Fig. 4. Vitamin D regulation of Ca2þ and redox signalling stability. The arrows represent those signalling components that are either enhanced (green arrows) or reduced (red
arrows) by Vitamin D and Nrf-2. The main reactive oxygen species (ROS) in cells are superoxide (O2
_.), hydrogen peroxide (H2O2) and peroxynitrite (ONOO). The dashed lines
represent the many interactions that operate between the Ca2þ and redox signalling pathways. The yellow box summarizes some of the redox and Ca2þ signalling components that
are controlled by the Vitamin D/Nrf2/klotho regulatory system.