ELISA detection of circulating levels of LIF, OSM, and CNTF in septic shock

Oncostatin M Receptor Type II Knockout Mitigates Inflammation and Improves Survival from Sepsis in Mice

Sepsis remains one of the leading causes of death worldwide. Oncostatin M (OSM), an interleukin (IL)-6 family cytokine, can be found at high levels in septic patients. However, little is known about its role in sepsis. This study aimed to determine if the genetic knockout of OSM receptor (OSMR) type II signaling would improve survival in a murine model of sepsis. Aged (>50 weeks) OSMR type II knockout (KO) mice and wild-type (WT) littermates received an intraperitoneal injection of fecal slurry (FS) or vehicle. The KO mice had better survival 48 h after the injection of FS than the WT mice (p = 0.005). Eighteen hours post-FS injection, the KO mice had reduced peritoneal, serum, and tissue cytokine levels (including IL-1β, IL-6, TNFα, KG/GRO, and IL-10) compared to the WT mice (p < 0.001 for all). Flow cytometry revealed decreased recruitment of CD11b⁺ F4/80⁺ Ly6c^high+ macrophages in the peritoneum of KO mice compared to WT mice (34 ± 6 vs. 4 ± 3%, P_Int = 0.005). Isolated peritoneal macrophages from aged KO mice had better live E. coli killing capacity than those from WT mice (p < 0.001). Peritoneal lavage revealed greater bacterial counts in KO mice than in WT mice (KO: 305 ± 22 vs. 116 ± 6 CFU (×10⁹)/mL; p < 0.001). In summary, deficiency in OSMR type II receptor signaling provided a survival benefit in the progression of sepsis. This coincided with reduced serum levels of pro-inflammatory (IL-1β, TNFα, and KC/GRO) and anti-inflammatory markers (IL-10), increased bacterial killing ability of macrophages, and reduced macrophage infiltration into to site of infection.

Oncostatin M: a Potential Biomarker to Predict Infection in Patients with Left Ventricular Assist Devices

Infection is a serious adverse event limiting left ventricular assist device (LVAD) therapy in advanced heart failure patients, but a reliable means to identify patients at increased risk of infection is still lacking. We hypothesized that preoperative elevated levels of plasma Oncostatin M (OSM), a cytokine marker of leukocyte activation and inflammation, would be predictive of subsequent infection. We measured plasma OSM in 41 LVAD patients one day before LVAD implantation and postoperatively over two months. Preoperative plasma OSM levels were normal in 27 patients (group A, 4.9 ± 3.2 pg/ml) but elevated in 14 patients (group B, 1649.0 ± 458.9 pg/ml) ( p = 0.003). Early postoperative levels rose in both groups and declined rapidly in group A, with group B declining slowly over two months. Significantly more infections developed in group B than group A patients over two months postimplantation ( p = 0.004). No other routine clinical assessment or laboratory testing afforded this differentiation. These findings suggest that preoperative plasma OSM levels may assist in identifying patients at increased risk of infections after LVAD implantation.

Ciliary neurotrophic factor is increased in the plasma of patients with obesity and its levels correlate with diabetes and inflammation indices

To establish whether obesity involves activation of endogenous ciliary neurotrophic factor (CNTF) signalling, we evaluated its plasma levels in patients with obesity and correlated its values with the major clinical and haematological indices of obesity, insulin resistance and systemic inflammation. This study involved 118 subjects: 39 healthy controls (19 men), 39 subjects with obesity (19 men) and 40 subjects with obesity and diabetes (20 men). Plasma CNTF and CNTF receptor α (CNTFRα) were measured using commercial ELISA kits. The results showed that plasma CNTF was significantly higher in males and females with obesity with and without diabetes than in healthy subjects. Women consistently exhibited higher levels of circulating CNTF. In both genders, CNTF levels correlated significantly and positively with obesity (BMI, WHR, leptin), diabetes (fasting insulin, HOMA index and HbA1c) and inflammation (IL-6 and hsCRP) indices. Circulating CNTFRα and the CNTF/CNTFRα molar ratio tended to be higher in the patient groups than in controls. In conclusion, endogenous CNTF signalling is activated in human obesity and may help counteract some adverse effects of obesity. Studies involving a higher number of selected patients may reveal circulating CNTF and/or CNTFRα as potential novel diagnostic and/or prognostic markers of obesity, diabetes and associated diseases.

Neutrophil-Derived Oncostatin M Triggers Diverse Signaling Pathways during Pneumonia

Pneumonia is a major public health concern, causing significant morbidity and mortality annually despite the broad use of antimicrobial agents. Underlying many of the severe sequelae of acute lung infections is dysfunction of the immune response, which remains incompletely understood yet is an attractive target of adjunct therapy in pneumonia. Here, we investigate the role of oncostatin M (OSM), a pleiotropic cytokine of the interleukin-6 (IL-6) family, and how its signaling modulates multiple innate immune pathways during pneumonia. Previously, we showed that OSM is necessary for neutrophil recruitment to the lungs during pneumonia by stimulating STAT3-driven CXCL5 expression. In this study, transcriptional profiling of whole-lung pneumonia with OSM neutralization revealed 241 differentially expressed genes following only 6 h of infection. Many downregulated genes are associated with STAT1, STAT3, and interferon signaling, suggesting these pathways are induced by OSM early in pneumonia. Interestingly, STAT1 and STAT3 activation was subsequently upregulated with OSM neutralization by 24 h, suggesting that OSM interruption dysregulates these central signaling pathways. When we investigated the source of OSM in pneumonia, neutrophils and, to a lesser extent, macrophages appear to be primary sources, suggesting a positive feedback loop of OSM production by neutrophils. From these studies, we conclude that OSM produced by recruited neutrophils tunes early innate immune signaling pathways, improving pneumonia outcomes.

