We used mouse microglial cells in culture activated by lipopolysaccharide (LPS, 10 ng/ml) to study the anti‐inflammatory potential of cannabidiol (CBD), the major nonpsychoactive component of cannabis. Under LPS stimulation, CBD (1–10 μM) potently inhibited the release of prototypical proinflammatory cytokines (TNF‐α and IL‐1β) and that of glutamate, a noncytokine mediator of inflammation. The effects of CBD were predominantly receptor‐independent and only marginally blunted by blockade of CB2 receptors. We established that CBD inhibited a mechanism involving, sequentially, NADPH oxidase‐mediated ROS production and NF‐κB‐dependent signaling events. In line with these observations, active concentrations of CBD demonstrated an intrinsic free‐radical scavenging capacity in the cell‐free DPPH assay. Of interest, CBD also prevented the rise in glucose uptake observed in microglial cells challenged with LPS, as did the inhibitor of NADPH oxidase apocynin and the inhibitor of IκB kinase‐2, TPCA‐1. This indicated that the capacity of CBD to prevent glucose uptake also contributed to its anti‐inflammatory activity. Supporting this view, the glycolytic inhibitor 2‐deoxy‐d‐glucose (2‐DG) mimicked the antioxidant/immunosuppressive effects of CBD. Interestingly, CBD and 2‐DG, as well as apocynin and TPCA‐1 caused a reduction in glucose‐derived NADPH, a cofactor required for NADPH oxidase activation and ROS generation. These different observations suggest that CBD exerts its anti‐inflammatory effects towards microglia through an intrinsic antioxidant effect, which is amplified through inhibition of glucose‐dependent NADPH synthesis. These results also further confirm that CBD may have therapeutic utility in conditions where neuroinflammatory processes are prominent.

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Inflammatory mechanisms are proposed to play a role in l -DOPA-induced dyskinesia. Cyclooxygenase-2 (COX2) contributes to inflammation pathways in the periphery and is constitutively expressed in the central nervous system. Considering that inhibition of nitric oxide (NO) formation attenuates l -DOPA-induced dyskinesia, this study aimed at investigating if a NO synthase (NOS) inhibitor would change COX2 brain expression in animals with l -DOPA-induced dyskinesia. To this aim, male Wistar rats received unilateral 6-hydroxydopamine microinjection into the medial forebrain bundle were treated daily with l -DOPA (21 days) combined with 7-nitroindazole or vehicle. All hemi-Parkinsonian rats receiving l -DOPA showed dyskinesia. They also presented increased neuronal COX2 immunoreactivity in the dopamine-depleted dorsal striatum that was directly correlated with dyskinesia severity. Striatal COX2 co-localized with choline-acetyltransferase, calbindin and DARPP-32 (dopamine-cAMP-regulated phosphoprotein-32), neuronal markers of GABAergic neurons. NOS inhibition prevented l -DOPA-induced dyskinesia and COX2 increased expression in the dorsal striatum. These results suggest that increased COX2 expression after l -DOPA long-term treatment in Parkinsonian-like rats could contribute to the development of dyskinesia.

Inflammation in Parkinson's disease (PD) is a new concept that has gained ground due to the potential of mitigating dopaminergic neuron death by decreasing inflammation. The solution to this question is likely to be complex. We propose here that the significance of inflammation in PD may go beyond the nigral cell death. The pathological process that underlies PD requires years to reach its full extent. A growing body of evidence has been accumulated on the presence of multiple inflammatory signs in the brain of PD patients even in very late stages of the disease. Because neuron-microglia-astrocyte interactions play a major role in the plasticity of neuronal response to l-DOPA in post-synaptic neurons, we focused this review on our recent results of l-DOPA-induced dyskinesia in rodents correlating it to significant findings regarding glial cells and neuroinflammation. We showed that in the rat model of PD/l-DOPA-induced dyskinesia there was an increased expression of inflammatory markers, such as the enzymes COX2 in neurons and iNOS in glial cells, in the dopamine-denervated striatum. The gliosis commonly seem in PD was associated with modifications in astrocytes and microglia that occur after chronic treatment with l-DOPA. Either as a cause, consequence, or promoter of progression of neuronal degeneration, inflammation plays a role in PD. The key aims of current PD research ought to be to elucidate (a) the time sequence in which the inflammatory factors act in PD patient brain and (b) the mechanisms by which neuroinflammatory response contributes to the collateral effects of l-DOPA treatment.

