Dysregulation of Nrf2 redox pathway in macrophages under diabetic microenvironment

In the present study, we characterized the aberration in Nrf2 signaling in macrophages under a hyperglycemic microenvironment that reflects diabetic wounds in vitro and studied the effect of an Nrf2 activator pterostilbene (PTS) in these experimental conditions. Macrophages were exposed to pro-inflammatory cytokines TNFα and IFNγ with (HG+) or without high glucose (NG+) followed by the treatment with or without PTS. Western blotting was undertaken to assess the Nrf2 translocation from cytosol to nucleus followed by its downstream and upstream mediators, heme oxygenase-1 and Akt, respectively, the latter via phosphorylation. Quantitative PCR was also carried out to check the expression of macrophage mannose receptor CD206. We found a 2-fold reduction in the activation of Nrf2 in the HG+ group at 24 h compared to NG+, which was significantly improved by the treatment with PTS. Reduction in the levels of heme oxygenase-1 and phosphorylation of Akt in the HG+ group was also ameliorated by PTS. Furthermore, the gene expression of CD206 that was significantly reduced in the HG+ group was also restored by PTS treatment. The disruption of Nrf2 signaling in macrophages in a hyperglycemic microenvironment in vitro may indeed reflect diabetic wounds, as opposed to other non-diabetic wounds.