Highly sensitive peptide-4-methylcoumaryl-7-amide substrates for blood-clotting proteases and trypsin

The Transmembrane Protease Serine 2 (TMPRSS2) Non-Protease Domains Regulating Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Spike-Mediated Virus Entry

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters cells by binding to the angiotensin-converting enzyme 2 (hACE2) receptor. This process is aided by the transmembrane protease serine 2 (TMPRSS2), which enhances entry efficiency and infectiousness by cleaving the SARS-CoV-2 surface glycoprotein (Spike). The cleavage primes the Spike protein, promoting membrane fusion instead of receptor-mediated endocytosis. Despite the pivotal role played by TMPRSS2, our understanding of its non-protease distinct domains remains limited. In this report, we present evidence indicating the potential phosphorylation of a minimum of six tyrosine residues within the cytosolic tail (CT) of TMPRSS2. Via the use of TMPRSS2 CT phospho-mimetic mutants, we observed a reduction in TMPRSS2 protease activity, accompanied by a decrease in SARS-CoV-2 pseudovirus transduction, which was found to occur mainly via the endosomal pathway. We expanded our investigation beyond TMPRSS2 CT and discovered the involvement of other non-protease domains in regulating infection. Our co-immunoprecipitation experiments demonstrated a strong interaction between TMPRSS2 and Spike. We revealed a 21 amino acid long TMPRSS2-Spike-binding region (TSBR) within the TMPRSS2 scavenger receptor cysteine-rich (SRCR) domain that contributes to this interaction. Our study sheds light on novel functionalities associated with TMPRSS2's cytosolic tail and SRCR region. Both of these regions have the capability to regulate SARS-CoV-2 entry pathways. These findings contribute to a deeper understanding of the complex interplay between viral entry and host factors, opening new avenues for potential therapeutic interventions.

Double deficiency of cathepsin B and L in the mouse pancreas alters trypsin activity without affecting acute pancreatitis severity

BACKGROUND

Premature intracellular trypsinogen activation has long been considered a key initiator of acute pancreatitis (AP). Cathepsin B (CTSB) activates trypsinogen, while cathepsin L (CTSL) inactivates trypsin(ogen), and both proteins play a role in the onset of AP.

METHODS

AP was induced by 7 hourly intraperitoneal injections of cerulein (50 μg/kg) in wild-type and pancreas-specific conditional Ctsb knockout (Ctsb^Δpan), Ctsl knockout (Ctsl^Δpan), and Ctsb;Ctsl double-knockout (Ctsb^Δpan;Ctsl^Δpan) mice. Pancreatic samples were collected and analyzed by histology, immunohistochemistry, real-time PCR, and immunoblots. Trypsin activity was measured in pancreatic homogenates. Peripheral blood was collected, and serum amylase activity was measured.

RESULTS

Double deletion of Ctsb and Cstl did not affect pancreatic development or mouse growth. After 7 times cerulein injections, double Ctsb and Ctsl deficiency in mouse pancreases increased trypsin activity to the same extent as that in Ctsl-deficient mice, while Ctsb deficiency decreased trypsin activity but did not affect the severity of AP. Ctsb^Δpan;Ctsl^Δpan mice had comparable serum amylase activity and histopathological changes and displayed similar levels of proinflammatory cytokines, apoptosis, and autophagy activity compared with wild-type, Ctsb^Δpan, and Ctsl^Δpan mice.

CONCLUSION

Double deletion of Ctsb and Ctsl in the mouse pancreas altered intrapancreatic trypsin activity but did not affect disease severity and inflammatory response after cerulein-induced AP.

New insights into the hemolymph coagulation cascade of horseshoe crabs initiated by autocatalytic activation of a lipopolysaccharide-sensitive zymogen

The concept of a chain reaction of proteolytic activation of multiple protease zymogens was first proposed to explain the blood clotting system in mammals as an enzyme cascade. In multicellular organisms, similar enzyme cascades are widely present in signal transduction and amplification systems. The initiation step of the blood coagulation cascade often consists of autocatalytic activation of the corresponding zymogens located on the surfaces of host- or foreign-derived substances at injured sites. However, the molecular mechanism underlying the concept of autocatalytic activation remains speculative. In this review, we will focus on the autocatalytic activation of prochelicerase C on the surface of lipopolysaccharide as a potential initiator of hemolymph coagulation in horseshoe crabs. Prochelicerase C is presumed to have evolved from a common complement factor in Chelicerata; thus, evolutionary insights into the hemolymph coagulation and complement systems in horseshoe crabs will also be discussed.

USP25 Deficiency Exacerbates Acute Pancreatitis via Up-Regulating TBK1-NF-κB Signaling in Macrophages

BACKGROUND & AIMS

Severe acute pancreatitis can easily lead to systemic inflammatory response syndrome and death. Macrophages are known to be involved in the pathophysiology of acute pancreatitis (AP), and macrophage activation correlates with disease severity. In this study, we examined the role of ubiquitin-specific protease 25, a deubiquitinating enzyme and known regulator of macrophages, in the pathogenesis of AP.

METHODS

We used L-arginine, cerulein, and choline-deficient ethionine-supplemented diet-induced models of AP in Usp25^-/- mice and wild-type mice. We also generated bone marrow Usp25^-/- chimeric mice and initiated L-arginine-mediated AP. Primary acinar cells and bone marrow-derived macrophages were isolated from wild-type and Usp25^-/- mice to dissect molecular mechanisms.

RESULTS

Our results show that Usp25 deficiency exacerbates pancreatic and lung injury, neutrophil and macrophage infiltration, and systemic inflammatory responses in L-arginine, cerulein, and choline-deficient ethionine-supplemented diet-induced models of AP. Bone marrow Usp25^-/- chimeric mice challenged with L-arginine show that Usp25 deficiency in macrophages exaggerates AP by up-regulating the TANK-binding kinase 1 (TBK1)-nuclear factor-κB (NF-κB) signaling pathway. Similarly, in vitro data confirm that Usp25 deficiency enhances the TBK1-NF-κB pathway, leading to increased expression of inflammatory cytokines in bone marrow-derived macrophages.

CONCLUSIONS

Usp25 deficiency in macrophages enhances TBK1-NF-κB signaling, and the induction of inflammatory chemokines and type I interferon-related genes exacerbates pancreatic and lung injury in AP.

Parallel imaging of coagulation pathway proteases activated protein C, thrombin, and factor Xa in human plasma

Activated protein C (APC), thrombin, and factor (f) Xa are vitamin K-dependent serine proteases that are key factors in blood coagulation. Moreover, they play important roles in inflammation, apoptosis, fibrosis, angiogenesis, and viral infections. Abnormal activity of these coagulation factors has been related to multiple conditions, such as bleeding and thrombosis, Alzheimer's disease, sepsis, multiple sclerosis, and COVID-19. The individual activities of APC, thrombin, and fXa in coagulation and in various diseases are difficult to establish since these proteases are related and have similar substrate preferences. Therefore, the development of selective chemical tools that enable imaging and discrimination between coagulation factors in biological samples may provide better insight into their roles in various conditions and potentially aid in the establishment of novel diagnostic tests. In our study, we used a large collection of unnatural amino acids, and this enabled us to extensively explore the binding pockets of the enzymes' active sites. Based on the specificity profiles obtained, we designed highly selective substrates, inhibitors, and fluorescent activity-based probes (ABPs) that were used for fast, direct, and simultaneous detection of APC, thrombin, and fXa in human plasma.

Using a collection of natural and unnatural amino acids, we synthesized a set of fluorescent activity-based probes for the fast, direct, and simultaneous detection of coagulation factors in human plasma.

