Acute Antiapoptotic Effects of Hydrocortisone in the Hippocampus of Neonatal Rats

Glucocorticoids in a Neonatal Hyperoxic Lung Injury Model: Pulmonary and Neurotoxic effects

BACKGROUND

We aimed to compare the effect of dexamethasone (Dex), hydrocortisone (Hc), and methylprednisolone (Mpz) at equivalent doses on somatic growth, lung healing, and neurotoxicity in a hyperoxic rat model. We hypothesized that Mpz and Hc would be superior to Dex with less neurotoxicity by exerting similar therapeutic efficacy on the injured lung.

METHODS

Neonatal rats were randomized to control, bronchopulmonary dysplasia (BPD), Dex, Hc, and Mpz groups. All drugs were administered daily following day 15 over 7 days. Histopathological and immunohistochemical analyses of the lung and brain were performed on day 22.

RESULTS

All types had much the same impact on lung repair. Oxidative markers in the lung were similar in the steroid groups. While nuclear factor erythroid 2-related factor and heat-shock protein 70 dropped following steroid treatment, no difference was noted in other biochemical markers in the brain between the study groups. Apoptotic activity and neuron loss in the parietal cortex and hippocampus were noted utmost in Dex, but alike in other BPD groups.

CONCLUSIONS

Mpz does not appear to be superior to Dex or Hc in terms of pulmonary outcomes and oxidative damage in the brain, but safer than Dex regarding apoptotic neuron loss.

IMPACT

This is the first study that compared the pulmonary efficacy and neurotoxic effects of Dex, Hc, and Mpz simultaneously in an established BPD model. This study adds to the literature on the importance of possible antioxidant and protective effects of glucocorticoid therapy in an oxidative stress-exposed brain. Mpz ended up with no more additional neuron loss or apoptosis risk by having interchangeable effects with others for the treatment of established BPD. Mpz and Hc seem safe as a rescue therapy in terms of adverse outcomes for established BPD in which lung and brain tissue is already impaired.

Cortisol limits selected actions of synthetic glucocorticoids in the airway epithelium

Cortisol, a physiologic glucocorticoid (GC), is essential for growth and differentiation of the airway epithelium. Epithelial function influences inflammation in chronic respiratory diseases. Synthetic GCs, including inhaled corticosteroids, exert anti-inflammatory effects in airway epithelium by transactivation of genes and by inhibition of proinflammatory cytokine release. We examined the effect of cortisol on the actions of synthetic GCs in the airway epithelium, demonstrating that cortisol acts like a partial agonist at the GC receptor (GR), limiting GC-induced GR-dependent transcription in the BEAS-2B human bronchial epithelial cell line. Cortisol also limited the inhibition of granulocyte macrophage colony-stimulating factor release by synthetic GCs in TNF-α-activated BEAS-2B cells. The relevance of these findings is supported by observations on tracheal epithelium obtained from mice treated for 5 d with systemic GC, showing limitations in selected GC effects, including inhibition of IL-6. Moreover, gene transactivation by synthetic GCs was compromised by standard air-liquid interface (ALI) growth medium cortisol concentration (1.4 μM) in the ALI-differentiated organotypic culture of primary human airway epithelial cells. These findings suggest that endogenous corticosteroids may limit certain actions of synthetic pharmacological GCs and contribute to GC insensitivity, particularly when corticosteroid levels are elevated by stress.-Prodanovic, D., Keenan, C. R., Langenbach, S., Li, M., Chen, Q., Lew, M. J., Stewart, A. G. Cortisol limits selected actions of synthetic glucocorticoids in the airway epithelium.

Anoxia ameliorates the dexamethasone-induced neurobehavioral alterations in the neonatal male rat pups

Glucocorticoids and hypoxia are two essential factors affecting the brain development during labor and delivery. In addition to the neurobehavioral alterations induced separately by these factors, glucocorticoids can attenuate the deleterious consequences of severe hypoxia-ischemia on the brain development, acting as a neuroprotective agent in combination with hypoxia. The role of hypoxia in the combined action with corticosteroids is less clear. Severe hypoxia-ischemia results in the massive activation of caspase-3, masking any other effects of hypoxia on the neonatal brain exposed to glucocorticoids. As a result, the effects of mild hypoxia on the developing brain pretreated with glucocorticoids remain unclear. To analyze this problem, 2-day-old male rats were treated with dexamethasone (DEX) before the subsequent exposure to mild 10-min anoxia or normoxia. The treatment with only DEX resulted in the delay in the development of the negative geotaxis reaction and in the decrease in locomotor activity of the neonatal male pups. The mild anoxic event attenuated these DEX-induced neurobehavioral alterations. The treatment with DEX, but not the mild anoxic exposure alone, resulted in the delayed upregulation of active caspase-3 in the prefrontal cortex and in the brainstem of the male pups. This glucocorticoid-induced upregulation of active caspase-3 was prevented by the anoxic event. The present findings evidence that mild anoxia is capable of ameliorating the glucocorticoid-induced neurodevelopmental alterations in the neonatal rats if the artificial or the naturally occurring increase in the levels of glucocorticoids occurred just before the episode of hypoxia.

