Enhanced production of interferon-gamma as a possible cause of protein-losing enteropathy after modified Fontan operation

Protein-losing enteropathy recurrence after pediatric heart transplantation: Multicenter case series

BACKGROUND

Protein-losing enteropathy (PLE) is a devastating complication of the Fontan circulation. Although orthotopic heart transplantation (HTx) typically results in resolution of PLE symptoms, isolated cases of PLE relapse have been described after HTx.

METHODS

Patients with Fontan-related PLE who had undergone HTx at participating centers and experienced relapse of PLE during follow-up were retrospectively identified. Available data related to pre- and post-HTx characteristics and PLE events were collected.

RESULTS

Eight patients from four different centers were identified. Median time from Fontan procedure to the development of PLE was 8 years, and median age at HTx was 17 years (range 7.7-21). In all patients, PLE resolved at a median time of 1 month after HTx (0.3-5). PLE recurrences occurred at a median time of 7.5 months after HTx (2-132). Each occurrence was associated with one or more significant clinical events; most commonly cellular- or antibody-mediated rejection; and less commonly graft dysfunction, infection, thrombosis, and posttransplant lymphoproliferative disease. PLE recurrences resolved after the successful treatment of the concomitant event, after a median time of 2 months in seven cases, while persisted and recurred in one patient in association with atypical mycobacterium infection and subsequent PTLD onset and relapses. Six patients were alive during follow-up at a median time of 4 years (1.3-22.5) after HTx.

CONCLUSIONS

This is the largest series of PLE recurrence after HTx. All cases were associated with one or more concomitant and significant clinical events. PLE typically resolved after resolution of the inciting clinical event.

Are children with protein-losing enteropathy after the Fontan operation at increased risk of cytomegalovirus enteropathy? A report of two cases

INTRODUCTION

Aetiology of protein-losing enteropathy in single-ventricle type CHD is multi-factorial.

REPORT

We describe two Fontan patients with protein-losing enteropathy who presented with cytomegalovirus-associated colitis.

DISCUSSION

Fontan patients display risk factors for cytomegalovirus-induced gastroenteropathy that may affect lymph angiogenesis, disease development, and progression.

CONCLUSION

Cytomegalovirus enteropathy may be common among Fontan patients who suffer from protein-losing enteropathy. Polymerase chain reaction is important for detection.

Effectiveness of High-dose Spironolactone Therapy in a Patient with Recurrent Protein-losing Enteropathy after the Fontan Procedure

Protein-losing enteropathy (PLE) is a rare and life-threatening complication that occurs after the Fontan procedure. We herein report the case of an 11-year-old Japanese boy who developed PLE six times after undergoing the Fontan procedure. High-dose spironolactone therapy has been effective for 2 years. His high level of serum aldosterone decreased to a nearly normal range and spironolactone may have a diuretic and anti-inflammatory potential.

Haemodynamic characteristics before and after the onset of protein losing enteropathy in patients after the Fontan operation

OBJECTIVES

Determinant risk factors for developing protein losing enteropathy (PLE), including haemodynamics, remain unclear in patients after the Fontan operation.

METHODS

Our purpose was to characterize the serial PLE haemodynamics before and after the onset and to determine the risk factors based on the cardiac catheterization-based analysis.

RESULTS

Of 354 Fontan survivors who had undergone postoperative cardiac catheterizations, we experienced 26 PLE patients during the follow-up. Non-left ventricular morphology systemic ventricle, functional one-lung pulmonary circulation and an early postoperative high central venous pressure (CVP) were associated with the PLE onset and the high CVP (odds ratio (OR) = 1.19 per 1 mmHg, 95% confidence interval (CI) 1.04-1.37, especially ≥12 mmHg, OR = 3.09, 95% CI 1.25-7.64, P < 0.05 for both) and one-lung pulmonary circulation (OR = 10.0-10.5, P < 0.001) independently predicted the onset. At the time of the PLE onset, a Fontan route stenosis/obstruction, arrhythmias, ventricular dysfunction/heart failure and pulmonary arterio-venous fistulae were demonstrated in 10 (38%), 8 (31%), 4 (15%) and 3 (12%) patients, respectively. When compared with 56 excellent Fontan survivors, the high CVP, ventricular end-diastolic pressure, and pulmonary artery resistance, and the low arterial oxygen saturation, systemic artery pressure, and ventricular ejection fraction characterized the pre-PLE Fontan haemodynamics (P < 0.05-0.0001). However, the following intensive treatments reduced the CVP, systemic artery pressure and cardiac output (P < 0.05-0.01), resulting in haemodynamics no different from those of the excellent survivors, except for the low systemic pressure (P < 0.0001).

