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Time-resolved immunofluorometric assays for trypsinogen-1 and 2 in serum reveal preferential elevation of trypsinogen-2 in pancreatitis.

We have developed sensitive time-resolved immunofluorometric assays for the two trypsinogen isoenzymes, trypsinogen-1 and trypsinogen-2, which also are called cationic and anionic trypsinogen, respectively. The assays use monoclonal antibodies produced by immunization with tumor-associated trypsinogen that is isolated from mucinous ovarian cyst fluid. In each assay, one antibody is immobilized onto the walls of polystyrene microtiter strip wells and the other is labeled with an europium(III) chelate. The cross-reaction of each trypsinogen isoenzyme in the assay for the other isoenzyme is less than 1%. The detection limits are 0.1 micrograms/L for trypsinogen-1 and 0.3 micrograms/L for trypsinogen-2. In sera of healthy subjects and patients with extrapancreatic disease the concentration of trypsinogen-1 is higher (median, 21 micrograms/L) than that of trypsinogen-2 (median, 17 micrograms/L), but in acute pancreatitis the ratio is reversed. In acute pancreatitis the concentration of trypsinogen-2 is 50-fold higher than in controls, whereas the difference in trypsinogen-1 concentrations is only 15-fold. The corresponding difference in immunoreactive trypsin measured by a commercially available radioimmunoassay was also only 10-fold.

Acute Disease↗

Interaction between trypsinogen isoforms in genetically determined pancreatitis: mutation E79K in cationic trypsin (PRSS1) causes increased transactivation of anionic trypsinogen (PRSS2).

The human pancreas secretes two major trypsinogen isoforms, cationic and anionic trypsinogen. To date, 19 genetic variants have been identified in the cationic trypsinogen gene (PRSS1) of patients with hereditary, familial, or sporadic chronic pancreatitis. A common feature of cationic trypsinogen mutants studied so far is an increased propensity for autocatalytic activation (autoactivation). This is thought to lead to premature intrapancreatic digestive protease activation. In contrast, no pancreatitis-associated mutations have been found in the anionic trypsinogen gene (PRSS2), suggesting that this isoform might play a relatively unimportant role in pancreatitis. To challenge this notion, here we describe the unique properties of the E79K cationic trypsinogen mutation (c.235G>A), which was identified in three European families affected by sporadic or familial pancreatitis cases. In vitro analysis of recombinant wild-type and mutant enzymes revealed that catalytic activity of E79K trypsin was normal, and its inhibition by pancreatic secretory trypsin inhibitor was unaffected. Although the E79K mutation introduces a potential new tryptic cleavage site, autocatalytic degradation (autolysis) of E79K-trypsin was also unchanged. Furthermore, in contrast to previously characterized disease-causing mutations, E79K markedly inhibited autoactivation of cationic trypsinogen. Remarkably, however, E79K trypsin activated anionic trypsinogen two-fold better than wild-type cationic trypsin did, while the common pancreatitis-associated mutants R122H or N29I had no such effect. The observations not only suggest a novel mechanism of action for pancreatitis-associated trypsinogen mutations, but also highlight the importance of interactions between the two major trypsinogen isoforms in the development of genetically determined chronic pancreatitis.

Adult↗

Acute pancreatitis in Soweto, South Africa: relationship between trypsinogen load, trypsinogen activation, and fibrinolysis.

OBJECTIVE: It is not known why acute pancreatitis in Soweto, South Africa, pursues an aggressive course. We sought clues from circulating trypsinogen load at admission as marker of initial acinar injury, trypsinogen activation using the carboxypeptidase B activation peptide as surrogate, proteinase inhibitors, the coagulation-fibrinolysis axis, indicators of inflammation, oxidative stress markers, and antioxidant status. This article reports on the first four aspects. METHODS: The study involved 24 consecutive patients with a first attack. All of them were admitted within 24 h, and 22 were alcoholic. Urine was analyzed for anionic trypsinogen and the carboxypeptidase B activation peptide. Serum was tested for anionic and cationic trypsinogen, alpha1 proteinase inhibitor and alpha2 macroglobulin. Plasma from a subset was assayed for soluble fibrin, cross-linked fibrin degradation products (surrogates for thrombin and plasmin activity, respectively), and tissue-type plasminogen activator and inhibitor. RESULTS: Soweto controls had higher serum anionic trypsinogen (p = 0.004) and plasminogen activator:inhibitor ratio (p = 0.047) than U.K. controls. The outcome of acute pancreatitis was mild in 17 but severe in seven with three deaths, two on day 2. In mild pancreatitis, intense plasmin activity (p < 0.001) accompanied the surge in trypsinogen, especially anionic (p < 0.001), but without increased thrombin activity and in five patients without trypsinogen activation. In severe pancreatitis, further significant increments in plasmin activity and trypsinogens were accompanied by increased thrombin activity (p = 0.013) and trypsinogen activation (p = 0.046). There was no correlation between surrogates of plasmin and thrombin activity, or between either and the carboxypeptidase B activation peptide, which showed a curvilinear relationship to total serum trypsinogen. CONCLUSIONS: The aggressive nature of alcoholic acute pancreatitis in Soweto seems to reflect early profound fibrinolysis, which precedes coagulation and is initially independent of trypsin. Subclinical acinar-cell injury and a profibrinolytic diathesis in outwardly healthy Sowetans may predispose to this problem.

