Interleukin-1 and neuronal injury: mechanisms, modification, and therapeutic potential

Regulation of microglial behavior by ion channel activity

Microglia play an important role in the central nervous system, where these cells, it is believed, have both neuroprotective and neurotoxic effects. In response to acute brain injury or during neurodegenerative and neuroinflammatory diseases, activated microglial cells undergo shape changes, migrate to the affected sites of neuronal damage, proliferate, and release a variety of substances, such as cytokines and reactive oxygen species (ROS). This review summarizes the physiological mechanisms underlying microglial activation and deactivation processes, with particular focus on the involvement of microglial ion channels. Microglial ion channels have been shown to be capable, by regulating membrane potential, cell volume, and intracellular ion concentrations, of modulating or facilitating proliferation, migration, cytokine secretion, shape changes, and the respiratory burst of microglial cells.

A randomised phase II study of interleukin-1 receptor antagonist in acute stroke patients

OBJECTIVES

The cytokine interleukin (IL)-1 mediates ischaemic brain damage in rodents. The endogenous, highly selective, IL-1 receptor antagonist (IL-1ra) protects against ischaemic cerebral injury in a range of experimental settings, and IL-1ra causes a marked reduction of cell death when administered peripherally or at a delay in transient cerebral ischaemia. We report here the first randomised, double blind, placebo controlled trial of recombinant human IL-1ra (rhIL-1ra) in patients with acute stroke.

METHODS

Patients within 6 hours of the onset of symptoms of acute stroke were randomised to rhIL-1ra or matching placebo. Test treatment was administered intravenously by a 100 mg loading dose over 60 seconds, followed by a 2 mg/kg/h infusion over 72 h. Adverse events and serious adverse events were recorded for up to 3 months, serial blood samples were collected for biological markers up to 3 months, and 5-7 day brain infarct volume was measured by computed tomography.

RESULTS

No adverse events were attributed to study treatment among 34 patients randomised. Markers of biological activity, including neutrophil and total white cell counts, C reactive protein, and IL-6 concentrations, were lower in rhIL-1ra treated patients. Among patients with cortical infarcts, clinical outcomes at 3 months in the rhIL-1ra treated group were better than in placebo treated.

CONCLUSIONS

These data suggest that rhIL-1ra is safe and well tolerated in acute stroke. In addition, rhIL-1ra exhibited biological activity that is relevant to the pathophysiology and clinical outcome of ischaemic stroke. Our findings identify rhIL-1ra as a potential new therapeutic agent for acute stroke.

Antagonism of the interleukin-1 receptor following traumatic brain injury in the mouse reduces the number of nitric oxide synthase-2-positive cells and improves anatomical and functional outcomes

Interleukin (IL)-1beta plays an important role in the inflammatory response that results from traumatic brain injury and antagonism of the actions of this cytokine can affect outcome. We subjected male mice to aseptic cryogenic injury and assessed recovery through anatomical, histological and functional measures following treatment with recombinant mouse IL-1 receptor antagonist (IL-1ra). A single dose (1 microg, i.c.v.) at the time of injury reduced lesion volume 3 days later, as assessed by Nissl staining, and also the number (30%) of FluoroJade-positive degenerating neurones. Mice treated with IL-1ra performed better on the beam balance and in the grid test as compared with vehicle-treated animals. Furthermore, IL-1ra-treated animals showed fewer (40%) nitric oxide synthase-2-positive cells in and around the lesion. These data suggest that activation of the IL-1 receptor following trauma contributes to the pathology and that antagonism can reduce both anatomical and functional consequences of neuroinflammation.

Interleukin-1 and neuronal injury

Interleukin-1 is a pro-inflammatory cytokine that has numerous biological effects, including activation of many inflammatory processes (through activation of T cells, for example), induction of expression of acute-phase proteins, an important function in neuroimmune responses and direct effects on the brain itself. There is now extensive evidence to support the direct involvement of interleukin-1 in the neuronal injury that occurs in both acute and chronic neurodegenerative disorders. This article discusses the key evidence of a role for interleukin-1 in acute neurodegeneration - for example, stroke and brain trauma - and provides a rationale for targeting the interleukin-1 system as a therapeutic strategy.