Historical overview of the interleukin-6 family cytokine

Interleukin-6 (IL-6) has been identified as a 26-kD secreted protein that stimulates B cells to produce antibodies. Later, IL-6 was revealed to have various functions that overlap with other IL-6 family cytokines and use the common IL-6 signal transducer gp130. IL-6 stimulates cells through multiple pathways, using both membrane and soluble IL-6 receptors. As indicated by the expanding market for IL-6 inhibitors, it has become a primary therapeutic target among IL-6 family cytokines. Here, we revisit the discovery of IL-6; discuss insights regarding the roles of this family of cytokines; and highlight recent advances in our understanding of regulation of IL-6 expression.

Two Gene Set Variation Index as Biomarker of Bacterial and Fungal Sepsis

Background

The incidence of sepsis has been increasing in recent years. The molecular mechanism of different pathogenic sepsis remains elusive, and biomarkers of sepsis against different pathogens are still lacking.

Methods

The microarray data of bacterial sepsis, fungal sepsis, and mock-treated samples were applied to perform differentially expressed gene (DEG) analysis to identify a bacterial sepsis-specific gene set and a fungal sepsis-specific gene set. Functional enrichment analysis was used to explore the body's response to bacterial sepsis and fungal sepsis. Gene set variation analysis (GSVA) was used to score individual samples against the two pathogen-specific gene sets, and each sample gets a GSVA index. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic value of sepsis. An independent data set was used to validate the bacterial sepsis-specific GSVA index.

Results

The genes differentially expressed only in bacterial sepsis and the genes differentially expressed only in fungal sepsis were significantly involved in different biological processes (BPs) and pathways. This indicated that the body's responses to fungal sepsis and bacterial sepsis are varied. Twenty-two genes were identified as bacterial sepsis-specific genes and upregulated in bacterial sepsis, and 23 genes were identified as fungal sepsis-specific genes and upregulated in fungal sepsis. ROC curve analysis showed that both of the two pathogen sepsis-specific GSVA indexes may be a reliable biomarker for corresponding pathogen-induced sepsis (AUC = 1.000), while the mRNA of CALCA (also known as PCT) have a poor diagnostic value with AUC = 0.512 in bacterial sepsis and AUC = 0.705 in fungi sepsis. In addition, the AUC of the bacterial sepsis-specific GSVA index in the independent data set was 0.762.

Conclusion

We proposed a bacterial sepsis-specific gene set and a fungal sepsis-specific gene set; the bacterial sepsis GSVA index may be a reliable biomarker for bacterial sepsis.

Ciliary Neurotrophic Factor Acts on Distinctive Hypothalamic Arcuate Neurons and Promotes Leptin Entry Into and Action on the Mouse Hypothalamus

In humans and experimental animals, the administration of ciliary neurotrophic factor (CNTF) reduces food intake and body weight. To gain further insights into the mechanism(s) underlying its satiety effect, we: (i) evaluated the CNTF-dependent activation of the Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) pathway in mouse models where neuropeptide Y (NPY) and pro-opiomelanocortin (POMC) neurons can be identified by green fluorescent protein (GFP); and (ii) assessed whether CNTF promotes leptin signaling in hypothalamic feeding centers. Immunohistochemical experiments enabled us to establish that intraperitoneal injection of mouse recombinant CNTF activated the JAK2-STAT3 pathway in a substantial proportion of arcuate nucleus (ARC) NPY neurons (18.68% ± 0.60 in 24-h fasted mice and 25.50% ± 1.17 in fed mice) but exerted a limited effect on POMC neurons (4.15% ± 0.33 in 24-h fasted mice and 2.84% ± 0.45 in fed mice). CNTF-responsive NPY neurons resided in the ventromedial ARC, facing the median eminence (ME), and were surrounded by albumin immunoreactivity, suggesting that they are located outside the blood-brain barrier (BBB). In both normally fed and high-fat diet (HFD) obese animals, CNTF activated extracellular signal-regulated kinase signaling in ME β1- and β2-tanycytes, an effect that has been linked to the promotion of leptin entry into the brain. Accordingly, compared to the animals treated with leptin, mice treated with leptin/CNTF showed: (i) a significantly greater leptin content in hypothalamic protein extracts; (ii) a significant increase in phospho-STAT3 (P-STAT3)-positive neurons in the ARC and the ventromedial hypothalamic nucleus of normally fed mice; and (iii) a significantly increased number of P-STAT3-positive neurons in the ARC and dorsomedial hypothalamic nucleus of HFD obese mice. Collectively, these data suggest that exogenously administered CNTF reduces food intake by exerting a leptin-like action on distinctive NPY ARC neurons and by promoting leptin signaling in hypothalamic feeding centers.

