Interferon-beta inhibits mitogen induced astrocyte proliferation in vitro

Neuroglial components of brain lesions may provide new therapeutic strategies for multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune and demyelinating disease of the central nervous system (CNS) which leads to focal demyelinated lesions in the brain and spinal cord. Failure of remyelination contributes to chronic disability in young adults. Characterization of events occurring during the demyelination and remyelination processes and those of which subsequently limit remyelination or contribute to demyelination can provide the possibility of new therapies development for MS. Most of the currently available therapies and investigations modulate immune responses and mediators. Since most therapeutic strategies have unsatisfied outcomes, developing new therapies that enhance brain lesion repair is a priority. A close look at cellular and chemical components of MS lesions will pave the way to a better understanding of lesions pathology and will provide possible opportunities for repair strategies and targeted pharmacotherapy. This review summarizes the lesion components and features, particularly the detrimental elements, and discusses the possibility of suggesting new potential targets as therapies for demyelinating diseases like MS.

Molecular Effects of FDA-Approved Multiple Sclerosis Drugs on Glial Cells and Neurons of the Central Nervous System

Multiple sclerosis (MS) is characterized by peripheral and central inflammatory features, as well as demyelination and neurodegeneration. The available Food and Drug Administration (FDA)-approved drugs for MS have been designed to suppress the peripheral immune system. In addition, however, the effects of these drugs may be partially attributed to their influence on glial cells and neurons of the central nervous system (CNS). We here describe the molecular effects of the traditional and more recent FDA-approved MS drugs Fingolimod, Dimethyl Fumarate, Glatiramer Acetate, Interferon-β, Teriflunomide, Laquinimod, Natalizumab, Alemtuzumab and Ocrelizumab on microglia, astrocytes, neurons and oligodendrocytes. Furthermore, we point to a possible common molecular effect of these drugs, namely a key role for NFκB signaling, causing a switch from pro-inflammatory microglia and astrocytes to anti-inflammatory phenotypes of these CNS cell types that recently emerged as central players in MS pathogenesis. This notion argues for the need to further explore the molecular mechanisms underlying MS drug action.

Neurodegeneration in multiple sclerosis: novel treatment strategies

In recent years it has become clear that the neuronal compartment already plays an important role early in the pathology of multiple sclerosis (MS). Neuronal injury in the course of chronic neuroinflammation is a key factor in determining long-term disability in patients. Viewing MS as both inflammatory and neurodegenerative has major implications for therapy, with CNS protection and repair needed in addition to controlling inflammation. Here, the authors' review recently elucidated molecular insights into inflammatory neuronal/axonal pathology in MS and discuss the resulting options regarding neuroprotective and regenerative treatment strategies.

Regulatory effects of interferon-β on osteopontin and interleukin-17 expression in multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease characterized by autoimmune inflammation in the central nervous system. Despite over a decade of use of interferon-β (IFN-β) in the treatment of MS, its mechanisms of action are still not fully elucidated. New data now demonstrate that the 2 important proinflammatory cytokines involved in the pathogenesis of MS, osteopontin (OPN) and interleukin-17 (IL-17), are regulated by IFN-β. This review discusses the role of OPN and IL-17 in the development of MS and how the downregulation of the levels of OPN and interleukin-17 contributes to the therapeutic effects of IFN-β in MS.

Immunomodulatory drug treatment in multiple sclerosis

The fundamental role of inflammatory immune processes in the pathology of multiple sclerosis (MS) provides the rationale for immunomodulatory therapies that attempt to shift the immune system from pro-inflammatory to anti-inflammatory pathways and induce regulatory mechanisms. Growing understanding of immune cellular and molecular mechanisms together with modern biotechnology engendered promising immunomodulatory treatment strategies, with novel mechanisms of actions and different levels of specificity. These include inhibitory molecules, monoclonal antibodies, cell therapies and agents that are administered orally or by infrequent infusions. Several of these treatments have demonstrated impressive efficacy in Phase II and III clinical trials by reducing disease activity and accumulation of disability. However, with the advent of potent therapies, rare but severe adverse effects, such as CNS infections and malignancies, have occurred. This article describes current and upcoming immunomodulatory strategies for MS therapy. The potential of immunomodulatory treatments to counteract the inflammatory characteristics of MS and support neuroprotective processes is discussed.

