Two-dimensional gel analysis of secreted proteins induced by interleukin-1 beta in rat astrocytes

Deciphering variability in the role of interleukin-1β in Parkinson's disease

Although the role of inflammation in neurodegeneration has been well acknowledged, less is known on the issue of each cytokine in specific neurodegenerative diseases. In this review, we will present evidence elucidating that interleukin-1β (IL-1β) has a multi-faceted character in pathogenesis of Parkinson's disease, which is a progressive neurodegenerative disorder. Increased levels of IL-1β were found in PD patients. Besides, PD symptoms were observed in IL-1β wild-type, but not deficient, animals. These lines of evidence suggest that IL-1β may contribute to the initiation or progression of PD. On the other hand, some studies reported decreased levels of IL-1β in PD patients. Also, genetic studies provided evidence suggesting that IL-1β may protect individuals against PD. Presumably, the broad range of IL-1β role is due to its interaction with both upstream and downstream mediators. Differences in IL-1β levels could be because of glia population (i.e. microglia and astrocytes), mitogen-activated protein kinase and nuclear factor κ light-chain-enhancer of activated B cells signaling pathways, and several mediators (including cyclooxygenase, neurotrophic factors, reactive oxygen species, caspases, heme oxygenase-1, and matrix metalloproteinases). Although far from practice at this point, unraveling theoretical therapeutic targets based on the up-down IL-1β neuroweb could facilitate the development of strategies that are likely to be used for pharmaceutical designs of anti-neurodegenerative drugs of the future.

Activation of C6 glioblastoma cell ceruloplasmin expression by neighboring human brain endothelia-derived interleukins in an in vitro blood-brain barrier model system

Background

Iron transport across the blood–brain barrier (BBB) involves the cooperation of brain microvascular endothelial cells (BMVEC) and their neighboring astrocytes. Astrocytes secrete a soluble form of ceruloplasmin (sCp) which, in turn, acts to export iron from ferroportin (Fpn) on the basolateral surface of BMVEC. Although regulation of astrocyte sCp gene expression has been demonstrated to be influenced by interleukin-1 beta (IL-1β) and interleukin-6 (IL-6), the role of neighboring BMVEC in this regulation has yet to be determined and is the basis for this work.

Results

We provide evidence that human BMVEC (hBMVEC) IL-1β and IL-6 positively influence the expression of sCp transcript by neighboring C6 glioma cells (astrocytes). The effect of hBMVEC on C6 glioma sCp expression at the level of transcript and protein was repressed via the addition of IL-1β and IL-6 pathway inhibitors (IL-1 receptor antagonist protein and SC144, respectively). Stimulation of hBMVEC interleukin gene expression by apical exposure to bacterial endotoxin lipopolysaccharide significantly enhanced hBMVEC-mediated C6 glioma sCp gene expression.

Conclusion

hBMVEC influence the gene expression of neighboring C6 glioma sCp. This change in gene expression is mediated by the secretion of IL-1β and IL-6 from hBMVEC. Furthermore, the hBMVEC-induced increase in neighboring C6 glioma sCp gene expression leads to an increased rate of hBMVEC iron efflux. Taken together, our results indicate that hBMVEC-secreted cytokine activity increases the gene expression of neighboring C6 glioma sCp, which reciprocally acts on basolateral hBMVEC Fpn to enhance brain iron import.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-014-0065-7) contains supplementary material, which is available to authorized users.

[The relevance of the inflammatory response in the injured brain]

Research efforts in recent years have defined traumatic brain injury (TBI) as a predominantly immunological and inflammatory disorder. This perception is based on the fact that the overwhelming neuroinflammatory response in the injured brain contributes to the development of posttraumatic edema and to neuropathological sequelae which are, in large part, responsible for the adverse outcome. While the "key" mediators of neuroinflammation, such as the cytokine cascade and the complement system, have been clearly defined by studies in experimental TBI models, their exact pathways of interaction and pathophysiological implications remain to be further elucidated. This lack of knowledge is partially due to the concept of a "dual role" of the neuroinflammatory response after TBI. This notion implies that specific inflammatory molecules may mediate diverse functions depending on their local concentration and kinetics of expression in the injured brain. The inflammation-induced effects range from beneficial aspects of neuroprotection to detrimental neurotoxicity. The lack of success in pushing anti-inflammatory therapeutic concepts from"bench to bedside" for patients with severe TBI strengthens the further need for advances in basic research on the molecular aspects of the neuroinflammatory network in the injured brain. The present review summarizes the current knowledge from experimental studies in this field of research and discusses potential future targets of investigation.

Interleukin-1β enhances the angiotensin-induced expression of plasminogen activator inhibitor-1 through angiotensin receptor upregulation in human astrocytes

Plasminogen activator inhibitor-1 (PAI-1) regulates not only fibrinolysis but extracellular matrix remodeling, and angiotensin II is known to play an important role in controlling the expression of PAI-1 in astrocytes. We have studied the effect of interleukin-1beta (IL-1beta), one of major cytokines also active in the nervous system, on the angiotensin II-induced expression of PAI-1 in human astrocytes. Cultures of normal human astrocytes were stimulated with IL-1beta and angiotensin II, and the expression of mRNAs for angiotensin II type 1 receptor (AT1) and PAI-1 was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) or real-time quantitative PCR. PAI-1 protein in astrocyte-conditioned medium was measured by enzyme-linked immunosorbent assay (ELISA). IL-1beta enhanced the expression of AT1 in astrocytes in time- and concentration-dependent manners. After 24-h stimulation, 10 ng/ml IL-1beta and 10 nM angiotensin II increased the levels of PAI-1 protein in astrocyte-conditioned medium by 1.9-fold and 1.8-fold of the basal value, respectively. There was no synergistic effect when the cells were stimulated simultaneously with IL-1beta and angiotensin II. When the cells were stimulated, with angiotensin II, 16 h after the stimulation with IL-1beta, the production of PAI-1 was enhanced by 1.4-fold as compared to the cells stimulated only with IL-1beta. CV-11794, an AT1 antagonist, inhibited the enhanced PAI-1 production in response to angiotensin II. We conclude that IL-1beta increases angiotensin II-induced PAI-1 secretion by astrocytes through the induction of AT1, and the enhanced secretion of PAI-1 may modulate functions of plasminogen activators in the nervous system.

