Intestinal barrier dysfunction as a key driver of severe COVID-19

The intestinal lumen harbors a diverse consortium of microorganisms that participate in reciprocal crosstalk with intestinal immune cells and with epithelial and endothelial cells,forming a multi-layered barrier that enables the efficient absorption of nutrients without an excessive influx of pathogens.Despite being a lung-centered disease,severe coronavirus disease 2019(COVID-19)affects multiple systems,including the gastrointestinal tract and the pertinent gut barrier function.Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)can inflict either direct cytopathic injury to intestinal epithelial and endothelial cells or indirect immune-mediated damage.Alternatively,SARS-CoV-2 undermines the structural integrity of the barrier by modifying the expression of tight junction proteins.In addition,SARS-CoV-2 induces profound alterations to the intestinal microflora at phylogenetic and metabolomic levels(dysbiosis)that are accompanied by disruption of local immune responses.The ensuing dysregu-lation of the gut-lung axis impairs the ability of the respiratory immune system to elicit robust and timely responses to restrict viral infection.The intestinal vasculature is vulnerable to SARS-CoV-2-induced endothelial injury,which simultaneously triggers the activation of the innate immune and coagulation systems,a condition referred to as“immunothrombosis”that drives severe thrombotic complications.Finally,increased intestinal permeability allows an aberrant dissemination of bacteria,fungi,and endotoxin into the systemic circulation and contributes,to a certain degree,to the over-exuberant immune responses and hyper-inflammation that dictate the severe form of COVID-19.In this review,we aim to elucidate SARS-CoV-2-mediated effects on gut barrier homeostasis and their implications on the progression of the disease.

Pathophysiology of increased intestinal permeability in obstructive jaundice

Despite advances in preoperative evaluation and postoperative care, intervention, especially surgery, for relief of obstructive jaundice still carries high morbidity and mortality rates, mainly due to sepsis and renal dysfunction. The key event in the pathophysiology of obstructive jaundice-associated complications is endotoxemia of gut origin because of intestinal barrier failure. This breakage of the gut barrier in obstructive jaundice is multi-factorial, involving disruption of the immunologic, biological and mechanical barrier. Experimental and clinical studies have shown that obstructive jaundice results in increased intestinal permeability. The mechanisms implicated in this phenomenon remain unresolved, but growing research interest during the last decade has shed light in our knowledge in the field. This review summarizes the current concepts in the pathophysiology of obstructive jaundice-induced gut barrier dysfunction, analyzing pivotal factors, such as altered intestinal tight junctions expression, oxidative stress and imbalance of enterocyte proliferation and apoptosis. Clinicians handling patients with obstructive jaundice should not neglect protecting the intestinal barrier function before, during and after intervention for the relief of this condition, which may improve their patients’ outcome.

Experimental obstructive jaundice alters claudin-4 expression in intestinal mucosa: Effect of bombesin and neurotensin

瞄准：调查试验性的妨碍的黄疸和外长的 bombesin 和 neurotensin (NT )(BBS ) 的影响紧密的连接(TJ ) 的表示上的管理在老鼠的肠上皮的蛋白质 claudin-4。方法：四十只男 Wistar 老鼠随机被划分成五个组：我 = 控制， II = 假冒操作， III = 胆汁管结扎(BDL ) ， IV = BDL+BBS (30 microg/kg 每 d ) ， V = BDL+NT (300 microg/kg 每 d ) 。在 d 的实验的结束 10，内毒素在门和大动脉的血被测量。终端回肠的织物节组织学地被检验并且免疫组织化学地为在肠上皮的 claudin-4 表示的评估。结果：妨碍的黄疸导致了重要的门和大动脉的 endotoxemia 表明的肠的障碍失败。Claudin-4 表示显著地被增加在上面在 jaundiced 老鼠的第三根绒毛并且一起来它的侧面的分发的规定被注意。BBS 或 NT 的管理恢复了 claudin-4 表示到控制状态并且显著地减少了门和大动脉的 endotoxemia。结论：在肠上皮的试验性的妨碍的黄疸增加 claudin-4 表示，它可以是贡献粘膜障碍的混乱的一个关键因素。毁坏规章的肽 BBS， NT 能阻止这扇改变和还原剂门和全身的 endotoxemia。

Bile duct ligation in rats: A reliable model of hepatorenal syndrome?

