P-selectin inhibition reduces severity of acute experimental pancreatitis

Toll-like receptor 4 in pancreatic damage and immune infiltration in acute pancreatitis

Acute pancreatitis is a complex inflammatory disease resulting in extreme pain and can result in significant morbidity and mortality. It can be caused by several factors ranging from genetics, alcohol use, gall stones, and ductal obstruction caused by calcification or neutrophil extracellular traps. Acute pancreatitis is also characterized by immune cell infiltration of neutrophils and M1 macrophages. Toll-like receptor 4 (TLR4) is a pattern recognition receptor that has been noted to respond to endogenous ligands such as high mobility group box 1 (HMGB1) protein and or exogenous ligands such as lipopolysaccharide both of which can be present during the progression of acute pancreatitis. This receptor can be found on a variety of cell types from endothelial cells to resident and infiltrating immune cells leading to production of pro-inflammatory cytokines as well as immune cell activation and maturation resulting in the furthering of pancreatic damage during acute pancreatitis. In this review we will address the various mechanisms mediated by TLR4 in the advancement of acute pancreatitis and how targeting this receptor could lead to improved outcomes for patients suffering from this condition.

High-Dose Vitamin C Alleviates Pancreatic Necrosis by Inhibiting Platelet Activation Through the CXCL12/CXCR4 Pathway in Severe Acute Pancreatitis

Background

Platelet activation in the early stage of pancreatitis is the key step developing into pancreatic necrosis. Studies suggested that vitamin C (Vit C) can inhibit platelet activity by targeting CXCL12/CXCR4 pathway. High-dose Vit C were showed to reduce pancreatic necrosis in severe acute pancreatitis (SAP) but the mechanism remains unclear. Here we speculate high-dose Vit C reduce pancreatic necrosis by inhibiting platelet activation through downregulating CXCL12/CXCR4 pathway.

Methods

The pancreatic microcirculation of rats was observed by intravital microscopy. The platelet activity of SAP rats treated with or without high-dose Vit C was analyzed by platelet function test. Besides, the activity of platelets preincubated with high-dose Vit C or vehicle from SAP patients was also evaluated. Then, the TFA (CXCR4 agonist) and rCXCL12 were used to neutralize the effect of high-dose Vit C in SAP rats treated with high-dose Vit C. Meanwhile, the levels of enzymes and inflammatory cytokines in rat plasma, and rats' pancreatic histopathology and mortality were assessed.

Results

Platelets from animals and patients with SAP are more sensitive to agonists and are more easily activated. Administration of high-dose Vit C significantly ameliorated excessive activation of platelets in SAP rats, ultimately increasing the microvessel density and inducing microthrombus and blood stasis; these results were consistent with clinical sample analysis. Moreover, high-dose Vit C significantly inhibited the release of amylase, lipase, TNF-α, and IL-6 in SAP rat plasma, reducing pancreatic damage and the mortality of SAP rats. However, using TFA and rCXCL12 significantly reversed the effect of high-dose Vit C on excessive activation of platelets, aggravating microcirculation impairment and pancreatic damage.

Conclusion

The present study suggests that high-dose Vit C can ameliorate pancreatic necrosis by improving microcirculation disorders of SAP. For the first time, the underlying mechanism is related with inhibiting platelet activation through the CXCL12/CXCR4 pathway.

The Signaling Pathway of the ADP Receptor P2Y12 in the Immune System: Recent Discoveries and New Challenges

P2Y12 is a G-protein-coupled receptor that is activated upon ADP binding. Considering its well-established role in platelet activation, blocking P2Y12 has been used as a therapeutic strategy for antiplatelet aggregation in cardiovascular disease patients. However, receptor studies have shown that P2Y12 is functionally expressed not only in platelets and the microglia but also in other cells of the immune system, such as in monocytes, dendritic cells, and T lymphocytes. As a result, studies were carried out investigating whether therapies targeting P2Y12 could also ameliorate inflammatory conditions, such as sepsis, rheumatoid arthritis, neuroinflammation, cancer, COVID-19, atherosclerosis, and diabetes-associated inflammation in animal models and human subjects. This review reports what is known about the expression of P2Y12 in the cells of the immune system and the effect of P2Y12 activation and/or inhibition in inflammatory conditions. Lastly, we will discuss the major problems and challenges in studying this receptor and provide insights on how they can be overcome.

