60 parturients with postpartum haemorrhage of more than 1500 ml to receive either ROTEM-guided or conventional treatment, with 54 patients included in the final analysis. The primary outcome was consumption of blood products, and secondarily we assessed for possible side-effects of managing blood loss such as thromboembolic complications, infections, and transfusion reactions.

RESULTS

The median (25th-75th percentile) number of RBC units transfused was 2 (1-4) in the ROTEM group and 3 (2-4) in the control group (P=0.399). The median number of OctaplasLG® units given was 0 in both groups (0-0 and 0-2) (P=0.030). The median total estimated blood loss was 2500 ml (2100-3000) in the ROTEM group and 3000 ml (2200-3100) in the control group (P=0.033). No differences were observed in secondary outcomes.

CONCLUSIONS

ROTEM-guided treatment of postpartum haemorrhage could have a plasma-sparing effect but possibly only a small reduction in total blood loss.

CLINICAL TRIAL REGISTRATION

NCT02461251.

The recombinant disintegrin, jarastatin, inhibits platelet adhesion and endothelial cell migration

Integrins are transmembrane heterodimeric glycoproteins, present in most cell types that act as mechanoreceptors, connecting extracellular matrix proteins to the cytoskeleton of the cell, mediating several physiological and pathological processes. The disintegrins are peptides capable of modulating the activity of integrins, such as αIIbβ3, responsible for the platelet aggregation and αvβ3, related to angiogenesis. The aim of this study was to produce the recombinant disintegrin jarastatin (rJast), to evaluate its secondary structure and biological activity. rJast was expressed in the yeast Komagataella phaffii (earlier Pichia pastoris) purified using molecular exclusion chromatography and the internal sequence and molecular mass were confirmed by mass spectrometry. The yield was approximately 40 mg/L of culture. rJast inhibited platelet aggregation induced by 2-4 μM ADP, 10 nM thrombin, and 1 μg/mL collagen (IC₅₀ of 244.8 nM, 166.3 nM and 223.5 nM, respectively). It also blocked the adhesion of platelets to collagen under continuous flow in approximately 60% when used 1 μM. We also evaluated the effect of rJast on HMEC-1 cells. rJast significantly inhibited the adhesion of these cells to vitronectin, as well as cell migration (IC₅₀ 1.77 μM) without changing the viability. Conclusions: rJast was successfully expressed with activity in human platelets aggregation identical to the native molecule. Also, rJast inhibits adhesion and migration of endothelial cells. Thus, being relevant for the development of anti-thrombotic and anti-angiogenic drugs.

Prostaglandin E2 Exerts Biphasic Dose Response on the PreBötzinger Complex Respiratory-Related Rhythm

Inflammation in infants can cause respiratory dysfunction and is potentially life-threatening. Prostaglandin E2 (PGE2) is released during inflammatory events and perturbs breathing behavior in vivo. Here we study the effects of PGE2 on inspiratory motor rhythm generated by the preBötzinger complex (preBötC). We measured the concentration dependence of PGE2 (1 nM-1 μM) on inspiratory-related motor output in rhythmic medullary slice preparations. Low concentrations (1–10 nM) of PGE2 increased the duration of the inspiratory burst period, while higher concentrations (1 μM) decreased the burst period duration. Using specific pharmacology for prostanoid receptors (EP1-4R, FPR, and DP2R), we determined that coactivation of both EP2R and EP3R is necessary for PGE2 to modulate the inspiratory burst period. Additionally, biased activation of EP3 receptors lengthened the duration of the inspiratory burst period, while biased activation of EP2 receptors shortened the burst period. To help delineate which cell populations are affected by exposure to PGE2, we analyzed single-cell RNA-Seq data derived from preBötC cells. Transcripts encoding for EP2R (Ptger2) were differentially expressed in a cluster of excitatory neurons putatively located in the preBötC. A separate cluster of mixed inhibitory neurons differentially expressed EP3R (Ptger3). Our data provide evidence that EP2 and EP3 receptors increase the duration of the inspiratory burst period at 1–10 nM PGE2 and decrease the burst period duration at 1 μM. Further, the biphasic dose response likely results from differences in receptor binding affinity among prostanoid receptors.

The NSAID glafenine rescues class 2 CFTR mutants via cyclooxygenase 2 inhibition of the arachidonic acid pathway

Most cases of cystic fibrosis (CF) are caused by class 2 mutations in the cystic fibrosis transmembrane regulator (CFTR). These proteins preserve some channel function but are retained in the endoplasmic reticulum (ER). Partial rescue of the most common CFTR class 2 mutant, F508del-CFTR, has been achieved through the development of pharmacological chaperones (Tezacaftor and Elexacaftor) that bind CFTR directly. However, it is not clear whether these drugs will rescue all class 2 CFTR mutants to a medically relevant level. We have previously shown that the nonsteroidal anti-inflammatory drug (NSAID) ibuprofen can correct F508del-CFTR trafficking. Here, we utilized RNAi and pharmacological inhibitors to determine the mechanism of action of the NSAID glafenine. Using cellular thermal stability assays (CETSAs), we show that it is a proteostasis modulator. Using medicinal chemistry, we identified a derivative with a fourfold increase in CFTR corrector potency. Furthermore, we show that these novel arachidonic acid pathway inhibitors can rescue difficult-to-correct class 2 mutants, such as G85E-CFTR > 13%, that of non-CF cells in well-differentiated HBE cells. Thus, the results suggest that targeting the arachidonic acid pathway may be a profitable way of developing correctors of certain previously hard-to-correct class 2 CFTR mutations.

