Inflammation and blood-brain barrier breach remote from the primary injury following neurotrauma

Abstract

BackgroundFollowing injury to the central nervous system, increased microglia, secretion of pro- and anti-inflammatory cytokines, and altered blood-brain barrier permeability, a hallmark of degeneration, are observed at and immediately adjacent to the injury site. However, few studies investigate how regions remote from the primary injury could also suffer from inflammation and secondary degeneration.MethodsAdult female Piebald-Viral-Glaxo (PVG) rats underwent partial transection of the right optic nerve, with normal, age-matched, unoperated animals as controls. Perfusion-fixed brains and right optic nerves were harvested for immunohistochemical assessment of inflammatory markers and blood-brain barrier integrity; fresh-frozen brains were used for multiplex cytokine analysis.ResultsImmediately ventral to the optic nerve injury, immunointensity of both the pro-inflammatory biomarker inducible nitric oxide synthase (iNOS) and the anti-inflammatory biomarker arginase-1 (Arg1) increased at 7 days post-injury, with colocalization of iNOS and Arg1 immunoreactivity within individual cells. CD11b+ and CD45+ cells were increased 7 days post-injury, with altered BBB permeability still evident at this time. In the lower and middle optic tract and superior colliculus, IBA1+ resident microglia were first increased at 3 days; ED1+ and CD11b+ cells were first increased in the middle and upper tract and superior colliculus 7 days post-injury. Increased fibrinogen immunoreactivity indicative of altered BBB permeability was first observed in the contralateral upper tract at 3 days and middle tract at 7 days post-injury. Multiplex cytokine analysis of brain homogenates indicated significant increases in the pro-inflammatory cytokines, IL-2 and TNFα, and anti-inflammatory cytokine IL-10 1 day post-injury, decreasing to control levels at 3 days for TNFα and 7 days for IL-2. IL-10 was significantly elevated at 1 and 7 days post-injury with a dip at 3 days post-injury.ConclusionsPartial injury to the optic nerve induces a complex remote inflammatory response, characterized by rapidly increased pro- and anti-inflammatory cytokines in brain homogenates, increased numbers of IBA1+ cells throughout the visual pathways, and increased CD11b+ and ED1+ inflammatory cells, particularly towards the synaptic terminals. BBB permeability can increase prior to inflammatory cell infiltration, dependent on the brain region.

Lycium barbarum (Wolfberry) Increases Retinal Ganglion Cell Survival and Affects both Microglia/Macrophage Polarization and Autophagy after Rat Partial Optic Nerve Transection

“…Secondly, CD68 was used in this study and Iba-1 was used in the previous study. These two different antibodies may not label exactly the same number or category of microglia/ macrophages because not all CD68 positive cells are positive for Iba-1, a point that has been shown in different studies 11 .…”

“…Many studies have used this model [4][5][6][7][8][9][10][11][12][13] . In these previous studies, PONT in rats was administrated from the superior side of optic nerves; however, in this study we cut the optic nerves from the temporal side and found that this operation was much easier to conduct than from the superior side due to the lack of obstruction from rectus superior and obliquus superior eye muscles ( Fig.…”

Differential responses to increasing numbers of mild traumatic brain injury in a rodent closed‐head injury model

“…However, it is increasingly understood that these markers can be co‐expressed and increased in the same cells following injury (Smith et al . ), and are therefore not definitive indicators of pro‐ or anti‐inflammatory events.…”

Chronic Consumption of Bovine Dairy Milk Attenuates Dietary Saturated Fatty Acid-Induced Blood-Brain Barrier Dysfunction

“…Non-specific binding sites were blocked with 10% goat serum in PBS for 30 min. Sections were then incubated with goat anti-mouse IgG conjugated with Alexa 488 fluorophore (1:200, Invitrogen, USA) at 4 • C for 20 h. Sections were then washed with PBS before application of The expression of ionized calcium-binding adaptor protein-1 (Iba-1) was determined as a measure of neuroinflammation by indicating microglial recruitment, as described previously (19). Twenty Micrometer thick cryosections of the right brain hemispheres were incubated in Tris-EDTA (T.E) buffer (10 mM, pH 6.0) for 20 h at 37 • C for antigen retrieval.…”