The Role of Oxidative Stress in Ischaemic Stroke and the Influence of Gut Microbiota.

Ischaemic stroke is the most prevalent stroke subtype, accounting for 80-90% of all cases worldwide, and remains a leading cause of morbidity and mortality. Its pathophysiology involves complex molecular cascades, with oxidative stress playing a central role. During cerebral ischaemia, reduced blood flow deprives neurons of essential oxygen and nutrients, triggering excitotoxicity, mitochondrial dysfunction, and excessive production of reactive oxygen and nitrogen species (RONS). Not only do these species damage cellular components, but they also activate inflammatory pathways, particularly those mediated by the transcription factor nuclear factor kappa-B (NF-κB). The pro-inflammatory milieu intensifies neuronal damage, compromises blood-brain barrier integrity, and exacerbates reperfusion-induced damage. Recent findings highlight the importance of the gut microbiota in modulating stroke outcomes, primarily through metabolic and immunological interactions along the gut-brain axis. Dysbiosis, characterised by reduced microbial diversity and an imbalance between beneficial and harmful strains, has been linked to increased systemic inflammation, oxidative stress, and worse prognoses. Specific gut-derived metabolites, including short-chain fatty acids (SCFAs) and trimethylamine N-oxide (TMAO), appear to either mitigate or intensify neuronal injury. SCFAs may strengthen the blood-brain barrier and temper inflammatory responses, whereas elevated TMAO levels may increase thrombotic risk. This narrative review consolidates both experimental and clinical data demonstrating the central role of oxidative stress in ischaemic stroke pathophysiology and explores the gut microbiota's ability to modulate these damaging processes. Therapeutic strategies targeting oxidative pathways or rebalancing gut microbial composition, such as antioxidant supplementation, dietary modulation, probiotics, and faecal microbiota transplantation, present promising paradigms for stroke intervention. However, their widespread clinical implementation is hindered by a lack of large-scale, randomised trials. Future efforts should employ a multidisciplinary approach to elucidate the intricate mechanisms linking oxidative stress and gut dysbiosis to ischaemic stroke, thereby paving the way for novel, mechanism-based therapies for improved patient outcomes.