Widespread axonal injury in gunshot wounds to the head using amyloid precursor protein as a marker

Neuroendocrine Dysfunction in the Acute Setting of Penetrating Brain Injury: A Systematic Review

BACKGROUND

Data on neuroendocrine dysfunction (NED) in the acute setting of penetrating brain injury (PBI) are scarce, and the clinical approach to diagnosis and treatment remains extrapolated from the literature on blunt head trauma.

METHODS

Three databases were searched (PubMed, Scopus, and Cochrane). Risk of bias was computed using the Newcastle-Ottawa Scale, or the methodological quality of case series and case reports, as indicated. This systematic review was registered in PROSPERO (42020172163).

RESULTS

Six relevant studies involving 58 patients with PBI were included. Two studies were prospective cohort analyses, whereas 4 were case reports. The onset of NED was acute in all studies, by the first postinjury day. Risk factors for NED included worse injury severity and the presence of cerebral edema on imaging. Dysfunction of the anterior hypophysis involved the hypothalamic-pituitary-thyroid axis, treated with hormonal replacement, and hypocortisolism, treated with hydrocortisone. The prevalence of central diabetes insipidus was up to 41%. Most patients showed persistent NED months after injury. In separate reports, diabetes insipidus and hypocortisolism showed an association with higher mortality. The available literature for this review is poor, and the studies included had overall low quality with high risk of bias.

CONCLUSIONS

NED seems to be prevalent in the acute phase of PBI, equally involving both anterior and posterior hypophysis. Despite a potential association between NED and mortality, data on the optimal management of NED are limited. This situation defines the need for prospective studies to better characterize the clinical features and optimal therapeutic interventions for NED in PBI.

Neurotrauma

Traumatic brain injury remains a major cause of morbidity and mortality throughout the world, affecting young and old alike. Pathologic data have been developed through observations of human autopsies and developing animal models to investigate mechanisms, although animal models do not represent the polypathology of human brain injury and there are likely to be significant differences in the anatomic basis of injury and cellular responses between species. Traumatic brain injury can be defined pathologically as either focal or diffuse, and can be considered to be either primary, directly related to the force associated with the neurotrauma, or secondary, developing as a downstream consequence of the neurotrauma. While neuropathology has traditionally focused on severe head injury, there is increasing recognition of the long-term consequences of traumatic brain injury, particularly repetitive mild traumatic brain injury, and a possible long-term association with chronic traumatic encephalopathy.

Surgical management of civilian gunshot wounds to the head

Each year close to 20000 Americans are involved in gunshot wounds to the head (GSWH). Over 90% of the victims of GSWH eventually fail to survive and only a meager 5% of the patients have a chance to continue with a useful life. One of the fundamental jobs of providers is to realize who the best candidate for the best possible management is. Recent evidence indicates that a good Glasgow Coma Scale (GCS) score at the time of admission puts such patients at high priority for management. Lack of abnormal pupillary response to light, trajectory of slug away for central gray, and visibility of basal cisterns upgrade the need for utmost care for such a victim. Surgical management is careful attention to involvement of air sinuses and repair of base dura. Patients with diffuse injury should have intraventricular intracranial pressure (ICP) monitoring and if needed a timely decompressive craniectomy. Since close to 2% of patients with penetrating brain injury may harbor a vascular injury, subjects with injuries close to the Sylvian fissure and those with the fragment crossing two dural compartments should have computed tomography angiography and if needed digital subtraction angiography to rule out traumatic intracranial aneurysms. In case of a positive study, these patients should have endovascular management of their vascular injuries in order to prevent catastrophic intracerebral hematomas and permanent deficit. Although supported by class III data, subjects of GSWH need to be on broad spectrum antibiotics for a period of 3-5 days. If cerebrospinal fluid (CSF) fistulas are observed at any time during the patient's hospital course, they should be taken very seriously and appropriate management is needed to prevent deep intracranial infections.

Mechanism of glial differentiation of neural progenitor cells by amyloid precursor protein

BACKGROUND

We found that human neural progenitor cells (HNPCs) exposed to high concentrations of amyloid precursor protein (APP) or transplanted into APP transgenic mice (APP23) primarily differentiated into astrocytes, suggesting that pathological alterations of APP processing in Alzheimer's disease (AD) may prevent neuronal differentiation of HNPCs.

OBJECTIVES

To investigate the mechanism of APP-induced glial differentiation of HNPCs.

METHODS

We treat HNPCs with APP and analyze the expression and phosphorylation of signaling molecules using PCR and Western blots. To confirm the involvement of the factors, RNA interference of the signaling molecule is conducted.