Acute Disease↗

Differential regulation of trypsinogen mRNA translation: full-length mRNA sequences encoding two oppositely charged trypsinogen isoenzymes in the dog pancreas.

In the absence of changes in functional mRNA levels, stimulation of the pancreas with caerulein, a peptide analog of cholecystokinin, has been previously shown to increase the synthesis of anionic but not cationic trypsinogen. To look for structure-function correlations, a high-yield, full-length cDNA library has been constructed from canine pancreatic poly(A)+ mRNA. Full-length clones coding for the two major trypsinogen isoenzyme forms have been identified by colony hybridization and verified by in vitro translation of hybrid-selected mRNA in the presence of microsomal membranes and an optimal redox potential. Disulfide-bonded translation products were separated and identified by two-dimensional isoelectric focusing-sodium dodecyl sulfate-gel electrophoresis. Nucleotide sequence analysis allowed us to deduce the amino acid sequences for the anionic and cationic forms of canine trypsinogen, which contain 232 and 231 residues, respectively (77% amino acid identity), and the 15-residue amino terminal signal sequences (53% amino acid identity) associated with the two presecretory forms. Measurements of relative and absolute mRNA levels, when related to relative protein synthesis values, indicated that the translational efficiency of anionic trypsinogen mRNA exceeded that of cationic trypsinogen mRNA by 1.5- to 2.9-fold under basal conditions. Analysis of the 5' noncoding regions of trypsinogen mRNAs revealed a striking conservation of sequence (10 of 12 bases) between dog and rat anionic trypsinogen forms. This contrasted markedly with the divergence of the 5' noncoding regions observed between dog anionic and cationic trypsinogen mRNAs.

Amino Acid Sequence↗

Expression of trypsinogen-1, trypsinogen-2, and tumor-associated trypsin inhibitor in ovarian cancer: prognostic study on tissue and serum.

PURPOSE: The purpose is to study the prognostic significance of tissue expression of trypsinogen-1, trypsinogen-2, and tumor-associated trypsin inhibitor (TATI) and serum concentration of trypsinogen-2, trypsin-2-API (complex of trypsin-2 with alpha-1-proteinase inhibitor), and TATI in epithelial ovarian cancer. EXPERIMENTAL DESIGN: Expression of trypsinogen-1, trypsinogen-2, and TATI was determined by immunohistochemistry with monoclonal antibodies in tissue sections of tumors from 119 patients with untreated primary epithelial ovarian cancer. Preoperative serum concentrations of trypsinogen-2, trypsin-2-API and TATI were analyzed using specific immunoassays. RESULTS: Fifty-four percent of the tumors expressed trypsinogen-1, 45% expressed trypsinogen-2, and 30% expressed TATI. In patients with stage III and IV disease, TATI tissue expression (P = 0.002) and elevated TATI concentration in serum (P = 0.048) were associated with adverse cancer-specific and progression-free survival in univariate analysis. In multivariate analysis, TATI tissue expression (P = 0.005), tumor grade (P = 0.0001), histological type (P = 0.02), and stage (P = 0.0005) were independent prognostic factors for adverse cancer-specific survival and TATI tissue expression (P = 0.006) and grade (P = 0.0003) for progression-free survival. In multivariate analysis of all patients and those with advanced disease, serum trypsin-2-API concentration was an adverse prognostic factor for cancer-specific and progression-free survival, and it was independent of stage and histological type of the tumor (P <or= 0.01). CONCLUSIONS: Tissue expression of TATI and an elevated preoperative serum concentration of trypsin-2-API are strong independent prognostic factors in advanced epithelial ovarian cancer. These results suggest that trypsin expression plays a role in the progression of ovarian cancer. TATI and trypsin-2-API are of potential use as an aid for stratification of randomized studies and for selecting treatment strategies.

