Spatio-temporal analysis of the Nrf2 activation in transgenic reporter mouse fed with high dosage of saturated or unsaturated fatty acids using in vivo bioluminescent imaging

Nuclear factor-E2 related factor 2 (Nrf2) induces the transcription of genes coding for antioxidant enzymes by binding to the Antioxidant Response Element (ARE) to contrast oxidative stress in organisms. The aim of the study was to evaluate the activation of Nrf2 in transgenic reporter mice fed saturated or polyunsaturated fatty acids and the anti-inflammatory effect of estrogens on organism. Forty-eight ARE CRE OMO reporter mice were divided into 3 groups, consisting of 16 animals, based on presence/absence of estrogens (ovariectomized female, OVX; sham female, SH; male, MA). Each group was further split in 4 subgroups of 4 animals each and fed different diets (7.5% lard, 7.5% tuna oil, 20.0% lard and 20.0% tuna oil). All diets were isonitrogenous; low fat diets were mutually isocaloric, as well as high fat diets. Twice weekly animals were injected i.p. with 100mL luciferin 15 min before the imaging session (5 min., Charge Couple Device Camera, CCD) and kept under anaesthesia while performing ventral acquisition. Photon emission in selected body areas was measured using the Living Image Software. On day 70, experimental mice were subjected to a challenge with Sodium Arsenite and subsequently sacrificed. Specific organs (i.e. brain, muscle, heart, abdominal adipose tissue, urinary bladder, stomach, liver, lung, kidney, intestine, seminal vesicles, testis, spleen, bone, ovary and uterus) were dissected and immediately subjected to ex vivo imaging session. Data were analysed by MIXED and GLM procedures of SAS software and significant differences were declared for p<.05. The results showed that dietary treatments did not affect body weight and feed intake as well as Nrf2 expression in both pre- and postchallenge phases, excepting for the abdominal region (p¼.031 pre-challenge); in this area, during the pre-challenge phase, OVX showed lower Nrf2 activation (p<.001). Ex vivo results outlined a significant effect of the challenge on all the considered organs (p<.001), while OVX subjects had higher Nrf2 expression on urinary bladder and kidney (p<.05) and high fat diet increased Nrf2 in urinary bladder (p<.05).Based on our findings, there is not any difference between addition of saturated or n-3 polyunsaturated fatty acids on oxidative stress. This study confirmed the protective role of estrogens under physiological condition.