| Background and objective Recently, stroke has been the most common neurological disease, with increasing incidence and prevalence, which has become the second-leading cause of death after heart disease in the world, but which is the first cause of death in China.Acute ischemic stroke(AIS) accounts for about 80% of stroke, usually leading to hemiparalysis, aphasia, cognition impairment, depression and other severe adverse events, which brings heavy burden and great injury for society, families and patients.It is the most important treatment for patients to re-canalize occlusive vessels and recovery blood flow as soon as possible.Although thrombolytic therapy is regarded as preferred treatment, just less than 3% patients can benefit; Intravascular therapy is at the exploratory stage, less patients can be cured. The majority of AIS can cause cell necrosis, apoptosis, autophagy of neurons and related inflammatory reaction, and activate aquaporins(AQPs) and destroy blood-brain barrier(BBB), as a result, which bring about brain edema, high intracranial pressure and the secondary damage for brain tissue. Therefore, the exploration of pathogenisis and the application of preventive measures have become a hot spot at present.Tumor necrosis factor-?(TNF-?) is a key inflammatory factor with low expression in normal cerebral tissues. As the initial factor of inflammatory reaction, AIS can increase the expression level of TNF-? and can induce the expressions of IL-1, IL-6, IL-8 and FM-CSF to participate in immune response and inflammatory reaction, directly leading to brain edema and aggravate the brain injury. AQP-4, a subtype of aquaporins, which is the most widespread, abundant and earliest aquaporin, plays an important role in the central nervous system. It is well-known that AQP-4 can regulate water metabolism of normal brain tissue and play an important role in the formation of brain edema in the AIS. Statins, known as 3-hydroxy-3-methylglutaryl coenzyme A(HMG-Co A) reductase inhibitors, have become fist-line treatment for AIS. Besides regulation of lipid and stabilization of plaque, stains can execute anti-inflammation, anti-apoptosis, anti-autophagy, anti-free radicals and pro-revascularization, pro-generation of neurons. Moreover, statins are applied to the second prevention of atherosclerotic cardiovascular disease(ASCVD) based on many clinical guideline recommendations. There is no doubt that atorvastatin are the common lipid-regulated drugs with high safety and better tolerability, but whether atorvastatin can affect the expression of AQP-4 by monitoring the expression of TNF-? to alleviate brain edema remains unclear. According to the above-mentioned debates, our study aims to establish focal ischemic model in rats and observe the dynamic change of AQP-4, TNF-? and brain water content and then explores the effect of atorvastatin on brain edema and its mechanism to provide theoretical basis for the clinical treatment.Materials and methods 108 healthy male SD rats with the weight of 300±20g were randomly divided into sham-operation group, model group and treatment group;36 rats in each group, which were grouped into 1st-day group, 3rd-day group and 7th-day group, each subgroup had 12 rats. In the sham-operation group, the blood vessel on the left neck of rat was only conducted separated without ligation and suture; Perpetual focal cerebral ischemic model by adopted Middle Cerebral Artery Occlusion(MCAO) on the left side, Longa five-score scale of one to three points was regarded as successful model when rateswaked. After that, the sham-operation group and the model group performed gavage administration by normal saline of 1ml once a day until the corresponding observation time point; the treatment group was given atorvastatin 4mg/(kg.d)(atorvastatin with 1ml saline solution) irrigation stomach once a day until the corresponding observation time point. Before rats were executed, Longa scale was used to evaluate the neurological impairment; After rats were executed, brain water content was calculated to assess the severe of brain edema, the expression of TNF-? m RNA and AQP-4 m RNA were evaluated by RT-PCR, the expression of AQP-4 protein was detected by Western blotting.Results 1.Longa's neurological function score The rats in each group were evaluated by the Longa's neurological function score before being killed. The manifestation of neurological deficit in the sham operation group's rats were not observed with the score of zero, Both model group and treatment group's rats had different degree of neurological impairment; and there were significant statistical differences in the Longa's neurological function score among each group at the same time point(P<0.001). 2.The brain water content The sham operation group had non-obvious dynamic change of brain water content. But in model group and treatment group, the brain water content was increased at the 1st day, peaked at the 3rd day, and was decreased at the 7th day. At the same time points, the brain water content of sham operation group was less than that of the remaining groups(P<0.001). And the treatment group with less content displayed the significant difference compared with the model group(P<0.001). 3.TNF-? m RNA The expression level of TNF-? m RNA in sham operation group indicated no obvious change, which rose at the 1st day, ranked the top at the 3rd day and reduced at the 7th day in model group and treatment group. Moreover, the model group as well as the treatment group had significantly higher expression level of TNF-? m RNA compared with sham operation group(P<0.001), the less expression level wasfound in the treatment group relative to the model group(P<0.001). 4.AQP-4 m RNA and AQP-4 Protein The dynamic changes of expression levels of AQP-4 m RNA and AQP-4 protein were similar to the expression level of TNF-? m RNA. Namely, no obvious changes were found in the sham operation group. The expression levels rose at the 1st day, ranked the top at the 3rd day and reduced at the 7th day in model group and treatment group. Compared with sham operation group, the rest groups had higher expression levels of AQP-4 m RNA and AQP-4 protein, with statistical differences(P<0.001). And the treatment group had less expression levels than model group(P<0.001). 5. The correlation analysis of TNF-? m RNA and AQP-4 m RNA expression levels There was no linear correlation between TNF-? m RNA and AQP-4 m RNA in sham group at each time point(P>0.05); there was linear correlation between TNF-? m RNA and AQP-4 m RNA in model group and treatment group at each time point(P<0.05), and which was positive correlation.Conclusion 1.The brain edema in rats with focal cerebral ischemia shows dynamic changes, which instantaneously increases then decreases, and reaches the peak at the 3rd day. 2.Atorvastatin may reduce neurological deficits caused by focal cerebral ischemia,with the function of protecting the brain, which may be related to the decrease of brain edema after cerebral ischemia. 3.Atorvastatin inhibits the expression levels of TNF-? m RNA,AQP-4 m RNA and AQP-4 protein,and relievs brain edema,so as to play a role in protecting brain. 4.The expression levels of TNF-? m RNA and AQP-4 m RNA in rats with focal cerebral ischemia is positive correlation, the expression of TNF-? m RNA may induce the expression of AQP-4 m RNA, so as to aggravate the formation of brain edema. |
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