Expression of osteoactivin in rat and human liver and isolated rat liver cells

GPNMB regulates the differentiation and transformation of monocyte-derived macrophages during MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) is an increasingly concerning global health issue characterized by pronounced hepatic steatosis and liver fibrosis. Hepatic monocyte-derived macrophages (MDMs) are crucial in the pathogenesis of liver fibrosis under MASLD. Nevertheless, the precise functions of MDMs and the underlying mechanisms governing their differentiation remain inadequately elucidated. In this study, we revealed an orchestrator of this process: Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB), one of the characteristic genes of MDMs. Notably, myeloid-specific Gpnmb-knockout contributed to the retention of resident Kupffer cells (KCs) and rerouted monocyte differentiation towards a monocyte-derived macrophage subset that occupies the Kupffer cell niche (MoKC subset, resembling resident KCs), thereby impeding the formation of hepatic lipid-associated macrophages (LAMs). This transition has a profound impact, manifested in significantly reduced steatosis and modestly decreased liver fibrosis in myeloid-specific Gpnmb-knockout mice. In conclusion, our research clarifies the complex interactions between Gpnmb and MDMs and underscores the therapeutic potential of targeting Gpnmb within MDMs to manage MASLD.

The expression and function of Gpnmb in lymphatic endothelial cells

The lymphatic system functions in fluid homeostasis, lipid absorption and the modulation of the immune response. The role of Gpnmb (osteoactivin), an established osteoinductive molecule with newly identified anti-inflammatory properties, has not been studied in lymphangiogenesis. Here, we demonstrate that Gpnmb increases lymphatic endothelial cell (LEC) migration and lymphangiogenesis marker gene expression in vitro by enhancing pro-autophagic gene expression, while no changes were observed in cell proliferation or viability. In addition, cellular spreading and cytoskeletal reorganization was not altered following Gpnmb treatment. We show that systemic Gpnmb overexpression in vivo leads to increases in lymphatic tubule number per area. Overall, data presented in this study suggest Gpnmb is a positive modulator of lymphangiogenesis.

Mechanistic study of the regulation of mitochondrial function by the GPNMB/Nrf2/NF-κB signaling pathway mediated by Quzhi Tang to alleviate chondrocyte senescence

ETHNOPHARMACOLOGICAL RELEVANCE

Quzhi Tang (QZT) is a compound formula consisting of six traditional Chinese medicinal herbs. It has achieved good clinical results in the treatment of knee osteoarthritis (KOA), and the potential drug mechanisms involved are worth exploring in depth.

MATERIALS AND METHODS

Using single-cell transcriptome analysis, this study identified the key target of senescence, GPNMB. Then, it investigated the mechanism by which QZT regulates the GPNMB/Nrf2/NF-κB signaling pathway to repair mitochondrial damage and ameliorate the process of chondrocyte senescence.

RESULTS

We collected cartilage tissues from mice and identified GPNMB as a key target of chondrocyte senescence by combining transcriptomics, histopathology, molecular biology, and immunology methods. The effects of QZT on the level of chondrocyte senescence in mice and its ameliorative effect on KOA were studied. In in vivo experiments, we explored the mechanism of GPNMB in the development of senescence in detail and revealed that, after siRNA-GPNMB interference, chondrocytes exhibited reduced impairment of mitochondrial function and senescence under equal amounts of stimuli, increasing Nrf2 expression and reducing NF-κB expression. In addition, the level of oxidative stress increased in chondrocytes overexpressing GPNMB after lentiviral infiltration, aggravating the impairment of mitochondrial function. After treatment with QZT, chondrocytes overexpressing GPNMB were able to increase Nrf2 expression, decrease NF-κB expression, repair mitochondrial damage, and improve the degree of chondrocyte aging.

CONCLUSION

We concluded that the GPNMB/Nrf2/NF-κB signaling pathway plays an important role in chondrocyte senescence and that QZT was able to reduce intracellular oxidative stress and restore impaired mitochondrial function by regulating the expression level of the GPNMB/Nrf2/NF-κB signaling pathway, reducing the level of chondrocyte senescence in the KOA process.

Glycoprotein non-metastatic melanoma protein B (GPNMB): An attractive target in atherosclerosis

Atherosclerosis (AS), the leading cause of cardiovascular diseases, is heavily influenced by inflammation, lipid accumulation, autophagy, and aging. The expression of glycoprotein non-metastatic melanoma B (GPNMB) has been observed to correlate with lipid content, inflammation, and aging, progressively increasing as atherosclerosis advances through its various stages, from baseline to early and advanced phases. However, the interaction between GPNMB and AS is controversial. Knockout of GPNMB has been shown to increase atherosclerotic plaque burden in mice. Conversely, targeted elimination of GPNMB-positive cells reduced atherosclerotic burden. These seemingly contradictory findings underscore the complexity of the issue and highlight the need for further research to reconcile these discrepancies and to elucidate the precise role of GPNMB in the pathogenesis of AS.

Mechanism of hydroxysafflor yellow A on acute liver injury based on transcriptomics

Objective: To investigate how Hydroxysafflor yellow A (HSYA) effects acute liver injury (ALI) and what transcriptional regulatory mechanisms it may employ.

Methods: Rats were randomly divided into five groups (n = 10): Control, Model, HSYA-L, HSYA-M, and HSYA-H. In the control and model groups, rats were intraperitoneally injected with equivalent normal saline, while in the HSYA groups, they were also injected with different amounts of HSYA (10, 20, and 40 mg/kg/day) once daily for eight consecutive days. One hour following the last injection, the control group was injected into the abdominal cavity with 0.1 ml/100 g of peanut oil, and the other four groups got the same amount of a peanut oil solution containing 50% CCl4. Liver indexes were detected in rats after dissection, and hematoxylin and eosin (HE) dyeing was utilized to determine HSYA’s impact on the liver of model rats. In addition, with RNA-Sequencing (RNA-Seq) technology and quantitative real-time PCR (qRT-PCR), differentially expressed genes (DEGs) were discovered and validated. Furthermore, we detected the contents of anti-superoxide anion (anti-O2−) and hydrogen peroxide (H2O2), and verified three inflammatory genes (Icam1, Bcl2a1, and Ptgs2) in the NF-kB pathway by qRT-PCR.

Results: Relative to the control and HSYA groups, in the model group, we found 1111 DEGs that were up-/down-regulated, six of these genes were verified by qRT-PCR, including Tymp, Fabp7, Serpina3c, Gpnmb, Il1r1, and Creld2, indicated that these genes were obviously involved in the regulation of HSYA in ALI model. Membrane rafts, membrane microdomains, inflammatory response, regulation of cytokine production, monooxygenase activity, and iron ion binding were significantly enriched in GO analysis. KEGG analysis revealed that DEGs were primarily enriched for PPAR, retinol metabolism, NF-kB signaling pathways, etc. Last but not least, compared with the control group, the anti-O2− content was substantially decreased, the H2O2 content and inflammatory genes (Icam1, Bcl2a1, and Ptgs2) levels were considerably elevated in the model group. Compared with the model group, the anti-O2− content was substantially increased, the H2O2 content and inflammatory genes (Icam1, Bcl2a1, and Ptgs2) levels were substantially decreased in the HSYA group (p < 0.05).

Conclusion: HSYA could improve liver function, inhibit oxidative stress and inflammation, and improve the degree of liver tissue damage. The RNA-Seq results further verified that HSYA has the typical characteristics of numerous targets and multiple pathway. Protecting the liver from damage by regulating the expression of Tymp, Fabp7, Serpina3c, Gpnmb, Il1r1, Creld2, and the PPAR, retinol metabolism, NF-kappa B signaling pathways.

