The protective effect of low-dose nicotine on ischemia stroke by maintaining the integrity of the blood-brain barrier.

Introduction: Increasing evidence has shown that low-dose nicotine could have preventive and therapeutic effects on ischemic stroke (IS). Nevertheless, direct evidence is still missing, especially key molecules and signal pathways.

Methods: Mice were randomly assigned to one of three groups: the sham group, the control group, and the nicotine-treated group. In the control group, mice were subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). In the nicotine-treated group, mice were exposed to 12 μg/ml nicotine in their drinking water for 1 month prior to undergoing surgery. For in vitro blood-brain barrier (BBB) model, hCMEC/D3 monolayers were prepared on Transwells and pre-treated with nicotine for 48 hours and then subjected to oxygen-glucose deprivation/reoxygenation (OGD/R). Moreover, RNA-seq was adopted to explore the potential targets and signaling pathways regarding the protective role of nicotine.

Results: MCAO/R resulted in significantly compromised BBB integrity and serious brain damage. Notably, pretreatment of mice with 12μg/ml nicotine for one month significantly reduced IS-induced BBB damage and its associated brain injury. In addition, the permeability of hCMEC/D3 monolayer endothelial cells was significantly reduced under OGD/R conditions, which could be ameliorated by nicotine pretreatment. The RNA-seq results showed that TGF-β and Wnt signaling pathways were associated with pathways associated with DEGs between OGD/R and OGD/R plus nicotine treatment. Finally, the activation of Wnt/β-catenin pathways could be antagonized by the α7 nicotine acetylcholine receptor (α7 nAChR) inhibitor α-BTX.

Conclusions: These results demonstrate that nicotine treatment could alleviates the IS-compromised integrity of BBB by regulating the Wnt signal pathway through α7 nAChR.

Implications: The study demonstrates that nicotine at low concentrations exerts neuro-protective effects by supporting the integrity of BBB and subsequent endothelial viability after ischemic stroke. This finding suggests that targeting the BBB, especially endothelial cells, with nicotine treatment is a promising therapeutic strategy for brain injury after ischemic stroke.