Potential Effects of SARS-Cov-2 on the Gastrointestinal Tract and Liver
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Biomedicine & Pharmacotherapy 133 (2021) 111064 Contents lists available at ScienceDirect Biomedicine & Pharmacotherapy journal homepage: www.elsevier.com/locate/biopha Review Potential effects of SARS-CoV-2 on the gastrointestinal tract and liver Han-Yu Lei a,b,1, Ying-He Ding a,b,1, Kai Nie a,b,1, Yin-Miao Dong a,b, Jia-Hao Xu a,b, Meng-Ling Yang a,b, Meng-Qi Liu a,b, Le Wei a,b, MI Nasser c, Lin-Yong Xu d,*, Ping Zhu c,*, Ming-Yi Zhao a,* a Department of Pediatrics, The Third Xiangya Hospital, Central South University, Changsha, Hunan, PR China b Xiangya School of Medicine, Central South University, Changsha, Hunan, PR China c Guangdong Cardiovascular Institute, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong, PR China d Xiangya School of Life Science, Central South University, Changsha, Hunan, PR China ARTICLE INFO ABSTRACT Keywords: COVID-19 is a pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Early re COVID-19 ported symptoms include fever, cough, and respiratory symptoms. There were few reports of digestive symptoms. Liver injury However, with COVID-19 spreading worldwide, symptoms such as vomiting, diarrhoea, and abdominal pain Gastrointestinal tract have gained increasing attention. Research has found that angiotensin-converting enzyme 2 (ACE2), the SARS- Gut-lung axis CoV-2 receptor, is strongly expressed in the gastrointestinal tract and liver. Whether theoretically or clinically, Inflammatory cytokine storm Liver transplant many studies have suggested a close connection between COVID-19 and the digestive system. In this review, we summarize the digestive symptoms reported in existing research, discuss the impact of SARS-CoV-2 on the gastrointestinal tract and liver, and determine the possible mechanisms and aetiology, such as cytokine storm. In- depth exploration of the relationship between COVID-19 and the digestive system is urgently needed. 1. Introduction the original underlying conditions can impact patient treatment and prognosis not only in COVID-19 cases but also in gastrointestinal COVID-19, which is caused by SARS-CoV-2, is a significant global diseases. public health problem. As of 29 October 2020, there have been The liver is the body’s largest digestive gland for biligenesis and approximately 44,380,000 confirmedcases of COVID-19 and 1,170,000 detoxification. Liver damage is sometimes identified as a typical deaths worldwide [1]. SARS-CoV-2 belongs to the beta coronavirus occurrence in COVID-19 patients. Through pathology and blood tests, family, which enters cells through the ACE2 receptor [2]. Symptoms the mechanisms of liver injury mainly arise from direct viral infection, involving the digestive system were not evident among patients drug cytotoxicity, and inflammatory immune response. Alternative ex suffering from the initial disease in Wuhan, China. Only 2.6 % had planations include hypoxic hepatitis, hepatic congestion related to me diarrhoea and 2% had chronic diseases of the liver [3]. As the case chanical ventilation (PEEP), and gut barrier dysfunction [4]. Indeed, complexity grows, more and more patients have reported digestive notable facts include the identification of ACE2-positive cells in liver system symptoms. The disorder, with diarrhoea arising most often, is tissues, which turn the liver into a potential target for SARS-CoV-2 marked by diarrhoea, anorexia, nausea, vomiting, abdominal discom infection. Moreover, it has been shown that the associations between fort, and gastrointestinal bleeding. Several potential mechanisms for the prior liver diseases and COVID-19 will contribute to worse clinical development of gastrointestinal problems have been suggested. These outcomes and should be taken seriously during care. Specifically, we include virus-induced cytopathic impacts through ACE2, focus on liver transplant recipients with COVID-19 due to their altered immune-mediated inflammatory cytokine storm, the function of the immune state and disease susceptibility. Further studies in COVID-19 gut-lung axis as well as drug-related harm. These pathways can also patients call for a better understanding of pathogenesis and for contribute to sepsis and acute respiratory distress syndrome (ARDS), optimal treatment of COVID-19. which are the leading causes of death in COVID-19 patients. However, Based on the above statement, we propose that the development and * Corresponding authors. E-mail addresses: [email protected] (L.-Y. Xu), [email protected] (P. Zhu), [email protected] (M.-Y. Zhao). 1 Hanyu Lei, Yinghe Ding, and Kai Nie contributed equally. https://doi.org/10.1016/j.biopha.2020.111064 Received 22 July 2020; Received in revised form 7 November 2020; Accepted 20 November 2020 Available online 28 November 2020 0753-3322/© 2020 Published by Elsevier Masson SAS. