TLR signaling modulates side effects of anticancer therapy in the small intestine.

Intestinal mucositis represents the most common complication of intensive chemotherapy, which has a severe adverse impact on quality of life of cancer patients. However, the precise pathophysiology remains to be clarified, and there is so far no successful therapeutic intervention. In this study, we investigated the role of innate immunity through TLR signaling in modulating genotoxic chemotherapy-induced small intestinal injury in vitro and in vivo. Genetic deletion of TLR2, but not MD-2, in mice resulted in severe chemotherapy-induced intestinal mucositis in the proximal jejunum with villous atrophy, accumulation of damaged DNA, CD11b(+)-myeloid cell infiltration, and significant gene alterations in xenobiotic metabolism, including a decrease in ABCB1/multidrug resistance (MDR)1 p-glycoprotein (p-gp) expression. Functionally, stimulation of TLR2 induced synthesis and drug efflux activity of ABCB1/MDR1 p-gp in murine and human CD11b(+)-myeloid cells, thus inhibiting chemotherapy-mediated cytotoxicity. Conversely, TLR2 activation failed to protect small intestinal tissues genetically deficient in MDR1A against DNA-damaging drug-induced apoptosis. Gut microbiota depletion by antibiotics led to increased susceptibility to chemotherapy-induced mucosal injury in wild-type mice, which was suppressed by administration of a TLR2 ligand, preserving ABCB1/MDR1 p-gp expression. Findings were confirmed in a preclinical model of human chemotherapy-induced intestinal mucositis using duodenal biopsies by demonstrating that TLR2 activation limited the toxic-inflammatory reaction and maintained assembly of the drug transporter p-gp. In conclusion, this study identifies a novel molecular link between innate immunity and xenobiotic metabolism. TLR2 acts as a central regulator of xenobiotic defense via the multidrug transporter ABCB1/MDR1 p-gp. Targeting TLR2 may represent a novel therapeutic approach in chemotherapy-induced intestinal mucositis.

Loss of TLR2 worsens spontaneous colitis in MDR1A deficiency through commensally induced pyroptosis.

Variants of the multidrug resistance gene (MDR1/ABCB1) have been associated with increased susceptibility to severe ulcerative colitis (UC). In this study, we investigated the role of TLR/IL-1R signaling pathways including the common adaptor MyD88 in the pathogenesis of chronic colonic inflammation in MDR1A deficiency. Double- or triple-null mice lacking TLR2, MD-2, MyD88, and MDR1A were generated in the FVB/N background. Deletion of TLR2 in MDR1A deficiency resulted in fulminant pancolitis with early expansion of CD11b(+) myeloid cells and rapid shift toward TH1-dominant immune responses in the lamina propria. Colitis exacerbation in TLR2/MDR1A double-knockout mice required the unaltered commensal microbiota and the LPS coreceptor MD-2. Blockade of IL-1ß activity by treatment with IL-1R antagonist (IL-1Ra; Anakinra) inhibited colitis acceleration in TLR2/MDR1A double deficiency; intestinal CD11b(+)Ly6C(+)-derived IL-1ß production and inflammation entirely depended on MyD88. TLR2/MDR1A double-knockout CD11b(+) myeloid cells expressed MD-2/TLR4 and hyperresponded to nonpathogenic Escherichia coli or LPS with reactive oxygen species production and caspase-1 activation, leading to excessive cell death and release of proinflammatory IL-1ß, consistent with pyroptosis. Inhibition of reactive oxygen species-mediated lysosome degradation suppressed LPS hyperresponsiveness. Finally, active UC in patients carrying the TLR2-R753Q and MDR1-C3435T polymorphisms was associated with increased nuclear expression of caspase-1 protein and cell death in areas of acute inflammation, compared with active UC patients without these variants. In conclusion, we show that the combined defect of two UC susceptibility genes, MDR1A and TLR2, sets the stage for spontaneous and uncontrolled colitis progression through MD-2 and IL-1R signaling via MyD88, and we identify commensally induced pyroptosis as a potential innate immune effector in severe UC pathogenesis.

Toll-like receptor 4 variant D299G induces features of neoplastic progression in Caco-2 intestinal cells and is associated with advanced human colon cancer.