Oncostatin M Plays a Critical Role in Survival after Acute Intestinal Ischemia: Reperfusion Injury

Background: Acute intestinal ischemia-reperfusion injury (AIIRI) is a devastating clinical condition relevant to multiple diseases processes, including sepsis, trauma, transplantation, and burns. An AIIRI is a contributor to the development of multiple organ dysfunction syndrome (MODS). Oncostatin M (OSM)/oncostatin M receptor (OSMR) signaling is an unrecognized and novel candidate pathway for the mediation of MODS. In this study, we hypothesized that OSM mediates the injury mechanism of AIIRI leading to MODS. Methods: Wild-type (WT) and OSMR-knockout (OSMR^-/-) C57BL/6 mice underwent AIIRI using a well-established model of selective occlusion of the superior mesenteric artery (SMA). Serum cytokine concentrations were measured using a multiplex detection system. Further tissue analysis was conducted with polymerase chain reaction, enzyme-linked immunosorbent assay, Western blots, and histologic review. Results: Survival was significantly higher in WT than in OSMR^-/- groups at 30 minutes of ischemia with 2 hours of reperfusion (100% versus 42.9%; P = 0.015). No significant differences in the degree of local intestinal injury was seen in the two groups. In contrast, the degree of lung injury, as evidenced by myeloperixodase activity, was lower in OSMR^-/- animals in the early AIIRI groups. There was a greater degree of renal dysfunction in OSMR^-/- mice. Oncostatin M mediated interleukin (IL)-10 upregulation, with WT animals having significantly lower IL-10 concentrations (52.04 ± 23.06 pg/mL versus 324.37 ± 140.35 pg/mL; P = 0.046). Conclusion: Oncostatin M signalling is essential during acute intestinal ischemia-reperfusion injury. An OSMR deficiency results in decreased early lung injury but increased renal dysfunction. There was a significantly increased mortality rate after AIIRI in mice with OSMR deficiency. Augmentation of OSM may be a novel immunomodulatory strategy for AIIRI.

Action of Administered Ciliary Neurotrophic Factor on the Mouse Dorsal Vagal Complex

Ciliary neurotrophic factor (CNTF) induces weight loss in obese rodents and humans through activation of the hypothalamic Jak-STAT (Janus kinase-signal transducer and activator of transcription) signaling pathway. Here, we tested the hypothesis that CNTF also affects the brainstem centers involved in feeding and energy balance regulation. To this end, wild-type and leptin-deficient (ob/ob and db/db) obese mice were acutely treated with intraperitoneal recombinant CNTF. Coronal brainstem sections were processed for immunohistochemical detection of STAT3, STAT1, STAT5 phosphorylation and c-Fos. In wild-type mice, CNTF treatment for 45 min induced STAT3, STAT1, and STAT5 phosphorylation in neurons as well as glial cells of the area postrema; here, the majority of CNTF-responsive cells activated multiple STAT isoforms, and a significant proportion of CNTF-responsive glial cells bore the immaturity and plasticity markers nestin and vimentin. After 120 min CNTF treatment, c-Fos expression was intense in glial cells and weak in neurons of the area postrema, it was intense in several neurons of the rostral and caudal solitary tract nucleus (NTS), and weak in some cholinergic neurons of the dorsal motor nucleus of the vagus. In the ob/ob and db/db mice, Jak-STAT activation and c-Fos expression were similar to those induced in wild-type mouse brainstem. Treatment with CNTF (120 min, to induce c-Fos expression) and leptin (25 min, to induce STAT3 phosphorylation) demonstrated the co-localization of the two transcription factors in a small neuron population in the caudal NTS portion. Finally, weak immunohistochemical CNTF staining, detected in funiculus separans, and meningeal glial cells, matched the modest amount of CNTF found by RT-qPCR in micropunched area postrema tissue, which in contrast exhibited a very high amount of CNTF receptor. Collectively, the present findings show that the area postrema and the NTS exhibit high, distinctive responsiveness to circulating exogenous and, probably, endogenous CNTF.

Oncostatin M Confers Neuroprotection against Ischemic Stroke

Cell-surface receptors provide potential targets for the translation of bench-side findings into therapeutic strategies; however, this approach for the treatment of stroke is disappointing, at least partially due to an incomplete understanding of the targeted factors. Previous studies of oncostatin M (OSM), a member of the gp130 cytokine family, have been limited, as mouse models alone may not strongly resemble the human condition enough. In addition, the precise function of OSM in the CNS remains unclear. Here, we report that human OSM is neuroprotective in vivo and in vitro by recruiting OSMRβ in the setting of ischemic stroke. Using gain- and loss-of-function approaches, we demonstrated that decreased neuronal OSMRβ expression results in deteriorated stroke outcomes but that OSMRβ overexpression in neurons is cerebroprotective. Moreover, administering recombinant human OSM to mice before the onset of I/R showed that human OSM can be protective in rodent models of ischemic stroke. Mechanistically, OSM/OSMRβ activate the JAK2/STAT3 prosurvival signaling pathway. Collectively, these data support that human OSM may represent a promising drug candidate for stroke treatment.

SIGNIFICANCE STATEMENT

OSM, a member of the gp130 cytokine family, regulates neuronal function and survival. OSM engages a second receptor, either LIFRα or OSMRβ, before recruiting gp130. However, it is not clear whether OSM/OSMRβ signaling is involved in neuroprotection in the setting of ischemic stroke. Recent studies show that, compared with mouse disease models, the OSM receptor system in rats more closely resembles that in humans. In the present study, we use genetic manipulations of OSMRβ in both mouse and rat stroke models to demonstrate that OSMRβ in neurons is critical for neuronal survival during cerebral ischemic/reperfusion. Interestingly, administration of human OSM also leads to improved stroke outcomes. Therefore, OSM may represent a promising drug candidate for stroke treatment.

