Pathophysiology and diagnostic value of urinary trypsin inhibitors

Diagnostic potential for urinary proteomics

Urine represents a modified ultrafiltrate of plasma, with protein concentrations typically approximately 1000-fold lower than plasma. Urine’s low protein concentration might suggest it to be a less promising diagnostic specimen than plasma. However, urine can be obtained noninvasively and tests of many urinary proteins are well-established in clinical practice. Proteomic technologies expand opportunities to analyze urinary proteins, identifying more than 1000 proteins and peptides in urine. Urine offers a sampling of most plasma proteins, with increased proportions of low-molecular-weight protein and peptide components. Urine also offers enriched sampling of proteins released along the urinary tract. Although urine presents some challenges as a diagnostic specimen, its diverse range of potential markers offers great potential for diagnosis of both systemic and kidney diseases. Examples of clinical situations where this may be of value are for more sensitive detection of kidney transplant rejection or of renal toxicity of medications.

The human urinary proteome contains more than 1500 proteins, including a large proportion of membrane proteins

A high confidence set of proteins in urine from healthy donors is described as a reference urinary proteome.

Background

Urine is a desirable material for the diagnosis and classification of diseases because of the convenience of its collection in large amounts; however, all of the urinary proteome catalogs currently being generated have limitations in their depth and confidence of identification. Our laboratory has developed methods for the in-depth characterization of body fluids; these involve a linear ion trap-Fourier transform (LTQ-FT) and a linear ion trap-orbitrap (LTQ-Orbitrap) mass spectrometer. Here we applied these methods to the analysis of the human urinary proteome.

Results

We employed one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis and reverse phase high-performance liquid chromatography for protein separation and fractionation. Fractionated proteins were digested in-gel or in-solution, and digests were analyzed with the LTQ-FT and LTQ-Orbitrap at parts per million accuracy and with two consecutive stages of mass spectrometric fragmentation. We identified 1543 proteins in urine obtained from ten healthy donors, while essentially eliminating false-positive identifications. Surprisingly, nearly half of the annotated proteins were membrane proteins according to Gene Ontology (GO) analysis. Furthermore, extracellular, lysosomal, and plasma membrane proteins were enriched in the urine compared with all GO entries. Plasma membrane proteins are probably present in urine by secretion in exosomes.

Conclusion

Our analysis provides a high-confidence set of proteins present in human urinary proteome and provides a useful reference for comparing datasets obtained using different methodologies. The urinary proteome is unexpectedly complex and may prove useful in biomarker discovery in the future.

Bikunin (Urinary Trypsin Inhibitor): Structure, Biological Relevance, And Measurement

Inflammatory processes, such as phagocytosis, coagulation, and vascular dilation, promote the release of serine proteases by neutrophils, macrophages, mast cells, lymphocytes, and the epithelial or endothelial cells. These proteases further facilitate the release of inflammatory cytokines and growth factors as well as take part in signal-cell proliferation through protease-activated receptors (PARs). Controlling the action of this cascade is necessary to prevent further damage to the normal tissues. One of the main anti-inflammatory response mediators is bikunin (Bik) that is responsible for inhibiting the activity of many serine proteases such as trypsin, thrombin, chymotrypsin, kallikrein, plasmin, elastase, cathepsin, Factors IXa, Xa, XIa, and XlIa. During the acute-phase response, Bik is released into plasma from proinhibitors primarily due to increased elastase activity. Bik is a glycoprotein, also referred to as urinary trypsin inhibitor, which in plasma inhibits the trypsin family of serine proteases by binding to either of the two Kunitz-binding domains. Bik also accumulates in urine. In conditions such as infection, cancer, tissue injury during surgery, kidney disease, vascular disease, coagulation, and diabetes, the concentrations of Bik in plasma and urine are increased. Several trypsin inhibitory assays for urine and immunoassays for both blood and urine have been described for measuring Bik. In addition to presenting the synthesis, structure, and pathophysiology of Bik, we will summarize various diagnostic approaches for measuring Bik. Analysis of Bik may provide a rapid approach in assessing various conditions involving the inflammatory processes.

The activation of neutrophil elastase-mediated fibrinolysis is not sufficient to overcome the fibrinolytic shutdown of disseminated intravascular coagulation associated with systemic inflammation

INTRODUCTION

We conducted a prospective study to test the hypothesis that the activation of neutrophil elastase-mediated fibrinolysis is insufficient to overcome the fibrinolytic shutdown of disseminated intravascular coagulation (DIC) in patients associated with systemic inflammation.

MATERIALS AND METHODS

We investigated 45 consecutive patients with systemic inflammatory response syndrome (SIRS) and sepsis, classified as 11 DIC and 34 non-DIC. Fibrin degradation products by neutrophil elastase (Elastase-XDP) and by plasmin (FDP), cross-linked fibrin degradation products (D-dimer), soluble fibrin, antithrombin, protein C, plasminogen activator inhibitor-1 (PAI-1), and urinary trypsin inhibitor (UTI) were measured within 24 h after the patients met either the SIRS or sepsis criteria (day 0), as well as on days 2 and 4.