Differential effects of interleukin-1beta on neurotoxicity, cytokine induction and glial reaction in specific brain regions

An appropriate inflammatory response is crucial for the maintenance of tissue homeostasis. The inflammatory responses seen in the brain parenchyma differ from those elicited in the periphery, ventricles and meninges. However, although an inflammatory component has been associated with many CNS diseases, the differences among parenchymal inflammatory responses in different brain regions have not yet been fully elucidated. Here, we performed a systematic comparison of the effects of a common pro-inflammatory stimulus, IL-1beta, on the hippocampus, substantia nigra, striatum and cortex. We determined various responses, including cytokine mRNA induction, glial activation, immune cell infiltration and changes in neuronal integrity, in both injected and adjacent regions 1 and 6 days after the injection of IL-1beta. We found that the mRNA for TGF-beta was up-regulated in a region-specific manner after IL-1beta administration. Contrary to its response in the periphery, IL-1alpha showed no detectable induction in the tested parenchymal regions. In addition, cytokine induction was also sometimes observed in regions distant from the site of injection. Interestingly, IL-1beta-mediated neurodegeneration was observed in the dentate gyrus of the hippocampus, but not in the other tested regions. The cellular recruitment mediated by IL-1 beta injection consisted mainly of polymorphonuclear cells (PMN), which correlated with IL-1betamRNA induction even in regions far from the injection site. These results indicate that various parenchymal regions show different inflammatory responses and neurodegeneration in response to IL-1beta. Taken together, our results provide a more precise picture of regional inflammation in the brain and should provide a basis for differential interpretation of results based on regional inflammatory differences.

Norepinephrine protects cortical neurons against microglial-induced cell death

Interleukin-1 beta (IL-1beta) is one of the main cytokines involved in the inflammatory response; it has multiple effects that can contribute to cell damage, one of which is the upregulation of the inducible form of nitric oxide (NO) synthase (NOS2) in certain cell types. We demonstrated previously that in vivo, cortical microglial inflammatory responses were increased when noradrenaline (NE) levels were depleted, suggesting that NE can reduce microglial activation. In the present report, we examined the role of IL-1beta in neurotoxicity induced by microglial-conditioned media, and possible neuroprotective effects of NE. Incubation of cortical neurons with conditioned media (CM) obtained from lipopolysaccharide (LPS)-treated microglia induced neuronal NOS2 expression and increased neuronal cell death, and these responses were reduced if the neurons were coincubated with interleukin-1 receptor antagonist. Cotreatment of microglial cells with LPS plus NE potently blocked IL-1beta production and reduced the ability of the CM to induce neuronal NOS2 and cell death. These results suggest that microglial release of IL-1beta is an important activator of neuronal inflammatory responses, and that protective effects of NE upon neurons involve a reduction of microglial-derived IL-1beta.

Interleukin-1beta enhances NMDA receptor-mediated current but inhibits excitatory synaptic transmission

Interleukin (IL)-1beta is often characterized as the prototypic proinflammatory cytokine but is involved in various pathophysiological conditions in the central nervous system (CNS). A whole-cell recording technique was used to observe its effect on N-methyl-D-aspartate (NMDA)-evoked currents and spontaneous synaptic activity in cultured rat hippocampal neurons. The results showed that the frequencies but not the amplitudes of spontaneous excitatory postsynaptic currents (sEPSC) and miniature excitatory postsynaptic currents (mEPSC) were decreased by 10 or 100 ng/ml IL-1beta. IL-1beta at these concentrations also increased the NMDA receptor-mediated current. In addition, 10 ng/ml IL-1beta significantly increased the amplitude of the voltage-dependent Ca2+ current (I(Ca)). The increase in I(Ca) following treatment of cultures with IL-1beta resulted mainly from an increase in L-type current. These data suggest that IL-1beta modulates hippocampus-related functions via its effect on synaptic activity and Ca2+ signaling in neurons.

