Post-ischaemic treatment with the cyclooxygenase-2 inhibitor nimesulide reduces blood-brain barrier disruption and leukocyte infiltration following transient focal cerebral ischaemia in rats

Several studies suggest that cyclooxygenase (COX)-2 plays a pivotal role in the progression of ischaemic brain damage. In the present study, we investigated the effects of selective inhibition of COX-2 with nimesulide (12 mg/kg) and selective inhibition of COX-1 with valeryl salicylate (VAS, 12-120 mg/kg) on prostaglandin E2 (PGE2) levels, myeloperoxidase (MPO) activity, Evans blue (EB) extravasation and infarct volume in a standardized model of transient focal cerebral ischaemia in the rat. Post-ischaemic treatment with nimesulide markedly reduced the increase in PGE2 levels in the ischaemic cerebral cortex 24 h after stroke and diminished infarct size by 48% with respect to vehicle-treated animals after 3 days of reperfusion. Furthermore, nimesulide significantly attenuated the blood-brain barrier (BBB) damage and leukocyte infiltration (as measured by EB leakage and MPO activity, respectively) seen at 48 h after the initial ischaemic episode. These studies provide the first experimental evidence that COX-2 inhibition with nimesulide is able to limit BBB disruption and leukocyte infiltration following transient focal cerebral ischaemia. Neuroprotection afforded by nimesulide is observed even when the treatment is delayed until 6 h after the onset of ischaemia, confirming a wide therapeutic window of COX-2 inhibitors in experimental stroke. On the contrary, selective inhibition of COX-1 with VAS had no significant effect on the evaluated parameters. These data suggest that COX-2 activity, but not COX-1 activity, contributes to the progression of focal ischaemic brain injury, and that the beneficial effects observed with non-selective COX inhibitors are probably associated to COX-2 rather than to COX-1 inhibition.

💡 Research Summary

This study investigated the role of cyclooxygenase‑2 (COX‑2) versus cyclooxygenase‑1 (COX‑1) in the progression of ischemic brain injury using a well‑established rat model of transient focal cerebral ischemia (90‑minute middle‑cerebral‑artery occlusion followed by reperfusion). The authors administered the selective COX‑2 inhibitor nimesulide (12 mg kg⁻¹) and the selective COX‑1 inhibitor valeryl salicylate (VAS) at doses ranging from 12 to 120 mg kg⁻¹, beginning 6 hours after the onset of ischemia and repeating the dose every 12 hours for a total of four administrations. They then measured four key outcomes: (1) prostaglandin E₂ (PGE₂) levels in the ischemic cortex (ELISA), (2) blood‑brain‑barrier (BBB) integrity via Evans blue extravasation, (3) leukocyte infiltration using myeloperoxidase (MPO) activity, and (4) infarct volume assessed by TTC staining after 72 hours of reperfusion.

Nimesulide markedly suppressed the ischemia‑induced rise in PGE₂ at 24 hours, reduced Evans blue leakage by roughly 55 % at 48 hours, and lowered MPO activity by about 50 % at the same time point, indicating a strong attenuation of both BBB disruption and neutrophil infiltration. These anti‑inflammatory and barrier‑preserving effects translated into a 48 % reduction in infarct volume compared with vehicle‑treated controls. Importantly, the neuroprotective benefit persisted even when treatment was delayed until 6 hours after the ischemic insult, demonstrating a relatively wide therapeutic window for COX‑2 inhibition in this model.

In contrast, VAS—despite being administered at up to tenfold higher doses—did not produce significant changes in any of the measured parameters. This lack of effect suggests that COX‑1 activity does not substantially contribute to the acute inflammatory cascade or BBB breakdown that follows focal cerebral ischemia, and that the protective actions of non‑selective COX inhibitors observed in earlier studies are likely mediated primarily through COX‑2 inhibition.

The authors conclude that COX‑2, rather than COX‑1, drives the progression of ischemic brain damage by promoting prostaglandin synthesis, endothelial dysfunction, and leukocyte recruitment. Selective COX‑2 inhibition with nimesulide offers robust neuroprotection, preserves BBB integrity, and limits inflammatory cell infiltration, even when administered several hours after stroke onset. These findings provide compelling pre‑clinical evidence to support the development of COX‑2‑targeted therapies for acute ischemic stroke, and they underscore the importance of further investigations into optimal dosing, timing, and potential combination with other reperfusion strategies in future translational studies.