Increased expression of midkine in the rat colon during healing of experimental colitis

Midkine level may be used as a noninvasive biomarker in Crohn’s disease

Background/aim

Crohn’s disease (CD) is a kind of inflammatory bowel disease. Midkine (MDK) is an endogenous inflammatory marker. We aimed to investigate the relationship between MDK levels and inflammation and hence determine whether MDK can be used as a noninvasive biomarker in active CD.

Materials and methods

Sixty-five consecutive patients over the age of 18 with CD and 36 healthy controls were included in this study. CD patients’ venous blood samples were taken before treatment. Serum MDK levels were determined in human plasma samples by enzyme-linked immunosorbent assay (ELISA) method.

Results

The mean age of the study patients was 44.8 ± 12.5 years, 35 patients were female, and 30 were male. Of these 65 patients, 37 had active CD and 28 were in the remission phase. MDK levels were significantly higher in active and remission CD than in healthy controls (P = 0.01, P = 0.038, respectively).

Conclusion

We report that there is an association between MDK levels and CD activation, and therefore with enhanced inflammation. MDK levels were significantly correlated with inflammatory indices. In line with our findings, we suggest the theory that MDK inhibitors may be useful in treating Crohn’s disease.

Elevated plasma midkine and pleiotrophin levels in patients with systemic lupus erythematosus

Emerging evidence suggests that two heparin-binding growth factor, midkine and pleiotrophin are implicated in the pathogenesis of autoimmune diseases including SLE. To investigate the plasma midkine and pleiotrophin levels in SLE patients, as well as their correlation with major clinical parameters and interleukin-17 (IL-17) level in SLE, 83 SLE patients and 123 controls including 20 rheumatoid arthritis (RA) patients, 21 Sjögren's syndrome (SS) patients and 82 healthy controls (HCs) were recruited. Plasma midkine, pleiotrophin and IL-17 levels were detected by ELISA. Midkine and pleiotrophin levels were significantly higher in SLE, RA and SS patients compared with HCs (all P < 0.05). There were significantly lower midkine and pleiotrophin levels in SLE compared to SS (P < 0.05 and P < 0.01, respectively). No significant differences in midkine and pleiotrophin levels were found between SLE and RA (P = 0.240 and P = 0.074, respectively). Both plasma midkine and pleiotrophin levels were associated with rash and anti-SSA in SLE. In addition, both midkine and pleiotrophin levels were positively associated with IL-17 level in SLE (both P < 0.001). Area under curve (AUC) of the receiver operating characteristic (ROC) curve for midkine and pleiotrophin were 0.606 (0.527–0.681) and 0.605 (0.526–0.680) respectively. In conclusion, elevated plasma midkine and pleiotrophin levels and their associations with rash, anti-SSA and IL-17 in SLE patients suggest their involvement in this disease.

G protein-coupled receptor 35 contributes to mucosal repair in mice via migration of colonic epithelial cells

G protein-coupled receptor 35 (GPR35), a receptor for lysophosphatidic acid, is highly expressed in the gastrointestinal tract. Recently, GPR35 has been implicated in the onset of inflammatory bowel disease (IBD), but its role in physiological and pathological processes in the colon remains undefined. In this study, we investigated the contribution of GPR35-mediated signalling to mucosal repair of colonic epithelium in IBD. GPR35 function was examined in a wound healing model, using young adult mouse colon epithelium (YAMC) cells, and in a dextran sulphate sodium (DSS)-induced mouse model of colitis. Cell proliferation, mRNA expression, extracellular signal-regulated kinase (ERK) activation, and protein localization were determined by MTT assay, quantitative RT-PCR, western blotting, and immunohistochemistry, respectively. GPR35 agonists (YE120, zaprinast, and pamoic acid) promoted wound repair in a concentration-dependent manner independently of cell proliferation, whereas a specific GPR35 antagonist CID2745687, forskolin, and pertussis toxin reversed the YE120-induced effect. YE120 increased the mRNA expression of fibronectin and its receptor integrin α5, and ERK1/2 phosphorylation, but these responses were attenuated by CID2745687 and forskolin. Furthermore, the severity of DSS-induced colitis was significantly reduced by daily injections of pamoic acid via upregulation of fibronectin and integrin α5 in the colonic epithelium. GPR35 signalling promotes mucosal repair by inducing fibronectin and integrin α5 expression, coupling to Gi protein, and activating ERK1/2 in colonic epithelial cells. These findings define GPR35 as a candidate therapeutic target in IBD.

