Intravenous immunoglobulin (IVIg) dampens neuronal toll-like receptor-mediated responses in ischemia

Background: Ischemic stroke causes a high rate of deaths and permanent neurological damage in survivors. Ischemic stroke triggers the release of damage-associated molecular patterns (DAMPs) such as high-mobility group box 1 (HMGB1), which activate toll-like receptors (TLRs) and receptor for advanced glycation endproducts (RAGE) in the affected area, leading to an exaggerated inflammatory response and cell death. Both TLRs and RAGE are transmembrane pattern recognition receptors (PRRs) that have been shown to contribute to ischemic stroke-induced brain injury. Intravenous immunoglobulin (IVIg) preparations obtained by fractionating human blood plasma are increasingly being used as an effective therapeutic agent in the treatment of several inflammatory diseases. Its use as a potential therapeutic agent for treatment of stroke has been proposed, but little is known about the direct neuroprotective mechanisms of IVIg. We therefore investigate whether IVIg exerts its beneficial effects on the outcome of neuronal injury by modulating HMGB1-induced TLR and RAGE expressions and activations. Methods: Primary cortical neurons were subjected to glucose deprivation or oxygen and glucose deprivation conditions and treated with IVIg and recombinant HMGB1. C57/BL6J mice were subjected to middle cerebral artery occlusion, followed by reperfusion, and IVIg was administered intravenously 3 h after the start of reperfusion. Expression of TLRs, RAGE and downstream signalling proteins in neurons and brain tissues were evaluated by immunoblot. Results: Treatment of cultured neurons with IVIg reduced simulated ischemia-induced TLR2, TLR4, TLR8 and RAGE expressions, pro-apoptotic caspase-3 cleavage and phosphorylation of the cell death-associated kinases such as c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK) as well as the p65 subunit of nuclear factor kappa B (NF-κB). These results were recapitulated in an in vivo model of stroke. IVIg treatment also upregulated the anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) in cortical neurons under ischemic conditions. Finally, IVIg protected neurons against HMGB1-induced neuronal cell death by modulating TLR and RAGE expressions and signalling pathways. Conclusions: Taken together, these results provide a rationale for the potential use of IVIg to target inappropriately activated components of the innate immune system following ischemic stroke

Intravenous immunoglobulin (IVIg) provides protection against endothelial cell dysfunction and death in ischemic stroke

The brain endothelium is a key component of the blood brain barrier which is compromised following ischemia, allowing infiltration of damaging immune cells and other inflammatory molecules into the brain. Intravenous immunoglobulin (IVIg) is known to reduce infarct size in a mouse model of experimental stroke.Flow cytometry analysis showed that the protective effect of IVIg in ischemia and reperfusion injury in vivo is associated with reduced leukocyte infiltration, suggesting an involvement of the endothelium. In an in vitro model of ischemia, permeability analysis of the mouse brain endothelial cell line bEnd.3 revealed that IVIg prevented the loss of permeability caused by oxygen and glucose deprivation (OGD). In addition, western blot analysis of these brain endothelial cells showed that IVIg prevented the down-regulation of tight junction proteins claudin 5 and occludin and the decline in anti-apoptotic proteins Bcl-2 and Bcl-XL caused by OGD.IVIg protects endothelial cells from ischemic insult. These studies support the use of IVIg as a pharmacological intervention for stroke therapy

Intravenous immunoglobulin (IVIg) provides protection against endothelial cell dysfunction and death in ischemic stroke

