Functional and clinical aspects of the myelomonocyte protein calprotectin

The effect of intestinal colonization of germ-free pigs with Escherichia coli on calprotectin levels in plasma, intestinal and bronchoalveolar lavages

Calprotectin levels were measured by ELISA in plasma, terminal small bowel lavage and bronchoalveolar lavage from 8-day-old germ-free piglets or gnotobiotic piglets 24 h after colonization with one of the following Escherichia coli strains: non-pathogenic O86, probiotic Nissle 1917 or enteropathogenic O55. The concentration of calprotectin in plasma was about 30 ng/ml only in germ-free piglets and piglets associated with non-pathogenic E. coli. Piglets infected with O55 showed a significant increase of plasma calprotectin and the highest mean level of calprotectin in the bronchoalveolar lavage, which was coincident with septicaemia. However, in the lumen of the small intestine, E. coli Nissle 1917 alone elicited a significant increase of the calprotectin level which was confirmed by immunofluorescence and APAAP immunohistochemistry on cryostat sections through the small bowel. The relevance of this finding to the therapeutic effect of E. coli Nissle 1917 in inflammatory bowel disease is discussed.

Novel application of ProteinChip technology exploring acute rejection markers of rat small bowel transplantation

BACKGROUND

Because no biomarker that reflects small bowel allograft rejection is available, we applied surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) to develop noninvasive markers required for routine diagnosis.

METHODS

Heterotopic small bowel transplantation (SBT) was performed in rats, and they were divided into four experimental groups: sham-operated rats (sham), syngeneic transplants (syngeneic), allogeneic transplants (allogeneic), allogeneic transplants received FK506 (allo+FK). Plasma samples were analyzed with SELDI ProteinChip arrays to detect peaks that predominated in the allogeneic model. Possible biomarkers were identified in combination with SELDI retentate chromatography mass spectrometry (RCMS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The identified protein was further analyzed by immunohistochemistry.

RESULTS

An increase in the level of a 14.8-kDa protein, identified as lysozyme, was observed specifically in the plasma of the allogeneic group; the levels of this protein remained unchanged in the plasma of the other groups. On the other hand, the levels of a 10.1-kDa and a 13.0-kDa protein, identified as migration inhibitory factor-related proteins (MRP), MRP-8 and MRP-14, respectively, began to increase from an early stage of acute rejection. We also observed that lysozyme-positive macrophages had strongly infiltrated the lamina propria during acute rejection.

CONCLUSIONS

We identified three plasma proteins-MRP-8, MRP-14, and lysozyme-that increased during small bowel allograft rejection. The identified proteins appeared to be markers for inflammation associated with allograft rejection. This proteomic approach will be useful for the identification of candidate biomarkers.

Human neutrophil calprotectin reduces the susceptibility of Borrelia burgdorferi to penicillin

Borrelia burgdorferi, the spirochetal agent of Lyme disease, is susceptible to killing by a variety of polymorphonuclear leukocyte (PMN) components. Some are most effective against metabolically active B. burgdorferi. The abundant PMN cytoplasmic protein calprotectin, elevated 10- to 100-fold in inflammation, inhibits the growth of spirochetes through chelation of the essential cation, Zn. Since the action of some therapeutic antibiotics depends on bacterial division, we investigated the antibiotic sensitivities of spirochetes in calprotectin. In physiologic calprotectin, B. burgdorferi is not eliminated by therapeutic doses of penicillin G; in contrast, doxycycline is effective. Calprotectin may modify the clearance of spirochetes at sites of inflammation.

Chazin W, Yui S. Regulation of S100A8/A9 (calprotectin) binding to tumor cells by zinc ion and its implication for apoptosis-inducing activity

S100A8/A9 (calprotectin), which is released by neutrophils under inflammatory conditions, has the capacity to induce apoptosis in various cells. We previously reported that S100A8/A9 induces apoptosis of EL-4 lymphoma cells via the uptake of extracellular zinc in a manner similar to DTPA, a membrane-impermeable zinc chelator. In this study, S100A8/A9-induced apoptosis was examined in several cell lines that are weakly sensitive to DTPA, suggesting S100A8/A9 is directly responsible for apoptosis in these cells. Since zinc inhibits apoptosis of MM46, one of these cells, the regulation by zinc of the capacity of S100A8/A9 to bind MM46 cells was studied. When MM46 cells were incubated with S100A8/A9 in standard or zinc-depleted medium, the amounts of S100A8/A9 bound to cells was markedly lower at 3 h than at 1 h. In contrast, when MM46 cells were incubated with S100A8/A9 in the presence of high levels of zinc, binding to cells was the same at 1 and 3 h. When the cells were permeabilized with saponin prior to analysis, a larger amount of cell-associated S100A8/A9 was detected at 3 h. The amount was further increased in cells treated with chloroquine, suggesting that S100A8/A9 was internalized and degraded in lysosomes. Although it has been reported that S100A8/A9 binds to heparan sulfate on cell membranes, the amount of S100A8/A9 bound to MM46 cells was not reduced by heparinase treatment, but was reduced by trypsin treatment. These results suggest that S100A8/A9 induces apoptosis by direct binding to MM46 cells, and that this activity is regulated by zinc.

Technology insight: calprotectin, lactoferrin and nitric oxide as novel markers of inflammatory bowel disease

Distinguishing patients with inflammatory bowel disease from those with irritable bowel syndrome can be difficult. A simple and reliable test that detects intestinal inflammation would therefore be very useful in the clinic. If such a test parameter correlated with the intensity of the inflammatory reaction it could also be used to monitor disease activity. Calprotectin, lactoferrin and nitric oxide are produced and released locally in much greater quantities in the inflamed gut than in the noninflamed gut. These compounds can be readily measured in fecal samples (calprotectin and lactoferrin) or directly in the intestinal lumen (nitric oxide gas). Here, we discuss what is known about these markers, how they could be used in clinical practice and how they can complement existing techniques used for the diagnosis and monitoring of inflammatory bowel disease.

Severe anemia and neutropenia associated with hyperzincemia and hypercalprotectinemia

Calprotectin, also known as the S100A8/A9 or MRP8/14 complex, is a major calcium-binding protein in the cytosol of neutrophils, monocytes, and keratinocytes. It differs from other S100 proteins in its zinc-binding capacity. The authors describe a 4-year-old girl with severe anemia, neutropenia, inflammation, and severe growth failure. Bone marrow examination showed moderate dyserythropoiesis. No hemolysis, iron deficiency, hemoglobinopathies, immunologic diseases, or autoantibodies were detected. Serum levels of copper and ceruloplasmin were within the normal range, although the serum zinc concentration was markedly increased (310 microg/dL). Urinary zinc excretion and erythrocyte zinc concentrations were within the normal range. Family studies showed normal zinc and copper plasma levels. The patient's plasma calprotectin concentration showed a 6,000-fold increase (2,900 mg/L) compared with normal values. The calprotectin concentration is known to be elevated in many inflammatory conditions but is generally below 10 mg/L and thus far below the levels reported in this patient. The authors describe this case as an inborn error of zinc metabolism caused by dysregulation of calprotectin metabolism, which mainly presented with the features of microcytic anemia and inflammation.

Faecal calprotectin in the assessment of Crohn's disease activity

BACKGROUND

Clinical and laboratory assessment of activity in Crohn's disease (CD) correlate poorly with endoscopic findings. Calprotectin is a calcium-binding protein abundant in neutrophil cytosol, and extremely stable in faeces. Faecal calprotectin (FC) is an excellent surrogate marker of neutrophil influx into the bowel lumen.

