p53 upregulated mediator of apoptosis (Puma) deficiency increases survival of adult neural stem cells generated physiologically in the hippocampus, but does not protect stem cells generated in surplus after an excitotoxic lesion

ObjectivesNeurogenesis occurs in the mammalian brain throughout adulthood and increases in response to metabolic, toxic or traumatic insults. To remove potentially superfluous or unwanted neural stem cells/neuronal progenitors, their rate of proliferation and differentiation is fine-tuned against their rate of apoptosis. Apoptosis requires the transcriptional and posttranslational activation of Bcl-2-homolgy domain 3 (BH3)-only proteins. Previously, we demonstrated that the BH3-only protein p53-upregulated mediator of apoptosis (Puma) controls the physiological rate of apoptosis of neural precursor cells in the adult mouse hippocampus. Puma’s role in controlling a lesion-induced increase in neural stem cells is currently not known.MethodsWe employed a model of local, N-methyl-D-asparte (NMDA)-induced excitotoxic injury to the CA1 hippocampal subfield and immunofluorescence labelling to produce increased neural stem cell proliferation/ neurogenesis in the dentate gyrus at two survival times following the excitotoxic lesion.ResultsDeletion of puma failed to rescue any NMDA-induced increase in adult born cells as assessed by BrdU or Doublecortin labelling in the long-term. No difference in the proportion of BrdU/NeuN-positive cells comparing the different genotypes and treatments suggested that the phenotypic fate of the cells was preserved regardless of the genotype and the treatment.ConclusionsWhile neurogenesis is up-regulated in puma-deficient animals following NMDA-induced excitotoxicity to the hippocampal CA1 subfield, puma deficiency could not protect this surplus of newly generated cells from apoptotic cell death.

Effects of Excitotoxic Lesion with Inhaled Anesthetics on Nervous System Cells of Rodents

Different anesthesia methods can variably influence excitotoxic lesion effects on the brain. The main purpose of this review is to identify potential differences in the toxicity to nervous system cells of two common inhalation anesthesia methods, isoflurane and sevoflurane, used in combination with an excitotoxic lesion procedure in rodents. The use of bioassays in animal models has provided the opportunity to examine the role of specific molecules and cellular interactions that underlie important aspects of neurotoxic effects relating to calcium homeostasis and apoptosis activation. Processes induced by NMDA antagonist drugs involve translocation of Bax protein to mitochondrial membranes, allowing extra-mitochondrial leakage of cytochrome C, followed by sequence of changes that ending in activation of CASP-3. The literature demonstrates that the use of these anesthetics in excitotoxic surgery increases neuroinflammation activity facilitating the effects of apoptosis and necrosis on nervous system cells, depending on the concentration and exposure duration of the anesthetic. High numbers of microglia and astrocytes and high levels of proinflammatory cytokines and caspase activation possibly mediate these inflammatory responses. However, it is necessary to continue studies in rodents to understand the effect of the use of inhaled anesthetics with excitotoxic lesions in different developmental stages, including newborns, juveniles and adults. Understanding the mechanisms of regulation of cell death during development can potentially provide tools to promote neuroprotection and eventually achieve the repair of the nervous system in pathological conditions.

Upregulation of GH, but not IGF1, in the hippocampus of the lactating dam after kainic acid injury

Lactation embodies a natural model of morphological, neurochemical, and functional brain plasticity. In this reproductive stage, the hippocampus of the female is less sensitive to excitotoxins in contrast to nulliparity. Growth hormone (GH) and insulin-like growth factor 1 (IGF1) are known to be neuroprotective in several experimental models of brain lesion. Here, activation of the GH–IGF1 pituitary–brain axis following kainic acid (7.5 mg/kg i.p. KA) lesion was studied in lactating and nulliparous rats. Serum concentrations of GH and IGF1 were uncoupled in lactation. Compared to virgin rats, the basal concentration of GH increased up to 40% but IGF1 decreased 58% in dams, and only GH increased further after KA treatment. In the hippocampus, basal expression of GH mRNA was higher (2.8-fold) in lactating rats than in virgin rats. GH mRNA expression in lactating rats increased further after KA administration in the hippocampus and in the hypothalamus, in parallel to GH protein concentration in the hippocampus of KA-treated lactating rats (43% vs lactating control), as detected by Western blot and immunofluorescence. Except for the significantly lower mRNA concentration in the liver of lactating rats, IGF1 expression was not altered by the reproductive condition or by KA treatment in the hippocampus and hypothalamus. Present results indicate upregulation of GH expression in the hippocampus after an excitotoxic lesion, suggesting paracrine/autocrine actions of GH as a factor underlying neuroprotection in the brain of the lactating dam. Since no induction of IGF1 was detected, present data suggest a direct action of GH.

Persistently Altered Metabolic Phenotype following Perinatal Excitotoxic Brain Injury

Excitotoxicity plays a key role during insults to the developing brain such as neonatal encephalopathy, stroke, and encephalopathy of prematurity. Such insults affect many thousands of infants each year. Excitotoxicity causes frank lesions due to cell death and gliosis and disturbs normal developmental process, leading to deficits in learning, memory, and social integration that persist into adulthood. Understanding the underlying processes of the acute effects of excitotoxicity and its persistence during brain maturation provides an opportunity to identify mechanistic or diagnostic biomarkers, thus enabling and designing possible therapies. We applied mass spectrometry to provide metabolic profiles of brain tissue and plasma over time following an excitotoxic lesion (intracerebral ibotenate) to the neonatal (postnatal day 5) mouse brain. We found no differences between the plasma from the control (PBS-injected) and excitotoxic (ibotenate-injected) groups over time (on postnatal days 8, 9, 10, and 30). In the brain, we found that variations in amino acids (arginine, glutamine, phenylananine, and proline) and glycerophospholipids were sustaining acute and delayed (tertiary) responses to injury. In particular, the effect of the excitotoxic lesion on the normal profile of development was linked to alterations in a fingerprint of glycerophospolipids and amino acids. Specifically, we identified increases in the amino acids glutamine, proline, serine, threonine, tryptophan, valine, and the sphingolipid SM C26:1, and decreases in the glycerophospholipids, i.e., the arachidonic acid-containing phosphatidylcholine (PC aa) C30:2 and the PC aa C32:3. This study demonstrates that metabolic profiling is a useful approach to identify acute and tertiary effects in an excitotoxic lesion model, and generating a short list of targets with future potential in the hunt for identification, stratification, and possibly therapy.

THE MORHOLOGIC EVALUATION OF MICROGLIAL REACTIONS IN WHITE MATTER OF THE BRAIN IN PATIENTS WITH CHRONIC HCV INFECTION

Disorders of the central nervous system observed in patients with chronic HCV infection seem to be associated with excitotoxic lesion of neurons caused by infected microglial cells. Despite the high interest in this problem, the morphological changes of infected microglia remain uninvestigated. The paper presents the results of the morphologic study of microglial reactions in white matter of the brain in 40 patients who died of chronic HCV-infection. The study found the structural and quantitative changes of infected microglia in different parts of the brain, which is caused by the activation of these cells by HCV.