We have previously shown that lithium treatment immediately after hypoxia-ischemia (HI) in neonatal rats affords both short- and long-term neuroprotection. The aim of this study was to evaluate possible therapeutic benefits when lithium treatment was delayed 5 days, a time point when most cell death is over.
Eight-day-old male rats were subjected to unilateral HI and 2 mmol/kg lithium chloride was injected intraperitoneally 5 days after the insult. Additional lithium injections of 1 mmol/kg were administered at 24 h intervals for the next 14 days. Brain injury was evaluated 12 weeks after HI. Serum cytokine measurements and behavioral analysis were performed before sacrificing the animals.
Brain injury, as indicated by tissue loss, was reduced by 38.7%, from 276.5±27.4 mm3 in the vehicle-treated group to 169.3±25.9 mm3 in the lithium-treated group 12 weeks after HI (p<0.01). Motor hyperactivity and anxiety-like behavior after HI were normalized by lithium treatment. Lithium treatment increased neurogenesis in the dentate gyrus as indicated by doublecortin labeling. Serum cytokine levels, including IL-1α, IL-1β, and IL-6, were still elevated as late as 5 weeks after HI, but lithium treatment normalized these cytokine levels.
Delayed lithium treatment conferred long-term neuroprotection in neonatal rats after HI, and this opens a new avenue for future development of treatment strategies for neonatal brain injury that can be administered after the acute injury phase.
Preterm brain injury consists primarily of periventricular leukomalacia accompanied by elements of gray-matter injury, and these injuries are associated with cerebral palsy and cognitive impairments. Inflammation is believed to be an important contributing factor to these injuries. The aim of this study was to examine the immune response in a postnatal day (PND) 5 mouse model of preterm brain injury induced by hypoxia-ischemia (HI) that is characterized by focal white and gray-matter injury.
C57Bl/6 mice at PND 5 were subjected to unilateral HI induced by left carotid artery ligation and subsequent exposure to 10% O2 for 50 minutes, 70 minutes, or 80 minutes. At seven days post-HI, the white/gray-matter injury was examined. The immune responses in the brain after HI were examined at different time points after HI using RT-PCR and immunohistochemical staining.
HI for 70 minutes in PND 5 mice induced local white-matter injury with focal cortical injury and hippocampal atrophy, features that are similar to those seen in preterm brain injury in human infants. HI for 50 minutes resulted in a small percentage of animals being injured, and HI for 80 minutes produced extensive infarction in multiple brain areas. Various immune responses, including changes in transcription factors and cytokines that are associated with a T-helper (Th)1/Th17-type response, an increased number of CD4+ T-cells, and elevated levels of triggering receptor expressed on myeloid cells 2 (TREM-2) and its adaptor protein DNAX activation protein of 12 kDa (DAP12) were observed using the HI 70 minute preterm brain injury model.
We have established a reproducible model of HI in PND 5 mice that produces consistent local white/gray-matter brain damage that is relevant to preterm brain injury in human infants. This model provides a useful tool for studying preterm brain injury. Both innate and adaptive immune responses are observed after HI, and these show a strong pro-inflammatory Th1/Th17-type bias. Such findings provide a critical foundation for future studies on the mechanism of preterm brain injury and suggest that blocking the Th1/Th17-type immune response might provide neuroprotection after preterm brain injury.
Brain injury; Preterm; Hypoxia-ischemia; Immune response
The relationship between genetic factors and the development of cerebral palsy (CP) has recently attracted much attention. Polymorphisms in the genes encoding proinflammatory cytokines have been shown to be associated with susceptibility to perinatal brain injury and development of CP. Interleukin-6 (IL-6) is a proinflammatory cytokine that plays a pivotal role in neonatal brain injury, but conflicting results have been reported regarding the association between IL-6 single nucleotide polymorphisms (SNPs) and CP. The purpose of this study was to analyze IL-6 gene polymorphisms and protein expression and to explore the role of IL-6 in the Chinese CP population.
A total of 753 healthy controls and 713 CP patients were studied to detect the presence of five SNPs (rs1800796, rs2069837, rs2066992, rs2069840, and rs10242595) in the IL-6 locus. Of these, 77 healthy controls and 87 CP patients were selected for measurement of plasma IL-6 by Luminex assay. The SHEsis program was used to analyze the genotyping data. For all comparisons; multiple testing on each individual SNP was corrected by the SNPSpD program.
