Type II Activation of Macrophages and Microglia by Immune Complexes Enhances Th17 Biasing in an IL-6-Independent Manner

Suppression of microglial Ccl2 reduces neuropathic pain associated with chronic spinal compression

Introduction

Chronic spinal compression is a common complication of spinal cord injury (SCI), which can lead to spinal stenosis or herniated discs. The ensuing neuropathic pain is often associated with the activation of microglia. In this investigation, our objective was to explore whether modifying the levels of chemokine (C-C motif) ligand 2 (Ccl2) in microglia could alleviate neuropathic pain resulting from chronic spinal compression.

Methods

We used a public database to look for major altered gene associated in a SCI model established in rats. We then employed adeno-associated virus (AAV) vectors, expressing siRNA for the identified significantly altered gene under a microglia-specific TMEM119 promoter. We also tested the impact of this treatment in microglia in vivo on the severity of chronic spinal compression and associated pain using a ttw mouse model for progressive spinal compression.

Results

We identified chemokine (C-C motif) ligand 2 (Ccl2) as the primary gene altered in microglia within a rat SCI model, utilizing a public database. Microglial Ccl2 levels were then found to be significantly elevated in disc specimens from SCI patients diagnosed with chronic spinal compression and strongly correlated with the Thompson classification of the degeneration level and pain score. Depletion of Ccl2 in microglia-specific TMEM119 promoter were developed to transfect mouse microglia in vitro, resulting in a proinflammatory to anti-inflammatory phenotypic adaption. In vivo depletion of Ccl2 in microglia mitigated the severity of chronic spinal compression and related pain in ttw mice, likely due to significant changes in pain-associated cytokines and factors.

Conclusion

Disc microglia expressing high levels of Ccl2 may contribute to chronic spinal compression and SCI-associated pain. Therapeutically targeting Ccl2 in microglia could offer a potential avenue for treating chronic spinal compression and SCI-associated pain.

Localisation of clozapine during experimental autoimmune encephalomyelitis and its impact on dopamine and its receptors

Multiple sclerosis is a disease characterised by axonal demyelination in the central nervous system (CNS). The atypical antipsychotic drug clozapine attenuates experimental autoimmune encephalomyelitis (EAE), a mouse model used to study multiple sclerosis, but the precise mechanism is unknown and could include both peripheral and CNS-mediated effects. To better understand where clozapine exerts its protective effects, we investigated the tissue distribution and localisation of clozapine using matrix-assisted laser desorption ionization imaging mass spectrometry and liquid chromatography-mass spectrometry. We found that clozapine was detectable in the brain and enriched in specific brain regions (cortex, thalamus and olfactory bulb), but the distribution was not altered by EAE. Furthermore, although not altered in other organs, clozapine levels were significantly elevated in serum during EAE. Because clozapine antagonises dopamine receptors, we analysed dopamine levels in serum and brain as well as dopamine receptor expression on brain-resident and infiltrating immune cells. While neither clozapine nor EAE significantly affected dopamine levels, we observed a significant downregulation of dopamine receptors 1 and 5 and up-regulation of dopamine receptor 2 on microglia and CD4+-infiltrating T cells during EAE. Together these findings provide insight into how neuroinflammation, as modelled by EAE, alters the distribution and downstream effects of clozapine.

Clozapine reduces infiltration into the CNS by targeting migration in experimental autoimmune encephalomyelitis

Background

Atypical antipsychotic agents, such as clozapine, are used to treat schizophrenia and other psychiatric disorders by a mechanism that is believed to involve modulating the immune system. Multiple sclerosis is an immune-mediated neurological disease, and recently, clozapine was shown to reduce disease severity in an animal model of MS, experimental autoimmune encephalomyelitis (EAE). However, the mode of action by which clozapine reduces disease in this model is poorly understood.

Methods

Because the mode of action by which clozapine reduces neuroinflammation is poorly understood, we used the EAE model to elucidate the in vivo and in vitro effects of clozapine.

