Matteo Vidali

Immune response towards lipid peroxidation products as a predictor of progression of non-alcoholic fatty liver disease to advanced fibrosis

Aims: Factors responsible for the progression of non-alcoholic fatty liver disease (NAFLD) to more severe liver injury are poorly understood. In the present study, we investigated the association between immune reactions triggered by oxidative stress and stage of NAFLD. Methods: Titres of IgG against human serum albumin adducted with malondialdehyde (MDA-HSA) or arachidonic acid hydroperoxide (AAHP) and against oxidised cardiolipin (Ox-CL) were measured in 167 NAFLD patients with steatosis only (n = 79), steatohepatitis (n = 74), or steatosis plus cirrhosis (n = 14), and in 59 age and sex matched controls. Results: Circulating IgG against lipid peroxidation products was significantly higher (p<0.001) in NAFLD patients than in controls. Oxidative stress dependent immune responses were not associated with obesity, type 2 diabetes, or with serum cholesterol, ferritin, or aminotransferase levels. Titres of lipid peroxidation related antibodies were also independent of the extent of steatosis and were similarly distributed in patients with and without necroinflammation. In contrast, the same antibodies were significantly increased in patients with advanced fibrosis or cirrhosis. Logistic regression analysis confirmed that anti-MDA antibodies were independently associated with progression of NALFD and that NAFLD patients with titres of anti-MDA-HSA antibodies above the control threshold value had a threefold (relative risk 2.82 (95% confidence interval 1.35–5.90); p = 0.007) higher risk of having advanced fibrosis/cirrhosis than patients whose antibody titres were within the control range. Conclusions: These results indicate that the presence of immune reactions triggered by oxidative stress can be an independent predictor of progression of NAFLD to advanced fibrosis.

Lipid peroxidation contributes to immune reactions associated with alcoholic liver disease

Increasing evidence indicates the involvement of immune reactions in the pathogenesis of alcoholic liver disease. We have investigated whether ethanol-induced oxidative stress might contribute to immune response in alcoholics. Antibodies against human serum albumin modified by reaction with malondialdehyde (MDA), 4-hydroxynonenal (HNE), 2-hexenal, acrolein, methylglyoxal, and oxidized arachidonic and linoleic acids were measured by ELISA in 78 patients with alcoholic cirrhosis and/or hepatitis, 50 patients with nonalcoholic cirrhosis, 23 heavy drinkers with fatty liver, and 80 controls. Titers of IgG-recognizing epitopes derived from MDA, HNE, and oxidized fatty acids were significantly higher in alcoholic as compared to nonalcoholic cirrhotics or healthy controls. No differences were instead observed in the titers of IgG-recognizing acrolein-, 2-hexenal-, and methylglyoxal-modified albumin. Alcoholics showing high IgG titers to one adduct tended to have high titers to all the others. However, competition experiments showed that the antigens recognized were structurally unrelated. Anti-MDA and anti-HNE antibodies were significantly higher in cirrhotics with more severe disease as well as in heavy drinkers with cirrhosis or extensive fibrosis than in those with fatty liver only. We conclude that antigens derived from lipid peroxidation contribute to the development of immune responses associated with alcoholic liver disease.

Interplay between oxidative stress and hepatic steatosis in the progression of chronic hepatitis C

BACKGROUND/AIMS The contribution of oxidative stress to the pathogenesis of chronic hepatitis C (CHC) is still poorly elucidated. This study investigated the relationship between oxidative stress, insulin resistance, steatosis and fibrosis in CHC. METHODS IgG against malondialdehyde-albumin adducts and HOMA-IR were measured as markers of oxidative stress and insulin resistance, respectively, in 107 consecutive CHC patients. RESULTS Oxidative stress was present in 61% of the patients, irrespective of age, gender, viral load, BMI, aminotransferase level, histology activity index (HAI) and HCV genotype. Insulin resistance and steatosis were evident in 80% and 70% of the patients, respectively. In the patients infected by HCV genotype non-3, but not in those with genotype 3 infection HOMA-IR (p<0.03), steatosis (p=0.02) and fibrosis (p<0.05) were higher in the subjects with oxidative stress than in those without. Multiple regression analysis revealed that, HOMA-IR (p<0.01), fibrosis (p<0.01) and oxidative stress (p<0.05) were independently associated with steatosis, whereas steatosis was independently associated with oxidative stress (p<0.03) and HOMA-IR (p<0.02). Steatosis (p<0.02) and HAI (p=0.007) were also independent predictors of fibrosis. CONCLUSIONS In patients infected by HCV genotype non-3, oxidative stress and insulin resistance contribute to steatosis, which in turn exacerbates both insulin resistance and oxidative stress and accelerates the progression of fibrosis.

