Page 93 - JCTR-11-4

Journal of Clinical and
Translational Research NADPH oxidase inhibition in a rodent stroke model

the most severely affected animals, could explain the The present study also indicates that sub-acute (11 days
higher average mNSS score on day 2 in vehicle-treated post-MCAO) cognitive function, assessed using a Y-maze
survivors compared to VAS2870 survivors, where measure of working memory, was not improved following
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potentially more severely affected animals survived. VAS2870 treatment. Evidence suggests that NADPH
Alternatively, this transient worsening could suggest oxidase-mediated ROS production in chronic and acute
complex acute pharmacological/off-target effects of cerebral ischaemia/hypoperfusion results in cognitive
NADPH oxidase inhibition immediately post-stroke, impairment; 85-87 however, there is very little evidence
such as thiol alkylation at the ryanodine receptor-Ca exploring the effect of NADPH oxidase inhibition on
2+
channel, replication of some ROS effects on redox status, cerebral ischaemic damage on induced cognitive function
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or inhibition of basal mitochondrial respiration and at sub-acute time points. Although one study demonstrated
cytotoxicity. In addition, the concentration-dependent cognitive function recovery with NOX2 inhibition at a sub-
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role of ROS in excitatory pathway neuromodulation, acute time point using a Rac-1 guanosine triphosphatase
including calcium modulation, α-amino-3-hydroxy-5- inhibitor, methodological differences exist, including
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methyl-4-isoxazolepropionic acid receptor transport, pre-treatment versus our post-reperfusion administration
and long-term potentiation, 64-66 must be considered. and global versus focal ischaemia models, potentially
Disentangling these possibilities requires further explaining the differences in findings. Sub-acute cognitive
investigation. Systemic VAS2870 treatment side effects effects of post-stroke NADPH oxidase inhibition remain
and impacts beyond NADPH oxidase inhibition, such sparsely investigated.
as reduced platelet aggregation through NADPH- Furthermore, VAS2870 administration revealed
independent pathways blocking downstream protein no significant impact on neurogenesis and vascular
kinase-C signalling, and effects on cell proliferation density markers at day 11 post-stroke. This aligns with
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and immune regulation, 68,69 necessitate safety evaluations the proposed dual role of NADPH oxidase-derived
and broader physiological impact assessment. ROS in both injury and repair processes, 32,44,50,51,88
Considering the complexity of NADPH oxidase roles, with concentration-dependent effects on endothelial
15
including potential involvement in both detrimental proliferation and migration, 88,89 as well as modulation of
and physiological signalling, 70,71 broad inhibition may hippocampal plasticity and neurogenesis. 90,91 One potential
counteract overall functional recovery. 62,63,72 Comparing explanation is that ROS concentrations achieved here were
with other neuroprotection studies 32,48 requires potentially below the threshold required to significantly
consideration of these mechanistic complexities and alter these processes within the timeframe studied, or that
methodological differences in administration, timing, the effects of inhibition were too subtle to detect using the
and how early functional scores relate to survival in those methods utilised in this study. Similarly, the absence of
specific paradigms. The mNSS used here while assessing significant changes in circulating cytokines or antioxidant
a range of sensorimotor functions, including postural capacity at day 11 suggests limited lasting impact from
abnormalities, forelimb strength, locomotor activity, this acute intervention on these systemic antioxidant and
hemi-neglect and sensory capabilities, is a composite inflammatory measures. This could indicate primarily
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and subjective measure that does not provide behaviour- central nervous system localised or transient effects of
specific information, potentially masking deficits. acute NADPH oxidase inhibition on these pathways.
Furthermore, spontaneous sensorimotor function
recovery following unilateral brain injury 74-76 further Collectively, these results underscore the inherent
impacts test accuracy. Neurological function post-MCAO challenge of achieving broad therapeutic success
positively correlates with infarct volume and is affected by targeting a single pathway within the complex
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by damage location. MCAO infarct volume can be highly pathophysiology of stroke. The limited efficacy of VAS2870
variable, with tissue damage ranging from predominantly beyond acute survival likely reflects the multifactorial
striatal to expansive infarcts encompassing much of nature of ischaemic injury, driven by intricate interactions
the cortex, 78,79 leading to diverse outcomes in various between OS, inflammation and neurodegeneration. 13,14,70,71
behaviours, including locomotor activity, skilled motor The documented interplay between inflammation and
control, sensorimotor processing, and motivation/ NADPH oxidase activity, where inflammation can
reward-seeking behaviours. 80-83 This variability, combined drive NADPH oxidase activity and NADPH oxidase-
with potential survival bias, incomplete 48-h MRI data, derived ROS can perpetuate inflammation, 70,71 provides a
and reduced group sizes from differential mortality, limits strong rationale for why OS inhibition alone may prove
definitive conclusions on the relationship between infarct insufficient. The therapeutic modulation of NADPH
volume/location and functional outcome, requiring more oxidase is further complicated by potential complex or
extensive assessment. even counter-regulatory effects. 50

Volume 11 Issue 4 (2025) 87 doi: 10.36922/jctr.25.00018