Lipopolysaccharide-induced Brain Injury Research Articles

Enhanced meningeal lymphatic drainage ameliorates lipopolysaccharide-induced brain injury in aged mice

BackgroundSepsis-associated encephalopathy (SAE) is an acute cerebral dysfunction caused by sepsis. Neuroinflammation induced by sepsis is considered a potential mechanism of SAE; however, very little is known about the role of the meningeal lymphatic system in SAE.MethodsSepsis was established in male C57BL/6J mice by intraperitoneal injection of 5 mg/kg lipopolysaccharide, and the function of meningeal lymphatic drainage was assessed. Adeno-associated virus 1-vascular endothelial growth factor C (AAV1-VEGF-C) was injected into the cisterna magna to induce meningeal lymphangiogenesis. Ligation of deep cervical lymph nodes (dCLNs) was performed to induce pre-existing meningeal lymphatic dysfunction. Cognitive function was evaluated by a fear conditioning test, and inflammatory factors were detected by enzyme-linked immunosorbent assay.ResultsThe aged mice with SAE showed a significant decrease in the drainage of OVA-647 into the dCLNs and the coverage of the Lyve-1 in the meningeal lymphatic, indicating that sepsis impaired meningeal lymphatic drainage and morphology. The meningeal lymphatic function of aged mice was more vulnerable to sepsis in comparison to young mice. Sepsis also decreased the protein levels of caspase-3 and PSD95, which was accompanied by reductions in the activity of hippocampal neurons. Microglia were significantly activated in the hippocampus of SAE mice, which was accompanied by an increase in neuroinflammation, as indicated by increases in interleukin-1 beta, interleukin-6 and Iba1 expression. Cognitive function was impaired in aged mice with SAE. However, the injection of AAV1-VEGF-C significantly increased coverage in the lymphatic system and tracer dye uptake in dCLNs, suggesting that AAV1-VEGF-C promotes meningeal lymphangiogenesis and drainage. Furthermore, AAV1-VEGF-C reduced microglial activation and neuroinflammation and improved cognitive dysfunction. Improvement of meningeal lymphatics also reduced sepsis-induced expression of disease-associated genes in aged mice. Pre-existing lymphatic dysfunction by ligating bilateral dCLNs aggravated sepsis-induced neuroinflammation and cognitive impairment.ConclusionThe meningeal lymphatic drainage is damaged in sepsis, and pre-existing defects in this drainage system exacerbate SAE-induced neuroinflammation and cognitive dysfunction. Promoting meningeal lymphatic drainage improves SAE. Manipulation of meningeal lymphangiogenesis could be a new strategy for the treatment of SAE.

PPAR Gamma Receptor: A Novel Target to Improve Morbidity in Preterm Babies.

Worldwide, three-quarters of a million babies are born extremely preterm (<28 weeks gestation) with devastating outcomes: 20% die in the newborn period, a further 35% develop bronchopulmonary dysplasia (BPD), and 10% suffer from cerebral palsy. Pioglitazone, a Peroxisome Proliferator Activated Receptor Gamma (PPARγ) agonist, may reduce the incidence of BPD and improve neurodevelopment in extreme preterm babies. Pioglitazone exerts an anti-inflammatory action mediated through Nuclear Factor-kappa B repression. PPARγ signalling is underactive in preterm babies as adiponectin remains low during the neonatal period. In newborn animal models, pioglitazone has been shown to be protective against BPD, necrotising enterocolitis, and lipopolysaccharide-induced brain injury. Single Nucleotide Polymorphisms of PPARγ are associated with inhibited preterm brain development and impaired neurodevelopment. Pioglitazone was well tolerated by the foetus in reproductive toxicology experiments. Bladder cancer, bone fractures, and macular oedema, seen rarely in adults, may be avoided with a short treatment course. The other effects of pioglitazone, including improved glycaemic control and lipid metabolism, may provide added benefit in the context of prematurity. Currently, there is no formulation of pioglitazone suitable for administration to preterm babies. A liquid formulation of pioglitazone needs to be developed before clinical trials. The potential benefits are likely to outweigh any anticipated safety concerns.

