Differential Effects of Paracrine Factors on the Survival of Cells of the Neurovascular Unit during Oxygen Glucose Deprivation

Redžić, Zoran B.; Rabie, Tamer Samah; Sutherland, Brad A.; Buchan, Alastair

doi:10.1111/ijs.12197

Cited by 28 publications

(25 citation statements)

References 27 publications

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“…All our data points to the fact that endothelial cells experience O 2 and glucose deprivation more severely than the other cell types and show a higher susceptibility. Two publications by Ceruti et al and Redzic et al recently compared survival of primary rat ECs, ACs and PCs under OGD (0% O 2 ) conditions and similarly concluded that ECs are more susceptible than ACs and PCs [ 36 , 37 ]. Importantly, our data further suggests that ACs tolerate ischemic injury better than PCs.…”

Section: Discussionmentioning

confidence: 99%

Differential responses of blood-brain barrier associated cells to hypoxia and ischemia: a comparative study

Engelhardt

Huang

Patkar

et al. 2015

Fluids Barriers CNS

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BackgroundUndisturbed functioning of the blood–brain barrier (BBB) crucially depends on paracellular signaling between its associated cells; particularly endothelial cells, pericytes and astrocytes. Hypoxic and ischemic injuries are closely associated with disturbed BBB function and the contribution of perivascular cells to hypoxic/ischemic barrier regulation has gained increased attention. Regardless, detailed information on the basal hypoxic/ischemic responses of the barrier-associated cells is rare and the outcome of such cell-specific responses on BBB modulation is not well understood. This study investigated crucial parameters of hypoxic/ischemic adaptation in order to characterize individual perivascular cell responses to stress conditions.MethodsThe brain microvascular endothelial cell line RBE4 (EC cell line) as well as primary rat brain endothelial cells (ECs), pericytes (PCs) and astrocytes (ACs) were exposed to 24 and 48 hours of oxygen deprivation at 1% and 0.2% O2. All primary cells were additionally subjected to combined oxygen and glucose deprivation mimicking ischemia. Central parameters of cellular adaptation and state, such as HIF-1α and HIF-1 target gene induction, actin cytoskeletal architecture, proliferation and cell viability, were compared between the cell types.ResultsWe show that endothelial cells exhibit greater responsiveness and sensitivity to oxygen deprivation than ACs and PCs. This higher sensitivity coincided with rapid and significant stabilization of HIF-1α and its downstream targets (VEGF, GLUT-1, MMP-9 and PHD2), early disruption of the actin cytoskeleton and metabolic impairment in conditions where the perivascular cells remain largely unaffected. Additional adaptation (suppression) of proliferation also likely contributes to astrocytic and pericytic tolerance during severe injury conditions. Moreover, unlike the perivascular cells, ECs were incapable of inducing autophagy (monitored via LC3-II and Beclin-1 expression) - a putative protective mechanism. Notably, both ACs and PCs were significantly more susceptible to glucose than oxygen deprivation with ACs proving to be most resistant overall.ConclusionIn summary this work highlights considerable differences in sensitivity to hypoxic/ischemic injury between microvascular endothelial cells and the perivascular cells. This can have marked impact on barrier stability. Such fundamental knowledge provides an important foundation to better understand the complex cellular interactions at the BBB both physiologically and in injury-related contexts in vivo.

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Section: Discussionmentioning

confidence: 99%

Differential responses of blood-brain barrier associated cells to hypoxia and ischemia: a comparative study

Engelhardt

Huang

Patkar

et al. 2015

Fluids Barriers CNS

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“…In this context, vascular endothelial growth factor (VEGF) could be one major factor for BBB breakdown in our model. It was shown that VEGF was significantly upregulated in astrocytes after OGD or hypoxia, and it was postulated that this is responsible for BBB damage (Redzic et al, 2013 ). With regard to our model, C6 cells secreted significant amounts of VEGF which was further upregulated via hypoxia (Boveri et al, 2005 ; Yeh et al, 2008 ).…”

Section: Discussionmentioning

confidence: 99%

The pivotal role of astrocytes in an in vitro stroke model of the blood-brain barrier

Neuhaus¹,

Gaiser²,

Mahringer³

et al. 2014

Front. Cell. Neurosci.