The two most widely used experimental models of advanced liver disease are the administration of carbon tetrachloride, and common bile duct ligation (BDL), however, neither has been systematically evaluated as a model of hepatorenal syndrome (HRS). The BDL model in rats, studied at diverse time points, induced a progressive renal dysfunction without structural changes in the kidney. The authors concluded that BDL is a good model for further studies of HRS and its treatment. However, the renal impairment observed at the acute phase of the BDL model is based on a different pathophysiology than that of HRS. Specifi cally, in acute obstructive jaundice, cholemia predominates over parenchymal liver disease (reversible at this stage without portal hypertension or cirrhosis) and independently induces negative inotropic and chronotropic effects on the heart, impaired sympathetic vasoconstriction response and profound natriuresis and diuresis that might lead to volume depletion. In addition, systemic endotoxemia contributes to the prerenal etiology of renal impairment and promotes direct nephrotoxicity and acute tubular necrosis. On the other hand, the renal failure observed in the chronic BDL model (with development of biliary cirrhosis, portal hypertension and ascites) shares pathophysiological similarities with HRS, but the accordance of the chronic BDL model to the diagnostic criteria of HRS (e.g. absence of spontaneous bacterial peritonitis, no renal function improvement after plasma volume expansion) should have been confirmed. In conclusion, we think that the BDL model is not suitable for the study of the natural history of HRS, but the chronic BDL model might be valid for the study of established HRS and its potential therapies.

Acute upper gastrointestinal bleeding in octοgenarians:Clinical outcome and factors related to mortality

AIM: To evaluate the aetiology, clinical outcome and factors related to mortality of acute upper gastrointestinal bleeding (AUGIB) in octogenarians. METHODS: We reviewed the records of all patients over 65 years old who were hospitalised with AUGIB in two hospitals from January 2006 to December of 2006. Patients were divided into two groups: Group A (65-80 years old) and Group B (> 80 years old). RESULTS: Four hundred and sixteen patients over 65 years of age were hospitalized because of AUGIB. Group A included 269 patients and Group B 147 patients. Co-morbidity was more common in octogenarians (P = 0.04). The main cause of bleeding was peptic ulcer in both groups. Rebleeding and emergency surgery were uncommon in octogenarians and not different from those in younger patients. In-hospital complications were more common in octogenarians (P = 0.05) and more patients died in the group of octogenarians compared to the younger age group (P = 0.02). Inability to perform endoscopic examination (P = 0.002), presence of high risk for rebleeding stigmata (P = 0.004), urea on admission (P = 0.036), rebleeding (P = 0.004) and presenceof severe co-morbidity (P < 0.0001) were related to mortality. In multivariate analysis, only the presence of severe co-morbidity was independently related to mortality (P = 0.032). CONCLUSION: While rebleeding and emergency surgery rates are relatively low in octogenarians with AUGIB, the presence of severe co-morbidity is the main factor of adverse outcome.

Pentoxifylline:A first line treatment option for severe alcoholic hepatitis and hepatorenal syndrome?

Although favourable results of pentoxifylline (PTX) used in treatment of severe alcoholic hepatitis patients with a Maddrey discriminant function score ≥ 32 have been previously reported, it is not currently recommended as a first line treatment for alcoholic hepatitis owing to lack of evidence for its efficacy as compared to the standard treatment with corticosteroids. In a very recent issue of World Journal of Gastroenterology, Dr. De BK and colleagues compared for the first time the two treatment modalities head to head in a randomized controlled study, demonstrating the advantage of PTX over corticosteroids in terms of patients' survival and risk-benefit profile. The advantage of PTX over corticosteroids in survival of patients with severe alcoholic hepatitis was found to be related to the prevention of hepatorenal syndrome in their study. This study raises the question of the use of PTX as a standard treatment for severe alcoholic hepatitis. Considering the fact that PTX presented a spectacular efficiency in prevention of hepatorenal syndrome in their study as well as that previous studies have shown that this effect is possibly related to a primary renoprotective action because it is irrelevant of tumor necrosis factor-α synthesis inhibition or improved liver function, we tempted to speculate that PXT might be an effective option for prevention and/or treatment of hepatorenal syndrome complicating other forms of advanced liver disease. This attractive theory remains to be elucidated by pressing future studies in view of the lack of effective treatment modalities for hepatorenal syndrome.