Interleukin-1β exacerbates and interleukin-1 receptor antagonist attenuates neuronal injury and microglial activation after excitotoxic damage in organotypic hippocampal slice cultures

The effects of interleukin (IL)-1beta and IL-1 receptor antagonist (IL-1ra) on neurons and microglial cells were investigated in organotypic hippocampal slice cultures (OHSCs). OHSCs obtained from rats were excitotoxically lesioned after 6 days in vitro by application of N-methyl-D-aspartate (NMDA) and treated with IL-1beta (6 ng/mL) or IL-1ra (40, 100 or 500 ng/mL) for up to 10 days. OHSCs were then analysed by bright field microscopy after hematoxylin staining and confocal laser scanning microscopy after labeling of damaged neurons with propidium iodide (PI) and fluorescent staining of microglial cells. The specificity of PI labeling of damaged neurons was validated by triple staining with neuronal and glial markers and it was observed that PI accumulated in damaged neurons only but not in microglial cells or astrocytes. Treatment of unlesioned OHSCs with IL-1beta did not induce neuronal damage but caused an increase in the number of microglial cells. NMDA lesioning alone resulted in a massive increase in the number of microglial cells and degenerating neurons. Treatment of NMDA-lesioned OHSCs with IL-1beta exacerbated neuronal cell death and further enhanced microglial cell numbers. Treatment of NMDA-lesioned cultures with IL-1ra significantly attenuated NMDA-induced neuronal damage and reduced the number of microglial cells, whereas application of IL-1ra in unlesioned OHSCs did not induce significant changes in either cell population. Our findings indicate that: (i) IL-1beta directly affects the central nervous system and acts independently of infiltrating hematogenous cells; (ii) IL-1beta induces microglial activation but is not neurotoxic per se; (iii) IL-1beta enhances excitotoxic neuronal damage and microglial activation and (iv) IL-1ra, even when applied for only 4 h, reduces neuronal cell death and the number of microglial cells after excitotoxic damage.

Differential actions of IL-1 alpha and IL-1 beta in glial cells share common IL-1 signalling pathways

The cytokine interleukin (IL)-1 plays important roles in peripheral and central inflammation via the actions of two ligands IL-1 alpha and IL-1beta that bind to the IL-1 type I receptor (IL-1RI) and trigger identical responses. However, some recent evidence suggests that IL-1alpha and IL-1beta may have differential actions in the CNS. The aim of this study was to characterise the molecular mechanisms responsible for their differential actions in the brain. We show that, while IL-1alpha and IL-1beta induce identical IL-1 signalling pathways, IL-1beta is significantly more potent than IL-1alpha in stimulating IL-6 release in primary mixed glia. These data suggest that the differential effects of IL-1alpha and IL-1beta on glial cells are mediated by alternative pathways to the classical IL-1 signalling cascade.

Therapeutic potential of targeting IL-1 and IL-18 in inflammation

Interleukin (IL)-1 and IL-18 are cytokines that play a major role in autoimmune and inflammatory human disease. Both cytokines drive a wide range of pro-inflammatory effector networks in many cell types and use common signal transduction cascades. IL-1, IL-18 and other members of the IL-1 superfamily are expressed at elevated levels in tissue and fluid samples isolated from patients with many chronic inflammatory diseases. These cytokines are primary drivers in acute and chronic animal models of inflammation and their blockade has been shown to ameliorate disease in preclinical studies. Biological agents that target IL-1 have demonstrated efficacy in patients with rheumatoid arthritis, and further agents targeting IL-1 or IL-18 neutralisation are in clinical development. The potential for such agents spans human disease where tissue destruction is a primary end point of cytokine action.

Closed head injury--an inflammatory disease?

Closed head injury (CHI) remains the leading cause of death and persisting neurological impairment in young individuals in industrialized nations. Research efforts in the past years have brought evidence that the intracranial inflammatory response in the injured brain contributes to the neuropathological sequelae which are, in large part, responsible for the adverse outcome after head injury. The presence of hypoxia and hypotension in the early resuscitative period of brain-injured patients further aggravates the inflammatory response in the brain due to ischemia/reperfusion-mediated injuries. The profound endogenous neuroinflammatory response after CHI, which is phylogenetically aimed at defending the intrathecal compartment from invading pathogens and repairing lesioned brain tissue, contributes to the development of cerebral edema, breakdown of the blood-brain barrier, and ultimately to delayed neuronal cell death. However, aside from these deleterious effects, neuroinflammation has been recently shown to mediate neuroreparative mechanisms after brain injury as well. This "dual effect" of neuroinflammation was the focus of extensive experimental and clinical research in the past years and has lead to an expanded basic knowledge on the cellular and molecular mechanisms which regulate the intracranial inflammatory response after CHI. Thus, head injury has recently evolved as an inflammatory and immunological disease much more than a pure traumatological, neurological, or neurosurgical entity. The present review will summarize the so far known mechanisms of posttraumatic neuroinflammation after CHI, based on data from clinical and experimental studies, with a special focus on the role of pro-inflammatory cytokines, chemokines, and the complement system.