Neuronal injury in chronic CNS inflammation

INTRODUCTION

Multiple sclerosis (MS) is the most common chronic inflammatory disease of the central nervous system which is characterized by inflammatory demyelination and neurodegeneration. Neurological symptoms include sensory disturbances, optic neuritis, limb weakness, ataxia, bladder dysfunction, cognitive deficits and fatigue.

PATHOPHYSIOLOGY

The inflammation process with MS is promoted by several inflammatory cytokines produced by the immune cells themselves and local resident cells like activated microglia. Consecutive damaging pathways involve the transmigration of activated B lymphocytes and plasma cells, which synthesize antibodies against the myelin sheath, boost the immune attack, and result in ultimate loss of myelin. Likewise, activated macrophages and microglia are present outside the lesions in the normal-appearing CNS tissue contributing to tissue damage. In parallel to inflammatory demyelination, axonal pathology occurs in the early phase which correlates with the number of infiltrating immune cells, and critically contributes to disease severity. The spectrum of neuronal white matter and cortical damage ranges from direct cell death to subtle neurodegenerative changes such as loss of dendritic ramification and the extent of neuronal damage is regarded as a critical factor for persisting neurological deficits. Under normal conditions, CNS microglia safeguards organ integrity by constantly scanning the tissue and responding rapidly to danger signals. The main task of microglial cells is to encapsulate dangerous foci and remove apoptotic cells and debris to protect the surrounding CNS tissue; this assists with tissue regeneration in toxin-induced demyelination. In the absence of lymphocytic inflammation and in the context of non-autoimmune, pathogen-associated triggered inflammation, microglial cells protect the neuronal compartment. These mechanisms seem to be inverted in MS and other chronic neurodegenerative disorders because activated microglia and peripherally derived macrophages are shifted towards a strongly pro-inflammatory phenotype and produce the proinflammatory cytokines TNF-α and interleukin (IL)1-β, as well as potentially neurotoxic substances including nitric oxide, oxygen radicals and proteolytic enzymes. Microglial silencing reduces clinical severity, demonstrating their active involvement in damage processes and in the immune attack against the CNS. In light of this, it is questionable whether microglia and monocyte-derived macrophages, the very last downstream effector cells in the immune reaction, actually have the capacity to influence their fate. It is more likely that the adaptive immune system orchestrates the attack against CNS cells and drives microglia and macrophages to attack oligodendrocytes and neurons.

NEUROPROTECTIVE STRATEGIES

Currently, Glatiramer acetate (GA) and the interferon-β (IFN-β) variants are established as first-line disease modifying treatments that reduce the relapse rate, ameliorate relapse severity and delay the progression of disability in patients with relapsing-remitting MS. Similarily, sphingosine-1-phosphate (S1P) receptor agonists which influence lymphocyte migration through T cells-trapping in secondary lymphatic organs ameliorates astrogliosis and promotes remyelination by acting on S1P-receptors on astrocytes and oligodendrocytes. Ion channel blockers (e.g. sodium channel blockers), currently used for other indications, are now tested in neurodegenerative diseases to restore intracellular ion homeostasis in neurons. Axonal degeneration was significantly reduced and functional outcome was improved during treatment with Phenytoin, Flecainide and Lamotrigine. Although evidence for a direct protective effect on axons is still missing, additional immune-modulatory actions of sodium channel blockers on microglia and macrophages are likely available. In vitro-studies in axons subjected to anoxia in vitro or exposure to elevated levels of nitric oxide (NO) in vivo demonstrated the involvement of a direct effect on axons. As increased intracellular calcium levels contribute to axonal damage through activation of different enzymes such as proteases, blockade of voltage gated calcium channels is another promising target. For example, nitrendipin and bepridil ameliorate axonal loss and clinical symptoms in different models of chronic neurodegeneration. In addition to these exogenous neuroprotective patheways, endogenous neuroprotective mechanisms including neurotrophins, (re)myelination and, neurogenesis support restauration of neuronal integrity.

