Bacterial translocation : cause of activated intestinal macrophages in decompensated liver disease

Abstract

Background and Aim: Bacterial infections are a well described complication of cirrhosis and occur in 37% of hospitalized patients. Culture positive infections in addition to the presence of bacterial products and DNA lead to loss of liver function and decompensation in cirrhosis. The mechanisms and molecular pathways associated with Bacterial Translocation (BT) are unknown. The aims of this study were to determine: i. macrophage phenotype and molecular pathways associated with bacterial translocation ii. if intestinal macrophages in liver cirrhosis are capable of modulating intestinal permeability.iii. structural integrity of the epithelial barrier. Methods: Duodenal biopsies and serum samples were collected from 29 patients with decompensated cirrhosis, 15 patients with compensated and 19 controls. Duodenal macrophages were characterized by means of flow cytometry and IHC. Gene expression analysis was performed to determine molecular pathways involved in BT. Inflammatory cytokine determination was done in serum and culture supernatant by means of customized cytometric bead arrays. Results: Patients with decompensated cirrhosis demonstrated: increased frequency of CD33+/CD14+/TREM-1+ and iNOS+ macrophages in their duodenum, elevated mRNA levels of nitric oxide synthase 2 (NOS2), chemokine ligand 2 (CCL2), chemokine ligand 13 (CCL13) and interleukin 8 (IL8) and increased serum levels of interleukin 6 (IL6), IL8 and lipopolysaccharides (LPS). Additionally, patients with decompensated cirrhosis showed an increase in NO, IL6, IL8 and CCL2 levels in culture supernatant after short term duodenal biopsy culture. Although the epithelial barrier on EM seemed intact, significantly increased expression of the “pore” forming tight junction claudin 2 was observed. Conclusion: This study showed the presence of activated CD14+Trem- 1+iNOS+ intestinal macrophages and increased levels of NO, IL-6 and claudin-2 levels in the duodenum of patients with decompensated liver cirrhosis, suggesting that these factors enhance intestinal permeability to bacterial products.

Afrikaans: Inleiding: Bakteriele infeksie is ‘n beskryfde komplikasie van lewersirrose wat in 37% van gehospitaliseerde pasiente voorkom. Kultuur positiewe infeksies asook die teenwoordigheid van bakteriele produkte en DNA lei tot verlies van lewerfunksie en dekompensasie. Die molekulere meganismes wat verband hou met bakteriele translokasie is nog onbekend. Die doel van hierdie studie was om: i. Makrofaag fenotipe en molekulere meganismes geassosieerd met bakteriele translokasie te beskryf, ii. te bepaal of intestinale makrofage dermdeurlaatbaarheid beinvloed, asook iii. om die struktruele integriteit van die dermwand te bepaal. Methods: Serum en dunderm biopsies was verkry van 29 pasiente met gedekompenseerde lewer sirrose, 15 pasiente met gekompenseerde sirrose en 19 kontroles. Dunderm makrofage was gekarakteriseer met behulp van vloeisitometrie en immunohistochemie. Molekulere meganisms belangrik tydens bakteriele translokasie was bepaal met behulp van geneekspressie. Serum en selkultuur supernatant sitokien bepalings was met Bioplex assays gedoen. Resultate: Pasiente met gedekompenseerde sirrose demonstreer: ‘n verhoogde frekwensie van CD33+/CD14+/TREM-1+ en iNOS+ makrofage in hul dunderm, verhoogde mRNA vlakke van NOS2, CCL2, CCL13 en IL8 asook verhoogde serum vlakke van IL6, IL8, LPS. Addisioneel het pasiente met gedekompenseerde sirrose vehoogde supernatant vlakke van NO, IL6, IL8 and CCL2 na kort termyn dunderm biopsie kulture. Alhoewel elekronmikroskopie gewys het dat die dundermwand intak is, was daar statisties-beduidend verhoogde ekspressie van die “porie” vormende vasteaansluitings- proteien, claudin 2 sigbaar. Gevolgtrekking: Gesamentlik het die studie gewys dat geaktiveerde CD14+/Trem-1+/iNOS+ intestinale makrofage asook verhoogde vlakke van NO, IL-6 en claudin-2 teenwoordig is in die dunderm van pasiente met gedekompenseerde sirrose. Dit dui daarop dat diè faktore derm deurlaatbaarheid vir bakteriele produkte kan verhoog.