When activated, microglial cells have the potential not only to secrete typical proinflammatory mediators but also to release the neurotransmitter glutamate in amounts that may promote excitotoxicity. Here, we wished to determine the potential of the Parkinson's disease (PD) protein α‐Synuclein (αS) to stimulate glutamate release using cultures of purified microglial cells. We established that glutamate release was robustly increased when microglial cultures were treated with fibrillary aggregates of αS but not with the native monomeric protein. Promotion of microglial glutamate release by αS aggregates (αSa) required concomitant engagement of TLR2 and P2X7 receptors. Downstream to cell surface receptors, the release process was mediated by activation of a signaling cascade sequentially involving phosphoinositide 3‐kinase (PI3K) and NADPH oxidase, a superoxide‐producing enzyme. Inhibition of the Xc‐ antiporter, a plasma membrane exchange system that imports extracellular l‐cystine and exports intracellular glutamate, prevented the release of glutamate induced by αSa, indicating that system Xc‐ was the final effector element in the release process downstream to NADPH oxidase activation. Of interest, the stimulation of glutamate release by αSa was abrogated by dopamine through an antioxidant effect requiring D1 dopamine receptor activation and PI3K inhibition. Altogether, present data suggest that the activation of microglial cells by αSa may possibly result in a toxic build‐up of extracellular glutamate contributing to excitotoxic stress in PD. The deficit in dopamine that characterizes this disorder may further aggravate this process in a vicious circle mechanism.

: Aggregated forms of the synaptic protein α-synuclein (αS) have been proposed to operate as a molecular trigger for microglial inflammatory processes and neurodegeneration in Parkinson´s disease. Here, we used brain microglial cell cultures activated by fibrillary forms of recombinant human αS to assess the anti-inflammatory and neuroprotective activities of the antibiotic rifampicin (Rif) and its autoxidation product rifampicin quinone (RifQ). Pretreatments with Rif and RifQ reduced the secretion of prototypical inflammatory cytokines (TNF-, IL-6) and the burst of oxidative stress in microglial cells activated with αS fibrillary aggregates. Note, however, that RifQ was constantly more efficacious than its parent compound in reducing microglial activation. We also established that the suppressive effects of Rif and RifQ on cytokine release was probably due to inhibition of both PI3K- and non-PI3K-dependent signaling events. The control of oxidative stress appeared, however, essentially dependent on PI3K inhibition. Of interest, we also showed that RifQ was more efficient than Rif in protecting neuronal cells from toxic factors secreted by microglia activated by αS fibrils. Overall, data with RifQ are promising enough to justify further studies to confirm the potential of this compound as an anti-parkinsionian drug.

These data lend support to the idea that cAMP signaling system contribute to the hyperactivity induced by developmental alcohol exposure and provide evidence for the potential therapeutic use of vinpocetine in FASD.

Amantadine is the noncompetitive antagonist of N-methyl-D-aspartate, receptor activated by the excitatory neurotransmitter glutamate. It is the only effective medication used to alleviate dyskinesia induced by L-3,4-dihydroxyphenylalanine (L-DOPA) in Parkinson's disease patients. Unfortunately, adverse effects as abnormal involuntary movements (AIMs) known as L-DOPA-induced dyskinesia limit its clinical utility. Combined effective symptomatic treatment modalities may lessen the liability to undesirable events. Likewise drugs known to interfere with nitrergic system reduce AIMs in animal models of Parkinson's disease. We aimed to analyze an interaction between amantadine, neuronal nitric oxide synthase inhibitor (7-nitroindazole, 7NI), and nitric oxide donor (sodium nitroprusside, SNP) in 6-hydroxydopamine-(6-OHDA)-lesioned rats (microinjection in the medial forebrain bundle) presenting L-DOPA-induced dyskinesia (20 mg/kg, gavage, during 21 days). We confirm that 7NI-30 mg/kg, SNP-2/4 mg/kg and amantadine-40 mg/kg, individually reduced AIMs. Our results revealed that co-administration of sub-effective dose of amantadine (10 mg/kg) plus sub-effective dose of 7NI (20 mg/kg) potentiates the effect of reducing AIMs scores when compared to the effect of the drugs individually. No superior benefit on L-DOPA-induced AIMs was observed with the combination of amantadine and SNP. The results revealed that combination of ineffective doses of amantadine and 7NI represents a new strategy to increase antidyskinetic effect in L-DOPA-induced AIMs. It may provide additional therapeutic benefits to Parkinson's disease patients from these disabling complications at lower and thus safer and more tolerable doses than required when either drug is used alone. To close, we discuss the paradox of both nitric oxide synthase inhibitor and/or donor produced AIMs reduction by targeting nitric oxide synthase.