Two-dimensional electrophoretic patterns of acute-phase human serum proteins in the course of bacterial and viral diseases

Differences in the Synovial Fluid Proteome of Septic and Aseptic Implant Failure

Implant loosening is a severe complication after total joint replacement. Here, differential diagnosis between septic and aseptic cases is crucial for further surgical treatment, but low-grade periprosthetic joint infections (PJIs) in particular remain a challenge. In this study, we analyzed the synovial fluid proteome of 21 patients undergoing revision surgery for septic (eight cases) or aseptic (thirteen cases) implant failure using LC-MS/MS to identify potential new biomarkers as future diagnostic tools. Staphylococci were found in four cases, Streptococci in two cases, Serratia marcescens and Cutibacterium acnes in one case. Proteomic analysis of the synovial fluid resulted in the identification of 515 different proteins based on at least two peptides. A statistical comparison revealed 37 differentially abundant proteins (p < 0.05), of which 17 proteins (46%) showed a higher abundance in the septic group. The proteins with the highest fold change included the known marker proteins c-reactive protein (7.57-fold) and the calprotectin components protein S100-A8 (4.41-fold) and protein S100-A9 (3.1-fold). However, the protein with the highest fold change was leucine-rich alpha-2-glycoprotein 1 (LRG1) (9.07-fold), a currently discussed new biomarker for inflammatory diseases. Elevated LRG1 levels could facilitate the diagnosis of PJI in the future, but their significance needs to be further investigated.

LRG1: an emerging player in disease pathogenesis

The secreted glycoprotein leucine-rich α-2 glycoprotein 1 (LRG1) was first described as a key player in pathogenic ocular neovascularization almost a decade ago. Since then, an increasing number of publications have reported the involvement of LRG1 in multiple human conditions including cancer, diabetes, cardiovascular disease, neurological disease, and inflammatory disorders. The purpose of this review is to provide, for the first time, a comprehensive overview of the LRG1 literature considering its role in health and disease. Although LRG1 is constitutively expressed by hepatocytes and neutrophils, Lrg1-/- mice show no overt phenotypic abnormality suggesting that LRG1 is essentially redundant in development and homeostasis. However, emerging data are challenging this view by suggesting a novel role for LRG1 in innate immunity and preservation of tissue integrity. While our understanding of beneficial LRG1 functions in physiology remains limited, a consistent body of evidence shows that, in response to various inflammatory stimuli, LRG1 expression is induced and directly contributes to disease pathogenesis. Its potential role as a biomarker for the diagnosis, prognosis and monitoring of multiple conditions is widely discussed while dissecting the mechanisms underlying LRG1 pathogenic functions. Emphasis is given to the role that LRG1 plays as a vasculopathic factor where it disrupts the cellular interactions normally required for the formation and maintenance of mature vessels, thereby indirectly contributing to the establishment of a highly hypoxic and immunosuppressive microenvironment. In addition, LRG1 has also been reported to affect other cell types (including epithelial, immune, mesenchymal and cancer cells) mostly by modulating the TGFβ signalling pathway in a context-dependent manner. Crucially, animal studies have shown that LRG1 inhibition, through gene deletion or a function-blocking antibody, is sufficient to attenuate disease progression. In view of this, and taking into consideration its role as an upstream modifier of TGFβ signalling, LRG1 is suggested as a potentially important therapeutic target. While further investigations are needed to fill gaps in our current understanding of LRG1 function, the studies reviewed here confirm LRG1 as a pleiotropic and pathogenic signalling molecule providing a strong rationale for its use in the clinic as a biomarker and therapeutic target.

Paradoxical Roles of Leucine-Rich α2-Glycoprotein-1 in Cell Death and Survival Modulated by Transforming Growth Factor-Beta 1 and Cytochrome c

Leucine-rich α₂-glycoprotein-1 (LRG1) has been shown to impact both apoptosis and cell survival, pleiotropic effects similar to one of its known ligands, transforming growth factor-beta 1 (TGF-β1). Recent studies have given insight into the TGF-β1 signaling pathways involved in LRG1-mediated death versus survival signaling, i.e., canonical or non-canonical. Interaction of LRG1 with another ligand, extracellular cytochrome c (Cyt c), promotes cell survival, at least for lymphocytes. LRG1 has been shown to bind Cyt c with high affinity, higher than it binds TGF-β1, making it sensitive to small changes in the level of extracellular Cyt c within a microenvironment that may arise from cell death. Evidence is presented here that LRG1 can bind TGF-β1 and Cyt c simultaneously, raising the possibility that the ternary complex may present a signaling module with the net effect of signaling, cell death versus survival, determined by the relative extent to which the LRG1 binding sites are occupied by these two ligands. A possible role for LRG1 should be considered in studies where extracellular effects of TGF-β1 and Cyt c have been observed in media supplemented with LRG1-containing serum.

A panel of urine-derived biomarkers to identify sepsis and distinguish it from systemic inflammatory response syndrome

Sepsis is a potentially fatal condition caused by infection. It is frequently difficult to distinguish sepsis from systemic inflammatory response syndrome (SIRS), often resulting in poor prognoses and the misuse of antibiotics. Hence, highly sensitive and specific biomarkers are needed to differentiate sepsis from SIRS. Urine samples were collected and segregated by group (a sepsis group, a SIRS group, and a healthy control group). iTRAQ was used to identify the differentially expressed proteins among the three groups. The identified proteins were measured by ELISA in urine samples. Finally, all the acquired data were analyzed in SPSS. C-reactive protein, leucine-rich alpha glycoprotein-1 and serum amyloid A (SAA) protein were differentially expressed among the three groups. The adjusted median concentrations of urinary C-reactive protein were 1337.6, 358.7, and 2.4 in the sepsis, SIRS, and healthy control groups, respectively. The urinary leucine-rich alpha glycoprotein-1 levels in these three groups were 1614.4, 644.5, and 13.6, respectively, and the levels of SAA were 6.3, 2.9, and 0.07, respectively. For all three of these measures, the sepsis group had higher levels than the SIRS group (P < 0.001), and the SIRS group had higher levels than the healthy control group. When combined, the three biomarkers had a sensitivity of 0.906 and a specificity of 0.896 in distinguishing sepsis from SIRS. Urinary C-reactive protein, urinary leucine-rich alpha glycoprotein-1 and urinary SAA have diagnostic value in cases of sepsis. This initial study suggests the possibility of improved differential diagnosis between sepsis and systemic inflammatory response syndrome; additional confirmation is necessary to corroborate the findings.

Novel molecular biomarkers and diagnosis of acute appendicitis in children

Reliable and efficient diagnosis of pediatric appendicitis is essential for the establishment of a clinical management plan and improvement of patient outcomes. Current strategies used to diagnose a child presenting with a suspected appendicitis include laboratory studies, clinical scores and diagnostic imaging. Although these modalities work in conjunction with each other, one optimal diagnostic strategy has yet to be agreed upon. The recent introduction of precision medicine techniques such as genomics, transcriptomics, proteomics and metabolomics has increased both the diagnostic sensitivity and specificity of appendicitis. Using these novel strategies, the integration of precision medicine into clinical practice via point-of-care technologies is a plausible future. These technologies would assist in the screening, diagnosis and prognosis of pediatric appendicitis.

Comparison of leucine-rich alpha-2-glycoprotein-1 (LRG-1) plasma levels between patients with and without appendicitis, a case-controlled study

Acute appendicitis (AA) is the first cause of emergency surgery. Leucine-Rich Alpha-2-Glycoprotein 1 (LRG1) has been shown to be a potential biomarker in cases of AA in children, but there are conflicting results for its use in adults. The objective of this study is to compare the median plasma values of LRG1 in patients with acute abdomen with and without appendicitis. This case–control study was conducted prospectively at the emergency room (ER) of a tertiary teaching hospital, between March 1st, 2011 and December 31st, 2012. Patients with recent abdominal pain, aged 18–70 years who attended at the ER were included in the study. Blood samples were drawn at the first presentation. Those who were submitted to surgery and had a pathology report of AA were considered as cases. Those without a need for surgery and treated for other conditions, e.g., pelvic inflammatory disease, were considered as controls. Follow-up in controls was made up to 30 days. LRG1 plasma median values were measured using an ELISA kit and compared between groups. A total of 28 participants, 14 cases with acute appendicitis and 14 controls, were included. The median (range) values of leucine-rich alpha-2-glycoprotein-1 level in the group with appendicitis and control group were 8.8 ng/ml (5.5–31) and 11 (4.6–108) ng/ml, respectively (Mann–Whitney test P = 0.26). Median plasma leucine-rich alpha-2-glycoprotein-1 levels were not useful in diagnosing Acute Appendicitis in patients with acute abdominal pain.