AIM

To assess whether FC concentration from a spot stool sample reliably detects active inflammation in patients with CD.

DESIGN

Cross-sectional comparative study.

METHODS

Subjects had a previously confirmed diagnosis of CD and were suspected on clinical grounds to be in the midst of a relapse. Thirty-five entered the study; they underwent radiolabelled white cell scanning (WCS) and had a stool sample collected for calprotectin measurement on the same day. A Crohn's disease activity index (CDAI) was also calculated for each. The WCS scans were scored at six standard sites to give a mean total, 'extent', 'severity' and 'combined extent and severity' scores.

RESULTS

FC was significantly and positively correlated with mean total (r = 0.73, p < 0.001), 'extent' (r = 0.71, p < 0.001), 'severity' (r = 0.64, p < 0.001) and combined 'extent and severity' WCS scores (r = 0.71, p < 0.001). A cut-off of faecal calprotectin > 100 microg/g gave a sensitivity of 80%, specificity of 67%, positive predictive value of 87% and a negative predictive value of 64% in identifying those with and without any inflammation on WCS. There was, however, no significant correlation between CDAI and mean total WCS score (r = 0.21, p = 0.24), nor between CDAI and FC (r = 0.33, p = 0.06).

DISCUSSION

While the CDAI does not accurately reflect inflammatory activity in CD, a one-off FC reliably detects the presence or absence of intestinal inflammation in adult patients with CD, compared to WCS.

Calprotectin plasma level is elevated in preeclampsia

BACKGROUND

Calprotectin is a protein found in myelomonocytic cells and plays a role in various physiological functions such as inflammatory processes and antiproliferation of cells, and in the neutrophil defense against bacterial infections. Preeclampsia is characterized by maternal endothelial dysfunction and by insufficient trophoblast invasion into the maternal endometrium (decidua). In addition, preeclampsia is associated with maternal leukocyte activation and we therefore wanted to investigate whether calprotectin levels in plasma from women with preeclampsia differed from the levels in normotensive pregnant and nonpregnant women.

METHOD

Calprotectin measurements were included in a case-control study of 20 preeclamptic women matched with 20 normotensive pregnant women regarding age, pregnancy length, parity and body mass index (BMI). We also measured calprotectin in 12 nonpregnant women. Calprotectin plasma levels were analyzed using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

We discovered significantly elevated plasma calprotectin levels in preeclamptic patients compared to matched normotensive pregnancies: 768 (612-1016) microg/L vs. 445 (276-598) microg/L (medians, 25, 75 percentiles, respectively), p = 0.002.

CONCLUSIONS

The elevated plasma calprotectin levels demonstrated in the preeclampsia group supports the notion that leukocytes are activated in preeclampsia. The elevated calprotectin level might constitute a part of the innate defense in myelomonocytic cells against microorganisms in pregnancy. We suggest further elucidation of a role for calprotectin in the development of pregnancy disorders such as preeclampsia.

Myeloid-related protein (MRP)8/14 (calprotectin) and its subunits MRP8 and MRP14 in plaque-induced early gingival inflammation

BACKGROUND

The inflammatory myeloid-related protein, MRP8/14, also called calprotectin, and its subunits MRP8 and MRP14 have been detected and identified recently in gingival crevicular fluid (GCF). It has been suggested that the type and phase of inflammation can be discriminated on the basis of differences in the expression of calprotectin and its subunits, released during activation and/or death of granulocytes and monocytes. The purpose of this study was to quantify calprotectin and its subunits (MRPs) simultaneously in the GCF during the initial phase of experimentally induced gingivitis, and to examine their inter- and intra-individual variations.

MATERIAL AND METHODS

Fifteen healthy non-smoking subjects, aged 18-30, were involved in this study. An initial hygiene phase (days -11 to 0) was followed by 10 days of undisturbed plaque accumulation. At days -11, -3, 0, 10, 11, clinical parameters were recorded and GCF samples collected with Durapore strips from 12 sites in each subject. Quantitative analyses of total proteins, MRP8/14, MRP14 and MRP8 were performed by ELISA procedures.

RESULTS

During the experimental phase with no oral hygiene (days 0-10), the clinical parameters Plaque Index, Gingival Index (GI) and bleeding on probing increased as expected, confirming that plaque accumulation leads to gingival inflammation. Levels of the MRPs were individually variable. They increased with plaque accumulation in one-half of the subjects, and decreased in the other subjects. The levels of MRP8/14 and MRP14 at subject recruitment (day -11) could predict a significant part of the GI at day 10. Only minute amounts of the subunits MRP8 and MRP14 were detected in comparison with the complex MRP8/14 throughout the experiment. Considerable variations were noted among sites within subjects.

CONCLUSION

The expression of calprotectin in the early phase of experimental gingivitis is variable between subjects, and two groups of subjects can be differentiated according to their response patterns. Clinical parameters at the very first visit (day -11) seemed to be different in the two response groups. The results of the present investigation indicate that the inflammatory response to plaque accumulation depends on the initial status of the subjects, which may not be leveled out by the introduction of perfect oral hygiene. Whether these patterns reflect a different susceptibility to periodontal diseases remains to be determined.

Fungal susceptibility to zinc deprivation

Calprotectin is a neutrophil-derived antimicrobial protein that competes with microorganisms for zinc. The zinc-specific effect of calprotectin against Candida albicans appears to be related to this organism's marked susceptibility to deprivation of this metal. However, it is not known whether this susceptibility is particular to C albicans or whether it is a characteristic of pathogenic fungi in general. As a means of deciding between these 2 possibilities, we undertook the study reported here to compare the susceptibility to zinc deprivation of 6 other pathogenic fungal species in addition to that of C albicans . We tested the effect of metals in reversing growth inhibition of the 7 fungi against abscess-fluid supernatant (a source of calprotectin) and 3 chemical chelators. Data were expressed as the concentration of metal required to bring about 50% restoration of growth. Zinc was found to be much more potent than the other metals tested in reversing growth inhibition of all the organisms by human abscess fluid and all 3 chemical chelators. Copper and manganese also had some effect. In some cases, chelator stability constants were higher for other metals than for zinc; in particular, although diethylenetriaminopentaacetic acid has a stability constant for iron almost 10(10) times greater than that for zinc, zinc was more effective than iron in reversing growth inhibition by this chelator against all of the organisms. These results suggest that marked susceptibility to zinc deprivation is a general characteristic of pathogenic fungi.

Diagnostic accuracy of faecal calprotectin estimation in prediction of abnormal small bowel radiology

BACKGROUND

[corrected] Patients being investigated for symptoms of abdominal pain, diarrhoea and or weight loss often undergo small bowel radiology as part of their diagnostic workup mainly to exclude inflammatory bowel disease.

AIM

To assess and compare the utility of a single faecal calprotectin estimation to barium follow through as well as conventional inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein in exclusion of intestinal inflammation.

METHODS

Seventy-three consecutive cases undergoing barium follow through for investigation of symptoms of diarrhoea and or abdominal pain with or without weight loss were studied. The control group comprised 25 cases with known active Crohn's disease (positive controls), 26 normal healthy volunteers (negative controls) and 25 cases of irritable bowel syndrome diagnosed by Rome II criteria. Symptoms, erythrocyte sedimentation rate and C-reactive protein were recorded at recruitment and a single stool sample assayed for calprotectin within 7 days prior to or after barium follow through.

