Hepatocyte apoptosis is a pathologic feature of human alcoholic hepatitis
Introduction
Alcoholic hepatitis (AH) is a toxic liver disease resulting from excessive alcohol use. Although the clinical spectrum of the disease includes both non-icteric and icteric presentations, an estimated mortality of more than 50% occurs in severe forms of icteric AH [1]. Moreover, AH, even as a mild, non-icteric disease, predisposes to the development of cirrhosis [2]. Due to the continued use of alcohol in most cultures, AH remains a significant public health problem. In alcoholics with liver disease, the incidence of uncomplicated AH has been estimated to be up to 33% in the US. However, the true incidence might be higher, since the diagnosis requires biopsy confirmation and is therefore often missed, especially in milder forms of AH [3]. Treatment options for AH remain limited, in part, because the pathophysiology of AH remains poorly understood. Insight into the mechanisms of disease could therefore lead to new therapeutic approaches to prevent the short- and long-term sequelae of AH.
Apoptosis is a form of cell death characterized by stereotypic morphological and biochemical features [4]. Apoptosis is now recognized as one of the initiating events in toxic liver injury, and is increasingly recognized as a key mechanism in tissue inflammation and fibrosis. For example, in kidney and lung tissues, the inhibition of apoptosis abrogates the inflammatory response following ischemia/reperfusion injury and prevents drug-induced fibrosis, respectively [5], [6]. In experimental models of liver injury, hepatocyte apoptosis is associated with an increase in hepatocyte derived enzymes, a clinical indicator of liver injury [7]. If the magnitude of liver cell apoptosis is sufficient to overwhelm the removal process, a loss of tissue architecture and organ failure can occur [8], [9]. Morphological evidence of apoptosis has been identified in such diverse clinical liver diseases as viral hepatitis, cholestasis, and copper overload states [10]. Thus, apoptosis appears to be a key event in many pathophysiological processes affecting the liver, and the inhibition of apoptosis holds promise as a therapeutic strategy for human liver diseases.
Recently, it has been suggested that hepatocyte apoptosis is also a feature of alcohol-induced liver disease [11]. Chronic alcohol administration in mice results in a significant time-dependent increase of apoptotic bodies in hepatocytes, especially around terminal hepatic venules. Similar to human AH, these changes were potentially reversible after the discontinuation of alcohol [12]. Although these experimental data demonstrate that apoptosis plays role in alcoholic liver injury, only one study suggests that apoptosis occurs in AH [13]. However, this study was limited in the number of patients examined (n=5), did not quantitate the magnitude of apoptosis, nor was apoptosis correlated with disease severity. Moreover, the studies used the TUNEL assay to identify apoptosis (an assay based on DNA damage) and did not determine if caspase activation occurred (an essential feature of apoptosis). Thus, the purpose of the present study was to quantitate hepatocyte apoptosis in patients with biopsy-proven AH, to determine if caspase activation occurs and to correlate the rates of apoptosis with the disease severity. In addition, we determined the expression of the Fas receptor and tumor necrosis factor-α receptor 1 (TNF-R1) because these death receptors have been associated with hepatocyte apoptosis in other diseases.
Section snippets
Patient groups
This is a retrospective study approved by the Mayo Clinic Institutional Review Board, employing archived liver biopsy specimens which were fixed and embedded in paraffin by standard procedures. All patients had undergone a liver biopsy to confirm the clinical diagnosis of AH. Liver biopsy material was obtained from 26 patients with AH. Histologically normal liver specimens were obtained from the 27 patients who underwent hepatic resection for colorectal metastases. The diagnosis of AH was based
Is hepatocyte apoptosis increased in AH?
To address this question, hepatocyte apoptosis was assessed in patients with AH and in controls using two different techniques. First, TUNEL-staining was used to identify apoptosis in liver specimens. In normal livers, only rare TUNEL-positive cells were identified. In contrast, TUNEL-positive cells were readily observed in the tissue of patients with AH (Fig. 1a). The quantitation of these TUNEL-positive cells showed a six-fold increase in the AH patient group (2.0±0.31 apoptotic cells/×400
Discussion
In the present study, we have demonstrated that hepatocyte apoptosis is a prominent feature of AH and is significantly increased in patients with this disease. Moreover, the number of apoptotic cells appears to correlate with the severity of AH, as hepatocyte apoptosis was most pronounced in patients with high bilirubin- and AST-levels, and grade 4 steatohepatitis. Collectively, these data suggest that apoptosis plays an important role in the pathophysiology of AH. In addition, Fas, but not
Acknowledgements
This work was supported by grants from the National Institutes of Health (DK41876, GJ Gores), the Deutsche Forschungsgemeinschaft (Ru742/1-1, C Rust), the Gainey Foundation, St. Paul, MN, and by the Mayo Foundation, Rochester, MN.
References (31)
Alcoholic hepatitis
Clin Gastroenterol
(1981)Nuclear changes in apoptosis
Curr Opin Cell Biol
(1995)Liver apoptosis
J Hepatol
(1997)- et al.
Histological grading and staging of chronic hepatitis
J Hepatol
(1995) - et al.
Measurement of cell death
Methods Cell Biol
(1998) - et al.
Oxidative stress-mediated apoptosis of hepatocytes exposed to acute ethanol intoxication
Hepatology
(1997) - et al.
Chronic ethanol feeding increases apoptosis and cell proliferation in rat liver
J Hepatol
(1994) - et al.
The central executioners of apoptosis: caspases or mitochondria?
Trends Cell Biol
(1998) - et al.
Raised plasma soluble Fas and Fas-ligand in alcoholic liver disease
Lancet
(1998) - et al.
Selective glutathione depletion of mitochondria by ethanol sensitizes hepatocytes to tumor necrosis factor
Gastroenterology
(1998)
Antibodies to tumor necrosis factor alfa attenuate hepatic necrosis and inflammation caused by chronic exposure to ethanol in the rat
Hepatology
The treatment of alcoholic hepatitis
Alcohol Alcohol
Alcoholic hepatitis: clinicopathologic features and therapy
Semin Liver Dis
Inhibition of apoptosis induced by ischemia-reperfusion prevents inflammation
J Clin Invest
Essential roles of the Fas–Fas ligand pathway in the development of pulmonary fibrosis
J Clin Invest
Cited by (242)
Transcription Factor Forkhead Box O1 Mediates Transforming Growth Factor-β1–Induced Apoptosis in Hepatocytes
2023, American Journal of PathologyCell death PET/CT imaging of rat hepatic fibrosis with <sup>18</sup>F-labeled small molecule tracer
2021, Nuclear Medicine and BiologyCitation Excerpt :The pathogenesis mechanism of hepatic fibrosis is complex and diverse [3]. Clinical data and animal models have suggested that hepatocyte death is a key trigger of liver disease progression, then manifested by the subsequent development of inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma [10–16]. On the other hand, fibrogenic cell death is an important mechanism for the resolution of liver fibrosis [30].
Hepatoprotective effect of plant polysaccharides from natural resources: A review of the mechanisms and structure-activity relationship
2020, International Journal of Biological MacromoleculesDistinct Types of Cell Death and Implications in Liver Diseases: An Overview of Mechanisms and Application
2023, Journal of Clinical and Translational HepatologyResearch progress on the modulating effect of edible mushroom polysaccharides on alcoholic liver disease
2023, Tianran Chanwu Yanjiu yu Kaifa