Pathogenesis and Therapy of Coagulation Disorders in Severe Acute Pancreatitis

Ischemia superimposed upon pancreatic edema leads to acute necrotizing pancreatitis. One possible mechanism contributing to ischemia is intravascular thrombogenesis since fibrin deposits have been detected in pancreatic capillaries by electron microscope. Current experimental and clinical data provided compelling evidence that the disorders in the blood coagulation system play a critical role in the pathogenesis of severe acute pancreatitis (SAP). This leads to microcirculatory failure of intra- and extrapancreatic organs and multiple organ failure and increases the case fatality rate. However, the mechanism of coagulopathy underlying SAP is not yet clear, although some anticoagulant drugs have entered clinical practice showing improvement in prognosis. Thus, enhanced understanding of the process might improve the treatment strategies with safety and high efficacy. Herein, the pathogenesis of the coagulation system of SAP was reviewed with a focus on the coagulation pathway, intercellular interactions, and complement system, thereby illustrating some anticoagulant therapies and potential therapeutic targets.

Role of Hydrogen Sulfide, Substance P and Adhesion Molecules in Acute Pancreatitis

Inflammation is a natural response to tissue injury. Uncontrolled inflammatory response leads to inflammatory disease. Acute pancreatitis is one of the main reasons for hospitalization amongst gastrointestinal disorders worldwide. It has been demonstrated that endogenous hydrogen sulfide (H₂S), a gasotransmitter and substance P, a neuropeptide, are involved in the inflammatory process in acute pancreatitis. Cell adhesion molecules (CAM) are key players in inflammatory disease. Immunoglobulin (Ig) gene superfamily, selectins, and integrins are involved at different steps of leukocyte migration from blood to the site of injury. When the endothelial cells get activated, the CAMs are upregulated which leads to them interacting with leukocytes. This review summarizes our current understanding of the roles H₂S, substance P and adhesion molecules play in acute pancreatitis.

The Role of Neutrophils and Neutrophil Extracellular Traps in Acute Pancreatitis

Leukocyte invasion (neutrophils and monocytes/macrophages) is closely related to the severity of acute pancreatitis (AP) and plays an important role in the systemic inflammatory response and other organ injuries secondary to AP. Increased and sustained activation of neutrophils are major determinants of pancreatic injury and inflammation. After the onset of AP, the arrival of the first wave of neutrophils occurs due to a variety of triggers and is critical for the exacerbation of inflammation. In this review, we summarize the functional characteristics of neutrophils, elastase, and heparin-binding proteins in granules, the mechanisms of neutrophil recruitment and the role of neutrophil extracellular traps (NETs) in AP.

[Inflammatory diseases of the pancreas: what new do we know about the mechanisms of their development in the 21st century?]

Inflammatory diseases of the pancreas can range from acute to acute recurrent and chronic pancreatitis. With the improvement of laboratory diagnostics in the 21st century, the mechanisms of the pro-inflammatory and anti-inflammatory role of tight junctions, in particular the transmembrane proteins occludin, claudine and JAMs, cytoplasmic Zo-proteins, and adherens junctions, in particular -catenin, -catenin, E-cadherin, selectins and ICAMs in the pathogenesis of acute and chronic pancreatitis have become more clear. The study of genetic factors in the development of acute and chronic pancreatitis showed the role of mutations in the genes SPINK1 N34S, PRSS1, CEL-HYB in the progression of the disease.

Pancreas-specific deletion of protein kinase D attenuates inflammation, necrosis, and severity of acute pancreatitis

BACKGROUND

Protein kinase D (PKD) family, which includes PKD/PKD1, PKD2, and PKD3, has been increasingly implicated in the regulation of multiple cellular functions and human diseases. We recently reported that pharmacologic inhibition of PKD ameliorated the pathologic responses and severity of pancreatitis. However, to further investigate the importance of PKD family members in pancreatitis, it is necessary to explore the effects of pancreas-specific genetic inhibition of PKD isoform on pathology of pancreatitis.

METHODS

We generated a mouse model (referred as PKD3Δpanc mice) with pancreas-specific deletion of PKD3, the predominant PKD isoform in mouse pancreatic acinar cells, by crossing Pkd3flox/flox mice with Pdx1-Cre transgenic mice which express Cre recombinase under the control of the mouse Pdx1 promoter. Pancreas-specific deletion of the PKD3 gene and PKD3 protein was confirmed by PCR and Western blot analysis. Experimental pancreatitis was induced in PKD3Δpanc and Pkd3flox/flox (control mice) littermates by intraperitoneal injections of cerulein or L-arginine.