RESULTS

The median calprotectin value in the active Crohn's group, irritable bowel syndrome group and normal volunteers was 227 microg/g of stool, 19 and 10 microg/g respectively (P < 0.0001). A faecal calprotectin above a cut-off value of 60 microg/g was able to predict all nine cases with an abnormal barium follow through as well as all six cases with a normal barium follow through but with organic intestinal disease. The negative predictive value of a single calprotectin result below 60 microg/g of stool was 100% compared with 91% each for erythrocyte sedimentation rate > 10 mm and C-reactive protein > 6 mg/L and 84% for a combination of erythrocyte sedimentation rate and C-reactive protein in predicting absence of organic intestinal disease.

CONCLUSION

A single stool calprotectin value < 60 microg/g of stool obviates the need for further barium radiology of the small bowel, is more accurate than measurement of erythrocyte sedimentation rate or C-reactive protein and effectively excludes Crohn's disease or non-functional gastrointestinal disease.

Testing for faecal calprotectin (PhiCal) in the Norwegian Colorectal Cancer Prevention trial on flexible sigmoidoscopy screening: comparison with an immunochemical test for occult blood (FlexSure OBT)

BACKGROUND

Screening for colorectal cancer (CRC) using guaiac based faecal occult blood tests (FOBT) has an estimated programme sensitivity of >60% but <30% for strictly asymptomatic CRC in a single screening round. In search for improved non-invasive tests for screening, we compared a test for faecal calprotectin (PhiCal) with a human haemoglobin immunochemical FOBT (FlexSure OBT).

METHODS

In the Norwegian Colorectal Cancer Prevention (NORCCAP) trial, screenees in one screening arm were offered screening with combined flexible sigmoidoscopy (FS) and FlexSure OBT. They were also requested to bring a fresh frozen sample of stool for the PhiCal test which was performed on samples from screenees with CRC (n = 16), high risk adenoma (n = 195), low risk adenoma (n = 592), and no adenoma (n = 1518) (2321 screenees in total). A positive PhiCal test was defined by a calprotectin level > or =50 microg/g.

RESULTS

The PhiCal test was positive in 24-27% of screenees whether they had no adenoma, low risk adenoma, or high risk adenoma. Ten (63%) of 16 CRCs gave a positive PhiCal test. The total positivity rate in this population was 25% for the PhiCal test compared with 12% for FlexSure OBT, with a sensitivity for advanced neoplasia of 27% and 35%, respectively. Specificity for "any neoplasia" was 76% for the PhiCal test and 90% for FlexSure OBT.

CONCLUSIONS

In colorectal screening, the performance of the PhiCal test on a single spot from one stool sample was poorer than a single screening round with FlexSure OBT and cannot be recommended for population screening purposes. The findings indicate a place for FlexSure OBT in FOBT screening.

Molecular stool screening for colorectal cancer

BACKGROUND

Mass screening for colorectal cancer reduces mortality and, with recent advances in molecular genetics, molecular stool-based tests have produced promising results. This article reviews this innovation and discusses its clinical significance.

METHODS

Medline searches were used to identify recent key articles relating to stool-based testing. Further articles were obtained by manual scanning of the reference lists of identified papers.

RESULTS

Current screening methods are based on endoscopic, radiological and stool-based testing. Recent recognition of the adenoma-carcinoma sequence and pathophysiological studies of colonic epithelium have enabled tumour markers to be used in the screening setting. Non-invasive molecular stool testing has now been shown to have a high sensitivity and specificity.

CONCLUSION

Recent studies on molecular stool-based testing have shown higher sensitivity and specificity than earlier studies, but larger clinical trials are required. Laboratory methods are still undergoing research, with the aim of improving sensitivity to allow large-scale testing.

Mechanism of apoptosis induced by S100A8/A9 in colon cancer cell lines: the role of ROS and the effect of metal ions

The protein complex S100A8/A9, abundant in the cytosol of neutrophils, is secreted from the cells upon cellular activation and induces apoptosis in tumor cell lines and normal fibroblasts in a zinc-reversible manner. In the present study, we present evidence that the S100A8/A9 also exerts its apoptotic effect by a zinc-independent mechanism. Treatment of the colon carcinoma cells with different concentrations of human S100A8/A9 or the metal ion chelator diethylenetriaminepentacetic acid (DTPA) resulted in a significant increase of cell death. Annexin V/phosphatidylinositol and Hoechst 33258 staining revealed that cell death was mainly of the apoptotic type. A significant increase in the activity of caspase-3 and -9 was observed in both cell lines after treatment. Caspase-8 activation was negligible in both cell lines. The cytotoxicity/apoptotic effect of human S100A8/A9 and DTPA was inhibited significantly (P<0.05) by Zn(+2) and Cu(+2), more effectively than by Ca(2+) and Mg(2+). The antioxidant N-acetyl-L-cysteine inhibited the cytotoxicity/apoptotic effect of S100A8/A9 and DTPA. However, as a result of the different time-courses of both agents and that the S100A8/A9-induced apoptosis was not completely reversed, we conclude that S100A8/A9 exerts its apoptotic effect on two colon carcinoma cell lines through a dual mechanism: one via zinc exclusion from the target cells and the other through a yet-undefined mechanism, probably relaying on the cell-surface receptor(s).

Proinflammatory cytokines upregulate expression of calprotectin (L1 protein, MRP-8/MRP-14) in cultured human keratinocytes

BACKGROUND

Normal skin contains no epidermal calprotectin. In biopsies from various inflammatory skin disorders, however, this antimicrobial protein occurs in the cytoplasm of keratinocytes.

OBJECTIVES

To exclude the possibility of epidermal uptake of calprotectin from granulocytes and macrophages in diseased skin, we investigated whether cytokine-stimulated human keratinocytes can express calprotectin in vitro.

METHODS

Keratinocytes from healthy individuals were cultured in serum-free keratinocyte medium. The cells were stimulated with different cytokines [interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-10 and IL-13], both separately and in various combinations. Cytoplasmic protein levels of calprotectin were measured by an enzyme-linked immunosorbent assay performed on fixed adherent keratinocytes, and mRNA expression was determined by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Calprotectin was produced by cytokine-stimulated keratinocytes, especially in response to combinations of the proinflammatory cytokines, which showed an additive upregulatory effect. When expression of mRNA for the light (MRP-8) and heavy (MRP-14) calprotectin chain was determined by RT-PCR, their respective levels were shown to be increased four- to ninefold and three- to fivefold after 24 h of combined stimulation with IFN-gamma and TNF-alpha. The time course of calprotectin production showed no significant elevation for the first 16 h but then increased and peaked after 36 h.

CONCLUSIONS

Cultured human keratinocytes stimulated with proinflammatory cytokines produce calprotectin, suggesting that epidermal expression of this antimicrobial protein in diseased skin reflects compartmentalized synthesis rather than uptake from dermal inflammatory cells.

Role of faecal calprotectin as non-invasive marker of intestinal inflammation

BACKGROUND/AIM

Faecal calprotectin, a neutrophil granulocyte cytosol protein, is considered a promising marker of intestinal inflammation. We assessed and compared the faecal calprotectin concentration in patients with organic and functional chronic intestinal disorders.

PATIENTS AND METHODS

The study was carried out, using a commercially available ELISA test, measuring calprotectin in stool samples collected from 131 patients with inflammatory bowel diseases, 26 with intestinal neoplasms, 48 with irritable bowel syndrome and 34 healthy subjects.

