Oncostatin M, a multifunctional cytokine

S100A7 (psoriasin) is induced by the proinflammatory cytokines oncostatin-M and interleukin-6 in human breast cancer

S100A7 promotes aggressive features in breast cancer, although regulation of its expression is poorly understood. As S100A7 associates with inflammation in skin and breast tissue, we hypothesized that inflammatory cytokines may regulate S100A7 in breast cancer. We therefore examined the effects of several cytokines, among which oncostatin-M (OSM) and the related cytokine, interleukin (IL)-6, showed the most significant effects on S100A7 expression in breast tumor cells in vitro. Both cytokines consistently induced S100A7 expression in three cell lines (MCF7, T47D and MDA-MB-468) in a dose- and time-dependent manner. Induction of S100A7 was inhibited by blockade of STAT3, phosphatidylinositol 3 kinase (PI3K) and ERK1/2 signaling and small interference RNA (siRNA)-mediated knockdown of S100A7 eliminated the promigratory effects of OSM treatment. S100A7 mRNA levels in a case-control cohort of breast tumors (n=20) were significantly associated with expression of the OSM receptor beta (OSMRbeta) chain (P=0.0098). This association was confirmed using publicly available microarray data from an independent breast tumor cohort (n=201, P=0.0005) and a correlation between S100A7 and poor patient survival was observed specifically in cases with high OSMRbeta expression (HR=2.35; P=0.0396; n=85). We conclude that inflammatory cytokines can regulate S100A7 expression and that S100A7 may mediate some of their effects in breast cancer.

The epidermal growth factor receptor ligand amphiregulin is a negative regulator of hepatic acute-phase gene expression

BACKGROUND/AIMS

The modulation of the hepatic acute-phase reaction (APR) that occurs during inflammation and liver regeneration is important for allowing normal hepatocellular proliferation and the restoration of homeostasis. Activation of acute-phase protein (APP) gene expression by interleukin-6 (IL-6)-type cytokines is thought to be counteracted by growth factors released during hepatic inflammation and regeneration. The epidermal growth factor receptor (EGFR) ligand amphiregulin (AR) is readily induced by inflammatory signals and plays a nonredundant protective role during liver injury. In this paper, we investigated the role of AR as a modulator of liver APP gene expression.

METHODS

Expression of APP genes was measured in the livers of AR(+/+) and AR(-/-)mice during inflammation and regeneration and in cultured liver cells treated with AR and oncostatin M (OSM). Crosstalk between AR and OSM signalling was studied.

RESULTS

APP genes were overexpressed in the livers of AR(-/-) mice during inflammation and hepatocellular regeneration. In cultured AR-null hepatocytes and human hepatocellular carcinoma (HCC) cells after AR knockdown, APP gene expression is enhanced. AR counteracts OSM-triggered signal transducer and activator of transcription 3 signalling in hepatocytes and attenuates APP gene transcription.

CONCLUSIONS

Our data support the relevance of EGFR-mediated signalling in the modulation of cytokine-activated pathways. We have identified AR as a key regulator of hepatic APP gene expression during inflammation and liver regeneration.

TILRR, a novel IL-1RI co-receptor, potentiates MyD88 recruitment to control Ras-dependent amplification of NF-kappaB

Host defense against infection is induced by Toll-like and interleukin (IL)-1 receptors, and controlled by the transcription factor NF-κB. Our earlier studies have shown that IL-1 activation impacts cytoskeletal structure and that IL-1 receptor (IL-1RI) function is substrate-dependent. Here we identify a novel regulatory component, TILRR, which amplifies activation of IL-1RI and coordinates IL-1-induced control with mechanotransduction. We show that TILRR is a highly conserved and widely expressed enhancer of IL-1-regulated inflammatory responses and, further, that it is a membrane-bound glycosylated protein with sequence homology to members of the FRAS-1 family. We demonstrate that TILRR is recruited to the IL-1 receptor complex and magnifies signal amplification by increasing receptor expression and ligand binding. In addition, we show that the consequent potentiation of NF-κB is controlled through IL-1RI-associated signaling components in coordination with activation of the Ras GTPase. Using mutagenesis, we demonstrate that TILRR function is dependent on association with its signaling partner and, further, that formation of the TILRR-containing IL-1RI complex imparts enhanced association of the MyD88 adapter during ligand-induced activation of NF-κB. We conclude that TILRR is an IL-1RI co-receptor, which associates with the signaling receptor complex to enhance recruitment of MyD88 and control Ras-dependent amplification of NF-κB and inflammatory responses.

Oncostatin M and leukemia inhibitory factor increase hepcidin expression in hepatoma cell lines

Overproduction of hepcidin by interleukin-6 (IL-6) is considered to be the main factor responsible for the development of anemia in inflammatory conditions. Since oncostatin M (OSM), a member of the IL-6 family, plays an important role in immune and inflammatory responses, we assessed the effect of OSM on hepcidin expression, as well as that of leukemia inhibitory factor (LIF), another member of the IL-6 family. We found that hepcidin expression was markedly induced by OSM and LIF in a time- and dose-dependent manner in hepatoma cell lines, and this expression was induced independent of IL-6/IL-6 receptor signaling. Luciferase assay revealed that OSM and LIF stimulated a -1.3-kb hepcidin promoter. This effect was markedly reduced when the signal transducer and activator of transcription (STAT) site of the promoter was mutated, and was almost completely abolished in the presence of AG-490, a Janus kinase (JAK) inhibitor. Hence, the JAK/STAT pathway plays a major role in OSM- and LIF-induced activation of the hepcidin promoter. In conclusion, we demonstrated that OSM and LIF can induce hepcidin expression mainly through the JAK/STAT pathways. Further studies are warranted to evaluate the clinical significance of OSM and LIF in the development of anemia in various inflammatory diseases.

Interleukin-6 subfamily cytokines and rheumatoid arthritis: role of antagonists

Many cytokines have been implicated in the inflammatory pathways that characterize rheumatoid arthritis (RA) and related inflammatory diseases of the joints. These include members of the interleukin-6 (IL-6) family of cytokines, several of which have been detected in excess in the synovial fluid from RA patients. What makes the IL-6 group of cytokines a family is their common use of the glycoprotein 130 (gp130) receptor subunit, to which they bind with different affinities. Several strategies have been developed to block the pro-inflammatory activities of IL-6 subfamily cytokines. These include the application of monoclonal antibodies, the creation of mutant form(s) of the cytokine with enhanced binding affinity to gp130 receptor and the generation of antagonists by selective mutagenesis of the specific cytokine/gp130 receptor-binding site(s). The rationale for the use of anti-cytokine therapy in inflammatory joint diseases is based on evidence from studies in vitro and in vivo, which implicate major cytokines such as interleukin-1 (IL-1), tumour necrosis factor (TNF)-alpha and IL-6 in RA pathogenesis. In particular, IL-6 subfamily antagonists have a wide range of potential therapeutic and research applications. This review focuses on the role of some of the IL-6 subfamily cytokines in the pathogenesis of the inflammatory diseases of the joints (IJDs), such as RA. In addition, an overview of the recently developed antagonists will be discussed.

