Abstract
BackgroundIntravenous (IV) immunoglobulin (Ig) treatment is known to alleviate behavioral deficits and increase survival in the experimentally induced model of sepsis. To delineate the mechanisms by which IVIg treatment prevents neuronal dysfunction, an array of immunological and apoptosis markers was investigated.MethodsSepsis was induced by cecal ligation perforation (CLP) in rats. The animals were divided into five groups: sham, control, CLP + saline, CLP + immunoglobulin G (IgG) (250 mg/kg, iv), and CLP + immunoglobulins enriched with immunoglobulin M (IgGAM) (250 mg/kg, iv). Blood and brain samples were taken in two sets of experiments to see the early (24 h) and late (10 days) effects of treatment. Total complement activity, complement 3 (C3), and soluble complement C5b-9 levels were measured in the sera of rats using ELISA-based methods. Cerebral complement, complement receptor, NF-κB, Bax, and Bcl-2 expressions were analyzed by western blot and/or RT-PCR methods. Immune cell infiltration and gliosis were examined by immunohistochemistry using CD3, CD4, CD8, CD11b, CD19, and glial fibrillary acidic protein antibodies. Apoptotic neuronal death was investigated by TUNEL staining.ResultsIVIgG and IgGAM administration significantly reduced systemic complement activity and cerebral C5a and C5a receptor expression. Likewise, both treatment methods reduced proapoptotic NF-κB and Bax expressions in the brain. IVIgG and IgGAM treatment induced considerable amelioration in glial cell proliferation and neuronal apoptosis which were increased in non-treated septic rats.ConclusionsWe suggest that IVIgG and IgGAM administration ameliorates neuronal dysfunction and behavioral deficits by reducing apoptotic cell death and glial cell proliferation. In both treatment methods, these beneficial effects might be mediated through reduction of anaphylatoxic C5a activity and subsequent inhibition of inflammation and apoptosis pathways.
Highlights
Intravenous (IV) immunoglobulin (Ig) treatment is known to alleviate behavioral deficits and increase survival in the experimentally induced model of sepsis
The results of the present study indicate that intravenous immunoglobulin (IVIg) treatment exerts its beneficial effects on sepsis-induced neuronal dysfunction primarily through reduction of C5a-mediated gliosis and apoptosis
Our results suggest that novel treatment methods based on interruption of C5a−C5a receptor interaction might ameliorate septic encephalopathy and presumably chronic cognitive dysfunction observed in sepsis survivors
Summary
Intravenous (IV) immunoglobulin (Ig) treatment is known to alleviate behavioral deficits and increase survival in the experimentally induced model of sepsis. Intravenous immunoglobulin (IVIg) improved the integrity of the BBB and inhibited cecal ligation and perforation (CLP)-induced symptoms of sickness behavior in rats [6] In this experimental trial, we aimed to delineate mechanisms by which IVIg treatment prevents neuronal dysfunction. Given the well-known significance of the complement system in sepsis and the well-established regulatory effect of IVIg on complement activation, we hypothesized that IVIg treatment improves septic encephalopathy through the inhibition of complement-mediated neuronal destruction To test this hypothesis and find out the specific complement factors involved in septic encephalopathy, we measured the expression levels of an array of complement factors (C1q, C3, and C9 for evaluation of classical and common complement pathways; C3a, C5a, and their receptors for anaphylatoxic component of the complement system) and evaluated expression alterations in parallel to cerebral apoptosis and gliosis in the brain samples of septic rats
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