RESULTS

Median faecal calprotectin was significantly increased in Crohn's disease (231 microg/g, 95% confidence interval (CI) 110-353 microg/g), ulcerative colitis (167 microg/g, 95% CI 59-276 microg/g), and neoplasms (105 microg/g, 95% CI 0-272 microg/g), whereas normal values were found in patients with irritable bowel syndrome (22 microg/g, 95% CI 9-35 microg/g) and in healthy subjects (11 microg/g, 95% CI 3-18 microg/g). A positive correlation was observed with clinical activity scores in Crohn's disease and ulcerative colitis. In both groups, patients with clinically active disease showed higher calprotectin levels than those observed in patients with quiescent disease (405 microg/g, 95% CI 200-610 microg/g vs. 213 microg/g, 95% CI 85-341 microg/g in CD patients, p<0.05, and 327 microg/g, 95% CI 104-550 microg/g vs. 123 microg/g, 95% CI 40-206 microg/g in UC patients, p<0.001).

CONCLUSIONS

Faecal calprotectin appears to be a promising and non-invasive biomarker of intestinal inflammation. If these findings are confirmed, it may provide a useful test for the diagnosis and follow up of inflammatory bowel diseases.

Calprotectin, an abundant cytosolic protein from human polymorphonuclear leukocytes, inhibits the growth of Borrelia burgdorferi

We previously showed that numerous polymorphonuclear leukocyte (PMN) granule components efficiently kill Borrelia burgdorferi, the agent of Lyme disease. In addition, motile, granule-poor cytoplasts (U-Cyt) from human blood PMN can exert anti-Borrelia activity against opsonized B. burgdorferi independently of oxidative mechanisms. Here we show that lysates of U-Cyt also possess anti-Borrelia activity, a portion of which comes from the abundant cytosolic protein calprotectin. The anti-Borrelia activity of U-Cyt lysates and recombinant calprotectin was partially or completely reversed by specific antibody to calprotectin and by Zn(2+), a cation essential for the growth of B. burgdorferi and known to inhibit the antimicrobial activity of calprotectin. Quantitative microscopic and regrowth assays revealed that calprotectin acted in a bacteriostatic fashion against B. burgdorferi. We conclude that calprotectin, a potent bacteriostatic agent from a cell primarily recognized for its oxidative and granular antibacterial mechanisms, may play a modulatory role in infection by the Lyme spirochete, particularly at sites of acute inflammation.

Emerging role of calprotectin in gastroenterology

Calprotectin is a calcium and zinc binding protein of the S100 family derived predominantly from neutrophils and monocytes. It is detectable in body fluids and tissue samples and is emerging as a valuable marker in the diagnosis, and the monitoring and determining of the prognosis of commonly encountered gastroenterological conditions. Fecal calprotectin, in particular, has for a long time been regarded as a promising marker of gastrointestinal pathology and has now been established as a routine test in Norway and at several centers in the UK.

Calprotectin (S100A8/S100A9), an inflammatory protein complex from neutrophils with a broad apoptosis-inducing activity

Calprotectin, a complex of two calcium-binding proteins that belong to the S100 protein family, is abundant in the cytosolic fraction of neutrophils. A high level of calprotectin reportedly exists in extracellular fluid during various inflammatory conditions, such as rheumatoid arthritis, cystic fibrosis and abscesses. However, the exact biological role(s) of the factor is now under investigation. We recently observed that neutrophils contain a factor that shows growth-inhibitory and apoptosis-inducing activities against various cell types including tumor cells and normal fibroblasts, and we identified that factor as calprotectin. The findings suggest that calprotectin exerts a regulatory activity in inflammatory processes through its effect on the survival or growth states of cells participating in the inflammatory reaction. It is also possible that calprotectin, at a high concentration, might have a deleterious effect on fibroblasts and influence the recovery of inflammatory tissue. Therefore, the protein factor may be a new drug target to control inflammatory reactions. We found that a few of the Amaryllidaceae alkaloids effectively inhibited the growth-inhibitory and apoptosis-inducing activities of calprotectin. In this article, we focus on the biological functions of calprotectin in extracellular fluids, focusing on its apoptosis-inducing activity.

Diagnostic accuracy of fecal calprotectin assay in distinguishing organic causes of chronic diarrhea from irritable bowel syndrome: a prospective study in adults and children

BACKGROUND

Fecal calprotectin (FC) has been proposed as a marker of inflammatory bowel disease (IBD), but few studies have evaluated its usefulness in patients with chronic diarrhea of various causes. We evaluated the diagnostic accuracy of a FC assay in identifying "organic" causes of chronic diarrhea in consecutive adults and children.

METHODS

We consecutively enrolled 70 adult patients (30 males, 40 females; median age, 35 years) and 50 children (20 males, 30 females; median age, 3.5 years) with chronic diarrhea of unknown origin. All patients underwent a complete work-up to identify the causes of chronic diarrhea. FC was measured by ELISA.

RESULTS

In adult patients, FC showed 64% sensitivity and 80% specificity with 70% positive and 74% negative predictive values for organic causes. False-positive results (8 of 40 cases) were associated with the use of aspirin (3 cases) or nonsteroidal antiinflammatory drugs (1 case) and with the presence of concomitant liver cirrhosis (3 cases). False-negative results mainly included patients suffering from celiac disease (5 cases). Patients with IBD (9 cases) were identified with 100% sensitivity and 95% specificity. In pediatric patients, sensitivity was 70%, specificity was 93%, and positive and negative predictive values were 96% and 56%. False-negative results (11 of 35 cases) were associated mainly with celiac disease (6 cases) or intestinal giardiasis (2 cases).

CONCLUSIONS

FC assay is an accurate marker of IBD in both children and adult patients. In adults, false negatives occur (e.g., in celiac disease) and false-positive results are seen in cirrhosis or users of nonsteroidal antiinflammatory drugs. Diagnostic accuracy is higher in children.

Ascites fluid and plasma calprotectin concentrations in liver disease

BACKGROUND

Calprotectin, a marker of neutrophil activation, has been associated with a poor prognosis in alcohol-induced cirrhosis. The aims were to study concentrations of calprotectin in patients with various liver diseases, and to further investigate the prognostic value of calprotectin in cirrhosis.

METHODS

Plasma calprotectin concentrations were determined in 84 patients with alcohol-induced liver disease, 32 hepatitis B or C infected patients, 33 patients with liver disease of other aetiologies, 7 patients with combined aetiologies and in 24 patients with malignant disease. Thirty healthy individuals were included as controls. Ascites calprotectin concentrations were determined in patients with ascites (n = 75). Follow-up for survival was performed after a median observation period of 10 months.

RESULTS

Increased plasma and ascites calprotectin concentrations were observed in malignant disease compared to non-malignant disease (P < 0.0001). Plasma calprotectin concentrations were low in viral liver disease compared to patients with non-viral liver disease (P = 0.02) and to controls (P = 0.0002). Plasma calprotectin (>median) was a highly significant marker of poor survival in alcohol-induced cirrhosis (P = 0.001), but was of no prognostic value in non-alcohol-induced cirrhosis (P = 0.88). In decompensated cirrhosis high (>upper quartile) ascites calprotectin concentrations were associated with an increased mortality (P = 0.002), as were high (>median) plasma calprotectin levels (P = 0.009).

CONCLUSION

The prognostic importance of calprotectin in alcohol-induced cirrhosis is confirmed and demonstrated as specific for alcohol-induced liver disease. Low calprotectin levels are indicated in viral liver disease, and an association between high ascites calprotectin levels and malignant ascites was observed.