Thrombin induces the expression of oncostatin M via AP-1 activation in human macrophages: a link between coagulation and inflammation

Macrophages as inflammatory cells are involved in the pathogenesis of atherosclerosis that today is recognized as an inflammatory disease. Activation of coagulation leads to the late complication of atherosclerosis, namely atherothrombosis with its clinical manifestations stroke, unstable angina, myocardial infarction, and sudden cardiac death. Thus inflammation and coagulation play fundamental roles in the pathogenesis of atherosclerosis. We show that the coagulation enzyme thrombin up-regulates oncostatin M (OSM), a pleiotropic cytokine implicated in the pathophysiology of vascular disease, in human monocyte-derived macrophages (MDMs) up to 16.8-fold. A similar effect was seen in human peripheral blood monocytes and human plaque macrophages. In MDMs, the effect of thrombin on OSM was abolished by PPACK and mimicked by a PAR-1-specific peptide. Thrombin induced phosphorylation of ERK1/2 and p38 in MDMs. The ERK1/2 inhibitor PD98059 blocked the effect of thrombin on OSM production in MDMs, whereas the p38 inhibitor SB202190 had no effect. Thrombin induced translocation of c-fos and c-jun to the nucleus of MDMs. Using OSM promoter-luciferase reporter constructs transfected into MDMs, we show that a functional AP-1 site is required for promoter activation by thrombin. We present another link between coagulation and inflammation, which could impact on the pathogenesis of atherosclerosis.

Catechins inhibit CXCL10 production from oncostatin M-stimulated human gingival fibroblasts

CXC chemokine ligand 10 (CXCL10) plays a pivotal role in the recruitment of Th1 cells and, thus, in the development of periodontal disease. Epigallocatechin gallate (EGCG) and epicatechin gallate (ECG), the major catechins derived from green tea, have multiple beneficial effects, but the effects of catechins on CXCL10 production from human gingival fibroblasts (HGFs) is not known. In this study, we investigated the mechanisms by which EGCG and ECG inhibit oncostatin M (OSM)-induced CXCL10 production in HGFs. HGFs constitutively expressed glycoprotein 130 and OSM receptor beta (OSMR beta), which are OSM receptors. OSM increased CXCL10 production in a concentration-dependent manner. EGCG and ECG prevented OSM-mediated CXCL10 production by HGFs. Inhibitors of p38 mitogen-activated protein kinase, c-Jun N-terminal kinase (JNK), phosphatidylinositol-3-OH kinase and signal transducer and activator of transcription (STAT)3 decreased OSM-induced CXCL10 production. EGCG significantly prevented OSM-induced phosphorylation of JNK, Akt (Ser473) and STAT3 (Tyr705 and Ser727). ECG prevented phosphorylation of JNK and Akt (Ser473). In addition, EGCG and ECG attenuated OSMR beta expression on HGFs. These data provide a novel mechanism through which the green tea flavonoids, catechins, can provide direct benefits in periodontal disease.

Hypoxia-inducible factor 1alpha is up-regulated by oncostatin M and participates in oncostatin M signaling

The interleukin-6-type cytokine oncostatin M (OSM) acts via the Janus kinase/signal transducer and activator of transcription pathway as well as via activation of mitogen-activated protein kinases and is known to critically regulate processes such as liver development and regeneration, hematopoiesis, and angiogenesis, which are also determined by hypoxia with the hypoxia-inducible factor 1alpha (HIF1alpha) as a key component. Here we show that treatment of hepatocytes and hepatoma cells with OSM leads to an increased protein level of HIF1alpha under normoxic and hypoxic conditions. Furthermore, the OSM-dependent HIF1alpha increase is mediated via Janus kinase/signal transducer and activator of transcription 3 and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 pathways. OSM-mediated HIF1alpha up-regulation did not result from an increase in HIF1alpha protein stability but from increased transcription from the HIF1alpha gene. In addition, we show that the OSM-induced HIF1alpha gene transcription and the resulting enhanced HIF1alpha protein levels are important for the OSM-dependent vascular endothelial growth factor and plasminogen activator inhibitor 1 gene induction associated with several diseases.

CONCLUSION

HIF1alpha levels increase significantly after treatment of hepatocytes and hepatoma cells with OSM, and HIF1alpha contributes to OSM downstream signaling events, pointing to a cross-talk between cytokine and hypoxia signaling in processes such as liver development and regeneration.

The upregulation of oncostatin M in inflamed human dental pulps

AIM

To compare oncostatin M (OSM) expression in clinically healthy and inflamed specimened human pulp tissue.

METHODOLOGY

Thirty pulpal tissue specimens (15 clinically healthy and 15 inflamed) were obtained from extracted third molars with informed consent from patients. The levels of OSM were compared between clinically healthy pulp and inflamed pulp tissues using the semi-quantitative reverse-transcriptase polymerase chain reaction. In addition, immunohistochemistry was used to identify the in situ localization of OSM expression in pulp specimens. For testing of differences in the OSM between the clinically healthy and inflamed human dental pulps, the Wilcoxon-Mann-Whitney rank sum test was applied. Differences in OSM expression between tissue with low and high levels of inflammation were subsequently analysed by Fisher's exact test.

RESULTS

Inflamed pulps exhibited significantly higher OSM mRNA gene expression than clinically healthy pulps (P < 0.05). Immunohistochemistry demonstrated that OSM expression was significantly higher in inflamed than clinically healthy pulps (P < 0.05). OSM staining was detected in odontoblasts, fibroblasts, inflammatory infiltrates and endothelial cells.

CONCLUSIONS

Oncostatin M expression was elevated in inflamed pulp tissue. OSM is potentially involved in the disease process of pulpal inflammation.

Long term oncostatin M treatment induces an osteocyte-like differentiation on osteosarcoma and calvaria cells

Previous in vitro studies on primary osteoblastic and osteosarcoma cells (normal and transformed osteoblasts) have shown that oncostatin M (OSM), a member of the interleukin-6 family, possesses cytostatic and pro-apoptotic effects in association with complex and poorly understood activities on osteoblast differentiation. In this study, we use rat osteosarcoma cells transduced with lentiviral particles encoding OSM (lvOSM) to stably produce this cytokine. We show that after several weeks of culture, transduced OSRGA and ROS 17/2.8 cells are growth inhibited and sensitized to apoptosis induced by the kinase inhibitor Staurosporine (Sts). Moreover, this long term OSM treatment induces (i) a decrease in osteoblastic markers, (ii) morphological changes leading to an elongated and/or stellate shape and (iii) an increase in osteocytic markers (sclerostin and/or E11), suggesting an osteocyte-like differentiation. We also show that non transformed rat calvaria cells transduced with lvOSM differentiate into stellate shaped cells expressing sclerostin, E11, Phex and functional hemichannels. Together, these results indicate that osteosarcoma cells stably producing OSM do not develop resistance to this cytokine and thus could be a valuable new tool to study the anti-cancer effect of OSM in vivo. Moreover, OSM-over-expressing osteoblastic cells differentiate into osteocyte-like cells, the major cellular contingent in bone, providing new culture conditions for this cell type which is difficult to obtain in vitro.

