An ancient cytokine, astakine, mediates circadian regulation of invertebrate hematopoiesis

Abstract

Invertebrate circulating hemocytes are key players in the innate immune defense and their continuous renewal from hematopoietic tissues is tightly regulated in crustaceans by astakine, a new family of cytokines sharing a prokineticin (PROK) domain. In vertebrates, brain PROKs function as transmitters of circadian rhythms and we present evidence that hemocyte release from hematopoietic tissues in crayfish is under circadian regulation, a direct result of rhythmic expression of astakine. We demonstrate that the observed variation in astakine expression has an impact on innate immunity assessed as susceptibility to a pathogenic Pseudomonas species. These findings enlighten the importance of comparing immune responses at fixed times not to neglect circadian regulation of innate immunity. Moreover, our results entail an evolutionary conserved function for prokineticins as mediators of circadian rhythm, and for the first time show a role for this domain in circadian regulation of hematopoiesis that may have implications also in vertebrates.

Temperature regulates circadian rhythms of immune responses in red swamp crayfish Procambarus clarkii

“…Aeromonas hydrophila used in the present study were originally isolated from water of artificial lake within Qingdao Agricultural University and cultured in LuriaeBertani's rich nutrient medium supplemented with 100 mg L À1 ampicillin overnight at 28 C. Subsequently, bacteria were washed three times with CFS (Crayfish Saline Buffer, 0.2 M NaCl, 5.4 mM KCl, 10 mM CaCl 2 , 2 mM NaHCO 3 , pH 6.8) [22] to remove the culture medium and dissolved in CFS. Bacterial concentration was measured with viable plate counts and recorded by colony forming units (CFUs) per milliliter.…”

“…To measure total hemocyte count (THC) in hemolymph of crayfish, hemolymph was sampled at different time points after treatment with 24 C/18 C 12 h/12 h temperature cycles, and fixed with 10% formalin in CFS according to Watthanasurorot et al [22]. Hemolymph was dropped onto a clean hemocytometer and THC was examined under phase-contrast microscope.…”

Unique diversity of the venom peptides from the scorpion Androctonus bicolor revealed by transcriptomic and proteomic analysis

“…Recently, it was found that Astakines play essential roles in the hematopoiesis of invertebrates [68,69].…”

Crustacean hematopoiesis and the astakine cytokines

“…38 Ast1 is highly expressed in the early morning after a dark period, and expression gradually decreases during exposure to light. Recent genetic and physiologic evidence has shown that vertebrate PROKs are transmitters of circadian rhythms of the suprachiasmatic nucleus in the brain of mammals.…”