Discovery of caffeoylisocitric acid as a Keap1-dependent Nrf2 activator and its effects in mesangial cells under high glucose.

Diabetic nephropathy (DN) is one of the severe microvascular complications of diabetes mellitus. Oxidative stress resulting from aberrant metabolism of glucose mediates renal inflammation and fibrosis in the progression of DN. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor regulating the expression of antioxidant enzymes. Activating Nrf2 will give a promising therapy for DN. To discover novel Nrf2 activators, we have investigated caffeoylisocitric acid using mesangial cells under high glucose. The results showed at 10 μM, caffeoylisocitric acid significantly inhibited the self-limited proliferation of mesangial cells induced by high glucose. Further assessments have disclosed caffeoylisocitric acid mitigated oxidative stress, inflammation and accumulation of extracellular matrix resulting from high glucose via inactivating MAPK signalling. Meanwhile activation of Nrf2 was observed and involved in these effects through the interaction between Keap1 and caffeoylisocitric acid to disrupt Keap1-Nrf2 complex. Therefore, caffeoylisocitric acid is a promising Nrf2 activator targeting DN.