Effect of bombesin and neurotensin on gut barrier function in partially hepatectomized rats

AIM: To investigate the effect of regulatory peptides bombesin (BBS) and neurotensin (NT) on intestinal barrier function in partially hepatectomized rats.METHODS: Ninety male Wistar rats were randomly divided into five groups: Ⅰ (n = 10): controls, Ⅱ (n =20): sham operated, Ⅲ (n = 20): partial hepatectomy 70% (PHx), Ⅳ (n = 20): PHx+BBS (30 μg/kg/d), Ⅴ (n= 20): PHx+NT (300 μg/kg/d). Groups Ⅳ and Ⅴ were treated for 8 days before PHx and 48 h post surgery.At the end of the experiment, on day 10, intestinal barrier function was assessed by measuring endotoxin concentrations in portal and aortic blood. Tissue sections of the terminal ileum were examined histologically and villus density, mucosal thickness, mitotic activity and apoptosis in crypts were assessed. In addition, ileal mucosa was analyzed for DNA and protein content and microbiological analysis was performed in cecal contents.To estimate intestinal oxidative stress, lipid peroxidation was determined on tissue homogenates from terminal ileum.RESULTS: BBS or NT administration significantly reduced portal and systemic endotoxemia observed 48 h after partial hepatectomy. In hepatectomized rats (group Ⅲ), a trend towards induction of mucosal atrophy was observed, demonstrated by the reduction of villus density, mucosal thickness, protein content and significant reduction of DNA, while these alterations were reversed by regulatory peptides administration.This trophic effect of BBS and NT was accompanied by induction of mitoses above control levels and a significant reduction of apoptosis in intestinal crypts.Intestinal lipid peroxidation was found significantly lower in PHx group and regulatory peptides exerted an antioxidant action, further decreasing this parameter of oxidative stress. The bacterial population of E. coli and aerobic Gram (+) cocci was increased in cecal content of hepatectomized rats, while this parameter was not affected by the administration of BBS or NT.CONCLUSION: Gut regulatory peptides BBS and NT improve intestinal barrier function and reduce endotoxemia in experimental partial hepatectomy. This effect is, at least in part, mediated by their trophic,antiapoptotic, mitogenic, and antioxidant effect on the intestinal epithelium. This observation might be of potential value in patients undergoing liver resection.

Serum cytokine profile in patients with hepatitis B e antigen-negative chronic active hepatitis B and inactive hepatitis B virus carriers

An insufficient cellular immune response seems to be critical for the immunopathogenesis of chronic hepatitis B virus infection.We have previously demonstrated no differences of T-lymphocyte subsets in blood between inactive hepatitis B s antigen(HBsAg) carriers and patients with HBeAg-negative chronic active hepatitis B.This study investigated the peripheral blood cytokine profile in patients with HBeAg-negative chronic active hepatitis B infection(Group A,n = 21) and inactive HBsAg carriers(Group B,n = 13).Serum cytokines [interferon(IFN)-γ,tumor necrosis factor-α,interleukin(IL)-1b,IL-4,IL-12,IL-10,IL-2,IL-5,IL-8] were analyzed by using flow cytometry.Patients with chronic active disease presented with significantly decreased levels of IFN-γ and IL-10 compared to inac-tive carriers(P = 0.048 and P = 0.008,respectively).In HBeAg-negative chronic active hepatitis B patients,a significant negative correlation of IFN-γ levels with serum hepatitis B viral load was noted(P = 0.021).In conclusion,patients with HBeAg-negative chronic active hepatitis B and HBsAg inactive carriers display a different cytokine profile.Decreased Th1 response observed in patients with chronic active hepatitis B could be implicated in the persistence of virus replication and ongoing progression of liver disease.

Enterocytes’tight junctions:From molecules to diseases

Tight junctions(TJs)are structures between cells where cells appear in the closest possible contact.They are responsible for sealing compartments when epithelial sheets are generated.They regulate the permeability of ions,(macro)molecules and cells via the paracellular pathway.Their structure at the electron microscopic level has been well known since the 1970s;however,only recently has their macromolecular composition been revealed.This review first examines the major macromolecular components of the TJs(occludin,claudins,junctional adhesion molecule and tricellulin)and then the associated macromolecules at the intracellular plaque[zonula occludens(ZO)-1,ZO-2,ZO-3,AF-6,cingulin,7H6].Emphasis is given to their interactions in order to begin to understand the mode of assembly of TJs.The functional significance of TJs is detailed and several mechanisms and factors involved are discussed briefly.Emphasis is given to the role of intestinal TJs and the alterations observed or speculated in diverse disease states.Specifically,intestinal TJs may exert a pathogenetic role in intestinal(inflammatory bowel disease,celiac disease)and extraintestinal diseases (diabetes type 1,food allergies,autoimmune diseases).Additionally,intestinal TJs may be secondarily disrupted during the course of diverse diseases,subsequently allowing the bacterial translocation phenomenon and promoting the systemic inflammatory response,which is often associated with clinical deterioration.The major questions in the field are highlighted.

