Minocycline inhibits the mice's microglia activation caused by chronic hypoxia-hypercapnia

Objective: To observe the effects of minocycline on mice's microglia activation induced by chronic hypoxia-hypercapnia.Methods: Thirty C57BL/6 mice were divided randomly into three groups:the control group(NC),the chronic hypoxia-hypercapnia-saline group(MS)and the chronic hypoxia-hypercapnia-minocycline group(MM).The latter two groups were placed in the special closed cabin with hypoxia and hypercapnia for 8 hr a day,4 weeks,in which there was O2 9%～11% and CO2 5%～6%.After 2 weeks the MS group was injected intraperitoneally with saline while the MM group was treated with 45 mg/kg minocycline respectively.when fed to the required time,all the mice were anesthetized with 10% chloral hydrate intraperitoneally,and then sacrificed.The hippocampus was quickly isolated,the right hippocampus was used for detection of the microglia activation by immunohistochemisty,and the left side was used for determination the expression of IBA-1 mRNA,MMP-9 mRNA by real time PCR.Results: The hippocampus of the NC group had brown scattered microglia(resting state,dendritic,small cell body,more processes),the MS group had some degrees of microglia activation(hypertrophy cell body,less neurite),and the MM group had scattered microglia activation.Compared with that of the NC group,expression of IBA-1 mRNA and more MMP-9 mRNA was more increased in the MS group.however,in the MM group expression of IBA-1 mRNA and MMP-9 mRNA was less increased compared with that of the MS group.Conclusion: Some degrees of microglia activation in the mice's hippocampus may be induced by chronic hypoxia-hypercapnia;Minocycline may inhibit the mice's microglia activation induced by chronic hypoxia-hypercapnia,and its mechanism may be associated with decreasing the MMP-9 secretion.