There were no differences in allele or genotype frequencies between the overall CP patients and controls among the five genetic polymorphisms. However, subgroup analysis found significant sex-related differences in allele and genotype frequencies. Differences were found between spastic CP and controls in males for rs2069837; between CP with periventricular leukomalacia and controls in males for rs1800796 and rs2066992; and between term CP and controls in males for rs2069837. Plasma IL-6 levels were higher in CP patients than in the controls, and this difference was more robust in full-term male spastic CP patients. Furthermore, the genotype has an effect on IL-6 synthesis.
The influence of IL-6 gene polymorphisms on IL-6 synthesis and the susceptibility to CP is related to sex and gestational age.
Cytokine; Inflammation; Periventricular leukomalacia; Single nucleotide polymorphisms
Maternal deaths occur mostly in developing countries and the majority of them are preventable. This study analyzes changes in maternal mortality and related causes in Henan Province, China, between 1996 and 2009, in an attempt to provide a reliable basis for introducing effective interventions to reduce the maternal mortality ratio (MMR), part of the fifth Millennium Development Goal.
Methods and Findings
This population-based maternal mortality survey in Henan Province was carried out from 1996 to 2009. Basic information was obtained from the health care network for women and children and the vital statistics system, from specially trained monitoring personnel in 25 selected monitoring sites and by household survey in each case of maternal death. This data was subsequently reported to the Henan Provincial Maternal and Child Healthcare Hospital. The total MMR in Henan Province declined by 78.4%, from 80.1 per 100 000 live births in 1996 to 17.3 per 100 000 live births in 2009. The decline was more pronounced in rural than in urban areas. The most common causes of maternal death during this period were obstetric hemorrhage (43.8%), pregnancy-induced hypertension (15.8%), amniotic fluid embolism (13.9%) and heart disease (8.0%). The MMR was higher in rural areas with lower income, less education and poorer health care.
There was a remarkable decrease in the MMR in Henan Province between 1996 and 2009 mainly in the rural areas and MMR due to direct obstetric causes such as obstetric hemorrhage. This study indicates that improving the health care network for women, training of obstetric staff at basic-level units, promoting maternal education, and increasing household income are important interventional strategies to reduce the MMR further.
The aim of this study was to evaluate the long-term effects of lithium treatment on neonatal hypoxic-ischemic brain injury, inflammation, and neural stem/progenitor cell (NSPC) proliferation and survival. Nine-day-old male rats were subjected to unilateral hypoxia-ischemia (HI) and 2 mmol/kg lithium chloride was injected intraperitoneally immediately after the insult. Additional lithium injections, 1 mmol/kg, were administered at 24-hour intervals for 7 days. Animals were killed 6, 24, 72 hours, or 7 weeks after HI. Lithium reduced total tissue loss by 69%, from 89.4±14.6 mm3 in controls (n=15) to 27.6±6.2 mm3 in lithium-treated animals (n=14) 7 weeks after HI (P<0.001). Microglia activation was inhibited by lithium treatment, as judged by Iba-1 and galectin-3 immunostaining, and reduced interleukin-1β and CCL2 levels. Lithium increased progenitor, rather than stem cell, proliferation in both nonischemic and ischemic brains, as judged by 5-bromo-2-deoxyuridine labeling 24 and 72 hours as well as by phospho-histone H3 and brain lipid-binding protein labeling 7 weeks after HI. Lithium treatment also promoted survival of newborn NSPCs, without altering the relative levels of neuronal and astroglial differentiation. In summary, lithium conferred impressive, morphological long-term protection against neonatal HI, at least partly by inhibiting inflammation and promoting NSPC proliferation and survival.
asphyxia; inflammation; microglia; neurogenesis; stem cell
A considerable proportion of all newly generated cells in the hippocampus will die before becoming fully differentiated, both under normal and pathological circumstances. The caspase-independent apoptosis-inducing factor (AIF) has not been investigated previously in this context.