Evaluation of leucine-rich alpha-2 glycoprotein as a biomarker of fetal infection

This study aimed to determine the association between umbilical cord leucine-rich alpha-2 glycoprotein (LRG) and fetal infection and investigate the underlying mechanism of LRG elevation in fetuses. We retrospectively reviewed the medical records of patients who delivered at Osaka University Hospital between 2012 and 2017 and selected those with histologically confirmed chorioamnionitis (CAM), which is a common pregnancy complication that may cause neonatal infection. The participants were divided into two groups: CAM with fetal infection (CAM-f[+] group, n = 14) and CAM without fetal infection (CAM-f[−] group, n = 31). Fetal infection was defined by the histological evidence of funisitis. We also selected 50 cases without clinical signs of CAM to serve as the control. LRG concentrations in sera obtained from the umbilical cord were unaffected by gestational age at delivery, neonatal birth weight, nor the presence of noninfectious obstetric complications (all, p > 0.05). Meanwhile, the LRG levels (median, Interquartile range [IQR]) were significantly higher in the CAM-f(+) group (10.37 [5.21–13.7] μg/ml) than in the CAM-f(−) (3.61 [2.71–4.65] μg/ml) or control group (3.39 [2.81–3.93] μg/ml; p < 0.01). The area under the receiver operating characteristic (ROC) curve of LRG for recognizing fetal infection was 0.92 (optimal cutoff, 5.08 μg/ml; sensitivity, 86%; specificity, 88%). In a mouse CAM model established by lipopolysaccharide administration, the fetal LRG protein in sera and LRG mRNA in the liver were significantly higher than those in phosphate-buffered saline (PBS)-administered control mice (p < 0.01). In vitro experiments using a fetal liver-derived cell line (WRL68) showed that the expression of LRG mRNA was significantly increased after interleukin (IL)-6, IL-1β, and tumor necrosis factor- alpha (TNF-α) stimulation (p < 0.01); the induction was considerably stronger following IL-6 and TNF-α stimulation (p < 0.01). In conclusion, LRG is an effective biomarker of fetal infection, and fetal hepatocytes stimulated with inflammatory cytokines may be the primary source of LRG production in utero.

Proteomic analysis of synovial fluid from rheumatic arthritis and spondyloarthritis patients

Background

The aetiologies and pathogeneses of the joint diseases rheumatoid arthritis (RA) and spondyloarthritis (SpA) are still not fully elucidated. To increase our understanding of the molecular pathogenesis, we analysed the protein composition of synovial fluid (SF) from rheumatoid arthritis (RA) and spondyloarthritis (SpA) patients.

Methods

Fifty-six synovial fluid samples (RA, n = 32; SpA, n = 24) were digested with trypsin, and the resulting peptides were separated by liquid chromatography and analysed by tandem mass spectrometry. Additionally, the concentration of cell-free DNA (cfDNA) in the synovial fluid was measured, and plasma C-reactive protein (CRP) was determined.

Results

Three hundred thirty five proteins were identified within the SF. The more abundant proteins seen in RA SF were inflammatory proteins, including proteins originating from neutrophil granulocytes, while SpA SF had less inflammatory proteins and a higher concentration of haptoglobin. The concentration of cell-free DNA in the SF increased together with proteins that may have originated from neutrophils. Plasma CRP levels in both RA and SpA, correlated to other acute phase reactants.

Conclusions

The proteomic results underline that neutrophils are central in the RA pathology but not in SpA, and even though inhibitors of neutrophils (migration, proteinase inhibitors) were present in the SF it was not sufficient to interrupt the disease process.

Plasma Leucine-Rich α-2-Glycoprotein 1 Predicts Cardiovascular Disease Risk in End-Stage Renal Disease

Plasma leucine-Rich α-2-glycoprotein 1 (LRG1) is an innovative biomarker for inflammation and angiogenesis. Many adverse pathophysiological changes including inflammation, atherosclerosis, and premature mortality is associated with End-stage renal disease (ESRD). However, whether levels of plasma LRG1 correlate with the co-morbidities of ESRD patients is unknown. Plasma LRG1 and high-sensitivity C-reactive protein (hsCRP) were analyzed by ELISA in 169 hemodialysis patients from the Immunity in ESRD (iESRD) study. Patient demographics and comorbidities at the time of enrollment were recorded. Peripheral blood monocyte and T cell subsets were assessed by multicolor flow cytometry. In the univariate analysis, a higher level of LRG1 was associated with the presence of cardiovascular disease (CVD) and peripheral arterial occlusive disease (PAOD). In multivariate logistic regression models, higher LRG1 tertile was significantly associated with PAOD (odds ratio = 3.49) and CVD (odds ratio = 1.65), but not with coronary artery disease, history of myocardial infarction, or stroke after adjusting for gender, diabetes, hemoglobin, albumin, calcium-phosphate product, and level of hsCRP. In addition, the level of LRG1 had a positive correlation with IL-6, hsCRP, and also more advanced T cell differentiation. The association suggests that LRG1 participates in the progression of atherosclerosis by inducing inflammation. Therefore, the role of LRG1 in coexisting inflammatory response should be further investigated in the pathogenesis of cardiovascular morbidity and mortality in patients with ESRD.

Cognitive impairment and CSF proteome modification after oral bacteriotherapy in HIV patients

OBJECTIVE

To investigate whether a probiotic supplementation to cART patients modifies the cerebrospinal fluid (CSF) proteome and improves neurocognitive impairment.

METHODS

26 CSF samples from 13 HIV-positive patients [six patients living with HIV (PLHIV) and seven patients with a history of AIDS (PHAIDS)] were analyzed. All patients underwent to neurocognitive evaluation and blood sampling at baseline and after 6 months of oral bacteriotherapy. Immune phenotyping and activation markers (CD38 and HLA-DR) were evaluated on peripheral blood mononuclear cells (PBMC). Plasma levels of IL-6, sCD14, and MIP-1β were detected, by enzyme-linked immunosorbent assay (ELISA). Functional proteomic analysis of CSF sample was conducted by two-dimensional electrophoresis; a multivariate analysis was performed by principal component analysis (PCA) and data were enriched by STRING software.

RESULTS

Oral bacteriotherapy leads to an improvement on several cognitive test and neurocognitive performance in both groups of HIV-positive subjects. A reduction in the percentage of CD4⁺CD38⁺HLA-DR⁺ T cells was also observed at peripheral level after the probiotic intake (p = 0.008). In addition, the probiotic supplementation to cART significantly modifies protein species composition and abundance at the CSF level, especially those related to inflammation (β2-microglobulin p = 0.03; haptoglobin p = 0.06; albumin p = 0.003; hemoglobin p = 0.003; immunoglobulin heavy chains constant region p = 0.02, transthyretin p = 0.02) in PLHIV and PHAIDS.

CONCLUSIONS

Our results suggest that oral bacteriotherapy as a supplement to cART could exert a role in the amelioration of inflammation state at peripheral and CNS level.

Plasma proteome profiling reveals differentially expressed lipopolysaccharide-binding protein among leptospirosis patients

BACKGROUND

Human leptospirosis, or commonly known as "rat urine disease" is a zoonotic disease that is caused by the bacteria called Leptospira sp. The incidence rate of leptospirosis has been under-reported due to its unspecific clinical symptoms and the limitations of current laboratory diagnostic methods. Leptospirosis can be effectively treated with antibiotics in the early stage, and it is a curable disease but the accuracy to diagnose the infection is rarely achieved.

METHODS

The present pilot study investigated plasma protein profiles of leptospirosis patients and compared them against two control groups which consisted of dengue patients and healthy individuals. The plasma protein digests were analyzed using shotgun approach by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Protein abundances were estimated from the exponentially modified protein abundance index (emPAI) values. Plasma proteins in leptospirosis patients with at least two-fold differential expression compared to dengue and healthy control groups (p < 0.05, ANOVA) were identified.

RESULTS

Lipopolysaccharide (LPS)-binding protein (LBP) was found to be the only protein that has significant different expression between leptospirosis and the two control groups. The expression levels of leucine-rich alpha-2-glycoprotein (LRG1) and alpha-1-antichymotrypsin (ACT) were different significantly between leptospirosis and healthy group but not to the dengue control group.