Biomechanical and proteomic analysis of INF- beta-treated astrocytes

Astrocytes have a key role in the pathogenesis of several diseases including multiple sclerosis and were proposed as the designed target for immunotherapy. In this study we used atomic force microscopy (AFM) and proteomics methods to analyse and correlate the modifications induced in the viscoleastic properties of astrocytes to the changes induced in protein expression after interferon- beta (IFN-beta) treatment. Our results indicated that IFN-beta treatment resulted in a significant decrease in the Young's modulus, a measure of cell elasticity, in comparison with control cells. The molecular mechanisms that trigger these changes were investigated by 2DE (two-dimensional electrophoresis) and confocal analyses and confirmed by western blotting. Altered proteins were found to be involved in cytoskeleton organization and other important physiological processes.

Resveratrol prevents memory deficits and the increase in acetylcholinesterase activity in streptozotocin-induced diabetic rats

The objective of the present study was to investigate the effect of the administration of resveratrol (RV) on memory and on acetylcholinesterase (AChE) activity in the cerebral cortex, hippocampus, striatum, hypothalamus, cerebellum and blood in streptozotocin-induced diabetic rats. The animals were divided into six groups (n=6-13): Control/saline; Control/RV 10 mg/kg; Control/RV 20 mg/kg; Diabetic/saline; Diabetic/RV 10 mg/kg; Diabetic/RV 20 mg/kg. One day after 30 days of treatment with resveratrol the animals were submitted to behavioral tests and then submitted to euthanasia and the brain structures and blood were collected. The results showed a decrease in step-down latency in diabetic/saline group. Resveratrol (10 and 20 mg/kg) prevented the impairment of memory induced by diabetes. In the open field test, no significant differences were observed between the groups. In relation to AChE activity, a significant increase in diabetic/saline group (P<0.05) was observed in all brain structures compared to control/saline group. However, AChE activity decreased significantly in control/RV10 and control/RV20 (P<0.05) groups in cerebral cortex, hippocampus and striatum, while no significant differences were observed in diabetic/RV10 and diabetic/RV20 groups in all brain structures compared to control/saline group. Blood AChE activity increased significantly in diabetic/saline group (P<0.05) decreased in control/RV10, control/RV20 and diabetic/RV20 groups (P<0.05) compared to control/saline group. In conclusion, the present findings showed that treatment with resveratrol prevents the increase in AChE activity and consequently memory impairment in diabetic rats, demonstrating that this compound can modulate cholinergic neurotransmission and consequently improve cognition.

Astrocytes in multiple sclerosis: a product of their environment

It has long been thought that astrocytes, like other glial cells, simply provide a support mechanism for neuronal function in the healthy and inflamed central nervous system (CNS). However, recent evidence suggests that astrocytes play an active and dual role in CNS inflammatory diseases such as multiple sclerosis (MS). Astrocytes not only have the ability to enhance immune responses and inhibit myelin repair, but they can also be protective and limit CNS inflammation while supporting oligodendrocyte and axonal regeneration. The particular impact of these cells on the pathogenesis and repair of an inflammatory demyelinating process is dependent upon a number of factors, including the stage of the disease, the type and microenvironment of the lesion, and the interactions with other cell types and factors that influence their activation. In this review, we summarize recent data supporting the idea that astrocytes play a complex role in the regulation of CNS autoimmunity.