Chemogenetic activation of the HPC-mPFC pathway improves cognitive dysfunction in lipopolysaccharide -induced brain injury.

Rationale: Although sepsis-associated encephalopathy (SAE) is a common psychiatric complication in septic patients, the underlying mechanisms remain unclear. Here, we explored the role of the hippocampus (HPC) - medial prefrontal cortex (mPFC) pathway in cognitive dysfunction in lipopolysaccharide-induced brain injury. Methods: Lipopolysaccharide (LPS, 5 mg/kg, intraperitoneal) was used to induce an animal model of SAE. We first identified neural projections from the HPC to the mPFC via a retrograde tracer and virus expression. The activation viruses (pAAV-CaMKIIα-hM3Dq-mCherry) were injected to assess the effects of specific activation of mPFC excitatory neurons on cognitive tasks and anxiety-related behaviors in the presence of clozapine-N-oxide (CNO). Activation of the HPC-mPFC pathway was evaluated via immunofluorescence staining of c-Fos-positive neurons in mPFC. Western blotting was performed to determine protein levels of synapse- associated factors. Results: We successfully identified a structural HPC-mPFC connection in C57BL/6 mice. LPS-induced sepsis induces cognitive impairment and anxiety-like behaviors. Chemogenetic activation of the HPC-mPFC pathway improved LPS-induced cognitive dysfunction but not anxiety-like behavior. Inhibition of glutamate receptors abolished the effects of HPC-mPFC activation and blocked activation of the HPC-mPFC pathway. The glutamate receptor-mediated CaMKII/CREB/BDNF/TrKB signaling pathway influenced the role of the HPC-mPFC pathway in sepsis-induced cognitive dysfunction. Conclusions: HPC-mPFC pathway plays an important role in cognitive dysfunction in lipopolysaccharide-induced brain injury. Specifically, the glutamate receptor-mediated downstream signaling appears to be an important molecular mechanism linking the HPC-mPFC pathway with cognitive dysfunction in SAE.

Tanshinone IIA protected against lipopolysaccharide-induced brain injury through the protective effect of the blood-brain barrier and the suppression of oxidant stress and inflammatory response.

Brain microvascular endothelial cells are essential components of the blood-brain barrier (BBB) that acts as a selective physical barrier and plays protective roles in maintaining brain homeostasis. Tanshinone IIA (Tan IIA), isolated from Salvia miltiorrhiza Bunge, exhibited healthy effects such as antioxidant effects, anti-inflammatory effects, and cardiovascular protective effects. Here, we tried to investigate the positive effect and the potential mechanism of Tan IIA on the lipopolysaccharide (LPS)-induced brain injury in mice and brain microvascular endothelial cells in vitro. In vivo, Tan IIA inhibited the brain injury, and the enhancement of blood-brain barrier permeability in the LPS-induced brain injury in mice. Moreover, Tan IIA suppressed inflammatory response and oxidant response in LPS-treated mice evidenced by low levels of serum TNF-α and IL-1β, high superoxide dismutase (SOD) activity and low malondialdehyde (MDA) in the brain. In vitro, Tan IIA suppressed the generation of reactive oxygen species (ROS) and MDA, and promoted SOD activity in LPS-stimulated brain microvascular endothelial cells. Moreover, Tan IIA promoted the expression of Claudin5, ZO-1, Nrf2, HO-1 and NQO1 in LPS-stimulated brain microvascular endothelial cells. In conclusion, Tan IIA protected against the LPS-induced brain injury via the suppression of oxidant stress and inflammatory response and protective effect of the BBB through activating Nrf2 signaling pathways and rescue of the tight junction proteins in microvascular endothelial cells, supporting the application of Tan IIA and Salvia miltiorrhiza Bunge as food supplements for the treatment of brain disease.