RESULTS

Compared to the control mice, PKD3Δpanc mice displayed significant attenuation in inflammation, necrosis, and severity of pancreatitis in both experimental models. PKD3Δpanc mice had markedly decreased NF-κB and trypsinogen activation, pancreatic mRNA expression of multiple inflammatory molecules, and the receptor-interacting protein kinase 1 (RIP1) activation in pancreatitis. PKD3Δpanc mice also had less pancreatic ATP depletion, increased pro-survival Bcl-2 family protein expression, and autophagy promotion.

CONCLUSION

With PKD3Δpanc mouse model, we further demonstrated that PKD plays a critical role in pathobiological process of pancreatitis and PKD constitutes a novel therapeutic target to treat this disorder.

P2Y12 Receptor Antagonist Clopidogrel Attenuates Lung Inflammation Triggered by Silica Particles

Silicosis is an occupational lung disease caused by inhalation of silica particles. It is characterized by intense lung inflammation, with progressive and irreversible fibrosis, leading to impaired lung function. Purinergic signaling modulates silica-induced lung inflammation and fibrosis through P2X7 receptor. In the present study, we investigate the role of P2Y12, the G-protein-coupled subfamily prototype of P2 receptor class in silicosis. To that end, BALB/c mice received an intratracheal injection of PBS or silica particles (20 mg), without or with P2Y12 receptor blockade by clopidogrel (20 mg/kg body weight by gavage every 48 h) - groups CTRL, SIL, and SIL + Clopi, respectively. After 14 days, lung mechanics were determined by the end-inflation occlusion method. Lung histology was analyzed, and lung parenchyma production of nitric oxide and cytokines (IL-1β, IL-6, TNF-α, and TGF-β) were determined. Silica injection reduced animal survival and increased all lung mechanical parameters in relation to CTRL, followed by diffuse lung parenchyma inflammation, increased neutrophil infiltration, collagen deposition and increased pro-inflammatory and pro-fibrogenic cytokine secretion, as well as increased nitrite production. Clopidogrel treatment prevented silica-induced changes in lung function, and significantly reduced lung inflammation, fibrosis, as well as cytokine and nitrite production. These data suggest that inhibition of P2Y12 signaling improves silica-induced lung inflammation, preventing lung functional changes and mortality. Our results corroborate previous observations of silica-induced lung changes and expand the understanding of purinergic signaling in this process.

ADP exerts P2Y12 -dependent and P2Y12 -independent effects on primary human T cell responses to stimulation

Purinergic signaling plays a complex role in inflammation. Nucleotides released by T lymphocytes, endothelial cells, and platelets during inflammation induce cellular responses by binding to receptors that regulate intracellular signaling pathways. Previous studies have found that purinergic signaling can have both proinflammatory and anti-inflammatory effects, but the roles of specific pathways in specific cell types are poorly understood. We investigated the role of the P2Y₁₂ signaling pathway in the activation of T lymphocytes in vitro. We isolated peripheral blood mononuclear cells (PBMCs) from healthy donors and pretreated them with ADP (a P2Y₁₂ agonist), AR-C69931MX (a P2Y₁₂ antagonist), or both. We then stimulated PBMC using phytohemagglutinin (PHA) or anti-CD3/CD28 antibodies. We found that ADP affects T cell responses in term of cell activity and receptor expression through both P2Y₁₂-dependent and P2Y₁₂-independent pathways and other responses (cytokine secretion) primarily through P2Y₁₂ -independent pathways. The ADP-mediated effect changed over time and was stimulus-specific.

