Human Calprotectin Research Articles

The pro-apoptotic and pro-inflammatory effects of calprotectin on human periodontal ligament cells.

Calprotectin, a heterodimer of S100A8 and S100A9 subunits, is associated with inflammatory disorders such as rheumatoid arthritis and cystic fibrosis. Although calprotectin levels are increased significantly in the gingival crevicular fluid (GCF) of periodontitis patients, its effects on periodontal ligament cells (PDLCs) remain largely unknown. The aim of this study was to evaluate calprotectin levels in the GCF of generalized aggressive periodontitis (AgP) patients and to investigate the effects of recombinant human calprotectin (rhS100A8/A9) and its subunits (rhS100A8 and rhS100A9) in PDLCs. Both the concentration and amount of crevicular calprotectin were significantly higher in the AgP group compared with healthy controls. In addition, the GCF calprotectin levels were correlated positively with clinical periodontal parameters including bleeding index, probing depth, and clinical attachment loss. rhS100A8/A9 promoted cell apoptosis, whereas rhS100A8 and rhS100A9 individually exerted little effect on apoptosis in PDLCs. rhS100A9 and rhS100A8/A9 increased the activation of nuclear factor-κB (NF-κB) by promoting the nuclear translocation of p65 in PDLCs, subsequently inducing expression of the pro-inflammatory cytokines IL-6, IL-8, TNFα, and COX2. Treatment with an NF-κB inhibitor partially reversed the rhS100A9- and rhS100A8/A9-induced upregulation of the pro-inflammatory cytokines. rhS100A9, and not rhS100A8, was mainly responsible for the pro-inflammatory role of calprotectin. Collectively, our results suggest that calprotectin promotes apoptosis and the inflammatory response in PDLCs via rhS100A9. These findings might help identify novel treatments for periodontitis.

In solution cation-induced secondary and tertiary structure alterations of human calprotectin.

Calprotectin (CP) is widely considered to have diverse roles including growth inhibitory and apoptosis induction in a number of tumor cell lines and antimicrobial activities. As CP has been proposed to bind metal ions with high affinity, we have studied its functional and primarily its structural behavior upon Zn(2+) and Mn(2+) chelation solely and along with Ca(2+). We employed fluorescence spectroscopy and circular dichroism to determine the resulting modifications. Based upon our findings it is clear that treating CP with ions effectively weakened its natural growth inhibitory activity. Moreover, structural analysis of Zn(2+) and Mn(2+)-treated CPs indicated remarkable alterations in the regular secondary structures in favor of irregular structures while Zn(2+) and Mn(2+) treatment of CP after incubation with Ca(2+) displayed no remarkable shifts. Tertiary structure investigation using fluorescence spectroscopy showed that CP undergoes conformational changes upon Zn(2+) and Mn(2+) treatment whereby Trp residues of protein is slightly exposed to the hydrophilic environment, compactness of CP is compromised, whereas in Ca(2+)-treated CP, the tertiary structure integrity is intact upon Zn(2+) and Mn(2+) chelation. Interestingly, CP structural modifications upon Zn(2+) and Mn(2+) treatment was significantly comparable, probably due to similar radii and charges of ions. Taken all together, we have concluded that CP maintains its normal nature in Ca(2+)-loaded state when treated with Zn(2+) and Mn(2+) ions. It can be suggested that Ca(2+) not only stabilize CP structure but also helps CP to keep its structure upon metal ions chelation which is involved in host organism defense system.

Contributions of the S100A9 C-terminal tail to high-affinity Mn(II) chelation by the host-defense protein human calprotectin.

Human calprotectin (CP) is an antimicrobial protein that coordinates Mn(II) with high affinity in a Ca(II)-dependent manner at an unusual histidine-rich site (site 2) formed at the S100A8/S100A9 dimer interface. We present a 16-member CP mutant family where mutations in the S100A9 C-terminal tail (residues 96-114) are employed to evaluate the contributions of this region, which houses three histidines and four acidic residues, to Mn(II) coordination at site 2. The results from analytical size-exclusion chromatography, Mn(II) competition titrations, and electron paramagnetic resonance spectroscopy establish that the C-terminal tail is essential for high-affinity Mn(II) coordination by CP in solution. The studies indicate that His103 and His105 (HXH motif) of the tail complete the Mn(II) coordination sphere in solution, affording an unprecedented biological His6 site. These solution studies are in agreement with a Mn(II)-CP crystal structure reported recently (Damo, S. M.; et al. Proc. Natl. Acad. Sci. U.S.A. 2013, 110, 3841). Remarkably high-affinity Mn(II) binding is retained when either H103 or H105 are mutated to Ala, when the HXH motif is shifted from positions 103-105 to 104-106, and when the human tail is substituted by the C-terminal tail of murine S100A9. Nevertheless, antibacterial activity assays employing human CP mutants reveal that the native disposition of His residues is important for conferring growth inhibition against Escherichia coli and Staphylococcus aureus. Within the S100 family, the S100A8/S100A9 heterooligomer is essential for providing high-affinity Mn(II) binding; the S100A7, S100A9(C3S), S100A12, and S100B homodimers do not exhibit such Mn(II)-binding capacity.

