Trauma to the developing brain leads to necrotic lesion at the site of injury and delayed apoptotic neurodegeneration at distant sites mainly in the thalamus, caudate nucleus and cortex. We studied the distribution and timely activation of monocytes/macrophages, microglia, astrocytes and two inflammatory cytokines, interleukin (IL)-1s and IL-18, 2 h to 14 days following trauma using biochemistry and immunohistochemistry. A marked increase of mRNA and protein levels for IL-1s and IL-18 was detected 2-12 h after injury. Apoptotic cell death affects mostly neuronal populations ipsilateral to the injury 6 h to 5 days later. Microglial activation was first evident at 12 h, peaked at 36-48 h and decreased substantially by 5 days. Astrocytic activation started at 18 h, peaked at 48 h and gradually declined by 14 days after trauma. The activation of immune and glial cells together with increased expression of both interleukins occurred at the site of primary and secondary damages. Our findings suggest that reactive microglia/astrocytes at the sites of secondary lesions might maintain apoptotic neurodegeneration over several days after traumatic injury to the immature brain but they might also promote tissue repair. Understanding the role of glial cells to progression of inflammation and apoptotic neurodegeneration together with tissue repair in the developing brain may provide valuable information to guide treatment after brain trauma.
Abstract Objective Marijuana and alcohol are most widely abused drugs among women of reproductive age. Neurocognitive deficits have been reported in children whose mothers used marijuana during pregnancy. Maternal consumption of ethanol is known to cause serious developmental deficits Methods Infant rats and mice received systemic injections of Δ 9 ‐tetrahydrocannabinol (THC; 1–10mg/kg) or the synthetic cannabinoid WIN 55,212‐2 (1–10mg/kg), alone or in combination with subtoxic and toxic ethanol doses, and apoptotic neurodegeneration was studied in the brains Results Acute administration of THC (1–10mg/kg), the principal psychoactive cannabinoid of marijuana, markedly enhanced proapoptotic properties of ethanol in the neonatal rat brain. THC did not induce neurodegeneration when administered alone. Neuronal degeneration became disseminated and severe when THC was combined with a mildly intoxicating ethanol dose (3gm/kg), with the effect of this drug combination resembling the massive apoptotic death observed when administering ethanol alone at much higher doses. The detrimental effect of THC was mimicked by the synthetic cannabinoid WIN 55,212‐2 (1–10mg/kg) and counteracted by the CB 1 receptor antagonist SR141716A (0.4mg/kg). THC enhanced the proapoptotic effect of the GABA A agonist phenobarbital and the N ‐methyl‐ D ‐aspartate receptor antagonist dizocilpine. Interestingly, infant CB 1 receptor knock‐out mice were less susceptible to the neurotoxic effect of ethanol. Furthermore, the CB 1 receptor antagonist SR141716A ameliorated neurotoxicity of ethanol Interpretation These observations indicate that CB 1 receptor activation modulates GABAergic and glutamatergic neurotransmission and primes the developing brain to suffer apoptotic neuronal death. Ann Neurol 2007
Age dependency of apoptotic neurodegeneration was studied in the developing rat brain after percussion head trauma. In 7-day-old rats, mechanical trauma, applied by means of a weight drop device, was shown to trigger widespread cell death in the hemisphere ipsilateral to the trauma site, which first appeared at 6 hours, peaked at 24 hours, and subsided by 5 days after trauma. Ultrastructurally, degenerating neurons displayed features consistent with apoptosis. A decrease of bcl-2 in conjunction with an increase of c-jun mRNA levels, which were evident at 1 hour after trauma and were accompanied by elevation of CPP 32-like proteolytic activity and oligonucleosomes in vulnerable brain regions, confirmed the apoptotic nature of this process. Severity of trauma-triggered apoptosis in the brains of 3- to 30-day-old rats was age dependent, was highest in 3- and 7-day-old animals, and demonstrated a subsequent rapid decline. Adjusting the mechanical force in accordance with age-specific brain weights revealed a similar vulnerability profile. Thus, apoptotic neurodegeneration contributes in an age-dependent fashion to neuropathological outcome after head trauma, with the immature brain being exceedingly vulnerable. These results help explain unfavorable outcomes of very young pediatric head trauma patients and imply that, in this group, an antiapoptotic regimen may constitute a successful neuroprotective approach. Ann Neurol 1999;45:724–735
Background and Aims Oxygen toxicity contributes to the pathogenesis of cerebral palsy in survivors of preterm birth. We demonstrated previously that hyperoxia-induced apoptosis during infancy is associated with oxidative stress, decreased expression of neurotrophins and increase of pro-inflammatory cytokines. To explore further pathogenetic mechanisms of hyperoxia we investigated the impact of supraphysiologic oxygen levels on Latexin, a maker representing cortical connectivity and Glyoxalase 1, which is part of an antioxidant defence mechanism. Methods Six day old rat pups were sacrificed after a 24 hour exposure with their mothers to 80% oxygen. Brains were either examined histologically to visualize degenerating cells (De Olmos silver and Fluoro Jade staining) or were processed for Western blotting and realtime PCR analysis. Results Oxygen exposure triggered cell death. Western blotting and realtime PCR experiments demonstrated significant upregulation of Glyoxalase 1 and Latexin following oxygen exposure. Conclusion These findings suggest that hyperoxia induces a change in the regulation of proteins involved in neuronal connectivity and oxidative stress in cortical structures.