Transmembrane serine protease 2 (TMPRSS2) proteolytically activates the epithelial sodium channel (ENaC) by cleaving the channel's γ-subunit

The epithelial sodium channel (ENaC) is a heterotrimer consisting of α-, β-, and γ-subunits. Channel activation requires proteolytic release of inhibitory tracts from the extracellular domains of α-ENaC and γ-ENaC; however, the proteases involved in the removal of the γ-inhibitory tract remain unclear. In several epithelial tissues, ENaC is coexpressed with the transmembrane serine protease 2 (TMPRSS2). Here, we explored the effect of human TMPRSS2 on human αβγ-ENaC heterologously expressed in Xenopus laevis oocytes. We found that coexpression of TMPRSS2 stimulated ENaC-mediated whole-cell currents by approximately threefold, likely because of an increase in average channel open probability. Furthermore, TMPRSS2-dependent ENaC stimulation was not observed using a catalytically inactive TMPRSS2 mutant and was associated with fully cleaved γ-ENaC in the intracellular and cell surface protein fractions. This stimulatory effect of TMPRSS2 on ENaC was partially preserved when inhibiting its proteolytic activity at the cell surface using aprotinin but was abolished when the γ-inhibitory tract remained attached to its binding site following introduction of two cysteine residues (S155C–Q426C) to form a disulfide bridge. In addition, computer simulations and site-directed mutagenesis experiments indicated that TMPRSS2 can cleave γ-ENaC at sites both proximal and distal to the γ-inhibitory tract. This suggests a dual role of TMPRSS2 in the proteolytic release of the γ-inhibitory tract. Finally, we demonstrated that TMPRSS2 knockdown in cultured human airway epithelial cells (H441) reduced baseline proteolytic activation of endogenously expressed ENaC. Thus, we conclude that TMPRSS2 is likely to contribute to proteolytic ENaC activation in epithelial tissues in vivo.

A mutant equipped with a regenerated disulfide for the missing his loop of a serine protease zymogen in the horseshoe crab coagulation cascade

The lipopolysaccharide-triggered coagulation cascade in horseshoe crabs is composed of three zymogens belonging to the trypsinogen family: prochelicerase C, prochelicerase B (proB), and the proclotting enzyme (proCE). Trypsinogen-family members contain three conserved disulfides located around the active site. While it is known that proB evolutionarily lost one of the disulfides, the His-loop disulfide, the roles of the missing His-loop disulfide in proB remain unknown. Here we prepared a proB mutant, named proB-murasame, equipped with a regenerated His-loop disulfide. The activation rate by upstream α-chelicerase C for proB-murasame was indistinguishable from that for wild-type (WT) proB. The resulting protease chelicerase B-murasame exhibited an 8-fold higher kcat value for downstream proCE than WT chelicerase B, whereas the Km value of chelicerase B-murasame was equivalent to that of WT chelicerase B. WT serpins-1, -2, and -3, identified as scavengers for the cascade, had no reactivity against WT chelicerase B, whereas chelicerase B-murasame was inhibited by WT serpin-2, suggesting that WT chelicerae B may trigger as-yet-unsolved phenomena after performing its duty in the cascade. The reconstituted lipopolysaccharide-triggered cascade containing proB-murasame exhibited ∼5-fold higher CE production than that containing WT proB. ProB-murasame might be used as a high value-adding reagent for lipopolysaccharide detection.

Zymogen-locked mutant prostasin (Prss8) leads to incomplete proteolytic activation of the epithelial sodium channel (ENaC) and severely compromises triamterene tolerance in mice

AIM

The serine protease prostasin (Prss8) is expressed in the distal tubule and stimulates proteolytic activation of the epithelial sodium channel (ENaC) in co-expression experiments in vitro. The aim of this study was to explore the role of prostasin in proteolytic ENaC activation in the kidney in vivo.

METHODS

We used genetically modified knockin mice carrying a Prss8 mutation abolishing proteolytic activity (Prss8-S238A) or a mutation leading to a zymogen-locked state (Prss8-R44Q). Mice were challenged with low sodium diet and diuretics. Regulation of ENaC activity by Prss8-S238A and Prss8-R44Q was studied in vitro using the Xenopus laevis oocyte expression system.

RESULTS

Co-expression of murine ENaC with Prss8-wt or Prss8-S238A in oocytes caused maximal proteolytic ENaC activation, whereas ENaC was activated only partially in oocytes co-expressing Prss8-R44Q. This was paralleled by a reduced proteolytic activity at the cell surface of Prss8-R44Q expressing oocytes. Sodium conservation under low sodium diet was preserved in Prss8-S238A and Prss8-R44Q mice but with higher plasma aldosterone concentrations in Prss8-R44Q mice. Treatment with the ENaC inhibitor triamterene over four days was tolerated in Prss8-wt and Prss8-S238A mice, whereas Prss8-R44Q mice developed salt wasting and severe weight loss associated with hyperkalemia and acidosis consistent with impaired ENaC function and renal failure.

CONCLUSION

Unlike proteolytically inactive Prss8-S238A, zymogen-locked Prss8-R44Q produces incomplete proteolytic ENaC activation in vitro and causes a severe renal phenotype in mice treated with the ENaC inhibitor triamterene. This indicates that Prss8 plays a role in proteolytic ENaC activation and renal function independent of its proteolytic activity.

Fatty acid ethyl ester (FAEE) associated acute pancreatitis: An ex-vivo study using human pancreatic acini

BACKGROUND & AIM

Fatty acid ethyl esters (FAEEs), are produced by non-oxidative alcohol metabolism and can cause acinar cell damage and subsequent acute pancreatitis in rodent models. Even though experimental studies have elucidated the FAEE mediated early intra-acinar events, these mechanisms have not been well studied in humans. In the present study, we evaluate the early intra-acinar events and inflammatory response in human pancreatic acinar tissues and cells in an ex-vivo model.

METHODS

Experiments were conducted using normal human pancreatic tissues exposed to FAEE. Subcellular fractionation was performed on tissue homogenates and trypsin and cathepsin B activities were estimated in these fractions. Acinar cell injury was evaluated by histology and immunohistochemistry. Cytokine release from exposed acinar cells was evaluated by performing Immuno-fluorescence. Serum was collected from patients with AP within the first 72 h of symptom onset for cytokine estimation using FACS.

RESULTS

We observed significant trypsin activation and acinar cell injury in FAEE treated tissue. Cathepsin B was redistributed from lysosomal to zymogen compartment at 30 min of FAEE exposure. IHC results indicated the presence of apoptosis in pancreatic tissue at 1 & 2hrs of FAEE exposure. We also observed a time dependent increase in secretion of cytokines IL-6, IL-8, TNF-α from FAEE treated acinar tissue. There was also a significant elevation in plasma cytokines in patents with alcohol associated AP within 72 h of symptom onset.

CONCLUSION

Our data suggest that alcohol metabolites can cause acute acinar cell damage and subsequent cytokine release which could eventually culminant in SIRS.

Modeling Thrombin Generation in Plasma under Diffusion and Flow

We investigate the capacity of published numerical models of thrombin generation to reproduce experimentally observed threshold behavior under conditions in which diffusion and/or flow are important. Computational fluid dynamics simulations incorporating species diffusion, fluid flow, and biochemical reactions are compared with published data for thrombin generation in vitro in 1) quiescent plasma exposed to patches of tissue factor and 2) plasma perfused through a capillary coated with tissue factor. Clot time is correctly predicted in individual cases, and some models qualitatively replicate thrombin generation thresholds across a series of tissue factor patch sizes or wall shear rates. Numerical results suggest that there is not a genuine patch size threshold in quiescent plasma-clotting always occurs given enough time-whereas the shear rate threshold observed under flow is a genuine physical limit imposed by flow-mediated washout of active coagulation factors. Despite the encouraging qualitative results obtained with some models, no single model robustly reproduces all experiments, demonstrating that greater understanding of the underlying reaction network, and particularly of surface reactions, is required. In this direction, additional simulations provide evidence that 1) a surface-localized enzyme, speculatively identified as meizothrombin, is significantly active toward the fluorescent thrombin substrate used in the experiments or, less likely, 2) thrombin is irreversibly inhibited at a faster-than-expected rate, possibly explained by a stimulatory effect of plasma heparin on antithrombin. These results highlight the power of simulation to provide novel mechanistic insights that augment experimental studies and build our understanding of complex biophysicochemical processes. Further validation work is critical to unleashing the full potential of coagulation models as tools for drug development and personalized medicine.

Roles of the clip domains of two protease zymogens in the coagulation cascade in horseshoe crabs

The lipopolysaccharide (LPS)-triggered coagulation cascade in horseshoe crabs comprises three protease zymogens: prochelicerase C (proC), prochelicerase B (proB), and the proclotting enzyme (proCE). The presence of LPS results in autocatalytic activation of proC to α-chelicerase C, which, in turn, activates proB to chelicerase B, converting proCE to the clotting enzyme (CE). ProB and proCE contain an N-terminal clip domain, but the roles of these domains in this coagulation cascade remain unknown. Here, using recombinant proteins and kinetics and binding assays, we found that five basic residues in the clip domain of proB are required to maintain its LPS-binding activity and activation by α-chelicerase C. Moreover, an amino acid substitution at a potential hydrophobic cavity in proB's clip domain (V55A-proB) reduced both its LPS-binding activity and activation rate. WT proCE exhibited no LPS-binding activity, and the WT chelicerase B-mediated activation of a proCE variant with a substitution at a potential hydrophobic cavity (V53A-proCE) was ∼4-fold slower than that of WT proCE. The k _cat/K_m value of the interaction of WT chelicerase B with V53A-proCE was 7-fold lower than that of the WT chelicerase B-WT proCE interaction. The enzymatic activities of V55A-chelicerase B and V53A-CE against specific peptide substrates were indistinguishable from those of the corresponding WT proteases. In conclusion, the clip domain of proB recruits it to a reaction center composed of α-chelicerase C and LPS, where α-chelicerase C is ready to activate proB, leading to chelicerase B-mediated activation of proCE via its clip domain.

