Hedgehog signaling has a protective effect in glucocorticoid-induced mouse neonatal brain injury through an 11βHSD2-dependent mechanism
Vivi M. Heine, David H. Rowitch
Vivi M. Heine, David H. Rowitch
Published January 26, 2009
Citation Information: J Clin Invest. 2009;119(2):267-277. https://doi.org/10.1172/JCI36376.
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Research Article

Hedgehog signaling has a protective effect in glucocorticoid-induced mouse neonatal brain injury through an 11βHSD2-dependent mechanism

Abstract

Glucocorticoids (GCs) are administered to human fetuses at risk of premature delivery and to infants with life-threatening respiratory and cardiac conditions. However, there are ongoing concerns about adverse effects of GC treatment on the developing human brain, although the precise molecular mechanisms underlying GC-induced brain injury are unclear. Here, we identified what we believe to be novel cross-antagonistic interactions of Sonic hedgehog (Shh) and GC signaling in proliferating mouse cerebellar granule neuron precursors (CGNPs). Chronic GC treatment (from P0 through P7) in mouse pups inhibited Shh-induced proliferation and upregulation of expression of N-myc, Gli1, and D-type cyclin protein in CGNPs. Conversely, acute GC treatment (on P7 only) caused transient apoptosis. Shh signaling antagonized these effects of GCs, in part by induction of 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2). Importantly, 11βHSD2 antagonized the effects of the GCs corticosterone, hydrocortisone, and prednisolone, but not the synthetic GC dexamethasone. Our findings indicate that Shh signaling is protective in the setting of GC-induced mouse neonatal brain injury. Furthermore, they led us to propose that 11βHSD2-sensitive GCs (e.g., hydrocortisone) should be used in preference to dexamethasone in neonatal human infants because of the potential for reduced neurotoxicity.

Authors

Vivi M. Heine, David H. Rowitch

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Figure 4

Cross-antagonistic Shh-GC signaling regulates CGNP proliferation in vitro.

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Cross-antagonistic Shh-GC signaling regulates CGNP proliferation in vitr...
(A) Immunocytochemistry for pH3 of CGNP cultures, generated from WT or Math1cre,SmoM2 animals, and treated with Shh alone or in combination with 40 μM Dex. (B) To determine the optimal dose to inhibit CGNP proliferation, cultures were exposed to different doses of Dex and Pred for 24 h. The number of pH3+ cells in the WT cultures significantly decreased with increasing Dex (black triangles) and were unaffected by Pred (black circles). The number of pH3+ cells in the Math1cre,SmoM2 cultures were not affected up to 40 μM Dex (blue circles). (C) At 60–160 μM Dex, the number of pH3+ cells in the Math1cre,SmoM2 cultures was dose-dependently affected (blue circles). Conversely, Math1cre,SmoM2 cultures were protected against Pred up to 120 μM (red squares). (D) Protein lysates were prepared from CGNPs treated with vehicle, Shh, or Shh plus 40 μM Dex for 24 h. Western blot analysis showed that Dex treatment decreased cyclin D1, N-myc, Gli1, and cyclin D2 protein expression. (E) Western blot analysis of Math1cre,SmoM2 CGNPs showed that cyclin D1 levels were greatly upregulated, independent of Shh administration, and were unchanged after 40 μM Dex treatment. Furthermore, cyclin D2, Gli1, and N-myc levels were unchanged. Samples were run on the same gel but were noncontiguous. Scale bar: 50 μm. Exact P values are shown in Results.