Post-injury treatment with lipopolysaccharide or lipooligosaccharide protects rat neuronal and glial cell cultures

Dose-Dependent Microglial and Astrocytic Responses Associated With Post-ischemic Neuroprotection After Lipopolysaccharide-Induced Sepsis-Like State in Mice

In contrast to lipopolysaccharide (LPS)-induced preconditioning, which has repeatedly been examined in the past, the effects of post-ischemic LPS-induced sepsis, although clinically considerably more important, have not systemically been studied. We exposed mice to transient intraluminal middle cerebral artery occlusion (MCAO) and examined the effects of intraperitoneal LPS (0.1 or 1 mg/kg) which was administered 24 h post-ischemia. Post-ischemic glial reactivity, neuronal survival and neurological outcome were differently modulated by the higher and the lower LPS dose. Although both doses promoted neuronal survival after 72 h, the underlying mechanisms were not similar. Mice receiving 1 mg/kg LPS exhibited transient hypothermia at 1 and 3 hours post sepsis (hps), followed by reduced focal neurological deficits at 24, 48 and 72 hps. The lower dose (0.1 mg/kg) did not induce hypothermia, but reduced microglia/macrophage activation with the appearance of an anti-inflammatory CD206 positive cell phenotype in the brain parenchyma. Together, our results indicate a novel, dose-dependent modulation of microglial cells that is intricately involved in brain protection.

The effect of Lipopolysaccharide (LPS) pretreatment on hippocampal apoptosis in traumatic rats

Objectives: Traumatic brain injury (TBI) is a serious medical problem that affects the quality of life. Apoptosis is a form of programmed cell death that happens after trauma. Effector caspases are responsible for initiating apoptosis.Methods: In the present study, we examined the effect of LPS preconditioning (0.1 and 0.5 mg/kg, ip; 5 days prior controlled cortical injury) on apoptosis, 4 and 12 hours after trauma. We investigated possible mechanisms on the expression of caspase3 and caspase7 in hippocampal CA1 and CA3 areas by using immunohistochemistry and Western blotting techniques and also TUNEL-positive cells.Results: Higher expression of caspase3 and caspase7 were accompanied by a higher number of dead neurons in traumatic rats 4 and 12 hours after trauma(P < 0.05). LPS preconditioning decreased caspase3 and caspase7over-expression and the number of dead neurons in the hippocampus(P < 0.05).Discussion: Our data indicate that LPS preconditioning inhibits neural damage and apoptosis induced by trauma in the hippocampus.

Toll like receptor 4 activation can be either detrimental or beneficial following mild repetitive traumatic brain injury depending on timing of activation

A history of repeated concussion has been linked to the later development of neurodegeneration, which is associated with the accumulation of hyperphosphorylated tau and the development of behavioral deficits. However, the role that exogenous factors, such as immune activation, may play in the development of neurodegeneration following repeated mild traumatic brain injury (rmTBI) has not yet been explored. To investigate, male Sprague-Dawley rats were administered three mTBIs 5days apart using the diffuse impact-acceleration model to generate ∼100G. Sham animals underwent surgery only. At 1 or 5days following the last injury rats were given the TLR4 agonist, lipopolysaccharide (LPS, 0.1mg/kg), or saline. TLR4 activation had differential effects following rmTBI depending on the timing of activation. When given at 1day post-injury, LPS acutely activated microglia, but decreased production of pro-inflammatory cytokines like IL-6. This was associated with a reduction in neuronal injury, both acutely, with a restoration of levels of myelin basic protein (MBP), and chronically, preventing a loss of both MBP and PSD-95. Furthermore, these animals did not develop behavioral deficits with no changes in locomotion, anxiety, depressive-like behavior or cognition at 3months post-injury. Conversely, when LPS was given at 5days post-injury, it was associated acutely with an increase in pro-inflammatory cytokine production, with an exacerbation of neuronal damage and increased levels of aggregated and phosphorylated tau. At 3months post-injury, there was a slight exacerbation of functional deficits, particularly in cognition and depressive-like behavior. This highlights the complexity of the immune response following rmTBI and the need to understand how a history of rmTBI interacts with environmental factors to influence the potential to develop later neurodegeneration.

Lipopolysaccharide preconditioning prevents acceleration of kindling epileptogenesis induced by traumatic brain injury

10-20% of symptomatic epilepsies are post-traumatic. We examined effect of LPS preconditioning on epileptogenesis after controlled cortical impact (CCI). LPS (0.01, 0.1 and 0.5 mg/kg) was injected i.p. to rats 5 days before induction of CCI to parieto-temporal cortex. Kindling started 24h after CCI by i.p. injection of 30 mg/kg of pentylenetetrazole every other day until manifestation of 3 consecutive generalized seizures. CCI injury accelerated the rate of kindled seizures acquisition. LPS (0.1 and 0.5 mg/kg) prevented the acceleration of kindling. LPS preconditioning significantly decreased IL-1β and TNF-α over-expression and the number of damaged neurons in the hippocampus of traumatic rats.

