Panax notoginseng saponins (PNS), the main active ingredient of herbal medicine Panax notoginseng, has been generally applied for the therapy of cardiovascular and cerebrovascular diseases, especially for stroke. It is believed that PNS has obvious anti-inflammatory effect, however, the roles of PNS on microglia after stroke have not been completely explored and the underlying mechanism of microglia-mediated inflammation remains to be clarified. In this study, cerebral ischemia injury was induced by photothrombotic (PT) stroke in mice. Two days after operation, PNS administration alleviated ischemic brain injury by increasing grip strength, relieving neurological deficits, improving local cerebral blood flow, and reducing pathological damage in the brain cortex and hippocampus. Moreover, microglial activation occurred in the acute stage after stroke and mediated inflammation, whereas PNS administration could inhibit microglial activation and inflammation. Meanwhile, we firstly demonstrated that PKM2 expression was upregulated in the nucleus of activated microglia after stroke, which could be inhibited after PNS administration. We hypothesized that suppression of nuclear PKM2 upregulation in microglia along with downregulation of HIF-1α/PKM2/STAT3 signaling could partially underlie the potential anti-inflammatory mechanism of PNS against ischemic brain injury. Our findings offer some new standpoints about PNS against microglia-mediated inflammation after stroke. Despite strengths, this study has limitation. PKM2 is not specifically expressed by microglia, but could be expressed by neurons, vascular endothelial cells, etc. Here we only explored the effect of PKM2 on activated microglia, and we would further investigate the impact of PKM2 expressed in other cells on stroke outcome in the future.

Background. Astrogliosis can result in astrocytes with hypertrophic morphology after injury, indicated by extended processes and swollen cell bodies. Lipocalin-2 (LCN2), a secreted glycoprotein belonging to the lipocalin superfamily, has been reported to play a detrimental role in ischaemic brains and neurodegenerative diseases. Sailuotong (SLT) capsule is a standardized three-herb preparation composed of ginseng, ginkgo, and saffron for the treatment of vascular dementia. Although recent clinical trials have demonstrated the beneficial effect of SLT on vascular dementia, its potential cellular mechanism has not been fully explored. Methods. Male adult Sprague-Dawley (SD) rats were subjected to microsphere-embolized cerebral ischaemia. Immunostaining and Western blotting were performed to assess astrocytic reaction. Human astrocytes exposed to oxygen-glucose deprivation (OGD) were used to elucidate the effects of SLT-induced inflammation and astrocytic reaction. Results. A memory recovery effect was found to be associated with the cerebral ischaemia-induced expression of inflammatory proteins and the suppression of LCN2 expression in the brain. Additionally, SLT reduced the astrocytic reaction, LCN2 expression, and the phosphorylation of STAT3 and JAK2. For in vitro experiments, OGD-induced expression of inflammation and LCN2 was also decreased in human astrocyte by the SLT treatment. Moreover, LCN2 overexpression significantly enhanced the above effects. SLT downregulated these effects that were enhanced by LCN2 overexpression. Conclusions. SLT mediates neuroinflammation, thereby protecting against ischaemic brain injury by inhibiting astrogliosis and suppressing neuroinflammation via the LCN2-JAK2/STAT3 pathway, providing a new idea for the treatment strategy of ischaemic stroke.