Microbes Evolution Phylogeny and Infections (MEPHI), Institut de recherche pour le Développement (IRD), Assistance Publique Hôpitaux de Marseille (APHM), Institut Hospitalo-Universitaire (IHU)-Méditerranée Infection, Marseille, France.
Aix-Marseille Université, Marseille, France.
Front Cell Infect Microbiol. 2022 May 4;12:798767. doi: 10.3389/fcimb.2022.798767. eCollection 2022.
COVID-19 is the biggest pandemic the world has seen this century. Alongside the respiratory damage observed in patients with severe forms of the disease, gastrointestinal symptoms have been frequently reported. These symptoms (e.g., diarrhoea), sometimes precede the development of respiratory tract illnesses, as if the digestive tract was a major target during early SARS-CoV-2 dissemination. We hypothesize that in patients carrying intestinal SARS-CoV-2, the virus may trigger epithelial barrier damage through the disruption of E-cadherin (E-cad) adherens junctions, thereby contributing to the overall gastrointestinal symptoms of COVID-19. Here, we use an intestinal Caco-2 cell line of human origin which expresses the viral receptor/co-receptor as well as the membrane anchored cell surface adhesion protein E-cad to investigate the expression of E-cad after exposure to SARS-CoV-2. We found that the expression of /E-cad mRNA was significantly lower in cells infected with SARS-CoV-2 at 24 hours post-infection, compared to virus-free Caco-2 cells. The viral receptor ACE2 mRNA expression was specifically down-regulated in SARS-CoV-2-infected Caco-2 cells, while it remained stable in HCoV-OC43-infected Caco-2 cells, a virus which uses HLA class I instead of ACE2 to enter cells. It is worth noting that SARS-CoV-2 induces lower transcription of TMPRSS2 (involved in viral entry) and higher expression of BAT1 mRNA (that encodes a protein known to co-express with ACE2 on intestinal cells). At 48 hours post-exposure to the virus, we also detected a small but significant increase of soluble E-cad protein (sE-cad) in the culture supernatant of SARS-CoV-2-infected Caco-2 cells. The increase of sE-cad release was also found in the intestinal HT29 cell line when infected by SARS-CoV-2. Beside the dysregulation of E-cad, SARS-CoV-2 infection of Caco-2 cells also leads to the dysregulation of other cell adhesion proteins (occludin, JAMA-A, zonulin, connexin-43 and PECAM-1). Taken together, these results shed light on the fact that infection of Caco-2 cells with SARS-CoV-2 affects tight-, adherens-, and gap-junctions. Moreover, intestinal tissues damage was associated to the intranasal SARS-CoV-2 infection in human ACE2 transgenic mice.
COVID-19 是本世纪全球遭遇的最大规模的流行病。除了在患有严重疾病的患者中观察到的呼吸道损伤外，还经常报告胃肠道症状。这些症状（例如腹泻）有时先于呼吸道疾病的发展，似乎在 SARS-CoV-2 早期传播过程中，消化道是主要靶点。我们假设，在携带肠道 SARS-CoV-2 的患者中，病毒可能通过破坏 E-钙粘蛋白（E-cad）黏附连接来触发上皮屏障损伤，从而导致 COVID-19 的整体胃肠道症状。在这里，我们使用源自人源的肠 Caco-2 细胞系，该细胞系表达病毒受体/辅助受体以及膜锚定细胞表面黏附蛋白 E-cad，以研究暴露于 SARS-CoV-2 后 E-cad 的表达。我们发现，与未感染病毒的 Caco-2 细胞相比，感染 SARS-CoV-2 的细胞在感染后 24 小时，E-cad mRNA 的表达明显降低。SARS-CoV-2 感染的 Caco-2 细胞中病毒受体 ACE2 mRNA 的表达被特异性下调，而在使用 HLA Ⅰ类而不是 ACE2 进入细胞的 HCoV-OC43 感染的 Caco-2 细胞中，ACE2 mRNA 的表达保持稳定。值得注意的是，SARS-CoV-2 诱导 TMPRSS2（参与病毒进入）的转录水平降低，而 BAT1 mRNA（编码一种已知与 ACE2 在肠道细胞上共同表达的蛋白）的表达增加。暴露于病毒 48 小时后，我们还在 SARS-CoV-2 感染的 Caco-2 细胞的培养上清液中检测到可溶性 E-cad 蛋白（sE-cad）的小但显著增加。当 SARS-CoV-2 感染 HT29 细胞系时，也发现了 sE-cad 释放的增加。除了 E-cad 的失调外，SARS-CoV-2 感染 Caco-2 细胞还导致其他细胞黏附蛋白（occludin、JAMA-A、zonulin、connexin-43 和 PECAM-1）的失调。总的来说，这些结果表明，SARS-CoV-2 感染 Caco-2 细胞会影响紧密连接、黏附连接和缝隙连接。此外，在人源 ACE2 转基因小鼠中，鼻内 SARS-CoV-2 感染与肠道组织损伤有关。