Oncostatin M pathway plays a major role in the renal acute phase response

The acute phase response is traditionally characterized by hepatic synthesis of proteins as an inflammatory response to injury, with interleukin-6 (IL-6) being the key mediator. In contrast, microarray studies in human renal transplant implantation biopsies indicate a strong acute phase response in the deceased donor kidney, associated with a significant upregulation of oncostatin M receptor β (OSMR). The aim of this study was to determine whether the kidney can generate a strong acute phase response, mediated by the OSM/OSMR gateway. Genes associated with the IL-6 cytokine family and acute phase reactants were analyzed by real-time RT-PCR in four groups of human biopsies spanning a spectrum of renal injury. OSM, OSMR, and fibrinogen β (FGB) were progressively more highly expressed from prenephrectomy, living donor, deceased donor, to discarded donor kidneys, suggesting correlation with severity of injury and local renal synthesis. Acute phase response gene expression was analyzed in human proximal tubular cells in culture in response to OSM. OSM induced a significant increase in expression of FGB, OSMR, serpin peptidase inhibitor A1, IL-6, and lipopolysaccharide binding protein, and a decrease in IL-6R. These changes were largely attenuated by coincubation with an OSMR blocking antibody, indicating the OSM effect was mediated through OSMR. OSM also resulted in a significantly altered expression of acute phase genes compared with IL-6 or leukemia inhibitory factor, suggesting that OSM is the predominant cytokine mediating the renal tubular acute phase response. In conclusion, the renal parenchyma is capable of generating a strong acute phase response, likely mediated via OSM/OSMR.

Oncostatin M regulates secretoglobin 3A1 and 3A2 expression in a bidirectional manner

Secretoglobin (SCGB) 3A1 and 3A2 are members of the small molecular weight secretoglobin gene superfamily. SCGB3A1 is a tumor suppressor gene, whereas SCGB3A2 has anti-inflammatory properties. Both genes are mainly expressed in the lung and trachea in mice. Whether the expression and/or function of these two genes are related is not known. Here we show that the expression of SCGB3A1 and SCGB3A2 are bidirectionally regulated by oncostatin M (OSM) when examined in a mouse transformed Clara cell line (mtCC); SCGB3A1 is up-regulated by OSM, while SCGB3A2 is down-regulated in a time- and dose-dependent manner. OSM-activated STAT3/5, through binding to the STAT-binding element located at -201 to -209 bp in the mouse Scgb3a1 gene promoter, and the extracellular signal-regulated kinase (ERK)- and p38-mitogen-activated protein kinase (MAPK) pathways are responsible for the OSM-induced up-regulation of SCGB3A1 expression. On the other hand, the -113 to -273 bp region in the Scgb3a2 promoter appears to be responsible for the OSM induced down-regulation of the gene. No significant differences in the levels or patterns of specific DNA-binding proteins were found in the -113 to -273 bp region as determined by electrophoretic mobility shift assays. Neither the ERK- nor p38-MAPK pathways were involved in the OSM-induced reduction of Scgb3a2 promoter activity. These results suggest that OSM-induced suppression of SCGB3A2 expression is an indirect effect of OSM. Expression of the Clara cell marker, CYP2F2, was markedly decreased upon OSM treatment in parallel with the decrease of SCGB3A2 expression in mtCC cells. The differential regulation of Scgb3a1 and Scgb3a2 gene expression by OSM may explain the unique functions of these genes in the lung.

A dual role for oncostatin M signaling in the differentiation and death of mammary epithelial cells in vivo

Recent studies in breast cancer cell lines have shown that oncostatin M (OSM) not only inhibits proliferation but also promotes cell detachment and enhances cell motility. In this study, we have looked at the role of OSM signaling in nontransformed mouse mammary epithelial cells in vitro using the KIM-2 mammary epithelial cell line and in vivo using OSM receptor (OSMR)-deficient mice. OSM and its receptor were up-regulated approximately 2 d after the onset of postlactational mammary regression, in response to leukemia inhibitory factor (LIF)-induced signal transducer and activator of transcription-3 (STAT3). This resulted in sustained STAT3 activity, increased epithelial apoptosis, and enhanced clearance of epithelial structures during the remodeling phase of mammary involution. Concurrently, OSM signaling precipitated the dephosphorylation of STAT5 and repressed expression of the milk protein genes beta-casein and whey acidic protein (WAP). Similarly, during pregnancy, OSM signaling suppressed beta-casein and WAP gene expression. In vitro, OSM but not LIF persistently down-regulated phosphorylated (p)-STAT5, even in the continued presence of prolactin. OSM also promoted the expression of metalloproteinases MMP3, MMP12, and MMP14, which, in vitro, were responsible for OSM-specific apoptosis. Thus, the sequential activation of IL-6-related cytokines during mammary involution culminates in an OSM-dependent repression of epithelial-specific gene expression and the potentiation of epithelial cell extinction mediated, at least in part, by the reciprocal regulation of p-STAT5 and p-STAT3.

Leukemia inhibitory factor contributes to hepatocyte-like differentiation of human bone marrow mesenchymal stem cells

The current majority of protocols for hepatocyte differentiation of mesenchymal stem cells (MSCs) are conducted using oncostatin M (OSM) as an inducer of hepatocyte-like maturation. As leukemia inhibitory factor (LIF) and OSM share similar signaling pathways, we examined whether LIF could play a role in the hepatocyte differentiation process. A differentiation protocol was designed using LIF as a maturation cytokine and this was compared with standard and control protocols applied to human MSCs of bone marrow origin. We observed that mesenchymal-derived hepatocyte-like cells (MDHLCs) acquired similar morphological changes when exposed to LIF or to OSM. Using protein and gene expression assays, we noticed a comparable hepatic marker expression in both differentiation conditions. Furthermore, LIF and OSM allowed the acquisition of equivalent levels of hepatocyte-like functionality as attested by evaluation of urea secretion and glycogen deposition. However, no increase in the expression of hepatocyte-like features could be observed in MDHLCs after a combined exposition to LIF and OSM. In conclusion, we demonstrated that LIF can play a similar role as OSM in the hepatocyte differentiation process of human MSCs.

Tenascin-X and leukemia inhibitory factor receptor are down-regulated in leiomyoma compared with normal myometrium

OBJECTIVE

Uterine leiomyomas are the most common tumor of the uterus. But the molecular causes of uterine leiomyoma remain unclear. We conducted the current investigation in order to elucidate the molecular mechanisms in the development of uterine leiomyoma.

METHODS

We employed a new and accurate reverse transcription-polymerase chain reaction (RT-PCR) method that involved annealing control primers (ACPs) to identify the genes that are differently expressed in uterine leiomyoma.

RESULTS

Using 120 ACPs, we identified and sequenced 14 differently expressed genes (DEGs) in uterine leiomyoma compared with normal myometrium. Basic Local Alignment Search Tool (BLAST) searches were performed to examine the known functions of these genes associated with uterine leiomyoma. We confirmed differently expressed patterns in more cases using the RT-PCR method. We also detected two novel genes, Tenascin-X and Leukemia Inhibitory Factor Receptor (LIFR), which had not yet been reported to have any functions associated with uterine leiomyoma. RT-PCR confirmation shows that both of these two genes are down-regulated in uterine leiomyoma.