Measuring digestive protease activation in the mouse pancreas

Intrapancreatic activation of digestive proteases, trypsin and chymotrypsin in particular, is a hallmark of pancreatitis. In experimental rodent models, protease activation is routinely measured from pancreatic homogenates using fluorogenic peptide substrates. Here we investigated the optimal conditions for the determination of intrapancreatic trypsin and chymotrypsin activation elicited by a single intraperitoneal injection of cerulein in C57BL/6N mice. We found that these protease assays were significantly improved by using lower amounts of pancreatic homogenate and exclusion of bovine serum albumin from the assay buffer. Furthermore, pancreatic homogenates had to be freshly prepared and assayed; as freezing and thawing stimulated protease activation. Finally, replacement of the widely used Boc-Gln-Ala-Arg-AMC trypsin substrate with Z-Gly-Pro-Arg-AMC reduced the background activity in saline-treated control mice and thereby increased the extent of cerulein-induced trypsin activation. Using the optimized protocol, we reproducibly measured 20-fold and 200-fold increases in the intrapancreatic trypsin and chymotrypsin activity, respectively, in mice given cerulein.

Enhanced proliferation of pancreatic acinar cells in MRL/MpJ mice is driven by severe acinar injury but independent of inflammation

Adult pancreatic acinar cells have the ability to re-enter the cell cycle and proliferate upon injury or tissue loss. Despite this mitotic ability, the extent of acinar proliferation is often limited and unable to completely regenerate the injured tissue or restore the initial volume of the organ, thus leading to pancreatic dysfunction. Identifying molecular determinants of enhanced proliferation is critical to overcome this issue. In this study, we discovered that Murphy Roths Large (MRL/MpJ) mice can be exploited to identify molecular effectors promoting acinar proliferation upon injury, with the ultimate goal to develop therapeutic regimens to boost pancreatic regeneration. Our results show that, upon cerulein-induced acinar injury, cell proliferation was enhanced and cell cycle components up-regulated in the pancreas of MRL/MpJ mice compared to the control strain C57BL/6. Initial damage of acinar cells was exacerbated in these mice, manifested by increased serum levels of pancreatic enzymes, intra-pancreatic trypsinogen activation and acinar cell apoptosis. In addition, MRL/MpJ pancreata presented enhanced inflammation, de-differentiation of acinar cells and acinar-to-ductal metaplasia. Manipulation of inflammatory levels and mitogenic stimulation with the thyroid hormone 5,3-L-tri-iodothyronine revealed that factors derived from initial acinar injury rather than inflammatory injury promote the replicative advantage in MRL/MpJ mice.

Apixaban decreases brain thrombin activity in a male mouse model of acute ischemic stroke

Factor Xa (FXa) plays a critical role in the coagulation cascade by generation of thrombin. During focal ischemia thrombin levels increase in the brain tissue and cause neural damage. This study examined the hypothesis that administration of the FXa inhibitor, apixaban, following focal ischemic stroke may have therapeutic potential by decreasing brain thrombin activity and infarct volume. Male mice were divided into a treated groups that received different doses of apixaban (2, 20, 100 mg/kg administered I.P.) or saline (controls) immediately after blocking the middle cerebral artery (MCA). Thrombin activity was measured by a fluorescence assay on fresh coronal slices taken from the mice brains 24 hr following the MCA occlusion. Infarct volume was assessed using triphenyltetrazolium chloride staining. A high dose of apixaban (100 mg/kg) significantly decreased thrombin activity levels in the ipsilateral hemisphere compared to the control group (Slice#5, p = .016; Slice#6, p = .016; Slice#7, p = .016; Slice#8, p = .036; by the nonparametric Mann-Whitney test). In addition, treatment with apixaban doses of both 100 mg/kg (32 ± 8% vs. 76 ± 7% in the treatment vs. control groups respectively; p = .005 by the nonparametric Mann-Whitney test) and 20 mg/kg (43 ± 7% vs. 76 ± 7% in the treatment vs. control groups respectively; p = .019 by the nonparametric Mann-Whitney test) decreased infarct volumes in areas surrounding the ischemic core (Slices #3 and #8). No brain hemorrhages were observed either in the treated or control groups. In summary, I.P. administration of high dose of apixaban immediately after MCA occlusion decreases brain thrombin activity and reduces infarct size.

Utilization of Vibrio cholerae as a Model Organism to Screen Natural Product Libraries for Identification of New Antibiotics

The development of antibiotic-resistant bacteria requires increasing research efforts in drug discovery. Vibrio cholerae can be utilized as a model gram-negative enteric pathogen in high- and medium-throughput screening campaigns to identify antimicrobials with different modes of action. In this chapter, we describe methods for the optimal growth of V. cholerae in 384-well plates, preparation of suitable microtiter natural product sample libraries, as well as their screening using measurements of bacterial density and activity of type II secretion-dependent protease as readouts. Concomitant LC-MS/MS profiling and spectral data networking of assay sample libraries facilitate dereplication of putative known and/or nuisance compounds and efficient prioritization of samples containing putative new natural products for further investigation.

Acinar injury and early cytokine response in human acute biliary pancreatitis

Clinical acute pancreatitis (AP) is marked by an early phase of systemic inflammatory response syndrome (SIRS) with multiorgan dysfunction (MODS), and a late phase characterized by sepsis with MODS. However, the mechanisms of acinar injury in human AP and the associated systemic inflammation are not clearly understood. This study, for the first time, evaluated the early interactions of bile acid induced human pancreatic acinar injury and the resulting cytokine response. We exposed freshly procured resected human pancreata to taurolithocolic acid (TLCS) and evaluated for acinar injury, cytokine release and interaction with peripheral blood mononuclear cells (PBMCs). We observed autophagy in acinar cells in response to TLCS exposure. There was also time-dependent release of IL-6, IL-8 and TNF-α from the injured acini that resulted in activation of PBMCs. We also observed that cytokines secreted by activated PBMCs resulted in acinar cell apoptosis and further cytokine release from them. Our data suggests that the earliest immune response in human AP originates within the acinar cell itself, which subsequently activates circulating PBMCs leading to SIRS. These findings need further detailed evaluation so that specific therapeutic targets to curb SIRS and resulting early adverse outcomes could be identified and tested.

The Kunitz Domain I of Hepatocyte Growth Factor Activator Inhibitor-2 Inhibits Matriptase Activity and Invasive Ability of Human Prostate Cancer Cells

Dysregulation of pericellular proteolysis is often required for tumor invasion and cancer progression. It has been shown that down-regulation of hepatocyte growth factor activator inhibitor-2 (HAI-2) results in activation of matriptase (a membrane-anchored serine protease), human prostate cancer cell motility and tumor growth. In this study, we further characterized if HAI-2 was a cognate inhibitor for matriptase and identified which Kunitz domain of HAI-2 was required for inhibiting matriptase and human prostate cancer cell motility. Our results show that HAI-2 overexpression suppressed matriptase-induced prostate cancer cell motility. We demonstrate that HAI-2 interacts with matriptase on cell surface and inhibits matriptase proteolytic activity. Moreover, cellular HAI-2 harnesses its Kunitz domain 1 (KD1) to inhibit matriptase activation and prostate cancer cell motility although recombinant KD1 and KD2 of HAI-2 both show an inhibitory activity and interaction with matriptase protease domain. The results together indicate that HAI-2 is a cognate inhibitor of matriptase, and KD1 of HAI-2 plays a major role in the inhibition of cellular matritptase activation as well as human prostate cancer invasion.

