Page 81 - JCTR-11-4

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

1. Introduction antioxidant treatment has shown pre-clinical promise in
attenuating stroke damage, but these approaches failed
Although stroke research has led to improvements in to progress to clinical success. 16,17 Therefore, effective
projected life expectancy following stroke, it remains translation of pre-clinical findings to clinical therapies that
1
the third leading cause of mortality, after heart disease mitigate OS-driven BBB dysfunction by targeting specific

and COVID-19, and a leading cause of disease burden. mechanisms implicated in ROS production and OS
1
Ischaemic stroke, resulting from cerebral blood flow (CBF) exacerbation, without disrupting essential ROS functions,
interruption, accounts for approximately 87% of all stroke remains a critical unmet need.
cases and is a major source of disability adjusted life years,
2
morbidity, and mortality. Without the implementation of A source of ischaemia-induced pathophysiological
3,4
primary, risk-factor-focused prevention strategies, stroke- levels of ROS is nicotinamide adenine dinucleotide
related mortality/burden will continue to rise globally, phosphate (NADPH) oxidase, a major enzymatic source
particularly in low-income countries. Thus, there is a of ROS within the cerebrovasculature and cerebral
5
continued need for targeted approaches to understand and cells. 18-22 NADPH oxidases, a family of enzymes dedicated
treat the acute cellular impacts of ischaemic stroke. to ROS production, have the capacity to produce large
amounts of ROS. To date, seven NADPH oxidase isoforms
Following ischaemic stroke, CBF restoration is the (NOXs) have been identified (NOX 1–5 and dual oxidase
present primary clinical treatment strategy to improve 1–2). Vascular NADPH oxidase isoforms contribute to
23
patient outcomes. At present, tissue plasminogen activator vascular tone through low-level ROS production 24,25 and
is the only pharmacological treatment used. In addition, physiological redox signalling under basal conditions—
6
the use and availability of direct clot removal using distinct from the inducible phagocytic form —but
24
endovascular thrombectomy is increasingly prevalent. become key drivers of pathology upon overactivation
7
However, restrictive eligibility criteria—including a limited during ischaemia. Specifically, NOX2 and NOX4 have been
therapeutic time window (4.5 h from symptom onset), low reported to be the predominant isoforms within the brain,
global availability/administration rates, low recanalisation with NOX4 being the most abundant vascular isoform. 26-28
rates and haemorrhagic transformation risk—result in The NOX4 isoform exhibits higher cerebrovascular
fewer than 5% of stroke patients being treated worldwide. 2,8,9 expression than within the periphery, 29,30 and both NOX2
Although many pharmaceutical therapeutics have shown and NOX4 have been implicated in stroke injury. 29,31-34
pre-clinical successes, these have largely failed to progress Under ischaemic conditions, NADPH oxidase is a primary
beyond clinical trials. 10,11 Consequently, they have failed source of increased superoxide production. 18,32,35-38
to advance the present status quo of ischaemic stroke Furthermore, NOX4-generated superoxide is rapidly
treatment. Despite this, there remains a critical need to converted to hydrogen peroxide and mediates glutamate
improve clinical outcomes using novel neuroprotective neurotoxicity, 39-41 a significant pathophysiological
treatments to address the unmet need for standalone or ischaemic cascade mechanism. Increased NADPH oxidase
combined effective therapeutic treatments in the clinic. activity coincides with both increased NADPH oxidase
One pathway to consider is oxidative stress (OS), enzymes’ microRNA and protein expressions within
induced by the surge in reactive oxygen species the peri-infarct region 2–48 h after cerebral ischaemia
(ROS) produced during ischaemic stroke. While ROS injury. 29,31-34 Inhibition and reduced expression of NADPH
are normally present at low levels and essential for oxidase have been reported to result in neuroprotection
physiological signalling, cellular homeostasis and vascular and reduced functional deficits, 32,33,42 suggesting that
tone, redox homeostasis is disrupted under ischaemic the targeted inhibition of NADPH oxidase is a potential
conditions, triggering a substantial overproduction of therapeutic avenue. Targeted ROS inhibition is required
ROS (e.g., superoxide/hydrogen peroxide). This surge to promote continued vascular function 20,22 and reduce
12
overwhelms endogenous antioxidant defence mechanisms, pro-inflammatory ROS functions without impeding anti-
resulting in the pathophysiological effects of ROS and inflammatory or functional immune responses. The
43
OS. OS compromises the integrity of the blood–brain pivotal role NADPH oxidase plays in OS in laboratory
barrier (BBB), leading to its dysfunction and increased conditions combined with the limited success of broad-
44
permeability through mechanisms, including endothelial spectrum general antioxidants at clinical trial, such as
cell damage, inflammatory gene expression and DNA NXY-059 (SAINT I/II trials) 16,17 and the established
fragmentation. 6,13,14 The resultant BBB compromise role of NADPH oxidase-derived OS in post-stroke
facilitates neuroinflammation and contributes significantly pathophysiology, including BBB disruption, 6,12-15 further
to the formation of cerebral oedema, a major factor in early support the rationale of targeting specific enzymatic
mortality after stroke. Targeting excessive ROS using sources of OS through NADPH oxidase inhibition.
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Volume 11 Issue 4 (2025) 75 doi: 10.36922/jctr.25.00018