TY - JOUR
T1 - Cold exposure causes cell death by depolarization-mediated Ca2+ overload in a chill-susceptible insect
AU - Bayley, Jeppe Seamus
AU - Winther, Christian Bak
AU - Andersen, Mads Kuhlmann
AU - Grønkjær, Camilla
AU - Nielsen, Ole Bækgaard
AU - Pedersen, Thomas Holm
AU - Overgaard, Johannes
PY - 2018
Y1 - 2018
N2 - Cold tolerance of insects is arguably among the most important traits defining their geographical distribution. Even so, very little is known regarding the causes of cold injury in this species-rich group. In many insects it has been observed that cold injury coincides with a cellular depolarization caused by hypothermia and hyperkalemia that develop during chronic cold exposure. However, prior studies have been unable to determine if cold injury is caused by direct effects of hypothermia, by toxic effects of hyperkalemia, or by the depolarization that is associated with these perturbations. Here we use a fluorescent DNA-staining method to estimate cell viability of muscle and hindgut tissue from Locusta migratoria and show that the cellular injury is independent of the direct effects of hypothermia or toxic effects of hyperkalemia. Instead, we show that chill injury develops due to the associated cellular depolarization. We further hypothesized that the depolarization-induced injury was caused by opening of voltage-sensitive Ca2+ channels, causing a Ca2+ overload that triggers apoptotic/necrotic pathways. In accordance with this hypothesis, we show that hyperkalemic depolarization causes a marked increase in intracellular Ca2+ levels. Furthermore, using pharmacological manipulation of intra- and extracellular Ca2+ concentrations as well as Ca2+ channel conductance, we demonstrate that injury is prevented if transmembrane Ca2+ flux is prevented by removing extracellular Ca2+ or blocking Ca2+ influx. Together these findings demonstrate a causal relationship between cold-induced hyperkalemia, depolarization, and the development of chill injury through Ca2+-mediated necrosis/apoptosis.
AB - Cold tolerance of insects is arguably among the most important traits defining their geographical distribution. Even so, very little is known regarding the causes of cold injury in this species-rich group. In many insects it has been observed that cold injury coincides with a cellular depolarization caused by hypothermia and hyperkalemia that develop during chronic cold exposure. However, prior studies have been unable to determine if cold injury is caused by direct effects of hypothermia, by toxic effects of hyperkalemia, or by the depolarization that is associated with these perturbations. Here we use a fluorescent DNA-staining method to estimate cell viability of muscle and hindgut tissue from Locusta migratoria and show that the cellular injury is independent of the direct effects of hypothermia or toxic effects of hyperkalemia. Instead, we show that chill injury develops due to the associated cellular depolarization. We further hypothesized that the depolarization-induced injury was caused by opening of voltage-sensitive Ca2+ channels, causing a Ca2+ overload that triggers apoptotic/necrotic pathways. In accordance with this hypothesis, we show that hyperkalemic depolarization causes a marked increase in intracellular Ca2+ levels. Furthermore, using pharmacological manipulation of intra- and extracellular Ca2+ concentrations as well as Ca2+ channel conductance, we demonstrate that injury is prevented if transmembrane Ca2+ flux is prevented by removing extracellular Ca2+ or blocking Ca2+ influx. Together these findings demonstrate a causal relationship between cold-induced hyperkalemia, depolarization, and the development of chill injury through Ca2+-mediated necrosis/apoptosis.
KW - Calcium
KW - Cold injury
KW - Depolarization
KW - Hyperkalemia
KW - Insect
UR - http://www.scopus.com/inward/record.url?scp=85054708885&partnerID=8YFLogxK
U2 - 10.1073/pnas.1813532115
DO - 10.1073/pnas.1813532115
M3 - Journal article
C2 - 30254178
SN - 0027-8424
VL - 115
SP - E9737-E9744
JO - Proceedings of the National Academy of Sciences
JF - Proceedings of the National Academy of Sciences
IS - 41
ER -