GPNMB Extracellular Fragment Protects Melanocytes from Oxidative Stress by Inhibiting AKT Phosphorylation Independent of CD44

Glycoprotein non-metastatic melanoma protein B (GPNMB) is a type I transmembrane glycoprotein that plays an important role in cancer metastasis and osteoblast differentiation. In the skin epidermis, GPNMB is mainly expressed in melanocytes and plays a critical role in melanosome formation. In our previous study, GPNMB was also found to be expressed in skin epidermal keratinocytes. In addition, decreased GPNMB expression was observed in the epidermis of lesional skin of patients with vitiligo. However, the exact role of keratinocyte-derived GPNMB and its effect on vitiligo is still unknown. In this study, we demonstrated that GPNMB expression was also decreased in rhododendrol-induced leukoderma, as seen in vitiligo. The extracellular soluble form of GPNMB (sGPNMB) was found to protect melanocytes from cytotoxicity and the impairment of melanogenesis induced by oxidative stress. Furthermore, the effect of rGPNMB was not altered by the knockdown of CD44, which is a well-known receptor of GPNMB, but accompanied by the suppressed phosphorylation of AKT but not ERK, p38, or JNK. In addition, we found that oxidative stress decreased both transcriptional GPNMB expression and sGPNMB protein expression in human keratinocytes. Our results suggest that GPNMB might provide novel insights into the mechanisms related to the pathogenesis of vitiligo and leukoderma.

Anti-inflammatory role of Gpnmb in adipose tissue of mice

Obesity can cause a chronic, low-grade inflammation, which is a critical step in the development of type II diabetes and cardiovascular diseases. Inflammation is associated with the expression of glycoprotein nonmetastatic melanoma protein b (Gpnmb), which is mainly expressed by macrophages and dendritic cells. We generated a Gpnmb-knockout mouse line using Crispr-Cas9 to assess the role of Gpnmb in a diet-induced obesity. The absence of Gpnmb did not affect body weight gain and blood lipid parameters. While wildtype animals became obese but remained otherwise metabolically healthy, Gpnmb-knockout animals developed, in addition to obesity, symptoms of metabolic syndrome such as adipose tissue inflammation, insulin resistance and liver fibrosis. We observed a strong Gpnmb expression in adipose tissue macrophages in wildtype animals and a decreased expression of most macrophage-related genes independent of their inflammatory function. This was corroborated by in vitro data showing that Gpnmb was mostly expressed by reparative macrophages while only pro-inflammatory stimuli induced shedding of Gpnmb. The data suggest that Gpnmb is ameliorating adipose tissue inflammation independent of the polarization of macrophages. Taken together, the data suggest an immune-balancing function of Gpnmb that could delay the metabolic damage caused by the induction of obesity.

Macrophages and cancer stem cells: a malevolent alliance

Myeloid cells infiltrating tumors are gaining ever growing attention in the last years because their pro-tumor and immunosuppressive functions are relevant for disease progression and therapeutic responses. The functional ambiguity of tumor-associated macrophages (TAMs), mostly promoting tumor evolution, is a challenging hurdle. This is even more evident in the case of cancer stem cells (CSCs); as active participants in the specialized environment of the cancer stem cell niche, TAMs initiate a reciprocal conversation with CSCs. TAMs contribute to protect CSCs from the hostile environment (exogenous insults, toxic compounds, attacks from the immune cells), and produce several biologically active mediators that modulate crucial developmental pathways that sustain cancer cell stemness. In this review, we have focused our attention on the interaction between TAMs and CSCs; we describe how TAMs impact on CSC biology and, in turn, how CSCs exploit the tissue trophic activity of macrophages to survive and progress. Since CSCs are responsible for therapy resistance and tumor recurrence, they are important therapeutic targets. In view of the recent success in oncology obtained by stimulating the immune system, we discuss some macrophage-targeted therapeutic strategies that may also affect the CSCs and interrupt their malevolent alliance.

Immunophenotypic analysis of the distribution of hepatic macrophages, lymphocytes and hepatic stellate cells in the adult rat liver

The liver consists of parenchymal hepatocytes and non-parenchymal cells. Non-parenchymal cells, Kupffer cells, hepatic stellate cells and cholangiocytes have crucial roles in liver homeostasis and liver pathology. To establish baseline data, this study investigated immunohistochemically the distribution of non-parenchymal cells in perivenular areas (PV), periportal areas (PP) and Glisson's sheath (GS) of adult rat liver. Liver tissues were collected from the left lateral lobe of rats. CD163-positive macrophages were seen along the sinusoid of PV and PP areas, indicating Kupffer cells. Double immunofluorescence showed, Kupffer cells partly co-expressed CD68 and MHC class II antigens in the liver. The numbers of Kupffer cells were significantly high in PP areas as compared with PV or GS areas. CD68-positive exudative macrophages were highly localized in PP and GS areas and a comparatively low PV area. MHC class II-positive dendritic cells (activated macrophages) were localized mainly in GS. Granzyme B-positive NK cells were mainly localized in the Glisson's sheath. CD3-positive T cells and CD20-positive B cells were distributed along the sinusoids of the PP and PV areas of hepatic lobules. Vimentin and glial fibrillary acidic protein (GFAP)-positive hepatic stellate cells were localized along sinusoids in the hepatic lobules of the liver. Cholangiocytes reacting to cytokeratin 19 were seen on interlobular bile ducts in Glisson's sheath of the liver. This study shows that heterogeneous macrophage populations, liver-resident lymphocytes and hepatic stellate cells localized in PP and PV areas or GS areas of the liver with cells specific patterns.

The Role of GPNMB in Inflammation

Inflammation is a response to a lesion in the tissue or infection. This process occurs in a specific manner in the central nervous system and is called neuroinflammation, which is involved in neurodegenerative diseases. GPNMB, an endogenous glycoprotein, has been recently related to inflammation and neuroinflammation. GPNMB is highly expressed in macrophages and microglia, which are cells involved with innate immune response in the periphery and the brain, respectively. Some studies have shown increased levels of GPNMB in pro-inflammatory conditions, such as LPS treatment, and in pathological conditions, such as neurodegenerative diseases and cancer. However, the role of GPNMB in inflammation is still not clear. Even though most studies suggest that GPNMB might have an anti-inflammatory role by promoting inflammation resolution, there is evidence that GPNMB could be pro-inflammatory. In this review, we gather and discuss the published evidence regarding this interaction.

Elevated circulating Gpnmb levels are associated with hyperthyroidism

BACKGROUND

Glycoprotein non-metastatic protein B (Gpnmb) has been identified as a new cytokine secreted by hepatocyte that plays an important role in balancing lipid homeostasis and development of obesity and metabolic disorders. However, information is not available regarding the association between circulating Gpnmb and hyperthyroid in humans.

METHODS

We measured serum Gpnmb in 180 hyperthyroid patients and 82 healthy subjects that were recruited from the clinic. Of them, 46 hyperthyroid patients received thionamide treatment for 3 months.

RESULTS

Hyperthyroid subjects had higher levels of circulating Gpnmb than healthy controls (47.8 ± 10.1 ng/mL vs 31.0 ± 4.9 ng/mL, P < 0.001). Subjects with higher levels of serum free triiodothyronine (T3) and free thyroxine (T4) had higher levels of circulating Gpnmb. After thionamide treatment, levels of circulating Gpnmb in hyperthyroid subjects remarkably declined with significant improvement of thyroid function (P < 0.001). Furthermore, the change of circulating Gpnmb levels was significantly associated with basal metabolic rate (BMR) and thyroid hormones, including free T3 and free T4, adjusting for age, gender, smoking and BMI before thionamide treatment. In multivariable logistic regression analyses, circulating Gpnmb was significantly associated with risks of hyperthyroidism (OR (95% CI): 1.44 (1.20-1.74), P < 0.001), adjusted for age, gender, BMI, fasting glucose, HOMA-IR, LDL-cholesterol, ALT and AST.

CONCLUSIONS

These findings indicate that circulating Gpnmb concentrations are independently associated with hyperthyroid, suggesting that circulating Gpnmb may be a predictor of risk for hyperthyroidism and can be used for therapeutic monitoring.