Results

In this study, we report that clozapine treatment reduced the infiltration of peripheral immune cells into the central nervous system (CNS) and that this correlated with reduced expression of the chemokines CCL2 and CCL5 transcripts in the brain and spinal cord. We assessed to what extent immune cell populations were affected by clozapine treatment and we found that clozapine targets the expression of chemokines by macrophages and primary microglia. Furthermore, in addition to decreasing CNS infiltration by reducing chemokine expression, we found that clozapine directly inhibits chemokine-induced migration of immune cells. This direct target on the immune cells was not mediated by a change in receptor expression on the immune cell surface but by decreasing downstream signaling via these receptors leading to a reduced migration.

Conclusions

Taken together, our study indicates that clozapine protects against EAE by two different mechanisms; first, by reducing the chemoattractant proteins in the CNS; and second, by direct targeting the migration potential of peripheral immune cells.

Effects of Post-Treatment Hydrogen Gas Inhalation on Uveitis Induced by Endotoxin in Rats

Background

Molecular hydrogen (H₂) has been widely reported to have benefiicial effects in diverse animal models and human disease through reduction of oxidative stress and inflammation. The aim of this study was to investigate whether hydrogen gas could ameliorate endotoxin-induced uveitis (EIU) in rats.

Material/Methods

Male Sprague-Dawley rats were divided into a normal group, a model group, a nitrogen-oxygen (N-O) group, and a hydrogen-oxygen (H-O) group. EIU was induced in rats of the latter 3 groups by injection of lipopolysaccharide (LPS). After that, rats in the N-O group inhaled a gas mixture of 67% N₂ and 33% O₂, while those in the H-O group inhaled a gas mixture of 67% H₂ and 33% O₂. All rats were graded according to the signs of uveitis after electroretinography (ERG) examination. Protein concentration in the aqueous humor (AqH) was measured. Furthermore, hematoxylin-eosin staining and immunostaining of anti-ionized calcium-binding adapter molecule 1 (Iba1) in the iris and ciliary body (ICB) were carried out.

Results

No statistically significant differences existed in the graded score of uveitis and the b-wave peak time in the Dark-adapted 3.0 ERG among the model, N-O, and H-O groups (P>0.05), while rats of the H-O group showed a lower concentration of AqH protein than that of the model or N-O group (P<0.05). The number of the infiltrating cells in the ICB of rats from the H-O group was not significantly different from that of the model or N-O group (P>0.05), while the activation of microglia cells in the H-O group was somewhat reduced (P<0.05).

Conclusions

Post-treatment hydrogen gas inhalation did not ameliorate the clinical signs, or reduce the infiltrating cells of EIU. However, it inhibited the elevation of protein in the AqH and reduced the microglia activation.

Activation of T cells by dendritic cells exposed to a reference sensitizer: Towards a promising model to assess the allergenic potential of chemicals

BACKGROUND

Low molecular weight chemicals constitute one of the major causes of occupational allergies. European legislation on chemicals recommends limiting the use of in vivo models for assessing the sensitizing potential of chemicals, and encourages the development of integrated alternative methods. An in vitro mouse model of bone marrow-derived dendritic cells (BMDCs) that showed good accuracy (75%) and sensitivity (69%) has previously been developed to assess the sensitizing potential of chemicals.

OBJECTIVE

To assess the ability of BMDCs to activate T cells (TCs) in vitro.

METHODS

BMDCs pre-exposed to the reference sensitizer ammonium hexachloroplatinate (AHCP) were co-cultured with different subpopulations of TCs. TC activation was assessed by surface marker expression, proliferation, and cytokine release.

RESULTS

The results showed significant activation of TCs co-cultured with dendritic cells pre-exposed to AHCP as evaluated by CD124 expression, proliferation, and cytokine secretion. Moreover, the response of TCs appeared to be Th2-oriented. Naive TCs were shown to be involved in this response, and the removal of regulatory TCs did not improve the cell response.

CONCLUSIONS

The BMDCs used in this previously developed model appear to have the ability to activate TCs, confirming that the BMDC model represents a reliable assay for assessing the sensitizing potential of chemicals.