Arachidonic Acid-Dependent Pathway Inhibition in Platelets: its Role in Multiple Injury-Induced Coagulopathy and the Potential Mechanisms

BACKGROUND

Our previous study demonstrated the types of platelet dysfunction varied at early stage (∼3 h) in trauma-induced coagulopathy (TIC) caused by different types of injuries. And arachidonic acid (AA)-dependent pathway inhibition in platelet seemed to be specific for TIC caused by multiple injury (MI). The aim of this research was to further study AA-dependent pathway inhibition in platelets in a rat model of TIC caused by MI and to explore its potential mechanisms.

METHODS

Sprague-Dawley rat model of TIC caused by MI was established. We used thrombelastography with platelet mapping as a measure of platelet function to assess the inhibitory extent of AA-dependent activation pathway. Flow cytometry was used to determine the expression of activation-dependent granular protein P-selectin (CD62P). In addition, the plasma levels of 6-Keto-prostaglandin F1 alpha (6-Keto-PGF1α), Prostaglandin E2, and Thromboxane B2 were assessed by enzyme-linked immuno sorbent assay.

RESULTS

The inhibition rate of AA-dependent pathway after injury was significantly higher than that of control. The maximum amplitude decreased in the MI group, compared with that of control. The percentage of CD62P expression in the MI group was remarkably lower than that of control after AA treatment. The plasma concentrations of 6-Keto-PGF1α and PGE2 increased in the MI group.

CONCLUSION

Platelets inhibition was observed in TIC caused by MI at early stage after injury, which might be partially attributed to AA-dependent activation pathway dysfunction. The increase of plasma Prostacyclin and PGE2 levels may contribute to the inhibition process.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Supplemental Fibrinogen Restores Platelet Inhibitor-Induced Reduction in Thrombus Formation without Altering Platelet Function: An In Vitro Study

BACKGROUND

 For patients treated with dual antiplatelet therapy, standardized drug-specific 3-to-7 day cessation is recommended prior to major surgery to reach sufficient platelet function recovery. Here we investigated the hypothesis that supplemental fibrinogen might mitigate the inhibitory effects of antiplatelet therapy.

METHODS AND RESULTS

 To this end blood from healthy donors was treated in vitro with platelet inhibitors, and in vitro thrombus formation and platelet activation were assessed. Ticagrelor, acetylsalicylic acid, the combination of both, and tirofiban all markedly attenuated the formation of adherent thrombi, when whole blood was perfused through collagen-coated microchannels at physiological shear rates. Addition of fibrinogen restored in vitro thrombus formation in the presence of antiplatelet drugs and heparin. However, platelet activation, as investigated in assays of P-selectin expression and calcium flux, was not altered by fibrinogen supplementation. Most importantly, fibrinogen was able to restore in vitro thrombogenesis in patients on maintenance dual antiplatelet therapy after percutaneous coronary intervention.

CONCLUSION

 Thus, our in vitro data support the notion that supplementation of fibrinogen influences the perioperative hemostasis in patients undergoing surgery during antiplatelet therapy by promoting thrombogenesis without significantly interfering with platelet activation.

The EP1/EP3 receptor agonist 17-pt-PGE2 acts as an EP4 receptor agonist on endothelial barrier function and in a model of LPS-induced pulmonary inflammation

Endothelial dysfunction is a hallmark of inflammatory conditions. We recently demonstrated that prostaglandin (PG)E₂ enhances the resistance of pulmonary endothelium in vitro and counteracts lipopolysaccharide (LPS)-induced pulmonary inflammation in vivo via EP4 receptors. The aim of this study was to investigate the role of the EP1/EP3 receptor agonist 17-phenyl-trinor-(pt)-PGE₂ on acute lung inflammation in a mouse model. In LPS-induced pulmonary inflammation in mice, 17-pt-PGE₂ reduced neutrophil infiltration and inhibited vascular leakage. These effects were unaltered by an EP1 antagonist, but reversed by EP4 receptor antagonists. 17-pt-PGE₂ increased the resistance of pulmonary microvascular endothelial cells and prevented thrombin-induced disruption of endothelial junctions. Again, these effects were not mediated via EP1 or EP3 but through activation of the EP4 receptor, as demonstrated by the lack of effect of more selective EP1 and EP3 receptor agonists, prevention of these effects by EP4 antagonists and EP4 receptor knock-down by siRNA. In contrast, the aggregation enhancing effect of 17-pt-PGE₂ in human platelets was mediated via EP3 receptors. Our results demonstrate that 17-pt-PGE₂ enhances the endothelial barrier in vitro on pulmonary microvascular endothelial cells, and accordingly ameliorates the recruitment of neutrophils, via EP4 receptors in vivo. This suggests a beneficial effect of 17-pt-PGE₂ on pulmonary inflammatory diseases.

Oxidized plasma albumin promotes platelet-endothelial crosstalk and endothelial tissue factor expression

Plasma advanced oxidation protein products (AOPPs), a class of pro-inflammatory pathogenic mediators, accumulate in subjects with chronic kidney disease. Whether AOPPs contribute to coagulation abnormalities, which are frequently seen in uremic patients, is unknown. Here we report that AOPPs activate platelets via a CD36-mediated signaling pathway. Activation of signaling pathways by AOPP-platelet interaction resulted in the expression of several platelet activation markers and rapidly induced the expression of CD40 ligand, triggering platelet adhesion to endothelial cells and promoting endothelial tissue factor expression. AOPPs and serum tissue factor levels were considerably increased in end stage renal disease patients on hemodialysis and a significant correlation of AOPPs and serum tissue factor was found. Interestingly, serum levels of AOPPs and tissue factor were substantially lower in stable kidney transplant patients when compared with hemodialysis patients. Given that CD36 is known to transduce the effects of oxidized lipids into platelet hyperactivity, our findings reveal previously unknown pro-thrombotic activities of oxidized plasma albumin via a CD36 dependent pathway.