Midkine is up-regulated in both cancerous and inflamed bowel, reflecting lymph node metastasis in colorectal cancer and clinical activity of ulcerative colitis

Midkine is a multifunctional cytokine and growth factor displaying proinflammatory and pro-tumorigenic activity. Its association with bowel diseases has not been fully elucidated. Our purpose was to delineate midkine expression pattern by RT-qPCR in inflamed/cancerous bowel (n=208) and whole blood (n=150) in colorectal cancer (CRC), Crohn's disease (CD), and ulcerative colitis (UC) and to evaluate midkine dynamics in early postoperative period following colorectal surgery. The expression of midkine was significantly up-regulated in stage III CRC and independently associated with lymph node metastasis. The expression of midkine in whole blood was up-regulated solely in N1 CRC. Midkine expression in cancer-free tissue (CRC) was also elevated and dependent on CRC advancement. In IBD, inflammation increased the bowel expression of midkine solely in UC, in a manner proportional to the disease clinical activity. Large and small bowel differed with respect to the expression of midkine in quiescent tissue (higher in small bowel) and to its correlation pattern with chemokines (in a large bowel) and angiogenic factors and cell cycle regulators (in a small bowel). Circulating midkine and its expression in whole blood dropped directly following colorectal surgery; however, the concentration of midkine in serum was restored on postoperative day three. Midkine is involved in bowel inflammation in UC and lymph node metastasis in CRC, rendering midkine an attractive target for their treatment. Owing to midkine elevation in early postoperative period and its overexpression in tumor-adjacent tissue, targeting midkine might be considered also as a prevention of CRC recurrence following curative tumor resection.

An optimized method for accurate quantification of cell migration using human small intestine cells

Quantifying the ability of a compound to modulate cell migration rate is a crucial part of many studies including those on chemotaxis, wound healing and cancer metastasis. Existing migration assays all have their strengths and weaknesses. The "scratch" assay is the most widely used because it seems appealingly simple and inexpensive. However, the scratch assay has some important limitations, as the tool introducing the "wound" might injure/stress the boundary cells and/or harm underlying matrix coatings, which in both cases will affect cell migration. This described method is a Cell Exclusion Zone Assay, in which cell-free areas are created by growing cells around removable silicone stoppers. Upon appropriate staining with fluorescent dyes and microscopically visualizing the monolayers, the migration rate is then quantified by counting the cells (nuclei) intruding the void area left by the silicone insert. In the current study human small intestine epithelial cells were seeded on a physiological substrate matrix to produce collectively migrating monolayers. Different substrates were tested to determine the optimal surface for enterocyte adherence and migration and morphological changes monitored. Recombinant human epidermal growth factor and osteopontin purified from urine were tested to see if the established migration assay produces accurate and reliable migration data with human small intestine cells. The obtained data accurately confirmed that the two bioactive proteins modulate cellular migration in a dose-dependent manner. The presented assay can likely be converted for use with other adherent cell lines or substrate matrices and allows for high throughput, while cost is kept low and versatility high. Co-staining can be applied in order to assay for cell death, different cell types, cell stress and others allowing intricate analysis of migration rate of mixed populations and correction for cell viability.

Midkine in vitamin D deficiency and its association with anti-Saccharomyces cerevisiae antibodies

OBJECTIVES AND DESIGN

The growth factor midkine (MK) is a protein that is involved in cancer, inflammation, immunity. Vitamin D is a potent immunomodulator. Anti-Saccharomyces cerevisiae antibody (ASCA) is reported in autoimmune disorders, some of which are among the causes of vitamin D deficiency. The objective of this study was to investigate a possible association of MK and ASCA with vitamin D deficiency.

MATERIALS AND METHODS

208 adults presented to internal medicine outpatient clinic for history and physical examination has been studied. Serum biochemistry, vitamin D, MK, ASCA-IgG and -IgA, IL-1β, IL-6, IL-8, TNF-α, PDGF, VEGF were obtained.

RESULTS

Vitamin D deficiency was 74.2%. Serum MK level was significantly higher in vitamin D-deficient compared to vitamin D-sufficient individuals (1138.1 ± 262.8 vs 958.6 ± 189 pg/mL, respectively; P < 0.009). Serum MK levels were also significantly higher in both ASCA-IgG and -IgA positives compared to negatives (1318.5 ± 160.3 vs 1065.5 ± 256.1, P = 0.008 and 1347.7 ± 229.7 vs 1070.1 ± 250.9 pg/mL, P = 0.011, respectively). Vitamin D was significantly lower in ASCA positives (P = 0.044).Vitamin D showed positive correlation with IL-1β (r 0.338, P < 0.009) and negative correlation with VEGF (r -0.366, P < 0.004).