CONCLUSION

This is the first plasma proteome-based study on leptospirosis that reports the differential expression of LBP compared to both dengue and healthy controls, which has not been previously reported in the context of leptospirosis.

Leucine-rich alpha-2-glycoprotein-1 is up-regulated in colorectal cancer and is a tumor promoter

Background

Leucine-rich α-2-glycoprotein-1 (LRG1) is differentially expressed in many kinds of diseases including cancer, however, it has not been thoroughly studied yet.

Purpose

The objective of this study was to detect the expression and potential mechanism of LRG1 in colorectal cancer (CRC). In our study, we examined LRG1 levels in CRC tissue and plasma with quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. The effect of LRG1 on cancer cells was detected with transwell and MTT assays.

Results

The average plasma LRG1 level in CRC was significantly higher than in polyp group (P=0.002) and healthy controls (P<0.001). Second, plasma LRG1 was positively associated with CA19-9 (r=0.133, P=0.039) and neutrophil ratio (r=0.403, P<0.001). Third, plasma LRG1 of stage IV patients was dramatically different from that of stage I, stage II or stage III patients (P<0.001). LRG1 mRNA expression levels were about 2-fold higher in CRCs compared to normal tissues (P<0.001). And levels of plasma LRG1 were found to be a risk factor in CRC in univariate survival analysis of colorectal prognosis (P=0.013, hazard ratio [HR]=1.803, 95% CI: 1.521-2.137), and multivariate analysis showed that LRG1 was an independent risk factor (P<0.001, HR=1.492, 95% CI: 1.223-1.820). The patients with higher plasma LRG1 value presented with poorer outcome (P=0.013). Functional experiments showed that LRG1 could promote the invasion and growth ability of cells. LRG1 was increased in plasma and tissue compared with that of controls and LRG1 may predict prognosis of CRC patients and LRG1 maybe a tumor promoter.

Conclusion

LRG1 is increased in CRC patients and might serve as a tumor promoter.

Serum leucine-rich alpha-2-glycoprotein-1 with fucosylated triantennary N-glycan: a novel colorectal cancer marker

BACKGROUND

Carcinoembryonic antigen (CEA) and carbohydrate antigen (CA)19-9 are used in clinical practice as tumor markers to diagnose or monitor colorectal cancer (CRC) patients, However, their specificities and sensitivities are not ideal, and novel alternatives are needed. In this study, mass spectrometry was used to search for screening markers, focusing on glycan alterations of glycoproteins in the sera of CRC patients.

METHODS

Glycopeptides were prepared from serum glycoproteins separated from blood samples of 80 CRC patients and 50 healthy volunteers, and their levels were measured by liquid chromatography time-of flight mass spectrometry (LC-TOF-MS).

RESULTS

Leucine-rich alpha-2-glycoprotein-1 with fucosylated triantennary N-glycan (LRG-FTG) was identified as CRC marker after evaluating 30,000 candidate glycopeptide peaks. The average LRG-FTG level in CRC patients (1.25 ± 0.973 U/mL) was much higher than that in healthy volunteers (0.496 ± 0.433 U/mL, P < 10^- 10), and its sensitivity and specificity exceeded those of CA19-9. The combination of CEA and LRG-FTG showed a complementary effect and had better sensitivity (84%), specificity (90%), and AUC (0.91 by ROC analysis) than each marker alone or any other previously reported marker. LRG-FTG alone or combined with CEA also corresponded well with patient response to treatment.

CONCLUSIONS

We identified LRG-FTG as a new CRC marker, with a sensitivity and specificity exceeding CA19-9. The combination of LRG-FTG and CEA showed much higher sensitivity and specificity than each marker alone. Further validation beyond this initial exploratory cohort is warranted.

Leucine-rich α2-glycoprotein overexpression in the brain contributes to memory impairment

We previously reported increase in leucine-rich α2-glycoprotein (LRG) concentration in cerebrospinal fluid is associated with cognitive decline in humans. To investigate relationship between LRG expression in the brain and memory impairment, we analyzed transgenic mice overexpressing LRG in the brain (LRG-Tg) focusing on hippocampus. Immunostaining and Western blotting revealed age-related increase in LRG expression in hippocampal neurons in 8-, 24-, and 48-week-old controls and LRG-Tg. Y-maze and Morris water maze tests indicated retained spatial memory in 8- and 24-week-old LRG-Tg, while deteriorated in 48-week-old LRG-Tg compared with age-matched controls. Field excitatory postsynaptic potentials declined with age in LRG-Tg compared with controls at 8, 24, and 48 weeks. Paired-pulse ratio decreased with age in LRG-Tg, while increased in controls. As a result, long-term potentiation was retained in 8- and 24-week-old LRG-Tg, whereas diminished in 48-week-old LRG-Tg compared with age-matched controls. Electron microscopy observations revealed fewer synaptic vesicles and junctions in LRG-Tg compared with age-matched controls, which became significant with age. Hippocampal LRG overexpression contributes to synaptic dysfunction, which leads to memory impairment with advance of age.

Leucine-rich α2-glycoprotein as the acute-phase reactant to detect systemic juvenile idiopathic arthritis disease activity during anti-interleukin-6 blockade therapy: A case series

OBJECTIVES

To assess the role of leucine-rich α2-glycoprotein (LRG) as a biomarker for monitoring systemic juvenile idiopathic arthritis (s-JIA) disease activity during interleukin (IL)-6 blockade treatment.

METHODS

We serially measured serum LRG levels in four s-JIA patients treated with the anti-IL-6 receptor antibody tocilizumab and determined the correlation between clinical symptoms and other inflammatory biomarkers and proinflammatory cytokines, including IL-18, IL-6, neopterin, and tumor necrosis factor-α receptor type I and II. The serum levels of LRG and proinflammatory cytokines were determined using enzyme-linked immunosorbent assay.

RESULTS

Serum LRG levels increased concomitantly with s-JIA disease flare-up and macrophage activation syndrome development. Furthermore, even in the clinically inactive phase, serum LRG levels were well above normal values. There were no correlations between serum LRG levels and indicators of s-JIA disease activity other than aspartate aminotransferase. There were significant positive correlations between serum LRG levels and proinflammatory cytokines.

CONCLUSIONS

Serum LRG levels might be a unique and potential biomarker of s-JIA disease activity during IL-6 blockade treatment.

Leucine Rich α-2 Glycoprotein: A Novel Neutrophil Granule Protein and Modulator of Myelopoiesis

Leucine-rich α2 glycoprotein (LRG1), a serum protein produced by hepatocytes, has been implicated in angiogenesis and tumor promotion. Our laboratory previously reported the expression of LRG1 in murine myeloid cell lines undergoing neutrophilic granulocyte differentiation. However, the presence of LRG1 in primary human neutrophils and a role for LRG1 in regulation of hematopoiesis have not been previously described. Here we show that LRG1 is packaged into the granule compartment of human neutrophils and secreted upon neutrophil activation to modulate the microenvironment. Using immunofluorescence microscopy and direct biochemical measurements, we demonstrate that LRG1 is present in the peroxidase-negative granules of human neutrophils. Exocytosis assays indicate that LRG1 is differentially glycosylated in neutrophils, and co-released with the secondary granule protein lactoferrin. Like LRG1 purified from human serum, LRG1 secreted from activated neutrophils also binds cytochrome c. We also show that LRG1 antagonizes the inhibitory effects of TGFβ1 on colony growth of human CD34⁺ cells and myeloid progenitors. Collectively, these data invoke an additional role for neutrophils in innate immunity that has not previously been reported, and suggest a novel mechanism whereby neutrophils may modulate the microenvironment via extracellular release of LRG1.

