Neurotrophic role of interleukin-6 and soluble interleukin-6 receptors in N1E-115 neuroblastoma cells

Intraperitoneal administration of adipose tissue-derived stem cells for the rescue of retinal degeneration in a mouse model via indigenous CNTF up-regulation by IL-6

As the world's population begins to age, retinal degeneration is an increasing problem, and various treatment modalities are being developed. However, there have been no therapies for degenerative retinal conditions that are not characterized by neovascularization. We investigated whether transplantation of mouse adipose tissue-derived stem cells (mADSC) into the intraperitoneal space has a rescue effect on NaIO3 -induced retinal degeneration in mice. In this study, mADSC transplantation recovered visual function and preserved the retinal outer layer structure compared to the control group without any integration of mADSC into the retina. Moreover, endogenous ciliary neurotrophic factor (CNTF) was elevated in the retinas of mADSC-treated mice. We found that lipopolysaccharide (LPS) or LPS-stimulated monocyte supernatant induced the secretion of granulocyte colony stimulating factor (GCSF), CD54, CXCL10, interleukin-6 (IL-6), and CCL5 from the mADSC by cytokine array. Network inference was conducted to investigate signaling networks related to CNTF regulation. Based on bioinformatics data, the expression of IL-6 was related to the expression of CNTF. Additionally, intravitreal injection of IL-6 in rats produced up-regulation of endogenous CNTF in the retina. mADSC had a rescue effect on retinal degeneration through the up-regulation of endogenous CNTF by IL-6. Thus, transplantation of mADSC could be a potential treatment option for retinal degeneration.

Low-Dose Pulsatile Interleukin-6 As a Treatment Option for Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) remains one of the most common and serious complications of diabetes. Currently, pharmacological agents are limited to treating the pain associated with DPN, and do not address the underlying pathological mechanisms driving nerve damage, thus leaving a significant unmet medical need. Interestingly, research conducted using exercise as a treatment for DPN has revealed interleukin-6 (IL-6) signaling to be associated with many positive benefits such as enhanced blood flow and lipid metabolism, decreased chronic inflammation, and peripheral nerve fiber regeneration. IL-6, once known solely as a pro-inflammatory cytokine, is now understood to signal as a multifunctional cytokine, capable of eliciting both pro- and anti-inflammatory responses in a context-dependent fashion. IL-6 released from muscle in response to exercise signals as a myokine and as such has a unique kinetic profile, whereby levels are transiently elevated up to 100-fold and return to baseline levels within 4 h. Importantly, this kinetic profile is in stark contrast to long-term IL-6 elevation that is associated with pro-inflammatory states. Given exercise induces IL-6 myokine signaling, and exercise has been shown to elicit numerous beneficial effects for the treatment of DPN, a causal link has been suggested. Here, we discuss both the clinical and preclinical literature related to the application of IL-6 as a treatment strategy for DPN. In addition, we discuss how IL-6 may directly modulate Schwann and nerve cells to explore a mechanistic understanding of how this treatment elicits a neuroprotective and/or regenerative response. Collectively, studies suggest that IL-6, when administered in a low-dose pulsatile strategy to mimic the body's natural response to exercise, may prove to be an effective treatment for the protection and/or restoration of peripheral nerve function in DPN. This review highlights the studies supporting this assertion and provides rationale for continued investigation of IL-6 for the treatment of DPN.

Fas and TRAIL 'death receptors' as initiators of inflammation: Implications for cancer