CONCLUSIONS

MK was significantly elevated in vitamin D deficiency and associated with ASCA positivity which was significantly increased in vitamin D deficiency. These findings suggested that molecular mechanism of vitamin D deficiency may be related with some inflammatory processes.

The impact of ATRA on shaping human myeloid cell responses to epithelial cell-derived stimuli and on T-lymphocyte polarization

Vitamin A plays an essential role in the maintenance of gut homeostasis but its interplay with chemokines has not been explored so far. Using an in vitro model system we studied the effects of human colonic epithelial cells (Caco2, HT-29, and HCT116) derived inflammatory stimuli on monocyte-derived dendritic cells and macrophages. Unstimulated Caco2 and HT-29 cells secreted CCL19, CCL21, and CCL22 chemokines, which could attract dendritic cells and macrophages and induced CCR7 receptor up-regulation by retinoic-acid resulting in dendritic cell migration. The chemokines Mk, CXCL16, and CXCL7 were secreted by all the 3 cell lines tested, and upon stimulation by IL-1β or TNF-α this effect was inhibited by ATRA but had no impact on CXCL1, CXCL8, and CCL20 secretion in response to IL-1β. In the presence of ATRA the supernatants of these cells induced CD103 expression on monocyte-derived dendritic cells and when conditioned by ATRA and cocultured with CD4⁺ T-lymphocytes they reduced the proportion of Th17 T-cells. However, in the macrophage-T-cell cocultures the number of these effector T-cells was increased. Thus cytokine-activated colonic epithelial cells trigger the secretion of distinct combinations of chemokines depending on the proinflammatory stimulus and are controlled by retinoic acid, which also governs dendritic cell and macrophage responses.

The cytokine midkine supports neutrophil trafficking during acute inflammation by promoting adhesion via β2 integrins (CD11/CD18)

Emerging evidence suggests a role of the cytokine midkine (MK) in inflammation. In this study, its functional relevance for recruitment of polymorphonuclear neutrophils (PMNs) during acute inflammation was investigated. Intravital microscopy and histologic analysis of tumor necrosis factor-α-stimulated cremaster muscle venules revealed severely compromised leukocyte adhesion and extravasation in MK(-/-) mice compared with MK(+/+) animals. Systemic administration of recombinant MK completely rescued the adhesion defect in MK(-/-) mice. In a hind limb ischemia model, leukocyte accumulation in MK(-/-) mice was significantly diminished compared with MK(+/+) animals. However, MK did not lead to an inflammatory activation of PMNs or endothelial cells suggesting that it does not serve as classical proinflammatory cytokine. Unexpectedly, immobilized MK mediated PMN adhesion under static and flow conditions, whereas PMN-derived MK was dispensable for the induction of adhesion. Furthermore, adhesion strengthening remained unaffected by MK. Flow cytometry revealed that immobilized, but not soluble MK, significantly promoted the high affinity conformation of β2 integrins of PMNs. Blocking studies of low-density lipoprotein receptor-related protein 1 (LRP1) suggested that LRP1 may act as a receptor for MK on PMNs. Thus, MK seems to support PMN adhesion by promoting the high affinity conformation of β2 integrins, thereby facilitating PMN trafficking during acute inflammation.

Midkine in inflammation

The 13 kDa heparin-binding growth factor midkine (MK) was originally identified as a molecule involved in the orchestration of embryonic development. Recent studies provided evidence for a new role of MK in acute and chronic inflammatory processes. Accordingly, several inflammatory diseases including nephritis, arthritis, atherosclerosis, colitis, and autoimmune encephalitis have been shown to be alleviated in the absence of MK in animal models. Reduced leukocyte recruitment to the sites of inflammation was found to be one important mechanism attenuating chronic inflammation when MK was absent. Furthermore, MK was found to modulate expression of proinflammatory cytokines and the expansion of regulatory T-cells. Here, we review the current understanding of the role of MK in different inflammatory disorders and summarize the knowledge of MK biology.

