BACKGROUND: Ischemic stroke is a serious threat to human health. After ischemia and hypoxia, astrocyte expresses lipocalin-2 in large amounts to aggravate brain injury, but the specific mechanism is not clear. Hydroxysafflor yellow A has anti-ischemia, anti-oxidation, anti-thrombosis and anti-inflammatory effects. However, whether hydroxysafflor yellow A affects the expression of lipocalin-2 in astrocytes after cerebral ischemia and hypoxia and its mechanism are not clear. OBJECTIVE: To investigate the effect and mechanism of hydroxysafflor yellow A on the expression of lipocalin-2 in astrocytes after cerebral ischemia and reperfusion. METHODS: (1) Thirty adult SD rats were randomly divided into three groups: sham operation group, middle cerebral artery occlusion and reperfusion group, and hydroxysafflor yellow A group. The middle cerebral artery occlusion and reperfusion model was established in the latter two groups, and hydroxysafflor yellow A group was intraperitoneally injected with 12 mg/kg hydroxysafflor yellow A after reperfusion. Longa score was used to evaluate the degree of neurological impairment. Infarct volume was determined by TTC staining. JAK2/STAT3 pathway and lipocalin-2 expression were detected by western blot assay and immunofluorescence. Levels of interleukin 1β, interleukin 6 and tumor necrosis factor α were detected by ELISA. (2) Astrocytes were divided into four groups: Normal group, glucose-oxygen deprivation group, hydroxysafflor yellow A group and AG490 group. In the latter three groups, glucose-oxygen deprivation and glucose-oxygen recovery models were established. Astrocytes were treated with 75 μmol/L hydroxysafflor yellow A and 10 μmol/L tyrosine phosphorylation inhibitor AG490 for 8 hours during glucose-oxygen deprivation, respectively. The mechanism of hydroxysafflor yellow A on lipocalin-2 was further verified. RESULTS AND CONCLUSION: (1) Compared with the sham operation group, cerebral infarction was significantly increased in the middle cerebral artery occlusion and reperfusion group, accompanied by aggravated neurological impairment (P < 0.01). Hydroxysafflor yellow A treatment could reduce cerebral infarction volume and improve neurological function (P < 0.01). (2) The expressions of p-JAK2, p-STAT3 and lipocalin-2 in the middle cerebral artery occlusion and reperfusion group were higher than those in the sham operation group (P < 0.01). Hydroxysafflor yellow A treatment reduced the expressions of JAK2, STAT3 and lipocalin-2 (P < 0.01). (3) The expression levels of interleukin 1β, interleukin-6 and tumor necrosis factor α in the middle cerebral artery occlusion and reperfusion group were higher than those in the sham operation group (P < 0.01). Hydroxysafflor yellow A inhibited the expressions of interleukin 1β, interleukin-6 and tumor necrosis factor α (P < 0.01). (4) In vitro, the expressions of p-JAK2, p-STAT3 and lipocalin-2 in the glucose-oxygen deprivation group were significantly higher than those in the normal group (P < 0.01). After adding AG490, the phosphorylation of JAK2 and STAT3 decreased, and the expression of lipocalin-2 was inhibited (P < 0.01). The results suggest that hydroxysafflor yellow A may inhibit the expression of lipocalin-2 in astrocytes after ischemia and hypoxia by regulating the JAK2/STAT3 signaling pathway, thereby reducing brain injury. [ABSTRACT FROM AUTHOR]