Effect of neuregulin on inflammatory reaction following cerebral ischemia-reperfusion injury in rats

Objective To observe the expression of matrix metalloproteinase-9 (MMP-9) and the regulation of neuregulin-1β (NRG-1β) in brain tissue in rats following cerebral ischemia/reperfusion injury. Methods The animal models of middle cerebral artery occlusion/reperfusion (MCAO/R) were established by a monofilament method from left external-internal carotid artery in 200 adult healthy male Wistar rats. The rat models in the treatment group (75 rats) and in control group (75 rats) were injected with 1.5%NRG-1β 5 μl and 0.1 mol/L PBS 5 μl, respectively, from internal carotid artery (ICA). The cerebral infarct volume was measured by TFC stain, the apoptosis was identified with in situ TUNEL method, and the expression of MMP-9 was detected by immunohistochemical and immunofluorescent double staining and Western blotting analysis. Results Cerebral ischemia-reperfusion can induce apoptosis and expression of MMP-9 in cerebral cortex and striatum. With the ischemic time prolonging, the number of apototic cells in cortex from ischemic 0, 0. 5, 1.0, 1.5 and 2. 0 h increased from 1.78 ± 0. 15,5. 78 ± 0. 51,10. 35 ± 0. 77, 21.50 ± 1.19 to 32. 00 ± 1.78, while the number of apoptotic cells in stratum from ischemic also increased significantly from 1.46±0.21, 4. 12±0.54, 7.33±0.71, 16.54 ± 1.63 to 19.03± 1.44 (t =9.31- 37.78, P < 0. 01) and the expression of MMP-9 increased significantly (t = 7.73-27.75, P < 0. 01) in the control group. With NRG-1β treatment, the number of apoptotie cells in cortex from ischemic 0, 0. 5,1.0, 1.5 and 2. 0 h reduced from 1.66±0. 11,4. 80±0. 61,5.63±0. 56, 9.75±1.22 to 13.54 ±1.26; while the number of apoptotic cells in striatum from ischemic also decreased significantly from 1.34 ± 0. 14, 3.35 ± 0. 32, 4. 55± 0. 50, 7. 63 ±1.41 to 10. 46 ± 0. 98 (t = 2. 74-18. 93, P < 0. 05), the expression of MMP-9 decreased (t = 3.85-12. 09, P < 0. 01), and the infarct volume decreased significantly (t = 4. 645-13. 043,P < 0. 01) compared with those in the control group at the same timepoint and the corresponding region. Conclusions The expression of MMP-9 is increased after cerebral ischemia/ reperfusion, and it may contribute to the inflammatory reaction. NRG-1β might down-regulate the expression of MMP-9 to inhibit apoptosis inducing by inflammatory reaction in cerebral ischemic reperfusion. Key words: Brain ischemia;  Reperfusion injury;  Neuregulins;  Matrix metalloproteinase 9;  Immunohistochemistry;  Blotting; western