Class I histone deacetylase inhibition improves pancreatitis outcome by limiting leukocyte recruitment and acinar-to-ductal metaplasia

BACKGROUND AND PURPOSE

Pancreatitis is a common inflammation of the pancreas with rising incidence in many countries. Despite improvements in diagnostic techniques, the disease is associated with high risk of severe morbidity and mortality and there is an urgent need for new therapeutic interventions. In this study, we evaluated whether histone deacetylases (HDACs), key epigenetic regulators of gene transcription, are involved in the development of the disease.

EXPERIMENTAL APPROACH

We analysed HDAC regulation during cerulein-induced acute, chronic and autoimmune pancreatitis using different transgenic mouse models. The functional relevance of class I HDACs was tested with the selective inhibitor MS-275 in vivo upon pancreatitis induction and in vitro in activated macrophages and primary acinar cell explants.

KEY RESULTS

HDAC expression and activity were up-regulated in a time-dependent manner following induction of pancreatitis, with the highest abundance observed for class I HDACs. Class I HDAC inhibition did not prevent the initial acinar cell damage. However, it effectively reduced the infiltration of inflammatory cells, including macrophages and T cells, in both acute and chronic phases of the disease, and directly disrupted macrophage activation. In addition, MS-275 treatment reduced DNA damage in acinar cells and limited acinar de-differentiation into acinar-to-ductal metaplasia in a cell-autonomous manner by impeding the EGF receptor signalling axis.

CONCLUSIONS AND IMPLICATIONS

These results demonstrate that class I HDACs are critically involved in the development of acute and chronic forms of pancreatitis and suggest that blockade of class I HDAC isoforms is a promising target to improve the outcome of the disease.

Disruption of Small GTPase Rab7 Exacerbates the Severity of Acute Pancreatitis in Experimental Mouse Models

Although aberrations of intracellular vesicle transport systems towards lysosomes including autophagy and endocytosis are involved in the onset and progression of acute pancreatitis, the molecular mechanisms underlying such aberrations remain unclear. The pathways of autophagy and endocytosis are closely related, and Rab7 plays crucial roles in both. In this study, we analyzed the function of Rab7 in acute pancreatitis using pancreas-specific Rab7 knockout (Rab7Δpan) mice. In Rab7Δpan pancreatic acinar cells, the maturation steps of both endosomes and autophagosomes were deteriorated, and the lysosomal functions were affected. In experimental models of acute pancreatitis, the histopathological severity, serum amylase concentration and intra-pancreatic trypsin activity were significantly higher in Rab7Δpan mice than in wild-type mice. Furthermore, the autophagy process was blocked in Rab7Δpan pancreas compared with wild-type mice. In addition, larger autophagic vacuoles that colocalize with early endosome antigen 1 (EEA1) but not with lysosomal-associated membrane protein (LAMP)-1 were much more frequently formed in Rab7Δpan pancreatic acinar cells. Accordingly, Rab7 deficiency exacerbates the severity of acute pancreatitis by impairing the autophagic and endocytic pathways toward lysosomes.

Moderate plasma dilution using artificial plasma expanders shifts the haemostatic balance to hypercoagulation

Artificial plasma expanders (PEs) are widely used in modern transfusion medicine. PEs do not contain components of the coagulation system, so their infusion in large volumes causes haemodilution and affects haemostasis. However, the existing information on this effect is contradictory. We studied the effect of the very process of plasma dilution on coagulation and tested the hypothesis that moderate dilution with a PE should accelerate clotting owing to a decrease in concentration of coagulation inhibitors. The standard clotting times, a thrombin generation test, and the spatial rate of clot growth (test of thrombodynamics) were used to assess donor plasma diluted in vitro with various PEs. The pH value and Ca⁺² concentration were maintained strictly constant in all samples. The effect of thrombin inhibitors on dilution-induced hypercoagulation was also examined. It was shown that coagulation was enhanced in plasma diluted up to 2.0-2.5-fold with any PE. This enhancement was due to the dilution of coagulation inhibitors in plasma. Their addition to plasma or PE could partially prevent the hypercoagulation shift.

Acute acinar pancreatitis blocks vesicle-associated membrane protein 8 (VAMP8)-dependent secretion, resulting in intracellular trypsin accumulation

Zymogen secretory granules in pancreatic acinar cells express two vesicle-associated membrane proteins (VAMP), VAMP2 and -8, each controlling 50% of stimulated secretion. Analysis of secretion kinetics identified a first phase (0-2 min) mediated by VAMP2 and second (2-10 min) and third phases (10-30 min) mediated by VAMP8. Induction of acinar pancreatitis by supramaximal cholecystokinin (CCK-8) stimulation inhibits VAMP8-mediated mid- and late-phase but not VAMP2-mediated early-phase secretion. Elevation of cAMP during supramaximal CCK-8 mitigates third-phase secretory inhibition and acinar damage caused by the accumulation of prematurely activated trypsin. VAMP8^-/- acini are resistant to secretory inhibition by supramaximal CCK-8, and despite a 4.5-fold increase in total cellular trypsinogen levels, are fully protected from intracellular trypsin accumulation and acinar damage. VAMP8-mediated secretion is dependent on expression of the early endosomal proteins Rab5, D52, and EEA1. Supramaximal CCK-8 (60 min) caused a 60% reduction in the expression of D52 followed by Rab5 and EEA1 in isolated acini and in in vivo The loss of D52 occurred as a consequence of its entry into autophagic vacuoles and was blocked by lysosomal cathepsin B and L inhibition. Accordingly, adenoviral overexpression of Rab5 or D52 enhanced secretion in response to supramaximal CCK-8 and prevented accumulation of activated trypsin. These data support that acute inhibition of VAMP8-mediated secretion during pancreatitis triggers intracellular trypsin accumulation and loss of the early endosomal compartment. Maintaining anterograde endosomal trafficking during pancreatitis maintains VAMP8-dependent secretion, thereby preventing accumulation of activated trypsin.

Novel method to rescue a lethal phenotype through integration of target gene onto the X-chromosome

The loss-of-function mutations of serine protease inhibitor, Kazal type 1 (SPINK1) gene are associated with human chronic pancreatitis, but the underlying mechanisms remain unknown. We previously reported that mice lacking Spink3, the murine homologue of human SPINK1, die perinatally due to massive pancreatic acinar cell death, precluding investigation of the effects of SPINK1 deficiency. To circumvent perinatal lethality, we have developed a novel method to integrate human SPINK1 gene on the X chromosome using Cre-loxP technology and thus generated transgenic mice termed “X-SPINK1“. Consistent with the fact that one of the two X chromosomes is randomly inactivated, X-SPINK1 mice exhibit mosaic pattern of SPINK1 expression. Crossing of X-SPINK1 mice with Spink3^+/− mice rescued perinatal lethality, but the resulting Spink3^−/−;XX^SPINK1 mice developed spontaneous pancreatitis characterized by chronic inflammation and fibrosis. The results show that mice lacking a gene essential for cell survival can be rescued by expressing this gene on the X chromosome. The Spink3^−/−;XX^SPINK1 mice, in which this method has been applied to partially restore SPINK1 function, present a novel genetic model of chronic pancreatitis.

Novel fluorescent substrates for detection of trypsin activity and inhibitor screening by self-quenching

A group of self-quenching-based substrates with two fluorescent peptides for detection of trypsin activity was designed and synthesized. The substrates could be easily synthesized using simple solid-phase peptide synthesis techniques. Two fluorescent peptide substrates for trypsin were conjugated to the amino groups of lysine as a branched unit. The fluorescence of these substrates was self-quenched owing to the highly assembled fluorophores on the substrates. The release of these concentrated fluorophores by proteases allows for fluorescence recovery. Self-quenching reduced the fluorescence of the substrates by 64.1%, and the fluorescence intensity was recovered by the release of the fluorophores from the substrate peptides via tryptic cleavage. The kinetic assay revealed that the k_cat/K_m values of the substrates were almost comparable to those of the standard fluorescent probe, peptide-MCA. The detection limit for trypsin was 111pM, and the calculation of IC₅₀ and K_i values for the Bowman-Birk inhibitor was achieved using these substrates. These easily synthesizable self-quenching-based substrates have the potential to be useful for the detection of other disease-related protease activities.

Release of Cathepsin B in Cytosol Causes Cell Death in Acute Pancreatitis

BACKGROUND & AIMS

Experimental studies in acute pancreatitis (AP) suggest a strong association of acinar cell injury with cathepsin B-dependent intracellular activation of trypsin. However, the molecular events subsequent to trypsin activation and their role, if any, in cell death is not clear. In this study, we have explored intra-acinar events downstream of trypsin activation that lead to acinar cell death.

