Evidence for an early innate immune response in the motor cortex of ALS.

BACKGROUND: Recent evidence indicates the importance of innate immunity and neuroinflammation with microgliosis in amyotrophic lateral sclerosis (ALS) pathology. The MCP1 (monocyte chemoattractant protein-1) and CCR2 (CC chemokine receptor 2) signaling system has been strongly associated with the innate immune responses observed in ALS patients, but the motor cortex has not been studied in detail. METHODS: After revealing the presence of MCP1 and CCR2 in the motor cortex of ALS patients, to elucidate, visualize, and define the timing, location and the extent of immune response in relation to upper motor neuron vulnerability and progressive degeneration in ALS, we developed MCP1-CCR2-hSOD1G93A mice, an ALS reporter line, in which cells expressing MCP1 and CCR2 are genetically labeled by monomeric red fluorescent protein-1 and enhanced green fluorescent protein, respectively. RESULTS: In the motor cortex of MCP1-CCR2-hSOD1G93A mice, unlike in the spinal cord, there was an early increase in the numbers of MCP1+ cells, which displayed microglial morphology and selectively expressed microglia markers. Even though fewer CCR2+ cells were present throughout the motor cortex, they were mainly infiltrating monocytes. Interestingly, MCP1+ cells were found in close proximity to the apical dendrites and cell bodies of corticospinal motor neurons (CSMN), further implicating the importance of their cellular interaction to neuronal pathology. Similar findings were observed in the motor cortex of ALS patients, where MCP1+ microglia were especially in close proximity to the degenerating apical dendrites of Betz cells. CONCLUSIONS: Our findings reveal that the intricate cellular interplay between immune cells and upper motor neurons observed in the motor cortex of ALS mice is indeed recapitulated in ALS patients. We generated and characterized a novel model system, to study the cellular and molecular basis of this close cellular interaction and how that relates to motor neuron vulnerability and progressive degeneration in ALS.

Reduction of the foreign body response and neuroprotection by apyrase and minocycline in chronic cannula implantation in the rat brain.

Implantation of electrodes or cannulae into the brain is accompanied by a tissue response referred to as foreign body response. Adenosine triphosphate (ATP) is one of the signalling molecules released by injured cells which mediate the chemoattraction of microglial cells. The constitutive release of pro-inflammatory and cytotoxic substances by microglial cells in chronic implants exacerbates neuronal cell death and the immune response. This study aimed to interfere with the initial events of the foreign body response in order to mitigate neurotoxicity and inflammation. For this purpose, the ATP-hydrolysing enzyme apyrase and the antibiotic minocycline with a broad range of anti-inflammatory, anti-apoptotic and glutamate-antagonist properties were locally infused during cannula implantation in the caudal forelimb area of the motor cortex in Lister Hooded rats. The rats' motor performance was assessed in a skilled reaching task and the distribution of neurons and glial cells in the vicinity of the implant was examined 2 and 6 weeks post-implantation. Apyrase as well as minocycline increased the number of surviving neurons and reduced microglial activation. Moreover, minocycline improved the motor performance and, additionally, caused a temporary reduction in astrogliosis, suggesting it as a possible therapeutic candidate to improve the biocompatibility of chronic brain implants.

Rewiring of the corticospinal tract in the adult rat after unilateral stroke and anti-Nogo-A therapy.