The soluble glycoprotein NMB (GPNMB) produced by macrophages induces cancer stemness and metastasis via CD44 and IL-33

In cancer, myeloid cells have tumor-supporting roles. We reported that the protein GPNMB (glycoprotein nonmetastatic B) was profoundly upregulated in macrophages interacting with tumor cells. Here, using mouse tumor models, we show that macrophage-derived soluble GPNMB increases tumor growth and metastasis in Gpnmb-mutant mice (DBA/2J). GPNMB triggers in the cancer cells the formation of self-renewing spheroids, which are characterized by the expression of cancer stem cell markers, prolonged cell survival and increased tumor-forming ability. Through the CD44 receptor, GPNMB mechanistically activates tumor cells to express the cytokine IL-33 and its receptor IL-1R1L. We also determined that recombinant IL-33 binding to IL-1R1L is sufficient to induce tumor spheroid formation with features of cancer stem cells. Overall, our results reveal a new paracrine axis, GPNMB and IL-33, which is activated during the cross talk of macrophages with tumor cells and eventually promotes cancer cell survival, the expansion of cancer stem cells and the acquisition of a metastatic phenotype.

GPNMB is expressed in human epidermal keratinocytes but disappears in the vitiligo lesional skin

GPNMB is involved in multiple cellular functions including cell adhesion, stress protection and stem cell maintenance. In skin, melanocyte-GPNMB is suggested to mediate pigmentation through melanosome formation, but details of keratinocyte-GPNMB have yet to be well understood. We confirmed the expression of GPNMB in normal human epidermal keratinocytes (NHEKs) by reducing the expression using siRNA. A higher calcium concentration of over 1.25 mM decreased the GPNMB expression. Histological staining showed that GPNMB was expressed in the basal layer of normal skins but completely absent in vitiligo skins. The normal expression of GPNMB in nevus depigmentosus skin suggested that lack of GPNMB is characteristic of vitiligo lesional skins. IFN-γ and IL-17A, two cytokines with possible causal roles in vitiligo development, inhibited GPNMB expression in vitro. Approximately 4–8% of the total GPNMB expressed on NHEKs were released possibly by ADAM 10 as a soluble form, but the process of release was not affected by the cytokines. The suppressive effect of IFN-γ on GPNMB was partially via IFN-γ/JAK2/STAT1 signaling axis. Decreased GPNMB expression in keratinocytes may affect melanocyte maintenance or survival against oxidative stress although further studies are needed. These findings indicate a new target for vitiligo treatment, focusing on the novel role of IFN-γ and IL-17 in downregulating keratinocyte-GPNMB.

Glycoprotein Nonmetastatic Melanoma Protein B (GPNMB) Ameliorates the Inflammatory Response in Periodontal Disease

Glycoprotein nonmetastatic melanoma protein B (GPNMB) is a type I transmembrane protein that can modulate osteoblasts and bone mineralization. Periodontal disease (PD) is characterized by gum inflammation, alveolar bone resorption, and tooth loss. In this study, we found that GPNMB is highly expressed in inflamed periodontal tissue through microarray and immunohistochemistry (IHC) assays. The role of GPNMB in the pathogenesis of PD was evaluated with primary human periodontal ligament cells (hPDLCs) treated with lipopolysaccharide (LPS) and a GPNMB-expressing lentivirus (lenti-GP). In the hPDLCs treated with LPS and lenti-GP, the expression of tumor necrosis factor (TNF)-α and interleukin (IL)-6 was suppressed and that of IL-10 was upregulated. GPNMB significantly decreased apoptosis in the hPDLCs treated with LPS. GPNMB could upregulate the expression of Jumonji domain-containing protein 3 (Jmjd3), a histone 3 lysine 27 (H3K27) demethylase that is linked to the modulation of the inflammatory response and apoptosis. Taken together, our data find that GPNMB is highly expressed in gum tissue with PD and may be an anti-inflammatory player in the pathogenesis of PD.

Glycoprotein non-metastatic melanoma B expression after hepatic ischemia reperfusion and the effect of silibinin

Background

Glycoprotein non-metastatic melanoma B (GPNMB) is a transmembrane glycoprotein with various roles in inflammation regulation, tissue remodeling and oncogenesis. Clinical situations implicating alterations in its expression include ischemic injury, cirrhosis and fatty liver disease amongst other. We examine its expression in hepatic and renal tissue following hepatic ischemia-reperfusion (I/R) in a rat model, with and without intravenous silibinin administration, as a silibinin-hydroxypropyl-β-cyclodextrin lyophilized complex (SLB-HP-β-CD).

Methods

Sixty-three Wistar rats were divided into 3 groups: sham group (virtual intervention; 7 animals), control (C) group (45 min of ischemia, followed by reperfusion and euthanasia at 60, 120, 180 and 240 min; 28 animals equally divided), and silibinin (Si) group (45 min of ischemia, intravenous administration of SLB-HP-β-CD, reperfusion and euthanasia at the same time points; 28 animals equally divided). GPNMB expression was examined in liver and kidney tissue.

Results

GPNMB expression was significantly increased following hepatic I/R in the control group, in kidney tissue, in a time dependent manner. In the silibinin group, GPNMB expression significantly decreased with time compared to the control group in both liver and kidney tissue (P<0.05).

Conclusions

Hepatic I/R causes increase of GPNMB levels both in liver and kidney tissues, which may reflect tissue injury. Silibinin seems to act protectively on both liver and kidney, and can be potentially used as a therapeutic approach against hepatic I/R injury.

Glycoprotein Non-Metastatic Protein B: An Emerging Biomarker for Lysosomal Dysfunction in Macrophages

Several diseases are caused by inherited defects in lysosomes, the so-called lysosomal storage disorders (LSDs). In some of these LSDs, tissue macrophages transform into prominent storage cells, as is the case in Gaucher disease. Here, macrophages become the characteristic Gaucher cells filled with lysosomes laden with glucosylceramide, because of their impaired enzymatic degradation. Biomarkers of Gaucher cells were actively searched, particularly after the development of costly therapies based on enzyme supplementation and substrate reduction. Proteins selectively expressed by storage macrophages and secreted into the circulation were identified, among which glycoprotein non-metastatic protein B (GPNMB). This review focusses on the emerging potential of GPNMB as a biomarker of stressed macrophages in LSDs as well as in acquired pathologies accompanied by an excessive lysosomal substrate load in macrophages.

GPNMB methylation: a new marker of potentially carcinogenic colon lesions

Background

Epigenetic plays an important role in colorectal neoplasia process. There is a need to determine sound biomarkers of colorectal cancer (CRC) progression with clinical and therapeutic implications. Therefore, we aimed to examine the role and methylation status of Glyco Protein Non-Metastatic GPNM B (GPNMB) gene in normal, adenoma and CRC in African American (AA) patients.

Methods

The methylation status of 13 CpG sites (chr7: 23287345–23,287,426) in GPNMB gene’s promoter, was analyzed by pyrosequencing in human CRC cell lines (HCT116, SW480, and HT29) and microdissected African American paraffin embedded samples (20 normal, 21 non-advanced adenoma (NA), 48 advanced adenoma (AD), and 20 cancer tissues. GPNMB expression was analyzed by immunohistochemistry (IHC) on tissue microarrays (TMA). Correlations between GPNMB methylation and expression with clinicopathological features were analyzed. GPNMB functional analysis was performed in triplicates using cell proliferation, migration and invasion assays in HCT116 colon cell line after stable transfection with a GPNMB-cDNA expression vector.

Results

GPNMB methylation was lower in normal mucosa compared to CRC samples (1/20 [5%] vs. 18/20 [90%]; P < 0.001). AD also had a significantly higher GPNMB methylation frequency than normal colon samples (42/48 [88%] vs 1/20 [5%]; P < 0.001). GPNMB was more frequently methylated in AD than in matched normal mucosa from three patients (3/3 [100%] vs 1/3 [33.3%]; P < 0.001). The frequency of GPNMB methylation in NA differed significantly from that in the normal mucosa (16/21 [76%] vs 1/20 [5%]; P = 0.008). There was statistically significant correlation of higher methylation at advanced stages and lower methylation at stage 1 CRCs (P < 0.05). In agreement with these findings, GPNMB protein expression decreased in CRC tissues compared with AD and NA colon mucosa (p < 0.05). GPNMB overexpression in HCT116 colon cancer cell line decreased cell proliferation [(24 h, P = 0.02), (48 h, P < 0.001, 72 h, P = 0.007)], invasion (p < 0.05) and migration (p > 0.05) compared to the mock-transfected cells.

Conclusion

Our data indicate a high methylation profile leading to a lower GPNMB expression in adenoma and CRC samples. The functional analysis established GPNMB as a potential tumor suppressor gene. As such, GPNMB might be useful as a biomarker of adenomas with high carcinogenic potential.