RESULTS

APP treatment caused inductions of CNTF, gp130 and JAK1 gene expressions, and STAT3 phosphorylation, while silencing of these genes by RNA interference suppressed the glial differentiation of the cells, indicating involvement of the IL-6/gp130 pathway. APP also increased the generation of notch intracellular domain and gene expression of Hes1, indicating that glial differentiation of HNPCs may be mediated by the notch signaling.

CONCLUSION

These results indicate that APP may regulate HNPC differentiation through activation of both the IL-6/gp130 and notch signaling pathway. Although the importance of adult neurogenesis is not clear, glial differentiation of HNPCs may cause problems in maintaining normal brain function and may contribute to the AD pathology.

Modulation of human neural stem cell differentiation in Alzheimer (APP23) transgenic mice by phenserine

In a previous study, we found that human neural stem cells (HNSCs) exposed to high concentrations of secreted amyloid-precursor protein (sAPP) in vitro differentiated into mainly astrocytes, suggesting that pathological alterations in APP processing during neurodegenerative conditions such as Alzheimer's disease (AD) may prevent neuronal differentiation of HNSCs. Thus, successful neuroplacement therapy for AD may require regulating APP expression to favorable levels to enhance neuronal differentiation of HNSCs. Phenserine, a recently developed cholinesterase inhibitor (ChEI), has been reported to reduce APP levels in vitro and in vivo. In this study, we found reductions of APP and glial fibrillary acidic protein (GFAP) levels in the hippocampus of APP23 mice after 14 days treatment with (+)-phenserine (25 mg/kg) lacking ChEI activity. No significant change in APP gene expression was detected, suggesting that (+)-phenserine decreases APP levels and reactive astrocytes by posttranscription regulation. HNSCs transplanted into (+)-phenserine-treated APP23 mice followed by an additional 7 days of treatment with (+)-phenserine migrated and differentiated into neurons in the hippocampus and cortex after 6 weeks. Moreover, (+)-phenserine significantly increased neuronal differentiation of implanted HNSCs in hippocampal and cortical regions of APP23 mice and in the CA1 region of control mice. These results indicate that (+)-phenserine reduces APP protein in vivo and increases neuronal differentiation of HNSCs. Combination use of HNSC transplantation and treatment with drugs such as (+)-phenserine that modulate APP levels in the brain may be a useful tool for understanding mechanisms regulating stem cell migration and differentiation during neurodegenerative conditions in AD.

Potential use of stem cells in neuroreplacement therapies for neurodegenerative diseases

The use of stem cells for neuroreplacement therapy is no longer science fiction--it is science fact. We have succeeded in the development of neural and mesenchymal stem cell transplantation to produce neural cells in the brain. We have also seen improvement in cognitive function following stem cell transplantation in a memory-impaired aged animal model. These results promise a bright future for stem cell therapies in neurodegenerative diseases. Before we begin to think about clinical applications beyond the present preclinical studies, we have to consider the pathophysiological environment of individual diseases and weigh the factors that affect stem cell biology. Here, I not only review potential therapeutic applications of stem cell strategies in neurodegenerative diseases, but also discuss stem cell biology regarding factors that are altered under disease conditions.

Axonal injury in children after motor vehicle crashes: extent, distribution, and size of axonal swellings using beta-APP immunohistochemistry

The brains of 32 children (3 months to 16 years) who died as a result of motor vehicle collisions were examined for axonal injury using beta-APP immunohistochemistry. The extent and distribution of axonal injury was assessed and quantified throughout the forebrain, brainstem and cerebellum. The mean diameter of immunoreactive axons in the corpus callosum was measured for this pediatric group and, for comparison, a small adult sample. beta-APP immunoreactivity was seen in 14 pediatric cases (survival 35 mins to 87 h), most frequently in the parasagittal white matter (12/14), the corpus callosum (11/14), the brainstem (10/14) and cerebellum (9/14). In 2 cases, axon swelling was visualized in the internal capsule after only 35-45-min survival, earlier than has previously been reported. No immunoreactivity was seen in the remaining 18 cases who died within 1 h. The extent and distribution of axonal injury throughout the brain showed a rapid early increase with increasing survival time and then a slower progression. The diameter of individual callosal axons increased with increasing survival times, rapidly over the first 24 h and then more slowly. There was no statistical difference (p < 0.05) for callosal axon diameters at different survival times between the children and the adults sampled here. The extent and distribution of axonal injury throughout the brain appears to be similar in children to that previously reported in adults. The spatial and temporal spread of axonal damage suggests there may be therapeutic potential for the process to be arrested or slowed in its early stages.