CONCLUSION

Our results suggest that Tenascin-X and LIFR may play a role in the development of uterine leiomyoma. Although further studies are required to establish the precise mechanisms with which these genes are involved in the genesis of uterine leiomyoma, the present research is significant in that it is the first study which detects down-regulated novel genes in uterine leiomyoma using the ACP system.

Formation of large vacuoles induced by cooperative effects of oncostatin M and dexamethasone in human fetal liver cells

The morphology of human fetal liver cells treated with both oncostatin M and dexamethasone was strikingly different from those of cells treated with either oncostatin M or dexamethasone alone. Cotreatment with oncostatin M and dexamethasone resulted in the appearance of numerous large vacuoles. The size of the vacuoles varied among individual cells, ranging from 0.05 to 20 mum depending on the cell. Electron microscopy indicated that swollen large vacuoles in the human fetal liver cells were generally electron lucent. On the other hand, relatively small vacuoles about 2 mum in diameter were discrete structures that contained electron-dense material, such as partially degraded cytoplasmic membrane, cytoplasm, or organelle components. An autophagosome-like organelle was formed in cytoplasm. Electron microscopic analysis indicated direct fusion among the vacuoles formed in the cytoplasm of human fetal liver cells. To our knowledge, this is the first report of large swollen vacuoles formed in cells by the cooperative effects of oncostatin M and dexamethasone.

PMA induces stabilization of oncostatin M mRNA in human lymphoma U937 cells

OSM (oncostatin M) is a pleiotropic cytokine belonging to the IL (interleukin) 6 family that modulates the growth of some cancer cell lines. We have found that PMA treatment of human U937 lymphoma cells increased the steady-state levels of OSM mRNA. Furthermore, the half-life of OSM mRNA was increased from 2.3 to 6.2 h. Measurement of mRNA/hnRNA (heterogeneous nuclear RNA) ratios in PMA-treated cells suggests further that the increase in OSM mRNA is due to enhanced mRNA stability. Consistent with this, synthetic OSM mRNA transcripts decayed faster in extracts of untreated U937 cells than in extracts of PMA-treated cells. The 3'-untranslated region of OSM mRNA contains a putative ARE (AU-rich element) that may play a role in mRNA stabilization. Addition of the OSM ARE motif to the 3'-end of beta-globin mRNA increased its decay rate in vitro. Decay assays with beta-globin-ARE(OSM) and beta-globin transcripts indicate that PMA induces mRNA stabilization in an ARE-dependent manner. PMA also induces at least five OSM ARE-binding proteins. Supershift assays indicated that HuR is present in PMA-induced OSM mRNA-protein complexes. PMA treatment appears to induce translocation of HuR from the nucleus to the cytoplasm. RNA-decay assays indicated that HuR stabilizes OSM RNA in vitro. Additionally, immunodepletion of HuR from U937 cell extracts led to more rapid decay of OSM transcripts. Collectively, these findings suggest that the ARE plays a role in PMA-induced stabilization of OSM mRNA and that this process involves multiple ARE-binding proteins, including HuR.

Signaling networks in hepatic oval cell activation

Oval cells are hypothesized to be the progeny of intrahepatic stem cells, also referred to as adult liver stem cells. The mechanisms by which these cells are activated to proliferate and differentiate during liver regeneration is important for the development of new therapies to treat liver disease. Oval cell activation is the first step in progenitor-dependent liver regeneration in response to certain types of injury. This review describes what is currently known about the factors involved in oval cell activation, proliferation, migration, and differentiation.

Neuregulin-1: a potential endogenous protector in perinatal brain white matter damage

Brain white matter damage, an important antecedent of long-term disabilities among preterm infants, has both endogenous and exogenous components. One of the endogenous components is the paucity of developmentally regulated protectors. Here we expand on this component, discussing the potential roles of one putative protector, neuregulin (NRG)-1, in brain development and damage. We outline how NRG-1 might be involved in perinatal brain damage pathomechanisms and suggest that NRG-1 might be one target for intervention.

Oncostatin M promotes osteogenesis and suppresses adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells

Oncostatin M (OSM) is a multifunctional cytokine of the interleukin-6 family and has been implicated in embryonic development, differentiation, inflammation, and regeneration of liver and bone. In the present study, we demonstrated that treatment of human adipose mesenchymal stem cells (hADSCs) with OSM-attenuated adipogenic differentiation, as indicated by decreased accumulation of intracellular lipid droplets and down-regulated expression of adipocytic markers, such as lipoprotein lipase and PPARgamma. However, OSM treatment stimulated osteogenic differentiation, as demonstrated by the increase in matrix mineralization and expression levels of osteogenic differentiation markers, including alkaline phosphatase, Runx2, and osteocalcin. OSM treatment induced activation of JAK2, JAK3, and ERK in hADSCs, and pre-treatment of hADSCs with the JAK2 inhibitor, AG490, significantly restored the OSM-induced inhibition of adipogenic differentiation. Whereas, the JAK3 inhibitor, WHI-P131, and the MEK inhibitor, U0126, had no effects on the anti-adipogenic activity of OSM. On the other hand, the pro-osteogenic activity of OSM was prevented by treatment of the cells with WHI-P131 or U0126, but not with AG490. These results indicate that distinct signaling pathways, including JAK2, JAK3, and MEK-ERK, play specific roles in the OSM-induced anti-adipogenic and pro-osteogenic differentiation of hADSCs.

Oncostatin M-induced effects on EMT in human proximal tubular cells: differential role of ERK signaling

Growing evidence suggests that a proportion of interstitial myofibroblasts detected during renal tubulointerstitial fibrosis originates from tubular epithelial cells by a process called epithelial-mesenchymal transition (EMT). The IL-6-type cytokine oncostatin M (OSM) has been recently implicated in the induction of EMT. We investigated OSM effects on the expression of both cell-cell contact proteins and mesenchymal markers and studied OSM-induced intracellular signaling mechanisms associated with these events in human proximal tubular cells. Human recombinant OSM attenuated the expression of N-cadherin, E-cadherin, and claudin-2 in human kidney-2 (HK-2) cells associated with the induction of HK-2 cell scattering in 3D collagen matrices. Conversely, expression of collagen type I, vimentin, and S100A4 was induced by OSM. OSM-stimulated cell scattering was inhibited by antibodies against gp130. Besides inducing phosphorylation of Stat1 and Stat3, OSM led to a strong concentration- and time-dependent phosphorylation of the mitogen-activated protein kinases ERK1, ERK2, and ERK5. MEK1/2 inhibitor U0126 (10 muM) blocked basal and OSM-induced ERK1/2 phosphorylation but not phosphorylation of either ERK5 or Stat1/3. Both synthetic MEK1/2 inhibitors U0126 and Cl-1040, when used at concentrations which inhibit ERK1/2 phosphorylation but not ERK5 phosphorylation, restored N-cadherin expression in the presence of OSM, inhibited basal claudin-2 expression, but did not affect either basal or OSM-inhibited E-cadherin expression or OSM-induced expression of collagen type I and vimentin. These results suggest that in human proximal tubular cells ERK1/2 signaling represents an important component of OSM's inhibitory effect on N-cadherin expression. Furthermore, functional ERK1/2 signaling is necessary for basal claudin-2 expression.

