The circadian gene Rev-erbα improves cellular bioenergetics and provides preconditioning for protection against oxidative stress

Diurnal oscillations in the expression of antioxidant genes imply that protection against oxidative stress is circadian-gated. We hypothesized that stabilization of the core circadian gene Rev-erb alpha (Nr1d1) improves cellular bioenergetics and protects against nutrient deprivation and oxidative stress. Compared to WT, mouse lung fibroblasts (MLG) stably transfected with a degradation resistant Rev-erb alpha (Ser(55/59) to Asp; hence referred to as SD) had 40% higher protein content, 1.5-fold higher mitochondrial area (con focal microscopy), doubled oxidative phosphorylation by high-resolution respirometry (Oroboros) and were resistant to glucose deprivation for 24 h. This resulted from a 4-fold reduction in mitophagy (L3CB co-localized with MitoTracker Red) versus WT. Although PGC1 alpha protein expression was comparable between SD and WT MLG cells, the role of mitochondrial biogenesis in explaining increased mitochondrial mass in SD cells was less clear. Embryonic fibroblasts (MEF) from C57BI/6-SD transgenic mice, had a 9-fold induction of FoxO1 mRNA and increased mRNA of downstream antioxidant targets heme oxygenase-1 (HO-1), Mn superoxide dismutase and catalase (1.5, 2 fold and 2 fold respectively) versus WT. This allowed the SD cells to survive 1 h incubation with 500 mu M H2O2 as well as 24 h of exposure to 95% O-2 and remain attached whereas most WT cells did not. These observations establish a mechanistic link between the metabolic functions of Rev-erb alpha with mitochondrial homeostasis and protection against oxidative stress. (C) 2016 Elsevier Inc. All rights reserved.