Quach Andrew, Jayaratne Rashini R, Lee Beom Jae, Ibeawuchi Stella-Rita, Lim Eileen, Das Soumita, Barrett Kim E
School of Medicine, Division of Gastroenterology, Department of Medicine, University of California San Diego, La Jolla, CA, USA.
Department of Gastroenterology, Korea University Guro Hospital, Seoul, Republic of Korea.
J Physiol. 2022 Apr;600(8):1851-1865. doi: 10.1113/JP282585. Epub 2022 Feb 16.
Infections with non-typhoidal Salmonella spp. represent the most burdensome foodborne illnesses worldwide, yet despite their prevalence, the mechanism through which Salmonella elicits diarrhoea is not entirely known. Intestinal ion transporters play important roles in fluid and electrolyte homeostasis in the intestine. We have previously shown that infection with Salmonella caused decreased colonic expression of the chloride/bicarbonate exchanger SLC26A3 (down-regulated in adenoma; DRA) in a mouse model. In this study, we focused on the mechanism of DRA downregulation during Salmonella infection, by using murine epithelial enteroid-derived monolayers (EDMs). The decrease in DRA expression caused by infection was recapitulated in EDMs and accompanied by increased expression of Atonal Homolog 1 (ATOH1), the goblet cell marker Muc2 and the enteroendocrine cell marker ChgA. This suggested biased epithelial differentiation towards the secretory, rather than absorptive phenotype. In addition, the downstream Notch effector, Notch intracellular domain (NICD) and Hes1 were decreased following Salmonella infection. The relevance of Notch signalling was further investigated using a γ-secretase inhibitor, which recapitulated the downregulation in Hes1 and DRA as well as upregulation in ATOH1 and Muc2 seen following infection. Our findings suggest that Salmonella infection may result in a shift from absorptive to secretory cell types through Notch inhibition, which explains why there is a decreased capacity for absorption and ultimately the accumulation of diarrhoeal fluid. Our work also shows the value of EDMs as a model to investigate mechanisms that might be targeted for therapy of diarrhoea caused by Salmonella infection. KEY POINTS: Salmonella is a leading foodborne pathogen known to cause high-chloride-content diarrhoea. Salmonella infection of murine enteroid-derived monolayers decreased DRA expression. Salmonella infection resulted in upregulation of the secretory epithelial marker ATOH1, the goblet cell marker Muc2 and the enteroendocrine cell marker ChgA. Downregulation of DRA may result from infection-induced Notch inhibition, as reflected by decreased expression of Notch intracellular domain and Hes1, as well as from decreased HNF1α signalling. The imbalance in intestinal epithelial differentiation favouring secretory over absorptive cell types is a possible mechanism by which Salmonella elicits diarrhoea and may be relevant therapeutically.
非伤寒沙门氏菌感染是全球最具负担的食源性疾病，然而尽管其普遍存在，但沙门氏菌引发腹泻的机制尚不完全清楚。肠道离子转运体在肠道液体和电解质稳态中发挥重要作用。我们之前在小鼠模型中表明，沙门氏菌感染导致结肠中氯化物/碳酸氢盐交换体SLC26A3（腺瘤下调基因；DRA）的表达降低。在本研究中，我们通过使用小鼠上皮肠样细胞衍生单层（EDM）来聚焦沙门氏菌感染期间DRA下调的机制。感染导致的DRA表达降低在EDM中得到重现，并伴随着无调性同源物1（ATOH1）、杯状细胞标志物Muc2和肠内分泌细胞标志物ChgA的表达增加。这表明上皮细胞分化偏向分泌型而非吸收型表型。此外，沙门氏菌感染后下游Notch效应分子Notch胞内结构域（NICD）和Hes1减少。使用γ-分泌酶抑制剂进一步研究了Notch信号通路的相关性，该抑制剂重现了感染后Hes1和DRA的下调以及ATOH1和Muc2的上调。我们的研究结果表明，沙门氏菌感染可能通过Notch抑制导致从吸收型细胞类型向分泌型细胞类型的转变，这解释了为什么吸收能力下降并最终导致腹泻液的积聚。我们的工作还展示了EDM作为一种模型在研究可能成为沙门氏菌感染所致腹泻治疗靶点的机制方面的价值。关键点：沙门氏菌是一种主要的食源性病原体，已知会导致高氯含量腹泻。小鼠肠样细胞衍生单层的沙门氏菌感染降低了DRA表达。沙门氏菌感染导致分泌型上皮标志物ATOH1、杯状细胞标志物Muc2和肠内分泌细胞标志物ChgA上调。DRA的下调可能是由于感染诱导的Notch抑制，表现为Notch胞内结构域和Hes1表达降低，以及HNF1α信号通路减弱。肠道上皮分化偏向分泌型而非吸收型细胞类型的失衡是沙门氏菌引发腹泻的一种可能机制，并且可能具有治疗相关性。
