Pathophysiological role of platelets and platelet system in acute pancreatitis

Acute pancreatitis induces a transient hypercoagulable state in murine models

BACKGROUND/OBJECTIVES

Although understudied, risk of venous thromboembolism (VTE) appears to be increased during acute pancreatitis (AP). We aimed to further characterize a hypercoagulable state associated with AP utilizing thromboelastography (TEG), a readily available, point of care test.

METHODS

AP was induced in C57/Bl6 mice using l-arginine and caerulein. TEG was performed with citrated native samples. The maximum amplitude (MA) and coagulation index (CI), a composite marker of coagulability, were evaluated. Platelet aggregation was assessed using whole blood collagen-activated platelet impedance aggregometry. Circulating tissue factor (TF), the initiator of extrinsic coagulation, was measured with ELISA. A VTE model using IVC ligation followed by measurement of clot size and weight was evaluated. After IRB approval and consent, blood samples from patients hospitalized with a diagnosis of AP were evaluated by TEG.

RESULTS

Mice with AP displayed a significant increase in MA and CI, consistent with hypercoagulability. Hypercoagulability peaked at 24 h after induction of pancreatitis, then returned to baseline by 72 h. AP resulted in significantly increased platelet aggregation and elevated circulating TF. Increased clot formation with AP was observed in an in vivo model of deep vein thrombosis. In a proof of concept, correlative study, over two thirds of patients with AP demonstrated an elevated MA and CI compared to the normal range, consistent with hypercoagulability.

CONCLUSIONS

Murine acute pancreatitis results in a transient hypercoagulable state that can be assessed by TEG. Correlative evidence for hypercoagulability was also demonstrated in human pancreatitis. Further study to correlate coagulation measures to incidence of VTE in AP is warranted.

Proteomic-Based Platelet Activation-Associated Protein SELP May Be a Novel Biomarker for Coagulation and Prognostic in Essential Thrombocythemia

Abnormal platelet activation can lead to thrombosis in essential thrombocythemia (ET) and thus impact patient prognosis. Platelet activation-associated proteins are key molecules for platelet activation. However, it is unclear which proteins are most closely associated with the disease's prognosis. To determine which platelet activation-related proteins can be employed as ET patient prognosis predictors, we used label-free quantification (LFQ) and parallel reaction monitoring (PRM) technology and first determined the serum proteomic expression levels and the differential proteins of ET patients. Then, based on the IPSET (International Prognostic Score for ET), the differential protein associated with the prognostic score was found. To investigate potential processes affecting prognosis, the connection of this protein with prognostic markers, such as thrombotic history, age, white blood cell count, coagulation factors, and inflammatory factors, were further examined. The levels of platelet activation-related proteins GPIbα, SELP, PF4, MMP1, and FLNA were significantly higher in ET patients, according to LFQ and PRM analyses (p < 0.01). Based on regression analysis of the IPSET prognostic score, it is suggested that the SELP level was positively correlated with the prognostic score and prognostic risk factor analysis (p < 0.05). Further regression analysis of SELP with coagulation factors showed that antithrombin (AT-III) was negatively correlated with SELP levels (p < 0.05). Further regression analysis of the inflammatory factors with AT-III and SELP revealed that IL-10, IL-12P70, and IL-31 were negatively correlated with AT-III and SELP (p < 0.01). Platelet activation pathway-related proteins are expressed more frequently in ET patients, and serum SELP may be a prognostic marker for these individuals by encouraging leukocyte increase and inflammatory factor expression and causing aberrant coagulation.

Dynamic Nomogram for Predicting Thrombocytopenia in Adults with Acute Pancreatitis

Objective

Thrombocytopenia increases the risk of hemorrhage in patients with acute pancreatitis (AP), leading to poor clinical outcomes. Currently, there is no reliable tool for the early assessment of thrombocytopenia in these patients. We aimed to develop a nomogram based on available clinical parameters and validate its efficacy in predicting thrombocytopenia.

Methods

This was a retrospective study. All the data were extracted from an electronic database from May 2018 to May 2019. Patients with a diagnosis of AP and staying in the intensive care unit for more than 3 days were retrospectively analyzed. A clinical signature was built based on reproducible features, using the least absolute shrinkage and selection operator method (LASSO), and logistic regression established the model (P < 0.05). Nomogram performance was determined by its discrimination, calibration, and clinical usefulness.