Discovery and translation of a target engagement marker for AMP-activated protein kinase (AMPK)

BACKGROUND

Activation of the AMP-activated protein kinase (AMPK) is an attractive approach for the treatment of type 2 diabetes. AMPK activation reduces glucose levels in animal models of type 2 diabetes by increasing glucose uptake in skeletal muscles and reducing hepatic glucose production. Furthermore, AMPK activation ameliorates hepatic steatosis in animal models. For the clinical development of AMPK activators it is essential to have a reliable target engagement marker for appropriate dose finding and to support proof of clinical principle. While the activation of AMPK by quantification of the phosphorylation of AMPK at Thr172 in target tissues can be assessed pre-clinically, this is not feasible in clinical studies. Therefore, we attempted to identify and translate a peripheral target engagement biomarker downstream of AMPK activation for clinical use in blood samples.

METHODS

For pharmacological activation of AMPK, two AMPK activators were synthesized (compound 1 and 2). A compound with structural similarities but no pharmacological effect on AMPK phosphorylation was synthesized as negative control (compound 3). Whole blood from healthy volunteers was incubated with an AMPK activator for up to 6 hours and mRNA sequencing was performed. Additionally, human PBMCs were isolated to evaluate Thr172-phosphorylation of AMPK in Western blots. In order to enable identification of translatable biomarker candidates, blood samples from HanWistar rats treated for two weeks with an AMPK activator were also subjected to mRNA sequencing. Furthermore, concentration-response curves for four biomarker candidates were recorded in human blood samples using Nanostring nCounter technology. Finally, ZDF rats were treated with increasing doses of compound 2 for five weeks to investigate the glucose-lowering efficacy. To investigate changes of mRNA expression of two selected biomarker candidates in this ZDF rat study, qRT-PCR was performed.

RESULTS

Pharmacological activation of AMPK in human PBMCs revealed an increase in Thr172-phosphorylation of AMPK, confirming target engagement in these blood cells. RNA sequencing of human blood samples identified 608 deregulated genes after AMPK activation. Additionally, AMPK activation led to deregulation of 367 genes in whole blood from HanWistar rats which mapped to the respective human genes. 22 genes out of the intersection of genes deregulated in both species are proposed as potential translatable target engagement biomarker candidates. The most prominent genes were transmembrane glycoprotein NMB (GPNMB, osteoactivin), calcium-binding protein A9 (S100A9), peptidoglycan recognition protein (PGLYRP1) and Ras homolog gene family, member B (RHOB). Specificity for AMPK was shown by testing inactive compound 3 in HanWistar rats. The exposure-effect relationship for GPNMB was investigated in a subchronic study in diabetic ZDF rats. GPNMB showed a dose-dependent up-regulation both acutely and after subchronic dosing. GPNMB up-regulation correlated with an increased Thr172-phosphorylation of AMPK in liver and quadriceps muscle in rats.

CONCLUSION

GPNMB has been identified as a translatable target engagement biomarker for use in clinical studies.

Gender difference in NASH susceptibility: Roles of hepatocyte Ikkβ and Sult1e1

Myeloid cell and hepatocyte IKKβ may mediate the genesis of obesity and insulin resistance in mice fed high fat diet. However, their gender-specific roles in the pathogenesis of non-alcoholic steatohepatitis (NASH) are not known. Here we demonstrate myeloid IKKβ deficiency prevents Western diet-induced obesity and visceral adiposity in females but not in males, and attenuates hyperglycemia, global IR, and NASH in both genders. In contrast, all metabolic sequela including NASH are aggravated by hepatocyte IKKβ deficiency (IkbkbΔhep) in male but not female mice. Gene profiling identifies sulfotransferase family 1E (Sult1e1), which encodes a sulfotransferase E1 responsible for inactivation of estrogen, as a gene upregulated in NASH in both genders and most conspicuously in male IkbkbΔhep mice having worst NASH and lowest plasma estradiol levels. LXRα is enriched to LXRE on Sult1e1 promoter in male WT and IkbkbΔhep mice with NASH, and a Sult1e1 promoter activity is increased by LXRα and its ligand and augmented by expression of a S32A mutant of IκBα. These results demonstrate striking gender differences in regulation by IKKβ of high cholesterol saturated fat diet-induced metabolic changes including NASH and suggest hepatocyte IKKβ is protective in male due at least in part to its ability to repress LXR-induced Sult1e1. Our findings also raise a caution for systemic IKK inhibition for the treatment of NASH as it may exacerbate the disease in male patients.

Glycoprotein non-metastatic melanoma protein b (Gpnmb) is highly expressed in macrophages of acute injured kidney and promotes M2 macrophages polarization

Acute kidney injury (AKI) is an increasingly common disorder that is strongly linked to short- and long-term morbidity and mortality. During AKI process, macrophages, one of the important immune response cells, can polarize into M1 and M2 subtype from M0 subtype. It is well-known that M1 macrophages play a pro inflammatory role while M2 macrophages play an anti-inflammatory role. Glycoprotein non-metastatic melanoma protein b (Gpnmb) is a glycosylated transmembrane protein highly expressed in numerous cells, including osteoblasts, dendritic cells and macrophages. Gpnmb serves as a negative regulator of inflammation in macrophages and has a protective effect on injuries. In acute kidney injury, the macrophage has been shown diverse roles depending on different phenotype. This study provided gene expression and protein expression evidence that Gpnmb was highly expressed in M2 macrophages in the damaged areas of kidney after ischemia-reperfusion injury. Then, we successful isolated and culture mouse bone marrow-derived macrophages (BMMφ) and found that Gpnmb showed different expression levels in M0, M1 and M2 BMMφ: lowest in M1, highest in M2. After knocking down Gpnmb with si-Gpnmb, BMMφ M2 polarization and secretion of anti-inflammatory cytokines IL-10 and TGF-β were inhibited, while M1 polarization and secretion of proinflammatory cytokines IL-1β and TNF-α were promoted. Moreover, IL-4-STAT6 pathway was involved in the promotion of M2 polarization by Gpnmb. Taken together, Gpnmb may serve as a potential biomarker of AKI and play a protective role against the AKI by modulating the polarization of macrophage.

Prospects of osteoactivin in tissue regeneration

INTRODUCTION

Osteoactivin (OA) was first discovered in an osteopetrotic rat model using mRNA differential display a decade ago and has been studied recently. OA in bone tissue can directly or indirectly regulate the differentiation of osteoblasts by influencing cell behaviours, such as proliferation and adhesion, as well as inducing serial signal cascades, which would be of great importance in the field of tissue engineering. The results of recent studies have further demonstrated that OA plays a critical role in the differentiation and function of cells, especially in bone formation and fracture healing. Areas covered: The discovery, structure, and function of OA as well as its therapeutic potential in tissue regeneration of bone defects, kidney injury, liver damage, and muscle atrophy. Expert opinion: OA has great potential in promoting the regeneration of damaged tissues, particularly bone tissue, which is supported by a large body of data. Future studies should focus on exploring the underlying mechanism of OA as well as pursuing the ideal form of OA-related regenerative medicine.

Growth and repair factors, osteoactivin, matrix metalloproteinase and heat shock protein 72, increase with resolution of inflammation in musculotendinous tissues in a rat model of repetitive grasping

BACKGROUND

Expression of the growth factor osteoactivin (OA) increases during tissue degeneration and regeneration, fracture repair and after denervation-induced disuse atrophy, concomitant with increased matrix metalloproteinases (MMPs). However, OA's expression with repetitive overuse injuries is unknown. The aim of this study was to evaluate: 1) OA expression in an operant rat model of repetitive overuse; 2) expression of MMPs; 3) inflammatory cytokines indicative of injury or inflammation; and 4) the inducible form of heat shock protein 70 (HSPA1A/HSP72) as the latter is known to increase during metabolic stress and to be involved in cellular repair. Young adult female rats performed a high repetition negligible force (HRNF) food retrieval task for up to 6 weeks and were compared to control rats.