The brain endothelium is a key component of the blood brain barrier which is compromised following ischemia, allowing infiltration of damaging immune cells and other inflammatory molecules into the brain. Intravenous immunoglobulin (IVIg) is known to reduce infarct size in a mouse model of experimental stroke.Flow cytometry analysis showed that the protective effect of IVIg in ischemia and reperfusion injury in vivo is associated with reduced leukocyte infiltration, suggesting an involvement of the endothelium. In an in vitro model of ischemia, permeability analysis of the mouse brain endothelial cell line bEnd.3 revealed that IVIg prevented the loss of permeability caused by oxygen and glucose deprivation (OGD). In addition, western blot analysis of these brain endothelial cells showed that IVIg prevented the down-regulation of tight junction proteins claudin 5 and occludin and the decline in anti-apoptotic proteins Bcl-2 and Bcl-XL caused by OGD.IVIg protects endothelial cells from ischemic insult. These studies support the use of IVIg as a pharmacological intervention for stroke therapy

Combination Therapy with Low-Dose IVIG and a C1-esterase Inhibitor Ameliorates Brain Damage and Functional Deficits in Experimental Ischemic Stroke

Acute ischemic stroke causes a high rate of deaths and permanent neurological deficits in survivors. Current interventional treatment, in the form of enzymatic thrombolysis, benefits only a small percentage of patients. Brain ischemia triggers mobilization of innate immunity, specifically the complement system and Toll-like receptors (TLRs), ultimately leading to an exaggerated inflammatory response. Here we demonstrate that intravenous immunoglobulin (IVIG), a scavenger of potentially harmful complement fragments, and C1-esterase inhibitor (C1-INH), an inhibitor of complement activation, exert a beneficial effect on the outcome of experimental brain ischemia (I) and reperfusion (R) injury induced by transient occlusion of middle cerebral artery in mice. Both IVIG and C1-INH significantly and in a dose-responsive manner reduced brain infarction size, neurological deficit and mortality when administered to male mice 30\ua0min before ischemia or up to 6\ua0h after the onset of reperfusion. When combined, suboptimal doses of IVIG and C1-INH potentiated each other's neuroprotective therapeutic effects. Complement C3 and TLR2 signals were colocalized and significantly greater in brain cells adjacent to infracted brain lesions when compared to the corresponding regions of the contralateral hemisphere and to control (sham) mice. Treatment with IVIG and C1-INH effectively reduced deposition of C3b and downregulated excessive TLR2 and p-JNK1 expression at the site of I/R injury. Taken together, these results provide a rationale for potential use of IVIG and C1-INH, alone or in combination with ischemic stroke and other neurological conditions that involve inappropriately activated components of the innate immune system

IVIg attenuates complement and improves spinal cord injury outcomes in mice

Objective: Traumatic spinal cord injury ( SCI) elicits immediate neural cell death, axonal damage, and disruption of the blood-spinal cord barrier, allowing circulating immune cells and blood proteins into the spinal parenchyma. The inflammatory response to SCI involves robust complement system activation, which contributes to secondary injury and impairs neurological recovery. This study aimed to determine whether intravenous immunoglobulin ( IVIg), an FDA-approved treatment for inflammatory conditions, can scavenge complement activation products and improve recovery from contusive SCI. Methods: We used functional testing, noninvasive imaging, and detailed postmortem analysis to assess whether IVIg therapy is effective in a mouse model of severe contusive SCI. Results: IVIg therapy at doses of 0.5-2 g/kg improved the functional and histopathological outcomes from SCI, conferring protection against lesion enlargement, demyelination, central canal dilation, and axonal degeneration. The benefits of IVIg were detectable through noninvasive diffusion tensor imaging ( DTI), with IVIg treatment counteracting the progressive SCI-induced increase in radial diffusivity ( RD) in white matter. Diffusion indices significantly correlated with the functional performance of individual mice and accurately predicted the degree of myelin preservation. Further experiments revealed that IVIg therapy reduced the presence of complement activation products and phagocytically active macrophages at the lesion site, providing insight as to its mechanisms of action. Interpretation: Our findings highlight the potential of using IVIg as an immunomodulatory treatment for SCI, and the value of DTI to assess tissue damage and screen for the efficacy of candidate intervention strategies in preclinical models of SCI, both quantitatively and noninvasively