BACKGROUND & AIMS: The Toll-like receptor (TLR) 4 mediates homeostasis of the intestinal epithelial cell (IEC) barrier. We investigated the effects of TLR4-D299G on IEC functions. METHODS: We engineered IECs (Caco-2) to stably overexpress hemagglutinin-tagged wild-type TLR4, TLR4-D299G, or TLR4-T399I. We performed gene expression profiling using DNA microarray analysis. Findings were confirmed by real-time, quantitative, reverse-transcriptase polymerase chain reaction, immunoblot, enzyme-linked immunosorbent assay, confocal immunofluorescence, and functional analyses. Tumorigenicity was tested using the CD1 nu/nu mice xenograft model. Human colon cancer specimens (N = 214) were genotyped and assessed for disease stage. RESULTS: Caco-2 cells that expressed TLR4-D299G underwent the epithelial-mesenchymal transition and morphologic changes associated with tumor progression, whereas cells that expressed wild-type TLR4 or TLR4-T399I did not. Caco-2 cells that expressed TLR4-D299G had significant increases in expression levels of genes and proteins associated with inflammation and/or tumorigenesis compared with cells that expressed other forms of TLR4. The invasive activity of TLR4-D299G Caco-2 cells required Wnt-dependent activation of STAT3. In mice, intestinal xenograft tumors grew from Caco-2 cells that expressed TLR4-D299G, but not cells that expressed other forms of TLR4; tumor growth was blocked by a specific inhibitor of STAT3. Human colon adenocarcinomas from patients with TLR4-D299G were more frequently of an advanced stage (International Union Against Cancer [UICC] ≥III, 70% vs 46%; P = .0142) with metastasis (UICC IV, 42% vs 19%; P = .0065) than those with wild-type TLR4. Expression of STAT3 messenger RNA was higher among colonic adenocarcinomas with TLR4-D299G than those with wild-type TLR4. CONCLUSIONS: TLR4-D299G induces features of neoplastic progression in intestinal epithelial Caco-2 cells and associates with aggressive colon cancer in humans, implying a novel link between aberrant innate immunity and colonic cancerogenesis.

Randomized trial of low-volume PEG solution versus standard PEG + electrolytes for bowel cleansing before colonoscopy.

OBJECTIVES: Polyethylene glycol (PEG)-based gut lavage solutions are safe and effective, but require consumption of large volumes of fluid. We compared a new 2 L solution of PEG plus ascorbic acid (PEG + Asc) with standard 4 L PEG with electrolytes (PEG + E) for bowel cleansing before colonoscopy to determine efficacy, safety, and patient acceptability. METHODS: Consenting adult inpatients scheduled to undergo colonoscopy were randomized to receive either 2 L PEG + Asc or 4 L PEG + E. Preparations were taken as split doses the evening before colonoscopy and the following morning. The PEG + Asc group took 1 L at each administration (i.e., total dose of 2 L). The PEG + E group took 2 L at each administration (i.e., total dose of 4 L). Bowel cleansing success was assessed via videotapes by independent, blinded raters. Statistical noninferiority was predefined as a difference of <15% in the lower limit of the 97.5% confidence interval for treatment difference. Patient views on the preparations were elicited. Adverse events were noted. RESULTS: Successful gut cleansing was achieved in 136 of 153 (88.9%) cases of the PEG + Asc group and 147 of 155 (94.8%) cases of the 4 L PEG + E group (mean difference -5.9 [-12.0-infinity]). The difference fell within the predefined limit for noninferiority. Clinical and laboratory parameters showed no difference in safety profile. Patient ratings of acceptability and taste were better for the PEG + Asc group than for the PEG + E group (P < 0.025). CONCLUSIONS: The combination of ascorbic acid and PEG-based bowel preparation reduces the volume patients have to drink without compromising efficacy or safety. The low-volume PEG + Asc preparation was more acceptable to patients, and should, therefore, improve effectiveness in routine practice.

Trypsin-sensitive modulation of intestinal epithelial MD-2 as mechanism of lipopolysaccharide tolerance.

Intestinal epithelial cells (IEC) are constantly exposed to both high concentrations of the bacterial ligand LPS and the serine protease trypsin. MD-2, which contains multiple trypsin cleavage sites, is an essential accessory glycoprotein required for LPS recognition and signaling through TLR4. The aim of this study was to characterize the expression and subcellular distribution of intestinal epithelial MD-2 and to delineate potential functional interactions with trypsin and then alteration in inflammatory bowel disease (IBD). Although MD-2 protein expression was minimal in primary IEC of normal colonic or ileal mucosa, expression was significantly increased in IEC from patients with active IBD colitis, but not in ileal areas from patients with severe Crohn's disease. Endogenous MD-2 was predominantly retained in the calnexin-calreticulin cycle of the endoplasmic reticulum; only a small fraction was exported to the Golgi. MD-2 expression correlated inversely with trypsin activity. Biochemical evidence and in vitro experiments demonstrated that trypsin exposure resulted in extensive proteolysis of endogenous and soluble MD-2 protein, but not of TLR4 in IEC, and was associated with desensitization of IEC to LPS. In conclusion, the present study suggests that endoplasmic reticulum-associated MD-2 expression in IBD may be altered by ileal protease in inflammation, leading to impaired LPS recognition and hyporesponsiveness through MD-2 proteolysis in IEC, thus implying a physiologic mechanism that helps maintain LPS tolerance in the intestine.