Interferon-beta protects astrocytes against tumour necrosis factor-induced apoptosis via activation of p38 mitogen-activated protein kinase

Several large clinical trials have demonstrated that interferon-beta (IFN-beta) therapy is effective in the treatment of multiple sclerosis (MS) patients. However, the mechanisms underlying the beneficial effects of IFN-beta are not fully understood. Most of the effort in the study of the relevant mechanisms of IFN-beta has dealt with its immunomodulatory actions. However, the beneficial effects of IFN-beta in MS patients may also depend on non-immune mechanisms, including the modulation of astrocyte function. In the present work, we have found that IFN-beta treatment protects astrocytes against tumour necrosis factor-induced apoptosis via activation of p38 mitogen-activated protein kinase. We propose that this effect may be of importance to protect astrocytes against apoptosis within the demyelinated plaques of the MS.

Delivery of interferon-beta to the monkey nervous system following intranasal administration

We determined the nervous system targeting of interferon-beta1b (IFN-beta1b), a 20 kDa protein used to treat the relapsing-remitting form of multiple sclerosis, following intranasal administration in anesthetized, adult cynomolgus monkeys. Five animals received an intranasal bolus of [(125)I]-labeled IFN-beta1b, applied bilaterally to the upper nasal passages. Serial blood samples were collected for 45 min, after which the animals were euthanized by transcardial perfusion-fixation. High resolution phosphor imaging of tissue sections and gamma counting of microdissected tissue were used to obtain the distribution and concentration profiles of [(125)I]-IFN-beta1b in central and peripheral tissues. Intranasal administration resulted in rapid, widespread targeting of nervous tissue. The olfactory bulbs and trigeminal nerve exhibited [(125)I]-IFN-beta1b levels significantly greater than in peripheral organs and at least one order of magnitude higher than any other nervous tissue area sampled. The basal ganglia exhibited highest [(125)I]-IFN-beta1b levels among CNS regions other than the olfactory bulbs. Preferential IFN-beta1b distribution to the primate basal ganglia is a new finding of possible clinical importance. Our study suggests both IFN-beta and IFN-alpha, which share the same receptor, may be bound with relatively high affinity in these structures, possibly offering new insight into a neurovegetative syndrome induced by IFN-alpha therapy and suspected to involve altered dopamine neurotransmission in the basal ganglia. Most importantly, our results suggest intranasally applied macromolecules may bypass the blood-brain barrier and rapidly enter the primate CNS along olfactory- and trigeminal-associated extracellular pathways, as shown previously in the rat. This is the first study to finely detail the central distribution of a labeled protein after intranasal administration in non-human primates.

Mechanisms of interferon-beta-induced survival in fetal and neonatal primary astrocytes

BACKGROUND

We have previously shown that interferon-beta (IFN-beta) is a potent promoter of astrocyte survival. Although the mechanism(s) by which IFN-beta promotes astrocyte survival have not been completely elucidated, it has been shown that IFN-beta directly stimulates survival signaling pathways. In the present report, we took advantage of the differences in the susceptibility of fetal and neonatal astrocytes to apoptosis to further investigate the mechanism(s) underlying the antiapoptotic effect of IFN-beta.

METHODS

Primary monolayer cultures of cortical astrocytes were established from neonatal (3- to 6-day-old) or fetal (embryonic days: E15 or E17) Sprague-Dawley rat cerebral cortices. Apoptotic cell death was determined by fluorescent-microscopic analysis of staining patterns of cell DNA with Hoechst 33258, and determination of annexin V binding.Akt phosphorylation was detected by Western blottingusing a commercial kit that allows specific recognition of both non-phosphorylated and serine-phosphorylated Akt.

RESULTS

In the present work, we have found that primary astrocytes obtained from neonatal rats are resistant to apoptosis induced by serum starvation, though cell death may be induced by combining serum starvation with sodium butyrate treatment. This effect is counteracted by IFN-beta treatment through a mechanism that involves phosphatidylinositol 3-kinase stimulation.