P2.113 Urinary Calprotectin: A Biomarker of Urethral Inflammation

BackgroundThere is currently no reliable indicator of inflammation available for the evaluation of genital tract syndromes. We investigated the association of urinary calprotectin concentration, an innate immune system mediator protein,...

High-Affinity Manganese Coordination by Human Calprotectin Is Calcium-Dependent and Requires the Histidine-Rich Site Formed at the Dimer Interface

Calprotectin (CP) is a transition metal-chelating antimicrobial protein of the calcium-binding S100 family that is produced and released by neutrophils. It inhibits the growth of various pathogenic microorganisms by sequestering the transition metal ions manganese and zinc. In this work, we investigate the manganese-binding properties of CP. We demonstrate that the unusual His(4) motif (site 2) formed at the S100A8/S100A9 dimer interface is the site of high-affinity Mn(II) coordination. We identify a low-temperature Mn(II) spectroscopic signal for this site consistent with an octahedral Mn(II) coordination sphere with simulated zero-field splitting parameters D = 270 MHz and E/D = 0.30 (E = 81 MHz). This analysis, combined with studies of mutant proteins, suggests that four histidine residues (H17 and H27 of S100A8; H91 and H95 of S100A9) coordinate Mn(II) in addition to two as-yet unidentified ligands. The His(3)Asp motif (site 1), which is also formed at the S100A8/S100A9 dimer interface, does not provide a high-affinity Mn(II) binding site. Calcium binding to the EF-hand domains of CP increases the Mn(II) affinity of the His(4) site from the low-micromolar to the mid-nanomolar range. Metal-ion selectivity studies demonstrate that CP prefers to coordinate Zn(II) over Mn(II). Nevertheless, the specificity of Mn(II) for the His(4) site provides CP with the propensity to form mixed Zn:Mn:CP complexes where one Zn(II) ion occupies site 1 and one Mn(II) ion occupies site 2. These studies support the notion that CP responds to physiological calcium ion gradients to become a high-affinity transition metal ion chelator in the extracellular space where it inhibits microbial growth.

Calcium Ion Gradients Modulate the Zinc Affinity and Antibacterial Activity of Human Calprotectin

Calprotectin (CP) is an antimicrobial protein produced and released by neutrophils that inhibits the growth of pathogenic microorganisms by sequestering essential metal nutrients in the extracellular space. In this work, spectroscopic and thermodynamic metal-binding studies are presented to delineate the zinc-binding properties of CP. Unique optical absorption and EPR spectroscopic signatures for the interfacial His(3)Asp and His(4) sites of human calprotectin are identified by using Co(II) as a spectroscopic probe. Zinc competition titrations employing chromophoric Zn(II) indicators provide a 2:1 Zn(II):CP stoichiometry, confirm that the His(3)Asp and His(4) sites of CP coordinate Zn(II), and reveal that the Zn(II) affinity of both sites is calcium-dependent. The calcium-insensitive Zn(II) competitor ZP4 affords dissociation constants of K(d1) = 133 ± 58 pM and K(d2) = 185 ± 219 nM for CP in the absence of Ca(II). These values decrease to K(d1) ≤ 10 pM and K(d2) ≤ 240 pM in the presence of excess Ca(II). The K(d1) and K(d2) values are assigned to the His(3)Asp and His(4) sites, respectively. In vitro antibacterial activity assays indicate that the metal-binding sites and Ca(II)-replete conditions are required for CP to inhibit the growth of both Gram-negative and -positive bacteria. Taken together, these data provide a working model whereby calprotectin responds to physiological Ca(II) gradients to become a potent Zn(II) chelator in the extracellular space.

Cytotoxic effects of human calprotectin on gastric cancer cell line is attenuated by etoposide.