Leucine-rich α-2-glycoprotein promotes TGFβ1-mediated growth suppression in the Lewis lung carcinoma cell lines

Leucine-rich α2-glycoprotein (LRG) is an approximately 50-kDa glycoprotein that has been found to be elevated in the sera of patients with several types of cancer. LRG directly binds to transforming growth factor beta 1 (TGFβ1) and modulates TGFβ1 signaling in endothelial cells; however, the precise function of LRG in cancer remains unclear. This study aimed to investigate the role of LRG in cancer. Lewis lung carcinoma (LLC) cells hardly expressed LRG. The growth of LLC tumors allografted in the LRG knockout (KO) mice was significantly increased compared with wild-type (WT) mice. Conversely, overexpression of LRG significantly inhibited the growth of LLC tumors in WT mice. In the presence of LRG, TGFβ1 significantly inhibited the proliferation of LLC cells and human hepatocellular carcinoma Hep3B cells in vitro by inducing apoptosis via the potent activation of smad2 and its downstream signaling pathway. Furthermore, administration of a TGFβR1 inhibitor (SB431542) significantly enhanced the growth of LLC tumors in WT mice compared with LRG KO mice via inhibition of apoptosis. We propose that LRG potentiates the effect of TGFβ1 in cancer cells whose growth is suppressed in the presence of TGFβ1.

Serum leucine-rich α2-glycoprotein is a useful biomarker for monitoring disease activity in patients with adult-onset Still's disease

OBJECTIVE

To investigate whether serum leucine-rich α2-glycoprotein (LRG) levels are elevated in patients with adult-onset Still's disease (AOSD) and determine their correlation with disease activity parameters.

METHOD

We enrolled 39 patients with AOSD, 47 patients with rheumatoid arthritis (RA), and 39 controls. Forty-five serum samples from the patients with AOSD were assayed for LRG using an enzyme-linked immunosorbent assay (ELISA). Comprehensive AOSD activity was determined by a modified Pouchot score.

RESULTS

Serum LRG levels were significantly elevated in patients with AOSD (128.8±40.8 ng/mL) compared to those in patients with RA and in controls (33.9±15.2 ng/mL, p<0.001 and 22.4±6.1 ng/mL, p<0.001, respectively). Patients with active AOSD had significantly higher LRG levels than those with inactive disease (141.4±31.3 ng/mL vs. 79.8±37.1 ng/mL, p=0.002). Serum LRG levels were positively correlated with C-reactive protein (CRP; γ=0.387, p=0.015), lactate dehydrogenase (LDH; γ=0.370, p=0.026), ferritin (γ=0.687, p<0.001) levels, and the modified Pouchot score (γ=0.756, p<0.001). Serum LRG levels decreased significantly after treatment in all six patients with active AOSD who had follow-up evaluations (p=0.007). The best cut-off value for LRG to distinguish AOSD from RA was 67.9 ng/mL, with a sensitivity of 92.3% and a specificity of 97.9%.

CONCLUSIONS

Serum LRG levels were increased in patients with AOSD and correlated well with disease activity measures. LRG may be a useful biomarker for distinguishing AOSD from RA and for monitoring the disease activity of AOSD.

Identification of host-immune response protein candidates in the sera of human oral squamous cell carcinoma patients

One of the most common cancers worldwide is oral squamous cell carcinoma (OSCC), which is associated with a significant death rate and has been linked to several risk factors. Notably, failure to detect these neoplasms at an early stage represents a fundamental barrier to improving the survival and quality of life of OSCC patients. In the present study, serum samples from OSCC patients (n = 25) and healthy controls (n = 25) were subjected to two-dimensional gel electrophoresis (2-DE) and silver staining in order to identify biomarkers that might allow early diagnosis. In this regard, 2-DE spots corresponding to various up- and down-regulated proteins were sequenced via high-resolution MALDI-TOF mass spectrometry and analyzed using the MASCOT database. We identified the following differentially expressed host-specific proteins within sera from OSCC patients: leucine-rich α2-glycoprotein (LRG), alpha-1-B-glycoprotein (ABG), clusterin (CLU), PRO2044, haptoglobin (HAP), complement C3c (C3), proapolipoprotein A1 (proapo-A1), and retinol-binding protein 4 precursor (RBP4). Moreover, five non-host factors were detected, including bacterial antigens from Acinetobacter lwoffii, Burkholderia multivorans, Myxococcus xanthus, Laribacter hongkongensis, and Streptococcus salivarius. Subsequently, we analyzed the immunogenicity of these proteins using pooled sera from OSCC patients. In this regard, five of these candidate biomarkers were found to be immunoreactive: CLU, HAP, C3, proapo-A1 and RBP4. Taken together, our immunoproteomics approach has identified various serum biomarkers that could facilitate the development of early diagnostic tools for OSCC.

Novel serum and urine markers for pediatric appendicitis

OBJECTIVES

The objective was to describe the association between two novel biomarkers, calprotectin and leucine-rich alpha glycoprotein-1 (LRG), and appendicitis in children.

METHODS

This was a prospective, cross-sectional study of children 3 to 18 years old presenting to a pediatric emergency department (ED) with possible appendicitis. Blood and urine samples were assayed for calprotectin and LRG via enzyme-linked immunosorbent assay (ELISA). Final diagnosis was determined by histopathology or telephone follow-up. Biomarker levels were compared for subjects with and without appendicitis. Recursive partitioning was used to identify thresholds that predicted appendicitis.

RESULTS

Of 176 subjects, mean (±SD) age was 11.6 (±4.0) years and 52% were male. Fifty-eight patients (34%) were diagnosed with appendicitis. Median plasma calprotectin, serum LRG, and urine LRG levels were higher in appendicitis versus nonappendicitis (p < 0.008). When stratified by perforation status, median plasma calprotectin and serum LRG levels were higher in nonperforated appendicitis versus nonappendicitis (p < 0.01). Median serum LRG, urine LRG, and plasma calprotectin levels were higher in perforated appendicitis compared to nonperforated appendicitis (p < 0.05). Urine calprotectin did not differ among groups. A serum LRG < 40,150 ng/mL, a urine LRG < 42 ng/mL, and a plasma calprotectin < 159 ng/mL, each provided a sensitivity and negative predictive value of 100% to identify children at low risk for appendicitis, but with specificities ranging from 23% to 35%. The standard white blood cell (WBC) count achieved 100% sensitivity at a higher specificity than both novel biomarkers.

CONCLUSIONS

Plasma calprotectin and serum/urine LRG are elevated in pediatric appendicitis. No individual marker performed as well as the WBC count.

Clinical proteomics: current status, challenges, and future perspectives

This account will give an overview and evaluation of the current advances in mass spectrometry (MS)-based proteomics platforms and technology. A general review of some background information concerning the application of these methods in the characterization of molecular sizes and related protein expression profiles associated with different types of cells under varied experimental conditions will be presented. It is intended to provide a concise and succinct overview to those clinical researchers first exposed to this foremost powerful methodology in modern life sciences of postgenomic era. Proteomic characterization using highly sophisticated and expensive instrumentation of MS has been used to characterize biological samples of complex protein mixtures with vastly different protein structure and composition. These systems are then used to highlight the versatility and potential of the MS-based proteomic strategies for facilitating protein expression analysis of various disease-related organisms or tissues of interest. Major MS-based strategies reviewed herein include (1) matrix-assisted laser desorption ionization-MS and electron-spray ionization proteomics; (2) one-dimensional or two-dimensional gel-based proteomics; (3) gel-free shotgun proteomics in conjunction with liquid chromatography/tandem MS; (4) Multiple reaction monitoring coupled tandem MS quantitative proteomics and; (5) Phosphoproteomics based on immobilized metal affinity chromatography and liquid chromatography-MS/MS.

Leucine-rich alpha-2-glycoprotein-1 is upregulated in sera and tumors of ovarian cancer patients

BACKGROUND

New biomarkers that replace or are used in conjunction with the current ovarian cancer diagnostic antigen, CA125, are needed for detection of ovarian cancer in the presurgical setting, as well as for detection of disease recurrence. We previously demonstrated the upregulation of leucine-rich alpha-2-glycoprotein-1 (LRG1) in the sera of ovarian cancer patients compared to healthy women using quantitative mass spectrometry.

METHODS

LRG1 was quantified by ELISA in serum from two relatively large cohorts of women with ovarian cancer and benign gynecological disease. The expression of LRG1 in ovarian cancer tissues and cell lines was examined by gene microarray, reverse-transcriptase polymerase chain reaction (RT-PCR), Western blot, immunocytochemistry and mass spectrometry.

