Department of Biology, York University, Toronto, ON, Canada M3J 1P3
Department of Biology, York University, Toronto, ON, Canada M3J 1P3.
J Exp Biol. 2018 Oct 1;221(Pt 19):jeb185884. doi: 10.1242/jeb.185884.
For insects, chilling injuries that occur in the absence of freezing are often related to a systemic loss of ion and water balance that leads to extracellular hyperkalemia, cell depolarization and the triggering of apoptotic signalling cascades. The ability of insect ionoregulatory organs (e.g. the Malpighian tubules) to maintain ion balance in the cold has been linked to improved chill tolerance, and many neuroendocrine factors are known to influence ion transport rates of these organs. Injection of micromolar doses of CAPA (an insect neuropeptide) have been previously demonstrated to improve cold tolerance, but the mechanisms through which it impacts chill tolerance are unclear, and low doses of CAPA have been previously demonstrated to cause anti-diuresis in insects, including dipterans. Here, we provide evidence that low (femtomolar) and high (micromolar) doses of CAPA impair and improve chill tolerance, respectively, via two different effects on Malpighian tubule ion and water transport. While low doses of CAPA are anti-diuretic, reduce tubule K clearance rates and reduce chill tolerance, high doses facilitate K clearance from the haemolymph and increase chill tolerance. By quantifying CAPA peptide levels in the central nervous system, we estimated the maximum achievable hormonal titres of CAPA and found further evidence that CAPA may function as an anti-diuretic hormone in We provide the first evidence of a neuropeptide that can negatively affect cold tolerance in an insect and further evidence of CAPA functioning as an anti-diuretic peptide in this ubiquitous insect model.
对于昆虫来说，在没有冻结的情况下发生的冷伤通常与离子和水平衡的系统性丧失有关，这会导致细胞外高钾血症、细胞去极化和凋亡信号级联的触发。昆虫离子调节器官（例如，马氏管）在寒冷中维持离子平衡的能力与提高耐寒性有关，许多神经内分泌因素被认为会影响这些器官的离子运输速率。先前已经证明，注射微摩尔剂量的 CAPA（一种昆虫神经肽）可以提高耐寒性，但它影响耐寒性的机制尚不清楚，并且先前已经证明低剂量的 CAPA 会导致昆虫，包括双翅目昆虫的抗利尿作用。在这里，我们提供的证据表明，低（飞摩尔）和高（微摩尔）剂量的 CAPA 通过对马氏管离子和水转运的两种不同影响分别损害和提高耐寒性。虽然低剂量的 CAPA 具有抗利尿作用，降低小管 K 清除率并降低耐寒性，但高剂量有助于从血液中清除 K 并提高耐寒性。通过定量中央神经系统中的 CAPA 肽水平，我们估计了 CAPA 的最大可实现激素效价，并进一步证明 CAPA 可能在昆虫中作为抗利尿激素发挥作用。我们提供了第一个证据，证明一种神经肽可以在昆虫中对耐寒性产生负面影响，并进一步证明 CAPA 在这种普遍存在的昆虫模型中作为抗利尿肽发挥作用。