Severe acute pancreatitis: nonsurgical treatment of infected necroses.

OBJECTIVES: In acute pancreatitis, infection of necrosis is associated with a substantial mortality of 15% to >50% even if immediate necrosectomy, the recommended standard treatment, is performed, mainly because of the patients' critical systemic and unstable local conditions at the time of manifestation of infection. We investigated whether this dreaded complication can be managed conservatively. METHODS: We evaluated 88 consecutive patients with severe (APACHE II score, > or =11; Ranson score, > or =4) acute necrotizing pancreatitis who received ICU treatment including early antibiotic prophylaxis. Twenty-eight patients were included who developed infection of necroses, verified by fine needle aspiration, 19 +/- 6 days after admission. No patient received urgent surgery; rather, in all patients, nonsurgical therapy was continued after adapting the antibiotic regimen to bacteriology. In the further course, 12 patients were excluded due to refractory local complications eventually requiring surgical treatment 36 +/- 14 days after diagnosis of infection. RESULTS: Sixteen patients (APACHE II score: 18.1 [11-33]; Ranson score, 5.9 [4-10]) were managed with medical treatment alone. Six patients recovered without further complications; 10 patients (62%) developed single or multiple organ failure, and 2 died (mortality, 12%). CONCLUSION: These data suggest that in patients with acute necrotizing pancreatitis and infected necroses, surgery can be avoided without compromising prognosis and outcome.

Prophylactic antibiotic treatment in patients with predicted severe acute pancreatitis: a placebo-controlled, double-blind trial.

BACKGROUND & AIMS: Antibiotic prophylaxis in necrotizing pancreatitis remains controversial. Until now, there have been no double-blind studies dealing with this topic. METHODS: A total sample size of 200 patients was calculated to demonstrate with a power of 90% that antibiotic prophylaxis reduces the proportion of patients with infected pancreatic necrosis from 40% placebo (PLA) to 20% ciprofloxacin/metronidazole (CIP/MET). One hundred fourteen patients with acute pancreatitis in combination with a serum C-reactive protein exceeding 150 mg/L and/or necrosis on contrast-enhanced CT scan were enrolled and received either intravenous CIP (2 x 400 mg/day) + MET (2 x 500 mg/day) or PLA. Study medication was discontinued and switched to open antibiotic treatment when infectious complications, multiple organ failure sepsis, or systemic inflammatory response syndrome (SIRS) occurred. After half of the planned sample size was recruited, an adaptive interim analysis was performed, and recruitment was stopped. RESULTS: Fifty-eight patients received CIP/MET and 56 patients PLA. Twenty-eight percent in the CIP/MET group required open antibiotic treatment vs. 46% with PLA. Twelve percent of the CIP/MET group developed infected pancreatic necrosis compared with 9% of the PLA group (P = 0.585). Mortality was 5% in the CIP/MET and 7% in the PLA group. In 76 patients with pancreatic necrosis on contrast-enhanced CT scan, no differences in the rate of infected pancreatic necrosis, systemic complications, or mortality were observed. CONCLUSIONS: This study detected no benefit of antibiotic prophylaxis with respect to the risk of developing infected pancreatic necrosis.

Two cases of pancreatic tuberculosis in nonimmunocompromised patients. A diagnostic challenge and a rare cause of portal hypertension.

Pancreatic tuberculosis is very rare, especially in immunocompetent patients, and represents a diagnostic challenge. We describe 2 cases of pancreatic tuberculosis mimicking carcinoma on CT scan. In the first case, explorative laparotomy revealed granulomatous inflammation suggestive of tuberculosis. Cultured smears from the pancreatic tail tested positive for Mycobacterium tuberculosis, and the patient responded well to antituberculous medication. In the second case, fine needle aspirate revealed tuberculosis. This case is unique with regard to development of portal hypertension in pancreatic tuberculosis. Antituberculous medication achieved little improvement, then the patient was lost to follow-up. In suspicion of carcinoma the patient underwent laparotomy in another hospital. Malignancy was excluded, and a purulent necrotic pancreas was resected. The patient finally improved without any antituberculous medication and remains well. Both patients were tested HIV-negative. We summarize the etiology, clinical presentation, diagnosis and treatment of a diagnostic dilemma, which should be considered in clinical practice.