Anti-neuroinflammatory Effects of Hwanggeumjakyak-tang on Lipopolysaccharide-induced Brain Injury Model in vivo and in vitro

Anti-neuroinflammatory Effects of <i>Hwanggeumjakyak-tang</i> on Lipopolysaccharide-induced Brain Injury Model <i>in vivo</i> and <i>in vitro</i>

Effect of Co Enzyme Q10 Alone or in Combination with Vitamin C on Lipopolysaccharide-Induced Brain Injury in Rats

Our was to determine the impact of CoenzymeQ10 (Co Q10) and vitamin C alone or in combination on oxidative stress in brain tissue of rats during endotoxemia induced by single intraperitoneal dose of Lipopolysaccharide (LPS), 500µg/kg. Both CoQ10&amp;vitamin C were given orally to rats with doses (200&amp;100 mg/kg) respectively for 7successive days prior induction of endotoxemia .LPS injected, with Co Q10 with doses (100 &amp;200 mg/kg) &amp;vit. C (50&amp;100 mg/kg).In addition CoQ10 and vitamin C together in doses (100&amp;50 mg/kg) &amp; (200&amp;100 mg/kg) respectively were added to LPS-treated rats. Then euthanized 4 hours later. Histopathological assessment of brain tissue was done. Results: LPS injection induced oxidative stress in brain tissue, resulting in marked increase in malondiadehyde (MDA), nitrite (NO) and Amyloid beta (Aβ), while decreasing reduced glutathione (GSH), paraoxonase-1 (PON1) and brain derived neurotrophic factor (BDNF).CoQ10 and vit.C administration with doses(200&amp;100 mg/ kg) before endotoxemia result in reduction of brain MDA, NO and Aβ, while increasing levels of GSH, PON1 and BDNF compared to controls. The addition of both Co Q10 &amp;vit.C to LPS- treated rats lead to decrease of brain NO, MDA and Aβ, also increase of GSH, PON1 and BDNF. This effect was more obviouswith high doses, this due to the ameliorating effect of both CoQ10 and vit.C on oxidative stress of brain tissue during endotoxemia.This consisted with the histopathological results. Conclusion: this work focuses on the possible role of CoQ10 &amp;vit.C as antioxidants in protecting brain tissue.

Perindopril ameliorates lipopolysaccharide-induced brain injury through modulation of angiotensin-II/angiotensin-1-7 and related signaling pathways

Localized tissue renin-angiotensin system (RAS) is an interesting pathway of organ damage. Here, the effect of the brain-penetrating angiotensin converting enzyme (ACE) inhibitor perindopril was studied on lipopolysaccharide (LPS)-induced brain damage, with and without exogenous angiotensin (Ang)-II administration. Animals were divided into 6 groups; a normal control group, an LPS control group (LPS, 3 mg/kg, i.p., single dose), two treatment groups receiving perindopril (1 and 2 mg/kg/day, i.p.) for 7 days before LPS administration, and two Ang-II/perindopril/LPS groups receiving perindopril and LPS, followed by a single dose of Ang-II solution (5 µl, i.c.v.). Brain tissue Ang-II, Ang-1-7, and NADPH oxidase were estimated using ELISA technique. Nuclear factor kappa-B (NF-ƙB-p65) was estimated using real time PCR technique, while phosphorylated NF-ƙB-p65 (p-NF-ƙB-p65), phosphorylated and non-phosphorylated protein kinase B (p-Akt and Akt) and phosphorylated inhibitor of kappa-B (p-IƙBa) were estimated by western blot analysis. Malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), glutathione-S-transferase (GST), catalase, nitrite and myloperoxidase (MPO) were estimated colorimetrically. Brain tissue inducible and endothelial nitric oxide synthases (iNOS and eNOS) were estimated immunohistochemically, confirmed by a histopathological study. LPS-intoxicated rats showed significantly elevated Ang-II, NADPH oxidase, NF-ƙB-p65, p-NF-ƙB-p65, p-IƙBa, p-Akt, Akt, p-Akt/Akt ratio, MDA, nitrite, MPO and iNOS levels, coupled with significantly suppressed Ang-1-7, GSH, SOD, GST, catalase, and eNOS levels, which were all corrected by pre-treatment with perindopril in both doses by varying degrees. Exogenous Ang-II significantly ameliorated the protective effects of perindopril. Conclusively, perindopril ameliorates LPS-induced brain damage through modulation of RAS, iNOS/eNOS, p-Akt/Akt and NF-ƙB signaling pathways.

