Detection of apoptotic caspase activation in sera from patients with chronic HCV infection is associated with fibrotic liver injury

Abstract

Chronic hepatitis C virus (HCV) infection is characterized by inflammatory liver damageand is associated with a high risk of development of cirrhosis and hepatocellular carcinoma. Although histological examination of liver biopsies is currently the gold standard for the detection of early liver damage, there is a strong need for better noninvasive methods. We recently demonstrated that the proapoptotic activation of caspases is considerably enhanced in histological sections from HCV-infected liver tissue, suggesting an important role of apoptosis in liver damage. Here, we investigated whether caspase activation is detectable also in sera from patients with chronic HCV infection. Using a novel enzyme-linked immunosorbent assay that selectively recognizes a proteolytic neoepitope of the caspase substrate cytokeratin-18, we demonstrate that caspase activity is markedly increased in the sera of HCV patients. Interestingly, while 27% of patients with chronic HCV infection showed normal aminotransferase levels despite inflammatory and fibrotic liver damage, more than 50% of those patients exhibited already elevated serum caspase activity. Moreover, 30% of patients with normal aminotransferase but elevated caspase activity revealed higher stages of fibrosis. In conclusion, compared with conventional surrogate markers such as aminotransferases, detection of caspase activity in serum might be a more sensitive method of detecting early liver injury. Thus, measurement of caspase activity might provide a novel diagnostic tool, especially for patients with normal aminotransferases but otherwise undiagnosed histologically active hepatitis and progressive fibrosis. H epatitis C virus (HCV) is estimated to infect upto 200 million people worldwide-more than 3% of the world population. 1 HCV infection is characterized by inflammatory liver damage and a long viral persistence associated with a high risk of developing cirrhosis and hepatocellular carcinoma. There is increasing evidence suggesting that liver cell damage in chronic HCV infection is mediated by the induction of apoptosis. [2][3][4][5][6] The importance of apoptosis in HCV infection has originally been proposed in view of patho-morphological features, including cell shrinkage and fragmentation of the nucleus-particularly in areas of piecemeal necrosis, the presence of acidophilic bodies, and focal cell dropouts in the liver lobule, which are characteristic features of individually infected hepatocytes. 7 The molecular mechanisms and signal transduction pathways that cause liver cell damage during HCV infection have not been clearly defined. Over the last few years there has been increasing evidence that death receptor/ligand systems, particularly CD95, play a crucial role in liver damage. Both CD95 and its ligand CD95L have been shown to be up-regulated in HCV infection. 8 -11 Various recent studies demonstrate that the key morphological alterations of apoptosis are mediated by a family of intracellular cysteine proteases, called caspases, that cleave several cellul...

Steatosis: Co-factor in other liver diseases

“…More recently, detection of apoptotic caspase activity in serum has been proposed as a sensitive method of detecting early liver injury in patients with chronic HCV. 38 Other Metabolic Factors. It has been argued that steatosis is simply a by-product of metabolic factors, principally insulin resistance, and that the latter may be the principal driver of enhanced fibrosis in HCV.…”

An apoptosis biomarker for prediction of nonalcoholic steatohepatitis

“…7 In addition, detection of caspase-generated CK-18 fragments in sera from patients with chronic hepatitis C virus (HCV) infection has recently been associated with fibrotic liver injury. 8 Another study showed a correlation of CK-18 fragment levels with the proportion of HCV-associated liver steatosis. 9 In this latter study, only patients with minimal inflammatory disease activity and low stages of fibrosis were included, suggesting that even under conditions of mild inflammation, CK-18 fragment levels correlate with the extent of steatosis.…”

Cre-estrogen receptor-mediated hepatitis C virus structural protein expression in mice

“…CK-18 is the major intermediate filament protein of liver cells and is important for hepatocyte integrity. During apoptosis, CK-18 is cleaved by caspases, which expose a new epitope that can be recognized by a mAb, and is a biomarker for hepatitis C activity in clinical practice (Bantel et al, 2004;Feldstein and Gores, 2004;Seidel et al, 2005). Using a commercial ELISA kit, it was found that serum CK-18 values in tamoxifen-treated double tg mice were slightly higher than those in control animals (Fig.…”

“…Hepatic caspase activity was determined in serum by the quantitative measurement of the apoptosis-associated neoepitope in the C-terminal domain of cytokeratin-18 (CK-18) using the M30-Apoptosense ELISA kit (Peviva; Alexis, Grünwald, Germany) (Bantel et al, 2004), according to the manufacturer's instructions.…”