Adult↗

Trypsinogen-2 and trypsinogen activation peptide (TAP) in urine of patients with acute pancreatitis.

BACKGROUND AND AIMS: There is an obvious clinical need for a simple test that can identify patients at risk of developing severe acute pancreatitis. In this work we compared urinary trypsinogen-2 with urinary trypsinogen activation peptide (TAP) and serum C-reactive protein (CRP) for early differentiation between mild and severe acute pancreatitis. PATIENTS AND METHODS: The study population consisted of 127 consecutive patients with acute pancreatitis of whom 29 had severe disease. Urinary trypsinogen-2 was measured by a quantitative immunofluorometric assay and TAP by a competitive immunoassay. Serum CRP was determined by immunoturbidimetry. RESULTS: The sensitivity and specificity to identify severe acute pancreatitis on admission was 72% and 81% for urinary trypsinogen-2, 64% and 82% for urinary TAP, and 29% and 93% for serum CRP, respectively. At 24 h after admission, the values were 82% and 78% for urinary trypsinogen-2, 52% and 92% for urinary TAP, and 84% and 72% for serum CRP, respectively. Receiver-operating characteristics curve analysis showed that the area under the curve was larger for urinary trypsinogen-2 than for urinary TAP and serum CRP on admission and 24 h after admission. On admission the positive likelihood ration for urinary trypsiongen-2 was 3.7, for urinary TAP 3.6, and 4.3 for serum CRP, respectively. The corresponding negative likelihood ratios were 0.34, 0.43, and 0.76, respectively. CONCLUSION: Urinary trypsinogen-2 was superior to serum CRP and as god as or even better than urinary TAP and in the early prediction of disease severity in acute pancreatitis. These results suggest that it could be a valuable adjunct in the early assessment of the severity of acute pancreatitis.

APACHE↗

Trypsinogen hL is not a new member of the human trypsinogen family, but a known mouse ortholog.

An allegedly novel human trypsinogen cDNA clone termed trypsinogen hL was recently reported in the Biological & Pharmaceutical Bulletin (2003; 26: 361-364). This "new" trypsinogen sequence was isolated by PCR using human lung cDNAs as template and was presumed to be a new member of the human trypsinogen family. However, trypsinogen hL does not match any sequence in the human genome; whereas it is 100% identical to mouse trypsinogen 7. Thus, trypsinogen hL is not of human origin, and its cloning from a human cDNA library was clearly a result of contamination with mouse genetic material. Publication of this cloning artifact could have been avoided by a simple BLAST search of GenBank or other sequence databanks.

Animals↗

Trypsinogen hL expressed in the human lung is a new member of the trypsinogen family.

Molecular cloning of cDNA encoding a new member of the trypsinogen family, named trypsinogen hL, was carried out by PCR using human lung cDNAs as templates. The primary structure of trypsinogen hL was found to be a prepro-protein and a catalytic triad, 64His, 108Asp and 201Ser. It was also found that trypsinogen hL is specifically expressed in the human lung, the expression level being 30-times higher than those in other tissues tested. A phylogenic tree analysis showed that trypsinogen hL is a new member of the trypsinogen family, a family of serine protease family proteins.

Base Sequence↗

Hydrogen exchange kinetics of bovine pancreatic trypsin inhibitor beta-sheet protons in trypsin-bovine pancreatic trypsin inhibitor, trypsinogen-bovine pancreatic trypsin inhibitor, and trypsinogen-isoleucylvaline-bovine pancreatic trypsin inhibitor.

Hydrogen exchange rates of six beta-sheet peptide amide protons in bovine pancreatic trypsin inhibitor (BPTI) have been measured in free BPTI and in the complexes trypsinogen-BPTI, trypsinogen-Ile-Val-BPTI, bovine trypsin-BPTI, and porcine trypsin-BPTI. Exchange rates in the complexes are slower for Ile-18, Arg-20, Gln-31, Phe-33, Tyr-35, and Phe-45 NH, but the magnitude of the effect is highly variable. The ratio of the exchange rate constant in free BPTI to the exchange rate constant in the complex, k/kcpIx, ranges from 3 to much greater than 10(3). Gln-31, Phe-45, and Phe-33 NH exchange rate constants are the same in each of the complexes. For Ile-18 and Tyr-35, k/kcpIx is much greater than 10(3) for the trypsin complexes but is in the range 14-43 for the trypsinogen complexes. Only the Arg-20 NH exchange rate shows significant differences between trypsinogen-BPTI and trypsinogen-Ile-Val-BPTI and between porcine and bovine trypsin-BPTI.