METHODS

Flexor digitorum muscles and tendons were collected from 22 young adult female rats performing a HRNF reaching task for 3 to 6 weeks, and 12 food restricted control (FRC) rats. OA mRNA levels were assessed by quantitative polymerase chain reaction (qPCR). OA, MMP-1, -2, -3, and -13 and HSP72 protein expression was assayed using Western blotting. Immunohistochemistry and image analysis was used to evaluate OA and HSP72 expression. ELISA was performed for HSP72 and inflammatory cytokines.

RESULTS

Flexor digitorum muscles and tendons from 6-week HRNF rats showed increased OA mRNA and protein expression compared to FRC rats. MMP-1, -2 and -3 progressively increased in muscles whereas MMP-1 and -3 increased in tendons with HRNF task performance. HSP72 increased in 6-week HRNF muscles and tendons, compared to controls, and co-localized with OA in the myofiber sarcolemma. IL-1alpha and beta increased transiently in tendons or muscles in HRNF week 3 before resolving in week 6.

CONCLUSION

The simultaneous increases of OA with factors involved in tissue repair (MMPs and HSP72) supports a role of OA in tissue regeneration after repetitive overuse.

Glycoprotein Nonmetastatic Melanoma B (Gpnmb)-Positive Macrophages Contribute to the Balance between Fibrosis and Fibrolysis during the Repair of Acute Liver Injury in Mice

Background and aims

Glycoprotein nonmetastatic melanoma B (Gpnmb), a transmembrane glycoprotein that is expressed in macrophages, negatively regulates inflammation. We have reported that Gpnmb is strongly expressed in the livers of rats fed a choline-deficient, L-amino acid-defined (CDAA) diet. However, the role of macrophage-expressed Gpnmb in liver injury is still unknown. This study aimed to clarify the characteristics of infiltrating macrophages that express Gpnmb, and the involvement of Gpnmb in the repair process in response to liver injury.

Methods

C57BL/6J, DBA/2J [DBA] and DBA/2J-Gpnmb⁺ [DBA-g+] mice were treated with a single intraperitoneal injection of carbon tetrachloride (CCl₄) at a dose of 1.0 mL/kg body weight. Mice were sacrificed at predetermined time points, followed by measurement of serum alanine aminotransferase (ALT) levels and histological examination. Expression of Gpnmb, pro-/anti-inflammatory cytokines, and profibrotic/antifibrotic factors were examined by quantitative RT-PCR and/or Western blotting. Immunohistochemistry, fluorescent immunostaining and flow cytometry were used to determine the expression of Gpnmb, CD68, CD11b and α-SMA, phagocytic activity, and the presence of apoptotic bodies. We used quantitative RT-PCR and ELISA to examine TGF-β and MMP-13 expression and the concentrations and supernatants of isolated infiltrating hepatic macrophages transfected with siGpnmb.

Results

In C57BL/6J mice, serum ALT levels increased at two days after CCl₄ injection and decreased at four days. Gpnmb expression in the liver was stimulated four days after CCl₄ injection. Histological examination and flow cytometry showed that Gpnmb-positive cells were almost positive for CD68-positive macrophages, contained engulfed apoptotic bodies and exhibited enhanced phagocytic activity. Isolated infiltrating hepatic macrophages transfected with siGpnmb showed high MMP-13 secretion. There was no significant difference in the magnitude of CCl₄-induced liver injury between DBA-g+ and DBA mice. However, hepatic MMP-13 expression, as well as α-SMA expression and collagen production, increased significantly in DBA-g+ compared with DBA mice.

Conclusions

Gpnmb-positive macrophages infiltrate the liver during the recovery phase of CCl₄–induced acute liver injury and contribute to the balance between fibrosis and fibrolysis in the repair process following acute liver injury.

Beneficial impact of Gpnmb and its significance as a biomarker in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide. Gpnmb is classified as a type 1 membrane protein and its soluble form is secreted by ADAM10-mediated cleavage. Gpnmb mRNA was found in the Kupffer cells and white adipose tissues (WATs) and its upregulation in obesity was recently found. Here, we generated aP2 promoter-driven Gpnmb transgenic (Tg) mice and the overexpression of Gpnmb ameliorated the fat accumulation and fibrosis of the liver in diet-induced obesity model. Soluble form of Gpnmb in sera was elevated in Gpnmb Tg mice and Gpnmb concentrated in hepatic macrophages and stellate cells interacted with calnexin, which resulted in the reduction of oxidative stress. In the patients with non-alcoholic steatohepatitis, serum soluble GPNMB concentrations were higher compared with the patients with simple steatosis. The GPNMB is a promising biomarker and therapeutic target for the development and progression of NAFLD in obesity.

The extracellular fragment of GPNMB (Glycoprotein nonmelanosoma protein B, osteoactivin) improves memory and increases hippocampal GluA1 levels in mice

Glycoprotein nonmelanoma protein B (GPNMB, alias osteoactivin), a type I transmembrane glycoprotein, is cleaved by extracellular proteases, resulting in release of an extracellular fragment (ECF). GPNMB is widely expressed by neurons within the CNS, including the hippocampus; however, its function in the brain remains unknown. Here, we investigated the role of GPNMB in memory and learning by using transgenic (Tg) mice over-expressing GPNMB (Tg mice on a BDF-1 background) and ECF-treated mice. In the hippocampus of both wild-type and Tg mice, GPNMB was highly expressed in neurons and astrocytes. Tg mice exhibited memory improvements in two types of learning tasks but were impaired in a passive-avoidance test. In Tg mice, the hippocampus displayed increased levels of the α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor subunit GluA1. Intracerebroventricular administration of ECF (50 ng) to Institute of Cancer Research (ICR) mice also improved memory in a passive-avoidance test and increased hippocampal GluA1 levels 24 h after treatment. In Tg mice and ECF (0.25 μg/mL)-treated hippocampal slices, long-term potentiation was promoted. These findings suggest that GPNMB may be a novel target for research on higher order brain functions.

Role of inflammation in the aging bones

Chronic inflammation in aging is characterized by increased inflammatory cytokines, bone loss, decreased adaptation, and defective tissue repair in response to injury. Aging leads to inherent changes in mesenchymal stem cell (MSC) differentiation, resulting in impaired osteoblastogenesis. Also, the pro-inflammatory cytokines increase with aging, leading to enhanced myelopoiesis and osteoclastogenesis. Bone marrow macrophages (BMMs) play pivotal roles in osteoblast differentiation, the maintenance of hematopoietic stem cells (HSCs), and subsequent bone repair. However, during aging, little is known about the role of macrophages in the differentiation and function of MSC and HSC. Aged mammals have higher circulating pro-inflammatory cytokines than young adults, supporting the hypothesis of increased inflammation with aging. This review will aid in the understanding of the potential role(s) of pro-inflammatory (M1) and anti-inflammatory (M2) macrophages in differentiation and function of osteoblasts and osteoclasts in relation to aging.

Time-dependent network analysis reveals molecular targets underlying the development of diet-induced obesity and non-alcoholic steatohepatitis

Prolonged high-fat diet leads to the development of obesity and multiple comorbidities including non-alcoholic steatohepatitis (NASH), but the underlying molecular basis is not fully understood. We combine molecular networks and time course gene expression profiles to reveal the dynamic changes in molecular networks underlying diet-induced obesity and NASH. We also identify hub genes associated with the development of NASH. Core diet-induced obesity networks were constructed using Ingenuity pathway analysis (IPA) based on 332 high-fat diet responsive genes identified in liver by time course microarray analysis (8 time points over 24 weeks) of high-fat diet-fed mice compared to normal diet-fed mice. IPA identified five core diet-induced obesity networks with time-dependent gene expression changes in liver. These networks were associated with cell-to-cell signaling and interaction (Network 1), lipid metabolism (Network 2), hepatic system disease (Network 3 and 5), and inflammatory response (Network 4). When we merged these core diet-induced obesity networks, Tlr2, Cd14, and Ccnd1 emerged as hub genes associated with both liver steatosis and inflammation and were altered in a time-dependent manner. Further, protein-protein interaction network analysis revealed Tlr2, Cd14, and Ccnd1 were interrelated through the ErbB/insulin signaling pathway. Dynamic changes occur in molecular networks underlying diet-induced obesity. Tlr2, Cd14, and Ccnd1 appear to be hub genes integrating molecular interactions associated with the development of NASH. Therapeutics targeting hub genes and core diet-induced obesity networks may help ameliorate diet-induced obesity and NASH.

