Modulating Astrocyte Transition after Stroke to Promote Brain Rescue and Functional Recovery: Emerging Targets Include Rho Kinase

Interesting discussion of possible hyperacute therapies and the neuronal cascade of death but seems to be no useful translational protocols available for use by survivors.

Modulating Astrocyte Transition after Stroke to Promote Brain Rescue and Functional Recovery: Emerging Targets Include Rho Kinase

Hima Charika S. Abeysinghe ^1,2, Ellie L. Phillips ³, Heung Chin-Cheng ³, Philip M. Beart ⁴ and Carli L. Roulston ^1,*

¹

Neurotrauma Research, Department of Medicine, St Vincent’s Campus, University of Melbourne, Parkville, VIC 3065, Australia

²

Department of Surgery, St Vincent’s Campus, University of Melbourne, Parkville, VIC 3065, Australia

³

Department of Biochemistry and Molecular Biology, Bio21 Insitute, University of Melbourne, Parkville, VIC 3010, Australia

⁴

The Florey Institute of Neuroscience and Mental Health, Melbourne Brain Centre, Parkville, VIC 3010, Australia

*

Correspondence: Tel.: +61-3-9288-3242; Fax: +61-3-9416-2581

Academic Editor: Chris Sobey

Received: 30 November 2015 / Accepted: 5 February 2016 / Published: 26 February 2016

Abstract

: Stroke is a common and serious condition, with few therapies. Whilst previous focus has been directed towards biochemical events within neurons, none have successfully prevented the progression of injury that occurs in the acute phase. New targeted treatments that promote recovery after stroke might be a better strategy and are desperately needed for the majority of stroke survivors. Cells comprising the neurovascular unit, including blood vessels and astrocytes, present an alternative target for supporting brain rescue and recovery in the late phase of stroke, since alteration in the unit also occurs in regions outside of the lesion. One of the major changes in the unit involves extensive morphological transition of astrocytes resulting in altered energy metabolism, decreased glutamate reuptake and recycling, and retraction of astrocyte end feed from both blood vessels and neurons. Whilst globally inhibiting transitional change in astrocytes after stroke is reported to result in further damage and functional loss, we discuss the available evidence to suggest that the transitional activation of astrocytes after stroke can be modulated for improved outcomes. In particular, we review the role of Rho-kinase (ROCK) in reactive gliosis and show that inhibiting ROCK after stroke results in reduced scar formation and improved functional recovery. 

7. Conclusions

Breakdown in the neurovascular unit after stroke involves reactive morphological transition of astrocytes that initially protect the brain against the ischaemic insult but ultimately results in extensive glial scar formation and spread of injury. The glial scar is also a major impediment to the recovery processes through lost neural connectivity in surviving pathways due to breakdown in the neurovascular unit, as well as preventing nerve regeneration through inhibition of axonal growth cone extension. Whilst inhibiting the initial activation of astrocytes after stroke results in bad outcomes, modulating this response might be better approach, where initial responses by astrocytes are preserved, but overall glial scarring reduced. The Rho-kinase pathway is a potential target for modulating this effect. Its inhibitor, Fasudil, has previously been investigated as a potential neuroprotectant following stroke, with positive results. However as ROCK is involved in multiple signaling pathways, it is likely to have an additional mechanism. As such, new evidence suggests that inhibition of ROCK stabilizes astrocytes after stroke by retaining their trophic reactive phenotype without over activation and scar formation, even when treatment is significantly delayed in vivo. This approach results in better long term functional outcomes and importantly highlights the need to address different approaches to treating stroke beyond targeting specific events within neurons.

 

Neuroproteomics approach & neurosystems biology analysis: ROCK inhibitors as promising therapeutic targets in neurodegeneration & neurotrauma

You'll have to talk to your researcher and doctor about what this could mean. 

Neuroproteomics approach & neurosystems biology analysis: ROCK inhibitors as promising therapeutic targets in neurodegeneration & neurotrauma

Several common degenerative mechanisms and mediators underlying the neuronal injury pathways characterize several neurodegenerative diseases including Alzheimer's Parkinson's, and Huntington's disease, as well as brain neurotrauma. Such common ground invites the emergence of new approaches and tools to study the altered pathways involved in neural injury alongside with neuritogenesis, an intricate process that commences with neuronal differentiation.