Evaluation of midkine and anterior gradient 2 in a multimarker panel for the detection of ovarian cancer

The aims of this study were: to characterise and compare plasma concentrations of midkine (MDK) in normal healthy women with concentrations observed in women with ovarian cancer; and to establish and compare the performance of MDK with that of anterior gradient 2 protein (AGR2) and CA125 in the development of multi-analyte classification algorithms for ovarian cancer. Median plasma concentrations of immunoreactive MDK, AGR2 and CA125 were significantly greater in the case cohort (909 pg/ml, 765 pg/ml and 502 U/ml, respectively n = 46) than in the control cohort (383 pg/ml, 188 pg/ml and 13 U/ml, respectively n = 61) (p < 0.001). The area under the receiver operator characteristic curve (AUC) for MDK and AGR2 was not significantly different (0.734 ± 0.046 and 0.784 ± 0.049, respectively, mean ± SE) but were both significantly less than the AUC for CA125 (0.934 ± 0.030, p < 0.003). When subjected to stochastic gradient boosted logistic regression modelling, the AUC of the multi-analyte panel (MDK, AGR2 and CA125, 0.988 ± 0.010) was significantly greater than that of CA125 alone (0.934 ± 0.030, p = 0.035). The sensitivity and specificity of the multi-analyte algorithm were 95.2 and 97.7%, respectively. Within the study cohort, CA125 displayed a sensitivity and specificity of 87.0 and 94.6%, respectively. The data obtained in this study confirm that both MDK and AGR2 individually display utility as biomarkers for ovarian cancer and that in a multi-analyte panel significantly improve the diagnostic utility of CA125 in symptomatic women.

Circulating midkine in Crohn's disease: clinical implications

BACKGROUND

A noninvasive marker facilitating differential diagnosis in Crohn's disease (CD) is sought after. Midkine is a heparin-binding growth factor of angiogenic and chemotactic properties, positively evaluated as a tumor marker, and a possible association with CD has not yet been investigated.

METHODS

Circulating midkine was measured in 91 CD patients and 108 controls and related to disease clinical and biochemical activity, inflammation severity, and angiogenesis. Midkine diagnostic value in comparison with C-reactive protein (CRP) was evaluated by receiver operating characteristic (ROC) analysis.

RESULTS

Circulating midkine was elevated both in quiescent and active disease compared to controls (147, 506, and 93 pg/mL, respectively), and corresponded well with disease activity (r = 0.49, P < 0.001). Midkine significantly correlated with inflammatory indices: CRP (r = 0.49), erythrocyte sedimentation rate (r = 0.31), leukocytes (r = 0.48), platelets (r = 0.52), albumin (r = -0.49), transferrin (r = -0.47), and IL-6 (r = 0.54); hematological variables: hemoglobin (r = -0.38), hematocrit (r = -0.43), and iron (r = -0.58); angiogenic factors: vascular endothelial growth factor-A (r = 0.42), fibroblast growth factor-2 (r = 0.54), and platelet-derived growth factor-BB (r = 0.57). Midkine elevation corresponded well (r = -0.41) with the drop in paraoxonase-1 activity-a quorum-quenching factor. Midkine as a marker of active CD had sensitivity and specificity of 86% and 97%, respectively, whereas CRP was 83% and 92%.

CONCLUSIONS

CD is associated with an elevation of midkine, which corresponds well with disease activity and reflects the severity of inflammatory response and exacerbation of pathological angiogenesis. Midkine performance as a disease marker was slightly better than that of CRP. Its high specificity and likelihood ratios for positive test results might recommend midkine as a possible "ruling in" marker in CD.

Clinical relevance of circulating midkine in ulcerative colitis

BACKGROUND

Non-invasive biochemical markers are needed to support the diagnosis of ulcerative colitis (UC), an incurable disease of unknown pathology. Midkine is an angiogenic cytokine, chemotactic towards neutrophils and macrophages, and a T-regulatory cell suppressor.

METHODS

Serum midkine was measured immunoenzymatically in 93 UC patients and 108 healthy subjects, and evaluated with respect to disease status, endoscopic, inflammatory and angiogenic activity. The diagnostic value of midkine was compared to C-reactive protein (CRP) using receiver operating characteristics (ROC) analysis.

RESULTS

Midkine was higher (p<0.0001) in inactive (199 ng/L) and active UC (351 ng/L) compared with controls (93 ng/L), and reflected disease activity (r=0.427, p<0.001). Midkine was correlated with CRP, erythrocyte sedimentation rate (ESR), leukocytes, platelets, interleukin-6, paraoxonase-1, albumin, transferrin, iron, hemoglobin, and hematocrit. Midkine correlated with angiogenic factors: vascular endothelial growth factor-A and platelet-derived growth factor-BB. As a marker of UC, midkine showed a diagnostic accuracy of 85%, sensitivity of 72%, specificity of 82%, whereas CRP showed 83%, 65% and 91%, respectively. As a marker of active UC, midkine showed a diagnostic accuracy of 87%, sensitivity of 84%, specificity of 75%, whereas CRP showed 75%, 63% and 83%, respectively. Combined assessment of midkine and CRP improved sensitivity but substantially decreased specificity.

