Metabolic escape to glycolysis through SK channel activation inhibits ferroptosis and increases the life span of C. elegans in conditions of heat stress

Metabolic flexibility is a characteristic of essentially all cells in order to cope with environmental alterations. One example of adaptation is represented by a mitochondrial switch from oxidative phosphorylation (OXPHOS) to glycolysis. Attenuation of mitochondrial respiration and cell metabolic shifts have been proposed as therapeutic strategies against oxidative stress and neurodegeneration. Activation of small-conductance Ca2+-activated K+(SK) channels contribute to neuroprotection in conditions of oxidative stress by attenuating mitochondrial calcium ([Ca2+]m), mitochondrial reactive oxygen species (ROS) generation and mitochondrial respiration in neuronal cells. To date, potential effects of SK channels have never been studied in relation to metabolic reprogramming nor the subsequent effects on survival in whole organisms in conditions of oxidative stress. Therefore, we aim to understand the mechanism by which SK channels confer neuroprotection during ferroptosis, a form of cell death associated with oxidative stress, and whether metabolic reprogramming can be part of neuroprotection. Our data show that CyPPA, a positive modulator of SK channels, prevented cell death in conditions of ferroptosis and preserved mitochondrial function. High-resolution respiratory revealed that opening of SK channels alone resulted in a mild decrease of mitochondrial complex I activity. These effects were accompanied by a slight increase in mitochondrial ROS production and depolarization of the mitochondrial membrane, suggesting preconditioning mechanisms to be also involved in the neuroprotection. Experiments where mitochondrial ROS were scavenged showed reduced capacity of CyPPA to mediate neuroprotection. Interestingly, extracellular flux analysis by Seahorse flux analysis technology revealed a CyPPA-mediated initial increase in glycolysis followed by a slight reduction of OXPHOS activity. Induction of glycolysis was crucial for the neuroprotective effects of the SK channel opener, since substances that inhibit glycolysis were able to restore the cell sensitivity to ferroptosis even in the presence of CyPPA. Importantly, we found CyPPA to increase survival of C. elegans challenged with mitochondrial toxins in conditions of heat stress. These findings shed light on new molecular mechanisms mediated by SK channels that could explain the increased neuroprotective capacity in conditions of ferroptosis and neurodegeneration. Support or Funding Information A.M.D. is the recipient of a Rosalind Franklin Fellowship co-funded by the European Union and the University of Groningen. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.