Upregulation of Toll‐Like Receptors in Chronic Enteropathies in Dogs

Abstract

Background: Inflammatory bowel disease (IBD) is thought to result from a dysregulated interaction between the host immune system and commensal microflora. Toll-like receptors (TLRs) recognize microbe-associated molecular patterns (MAMPs), but their role in enteropathies in dogs is unknown.Hypothesis: That there is a dysregulation of TLRs recognizing bacterial MAMPs in dogs with IBD. Animals: Sixteen healthy beagles and 12 dogs with steroid-treated (ST) and 23 dogs with food-responsive (FR) diarrhea. Methods: Prospective, observational study. mRNA expression of canine TLR2, 4, and 9 was evaluated by quantitative realtime RT-PCR in duodenal and colonic biopsies obtained before and after standard therapy. Samples from control dogs were taken at necropsy, with additional biopsies of stomach, jejunum, ileum, and mesenteric lymph node in 6 dogs.Results: There were significant differences (P .017) in expression of TLR2, 4, and 9 between the 6 sampled locations in healthy control dogs (lymph node 4 small intestine ! colon). Before therapy, ST expressed more mRNA than control dogs for all 3 receptors (P o .05). There were no significant differences between pretreatment and posttreatment values, even though 32/ 35 dogs improved clinically. No associations were found when comparing receptor mRNA expression with either histology or clinical activity scores.Conclusions and Clinical Importance: Bacteria-responsive TLR2, 4, and 9 are upregulated in duodenal and colonic mucosa in IBD. This might lead to increased inflammation through interaction with the commensal flora. The absence of significant changes after therapy despite clinical improvement might point toward the existence of a genetic predisposition to IBD as described in human IBD.

Clinical utility of currently available biomarkers in inflammatory enteropathies of dogs

“…Genomic biomarkers include single nucleotide polymorphisms (SNPs) in TLR4 , TLR5 , nucleotide oligomerization domain (NOD)2 , and the neutrophil cytosolic factor (NCF2) gene,153, 154, 155, 156, 157, 158, 159, 160, 161 a reduction of genetic diversity (eg, T cell receptor repertoire),162 and also alterations in the expression of several other genes (eg, genes encoding TLR2, TLR4, TLR5, TLR9, caspase‐3, and B‐cell lymphoma [Bcl]‐2) 115, 163, 164, 165, 166. Overexpression of some marker genes also was associated with clinical disease severity 164, 165, 166.…”

Expression of serotonin, chromogranin-A, serotonin receptor-2B, tryptophan hydroxylase-1, and serotonin reuptake transporter in the intestine of dogs with chronic enteropathy

“…In many cases, particularly in retrospective studies, a definitive diagnosis cannot be made from the record available, and thus many authors prefer the less restrictive term "chronic enteropathy." 1,2,6 This term is used in our report because, in many of these cases, a true diagnosis of idiopathic inflammatory disease cannot be made with a high degree of certainty.…”

Fish‐meal diet enriched with omega‐3 PUFA and treatment of canine chronic enteropathies

“…CIBDAI values indicated: 0-3 ¼ healthy or clinically insignificant disease; 4-5 ¼ mild disease; 6-8 ¼ moderate disease; and !9 ¼ severe disease. As previously described [23], after the first endoscopy all dogs initially received the elimination diet for 14 days. Animals that showed a CIBDAI ranging between 0 and 3 within 14 days of treatment with the elimination diet were grouped (retrospectively) as FRD (n ¼ 14).…”

“…Procedures used for clinical examination and grouping of patients were as previously described [8,22,23]. Briefly, the CIBDAI in all sick dogs was monitored by an in-house expert who was unaware of the study.…”

“…Biopsies of $3 mg each were taken at two locations in the duodenum and colon [23]. Tissues from gastro-intestinally healthy dogs were collected after euthanasia with pentobarbiturate and stored in stabilization buffer (RNAlater, Ambion Inc, Austin, Tex) according to the manufacturer's instructions until analysis.…”