Endocrine Abstracts

Aim: We have proposed to study the modulation of the Notch pathway in diabetes having in mind the essential role played by the Notch system in the regulation of cell differentiation and angiogenesis.

Methods: The effect of hyperglycemia on Notch system was studied in vitro and in vivo using western blot, reporter gene assay or evaluation of target genes (qRT-PCR). The functional consequences of the Notch system modulation were studied by the assessment of the migration and angiogenesis potential. Notch pathway inhibition was induced either chemically with gamma secretase inhibitors (DAPT, L-685,458). The effect of the Notch inhibition on wound healing was evaluated in db/db mice.

Results: Hyperglycemia activates Notch pathway at several levels as shown by increased NICD level, increased reporter gene activity and enhanced expression of several essential target genes as evaluated both in vitro and in vivo. The inhibitory effect of high glucose on migration of HDF and angiogenesis was cancelled by blocking the Notch signaling with different gamma-secretase inhibitors (DAPT or L-685,458). Specific inhibition of different Notch receptors (1–4) by siRNA pointed out to a crucial role of Notch1 in migration and angiogenesis. Local treatment with gamma-secretase inhibitors (DAPT or L-685,458) improved the wound healing in db/db mice (percentage of wound closure on day 12 was 60±2% (DAPT), 70±4% (L-685,458) and 43±5% (placebo) respectively (P<0.01). Blocking Notch pathway in diabetic wounds was followed by increase in granulation and epidermal formation, increase in blood vessel formation and increase in expression of chemokine (SDF-1 alpha) responsible for better recruitment of EPCs.

Conclusions: Hyperglycemia activated Notch signaling with deleterious effects on cell migration and angiogenesis. Blocking the overactive Notch pathway by local treatment with gamma-secretase inhibitors improves wound healing rate in diabetic animal model.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.