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Stabilization of the blood-brain barrier during and after stroke can lead to less adverse outcome. For elucidation of underlying mechanisms and development of novel therapeutic strategies validated in vitro disease models of the blood-brain barrier could be very helpful. To mimic in vitro stroke conditions we have established a blood-brain barrier in vitro model based on mouse cell line cerebEND and applied oxygen/glucose deprivation (OGD). The role of astrocytes in this disease model was investigated by using cell line C6. Transwell studies pointed out that addition of astrocytes during OGD increased the barrier damage significantly in comparison to the endothelial monoculture shown by changes of transendothelial electrical resistance as well as fluorescein permeability data. Analysis on mRNA and protein levels by qPCR, western blotting and immunofluorescence microscopy of tight junction molecules claudin-3,-5,-12, occludin and ZO-1 revealed that their regulation and localisation is associated with the functional barrier breakdown. Furthermore, soluble factors of astrocytes, OGD and their combination were able to induce changes of functionality and expression of ABC-transporters Abcb1a (P-gp), Abcg2 (bcrp), and Abcc4 (mrp4). Moreover, the expression of proteases (matrixmetalloproteinases MMP-2, MMP-3, MMP-9, and t-PA) as well as of their endogenous inhibitors (TIMP-1, TIMP-3, PAI-1) was altered by astrocyte factors and OGD which resulted in significant changes of total MMP and t-PA activity. Morphological rearrangements induced by OGD and treatment with astrocyte factors were confirmed at a nanometer scale using atomic force microscopy. In conclusion, astrocytes play a major role in blood-brain barrier breakdown during OGD in vitro.

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“…How these die in stroke, and how this damage leads to dysfunction and partial recovery is less clear. In vitro data indicate that neurons are the most sensitive to oxygen/glucose deprivation, followed by endothelial cells, astrocytes, and microglia [8]. As with neurons, glutamate signaling may play a role in oligodendrocyte cell death after stroke, through both N-methyl-D-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid subtypes of the glutamate receptor [9].…”

Section: The Infarct Corementioning

confidence: 99%

“…In rodent stroke models, oligodendrocytes survive longer than neurons [10]. Astrocytes die at a somewhat later period in the same ischemic stimulus than neurons [8,11], and do so through mechanisms that involve swelling, adenosine triphosphate release and signaling through adenosine triphosphate receptors (P2Y 1 purinergic receptors [12]). With this differential sensitivity in mind, even in the short term in vivo, hours after the infarct, all cell types in the stroke core die.…”

Section: The Infarct Corementioning

confidence: 99%

The 3 Rs of Stroke Biology: Radial, Relayed, and Regenerative

Carmichael

2016

Neurotherapeutics

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Stroke not only causes initial cell death, but also a limited process of repair and recovery. As an overall biological process, stroke has been most often considered from the perspective of early phases of ischemia, how these inter-relate and lead to expansion of the infarct. However, just as the biology of later stages of stroke becomes better understood, the clinical realities of stroke indicate that it is now more a chronic disease than an acute killer. As an overall biological process, it is now more important to understand how early cell death leads to the later, limited recovery so as develop an integrative view of acute to chronic stroke. This progression from death to repair involves sequential stages of primary cell death, secondary injury events, reactive tissue progenitor responses, and formation of new neuronal circuits. This progression is radial: from the tissue that suffers the infarct secondary injury signals, including free radicals and inflammatory cytokines, radiate out from the stroke core to trigger later regenerative events. Injury and repair processes occur not just in the local stroke site, but are also triggered in the connected networks of neurons that had existed in the stroke center: damage signals are relayed throughout a brain network. From these relayed, distributed damage signals, reactive astrocytosis, inflammatory processes, and the formation of new connections occur in distant brain areas. In short, emerging data in stroke cell death studies and the development of the field of stroke neural repair now indicate a continuum in time and in space of progressive events that can be considered as the 3 Rs of stroke biology: radial, relayed, and regenerative.

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Differential Effects of Paracrine Factors on the Survival of Cells of the Neurovascular Unit during Oxygen Glucose Deprivation

Abstract: Microglia-derived signaling molecules, but not angiogenic factors, were protective for neurovascular unit cells during oxygen glucose deprivation. This finding could identify a potential therapeutic target for ischemic stroke.

Cited by 28 publications

References 27 publications

Differential responses of blood-brain barrier associated cells to hypoxia and ischemia: a comparative study

Differential responses of blood-brain barrier associated cells to hypoxia and ischemia: a comparative study

The pivotal role of astrocytes in an in vitro stroke model of the blood-brain barrier

The 3 Rs of Stroke Biology: Radial, Relayed, and Regenerative

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