Interplay between oxidative stress and immunity in the progression of alcohol-mediated liver injury

Inflammation is recognized increasingly as having an important role in the pathogenesis of alcoholic liver disease (ALD). Nonetheless, the mechanisms by which alcohol maintains hepatic inflammation are still characterized incompletely. Several studies have demonstrated that ethanol-induced oxidative stress promotes immune responses in ALD by stimulating both humoral and cellular reactions against liver proteins adducted to hydroxyethyl free radicals and several lipid peroxidation products. Moreover, ALD patients have autoantibodies targeting cytochrome P4502E1 and oxidized phospholipids. In both chronic alcohol-fed rats and heavy drinkers, the elevation of IgG against lipid peroxidation-derived antigens is associated with tumor necrosis factor-alpha production and the severity of liver inflammation. On this basis, we propose that allo- and autoimmune reactions associated with oxidative stress might contribute to fueling hepatic inflammation in ALD.

Oxidative stress as a trigger for cellular immune responses in patients with alcoholic liver disease

Serum antibodies reactive with neo‐antigens generated during ethanol metabolism have been identified in patients with alcoholic liver disease (ALD), although their role in the pathogenesis of disease remains unclear. In this study, we characterized peripheral blood mononuclear cell (PBMC) T‐cell and antibody responses to human serum albumin (HAS) adducted with acetaldehyde under reducing conditions (AcA‐HSA) or with malondialdehyde (MDA‐HSA) in patients with advanced ALD (AALD, n = 28), heavy drinkers with no liver disease (NALD, n = 14), and mild/moderate drinking controls (n = 22). Peak proliferative responses of PBMC were assessed in vitro by tritiated thymidine incorporation after the addition of optimized concentrations of antigen or OKT3. Antibody titers were determined by enzyme‐linked immunosorbent assay (ELISA). MDA‐HSA induced PBMC T‐cell proliferation was significantly higher in ALD than in NALD or control patients. Moreover, 10 of 28 (36%) of ALD patients had significant T‐cell proliferative responses to MDA‐HSA compared to 0 of 14 (0%, P = .02) of the NALD group and 2 of 22 (9%, P < .05) of controls. No significant difference in PBMC T‐cell response to Aca‐HSA was seen between subject groups. Patients with positive cellular responses to MDA had higher serum anti‐MDA antibody titers than those not exhibiting a positive cellular response (P < .005). In conclusion, the pattern of cellular and humoral responses to MDA adducts suggests that the development of these responses may be a susceptibility factor for the development of advanced alcoholic liver disease. The apparent importance of T‐cell responses to MDA adducts suggests that oxidative stress may represent an important stimulus for the development of cellular immune responses associated with advanced ALD. (HEPATOLOGY 2004;39:197–203.)

Role of the Interferon-Inducible Gene IFI16 in the Etiopathogenesis of Systemic Autoimmune Disorders

