Caspase-3 Contributes to ZO-1 and Cl-5 Tight-Junction Disruption in Rapid Anoxic Neurovascular Unit Damage

Abstract

BackgroundTight-junction (TJ) protein degradation is a decisive step in hypoxic blood-brain barrier (BBB) breakdown in stroke. In this study we elucidated the impact of acute cerebral ischemia on TJ protein arrangement and the role of the apoptotic effector protease caspase-3 in this context.Methodology/Principal FindingsWe used an in vitro model of the neurovascular unit and the guinea pig whole brain preparation to analyze with immunohistochemical methods the BBB properties and neurovascular integrity. In both methodological approaches we observed rapid TJ protein disruptions after 30 min of oxygen and glucose deprivation or middle cerebral artery occlusion, which were accompanied by strong caspase-3 activation in brain endothelial cells (BEC). Surprisingly only few DNA-fragmentations were detected with TUNEL stainings in BEC. Z-DEVD-fmk, an irreversible caspase-3 inhibitor, partly blocked TJ disruptions and was protective on trans-endothelial electrical resistance.Conclusions/SignificanceOur data provide evidence that caspase-3 is rapidly activated during acute cerebral ischemia predominantly without triggering DNA-fragmentation in BEC. Further we detected fast TJ protein disruptions which could be partly blocked by caspase-3 inhibition with Z-DEVD-fmk. We suggest that the basis for clinically relevant BBB breakdown in form of TJ disruptions is initiated within minutes during ischemia and that caspase-3 contributes to this process.

Melatonin ameliorates oxidative stress, modulates death receptor pathway proteins, and protects the rat cerebrum against bisphenol-A-induced apoptosis

“…In the current study, a significant upregulation of CD95 and activation of caspases-3 and 8, along with increased oxidative stress levels, may indicate activation of the extrinsic redoxsensitive machinery of apoptosis in the cerebrum after BPA treatment. Caspases-3 and 8 activation has been implicated in various neurodegenerative disorders [72]. The present results are in agreement with the finding that BPA exposure induces apoptosis and upregulation of Fas/ FasL and caspase-3 expression in the testes of mice [34].…”

Role of Caspases in Cytokine-Induced Barrier Breakdown in Human Brain Endothelial Cells

“…In this study, we have observed that hCMEC/D3 cells exposed to low cytokine concentrations increase effector caspase activation and ZO-1 delocalization in the absence of apoptosis. Indeed, Zehendner and colleagues (21) recently reported that in a model of the neurovascular unit, caspase-3 is strongly activated after 30 min of oxygen and glucose deprivation leading to ZO-1 and claudin-5 disorganization and barrier dysfunction associated with minimal DNA fragmentation. Disassembly of ZO-1 from the endothelial cell borders was not associated with changes in the total protein concentration, suggesting that TNF-a and IFN-g induced redistribution of ZO-1 rather than protein degradation.…”

“…However, caspase activation does not always lead to cell death (19), and it has been shown that hypoxia can induce caspase-9 and caspase-3 activation without apoptosis in neurons (20). Additionally, caspase-3 has been shown to be involved in ZO-1 and claudin-5 disassembly from the intercellular junctions independently of nuclear fragmentation during cerebral ischemia (21).…”

Salvaging brain ischemia by increasing neuroprotectant uptake via nanoagonist mediated blood brain barrier permeability enhancement

“…Quantitative densitometry analysis indicated that A 2A R level under hypoxia was 72% higher than that measured under normoxia. Apoptosis associated caspase-3 is an early marker of TJ disruption during acute cerebral ischemia [30]. Immunoblotting demonstrated a 186% increase of the active caspase-3 (17 kDa) in bEnd.3 cells under hypoxia, which implies the compromise of TJ tightness.…”