Adhesion molecules and pancreatitis

Acute and chronic pancreatitises are gastrointestinal inflammatory diseases, the incidence of which is increasing worldwide. Most (~ 80%) acute pancreatitis (AP) patients have mild disease, and about 20% have severe disease, which causes multiple organ failure and has a high mortality rate. Chronic pancreatitis (CP) is characterized by chronic inflammation and destruction of normal pancreatic parenchyma, which leads to loss of exocrine and endocrine tissues. Patients with CP also have a higher incidence of pancreatic ductal adenocarcinoma. Although a number of factors are associated with the development and progression of AP and CP, the underlying mechanism is unclear. Adhesion molecules play important roles in cell migration, proliferation, and signal transduction, as well as in development and tissue repair. Loosening of cell-cell adhesion between pancreatic acinar cells and/or endothelial cells increases solute permeability, resulting in interstitial edema, which promotes inflammatory cell migration and disrupts tissue structure. Oxidative stress, which is one of the important pathogenesis of pancreatitis, leads to upregulation of adhesion molecules. Soluble adhesion molecules are reportedly involved in AP. In this review, we focus on the roles of tight junctions (occludin, tricellulin, claudin, junctional adhesion molecule, and zonula occludin), adherens junctions (E-cadherin and p120-, α-, and β-catenin), and other adhesion molecules (selectin and intercellular adhesion molecules) in the progression of AP and CP. Maintaining the normal function of adhesion molecules and preventing their abnormal activation maintain the structure of the pancreas and prevent the development of pancreatitis.

E and P Selectins as Potential Markers in the Assessment of the Severity of Acute Pancreatitis

OBJECTIVES

Acute pancreatitis (AP) is commonly associated with the release of adhesion molecules such as E and P selectins. We designed the present study to evaluate the role of selectins as potential markers that could reflect the severity of the disease.

METHODS

One hundred fifty patients with AP constituted the patient group, whereas 70 healthy volunteers established the control group. In both groups, blood samples were taken for measurements of E selectin, P selectin, caspase-cleaved cytokeratin 18, and total soluble cytokeratin 18 levels on admission and days 1, 2, 4, and 6.

RESULTS

Values of E and P selectins on admission were both elevated compared with control subjects (P < 0.01). The nonsurvivors had higher values of E selectin (P < 0.04) and P selectin (P < 0.03) on admission. Levels of E and P selectin showed positive correlation with the length of stay (P < 0.05). E selectin on admission yielded a sensitivity of 75% and 78% specificity, whereas P selectin had a sensitivity of 67% and 91% specificity.

CONCLUSIONS

Selectin values in the early course of AP may play a role as indicators of overall prognosis, which may help physicians in better understanding the pathophysiology of a benign disease that may have serious and detrimental complications.

Higher Thrombin-Antithrombin III Complex Levels May Indicate Severe Acute Pancreatitis

AIM

Coagulation disorders may develop in association with severe acute pancreatitis (AP). Plasma thrombin-antithrombin III complex (TAT) levels are one of the principal markers of coagulation disorder. The purpose of this study was to evaluate TAT and other hemostatic parameters in patients with AP and to examine whether or not these parameters indicate the severity of AP.

METHOD

Forty-six patients with AP (14 severe, 32 non-severe) and a 30-member healthy control group were recruited. The severity of AP was determined using the revised Atlanta classification. ELISA was used to measure patients' plasma TAT levels.

RESULTS

The TAT levels of AP patients at presentation were higher than those of the control group (p = 0.005). The plasma TAT levels of patients with severe AP were also significantly higher than those of patients with non-severe AP (p = 0.05) and of the control group (p < 0.001). The general accuracy, sensitivity and specificity of TAT levels in predicting the severity of AP were 77.4, 77.8, and 77.3% respectively.

CONCLUSION

The coagulation cascade was activated in the AP patients in our study, and this was shown to become more pronounced as severity of the disease increased. Plasma TAT levels at the time of presentation in patients with AP can be used as a marker for predicting the severity of the disease.

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.

P2Y12 Receptor Modulates Sepsis-Induced Inflammation

OBJECTIVE

Platelets modulate hemostasis and immune responses via interactions with immune cells through secretion of immunemodulators and cell-cell interactions. The P2Y12 receptor mediates ADP-induced aggregation and secretion in platelets.

