The novel proteasome inhibitor BSc2118 protects against cerebral ischaemia through HIF1A accumulation and enhanced angioneurogenesis

Abstract

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.

Biodistribution and Efficacy Studies of the Proteasome Inhibitor BSc2118 in a Mouse Melanoma Model

“…Using this application schedule, no lethality was observed. Moreover as it was shown in a different publication, BSc2118 up to 60 mg/kg daily dose did not affect peripheral blood morphology in C57BL/6 mouse [36]. In contrast, bortezomib had to be given with at least a one-day break, whereas daily injection of 1 mg/kg body weight was lethal in most animals.…”

Alterations in the Ubiquitin Proteasome System in Persistent but Not Reversible Proteinuric Diseases

“…UPS upregulation occurred before disruption of foot processes and proteinuria in APN and therefore, could trigger progression by removal of important regulatory proteins. Inhibition of proteasomal degradation could then exert beneficial effects in rodent MGN, which has been shown in animal models of stroke 38 and necrotizing crescentic GN. 39 However, despite reducing foot-process protein degradation, broad proteasomal inhibition increased proteinuria in PHN in our study, arguing for proteolysis by the UPS as a reparative rather than a causative mechanism Relative glomerular mRNA expression levels of nephrin and a-actinin-4 in POL glomeruli (n=6; day 2), PHN glomeruli (n=6; 14 days), or PAN glomeruli (n=6; 4 weeks) to respective controls.…”

Role of the ubiquitin–proteasome system in brain ischemia: Friend or foe?

“…A single injection of BSc2118 provided long-term neuroprotection, reduced functional impairment, stabilized the blood-brain barrier by decreasing MMP9 activity and enhanced angioneurogenesis. The upregulation of the HIF1A transcription factor is also an important mediator in BSc2118-induced neuroprotection (Doeppner et al, 2012). Furthermore, BSc2118 treatment increased the levels of erythropoietin, brain-derived neurotrophic factor and vascular endothelial growth factor, suggesting that the proteasome inhibitor may provide acute neuroprotection in addition to enhancing brain remodeling (Doeppner et al, 2012).…”