Effect of penhyclidine hydrochloride on blood-brain barrier permeability in a rat model of lipopolysaccharide-induced brain injury

Objective To detect the effect of penhyclidine hydrochloride (PHC) on blood-brain barrier permeability in rats with lipopolysaccharide (LPS)-induced brain injury. Methods Eighty-one clear adult male SD rats were divided into control group, LPS group and PHC group according to the random number table, with 27 rats per group. The model of LPS-induced brain injury was established both in LPS and PHC groups. Rats were treated intraperitoneally with 2 mg/kg PHC in PHC group, while with the same volume of normal saline in control and LPS groups. Evans blue propagation through the brain was detected under the fluorescence microscope. Evans blue content was measured with a spectrophotometer. TNF-α content was measured with the Elisa assay. Brain water content was assessed with wet-to-dry weight ratios. Results Evans blue distribution in the cortex was obvious in LPS group, but decreased in PHC group. In control group contents of Evans blue in the cortex [(10.2±1.4)μg/g] and in the hippocampus[(11.3±0.8)μg/g] lowered as compared to these in LPS group [(234.8±14.7) and (23.1±1.9)μg/g] and PHC group [(71.0±8.7) and (15.2±1.9)μg/g] (P<0.01). Brain water content in control group was (73.5±1.8)%, increased to (85.3±1.6)% in LPS group and (78.9±1.2)% in PHC group (P<0.01). In control group contents of TNF-α in blood serum [(40.6±4.4) pg/ml], cerebrospinal fluid [(84.0±8.6)pg/ml] and brain tissue [(156.3±11.8) pg/ml] were significantly lower than these in LPS group[(93.4±7.2), (176.4±11.6) and (280.8±19.4)pg/ml] and PHC group[(79.9±5.9), (146.2±7.4) and (216.9±14.5) pg/ml] (P<0.01). And in comparison, all the measurements were lower in PHC group than in LPS group (P<0.01). Conclusion PHC can protect the BBB in rats with LPS-induced brain injury. Key words: Brain injuries; Blood-brain barrier; Penhyclidine hydrochloride

Mangiferin regulates interleukin-6 and cystathionine-b-synthase in lipopolysaccharide-induced brain injury.

Mangiferin has been extensively applied in different fields due to its anti-inflammatory properties. However, the precise mechanism used by mangiferin on lipopolysaccharide (LPS)-induced inflammation has not been elucidated. Here, we discuss the potential mechanism of mangiferin during a LPS-induced brain injury. Brain injury was induced in ICR mice via intraperitoneal LPS injection (5 mg/kg). Open- and closed-field tests were used to detect the behaviors of mice, while immunoblotting was performed to measure the expression of interleukin-6 (IL-6) and cystathionine-b-synthase (CBS) in the hippocampus after mangiferin was orally administered (p.o.). Mangiferin relieved LPS-induced sickness 6 and 24 h after LPS injection; in addition, this compound suppressed LPS-induced IL-6 production after 24 h of LPS induction as well as the downregulation of LPS-induced CBS expression after 6 and 24 h of LPS treatment in the hippocampus. Therefore, mangiferin attenuated sickness behavior by regulating the expression of IL-6 and CBS.