Fas (CD95/APO-1) and TRAIL (CD253, TNFSF10, APO2) are members of a subset of the TNF receptor superfamily known as 'death receptors'. To date, the overwhelming majority of studies on Fas and TRAIL (TNF-related apoptosis-inducing ligand) have explored the role of these receptors as initiators of apoptosis. However, sporadic reports also suggest that engagement of the Fas and TRAIL receptors can lead to other outcomes such as cytokine and chemokine production, cell proliferation, cell migration and differentiation. Indeed, although transformed cells frequently express Fas and TRAIL, most do not undergo apoptosis upon engagement of these receptors and significant effort has been devoted toward exploring how to sensitize such cells to the pro-apoptotic effects of 'death receptor' stimulation. Moreover, the expression of Fas and TRAIL receptors is greatly elevated in many cancer types such as hepatocellular carcinoma, renal carcinoma and ovarian cancer, suggesting that such tumors benefit from the expression of these receptors. Furthermore, several studies have shown that tumor proliferation, progression and invasion can be impaired through blocking or downregulation of Fas expression, but the mechanistic basis for these effects is largely unknown. Thus, the characterization of Fas and TRAIL as 'death receptors' is a gross oversimplification, especially in the context of cancer. It is becoming increasingly clear that 'death receptor' engagement can lead to outcomes, other than apoptosis, that become subverted by certain tumors to their benefit. Here we will discuss death-independent outcomes of Fas and TRAIL signaling and their implications for cancer.

F-spondin plays a critical role in murine neuroblastoma survival by maintaining IL-6 expression

F-spondin is associated with the regulation of axonal growth and the development of the nervous system. Its mechanism of action, however, is not clearly understood. In this study, we found that murine neuroblastoma Neuro-2a cells expressed a significant level of IL-6, but only trace amounts of IL-12, tumor necrosis factor alpha and nitric oxide. Knock-down of F-spondin mRNA in murine neuroblastoma NB41A3 and Neuro-2a cells using small interfering RNAs led to decreased IL-6 levels along with lower resistance to serum starvation and cytotoxic amyloid beta(1-42) (Abeta(1-42)) peptide. Restoring decline of F-spondin or IL-6 induced by F-spondin knock-down through adding exogenous F-spondin, IL-6 or over-expressing F-spondin reversed the cell death induced by Abeta(1-42) peptide or serum starvation. The decrease of IL-6 level was positively correlated with decrease of NF-kappaB and inhibition of p38 mitogen-activated protein kinase (MAPK). Over-expressing MEKK, a kinase activator of the p38 MAPK pathway, increased IL-6 production, restored the decrease of p38 induced by F-spondin knock-down, and rescued the cells from death caused by Abeta(1-42) peptide. Taken together, these results suggest that F-spondin may play a critical role in murine neuroblastoma survival under adverse conditions by maintaining IL-6 level via a MEKK/p38 MAPK/NF-kappaB-dependent pathway.

Interleukin-6 in the bone marrow microenvironment promotes the growth and survival of neuroblastoma cells

Neuroblastoma, the second most common solid tumor in children, frequently metastasizes to the bone marrow and the bone. Neuroblastoma cells present in the bone marrow stimulate the expression of interleukin-6 (IL-6) by bone marrow stromal cells (BMSC) to activate osteoclasts. Here we have examined whether stromal-derived IL-6 also has a paracrine effect on neuroblastoma cells. An analysis of the expression of IL-6 and its receptor, IL-6R, in 11 neuroblastoma cell lines indicated the expression of IL-6 in 4 cell lines and of IL-6R in 9 cell lines. Treatment of IL-6R-positive cells with recombinant human IL-6 resulted in signal transducer and activator of transcription-3 and extracellular signal-regulated kinase-1/2 activation. Culturing IL-6R-positive neuroblastoma cells in the presence of BMSC or recombinant human IL-6 increased proliferation and protected tumor cells from etoposide-induced apoptosis, whereas it had no effect on IL-6R-negative tumor cells. In vivo, neuroblastoma tumors grew faster in the presence of a paracrine source of IL-6. IL-6 induced the expression of cyclooxygenase-2 in neuroblastoma cells with concomitant release of prostaglandin-E2, which increased the expression of IL-6 by BMSC. Supporting a role for stromal-derived IL-6 in patients with neuroblastoma bone metastasis, we observed elevated levels of IL-6 in the serum and bone marrow of 16 patients with neuroblastoma bone metastasis and in BMSC derived from these patients. Altogether, the data indicate that stromal-derived IL-6 contributes to the formation of a bone marrow microenvironment favorable to the progression of metastatic neuroblastoma.