Interleukin-1 beta down-regulates the expression of metabotropic glutamate receptor 5 in cultured human astrocytes

Expression of metabotropic glutamate receptor 5 (mGluR5) protein is known to be plastic and to depend critically on the astrocytes' microenvironment. In the present study we investigated whether interleukins, which are involved in the immune response following brain injury, could contribute to the regulation of mGluR5 protein in human astrocytes in culture. Using Western blotting and immunocytochemistry, no detectable changes in the expression of the mGluR5 protein were observed with both interleukin 1beta and interleukin 6 in undifferentiated cultures (growing in serum free media). In contrast, in cultures that had been morphologically differentiated by exposure to epidermal growth factor (EGF), addition of interleukin 1beta (but not interleukin 6) reduced mGluR5 protein expression. In addition, stimulation of phosphoinositide hydrolysis by the selective group I agonist (S)-3,5-dihydroxyphenylglycine (DHPG) was reduced after exposure to interleukin 1beta. The suppressive effect on mGluR5 was prevented by the interleukin 1 receptor antagonist. Thus, interleukin 1beta may represent an additional pathway through which mGluR5 expression and function can be modulated in astrocytes under different pathological conditions associated with an inflammatory response.

Interactions between Alzheimer's disease and cerebral ischemia--focus on inflammation

Progressive memory impairment, beta-amyloid (Abeta) plaques associated with local inflammation, neurofibrillary tangles, and loss of neurons in selective brain areas are hallmarks of Alzheimer's disease (AD). Although beta-amyloid precursor protein (APP) and Abeta have a central role in the etiology of AD, it is not clear which forms of APP or Abeta are responsible for the neuronal vulnerability in AD brain. Brain ischemia, another cause of dementia in the elderly, has recently been recognized to contribute to the pathogenesis of AD and individuals with severe cognitive decline and possibly underlying AD are at increased risk for ischemic events in the brain. Moreover, the epsilon4 allele of apolipoprotein E (ApoE) is a risk factor for both AD and poor outcome following brain ischemia and hemorrhage. Several factors and molecular mechanisms that lower the threshold of neuronal death in models of AD have recently been described. Among these neuroinflammation seems to play an important role. The development and maturation of both AD neuropathology and ischemic lesions in the central nervous system are characterized by activation of glial cells and upregulation of inflammatory mediators. Indeed, anti-inflammatory approaches have proven to be beneficial in the prevention and treatment of AD-like neuropathology and ischemic injuries in vivo. This review summarizes some of the findings suggesting that neuronal overexpression of human APP renders the brain more vulnerable to ischemic injury and describes the factors that are involved in increased neuronal susceptibility to ischemic stroke.

Antiepileptogenic and anticonvulsant activity of interleukin-1β in amygdala-kindled rats

Ischaemic, excitotoxic and traumatic brain injuries have been associated with the occurrence of epileptic seizures. Microglia, the principal immune cells in the brain, produce a variety of proinflammatory and cytotoxic factors especially interleukin-1 (IL-1) early after an acute insult. We studied the effect of intracerebroventricularly administered IL-1beta on seizure acquisition and on fully kindled seizures in amygdala kindling model of epilepsy. IL-1beta (0.01 ng/rat) retarded acquisition of kindled behavioral seizures and growth of afterdischarges (AD). IL-1beta (0.01-10 ng/rat) also exhibited significant anticonvulsant effect on established kindled seizures and AD duration. This effect began 0.5 h after administration and was continued up to 72 h. Pretreatment of the kindled animals with nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl ester, or cyclooxygenase inhibitor, piroxicam, reversed the anticonvulsant effect of IL-1beta at early time points. Although most of the previous studies indicate a proconvulsant or convulsant property of IL-1, our results support a protective and antiepileptogenic role of IL-1beta.

Role of cytokines and chemokines in prion infections of the central nervous system

Prion infections of the central nervous system (CNS) are characterised by a reactive gliosis and the subsequent degeneration of neuronal tissue. The activation of glial cells, which precedes neuronal death, is likely to be initially caused by the deposition of misfolded, proteinase K-resistant, isoforms (termed PrP(res)) of the prion protein (PrP) in the brain. Cytokines and chemokines released by PrP(res)-activated glia cells may contribute directly or indirectly to the disease development by enhancement and generalisation of the gliosis and via cytotoxicity for neurons. However, the actual role of prion-induced glia activation and subsequent cytokine/chemokine secretion in disease development is still far from clear. In the present work, we review our present knowledge concerning the functional biology of cytokines and chemokines in prion infections of the CNS.

