Rotavirus Induces Intercellular Calcium Waves through ADP Signaling

Abstract

26Rotavirus causes severe diarrheal disease in children worldwide. A hallmark of rotavirus 27 infection is an increase in cytosolic calcium in infected small intestine epithelial cells. However, 28 the underlying mechanism(s) of rotavirus-cell signaling remains incompletely characterized. Here 29 we show that rotavirus-infected cells produce paracrine signals that manifest as intercellular 30 calcium waves (ICWs); which are observed in both cell lines and human intestinal enteroids 31 (HIEs). Rotavirus ICWs are caused by the release of extracellular adenosine diphosphate (ADP) 32 that activates P2Y1 purinergic receptors on neighboring cells and are blocked by P2Y1 33 antagonists or CRISPR/Cas9 knockout of P2Y1. This paracrine purinergic signal is critical for 34 rotavirus replication and diarrhea. Blocking the ICW signal reduces rotavirus replication; inhibits 35 rotavirus-induced serotonin release and fluid secretion; and reduces diarrhea severity in neonatal 36 mice. This is the first evidence that viruses exploit intercellular calcium waves to amplify diarrheal 37 signaling; a finding which have broad implications for gastrointestinal physiology. signaling molecules during RV infection, including enterotoxin NSP4, prostaglandins (PGE2), and 57 nitric oxide (NO) 7,15-17 . In this model, enterotoxin NSP4 can bind to neighboring, uninfected 58 enterocytes to activate Ca 2+ -activated chloride channels and cause secretory diarrhea 18,19 , and 59 PGE2 and NO may further activate fluid secretion processes 20,21 . Dysregulation of neighboring 60 enteroendocrine cells triggers the Ca 2+ -dependent release of serotonin, which stimulates the 61 enteric nervous system both to activate vomiting centers in the central nervous system and to 62 activate secretory reflex pathways in the gastrointestinal (GI) tract 5,22 . Thus, this model of RV-63 induced diarrhea addresses how limited infection at the middle-to-upper villi may cause 64 widespread dysregulation of host physiology and life-threatening disease. 65Herein we demonstrate that RV-infected cells signal to uninfected cells via an extracellular 66 purinergic signaling pathway. This newly identified pathway is a dominant driver of observed RV 67 disease processes, including replication, upregulation of PGE2-and NO-producing enzymes, 68 serotonin secretion, fluid secretion, and diarrhea in a neonatal mouse model. Our findings provide 69 new insights into the mechanism(s) of viral diarrhea and gastrointestinal physiology. 70 Results 71 Low multiplicity infection reveals intercellular calcium waves 72Previous studies have shown that RV significantly increases cytosolic Ca 2+ during infection 73 and disrupts host Ca 2+ -dependent processes to cause disease [23][24][25] . We used African Green 74 monkey kidney MA104 cells stably expressing the genetically-encoded calcium indicator (GECI) 75GCaMP5G or GCaMP6s to observe changes in cytosolic Ca 2+ during RV infection using live-cell 76 time-lapse epifluorescence imaging. We did not observe differences in response using either...

Organoids and organs-on-chips: Insights into human gut-microbe interactions

“…Transcriptional readouts such as qPCR and RNA sequencing is the most accessible means by which to profile the nature of inflammatory responses in any in vitro model system. Especially, the comprehensiveness of RNA sequencing can permit detailed insights into the type of immune response, which is induced in organoids by triggers such as viral infection (Chang-Graham et al, 2020;Drummond et al, 2017;Lamers et al, 2020).…”

“…A recently published virology study showed that the infection of intestinal organoids with rotavirus induced a paracrine ADP/ calcium signal through P2Y1 receptors that led to a deleterious inflammatory response (Chang-Graham et al, 2020). The suitability of an in vitro system for inflammation studies is therefore highly context dependent, with an advantage for organs-onchips where spatial control is important.…”