Intestinal barrier dysfunction in cirrhosis: Current concepts in pathophysiology and clinical implications

The intestinal lumen is a host place for a wide range of microbiota and sets a unique interplay between local immune system, inflammatory cells and intestinal epithelium, forming a physical barrier against microbial invaders and toxins. Bacterial translocation is the migration of viable or nonviable microorganisms or their pathogen-associated molecular patterns, such as lipopolysaccharide, from the gut lumen to the mesenteric lymph nodes, systemic circulation and other normally sterile extraintestinal sites. A series of studies have shown that translocation of bacteria and their products across the intestinal barrier is a commonplace in patients with liver disease. The deterioration of intestinal barrier integrity and the consulting increased intestinal permeability in cirrhotic patients play a pivotal pathophysiological role in the development of severe complications as high rate of infections, spontaneous bacterial peritonitis, hepatic encephalopathy, hepatorenal syndrome, variceal bleeding, progression of liver injury and hepatocellular carcinoma. Nevertheless, the exact cellular and molecular mechanisms implicated in the phenomenon of microbial translocation in liver cirrhosis have not been fully elucidated yet.

Pleiotropic effects of bombesin and neurotensin on intestinal mucosa: Not just trefoil peptides

Bombesin and neurotensin are neuropeptides which exert a wide spectrum of biological actions on gastrointestinal tissues influencing intestinal growth and adaptation, intestinal motility, blood flow, secretion, nutrient absorption and immune response. Based mainly on their well-established potent enterotrophic effect, numerous experimental studies investigated their potential positive effect on the atrophic or injured intestinal mucosa. These peptides proved to be effective mucosa-healing factors, but the potential molecular and cellular mechanisms for this action remained unresolved. In a recently published study (World J Gastroenterol 2008; 14(8): 1222-1230), it was shown that their protective effect on the intestine in experimentally induced inflammatory bowel disease was related to anti-inflammatory, antioxidant and antiapoptotic actions. These results are in close agreement with our previous studies on jaundiced and hepatectomized rats that showed a regulatory effect of bombesin and neurotensin on critical cellular processes such as enterocyte' proliferation and death, oxidative stress and redox equilibrium, tight junctions' formation and function, and inflammatory response. The pleiotropic effects of bombesin and neurotensin on diverse types of intestinal injury may justify their consideration for clinical trials.

Interleukin 12/interleukin 23 pathway: Biological basis and therapeutic effect in patients with Crohn's disease

Considering that both innate and adaptive immune responses are involved in the pathogenesis of Crohn's disease(CD), novel therapeutic options have significantly been developed. Biological agents represent an important addition to the conventional treatments for immuno-inflammatory conditions, acting as antagonists of adhesion molecules or various inflammatory cytokines. The interleukin 12(IL-12)/IL-23 common pathway has been found to play a determinant role in the induction of inflammation in adaptive immune responses. In particular, IL-23 promotes the differentiation of na?ve T helper cells into Th17 phenotype with the concomitant secretion of several inflammatory cytokines such as IL-17 and IL-22, whereas IL-12 induces the Th1 polarization and production of critical cytokines such as interferon-γ and tumor necrosis factor. Nowadays, there is increased interest regarding the role of IL-23 as a therapeutic target of CD through the blockage of IL-23 mediated pathways. In this editorial, we focus on the role of IL-12/IL-23 pathway in the regulation of mucosal immunity and in the induction and maintenance of chronic inflammation. In parallel, we critically discuss the available data regarding the therapeutic effect of the IL-12/IL-23 inhibitors and especially of ustekinumab, a human monoclonal antibody which has been recently approved by the United States Food and Drug Administration for the management of moderateto-severe CD and its potential to be used as first-line therapy in everyday clinical practice.

A rare etiology of post-endoscopic retrograde cholangiopancreatography pneumoperitoneum

Major complications of endoscopic retrograde cholangiopancreatography (ERCP) include pancreatitis, hemorrhage, cholangitis, and duodenal perforation. The occurrence of free air in the peritoneal cavity post- ERCP is a rare event (< 1%), which is usually the result of duodenal or ductal perforation related to therapeutic ERCP with sphincterotomy. We describe for the first time a different aetiology of pneumoperitoneum, in an 84-year-old woman with pancreatic cancer and a large hepatic metastasis, after ERCP with common bile duct stent deployment. Our patient developed, pneumoperitoneum due to air leakage from rupture of intrahepatic bile ducts and Glisson’s capsule in the area of a peripheral large hepatic metastasis. The potential mechanism underlying this complication might be post- ERCP pneumobilia and increased pressure of intrahepatic bile ducts leading to rupture of intrahepatic bile ducts in the liver metastatic mass owing to neoplastic tissue friability. This case indicates the need for close clinical and radiological observation of patients with hepatic masses (primary or metastatic) subjected to ERCP. In such patients, avoidance of excessive air insufflation during ERCP and/or placement of a nasogastric tube for bowel decompression immediately after ERCP might be a reasonable strategy to prevent such unusual complications.