In this paper effect of combinational usage of calprotectin and etoposide on AGS cell line is studied. Application of combined toxic agents such as etoposide and cicplatin are commonly used for chemotherapy purposes. As a matter of fact, calprotectin and etoposide were both applied on human gastric adenocarcinoma cell line (AGS) as antitumor agents. Both calprotectin and etoposide are topo II inhibitor. Etoposide is a lipophilic agent that can easily transport from membrane while calprotectin active intracellular pathway, probably by membrane surface receptor. Calprotectin was purified from human neutrophil by chromatography methods. The human gastric adenocarcinoma cell line was exposed to different concentrations and combinations of calprotectin and etoposide. MTT assay was applied for evaluation of cytotoxicity assay. Viability of AGS cell line was reduced in high dosages of calprotectin and etposide. In fact, overnight incubation of these two agents together has been shown less effective than individual usage. The result indicates that, the combination of both calprotectin and etoposide is considerably less cytotoxic on gastric cancer cells (AGS) than applying individually.

Proteomic Analysis of Human Saliva From Lung Cancer Patients Using Two-Dimensional Difference Gel Electrophoresis and Mass Spectrometry

Lung cancer is often asymptomatic or causes only nonspecific symptoms in its early stages. Early detection represents one of the most promising approaches to reduce the growing lung cancer burden. Human saliva is an attractive diagnostic fluid because its collection is less invasive than that of tissue or blood. Profiling of proteins in saliva over the course of disease progression could reveal potential biomarkers indicative of oral or systematic diseases, which may be used extensively in future medical diagnostics. There were 72 subjects enrolled in this study for saliva sample collection according to the approved protocol. Two-dimensional difference gel electrophoresis combined with MS was the platform for salivary proteome separation, quantification, and identification from two pooled samples. Candidate proteomic biomarkers were verified and prevalidated by using immunoassay methods. There were 16 candidate protein biomarkers discovered by two-dimensional difference gel electrophoresis and MS. Three proteins were further verified in the discovery sample set, prevalidation sample set, and lung cancer cell lines. The discriminatory power of these candidate biomarkers in lung cancer patients and healthy control subjects can reach 88.5% sensitivity and 92.3% specificity with AUC = 0.90. This preliminary data report demonstrates that proteomic biomarkers are present in human saliva when people develop lung cancer. The discriminatory power of these candidate biomarkers indicate that a simple saliva test might be established for lung cancer clinical screening and detection.

Study of apoptosis inducing activity of calprotectin on fibroblast cell

One of the prominent types of connective tissue cells is fibroblast that synthesizes and maintains the extracellular matrix of many animal tissues. Previous studies illustrated that calprotectin protein has different cytotoxicity effects on fibroblast cells. Calprotectin is abundant in the neutrophil cytosol; it has growth-inhibitory and apoptosis-inducing activities against various cell types such as tumor cells. The present study tries to introduce mechanism of growth inhibitory effect of calprotectin on human foreskin fibroblast cells (HFFF) and compare to etoposide (chemotherapy agent as control). Calprotectin was purified from human neutrophil by chromatography methods. HFFF cell lines were used, maintained in RPMI 1640 medium supplemented with 10% FCS in a humidified incubator (37 oC & 5% CO2). The HFFF cells were exposed to the different concentrations of calprotectin and etoposide for 24, 48 and 72 hours. Cell proliferation was assessed by using dimethylthiazol diphenyl tetrazolium bromide assay. Flow cytometric analysis was performed to evaluate the cytotoxic mechanism of calprotectin on HFFF cells. Our results revealed that calprotectin and etoposide induce growth inhibition of HFFF in dose- and time-dependent manners. Sensitivity of HFFF cells to cytotoxic effect of human calprotectin was highly remarkable. In addition, growth inhibitory effect of this cytotoxic agent mostly was governed through induction of apoptosis in the HFFF cells. Taken together, calprotectin not only has more potent anticancer activity in comparison with the etoposide, but it also is an apoptosis inducer that acts on the proliferation of normal cells like fibroblasts.

Structure and Mode of Action of Microplusin, a Copper II-chelating Antimicrobial Peptide from the Cattle Tick Rhipicephalus (Boophilus) microplus