CONCLUSIONS

UC is associated with increased circulating midkine, which corresponds with clinical, endoscopic, inflammatory and angiogenic activity, and anemia. Performance of midkine as a marker of UC or active UC was comparable to that of CRP.

Applications of proteomics in the study of inflammatory bowel diseases: Current status and future directions with available technologies

Inflammatory bowel diseases (IBD) are chronic, heterogeneous, and multifactorial intestinal inflammatory disorders. Major challenges in IBD research include identification of major pathogenic alterations of genes/proteins as well as effective biomarkers for early diagnosis, prognosis, and prediction of therapeutic response. Since proteins govern cellular structure and biological function, a wide selection of proteomic approaches enables effective characterization of IBD pathogenesis by investigating the dynamic nature of protein expression, cellular and subcellular distribution, posttranslational modifications, and interactions at both the cellular and subcellular levels. The aims of this review are to 1) highlight the current status of proteomic studies of IBD, and 2) introduce the available and emerging proteomic technologies that have potential applications in the study of IBD. These technologies include various mass spectrometry technologies, quantitative proteomics (2D-PAGE, ICAT, SILAC, iTRAQ), protein/antibody arrays, and multi-epitope-ligand cartography. This review also presents information and methodologies, from sample selection and enrichment to protein identification, that are not only essential but also particularly relevant to IBD research. The potential future application of these technologies is expected to have a significant impact on the discovery of novel biomarkers and key pathogenic factors for IBD.

Integrin alpha(v)beta(3) is a pleiotrophin receptor required for pleiotrophin-induced endothelial cell migration through receptor protein tyrosine phosphatase beta/zeta

We have previously shown that the angiogenic growth factor pleiotrophin (PTN) induces migration of endothelial cells through binding to its receptor protein tyrosine phosphatase beta/zeta (RPTPbeta/zeta). In this study, we show that a monoclonal antibody against alpha(nu)beta(3) but not alpha(5)beta(1) integrin abolished PTN-induced human endothelial cell migration in a concentration-dependent manner. Integrin alpha(nu)beta(3) was found to directly interact with PTN in an RGD-independent manner, whereas a synthetic peptide corresponding to the specificity loop of the beta(3) integrin extracellular domain ((177)CYDMKTTC(184)) inhibited PTN-alpha(nu)beta(3) interaction and totally abolished PTN-induced endothelial cell migration. Interestingly, alpha(nu)beta(3) was also found to directly interact with RPTPbeta/zeta, and PTN-induced Y773 phosphorylation of beta(3) integrin was dependent on both RPTPbeta/zeta and the downstream c-src kinase activation. Midkine was found to interact with RPTPbeta/zeta, but not with alpha(nu)beta(3), and caused a small but statistically significant decrease in cell migration. In the same line, PTN decreased migration of different glioma cell lines that express RPTPbeta/zeta but do not express alpha(nu)beta(3), while it stimulated migration of U87MG cells that express alpha(nu)beta(3) on their cell membrane. Overexpression or down-regulation of beta(3) stimulated or abolished, respectively, the effect of PTN on cell migration. Collectively, these data suggest that alpha(nu)beta(3) is a key molecule that determines the stimulatory or inhibitory effect of PTN on cell migration.

Profiling of mitochondrial associated proteins from rat colon

Mitochondrial dysfunction, damage and mutations of mitochondrial proteins give rise to a range of ill understood patterns of disease. Although there is significant general knowledge of the proteins and the functional processes of the mitochondria, there is little knowledge of difference about how mitochondria respond and how they are regulated in different organs and tissues. Proteomic profiling of mitochondria and associated proteins involved in mitochondrial regulation and trafficking within cells and tissues has the potential to provide insights into mitochondrial dysfunction associated with many human diseases. The rat colon mitoproteome analysis presented here provides a useful tool to assist in identification and interpretation of mitochondrial dysfunction implicated in colon pathogenesis. 2DPAGE followed by LC/MS/MS was used to identify 430 proteins from mitochondrial enriched fractions prepared from rat colon, resulting in 195 different proteins or approximately 50% of the resolved proteins being identified as multiple protein expression forms. Proteins associated with the colon mitoproteome were involved in calcium binding, cell cycle, energy metabolism and electron transport chain, protein folding, protein synthesis and degradation, redox regulation, structural proteins, signalling and transporter and channel proteins. The mitochondrial associated proteins identified in this study of colon tissue complement and are compared with other recently published mitoproteome analyses from other organ tissues, and will assist in revealing potentially organ specific roles of the mitochondria and organ specific disease associated with mitochondrial dysfunction.