Adult Long Evans rats received a photothrombotic stroke that destroyed >90% of the sensorimotor cortex unilaterally; they were subsequently treated intrathecally for 2 weeks with a function blocking antibody against the neurite growth inhibitory central nervous system protein Nogo-A. Fine motor control of skilled forelimb grasping improved to 65% of intact baseline performance in the anti-Nogo-A treated rats, whereas control antibody treated animals recovered to only 20% of baseline scores. Bilateral retrograde tract tracing with two different tracers from the intact and the denervated side of the cervical spinal cord, at different time points post-lesion, indicated that the intact corticospinal tract had extensively sprouted across the midline into the denervated spinal hemicord. The original axonal arbours of corticospinal tract fibres that had recrossed the midline were subsequently withdrawn, leading to a complete side-switch in the projection of a subpopulation of contralesional corticospinal tract axons. Anterograde tracing from the contralesional cortex showed a 2-3-fold increase of midline crossing fibres and additionally a massive sprouting of the pre-existing ipsilateral ventral corticospinal tract fibres throughout the entire cervical enlargement of the anti-Nogo-A antibody-treated rats compared to the control group. The laminar distribution pattern of the ipsilaterally projecting corticospinal tract fibres was similar to that in the intact spinal cord. These plastic changes were paralleled by a somatotopic reorganization of the contralesional motor cortex where the formation of an ipsilaterally projecting forelimb area was observed. Intracortical microstimulation of the contralesional motor cortex revealed that low threshold currents evoked ipsilateral movements and electromyography responses at frequent cortical sites in the anti-Nogo-A, but not in the control antibody-treated animals. Subsequent transection of the spared corticospinal tract in chronically recovered animals, treated with anti-Nogo-A, led to a reappearance of the initial lesion deficit observed after the stroke lesion. These results demonstrate a somatotopic side switch anatomically and functionally in the projection of adult corticospinal neurons, induced by the destruction of one sensorimotor cortex and the neutralization of the CNS growth inhibitory protein Nogo-A.

Anti-streptococcus IgM antibodies induce repetitive stereotyped movements: cell activation and co-localization with Fcα/µ receptors in the striatum and motor cortex.

Group A beta-hemolytic streptococcus (GABHS) infections are implicated in neuropsychiatric disorders associated with an increased expression of repetitive stereotyped movements. Anti-streptococcus IgG presumably cross-reacts with elements on basal ganglia cells, modifies their function, and triggers symptoms. IgM may play a unique role in precipitating behavioral disturbances since variations in cortico-striatal activity occur in temporal congruity with peak IgM titers during an orchestrated immune response. We discovered in Balb/c mice that single subcutaneous injections of mouse monoclonal IgM antibodies to streptococcus group A bacteria induce marked dose-dependent increases in repetitive stereotyped movements, including head bobbing, sniffing, and intense grooming. Effects were antibody- and antigen-specific: anti-streptococcus IgG stimulated ambulatory activity and vertical activity but not these stereotypies, while anti-KLH IgM reduced activity. We suggest that anti-streptococcus IgM and IgG play unique roles in provoking GABHS-related behavioral disturbances. Paralleling its stereotypy-inducing effects, anti-streptococcus IgM stimulated Fos-like immunoreactivity in regions linked to cortico-striatal projections involved in motor control, including subregions of the caudate, nucleus accumbens, and motor cortex. This is the first evidence that anti-streptococcus IgM antibodies induce in vivo functional changes in these structures. Moreover, there was a striking similarity in the distributions of anti-streptococcus IgM deposits and Fos-like immunoreactivity in these regions. Of further importance, Fcα/µ receptors, which bind IgM, were present- and co-localized with anti-streptococcus IgM in these structures. We suggest that anti-streptococcus IgM-induced alterations of cell activity reflect local actions of IgM that involve Fcα/µ receptors. These findings support the use of anti-streptococcus monoclonal antibody administration in Balb/c mice to model GABHS-related behavioral disturbances and identify underlying mechanisms.

Influence of anti-Nogo-A antibody treatment on the reorganization of callosal connectivity of the premotor cortical areas following unilateral lesion of primary motor cortex (M1) in adult macaque monkeys.

Following unilateral lesion of the primary motor cortex, the reorganization of callosal projections from the intact hemisphere to the ipsilesional premotor cortex (PM) was investigated in 7 adult macaque monkeys, in absence of treatment (control; n = 4) or treated with function blocking antibodies against the neurite growth inhibitory protein Nogo-A (n = 3). After functional recovery, though incomplete, the tracer biotinylated dextran amine (BDA) was injected in the ipsilesional PM. Retrogradely labelled neurons were plotted in the intact hemisphere and their number was normalized with respect to the volume of the core of BDA injection sites. (1) The callosal projections to PM in the controls originate mainly from homotypic PM areas and, but to a somewhat lesser extent, from the mesial cortex (cingulate and supplementary motor areas). (2) In the lesioned anti-Nogo-A antibody-treated monkeys, the normalized number of callosal retrogradely labelled neurons was up to several folds higher than in controls, especially in the homotypic PM areas. (3) Except one control with a small lesion and a limited, transient deficit, the anti-Nogo-A antibody-treated monkeys recovered to nearly baseline levels of performance (73-90 %), in contrast to persistent deficits in the control monkeys. These results are consistent with a sprouting and/or sparing of callosal axons promoted by the anti-Nogo-A antibody treatment after lesion of the primary motor cortex, as compared to untreated monkeys.