Stimulation of oval cell and hepatocyte proliferation by exogenous bombesin and neurotensin in partially hepatectomized rats

AIM:To investigate the effect of the neuropeptides bombesin(BBS)and neurotensin(NT)on oval cell proliferation in partially hepatectomized rats not pretreated with a known hepatocyte inhibitor.METHODS:Seventy male Wistar rats were randomly divided into five groups:Ⅰ=controls,Ⅱ=sham operated,Ⅲ=partial hepatectomy 70%(PHx),Ⅳ=PHx+ BBS(30μg/kg per day),Ⅴ=PHx+NT(300μg/kg per day).Forty eight hours after liver resection,portal en-dotoxin levels and hepatic glutathione redox state were determined.α-fetoprotein(AFP)mRNA(in situ hybridisation),cytokeratin-19 and Ki67 antigen expression (immunohistochemistry)and apoptosis(TUNEL)were evaluated on liver tissue samples.Cells with morphological features of oval cells that were cytokeratin-19 (+)and AFP mRNA(+)were scored in morphometric analysis and their proliferation was recorded.In addition,the proliferation and apoptotic rates of hepatocytes were determined.RESULTS:In the control and sham operated groups,oval cells were significantly less compared to groups Ⅲ,ⅣandⅤ(P<0.001).The neuropeptides BBS and NT significantly increased the proliferation of oval cells compared to groupⅢ(P<0.001).In addition,BBS and NT induced a significant increase of hepatocyte proliferation(P<0.001),whereas it decreased their apoptotic activity(P<0.001)compared to groupⅢ.BBS and NT significantly decreased portal endotoxemia (P<0.001)and increased the hepatic GSH:GSSG ratio (P<0.05 and P<0.001,respectively)compared to groupⅢ.CONCLUSION:BBS and NT stimulated oval cell proliferation in a model of liver regeneration,without use of concomitant suppression of hepatocyte proliferation as oval cell activation stimuli,and improved the hepatocyte regenerative response.This peptides-induced combined stimulation of oval cell and hepatocyte proliferation might serve as a possible treatment modality for several liver diseases.

Spontaneous cerebral abscess due to Bacillus subtilis in an immunocompetent male patient: A case report and review of literature

BACKGROUND Bacillus subtilis(B. subtilis) is considered a nonpathogenic microorganism of the genus Bacillus and a common laboratory contaminant. Only scarce reports of B. subtilis central nervous system infection have been reported, mainly in the form of pyogenic meningitis,usually in cases of direct inoculation by trauma or iatrogenically.CASE SUMMARY A 51-year-old man, with a free previous medical history, presented to the Emergency Department of our hospital complaining of recurrent episodes of left upper limb weakness, during the last month, which had been worsened the last 48 h. During his presentation in Emergency Department he experienced a generalized tonic-clonic grand mal seizure. Brain magnetic resonance imaging(MRI) scan with intravenous Gadolinium revealed a 3.3 cm × 2.7 cm lesion at the right parietal lobe surrounded by mild vasogenic edema, which included the posterior central gyrus. The core of the lesion showed relatively homogenous restricted diffusion. Post Gadolinium T1 W1 image, revealed a ring-shaped enhancement. Due to the imaging findings, brain abscess was our primary consideration. Detailed examination for clinical signs of infectious foci revealed only poor oral hygiene with severe tooth decay and periodontal disease, but without detection of dental abscess. The patient underwent surgical treatment with right parietal craniotomy and total excision of the lesion. Pus and capsule tissue grew B. subtilis and according to antibiogram intravenous ceftriaxone 2 g bids was administered for 4 wk. The patient remained asymptomatic and follow-up MRI scan two months after operation showed complete removal of the abscess.CONCLUSION This case highlights the ultimate importance of appropriate oral hygiene and dental care to avoid potentially serious infectious complications and second, B. subtilis should not be considered merely as laboratory contaminant especially when cultivated by appropriate central nervous system specimen.