Animals↗

Genes, cloned cDNAs, and proteins of human trypsinogens and pancreatitis-associated cationic trypsinogen mutations.

Historically, trypsinogens/trypsins have been one of the most extensively studied enzyme models of protein structure and function. They have received renewed attention after the identification of mutations in the cationic trypsinogen gene as being associated with hereditary pancreatitis. A survey of the literature revealed five cloned cDNAs, but only three protein products of human trypsinogens, and their nomenclature has been confusing. The availability of the complete genomic sequencing of the human trypsinogen gene family made it possible to provide a systematic review of the genes, cDNAs, and protein products of human trypsinogens and to clarify some controversial issues. Further, the confusing coexistence of two systems for naming the cationic trypsinogen mutations is addressed.

Alternative Splicing↗

Gene conversion-like missense mutations in the human cationic trypsinogen gene and insights into the molecular evolution of the human trypsinogen family.

Over the past decade, gene conversion has been shown increasingly to be a cause of human disease. Through this process, a functional gene is converted into a mutant by a homologous, nonfunctional one. In this article, we demonstrate that gene conversion is a likely cause of the mutations of the human cationic trypsinogen (PRSS1) gene that are associated with hereditary or sporadic pancreatitis, including the R122H (CGC>CAT: c.365-366 GC>AT), N29I (AAC>ATC: c.86A>T), and A16V (GCC>GTC: c.47C>T) missense mutations. This hypothesis is strongly supported by four lines of observation. First, human group I trypsinogen genes are tandemly repeated and share a high sequence homology between them. Secondly, a possible donor sequence for each variant is present in the PRSS1 gene's paralog(s). Thirdly, there exist uninterrupted sequence tracts ranging from 30 to 114 bp in the putatively converted regions. Finally, Chi-like and palindromic sequences are found in the vicinity of these missense mutations. This theory, if correct, will make the pancreatitis-associated PRSS1 mutations a unique example, as it shows that a functional gene may be converted by several paralogs, and that such an event may even occur between two functional genes (i.e., the N29I mutation), resulting in disease. This adds further to the diversity of genetic mechanisms underlying human disease. In addition, this genetic finding provides, for the first time, concrete evidence of the contribution made by gene conversion to the molecular evolution of the human trypsinogen family.

Base Sequence↗

Possible lysosomal activation of pancreatic zymogens. Activation of both human trypsinogens by cathepsin B and spontaneous acid. Activation of human trypsinogen 1.

Human trypsinogens 1 and 2 were activated at the same rate by pure human cathepsin B at pH 3.8. Human trypsinogen 1 was also spontaneously activated during incubation at acidic pH, activation being most rapid at pH 5.0. In contrast, trypsinogen 2 showed little or no activation under these conditions. The presence of calcium salts (20mM) delayed the onset of activation under all conditions tested. These findings support the proposal that premature activation of the pancreatic zymogens may result from their entry into the lysosomal system in pancreatitis.

Catalysis↗

Tumor-associated trypsinogen-2 (trypsinogen-2) activates procollagenases (MMP-1, -8, -13) and stromelysin-1 (MMP-3) and degrades type I collagen.

A critical step in cancer growth and metastasis is the dissolution of the extracellular matrix surrounding the malignant tumor, which leads to tumor cell invasion and dissemination. Type I collagen degradation involves the initial action of collagenolytic matrix metalloproteinases (MMP-1, -8, and -13) activated by MMP-3 (stromelysin-1). The role of interactive matrix serine proteinases (MSPs), including tumor-associated trypsinogens, has been unclear in collagenolysis. Now, we provide evidence that the major isoenzyme of human tumor-associated trypsinogens, trypsin-2, can directly activate three collagenolytic proMMPs as well as proMMP-3. These proMMP activations are inhibited by tumor-associated trypsin inhibitor (TATI). Furthermore, we demonstrate that trypsin-2 efficiently degrades native soluble type I collagen, which can be inhibited by TATI. However, cell culture studies showed that trypsin-2 transfection into the HSC-3 cell line did not result in MMP-1, -3, -8, and -13 activation but affected MMP-3 and -8 production at the protein level. These findings indicate that human trypsin-2 can be regarded as a potent tumor-associated matrix serine protease capable of being the initial activator of the collagenolytic MMP activation network as well as directly attacking type I collagen.

Blotting, Western↗