Potential role of IL-13 in neuroprotection and cortical excitability regulation in multiple sclerosis.

BACKGROUND: Inflammation triggers secondary neurodegeneration in multiple sclerosis (MS). OBJECTIVES: It is unclear whether classical anti-inflammatory cytokines have the potential to interfere with synaptic transmission and neuronal survival in MS. METHODS: Correlation analyses between cerebrospinal fluid (CSF) contents of anti-inflammatory cytokines and molecular, imaging, clinical, and neurophysiological measures of neuronal alterations were performed. RESULTS: Our data suggest that interleukin-13 (IL-13) plays a neuroprotective role in MS brains. We found, in fact, that the levels of IL-13 in the CSF of MS patients were correlated with the contents of amyloid-ß(1-42). Correlations were also found between IL-13 and imaging indexes of axonal and neuronal integrity, such as the retinal nerve fibre layer thickness and the macular volume evaluated by optical coherence tomography. Furthermore, the levels of IL-13 were related to better performance in the low-contrast acuity test and Multiple Sclerosis Functional Composite scoring. Finally, by means of transcranial magnetic stimulation, we have shown that GABAA-mediated cortical inhibition was more pronounced in patients with high IL-13 levels in the CSF, as expected for a neuroprotective, anti-excitotoxic effect. CONCLUSIONS: The present correlation study provides some evidence for the involvement of IL-13 in the modulation of neuronal integrity and synaptic function in patients with MS.

Motor cortex transcriptome reveals microglial key events in amyotrophic lateral sclerosis.

OBJECTIVE: To identify transcriptomic changes, neuropathologic correlates, and cellular subpopulations in the motor cortex of sporadic amyotrophic lateral sclerosis (ALS). METHODS: We performed massive RNA sequencing of the motor cortex of patients with ALS (n = 11) and healthy controls (HCs; n = 8) and analyzed gene expression alterations, differential isoform usage, and gene coexpression networks. Furthermore, we used cell type deconvolution algorithms with human single-nucleus RNA sequencing data as reference to identify perturbations in cell type composition associated with ALS. We performed immunohistochemical techniques to evaluate neuropathologic changes in this brain region. RESULTS: We report extensive RNA expression alterations at gene and isoform levels, characterized by the enrichment of neuroinflammatory and synaptic-related pathways. The assembly of gene coexpression modules confirmed the involvement of these 2 major transcriptomic changes, which also showed opposite directions related to the disease. Cell type deconvolution revealed an overrepresentation of microglial cells in ALS compared with HC. Notably, microgliosis was driven by a subcellular population presenting a gene expression signature overlapping with the recently described disease-associated microglia (DAM). Using immunohistochemistry, we further evidenced that this microglial subpopulation is overrepresented in ALS and that the density of pTDP43 aggregates negatively correlates with the proportion of microglial cells. CONCLUSIONS: DAM has a central role in microglia-related neuroinflammatory changes in the motor cortex of patients with ALS, and these alterations are coupled with a reduced expression of postsynaptic transcripts.

Natural killer cells modulate motor neuron-immune cell cross talk in models of Amyotrophic Lateral Sclerosis.