Proinflammatory activities of S100: proteins S100A8, S100A9, and S100A8/A9 induce neutrophil chemotaxis and adhesion

S100A8 and S100A9 are small calcium-binding proteins that are highly expressed in neutrophil and monocyte cytosol and are found at high levels in the extracellular milieu during inflammatory conditions. Although reports have proposed a proinflammatory role for these proteins, their extracellular activity remains controversial. In this study, we report that S100A8, S100A9, and S100A8/A9 caused neutrophil chemotaxis at concentrations of 10(-12)-10(-9) M. S100A8, S100A9, and S100A8/A9 stimulated shedding of L-selectin, up-regulated and activated Mac-1, and induced neutrophil adhesion to fibrinogen in vitro. Neutralization with Ab showed that this adhesion was mediated by Mac-1. Neutrophil adhesion was also associated with an increase in intracellular calcium levels. However, neutrophil activation by S100A8, S100A9, and S100A8/A9 did not induce actin polymerization. Finally, injection of S100A8, S100A9, or S100A8/A9 into a murine air pouch model led to rapid, transient accumulation of neutrophils confirming their activities in vivo. These studies 1) show that S100A8, S100A9, and S100A8/A9 are potent stimulators of neutrophils and 2) strongly suggest that these proteins are involved in neutrophil migration to inflammatory sites.

Leukocyte protein calprotectin and outcome in rheumatoid arthritis. A longitudinal study

OBJECTIVE

To determine if calprotectin is predictive for outcome in patients with rheumatoid arthritis (RA).

METHODS

Fifty six RA in-patients with variable disease duration were prospectively followed for five years. Clinical and laboratory data were collected to assess disease activity. Health Assessment Questionnaire (HAQ) and radiographic scores (of hands and wrists) as described by Larsen were used as outcome measures. Plasma calprotectin levels were determined with ELISA technique.

RESULTS

Significant correlations (r) were found cross-sectionally at follow-up between calprotectin concentration and other known parameters of disease activity and severity: CRP (r = 0.67). investigator's global assessment of disease activity (r = 0.57). Waaler titre (r = 0.50). HAQ score (r = 0.48) and number of swollen joints (r = 0.48). Calprotectin at baseline was not identified as an independent predictor for HAQ or radiographic progression in the multivariate analysis.

CONCLUSION

The results confirm calprotectin as a good measure of disease activity and joint inflammation in RA. However, the level of calprotectin at baseline was not predictive for radiographic damage or functional impairment five years later.

Hyperzincaemia and hypercalprotectinaemia: a new disorder of zinc metabolism

BACKGROUND

Calprotectin (complex of S100A8 and S100A9) is the major calcium and zinc-binding protein of phagocytes. We report a new syndrome with recurrent infections, inflammation, and hyperzincaemia associated with excessively high plasma concentrations of calprotectin.

METHODS

We measured calprotectin in plasma and protein fractions by ELISA assay and zinc by atomic absorption spectrometry. Plasma proteins were fractionated by size exclusion chromatography and electrophoresis. Mass spectra of purified proteins were determined by MALDI-TOFMS.

FINDINGS

We assessed five patients, two of whom are related. All patients had much the same biochemical findings of hyperzincaemia (77-200 micromol/L, reference range 11-18 micromol/L) and raised plasma calprotectin concentrations (1.4-6.5 g/L, reference range <1 mg/L). All patients presented with recurrent infections, hepatosplenomegaly, anaemia, and evidence of systemic inflammation. Three patients had cutaneous inflammation and three presented in infancy with severe growth failure. Size exclusion chromatography showed that zinc and calprotectin were associated in a broad fraction with molecular weight range 100-300 kDa. Analysis by electrophoresis and mass spectrometry showed that the patients' protein contained normal S100A8 and S100A9 subunits.

INTERPRETATION

Dysregulation of zinc metabolism associated with accumulation in plasma of S100A8 and S100A9 defines a new disease, which encompasses a pathological role for dysregulation of two members of the large S100 protein family.

Faecal calprotectin levels in infants with infantile colic, healthy infants, children with inflammatory bowel disease, children with recurrent abdominal pain and healthy children

This study investigated faecal calprotectin concentration, a measure of intestinal inflammation, in infants and children with abdominal pain. Faecal calprotectin was measured by an enzyme-linked immunosorbent assay kit in spot stool samples in 76 infants with typical infantile colic, 7 infants with transient lactose intolerance and 27 healthy infants. All infants were 2-10 wk of age. In addition, 19 children with recurrent abdominal pain (RAP; mean age 11.5 y), 17 with inflammatory bowel disease (IBD; mean age 11.1 y; 10 had Crohn's disease and 7 ulcerative colitis) and 24 healthy children (mean age 5.3 y) were studied. In infants with infantile colic the mean faecal calprotectin concentration was not different from that in healthy infants (278 +/- 105 vs 277 +/- 109 mg kg(-1), p = 0.97) or in infants with transient lactose intolerance (300.3 +/- 124 mg kg(-1), p = 0.60). The calprotectin level was similar in boys and girls and fell significantly with age (p = 0.04). Children with IBD had faecal calprotectin levels (293 +/- 218 mg kg(-1)) much higher than healthy children (40 +/- 28 mg kg(-1), p < 0.0001) and children with RAP without identified organic disease (18 +/- 24 mg kg(-1), p < 0.0001).

CONCLUSION

Faecal calprotectin may differentiate between functional abdominal pain and IBD in school-aged children. In young infants high faecal calprotectin levels are normal.

Faecal calprotectin: a marker of inflammation throughout the intestinal tract

Only a small proportion of patients with abdominal discomfort have organic disease, but a correct diagnosis can seldom be made by simple clinical examination. Additional diagnostic procedures must be employed, but these are expensive and demanding and carry a certain risk. Assessment of faecal concentrations of the neutrophil granulocyte-derived protein calprotectin can be used as a screening test--an 'ESR of the gut'--to select patients for further examination. The test can be performed on 1-2 g of random stool samples that can be sent to the laboratory by ordinary mail since the protein is remarkably stable in stools. The test has high sensitivities and specificities for gastrointestinal cancers and inflammatory bowel disease (IBD). Faecal calprotectin levels reflect the disease activity in IBD and can be used to monitor the response to treatment and detect relapses.

Implication of extracellular zinc exclusion by recombinant human calprotectin (MRP8 and MRP14) from target cells in its apoptosis-inducing activity

BACKGROUND

Calprotectin is a calcium-binding and zinc-binding protein complex that is abundant in the cytosol of neutrophils. This factor is composed of 8 and 14 kDa subunits, which have also been termed migration inhibitory factor-related proteins MRP8 and MRP14. We previously reported that rat calprotectin purified from inflammatory neutrophils induces apoptosis of various tumor cells or normal fibroblasts in a zinc-reversible manner.

AIM

The present study was undertaken to elucidate which subunit is responsible for the apoptosis-inducing activity, and to explore the mechanism of zinc-reversible apoptosis induction.

METHODS

The apoptosis-inducing activity of recombinant human MRP8 (rhMRP8) and recombinant human MRP14 (rhMRP14) was examined against EL-4 lymphoma cells in vitro. To determine whether zinc deprivation by calprotectin was essential for the cytotoxicity, the activity of calprotectin was tested under conditions where physical contact between the factor and the cells was precluded by a low molecular weight cut-off dialysis membrane.