Glycoprotein transmembrane nmb: an androgen-downregulated gene attenuates cell invasion and tumorigenesis in prostate carcinoma cells

BACKGROUND

Glycoprotein transmembrane nmb (GPNMB) gene was originally identified in osteoblasts and belongs to the pmel-17/nmb family. The function or regulation of GPNMB in the human prostate remains unknown.

METHODS

The expression of GPNMB in prostate carcinoma cells were determined by real-time reverse transcription-polymerase chain reaction (RT-qPCR) and immunoblot assays. Effects of ectopic GPNMB overexpression on cell proliferation, invasion, and tumorigenesis were determined by (3) H-thymidine incorporation, matrigel invasion, soft agar cloning assays, and murine xenograft study. Effects of GPNMB, p53, and androgen on target gene were assessed using RT-PCR, immunoblotting, and transient gene expression assays.

RESULTS

In vitro analysis using several prostate cell lines suggested that expression of GPNMB may be relevant to the extent of neoplasia. Ectopic overexpression of GPNMB significantly attenuated cell proliferation and invasion and exerted antitumorigenic activity on PC-3 cells in vitro and in vivo. GPNMB overexpression induced the gene expressions of N-myc downstream regulated gene 1 (Ndrg1) and maspin in PC-3 cells. Doxorubicin treatment or transient overexpression of p53 increased GPNMB expression. Androgen (R1881) treatment has a divergent effect on gene expression of prostate-specific antigen (PSA) and GPNMB in LNCaP cells. Androgen treatment enhanced cell proliferation but downregulated GPNMB protein expression in stably overexpressed androgen receptor (AR) CA-HPV-10 cells.

CONCLUSIONS

Together these results suggest that GPNMB gene is a p53- and androgen-dysregulated gene and should be regarded as an anti-tumor gene for prostate cancer. The enhancement of Ndrg1 and maspin gene expressions may account for the anti-proliferative and anti-invasive function of GPNMB in PC-3 cells.

Targeted overexpression of osteoactivin in cells of osteoclastic lineage promotes osteoclastic resorption and bone loss in mice

This study sought to test whether targeted overexpression of osteoactivin (OA) in cells of osteoclastic lineage, using the tartrate-resistant acid phosphase (TRAP) exon 1B/C promoter to drive OA expression, would increase bone resorption and bone loss in vivo. OA transgenic osteoclasts showed ∼2-fold increases in OA mRNA and proteins compared wild-type (WT) osteoclasts. However, the OA expression in transgenic osteoblasts was not different. At 4, 8, and 15.3 week-old, transgenic mice showed significant bone loss determined by pQCT and confirmed by μ-CT. In vitro, transgenic osteoclasts were twice as large, had twice as much TRAP activity, resorbed twice as much bone matrix, and expressed twice as much osteoclastic genes (MMP9, calciton receptor, and ADAM12), as WT osteoclasts. The siRNA-mediated suppression of OA expression in RAW264.7-derived osteoclasts reduced cell size and osteoclastic gene expression. Bone histomorphometry revealed that transgenic mice had more osteoclasts and osteoclast surface. Plasma c-telopeptide (a resorption biomarker) measurements confirmed an increase in bone resorption in transgenic mice in vivo. In contrast, histomorphometric bone formation parameters and plasma levels of bone formation biomarkers (osteocalcin and pro-collagen type I N-terminal peptide) were not different between transgenic mice and WT littermates, indicating the lack of bone formation effects. In conclusion, this study provides compelling in vivo evidence that osteoclast-derived OA is a novel stimulator of osteoclast activity and bone resorption.

Expression and immunolocalization of Gpnmb, a glioma-associated glycoprotein, in normal and inflamed central nervous systems of adult rats

Glycoprotein nonmetastatic melanoma B (Gpnmb) is a type I transmembrane protein implicated in cell differentiation, inflammation, tissue regeneration, and tumor progression. Gpnmb, which is highly expressed in glioblastoma cells, is a potential therapeutic target. However, little is known about its expression, cellular localization, and roles in non-tumorous neural tissues. In this study, we examined Gpnmb expression in the central nervous system of adult rats under both normal and inflammatory conditions. Reverse transcription-polymerase chain reaction analysis revealed that Gpnmb mRNA was expressed in the cerebrum, cerebellum, brain stem, and spinal cord of normal adult rats. Immunoperoxidase staining revealed that Gpnmb-immunoreactive cells were widely distributed in the parenchyma of all brain regions examined, with the cells being most prevalent in the hippocampal dentate gyrus, cerebellar cortex, spinal dorsal horn, choroid plexus, ependyma, periventricular regions, and in layers II and III of the cerebral cortex. Double immunofluorescence staining showed that these cells were co-stained most frequently with the microglia/macrophage marker OX42, and occasionally with the radial glia marker RC2 or the neuronal marker NeuN. Furthermore, an intraperitoneal injection of bacterial endotoxin lipopolysaccharide increased the number of Gpnmb and OX42 double-positive cells in the area postrema, which is one of the circumventricular organs, indicating infiltration of hematogenous macrophages. These results suggest that Gpnmb, which is expressed in microglia and macrophages in non-tumorous neural tissues, plays an important role in the regulation of immune/inflammatory responses.

Tumor-associated macrophages as incessant builders and destroyers of the cancer stroma

Tumor-Associated Macrophages (TAM) are key components of the reactive stroma of tumors. In most, although not all cancers, their presence is associated with poor patient prognosis. In addition to releasing cytokines and growth factors for tumor and endothelial cells, a distinguished feature of TAM is their high-rate degradation of the extra-cellular matrix. This incessant stroma remodelling favours the release of matrix-bound growth factors and promotes tumor cell motility and invasion. In addition, TAM produce matrix proteins, some of which are typical of the neoplastic tissues. The gene expression profile of TAM isolated from human tumors reveals a matrix-related signature with the up-regulation of genes coding for different matrix proteins, as well as several proteolytic enzymes. Among ECM components are: osteopontin, osteoactivin, collagens and fibronectin, including also a truncated isoform of fibronectin termed migration stimulation factor. In addition to serve as structural proteins, these matrix components have key functions in the regulation of the vessel network, in the inductionof tumor cell motility and degradation of cellular debris. Among proteolytic enzymes are: matrix metalloproteases, cathepsins, lysosomal and ADAM proteases, and the urokinase-type plasminogen activator. The degrading activity of TAM, coupled to the production of bio-active ECM proteins, co-operate to the build-up and maintenance of an inflammatory micro-environment which eventually promotes tumor progression.

Concomitant apoptosis and regeneration of liver cells as a mechanism of liver-tumor promotion by β-naphthoflavone involving TNFα-signaling due to oxidative cellular stress in rats

β-naphthoflavone (BNF) is a strong inducer of cytochrome P450 1A enzymes, and exerts liver tumor-promoting activity through enhancement of oxidative stress responses in rats. This study investigated the role of the tissue environment surrounding hepatocellular preneoplastic lesions in the early tumor-promotion stage by BNF, using enzymatically modified isoquercitrin (EMIQ) as an anti-oxidative chemopreventive agent. Male F344 rats were fed a diet containing BNF (0.5%) for 6 weeks, with or without EMIQ (0.2%) in the drinking water, 2 weeks after initiation with N-diethylnitrosamine, and were subjected to two-thirds partial hepatectomy 1 week after starting BNF-promotion. BNF-treatment increased concentrations of liver thiobarbituric acid-reactive substances, single liver cells expressing glutathione S-transferase placental form or heme oxygenase (HO)-1, and concomitant apoptosis and proliferation of liver cells. Transcript upregulation of anti-oxidative enzymes (Aldh1a1 and Nqo1), cell cycle-related molecules (Cdc20 and Cdkn2b) and inflammation-related molecules including proinflammatory cytokines (Ccl2, Col1a1, Il6, Nos2 and Serpine1) was also evident. Furthermore, BNF increased HO-1-expressing Kupffer cells and liver cells expressing tumor necrosis factor receptor 1 (TNFR1) and the TNFR1-associated death domain. Most of these BNF-induced fluctuations disappeared or were suppressed by EMIQ in conjunction with suppression of tumor-promotion. Tnf transcript levels with BNF were also suppressed by EMIQ. These results suggest that BNF-induced oxidative stress causes single liver cell toxicity, allowing subsequent concomitant apoptosis and regeneration involving inflammatory responses including TNFα-signaling, contributing to tumor promotion. Kupffer cells may act to protect against inflammatory stimuli induced as a result of oxidative cellular stress by BNF, causing proinflammatory cytokine level fluctuations.