RESULTS

Mean serum LRG1 was higher in 58 ovarian cancer patients than in 56 healthy women (89.33 ± 77.90 vs. 42.99 ± 9.88 ug/ml; p = 0.0008) and was highest among stage III/IV patients. In a separate set of 193 pre-surgical samples, LRG1 was higher in patients with serous or clear cell ovarian cancer (145.82 ± 65.99 ug/ml) compared to patients with benign gynecological diseases (82.53 ± 76.67 ug/ml, p < 0.0001). CA125 and LRG1 levels were moderately correlated (r = 0.47, p < 0.0001). LRG1 mRNA levels were higher in ovarian cancer tissues and cell lines compared to their normal counterparts when analyzed by gene microarray and RT-PCR. LRG1 protein was detected in ovarian cancer tissue samples and cell lines by immunocytochemistry and Western blotting. Multiple iosforms of LRG1 were observed by Western blot and were shown to represent different glycosylation states by digestion with glycosidase. LRG1 protein was also detected in the conditioned media of ovarian cancer cell culture by ELISA, Western blotting, and mass spectrometry.

CONCLUSIONS

Serum LRG1 was significantly elevated in women with ovarian cancer compared to healthy women and women with benign gynecological disease, and was only moderately correlated with CA125. Ovarian cancer cells secrete LRG1 and may contribute directly to the elevated levels of LRG1 observed in the serum of ovarian cancer patients. Future studies will determine whether LRG1 may serve as a biomarker for presurgical diagnosis, disease recurrence, and/or as a target for therapy.

Quantitative proteomic analysis by iTRAQ(R) for the identification of candidate biomarkers in ovarian cancer serum

BACKGROUND

Ovarian cancer is the most lethal gynecologic malignancy, with the majority of cases diagnosed at an advanced stage when treatments are less successful. Novel serum protein markers are needed to detect ovarian cancer in its earliest stage; when detected early, survival rates are over 90%. The identification of new serum biomarkers is hindered by the presence of a small number of highly abundant proteins that comprise approximately 95% of serum total protein. In this study, we used pooled serum depleted of the most highly abundant proteins to reduce the dynamic range of proteins, and thereby enhance the identification of serum biomarkers using the quantitative proteomic method iTRAQ(R).

RESULTS

Medium and low abundance proteins from 6 serum pools of 10 patients each from women with serous ovarian carcinoma, and 6 non-cancer control pools were labeled with isobaric tags using iTRAQ(R) to determine the relative abundance of serum proteins identified by MS. A total of 220 unique proteins were identified and fourteen proteins were elevated in ovarian cancer compared to control serum pools, including several novel candidate ovarian cancer biomarkers: extracellular matrix protein-1, leucine-rich alpha-2 glycoprotein-1, lipopolysaccharide binding protein-1, and proteoglycan-4. Western immunoblotting validated the relative increases in serum protein levels for several of the proteins identified.

CONCLUSIONS

This study provides the first analysis of immunodepleted serum in combination with iTRAQ(R) to measure relative protein expression in ovarian cancer patients for the pursuit of serum biomarkers. Several candidate biomarkers were identified which warrant further development.

Identification of candidate biomarkers in ovarian cancer serum by depletion of highly abundant proteins and differential in-gel electrophoresis

Ovarian cancer is the fifth leading cause of cancer death for women in the US, yet survival rates are over 90% when it is diagnosed at an early stage, highlighting the need for biomarkers for early detection. To enhance the discovery of tumor-specific proteins that could represent novel serum biomarkers for ovarian cancer, we depleted serum of highly abundant proteins which can mask the detection of proteins present in serum at low concentrations. Three commercial immunoaffinity columns were used in parallel to deplete the highly abundant proteins in serum from 60 patients with serous ovarian carcinoma and 60 non-cancer controls. Medium and low abundance serum proteins from each serum pool were then evaluated by the quantitative proteomic technique of differential in-gel electrophoresis. The number of protein spots that were elevated in ovarian cancer sera by at least twofold ranged from 36 to 248, depending upon the depletion and separation methods. From the 33 spots picked for MS analysis, nine different proteins were identified, including the novel candidate ovarian cancer biomarkers leucine-rich alpha2 glycoprotein-1 and ficolin 3. Western blotting validated the relative increases in serum protein levels for three of the proteins identified, demonstrating the utility of this approach for the identification of novel serum biomarkers for ovarian cancer.

Discovery and validation of urine markers of acute pediatric appendicitis using high-accuracy mass spectrometry

STUDY OBJECTIVE

Molecular definition of disease has been changing all aspects of medical practice, from diagnosis and screening to understanding and treatment. Acute appendicitis is among many human conditions that are complicated by the heterogeneity of clinical presentation and shortage of diagnostic markers. Here, we sought to profile the urine of patients with appendicitis, with the goal of identifying new diagnostic markers.

METHODS

Candidate markers were identified from the urine of children with histologically proven appendicitis by using high-accuracy mass spectrometry proteome profiling. These systemic and local markers were used to assess the probability of appendicitis in a blinded, prospective study of children being evaluated for acute abdominal pain in our emergency department. Tests of performance of the markers were evaluated against the pathologic diagnosis and histologic grade of appendicitis.

RESULTS

Test performance of 57 identified candidate markers was studied in 67 patients, with median age of 11 years, 37% of whom had appendicitis. Several exhibited favorable diagnostic performance, including calgranulin A (S100-A8), alpha-1-acid glycoprotein 1 (orosomucoid), and leucine-rich alpha-2-glycoprotein (LRG), with the receiver operating characteristic area under the curve and values of 0.84 (95% confidence interval [CI] 0.72 to 0.95), 0.84 (95% CI 0.72 to 0.95), and 0.97 (95% CI 0.93 to 1.0), respectively. LRG was enriched in diseased appendices, and its abundance correlated with severity of appendicitis.

CONCLUSION

High-accuracy mass spectrometry urine proteome profiling allowed identification of diagnostic markers of acute appendicitis. Usage of LRG and other identified biomarkers may improve the diagnostic accuracy of clinical evaluations of appendicitis.

Different altered stage correlative expression of high abundance acute-phase proteins in sera of patients with epithelial ovarian carcinoma

Background

The general enhanced expression of α₁-antichymotrypsin (ACT), clusterin (CLU), α₁-antitrypsin (AAT), haptoglobin β-chain (HAP), and leucine rich glycoprotein (LRG) in the sera of patients with epithelial ovarian carcinoma (EOCa) was recently reported. In the present study, we compared the expression of the serum acute-phase proteins (APPs) in the patients according to their stages of cancer.

Results

Different altered stage correlative expression of the high abundance serum APPs was demonstrated in sera of the patients studied. While the expression of ACT, HAP and AAT appeared to demonstrate positive correlation with the three initial stages of the cancer, inverse correlation was apparently detected in the expression of LRG and CLU. For patients who were diagnosed with stage IV of the cancer, expression of the serum APPs did not conform to the altered progression changes.

Conclusion

Our results highlight the potential prognostic significance of selective high abundance serum APPs in patients with EOCa.

Up-regulation of the expression of leucine-rich alpha(2)-glycoprotein in hepatocytes by the mediators of acute-phase response

Leucine-rich α₂-glycoprotein (LRG) is a plasma protein in which leucine-rich repeats (LRRs) were first discovered. Although the physiological function of LRG is not known, increases in the serum level of LRG have been reported in various diseases. In this study, we found that LRG was induced by recombinant human IL-6 in human hepatoma HepG2 cells. The induction of LRG by IL-6 was up-regulated synergistically with either IL-1β or TNFα in a pattern similar to those for type 1 acute-phase proteins. We also found that lipopolysaccharide (LPS) administered intraperitoneally to mice enhanced dose-dependently the expression of LRG mRNA in the liver as well as those for mouse major acute-phase proteins. These results strongly suggest that LRG was a secretory type 1 acute-phase protein whose expression was up-regulated by the mediator of acute-phase response.

Increased expression of one isoform of leucine-rich alpha-2-glycoprotein in peritoneal fluid of women with uterine leiomyomas

OBJECTIVE

To compare the peritoneal fluid (PF) proteome of women with and without uterine leiomyomas.

STUDY DESIGN

PF samples were collected at laparoscopy from 14 women with uterine leiomyomas and 14 patients without leiomyomas who underwent tubal sterilization. PF samples were subjected to two-dimensional gel electrophoresis, silver stained, digitally captured, and compared by computerised analysis. Protein spots with aberrant expression in PF of women with leiomyomas were identified by liquid chromatography tandem mass spectrometry.

