The unfolded protein response (UPR) drives events that promote diabetic retinopathy, including vascular endothelial growth factor (VEGF) upregulation in Müller cells. How UPR is activated in vivo in the diabetic retina is not well understood. CD40 is required for development of diabetic retinopathy, but whether CD40 mediates activation of UPR sensors is unknown. CD40 ligation in Müller cells caused phospholipase Cγ1 (PLCγ1)–dependent activation of UPR sensors (PERK, IRE1α, and ATF6α) and VEGF production dependent on PLCγ1 and UPR sensors. Diabetic Cd40−/− mice did not exhibit UPR activation or VEGF upregulation in the retina. These responses were restored in diabetic Cd40−/− mice rescued to express wild-type CD40 in Müller cells but not in mice rescued to express a CD40 mutation unable to recruit TRAF2/3. Intravitreal administration of a cell-permeable CD40-TRAF2/3–disrupting peptide reduced UPR activation, VEGF upregulation, and vascular leakage in diabetic mice. CD40 and TRAF2 in Müller cells from patients with diabetic retinopathy colocalized with activated UPR sensors and VEGF. Our study indicates that CD40 (via TRAF2/3 signaling) is an inducer of UPR activation that triggers VEGF production in Müller cells. This work uncovered inhibition of CD40-TRAF2/3 signaling as a potential approach to impair UPR activation, VEGF upregulation, and vascular leakage in diabetic retinopathy.
Article Highlights
- The unfolded protein response (UPR) promotes vascular endothelial growth factor (VEGF) upregulation and vascular leakage in diabetic retinopathy (DR), but how UPR is activated is poorly understood. We investigated the role of CD40 in UPR activation.
- CD40 acted through phospholipase Cγ1 (PLCγ1) to activate PERK, IRE1α, and ATF6α in Müller cells, leading to VEGF secretion.
- CD40-TRAF2/3 signaling drove activated UPR and VEGF expression in diabetic mice. CD40 and TRAF2 are coexpressed with activated UPR sensors and VEGF in patients with DR. A CD40-TRAF2/3–disrupting peptide reduced expression of activated UPR, VEGF, and vascular leakage in mice.
- CD40-TRAF2/3 blockade may reduce UPR activation, VEGF, and vascular leakage in patients with DR.
