Egg-Hatching Mechanism of Human Liver Fluke,Opisthorchis viverrini: A Role For Leucine Aminopeptidases From the Snail Host,Bithynia siamensis goniomphalos

Abstract

The human liver fluke Opisthorchis viverrini (Platyhelminthes, Trematoda, Digenea) uses snails of the genus Bithynia as first intermediate host. Peculiarly among trematodes, the eggs of O. viverrini hatch within the digestive tract of its snail host. It remains uncertain whether hatching in this species is mediated through mechanical fracture of the eggshell or by digestion with specific digestive enzymes. This study aimed to characterize enzymes with specific inhibitors and factors involved in the hatching activity of O. viverrini eggs. For measuring egg hatching in vivo, 50 O. viverrini mature eggs were fed to individual Bithynia siamensis goniomphalos snails at various temperature conditions for 24 hr. Ex vivo, mature eggs were incubated with crude snail extract and commercial leucine aminopeptidase (LAP). Egg-hatching of O. viverrini was temperature dependent, with optimal hatching occurring at 24-28 C, with a peak of hatching of 93.54% in vivo and 30.55% ex vivo occurring at these temperatures. Ex vivo hatching rates increased to 45.87% under anaerobic conditions at 28 C. Some 22.70% and 16.21% of heat-killed eggs also hatched within the snail digestive tract and snail extract, respectively, indicating that host molecules are involved in the hatching response. Most eggs hatch in the anterior regions of the digestive tract. Hatching was completely inhibited in the presence of bestatin, an inhibitor of LAP, but not in the presence of phosphatase inhibitors. Bestatin inhibition of hatching was reversible. Finally, egg hatching could be induced by addition of a porcine LAP. The results indicate that this digenean utilizes both LAP of the snail host and movement of miracidia for hatching.

Ubenimex combined with Albendazole for the treatment of Echinococcus multilocularis-induced alveolar echinococcosis in mice

“…Ubenimex is one of LAP inhibitors that can reduce the activity of LAP, and therefore it can reduce the digestion of liver tissues, fibrogenesis and infiltrative growth (8,47,48). It has also reported that Ubenimex can reduce the invasiveness and damage of other parasites like Leishmania, Human liver fluke, plasmodium by inhibiting the LAP proteins levels (27,49,50). In some malignant tumors, Ubenimex can also inhibit the migration and invasion by alleviating the activity of the LAP (CD13)/NAB1/MAPK pathway (51)(52)(53)(54).…”

The clock gene Cryptochrome 1 is involved in the photoresponse of embryonic hatching behavior in Bombyx mori

“…Egg hatching is a complex process that involves multiple synergies including neuronal activity, hormone secretion, protease synthesis and energy metabolism (Khampoosa et al, 2018; Konopová et al, 2020). Injecting corticotropin‐releasing hormone into the egg embryos of domestic chickens ( Gallus gallus ) results in the release of adrenocorticosteroids and thyroid hormones, speeding up egg hatching (Watanabe et al, 2017).…”

“…Egg hatching is a complex process that involves multiple synergies including neuronal activity, hormone secretion, protease synthesis and energy metabolism (Khampoosa et al, 2018;Konopová et al, 2020). Injecting F I G U R E 7 The putative pathway that the circadian clock regulates hatching rhythm of silkworm.…”