Host response biomarkers in the diagnosis of sepsis: a general overview

Critically ill patients who display a systemic inflammatory response syndrome (SIRS) are prone to develop nosocomial infections. The challenge remains to distinguish as early as possible among SIRS patients those who are developing sepsis. Following a sterile insult, damage-associated molecular patterns (DAMPs) released by damaged tissues and necrotic cells initiate an inflammatory response close to that observed during sepsis. During sepsis, pathogen-associated molecular patterns (PAMPs) trigger the release of host mediators involved in innate immunity and inflammation through identical receptors as DAMPs. In both clinical settings, a compensatory anti-inflammatory response syndrome (CARS) is concomitantly initiated. The exacerbated production of pro- or anti-inflammatory mediators allows their detection in biological fluids and particularly within the bloodstream. Some of these mediators can be used as biomarkers to decipher among the patients those who developed sepsis, and eventually they can be used as prognosis markers. In addition to plasma biomarkers, the analysis of some surface markers on circulating leukocytes or the study of mRNA and miRNA can be helpful. While there is no magic marker, a combination of few biomarkers might offer a high accuracy for diagnosis.

The enigmatic cytokine oncostatin m and roles in disease

Oncostatin M is a secreted cytokine involved in homeostasis and in diseases involving chronic inflammation. It is a member of the gp130 family of cytokines that have pleiotropic functions in differentiation, cell proliferation, and hematopoetic, immunologic, and inflammatory networks. However, Oncostatin M also has activities novel to mediators of this cytokine family and others and may have fundamental roles in mechanisms of inflammation in pathology. Studies have explored Oncostatin M functions in cancer, bone metabolism, liver regeneration, and conditions with chronic inflammation including rheumatoid arthritis, lung and skin inflammatory disease, atherosclerosis, and cardiovascular disease. This paper will review Oncostatin M biology in a historical fashion and focus on its unique activities, in vitro and in vivo, that differentiate it from other cytokines and inspire further study or consideration in therapeutic approaches.

The anorexigenic cytokine ciliary neurotrophic factor stimulates POMC gene expression via receptors localized in the nucleus of arcuate neurons

Ciliary neurotrophic factor (CNTF) is a neural cytokine that reduces appetite and body weight when administrated to rodents or humans. We have demonstrated recently that the level of CNTF in the arcuate nucleus (ARC), a key hypothalamic region involved in food intake regulation, is positively correlated with protection against diet-induced obesity. However, the comprehension of the physiological significance of neural CNTF action was still incomplete because CNTF lacks a signal peptide and thus may not be secreted by the classical exocytosis pathways. Knowing that CNTF distribution shares similarities with that of its receptor subunits in the rat ARC, we hypothesized that CNTF could exert a direct intracrine effect in ARC cells. Here, we demonstrate that CNTF, together with its receptor subunits, translocates to the cell nucleus of anorexigenic POMC neurons in the rat ARC. Furthermore, the stimulation of hypothalamic nuclear fractions with CNTF induces the phosphorylation of several signaling proteins, including Akt, as well as the transcription of the POMC gene. These data strongly suggest that intracellular CNTF may directly modulate POMC gene expression via the activation of receptors localized in the cell nucleus, providing a novel plausible mechanism of CNTF action in regulating energy homeostasis.

Vascular effects of glycoprotein130 ligands--part I: pathophysiological role

The vessel wall is no longer considered as only an anatomical barrier for blood cells but is recognized as an active endocrine organ. Dysfunction of the vessel wall occurs in various disease processes including atherosclerosis, hypertension, peripheral artery disease, aneurysms, and transplant and diabetic vasculopathies. Different cytokines were shown to modulate the behavior of the cells, which constitute the vessel wall such as immune cells, endothelial cells and smooth muscle cells. Glycoprotein 130 (gp130) is a common cytokine receptor that controls the activity of a group of cytokines, namely, interleukin (IL)-6, oncostatin M (OSM), IL-11, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), cardiotrophin-like cytokine (CLC), IL-27, and neuropoietin (NP). Gp130 and associated cytokines have abundantly diverse functions. Part I of this review focuses on the pathophysiological functions of gp130 ligands. We specifically describe vascular effects of these molecules and discuss the respective underlying molecular and cellular mechanisms.

Label-acquired magnetorotation as a signal transduction method for protein detection: aptamer-based detection of thrombin

This paper presents a new signal transduction method, called label-acquired magnetorotation (LAM), for the measurement of the concentration of proteins in solution. We demonstrate the use of LAM to detect the protein thrombin using aptamers, with a limit of detection of 300 pM. LAM is modeled after a sandwich assay, with a 10 μm nonmagnetic "mother" sphere as the capture component and with 1 μm magnetic "daughter" beads as the labels. The protein-mediated attachment of daughter beads to the mother sphere forms a rotating sandwich complex. In a rotating magnetic field, the rotational frequency of a sandwich complex scales with the number of attached magnetic beads, which scales with the concentration of the protein present in solution. This paper represents the first instance of the detection of a protein using LAM.

Analytic review: Interleukin-6 in surgery, trauma, and critical care: part I: basic science

A variety of cytokines play a role in the response to an inflammatory stimulus. The interleukin-6 (IL-6)-type cytokines are released in response to tissue injury or an inflammatory stimulus. They act locally and systemically to generate a variety of physiologic responses, principal among them is the acute phase response. The IL-6 type cytokines demonstrate pleiotropy and redundancy of actions. This is made possible by the distinctive characteristics of the IL-6 receptor complex, which contains an ubiquitous subunit that is shared by most IL-6-type cytokines, as well as a cytokine-specific subunit.

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.

CNTF, a pleiotropic cytokine: emphasis on its myotrophic role

Ciliary neurotrophic factor (CNTF) is a cytokine whose neurotrophic and differentiating effects over cells in the central nervous system (CNS) have been clearly demonstrated. This article summarizes the general characteristics of CNTF, its receptor and the signaling pathway that it activates and focuses on its effects over skeletal muscle, one of its major target tissues outside the central nervous system. The evidence for the existence of other molecules that signal through the same complex as CNTF is also reviewed.