METHODS

Acinar cells prepared from the pancreas of rats or mice (wild-type, trypsinogen 7, or cathepsin B-deleted) were stimulated with supramaximal cerulein, and the cytosolic activity of cathepsin B and trypsin was evaluated. Permeabilized acini were used to understand the differential role of cytosolic trypsin vs cytosolic cathepsin B in activation of apoptosis. Cell death was evaluated by measuring specific markers for apoptosis and necrosis.

RESULTS

Both in vitro and in vivo studies have suggested that during AP cathepsin B leaks into the cytosol from co-localized organelles, through a mechanism dependent on active trypsin. Cytosolic cathepsin B but not trypsin activates the intrinsic pathway of apoptosis through cleavage of bid and activation of bax. Finally, excessive release of cathepsin B into the cytosol can lead to cell death through necrosis.

CONCLUSIONS

This report defines the role of trypsin in AP and shows that cytosolic cathepsin B but not trypsin activates cell death pathways. This report also suggests that trypsin is a requisite for AP only because it causes release of cathepsin B into the cytosol.

Biomimetic Hybrid Nanocontainers with Selective Permeability

Chemistry plays a crucial role in creating synthetic analogues of biomacromolecular structures. Of particular scientific and technological interest are biomimetic vesicles that are inspired by natural membrane compartments and organelles but avoid their drawbacks, such as membrane instability and limited control over cargo transport across the boundaries. In this study, completely synthetic vesicles were developed from stable polymeric walls and easy-to-engineer membrane DNA nanopores. The hybrid nanocontainers feature selective permeability and permit the transport of organic molecules of 1.5 nm size. Larger enzymes (ca. 5 nm) can be encapsulated and retained within the vesicles yet remain catalytically active. The hybrid structures constitute a new type of enzymatic nanoreactor. The high tunability of the polymeric vesicles and DNA pores will be key in tailoring the nanocontainers for applications in drug delivery, bioimaging, biocatalysis, and cell mimicry.

Purification and characterization of a fish granzymeA involved in cell-mediated immunity

Granzymes are serine proteases involved in the induction of cell death against non-self cells. The enzymes differ in their primary substrate specificity and have one of four hydrolysis activities: tryptase, Asp-ase, Met-ase and chymase. Although granzyme genes have been isolated from several fishes, evidence for their involvement in cytotoxicity has not yet been reported. In the present study, we attempted to purify and characterize a fish granzyme involved in cytotoxicity using ginbuna crucian carp. The cytotoxicity of leukocytes was significantly inhibited by the serine protease inhibitor ''3, 4-dichloroisocoumarin''. In addition, we found that granzymeA-like activity (hydrolysis of Z-GPR-MCA) was inhibited by the same inhibitor and significantly enhanced by allo-antigen stimulation in vivo. Proteins from leukocyte extracts were subjected to two steps of chromatographic purification using benzamidine-Sepharose and SP-Sepharose. The molecular weight of the purified enzyme was estimated to be 26,900 Da by SDS-PAGE analysis. The purified enzyme displayed a Km of 220 μM, a Kcat of 21.7 sec(-1) and a Kcat/Km of 98,796 sec(-1) M(-1) with an optimal pH of 9.5 for the Z-GPR-MCA substrate. The protease was totally inhibited by serine protease inhibitors and showed granzymeA-like substrate specificity. Therefore, we conclude that the purified enzyme belongs to the mammalian granzymeA (EC 3.4.21.78) and appears to be involved in cytotoxicity in fish.

Calibrated kallikrein generation in human plasma

OBJECTIVES

The physiological role of the contact system remains inconclusive. No obvious clinical complications have been observed for factor XII (FXII), prekallikrein (PK), or high molecular weight kininogen deficiencies even though the contact system in vitro is associated with coagulation, fibrinolysis, and inflammation. A global generation assay measuring the initial phase of the contact system could be a valuable tool for studies of its physiological role.

DESIGN AND METHODS

We investigated whether such a method could be developed using the principle of the Calibrated Automated Thrombin generation method as a template.

RESULTS

A suitable kallikrein specific fluorogenic substrate was identified (K_M=0.91mM, k_cat=19s^-1), and kallikrein generation could be measured in undiluted plasma when silica was added as activator. Disturbing effects, including substrate depletion and the inner-filter effect, however, affected the signal. These problems were corrected for by external calibration with α₂-macroglobulin-kallikrein complexes. Selectivity studies of the substrate, experiments with FXII and PK depleted plasmas, and plasma with high or low complement C1-esterase inhibitor activity indicated that the obtained and calibrated signal predominantly was related to FXII-dependent kallikrein activity.

CONCLUSIONS

The findings described show that establishment of a kallikrein generation method is possible. Potentially, this setup could be used for clinical studies of the contact system.

Src kinases play a novel dual role in acute pancreatitis affecting severity but no role in stimulated enzyme secretion

In pancreatic acinar cells, the Src family of kinases (SFK) is involved in the activation of several signaling cascades that are implicated in mediating cellular processes (growth, cytoskeletal changes, apoptosis). However, the role of SFKs in various physiological responses such as enzyme secretion or in pathophysiological processes such as acute pancreatitis is either controversial, unknown, or incompletely understood. To address this, in this study, we investigated the role/mechanisms of SFKs in acute pancreatitis and enzyme release. Enzyme secretion was studied in rat dispersed pancreatic acini, in vitro acute-pancreatitis-like changes induced by supramaximal COOH-terminal octapeptide of cholecystokinin (CCK). SFK involvement assessed using the chemical SFK inhibitor (PP2) with its inactive control, 4-amino-7-phenylpyrazol[3,4-d]pyrimidine (PP3), under experimental conditions, markedly inhibiting SFK activation. In CCK-stimulated pancreatic acinar cells, activation occurred of trypsinogen, various MAP kinases (p42/44, JNK), transcription factors (signal transducer and activator of transcription-3, nuclear factor-κB, activator protein-1), caspases (3, 8, and 9) inducing apoptosis, LDH release reflective of necrosis, and various chemokines secreted (monocyte chemotactic protein-1, macrophage inflammatory protein-1α, regulated on activation, normal T cell expressed and secreted). All were inhibited by PP2, not by PP3, except caspase activation leading to apoptosis, which was increased, and trypsin activation, which was unaffected, as was CCK-induced amylase release. These results demonstrate SFK activation is playing a dual role in acute pancreatitis, inhibiting apoptosis and promoting necrosis as well as chemokine/cytokine release inducing inflammation, leading to more severe disease, as well as not affecting secretion. Thus, our studies indicate that SFK is a key mediator of inflammation and pancreatic acinar cell death in acute pancreatitis, suggesting it could be a potential therapeutic target in acute pancreatitis.

Elastase levels and activity are increased in dystrophic muscle and impair myoblast cell survival, proliferation and differentiation

In Duchenne muscular dystrophy, progressive loss of muscle tissue is accompanied by fibrosis, chronic inflammation and reduced muscle regenerative capacity. Although much is known about the development of fibrosis and chronic inflammation in muscular dystrophy, less is known about how they are mechanistically linked to loss of muscle regenerative capacity. We have developed a proteomics method to discover dystrophy-associated changes in the muscle progenitor cell niche, which identified serine proteases, and especially neutrophil elastase, as candidates. We show that elastase activity is increased in dystrophic (mdx^4cv) muscle and impairs myoblast survival in culture. While the effect of elastase on C2C12 cell survival correlates with the kinetics of elastase-mediated degradation of the substrate to which the cells adhere, the effect of elastase on satellite cell-derived primary myoblast growth and differentiation is substrate-independent and even more dramatic than the effect on C2C12 cells, suggesting a detrimental role for elastase on myogenesis in vivo. Additionally, elastase impairs differentiation of both primary and C2C12 myoblasts into myotubes. Our findings evidence the importance of neutrophil-mediated inflammation in muscular dystrophy and indicate elastase-mediated regulation of myoblast behaviour as a potential mechanism underlying loss of regenerative capacity in dystrophic muscle.