Interleukin-6 and soluble interleukin-6 receptor levels as markers of disease extent and prognosis in neuroblastoma

PURPOSE

To explore the relationships between interleukin-6 (IL-6) and soluble IL-6 receptor (sIL-6R) levels and disease extent and clinical outcome in childhood neuroblastoma.

EXPERIMENTAL DESIGN

Pretreatment peripheral blood (PB; n=53) and bone marrow (n=18) samples from patients with neuroblastoma were assayed by ELISA for IL-6 and sIL-6R. PB values were compared with healthy pediatric controls (n=28).

RESULTS

PB IL-6 levels were significantly elevated in patients with high-risk disease compared with those with low and intermediate risk disease (23.9 versus 4.3 pg/mL; P<0.001) and the normal control group (23.9 versus 3.3 pg/mL; P<0.001). Similarly, bone marrow IL-6 levels were higher in high-risk patients when compared with low- and intermediate-risk patients (15 versus 0 pg/mL; P<0.02). Other factors correlated with higher IL-6 levels were age of >18 months, bony metastases, and unfavorable histology. sIL-6R levels were not significantly correlated with disease stage. Patients with detectable PB IL-6 at diagnosis had significantly lower event-free survival rates (P<0.008). sIL-6R levels <2.5 x 10(4) pg/mL were also associated with a significantly worse event-free survival (P=0.016).

CONCLUSION

Elevated PB IL-6 levels correlated with features of high-risk neuroblastoma and poor prognosis in this population. Decreased PB sIL-6R levels correlated with the presence of metastatic disease. Further study of these markers in children with neuroblastoma seems warranted.

Inflammation, Depression and Dementia: Are they Connected?

Chronic inflammation is now considered to be central to the pathogenesis not only of such medical disorders as cardiovascular disease, multiple sclerosis, diabetes and cancer but also of major depression. If chronic inflammatory changes are a common feature of depression, this could predispose depressed patients to neurodegenerative changes in later life. Indeed there is now clinical evidence that depression is a common antecedent of Alzheimer's disease and may be an early manifestation of dementia before the cognitive declines becomes apparent. This review summarises the evidence that links chronic low grade inflammation with changes in brain structure that could precipitate neurodegenerative changes associated with Alzheimer's disease and other dementias. For example, neuronal loss is a common feature of major depression and dementia. It is hypothesised that the progress from depression to dementia could result from the activation of macrophages in the blood, and microglia in the brain, that release pro-inflammatory cytokines. Such cytokines stimulate a cascade of inflammatory changes (such as an increase in prostaglandin E2, nitric oxide in addition to more pro-inflammatory cytokines) and a hypersecretion of cortisol. The latter steroid inhibits protein synthesis thereby reducing the synthesis of neurotrophic factors and preventing reairto damages neuronal networks. In addition, neurotoxic end products of the tryptophan-kynurenine pathway, such as quinolinic acid, accumulate in astrocytes and neurons in both depression and dementia. Thus increased neurodegeneration, reduced neuroprotection and neuronal repair are common pathological features of major depression and dementia. Such changes may help to explain why major depression is a frequent prelude to dementia in later life.

Mechanisms of invasion and metastasis in human neuroblastoma

Neuroblastoma is the second most common solid tumor in children that is metastatic in 70% of patients at the time of diagnosis. The ability of neuroblastoma cells to colonize distant organs like the bone marrow and the bone is the result of close interactions between tumor cells and the microenvironment. Significant progress has been recently made in our understanding of the mechanisms that promote the colonization and invasion of the bone by neuroblastoma cells and these mechanisms are reviewed in this article. How this understanding is now allowing us to test new therapeutic agents specifically targeted at interfering with neuroblastoma metastasis is then discussed.

