Abstract 4364302: Neuroprotective Effect of Nitroxoline Against Transient Global Cerebral Ischemia in Rats Through Attenuation of Bromodomain-Containing Protein 4 and Downstream Pathway

Introduction: Bromodomain-containing protein 4 (BRD4), a member of the BET family, functions as an epigenetic reader and plays a pivotal role in regulating transcriptional responses to inflammation and cellular stress. Emerging evidence implicates BRD4 in the pathogenesis of cerebral ischemia-reperfusion injury (IRI). Nitroxoline (NTX), a clinically approved antibiotic commonly used for urinary tract infections, has recently gained attention for its potent inhibitory activity against BRD4. However, the therapeutic potential of NTX in attenuating oxidative stress, neuroinflammation, and neuronal degeneration following cerebral IRI has not been studied. Hypothesis: We hypothesized that NTX may confer neuroprotection in a rat model of transient global cerebral IRI by inhibiting BRD4-mediated neuroinflammatory signaling and associated apoptotic pathways. Methods: Male Sprague-Dawley rats (180–200 g) were used to establish transient global cerebral IRI via bilateral common carotid artery occlusion (BCCAo) for 30 minutes followed by 7 days of reperfusion. Experimental groups included: normal control, sham-operated, BCCAo, and BCCAo treated with NTX at doses of 12.5, 25, and 50 mg/kg administered orally. Neurobehavioral assessments (locomotor activity, open-field performance, and rotarod test) were conducted on Days 1, 3, and 7. On Day 8, rats were euthanized, and brain tissues were collected for biochemical analyses (MDA, GSH, catalase, SOD) and expression of key molecular markers (BRD4, phosphorylated NFκB p65, Nrf2, Bcl-2, Bax, and caspase-3). Pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) were quantified, and histological examinations (H&E and Nissl staining) were performed to assess neuronal integrity in hippocampal regions (CA1, CA3, dentate gyrus). Results: NTX treatment significantly improved behavioral outcomes and motor coordination in a dose-dependent manner compared to BCCAo group. Elevated levels of BRD4, p-NFκB p65, Bax, caspase-3, TNF-α, IL-1β, and IL-6 observed in BCCAo group were markedly reduced by NTX treatment. NTX also enhanced antioxidant defense, as evidenced by increased Nrf2 protein and improved redox balance. Histological analyses revealed reduced neuronal damage and preservation of hippocampal architecture in NTX-treated rats. Conclusion: This study demonstrates that NTX exerts neuroprotective effects against cerebral IRI, likely through BRD4 inhibition and downstream suppression of NFκB-driven inflammation and apoptosis.