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). H.-Y. Lei et al. Biomedicine & Pharmacotherapy 133 (2021) 111064 progression of COVID-19 are closely related to the gastrointestinal tract COVID-19 patients, which means that gastrointestinal symptoms could and the liver. However, there are currently few studies available; thus, be correlated with viral infections in patients with COVID-19. In nearly this article summarizes the relevant views and suggests potential half of the COVID-19 patients with digestive symptoms, viral RNA can mechanisms. be detected in their stool for determining the diagnosis and transmission [12]. The possibility of faecal–oral transmission of SARS-CoV-2 has 2. Gastrointestinal tract involvement in COVID-19 patients important implications and needs further study. Research has shown that SARS-CoV-2 enters cells through the ACE2 2.1. Gastrointestinal symptoms in patients with COVID-19 receiver [2]. Immunofluorescencedata have shown that ACE2 protein is abundantly expressed in gastric, duodenal, and rectal epithelial glan- COVID-19 typically develops in patients as a respiratory disease, dular cells, which promotes the possible entry of SARS-CoV-2 into host with some patients reporting gastrointestinal symptoms during disease cells [8]. Moreover, a study has suggested a possible mechanism for the episodes such as diarrhoea, anorexia, nausea, vomiting, stomach digestive symptoms in COVID-19 patients. ACE2 expression on the small discomfort, and gastrointestinal bleeding. We analysed COVID-19 clin- intestine surface cells can mediate viral invasion and expansion, trig- ical data to show gastrointestinal symptoms and their incidence in pa- gering gastrointestinal inflammation [13]. SARS-CoV-2 invades intesti- tients with COVID-19 (Table 1). Diarrhoea, with a rate ranging from 2.0 nal cells expressing ACE2, causing malabsorption, intestinal disorders, to 47.9%, is the most commonly reported gastrointestinal symptom in activation of the enteric nervous system, and, ultimately, diarrhoea. COVID-19 patients [3,5–9]. Even though the first COVID-19 clinical Interestingly, a previous study on other coronaviruses found that human article reported that only 1 in 38 patients had diarrhoea [3], the fre- intestinal epithelial cells’ high sensitivity to coronavirus increases their quency of diarrhoea is usually greater in later stages. A cohort of 73 replicative capacity [14]. Moreover, this gastrointestinal tropism can COVID-19 patients reported by Xiao et al. showed that diarrhoea was explain the frequent onset of coronaviral diarrhoea (Fig. 1). observed in up to 35.6 % of patients [8]. Similarly, the incidence of diarrhoea was up to 47.9 % in a cohort of 305 patients reported by Fang 2.3. Immune-mediated inflammatory cytokine storm et al. [6]. Although rarely reported, anorexia can occur frequently once diag- The pathogenesis of COVID-19 is not yet clear at the moment. nosed. Wang et al. reported an incidence of up to 39.9 % and Fang et al. Cytokine storms and cellular immune responses are believed to play a reported 33.1 % [6,7]. According to data, patients with nausea account key role in disease occurrence and development [15]. Cytokine distur- for 1.0–19.3 % [5–7,9]. Vomiting, stomach discomfort and gastroin- bance is an abnormal, dynamic pathogenesis inflammatory reaction to testinal bleeding can also be observed in COVID-19 patients, though external stimuli. SARS-CoV-2-infected cells release large numbers of with a low incidence. Regarding the available clinical studies, gastro- inflammatory mediators and chemokines that cause neutrophil aggre- intestinal symptoms are relatively common in patients with COVID-19, gation. While neutrophils mainly have an antiviral function, their se- even though they only manifest in some cases [10]. cretions, cytokines, and chemokines also promote the accumulation of In terms of pathology experiments, Xiao et al. [8] showed that H&E immune cells, which leads to over-reaction. The immune system of staining of the oesophagus, stomach, duodenum, and rectum showed no COVID-19 patients is, therefore, abnormal. Approximately 34.5 % of substantial mucosal epithelial harm. Occasional lymphocyte infiltration 197 patients showed neutrophilia [16], which is known to be a trigger was observed in the oesophageal squamous epithelium in this study. for ARDS and sepsis growth in COVID-19 patients. Secondary hemo- Although the lamina propria of the uterus, duodenum, and rectum were phagocytic lymph histiocytosis (SHLH), an underrecognized hyper- found to display an excess of infiltrating plasma cells and interstitial inflammatory syndrome, could also