389A Poster - 04. Stem cells, regeneration and tissue injury
Thursday April 07, 2:00 PM - 4:00 PM

Authors:
Mariya Prokhorenko; Jeremy Smyth

Affiliation: Uniformed Services University of the Health Sciences

Keywords:
n. injury; t. other (thermosensation, nociception)

Chronic pain following injury is a debilitating condition associated with serious comorbidities and opioid dependence. Understanding the neurological mechanisms that underlie the transition from initial injury to chronic pain is essential for prevention and treatment. This transition is mediated by central sensitization, which involves reversible changes to nociceptive neurocircuitry pathways in the central nervous system. Central sensitization research and therapeutics have focused on neuronal circuitry, whereas the roles of glial cells are poorly defined. Notably, astrocytes that normally maintain and modulate neuronal synapses become reactive and exhibit aberrant Ca²⁺ signals during central sensitization. However, how these Ca²⁺ signals are generated and how they modulate astrocyte function in central sensitization are unknown. Importantly, central sensitization involves significant upregulation of glutamate release at nociceptive synapses, and glutamate acts on astrocytes via metabotropic glutamate receptors to stimulate Ca²⁺ release from endoplasmic reticulum (ER) Ca²⁺ stores via inositol 1,4,5-tripshosphate receptors (IP₃R). We are testing the hypothesis that central sensitization requires astrocyte metabotropic signaling involving IP₃R-mediated Ca²⁺ release from ER Ca²⁺ stores and activation of store-operated Ca²⁺ entry (SOCE). We are testing this by combining powerful genetic tools with a robust model of central pain sensitization in Drosophila melanogaster. We assay central sensitization in flies by amputating a single leg and monitoring the response to subnoxious temperatures. Injured, sensitized animals exhibit increased jumping behavior at the subnoxious temperature, whereas animals without injury do not respond to this temperature. Using a combination of fluorescence imaging techniques, we show enhanced astrocyte Ca²⁺ signaling in the ventral nerve cord precedes behaviorally measured central sensitization after injury, including changes in live signaling using GCaMP and cumulative signaling using Transcriptional Reporter of Intracellular Calcium (TRIC). We also found that astrocyte-specific suppression of IP₃R as well as the SOCE components Stim and Orai attenuates nociceptive jumping behavior at one week following nerve injury, suggesting a key role for IP₃R and SOCE-mediated Ca²⁺ signaling in astrocytes during pain sensitization. Our results will bring new understanding to the role of astrocyte signaling in pain sensitization and may suggest novel therapeutic targets for the prevention or treatment of chronic pain.