CONCLUSIONS

IFN-beta can be considered as a neuroprotective agent and, therefore, part of its beneficial effects in multiple sclerosis (MS) treatment may depend on its capacity to protect astrocytes against the apoptotic cell death that occurs in the course of the MS lesions.

Effects of interferon-beta on oligodendroglial cells

The effect of interferon-beta (IFN-beta) for the treatment of multiple sclerosis (MS) is thought to be mediated by the modulation of immune cells. In addition, it has been shown that glial cells may be influenced by IFN-beta and a role during remyelination has been suggested. However, the mechanism is not yet clear and there are conflicting data. We have therefore systematically investigated proliferation, differentiation, toxicity, and cytoprotection of IFN-beta on oligodendroglia, both as a direct effect and mediated indirectly via other glial cells. Differentiation of oligodendrocyte progenitor cells (OPC) was significantly (p<0.01) inhibited by IFN-beta only when cultured in the presence with astrocytes and microglia. Proliferation was not changed, neither was IFN-beta toxic. There was no cytoprotective effect of IFN-beta on oligodendroglia injury induced by H2O2, NO, complement, or glutamate. Similarly, there was no cytoprotective effect mediated via treatment of astrocytes with IFN-beta. These data demonstrate that IFN-beta is neither toxic nor cytoprotective for oligodendrocytes. In summary, the only effect of IFN-beta was the inhibition of differentiation of OPC mediated indirectly via other glial cells. In vivo experiments will show how this effect may influence remyelination.

Acetylcholinesterase Activity in Rats Experimentally Demyelinated with Ethidium Bromide and Treated with Interferon Beta

The ethidium bromide (EB) demyelinating model was associated with interferon beta (IFN-beta) to evaluate acetylcholinesterase (AChE) activity in the striatum (ST), hippocampus (HP), cerebral cortex (CC), cerebellum (CB), hypothalamus (HY), pons (PN) and synaptosomes from the CC. Rats were divided into four groups: I control (saline), II (IFN-beta), III (EB) and IV (EB and IFN-beta). After 7, 15 and 30 days rats (n = 6) were sacrificed, and the brain structures were removed for enzymatic assay. AChE activity was found to vary in all the brain structures in accordance with the day studied (7-15-30 days) (P < 0.05). In the group III, there was an inhibition of the AChE activity in the ST, CB, HY, HP and also in synaptosomes of the CC (P < 0.05). It was observed that IFN-beta per se was capable to significantly inhibit (P < 0.05) AChE activity in the ST, HP, HY and synaptosomes of the CC. Our results suggest that one of the mechanisms of action of IFN-beta is through the inhibition of AChE activity, and EB could be considered an inhibitor of AChE activity by interfering with cholinergic neurotransmission in the different brain regions.

Neuroprotection in multiple sclerosis

In chronic inflammatory diseases like multiple sclerosis (MS), neuroprotection refers to strategies aimed at prevention of the irreversible damage of various neuronal and glial cell populations, and promoting regeneration. It is increasingly recognized that MS progression, in addition to demyelination, leads to substantial irreversible damage to, and loss of neurons, resulting in brain atrophy and cumulative disability. One of the most promising neuroprotective strategies involves the use of bone marrow derived stem cells. Both hematopoietic and non-hematopoietic (stromal) cells can, under certain circumstances, differentiate into cells of various neuronal and glial lineages. Neuronal stem cells have also been reported to suppress EAE by exerting direct in situ immunomodulating effects, in addition to their ability to provide a potential source for remyelination and neuroregeneration. Preliminary results from our laboratory indicate that intravenous or intracerebral/intraventricular injection of bone marrow derived stromal cells could differentiate in neuronal/glial cells and suppress the clinical signs of chronic EAE. Both bone marrow and neuronal stem cells may therefore have a therapeutic potential in MS. It seems that future treatment strategies for MS should combine immunomodulation with neuroprotective modalities to achieve maximal clinical benefit.

