Peripheral Blood Mononuclear Cell Expression Of Toll-like Receptors And Relation To Endotoxin Levels In HBV-associated Cirrhosis

Backgrounds & Aims: Endotoxins are complex lipopolysaccharides (LPS), major cell wall components in all Gram-negative bacteria. Bacterial endotoxins can enter the bloodstream, causing endotoxemia. Circulating endotoxin can induce an overwhelming inflammatory host response. The innate immune system (as opposed to the targeted antimicrobial response of the adaptive immune system) is the organism's first line of defense against microbial invasion. Endotoxin may play an important role in alteration immune defenses in cirrhotic patients. Recent data have demonstrated that mammalian Toll-like receptors (TLRs) participate in intracellular signaling initiated by endotoxin/LPS. CD14 has been recognized for many years as the major receptor responsible for the effects of LPS on macrophages, monocytes, and neutrophils. Mutations in some of the TLRs, most prominently TLR4 and TLR2, have been associated with increased susceptibility to infectious diseases, so TLR2 and TLR4 may be involved in mediating endotoxin effects in vivo. TLRs have also emerged as a key component of the innate immune system that triggers antimicrobial responses.So, the aims of this study is: 1) To study expression of TLR4 and TLR2 mRNA in peripheral blood mononuclear cell (PBMCs) in HBV-associated cirrhosis; 2) To study serum endotoxin and circulating tumor necrosis factor a (TNF-a) levels in cirrhosis, and its relevant to the expression of TLR4 and TLR2 mRNA. Those contributed to comprehensive the role of TLR2 and TLR4 in endotoxemia in HBV-associated cirrhosis.Methods: 29 patients with HBV-associated cirrhosis and 10 age-matched healthy controls were involved in this study. The diagnosis of HBV-associated cirrhosis was based on the criteria of our country reversed in 2001. The exclusion criteria included(1)Immunomodulatory drug use within the previous 6 weeks,(2)patients with renal insufficiency (serum creatinine>120 uml/L),(3) maiignancy,(4) aicohoi intake history(more than 20 g/d),(5) Infection or antibiotic drug use within the previous 6 weeks. Liver function were evaluated by Child-Pugh Criteria. To address this issue, we isolated peripheral blood monocytes from cirrhotic patients and controls, then we measured (1) circulating endotoxin and TNF-a levels; (2) peripheral blood mononuclear cell (PBMCs) expression of TLR4 and TLR2 by applying the reverse transcriptase polymerase chain reaction (RT-PCR) technique. (3)The data were correlated to serum levels of TNF-α.Results: Serum Endotoxin(0.050EU/ml VR 0.107EU/ml, P<0.05 ) and TNF-α(1.282pg/ml VR 2.076pg/ml, P<0.05) levels were significantly increased in patients with cirrhosis. Endotoxin levels did not correlate significantly with other parameters. PBMC expression of TLR2(0.651 VR 0.923, P<0.05) but not TLR4 was significantly up-regulated in cirrhosis and correlated significantly with serum TNF-αlevels.Conclusions: Up-regulation of PBMC expression of TLR2 but not TLR4 occurs in cirrhosis, which implies an important stimulatory role for Gram-positive microbial components but not endotoxin. TLR2 likely contributes to increased circulating TNF-αlevels in cirrhosis. These results suggest that expression of TLR2 is altered in PBC monocytes, which appear to be hypersensitive to LPS, resulting in increased secretion of pro-inflammatory cytokines.