Achieving a greater understanding of the impaired pathways of neuritogenesis would significantly help in uncovering detailed mechanisms of axonal regeneration. Among the several agents involved in neuritogenesis are the Rho and Rho kinases (ROCKs) which constitute key integral points in the Rho/ROCK pathway that is known to be disrupted in multiple neuropathologies such as spinal cord injury, traumatic brain injury and Alzheimer's disease. This in turn renders ROCK inhibition as a promising candidate for therapeutic targets for treatment of neurodegenerative diseases.

Among the novel tools to investigate the mechanisms involved in a specific disorder is the use of neuroproteomics/systems biology approach, a growing subfield of bioinformatics aiming to study and establishing a global assessment of the entire neuronal proteome, addressing the dynamic protein changes and interactions. This review aims to examine recent updates regarding how neuroproteomics aids in the understanding of molecular mechanisms of activation and inhibition in the area of neurogenesis and how Rho/ROCK pathway/ROCK inhibitors, primarily Y-27632 and Fasudil compounds, are applied in biological settings, promoting neuronal survival and neuroprotection that has direct future implications in neurotrauma.

ProBDNF Collapses Neurite Outgrowth of Primary Neurons by Activating RhoA

I am assuming that  not only do you need BDNF, you need to make sure the precursor BDNF does not hang around. Lets get some human testing.

ProBDNF Collapses Neurite Outgrowth of Primary Neurons by Activating RhoA

Background

Neurons extend their dendrites and axons to build functional neural circuits, which are regulated by both positive and negative signals during development. Brain-derived neurotrophic factor (BDNF) is a positive regulator for neurite outgrowth and neuronal survival but the functions of its precursor (proBDNF) are less characterized.

Methodology/Principal Findings

Here we show that proBDNF collapses neurite outgrowth in murine dorsal root ganglion (DRG) neurons and cortical neurons by activating RhoA via the p75 neurotrophin receptor (p75NTR). We demonstrated that the receptor proteins for proBDNF, p75NTR and sortilin, were highly expressed in cultured DRG or cortical neurons. ProBDNF caused a dramatic neurite collapse in a dose-dependent manner and this effect was about 500 fold more potent than myelin-associated glycoprotein. Neutralization of endogenous proBDNF by using antibodies enhanced neurite outgrowth in vitro and in vivo, but this effect was lost in p75NTR^−/− mice. The neurite outgrowth of cortical neurons from p75NTR deficient (p75NTR^−/−) mice was insensitive to proBDNF. There was a time-dependent reduction of length and number of filopodia in response to proBDNF which was accompanied with a polarized RhoA activation in growth cones. Moreover, proBDNF treatment of cortical neurons resulted in a time-dependent activation of RhoA but not Cdc42 and the effect was absent in p75NTR^−/− neurons. Rho kinase (ROCK) and the collapsin response mediator protein-2 (CRMP-2) were also involved in the proBDNF action.

Conclusions

proBDNF has an opposing role in neurite outgrowth to that of mature BDNF. Our observations suggest that proBDNF collapses neurites outgrowth and filopodial growth cones by activating RhoA through the p75NTR signaling pathway.

The Loop Diuretic Bumetanide Blocks Posttraumatic p75NTR Upregulation and Rescues Injured Neurons

We will never know if this might help stroke survivors because we have no fucking stroke leaders that followup promising research with human clinical trials. You'll be screwed forever until we destroy the existing stroke leadership.

 

 The Loop Diuretic Bumetanide Blocks Posttraumatic p75NTR Upregulation and Rescues Injured Neurons

Abstract

Injured neurons become dependent on trophic factors for survival. However, application of trophic factors to the site of injury is technically extremely challenging. Novel approaches are needed to circumvent this problem. Here, we unravel the mechanism of the emergence of dependency of injured neurons on brain-derived neurotrophic factor (BDNF) for survival. Based on this mechanism, we propose the use of the diuretic bumetanide to prevent the requirement for BDNF and consequent neuronal death in the injured areas. Responses to the neurotransmitter GABA change from hyperpolarizing in intact neurons to depolarizing in injured neurons. We show in vivo in rats and ex vivo in mouse organotypic slice cultures that posttraumatic GABA_A-mediated depolarization is a cause for the well known phenomenon of pathological upregulation of pan-neurotrophin receptor p75^NTR. The increase in intracellular Ca²⁺ triggered by GABA-mediated depolarization activates ROCK (Rho kinase), which in turn leads to the upregulation of p75^NTR. We further show that high levels of p75^NTR and its interaction with sortilin and proNGF set the dependency on BDNF for survival. Thus, application of bumetanide prevents p75^NTR upregulation and neuronal death in the injured areas with reduced levels of endogenous BDNF.