The p21-activated kinase, PAK2, is important in the activation of numerous pancreatic acinar cell signaling cascades and in the onset of early pancreatitis events

In a recent study we explored Group-1-p21-activated kinases (GP.1-PAKs) in rat pancreatic acini. Only PAK2 was present; it was activated by gastrointestinal-hormones/neurotransmitters and growth factors in a PKC-, Src- and small-GTPase-mediated manner. PAK2 was required for enzyme-secretion and ERK/1-2-activation. In the present study we examined PAK2's role in CCK and TPA-activation of important distal signaling cascades mediating their physiological/pathophysiological effects and analyzed its role in pathophysiological processes important in early pancreatitis. In rat pancreatic acini, PAK2-inhibition by the specific, GP.1.PAK-inhibitor, IPA-3-suppressed cholecystokinin (CCK)/TPA-stimulated activation of focal-adhesion kinases and mitogen-activated protein-kinases. PAK2-inhibition reversed the dual stimulatory/inhibitory effect of CCK/TPA on the PI3K/Akt/GSK-3β pathway. However, its inhibition did not affect PKC activation. PAK2-inhibition protected acini from CCK-induced ROS-generation; caspase/trypsin-activation, important in early pancreatitis; as well as from cell-necrosis. Furthermore, PAK2-inhibition reduced proteolytic-activation of PAK-2p34, which is involved in programmed-cell-death. To ensure that the study did not only rely in the specificity of IPA-3 as a PAK inhibitor, we used two other approaches for PAK inhibition, FRAX597 a ATP-competitive-GP.1-PAKs-inhibitor and infection with a PAK2-dominant negative(DN)-Advirus. Those two approaches confirmed the results obtained with IPA-3. This study demonstrates that PAK2 is important in mediating CCK's effect on the activation of signaling-pathways known to mediate its physiological/pathophysiological responses including several cellular processes linked to the onset of pancreatitis. Our results suggest that PAK2 could be a new, important therapeutic target to consider for the treatment of diseases involving deregulation of pancreatic acinar cells.

A novel histochemical method for the visualization of thrombin activity in the nervous system

Although thrombin has an important role in both central and peripheral nerve diseases, characterization of the anatomical distribution of its proteolytic activity has been limited by available methods. This study presents the development, challenges, validation and implementation of a novel histochemical method for visualization of thrombin activity in the nervous system. The method is based on the cleavage of the substrate, Boc-Asp(OBzl)-Pro-Arg-4MβNA by thrombin to liberate free 4-methoxy-2-naphthylamine (4MβNA). In the presence of 5-nitrosalicylaldehyde, free 4MβNA is captured, yielding an insoluble yellow fluorescent precipitate which marks the site of thrombin activity. The sensitivity of the method was determined in vitro using known concentrations of thrombin while the specificity was verified using a highly specific thrombin inhibitor. Using this method we determined the spatial distribution of thrombin activity in mouse brain following transient middle cerebral artery occlusion (tMCAo) and in mouse sciatic nerve following crush injury. Fluorescence microscopy revealed well-defined thrombin activity localized to the right ischemic hemisphere in cortical areas and in the striatum compared to negligible thrombin activity contralaterally. The histochemical localization of thrombin activity following tMCAo was in good correlation with the infarct areas per triphenyltetrazolium chloride staining and to thrombin activity measured biochemically in tissue punches (85 ± 35 and 20 ± 3 mU/ml, in the cortical and striatum areas respectively, compared to 7 ± 2 and 13 ± 2 mU/ml, in the corresponding contralateral areas; mean ± SEM; p<0.05). In addition, 24 h following crush injury, focal areas of highly elevated thrombin activity were detected in teased sciatic fibers. This observation was supported by the biochemical assay and western blot technique. The histochemical method developed in this study can serve as an important tool for studying the role of thrombin in physiological and pathological conditions.

Hydrogen Peroxide-Induced Oxidative Stress Activates Proteasomal Trypsin-Like Activity in Human U373 Glioma Cells

Degradation of oxidized or oxidatively modified proteins is an essential part of the cellular antioxidant defense system. 4-Hydroxy-2-nonenal, a major reactive aldehyde formed by lipid peroxidation, causes many types of cellular damage. The major proteolytic system for modified protein degradation is the ubiquitin-proteasome pathway. However, our previous studies using U937 human leukemic cells showed that 4-hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is degraded by cathepsin G. In the present study, U373 human glioma cells were cultured in the presence of hydrogen peroxide (H2O2) to investigate the relationships of proteasome and/or cathepsin G activities and H2O2-induced GAPDH degradation. Treatment of cells with H2O2 for 5 h in culture decreased GAPDH activity as well as its protein concentration in a concentration-dependent manner. Two proteasomal activities (peptidylglutamyl-peptide hydrolase and chymotrypsin-like hydrolase activities) and cathepsin G activity were decreased by H2O2 treatment in a concentration-dependent manner, but proteasomal trypsin-like hydrolase activity increased with cell exposure to high H2O2 concentrations. Among the protease inhibitors examined here, H2O2-induced activation of trypsin-like activity and GAPDH degradation were inhibited by the proteasome inhibitor lactacystin. Furthermore, H2O2-induced activation of trypsin-like activity was also inhibited by another proteasome inhibitor MG-132. These results suggested that proteasomal trypsin-like activity played an important role in eliminating oxidatively modified GAPDH formed in these cells during H2O2 exposure.

Early to Late Endosome Trafficking Controls Secretion and Zymogen Activation in Rodent and Human Pancreatic Acinar Cells

BACKGROUND & AIMS

Pancreatic acinar cells have an expanded apical endosomal system, the physiological and pathophysiological significance of which is still emerging. Phosphatidylinositol-3,5-bisphosphate (PI(3,5)P₂) is an essential phospholipid generated by PIKfyve, which phosphorylates phosphatidylinositol-3-phosphate (PI(3)P). PI(3,5)P₂ is necessary for maturation of early endosomes (EE) to late endosomes (LE). Inhibition of EE to LE trafficking enhances anterograde endosomal trafficking and secretion at the plasma membrane by default through a recycling endosome (RE) intermediate. We assessed the effects of modulating PIKfyve activity on apical trafficking and pancreatitis responses in pancreatic acinar cells.

METHODS

Inhibition of EE to LE trafficking was achieved using pharmacological inhibitors of PIKfyve, expression of dominant negative PIKfyve K1877E, or constitutively active Rab5-GTP Q79L. Anterograde endosomal trafficking was manipulated by expression of constitutively active and dominant negative Rab11a mutants. The effects of these agents on secretion, endolysosomal exocytosis of lysosome associated membrane protein (LAMP1), and trypsinogen activation in response to high-dose CCK-8, bile acids and cigarette toxin was determined.

RESULTS

PIKfyve inhibition increased basal and stimulated secretion. Adenoviral overexpression of PIKfyve decreased secretion leading to cellular death. Expression of Rab5-GTP Q79L or Rab11a-GTP Q70L enhanced secretion. Conversely, dominant-negative Rab11a-GDP S25N reduced secretion. High-dose CCK inhibited endolysosomal exocytosis that was reversed by PIKfyve inhibition. PIKfyve inhibition blocked intracellular trypsin accumulation and cellular damage responses to high CCK-8, tobacco toxin, and bile salts in both rodent and human acini.

CONCLUSIONS

These data demonstrate that EE-LE trafficking acutely controls acinar secretion and the intracellular activation of zymogens leading to the pathogenicity of acute pancreatitis.

Histone deacetylase regulates trypsin activation, inflammation, and tissue damage in acute pancreatitis in mice

BACKGROUND

The onset of acute pancreatitis (AP) is characterized by early protease activation followed by inflammation and organ damage, but the mechanisms are poorly understood.

AIMS

We hypothesized that histone deacetylase (HDAC) inhibition might exert protective effects on AP and investigated the role of HDAC in trypsin activation, inflammation, and tissue damage in severe AP.

METHODS

Male C57Bl/6 mice were treated i.p. with the HDAC inhibitor trichostatin A (2 mg/kg) prior to retrograde infusion of taurocholic acid (5 %) into the pancreatic duct. Serum levels of amylase and interleukin (IL)-6, pancreatic levels of macrophage inflammatory protein-2 (MIP-2) as well as tissue morphology and myeloperoxidase activity in the pancreas and lung were determined 24 h after taurocholate challenge. Trypsin activation was analyzed in isolated acinar cells. Quantitative RT-PCR was used to examine the expression of pro-inflammatory mediators in the pancreas.

RESULTS

Pretreatment with trichostatin A decreased amylase levels by 70 % and protected against tissue injury in the pancreas. Moreover, HDAC inhibition reduced systemic IL-6 by more than 95 % and pulmonary myeloperoxidase activity by 75 %. Notably, inhibition of HDAC abolished taurocholate-induced gene expression of cyclooxygenase-2, MIP-2, monocyte chemotactic protein-1, IL-6, and IL-1β in the pancreas. In addition, HDAC inhibition reduced cerulein-induced trypsinogen activation in isolated acinar cells.