RESULTS

In DIC patients, higher levels of soluble fibrin, PAI-1, and FDP and markedly lower levels of antithrombin and protein C were observed in comparison to those in non-DIC patients. DIC patients showed a significantly higher level of peak Elastase-XDP than non-DIC patients (25.7+/-5.9 vs. 16.3+/-2.6 microg/mL, respectively; p=0.0333). However, we could not find any substantial difference in the levels of Elastase-XDP, UTI, and D-dimer on each day during the study period between the two groups. Good correlations were observed between the levels of D-dimer and Elastase-XDP in both patients with and without DIC (r(s)=0.699 and r(s)=0.817, respectively), but the coefficients of determination in both groups showed low values and the slopes of the regression lines were less than 1.0. A multivariate logistic regression analysis showed the elevated peak Elastase-XDP levels to inversely correlate with death. On the other hand, the DIC patients showed a higher number of organ dysfunctions and a poorer prognosis than did the non-DIC patients.

CONCLUSIONS

The activation of the neutrophil elastase-mediated fibrinolytic pathway may be insufficient to overcome the fibrinolytic shutdown by PAI-1 and may in part explain the poor prognosis of DIC patients associated with systemic inflammation.

The presence of tryptase-positive and bikunin-negative mast cells in psoriatic skin lesions

Human mast cells are well known to produce a serine protease, tryptase, which appears to play a pathogenic role in various skin inflammations. It was previously reported that a rat homologue of bikunin may inhibit tryptase activity. Various type of cells (i.e. keratinocytes) are able to produce this protein inhibitor, it still remains unclear if bikunin is present in dermal inflammatory milieu, in which mast cells, through secretion of tryptase, play an inflammatory role. Therefore, the purpose of the present study was to exploit expression and production of bikunin in dermis and dermal constituents. We first compared the dermal mast cells in psoriatic lesions with those in lesional skin of atopic dermatitis or of chronic eczema by use of immunoelectron microscopy and immunohistochemical analyses using antibodies to bikunin and tryptase. Then, we tested what kinds of cytokines may regulate the de novo synthesis of bikunin. To do so, RNA was extracted from a human mastocytic cell line, HMC-1, reverse-transcribed, and semiquantitative RT-PCR was performed using primers specific for bikunin. With immunoelectron microscopy, bikunin was found to localize on the cell membrane, while tryptase was in the secretary granules of the mast cells. In psoriatic lesions, around 70% of dermal mast cells were positive for both tryptase and bikunin, and the remaining was mostly positive for tryptase, but the expression of bikunin was under the detection limit of the experimental setting. This observation was seen in only psoriatic lesions, even in almost cured lesions, while in atopic dermatitis or chronic eczema only mast cells doubly positive for bikunin and tryptase were seen. In HMC-1, bikunin was constitutively expressed at an mRNA level, which was upregulated by stimulation with interleukine-4, but was suppressed by interferon-gamma. Bearing in mind the concept that in psoriasis local cytokine milieu is shifted toward a Th1 pattern (predominant secretion of interferon-gamma), tryptase-positive, bikunin-negative mast cells may be induced.

Diversity in the degree of sulfation and chain length of the glycosaminoglycan moiety of urinary trypsin inhibitor isomers

Five isomers with different electric charge were fractionated from human urinary trypsin inhibitor (UTI) by anion exchange HPLC. Intact low-sulfated chondroitin 4-sulfate chains from the isomers were analyzed by HPLC and mass spectrometry. Unsaturated disaccharide composition analysis of the chondroitin sulfate chain revealed that the five isomers differ in the numbers of 4-sulfated disaccharide units. Intriguingly, we detected the presence of multiple novel isomers with different numbers of non-sulfated disaccharide units even in the same charge isomer fraction. Our results demonstrate that UTI can vary in terms of both the degree of sulfation and the length of the low-sulfated chondroitin 4-sulfate chain.

Elevated plasma cryofibrinogen in patients with active inflammatory bowel disease is morbigenous

AIM: To investigate the role of cryofibrinogen (CF) in active inflammatory bowel disease (IBD).

METHODS: CF was assayed in 284 subjects: 61 with active and 63 with inactive ulcerative colitis (UC), 45 who had proctocolectomy, 35 with active and 20 with inactive Crohn's disease (CD), 40 with other diseases and 20 healthy controls. Trypsin inhibitor (TI) and TI antibody (TI-Ab) were measured in plasma and CF complex by ELISA.

RESULTS: CF in active UC was strikingly high compared with all other groups (χ²<0.001). Similarly, CF was significantly higher in active CD than in inactive CD or in controls (χ²<0.01). In UC, high CF and TI-Ab were associated with the need for operations. Further, high CF, CF/fibrinogen ratio, low TI and high TI-Ab in plasma were associated with disease activity or refractoriness to medication. Elevated CF was not associated with acute reactants like C-reactive protein and white blood cell counts except for erythrocyte sedimentation rate, suggesting that elevated CF was not a consequence of acute inflammation.

CONCLUSION: Elevated CF in active IBD appears to be morbigenous. CF promotes IBD via two main mechanisms, quenching of TI (an anti-inflammatory substance) and impairing microvascular perfusion by forming protein aggregates. CF may also serve as a biomarker of chronic IBD. Additional studies are warranted to fully evaluate the role of CF in IBD and the outcome should contribute to a better understanding of the pathogenesis of IBD.