In amyotrophic lateral sclerosis (ALS), immune cells and glia contribute to motor neuron (MN) degeneration. We report the presence of NK cells in post-mortem ALS motor cortex and spinal cord tissues, and the expression of NKG2D ligands on MNs. Using a mouse model of familial-ALS, hSOD1G93A, we demonstrate NK cell accumulation in the motor cortex and spinal cord, with an early CCL2-dependent peak. NK cell depletion reduces the pace of MN degeneration, delays motor impairment and increases survival. This is confirmed in another ALS mouse model, TDP43A315T. NK cells are neurotoxic to hSOD1G93A MNs which express NKG2D ligands, while IFNγ produced by NK cells instructs microglia toward an inflammatory phenotype, and impairs FOXP3+/Treg cell infiltration in the spinal cord of hSOD1G93A mice. Together, these data suggest a role of NK cells in determining the onset and progression of MN degeneration in ALS, and in modulating Treg recruitment and microglia phenotype.

Allyl Sulfide Counteracts 1-Bromopropane-Induced Neurotoxicity by Inhibiting Neuroinflammation and Oxidative Stress.

Chronic exposure to 1-bromopropane (1-BP), an alternative to ozone-depleting solvents, produces potential neurotoxicity in occupational populations. However, no therapeutic strategy is available currently. Accumulating evidence suggests that cytochrome P4502E1 (CYP2E1) is critical for the active metabolism of 1-BP. The purpose of this study is aimed to test whether inhibition of CYP2E1 by allyl sulfide, a specific inhibitor of CYP2E1, could be able to protect against 1-BP-induced neurotoxicity. Male Wistar rats were intoxicated with 1-BP for 9 continuous weeks with or without allyl sulfide pretreatment. Results clearly demonstrated that 1-BP exposure induced decrease in NeuN+ cells and increase in cleaved caspase-3 expression and TUNEL+ cells in motor cortex of rats, which was significantly ameliorated by allyl sulfide. Allyl sulfide treatment also recovered the motor performance of rats treated with 1-BP. Mechanistically, allyl sulfide-inhibited 1-BP-induced expression of CYP2E1 in microglia, which was associated with suppression of microglial activation and M1 polarization in motor cortex of rats. Reduced oxidative stress was also observed in rats treated with combined allyl sulfide and 1-BP compared with 1-BP alone group. Furthermore, we found that allyl sulfide abrogated 1-BP-induced activation of Nuclear factor(NF)-κB and GSH/Thioredoxin/ASK1 pathways, the key factor for the maintenance of M1 microglial inflammatory response and oxidative stress-related neuronal apoptosis, respectively. Thus, our results showed that allyl sulfide exerted neuroprotective effects in combating 1-BP-induced neurotoxicity through inhibition of neuroinflammation and oxidative stress. Blocking CYP2E1 activity by allyl sulfide might be a promising avenue for the treatment of neurotoxicity elicited by 1-BP and other related neurotoxicants.

CX3CR1+ monocytes modulate learning and learning-dependent dendritic spine remodeling via TNF-α.

Impaired learning and cognitive function often occurs during systemic infection or inflammation. Although activation of the innate immune system has been linked to the behavioral and cognitive effects that are associated with infection, the underlying mechanisms remain poorly understood. Here we mimicked viral immune activation with poly(I:C), a synthetic analog of double-stranded RNA, and longitudinally imaged postsynaptic dendritic spines of layer V pyramidal neurons in the mouse primary motor cortex using two-photon microscopy. We found that peripheral immune activation caused dendritic spine loss, impairments in learning-dependent dendritic spine formation and deficits in multiple learning tasks in mice. These observed synaptic alterations in the cortex were mediated by peripheral-monocyte-derived cells and did not require microglial function in the central nervous system. Furthermore, activation of CX3CR1highLy6Clow monocytes impaired motor learning and learning-related dendritic spine plasticity through tumor necrosis factor (TNF)-α-dependent mechanisms. Taken together, our results highlight CX3CR1high monocytes and TNF-α as potential therapeutic targets for preventing infection-induced cognitive dysfunction.

IgG reactivity in the spinal cord and motor cortex in amyotrophic lateral sclerosis.