Tumor-associated leukemia inhibitory factor and IL-6 skew monocyte differentiation into tumor-associated macrophage-like cells

Tumor-associated macrophages (TAMs), the most abundant immunosuppressive cells in the tumor microenvironment, originate from blood monocytes and exhibit an IL-10(high)IL-12(low) M2 profile. The factors involved in TAM generation remain unidentified. We identify here leukemia inhibitory factor (LIF) and IL-6 as tumor microenvironmental factors that can promote TAM generation. Ovarian cancer ascites switched monocyte differentiation into TAM-like cells that exhibit most ovarian TAM functional and phenotypic characteristics. Ovarian cancer ascites contained high concentrations of LIF and IL-6. Recombinant LIF and IL-6 skew monocyte differentiation into TAM-like cells by enabling monocytes to consume monocyte-colony-stimulating factor (M-CSF). Depletion of LIF, IL-6, and M-CSF in ovarian cancer ascites suppressed TAM-like cell induction. We extended these observations to different tumor-cell line supernatants. In addition to revealing a new tumor-escape mechanism associated with TAM generation via LIF and IL-6, these findings offer novel therapeutic perspectives to subvert TAM-induced immunosuppression and hence improve T-cell-based antitumor immunotherapy efficacy.

The inflammatory cytokine oncostatin M induces PAI-1 in human vascular smooth muscle cells in vitro via PI 3-kinase and ERK1/2-dependent pathways

Plasminogen activator inhibitor-1 (PAI-1) plays a pivotal role in the regulation of the fibrinolytic system and in the modulation of extracellular proteolysis. Increased PAI-1 was found in atherosclerotic lesions, and high PAI-1 plasma levels were associated with coronary heart disease. Smooth muscle cells (SMC) are a major source of PAI-1 within the vascular wall, and PAI-1 was implicated in SMC migration, proliferation, and apoptosis. We treated human coronary artery SMC (HCASMC) and human aortic SMC (HASMC) with the glycoprotein 130 (gp130) ligands cardiotrophin-1, interleukin-6 (IL-6), leukemia inhibitory factor (LIF), or oncostatin M (OSM). Only OSM increased PAI-1 antigen and activity production significantly in these cells up to 20-fold. OSM upregulated mRNA specific for PAI-1 up to 4.5-fold in these cells. HCASMC and HASMC express gp130, OSM receptor, IL-6 receptor, and LIF receptor. OSM induced extracellular signal-regulated kinase (ERK) 1/2 and Akt phosphorylations in HASMC. A phosphatidylinositol 3-kinase inhibitor and a mitogen-activated protein/extracellular signal-regulated kinase inhibitor reduced Akt and ERK1/2 phosphorylation, respectively, and abolished OSM-induced PAI-1 upregulation. A janus kinase/signal transducer and activator of transcription inhibitor, a p38 mitogen-activated protein kinase inhibitor, or c-Jun NH2-terminal kinase inhibitor I did not inhibit the OSM-dependent PAI-1 induction. OSM enhanced proliferation of both HCASMC and HASMC by 77 and 90%, respectively. We hypothesize that, if the effect of OSM on PAI-1 expression in smooth muscle cells is operative in vivo, it could, via modulation of fibrinolysis and extracellular proteolysis, be involved in the development of vascular pathologies such as plaque progression, destabilization and subsequent thrombus formation, and restenosis and neointima formation.

Oncostatin M gene therapy attenuates liver damage induced by dimethylnitrosamine in rats

To assess the usefulness of oncostatin M (osm) gene therapy in liver regeneration, we examined whether the introduction of OSM cDNA enhances the regeneration of livers damaged by dimethylnitrosamine (DMN) in rats. Repeated injection of OSM cDNA enclosed in hemagglutinating virus of Japan envelope into the spleen resulted in the exclusive expression of OSM protein in Kupffer cells of the liver, which was accompanied by increases in body weight, liver weight, and serum albumin levels and the reduction of serum liver injury parameters (bilirubin, aspartate aminotransferase, and alanine aminotransferase) and a serum fibrosis parameter (hyaluronic acid). Histological examination showed that osm gene therapy reduced centrilobular necrosis and inflammatory cell infiltration and augmented hepatocyte proliferation. The apoptosis of hepatocytes and fibrosis were suppressed by osm gene therapy. Time-course studies on osm gene therapy before or after DMN treatment showed that this therapy was effective not only in enhancing regeneration of hepatocytes damaged by DMN but in preventing hepatic cytotoxicity caused by subsequent treatment with DMN. These results indicate that OSM is a key mediator for proliferation and anti-apoptosis of hepatocytes and suggest that osm gene therapy is useful, as preventive and curative means, for the treatment of patients with liver damage.

Coactivation of janus tyrosine kinase (Jak)1 positively modulates prolactin-Jak2 signaling in breast cancer: recruitment of ERK and signal transducer and activator of transcription (Stat)3 and enhancement of Akt and Stat5a/b pathways

Prolactin (PRL) receptors (PRLRs) have been considered selective activators of Janus tyrosine kinase (Jak)2 but not Jak1, Jak3, or Tyk2. We now report marked PRL-induced tyrosine phosphorylation of Jak1, in addition to Jak2, in a series of human breast cancer cell lines, including T47D, MCF7, and SKBR3. In contrast, PRL did not activate Jak1 in immortalized, noncancerous breast epithelial lines HC11, MCF10A, ME16C, and HBL-100, or in CWR22Rv1 prostate cancer cells or MDA-MB-231 breast cancer cells. However, introduction of exogenous PRLR into MCF10A, ME16C, or MDA-MB-231 cells reconstituted both PRL-Jak1 and PRL-Jak2 signals. In vitro kinase assays verified that PRL stimulated enzymatic activity of Jak1 in T47D cells, and PRL activated Jak1 and Jak2 with indistinguishable time and dose kinetics. Relative Jak2 deficiency did not cause PRLR activation of Jak1, because overexpression of Jak2 did not interfere with PRL activation of Jak1. Instead, PRL activated Jak1 through a Jak2-dependent mechanism, based on disruption of PRL activation of Jak1 after Jak2 suppression by 1) lentiviral delivery of Jak2 short hairpin RNA, 2) adenoviral delivery of dominant-negative Jak2, and 3) AG490 pharmacological inhibition. Finally, suppression of Jak1 by lentiviral delivery of Jak1 short hairpin RNA blocked PRL activation of ERK and signal transducer and activator of transcription (Stat)3 and suppressed PRL activation of Jak2, Stat5a, Stat5b, and Akt, as well as tyrosine phosphorylation of PRLR. The data suggest that PRL activation of Jak1 represents a novel, Jak2-dependent mechanism that may serve as a regulatory switch leading to PRL activation of ERK and Stat3 pathways, while also serving to enhance PRL-induced Stat5a/b and Akt signaling.

