Complement C5 regulates the expression of insulin-like growth factor binding proteins in chronic experimental allergic encephalomyelitis.

Complement activation plays a central role in autoimmune demyelination. To explore the possible effects of C5 on post-inflammatory tissue repair, we investigated the transcriptional profile induced by C5 in chronic experimental allergic encephalomyelitis (EAE) using oligonucleotide arrays. We used C5-deficient (C5-d) and C5-sufficient (C5-s) mice to compare the gene expression profile and we found that 390 genes were differentially regulated in C5-s mice as compared to C5-d mice during chronic EAE. Among them, a group of genes belonging to the family of insulin-like growth factor binding proteins (IGFBP) and transforming growth factor (TGF)-beta3 were found most significantly differentially regulated by C5. The dysregulation of these genes suggests that these proteins might be responsible for the gliosis and lack of remyelination seen in C5-d mice with chronic EAE.

Dendritic cells are abundant in non-lesional gray matter in multiple sclerosis.

We have analyzed the localization of dendritic cells (DCs) in non-lesional gray matter (NLGM) in comparison to non-lesional white matter (NLWM) and acute or chronic active multiple sclerosis (MS) lesions. Immunohistochemistry was performed on cryostat sections for DCs markers (CD209, CD205, CD83) and other markers for inflammatory cells (CD68, CD8, CD4, CD3, CCR7, CCR5). We found cells expressing CD209 and containing myelin basic protein in both perivascular and parenchymal areas of NLGM. Our findings showing the expression of CD209(+) cells in NLGM parenchymal areas are surprising relative to the previous literature which reported the presence of CD209(+) DCs only in MS plaque perivascular areas. Although less numerous than CD209(+) cells, NLGM cells expressing mature DCs marker CD205 were consistently detected in perivascular cuffs of most lesions. In double labeling experiments, some but not all of the CD209(+) cells also expressed CD68 and CCR5. We also found CD209(+) cells in close contact with CD3(+) lymphocytes suggesting that DCs might contribute to the local activation of pathogenic T cells in the NLGM. Since injury to the NLGM is one of the key factors associated with disability accumulation, targeting DCs may represent a possible new therapeutic approach in MS to prevent disease progression.

Complement activation in diabetic ketoacidosis brains.

The metabolic crisis of diabetic ketoacidosis (DKA) and its treatment can result in the life-threatening complication of clinical brain edema. However, there is limited information available regarding either the pathophysiology or histology of this acute complication. It has been reported that DKA and its treatment are associated with a systemic inflammatory response involving the activation of the complement cascade with increases of SC5b-9 serum level. We studied the brains of two patients, both of whom died as the result of DKA-related brain edema, for the presence of C5b-9, C1q and the expression of the CD59. Apoptosis was also evaluated by the TUNEL method. All regions of the brain demonstrated varying degrees of C5b-9 deposits on neurons, oligodendrocytes and blood vessels. C5b-9 was co-localized with C1q, suggesting the activation of classical pathway. No expression of CD59 was found on neurons, oligodendrocytes or blood vessels in DKA brain, but this complement inhibitor was present on these cells in the normal brain. Rarely, C5b-9 was co-localized with apoptotic neurons and OLG. Our data demonstrate that the metabolic crisis of DKA results in a loss of CD59 expression and assembly of C5b-9 on neurons and oligodendrocytes, suggesting that complement activation and C5b-9 may play a role in the pathophysiology of the brain edema of DKA.

C5b-9 terminal complex protects oligodendrocytes from apoptotic cell death by inhibiting caspase-8 processing and up-regulating FLIP.

Activation of the terminal complement cascade involving C5 to C9 proteins has a beneficial role for oligodendrocytes (OLG) in experimental allergic encephalomyelitis, an animal model of multiple sclerosis, by protecting them from apoptotic cell death. We have previously shown that sublytic C5b-9 complexes, through posttranslational regulation of Bad, inhibit the mitochondrial pathway of apoptosis induced by serum deprivation. In the present study, we examined the possible involvement of the caspase-8 and Fas pathway in OLG apoptosis and the role of C5b-9 in this process. In a serum-free defined medium, OLG undergo apoptosis and differentiation concomitantly. Under this condition, we found that caspase-8 processing was increased in association with Bid cleavage and markedly reduced expression of cellular FLIP long isoform protein. The caspase-8 inhibitor Z-IETD-FMK inhibited cell death associated with differentiation in a dose-dependent manner. Exposure to C5b-9 induced an inhibition of caspase-8 activation, Bid cleavage, and a significant increase in expression of cellular FLIP long isoform. These C5b-9 effects were reversed by PI3K inhibitor LY294002. C5b-9 also down-regulated the expression of FasL and the Fas-induced apoptosis. These data suggest that C5b-9 through PI3K signaling can rescue OLG from Fas-mediated apoptosis by regulating caspase-8 processing.

Potassium channels Kv1.3 and Kv1.5 are expressed on blood-derived dendritic cells in the central nervous system.

OBJECTIVE: Potassium (K(+)) channels on immune cells have gained attention recently as promising targets of therapy for immune-mediated neurological diseases such as multiple sclerosis (MS). We examined K(+) channels on dendritic cells (DCs), which infiltrate the brain in MS and may impact disease course. METHODS: We identified K(+) channels on blood-derived DCs by whole-cell patch-clamp analysis, confirmed by immunofluorescent staining. We also stained K(+) channels in brain sections from MS patients and control subjects. To test functionality, we blocked K(v)1.3 and K(v)1.5 in stimulated DCs with pharmacological blockers or with an inducible dominant-negative K(v)1.x adenovirus construct and analyzed changes in costimulatory molecule upregulation. RESULTS: Electrophysiological analysis of DCs showed an inward-rectifying K(+) current early after stimulation, replaced by a mix of voltage-gated K(v)1.3- and K(v)1.5-like channels at later stages of maturation. K(v)1.3 and K(v)1.5 were also highly expressed on DCs infiltrating MS brain tissue. Of note, we found that CD83, CD80, CD86, CD40, and interleukin-12 upregulation were significantly impaired on K(v)1.3 and K(v)1.5 blockade. INTERPRETATION: These data support a functional role of K(v)1.5 and K(v)1.3 on activated human DCs and further define the mechanisms by which K(+) channel blockade may act to suppress immune-mediated neurological diseases.