RESULTS

One isoform of leucine-rich alpha-2-glycoprotein (LRGm), one immunoglobulin light chain, and one unidentified protein (pI: 5.62; M(r): 51.1 kDa) had significantly higher expression in PF of women with leiomyomas. Two isoforms of fibrinogen gamma chain had decreased expression in PF of women with uterine leiomyomas. Following Bonferroni correction for multiple comparisons, the aberrant expressions of LRGm and of one isoform of fibrinogen gamma chain was confirmed. The expression of these molecules was not affected by the phase of the menstrual cycle.

CONCLUSIONS

Uterine leiomyomas are associated with changes in proteins present within the peritoneal fluid. The physiopathological relevance of the increased expression of LRGm in PF of women with uterine leiomyomas remains unclear.

ELISA for human serum leucine-rich alpha-2-glycoprotein-1 employing cytochrome c as the capturing ligand

Leucine-rich alpha-2-glycoprotein-1 (LRG) is a serum glycoprotein of unknown function that has shown promise based on qualitative assessments as a biomarker for certain diseases including microbial infections and cancer. However, the lack of a quantitative assay for LRG has limited its application. Here an indirect enzyme-linked immunosorbent assay (ELISA) for quantifying LRG in human serum is described in which cytochrome c is employed as the capturing ligand and a monoclonal antibody specific for LRG is used to detect the captured glycoprotein. Application of this assay in quantifying LRG in various patients' sera is demonstrated. The concentration of LRG in sera of control subjects as determined by this assay is approximately 50 microg/ml. Consistent with expectations from published reports, LRG was found to be significantly elevated in the sera of some patients with a bacterial infection (toxic shock syndrome, TSS). LRG was only slightly elevated in patients infected with the human immunodeficiency virus as compared to uninfected control subjects, while normal levels of LRG were observed in patients with non-infectious diseases (inflammatory arthritis and neurological disorders, primarily Parkinson's disease). Although LRG and C-reactive protein (CRP) are both produced by the liver and are classified as acute-phase proteins, there was no significant correlation between the levels of LRG and CRP in the sera of the patients. Thus, LRG and CRP measurements are non-redundant and indicate different physiological contexts. The ELISA described in this report should be useful to further assess serum LRG as a biomarker for clinical diagnostics.

Plasma proteomics of pancreatic cancer patients by multi-dimensional liquid chromatography and two-dimensional difference gel electrophoresis (2D-DIGE): up-regulation of leucine-rich alpha-2-glycoprotein in pancreatic cancer

We investigated the aberrant expression of plasma proteins in patients with pancreatic cancer. High-abundance plasma proteins (albumin, transferrin, haptoglobin, alpha-1-antitrypsin, IgG and IgA) were depleted by use of an immuno-affinity column, and low-abundance ones were separated into five fractions by anion-exchange chromatography. The fractionated plasma proteins were subjected to 2D-DIGE with highly sensitive fluorescent dyes. The quantitative protein expression profiles obtained by 2D-DIGE were compared between two plasma protein mixtures: one from five non-cancer bearing healthy donors and the other from five patients with pancreatic cancer. Among 1200 protein spots, we found that 33 protein spots were differently expressed between the two mixtures; 27 of these were up-regulated and six were down-regulated in cancer. Mass spectrometry and database searching allowed the identification of the proteins corresponding to the gel spots. Up-regulation of leucine-rich alpha-2-glycoprotein (LRG), which has not previously been implicated in pancreatic cancer, was observed. Western blotting with an anti-LRG antibody validated the up-regulation of LRG in an independent series of plasma samples from healthy controls, patients with chronic pancreatitis, and patients with pancreatic cancer. Our results demonstrate the application of a combination of multi-dimensional liquid chromatography with 2D-DIGE for plasma proteomics and suggest the clinical utility of LRG plasma level measurement.

Multi-Q: a fully automated tool for multiplexed protein quantitation

The iTRAQ labeling method combined with shotgun proteomic techniques represents a new dimension in multiplexed quantitation for relative protein expression measurement in different cell states. To expedite the analysis of vast amounts of spectral data, we present a fully automated software package, called Multi-Q, for multiplexed iTRAQ-based quantitation in protein profiling. Multi-Q is designed as a generic platform that can accommodate various input data formats from search engines and mass spectrometer manufacturers. To calculate peptide ratios, the software automatically processes iTRAQ's signature peaks, including peak detection, background subtraction, isotope correction, and normalization to remove systematic errors. Furthermore, Multi-Q allows users to define their own data-filtering thresholds based on semiempirical values or statistical models so that the computed results of fold changes in peptide ratios are statistically significant. This feature facilitates the use of Multi-Q with various instrument types with different dynamic ranges, which is an important aspect of iTRAQ analysis. The performance of Multi-Q is evaluated with a mixture of 10 standard proteins and human Jurkat T cells. The results are consistent with expected protein ratios and thus demonstrate the high accuracy, full automation, and high-throughput capability of Multi-Q as a large-scale quantitation proteomics tool. These features allow rapid interpretation of output from large proteomic datasets without the need for manual validation. Executable Multi-Q files are available on Windows platform at http://ms.iis.sinica.edu.tw/Multi-Q/.

Immunodepletion of albumin for two-dimensional gel detection of new mouse acute-phase protein and other plasma proteins

Immunodepletion of albumin to improve the 2-D gel resolution of human plasma proteins has recently been described. With the importance of mouse models in many studies in which serum or plasma is often analyzed, we have adopted this approach to immunoprecipitate mouse albumin and evaluated its effectiveness for 2-D separation of mouse plasma proteins. Purified polyclonal antibodies against mouse albumin were effective depleting intact albumin as well as its numerous fragments from mouse plasma samples. Removal of albumin resulted in better resolution of mouse plasma proteins. Three proteins, alpha2-macroglobulin, coagulation factor XII, and hemopexin, that were previously either undetectable or poorly resolved, were identified from albumin-depleted 2-D gels by peptide mass fingerprinting. Albumin depletion also led to partial loss of several other proteins such as clusterin and gelsolin. This loss can be attributed to the interaction with albumin itself because the specificity of the antibody was demonstrated by Western blot. When applying this method to the 2-D separation of plasma from inflamed mouse induced by cutaneous burn injury with superimposed Pseudomonas aeruginosa infection, the upregulation of inter alpha-trypsin inhibitor heavy chain 4 (ITIH4) and hemopexin was unambiguously detected along with other mouse acute-phase proteins (APP), including haptoglobin and serum amyloid A. Based on the significant increase of ITIH4, we propose that this protein is a new member of mouse APP that are upregulated during the inflammatory response.

Haptoglobin beta chain isoforms in the plasma and peritoneal fluid of women with endometriosis

OBJECTIVE

To estimate the expression of haptoglobin (Hp) beta chain isoforms in the peritoneal fluid (PF) and plasma (PL) of women with and without endometriosis.

DESIGN

Cross-sectional study.

SETTING

University hospital.

PATIENT(S)

Seventy-two patients with endometriosis and 35 controls.

INTERVENTION(S)

Peritoneal fluid and PL samples were subjected to two-dimensional gel electrophoresis, silver stained, digitally captured, and compared by semiquantitative computerized analysis.

MAIN OUTCOME MEASURE(S)

Expression of Hp beta chain isoforms.

RESULT(S)

No significant difference was observed in the frequency of expression of the Hp beta chain isoforms between the two groups. One beta chain isoform (HpbetaE; molecular weight, 38.40 +/- 0.94 kD; and isoelectric point, 5.63 +/- 0.17) had significantly higher expression in both the PF and PL of women with endometriosis than in the PF and PL of controls. No significant difference was observed in HpbetaE expression between women with mild (revised American Fertility Society [rAFS], stage I-II) and severe (rAFS, stage III-IV) endometriosis. In the control group, HpbetaE expression was correlated with the phase of the menstrual cycle.

CONCLUSION(S)

Women with endometriosis have higher PF and PL levels of HpbetaE. Further investigation should be aimed at producing antibodies against the HpbetaE-specific epitopes to determine whether its measurement may improve the clinical diagnosis of endometriosis.