Hintergrund: Intraventrikuläre Hirnblutung (IVH) und Posthämorrhagischer Hydrozephalus (PHHC) haben bei Frühgeborenen gravierenden Einfluss auf die neurologische Morbidität. Die Mechanismen, die im Rahmen von PHHC zur Schädigung von Hirnzellen führen, sind weitgehend unklar. In vorigen Studien fanden wir bei Patienten mit PHHC hohe Expression von IL-18 und IFN-γ im Liquor assoziiert mit zystischen Läsionen der weißen Hirnsubstanz (cystic white matter damage=cWMD). Um zu untersuchen, ob apoptotische Prozesse bei PHHC eine Rolle spielen und ob diese mit cWMD korrelieren, wurden in der aktuellen Studie Liquorkonzentrationen von soluble Fas (sFas) analysiert. Methode: Die Diagnose einer cWMD wurde bei Patienten mit PHHC mittels kraniellem Ultraschall gestellt bzw. ausgeschlossen. Liquorkonzentrationen von sFas wurden bei 8 PHHC Patienten ohne cWMD, 17 PHHC Patienten mit cWMD und 24 neurologisch gesunden Neugeborenen nach Lumbalpunktion zum Ausschluss einer Meningitis mittels ELISA bestimmt. Ergebnisse: sFas Liquorwerte von PHHC Patienten (Median 1,41ng/ml, Spannweite 0,51–3,06) waren höher als die der neurologisch gesunden Neugeborenen (Median 0ng/ml; Spannweite 0–0,43ng/ml; p=0,001). sFas Liquorwerte der PHHC Patienten mit cWMD (Median 1,47ng/ml, Spannweite 0,98–3,06ng/ml) waren signifikant höher als jene von PHHC Patienten ohne cWMD (Median 1,08ng/ml, Spannweite 0,51–2,79ng/ml; p=0,02). sFas Konzentrationen im Liquor korrelierten nicht mit Liquor-Protein, Gestationalter oder Geburtsgewicht. Diskussion/Fazit: Die vorliegenden Daten sprechen dafür, dass Apoptose bei Hirnparenchymchäden im Rahmen von PHHC eine Rolle spielt. Als Auslöser der Apoptose kommen u.a. inflammatorische Prozesse in Frage, da pro-apoptotische Zytokine wie IL-18 und IFN-γ bei Patienten mit PHHC und cWMD ebenfalls erhöht sind. Anhand der aktuellen Studie ist sFas ein potentieller Kandidat als klinischer Marker für cWMD. In künftigen Studien sollten Werte von sFas zu einem möglichst frühen Zeitpunkt nach IVH im Zusammenhang mit dem langfristigen klinischen Verlauf untersucht werden.
We have developed a model for head trauma in infant rats in an attempt to study mechanisms of neurodegeneration in the developing brain and were able to morphologically characterize two distinct types of brain damage. The first type or primary damage evolved within 4 hrs after trauma and occurred by an excitotoxic mechanism. The second type or secondary damage evolved within 6-24 hrs and occured by an apoptotic mechanism. Primary damage remained localized to the parietal cortex at the site of impact. Secondary damage affected distant sites such as the cingulate/retrosplenial cortex, subiculum, frontal cortex, thalamus, hippocampal dentate gyrus and striatum. Histological evidence of delayed cell death was preceded by decrease of bcl-2- in conjunction with increase of c-jun-mRNA-levels, already evident at 1 hr after trauma. Increase of CPP32-like activity and elevated concentrations of oligonucleosomes in affected brain regions represented additional findings to indicate that this secondary disseminated degenerative reaction is apoptotic in nature. At the age of 7 days, secondary apoptotic damage was more severe than primary excitotoxic damage, but its severity declined with increasing age. In 7-days-old rats, NMDA antagonists protected against primary excitotoxic damage but increased severity of secondary apoptotic damage whereas the free radical scavenger SPBN, the tumor necrosis factor (TNF) inhibitor pentoxifylline and the antioxidant N-acetylcystein mitigated apoptotic damage. These findings demonstrate that in the developing rat brain apoptosis and not excitotoxicity determines neuropathologic outcome following head trauma. Whereas radical scavengers and TNF-inhibitors may prove useful in treatment of pediatric head trauma, great caution should be applied in regards to the use of NMDA antagonists because of the inherent risk of apoptosis promotion.
In preterm human infants, briefly elevated concentrations of oxygen are associated with a prolonged increase in blood chemokine concentrations and the development of bronchopulmonary dysplasia (BPD). Caffeine given to preterm infants for the prevention or treatment of apnoea has been shown to reduce the rate of BPD. We tested the hypotheses that infant rats exposed to a combination of caffeine and hyperoxia would be less susceptible to lung injury than those exposed to hyperoxia alone and that caffeine decreases the pulmonary tissue expression of chemokines and leukocyte influx following hyperoxia. Using 6-day-old rat pups, we demonstrated that 24 h of 80% oxygen exposure caused pulmonary recruitment of neutrophils and macrophages. High levels of oxygen upregulated the expression of: the CXC chemokines, cytokine-induced neutrophil chemoattractant-1 and macrophage inflammatory protein-2; the CC-chemokine monocyte chemoattractant protein-1; the pro-inflammatory cytokines tumour necrosis factor-α and interleukin-6, as measured by realtime PCR after the administration of caffeine (10 mg · kg(-1) body weight); and attenuated chemokine and cytokine upregulation, as well as the influx of CD11b(+), ED-1(+) and myeloperoxidase(+) leukocytes. These experiments suggest that protective effects of caffeine in the neonatal lung are mediated, at least in part, by reduction of pulmonary inflammation.
