ROS-p38MAPK Pathway Regulates The Effect Of Iron Metabolism On Neuroinflammation-induced Cognitive Impairment In Mice

Part Ⅰ Iron metablism attenuates LPS-induced cognitive impairment in miceObjective Deferoxamine(DFO)was used to intervene lipopolysaccharide(LPS)-induced cognitive impairment to investigate effects of iron metabolism on neuroinflammation involved cognitive dysfunction in mice.Methods One hundred mice were randomly assigned into four groups:control,DFO,LPS,and LPS + DFO(n＝25 for each).Intracerebroventricular administration of 0.5μg DFO was commenced 3 days prior to microinjection of 2 μg LPS,while the control group received equal volume of aCSF(artificial cerebrospinal fluid).The MWM and novel object recognition test were carried out to measure the cognitive function.The status of microglia,levels of IL-1β and TNF-α,expression of Bax/Bcl-2,the activities of malondialdehyde(MDA)and superoxide dismutase(SOD),activation of p-p38/p38MAPK,as well as iron metabolic changes in the hippocampus were observed to evaluate the LPS-induced hippocampal damage and the neuroprotective effect of DFO and the role of ROS-p38MAPK in it.Results Treatment of mice with LPS resulted in deficits in cognitive performance in the Morris water maze and novel object recognition test without changing locomotor activity,which were ameliorated by pretreatment with 0.5μg DFO.DFO prevented LPS-induced microglial activation and elevations of IL-1β and TNF-a levels in the hippocampus.Moreover,DFO attenuated elevated Bax/Bcl-2 ratio,modulated p-p38/p38MAPK activity,and prevented LPS-induced increases of MDA and SOD levels in the hippocampus.DFO also significantly blocked LPS-induced iron accumulation and altered expression of proteins related to iron metabolism in the hippocampus.Discussion Our results suggest that DFO reduces LPS-induced hippocampal inflammation and consequently the pathological progression by regulating pathway,eventually improving memory performance.Part Ⅱ ROS(reactive oxygen species)is the downstream mechanism of iron regulating LPS-induced cognitive impairment in miceObjective To investigate effects of ROS on iron regulating LPS-induced cognitive impairment in mice by intervening with antioxidant vitamin C(Vit C).Methods One hundred mice were randomly assigned into four groups:control,Vit C,LPS,and LPS ＋Vit C(n = 25 for each).Intracerebroventricular administration of 10μg Vit C was commenced 30 min prior to microinjection of 2 μg LPS,while the control group received equal volume of aCSF(artificial cerebrospinal fluid).The MWM and novel object recognition test were carried out to measure the cognitive function.The status of microglia,levels of IL-1β and TNF-α,expression of Bax/Bcl-2,the activities of malondialdehyde(MDA)and superoxide dismutase(SOD),activation of p-p38/p38MAPK,as well as iron metabolic changes in the hippocampus were observed to evaluate the LPS-induced hippocampal damage and the neuroprotective effect of Vit C and the change of ROS-p38MAPK pathway.Results Vit C pretreatment attenuated LPS-induced deficits in cognitive performance in the Morris water maze and novel object recognition test without changing locomotor activity.Vit C prevented LPS-induced increases of MDA and SOD levels in the hippocampus,also prevented microglial activation and elevations of IL-1β and TNF-a levels.Moreover,Vit C attenuated elevated Bax/Bcl-2 ratio,modulated p-p38/p38MAPK activity.Vit C did not affect LPS-induced iron accumulation and expression changes of proteins related to iron metabolism in the hippocampus.Discussion Our results suggest that Vit C reduces LPS-induced hippocampal inflammation and consequently the pathological progression by suppressing oxidative stress,eventually improving memory performance.Part Ⅲ ROS-p38MAPK pathway is the patential mechanism of iron regulating LPS-induced cognitive impairment in miceObjective To investigate effects of ROS-p38MAPK pathway on iron regulating LPS-induced cognitive impairment in mice by intervening with p38MAPK inhibitor SB203580.Methods One hundred mice were randomly assigned into four groups:control,SB203580,LPS,and LPS ＋ SB203580(n = 25 for each).Intracerebroventricular administration of 10 μg SB203580 was commenced 30 min prior to micro injection of 2 μg LPS,while the control group received equal volume of aCSF(artificial cerebrospinal fluid).The MWM and novel object recognition test were carried out to measure the cognitive function.The status of microglia,levels of IL-1β and TNF-a,expression of Bax/Bcl-2,the activities of malondialdehyde(MDA)and superoxide dismutase(SOD),activation of p-p38/p38MAPK,as well as iron metabolic changes in the hippocampus were observed to evaluate the LPS-induced hippocampal damage and the neuroprotective effect of SB203580 and the change of ROS-p38MAPK pathway.Results SB203580 pretreatment attenuated LPS-induced deficits in cognitive performance in the Morris water maze and novel object recognition test without changing locomotor activity.SB203580 modulated p-p38/p38MAPK activity,prevented microglial activation and elevations of IL-1β and TNF-a levels.SB203580 attenuated elevated Bax/Bcl-2 ratio as well.Moreover,SB203580 prevented LPS-induced increases of MDA and SOD levels in the hippocampus without affecting LPS-induced iron accumulation and expression changes of proteins related to iron metabolism in the hippocampus.Discussion Our results suggest that SB203580 reduces LPS-induced hippocampal inflammation and consequently the pathological progression by suppressing ROS-p38MAPK pathway,eventually improving memory performance.ROS-p38MAPK pathway may act as the downstream role of iron regulating LPS-induced cognitive impairment in mice and there might exist a positive interaction between iron catalyzed ROS and p38 MAPK activation in the hippocampal neuroinflammation.Conclusions:DFO may possess a neuroprotective effect against LPS-induced neuroinflammation and cognitive deficits by preventing the ROS-p38MAPK pathway,attenuating microglia activation and cytokines release,alleviating oxidative stress and apoptosis.ROS-p38MAPK pathway could play an important role in iron regulating neurinflammation-induced cognitive impairment and there might exist a positive interaction between iron catalyzed ROS and p38 MAPK activation in the hippocampus.