Visible light reduces C. elegans longevity.

The transparent nematode Caenorhabditis elegans can sense UV and blue-violet light to alter behavior. Because high-dose UV and blue-violet light are not a common feature outside of the laboratory setting, we asked what role, if any, could low-intensity visible light play in C. elegans physiology and longevity. Here, we show that C. elegans lifespan is inversely correlated to the time worms were exposed to visible light. While circadian control, lite-1 and tax-2 do not contribute to the lifespan reduction, we demonstrate that visible light creates photooxidative stress along with a general unfolded-protein response that decreases the lifespan. Finally, we find that long-lived mutants are more resistant to light stress, as well as wild-type worms supplemented pharmacologically with antioxidants. This study reveals that transparent nematodes are sensitive to visible light radiation and highlights the need to standardize methods for controlling the unrecognized biased effect of light during lifespan studies in laboratory conditions.

Metabolic control of regulatory T cell (Treg) survival and function by Lkb1.

The metabolic programs of functionally distinct T cell subsets are tailored to their immunologic activities. While quiescent T cells use oxidative phosphorylation (OXPHOS) for energy production, and effector T cells (Teffs) rely on glycolysis for proliferation, the distinct metabolic features of regulatory T cells (Tregs) are less well established. Here we show that the metabolic sensor LKB1 is critical to maintain cellular metabolism and energy homeostasis in Tregs. Treg-specific deletion of Lkb1 in mice causes loss of Treg number and function, leading to a fatal, early-onset autoimmune disorder. Tregs lacking Lkb1 have defective mitochondria, compromised OXPHOS, depleted cellular ATP, and altered cellular metabolism pathways that compromise their survival and function. Furthermore, we demonstrate that the function of LKB1 in Tregs is largely independent of the AMP-activated protein kinase, but is mediated by the MAP/microtubule affinity-regulating kinases and salt-inducible kinases. Our results define a metabolic checkpoint in Tregs that couples metabolic regulation to immune homeostasis and tolerance.