Postnatal day 8 (P8) harlequin (Hq) mutant mice, expressing lower levels of AIF, and wild type littermates were injected with BrdU once daily for two days to label newborn cells. On P10 mice were subjected to hypoxia-ischemia (HI) and their brains were analyzed 4 h, 24 h or 4 weeks later. Overall tissue loss was 63.5% lower in Hq mice 4 weeks after HI. Short-term survival (4 h and 24 h) of labeled cells in the subgranular zone was neither affected by AIF downregulation, nor by HI. Long-term (4 weeks) survival of undifferentiated, BLBP-positive stem cells was reduced by half after HI, but this was not changed by AIF downregulation. Neurogenesis, however, as judged by BrdU/NeuN double labeling, was reduced by half after HI in wild type mice but preserved in Hq mice, indicating that primarily neural progenitors and neurons were protected. A wave of cell death started early after HI in the innermost layers of the granule cell layer (GCL) and moved outward, such that 24 h after HI dying cells could be detected in the entire GCL.
These findings demonstrate that AIF downregulation provides not only long-term overall neuroprotection after HI, but also protects neural progenitor cells, thereby rescuing hippocampal neurogenesis.
Apoptosis-inducing factor; Apoptosis; Asphyxia; Hippocampus; Neurogenesis; Cell proliferation
Inflammation is associated with perinatal brain injury but the underlying mechanisms are not completely characterized. Stimulation of Toll-like receptors (TLRs) through specific agonists induces inflammatory responses that trigger both innate and adaptive immune responses. The impact of engagement of TLR2 signaling pathways on the neonatal brain is still unclear. The aim of this study was to investigate the potential effect of a TLR2 agonist on neonatal brain development.
Mice were injected intraperitoneally (i.p.) once a day from postnatal day (PND) 3 to PND11 with endotoxin-free saline, a TLR2 agonist Pam3CSK4 (5 mg/kg) or Lipopolysaccharide (LPS, 0.3 mg/kg). Pups were sacrificed at PND12 or PND53 and brain, spleen and liver were collected and weighed. Brain sections were stained for brain injury markers. Long-term effects on memory function were assessed using the Trace Fear Conditioning test at PND50. After 9 days of Pam3CSK4 administration, we found a decreased volume of cerebral gray matter, white matter in the forebrain and cerebellar molecular layer that was accompanied by an increase in spleen and liver weight at PND12. Such effects were not observed in Pam3CSK4-treated TLR 2-deficient mice. Pam3CSK4-treated mice also displayed decreased hippocampus neuronal density, and increased cerebral microglia density, while there was no effect on caspase-3 or general cell proliferation at PND12. Significantly elevated levels of IL-1β, IL-6, KC, and MCP-1 were detected after the first Pam3CSK4 injection in brain homogenates of PND3 mice. Pam3CSK4 administration did not affect long-term memory function nor the volume of gray or white matter.
Repeated systemic exposure to the TLR2 agonist Pam3CSK4 can have a short-term negative impact on the neonatal mouse brain.
Isoflurane and related anesthetics are widely used to anesthetize children, ranging from premature babies to adolescents. Concerns have been raised about the safety of these anesthetics in pediatric patients, particularly regarding possible negative effects on cognition. The purpose of this study was to investigate the effects of repeated isoflurane exposure of juvenile and mature animals on cognition and neurogenesis. Postnatal day 14 (P14) rats and mice, as well as adult (P60) rats, were anesthetized with isoflurane for 35 mins daily for four successive days. Object recognition, place learning and reversal learning as well as cell death and cytogenesis were evaluated. Object recognition and reversal learning were significantly impaired in isoflurane-treated young rats and mice, whereas adult animals were unaffected, and these deficits became more pronounced as the animals grew older. The memory deficit was paralleled by a decrease in the hippocampal stem cell pool and persistently reduced neurogenesis, subsequently causing a reduction in the number of dentate gyrus granule cell neurons in isoflurane-treated rats. There were no signs of increased cell death of progenitors or neurons in the hippocampus. These findings show a previously unknown mechanism of neurotoxicity, causing cognitive deficits in a clearly age-dependent manner.