The regulatory role of Hyper-IL-6 in the differentiation of myeloid and erythroid progenitors derived from human cord blood

This study was designed to investigate the regulatory role of soluble interleukin-6 receptor (sIL-6R) and interleukin-6 (IL-6) fusion protein (Hyper-IL-6) in the differentiation of human myeloid and erythroid progenitors by a serum-free liquid suspension culture system, using the human cord blood-derived CD34(+)CD38(-) cells as a target. We found that Hyper-IL-6 promoted the generation of CD15(+) granulocytic and CD14(+) monocytic cells and suppressed that of CD14(-)CD1a(+) dendritic cells from CD36(-)CD15(-)CD14(-)CD1a(-)IL-6R(+) myeloid progenitors. Conversely, CD34(+)CD38(-) cell-derived early erythroid progenitors were negative for IL-6R expression. Hyper-IL-6 potentiated the generation of CD36(+)glycophorinA(high) mature erythroid cells from the IL-6R(-) early erythroid progenitors. Our results indicate that Hyper-IL-6 augments the generation of CD15(+) granulocytic, CD14(+) monocytic and CD36(+)glycophorinA(high) cell and suppresses that of CD14(-)CD1a(+) dendritic cells.

Tumor-derived macrophage migration inhibitory factor (MIF) inhibits T lymphocyte activation

Macrophage migration inhibitory factor (MIF) is a multi-functional cytokine that is considered a pro-inflammatory cytokine. However, our studies show that MIF, when produced in super-physiological levels by a murine neuroblastoma cell line (Neuro-2a) exceeding those normally seen during an immune response, inhibits cytokine-, CD3-, and allo-induced T-cell activation. MIF is also able to inhibit T cells that have already received an activation signal. The T-cell inhibitory effects of culture supernatants from neuroblastoma cells were reversed when the cells were transfected with dicer-generated si-RNA to MIF. When T cells were activated in vitro by co-culture with interleukin (IL)-2 and IL-15 and analyzed for cytokine production in the presence or absence of MIF-containing culture supernatant, inhibition of T-cell proliferation and induced cell death were observed even as the treated T cells produced high levels of interferon-gamma (IFN-gamma). The inhibitory effects of MIF were partially reversed when lymphocytes from IFN-gamma knockout mice were tested. We propose that the high levels of MIF produced by neuroblastoma cause activation induced T-cell death through an IFN-gamma pathway and may eliminate activated T cells from the tumor microenvironment and thus contribute to escape from immune surveillance.

Cobalamin (vitamin B(12)) positively regulates interleukin-6 levels in rat cerebrospinal fluid

We have previously demonstrated that the repeated intracerebroventricular (i.c.v.) microinjection of interleukin-6 (IL-6) prevented the myelinolytic lesions of cobalamin-deficient (Cbl-D) central neuropathy [or subacute combined degeneration (SCD)] in totally gastrectomized (TGX) rats. We therefore hypothesized that cobalamin (Cbl) may actually regulate IL-6 levels in rat cerebrospinal fluid (CSF). We measured IL-6 levels in the CSF of rats made Cbl-D by means of total gastrectomy (TG) or chronic feeding with a Cbl-D diet and killed at different times from the beginning of the experiment, and found that IL-6 levels significantly and progressively decreased over time. Chronic 2-month Cbl administration started 1 week after surgery prevented the decrease in IL-6 levels and, when it was started 2 months after surgery, it significantly increased IL-6 levels, but not to presurgical values. We also investigated whether IL-6 decrease might be ultimately due to the Cbl-deficiency-linked decrease in epidermal growth factor (EGF) synthesis. Repeated i.c.v. administrations of EGF to TGX rats did not modify CSF IL-6 levels. These results, together with those of a previous study showing the preventive effect of IL-6 treatment on SCD lesions, demonstrate that: (i) Cbl selectively regulates CSF IL-6 levels; and (ii) decreased IL-6 availability plays a role in the pathogenesis of the experimental SCD, in which no evidence of inflammatory and/or immunological reaction has been observed.