Temporal and spatial expression of osteoactivin during fracture repair

We previously identified osteoactivin (OA) as a novel secreted osteogenic factor with high expression in developing long bones and calvaria, and that stimulates osteoblast differentiation and matrix mineralization in vitro. In this study, we report on OA mRNA and protein expression in intact long bone and growth plate, and in fracture calluses collected at several time points up to 21 days post-fracture (PF). OA mRNA and protein were highly expressed in osteoblasts localized in the metaphysis of intact tibia, and in hypertrophic chondrocytes localized in growth plate, findings assessed by in situ hybridization and immunohistochemistry, respectively. Using a rat fracture model, Northern blot analysis showed that expression of OA mRNA was significantly higher in day-3 and day-10 PF calluses than in intact rat femurs. Using in situ hybridization, we examined OA mRNA expression during fracture healing and found that OA was temporally regulated, with positive signals seen as early as day-3 PF, reaching a maximal intensity at day-10 PF, and finally declining at day-21 PF. At day-5 PF, which correlates with chondrogenesis, OA mRNA levels were significantly higher in the soft callus than in intact femurs. Similarly, we detected high OA protein immunoexpression throughout the reparative phase of the hard callus compared to intact femurs. Interestingly, the secreted OA protein was also detected within the newly made cartilage matrix and osteoid tissue. Taken together, these results suggest the possibility that OA plays an important role in bone formation and serves as a positive regulator of fracture healing.

Hepatic changes of erythropoietin gene expression in a rat model of acute-phase response

An acute-phase response is the systemic reaction of an organism to insult (e.g. infection, trauma and burning). It represents the 'first line' of defence of the body to tissue-damaging attacks. In the present work, we used a rat model of an intra-muscular turpentine oil (TO) injection to analyse erythropoietin (EPO) gene expression changes in the liver, one of the main target organs of acute-phase cytokines. EPO began to increase in the serum of TO-treated animals 6 h after injection and reached a maximum at 24 h (125+/-20 pg/ml). The detection of total RNA by polymerase chain reaction analysis showed that the levels of EPO gene expression in the liver were considerably increased between 2 and 12 h by up to 20-fold at the peak after TO administration, followed by a gradual decrease over the next 48 h, although the values remained significantly higher compared with the control group. In the kidney, after a sudden slight increase, the values declined progressively to 3.5-fold decrease at 12 h after the injection. In the liver, a parallel upregulation of the hypoxia-inducible factor-1 (HIF-1) alpha gene was observed (up to 4.7-fold increase), while HIF-2 alpha gene expression remained unaltered. On the other hand, the protein of both genes became detectable after the injection and increased progressively over 24 h, with a subsequent decline. These results suggest that EPO may be added to the increasing group of positive acute-phase proteins and the liver might represent the major source of the hormone under these conditions in the rat.

Emerging therapeutic targets in breast cancer bone metastasis

In the past decade, our understanding of the molecular mechanisms that underlie breast cancer pathology and progression has dramatically improved. Using this knowledge, we have identified additional targets and developed novel therapeutic interventions in breast cancer. Together, these translational research efforts are helping to usher us into an age of personalized cancer therapy. Metastasis to bone is a common and devastating consequence of breast cancer. Bisphosphonates, which represent the current gold standard in bone metastasis therapies, are being improved with newer and more efficacious generations of these compounds being developed. Breast cancer growth in the bone requires activation of various signaling pathways in both cancer cells and stromal cells, including those that are stimulated by TGF-β and RANKL, and mediated through the Src tyrosine kinase. Bone cells and cancer cells alike express promising targets for therapeutic intervention, including Cathepsin K, CXCR4 and GPNMB. In this article we discuss the molecular mechanisms behind these pro-metastatic molecules and review the most recent findings in the clinical development of their associated targeted therapies.

Upregulation of monocyte/macrophage HGFIN (Gpnmb/Osteoactivin) expression in end-stage renal disease

BACKGROUND AND OBJECTIVES

Hematopoietic growth factor-inducible neurokinin 1 (HGFIN), also known as Gpnmb and osteoactivin, is a transmembrane glycoprotein that is expressed in numerous cells, including osteoclasts, macrophages, and dendritic cells. It serves as an osteoblast differentiation factor, participates in bone mineralization, and functions as a negative regulator of inflammation in macrophages. Although measurable at low levels in monocytes, monocyte-to-macrophage transformation causes substantial increase in HGFIN expression. HGFIN is involved in systemic inflammation, bone demineralization, and soft tissue vascular calcification.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We explored HGFIN expression in monocytes and monocyte-derived macrophages in 21 stable hemodialysis patients and 22 control subjects.

RESULTS

Dialysis patients exhibited marked upregulation of colony-stimulating factor and IL-6 and significant downregulation of IL-10 in intact monocytes and transformed macrophages. HGFIN expression in intact monocytes was negligible in control subjects but conspicuously elevated (8.6-fold) in dialysis patients. As expected, in vitro monocyte-to-macrophage transformation resulted in marked upregulation of HGFIN in cells obtained from both groups but much more so in dialysis patients (17.5-fold higher). Upregulation of HGFIN and inflammatory cytokines in the uremic monocyte-derived macrophages occurred when grown in the presence of either normal or uremic serum, suggesting the enduring effect of the in vivo uremic milieu on monocyte/macrophage phenotype and function.

CONCLUSIONS

Uremic macrophages exhibit increased HGFIN gene and protein expression and heightened expression of proinflammatory and a suppressed expression of anti-inflammatory cytokines. Further studies are needed to determine the role of heightened monocyte/macrophage HGFIN expression in the pathogenesis of ESRD-induced inflammation and vascular and soft tissue calcification.

Bioinformatic and statistical analysis of the optic nerve head in a primate model of ocular hypertension

BACKGROUND

The nonhuman primate model of glaucomatous optic neuropathy most faithfully reproduces the human disease. We used high-density oligonucleotide arrays to investigate whole genome transcriptional changes occurring at the optic nerve head during primate experimental glaucoma.

RESULTS

Laser scarification of the trabecular meshwork of cynomolgus macaques produced elevated intraocular pressure that was monitored over time and led to varying degrees of damage in different samples. The macaques were examined clinically before enucleation and the myelinated optic nerves were processed post-mortem to determine the degree of neuronal loss. Global gene expression was examined in dissected optic nerve heads with Affymetrix GeneChip microarrays. We validated a subset of differentially expressed genes using qRT-PCR, immunohistochemistry, and immuno-enriched astrocytes from healthy and glaucomatous human donors. These genes have previously defined roles in axonal outgrowth, immune response, cell motility, neuroprotection, and extracellular matrix remodeling.

CONCLUSION

Our findings show that glaucoma is associated with increased expression of genes that mediate axonal outgrowth, immune response, cell motility, neuroprotection, and ECM remodeling. These studies also reveal that, as glaucoma progresses, retinal ganglion cell axons may make a regenerative attempt to restore lost nerve cell contact.

Osteoactivin is a novel osteoclastic protein and plays a key role in osteoclast differentiation and activity

This study presents gene expression, protein expression, and in situ immunohistochemical evidence that osteoclasts express high levels of osteoactivin (OA), which had previously been reported to be an osteoblast-specific protein in bone. OA expression in osteoclasts was up-regulated upon receptor activator of NFkappaB ligand-induced differentiation. Suppression of functional activity of OA with neutralizing antibody reduced cell size, number of nuclei, fusion, and bone resorption activity of osteoclasts. OA was co-immunoprecipitated with integrin beta3 and beta1, indicating that OA co-localizes with integrin beta3 and/or beta1 in a hetero-polymeric complex in osteoclasts. These findings indicate that OA is a novel osteoclastic protein and plays a role in osteoclast differentiation and/or activity.

