Pharmacological inhibition of TLR4-NOX4 signal protects against neuronal death in transient focal ischemia.

Recent data have shown that TLR4 performs a key role in cerebral ischemia-reperfusion injury which serves as the origin of the immunological inflammatory reactions. However, the therapeutic effects of pharmacological inhibitions of TLR4 and its immediate down-stream pathway remain to be uncovered. In the present study, on mice, intracerebroventricular injection of resatorvid (TLR4 signal inhibitor; 0.01 µg) significantly reduced infarct volume and improved neurological score after middle cerebral artery occlusion and reperfusion. The levels of phospho-p38, nuclear factor-kappa B, and matrix metalloproteinase 9 expressions were significantly suppressed in the resatorvid-treated group. In addition, NOX4 associates with TLR4 after cerebral ischemia-reperfusion seen in mice and human. Genetic and pharmacological inhibitions of TLR4 each reduced NOX4 expression, leading to suppression of oxidative/nitrative stress and of neuronal apoptosis. These data suggest that resatorvid has potential as a therapeutic agent for stroke since it inhibits TLR4-NOX4 signaling which may be the predominant causal pathway.

Involvement of Toll-like receptors in ischemia-induced neuronal damage.

Cerebral ischemia is characterized by obvious inflammatory cell aggregations, up-regulation of cytokine expression, and increased expression of intercellular adhesion molecules. Like systemic bacterial infections, cerebral injury is also associated with innate immunity, a specific immunologic response that utilizes Toll-like receptors (TLRs). The involvement of TLRs in cerebral ischemia is now being confirmed using animal models. Recent reports reveal that mice that lack TLR2 and TLR4 show improved stroke outcomes and that TLR2 and 4 may contribute to neuronal injury that occurs after cerebral ischemia. In this review, we have summarized these recent reports concerning the association of TLRs with cerebral ischemia.

Fasudil and ozagrel in combination show neuroprotective effects on cerebral infarction after murine middle cerebral artery occlusion.

Rho kinase (ROCK), one of the serine/threonine kinases, is involved in pathologic conditions, and its activation causes neuronal cell death. Fasudil, a selective ROCK inhibitor, has been reported to cause increased cerebral blood flow (CBF) in the ischemic brain and protect against neuronal cell death by inhibiting ROCK. Ozagrel, a thromboxane A(2) synthase inhibitor, inhibits platelet aggregation and causes vasodilatation, thereby increasing CBF in cerebral thrombosis. The present study evaluates the combination therapy of fasudil and ozagrel on focal brain ischemia induced by middle cerebral artery occlusion (MCAO) in mice. Each monotherapy of fasudil at 10 mg/kg i.p. and ozagrel at 30 mg/kg i.p. significantly reduced cerebral infarction. The combination therapy of fasudil (3 mg/kg i.p.) and ozagrel (10 mg/kg i.p.), which are noneffective doses, resulted in reduction of cerebral infarction, and the protective effect was observed up to 5 min, but not 3 h, after reperfusion. Regional CBF after MCAO and phosphorylation of endothelial nitric-oxide synthase (NOS) significantly increased in response to the combination therapy, whereas these effects were not observed with monotherapy of either drug. The protective effect of combination treatment was antagonized by the treatment of a NOS inhibitor, nitro-l-arginine methyl ester hydrochloride. These findings indicate that the combination treatment of fasudil and ozagrel exhibits additive effects for neuroprotection after MCAO. These findings indicate that the combination treatment of fasudil and ozagrel may be useful as a potential therapeutic strategy for the treatment of stroke.

Proteomic approach with LCMS-IT-TOF identified an increase of Rab33B after transient focal cerebral ischemia in mice.

BACKGROUND: Several proteins are known to be markedly expressed in the brain during cerebral ischemia; however, the changes in protein profiles within the ischemic brain after an ischemic insult have not been fully elucidated. We studied the changes in the ischemic brain proteome after focal cerebral ischemia, induced by middle cerebral artery occlusion (MCAO) in mice. METHODS: LCMS-IT-TOF mass spectrometry was used to detect the changes in ischemic brain protein patterns after MCAO. We evaluated the protein expression detected in the ischemic area, by western blotting and immunohistochemistry. RESULTS: Nine unique proteins were identified from the ischemic area at 10 h after ischemic insult. Among these proteins, we focused on Rab33b, a member of RAS oncogene family and we found that Rab33b was up-regulated in the ischemic striatum and the number of Rab33B-positive cells increased in a time-dependent manner. Rab33B colocalized with Iba-1 positive microglia in the ischemic area. CONCLUSION: These findings suggest that LCMS-IT-TOF is useful for identifying changes in proteins after cerebral ischemia and that Rab33B is partially related to the pathogenesis of transient cerebral ischemia in mice.

Post-treatment of a BiP inducer prevents cell death after middle cerebral artery occlusion in mice.

We previously reported the effect of a selective inducer of BiP (a BiP inducer X; BIX) after permanent middle cerebral artery occlusion (MCAO) in mice. However, in acute stroke, almost all drugs have been used clinically after the onset of events. We evaluated the effect of post-treatment of BIX after permanent MCAO in mice, and examined its neuroprotective properties in in vivo mechanism. BIX (intracerebroventricular injection at 20µg) administered either at 5min or 3h after occlusion reduced both infarct volume and brain swelling, but at 6h after occlusion there was no reduction. BIX protected against the decrease in a dose-dependent manner. Furthermore, BIX reduced the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells induced by the ischemia in ischemic penumbra. These findings indicate that post-treatment with BIX after ischemia has neuroprotective effects against acute ischemic neuronal damage in mice even when given up to 3h after MCAO. BIX may therefore be a potential drug for stroke.

Metallothionein-III knockout mice aggravates the neuronal damage after transient focal cerebral ischemia.

Metallothioneins (MTs) are metal-binding proteins and have four isoforms. MT-III was, at first, found in the brains of patients with Alzheimer's disease. MT-III exists mainly in the central nervous system, and the main effects are thought to be anti-oxidative and regulate zinc levels. In some previous reports, MT-III exhibited neuroprotective effects in various pathological situations, but its detailed effects are still unclear. In the present study, we examined neuronal damage after a middle cerebral artery occlusion (MCAO) in MT-III knockout (KO) mice to elucidate the relationship between MT-III and cerebral infarction. There was no significant difference in cerebral infarction after 24-h permanent MCAO between the wild-type and MT-III KO mice. On the other hand, after 2-h MCAO and 22-h reperfusion, cerebral infarction in the MT-III KO mice was aggravated compared with the wild-type mice. Furthermore, fatal rate of MT-III KO mice increased from 3 days after MCAO, and neurological deficits at 5 and 7 days after MCAO of MT-III KO mice were worse than those of wild-type. We examined terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining and the immunostaining of an oxidative stress marker, 8-hydroxy-2'-deoxyguanosine (8-OHdG), at 24 h after transient MCAO. In the penumbra lesion, the positive cell numbers in both staining assays were higher in the MT-III KO mice than those of the wild-type mice. These findings indicate that neuronal damage was aggravated by reperfusion injury in the MT-III KO mice compared with the wild-type mice, suggesting that MT-III plays anti-oxidative and neuroprotective roles in transient cerebral ischemia.