Results

A total of 594 eligible patients were enrolled, of whom 399 were allocated to the training sets and the 195 in the test sets. The clinical features, including blood urea nitrogen (BUN), fibrinogen (FIB), and antithrombase III, were significantly associated with the incidence of thrombocytopenia after acute pancreatitis (p < 0.05) in training sets. The individualized nomogram showed good discrimination in the training sample (area under the receiver operating characteristic curve [AUC], 0.881) and in the validation sample (AUC, 0.883) with good calibration.

Conclusion

The proposed nomogram has good performance for predicting thrombocytopenia in patients with acute pancreatitis and may facilitate clinical decision-making.

The Interplay between Inflammation, Coagulation and Endothelial Injury in the Early Phase of Acute Pancreatitis: Clinical Implications

Acute pancreatitis (AP) is an inflammatory disease with varied severity, ranging from mild local inflammation to severe systemic involvement resulting in substantial mortality. Early pathologic events in AP, both local and systemic, are associated with vascular derangements, including endothelial activation and injury, dysregulation of vasomotor tone, increased vascular permeability, increased leukocyte migration to tissues, and activation of coagulation. The purpose of the review was to summarize current evidence regarding the interplay between inflammation, coagulation and endothelial dysfunction in the early phase of AP. Practical aspects were emphasized: (1) we summarized available data on diagnostic usefulness of the markers of endothelial dysfunction and activated coagulation in early prediction of severe AP; (2) we reviewed in detail the results of experimental studies and clinical trials targeting coagulation-inflammation interactions in severe AP. Among laboratory tests, d-dimer and angiopoietin-2 measurements seem the most useful in early prediction of severe AP. Although most clinical trials evaluating anticoagulants in treatment of severe AP did not show benefits, they also did not show significantly increased bleeding risk. Promising results of human trials were published for low molecular weight heparin treatment. Several anticoagulants that proved beneficial in animal experiments are thus worth testing in patients.

Neutrophil Extracellular Traps Induce Trypsin Activation, Inflammation, and Tissue Damage in Mice With Severe Acute Pancreatitis

BACKGROUND & AIMS

Neutrophils are involved in the development of acute pancreatitis (AP), but it is not clear how neutrophil-induced tissue damage is regulated. In addition to secreting antimicrobial compounds, activated neutrophils eliminate invading microorganisms by expelling nuclear DNA and histones to form extracellular web-like structures called neutrophil extracellular traps (NETs). However, NETs have been reported to contribute to organ dysfunction in patients with infectious diseases. We investigated whether NETs contribute to the development of AP in mice.

METHODS

AP was induced in C57BL/6 mice by infusion of taurocholate into the pancreatic duct or by intraperitoneal administration of L-arginine. Pancreata were collected and extracellular DNA was detected by Sytox green staining, levels of CXC chemokines, histones, and cytokines also were measured. Cell-free DNA was quantified in plasma samples. Signal transducer and activator of transcription 3 phosphorylation and trypsin activation were analyzed in isolated acinar cells. NETs were depleted by administration of DNase I to mice. Plasma was obtained from healthy individuals (controls) and patients with severe AP.

RESULTS

Infusion of taurocholate induced formation of NETs in pancreatic tissues of mice and increased levels of cell-free DNA in plasma. Neutrophil depletion prevented taurocholate-induced deposition of NETs in the pancreas. Administration of DNase I to mice reduced neutrophil infiltration and tissue damage in the inflamed pancreas and lung, and decreased levels of blood amylase, macrophage inflammatory protein-2, interleukin 6, and high-mobility groups protein 1. In mice given taurocholate, DNase I administration also reduced expression of integrin α M (macrophage-1 antigen) on circulating neutrophils. Similar results occurred in mice with L-arginine-induced AP. Addition of NETs and histones to acinar cells induced formation of trypsin and activation of signal transducer and activator of transcription 3; these processes were blocked by polysialic acid. Patients with severe AP had increased plasma levels of NET components compared with controls.

CONCLUSIONS

NETs form in the pancreata of mice during the development of AP, and NET levels are increased in plasma from patients with AP, compared with controls. NETs regulate organ inflammation and injury in mice with AP, and might be targeted to reduce pancreatic tissue damage and inflammation in patients.

Pathomorphological analysis of the pancreaticoduodenal organs in experimental pancreonecrosis induced by trypsin injection

Acute experimental pancreatitis induced by injection of trypsin into the pancreatic tissue exhibited characteristics of fulminant hemorrhagic pancreonecrosis (intense exudation of interlobular stroma, massive plasmo- and hemorrhages, foci of acinar cell autolysis involving by the end of day 1 an appreciable portion of the organ with formation of fields of necrosis and hemorrhagic imbibition of the glandular parenchyma, virtually completely without demarcation cellular reaction). Marked microcirculatory disorders and degenerative and necrobiotic changes in the duodenal mucosa and liver reflected the polyorgan nature of the pathological process. This model of hemorrhagic pancreonecrosis corresponded to the most severe forms of this conditions observed clinically.