RESULTS

The cytotoxicity of rhMRP14 against EL-4 cells was first detected at 10 microM in a standard medium, whereas rhMRP8 caused only marginal cytotoxicity at 40 microM. A mixture of both proteins showed higher specific activity (onset of cytotoxicity at 5 microM). When the cells were cultured in divalent cation-depleted medium, each dose-response curve was shifted to about a four-fold lower concentration range. Calprotectin was found to induce cell death even when the complex and the target cells were separated by dialysis membrane. A membrane-impermeable zinc chelator, diethylenetriamine pentaacetic acid (DTPA), also induced target cell apoptosis in a similar time-course as calprotectin. Moreover, the activities of calprotectin and DTPA were completely inhibited by the presence of zinc ions.

CONCLUSION

These data indicate that calprotectin has higher specific activity to induce apoptosis than the Individual subunits, and that the mechanism is exclusion of zinc from target cells.

Hyperzincemia with systemic inflammation: a heritable disorder of calprotectin metabolism with rheumatic manifestations?

A boy had infantile-onset systemic inflammation, growth failure, hepatosplenomegaly, anemia, leukocytopenia, progressive muscular dystrophy, and hypercalprotectinemia, resulting in marked hyperzincemia. His mother had a history of chronic arthritis since childhood and also showed hypercalprotectinemia/hyperzincemia. We postulate an inherent defect in calprotectin metabolism.

Calprotectin inhibits matrix metalloproteinases by sequestration of zinc

BACKGROUND/AIMS

Calprotectin, a 36 kDa protein present in neutrophil cytoplasm, has antimicrobial and apoptosis inducing activities, which are reversed by the addition of zinc. Matrix metalloproteinases (MMPs), a family of zinc dependent enzymes, are important in many normal biological processes including embryonic development, angiogenesis, and wound healing, but also pathological processes such as inflammation, cancer, and tissue destruction. The aim of this study was to investigate whether calprotectin can inhibit MMP activity, and whether such inhibition could be overcome by the addition of zinc.

METHODS

MMP activity was measured by the degradation of substrates precoated on to microwells, and visualised by Coomassie blue staining of residual substrate. Seven metalloproteinases (MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, and MMP-13) were tested against two substrates: gelatin and alpha-casein.

RESULTS

All MMPs except MMP-1 were active against gelatin, whereas MMP-7 was the only enzyme active against alpha-casein. The addition of calprotectin inhibited the activity of all the MMPs, but different concentrations of the protein, from 0.3 microM to > 11microM, were necessary to produce a 50% inhibition of the MMPs. Inhibition by calprotectin was largely overcome by the addition of zinc.

CONCLUSIONS

The findings suggest that calprotectin inhibits MMPs by sequestration of zinc. The data also suggest that MMPs have different affinities for zinc and that calprotectin has a lower zinc affinity than the MMPs.

Biological variability of fecal calprotectin in patients referred for colonoscopy without colonic inflammation or neoplasm

OBJECTIVE

Fecal calprotectin concentration in stool has recently been proposed as a marker of colonic neoplasm and inflammation, but the intraindividual day-to-day variability has so far received little attention. The present study was undertaken to determine the biological variability of fecal calprotectin in patients referred for colonoscopy.

METHODS

A prospective design was applied. In each of 14 consecutive patients submitted for colonoscopy, eight stool samples were collected before the endoscopy. A detailed questionnaire was used. Calprotectin was measured by quantitative enzyme-linked immunoassay, and standard deviation for the within-patient variability was estimated from one-way analysis of variance.

RESULTS

In absence of colonic neoplasm and inflammation, two populations of patients emerged: one (36%) with remarkably low and stable fecal calprotectin values all within the recommended cut-off of 50 microg/g, and one (64%) with labile values also beyond this limit. In this latter group. fecal calprotectin was 70 microg/g (mean) (single tests ranged from 9 to 461), and SD within patients was 52 microg/g, showing considerable day-to-day variation. History, concurrent diseases, or findings at colonoscopy could not explain labile values. A similar pattern was observed for spot variation in one stool sample from healthy volunteers, suggesting that factors other than disease contribute to the significant intraindividual biological variation of fecal calprotectin.

CONCLUSIONS

Day-to-day variation of fecal calprotectin is considerable in patients without colonic inflammation or neoplasm, for whom the pattern of stabile low fecal calprotectin may seem to be a valid negative predictor. The origin and pattern of fecal calprotectin excretion deserve further attention.

Calcitermin, a novel antimicrobial peptide isolated from human airway secretions

The human airways are protected from pathogenic colonization by a blanket of fluid impregnated with innate antimicrobial effector molecules. Among several previously uncharacterized components, we isolated a peptide that had activity primarily targeting Gram-negative bacteria. We named the peptide 'calcitermin' since its amino acid sequence and mass were equivalent to the 15 C-terminal residues of the S100 protein, calgranulin C. The antimicrobial activity of calcitermin was enhanced in acidic buffers (pH 5.4) and in the presence of micromolar concentrations of ZnCl(2). Analysis revealed a putative zinc-binding consensus sequence as well as an alpha-helical conformation in structure-promoting solvents.

A comparison of salivary calprotectin levels in subjects with and without oral candidiasis

OBJECTIVES

The purpose of this study was to compare salivary calprotectin levels in subjects with oral candidiasis to the levels in healthy age- and sex-matched control subjects and to investigate the relationship of salivary calprotectin to intensity of oral candidal carriage and infection and to predisposing factors for candidiasis.

STUDY DESIGN

Using enzyme-linked immunosorbent assay, we measured calprotectin in unstimulated whole saliva collected from 22 subjects with oral candidiasis and in saliva collected from 22 control subjects. Calprotectin levels in the 2 groups were compared by using the Wilcoxon signed rank test. The relationships between calprotectin levels and Candida counts were assessed by using the Spearman rank correlation test. The nonparametric 1-way analysis of variance test was used to study the relationship between calprotectin levels and presence of non-albicans Candida and individual predisposing factors for candidiasis. The Kruskal-Wallis test was used to evaluate the relationship between calprotectin and predisposing factors in subjects grouped by total number of predisposing factors identified.

RESULTS

No relationship was found between calprotectin and individual or total number of predisposing factors. Higher calprotectin levels were found in subjects with candidiasis, and calprotectin concentration positively correlated with intensity of candidal infection.

CONCLUSIONS

These findings suggest that calprotectin production, or release, or both, may be increased in subjects with candidiasis.

Calprotectin expression inhibits bacterial binding to mucosal epithelial cells

Squamous mucosal epithelial cells constitutively express calprotectin in the cytoplasm. To study how this antimicrobial protein complex confers epithelial resistance to invading bacteria, an epithelial cell line was stably transfected to express the calprotectin complex. Cells expressing calprotectin resist invasion by Listeria monocytogenes and Salmonella enterica serovar Typhimurium. Calprotectin expression was accompanied by altered actin organization, increased alpha3 integrin expression, and spreading cell morphology. In this study, we assessed whether calprotectin expression affects bacterial binding and uptake. Threefold-fewer Listeria organisms bound to the surfaces of calprotectin-expressing cells, and 10-fold fewer were localized intracellularly by immunofluorescence. Similarly, fewer Salmonella organisms bound to cells expressing calprotectin. Calprotectin-expressing and sham-transfected cells showed similar levels of expression of surface E-cadherin and intracellular adhesion molecule 1 (ICAM-1) by flow cytometry. Calprotectin-expressing transfectants expressed calprotectin on the cell surface as well as in the cytosol. In conclusion, two bacterial pathogens showed reduced binding to calprotectin-expressing epithelial cells. Calprotectin-expressing cells appeared to have internalized disproportionately fewer Listeria organisms, suggesting that reduced binding and translocation supplemented direct antimicrobial effects in calprotectin-expressing cells.

