Limitations of the Limulus amebocyte lysate test in demonstrating circulating lipopolysaccharides

Increased bactericidal/permeability increasing protein in patients with cirrhosis

BACKGROUND

High levels of endotoxin in patients with cirrhosis are thought to be responsible for the activation of tumour necrosis factor-alpha (TNF)-alpha-mediated pro-inflammatory pathways involved in haemodynamic alterations. Bactericidal/permeability increasing protein (BPI) is a protein found in neutrophils with endotoxin-binding and neutralization capacity. It is not known whether defective BPI production or release is present in cirrhosis.

AIMS

We investigated the levels of BPI in cirrhotic patients and its relation to other endotoxin-binding proteins and inflammatory markers.

METHODS

Plasmatic levels of BPI, lipopolysaccharide-binding protein, soluble CD14, TNF-alpha and BPI mRNA expression in neutrophils were determined in 130 patients and 30 healthy controls. The capacity of patients' plasma to inhibit lipopolysaccharide (LPS)-mediated TNF-alpha production by monocytes from healthy donors was assessed in vitro.

RESULTS

Patients with cirrhosis exhibited an increase in BPI mRNA and plasma level of BPI when compared with healthy controls (P<0.05). Child C group displayed the highest frequency of patients with a high concentration of BPI. A positive correlation was found between TNF-alpha and plasma levels of BPI (P<0.01). High levels of BPI in plasma were able to significantly reduce in vitro TNF-alpha release by monocytes after a challenge with LPS (8.54 +/- 1.04 vs. 10.44 +/- 0.85 pg/ml, P=0.028).

CONCLUSION

BPI is increased in cirrhotic patients, especially in those with more severe liver disease. The amount of BPI in the plasma correlated with the TNF-alpha level and was able to reduce LPS-mediated TNF production by monocytes. BPI possibly plays a regulatory role by antagonizing the pro-inflammatory mechanisms mediated by TNF-alpha.

A Global Assessment of the Inflammatory Response Elicited Upon Open Abdominal Aortic Aneurysm Repair

The inflammatory response during elective open infrarenal abdominal aortic aneurysm repair and its impact on outcome is investigated. Twenty high-risk patients were enrolled, and blood samples were obtained at 8 perioperative time points. Endotoxin, cytokines (tumor necrosis factor-α and interleukin-1β, and interleukin-6), CD11b expression, and nitric oxide were measured. Peak endotoxin levels occurred within 30 minutes of reperfusion and were higher among patients developing complications. Interleukin-6 levels increased during reperfusion, reaching a peak on the first postoperative day. Interleukin-6 increase correlated with aortic clamp time and morbidity. CD11b expression increased 30 minutes after reperfusion, and this effect was greater among patients who developed complications. Endotoxin may be important in the pathogenesis of multiple organ dysfunction syndrome. Activated neutrophils may have a central role in tissue injury after reperfusion. Intraoperative CD11b upregulation may be an early marker for postoperative complications after infrarenal abdominal aortic aneurysm repair.

Lipopolysaccharide-binding protein plasma levels and liver TNF-alpha gene expression in obese patients: evidence for the potential role of endotoxin in the pathogenesis of non-alcoholic steatohepatitis

BACKGROUND

Some lines of evidence suggest that endotoxin may induce non-alcoholic steatohepatitis (NASH) in a background of fatty liver. However, a clear association between increased endotoxemia and development of steatohepatitis in obese patients has not been confirmed. We aim to assess the endotoxemic state of patients with non-alcoholic fatty liver disease (NAFLD) and its relationship with the liver expression of TNF-alpha and the presence of NASH.

METHODS

Prospective study comprising 40 patients with morbid obesity who were diagnosed with NAFLD. Blood samples and liver biopsies were collected. Endotoxemia was assessed by the evaluation of circulating level of LPS-binding protein (LBP). Plasma levels of LBP and TNF-alpha were assessed by ELISA. The expression of TNF-alpha in liver tissue was evaluated by real-time PCR. Histological examination was performed to evaluate the presence of steatosis or NASH.

RESULTS

Levels of LBP were increased in obese patients with NAFLD. In addition, plasma level of LBP was increased in patients with steatohepatitis (14.2 +/- 3.9 microg/mL) when compared with patients with simple steatosis (11.5 +/- 3.2 microg/mL), P=0.041. The TNF-alpha mRNA expression in liver tissue was significantly higher in patients with NASH. This increment correlated with the rise in plasma levels of LBP (r=0.412, P=0.036).

CONCLUSION

NAFLD patients have elevated plasma levels of LBP and they are further increased in patients with NASH. This increase is related to a rise in TNF-alpha gene expression in the hepatic tissue which supports a role for endotoxemia in the development of steatohepatitis in obese patients.