Endocrine Abstracts

Delayed wound healing (WH), characterized by ischemia, is exacerbated by glucocorticoid (GC) excess. Local GC availability is regulated by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) which generates the GC cortisol from inactive cortisone. We previously reported improved WH in 11β-HSD1-null mice but regulation of 11β-HSD1 by hypoxia in human skin remains unknown. Primary human dermal fibroblasts (HDF, biological n=3), were treated with vehicle, IL1β (10 ng/ml), cortisol (100 nM), IL1β+cortisol, IL1β+cortisone (200 nM) or IL1β+cortisone+11β-HSD1 inhibitor (1 μM). Cells were incubated for 96 h in normoxia (21% O₂) or hypoxia (1% O₂). Gene expression was analysed by qPCR after normalizing to 18S rRNA. IL1β (vs vehicle) increased 11β-HSD1 mRNA by 198±130 and 288±125-fold (±S.E.M, P<0.05) in normoxia and hypoxia respectively. Hypoxia (vs normoxia) supressed 11β-HSD1 expression with IL1β+cortisol and IL1β+cortisone by 67±14 (P<0.05) and 41±28% (P=0.07) respectively, but not with IL1β+cortisone+11β-HSD1 inhibitor.

MMP1 and TIMP4 differentially modulate matrix remodelling during WH. Cortisol decreased IL1β-induced MMP1 by 64±12 (P=0.07) and 89±4% (P<0.05) in normoxia and hypoxia respectively and upregulated TIMP4 mRNA (independently of IL1β) by 4±0.5 and 2±0.05 (P<0.05) in normoxia and hypoxia respectively. Cortisone did not significantly reproduce the effects of cortisol for these genes. COX2 is integral to inflammation and WH. IL1β (vs. vehicle) increased COX2 expression by 87±28 and 183±76-fold (P<0.05) in normoxia and hypoxia respectively. In contrast to MMP1 and TIMP4, both cortisol and cortisone supressed IL1β-induced COX2 expression by 94±3 and 89±5% (P<0.05) respectively in normoxia and the suppression by cortisone was reversed by 11β-HSD1 inhibitor co-incubation (P<0.05). Interestingly, cortisone did not significantly reproduce the effects of cortisol in hypoxia likely due to lower 11β-HSD1 expression.

In summary, we demonstrate a previously unreported cortisol-dependent decrease in 11β-HSD1 expression in hypoxia which may represent a protective mechanism to limit GC exposure in ischemia. Further, we report gene-specific sensitivity to 11β-HSD1-derived cortisol which may regulate responses to inflammation and hypoxia in chronic wounds.