APPROACH AND RESULTS

Using a mouse model of intra-abdominal sepsis and acute lung injury, we investigated the role of the P2Y12 receptor in neutrophil migration and lung inflammation in P2Y12 null mice and in mice pretreated with the P2Y12 antagonist clopidogrel. Our data show a decrease in circulating white blood cells and a decrease in platelet activation and platelet-leukocyte interactions in treated mice compared with untreated mice. Additionally, lung injury and platelet sequestration were diminished in clopidogrel-treated mice compared with their untreated septic littermates. Similar results were observed in P2Y12 null mice: platelet activation and platelet-leukocyte aggregates were decreased in septic P2Y12 null mice compared with wild-type mice. P2Y12 null mice were refractory to lung injury compared with wild-type mice. Finally, to evaluate P2Y12-independent effects of clopidogrel, we pretreated P2Y12 null mice. Interestingly, the number of circulating neutrophils was reduced in treated septic P2Y12 null mice, suggesting neutrophils as a target for clopidogrel pleiotropic effects. No difference was observed in P2Y1 null mice during sepsis, indicating that the P2Y12 receptor is responsible for the effects.

CONCLUSIONS

P2Y12 null mice are refractory to sepsis-induced lung injury, suggesting a key role for activated platelets and the P2Y12 receptor during sepsis.

Therapeutic implications of innate immune system in acute pancreatitis

INTRODUCTION

Acute pancreatitis (AP) is an inflammatory disorder of the pancreas encompassing a cascade of cellular and molecular events. It starts from premature activation of zymogens with the involvement of innate immune system to a potential systemic inflammatory response and multiple organ failure. Leukocytes are the major cell population that participate in the propagation of the disease. Current understanding of the course of AP is still far from complete, limiting treatment options mostly to conservative supportive care. Emerging evidence has pointed to modulation of the immune system for strategic therapeutic development, by mitigating the inflammatory response and severity of AP. In the current review, we have focused on the role of innate immunity in the condition and highlighted therapeutics targeting it for treatment of this challenging disease.

AREAS COVERED

The current review has aimed to elaborate in-depth understanding of specific roles of innate immune cells, derived mediators and inflammatory pathways that are involved in AP. Summarizing the recent therapeutics and approaches applied experimentally that target immune responses to attenuate AP.

EXPERT OPINION

The current state of knowledge on AP, limitations of presently available therapeutic approaches and the promise of therapeutic implications of innate immune system in AP are discussed.

Inflammatory profiling of early experimental necrotizing pancreatitis

AIMS

Inflammatory mediators play a pivotal role in severe necrotizing pancreatitis (SNP). Therapeutic approaches aim at the early inflammatory liberation of cytokines to avoid systemic complications. The present study evaluates the kinetics of inflammatory mediator release in SNP.

MAIN METHODS

Experimental SNP was induced in male Wistar rats using the GDOC model. The animals were allocated into seven groups (n = 6/group). In group 1, sample harvesting was performed after sham operation while in groups 2-7 this was performed 1 h, 2 h, 4 h, 6 h, 9 h, and 12 h after initiation of SNP, respectively. Inflammatory mediator release,morphologic injury, and tissue MPO concentrations were evaluated between 1 and 12 h after induction.

KEY FINDINGS

Pancreatic injury showed a continuous increase over the observation period (p b 0.05, respectively). MPO levels in the pancreas and lungs increased until 12 h after induction (p b 0.05, respectively). Antiinflammatory IL-10 showed an early peak and the pro-inflammatory mediators TNFα and IL-1β peaked after 6 and 9 h, respectively (p b 0.05, respectively). HMGB1 levels constantly increased over time (p b 0.05, respectively).

SIGNIFICANCE

The present study shows the release of relevant pro- and anti-inflammatory mediators in SNP for the first time in one single experimental setup. Inflammatory mediators peak within the first few hours after SNP induction. Consequently, the effect of therapeutic approaches on early changes in cytokine release should be evaluated later than 2 h after initiation.

The role of P2Y₁₂ receptor and activated platelets during inflammation

Platelets play an important role not only during thrombosis, but also in modulating immune responses through their interaction with immune cells and by releasing inflammatory mediators upon activation. The P2Y12 receptor is a Gi-coupled receptor that not only regulates ADP-induced aggregation but can also dramatically potentiate secretion, when platelets are activated by other stimuli. Considering the importance of P2Y12 receptor in platelet function, a class of antiplatelet drugs, thienopyridines, have been designed and successfully used to prevent thrombosis. This review will focus on the role of activated platelets in inflammation and the effects that P2Y12 antagonism exerts on the inflammatory process. A change in platelet functions was noted in patients treated with thienopyridines during inflammatory conditions, suggesting that platelets may modulate the inflammatory response. Further experiments in a variety of animal models of diseases, such as sepsis, rheumatoid arthritis, myocardial infarction, pancreatitis and pulmonary inflammation have also demonstrated that activated platelets influence the inflammatory state. Platelets can secrete inflammatory modulators in a P2Y12-dependent manner, and, as a result, directly alter the inflammatory response. P2Y12 receptor may also be expressed in other cells of the immune system, indicating that thienopyridines could directly influence the immune system rather than only through platelets. Overall the results obtained to date strongly support the notion that activated platelets significantly contribute to the inflammatory process and that antagonizing P2Y12 receptor can influence the immune response.