Erythropoietin modulation of podocalyxin and a proposed erythroblast niche

Epo's erythropoietic capacity is ascribed largely to its antiapoptotic actions. In part via gene profiling of bone marrow erythroblasts, Epo is now shown to selectively down-modulate the adhesion/migration factors chemokine receptor-4 (Cxcr4) and integrin alpha-4 (Itga4) and to up-modulate growth differentiation factor-3 (Gdf3), oncostatin-M (OncoM), and podocalyxin like-1 (PODXL). For PODXL, Epo dose-dependent expression of this CD34-related sialomucin was discovered in Kit(+)CD71(high) proerythroblasts and was sustained at subsequent Kit(-)CD71(high) and Ter119(+) stages. In vivo, Epo markedly induced PODXL expression in these progenitors and in marrow-resident reticulocytes. This was further associated with a rapid release of PODXL(+) reticulocytes to blood. As studied in erythroblasts expressing minimal Epo receptor (EpoR) alleles, efficient PODXL induction proved dependence on an EpoR-PY343 Stat5 binding site. Moreover, in mice expressing an EpoR-HM F343 allele, compromised Epo-induced PODXL expression correlated with abnormal anucleated red cell representation in marrow. By modulating this select set of cell-surface adhesion molecules and chemokines, Epo is proposed to mobilize erythroblasts from a hypothesized stromal niche and possibly promote reticulocyte egress to blood.

Oncostatin M induces upregulation of claudin-2 in rodent hepatocytes coinciding with changes in morphology and function of tight junctions

In rodent livers, integral tight junction (TJ) proteins claudin-1, -2, -3, -5 and -14 are detected and play crucial roles in the barrier to keep bile in bile canaculi away from the blood circulation. Claudin-2 shows a lobular gradient increasing from periportal to pericentral hepatocytes, whereas claudin-1 and -3 are expressed in the whole liver lobule. Although claudin-2 expression induces cation-selective channels in tight junctions of epithelial cells, the physiological functions and regulation of claudin-2 in hepatocytes remain unclear. Oncostatin M (OSM) is a multifunctional cytokine implicated in the differentiation of hepatocytes that induces formation of E-cadherin-based adherens junctions in fetal hepatocytes. In this study, we examined whether OSM could induce expression and function of claudin-2 in rodent hepatocytes, immortalized mouse and primary cultured proliferative rat hepatocytes. In the immortalized mouse and primary cultured proliferative rat hepatocytes, treatment with OSM markedly increased mRNA and protein of claudin-2 together with formation of developed networks of TJ strands. The increase of claudin-2 enhanced the paracellular barrier function which depended on molecular size. The increase of claudin-2 expression induced by OSM in rodent hepatocytes was regulated through distinct signaling pathways including PKC. These results suggest that expression of claudin-2 in rodent hepatocytes may play a specific role as controlling the size of paracellular permeability in the barrier to keep bile in bile canaculi.

Interleukin-6 family cytokine M17 induces differentiation and nitric oxide response of goldfish (Carassius auratus L.) macrophages

Cytokines belonging to the interleukin-6 (IL-6) family function in many biological processes and display a high degree of redundancy within the family. Although a number of mRNA transcripts from teleost fish that resemble IL-6 family cytokines have been identified none have been functionally characterized to confirm their identity. We report on the identification and functional characterization of goldfish M17, a molecule possessing sequence and mRNA expression patterns similar to the mammalian and avian ciliary neurotrophic factor and mammalian leukemia inhibitory factor. Goldfish M17 was found to induce the production of nitric oxide in goldfish macrophages and stimulate the proliferation of macrophage progenitor cells when added in combination with cell-conditioned medium. Moreover, goldfish M17 was found to facilitate the differentiation of sorted monocytes into macrophages at biologically relevant concentrations.

Oncostatin M stimulates expression of stromal-derived factor-1 in human mesenchymal stem cells

Stromal-derived factor-1 (SDF-1) is a CXC chemokine that attracts leukocytes and endothelial progenitor cells. In the present study, we demonstrated that oncostatin M (OSM) stimulates expression and secretion of SDF-1 in both human adipose tissue-derived mesenchymal stem cells (hATSCs) and bone marrow-derived mesenchymal stem cells. The OSM-stimulated expression of SDF-1 in hATSCs was completely abrogated by pretreatment of the cells with U0126, an MEK-specific inhibitor, but not with AG490, a JAK2 inhibitor, or WHI-P131, a JAK3 inhibitor, suggesting that ERK, but not JAK2 and JAK3, is involved in the OSM-induced expression of SDF-1. Pretreatment of hATSCs with anti-VEGF neutralizing antibody or VEGF receptor inhibitors, SU5416 and KRN633, had no significant impact on the OSM induction of SDF-1. Furthermore, treatment of hATSCs with recombinant human VEGF165 or adenoviral overexpression of VEGF did not increase the expression of SDF-1. These results suggest that OSM induces secretion of SDF-1 through ERK-, but not VEGF-, dependent signaling pathways in mesenchymal stem cells.

Inhibition effect of Oncostatin M on metastatic human lung cancer cells 95-D in vitro and on murine melanoma cells B16BL6 in vivo

Oncostatin M (OSM) is a multifunctional regulator of cell growth and differentiation. It inhibits the growth of many types of tumor cells, but its role in metastasis is unknown. We studied the human OSM expressed and purified from reconstructed E. Coli on its activity of inhibiting metastasis of tumor cells by a series of assays in vitro and in vivo. Clone formation assay in soft agar was used to measure the inhibition activity of OSM on the proliferation of high metastatic human lung cancer cells 95-D. Cell attachment assay, cell migration assay and cell invasion assay were used to evaluate inhibition by OSM on 95-D cells of the adhesion ability, the migration ability, and the ability of cells to cross tissue barriers, respectively. Inhibition of OSM on secretion of MMP-2 and -9 secretion in 95-D cells was determined by Western blot. The in vivo inhibitory effect of OSM on metastasis of murine melanoma cells B16BL6 was examined in the pulmonary metastasis model. In vitro studies showed that OSM inhibited the proliferation of 95-D cells at low concentration. OSM also reduced the adhesion and invasion ability of 95-D cells and inhibited the secretion of MMP-2 and MMP-9 in OSM treated cells. In vivo results showed that OSM (20 microg/kg/d for 7 days) inhibited pulmonary metastasis at a rate of 20.7%. There were no differences in animal weights among the groups. These results suggest that OSM has the potential of being a clinical inhibitor on metastasis of some cancer cells.

Oncostatin M decreases adiponectin expression and induces dedifferentiation of adipocytes by JAK3- and MEK-dependent pathways

Adiponectin, an adipokine secreted from adipocytes, plays a crucial role in the regulation of glucose and lipid metabolism. In the present study, we examine the role of the IL-6 family of cytokines in the expression of adiponectin in human adipocytes derived from human adipose tissue-derived stromal cells. Oncostatin M (OSM), but not IL-6, attenuated the expression level of adiponectin dose- and time-dependently, and the inhibitory effect of OSM on adiponectin expression was as potent as that of TNF-alpha. The OSM-induced down-regulation of adiponectin expression was correlated with the down-regulation of PPARgamma2 and lipoprotein lipase, markers for adipogenic differentiation, and depletion of intracellular lipid droplets, suggesting dedifferentiation of adipocytes in response to OSM. OSM induced phosphorylation of STAT1, and treatment of adipocytes with JAK3 inhibitor WHI-P131 or MEK inhibitor U0126, but not with JAK2 inhibitor AG490, prevented the activation of STAT1. Furthermore, the OSM-induced suppression of adiponectin expression and dedifferentiation of adipocytes were ameliorated by WHI-P131 or U0126, but not by AG490. These results suggest that OSM inhibits adiponectin expression by inducing dedifferentiation of adipocytes through signaling pathways involving JAK3 and MEK, but not JAK2.