Establishment of Lipofection Protocol for Efficient miR-21 Transfection into Cortical Neurons In Vitro

Dysregulated microRNAs in neurons could cause many nervous system diseases. The therapeutic manipulation of these pathogenic microRNAs necessitates novel, efficient delivery systems to facilitate microRNA modulators targeting neurons with minimal off-target effects. The study aimed to establish a lipofection protocol to upregulate expression levels of miR-21 in neurons under different conditions, including different serum-free medium, transfection conditions, and reagent concentration, by evaluating the expression levels of miR-21 and neuron injury. The expression levels of miR-21 were higher in neurons transfected by Neurobasal-A than by DMEM. Expression levels of miR-21 were already the highest at the ratio RNAiMAX:miR-21 = 3:5, but the increase of RNAiMAX's concentration had not caused the further upregulation of expression level of miR-21. Neuron injury was condition dependent and dose dependent after transfection. Compared to S-Neurobasal groups, neurons have a smaller injury in N-Neurobasal groups, and compared to ratios RNAiMAX:miR-21 = 4:5, 5:5, neuron injury was smaller at ratios of RNAiMAX:miR-21 = 1:5, 2:5, 3:5. Without the pretreatment of starvation in vitro, the lipofection protocol was that RNAiMAX/miR-21 agomir complexes were diluted in Neurobasal-A at the ratio of RNAiMAX:miR-21 = 3:5.

Effect of siRNA‑induced inhibition of IL‑6 expression in rat cerebral gliocytes on cerebral edema following traumatic brain injury

The present study aimed to investigate the effect of RNA interference (RNAi) on the inhibition of interleukin (IL)‑6 expression in rat cerebral gliocytes in vitro and rat cerebral traumatic tissues in vivo, as well as the effect of RNAi on cerebral edema. pSUPER vectors containing IL‑6 small hairpin RNA (pSUPER‑IL‑6 1‑5) were designed, constructed and transfected into C6 rat glioma cells using cationic liposomes. ELISA was used to select the plasmid with the strongest interference effect. A freefall method was used to generate a rat brain injury model and rats were randomly divided into treatment, empty plasmid and control groups (n=14/group). IL‑6 levels, water content and sodium content were determined in the brain tissues at 24 and 72 h post‑injury. pSUPER‑IL‑6 was effectively transfected into C6 cells and was found to inhibit the expression of IL‑6 rather than IL‑8. The pSUPER‑IL‑6 1 vector was most effective in inducing RNAi. In vivo, IL‑6 levels were observed to be lowest in the interference group and there were statistically significant differences in water and sodium content among the experimental groups (P<0.05). RNAi was found to inhibit IL‑6 expression in vivo and in vitro in rat cerebral gliocytes, and the reduction of the IL‑6 levels was found to reduce post‑traumatic cerebral edema.

Post-injury conditioning with lipopolysaccharide or lipooligosaccharide reduces inflammation in the brain

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of mortality and disability in the Western world. The first stage of TBI results from the mechanical damage from an impact or blast. A second stage occurs as an inflammatory response to the primary injury and presents an opportunity for clinical intervention. In this study, we investigated the effect of pre- and post-injury treatment with lipopolysaccharide (LPS) from Escherichia coli and lipooligosaccharide (LOS) from Neisseria meningitidis on levels of cerebral inflammatory cells, circulating blood cells, and pro- and anti-inflammatory cytokine levels in a rat model of neuroinflammation induced by intrastriatal injection of IL-1β to mimic the second stage of TBI.

METHODS

LPS or LOS was administered intravenously (IV) or intranasally (IN) 2h pre- or post-injection of IL-1β. The rats were euthanized 12h following IL-1β injection. Brain sections were immunostained with antibody to ED-1, a microglia cell marker. Cells in whole blood were assessed with a VetScan HM2 analyzer, and cytokine levels in sera were analyzed with a Bio-Plex system.

RESULTS

Pre- and post-injury IV administration of LPS or LOS significantly reduced microglia in the brain, and IN pre-treatment with LPS or LOS showed a statistical trend towards reducing microglia. Pre- and post-treatment IV with LOS increased circulating levels of IL-2 and IL-4, whereas IN post-treatment with LPS reduced levels of the inflammatory cytokines, TNF-α and IFN-γ.

CONCLUSIONS

The findings strongly support continued investigation of post-conditioning with LPS or LOS as potential neuroprotective treatments for neuroinflammation from TBI.