RESUMO
Evidence has accumulated implicating complement activation in the pathogenesis of acute post-hypoxic-ischemic cerebral injury in infants who develop hypoxic-ischemic encephalopathy (HIE). However, the relationship between complement activation and subsequent neurological impairment is not known. We tested the hypothesis that in human neonates, post-hypoxic-ischemic complement activation within the central nervous system is positively associated with the acquisition of subsequent neurodevelopmental abnormalities. This prospective study included 18 full-term infants diagnosed with HIE following resuscitation at birth and seven control infants. Cerebrospinal fluid (CSF) samples were obtained from all infants in the first 24 hours of life as part of routine investigations to exclude sepsis and meningitis. Concentrations of terminal complement complexes (TCC), complement component 9 (C9), and albumin were quantified by enzyme-linked immunosorbent assay in all CSF samples. Neurological examination and Denver Developmental Screening Test II were performed at 6 and 12 months of life. Of the 18 HIE subjects, nine died, six survived with significant neurological impairment, and three had normal neurological outcomes. In the CSF of the 15 HIE infants who died or survived with abnormal outcomes, the mean concentration of TCC was increased compared with controls (p = 0.026) and the mean C9 concentration appeared to be decreased but the difference was not statistically significant (p = 0.056). Similar to the TCC concentration, the concentration of albumin in the CSF was significantly increased in infants with abnormal outcomes (p = 0.005). This study indicates that complement activation following resuscitation at birth, as manifested by increased TCC in the CNS, is positively correlated with the combination of the development of subsequent neurological sequelae and death. Further study incorporating larger sample sizes will be required to confirm this association. This step is essential before clinical trials of complement inhibitors can be justified in human neonates who suffer birth asphyxia.
Assuntos
Asfixia Neonatal/complicações , Doenças do Sistema Nervoso Central/etiologia , Proteínas do Sistema Complemento/metabolismo , Deficiências do Desenvolvimento/etiologia , Hipóxia-Isquemia Encefálica/complicações , Análise de Variância , Asfixia Neonatal/diagnóstico , Asfixia Neonatal/mortalidade , Asfixia Neonatal/terapia , Biomarcadores/análise , Doenças do Sistema Nervoso Central/epidemiologia , Doenças do Sistema Nervoso Central/fisiopatologia , Ativação do Complemento , Complemento C5 , Complemento C9 , Proteínas do Sistema Complemento/líquido cefalorraquidiano , Deficiências do Desenvolvimento/epidemiologia , Deficiências do Desenvolvimento/fisiopatologia , Feminino , Seguimentos , Humanos , Hipóxia-Isquemia Encefálica/diagnóstico , Hipóxia-Isquemia Encefálica/mortalidade , Hipóxia-Isquemia Encefálica/terapia , Incidência , Lactente , Recém-Nascido , Unidades de Terapia Intensiva Neonatal , Masculino , Exame Neurológico , Estudos Prospectivos , Valores de Referência , Medição de Risco , Índice de Gravidade de Doença , Estatísticas não Paramétricas , Análise de Sobrevida , Nascimento a TermoRESUMO
The role of complement in neonatal hypoxic-ischemic brain injury is not known. Therefore, cerebral spinal fluid (CSF) and post-mortem cerebral tissue were analyzed to determine whether complement is activated and complement component 9 (C9) is deposited on neurons in the central nervous systems (CNS) of newborn infants who developed moderate to severe hypoxic-ischemic encephalopathy (HIE). Control CSF samples were obtained during routine evaluation for possible sepsis from infants who were not depressed at birth. In ELISA assays of CSF obtained from 16 infants with HIE, compared to CSF from 7 control infants, the mean concentration of terminal complement complexes was elevated and the mean C9 concentration was diminished. Immunofluorescence microscopy of post-mortem frozen brain tissue obtained from two infants who expired at 4-5 days of life after severe HIE revealed that activated C9 was deposited on cells in all lobes. Double label immunofluorescence microscopy demonstrated that nearly all of the C9-positive cells were neurons and essentially all of the neurons were C9-positive. Immunoperoxidase immunohistochemistry of formalin-fixed tissue also confirmed the presence of many C9-positive cells, particularly in the hippocampus. The C9-positive cells usually manifested morphology consistent with neurons, most of which contained fragmented nuclei. In summary, complement was activated in the CNS of newborn infants who developed moderate to severe HIE. C9 was deposited on neurons, including morphologically apoptotic neurons. Further investigations into a possible role of complement in the pathogenesis of neonatal hypoxic-ischemic cerebral injury are warranted.