CONCLUSION

Our findings show that HDAC regulates trypsin activation, inflammation, and tissue damage in AP. Thus, targeting HDAC could serve as novel therapeutic approach in the management of severe AP.

Contact activation of blood coagulation on a defined kaolin/collagen surface in a microfluidic assay

Generation of active Factor XII (FXIIa) triggers blood clotting on artificial surfaces and may also enhance intravascular thrombosis. We developed a patterned kaolin (0 to 0.3 pg/μm(2))/type 1 collagen fibril surface for controlled microfluidic clotting assays. Perfusion of whole blood (treated only with a low level of 4 μg/mL of the XIIa inhibitor, corn trypsin inhibitor) drove platelet deposition followed by fibrin formation. At venous wall shear rate (100 s(-1)), kaolin accelerated onset of fibrin formation by ~100 sec when compared to collagen alone (250 sec vs. 350 sec), with little effect on platelet deposition. Even with kaolin present, arterial wall shear rate (1000 s(-1)) delayed and suppressed fibrin formation compared to venous wall shear rate. A comparison of surfaces for extrinsic activation (tissue factor TF/collagen) versus contact activation (kaolin/collagen) that each generated equal platelet deposition at 100 s(-1) revealed: (1) TF surfaces promoted much faster fibrin onset (at 100 sec) and more endpoint fibrin at 600 sec at either 100 s(-1) or 1000 s(-1), and (2) kaolin and TF surfaces had a similar sensitivity for reduced fibrin deposition at 1000 s(-1) (compared to fibrin formed at 100 s(-1)) despite differing coagulation triggers. Anti-platelet drugs inhibiting P2Y1, P2Y12, cyclooxygenase-1 or activating IP-receptor or guanylate cyclase reduced platelet and fibrin deposition on kaolin/collagen. Since FXIIa or FXIa inhibition may offer safe antithrombotic therapy, especially for biomaterial thrombosis, these defined collagen/kaolin surfaces may prove useful in drug screening tests or in clinical diagnostic assays of blood under flow conditions.

Vesicle associated membrane protein 8 (VAMP8)-mediated zymogen granule exocytosis is dependent on endosomal trafficking via the constitutive-like secretory pathway

Acinar cell zymogen granules (ZG) express 2 isoforms of the vesicle-associated membrane protein family (VAMP2 and -8) thought to regulate exocytosis. Expression of tetanus toxin to cleave VAMP2 in VAMP8 knock-out (-/-) acini confirmed that VAMP2 and -8 are the primary VAMPs for regulated exocytosis, each contributing ∼50% of the response. Analysis of VAMP8(-/-) acini indicated that although stimulated secretion was significantly reduced, a compensatory increase in constitutive secretion maintained total secretion equivalent to wild type (WT). Using a perifusion system to follow secretion over time revealed VAMP2 mediates an early rapid phase peaking and falling within 2-3 min, whereas VAMP8 controls a second prolonged phase that peaks at 4 min and slowly declines over 20 min to support the protracted secretory response. VAMP8(-/-) acini show increased expression of the endosomal proteins Ti-VAMP7 (2-fold) and Rab11a (4-fold) and their redistribution from endosomes to ZGs. Expression of GDP-trapped Rab11a-S25N inhibited secretion exclusively from the VAMP8 but not the VAMP2 pathway. VAMP8(-/-) acini also showed a >90% decrease in the early endosomal proteins Rab5/D52/EEA1, which control anterograde trafficking in the constitutive-like secretory pathway. In WT acini, short term (14-16 h) culture also results in a >90% decrease in Rab5/D52/EEA1 and a complete loss of the VAMP8 pathway, whereas VAMP2-secretion remains intact. Remarkably, rescue of Rab5/D52/EEA1 expression restored the VAMP8 pathway. Expressed D52 shows extensive colocalization with Rab11a and VAMP8 and partially copurifies with ZG fractions. These results indicate that robust trafficking within the constitutive-like secretory pathway is required for VAMP8- but not VAMP2-mediated ZG exocytosis.

Farnesyltransferase regulates neutrophil recruitment and tissue damage in acute pancreatitis

OBJECTIVES

The signaling mechanisms controlling organ damage in the pancreas in severe acute pancreatitis (AP) remain elusive. Herein, we examined the role of farnesyltransferase signaling in AP.

METHODS

Pancreatitis was provoked by the infusion of taurocholate into the pancreatic duct in C57BL/6 mice. Animals were treated with a farnesyltransferase inhibitor FTI-277 (25 mg/kg) before pancreatitis induction.

RESULTS

FTI-277 decreased the blood amylase levels, pancreatic neutrophil infiltration, hemorrhage, and edema formation in the pancreas in mice challenged with taurocholate. Farnesyltransferase inhibition reduced the myeloperoxidase levels in the pancreas and lungs in response to taurocholate infusion. However, FTI-277 had no effect on the taurocholate-provoked formation of macrophage inflammatory protein-2 in the pancreas. Interestingly, farnesyltransferase inhibition abolished the neutrophil expression of macrophage-1 antigen in mice with pancreatitis. In addition, FTI-277 decreased the taurocholate-induced activation of the rat sarcoma protein in the pancreas. An important role of farnesyltransferase was confirmed in L-arginine-induced pancreatitis.

CONCLUSIONS

These results demonstrate that farnesyltransferase signaling plays a significant role in AP by regulating neutrophil infiltration and tissue injury via the neutrophil expression of macrophage-1 antigen. Thus, our findings not only elucidate novel signaling mechanisms in pancreatitis but also suggest that farnesyltransferase might constitute a target in the management of severe AP.

Factor VIII assay mimicking in vivo coagulation conditions

Under certain circumstances, the determination of coagulation factor VIII (FVIII) is hampered by assay discrepancies between clotting and chromogenic approaches. These are observed in certain patients' plasma as well as in certain concentrates. We intended to develop a novel assay for the quantification of coagulation FVIII which reflects the physiological situation better than the established assays. It is based on plasma without chelation of divalent cations and simultaneously minimizes the generation of activated factors which could function as uncontrolled triggers of coagulation. FVIII deficient plasma is prepared with the aid of biotinylated antibodies against FVIII from normal plasma in presence of inhibitors of contact activation. To start the assay only tiny amounts of activated FIX serve as trigger. The FVIII determination is performed in a kinetic experiment and is based on the cleavage of a fluorogenic substrate for activated FX. FVIII concentrations between 0.01 and 1 IU mL(-1) are easily determined. Plasma-derived and recombinant FVIII concentrates were compared. All plasma-derived concentrates were found to contain FVIII activities within the specification of the manufacturer. Recombinant concentrates yielded only 35-50% of the claimed potency. The novel in vivo-like assay avoids the undue advantage or disadvantage of certain product characteristics by eliminating unphysiological assay conditions. Its usefulness could turn out in future experiments with plasma from haemophilia A patients.

Quantitative detection of thrombin activity in an ischemic stroke model

Thrombin, a central factor in thrombogenesis, affects cells in the brain through protease activated receptors. Low levels of thrombin activity are neuroprotective while higher levels are deleterious, and we have therefore developed a new method for its direct quantitative measurement in brain slices following stroke. Thrombin activity was measured by a fluorescent substrate on fresh coronal slices taken from the ipsilateral and contralateral hemispheres 24-72 h following permanent right middle cerebral artery occlusion. Prolyl endopeptidase and aminopeptidases were inhibited as a critical step to insure the specificity of the assay for thrombin detection. Infarct volume was assessed using TTC staining. Thrombin activity in the right ischemic hemisphere was significantly higher compared to the contralateral hemisphere (32 ± 6 and 27 ± 10 mU/ml, mean ± SE in the two most affected slices from the ischemic hemisphere vs. 21 ± 6 and 8 ± 2 mU/ml in corresponding contralateral slices; p < 0.05). Thrombin levels in the ischemic and contralateral hemispheres were significantly higher compared to healthy control mice and were above the range known to be protective to brain cells. A significant correlation was found between thrombin activity in the ischemic hemisphere and the infarct volume. Results of studies based on this method may translate into potential thrombin based therapies.