Interferon-beta stabilizes barrier characteristics of brain endothelial cells in vitro

Multiple sclerosis (MS) is accompanied by a breakdown of the blood-brain barrier (BBB) leading to edema formation and aggravation of the disease. Interferon-beta (IFN-beta) has been approved for the treatment of MS and besides its immunomodulatory effects has been demonstrated to lead to a stabilization of BBB integrity in vivo. To investigate whether human recombinant IFN-beta exerts direct effects on the BBB, we used an in vitro BBB model in which brain endothelial cells in coculture with astrocytes form a tight permeability barrier for 3H-inulin and 14C-sucrose. Removal of the astrocytes from the coculture or alternatively addition of histamine resulted in an increased paracellular permeability for small tracers across the brain endothelial cell monolayer. Strikingly, in the presence of IFN-beta, permeability increase under both conditions was inhibited. Permeability changes were accompanied by minor changes in the staining for tight junction-associated proteins in brain endothelial cell monolayers. Taken together, our data demonstrate a direct stabilizing effect of IFN-beta on BBB cerebral endothelial cells in vitro that might significantly contribute to the beneficial effects of IFN-beta treatment in MS in vivo.

Intranasal administration of interferon beta bypasses the blood–brain barrier to target the central nervous system and cervical lymph nodes: a non-invasive treatment strategy for multiple sclerosis

Intranasal (i.n.) administration of IFN beta-1b was examined as a route for targeted delivery to the rat central nervous system (CNS). Intranasal administration resulted in significant delivery throughout the CNS and cervical lymph nodes with low delivery to peripheral organs. At similar blood levels, intravenous (i.v.) administration of IFN beta-1b yielded 88-98% lower CNS levels and 100-1650% greater peripheral organ levels compared to intranasal. Autoradiography confirmed much greater delivery to the CNS with intranasal administration. Intranasally administered IFN beta-1b reached the brain intact and produced tyrosine phosphorylation of IFN receptor in the CNS. Intranasal administration offers a non-invasive method of drug delivery for multiple sclerosis (MS) that bypasses the blood-brain barrier (BBB) and directly targets the CNS and lymph nodes.

Attenuation of Experimental Autoimmune Encephalomyelitis and Nonimmune Demyelination by IFN-β plus Vitamin B12: Treatment to Modify Notch-1/Sonic Hedgehog Balance

Interferon-beta is a mainstay therapy of demyelinating diseases, but its effects are incomplete in human multiple sclerosis and several of its animal models. In this study, we demonstrate dramatic improvements of clinical, histological, and laboratory parameters in in vivo mouse models of demyelinating disease through combination therapy with IFN-beta plus vitamin B(12) cyanocobalamin (B(12)CN) in nonautoimmune primary demyelinating ND4 (DM20) transgenics, and in acute and chronic experimental autoimmune encephalomyelitis in SJL mice. Clinical improvement (p values <0.0001) was paralleled by near normal motor function, reduced astrocytosis, and reduced demyelination. IFN-beta plus B(12)CN enhanced in vivo and in vitro oligodendrocyte maturation. In vivo and in vitro altered expression patterns of reduced Notch-1 and enhanced expression of sonic hedgehog and its receptor were consistent with oligodendrocyte maturation and remyelination. IFN-beta-B(12)CN combination therapy may be promising for the treatment of multiple sclerosis.

Therapeutic strategies in multiple sclerosis. I. Immunotherapy

This review first addresses several general aspects of the immunotherapy of multiple sclerosis. Next, two approved immunomodulatory treatments, interferon-beta and copolymer-1 (glatiramer acetate), are reviewed in more detail. Finally, other immunosuppressive therapies and experimental strategies are briefly discussed.