Increased circulating levels of alpha1-antitrypsin and calprotectin are associated with reduced gas diffusion in the lungs

The aim was to examine the relationship of serum inflammatory markers to the level of single-breath diffusing capacity of carbon monoxide (TL,CO). A stratified sample (n = 1,121) of a Norwegian general population aged 18-73 yrs was examined. The inflammatory markers measured were calprotectin, a prominent protein in the cytosol fraction of neutrophil granulocytes, and alpha1-antitrypsin (alpha1-AT), the major inhibitor of neutrophil elastase in the lower respiratory system. Both markers have increased circulating levels in the course of an acute inflammatory reaction. Subjects with a TL,CO < 80% of predicted value had a higher level of both alpha1-AT (p = 0.003) and calprotectin (p < 0.03) than those with a TL,CO > 100%. In multiple linear regression analyses, alpha1-AT was still significantly associated with TL,CO after adjusting for sex, age, smoking habits, haemoglobin, carboxyhaemoglobin, forced expiratory volume in one second and alveolar volume. In a similar analysis, no significant overall association was found between calprotectin and TL,CO, but in a stratified analysis, calprotectin was significantly related to TL,CO in females. However, no significant sex interaction in the relationship between the inflammatory markers and TL,COo was found. The findings suggest that increased levels of alpha1-antitrypsin and of calprotectin are risk factors for decreased diffusing capacity of carbon monoxide.

Il-10 up-regulates macrophage expression of the S100 protein S100A8

The murine calcium binding protein S100A8 (A8) is a leukocyte chemoattractant, but high levels may be protective and scavenge hypochlorite. A8 is induced by LPS, IFN-gamma, and TNF in elicited macrophages. Th2 cytokines generally suppress proinflammatory gene expression, and IL-4 and IL-13 partially decreased A8 induction in macrophages and endothelial cells stimulated by LPS or IFN. In contrast, IL-10 synergized with LPS and IFN to increase mRNA levels > or =9-fold and secreted A8 levels approximately 4-fold. IL-10 decreased the optimal time of mRNA expression induced by LPS from 24 to 8 h. Blocking experiments indicated that endogenous IL-10 contributes to gene induction by LPS. Cooperation between IL-10 and LPS was not due to altered mRNA stability but was dependent on de novo protein synthesis. Transfection analysis with A8 luciferase constructs confirmed that synergy was due to increased transcription. The region of the promoter involved was localized to a 178-bp fragment flanking the transcription start site of the gene. This region was also responsible for the suppressive effects of IL-4 and IL-13. Forskolin, CTP-cAMP, and PGE(2) also enhanced LPS- and IFN-induced A8 mRNA, whereas indomethacin significantly reduced synergy between IL-10 and LPS. Mitogen-activated protein kinase/cyclooxygenase 2/cAMP pathways involving CCAAT-enhancing binding protein, located within the active promoter, may mediate A8 gene up-regulation in a manner mechanistically distinct to genes regulated by IL-10 via the STAT pathway. A8 exhibits pleiotropic effects, and the high levels secreted as a result of IL-10 synergy may regulate untoward inflammatory damage by virtue of its an antioxidant capacity.

Effect of metals on Candida albicans growth in the presence of chemical chelators and human abscess fluid

Calprotectin is a calcium- and zinc-binding protein that is present in abscess fluid supernatants and appears to inhibit microbial growth through competition for zinc. In the present study, growth inhibition by chemical chelators was compared with that produced by human abscess fluid to determine whether other chelators, perhaps with different metal specificities, would have the same or different patterns of metal reversibility as abscess fluid. Zinc was found to be more potent than the other metals tested in reversing C. albicans growth inhibition by human abscess fluid and three chemical chelators, even though in some cases the stability constants of certain of these chelators were higher for other metals. For example, in the presence of the chelator diethylenetriaminopentaacetic acid, zinc stimulated Candida growth at a 10-fold lower concentration than did iron, even though this chelator has a stability constant for iron that is almost 10(10) higher than that for zinc. These results suggest that the zinc specificity of calprotectin's C. albicans growth inhibition can best be explained by the marked sensitivity of this organism to zinc deprivation rather than by selective binding of this metal by the protein.

Fecal calprotectin levels predict colorectal inflammation among patients with chronic diarrhea referred for colonoscopy

OBJECTIVE

Chronic diarrhea is a relatively common condition with multiple diverse etiologies. Stool testing may serve as a diagnostic aid to discriminate the presence or absence of organic pathology, such as colorectal inflammation. Calprotectin (a leukocyte-derived protein) and hemoglobin can be measured quantitatively from stool and represent candidate inflammation biomarkers. The aim of this study was to assess and compare the screening performance of fecal calprotectin and fecal hemoglobin among colonoscopy referral patients with chronic diarrhea of unknown origin or chronic colitis of unknown activity.

METHODS

All subjects were identified prospectively and each submitted a single stool sample before purgation. Fecal calprotectin (PhiCal; Nycomed Pharma, Oslo, Norway) and fecal hemoglobin (HemoQuant; Mayo Medical Laboratories, Rochester, MN) assays were performed in separate laboratories by masked technicians. Colonoscopic and histological findings served as criterion standards for establishing the presence or absence of colorectal inflammation.

RESULTS

Among 110 subjects who provided complete fecal assay data, 29 (26%) had and 81 (74%) did not have colorectal inflammation. Increased fecal calprotectin levels were significantly (p = 0.0001) associated with the presence of colorectal inflammation, whereas fecal hemoglobin levels were not (p = 0.61). Direct comparison of the fecal assays revealed that calprotectin was a more sensitive biomarker for colorectal inflammation at all specificity levels (p = 0.0001).

CONCLUSIONS

In this study of colonoscopy referral patients, colorectal inflammation was reflected by fecal calprotectin but not by fecal hemoglobin levels. Assay of fecal calprotectin holds promise as a triage tool to identify inflammatory causes of chronic diarrhea.

Calprotectin (MRP8/14 protein complex) release during mycobacterial infection in vitro and in vivo

The calprotectin (MRP8/14) protein complex belongs to the S100 family of Ca2+ binding proteins and is expressed during myelomonocytic differentiation. MRP8/14 plasma levels were determined by ELISA in 35 patients with active pulmonary tuberculosis (TB) showing mild (n = 12), moderate (n = 11) or severe (n = 12) disease, 13 patients with active pulmonary sarcoidosis (SR) and 21 healthy controls. TB patients had significantly increased plasma levels of MRP8/14 in comparison with SR and controls, which significantly depended on the volume of lung tissue involved in the inflammatory process. In TB patients, there was no correlation between plasma levels of MRP8/14 and total white blood cell (WBC) count, and blood polymorphonuclear neutrophil (PMN) count. In SR patients, MRP8/14 plasma levels were twofold higher in comparison with controls, but were lower compared with mild TB, and correlated with PMN and WBC counts. Human monocytes infected and cultured for 7 days with Mycobacterium bovis bacillus Calmette-Guérin showed fivefold higher MRP8/14 levels in supernatants compared with unstimulated or purified protein derivative-stimulated cells. Human MRP8/14 significantly increased Mycobacterium tuberculosis H37Rv growth in liquid medium in a dose- and time-dependent manner. These findings suggest that MRP8/14 plays an important role in the immunopathogenesis of tuberculosis.