Genetic inhibition of protein kinase Cε attenuates necrosis in experimental pancreatitis

Understanding the regulation of death pathways, necrosis and apoptosis, in pancreatitis is important for developing therapies directed to the molecular pathogenesis of the disease. Protein kinase Cε (PKCε) has been previously shown to regulate inflammatory responses and zymogen activation in pancreatitis. Furthermore, we demonstrated that ethanol specifically activated PKCε in pancreatic acinar cells and that PKCε mediated the sensitizing effects of ethanol on inflammatory response in pancreatitis. Here we investigated the role of PKCε in the regulation of death pathways in pancreatitis. We found that genetic deletion of PKCε resulted in decreased necrosis and severity in the in vivo cerulein-induced pancreatitis and that inhibition of PKCε protected the acinar cells from CCK-8 hyperstimulation-induced necrosis and ATP reduction. These findings were associated with upregulation of mitochondrial Bak and Bcl-2/Bcl-xL, proapoptotic and prosurvival members in the Bcl-2 family, respectively, as well as increased mitochondrial cytochrome c release, caspase activation, and apoptosis in pancreatitis in PKCε knockout mice. We further confirmed that cerulein pancreatitis induced a dramatic mitochondrial translocation of PKCε, suggesting that PKCε regulated necrosis in pancreatitis via mechanisms involving mitochondria. Finally, we showed that PKCε deletion downregulated inhibitors of apoptosis proteins, c-IAP2, survivin, and c-FLIPs while promoting cleavage/inactivation of receptor-interacting protein kinase (RIP). Taken together, our findings provide evidence that PKCε activation during pancreatitis promotes necrosis through mechanisms involving mitochondrial proapoptotic and prosurvival Bcl-2 family proteins and upregulation of nonmitochondrial pathways that inhibit caspase activation and RIP cleavage/inactivation. Thus PKCε is a potential target for prevention and/or treatment of acute pancreatitis.

Pharmacological cholinergic stimulation as a therapeutic tool in experimental necrotizing pancreatitis

OBJECTIVES

The endogenous immune response is influenced by the stimulation of the vagal nerve. Stimulation or ablation has a direct impact on the release of pro- and anti-inflammatory mediators. In the progression of acute pancreatitis from local to systemic disease, these mediators play a pivotal role. This study evaluates the effect of pharmacologic stimulation of the cholinergic system on pancreatic damage in experimental necrotizing pancreatitis.

METHODS

Experimental severe necrotizing pancreatitis was induced in male Wistar rats using the glycodeoxycholic acid model. Animals with acute pancreatitis (n = 6) were compared with animals with acute pancreatitis and prophylactic or therapeutic pharmacologic activation of the cholinergic system using nicotine, physostigmine, or neostigmine (n = 36). Twelve hours after the induction of acute pancreatitis, morphological damage as well as the myeloperoxidase levels of the pancreas and the serum levels of high-mobility group box 1 protein were evaluated.

RESULTS

Prophylactic and delayed therapeutic application of nicotine, physostigmine, or neostigmine significantly attenuated the severity of acute pancreatitis 12 hours after the induction of severe necrotizing pancreatitis compared with untreated controls as evaluated with histological scores, myeloperoxidase, and high-mobility group box 1 levels (P < 0.05).

CONCLUSIONS

Stimulation of the cholinergic system is useful to attenuate damage in experimental acute pancreatitis. Not only prophylactic but also delayed application was effective in the present study.

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.

P-selectin mediates neutrophil rolling and recruitment in acute pancreatitis

BACKGROUND

The adhesive mechanisms regulating leucocyte-endothelium interactions in the pancreas remain elusive, but selectins may play a role. This study examined the molecular mechanisms mediating leucocyte rolling along the endothelium in the pancreas and the therapeutic potential of targeting the rolling adhesive interaction in acute pancreatitis (AP).