Effects of propofol on lipopolysaccharide-induced brain injury in rats

Objective To investigate the effects of propofol on lipopolysaccharide (LPS)-induced brain injury in rats.Methods Fifty-four pathogen-free SD rats of both sexes, aged 6 weeks, weighing 200-250 g, were randomly divided into 3 groups: control group (group C, n = 6) ; LPS group (group L, n = 24) ; propofol group (group P, n = 24) . Brain injury was produced by injection of LPS 1 mg/kg via the left internal carotid artery in L and P groups. Propofol 100 mg/kg was injected intraperitonealry immediately after the LPS administration in group P, while the equal volume of normal saline was given instead of propofol in group L. The equal volume of normal saline was given instead of LPS and propofol in group C. Six rats in each group were sacrificed and the brain tissues were immediately removed at 24 h after intraperitoneal administration in group C, and at 6, 24, 48 and 72 h after intraperitoneal administration in L and P groups for determination of brain water content, high-mobility group box 1 ( HMGB1) expression and NF-κB activity, and microscopic examination. Results The brain water content and NF-kB activity were significantly increased, and HMGB1 expression was up-regulated in group L as compared to group C (P ＜ 0.05) . The brain water content, expression of HMGB1 and NF-kB activity were significantly lower in group P than in group L ( P ＜ 0.05) . The microscopic examination showed that brain injury was attenuated in group P compared with group L. The brain water content was positively correlated with the HMGB1 expression and NF- κB activity (r = 0.692 and 0.769 respectively, P ＜ 0.05). Conclusion Propofol can reduce the LPS- induced brain injury by reducing inflammatory response of the brain tissues. Key words: Propofol; Brain injuries; Endotoxemia

Neuroprotective Effect of Oligodendrocyte Precursor Cell Transplantation in a Long-Term Model of Periventricular Leukomalacia

Perinatal white matter injury, or periventricular leukomalacia (PVL), is the most common cause of brain injury in premature infants and is the leading cause of cerebral palsy. Despite increasing numbers of surviving extreme premature infants and associated long-term neurological morbidity, our understanding and treatment of PVL remains incomplete. Inflammation- or ischemia/hypoxia-based rodent models, although immensely valuable, are largely restricted to reproducing short-term features of up to 3 weeks after injury. Given the long-term sequelae of PVL, there is a need for subchronic models that will enable testing of putative neuroprotective therapies. Here, we report long term characterization of a neonatal inflammation-induced rat model of PVL. We show bilateral ventriculomegaly, inflammation, reactive astrogliosis, injury to pre-oligodendrocytes, and neuronal loss 8 weeks after injury. We demonstrate neuroprotective effects of oligodendrocyte precursor cell transplantation. Our findings present a subchronic model of PVL and highlight the tissue protective effects of oligodendrocyte precursor cell transplants that demonstrate the potential of cell-based therapy for PVL.

Prophylaxis with α-lipoic acid against lipopolysaccharide-induced brain injury in rats

IntroductionLipopolysaccharide (LPS) stimulates the synthesis and release of reactive oxygen species that play an important role in the pathogenesis of tissue injuries. In this study the effect of early administration of the antioxidant α-lipoic acid (α-LA) on brain lipid peroxidation, brain hydrogen peroxide (H2O2) concentration, and brain total sulfhydryl group (-SH group) content was evaluated in rats with endotoxic shock induced by administration of LPS (Escherichia coli 026:B6, 30 mg/kg i.v.)Materials and MethodsRats were treated intravenously with normal saline or α-LA (60 mg/kg) 30 min after LPS injection. After 5 h of observation, the animals were killed and their brains were isolated for the measurements.ResultsInjection of LPS alone resulted in the development of shock and oxidative stress, the latter indicated by a significant increase in brain concentrations of thiobarbituric acid-reacting substances (TBARS) and H2O2 and a decrease in total brain -SH group content. Administration of α-LA after the LPS challenge resulted in an increase in total -SH group content and a decrease in TBARS and H2O2 concentration in the brain tissue compared with the LPS group.ConclusionThe results indicate that α-LA treatment effectively protected the brain tissue against endotoxin-induced oxidative stress. Administration of LA could be a useful adjunct to clinical application in the management of septic shock.

Alpha-Phenyl-n-tert-butyl-nitrone attenuates lipopolysaccharide-induced brain injury and improves neurological reflexes and early sensorimotor behavioral performance in juvenile rats.