Leptin regulation of the thyroids: negative regulation on thyroid hormone levels in euthyroid subjects and inhibitory effects on iodide uptake and Na+/I- symporter mRNA expression in rat FRTL-5 cells

Leptin receptors are distributed throughout the body and leptin has been shown to have various effects. As we have recently demonstrated a positive correlation between serum leptin levels and TSH in euthyroid subjects, we investigated the effect of leptin on the thyroids. It was observed that serum leptin levels were negatively correlated with free thyroxine/TSH ratios in the serum of euthyroid female subjects. This suggests that leptin may modulate TSH effects. RT-PCR for leptin receptor expression revealed that FRTL-5 cells possess the gene transcript to the long cytoplasmic form of the receptor. Leptin actually appeared to induce an increase in c-fos mRNA expression. However, it inhibited iodide uptake typically induced by both TSH and dibutyryl cAMP, while leptin did not inhibit TSH-induced cAMP production or TSH-stimulated DNA synthesis in 4H medium (in the absence of insulin and TSH). Leptin also was observed to inhibit TSH- and dibutyryl cAMP-induced Na+/I- symporter and thyroglobulin mRNA expression. Lastly, leptin was seen to inhibit TSH-stimulated thymidine incorporation in 5H medium. Taken together, these results suggest that leptin suppresses TSH-induced thyroid function. Therefore, we hypothesized that leptin may be one of the regulators of thyroid function in obese patients.

Exclusive neutrophil recruitment with oncostatin M in a human system

Oncostatin M (OSM), a member of the IL-6 family has been postulated to be a potent recruiter of leukocytes, however information regarding the molecular mechanism(s) underlying this event is extremely limited. Therefore, the aim of this study was to investigate the role of OSM-mediated leukocyte recruitment in a human system in vitro under flow conditions. A parallel-plate flow chamber assay was used to examine leukocyte recruitment from whole blood by human umbilical vein endothelium treated for 24 hours with OSM. OSM in a dose-response manner revealed very significant leukocyte rolling and adhesion reaching optimal levels at a very low concentration of OSM (10 ng/ml). The OSM-induced leukocyte rolling and adhesion was comparable to levels seen with tumor necrosis factor. OSM was extremely selective for neutrophil recruitment (96%) with <3% lymphocyte recruitment. By contrast, tumor necrosis factor-alpha revealed no such selectivity, recruiting 70% neutrophils and at least 25% lymphocytes and detectable levels of eosinophils at 24 hours. The molecular mechanism underlying the leukocyte recruitment seemed to be entirely dependent on P-selectin as leukocyte recruitment could be completely blocked by the addition of a P-selectin-blocking antibody. An elevation in both P-selectin message and protein was observed with 24 hours of OSM stimulation of endothelium. By contrast, E-selectin and VCAM-1 were not detectable after OSM stimulation. Similar results were seen with passaged dermal microvascular endothelium that does not have a prestored pool of P-selectin. Based on these results, we conclude that OSM may be a very selective potent recruiter of neutrophils in more prolonged inflammatory conditions, an event exclusively dependent on P-selectin.

Oncostatin M production by blood and alveolar neutrophils during acute lung injury

Polymorphonuclear neutrophils (PMN) are involved in the pathogenesis of acute lung injury (ALI), secreting numerous mediators such as proteases, reactive oxygen species, and cytokines. Because we had recently observed the ability of normal human PMN to degranulate and synthesize oncostatin M (OSM), an IL-6-family cytokine, we quantified OSM production ex vivo by highly purified blood and alveolar PMN from 24 ventilated patients with ALI, including some patients with severe pneumonia. Most of the patients had no detectable OSM in plasma, and OSM production by cultured blood PMN was similar to that of healthy controls. However, OSM was present in bronchoalveolar lavage (BAL) fluid supernatant, with significantly higher levels during pneumonia. In addition, alveolar OSM levels correlated with the number of PMN obtained by BAL, suggesting that PMN are an important source of OSM within the alveoli. Indeed, purified alveolar PMN from all of the patients, especially those with pneumonia, strongly produced OSM. Interestingly, in the latter patients, alveolar PMN always produced more OSM than autologous blood PMN. These results document the functional duality of PMN in ALI by showing the participation of PMN in the modulation of lung inflammation.

Leukemia-inhibitory factor-neuroimmune modulator of endocrine function

Leukemia-inhibitory factor (LIF) is a pleiotropic cytokine expressed by multiple tissue types. The LIF receptor shares a common gp130 receptor subunit with the IL-6 cytokine superfamily. LIF signaling is mediated mainly by JAK-STAT (janus-kinase-signal transducer and activator of transcription) pathways and is abrogated by the SOCS (suppressor-of cytokine signaling) and PIAS (protein inhibitors of activated STAT) proteins. In addition to classic hematopoietic and neuronal actions, LIF plays a critical role in several endocrine functions including the utero-placental unit, the hypothalamo-pituitary-adrenal axis, bone cell metabolism, energy homeostasis, and hormonally responsive tumors. This paper reviews recent advances in our understanding of molecular mechanisms regulating LIF expression and action and also provides a systemic overview of LIF-mediated endocrine regulation. Local and systemic LIF serve to integrate multiple developmental and functional cell signals, culminating in maintaining appropriate hormonal and metabolic homeostasis. LIF thus functions as a critical molecular interface between the neuroimmune and endocrine systems.