Microplusin, a Rhipicephalus (Boophilus) microplus antimicrobial peptide (AMP) is the first fully characterized member of a new family of cysteine-rich AMPs with histidine-rich regions at the N and C termini. In the tick, microplusin belongs to the arsenal of innate defense molecules active against bacteria and fungi. Here we describe the NMR solution structure of microplusin and demonstrate that the protein binds copper II and iron II. Structured as a single alpha-helical globular domain, microplusin consists of five alpha-helices: alpha1 (residues Gly-9 to Arg-21), alpha2 (residues Glu-27 to Asn-40), alpha3 (residues Arg-44 to Thr-54), alpha4 (residues Leu-57 to Tyr-64), and alpha5 (residues Asn-67 to Cys-80). The N and C termini are disordered. This structure is unlike any other AMP structures described to date. We also used NMR spectroscopy to map the copper binding region on microplusin. Finally, using the Gram-positive bacteria Micrococcus luteus as a model, we studied of mode of action of microplusin. Microplusin has a bacteriostatic effect and does not permeabilize the bacterial membrane. Because microplusin binds metals, we tested whether this was related to its antimicrobial activity. We found that the bacteriostatic effect of microplusin was fully reversed by supplementation of culture media with copper II but not iron II. We also demonstrated that microplusin affects M. luteus respiration, a copper-dependent process. Thus, we conclude that the antibacterial effect of microplusin is due to its ability to bind and sequester copper II.

Faecal DNA and calprotectin as biomarkers of acute intestinal toxicity in patients undergoing pelvic radiotherapy

Acute intestinal toxicity is a frequent complication that may lead to interruption of treatment in patients undergoing pelvic radiotherapy. Reliable, non-invasive biological markers to evidence their severity are not yet available. To test faecal DNA and calprotectin as potential biomarkers of intestinal toxicity caused by pelvic radiotherapy. Patients were categorized according to the location of the cancer as nonrectal (n = 25) and rectal (n = 27). Four stool samples were collected at weeks w0, w3, w5 (end of radiotherapy) and w7. Faecal DNA was determined by quantitative PCR and calprotectin by ELISA. Intestinal toxicity was scored according to the Common Toxicity Criteria. In the nonrectal group, acute diarrhoea toxicity was present in 80% of patients, faecal DNA increased 10-fold during radiotherapy (1.5 x 10(3) copies/mg dry weight, 9.5 x 10(2)-8.8 x 10(3) at w0, median and interquartile range vs. 1.3 x 10(4), 1.9 x 10(3)-3.9 x 10(4) at w5, P < 0.01), but was not recovered at w7 (3.4 x 10(3), 1.5 x 10(3)-4.1 x 10(4)) and calprotectin doubled during treatment at w3 and w5. No significant changes in faecal markers were found in the rectal group. Faecal excretion of human DNA and calprotectin increased during pelvic radiotherapy treatment, and may be a good objective biomarker of intestinal damage in nonrectal cancer patients.

A Comparative Study of Inhibitory Effect of Human Calprotectin on the Growth of Human Gingival Fibroblast and Foreskin Fibroblast

In the present study, cytotoxicity effects of calprotectin on Human Gingival Fibroblast (HGF) and Human Foreskin Fibroblast (HFFF) were compared. For these evaluations, both cells were exposed to the different concentrations of calprotectin, for 24, 48 and 72 h. Cell proliferation was assessed using MTT assay. Our results revealed that growth inhibition of calprotectin on HGF and HFFF occur in a dose- and time-dependent manner. Results of this investigation showed that sensitivity of HGF cells to cytotoxic effect of human calprotectin was more than HFFF. The results indicate that drug resistance process is different for the two kinds of fibroblast cells.

Human Calprotectin: Effect of Calcium and Zinc on its Secondary and Tertiary Structures, and Role of pH in its Thermal Stability

Calprotectin, a heterodimeric complex belonging to the S100 protein family, has been found predominantly in the cytosolic fraction of neutrophils. In the present study, human calprotectin was purified from neutrophils using two-step ion exchange chromatography. The purified protein was used for circular dichroism study and fluorescence analysis in the presence of calcium and zinc at physiological concentrations, as well as for assessment of its inhibitory activity on the K562 leukemia cell line. The thermal stability of the protein at pH 7.0 (physiological pH) and 8.0 (similar to intestinal pH) was also compared. The results of cell proliferation analysis revealed that human calprotectin initiated growth inhibition of the tumor cells in a dose-dependent manner. The intrinsic fluorescence emission spectra of human calprotectin (50 microg/ml) in the presence of calcium and zinc ions show a reduction in fluorescence intensity, reflecting a conformational change within the protein with exposure of aromatic residues to the protein surface that is important for the biological function of calprotectin. The far ultraviolet-circular dichroism spectra of human calprotectin in the presence of calcium and zinc ions at physiological concentrations show a decrease in the alpha-helical content of the protein and an increase in beta- and other structures. Our results also show that increasing the pH level from 7.0 to 8.0 leads to a marked elevation in the thermal stability of human calprotectin, indicating a significant role for pH in the stability of calprotectin in the gut.

Human β-defensins, faecal calprotectin and TNF-α values in stools of preterm and term newborns: Is there a role in innate defense?