Identification of neutrophil gelatinase-associated lipocalin (NGAL) as a discriminatory marker of the hepatocyte-secreted protein response to IL-1beta: a proteomic analysis

The liver is the major source of proteins used throughout the body for various functions. Upon injury or infection, an acute phase response (APR) is initiated in the liver that is primarily mediated by inflammatory cytokines such as interleukin-1beta (IL-1beta) and interleukin-6. Among others, the APR is characterized by an altered protein synthetic profile. We used two-dimensional gel electrophoresis to study the dynamics of changes in protein synthesis in hepatocytes exposed to these inflammatory cytokines. Protein profiles were quantified using image analysis and further analyzed using multivariate statistical methods. Our results indicate that IL-1beta and IL-6 each induces secreted protein responses with distinct dynamics and dose-dependence. Parallel stimulation by IL-1beta and IL-6 results in a protein pattern indistinguishable from the IL-1beta pattern, indicating a dominant effect of IL-1beta over IL-6 at the doses tested. Multidimensional scaling (MDS) of correlation distances between protein secretion levels revealed two protein pairs that are robustly co-secreted across the various cytokine stimulation conditions, suggesting shared regulatory pathways. Finally, we also used multivariate alternating conditional expectation (MACE) to identify transformation functions that discriminated the cytokine-stimulated and untreated hepatocyte-secreted protein profiles. Our analysis indicates that the expression of neutrophil gelatinase-associated lipocalin (NGAL) was sufficient to discriminate between IL-1beta and IL-6 stimulation. The combination of proteomics and multivariate analysis is expected to provide new information on the cellular regulatory networks involved in generating specific cellular responses.

Evaluation of an in vitro model of hepatic inflammatory response by gene expression profiling

The body's response to biochemical stress involves coordinated changes in the expression of several sets of genes that regulate its return to homeostasis. Although several cell culture systems have been utilized for studying such complex physiological events in vitro, their assessment has been limited to biochemical assays on individual genes and proteins, limiting interpretation of the results in a systems context. Advances in genomics provide an opportunity to provide a more comprehensive assessment. In this study, we have used DNA microarrays to profile gene expression dynamics during interleukin 6-stimulated inflammation in hepatocytes maintained in a stable, collagen double-gel in vitro model system. The observed expression profile was also compared with that obtained from rat liver tissue after burn injury to determine the extent and nature of responses captured by the in vitro system. Our results indicate that several aspects of the in vivo hepatic inflammatory response can be captured by the in vitro system at the molecular systems level. Statistical analysis of the mRNA profiles was also used to characterize the temporal response in each model system and demonstrate similar behavior. A small panel of molecules involved in the hepatic acute-phase response was also profiled, using quantitative kinetic polymerase chain reaction, to confirm these observations. These results indicate the utility of the stable hepatocyte culture system for expression profiling of inflammatory states and for providing insights into the interplay of changes in gene expression during complex physiological states.

The human plasma proteome: history, character, and diagnostic prospects

The human plasma proteome holds the promise of a revolution in disease diagnosis and therapeutic monitoring provided that major challenges in proteomics and related disciplines can be addressed. Plasma is not only the primary clinical specimen but also represents the largest and deepest version of the human proteome present in any sample: in addition to the classical "plasma proteins," it contains all tissue proteins (as leakage markers) plus very numerous distinct immunoglobulin sequences, and it has an extraordinary dynamic range in that more than 10 orders of magnitude in concentration separate albumin and the rarest proteins now measured clinically. Although the restricted dynamic range of conventional proteomic technology (two-dimensional gels and mass spectrometry) has limited its contribution to the list of 289 proteins (tabulated here) that have been reported in plasma to date, very recent advances in multidimensional survey techniques promise at least double this number in the near future. Abundant scientific evidence, from proteomics and other disciplines, suggests that among these are proteins whose abundances and structures change in ways indicative of many, if not most, human diseases. Nevertheless, only a handful of proteins are currently used in routine clinical diagnosis, and the rate of introduction of new protein tests approved by the United States Food and Drug Administration (FDA) has paradoxically declined over the last decade to less than one new protein diagnostic marker per year. We speculate on the reasons behind this large discrepancy between the expectations arising from proteomics and the realities of clinical diagnostics and suggest approaches by which protein-disease associations may be more effectively translated into diagnostic tools in the future.

The acute phase response of rainbow trout (Oncorhynchus mykiss) plasma proteins to viral, bacterial and fungal inflammatory agents

The innate arm of the immune system responds to inflammatory stimuli by the activation of phagocytes, and by altered levels of several plasma proteins. These changes in plasma proteins comprise a major component of the acute phase response, which is thought to be an adaptive response that contributes to regaining homeostasis after tissue injury or infection. In this study, rainbow trout (Oncorhynchus mykiss) were injected with a variety of potential inflammatory agents, and changes in the concentrations of plasma proteins were sought in polyacrylamide gels in which plasma proteins had been electrophoresed. Bacteria, viruses and yeast all induced changes in plasma protein profiles. Increases were first evident 2 days after injections, and most were evident within 1 week. The greatest number of changes occurred after injection with a Vibrio bacterin emulsified in Freund's incomplete adjuvant. While some proteins increased and others decreased following several treatments, other proteins changed only in response to injections of viruses or viral proteins, and others changed in response to bacterial components. Some proteins that increased after yeast injection decreased after injection of viral components. The partial amino acid sequence of one increased protein identified it as haptoglobin.

Gene expression profiling of mucosal addressin cell adhesion molecule-1+ high endothelial venule cells (HEV) and identification of a leucine-rich HEV glycoprotein as a HEV marker

High endothelial venule (HEV) cells support lymphocyte migration from the peripheral blood into secondary lymphoid tissues. Using gene expression profiling of mucosal addressin cell adhesion molecule-1(+) mesenteric lymph node HEV cells by quantitative 3'-cDNA collection, we have identified a leucine-rich protein, named leucine-rich HEV glycoprotein (LRHG) that is selectively expressed in these cells. Northern blot analysis revealed that LRHG mRNA is approximately 1.3 kb and is expressed in lymph nodes, liver, and heart. In situ hybridization analysis demonstrated that the mRNA expression in lymph nodes is strictly restricted to the HEV cells, and immunofluorescence analysis with polyclonal Abs against LRHG indicated that the LRHG protein is localized mainly to HEV cells and possibly to some lymphoid cells surrounding the HEVs. LRHG cDNA encodes a 342-aa protein containing 8 tandem leucine-rich repeats of 24 aa each and has high homology to human leucine-rich alpha(2)-glycoprotein. Similar to some other leucine-rich repeat protein family members, LRHG can bind extracellular matrix proteins that are expressed on the basal lamina of HEVs, such as fibronectin, collagen IV, and laminin. In addition, LRHG binds TGF-beta. These results suggest that LRHG is likely to be multifunctional in that it may capture TGF-beta and/or other related humoral factors to modulate cell adhesion locally and may also be involved in the adhesion of HEV cells to the surrounding basal lamina.

Maternal tobacco smoking and lung epithelium-specific proteins in amniotic fluid

The bronchiolar 16 kD Clara cell secretory protein (CC16) and the alveolar surfactant-associated protein A (SP-A) are secreted in the amniotic fluid (AF), where they reflect the growth and the maturity of the fetal lung. To evaluate the possible effects of in utero tobacco smoke exposure upon infant bronchoalveolar epithelium function and maturity, CC16 and SP-A levels were determined in AF obtained at term (36-41 wk) from 28 nonsmoking, 18 smoke-exposed, and 28 smoking mothers with uncomplicated pregnancies. Tobacco smoke exposure was assessed by questionnaire and the assay in AF and maternal urine of cotinine, a stable nicotine metabolite. The specificity of the changes of CC16 and SP-A concentrations in AF was assessed by comparison with nonpulmonary proteins of high- (albumin and transferrin) or low-molecular weight (beta2-microglobulin, retinol binding protein, cystatin-C). Pulmonary and nonpulmonary AF proteins were also compared by two-dimensional gel electrophoresis between smoking and nonsmoking mothers. The levels of CC16 and SP-A as well as low- and high-molecular-weight proteins were not significantly different between the three smoking categories. The protein pattern of AF, established by two-dimensional gel electrophoresis, did not reveal any quantitative or qualitative difference between nonsmoking (n = 10), smoke-exposed (n = 5), and smoking mothers (n = 5). By multiple regression analysis of possible determinants, tobacco smoke did not emerge as a significant predictor of CC16 and SP-A concentrations in AF. SP-A level was dependent only on gestational age at birth (r2 = 0.1, p = 0.001), whereas CC16 correlated only with the levels of low-molecular weight proteins (r2 = 0.2, p = 0.0001). The latter correlation suggests that CC16 enters AF not only as a result of its secretion at the surface of the respiratory tract but also partly following its elimination by the fetal kidney. This study suggests that maternal smoking during pregnancy is not associated with alterations of the secretory functions of the epithelium of the distal airways and the alveoli at term.