CONCLUSIONS

The pre-PLE haemodynamics was characterized by several impaired haemodynamics, while those after PLE only by a low systemic pressure. A high early postoperative CVP was the only haemodynamic predictor for a new onset of PLE. Strict selective criteria for the operation and strategies to eliminate CVP-raising factors are mandatory to prevent a new onset of PLE.

Protein-losing enteropathy and the Fontan operation

Protein-losing enteropathy (PLE) is a complex disorder characterized by enteric protein loss and often is associated with cardiovascular abnormalities, particularly those with elevated central venous pressure. The Fontan operation is a surgical procedure used to palliate patients with a functional single ventricle. Although the Fontan operation eliminates cyanosis and decreases the workload of the functionally single ventricle, it also elevates central venous pressure. This can result in hepatic and enteric congestion as well as PLE. Despite the universal elevation in central venous pressure, only a fraction of patients who have had a Fontan operation develop PLE. However, PLE is associated with significant morbidity and mortality. Presenting signs and symptoms of PLE include abdominal bloating, diarrhea, edema, pleural effusions, ascites, and failure to thrive. In this review, the authors discuss the diagnosis and prevalence of PLE after the Fontan operation and review currently available therapeutic strategies.

Steroid pulse therapy for protein-losing enteropathy after the Fontan operation

A 19-year-old male with Fontan circulation developed protein-losing enteropathy associated with acute enteritis. Although his central venous pressure was in the normal range, subcutaneous high molecular heparin injection and oral predonisolone administration were not effective. We initiated intravenous high-dose methyl-predonisolone (15 mg/kg/day) for 3 days followed by oral predonisolone (0.5 mg/kg/day) for 4 days and repeated the course in 2 weeks. The serum protein and albumin increased to the normal level at 2 months after pulse therapy. The patient has not shown any recurrence of such protein-losing enteropathy for 2 years without any steroid agents.

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

Patients with protein-losing enteropathy (PLE) fail to maintain intestinal epithelial barrier function and develop an excessive and potentially fatal efflux of plasma proteins. PLE occurs in ostensibly unrelated diseases, but emerging commonalities in clinical observations recently led us to identify key players in PLE pathogenesis. These include elevated IFN-gamma, TNF-alpha, venous hypertension, and the specific loss of heparan sulfate proteoglycans from the basolateral surface of intestinal epithelial cells during PLE episodes. Here we show that heparan sulfate and syndecan-1, the predominant intestinal epithelial heparan sulfate proteoglycan, are essential in maintaining intestinal epithelial barrier function. Heparan sulfate- or syndecan-1-deficient mice and mice with intestinal-specific loss of heparan sulfate had increased basal protein leakage and were far more susceptible to protein loss induced by combinations of IFN-gamma, TNF-alpha, and increased venous pressure. Similarly, knockdown of syndecan-1 in human epithelial cells resulted in increased basal and cytokine-induced protein leakage. Clinical application of heparin has been known to alleviate PLE in some patients but its unknown mechanism and severe side effects due to its anticoagulant activity limit its usefulness. We demonstrate here that non-anticoagulant 2,3-de-O-sulfated heparin could prevent intestinal protein leakage in syndecan-deficient mice, suggesting that this may be a safe and effective therapy for PLE patients.

Gastrointestinal bleeding and protein-losing enteropathy after the fontan operation

Gastrointestinal bleeding has not been reported in patients with protein-losing enteropathy. The investigators describe 3 patients with protein-losing enteropathy and gastrointestinal bleeding after Fontan operations. Bleeding occurred at the onset of protein-losing enteropathy, was macroscopic, led to anemia, and required blood transfusion in all patients. Invasive testing failed to demonstrate gastrointestinal pathology as a source of bleeding. In conclusion, unexplained gastrointestinal bleeding may be part of the clinical spectrum of protein-losing enteropathy.