Platelet activation in acute pancreatitis

OBJECTIVES

The aim of this study was to assess the functional state of platelets in patients with mild acute pancreatitis and severe acute pancreatitis (S-AP).

METHODS

The number of platelets and their morphological parameters were measured with Advia 2120. β-Thromboglobulin and platelet factor 4 concentrations were determined by enzyme-linked immunosorbent assay method. To evaluate the expression of platelet glycoproteins, flow cytometry method was used.

RESULTS

At the time of admission, a multiparameter evaluation of the platelets' function in AP patients showed enhanced platelet activation, which was reflected by an increase in the number of large platelets, concentration of degranulation markers (platelet factor 4 and β-thromboglobulin), expression of glycoprotein (Gp) IIb/IIIa, and decreased mean platelet component. Only in S-AP patients at day 1 a decreased number of platelets and high expression of P-selectin and GpIa were observed, which may suggest their prognostic value. At day 30, the procoagulation state was still present in S-AP patients, because of increased platelets and number of large platelets as well as high GpIIb/IIIa expression.

CONCLUSIONS

These results may indicate an important role of platelet activation in the pathogenesis of acute pancreatitis and the development of complications in S-AP.

Patterns of pathomorphological changes in acute necrotizing pancreatitis

Acinar necrosis is the basic microscopic sign of acute necrotizing pancreatitis (ANP). Microcirculation disorder is one of the major factors in the pathogenesis and morphogenesis of ANP besides free radicals and damage of enzymatic origin. This study is dedicated to the description of microscopic changes in the pancreatic stroma in ANP, which leads to destruction of the exocrine pancreas with a putative mechanism of endocrine function preservation. This study has been carried out on histological samples of pancreas from 224 patients with ANP. Histological staining was performed with hematoxylin-eosin (H&E), Masson, Gomori methods, and PAS. Microscopy was performed with magnifications of 40×, 100×, and 400×. Vascular endothelial desquamation, stasis, and sludge are typical changes in microcirculation observed in early stages of ANP. Initially, parietal circular intravascular microthrombosis accompanied by endothelial desquamation as early as stromal swelling occurs with no detectable necrosis. Residual stroma appears between areas of necrosis and intact pancreatic tissue. Mucoid swelling is first seen in the perivascular spaces extending to the parenchyma and changing into fibrinoid imbibition causing further necrosis. Reticulin argyrophilic backbone surrounding the pancreatic acini and small ducts decompose. Pancreatic structures, which may be preserved in necrotic tissue, include nerves, major ducts, and Langerhans islets.

Targeting P-selectin in acute pancreatitis

IMPORTANCE OF THE FIELD

Acute pancreatitis (AP) is a multifactorial disorder not fully understood yet. In particular, the pathogenetic pathways promoting a severe life-threatening course of AP are the subject of ongoing investigations. P-selectin has been shown to play a central role in the complex pathophysiology in AP as well as various other inflammatory conditions.

AREAS COVERED IN THIS REVIEW

P-selectin function in AP is reviewed with focus on its dual function as a mediator of leukocyte recruitment and cell adhesion, which implies the unique effect of linking both inflammation and coagulation, especially in the progression from mild to severe necrotizing AP. Potential therapeutic aspects are discussed with regard to the clinical situation.

WHAT THE READER WILL GAIN

A better understanding of the pathogenic role of P-selectin in AP and of the rationale for a therapeutic blockade.

TAKE HOME MESSAGE

P-selectin is a glycoprotein that mediates the adhesion of activated platelets and leukocytes to the vessel wall in various inflammatory conditions. Both pathophysiological steps are closely linked and play a key role in the course of severe AP. A treatment approach by inhibition of P-selectin could be of distinct interest as a therapeutic option in severe AP.

Ischemia-reperfusion injury and acute pancreatitis

Though the pathogenesis of acute pancreatitis is still not entirely clear, animal experiments and clinical studies suggest that ischemia-reperfusion injury plays an important role in the development of acute pancreatitis. The combined action of microcirculatory disturbance, increased free radical production, intracellular calcium overload, inflammatory mediators, leukocyte-platelet interaction, intestinal endotoxemia and other factors leads to pancreatic ischemia-reperfusion injury. Thus, ischemia-reperfusion injury is fundamental to the pathogenesis of acute pancreatitis. In this article, we will review the mechanisms behind the development of pancreatic ischemia-reperfusion injury in acute pancreatitis.