Neuroprotective role of minocycline in co-cultures of human fetal neurons and microglia.
ABSTRACT Bacterial infections during pregnancy often result in premature birth and neonatal white matter damage. During these infections, microglia, the resident immune cells of the CNS, undergo activation and contribute to further neuronal damage of the CNS. Minocycline, a second-generation tetracycline antibiotic, inhibits microglial activation and protects neurons in rodents but data about its effects on human cells are limited. We studied the mechanism of the neuroprotective effect of minocycline in either purified cell cultures or co-cultures of microglia and neurons from human fetal brain during inflammation induced by lipopolysaccharide (LPS). In neuron/microglial co-cultures, minocycline treatment prevented activation and proliferation of microglia and protected neurons as demonstrated by decreased neuronal cell death and a shift of Bcl-2 family proteins toward anti-apoptotic ratio. Notably, neither minocycline nor LPS had an effect on neurons in purified neuronal cultures. The ability of minocycline to regulate activation of human fetal microglia might be relevant in therapies used towards treating neonatal CNS infections.
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ABSTRACT: Preterm birth results in significant neurodevelopmental disability. The neonatal rodent model of chronic sublethal hypoxia faithfully mimics the effect of preterm birth on the developing brain. We employed this model to test the hypothesis that the hypoxia that accompanies preterm birth results in inappropriate signaling of apoptotic mechanisms in developing brain. We performed cortical cell counts, determinations of neuronal size and Western analyses of the apoptosis related proteins, Bcl-2 and Bax, in rat pups who were raised in chronic hypoxia (FiO2 9.5%) beginning on postnatal day 3 (P3) and extending for either 10 (P13) or 30 (P33) days. A third group of animals was exposed to 30 days of hypoxia followed by an additional 30 days in a normoxic environment (P63) to assess the potential for recovery from the initial effects of hypoxia. Age matched control pups were raised in room air throughout the experimental time period. Assessment of cortical cell number revealed a 25% reduction (P < 0.01) in total cell number following 30 days of hypoxic rearing. Glia were significantly reduced by 34% and 41% after 10 and 30 days of hypoxia, respectively, while neuron numbers were only significantly reduced (14%) after 30 days of hypoxia. Animals exposed to a hypoxic environment for 30 days followed by 30 days in a normoxic environment revealed some recovery of glial cell numbers, but no significant recovery of neuronal cell numbers. Measurement of cell size at both P13 and P33 revealed that neurons of layer III were significantly smaller in cross-sectional area in hypoxic compared with control rats (P < 0.01). However, no significant difference was noted in neuronal size following 30 days of normoxic recovery. Western blot analyses of Bcl-2 and Bax protein levels demonstrated a ratio favorable to Bax at multiple time points during the period of hypoxic exposure. These data suggest that chronic exposure to hypoxia during the perinatal period alters the production and maintenance of glial and neuronal cells and that glia and neurons demonstrate differential patterns of vulnerability and recovery following subsequent periods of normoxic exposure. It is hypothesized that the mechanisms responsible for these alterations in cortical cell number may depend on the state of differentiation of the different cell types at the time of hypoxic exposure.Seminars in Perinatology 12/2004; 28(6):379-88. · 2.81 Impact Factor
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ABSTRACT: Approximately 10% of newborns are born prematurely. Of these children, more than 10% will sustain neurological injuries leading to significant learning disabilities, cerebral palsy, or mental retardation, with very low birth weight infants having an even higher incidence of brain injury. Whereas intraventricular hemorrhage was the most common form of serious neurological injury a decade ago, periventricular white matter injury (PWMI) is now the most common cause of brain injury in preterm infants. The spectrum of chronic PWMI includes focal cystic necrotic lesions (periventricular leukomalacia; PVL) and diffuse myelination disturbances. Recent neuroimaging studies support that the incidence of PVL is declining, whereas diffuse cerebral white matter injury is emerging as the predominant lesion. Factors that predispose to PVL include prematurity, hypoxia, ischemia, and inflammation. It is believed that injury to oligodendrocyte (OL) progenitors contributes to the pathogenesis of myelination disturbances in PWMI by disrupting the maturation of myelin-myelin-forming oligodendrocytes. Other potential mechanisms of injury include activation of microglia and axonal damage. Chemical mediators that may contribute to white matter injury include reactive oxygen (ROS) and nitrogen species (RNS), glutamate, cytokines, and adenosine. As our understanding of the pathogenesis of PWMI improves, it is anticipated that new strategies for directly preventing brain injury in premature infants will evolve.Seminars in Perinatology 01/2005; 28(6):405-14. · 2.81 Impact Factor
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ABSTRACT: To evaluate the influence of confounding and sampling bias on the relationship between fetal growth restriction in a very-low-birthweight-defined cohort (VLBW, < or =1500 g) and bilateral spastic cerebral palsy (BSCP) at early school-age. Three hundred twenty-four of 407 long-term survivors of a regional cohort of VLBW newborns were followed until age 6 years. We categorized as small for gestational age (SGA) all infants whose birthweight Z-score was below -2 relative to published reference values. Uni- and multivariable logistic regression models were fit to estimate the risk of BSCP associated with SGA in the total sample, in subsamples defined by gestational age, and in a gestational age-matched case-control sample. In the total sample, no child below 28 weeks was SGA, and no child above 32 weeks had an appropriate birthweight for gestational age (AGA). The prevalence of BSCP was 14% in AGA and 2% in SGA infants. In both uni- and multivariable logistic regression analyses of the total sample, SGA was associated with a prominently reduced risk of BSCP (odds ratios range from 0.1 to 0.2, all 95% confidence limits exclude 1.0). However, analyses performed in samples defined by different gestational age cutoffs (24--31 weeks, 28--31 weeks) and in a sample using three gestational age-matched controls per BSCP-case did not show a protection by growth restriction (odds ratios range from 0.8 to 2.2, all 95% confidence limits include 1.0). In VLBW-defined samples, the apparent protective effect of SGA for BSCP can be explained, at least in part, by the highly skewed distribution of SGA over the available gestational age range. From this follows that study cohorts should be defined by gestational age and not by birthweight. In distorted samples like this one, even controlling for gestational age does not reduce the illusion of a reduced cerebral palsy risk for growth restricted infants. Only restriction of the sample by gestational age and/or matching for gestational age reveals the absence of this apparent protective effect.Early Human Development 10/2001; 64(2):79-89. · 2.02 Impact Factor