A significant role of leukemia inhibitory factor in the brain and periphery in endotoxin stimulation of adrenocorticotropin secretion in the rat

Leukemia inhibitory factor (LIF) is considered as another important cytokine regulating the activity of the hypothalamo-pituitary-adrenal axis. In this study, we examined the effects of intravenous (iv) and intracerebroventricular (icv) administrations of anti-LIF antibody on plasma adrenocorticotropin (ACTH) responses induced by intraperitoneal administration of lipopolysaccharide (LPS, 250 microg/kg) in male rats. Fifteen minutes before the LPS injection, anti-rat LIF antibody or control serum was given iv or icv. The antibody was administered at two different concentrations, i.e. undiluted and five-times diluted. Irrespective of the route of administration, the anti-LIF antibody partially but significantly suppressed ACTH responses to LPS, and its suppressive effect was similar between its two different concentrations. These results indicate that the anti-LIF antibody already exerted its maximal effects at its diluted preparation, and hence that the role of LIF in LPS-stimulated ACTH secretion is essentially partial. This is the first study to demonstrate in vivo that LIF in both the brain and general circulation plays a significant role in mediating endotoxin-stimulated ACTH secretion in the rat.

Divergent Inducible Expression of P-Selectin and E-Selectin in Mice and Primates

We used in vitro and in vivo approaches to examine whether tumor necrosis factor- (TNF-) and oncostatin M (OSM), cytokines that bind to distinct classes of receptors, differentially regulate expression of P- and E-selectin in murine and primate endothelial cells. In human umbilical vein endothelial cells, TNF- rapidly increased mRNA for E-selectin but not P-selectin. OSM elicited little or no change in mRNA for E-selectin, but induced a delayed and prolonged increase in P-selectin mRNA. TNF- and OSM did not cooperate to further enhance P- or E-selectin mRNA. Intravenous infusion of Escherichia coli, which markedly elevates plasma lipopolysaccharide and TNF-, increased mRNA for E-selectin but not P-selectin in baboons. In murine bEnd.3 endothelioma cells, TNF- and OSM individually and cooperatively increased mRNA and protein for both P- and E-selectin. Intravenous injection of these cytokines also individually and cooperatively increased mRNA for P- and E-selectin in mice. We conclude that the murine P- and E-selectin genes respond to both TNF- and OSM, whereas the primate P- and E-selectin genes have much more specialized responses. Such differences should be considered when extrapolating the functions of P- and E-selectin in murine models of inflammation to humans.

Divergent Inducible Expression of P-Selectin and E-Selectin in Mice and Primates

We used in vitro and in vivo approaches to examine whether tumor necrosis factor- (TNF-) and oncostatin M (OSM), cytokines that bind to distinct classes of receptors, differentially regulate expression of P- and E-selectin in murine and primate endothelial cells. In human umbilical vein endothelial cells, TNF- rapidly increased mRNA for E-selectin but not P-selectin. OSM elicited little or no change in mRNA for E-selectin, but induced a delayed and prolonged increase in P-selectin mRNA. TNF- and OSM did not cooperate to further enhance P- or E-selectin mRNA. Intravenous infusion of Escherichia coli, which markedly elevates plasma lipopolysaccharide and TNF-, increased mRNA for E-selectin but not P-selectin in baboons. In murine bEnd.3 endothelioma cells, TNF- and OSM individually and cooperatively increased mRNA and protein for both P- and E-selectin. Intravenous injection of these cytokines also individually and cooperatively increased mRNA for P- and E-selectin in mice. We conclude that the murine P- and E-selectin genes respond to both TNF- and OSM, whereas the primate P- and E-selectin genes have much more specialized responses. Such differences should be considered when extrapolating the functions of P- and E-selectin in murine models of inflammation to humans.

Adenovirus vector expressing mouse oncostatin M induces acute-phase proteins and TIMP-1 expression in vivo in mice

Mouse oncostatin M (MuOSM) regulates the production of acute-phase proteins by hepatocytes as well as tissue inhibitor of metalloproteinases-1 (TIMP-1) production by fibroblasts in vitro. We have generated an adenovirus (Ad) encoding MuOSM and tested the effects of administration of recombinant AdMuOSM to mice in vivo. On intramuscular injection, AdMuOSM (5 X 10(7) plaque-forming units, pfu) induced an increase in serum levels of interleukin-6 (IL-6) as well as the acute-phase proteins serum amyloid A (SAP) and alpha1-acid glycoprotein (AGP) at day 1. SAP and AGP concentrations were elevated to greater levels at day 3 and decreased to near control levels at day 7. Intratracheal treatment with AdMuOSM induced TIMP-1 mRNA levels (as assessed by Northern blots) that corresponded to the presence of transgene MuOSM mRNA levels. TIMP-1 was elevated at day 1 and day 3 and less consistently at day 7 after administration. Intraperitoneal treatment with AdMuOSM also resulted in elevation of TIMP-1 mRNA in lung tissue. These results show that AdMuOSM can induce both local and systemic effects and demonstrate in vivo effects of OSM that are consistent with in vitro studies on acute-phase protein and TIMP-1 expression.

Leukemia inhibitory factor, Interleukin 6, and other cytokines using the GP130 transducing receptor: roles in inflammation and injury

Inflammation refers to a complex set of mechanisms by which tissues respond to injury and infection. Among the many soluble mediators associated with this process, cytokines are known to be crucial in regulating a variety of cellular and molecular events. Leukemia inhibitory factor (LIF), interleukin 6 (IL-6), IL-11, and possibly other members of this cytokine family are key mediators in various inflammatory processes such as the acute-phase reaction, tissue damage, and infection. These cytokines can act in both pro-inflammatory and anti-inflammatory ways, depending on a number of variables. We emphasize here recent work utilizing knockout mice, which has highlighted the roles of LIF and IL-6, particularly in interactions between the immune and nervous systems.