The spinal cord and motor cortex of patients with amyotrophic lateral sclerosis (ALS) were examined with immunohistochemical methods for the presence of IgG. In 13 of 15 spinal cords, a population of motoneurons stained positively for IgG in a granular pattern, characteristic of binding to the rough endoplasmic reticulum. In 6 of 11 motor cortices, a proportion of pyramidal cells also stained positively for IgG. No such reactivity was noted in motoneurons of control human tissues, although positive IgG staining was present in astrocytes of ALS and control specimens. Reactive microglia and/or macrophages were detected in the territory of degenerating pyramidal tracts and ventral horns. The surface of most of these cells stained positively for IgG, and 50% stained positively for HLA-DR. The accumulation of IgG in motoneurons and the presence of immunologically active macrophages provide additional evidence for the participation of immunologic factors in the pathogenesis of ALS.

Comparison of two techniques for targeting the production of monoclonal antibodies against particular antigens.

We have compared the efficacy of two methods for enhancing the probability of producing monoclonal antibodies against particular target antigens in a complex mixture. These methods use two tissue extracts, one extract that contains (A) and one extract that does not contain (B) the target antigen(s) of interest. In the chemical immunosuppression approach, cyclophosphamide is used to suppress the mouse's response to common antigens in extract B before injection of extract A containing the target antigens. In the tolerization approach, neonatal mice are tolerized against the common antigens in extract B before injection of extract A containing the target antigens. Although small numbers of animals were used in this initial comparison, immunodot assays clearly indicate that the cyclophosphamide immunosuppression method yields significantly more monoclonal antibodies specific for the target antigen-containing extract A than does the tolerization method.

Deposits of IgG and C3 in the spinal cord and motor cortex of ALS patients.

Deposits of IgG and complement were demonstrated by direct immunofluorescent techniques with sections of motor cortex and spinal cord from amyotrophic lateral sclerosis (ALS) patients. Six of 16 ALS patients showed deposits within the spinal cord while 5 of 13 showed similar deposits within the motor cortex. The specificity of this staining was shown by blocking experiments and the use of conjugated F(ab')2. Similar deposits were found in the CNS in disease states associated with possible immune or infectious etiologies and were not found in the CNS of normal controls.

[Effect of the neurosensitization of female rats on the functional indices of the DNA-, RNA- and protein-synthesizing neuronal apparatus of the cerebral cortex and of the immune system in their progeny]. / Vliianie neirosensibilizatsii samok krys na nekotorye pokazateli sostoianiia DNK-RNK-beloksinteziruiushchego apparata neironov kory golovnogo mozga i immunnoi sistemy u potomstva.

Neurosensitization effects on the state of the ribonucleoprotein particles and chromatin in nuclei of the Vth layer cortical neurons were studied in female rats. Anti-brain antibodies were investigated in their offspring on the 30th and 60th days. On the 60th day the electron-cytochemical changes were found in the nuclei suggesting the deterioration of nucleolar DNA processing and inhibition of nucleolar functional activity. Anti-brain antibodies were also found in the blood. Direct antibodies interference in the function of cellular DNA-RNA-protein-synthetizing system seems plausible.

[Effect of training on the dynamics of the antigenic spectrum of rat brains]. / Vliianie obucheniia na dinamiku antigennogo spektra mozga krys.

Study of the time course of the content of 3 brain proteins in 6 different structures of the central nervous system 1 and 7 days after the conditioned reflex development has shown that both specific and nonspecific proteins of nervous tissue may participate in the processes that accompany the formation of the memory trace. The visual cortex appeared to be the most active in these processes, which may be accounted for by the use in this model of light as conditioned stimulus.

Immunological profile of amyotrophic lateral sclerosis patients and their cell-mediated immune responses to viral and CNS antigens.

The 'immunological profile' of amyotrophic lateral sclerosis (ALS) patients was established from standard tests for B- and T-cell function. This showed no significant difference from age and sex-matched other neurological (CNS) disease controls and normal subjects. Immune complex (IC) levels in ALS serum differed significantly from normal controls but not from CNS controls. There was no relation between the various indices of immune activity of IC levels and the clinical disability of the ALS patient or progression of the disease. Distribution of complement-fixing antibodies to poliovirus was similar to sera of ALS and control groups. The in vitro cell-mediated immune responses to poliovirus, however, were significantly greater in ALS patients than in CNS controls and were inversely related to the ALS disability score. Poliovirus has not been demonstrated in the CNS or extra-CNS tissues of ALS patients by conventional means but, if latent or defective poliovirus or related virus were present, this could account for sensitization and a possible autoimmune mechanism. ALS patients exhibited in vitro cellular immunity to ALS and normal CNS subfractions. These responses were not related to the ALS disability score or progression of the disease and probably represent epiphenomena.

