Neuronal oxidative stress in acute ischemic stroke: sources and contribution to cell injury

Oxidative stress has emerged as a key deleterious factor in brain ischemia and reperfusion. Malfunction of the oxidative respiratory chain in mitochondria combines with the activation of cytoplasmic oxidases to generate a burst of reactive oxygen species that cannot be neutralized by the cell’s antioxidant mechanisms. As a result, oxidative stress contributes directly to necrosis and apoptosis through a number of pathways in ischemic tissue. Pharmacological intervention with antioxidants or enhancers of endogenous antioxidant molecules is proving to be difficult due to the speed and scope of the oxidative impact. Additionally, the knowledge that neuronal fate in ischemic stroke is tightly linked to other brain cells like endothelial cells and astrocytes has shifted the focus of study from isolated neurons to the neurovascular unit. For this reason, recent efforts have been directed towards understanding the sources of oxidative stress in ischemic stroke and attempting to block the generation of oxygen radicals

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

Evidence for a detrimental role of TLR8 in ischemic stroke

Toll-like receptors (TLRs) are transmembrane pattern-recognition receptors that initiate signals in response to diverse pathogen-associated molecular patterns. Several groups have recently reported a role for TLR2 and TLR4 in ischemic stroke-induced brain injury. However, relatively little is known about the role of TLR8 in ischemic stroke. Here we provide the first evidence that TLR8 activation plays a detrimental role in stroke outcome by promoting neuronal apoptosis and T cell-mediated post-stroke inflammation. TLR8 is expressed in cerebral cortical neurons, where its levels and downstream signaling via JNK are increased in response to oxygen glucose deprivation (OGD). Treatment with a TLR8 agonist activated pro-apoptotic JNK and increased neuronal cell death during OGD. Furthermore, selective knockdown of TLR8 using siRNA protected SH-SY5Y cells following OGD, and TLR8 agonist administration in vivo increased mortality, neurological deficit and T cell infiltration following stroke. Taken together, our findings indicate a detrimental role for neuronal TLR8 signaling in the triggering of post-stroke inflammation and neuronal death

Intermittent fasting attenuates inflammasome activity in ischemic stroke

Recent findings have revealed a novel inflammatory mechanism that contributes to tissue injury in cerebral ischemia mediated by multi-protein complexes termed inflammasomes. Intermittent fasting (IF) can decrease the levels of pro-inflammatory cytokines in the periphery and brain. Here we investigated the impact of IF (16. h of food deprivation daily) for 4. months on NLRP1 and NLRP3 inflammasome activities following cerebral ischemia. Ischemic stroke was induced in C57BL/6J mice by middle cerebral artery occlusion, followed by reperfusion (I/R). IF decreased the activation of NF-κB and MAPK signaling pathways, the expression of NLRP1 and NLRP3 inflammasome proteins, and both IL-1β and IL-18 in the ischemic brain tissue. These findings demonstrate that IF can attenuate the inflammatory response and tissue damage following ischemic stroke by a mechanism involving suppression of NLRP1 and NLRP3 inflammasome activity