Measurement of leukemia inhibitory factor in biological fluids by radioimmunoassay

Leukemia inhibitory factor (LIF) exhibits multiple biological activities in various tissues, and we have shown that LIF activates POMC gene transcription in response to immune signals. As higher serum levels of LIF have been reported in septicemia, we measured LIF values in biological fluids by RIA. Immunoreactive LIF was detected in 303 of 428 human serum samples. Circulating LIF detection rates were 69% in acute inflammatory diseases, 83% in chronic inflammatory diseases, 61% in noninflammatory diseases, and 90% in cancer patients. Serum concentrations of human LIF was higher in patients with inflammatory disease than in noninflammatory disease (0.80 +/- 0.10 vs. 0.53 +/- 0.02 ng/mL; P < 0.05) or in cancer patients (0.44 +/- 0.06; P < 0.05). Higher serum human LIF levels were found in septicemia (0.78 +/- 0.14 ng/mL), pneumonia (0.80 +/- 0.10 ng/mL), acute bronchitis (0.88 +/- 0.09 ng/mL), other infections (1.01 +/- 0.17 ng/mL), and systemic lupus erythematosus (SLE; 0.79 +/- 0.06 ng/mL). In 7 septicemia patients, Gram-negative infection was associated with higher LIF levels (1.06 +/- 0.16 ng/mL) than was Gram-positive infection (0.58 +/- 0.14 ng/mL). In patients with acute inflammatory disease, serum LIF levels decreased within several days after hospitalization. To test circulating mouse (m) LIF changes in response to inflammatory stress, lipopolysaccharide (LPS) was injected ip to mice. LPS increased serum mLIF values concordantly with ACTH levels. After i.p. injection of 80 microg LPS, serum mLIF increased by 144% (P < 0.05), 173% (P < 0.05), and 134% at 30, 90, and 120 min respectively. In vitro, however, LPS did not increase ACTH and mLIF secretion from dispersed mouse primary pituitary cells. These results suggest that LIF is an important participant in the pathogenesis of the acute inflammatory response. The elevated serum LIF levels observed in inflammation do not appear to originate from the pituitary.

Effect of ciliary neurotrophic factor on body temperature and cerebrospinal fluid prostanoids in the cat

It has been proposed that ciliary neurotrophic factor (CNTF) belongs to the group of cytokines causing fever in response to infectious and inflammatory noxae. The present investigation was undertaken in the conscious cat to verify whether CNTF (human type, hCNTF) is pyrogenic when given either intravenously (i.v.) or intracerebroventricularly (i.c.v.) and correlate at the same time body temperature with cerebrospinal fluid (CSF) levels of prostaglandin (PG) E2 (i.e., the putative fever mediator in brain) and thromboxane (TX) B2 (the stable TXA2 byproduct) in untreated vs. treated animals. hCNTF (10 microg/kg i.v.; 1 microg i.c.v.) caused fever by both routes and the increase in body temperature was associated with an upward change in CSF PGE2. Conversely, CSF TXB2 showed no elevation. Similarly unaffected was CSF TXB2 by human interleukin 6 (hIL-6, 1 microg i.c.v.), a cytokine with known pyrogenic and PGE2-promoting actions sharing the signal-transducing mechanism with hCNTF. We conclude that CNTF lends itself to a role in the pathogenesis of fever. The modest PGE2 elevation relatively to other cytokines, specifically hIL-1, is ascribed to the fact that CNTF activates the inducible isoform of arachidonate cyclooxygenase, which is constitutively expressed in brain, without concomitantly promoting the formation of new enzyme.

Oncostatin M is a proinflammatory mediator. In vivo effects correlate with endothelial cell expression of inflammatory cytokines and adhesion molecules

Oncostatin M is a member of the IL-6 family of cytokines that is primarily known for its effects on cell growth. Endothelial cells have an abundance of receptors for oncostatin M, and may be its primary target. We determined if oncostatin M induces a key endothelial cell function, initiation of the inflammatory response. We found that subcutaneous injection of oncostatin M in mice caused an acute inflammatory reaction. Oncostatin M in vitro stimulated: (a) polymorphonuclear leukocyte (PMN) transmigration through confluent monolayers of primary human endothelial cells; (b) biphasic PMN adhesion through rapid P-selectin expression, and delayed adhesion mediated by E-selectin synthesis; (c) intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 accumulation; and (d) the expression of PMN activators IL-6, epithelial neutrophil activating peptide-78, growth-related cytokine alpha and growth-related cytokine beta without concomitant IL-8 synthesis. The nature of the response to oncostatin M varied with concentration, suggesting high and low affinity oncostatin M receptors independently stimulated specific responses. Immunohistochemistry showed that macrophage-like cells infiltrating human aortic aneurysms expressed oncostatin M, so it is present during a chronic inflammatory reaction. Therefore, oncostatin M, but not other IL-6 family members, fulfills Koch's postulates as an inflammatory mediator. Since its effects on endothelial cells differ significantly from established mediators like TNFalpha, it may uniquely contribute to the inflammatory cycle.