METHODS

Pancreatitis was induced by retrograde infusion of 5 per cent sodium taurocholate into the pancreatic duct, repeated intraperitoneal administration of caerulein (50 µg/kg) or intraperitoneal administration of L-arginine (4 g/kg) in C57BL/6 mice. A control and a monoclonal antibody against P-selectin were administered before and after induction of AP. Serum and tissue were sampled to assess the severity of pancreatitis, and intravital microscopy was used to study leucocyte rolling.

RESULTS

Taurocholate infusion into the pancreatic duct increased the serum level of trypsinogen, trypsinogen activation, pancreatic neutrophil infiltration, macrophage inflammatory protein (MIP) 2 formation and tissue damage. Immunoneutralization of P-selectin decreased the taurocholate-induced increase in serum trypsinogen (median (range) 17·35 (12·20-30·00) versus 1·55 (0·60-15·70) µg/l; P = 0·017), neutrophil accumulation (4·00 (0·75-4·00) versus 0·63 (0-3·25); P = 0·002) and tissue damage, but had no effect on MIP-2 production (14·08 (1·68-33·38) versus 3·70 (0·55-51·80) pg/mg; P = 0·195) or serum trypsinogen activating peptide level (1·10 (0·60-1·60) versus 0·45 (0-1·80) µg/l; P = 0·069). Intravital fluorescence microscopy revealed that anti-P-selectin antibody inhibited leucocyte rolling completely in postcapillary venules of the inflamed pancreas.

CONCLUSION

Inhibition of P-selectin protected against pancreatic tissue injury in experimental pancreatitis. Targeting P-selectin may be an effective strategy to ameliorate inflammation in AP.

Role of neutrophils in the activation of trypsinogen in severe acute pancreatitis

The relationship between inflammation and proteolytic activation in pancreatitis is an unresolved issue in pancreatology. The purpose of this study was to define the influence of neutrophils on trypsinogen activation in severe AP. Pancreatitis was induced by infusion of taurocholate into the pancreatic duct in C57BL/6 mice. For neutrophil depletion, an anti-Gr-1 antibody was administered before pancreatitis induction. Administration of the anti-Gr-1 antibody reduced circulating neutrophils by 97%. Pancreatic TAP and serum amylase levels increased 2 h and 24 h after induction of pancreatitis. Neutrophil depletion reduced pancreatic TAP and serum amylase levels at 24 h but not at 2 h after pancreatitis induction. Pancreatic MPO and infiltration of neutrophils, as well as MIP-2 levels, were increased 24 h after taurocholate infusion. Two hours after taurocholate administration, no significant pancreatic infiltration of neutrophils was observed. Injection of the anti-Gr-1 antibody abolished MPO activity, neutrophil accumulation, and MIP-2 levels, as well as acinar cell necrosis, hemorrhage, and edema in the pancreas at 24 h. Moreover, taurocholate-provoked tissue damage and MPO activity in the lung were normalized by neutrophil depletion. Intravital fluorescence microscopy revealed a 97% reduction of leukocytes in the pancreatic microcirculation after administration of the anti-Gr-1 antibody. Our data demonstrate that initial trypsinogen activation is independent of neutrophils, whereas later activation is dependent on neutrophils in the pancreas. Neutrophils are critical in mediating pancreatic and lung tissue damage in severe AP.

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.

Lessons from acute pancreatitis-induced thrombotic thrombocytopenic purpura

Acute pancreatitis is an inflammatory disease characterized by local tissue injury which can trigger a systemic inflammatory response. There is increasing evidence that endothelial dysfunction is one of the critical pathophysiologic manifestations in patients with severe form of acute pancreatitis. In keeping with this, there have been recent reports of a haematological disorder, thrombotic thrombocytopenic purpura (TTP), as being precipitated by acute pancreatitis. However, the patients who develop TTP, secondary to acute pancreatitis, do not always have the characteristic low levels of VonWillebrand multimer cleaving enzyme, ADAMTS-13 suggesting the involvement of other pathophysiological factors. On the contrary, the occurrence of acute pancreatitis in haemolytic diseases may suggest TTP as being a precipitating factor for the pancreatic inflammatory state. This review focuses on the association of these two conditions which have given insights into the role players and the pathogenic mechanisms leading to the development of either of these conditions.