Role of interleukin-1beta in the pathogenesis of diabetic retinopathy

AIM

To examine the role of cytokine interleukin-1beta (IL-1beta) in retinal capillary cell death in diabetes.

METHODS

The effect of glucose on the expression of IL-1beta was measured in the bovine retinal endothelial cells. The role of IL-1beta in the accelerated endothelial cell loss was determined by investigating the effect of human recombinant IL-1beta on their apoptosis in normal and high glucose conditions, and was confirmed using interleukin-1 receptor antagonist (IL-1ra).

RESULTS

High glucose increased IL-1beta expression by 60% compared with cells incubated in 5 mM glucose (p<0.05). Incubation of cells with IL-1beta increased NO levels by about 80% and activated NF-kappaB by 40%. In the same cells apoptosis was increased by 70% and caspase-3 activity was increased by 40%. Supplementation of IL-1beta in 20 mM glucose medium further increased nitric oxide and NF-kappaB, and accelerated apoptosis, and addition of IL-1ra significantly decreased glucose induced abnormalities and apoptosis.

CONCLUSIONS

IL-1beta accelerates apoptosis of retinal capillary cells via activation of NF-kappaB, and the process is exacerbated in high glucose conditions. These studies suggest a possible role of IL-1beta in the development of retinopathy in diabetes, and offer a possible rationale to test IL-1beta receptor antagonists to inhibit the development of diabetic retinopathy.

Reversible demyelination, blood-brain barrier breakdown, and pronounced neutrophil recruitment induced by chronic IL-1 expression in the brain

Interleukin-1beta (IL-1) expression is associated with a spectrum of neuroinflammatory processes related to chronic neurodegenerative diseases. The single-bolus microinjection of IL-1 into the central nervous system (CNS) parenchyma gives rise to delayed and localized neutrophil recruitment, transient blood-brain barrier (BBB) breakdown, but no overt damage to CNS integrity. However, acute microinjections of IL-1 do not mimic the chronic IL-1 expression, which is a feature of many CNS diseases. To investigate the response of the CNS to chronic IL-1 expression, we injected a recombinant adenovirus expressing IL-1 into the striatum. At the peak of IL-1 expression (days 8 and 14 post-injection), there was a marked recruitment of neutrophils, vasodilatation, and breakdown of the BBB. Microglia and astrocyte activation was evident during the first 14 days post-injection. At days 8 and 14, extensive demyelination was observed but the number of neurons was not affected by any treatment. Finally, at 30 days, signs of inflammation were no longer present, there was evidence of tissue reorganization, the BBB was intact, and the process of remyelination was noticeable. In summary, our data show that chronic expression of IL-1, in contrast to its acute delivery, can reversibly damage CNS integrity and implicates this cytokine or downstream components as major mediators of demyelination in chronic inflammatory and demyelinating diseases.

Activation of proinflammatory caspases by cathepsin B in focal cerebral ischemia

Cathepsins and caspases are two families of proteases that play pivotal roles in ischemic cell death. This study investigated the existence of a cross-talk between cathepsin B and proinflammatory caspases in stroke-induced cell death, as recently suggested by in vitro data. Cortical ischemic damage was induced in mice by distal and permanent occlusion of the middle cerebral artery. Cytoplasmic activation of cathepsin B was observed from the early stages of infarction, and displayed an activation pattern parallel to the activation pattern of caspase-1 and -11. Immunohistochemistry revealed the colocalization of cathepsin B with each caspase in cells of the infarct core. The apical position of cathepsin B in both caspase-activation cascades was confirmed by pretreatment of the animals with the cathepsin B inhibitor CA-074, which also potently protected cortical structures from ischemic damage, indicating involvement of the proteases in the lesion process. The results show that cathepsin B release is an early event following occlusion of cerebral arteries, which eventually triggers the activation of proinflammatory caspases in the absence of reperfusion. This new pathway may play a critical role in brain infarction by promoting inflammatory responses, and/or by amplifying the apoptotic process.

