bsc2118 and Brain-Ischemia

In view of its profound effect on cell survival and function, the modulation of the ubiquitin-proteasome-system has recently been shown to promote neurological recovery and brain remodeling after focal cerebral ischemia. Hitherto, local intracerebral delivery strategies were used, which can hardly be translated to human patients. We herein analyzed effects of systemic intraperitoneal delivery of the proteasome inhibitor BSc2118 on neurological recovery, brain injury, peripheral and cerebral immune responses, neurovascular integrity, as well as cerebral neurogenesis and angiogenesis in a mouse model of transient intraluminal middle cerebral artery occlusion. Systemic delivery of BSc2118 induced acute neuroprotection reflected by reduced infarct volume when delivered up to 9 h post-stroke. The latter was associated with reduced brain edema and stabilization of blood-brain-barrier integrity, albeit cerebral proteasome activity was only mildly reduced. Neuronal survival persisted in the post-acute stroke phase up to 28 days post-stroke and was associated with improved neurological recovery when the proteasome inhibitor was continuously delivered over 7 days. Systemic proteasome inhibition prevented stroke-induced acute leukocytosis in peripheral blood and reversed the subsequent immunosuppression, namely, the reduction of blood lymphocyte and granulocyte counts. On the contrary, post-ischemic brain inflammation, cerebral HIF-1α abundance, cell proliferation, neurogenesis, and angiogenesis were not influenced by the proteasome inhibitor. The modulation of peripheral immune responses might thus represent an attractive target for the clinical translation of proteasome inhibitors.

Topics: Animals; Blood-Brain Barrier; Brain Ischemia; Butanes; Drug Delivery Systems; Hypoxia-Inducible Factor 1, alpha Subunit; Immunosuppression Therapy; Leukocytosis; Male; Mice, Inbred C57BL; Neovascularization, Physiologic; Neuroprotection; Oligopeptides; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Recovery of Function; Stroke

Only a minority of stroke patients receive thrombolytic therapy. Therefore, new therapeutic strategies focusing on neuroprotection are under review, among which, inhibition of the proteasome is attractive, as it affects multiple cellular pathways. As proteasome inhibitors like bortezomib have severe side effects, we applied the novel proteasome inhibitor BSc2118, which is putatively better tolerated, and analysed its therapeutic potential in a mouse model of cerebral ischaemia. Stroke was induced in male C57BL/6 mice using the intraluminal middle cerebral artery occlusion model. BSc2118 was intrastriatally injected 12 h post-stroke in mice that had received normal saline or recombinant tissue-plasminogen activator injections during early reperfusion. Brain injury, behavioural tests, western blotting, MMP9 zymography and analysis of angioneurogenesis were performed for up to 3 months post-stroke. Single injections of BSc2118 induced long-term neuroprotection, reduced functional impairment, stabilized blood-brain barrier through decreased MMP9 activity and enhanced angioneurogenesis when given no later than 12 h post-stroke. On the contrary, recombinant tissue-plasminogen activator enhanced brain injury, which was reversed by BSc2118. Protein expression of the transcription factor HIF1A was significantly increased in saline-treated and recombinant tissue-plasminogen activator-treated mice after BSc2118 application. In contrast, knock-down of HIF1A using small interfering RNA constructs or application of the HIF1A inhibitor YC1 (now known as RNA-binding motif, single-stranded-interacting protein 1 (RBMS1)) reversed BSc2118-induced neuroprotection. Noteworthy, loss of neuroprotection after combined treatment with BSc2118 and YC1 in recombinant tissue-plasminogen activator-treated animals was in the same order as in saline-treated mice, i.e. reduction of recombinant tissue-plasminogen activator toxicity through BSc2118 did not solely depend on HIF1A. Thus, the proteasome inhibitor BSc2118 is a promising new candidate for stroke therapy, which may in addition alleviate recombinant tissue-plasminogen activator-induced brain toxicity.

Topics: Angiogenesis Inducing Agents; Animals; Behavior, Animal; Blood-Brain Barrier; Brain Ischemia; Butanes; Disease Models, Animal; Drug Interactions; Gene Knockdown Techniques; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Matrix Metalloproteinase 9; Mice; Mice, Inbred C57BL; Microinjections; Neurogenesis; Neuroprotective Agents; Oligopeptides; Proteasome Inhibitors; Recombinant Proteins; Recovery of Function; Thrombolytic Therapy; Tissue Plasminogen Activator