Glucocorticoids (GC) have potent anti-inflammatory effects, acting mainly through the glucocorticoid receptor (GR). However GCs have debilitating side effects and a safer alternative is required. 5α-tetrahydrocorticosterone (5αTHB, a metabolite of the natural rodent glucocorticoid corticosterone) may provide a solution: 5αTHB is anti-inflammatory in vivo, effective topically to suppress irritant dermatitis, but with fewer systemic adverse effects. Topical GCs have additional local side effects, in particular impaired wound healing, which occurs largely due to the inhibition of angiogenesis. Here it was hypothesised that 5αTHB suppresses angiogenesis less than hydrocortisone, a commonly prescribed topical therapeutic GC.
Angiogenesis was studied using an ex vivo model. Mouse (C57Bl6, male, 810 weeks) aortas were isolated, divided into rings (1 mm) and cultured in collagen gel with foetal calf serum and vascular endothelial growth factor to stimulate vessel outgrowth formation. The number of vessel outgrowths was counted after 7 days incubation with steroid or vehicle control (1 nM-10 μM, n=8/dose) to determine whether the steroids inhibited new vessel formation. Transcripts of genes involved in GC responsive pathways were quantified in rings exposed to hydrocortisone (1μM) or 5αTHB (3 μM), using qPCR. Data are mean+/−SEM; *P<0.05; vs control.
Vessel outgrowth was suppressed by both hydrocortisone (to 29%* control, 1μM, EC50 867 nM) and 5αTHB (to 30%* control, 3 μM, EC50 2399 nM) in a concentration dependent manner. Hydrocortisone modulated expression of inflammatory mediators and extracellular matrix remodelling genes in aortas. Compared to control Cxcl5 was lower (31%* control), Dusp1 higher (200%* control), Col4a1 higher (190%* control) and Mmp9 lower (16%* control) after hydrocortisone treatment. 5αTHB however had more limited effects, only decreasing abundance of Pecam1 mRNA (to 63%* control).
In conclusion, 5αTHB suppressed angiogenesis less than hydrocortisone, and in addition, exerted its actions on the aorta differently. This knowledge will help us to assess 5αTHBs potential as a safer topical anti-inflammatory treatment.