Genetic and Cellular Therapies for Cerebral Infarction

Neurosurgeons, working as surgical scientists, can have a prominent role in developing and implementing genetic and cellular therapies for cerebral ischemia. The rapid emergence of both genetic and cellular therapies for neural regeneration warrants a careful analysis before implementation of human studies to understand the pitfalls and promises of this strategy. In this article, we review the topic of genetic and cellular therapy for stroke to provide a foundation for practicing neurosurgeons and clinical scientists who may become involved in this type of work. In Part 1, we review preclinical approaches with gene transfer, such as 1) improved energy delivery, 2) reduction of intracellular calcium availability, 3) abrogation of effects of reactive oxygen species, 4) reduction of proinflammatory cytokine signaling, 5) inhibition of apoptosis mediators, and 6) restorative gene therapy, that are paving the way to develop new strategies to treat cerebral infarction. In Part 2, we discuss the results of studies that address the possibility of using cellular therapies for stroke in animal models and in human trials by reviewing 1) the basics of stem cell biology, 2) exogenous and 3) and endogenous cell sources for therapy, and 4) clinical considerations in cell therapy applications. These emerging technologies based on the advancements made in recent years in the fields of genetics, therapeutic cloning, neuroscience, stem cell biology, and gene therapy provide significant potential for new therapies for stroke.

Reanalysis of P2X7 receptor expression in rodent brain

P2X receptors are cationic-selective ion channels gated by extracellular ATP. There are seven subunits (P2X1-7), the first six of which are expressed throughout the peripheral and central nervous systems. P2X7 receptors are rapidly upregulated and activated as a result of inflammatory stimuli in immune cells, where they act not only as cationic channels but uniquely couple with rapid release of proinflammatory cytokines, cytoskeletal rearrangements, and apoptosis or necrotic cell death. The P2X7 receptor has been termed the cytolytic non-neuronal P2X receptor because it had not been detected in neurons until recently when it has been immunolocalized to several brain regions, particularly the hippocampus, and has been suggested to be involved in presynaptic modulation of transmitter release. Because its expression in brain neurons may have substantial functional implications, we have performed detailed immunocytochemical, immunoblot, and immunoprecipitation studies on brain and non-neuronal tissue using all currently available antibodies. We first examined rats, but staining patterns were inconsistent among antibodies; we therefore studied mice for which there are two P2X7 knock-out mice constructs available, one expressing the LacZ transgene. We found that P2X7 receptor protein is strongly and reliably detected in the submandibular gland and lung of wild-type mice but not in either of the P2X7-/- mice. However, we failed to find evidence for P2X7 receptor protein in hippocampal neurons or their input-output projections. Either the P2X7 protein in the hippocampus is below the limits of detection by the currently available methods or it is not present.

3,4‐Methylenedioxymethamphetamine increases interleukin‐1β levels and activates microglia in rat brain: studies on the relationship with acute hyperthermia and 5‐HT depletion

3,4-Methylenedioxymethamphetamine (MDMA) administration to rats produces acute hyperthermia and 5-HT release. Interleukin-1beta (IL-1beta) is a pro-inflammatory pyrogen produced by activated microglia in the brain. We examined the effect of a neurotoxic dose of MDMA on IL-1beta concentration and glial activation and their relationship with acute hyperthermia and 5-HT depletion. MDMA, given to rats housed at 22 degrees C, increased IL-1beta levels in hypothalamus and cortex from 1 to 6 h and [(3)H]-(1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)3-isoquinolinecarboxamide) binding between 3 and 48 h. Increased immunoreactivity to OX-42 was also detected. Rats became hyperthermic immediately after MDMA and up to at least 12 h later. The IL-1 receptor antagonist did not modify MDMA-induced hyperthermia indicating that IL-1beta release is a consequence, not the cause, of the rise in body temperature. When MDMA was given to rats housed at 4 degrees C, hyperthermia was abolished and the IL-1beta increase significantly reduced. The MDMA-induced acute 5-HT depletion was prevented by fluoxetine coadministration but the IL-1beta increase and hyperthermia were unaffected. Therefore, the rise in IL-1beta is not related to the acute 5-HT release but is linked to the hyperthermia. Contrary to IL-1beta levels, microglial activation is not significantly modified when hyperthermia is prevented, suggesting that it might be a process not dependent on the hyperthermic response induced by MDMA.