Innate antimicrobial peptides [defensins (D) are the most abundant in humans] are considered to play an important role in host defence against microbial invasion. In newborns a few investigations revealed the presence of human β-D (hβD) in tracheal aspirates and breast milk. Increase of faecal calprotectin (FC) in healthy newborns may be interpreted as a defence mechanism against yeast and fungi. Neonatal T-cells failed to produce a significant amount of TNF-α that could provide protection against infections.

On the mechanism of apoptosis-inducing activity of human calprotectin: Zinc sequestration, induction of a signaling pathway, or something else?

Calprotectin, a heterodimer present in neutrophil cytoplasm, has antimicrobial and apoptosis-inducing activities. At the moment, there are two general hypotheses about the mechanism of action of calprotectin: (i) exclusion of extracellular zinc by calprotectin, and consequently induction of apoptosis; (ii) binding of calprotectin to a cell membrane receptor, and consequently, activation of a signaling pathway for apoptosis. Here, we introduce another hypothesis, i.e. inhibition or destruction of "target" inside cells. We suggest that calprotectin might become internalized non-specifically, maybe in a process like pinocytosis. This process is probably independent of the zinc concentration. We also demonstrated that the internal target hypothesis successfully predicts cell survival behavior of cultured cells as a function of calprotectin concentration. Additional analyses should be performed to elucidate the real calprotectin "target".

Investigation on the Surface Hydrophobicity and Aggregation Kinetics of Human Calprotectin in the Presence of Calcium

Calcium and zinc binding protein, calprotectin is a multifunctional protein with broad spectrum antimicrobial and antitumoural activity. It was purified from human neutrophil, using a two-step ion exchange chromatography. Since surface hydrophobicity of calprotectin may be important in membrane anchoring, membrane penetration, subunits oligomerization and some biological roles of protein, in this study attempted to explore the effect of calcium in physiological range on the calprotectin lipophilicity. Incubation of human calprotectin (50 microg/ml) with different calcium concentrations showed that 1-anilino-8-naphthalene sulfonic acid (ANS) fluorescence intensity of the protein significantly elevates with calcium in a dose dependent manner, suggesting an increase in calprotectin surface hydrophobicity upon calcium binding. Our study also indicates that calcium at higher concentrations (6, 8 and 10 mM) induces aggregation of human calprotectin. Our finding demonstrates that the starting time and the rate constant of calprotectin aggregation depend on the calcium concentration.

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.

Mechanism of extracellular release of human neutrophil calprotectin complex

Calprotectin is an abundant cytosolic protein complex of human neutrophils with in vitro extracellular antimicrobial activity. Studies suggest that calprotectin may be actively secreted from intact HL-60 cells and that it can be translocated to polymorphonuclear neutrophil (PMN) cell membranes. To examine whether calprotectin is secreted extracellularly, we incubated soluble and particulate stimuli, including live and heat-inactivated Candida albicans, with whole blood and measured calprotectin levels in the plasma. We compared the release of calprotectin to that of lactoferrin, a protein known to be secreted by PMNs. Extracellular lactoferrin was detected after incubation with any of the particulate stimuli. In contrast, a significant increase in extracellular calprotectin was found only after incubation with live C. albicans. Specifically, the increase in extracellular calprotectin correlated directly with a proportional decrease in PMN viability. Our results indicate that human PMN calprotectin is not secreted extracellularly except as a result of cell disruption or death.

Distribution of osteopontin and calprotectin as matrix protein in calcium-containing stone.

We recently reported that osteopontin (OPN) and calprotectin (CPT) are present in the matrix of urinary calcium stones, and that OPN mRNA is expressed in the renal distal tubular cells. In the present study, we examined the immunohistochemical distributions of OPN and CPT in urinary stones. The stones used in this study were passed spontaneously from the upper urinary tract. One half of each of the stones was analyzed with an infrared spectrophotometer, and were shown to be comprised of calcium oxalate, calcium phosphate, uric acid and cystine. The other half of each stone was immersed in tetrasodium ethylenediamine-tetraacetate (EDTA) solution. The half-stones were embedded in paraffin and cut into 5-microm sections. The avidin-biotin-peroxidase complex technique was employed. A monoclonal antibody to human milk-derived OPN and a monoclonal antibody to human granulocyte-derived CPT were used as primary antibodies. The immunochemical study using the OPN and CPT antibodies showed positive staining of the matrix of the urinary calcium stones. The stones showed staining in two distinct zones: a core area was stained with randomly aggregated OPN and CPT, and peripheral layers were stained in concentric circles. On the basis of our observations, it is reasonable to presume that OPN and CPT play roles as the matrix in the structure of urinary calcium stones.