Our previous study showed that treatment with alpha-phenyl-n-tert-butyl-nitrone (PBN) after exposure to lipopolysaccharide (LPS) reduced LPS-induced white matter injury in the neonatal rat brain. The object of the current study was to further examine whether PBN has long-lasting protective effects and ameliorates LPS-induced neurological dysfunction. Intracerebral (i.c.) injection of LPS (1 mg/kg) was performed in postnatal day (P) 5 Sprague Dawley rat pups and PBN (100 mg/kg) or saline was administered intraperitoneally 5 min after LPS injection. The control rats were injected (i.c.) with sterile saline. Neurobehavioral tests were carried out from P3 to P21, and brain injury was examined after these tests. LPS exposure resulted in severe brain damage, including enlargement of ventricles bilaterally, loss of mature oligodendrocytes, impaired myelination as indicated by the decrease in myelin basic protein immunostaining, and alterations in dendritic processes in the cortical gray matter of the parietal cortex. Electron microscopic examination showed that LPS exposure caused impaired myelination as indicated by the disintegrated myelin sheaths in the juvenile rat brain. LPS administration also significantly affected neurobehavioral functions such as performance in righting reflex, wire hanging maneuver, cliff avoidance, negative geotaxis, vibrissa-elicited forelimb-placing test, beam walking, and gait test. Treatment with PBN, a free radical scavenger and antioxidant, provided protection against LPS-induced brain injury and associated neurological dysfunction in juvenile rats, suggesting that antioxidation might be an effective approach for therapeutic treatment of neonatal brain injury induced by infection/inflammation.

Role of interleukin-6 in lipopolysaccharide-induced brain injury and behavioral dysfunction in neonatal rats

There are increasing data in support of the hypothesis that inflammatory cytokines are involved in neonatal white matter damage. Despite extensive study of the proinflammatory cytokines tumor necrosis factor-α and interleukin-1β, the role of interleukin-6 in the development of white matter damage is largely unknown. In the present study, the role(s) of interleukin-6 in mediating lipopolysaccharide-induced brain injury and behavioral changes was investigated by the intracerebral injection of lipopolysaccharide with interleukin-6 neutralizing antibody in the 5-day-old rat brain. Brain injury was examined in brain sections at postnatal day 8 and postnatal day 21. Behavioral tests including righting reflex, wire hanging maneuver, cliff avoidance, locomotor activity, gait analysis, responses in the elevated plus-maze and passive avoidance were performed from postnatal day 3 to postnatal day 21. Changes in astroglia, microglia and oligodendrocytes were studied using immunohistochemistry in the postnatal day 21 rat brain. Our results show that interleukin-6 antibody attenuated lipopolysaccharide-induced brain lateral ventricle dilation and improved neurobehavioral performance. Interleukin-6 antibody also suppressed lipopolysaccharide-induced astrogliosis and microglial activation, and increased the number of oligodendrocytes in white matter. However, no changes of tumor necrosis factor-α and interleukin-1β were detected. In contrast, no histopathological changes and glial activation were observed in rats injected with only interleukin-6. The present study indicates that the contribution to brain injury by interleukin-6 depends on its interaction with other lipopolysaccharide-induced agents and not on interleukin-6 alone.