Case of desmoplastic infantile ganglioglioma secreting ceruloplasmin

Desmoplastic infantile ganglioglioma is a rare World Health Organization (WHO) grade I tumor commonly arising in early infancy and usually presenting with both solid and cystic components. We report a case of a large midline-enhancing desmoplastic infantile ganglioglioma in which newly formed cysts in communication with lateral ventricles contained highly proteinaceous fluid. Proteomic analysis of the fluid showed three proteins not normally found in cerebrospinal fluid. Immunohistochemical analysis of the tumor sample showed that the desmoplastic infantile ganglioglioma produced a high concentration of ceruloplasmin, which probably accounts for most of the 30- to 40-fold increase in protein compared with normal cerebrospinal fluid. To our knowledge, this is the first report of ceruloplasmin secretion by a brain tumor, and ongoing studies on the mechanism might yield novel approaches to reducing cyst production and protein content in an otherwise stable solid tumor.

Activation of the spinal cord complement cascade might contribute to mechanical allodynia induced by three animal models of spinal sensitization

The present series of experiments examined whether the complement cascade might play a key role in the expression of mechanical allodynia. Soluble complement receptor 1 (sCR1) was used to block the activation of the membrane attack pathway of the complement cascade. In doing so, sCR1 prevents the formation of the biologically active end products C3a, C5a, and membrane attack complexes (MACs). Intrathecal sCR1 had no effect on the behavioral responses of control groups. In contrast, blockade of this pathway abolished the expression of mechanical allodynia induced by peripheral nerve inflammation (sciatic inflammatory neuropathy model), partial sciatic nerve injury (chronic constriction injury model), and intrathecal injection of human immunodeficiency virus type 1 gp120, a viral envelope protein that activates glia. The fact that enhanced nociception was prevented or reversed in all 3 paradigms suggests that complement might be broadly involved in spinally mediated pain enhancement. The mechanisms whereby complement activation might potentially affect the functioning of microglia, astrocytes, and neurons are discussed. The complement cascade has not been previously implicated in spinal sensitization. These data suggest that complement activation within the spinal cord might contribute to enhanced pain states and provide additional evidence for immune regulation of pain transmission.

Interleukin-1beta up-regulates iron efflux in rat C6 glioma cells through modulation of ceruloplasmin and ferroportin-1 synthesis

A number of pathologies, including neurodegeneration and inflammation, have been associated with iron dysmetabolism in the brain. Hence, systems involved in iron homeostasis at the cellular level have aroused considerable interest in recent years. The iron exporter ferroportin-1 (FP) and the multicopper oxidase ceruloplasmin (CP) are essential for iron efflux from cells. By using RT-PCR, we demonstrate that FP and CP gene expression is up-regulated by treatment with the pro-inflammatory cytokine IL-1beta in rat C6 cells, taken as a glial cellular model. Following stimulation with IL-1beta, a higher expression level of CP and FP was also confirmed by Western blotting. Moreover, IL-1beta has been found to increase iron efflux from C6 cells, suggesting that both proteins may play a crucial role in iron homeostasis in pathological brain conditions, such as inflammatory and/or neurodegenerative diseases.

Astrocytic ceruloplasmin expression, which is induced by IL-1beta and by traumatic brain injury, increases in the absence of the IL-1 type 1 receptor

IL-1alpha and IL-1beta are induced immediately after insults to the brain, and signaling through the type 1 IL-1 receptor is essential for a normal microglial and astroglial response to injury. To better understand which genes are induced in astrocytes by IL-1beta, we used the unbiased technique of differential display to analyze mouse astroglial gene expression after IL-1beta treatment. Two novel genes were induced, as well as the gene for ceruloplasmin, a ferroxidase with antioxidant properties. Ceruloplasmin was analyzed further by Northern and Western blot. RNA and protein levels of ceruloplasmin were increased when astrocytes were treated with IL-1beta. To determine whether the IL-1 type 1 receptor (IL-1R1) is essential for the injury-induced expression of ceruloplasmin, a Western blot analysis was performed after a traumatic brain injury on mice that were IL-1R1-deficient. Ceruloplasmin increased significantly above controls after injury; however, injury-induced levels of ceruloplasmin were lower in IL-1R1-deficient (2.7-fold increase) than in the wild-type animals (3.5-fold increase). These data indicate that while IL-1R1 deletion has a slight effect on ceruloplasmin expression, it is not essential for either the basal or the induced expression of ceruloplasmin in vivo. Since ceruloplasmin buffers free copper, oxidizes ferrous iron, and catalyzes the dismutation of free radicals, increased levels of ceruloplasmin likely protect neurons and glia from sustaining damage after injury. Furthermore, as the IL-1R1 has been proposed to be a target for achieving neuroprotection after injury, these data suggest that the protection afforded by ceruloplasmin will be retained even when the IL-1R1 is antagonized.