Peripheral Blood Mononuclear Cell Expression of Toll–Like Receptors and Relation to Cytokine Levels in Cirrhosis

Abstract

Activation of macrophages by endotoxin is assumed responsible for increased circulating tumor necrosis factor ␣ (TNF-␣) and soluble TNF receptor (sTNFR) levels in cirrhosis. Relevant to this is expression of Toll-like receptor (TLR) 4 and TLR2, which is critically involved in production of TNF-␣ in response to endotoxin and Gram-positive microbial stimuli, respectively. The first studies on this in cirrhosis are reported here. In 36 cirrhotic patients and 32 controls, we measured (1) circulating endotoxin, TNF-␣, and sTNFR levels; (2) peripheral blood mononuclear cell (PBMC) expression of TLR4 and TLR2, and (3) in vitro TNF-␣ production by PBMCs stimulated with endotoxin or Staphylococcus aureus enterotoxin B (SEB). PBMC expression of TLR2, circulating TNF-␣ levels, and in vitro TNF-␣ production were reassessed after supplementation with a synbiotic regimen known to increase intestinal levels of Gram-positive bacteria. Endotoxin, TNF-␣, and sTNFR levels were significantly increased in cirrhosis. Endotoxin levels did not correlate significantly with other parameters. PBMC expression of TLR2 but not TLR4 was significantly up-regulated in cirrhosis and correlated significantly with serum TNF-␣ and sTNFR levels. In vitro TNF-␣ production by PBMCs stimulated by SEB was significantly blunted. Supplementation with the synbiotic regimen resulted in significant up-regulation of PBMC expression of TLR2. Serum TNF-␣ levels were further increased and in vitro TNF-␣ production further reduced in most patients. In conclusion, up-regulation of PBMC expression of TLR2 but not TLR4 occurs in cirrhosis, which implies, contrary to previous assumptions, an important stimulatory role for Gram-positive microbial components but not endotoxin. TLR2 likely contributes to increased circulating TNF-␣ and sTNFR levels in cirrhosis.

Synbiotic modulation of gut flora: Effect on minimal hepatic encephalopathy in patients with cirrhosis

“…29,30 However, a recent analysis of the peripheral blood mononuclear cell expression of toll-like receptor 4, responsible for signal transduction leading to the production of tumor necrosis factor-alpha in response to endotoxin, has cast doubt as to the importance of endotoxin as a stimulus for tumor necrosis factor-alpha overproduction in cirrhosis in the clinical setting, irrespective of the etiology of cirrhosis. 24 Whether related to reduction in endotoxemia or other mechanism, the Child-Turcotte-Pugh class improved in nearly 50% of our initially Child-Turcotte-Pugh class B or C synbiotic-treated patients, a proportion significantly higher than that in placebo-treated counterparts (8%). The Child-Turcotte-Pugh class also improved in 29% of patients treated with fermentable fiber alone.…”

“…A total of 97 consecutive outpatients with hepatic cirrhosis but no overt HE were screened for MHE, as described below. Cirrhosis was diagnosed histologically in 69 out of 97 (71%) patients and on clinical and radiological grounds 24 in the remaining 28 (29%) patients, in whom biopsy was contraindicated by uncontrolled coagulopathy and/or uncontrolled ascites. Patient characteristics, including the etiology of cirrhosis and Child-Turcotte-Pugh class, 25 are listed in Table 1.…”

“…Patients were considered to have alcohol-related cirrhosis if alcohol intake had been in excess of 80 g/day in men and 30 g/day in women for more than 5 years and if testing for viral, metabolic, and immune aetiologies was negative. 24 Only patients who had been abstinent from alcohol for at least 2 months, as corroborated by family members and/or caregivers, were included. Patients with histological features of alcoholic hepatitis were excluded.…”

“…26 Exclusion criteria also included a history within the previous 6 weeks of factors that may have influenced gut flora and circulating endotoxin and ammonia levels, including infection, treatment with antibiotics, lactulose or immunomodulatory drugs, and gastrointestinal hemorrhage. 24 In addition to intercurrent infection and gastrointestinal hemorrhage, patients with other possible causes of reversible hepatic functional decompensation, such as drug-related hepatotoxicity and choledocholithiasis, were excluded. Patients with other known precipitants of HE, including renal impairment, electrolyte imbalance, and complicating hepatocellular carcinoma, were also excluded.…”

Pattern recognition receptors: A contemporary view on liver diseases

“…154 Patients with cirrhosis have increased serum endotoxin levels, regardless of the etiology of liver disease. 155 Riordan et al 156 reported that in patients with cirrhosis patients the expression of TLR2 is upregulated on peripheral blood mononuclear cells (PBMC) and as a result, recognize Gram-positive bacterial products with a concurrent increase in serum TNF␣. Interestingly, TLR4 expression on PBMC did not significantly differ between controls and paitents with cirrhosis.…”