High glucose-induced barrier impairment of human retinal pigment epithelium is ameliorated by treatment with Goji berry extracts through modulation of cAMP levels

- High glucose impairs tight junctions of human retinal pigment epithelial cells.
- High glucose elevates intracellular cAMP levels in HRPE cells.
- Barrier impairment correlates with cAMP accumulation in HRPE cells.
- High glucose directly activates the intracellular soluble adenylyl cyclase (sAC).
- Goji berry extract and taurine reverse high glucose/sAC/cAMP disrupting barrier.

Human retinal pigment epithelium cells were used to investigate the mechanisms underlying blood-retinal barrier disruption under conditions of chronic hyperglycemia. The treatment with 25 mM glucose caused a rapid drop in the transepithelial electrical resistance (TEER), which was reversed by the addition of either a methanolic extract from Goji (Lycium barbarum L.) berries or its main component, taurine. Intracellular cAMP levels increased concurrently with the high glucose-induced TEER decrease, and were correlated to an increased activity of the cytosolic isoform of the enzyme adenylyl cyclase. The treatment with plant extract or taurine restored control levels. Data are discussed in view of a possible prevention approach for diabetic retinopathy.