Contribution of CD4+ T cell mediated inflammation to diarrhoea in patients with COVID-19

Farnesoid X receptor enhances epithelial ACE2 expression and inhibits virally induced IL-6 secretion: implications for intestinal symptoms of SARS-CoV-2

Intestinal inflammation and diarrhea are often associated with SARS-CoV-2 infection. The angiotensin converting enzyme 2 (ACE2) receptor plays a key role in SARS-CoV-2 pathogenesis, facilitating entry of the virus into epithelial cells, while also regulating mucosal inflammatory responses. Here, we investigated roles for the nuclear bile acid receptor farnesoid X receptor (FXR) in regulating ACE2 expression and virally mediated inflammatory responses in intestinal epithelia. Human colonic or ileal enteroids and cultured T84 and Caco-2 monolayers were treated with the FXR agonists, obeticholic acid (OCA) or GW4064, or infected with live SARS-CoV-2 (2019-nCoV/USA_WA1/2020). Changes in mRNA, protein, or secreted cytokines were measured by qPCR, Western blotting, and ELISA. Treatment of undifferentiated colonic or ileal enteroids with OCA increased ACE2 mRNA by 2.1 ± 0.4-fold (n = 3; P = 0.08) and 2.3 ± 0.2-fold (n = 3; P < 0.05), respectively. In contrast, ACE2 expression in differentiated enteroids was not significantly altered. FXR activation in cultured epithelial monolayers also upregulated ACE2 mRNA, accompanied by increases in ACE2 expression and secretion. Further experiments revealed FXR activation to inhibit IL-6 release from both Caco-2 cells infected with SARS-CoV-2 and T84 cells treated with the viral mimic, polyinosinic:polycytidylic acid, by 46 ± 12% (n = 3, P < 0.05) and 35 ± 6% (n = 8; P < 0.01), respectively. By virtue of its ability to modulate epithelial ACE2 expression and inhibit virus-mediated proinflammatory cytokine release, FXR represents a promising target for the development of new approaches to prevent intestinal manifestations of SARS-CoV-2.NEW & NOTEWORTHY Activation of the nuclear bile acid receptor, farnesoid X receptor (FXR), specifically upregulates ACE2 expression in undifferentiated colonic epithelial cells and inhibits virus-induced proinflammatory cytokine release. By virtue of these actions FXR represents a promising target for the development of new approaches to prevent intestinal manifestations of SARS-CoV-2 infection.

COVID-19 and Gastrointestinal Tract: From Pathophysiology to Clinical Manifestations

Background: Since its first report in Wuhan, China, in December 2019, COVID-19 has become a pandemic, affecting millions of people worldwide. Although the virus primarily affects the respiratory tract, gastrointestinal symptoms are also common. The aim of this narrative review is to provide an overview of the pathophysiology and clinical manifestations of gastrointestinal COVID-19. Methods: We conducted a systematic electronic search of English literature up to January 2023 using Medline, Scopus, and the Cochrane Library, focusing on papers that analyzed the role of SARS-CoV-2 in the gastrointestinal tract. Results: Our review highlights that SARS-CoV-2 directly infects the gastrointestinal tract and can cause symptoms such as diarrhea, nausea/vomiting, abdominal pain, anorexia, loss of taste, and increased liver enzymes. These symptoms result from mucosal barrier damage, inflammation, and changes in the microbiota composition. The exact mechanism of how the virus overcomes the acid gastric environment and leads to the intestinal damage is still being studied. Conclusions: Although vaccination has increased the prevalence of less severe symptoms, the long-term interaction with SARS-CoV-2 remains a concern. Understanding the interplay between SARS-CoV-2 and the gastrointestinal tract is essential for future management of the virus.

COVID-19 and Gut Injury

COVID-19 induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently a pandemic and it has led to more than 620 million patients with 6.56 million deaths globally. Males are more susceptible to COVID-19 infection and associated with a higher chance to develop severe COVID-19 than females. Aged people are at a high risk of COVID-19 infection, while young children have also increased cases. COVID-19 patients typically develop respiratory system pathologies, however symptoms in the gastrointestinal (GI) tract are also very common. Inflammatory cell recruitments and their secreted cytokines are found in the GI tract in COVID-19 patients. Microbiota changes are the key feature in COVID-19 patients with gut injury. Here, we review all current known mechanisms of COVID-19-induced gut injury, and the most acceptable one is that SARS-CoV-2 binds to angiotensin-converting enzyme 2 (ACE2) receptor on host cells in the GI tract. Interestingly, inflammatory bowel disease (IBD) is an inflammatory disorder, but the patients with IBD do not have the increased risk to develop COVID-19. There is currently no cure for COVID-19, but anti-viruses and monoclonal antibodies reduce viral load and shorten the recovery time of the disease. We summarize current therapeutics that target symptoms in the GI tract, including probiotics, ACE2 inhibitors and nutrients. These are promising therapeutic options for COVID-19-induced gut injury.

Spotlight on therapeutic efficiency of mesenchymal stem cells in viral infections with a focus on COVID-19

The SARS-COV-2 virus has infected the world at a very high rate by causing COVID-19 disease. Nearly 507 million individuals have been infected with this virus, with approximately 1.2% of these patients being dead, indicating that this virus has been out of control in many countries. While researchers are investigating how to develop efficient drugs and vaccines versus the COVID-19 pandemic, new superseded treatments have the potential to reduce mortality. The recent application of mesenchymal stem cells (MSCs) in a subgroup of COVID-19 patients with acute respiratory distress has created potential benefits as supportive therapy for this viral contagion in patients with acute conditions and aged patients with severe pneumonia. Consequently, within this overview, we discuss the role and therapeutic potential of MSCs and the challenges ahead in using them to treat viral infections, with highlighting on COVID-19 infection.