Alterações inflamatórias, secretórias e morfofuncionais em jejuno de camundongos C57BL/6 inoculados com a espícula do coronavírus SARS-COV-2

Abstract

INTRODUCTION: SARS-CoV-2 is the virus responsible for Coronavirus Disease 2019 (COVID-19), studies have reported the incidence of gastrointestinal symptoms including diarrhea, nausea/vomiting and abdominal pain. However, so far, experimental models that allow understanding the pathophysiology of COVID-19 in the gastrointestinal tract are extremely limited. Thus, inoculation of the SARS-CoV-2 spike into the jejunal loops could be an experimental tool to study the pathobiology of this virus in the GI tract. OBJECTIVE: To evaluate the inflammatory, secretory and morphofunctional alterations caused by the inoculation of the spike in the jejunal loops of mice. METHODS: For the in silico assays, molecular docking was performed to evaluate the interaction between the spike and the receptors involved in the secretion of intestinal electrolytes. The in vivo model was based on the intestinal loop method with spike inoculation in isolated jejunal loops. The animals were sacrificed, the intestinal loops and fluids collected for secretory, inflammatory, morphological, functional and contractile analyses. RESULTS: Our in silico data showed that the spike binds to CFTR (-1658.2 kcal.mol-1) and CaCC (-1593.3 kcal.mol-1). While in vivo data show that the inoculation peak showed an increase (p<0.05) in Volume of Intestinal Contents (VCI - 288.6 ± 60.45 µl), accompanied by Cl- secretion (0.07541 ± 0.006 mEq/L), intestinal edema (increase in wet weight - 109.2 ± 8.62 mg /cm) and increased (p<0.05) Myeloperoxidase (MPO) activity (14.59 ± 1.50 U/mg of tissue). Histopathological images showed that the spike induced migration of inflammatory cells (2.22 ± 0.06), epithelial changes (2.06 ± 0.07) and disarray in the mucosal histoarchitecture (1.97 ± 0.07). In addition, they present a decrease in the muscle layer (57.88 ± 0.866 µm), submucosa (37.98 ± 0.663 µm) and mucosa (120.9 ± 1.559 µm), with a reduction in depth (65.60 ± 1.142 µm) and width (38.21 ± 0.45 µm) of the crypts, decrease in the height of the villi (218 ± 3.84 µm) and enterocytes (12.73 ± 0.20 µm), respectively increasing the width (Villi: 77, 60 ± 1.69 µm; Enterocytes: 6.08 ± 0.10 µm). There was a decrease in Paneth cells (2.29 ± 0.05 - 20.3% per crypt) and goblet cells, including a decrease in neutral mucins (PAS) 12.15 ± 0.49), sulfomucins (AB pH 1.0 – 8.53 ± 0.34) and sialomucins (AB pH 2.5 – 6.26 ± 0.28). The spike promoted a decrease (p<0.05) in the expression of occludin (12.08 ± 1.60 kDa) and basal RET (9.29 ± 0.54 Ω/cm2) and showed a reduction (p<0.05) of the electromechanical response (0.123 ± 0.02 g ). CONCLUSION: It is concluded that the spike triggered changes in the intestinal mucosa, characterized by: 1) Secretion, including tissue dilation, accumulation of intestinal fluid and efflux of Cl- ions; 2) Inflammatory response, consisting of edema and polymorphonuclear infiltrate; 3) Histopathological changes in the jejunum; 4) Impairment of jejunal integrity, as a result of decreased expression of TJs occludin and basal RET and 5) Electromechanical functional changes, mediated by decreased intestinal contraction force.