Glucocorticoids are used to treat respiratory dysfunction associated with premature birth but have been shown to cause neurodevelopmental deficits when used therapeutically. Recently, we established that acute glucocorticoid exposure at clinically relevant doses produces neural progenitor cell apoptosis in the external granule layer of the developing mouse cerebellum and permanent decreases in the number of cerebellar neurons. As the cerebellum naturally matures and neurogenesis is no longer needed, the external granule layer decreases proliferation and permanently disappears during the second week of life. At this same time, corticosterone (the endogenous rodent glucocorticoid) release increases and a glucocorticoid-metabolizing enzyme that protects the external granule layer against glucocorticoid receptor stimulation (11B-Hydroxysteroid-Dehydrogenase-Type 2; HSD2) naturally disappears. Here we show that HSD2 inhibition or raising corticosterone to adult physiological levels can both independently increase neural progenitor cell apoptosis in the neonatal mouse. Conversely, glucocorticoid receptor antagonism decreased natural physiological apoptosis in this same progenitor cell population suggesting endogenous glucocorticoid stimulation may regulate apoptosis in the external granule layer. We also found that glucocorticoids HSD2 can effectively metabolize generate less external granule layer apoptosis then glucocorticoids this enzyme is ineffective at breaking down. This finding may explain why glucocorticoids this enzyme can metabolize are clinically effective at treating respiratory dysfunction yet seem to produce no neurodevelopmental deficits. Finally, we demonstrate that both acute and chronic glucocorticoid exposure produces external granule layer apoptosis but without appropriate control groups this effect becomes masked. These results are discussed in terms of their implications for glucocortiocid therapy and neurodevelopment during the perinatal period.

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Propylene Glycol (PG) is a common solvent used in medical preparations. It is “generally recognized as safe” at regulated concentrations, however its apoptotic potential is unknown. C57BL/6 mice (P4–30) were exposed to PG to examine whether PG could produce apoptosis in the developing CNS. PG triggered widespread apoptotic neurodegeneration with the greatest damage at P7. Significant apoptosis was observed at doses as low as 2mL/kg. These findings have implications for the safety of drug preparations used in pediatric medicine. The anticonvulsant phenobarbital (PB), which alone produces apoptosis in the immature CNS, is prepared in 68% PG and 10% Ethanol (EtOH). We assessed whether PG contributes to the neurotoxic potential of PB. The agents (both at sub-toxic doses) produce significantly more apoptosis when used in combination. In conclusion, finding an alternative non-apoptotic solvent that can be used as a substitute for PG may be beneficial to patients.

Zika virus (ZIKV) infection during pregnancy has been causally linked to a constellation of neurodevelopmental deformities in the fetus resulting in a disease termed congenital Zika syndrome (CZS). Here we detail how ZIKV infection produces extensive neuropathology in the developing mouse brain and spinal cord of both sexes. Surprisingly, neuropathology differs depending on viral strain with a French Polynesian isolate producing primarily excitotoxicity and a Brazilian isolate being almost exclusively apoptotic but occurring over a prolonged period that is more likely to produce severe hypoplasia. We also show exposure can produce a characteristic pattern of infection that mirrors neuropathology and ultimately results in gross morphological deformities strikingly similar to CZS. This research provides a valuable mouse model mirroring the clinical course of disease that can be used to test potential therapies to improve treatment and gain a better understanding of the disabilities associated with CZS.

Respiratory dysfunction is one of the most common causes of death associated with premature birth (Barton et al., 1999). In the United States, 7–10% of pregnant women receive antenatal glucocorticoid (GC) therapy (Matthews et al., 2004), while approximately 19% of very low birth weight infants receive postnatal GC therapy (Jobe, 2009). Clinical research suggests that GC treatment causes permanent neuromotor and cognitive deficits (Yeh et al., 2004) and stunts cerebellar growth (Parikh et al., 2007; Tam et al., 2011). We previously reported that GC-mediated neural progenitor cell (NPC) apoptosis may be responsible for cerebellar neuropathology (Maloney et al., 2011; Noguchi et al., 2008; Noguchi et al., 2011). The goal of the current study was to determine whether lithium protects NPCs from GC neuroapoptosis in vivo and in vitro. Given that it protects against a range of brain insults, we hypothesized that lithium would significantly attenuate GC induced NPC toxicity. We report that acute lithium pretreatment provides potent, cell-intrinsic neuroprotection against GC induced NPC toxicity in vivo and in vitro.

Objectives Caffeine (CAF) and sedative/anesthetic drugs (SADs) are often coadministered to premature infants in the neonatal intensive care unit (NICU). While SAD neurotoxicity in the developing brain is well established, it is not fully clear whether CAF interacts with SADs and whether this interaction is detrimental. Using a mouse model of prematurity, we hypothesized that CAF would increase apoptotic neurotoxicity when coadministered with SADs. Methods Postnatal day 3 mice were treated with vehicle or 80 mg/kg CAF prior to challenge with 6 mg/kg midazolam, 40 mg/kg ketamine, or 40 μg/kg fentanyl. Six hours later, pups were sacrificed for activated caspase 3 (AC3) immunohistochemistry, and number of AC3 positive cells per mm3 throughout neocortex, hippocampus, caudate, thalamus, and colliculi was analyzed. Results CAF caused a statistically significant increase in AC3 positive cells when coadministered with midazolam (p = 0.002), ketamine (p = 0.014), or fentanyl (p <0.001). Our composite dataset suggests that the addition of CAF to these SADs has a supra-additive effect, causing more neurotoxicity than expected. Conclusions CAF may augment the neurotoxic action of SADs indicated for neonatal sedation/anesthesia in the NICU by triggering widespread apoptosis in the developing brains of premature infants.

The external granule layer (EGL) is a proliferative region that produces over 90% of the neurons in the cerebellum but can also malignantly transform into a cerebellar tumor called the medulloblastoma (the most common malignant brain tumor in children). Current dogma considers Hedgehog stimulation a potent proliferative signal for EGL neural progenitor cells (NPCs) and medulloblastomas. However, the Hedgehog pathway also acts as a survival signal in the neural tube where it regulates dorsoventral patterning by controlling NPC apoptosis. Here we show Hedgehog stimulation is also a potent survival signal in the EGL and medulloblastomas that produces a massive apoptotic response within hours of signal loss in mice. This toxicity can be produced by numerous Hedgehog antagonists (vismodegib, cyclopamine, and jervine) and is Bax/Bak dependent but p53 independent. Finally, since glucocorticoids can also induce EGL and medulloblastoma apoptosis, we show Hedgehog's effects on apoptosis can occur independent of glucocorticoid stimulation. This effect may play a major role in cerebellar development by directing where EGL proliferation occurs thereby morphologically sculpting growth. It may also be a previously unknown major therapeutic effect of Hedgehog antagonists during medulloblastoma therapy. Results are discussed in terms of their implications for both cerebellar development and medulloblastoma treatment.

Apoptosis is triggered in the developing mammalian brain by sedative, anesthetic or antiepileptic drugs during late gestation and early life. Whether human children are vulnerable to this toxicity mechanism remains unknown, as there are no imaging techniques to capture it. Apoptosis is characterized by distinct structural features, which affect the way damaged tissue scatters ultrasound compared to healthy tissue. We evaluated whether apoptosis, triggered by the anesthetic sevoflurane in the brains of neonatal rhesus macaques, can be detected using quantitative ultrasound (QUS).