The acute phase response and innate immunity of fish

Tissue trauma or invasion by pathogens or parasites induce changes in the quantities of several macromolecules in animal body fluids. These changes comprise one aspect of the acute phase response (APR), which in toto involves metabolic changes in several organ systems. One clear indication of the response is the increase in synthesis and secretion by the liver of several plasma proteins, with simultaneous decreases in others. These acute phase proteins (APP) function in a variety of defense-related activities such as limiting the dispersal of infectious agents, repair of tissue damage, inactivation of proteases, killing of microbes and other potential pathogens, and restoration of the healthy state. Some APP are directly harmful to microbes, while others modify targets thus marking them for cell responses. Some work alone while others contribute to cascades. Proteins that are APP in mammals, and that have been identified in both teleosts and elasmobranchs include C-reactive protein, serum amyloid P, and several components of the Complement system. Others reported in teleosts include transferrin and thrombin. Of these, only CRP has been reported to increase in acute phase plasma. In trout, a precerebellin-like protein is an APP with unknown functions. A cDNA library enriched in fragments of transcripts that were more abundant in livers from fish undergoing an APR recently yielded sequences resembling 12 additional known APP, and as many others either not known to be APP, or not similar to others yet in public databases. It appears that, as in mammals, hepatocytes are the prime source of APP in fish, and that pro-inflammatory cytokines induce transcription of their genes.

The scaled volume as an image analysis variable for detecting changes in protein expression levels by silver stain

A new variable for measuring the relative intensities of silver stained protein spots on two-dimensional gels is described. The scaled volume (SV) more accurately measures the intensity of protein spots and accounts for differences frequently encountered when trying to compare two gels than other variables such as relative volume ratio, optical density, or relative optical density. The SV scales the signal of interest by the noise (gel background) with secondary signals removed (spots not of interest, e.g., technical artifacts). The SV of spot intensities offers a better dynamic response to protein amount for the model proteins studied here. Depending on the quantity of protein loaded onto gels, we have observed a coefficient of variation range of 0.2 to 1.3. We also observe that the SV silver stain response follows a characteristic exponential profile for different proteins.

Use of two-dimensional gel electrophoresis to measure changes in synovial fluid proteins from patients with rheumatoid arthritis treated with antibody to CD4

Synovial fluid proteins from microliter volumes of synovial fluid were resolved by two-dimensional polyacrylamide gel electrophoresis and detected by silver staining to investigate the feasibility of using two-dimensional (2D) electrophoresis in the clinical research setting and provide global disease information of disease progression. Several hundred proteins could be resolved as spots, many of which displayed the characteristic pattern of plasma-derived glycoproteins. The lowest level of detection was approximately 0.2 ng from a total of 50 microg of protein loaded. Most of the proteins could be identified on the basis of pI and molecular weight when compared with plasma protein maps on the World Wide Web. Unknown proteins were characterized by mass spectrometry of tryptic digests and by comparison with peptide databases. Synovial fluids from patients with rheumatoid arthritis were analyzed using this technique. Each subject received a fixed dose of antibody to CD4 as part of a phase II clinical trial to determine the efficacy of this immunosuppressive treatment in modifying disease activity. Synovial fluid was removed at day 0, followed by administration of antibody. Subsequent removal of synovial fluid and additional administration of antibody were carried out at different times thereafter. Changes in levels of acute-phase proteins were quantified by densitometry of silver-stained 2D polyacrylamide gels. Other parameters of disease progression such as serum C-reactive protein and physician's global assessment of clinical condition were used for comparison. In this way, changes in acute-phase proteins towards normal levels, as measured by 2D polyacrylamide gel electrophoresis, could be correlated with clinical improvement and conventional clinical chemistry measurements. Thus, the system can be used for quantitative analysis of protein expression in sites of autoimmune disease activity such as the synovial fluid of rheumatoid arthritis patients.

Postelectrophoretic staining of proteins separated by two-dimensional gel electrophoresis using SYPRO dyes

While the classical silver stain has been the method of choice for high sensitivity protein visualization on two-dimensional gel electrophoresis (2-D PAGE), post-electrophoretic fluorescent staining with the SYPRO group of dyes has emerged to challenge silver staining for proteome analysis. The latter offers improved sensitivity, higher dynamic range and easy handling. However, most of the published data were derived from analysis of 1-D gel separations. In this work, we have focused on three commercially available fluorescent dyes, SYPRO Ruby, SYPRO Orange and SYPRO Red (Molecular Probes, Eugene, OR, USA) and studied their sensitivity and dynamic range on 2-D PAGE. The use of a multiwavelength fluorescent scanner to image 2-D protein profiles visualized with fluorescent staining is discussed, and a detailed comparison with analysis by silver staining is also provided. These results demonstrate the advantages of using SYPRO dyes, which are in agreement with the literature based on 1-D gel electrophoresis, and give a more realistic understanding of the performance of these fluorescent dyes with 2-D PAGE.

Human bronchoalveolar lavage fluid protein two-dimensional database: study of interstitial lung diseases

Recently, we published an analytical two-dimensional electrophoresis (2-DE) protein map of human bronchoalveolar lavage fluid (BALF) using a pool of BALFs from various patients. In this report, the effect of lung disorders on the protein composition of the lung epithelial lining fluid was investigated by 2-DE of BALFs from individual patients with well-defined interstitial lung diseases: sarcoidosis, idiopathic pulmonary fibrosis (IPF) and hypersensitivity pneumonitis (HP), using improved experimental conditions. On these gels, about 600-1000 stained protein spots could be identified in a BALF sample containing 25 microg of protein, and our original human BALF protein database has, therefore, been considerably extended. Altogether, 429 protein spots corresponding to 66 different proteins (including isoforms, protein subunits and fragments) were identified by microsequence analysis and by matching with a human blood plasma 2-DE protein map available in the SWISS-2DPAGE database. A human 2-DE BALF database was established and is available on the World Wide Web (http://www.umh.ac.be/-biochim/proteomic.htm+ ++). The significance of the modifications observed between the different lung pathologies is discussed with the aim of understanding the mechanistic bases of lung disease pathogenesis and finding new potential lung markers of disorders.

Reference map of soluble proteins from Streptococcus thermophilus by two-dimensional electrophoresis

Streptococcus thermophilus is a lactic acid bacterium widely used for the production of fermented dairy products. The two-dimensional electrophoresis (2-DE) protein profile was obtained from three independent analyses of 2-DE gels of soluble proteins of the strain PB18. About 270 spots were detected by silver staining and the average molecular weight and isoelectric point of each protein spot were calculated to be 41 600 and 5.2, respectively. Twelve proteins were purified by chromatographic techniques because their concentration was too low for direct sequencing from blots. Eleven were located in the PB18 2-DE profile after silver staining. These preliminary results contribute to the setting up of a two-dimensional image (or reference map) of the proteins from S. thermophilus in order to identify and compare strains of various origin or to follow metabolic process such as stress. Bidimensional autoradiographs of two strains (PB18 and ST105) of S. thermophilus grown in exponential phase at 42 degrees C with [35S]methionine were compared with an image analysis system. Among the eleven located proteins in the 2-DE silver-stained profile, nine were found in PB18 and eight in ST105 autoradiographs. One protein was specific to PB18. The eight proteins could play the role of internal 2-D PAGE markers of p/ and Mr for S. thermophilus.

Tyrosine phosphorylation of the Helicobacter pylori CagA antigen after cag-driven host cell translocation

Helicobacter pylori strains associated with severe tissue damage and inflammation possess a unique genetic locus, cag, containing 31 genes originating from a distant event of horizontal transfer and retained as a pathogenicity island. The cag system is an Helicobacter-specific type IV secretion engine involved in cellular responses like induction of pedestals, secretion of IL-8, and phosphorylation of proteic targets. It has previously been reported that cocultivation of epithelial cells with Helicobacter pylori triggers signal transduction and tyrosine phosphorylation of a 145-kDa putative host cell protein. Herein, we demonstrate that this protein is not derived from the host but rather is the bacterial immunodominant antigen CagA, a virulence factor commonly expressed in peptic ulcer disease and thought to be an orphan of a specific biological function. Thus, CagA is delivered into the epithelial cells by the cag type IV secretion system where it is phosphorylated on tyrosine residues by an as yet unidentified host cell kinase and wired to eukaryotic signal transduction pathways and cytoskeletal plasticity.