The excretory/secretory products of fifth-stage larval Angiostrongylus cantonensis induces autophagy via the Sonic hedgehog pathway in mouse brain astrocytes

Angiostrongyliasis is induced by the nematode Angiostrongylus cantonensis and leads to eosinophilic meningitis and meningoencephalitis in humans. Excretory-secretory products (ESPs) are important investigation targets for studying the relationship between hosts and nematodes. These products assist worms in penetrating the blood-brain barrier and avoiding the host immune response. Autophagy is a catabolic process that is responsible for digesting cytoplasmic organelles, proteins, and lipids and removing them through lysosomes. This process is essential to cell survival and homeostasis during nutritional deficiency, cell injury and stress. In this study, we investigated autophagy induction upon treatment with the ESPs of the fifth-stage larvae (L5) of A. cantonensis and observed the relationship between autophagy and the Shh pathway. First, the results showed that A. cantonensis infection induced blood-brain barrier dysfunction and pathological changes in the brain. Moreover, A. cantonensis L5 ESPs stimulated autophagosome formation and the expression of autophagy molecules, such as LC3B, Beclin, and p62. The data showed that upon ESPs treatment, rapamycin elevated cell viability through the activation of the autophagy mechanism in astrocytes. Finally, we found that ESPs induced the activation of the Sonic hedgehog (Shh) signaling pathway and that the expression of autophagy molecules was increased through the Shh signaling pathway. Collectively, these results suggest that A. cantonensis L5 ESPs stimulate autophagy through the Shh signaling pathway and that autophagy has a protective effect in astrocytes.
Author summary In helminthes, Excretory-secretory products (ESPs) contains a wide range of molecules, including proteins, lipids, glycans, and nucleic acids, that assist in the penetration of host defensive barriers, reduction of oxidative stress, and avoid the host immune attack. It has been known as a key factor for parasite development, including feeding, invasion and molting. Therefore, ESPs is a valuable target for the investigation of the host-parasite relationships. However, only a few researches about the function of Angiostrongyliasis cantonensis ESPs have been verified to date. Angiostrongyliasis cantonensis, a blood-feeding nematode, and it is an important causative agent of eosinophilic meningitis and meningoencephalitis in human. Recent our studies have demonstrated that the A. cantonensis ESPs can induce oxidative stress, apoptosis, and immune response. In this study, we will use a mouse astrocytes as a model to investigate the signaling mechanisms of autophagy induction by ESPs treatment. First, the Microarray, Western blotting, and Transmission electron microscopy data demonstrated that A. cantonensis ESPs can induce autophagy generation in astrocytes. Next, ESPs-induced autophagy was activated via Sonic hedgehog (Shh) signaling, and it has a protective potential for astrocytes. These finding will provide new insights into the mechanisms and effects of the A. cantonensis ESPs.