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Absence of TLR4 reduces neurovascular unit and secondary inflammatory process after traumatic brain injury in mice.

ABSTRACT: Traumatic brain injury (TBI) initiates a neuroinflammatory cascade that contributes to neuronal damage and behavioral impairment. Toll-like receptors (TLRs) are signaling receptors in the innate immune system, although emerging evidence indicates their role in brain injury. We have therefore investigated the role played by TLR4 signaling pathway in the development of mechanisms of secondary inflammatory process in traumatic brain injury (TBI) differ in mice that lack a functional TLR4 signaling pathway.Controlled cortical impact injury was performed on TLR4 knockout (KO) mice (C57BL/10ScNJ) and wild-type (WT) mice (C57BL/10ScNJ). TBI outcome was evaluated by determination of infarct volume and assessment of neurological scores. Brains were collected at 24 h after TBI. When compared to WT mice, TLR4 KO mice had lower infarct volumes and better outcomes in neurological and behavioral tests (evaluated by EBST and rotarod test). Mice that lacked TLR4 had minor expression of TBI-induced GFAP, Chymase, Tryptase, IL-1?, iNOS, PARP and Nitrotyrosine mediators implicated in brain damage. The translocation of expression of p-JNK, I?B-? and NF-?B pathway were also lower in brains from TLR4 KO mice. When compared to WT mice, resulted in significant augmentation of all the above described parameters. In addition, apoptosis levels in TLR4 KO mice had minor expression of Bax while on the contrary with Bcl-2.Our results clearly demonstrated that absence of TLR4 reduces the development of neuroinflammation, tissues injury events associated with brain trauma and may play a neuroprotective role in TBI in mice.

SUBMITTER: Ahmad A

PROVIDER: S-EPMC3610903 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Absence of TLR4 reduces neurovascular unit and secondary inflammatory process after traumatic brain injury in mice.

Ahmad Akbar A Crupi Rosalia R Campolo Michela M Genovese Tiziana T Esposito Emanuela E Cuzzocrea Salvatore S

PloS one 20130328 3

<h4>Background</h4>Traumatic brain injury (TBI) initiates a neuroinflammatory cascade that contributes to neuronal damage and behavioral impairment. Toll-like receptors (TLRs) are signaling receptors in the innate immune system, although emerging evidence indicates their role in brain injury. We have therefore investigated the role played by TLR4 signaling pathway in the development of mechanisms of secondary inflammatory process in traumatic brain injury (TBI) differ in mice that lack a functio ...[more]

PMID: 23555560

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Project description:In addition to neurons, all components of the neurovascular unit (NVU), such as glial, endothelial, and basal membranes, are destroyed during traumatic brain injury (TBI). Previous studies have shown that excessive stimulation of calpain is crucial for cerebral injury after traumatic insult. The objective of this study was to investigate whether calpain activation participated in NVU disruption and edema formation in a mouse model of controlled cortical impact (CCI).One hundred and eight mice were divided into three groups: the sham group, the control group, and the MDL28170 group. MDL28170 (20 mg/kg), an efficient calpain inhibitor, was administered intraperitoneally at 5 min, 3 h, and 6 h after experimental CCI. We then measured neurobehavioral deficits, calpain activity, inflammatory mediator levels, blood-brain barrier (BBB) disruption, and NVU deficits using electron microscopy and histopathological analysis at 6 h and 24 h after CCI.The MDL28170 treatment significantly reduced the extent of both cerebral contusion (MDL28170 vs. vehicle group, 16.90 ± 1.01 mm? and 17.20 ± 1.17 mm? vs. 9.30 ± 1.05 mm? and 9.90 ± 1.17 mm?, both P < 0.001) and edema (MDL28170 vs. vehicle group, 80.76 ± 1.25% and 82.00 ± 1.84% vs. 82.55 ± 1.32% and 83.64 ± 1.25%, both P < 0.05), improved neurological scores (MDL28170 vs. vehicle group, 7.50 ± 0.45 and 6.33 ± 0.38 vs. 12.33 ± 0.48 and 11.67 ± 0.48, both P < 0.001), and attenuated NVU damage resulting (including tight junction (TJ), basement membrane, BBB, and neuron) from CCI at 6 h and 24 h. Moreover, MDL28170 markedly downregulated nuclear factor-?B-related inflammation (tumor necrosis factor-? [TNF-?]: MDL28170 vs. vehicle group, 1.15 ± 0.07 and 1.62 ± 0.08 vs. 1.59 ± 0.10 and 2.18 ± 0.10, both P < 0.001; inducible nitric oxide synthase: MDL28170 vs. vehicle group, 4.51 ± 0.23 vs. 6.23 ± 0.12, P < 0.001 at 24 h; intracellular adhesion molecule-1: MDL28170 vs. vehicle group, 1.45 ± 0.13 vs. 1.70 ± 0.12, P < 0.01 at 24 h) and lessened both myeloperoxidase activity (MDL28170 vs. vehicle group, 0.016 ± 0.001 and 0.016 ± 0.001 vs. 0.024 ± 0.001 and 0.023 ± 0.001, P < 0.001 and 0.01, respectively) and matrix metalloproteinase-9 (MMP-9) levels (MDL28170 vs. vehicle group, 0.87 ± 0.13 and 1.10 ± 0.10 vs. 1.17 ± 0.13 and 1.25 ± 0.12, P < 0.001 and 0.05, respectively) at 6 h and 24 h after CCI.These findings demonstrate that MDL28170 can protect the structure of the NVU by inhibiting the inflammatory cascade, reducing the expression of MMP-9, and supporting the integrity of TJ during acute TBI.

