| Background Periventricular leukomalacia (PVL) is the predominant form of brain injury and the leading known cause of neural development and behavioral deficits in premature infants.TLR4serves as a specific receptor for lipopolysaccharide, plays a critical role in immune response and inflammation. Recent studies have found that TLR4is involved in the pathogenesis of LPS mediated brain injury in preterm infants, and new researches show TLR4plays a very important role in inflammatory injury induced by ischemia reperfusion in heart, lung, liver, vascular. But the report of TLR4in PVL model induced by hypoxia ischemia was rare, further study is required.Objective Investigation on the expression of TLR4mRNA and protein level and cell apoptosis at different time points in the white matter tissues in3-day-old SD rats with cerebral hypoxia-ischemia(HI)to explore the role of TLR4and cell apoptosis in the pathogenesis of premature rats with Periventricular leukomalacia induced by hypoxia Ischemia. So.it could provide an experimental foundation for the research and treatment about Periventricular leukomalacia.Methods140postnatal3-day Sprague-Dawley rats weighing5.8-10.5g were randomly divided into the experimental group(n=75)and the control group(n=65)without the distinction of sex. The rats of the experimental group underwent ligation of right common carotid artery(ischemia).and then they were placed in6%O2and94%N2mixed gas for4hours(hypoxia)to make in preterm infants animal model of periventricular leukomalacia. Meanwhile sham surgeries were performed on the rats of the control group without exposing to hypoxia. Six rats in each subgroup were sacrificed at6h,12h,24h,3d,7d of recovery from hypoxia-ischemia. Brain tissues were maded to wax blockes, or saved in liquid nitrogen tank. After hypoxia-ischemia15pups died in the experimental group and5pups died in the control group. So, there were60animals entering to the experiment in each groups. Animal behavior was studied and animal body weight was measured at6h,12h,24h,3d,7d after hypoxia-ischemia and light microscopy was used to observe brain pathological changes. Besides, tunnel was used to measure cell apoptosis. In addition, the expression of TLR4in brain tissues were tested by immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR). SPSS17.0software was used to analyze the data,a=0.05was considered the level of significance.Results1. The animal behavior and pathologic change:The rats of experimental group showed manifestations of systemic cyanosis, irritability, restlessness, rigidity of limbs tic. incontinent, part of the animals died during hypoxia ischemia. All rats after HI showed lethargy, incoordination, abnormal Performance. Body weight gaining in the experimental group was significantly slower than the control group(P<0.05). Glial gap dilated was showed at6h post-HI; Glia swelling and rarefaction in the periventricular white matter were observed at12h post-HI; More wider glial gap, microglial hyperplasia. astrocytes hypertrophy were found at24h post-HI. The side of periventricular white matter widely osteoporosis was showed at3days post-HI. The empty vesicle had been found in the experimental group at7days post-HI.2. Apoptosis:the apoptosis percentage at corpus callosum and periventricular white matter rising occurred at6h post-HI, peaked at3days post-HI. reduced at7days post-HI. However, Lower apoptosis percentage was showed in the control group. There were significant differences at6h,12h,24h,3d,7d post-HI compared with the control group (P<0.05).3. The expression of TLR4at protein level status:the expression of TLR4at protein level at corpus callosum and periventricular white matter increased at6h post-HI, peaked at3days post-HI. reduced at7days post-HI in the experimental group. However, Lower expression of TLR4at protein level was showed in the control group. There were significant differences at6h,12h,24h,3d,7d post-HI compared with the control group(P<0.05).4. The expression of TLR4mRNA status:the expression of TLR4mRNA at corpus callosum and periventricular white matter increased at6h post-HI, peaked at3days post-HI, reduced at7days post-HI in the experimental group. However, Lower expression of TLR4mRNA was showed in the control group. There were significant differences at6h.12h,24h,3d,7d post-HI compared with the control group(P<0.05).5. To investigate the correlation of the expression of TLR4mRNA and TLR4at protein level showed:There was a positive correlation between them in premature rats with Periventricular leukomalacia induced by hypoxia Ischemia(r=0.675, P<0.05).6. To investigate the correlation of the expression of TLR4mRNA and apoptosis percentage showed:There was a positive correlation between them in premature rats with Periventricular leukomalacia induced by hypoxia Ischemia(r=0.575. P<0.05).7. To investigate the correlation of the expression of TLR4at protein level and apoptosis percentage showed:There was a positive correlation between them in premature rats with Periventricular leukomalacia induced by hypoxia Ischemia(r=0.774. P<0.05).Conclusions1. Unilateral common carotid artery ligation followed by4h exposure to6%oxygen at postnatal day3rats is the appropriate model of periventricular leukomalacia.2. Apoptosis palys an important role in the pathogenesis of periventricular leukomala-cia.3. TLR4is involved in the pathogenesis of periventricular leukomalacia caused by hypoxia ischemia.4. TLR4is likely to injure the neural cell by apoptosis. |
PDF Full Text Request