Oncostatin M is a neuroprotective cytokine that inhibits excitotoxic injury in vitro and in vivo

Oncostatin M (OsM) is a member of the interleukin (IL)-6 family of cytokines and is well known for its role in inflammation, cell proliferation, and hematopoiesis. OsM, together with its glycoprotein 130 containing receptor complex, is expressed and regulated in most cells of the central nervous system (CNS), yet the function of OsM within this compartment is poorly understood. Here we have investigated the effect of OsM using in vitro and in vivo models of excitotoxic injury. Using primary cultures of mouse cortical neurons, OsM was shown to reduce N-methyl-D-aspartate (NMDA) -induced neuronal death by 50% when added simultaneously with NMDA while pretreatment of neurons with OsM fully prevented NMDA toxicity indicating a profound protective effect of this cytokine. OsM was also shown to inhibit NMDA-mediated increase in levels of free intracellular calcium and to selectively reduce neuronal expression of the NR2C subunit of the NMDA receptor. Finally, using an in vivo model of excitotoxic injury, OsM significantly reduced the NMDA-induced lesion volume when coinjected with NMDA into the mouse striatum. Taken together, these results identify OsM as a powerful neuroprotective cytokine and provide a rational foundation to explore the therapeutic potential for OsM in diseases of the CNS.

Loss of oncostatin M receptor beta in metastatic melanoma cells

Oncostatin M (OSM) is an interleukin-6 (IL-6) type cytokine originally described by its capacity to inhibit melanoma proliferation in vitro. Here, the mechanisms involved in resistance to growth inhibition by OSM were analysed for the first time on a large panel of metastatic melanoma cell lines. OSM resistance did not strictly correlate with IL-6, interferon-gamma or tumor necrosis factor-alpha resistance. Rather, it correlated with a specific loss of the OSM receptor-beta (OSMRbeta) subunit, in conjunction with a lower level of histone acetylation in the OSMRbeta promoter region. Treatment of various OSM-resistant melanoma cells with the histone deacetylase inhibitor Trichostatin A increased activity and histone acetylation of the OSMRbeta promoter as well as expression of OSMRbeta mRNA and protein, allowing OSM to activate the signal transducer and activator of transcription 3 (STAT3) and to inhibit proliferation. Other defects associated with OSM resistance were identified at the level of OSMRbeta transcription or protein expression, as well as downstream of or parallel to STAT3 activation. Altogether, our results suggest a role for OSM in the prevention of melanoma progression and that metastatic melanoma cells could escape this growth control by the epigenetic silencing of OSMRbeta.

Pharmacological regulation of low density lipoprotein receptor expression: Current status and future developments

Plasma levels of low-density lipoprotein (LDL) cholesterol are considered to be a major risk factor for the development of cardiovascular diseases. The LDL receptor is the key component in the maintenance of cholesterol homeostasis in the body, playing a pivotal role by regulating the hepatic catabolism of LDL cholesterol. Many clinical studies using statins, which up-regulate the LDL receptor expression via a feedback mechanism, have demonstrated that the reduction of LDL cholesterol levels lowers the incidence of cardiovascular events in both primary and secondary prevention. In this context, new strategies designed to increase hepatic LDL receptor activity can be considered as attractive opportunities for future therapy. Several potential new drugs have been described in the last decade to up-regulate LDL receptor expression in vitro and in vivo, thus allowing the identification of new transcriptional and post-transcriptional mechanisms.

Oncostatin M expression is functionally connected to neutrophils in the early inflammatory phase of skin repair: implications for normal and diabetes-impaired wounds

In this study, we investigated the role of the cytokine oncostatin M (OSM) for wound biology. OSM and its specific OSM receptor subunit beta (OSMRbeta) were induced upon injury. OSM induction paralleled the early influx of polymorphonuclear neutrophils (PMN) into the wound. OSM protein was localized in PMN in very early wounds, whereas OSMRbeta could be detected on macrophages, keratinocytes, and fibroblasts later in repair. To establish a functional connection between PMN and OSM expression in wounds, we depleted mice from circulating PMN by injecting an anti-PMN monoclonal antibody (Ly-6G). PMN-depleted wounds were characterized by a nearly complete loss of OSM but not OSMRbeta mRNA and protein expression within the initial 16-24 hours after injury. PMN-rich chronic wounds from diabetic ob/ob mice were characterized by a strongly elevated OSM mRNA and protein expression as compared to healthy animals. Moreover, a leptin-mediated improvement of chronic wounds in ob/ob mice was paralleled by a complete inhibition of PMN influx associated again with a dramatic loss of OSM expression at the wound site. These data constitute strong evidence that OSM expression during wound inflammation is functionally connected to PMN infiltration.

Oncostatin M differentially regulates CXC chemokines in mouse cardiac fibroblasts

Ischemia-reperfusion injury in the heart is characterized by marked infiltration of neutrophils in the myocardial interstitial space. Studies in human, canine, and murine models have revealed oncostatin M (OSM) expression in infiltrating leukocytes. In an effort to assess possible roles of OSM in the myocardium, we used cardiac fibroblasts (mCFs) isolated from adult mouse heart to determine whether recombinant murine OSM regulates the synthesis and release of MIP2/CXCL2, KC/CXCL1, and LIX/CXCL5, which are three potent neutrophil chemoattractants in the mouse. Our results demonstrate that mCFs express OSM receptors and that, within the IL-6 cytokine family, OSM uniquely induces significant release of KC and LIX in mCFs. In addition, although OSM activates the JAK-signal transducers and activators of transcription and MAPK pathways, we demonstrate that the OSM-mediated CXC chemokine release in mCFs is also dependent on the activation of the phosphatidylinositol 3-kinase pathway.

Divergent effects of oncostatin M on astroglioma cells: influence on cell proliferation, invasion, and expression of matrix metalloproteinases

Oncostatin M (OSM), a cytokine of the interleukin-6 (IL-6) family, can either promote or inhibit cell growth in various normal and tumor cells. We addressed the effects of exogenous OSM on the proliferation and invasion of human astroglioma cells. In addition, we investigated one of the possible mechanisms involved: modulation of matrix metalloproteinase (MMP) expression and enzymatic activity. We found that OSM inhibited the proliferation of two human astroglioma cell lines (CH235-MG and U87-MG), and that this effect was not due to apoptosis. The inhibitory effect of OSM on proliferation was mediated through the gp130/OSMRbeta receptor complex. To extend these findings, we analyzed the effects of OSM on primary tumor cells from glioblastoma patients. OSM suppressed the proliferation of primary glioblastoma cells, but not that of normal astrocytes. Interestingly, OSM did not suppress astroglioma cell invasion. This may be due to the differential regulation of MMPs by OSM. We found that OSM inhibited the constitutive expression of MMP-2, while MMP-9 expression was enhanced in astroglioma cell lines. We conclude that OSM inhibits proliferation of human astroglioma cells and primary glioblastoma cells via the gp130/OSMRbeta receptor complex. However, OSM does not affect the invasive capacity of the astroglioma cells, which may be due to the divergent effects of OSM on MMP-2 and MMP-9 expression. Collectively, these findings suggest a complex role for OSM in astroglioma biology.