Influence of subunit combinations on signaling by receptors for oncostatin M, leukemia inhibitory factor, and interleukin-6

Oncostatin M (OSM), leukemia inhibitory factor (LIF), and interleukin-6 (IL-6) induce expression of a similar set of acute phase plasma protein genes in hepatic cells. The redundant action of these cytokines has been ascribed to the involvement of the common signal-transducing receptor subunit, gp130, in combination with cytokine-specific, ligand-binding subunits. To define the specificity of the signal transduction by the LIF/OSM receptor (a heterodimer of gp130 and LIF receptor (LIFR)) and the OSM-specific receptor (a heterodimer of gp130 and OSM receptor (OSMR)), we reconstituted the receptor function by transfection into receptor-negative Hep3B hepatoma cells. Both receptors activate DNA binding activity of STAT1, -3, and -5B and induce gene transcription through IL-6-responsive elements. The signaling-competent cytoplasmic domain regions of OSMR and LIFR were defined by the analysis of progressive carboxyl-terminal deletion constructs. The 36 residue carboxyl-terminal region containing the distal box 3 sequence motif of OSMR is required for signal transduction by the OSM-specific receptor. In contrast, signaling by LIFR did not display the same requirement for receptor domains and was not strictly dependent on the box 3 elements. The signaling by endogenous LIF and OSM receptors differed from that by IL-6R by the prominent activation of STAT5 as shown in the mouse hepatoma cell line, Hepa-1. The data suggest that the signaling specificity of the receptors for the three cytokines is determined by the composition of the cytoplasmic domains associated in the signal-competent receptor complex and that the signaling is not identical among these cytokine receptors.

Oncostatin M: a new potent inhibitor of iodine metabolism inhibits thyroid peroxidase gene expression but not DNA synthesis in porcine thyroid cells in culture

The functions of thyroid cells are regulated by a number of cytokines and growth factors in addition to TSH. Recent studies have revealed that several cytokines including interleukin (IL)-6 are involved in thyroid dysfunction. Oncostatin M (OSM) is a glycoprotein belonging to the same family of cytokines as IL-6, to which it is related by sequence and structural homology and the use of the signal-transducing receptor component gp130. We, therefore, studied the effect of OSM on iodide uptake and DNA synthesis by porcine thyroid cells in culture. OSM increased c-fos and c-jun mRNA levels but did not stimulate DNA synthesis. OSM inhibited iodide uptake stimulated by TSH; while IL-6 also inhibited iodide uptake, it was only about one-tenth as potent. IL-6 had about the same potency as OSM when it was added with soluble IL-6 receptor. OSM had no effect on cAMP production but inhibited iodide uptake stimulated by 8-bromo-cAMP and forskolin. These findings suggest that OSM exerts its inhibitory effects at the post-cAMP production step(s). OSM also inhibited thyroid peroxidase mRNA levels but had little effect on thyroglobulin mRNA levels. Investigations of the signal transduction system showed that gp130 and leukemia inhibitory factor (LIF) receptor beta subunit mRNA were detectable in porcine thyroid cells by reverse transcription (RT)-polymerase chain reaction (PCR). Together with the report that serum OSM and IL-6 concentrations are elevated to the same levels in patients with sepsis, these results suggest that OSM may contribute to the thyroid dysfunction in this condition.

Acute phase proteins and transformed cells

Acute phase proteins (APP) are plasma proteins whose concentration and glycosylation alters in response to tissue injury, inflammation, or tumor growth. Significant interspecies and sex differences in APP response exist. APP are produced mainly by hepatocytes, and their synthesis and glycosylation are controlled by a network consisting of cytokines, their soluble receptors, and glucocorticoids. The major cytokines involved in these processes belong to a group of interleukin-6-type cytokines that act through the hematopoietin receptor complex on hepatocytes and JAK-STAT signal transduction pathway. Transformed cells (hepatoma) display significant differences in synthesis of APP, cytokine responsiveness, expression of cytokine-receptor subunits and signal-transduction machinery. The most striking variability relates to the glycosylation alterations induced by cytokines. However, transformed cells (hepatoma) form a basic model for studying and understanding mechanisms controlling the synthesis and glycosylation of APP. Furthermore, APP may be secreted by transformed (tumor) cells of various origins and may display a growth factor-like function in certain cancer types.

Oncostatin M differentially regulates tissue inhibitors of metalloproteinases TIMP-1 and TIMP-3 gene expression in human synovial lining cells

Tissue inhibitor of metalloproteinases (TIMP) 1, 2 and 3 are related proteins that can form complexes with all known matrix metalloproteinases (MMPs). They inhibit the action of MMPs on extracellular matrix components. The balance of MMPs and TIMPs is important for tissue remodeling and its disturbance is believed to play a crucial role in pathophysiological processes such as tumor metastasis, destruction of cartilage and fibrosis. Cytokines and growth factors were found to regulate TIMPs and MMPs in a complex manner. In order to better understand the role of TIMPs in inflammatory joint diseases we have studied in vitro the regulation of TIMP-1 and TIMP-3 by inflammatory cytokines in cultured human synovial lining cells. We found that transforming growth factor beta 1 as well as interleukin-1 beta induce gene expression of both TIMP-1 and TIMP-3. In contrast, oncostatin M, an interleukin-6-type cytokine produced by activated T-lymphocytes and monocytes, had a differential effect on TIMP mRNA levels. After oncostatin M treatment, TIMP-1 expression was up-regulated but basal, as well as interleukin-1 beta-induced, TIMP-3 expression was inhibited. Interleukin-6 itself had no effect on synovial lining cells but a complex of interleukin-6 and the soluble interleukin-6 receptor induced activation of signal transducer and activator of transcription (STAT) factors in these cells and regulated TIMP-1 and TIMP-3 expression in a similar fashion as oncostatin M. Since TIMP-3 is matrix-associated whereas TIMP-1 is found in many body fluids, the role of oncostatin M during inflammatory processes might be to promote ECM degradation in the local environment but to prevent it systemically.