Applied glycoproteomics—approaches to study genetic-environmental collisions causing protein-losing enteropathy

Protein-losing enteropathy (PLE), the loss of plasma proteins through the intestine, is a life-threatening symptom associated with seemingly unrelated conditions including Crohn's disease, congenital disorder of glycosylation, or Fontan surgery to correct univentricular hearts. Emerging commonalities between these and other disorders led us to hypothesize that PLE develops when genetic insufficiencies collide with simultaneous or sequential environmental insults. Most intriguing is the loss of heparan sulfate (HS) proteoglycans (HSPG) specifically from the basolateral surface of intestinal epithelial cells only during PLE episodes suggesting a direct link to protein leakage. Reasons for HSPG loss are unknown, but genetic insufficiencies affecting HSPG biosynthesis, trafficking, or degradation may be involved. Here, we describe cell-based assays we devised to identify key players contributing to protein leakage. Results from these assays confirm that HS loss directly causes protein leakage, but more importantly, it amplifies the effects of other factors, e.g., cytokines and increased pressure. Thus, HS loss appears to play a central role for PLE. To transfer our in vitro results back to the in vivo situation, we established methods to assess enteric protein leakage in mice and present several genetically deficient strains mimicking intestinal HS loss observed in PLE patients. Preliminary results indicate that mice with haploinsufficient genes involved in HS biosynthesis or HSPG trafficking develop intestinal protein leakage upon additional environmental stress. Our goal is to model PLE in vitro and in vivo to unravel the pathomechanisms underlying PLE, identify patients at risk, and provide them with a safe and effective therapy.

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

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 alpha (TNFalpha). Here, we extend our in vitro model to assess the individual and combined effects of HS loss, interferon gamma (IFNgamma), TNFalpha, and increased pressure, and find that HS plays a central role in the patho-mechanisms underlying PLE. Increased pressure, mimicking venous hypertension seen in post-Fontan PLE patients, substantially increased protein leakage, but HS loss, IFNgamma, or TNFalpha alone had only minor effects. However, IFNgamma up-regulated TNFR1 expression and amplified TNFalpha-induced protein leakage. IFNgamma and TNFalpha 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, IFNgamma, and TNFalpha caused maximum protein leakage. Soluble heparin fully compensated for HS loss, providing a reasonable explanation for patient favorable response to heparin therapy.

Heparan sulfate depletion amplifies TNF-alpha-induced protein leakage in an in vitro model of protein-losing enteropathy

Protein-losing enteropathy (PLE), the excessive loss of plasma proteins through the intestine, often correlates with the episodic loss of heparan sulfate (HS) proteoglycans (HSPG) from the basolateral surface of intestinal epithelial cells. PLE onset is often associated with a proinflammatory state. We investigated whether loss of HS or treatment with the proinflammatory cytokine TNF-alpha directly causes protein leakage and whether a combination of both exacerbates this process. We established the first in vitro model of PLE and measured the flux of albumin/FITC through a monolayer of intestinal HT29 or Caco-2 cells grown on transwells and determined the integrity by transepithelial electrical resistance (TER). Loss of HS from the basolateral surface, either by heparanase digestion or by inhibition of HS synthesis, increased albumin flux 1.58 +/- 0.09-fold and reduced TER by 23.4 +/- 6.5%. TNF-alpha treatment increased albumin flux 4.04 +/- 0.03-fold and reduced TER by 75.7 +/- 4.7% but only slightly decreased HS content. The combined effects of HS loss and TNF-alpha treatment were not only additive, but synergistic, with a 7.00 +/- 0.11-fold increase in albumin flux and a 83.9 +/- 8.1% reduction of TER. Coincubation of TNF-alpha with soluble HS or heparin abolished these synergistic effects. Loss of basolateral HS directly causes protein leakage and amplifies the effects of the proinflammatory cytokine TNF-alpha. Our findings imply that loss of HSPGs renders patients more susceptible to PLE and offer a potential explanation for the favorable response some PLE patients have to heparin therapy.