45 research outputs found
Neuroinflammation, Mast Cells, and Glia: Dangerous Liaisons
The perspective of neuroinflammation as an epiphenomenon following neuron damage is being replaced by the awareness of glia and their importance in neural functions and disorders. Systemic inflammation generates signals that communicate with the brain and leads to changes in metabolism and behavior, with microglia assuming a pro-inflammatory phenotype. Identification of potential peripheral-to-central cellular links is thus a critical step in designing effective therapeutics. Mast cells may fulfill such a role. These resident immune cells are found close to and within peripheral nerves and in brain parenchyma/meninges, where they exercise a key role in orchestrating the inflammatory process from initiation through chronic activation. Mast cells and glia engage in crosstalk that contributes to accelerate disease progression; such interactions become exaggerated with aging and increased cell sensitivity to stress. Emerging evidence for oligodendrocytes, independent of myelin and support of axonal integrity, points to their having strong immune functions, innate immune receptor expression, and production/response to chemokines and cytokines that modulate immune responses in the central nervous system while engaging in crosstalk with microglia and astrocytes. In this review, we summarize the findings related to our understanding of the biology and cellular signaling mechanisms of neuroinflammation, with emphasis on mast cell-glia interactions
Experimental traumatic brain injury
Traumatic brain injury, a leading cause of death and disability, is a result of an outside force causing mechanical disruption of brain tissue and delayed pathogenic events which collectively exacerbate the injury. These pathogenic injury processes are poorly understood and accordingly no effective neuroprotective treatment is available so far. Experimental models are essential for further clarification of the highly complex pathology of traumatic brain injury towards the development of novel treatments. Among the rodent models of traumatic brain injury the most commonly used are the weight-drop, the fluid percussion, and the cortical contusion injury models. As the entire spectrum of events that might occur in traumatic brain injury cannot be covered by one single rodent model, the design and choice of a specific model represents a major challenge for neuroscientists. This review summarizes and evaluates the strengths and weaknesses of the currently available rodent models for traumatic brain injury
Rapid microglial activation induced by traumatic brain injury is independent of blood brain barrier disruption
Following CNS injury, microglia respond
and transform into reactive species exhibiting
characteristic morphological changes that have been
termed “activated” or “ameboid” microglia. In an
attempt to establish that microglial reactions induced
immediately after injury are caused by intrinsic
mechanisms rather than infiltration of blood and its
constituents, oxygenized Ringer’s solution was perfused
into the cerebral circulation of rats so that the circulating
blood could be eliminated prior to injury induction.
Under artificial respiration, a catheter was inserted from
the cardiac apex into the ascending aorta, and
oxygenized Ringer’s solution was immediately perfused
with a pulsatile blood pump, resulting in wash out of the
circulating blood from the brain within 1 min.
Subsequently, a cortical contusion was induced in the
unilateral parietal cortex using a controlled cortical
impact (CCI) device. At 5 min following the injury, the
brain was fixed by perfusion of fixative through the catheter and removed. Coronal vibratome sections were
then processed for CR3 immunohistochemistry to
examine the microglial activation. It appeared that
microglial activation with both morphological
transformation and an increase in CR3 immunoreactivity
was induced throughout the hemisphere ipsilateral to the
injury side exclusively, even in rats with elimination of
circulating blood. The microglial reactions did not differ
substantially from those observed in the control rats with
extensive BBB disruption. The present results thus
provide direct evidence that the microglial activation
induced immediately after injury is independent of
infiltration of circulating blood induced by concurrent
BBB disruption
Alterations in Blood-Brain Barrier Permeability to Large and Small Molecules and Leukocyte Accumulation after Traumatic Brain Injury: Effects of Post-Traumatic Hypothermia
We investigated the temporal and regional profile of blood-brain barrier (BBB) permeability to both large and small molecules after moderate fluid percussion (FP) brain injury in rats and determined the effects of post-traumatic modest hypothermia (33°C/4 h) on these vascular perturbations. The visible tracers biotin-dextrin-amine 3000 (BDA-3K, 3 kDa) and horseradish peroxidase (HRP, 44 kDa) were injected intravenously at 4 h or 3 or 7 days post-TBI. At 30 min after the tracer infusion, both small and large molecular weight tracers were detected in the contusion area as well as remote regions adjacent to the injury epicenter in both cortical and hippocampal structures. In areas adjacent to the contusion site, increased permeability to the small molecular weight tracer (BDA-3K) was evident at 4 h post-TBI and remained visible after 7 days survival. In contrast, the larger tracer molecule (HRP) appeared in these remote areas at acute permeable sites but was not detected at later post-traumatic time periods. A regionally specific relationship was documented at 3 days between the late-occurring permeability changes observed with BDA-3K and the accumulation of CD68-positive macrophages. Mild hypothermia initiated 30 min after TBI reduced permeability to both large and small tracers and the infiltration of CD68-positive cells. These results indicate that moderate brain injury produces temperature-sensitive acute, as well as more long-lasting vascular perturbations associated with secondary injury mechanisms