Faecal calprotectin levels in a high risk population for colorectal neoplasia

BACKGROUND

Faecal concentrations of the protein calprotectin have been found to be elevated in patients with colorectal neoplasia, suggesting that it might be used as a screening tool for colorectal cancer as well as adenomas.

AIMS

To measure the sensitivity and specificity of faecal calprotectin for the detection of adenomas in high risk individuals undergoing colonoscopy. Also, to investigate between and within stool variability of calprotectin concentrations.

SUBJECTS

A total of 814 patients planned for colonoscopy were included for the following indications: positive faecal occult blood test, 25; neoplasia surveillance, 605; newly detected polyp, 130; and family risk, 54.

METHODS

Two faecal samples from each of two stools were analysed using the PhiCal ELISA test device (Nycomed Pharma AS).

RESULTS

Adenoma patients had significantly higher calprotectin levels than normal subjects (median 9.1 (95% confidence interval 7.5-10.1) v 6.6 (5.6-7.4)mg/l). There was no significant decrease in calprotectin levels after polypectomy. Levels in cancer patients were significantly higher than those in all other subgroups (median 17.6 mg/l (11.5-31.0)). With a cut off limit of 10 mg/l, the sensitivity for cancer was 74% and for adenoma 43%. Corresponding specificity values were 64% for no cancer and 67% for no neoplasia (cancer+adenoma). Specificity varied from 71% for one stool sample to 63% for four samples. Stool variability was small, suggesting that two spots from one stool were as discriminative as two spots from each of two stools.

CONCLUSIONS

The sensitivity and specificity of faecal calprotectin levels as a marker for colorectal adenoma and carcinoma justifies its use in high risk groups, but specificity is too low for screening of average risk persons. Lack of a decrease in levels after polypectomy may be due to a more widespread leucocyte migration into the intestinal lumen than that at the polyp site, and needs further investigation.

Improved assay for fecal calprotectin

Fecal calprotectin is a marker of inflammatory and neoplastic disease in the lower gastrointestinal tract. A new fecal sample preparation procedure for the measurement of calprotectin has been developed, with higher calprotectin yield and lower contamination risk. Changes in the new method compared to the original [Roseth AG, Fagerhol MK, Aadland E, Schonsby H. Assessment of the neutrophil dominating protein calprotectin in feces. A methodologic study. Scand J Gastroenterol 1992;27(9):793-798] are smaller sample size, higher dilution of the sample, presence of dissociating agents in the extraction solution and procedure performed in closed disposable tubes. The extraction yield was 78% (41-100%) of total calprotectin, giving an overall five-fold increase compared to the original method. Samples with high calprotectin values were increased to a slightly higher degree, than low calprotectin samples, thus improving the separation between high and low calprotectin levels. Median calprotectin level in healthy subjects was 26 microg/g. Pathological samples with pancolitis showed levels up to 30000 microg/g. The mean C.V. (coefficient of variation) in blended feces was lower than that of unblended, suggesting uneven distribution of calprotectin. However, no significant difference between spot measurements was found when five samples from each of 47 stools were measured. Thus measurements of calprotectin in fecal samples were accurate and reproducible. No interference with foods or relevant oral pharmaceuticals or nutraceuticals was found.

Oxidation regulates the inflammatory properties of the murine S100 protein S100A8

The myeloid cell-derived calcium-binding murine protein, S100A8, is secreted to act as a chemotactic factor at picomolar concentrations, stimulating recruitment of myeloid cells to inflammatory sites. S100A8 may be exposed to oxygen metabolites, particularly hypochlorite, the major oxidant generated by activated neutrophils at inflammatory sites. Here we show that hypochlorite oxidizes the single Cys residue (Cys41) of S100A8. Electrospray mass spectrometry and SDS-polyacrylamide gel electrophoresis analysis indicated that low concentrations of hypochlorite (40 microM) converted 70-80% of S100A8 to the disulfide-linked homodimer. The mass was 20,707 Da, 92 Da more than expected, indicating additional oxidation of susceptible amino acids (possibly methionine). Phorbol 12-myristate 13-acetate activation of differentiated HL-60 granulocytic cells generated an oxidative burst that was sufficient to efficiently oxidize exogenous S100A8 within 10 min, and results implicate involvement of the myeloperoxidase system. Moreover, disulfide-linked dimer was identified in lung lavage fluid of mice with endotoxin-induced pulmonary injury. S100A8 dimer was inactive in chemotaxis and failed to recruit leukocytes in vivo. Positive chemotactic activity of recombinant Ala41S100A8 indicated that Cys41 was not essential for function and suggested that covalent dimerization may structurally modify accessibility of the chemotactic hinge domain. Disulfide-dependent dimerization may be a physiologically significant regulatory mechanism controlling S100A8-provoked leukocyte recruitment.

Overexpression, oxidative refolding, and zinc binding of recombinant forms of the murine S100 protein MRP14 (S100A9)

Recombinant murine MRP14 (mMRP14) was produced in Escherichia coli using the pGEX expression system. The mass of fusion protein, by electrospray ionization-mass spectrometry (ESI/MS), was 39,213 Da which compares well with the theoretical mass (39,210.4 Da). Thrombin digestion of fusion protein was expected at a cloned thrombin consensus sequence (. LVPRGS. ) located between glutathione S-transferase and mMRP14. Analysis of products of digestion by C4 reverse-phase HPLC and SDS-PAGE/Western blotting revealed two immunoreactive cleavage products with molecular weights around 13, 000. Masses of the two proteins determined by ESI/MS were 13,062 and 11,919 Da. The larger product corresponded to the expected mass of recombinant mMRP14 (13,061.9 Da). Analysis of the protein sequence of recombinant mMRP14 revealed a thrombin-like consensus sequence (. NNPRGH. ) located close to the C-terminus. The smaller protein corresponded to a truncated form of rec mMRP14 (rec MRP141-102) with a calculated mass of 11,918.6 Da. Optimization of the cleavage conditions resulted in >95% full-length rec mMRP14. Native mMRP14 contains one intramolecular disulfide bond between Cys79 and Cys90. The full-length recombinant protein was renatured and oxidized in ammonium acetate (pH approximately 7) for 96 h and formed >95% of the native intramolecular disulfide-bonded form. MRP141-102 bound substantially less 65Zn2+ compared to native mMRP14 or rec mMRP14 after transfer to polyvinylidene difluoride and incubation with 65ZnCl2, implicating the His residues located within the C-terminal domain in Zn2+ binding.

Evidence that calgranulin is produced by kidney cells and is an inhibitor of calcium oxalate crystallization

Urine produced by normal human kidneys is almost always supersaturated with respect to calcium oxalate (CaOx), the most common constituent of human kidney stones. Crystallization, with risk of renal damage and kidney stones, appears to be affected by molecules in urine that retard nucleation, growth, aggregation, and renal cell adherence of CaOx. The repertoire of such molecules is incompletely known. We have purified a 28-kDa protein from urine using salt precipitation, preparative isoelectric focusing, and sizing chromatography. Amino acid composition and NH2-terminal amino sequence analysis showed complete homology to calgranulin. Calgranulin was found to be a potent inhibitor of CaOx crystal growth (44% of control) and aggregation (50% of control) in the nanomolar range. Calgranulin cDNA was cloned from a human kidney expression library. Western analysis of human and rat kidney homogenates and mRNA temporal expression from two independent renal epithelial cell lines showed that calgranulin is produced in the kidney. Given its urinary abundance and potency, calgranulin may contribute importantly to the normal urinary inhibition of crystal growth and aggregation and therefore to the renal defense against clinical stone disease.