Project description:Traumatic CNS injury triggers a systemic inflammatory response syndrome (SIRS), in which circulating inflammatory cells invade body organs causing local inflammation and tissue damage. We have shown that the SIRS caused by spinal cord injury is greatly reduced by acute intravenous treatment with an antibody against the CD11d subunit of the CD11d/CD18 integrin expressed by neutrophils and monocyte/macrophages, a treatment that reduces their efflux from the circulation. Traumatic brain injury (TBI) is a frequently occurring injury after motor vehicle accidents, sporting and military injuries, and falls. Our studies have shown that the anti-CD11d treatment diminishes brain inflammation and oxidative injury after moderate or mild TBI, improving neurological outcomes. Accordingly, we examined the impact of this treatment on the SIRS triggered by TBI. The anti-CD11d treatment was given at 2h after a single moderate (2.5-3.0 atm) or 2 and 24h after each of three consecutive mild (1.0-1.5 atm) fluid percussion TBIs. Sham-injured, saline-treated rats served as controls. At 24h, 72 h, and 4 or 8 weeks after the single TBI and after the third of three TBIs, lungs of rats were examined histochemically, immunocytochemically and biochemically for downstream effects of SIRS including inflammation, tissue damage and expression of oxidative enzymes. Lung sections revealed that both the single moderate and repeated mild TBI caused alveolar disruption, thickening of inter-alveolar tissue, hemorrhage into the parenchyma and increased density of intra-and peri-alveolar macrophages. The anti-CD11d treatment decreased the intrapulmonary influx of neutrophils and the density of activated macrophages and the activity of myeloperoxidase after these TBIs. Moreover, Western blotting studies showed that the treatment decreased lung protein levels of oxidative enzymes gp91(phox), inducible nitric oxide synthase and cyclooxygenase-2, as well as the apoptotic pathway enzyme caspase-3 and levels of 4-hydroxynonenal-bound proteins (an indicator of lipid peroxidation). Decreased expression of the cytoprotective transcription factor Nrf2 reflected decreased lung oxidative stress. Anti-CD11d treatment also diminished the lung concentration of free radicals and tissue aldehydes. In conclusion, the substantial lung component of the SIRS after single or repeated TBIs is significantly decreased by a simple, minimally invasive and short-lasting anti-inflammatory treatment.

Project description:Traumatic brain injury (TBI) has a complex pathology in which the initial injury releases damage associated proteins that exacerbate the neuroinflammatory response during the chronic secondary injury period. One of the major pathological players in the inflammatory response after TBI is the inflammasome. Increased levels of inflammasome proteins during the acute phase after TBI are associated with worse functional outcomes. Previous studies reveal that the level of inflammasome proteins in biological fluids may be used as promising new biomarkers for the determination of TBI functional outcomes. In this study, we provide further evidence that inflammatory cytokines and inflammasome proteins in serum may be used to determine injury severity and predict pathological outcomes. In this study, we analyzed blood serum from TBI patients and respective controls utilizing Simple Plex inflammasome and V-PLEX inflammatory cytokine assays. We performed statistical analyses to determine which proteins were significantly elevated in TBI individuals. The receiver operating characteristics (ROC) were determined to obtain the area under the curve (AUC) to establish the potential fit as a biomarker. Potential biomarkers were then compared to documented patient Glasgow coma scale scores via a correlation matrix and a multivariate linear regression to determine how respective biomarkers are related to the injury severity and pathological outcome. Inflammasome proteins and inflammatory cytokines were elevated after TBI, and the apoptosis-associated speck like protein containing a caspase recruitment domain (ASC), interleukin (IL)-18, tumor necrosis factor (TNF)-α, IL-4 and IL-6 were the most reliable biomarkers. Additionally, levels of these proteins were correlated with known clinical indicators of pathological outcome, such as the Glasgow coma scale (GCS). Our results show that inflammatory cytokines and inflammasome proteins are promising biomarkers for determining pathological outcomes after TBI. Additionally, levels of biomarkers could potentially be utilized to determine a patient's injury severity and subsequent pathological outcome. These findings show that inflammation-associated proteins in the blood are reliable biomarkers of injury severity that can also be used to assess the functional outcomes of TBI patients.

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Absence of TLR4 reduces neurovascular unit and secondary inflammatory process after traumatic brain injury in mice.

Publications

Absence of TLR4 reduces neurovascular unit and secondary inflammatory process after traumatic brain injury in mice.

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