The Mechanism Study Of Melatonin Reducing Neuroinflammation And Improving Axonal Hypomyelination Of Periventricular White Matter Damage In Neonatal Sepsis Rats Through Telomerase Pathway

Neonatal sepsis can cause long-term neurological dysfunction and has seriously threatened the survival and health of children for ages.Unfortunately,relative therapies to promote functional recovery are still limited.There is ample evidence indicating a robust correlation between periventricular white matter damage(PWMD)and long-term neurological deficits.The vulnerability of oligodendrocytes to neuroinflammation elicited by microglial activation and the resultant myelination defects play a key role in the pathogenesis of PWMD.Promoting the differentiation and maturation of OPCs in PWM may have therapeutic effect on the long-term neurological dysfunction of neonatal sepsis.Melatonin is multiply interrelated to center nervous system function because of the important characteristic of melatonin that it readily passes through the blood-brain-barrier(BBB)and then accumulates in the central nervous system(CNS).In recent years,more and more attention has been paid to its anti-inflammatory,anti-oxidation,regulation of mitochondrial function and protection of nervous system.This study aimed to explore whether melatonin would affect the neuroinflammation and maturation of OPCs and,if so,whether this is via the telomerase pathway.Objective To investigate whether melatonin can reduce inflammation on PWM in neonatal sepsis rats,and promote the axonal hypomyelination caused by the neuroinflammation in PWM.To investigate whether melatonin reduce inflammation through telomerase.Methods Sprague–Dawley rats were intraperitoneally administrated with lipopolysaccharide(LPS)(1 mg/kg).Melatonin was intraperitoneally administered(10 mg/kg)at 0.5h after LPS injection.After 28 days,the ability of autonomous activity,sports endurance,sports coordination and learning and memory were tested by ethology.The expression level of inflammatory factors,TERT,oligodendrocyte differentiation related proteins and myelin maturation related proteins were detected by western blot,immunofluorescence and in situ hybridization at different times in three groups.The effect of LPS,melatonin and melatonin receptor antagonist,telomerase reverse transcriptase inhibitor on inflammatory factors,TERT and MT1 expression in BV-2 microglia cell was determined by western blot and immunofluorescence.The medium of BV2 cell were collected to treat primary OPCs.The expression level of oligodendrocyte differentiation related proteins and myelin maturation related proteins in primary OPCs were detected by western blot.Result 1.Compared with the sepsis group,the rats in the melatonin treatment groupspent longer time in the central area and traveled longer in the central area in the open field test;in the rotarod test,the latency of falling in the melatonin treatment group was longer than that in the sepsis group;in the Morris water maze task,the latency of escaping in the melatonin treatment group was shorter than that in the sepsis group,and the number of shuttles was more than that in the sepsis group.2.In sepsis group,microglia were activated 6h,1d and 3d after LPS injection,the expression of IL-1 ?,TNF-?,i-NOS protein increased,but the expression of MT1 and TERT decreased,while the activation of microglia was reduced and the expression of MT1 and TERT increased in the melatonin treatment group.After drug intervention 7,14 and 28 d,the expression of NG2 in melatonin treatment group was lower than that in sepsis group.The expression of MBP,PLP,CNPase,NFH,NFL and NFM was higher than that in sepsis group.Ultrastructural observation showed that the axons in the corpus callosum of sepsis group showed hypomyelination,even demyelination,while the axons in melatonin treatment group had complete myelination.3.Cell experiments showed that melatonin can reduce the high expression of inflammatory factors in BV-2 cells stimulated by LPS,which can be blocked by melatonin receptor inhibitors and telomerase reverse transcriptase inhibitors.LPS + melatonin BV2 cell conditioned medium can reverse the high expression of NG2 and the low expression of myelin maturation related protein in primary OPC cells induced by LPS BV2 cell conditioned medium.Conclusion Melatonin can reduce the neuroinflammation in the periventricular white matter of neonatal sepsis rats.Melatonin can improve the axonal hypomyelination of the PWM of neonatal sepsis rats by reduce the inflammation through its receptor.Melatonin may inhibit the inflammatory response by up regulating the expression of telomerase reverse transcriptase.