Attenuation of the electrophysiological function of the corpus callosum after fluid percussion injury in the rat

This study describes a new method used to evaluate axonal physiological dysfunction following fluid percussion induced traumatic brain injury (TBI) that may facilitate the study of the mechanisms and novel therapeutic strategies of posttraumatic diffuse axonal injury (DAI). Stimulated compound action potentials (CAP) were recorded extracellularly in the corpus callosum of superfused brain slices at 3 h, and 1, 3, and 7 days following central fluid percussion injury and demonstrated a temporal pattern of functional deterioration. The maximal CAP amplitude (CAPA) covaried with the intensity of impact 1 day following sham, mild (1.0-1.2 atm), and moderate (1.8-2.0 atm) injury (p < 0.05; 1.11 +/- 0.10, 0.82 +/- 0.11, and 0.49 +/- 0.08 mV, respectively). The CAPA in sham animals were approximately 1.1 mV and did not vary with survival interval (3 h, and 1, 3, and 7 days); however, they were significantly decreased at each time point following moderate injury (p < 0.05; 0.51 +/- 0.11, 0.49 +/- 0.08, 0.46 +/- 0.10, and 0.75 +/- 0.13 mV, respectively). The CAPA at 7 days in the injured group were higher than at 3 h, and 1 and 3 days. H&E and amyloid precursor protein (APP) light microscopic analysis confirmed previously reported trauma-induced axonal injury in the corpus callosum seen after fluid percussion injury. Increased APP expression was confirmed using Western blotting showing significant accumulation at 1 day (IOD 913.0 +/- 252.7; n = 3; p = 0.05), 3 days (IOD 753.1 +/- 159.1; n = 3; p = 0.03), and at 7 days (IOD 1093.8 = 105.0; n = 3; p = 0.001) compared to shams (IOD 217.6 +/- 20.4; n = 3). Thus, we report the characterization of white matter axonal dysfunction in the corpus callosum following TBI. This novel method was easily applied, and the results were consistent and reproducible. The electrophysiological changes were sensitive to the early effects of impact intensity, as well as to delayed changes occurring several days following injury. They also indicated a greater degree of attenuation than predicted by APP expression changes alone.

Brain injury: the pathophysiology of the first hours.'Talk and Die revisited'

In the 25 years since the 'Talk and Die' paper there have been substantial advances in the management of patients with severe closed head injury. This paper discusses developments in understanding of primary and secondary injury. Current management focuses on preventing secondary brain injury. That this has been successful is illustrated by a fall in mortality in recent decades. Evidence based guidelines have set standards of management but they do not take into account variations between individuals, between regions of the brain and variations with time from injury. Various monitoring techniques such as transcranial doppler, jugular venous oxygen saturation and ICP waveform analysis attempt to set individual therapeutic endpoints and to target therapy appropriately. Primary injury is no longer seen as a single irreversible event occurring at the time of impact, but rather as a process initiated by the impact and evolving over subsequent hours and days. Experimental studies have identified agents which reduce the evolution of brain injury and improve outcome. An experimental model of brain injury developed by the Adelaide He ad Injury Group identifies diffuse axonal injury as a target for therapeutic manipulation. Magnesium has been shown in other studies to improve outcome after diffuse brain injury. This has now been linked with upregulation of beta amyloid precursor prote in. Although this and several other experimental therapies have shown great promise, they have not so far produced benefit in large clinical studies. Avoiding secondary insults will remain the goal of management for the foreseeable future. Halting the evolution of the primary injury remains a highly sought after goal. Although elusive so far, it is likely to be the next major advance in clinical care.

The functions of the amyloid precursor protein gene

The amyloid precursor protein (APP) gene and its protein products have multiple functions in the central nervous system and fulfil criteria as neuractive peptides: presence, release and identity of action. There is increased understanding of the role of secretases (proteases) in the metabolism of APP and the production of its peptide fragments. The APP gene and its products have physiological roles in synaptic action, development of the brain, and in the response to stress and injury. These functions reveal the strategic importance of APP in the workings of the brain and point to its evolutionary significance.

Brain injury after survived gunshot to the head: reactive alterations at sites remote from the missile track