12 Effect of Anticytokine Treatment in A Mouse Model for Perinatal White Matter Lesions

Background: White matter lesions in neonates can result in motor handicaps such as cerebral palsy. Ischemia/ reperfusion and excitotoxic injuries have been considered probable aetiologies, but epidemiological data implicate that maternal-fetal infection and associated increase in circulating cytokines most likely also contributes to cerebral palsy. Tumor necrosis factorá (TNFá) is a cytokine that has a central position in the inflammatory cascade in many tissues and controls the release of other pro-inflammatory cytokines such as interleukin-1â (IL-1â). Numerous studies of systemic inflammatory diseases show that neutralization of TNFá with antibodies or soluble receptors inhibits the production of proinflammatory cytokines. Less is known about the effect of TNFá blocking agents in neonatal brain injury. In a study using lipopolysaccharide-induced brain injury, TNFá antibody had no effect whereas IL-1 receptor antagonist attenuated brain damage. Here, we have investigated the role of TNFá and in model of excitotoxic white matter lesion.Methods: The glutamate analog ibotenate was injected into the periventricular white matter of 5-day-old mice. At postnatal day 10, brains were sectioned in the coronal plane and the number of sections with brain damage was evaluated using cresyl-violet staining. The following groups of pups (n=8–10) were exposed to ibotenate: pretreatment (P1–5, i.p.) with IL-1â (10ng/kgx2), TNFá soluble receptor (etanercept, 100 μg/kgx1), IL-1 receptor antagonist (anakinra 0.3 g/kgx1) or PBS. Posttreatment (P5–7) with etanercept (1–500μg/kgx1), anakinra (0.3–1,0 g/kgx1) or PBS. In addition, TNFá knockouts (Jackson lab) and corresponding wild type mice were subjected to ibotenate intracerebral injection and pretreatment with IL-1â (10ng/kgx2).Results: TNFá soluble receptor or IL-1 receptor antagonist did not affect white matter lesions induced by ibotenate alone. Likewise, excitotoxic lesion did not differ between TNFá knockouts and wildtypes. However, if the excitotoxic lesion was enhanced by pretreatment with IL-1â, TNFá soluble receptor entirely attenuated this exacerbation (p<0.05).Conclusion: White matter damage induced by a combination of excitotoxicity and inflammation is reduced by a TNFá neutralizing agent. This indicates that TNFá is a key cytokine also in the brain and suggests a role for TNFá blocking drugs in preventing neonatal white matter lesions.

Differential roles of tumor necrosis factor-α and interleukin-1 β in lipopolysaccharide-induced brain injury in the neonatal rat

Increasing data provide support for the hypothesis that inflammatory cytokines mediate inflammation-induced injury to developing white matter. In the present study, roles of tumor necrosis factor-α (TNFα) and interleukin-1 β (IL-1β) in mediating lipopolysaccharide (LPS)-induced brain injury were investigated by co-administration of LPS with IL-1 receptor antagonist (IL-1ra) or TNFα antibody in the 5-day-old rat brain. Intracerebral injection of LPS and other agents was performed in a stereotaxic apparatus at the location of 1.0 mm posterior and 1.0 mm lateral to the bregma, and 2.0 mm deep to the skull surface at the left hemisphere. Brain injury was examined in brain sections 3 and 11 days after LPS injection. LPS-induced inflammatory responses were evidenced by great increases in TNFα and IL-1β concentrations in the neonatal rat brain 6 h after LPS injection. White matter rarefaction was observed in 71% (five out of seven) of the rat brains 3 days after LPS injection and bilateral ventricle dilation was found in 71% (five out of seven) of the P8 rat brains and in 100% of the P16 rat brains (four out of four). These alterations were not found in the control rat brains. No apparent histological changes in gray matter were observed in the LPS-injected rat brains. LPS injection also resulted in injuries to oligodendrocytes (OLs) and hypomyelination, as indicated by reduced immunostaining for O4 and myelin basic protein (MBP). Increased astrogliosis, as indicated by increased glial fibrillary acidic protein (GFAP) immunostaining, was also observed in the LPS-injected, but not the control rat brain. Co-administration of LPS with IL-1ra, but not with TNFα antibody, significantly attenuated LPS-induced white matter injury, as indicated by decreases in ventricle dilation, white matter rarefaction, GFAP positive staining and by improved O4 and MBP immunostaining. Co-administration of LPS with IL-1ra significantly reduced LPS-induced elevation of caspase-3 activity in the rat brain. While TNFα antibody had no effect on LPS-induced elevation of caspase-3 activity, co-administration of LPS with TNFα antibody partially, but significantly, decreased LPS-stimulated increase in IL-1β in the neonatal rat brain. These data suggest that IL-1β may play an important role in mediating LPS-induced brain injury and TNFα may have complicated, probably dual, effects in LPS-induced brain injury.