Src Dependent Pancreatic Acinar Injury Can Be Initiated Independent of an Increase in Cytosolic Calcium

Several deleterious intra-acinar phenomena are simultaneously triggered on initiating acute pancreatitis. These culminate in acinar injury or inflammatory mediator generation in vitro and parenchymal damage in vivo. Supraphysiologic caerulein is one such initiator which simultaneously activates numerous signaling pathways including non-receptor tyrosine kinases such as of the Src family. It also causes a sustained increase in cytosolic calcium- a player thought to be crucial in regulating deleterious phenomena. We have shown Src to be involved in caerulein induced actin remodeling, and caerulein induced changes in the Golgi and post-Golgi trafficking to be involved in trypsinogen activation, which initiates acinar cell injury. However, it remains unclear whether an increase in cytosolic calcium is necessary to initiate acinar injury or if injury can be initiated at basal cytosolic calcium levels by an alternate pathway. To study the interplay between tyrosine kinase signaling and calcium, we treated mouse pancreatic acinar cells with the tyrosine phosphatase inhibitor pervanadate. We studied the effect of the clinically used Src inhibitor Dasatinib (BMS-354825) on pervanadate or caerulein induced changes in Src activation, trypsinogen activation, cell injury, upstream cytosolic calcium, actin and Golgi morphology. Pervanadate, like supraphysiologic caerulein, induced Src activation, redistribution of the F-actin from its normal location in the sub-apical area to the basolateral areas, and caused antegrade fragmentation of the Golgi. These changes, like those induced by supraphysiologic caerulein, were associated with trypsinogen activation and acinar injury, all of which were prevented by Dasatinib. Interestingly, however, pervanadate did not cause an increase in cytosolic calcium, and the caerulein induced increase in cytosolic calcium was not affected by Dasatinib. These findings suggest that intra-acinar deleterious phenomena may be initiated independent of an increase in cytosolic calcium. Other players resulting in acinar injury along with the Src family of tyrosine kinases remain to be explored.

Inhibition of geranylgeranyltransferase attenuates neutrophil accumulation and tissue injury in severe acute pancreatitis

Leukocyte infiltration and acinar cell necrosis are hallmarks of severe AP, but the signaling pathways regulating inflammation and organ injury in the pancreas remain elusive. In the present study, we investigated the role of geranylgeranyltransferase in AP. Male C57BL/6 mice were treated with a geranylgeranyltransferase inhibitor GGTI-2133 (20 mg/kg) prior to induction of pancreatitis by infusion of taurocholate into the pancreatic duct. Pretreatment with GGTI-2133 reduced plasma amylase levels, pancreatic neutrophil recruitment, hemorrhage, and edema formation in taurocholate-evoked pancreatitis. Moreover, administration of GGTI-2133 decreased the taurocholate-induced increase of MPO activity in the pancreas and lung. Treatment with GGTI-2133 markedly reduced levels of CXCL2 in the pancreas and IL-6 in the plasma in response to taurocholate challenge. Notably, geranylgeranyltransferase inhibition abolished neutrophil expression of Mac-1 in mice with pancreatitis. Finally, inhibition of geranylgeranyltransferase had no direct effect on secretagogue-induced activation of trypsinogen in pancreatic acinar cells in vitro. A significant role of geranylgeranyltransferase was confirmed in an alternate model of AP induced by L-arginine challenge. Our findings show that geranylgeranyltransferase regulates neutrophil accumulation and tissue damage via expression of Mac-1 on neutrophils and CXCL2 formation in AP. Thus, these results reveal new signaling mechanisms in pancreatitis and indicate that targeting geranylgeranyltransferase might be an effective way to ameliorate severe AP.

NFATc3 regulates trypsinogen activation, neutrophil recruitment, and tissue damage in acute pancreatitis in mice

BACKGROUND & AIMS

The signaling mechanisms that regulate trypsinogen activation and inflammation in acute pancreatitis (AP) are unclear. We explored the involvement of the calcium- and calcineurin-dependent transcription factor nuclear factor of activated T cells (NFAT) in development of AP in mice.

METHODS

We measured levels of myeloperoxidase and macrophage inflammatory protein 2 (CXCL2), trypsinogen activation, and tissue damage in the pancreas 24 hours after induction of AP by retrograde infusion of taurocholate into the pancreatic ducts of wild-type, NFAT luciferase reporter (NFAT-luc), and NFATc3-deficient mice. We isolated acinar cells and measured NFAT nuclear accumulation, trypsin activity, and expression of NFAT-regulated genes.

RESULTS

Infusion of taurocholate increased the transcriptional activity of NFAT in the pancreas, aorta, lung, and spleen of NFAT-luc mice. Inhibition of NFAT with A-285222 blocked taurocholate-induced activation of NFAT in all organs. A-285222 also reduced taurocholate-induced increases in levels of amylase, myeloperoxidase, and CXCL2; activation of trypsinogen; necrosis of acinar cells; edema; leukocyte infiltration; and hemorrhage in the pancreas. NFATc3-deficient mice were protected from these effects of taurocholate. Similar results were obtained using an l-arginine-induced model of AP. Reverse-transcription polymerase chain reaction and confocal immunofluorescence analyses showed that NFATc3 is expressed by acinar cells. NFATc3 expression was activated by stimuli that increase intracellular calcium levels, and activation was prevented by the calcineurin blocker cyclosporin A or A-285222. Activation of trypsinogen by secretagogues in acinar cells was prevented by pharmacologic inhibition of NFAT signaling or lack of NFATc3. A-285222 also reduced expression of inflammatory cytokines such as CXCL2 in acinar cells.

CONCLUSIONS

NFATc3 regulates trypsinogen activation, inflammation, and pancreatic tissue damage during development of AP in mice and might be a therapeutic target.

A contaminant trypsin-like activity from the timothy grass pollen is responsible for the conflicting enzymatic behavior of the major allergen Phl p 1

We intend to solve whether or not Phl p 1 can be regarded as a protease. A group reported that Phl p 1 has papain-like properties and later on, that this allergen resembles cathepsin B, while another one demonstrated that Phl p 1 lacks proteinase activity and suggested that the measured activity may rise either from a recombinant Phl p 1 contaminant or as a result of an incompletely purified natural allergen. A third group reported Phl p 1 to act by a non-proteolytic activity mechanism. We report the purification of the natural Phl p 1 by means of hydrophobic interaction, gel filtration and STI-Sepharose affinity chromatographies. The Phl p 1 purity was assessed by silver-stained SDS-PAGE and by 'in-gel' and 'gel-free' approaches associated to mass spectrometry analyses. The proteolytic activity was measured using Boc-Gln-Ala-Arg-AMC and Z-Phe-Arg-AMC as substrates. While amidolytic activity could be measured with Phl p 1 after rechromatography on gel filtration, it however completely disappeared after chromatography on STI-Sepharose. The contaminant activity co-eluting with Phl p 1 was not affected by cysteine proteases inhibitors and other thiol-blocking agents, by metalloproteases inhibitors and by aspartic proteases inhibitors. However, it was completely inhibited by low molecular weight and proteinaceous serine proteases inhibitors. TLCK, but not TPCK, inhibited the contaminant activity, showing a trypsin-like behavior. The pH and temperature optimum were 8.0 and 37°C, respectively. These data indicated that Phl p 1 is not a protease. The contaminant trypsin-like activity should be considered when Phl p 1 allergenicity is emphasized.

Pancreatic secretory trypsin inhibitor I reduces the severity of chronic pancreatitis in mice overexpressing interleukin-1β in the pancreas

IL-1β is believed to play a pathogenic role in the development of pancreatitis. Expression of human IL-1β in pancreatic acinar cells produces chronic pancreatitis, characterized by extensive intrapancreatic inflammation, atrophy, and fibrosis. To determine if activation of trypsinogen is important in the pathogenesis of chronic pancreatitis in this model, we crossed IL-1β transgenic [Tg(IL1β)] mice with mice expressing a trypsin inhibitor that is normally produced in rat pancreatic acinar cells [pancreatic secretory trypsin inhibitor (PTSI) I]. We previously demonstrated that transgenic expression of PSTI-I [Tg(Psti1)] increased pancreatic trypsin inhibitor activity by 190%. Tg(IL1β) mice were found to have marked pancreatic inflammation, characterized by histological changes, including acinar cell loss, inflammatory cell infiltration, and fibrosis, as well as elevated myeloperoxidase activity and elevated pancreatic trypsin activity, as early as 6 wk of age. In contrast to Tg(IL1β) mice, pancreatitis was significantly less severe in dual-transgenic [Tg(IL1β)-Tg(Psti1)] mice expressing IL-1β and PSTI-I in pancreatic acinar cells. These findings indicate that overexpression of PSTI-I reduces the severity of pancreatitis and that pancreatic trypsin activity contributes to the pathogenesis of an inflammatory model of chronic pancreatitis.