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.