Decreased neuronal CD200 expression in IL-4-deficient mice results in increased neuroinflammation in response to lipopolysaccharide.

Maintenance of the balance between pro- and anti-inflammatory cytokines in the brain, which is affected by the activation state of microglia, is important for maintenance of neuronal function. Evidence has suggested that IL-4 plays an important neuromodulatory role and has the ability to decrease lipopolysaccharide-induced microglial activation and the production of IL-1beta. We have also demonstrated that CD200-CD200R interaction is involved in immune homeostasis in the brain. Here, we investigated the anti-inflammatory role of IL-4 and, using in vitro and in vivo analysis, established that the effect of lipopolysaccharide was more profound in IL-4(-/-), compared with wildtype, mice. Intraperitoneal injection of lipopolysaccharide exerted a greater inhibitory effect on exploratory behaviour in IL-4(-/-), compared with wildtype, mice and this was associated with evidence of microglial activation. We demonstrate that the increase in microglial activation is inversely related to CD200 expression. Furthermore, CD200 was decreased in neurons prepared from IL-4(-/-) mice, whereas stimulation with IL-4 enhanced CD200 expression. Importantly, neurons prepared from wildtype, but not from IL-4(-/-), mice attenuated the lipopolysaccharide-induced increase in pro-inflammatory cytokine production by glia. These findings suggest that the neuromodulatory effect of IL-4, and in particular its capacity to maintain microglia in a quiescent state, may result from its ability to upregulate CD200 expression on neurons.

Nonbullous neutrophilic dermatosis: Sweet's syndrome, neonatal lupus erythematosus, or both?

We describe a 5-day-old infant who fulfilled the diagnostic criteria for Sweet's syndrome, and the concurrent histologic and autoantibody features supporting the diagnosis of neonatal lupus. To our knowledge, this is the youngest case of Sweet's syndrome reported in the literature. Importantly, our findings further support the hypothesis that lupus erythematosus should be considered in the differential diagnosis of a nonbullous neutrophilic dermatosis, as it may represent the initial manifestation of the disease.

A pivotal role for interleukin-4 in atorvastatin-associated neuroprotection in rat brain.

Inflammatory changes, characterized by an increase in pro-inflammatory cytokine production and up-regulation of the corresponding signaling pathways, have been described in the brains of aged rats and rats treated with the potent immune modulatory molecule lipopolysaccharide (LPS). These changes have been coupled with a deficit in long-term potentiation (LTP) in hippocampus. The evidence suggests that anti-inflammatory agents, which attenuate the LPS-induced and age-associated increase in hippocampal interleukin-1beta (IL-1beta) concentration, lead to restoration of LTP. Here we report that atorvastatin, a member of the family of agents that act as inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase, exerts powerful anti-inflammatory effects in brain and that these effects are mediated by IL-4 and independent of its cholesterol-lowering actions. Treatment of rats with atorvastatin increased IL-4 concentration in hippocampal tissue prepared from LPS-treated and aged rats and abrogated the age-related and LPS-induced increases in pro-inflammatory cytokines, interferon-gamma (IFNgamma) and IL-1beta, and the accompanying deficit in LTP. The effect of atorvastatin on the LPS-induced increases in IFNgamma and IL-1beta was absent in tissue prepared from IL-4(-/-) mice. The increase in IL-1beta in LPS-treated and aged rats is associated with increased microglial activation, assessed by analysis of major histocompatibility complex II expression, and the evidence suggests that IFNgamma may trigger this activation. We propose that the primary effect of atorvastatin is to increase IL-4, which antagonizes the effects of IFNgamma, the associated increase in microglial activation, and the subsequent cascade of events.

The HMG-CoA reductase inhibitor, atorvastatin, attenuates the effects of acute administration of amyloid-beta1-42 in the rat hippocampus in vivo.

One response of the brain to stressors is to increase microglial activation with the consequent production of proinflammatory cytokines like interleukin-1beta (IL-1beta), which has been shown to exert an inhibitory effect on long-term potentiation (LTP) in the hippocampus. It has been consistently shown, particularly in vitro, that amyloid-beta (Abeta) peptides increase activation of microglia, while its inhibitory effect on LTP is well documented, and associated with the Abeta-induced increase in IL-1beta. Here we set out to establish whether the Abeta-induced inhibition of LTP in perforant path-granule cell synapses, was coupled with evidence of microglial activation and to assess whether atorvastatin, which is used primarily in the treatment of hyperlipidaemia but which possesses anti-inflammatory properties, might modulate the effect of Abeta on LTP. We report that intracerebroventricular injection of Abeta increased expression of several markers of microglial activation, and in parallel, inhibited LTP in dentate gyrus. The data show that atorvastatin abrogated the Abeta-induced microglial activation and the associated deficit in LTP. On the basis of the evidence presented, we propose that the action of atorvastatin is mediated by its ability to increase production of the anti-inflammatory cytokine, interleukin-4, which we report mimics several of the actions of atorvastatin in the rat hippocampus.

Eicosapentaenoic acid confers neuroprotection in the amyloid-beta challenged aged hippocampus.

Among the changes that occur in the hippocampus with age, is a deficit in long-term potentiation (LTP). This impairment is associated with inflammatory changes, which are typified by increased concentration of the pro-inflammatory cytokine interleukin-1beta (IL-1beta). Activated microglia are the most likely cell source of IL-1beta, but data demonstrating an age-related increase in microglial activation is equivocal. Here we demonstrate that the age-related deficit in LTP is accompanied by increased expression of cell surface markers of activated microglia (major histocompatibility complex II and CD40) and increased IL-1beta production, and that these changes may be stimulated by interferon-gamma. Treatment of aged rats with eicosapentaenoic acid (EPA) attenuates these changes and we suggest that IL-4 mediates the action of EPA. We demonstrate that aged rats exhibit an exaggerated response to intracerebroventricular injection of beta-amyloid peptide 1-40 (Abeta). Thus Abeta inhibited LTP in aged, but not young, rats and induced a further increase in hippocampal IL-1beta concentration. Of particular significance is the demonstration that EPA protects the aged brain so that the increased vulnerability to Abeta is ameliorated in EPA-treated rats.