Gunshot wounds to the brain usually lead to acute respiratory arrest or death after a brief survival period, even in cases involving only slight direct tissue damage. It can be assumed therefore that the damage extends beyond the zone of recognizable destruction and hemorrhages. To determine the true extent of the tissue injury resulting from gunshot wounds to the brain, we carried out microscopic investigations for reactive changes (emigration of leukocytes and macrophages, axonal expression of beta-amyloid precursor protein (beta-APP) in 10 cases of gunshot wound to the narrow channel of the brain with survival times >2h. Demonstration of leukocytes expressing naphthol AS-D chloroacetate esterase activity in the brain tissue at the border of the missile track established the vitality of the gunshot effect. The presence of macrophages (CD68-epitope) allowed demarcation of a 1-2mm wide necrotic zone around the permanent cavity. Within this zone and beyond, beta-APP showed an initial increase followed by a decline in the number of injured axons. Three types of beta-APP positive staining could be differentiated. In the immediate vicinity of the missile track beta-APP positive neurons were present at a distance of 2-4mm from the margin of the permanent cavity (type 1) as a result of primary injured neuronal tissue by the gunshot itself. At longer distances from the narrow channel and the permanent cavity single beta-APP positive axons or axon fragments and two additional types were found; type 2 shows a parallel, wave-like arrangement of the damaged fibers, which suggests that the injury was produced by mechanical acceleration of the brain tissue created by the energy the projectile expended within the brain; irregular aggregation of beta-APP positive axons or axon fragments within a local edema represents type 3, which may be attributed to secondary ischemia or edema.

Evaluation of brain damage resulting from penetrating and non-penetrating captive bolt stunning using lambs

OBJECTIVE

To compare the brain damage in sheep resulting from penetrating and non-penetrating captive bolt stunning.

DESIGN

The unrestrained heads of anaesthetised lambs were impacted in the temporal region with penetrating and non-penetrating captive bolt pistols (humane stunners) using a constant charge. Two hours after head impact, brains were perfusion-fixed with 4% paraformaldehyde. Coronal sections were stained with haematoxylin and eosin and immunohistochemically for amyloid precursor protein, a sensitive marker of axonal and neuronal reaction in brains after trauma. Pathological changes in these brains were then quantified by morphometric analysis.

RESULTS

The skull was fractured in 50% of lambs after a non-penetrating head impact and in all animals after a penetrating head wound. Impact contusions were present in 80% of lambs receiving a non-penetrating head injury and in all of those with a penetrating wound. Total contusion area was similar in both groups. Amyloid precursor protein-positive axons and neurons, and haemorrhage, were widely distributed in the brain after both head impact types, but there was no statistically significant difference between the two groups. Multifocal necrosis of the cerebellar granular layer was found in all lambs with non-penetrating head injury, but in none with a penetrating injury.

CONCLUSIONS

The structural brain damage, a mixture of focal and diffuse injury, produced by penetrating and non-penetrating captive bolt pistols was overall similar and of sufficient severity to suggest that both types of weapon are acceptable for euthanasia.

Brain injury after gunshot wounding: morphometric analysis of cell destruction caused by temporary cavitation

In addition to the primary destruction of brain tissue readily visible at autopsy (permanent track), gunshot wounding to the brain creates a pulsating temporary cavity due to radial expansion along the bullet's track. To determine the maximum extent of this temporary cavitation in brains of victims of gunshots from weapons with low muzzle velocity, we carried out morphometric studies on 20 cases of death from gunshot wounding to the head from bullets with a muzzle energy <500 J and a survival time of <90 min. The brains were fixed in formalin, examine macroscopically and microscopically, and subjected to morphometric analyses. Surrounding the permanent track, a narrow mantle-like zone of astrocyte destruction was found within an area of hemorrhagic extravasation. Axons near the permanent track had been broken into tiny fragments. The axonal damage lessened with increasing distance from the permanent track, although axons continued to be fragmented and to exhibit varicose changes and clumping until assuming their normal structure beyond 18 mm. Nerve cells were extremely shrunken close to the permanent track but gradually took on their normal shape with increasing distance. We also assessed the loss of glial fibrillary acid protein expression by astrocytes in the white matter, the extent of traumatic bleeding, and damage to axons and neurons as measured radially from the permanent track. Axonal and neuronal damage were found to extend about 18 mm radially from the permanent track, tapering gradually along the track from entry point to exit point. The destruction was probably produced by the temporary cavitation and accords with theoretical considerations and experimental observations.

Crossbow suicide: mechanisms of injury and neuropathologic findings

Crossbow injuries are rarely reported events in modern times. Two cases of death due to self-inflicted crossbow injuries to the head are reported in 2 men aged 18 and 27 years, respectively. Despite relatively low velocity and concussive force, the sharpness and propulsion force of crossbow bolts may be sufficient to enable penetration of the skull at short range. Due to the relatively low concussive force of the crossbow bolt, however, death may not be instantaneous but may occur from intraparenchymal cerebral damage sometime thereafter. Detailed neuropathologic evaluation of such cases may therefore demonstrate "red cell" hypoxic injury, as well as axonal injury, not limited to the region of the missile tract, but widely distributed, even to the point of extensive brain stem involvement. These changes may result from primary mechanical deformation at the time of injury, from secondary hypoxic damage, or from a combination of both factors. Immunohistochemical staining of brains for amyloid precursor protein to delineate more clearly the pattern of axonal damage may assist in determining the extent of injury in such cases.