Clozapine reduces chemokine-mediated migration of lymphocytes by targeting NF-κB and AKT phosphorylation

Multiple sclerosis is a disease characterised by demyelination of axons in the central nervous system. The atypical antipsychotic drug clozapine has been shown to attenuate disease severity in experimental autoimmune encephalomyelitis (EAE), a mouse model that is useful for the study of multiple sclerosis. However, the mechanism of action by which clozapine reduces disease in EAE is poorly understood. To better understand how clozapine exerts its protective effects, we investigated the underlying signalling pathways by which clozapine may reduce immune cell migration by evaluating chemokine and dopamine receptor-associated signalling pathways. We found that clozapine inhibits migration of immune cells by reducing chemokine production in microglia cells by targeting NF-κB phosphorylation and promoting an anti-inflammatory milieu. Furthermore, clozapine directly targets immune cell migration by changing Ca²⁺ levels within immune cells and reduces the phosphorylation of signalling protein AKT. Linking these pathways to the antagonising effect of clozapine on dopamine and serotonin receptors, we provide insight into how clozapine alters immune cells migration by directly targeting the underlying migration-associated pathways.

Repeated eticlopride administration increases dopamine D2 receptor expression and restores behavioral flexibility disrupted by methamphetamine exposure to male rats

Repeated methamphetamine exposure impairs reversal learning in laboratory animals and downregulates dopamine D₂ receptor expression. In the present study, we tested the possibility that repeated exposure to the dopamine D₂ antagonist, eticlopride, would increase D₂ receptor expression, improve behavioral flexibility and restore behavioral flexibility that was disrupted by exposure to methamphetamine in rats. Male Sprague-Dawley rats received repeated daily pretreatment with the dopamine D₂ antagonist, eticlopride (0.0 or 0.3 mg/kg/day, 14 days). Three days after the last treatment, whole brain (minus olfactory bulbs and cerebellum) dopamine D₂ receptor expression was measured using flow cytometry in one group and reversal learning performance was measured in another group. Reversal learning was also measured in other groups prior to and after methamphetamine exposure (0.0 or 2.0 mg/kg, 4 injections, 2 h apart, 1 day) followed by repeated eticlopride (0.0 or 0.3 mg/kg, 14 days) treatment. Eticlopride treatment increased D₂ receptor expression and improved reversal learning performance. Methamphetamine impaired reversal learning performance and eticlopride treatment reversed the deficit. These results suggest that repeated administration of eticlopride can restore behavioral flexibility and that upregulation of D₂ receptors might be an effective adjunct to treatment of methamphetamine misuse.

The Salvinorin Analogue, Ethoxymethyl Ether Salvinorin B, Promotes Remyelination in Preclinical Models of Multiple Sclerosis

Multiple sclerosis is a neurodegenerative disease associated with demyelination and neuroinflammation in the central nervous system. There is an urgent need to develop remyelinating therapies to better treat multiple sclerosis and other demyelinating diseases. The kappa opioid receptor (KOR) has been identified as a potential target for the development of remyelinating therapies; however, prototypical KOR agonists, such as U50,488 have side effects, which limit clinical use. In the current study, we investigated a Salvinorin A analog, ethoxymethyl ether Salvinorin B (EOM SalB) in two preclinical models of demyelination in C57BL/6J mice. We showed that in cellular assays EOM SalB was G-protein biased, an effect often correlated with fewer KOR-mediated side effects. In the experimental autoimmune encephalomyelitis model, we found that EOM SalB (0.1-0.3 mg/kg) effectively decreased disease severity in a KOR-dependent manner and led to a greater number of animals in recovery compared to U50,488 treatment. Furthermore, EOM SalB treatment decreased immune cell infiltration and increased myelin levels in the central nervous system. In the cuprizone-induced demyelination model, we showed that EOM SalB (0.3 mg/kg) administration led to an increase in the number of mature oligodendrocytes, the number of myelinated axons and the myelin thickness in the corpus callosum. Overall, EOM SalB was effective in two preclinical models of multiple sclerosis and demyelination, adding further evidence to show KOR agonists are a promising target for remyelinating therapies.

Nalfurafine reduces neuroinflammation and drives remyelination in models of CNS demyelinating disease

Objectives

Multiple sclerosis (MS) is a neurodegenerative disease characterised by inflammation and damage to the myelin sheath, resulting in physical and cognitive disability. There is currently no cure for MS, and finding effective treatments to prevent disease progression has been challenging. Recent evidence suggests that activating kappa opioid receptors (KOR) has a beneficial effect on the progression of MS. Although many KOR agonists like U50,488 are not suitable for clinical use because of a poor side‐effect profile, nalfurafine is a potent, clinically used KOR agonist with a favorable side‐effect profile.

Methods

Using the experimental autoimmune encephalomyelitis (EAE) model, the effect of therapeutically administered nalfurafine or U50,488 on remyelination, CNS infiltration and peripheral immune responses were compared. Additionally, the cuprizone model was used to compare the effects on non‐immune demyelination.

Results

Nalfurafine enabled recovery and remyelination during EAE. Additionally, it was more effective than U50,488 and promoted disease reduction when administered after chronic demyelination. Blocking KOR with the antagonist, nor‐BNI, impaired full recovery by nalfurafine, indicating that nalfurafine mediates recovery from EAE in a KOR‐dependent fashion. Furthermore, nalfurafine treatment reduced CNS infiltration (especially CD4⁺ and CD8⁺ T cells) and promoted a more immunoregulatory environment by decreasing Th17 responses. Finally, nalfurafine was able to promote remyelination in the cuprizone demyelination model, supporting the direct effect on remyelination in the absence of peripheral immune cell invasion.

Conclusions

Overall, our findings support the potential of nalfurafine to promote recovery and remyelination and highlight its promise for clinical use in MS.