Role of human HGFIN/nmb in breast cancer

Introduction

HGFIN, previously identified as nmb, and its homolog osteoactivin are single transmembrane proteins that are expressed in differentiated immune cells. These proteins exhibit properties that could potentiate tumorigenesis or decrease invasiveness. These seemingly opposing roles of HGFIN suggest that this protein might be central to malignancies and might also behave as a tumor suppressor. Consistent with the reported roles for HGFIN is the fact that this gene is regulated by p53 through multiple binding sites in the 5' flanking region, and is expressed in osteoblasts.

Methods

This study used siRNA to knock-out HGFIN in non-tumorigenic breast cells and ectopically expressed HGFIN in breast cancer cells. In addition, in situ hybridization studies analyzed primary breast tissues from archived breast surgeries. Reporter gene assays studied the untranslated exon 1 of HGFIN.

Results

HGFIN expression led to reduced cell growth of breast cancer cells and reduced migration. At the molecular level, reporter gene analyses determined the untranslated exon 1 to be a negative regulator of the upstream enhancing effect. Ectopic expression of wild-type p53 in breast cancer cells that expressed endogenous mutant p53 resulted in increased HGFIN reporter gene activities.

Conclusion

As the majority of cancer cells have mutations in p53, further studies on the relationship between p53 and HGFIN expression, and its role in tumor genesis and bone invasion, might uncover novel therapy targets for breast and other cancers. The results show a central role for p53 in HGFIN expression, which appears to determine the behavior of the cancer cells.

Serial analysis of gene expression (SAGE) in rat liver regeneration

We have applied serial analysis of gene expression for studying the molecular mechanism of the rat liver regeneration in the model of 70% partial hepatectomy. We generated three SAGE libraries from a normal control liver (NL library: 52,343 tags), from a sham control operated liver (Sham library: 51,028 tags), and from a regenerating liver (PH library: 53,061 tags). By SAGE bioinformatics analysis we identified 40 induced genes and 20 repressed genes during the liver regeneration. We verified temporal expression of such genes by real time PCR during the regeneration process and we characterized 13 induced genes and 3 repressed genes. We found connective tissue growth factor transcript and protein induced very early at 4h after PH operation before hepatocytes proliferation is triggered. Our study suggests CTGF as a growth factor signaling mediator that could be involved directly in the mechanism of liver regeneration induction.

Transgenic expression of osteoactivin in the liver attenuates hepatic fibrosis in rats

The role of osteoactivin (OA) in liver fibrogenesis remains unclear. After feeding wild-type (WT) and OA transgenic (OA-Tg) rats a choline-deficient, L-amino acid-defined (CDAA) diet for 12 weeks, we evaluated liver fibrosis. Hepatic fibrosis and expression of alpha-smooth muscle actin protein in OA-Tg rats were reduced in comparison to WT rats. Our examination of the expression of 31,100 genes by microarray analysis identified 177 and 256 genes that were upregulated and downregulated, respectively, by at least twofold in OA-Tg rat livers in comparison to WT rat livers. Of these genes, we confirmed a significant downregulation in the expression levels of tissue inhibitor of metalloproteinase-1 and -2, type I collagen, and platelet-derived growth factor receptor-alpha and -beta in the livers of OA-Tg rats. These results indicate that transgenic OA expression attenuates the development of hepatic fibrosis in association with the suppression of specific genes involved in its pathogenesis.

A Toxicogenomic Approach Revealed Hepatic Gene Expression Changes Mechanistically Linked to Drug-Induced Hemolytic Anemia

A variety of pharmaceutical compounds causes hemolytic anemia as a significant adverse effect and this toxicity restricts the clinical utility of these drugs. In this study, we applied microarray technology to investigate hepatic gene expression changes associated with drug-induced hemolytic anemia and to identify potential biomarker genes for this hematotoxicity. We treated female Sprague-Dawley rats with two hemolytic anemia-inducing compounds: phenylhydrazine and phenacetin. Hepatic gene expression profiles were obtained using a whole-genome oligonucleotide microarray with pooled RNA samples from individual rats within each dose group and analyzed in comparison with hepatic histopathology, hematology, and blood chemistry data. We identified a small subset of genes that were commonly deregulated in all the severe hemolytic conditions, some of which were considered to be involved in hepatic events characteristic of hemolytic anemia, such as hemoglobin biosynthesis, heme metabolism, and phagocytosis. Among them, we selected six upregulated genes as putative biomarkers, and their expression changes from microarray measurements were confirmed by quantitative real-time PCR using RNAs from individual animals. They were Alas2, beta-glo, Eraf, Hmox1, Lgals3, and Rhced. Expression patterns of all these genes showed high negative and positive correlation against erythrocyte counts and total bilirubin levels in circulation, respectively, suggesting that these genes may be the potential biomarkers for hemolytic anemia. These findings indicate that drug-induced hemolytic anemia may be detected based on hepatic changes in the expression of a subset of genes that are mechanistically linked to the hematotoxicity.

Hepcidin and hemojuvelin gene expression in rat liver damage: in vivo and in vitro studies

In this work, we used two rat models, partial hepatectomy (PH) and CCl(4) administration, to study the changes in iron pathways in response to hepatic damage. Liver injury induced changes in the hepatic gene expression of hepcidin, hemojuvelin (Hjv), several other proteins of iron metabolism, and several cytokines such as IL-1beta, IL-6, TNF-alpha, and IFN-gamma. Hepcidin gene expression was upregulated between 4 and 8 h with a maximum up to 16 h after surgery. However, Hjv gene expression was downregulated at the same time. An early upregulation of hepcidin (3 h) and downregulation of Hjv gene expression was found after CCl(4) administration. Transferrin receptor 1 and ferritin H gene expression was upregulated, whereas ferroportin 1 gene expression was downregulated. Hepatic IL-6 gene expression was upregulated early after PH and reached maximum 8 h after the PH. In CCl(4)-induced liver injury, IL-6, IL-1beta, TNF-alpha, and IFN-gamma upregulation were found at the maximum 12 h after the administration of the toxin. Treatment of isolated rat hepatocytes with IL-6 and, to a lesser extent, with IL-1beta but not with TNF-alpha or IFN-gamma dose dependently upregulated hepcidin and downregulated Hjv gene expression. In hepatic damage, changes of the hepatic gene expression of the main proteins involved in iron metabolism may be induced by locally synthesized mediators.

Cytokine-induced neutrophil chemoattractant-1 is released by the noninjured liver in a rat acute-phase model

The source of serum cytokine-induced neutrophil chemoattractant (CINC-1) and consequences of its presence in the tissue of synthesis have not been clearly elucidated under acute-phase situation. To pursue this question, turpentine oil (TO) was intramuscularly injected into rats, and RNA and local protein levels of acute-phase cytokines and of CINC-1 were studied in the TO injected gluteal muscle, as well as in noninjured muscle, in the liver, kidney, lung and spleen. The serum levels of acute-phase mediators and of CINC-1 were measured together with total leukocyte subpopulations. Recruitment of inflammatory cells in muscle and in the other organs was investigated by quantitative immunohistochemical methods. The effect of acute-phase mediators, including interferon gamma (IFN-gamma) on the synthesis of CINC-1 in cultured hepatocytes was also investigated at the RNA and protein level. We found that the sera of the TO-treated rats contained elevated levels of IL-6, IL-1beta and CINC-1. Increased serum levels of IFN-gamma were also observed not only in the injured muscle but also and to a higher extent in the liver. However, while neutrophils and mononuclear phagocytes were found in the injured muscle, no inflammatory cells were detected at the non-'inflamed' site, namely, the liver or in the other organs. In vitro, treatment of cultured hepatocytes with IL-1beta led to elevated CINC-1 gene expression. This was true to a lesser extent upon IL-6 and tumor necrosis factor (TNF-alpha) exposure. Interestingly, IFN-gamma did not effect CINC-1 gene expression. These results indicate that CINC-1 behaves as an acute-phase protein and its expression is inducible in hepatocytes. However, CINC-1-production in the liver does not lead to recruitment of inflammatory cells into the organ.