Toxic Effects of Lithium Chloride during Early Neonatal Period of Rat Development

Lithium chloride (85, 255, or 255+127 μg/kg) or dexamethasone (0.2 or 2 mg/kg) were subcutaneously injected to 3-day-old rat pups, whose excretory system did not yet attain functional maturity. Both agents retarded the growth of rat pups and delayed the appearance of negative geotaxis. LD50 and therapeutic index of lithium chloride were 255 μg/kg and TI≤3, respectively. Thus, lithium salts even in low doses can be highly toxic for the developing organism.

Effect of dexamethasone on intelligence and hearing in preterm infants: a meta-analysis

OBJECTIVE

A meta-analysis of published randomized controlled trials investigating the long-term effect of dexamethasone on the nervous system of preterm infants.

DATA SOURCES

Online literature retrieval was conducted using The Cochrane Library (from January 1993 to June 2013), EMBASE (from January 1980 to June 2013), MEDLINE (from January 1963 to June 2013), OVID (from January 1993 to June 2013), Springer (from January 1994 to June 2013) and Chinese Academic Journal Full-text Database (from January 1994 to June 2013). Key words were preterm infants and dexamethasone in English and Chinese.

STUDY SELECTION

Selected studies were randomized controlled trials assessing the effect of intravenous dexamethasone in preterm infants. The quality of the included papers was evaluated and those without the development of the nervous system and animal experiments were excluded. Quality assessment was performed through bias risk evaluation in accordance with Cochrane Handbook 5.1.0 software in the Cochrane Collaboration. The homogeneous studies were analyzed and compared using Revman 5.2.6 software, and then effect model was selected and analyzed. Those papers failed to be included in the meta-analysis were subjected to descriptive analysis.

MAIN OUTCOME MEASURES

Nervous system injury in preterm infants.

RESULTS

Ten randomized controlled trials were screened, involving 1,038 subjects. Among them 512 cases received dexamethasone treatment while 526 cases served as placebo control group and blank control group. Meta-analysis results showed that the incidence of cerebral palsy, visual impairment and hearing loss in preterm infants after dexamethasone treatment within 7 days after birth was similar to that in the control group (RR = 1.47, 95%CI: 0.97-2.21; RR = 1.46, 95%CI: 0.97-2.20; RR = 0.80, 95%CI: 0.54-1.18; P > 0.05), but intelligence quotient was significantly decreased compared with the control group (MD = -3.55, 95%CI: -6.59 to -0.51; P = 0.02). Preterm infants treated with dexamethasone 7 days after birth demonstrated an incidence of cerebral palsy and visual impairment, and changes in intelligence quotient similar to those in the control group (RR = 1.26, 95%CI: 0.89-1.79; RR = 1.37, 95%CI: 0.73-2.59; RR = 0.53, 95%CI: 0.32-0.89; RR = 1.66, 95%CI: -4.7 to 8.01; P > 0.05). However, the incidence of hearing loss was significantly increased compared with that in the control group (RR = 0.53, 95%CI: 0.32-0.89; P = 0.02).

CONCLUSION

Dexamethasone may affect the intelligence of preterm infants in the early stages after birth, but may lead to hearing impairment at later stages after birth. More reliable conclusions should be made through large-size, multi-center, well-designed randomized controlled trials.

Dexamethasone suppresses the locomotor response of neonatal rats to novel environment

Locomotion of animals in the novel environment is determined by two main factors-the intrinsic motor activity and the specific locomotor response to novelty. Glucocorticoids alter neurobehavioral development of mammals and its locomotor manifestations. However, it remains unclear whether the intrinsic and/or the novelty-induced activity are affected by glucocorticoids during early life. Here, the principal component analysis was used to determine the main factors that underlie alterations in locomotion of rat pups treated with dexamethasone. It was shown that neonatal rats exhibited an enhanced locomotion in the novel environment beginning from postnatal day (PD) 5. We found for the first time that this reaction was significantly suppressed by dexamethasone. The effect was specific to the novelty-induced component of behavior, while the intrinsic locomotor activity was not affected by glucocorticoid treatment. The suppression of the behavioral response to novelty was maximal at PD7 and vanquished at PD10-11. In parallel with the hormonal effect on the behavior, dexamethasone upregulated the main cell death executor-active caspase-3 in the prefrontal cortex of 7-day old rats. Thus, dexamethasone-induced alterations in the novelty-related behavior may be the earliest visible signs of the brain damage that could lead to forthcoming depressive state or schizophrenia, emerging as a result of neonatal stress or glucocorticoid treatment.