reversal learning; procedural memory; declarative memory; IntelliCage; juvenile brain; object recognition
Cyclophilin D (CypD), a regulator of the mitochondrial membrane permeability transition pore (PTP), enhances Ca2+-induced mitochondrial permeabilization and cell death in the brain. However, the role of CypD in hypoxic-ischemic (HI) brain injury at different developmental ages is unknown. At postnatal day (P) 9 or P60, littermates of CypD-deficient [knock-out (KO)], wild-type (WT), and heterozygous mice were subjected to HI, and brain injury was evaluated 7 d after HI. CypD deficiency resulted in a significant reduction of HI brain injury at P60 but worsened injury at P9. After HI, caspase-dependent and -independent cell death pathways were more induced in P9 CypD KO mice than in WT controls, and apoptotic activation was minimal at P60. The PTP had a considerably higher induction threshold and lower sensitivity to cyclosporin A in neonatal versus adult mice. On the contrary, Bax inhibition markedly reduced caspase activation and brain injury in immature mice but was ineffective in the adult brain. Our findings suggest that CypD/PTP is critical for the development of brain injury in the adult, whereas Bax-dependent mechanisms prevail in the immature brain. The role of CypD in HI shifts from a predominantly prosurvival protein in the immature to a cell death mediator in the adult brain.
brain injury; hypoxia-ischemia; mitochondria; development; cyclophilin D; cell death
Multiple cellular stressors, including activation of the tumour suppressor p53, can stimulate autophagy. Here we show that knockout, knockdown or pharmacological inhibition of p53 can induce autophagy in human, mouse and nematode cells. Enhanced autophagy improved the survival of p53-deficient cancer cells under conditions of hypoxia and nutrient depletion, allowing them to maintain high ATP levels. Inhibition of p53 led to autophagy in enucleated cells, and cytoplasmic, not nuclear, p53 was able to repress the enhanced autophagy of p53-/- cells. Many different inducers of autophagy (for example, starvation, rapamycin and toxins affecting the endoplasmic reticulum) stimulated proteasome-mediated degradation of p53 through a pathway relying on the E3 ubiquitin ligase HDM2. Inhibition of p53 degradation prevented the activation of autophagy in several cell lines, in response to several distinct stimuli. These results provide evidence of a key signalling pathway that links autophagy to the cancer-associated dysregulation of p53.
Upon cerebral hypoxia-ischemia (HI), apoptosis-inducing factor (AIF) can move from mitochondria to nuclei, participate in chromatinolysis, and contribute to the execution of cell death. Previous work (Cande, C., N. Vahsen, I. Kouranti, E. Schmitt, E. Daugas, C. Spahr, J. Luban, R.T. Kroemer, F. Giordanetto, C. Garrido, et al. 2004. Oncogene. 23:1514–1521) performed in vitro suggests that AIF must interact with cyclophilin A (CypA) to form a proapoptotic DNA degradation complex. We addressed the question as to whether elimination of CypA may afford neuroprotection in vivo. 9-d-old wild-type (WT), CypA+/−, or CypA−/− mice were subjected to unilateral cerebral HI. The infarct volume after HI was reduced by 47% (P = 0.0089) in CypA−/− mice compared with their WT littermates. Importantly, CypA−/− neurons failed to manifest the HI-induced nuclear translocation of AIF that was observed in WT neurons. Conversely, CypA accumulated within the nuclei of damaged neurons after HI, and this nuclear translocation of CypA was suppressed in AIF-deficient harlequin mice. Immunoprecipitation of AIF revealed coprecipitation of CypA, but only in injured, ischemic tissue. Surface plasmon resonance revealed direct molecular interactions between recombinant AIF and CypA. These data indicate that the lethal translocation of AIF to the nucleus requires interaction with CypA, suggesting a model in which two proteins that normally reside in separate cytoplasmic compartments acquire novel properties when moving together to the nucleus.
Mitochondria are key contributors to many forms of cell death including those resulting from neonatal hypoxic-ischemic brain injury. Mice have become increasingly popular in studies of brain injury, but there are few reports evaluating mitochondrial isolation procedures for the neonatal mouse brain. Using evaluation of respiratory activity, marker enzymes, western blotting and electron microscopy, we have compared a previously published procedure for isolating mitochondria from neonatal mouse brain (method A) with procedures adapted from those for adult rats (method B) and neonatal rats (method C). All three procedures use Percoll density gradient centrifugation as a key step in the isolation but differ in many aspects of the fractionation procedure and the solutions used during fractionation. Methods A and B both produced highly enriched fractions of well-coupled mitochondria with high rates of respiratory activity. The fraction from method C exhibited less preservation of respiratory properties and was more contaminated with other subcellular components. Method A offers the advantage of being more rapid and producing larger mitochondrial yields making it useful for routine applications. However, method B produced mitochondria that were less contaminated with synaptosomes and associated cytosolic components that suits studies that have a requirement for higher mitochondrial purification.
brain; mitochondrial isolation; mouse; neonatal