Heparan Sulfate Plays a Central Role in a Dynamic in Vitro Model of Protein-losing Enteropathy

Abstract

Protein-losing enteropathy (PLE), the loss of plasma proteins through the intestine, is a symptom in ostensibly unrelated diseases. Emerging commonalities indicate that genetic insufficiencies predispose for PLE and environmental insults, e.g. viral infections and inflammation, trigger PLE onset. The specific loss of heparan sulfate (HS) from the basolateral surface of intestinal epithelial cells only during episodes of PLE suggests a possible mechanistic link. In the first tissue culture model of PLE using a monolayer of intestinal epithelial HT29 cells, we proved that HS loss directly causes protein leakage and amplifies the effects of the proinflammatory cytokine tumor necrosis factor ␣ (TNF␣). Here, we extend our in vitro model to assess the individual and combined effects of HS loss, interferon ␥ (IFN␥), TNF␣, and increased pressure, and find that HS plays a central role in the patho-mechanisms underlying PLE. Increased pressure, mimicking venous hypertension seen in postFontan PLE patients, substantially increased protein leakage, but HS loss, IFN␥, or TNF␣ alone had only minor effects. However, IFN␥ up-regulated TNFR1 expression and amplified TNF␣-induced protein leakage. IFN␥ and TNF␣ compromised the integrity of the HT29 monolayer and made it more susceptible to increased pressure. HS loss itself compromises the integrity of the monolayer, amplifying the effects of pressure, but also amplifies the effects of both cytokines. In the absence of HS a combination of increased pressure, IFN␥, and TNF␣ caused maximum protein leakage. Soluble heparin fully compensated for HS loss, providing a reasonable explanation for patient favorable response to heparin therapy.

Heparan sulfate and syndecan-1 are essential in maintaining murine and human intestinal epithelial barrier function

“…Emerging commonalities from clinical observations of PLE patients alerted us to key features of PLE pathogenesis (9)(10)(11). It is episodic, and the onset is often associated with viral infections and increased IFN-γ levels (12,13) as well as with a proinflammatory state and increased TNF-α levels (14).…”

Enoxaparin Improves the Course of Dextran Sodium Sulfate-Induced Colitis in Syndecan-1-Deficient Mice

“…14,15 Furthermore, the outcome of heparin therapy may depend on the degree to which Sdc1 expression is reduced in inflammatory bowel disease (IBD) patients. 19 Moreover, the expression of Sdc1 and the proinflammatory cytokine tumor necrosis factor-␣ (TNF-␣) are inversely correlated in the colonic mucosa of patients with Crohn's disease, 20 and a reduction of Sdc1 expression has been shown to result in increased TNF-␣ signaling in an in vitro model of protein-losing enteropathy, 19,21 further suggesting a regulatory role for Sdc1 in proinflammatory cytokine signaling.…”

Protein losing enteropathy in children

“…This genetic predisposition has been shown in patients with congenital glycolysation defect 1b and 1c. In these patient, genetically inadequate N-glycolysation leads to HSPG dysfunction (5,20). This genetic disorder causes to a predisposition to PLE and environmental factors including intervening viral infections or inflammation cause to onset of PLE (5,23).…”

“…Protein-losing enteropathy is a clinical condition which develops as a life-threatening complication of some diseases which are not related with each other including primary intestinal lymphangiectasia (PIL), inflammatory bowel diseases, congenital glycolysation disorder and systemic lupus erythematosus (5). PLE may develop in many diseases which cause mucosal inflammation in the gastrointestinal system.…”