Oncostatin M induces proliferation of human adipose tissue-derived mesenchymal stem cells

Interleukin-6 (IL-6) subfamily of cytokines, including oncostatin M (OSM), leukemia inhibitory factor (LIF), and IL-6, has been implicated in a variety of physiological responses, such as cell growth, differentiation, and inflammation. In the present study, we demonstrated that both OSM and LIF stimulated the proliferation of human adipose tissue-derived mesenchymal stem cells (hATSCs), however, IL-6 had no effect on cell proliferation. OSM treatment induced phosphorylation of ERK, and pretreatment with U0126, a MEK inhibitor, prevented the OSM-stimulated proliferation of hATSCs, suggesting that the MEK/ERK pathway is involved in the OSM-induced proliferation. Treatment with OSM also induced phosphorylation of JAK2 and JAK3, and pretreatment of the cells with WHI-P131, a JAK3 inhibitor, but not with AG490, a JAK2 inhibitor, attenuated the OSM-induced proliferation of hATSCs. Furthermore, OSM treatment elicited phosphorylation of STAT1 and STAT3, and pretreatment with WHI-P131 specifically prevented the OSM-induced phosphorylation of STAT1, without affecting the OSM-induced phosphorylation of ERK and STAT3. These results suggest that two separate signaling pathways, such as MEK/ERK and JAK3/STAT1, are independently involved in the OSM-stimulated proliferation of hATSCs.

Beta-adrenergic receptor agonists induce the release of granulocyte chemotactic protein-2, oncostatin M, and vascular endothelial growth factor from macrophages

Vascular endothelial growth factor (VEGF), oncostatin M (OSM), and granulocyte chemotactic protein-2 (GCP-2/CXCL6) are up-regulated in U937 macrophages and peripheral blood macrophages exposed to LPS, beta-adrenergic receptor (beta2-AR) agonists (e.g. zilpaterol, and clenbuterol) and some other agents that induce intracellular cAMP (prostaglandin E2, forskolin, and butyryl cAMP). LPS in combination with beta2-agonists and cAMP elevating agents had an additional effect on the release of VEGF, OSM, and CXCL6. These proteins are up-regulated after 16-24 h of exposure and this is mediated by the beta2-AR, as determined by time course experiments and the use of a specific beta2-AR antagonist (ICI 118551). Beta2-AR agonists are used as bronchodilators in the treatment of asthma, but appear to have no effect on the chronic inflammation of the disease. However, the up-regulation of VEGF, OSM, and CXCL6 may have adverse effects on the inflammatory process of asthma. These mediators are involved in the recruitment of neutrophils, airway remodelling and angiogenesis, known features of chronic inflammatory diseases. We propose that the up-regulation of these proteins could play a role in the adverse effects of prolonged excessive usage of beta2-AR agonists on the airways besides the desensitization of the beta2-AR.

Acute phase mediator oncostatin M regulates affinity of α1-protease inhibitor for concanavalin A in hepatoma-derived but not lung-derived epithelial cells

Quantitative changes in plasma protein concentrations during tissue injury or inflammation (acute phase response) are often accompanied by specific alterations in the carbohydrate moieties of these proteins. The glycosylation changes comprise alterations in the type of branching of the carbohydrate structures as revealed by modulated reactivity of acute phase glycoproteins with the lectin concanavalin A. Interestingly, inflammation-induced changes in the glycosylation of acute phase proteins have been shown to affect the functional properties of these proteins. In this study we demonstrate that synthesis of acute phase protein alpha(1)-PI, the controlling inhibitor of neutrophil elastase, is significantly up-regulated in hepatic and lung-derived epithelial cells by the inflammatory mediator oncostatin M. Although oncostatin M markedly altered the concanavalin A reactivity of hepatic alpha(1)-PI, lung-derived epithelial cells did not change the pattern of alpha(1)-PI glycan branching upon stimulation with oncostatin M. These results indicate that inflammation-induced changes in glycosylation of alpha(1)-PI may have different impacts on functional properties of liver and lung-synthesized alpha(1)-PI.

Raf and VEGF: emerging therapeutic targets in Kaposi's sarcoma-associated herpesvirus infection and angiogenesis in hematopoietic and nonhematopoietic tumors

Kaposi's sarcoma-associated herpesvirus (KSHV) is etiologically associated with several cancers including Kaposi's sarcoma (KS), primary effusion lymphoma, and multicentric Castleman's disease. KSHV-mediated pathogenesis is dependent mainly on KSHV infection as well as on the microenvironment provided by the growth factors (GFs)/inflammatory cytokines (ICs). Recently, we determined that oncoprotein Raf enhances KSHV infection of target cells. Interestingly, Raf regulates the expression of a variety of GFs/ICs including those involved in angiogenesis such as vascular endothelial growth factor (VEGF). In this review, we discuss the effect of the Raf-GF/IC autocrine/paracrine loop on KSHV infection of both hematopoietic and nonhematopietic cells, and associated disease conditions.

In vivo activities of cytokine oncostatin M in the regulation of plasma lipid levels

Our previous studies have demonstrated the activity of oncostatin M (OM) in stimulating the transcription of the human LDL receptor (LDLR) gene in HepG2 cells through a sterol-independent regulatory mechanism. The current studies were designed to determine whether this in vitro property of OM could be recapitulated in vivo to increase LDLR expression in cholesterol-loaded livers and consequently decrease plasma levels of LDL-cholesterol (LDL-C) and total cholesterol (TC) using hypercholesterolemic hamsters as an experimental model. We show that administration of human recombinant OM for 7 days in hamsters fed a high-fat diet significantly reduced plasma levels of TC, LDL-C, and triglyceride in dose- and time-dependent manners. This lipid-lowering effect was associated with increased hepatic LDLR mRNA expression, as determined by quantitative real-time RT-PCR. Additionally, hepatic fat storage and cholesterol content in the hypercholesterolemic animals were substantially reduced by OM treatment. As a consequence, the increased aminotransferase levels in the high-fat diet-fed hamsters were normalized nearly to baseline values. These results not only corroborate the in vitro finding of OM in the regulation of LDLR but also, for the first time, demonstrate that OM has a strong lipid-lowering effect under in vivo conditions in which the levels of circulating LDL-C are high and liver LDLR transcription is repressed.

Oncostatin M: a pleiotropic cytokine in the central nervous system

Oncostatin M (OSM), a member of the interleukin-6 (IL-6) cytokine family, has yet to be well studied, especially in the context of the central nervous system (CNS). The biological functions of OSM are complex and variable, depending on the cellular microenvironment. Inflammatory responses and tumor development are among two of the major events that OSM is involved in. Although OSM levels remain low in the normal CNS, elevated expression occurs in pathological conditions. Therefore, it is crucial to understand the regulation of OSM to control its expression and/or its effects. Accumulating data demonstrate that OSM binds to specific receptor complexes, then activates two major signaling pathways: Janus Kinase-Signal Transducers and Activators of Transcription (JAK-STAT) and Mitogen-Activated Protein Kinase (MAPK), to regulate downstream events. In this review, we focus on the biological functions of OSM, the signaling pathways of OSM in the CNS, and OSM involvement in CNS diseases.