The role of asymmetry of nervous and immune systems in the formation of cellular immunity of (CBaxC57Bl/6) F1 mice.

We have previously shown the existence of functional asymmetry of the immune system and the role of brain hemispheres and different lobes of thymus in the development of humoral immune response in (CBA x C57Bl/6) F1 mice. The role of asymmetry of the nervous and immune systems in the formation of the cellular immune response [delayed-type hypersensitivity (DTH) reaction] in these mice has been studied in our work. In order to test the influence of asymmetry of the primary immune organs, thymus, on the cellular immune response, mice were thymectomized and then we studied the effect of the injection of cells from contralateral thymus lobes of right-dominant and left-dominant donors by motor asymmetry on how pronounced the DTH reaction in the back left paw was. The injection of thymocytes from right-dominant donors appeared to result in significant differences in DTH reaction between left- and right-handed mice. At the same time, our experiments failed to discover any pronounced role of thymus asymmetry in the formation of DTH reaction. In order to test the influence of asymmetry of peripheral immune organs, regional lymph nodes, on the regulation of cellular immune response, we compared the DTH reaction in left and right paws of mice. We found that the intensity of the DTH reaction to sheep red blood cells in the front paws of (CBA x C57Bl/6) F1 mice depends not only on whether the antigen is injected into the left or right paw but also on the motor asymmetry of the hemispheres. While comparing the DTH reaction in the back left and right paw of mice we showed that in both right- and left-handed mice it was much more pronounced in the left paw than in the right one. The data obtained testify to the functional asymmetry of bilateral lymph nodes located near the forming cellular immune reaction. Thus, the results obtained show that the intensity of DTH reaction in (CBA x C57Bl/6) F1 mice depends on the functional asymmetry of regional lymph nodes and motor of brain hemispheres. The thymus functional asymmetry is of slight importance in DTH reaction.

Localization of glutaminase-like and aspartate aminotransferase-like immunoreactivity in neurons of cerebral neocortex.

The distribution of glutaminase (GLNase)- and aspartate aminotransferase (AATase)-immunoreactive cells was examined in the cerebral neocortex of rat and guinea pig and in the somatic sensorimotor and primary visual cortex of the Macaca fascicularis monkey. These enzymes are involved in the metabolism of glutamate and aspartate, two amino acids thought to be excitatory amino acid transmitters for cortical neurons. In each of the species examined a large percentage of layer V and VI pyramidal neurons have pronounced glutaminase-like immunoreactivity (GLNase IR). In contrast, neurons in layers I, II, and IV show little GLNase IR. Layer III in the rat and guinea pig contains only a few, densely labeled GLNase-like-immunoreactive (GLNase-Ir) pyramidal neurons, whereas in the monkey the number of GLNase-Ir cells in layer III varies between cytoarchitectonic fields. Area 3b of the primary somatic sensory cortex and area 17 (primary visual cortex) contain few GLNase-Ir cells in layer III. However, layer III contains moderate numbers of GLNase IR in cells in areas 3a, 1, 2, 5, and in the primary motor cortex. Within the motor cortex the largest pyramidal ("Betz") cells are not labeled. In marked contrast to the results with antibody to GLNase, antibody to AATase labels cells that appear nonpyramidal in form, and these cells are in all cortical layers in each of the species examined. This distribution is roughly similar throughout all areas of rodent neocortex, but in monkey visual cortex AATase-immunoreactive neurons are more numerous in layers II-III, IVc, and VI. When combined with the findings of other studies, our results suggest that GLNase IR marks pyramidal neurons that use an excitatory amino acid transmitter. Antibody to AATase appears to mark intrinsic cortical neurons. The AATase immunoreactivity of these cells could indicate that they use an excitatory amino acid transmitter. However, their form and distribution in cortex suggest that this antibody labels GABAergic neurons.