Abstract:  Interferons (IFNs) are now known to exert a multitude of immunological functions on both the innate and adaptive immunity. Given their pleiotropic effects on the immune system, it is conceivable that excess type I IFN or aberrant regulation of its signaling could contribute to autoimmunity. Several lines of evidence link IFNs to autoimmune disorders, in particular to systemic lupus erythematosus (SLE) and systemic sclerosis (SSc). Expression of a spectrum of genes that constitutes an “IFN signature” is the most significant observation indicating that IFNs may be dominant among the pathogenic mediators involved in some autoimmune diseases. A family of IFN‐inducible genes, designated HIN‐200 in the human and IFI‐200 in the murine species, encodes evolutionary related human (IFI16, MNDA, AIM2, IFIX) and murine proteins (Ifi202 a, Ifi202b, Ifi203, Ifi204, Ifi205/D3). Physiological IFI16 expression was found in cells of the immune system, in endothelial cells, and in stratified squamous epithelia, such as skin. The presence of anti‐IFI16 antibodies was reported in SLE and primary/secondary Sjögrens syndrome. More recently, we reported that anti‐IFI16 autoantibodies differentiate limited cutaneous systemic sclerosis (lcSSc) from diffuse systemic sclerosis (dcSSc). Molecular studies performed in primary endothelial cells overexpressing IFI16 demonstrated that it may be involved in the early steps of inflammation by modulating endothelial cell function, such as expression of adhesion molecules and chemokine production, cell growth, and apoptosis. Moreover, here we report that IFI16 expression is induced by proinflammatory cytokines. In this article the role of the IFI16 protein and its corresponding autoantibodies in the etiopathogenesis of systemic autoimmune diseases, in which chronic inflammation is involved, are discussed.

Immune mechanisms in alcoholic liver disease

Growing evidence indicates that inflammatory reactions play an important role in the pathogenesis of alcoholic liver disease (ALD). The implication of immunity in fueling chronic inflammation in ALD has emerged from clinical and experimental evidence showing the recruitment and the activation of lymphocytes in the inflammatory infiltrates of ALD and has received further support by the recent demonstration of a role of Th17 lymphocytes in alcoholic hepatitis. Nonetheless, the mechanisms by which alcohol triggers adaptive immune responses are still incompletely characterized. Patients with advanced ALD show a high prevalence of circulating IgG and T-lymphocytes towards epitopes derived from protein modification by hydroxyethyl free radicals (HER) and end-products of lipid peroxidation. In both chronic alcohol-fed rats and heavy drinkers the elevation of IgG against lipid peroxidation-derived antigens is associated with an increased production of pro-inflammatory cytokines/chemokines and with the severity of histological signs of liver inflammation. Moreover, CYP2E1-alkylation by HER favors the development of anti-CYP2E1 auto-antibodies in a sub-set of ALD patients. Altogether, these results suggest that allo- and auto-immune reactions triggered by oxidative stress might contribute to fuel chronic hepatic inflammation during the progression of ALD.

Antiphospholipid antibodies associated with alcoholic liver disease specifically recognise oxidised phospholipids

BACKGROUND Circulating antiphospholipid antibodies (aPL) are often detected in patients with alcoholic liver disease (ALD) but little is known about the causes of their formation. AIMS We have evaluated whether ethanol mediated oxidative injury might promote the development of aPL in ALD. PATIENTS AND METHODS IgG against β2 glycoprotein 1 (β2-GP1), cardiolipin, and human serum albumin (HSA) complexed with either oxidised arachidonic acid (HSA-APP) or malondialdehyde (HSA-MDA) were assayed by ELISA in heavy drinkers with or without ALD and in healthy subjects. RESULTS Circulating IgG recognising cardiolipin were significantly higher in ALD patients than in controls. However, anticardiolipin reactivity of ALD sera was only evident using, as the antigen, oxidised cardiolipin but not oxidation protected cardiolipin. In ALD patients, individual values of IgG antioxidised cardiolipin were associated with the titres of antibodies against HSA-MDA and HSA-APP (r=0.68 and 0.72, respectively; p<0.0001) used as markers of oxidative stress. ALD patients also displayed increased levels of antibodies against phospholipid binding protein β2-GP1, and individual reactivity towards oxidised cardiolipin and β2-GP1 were highly correlated (r=0.85; p<0.0001). IgG binding to oxidised cardiolipin, HSA-MDA, and HSA-APP was also significantly higher in β2-GP1 positive than in β2-GP1 negative sera. However, preadsorption of β2-GP1 positive sera on β2-GP1 coated ELISA plates reduced reactivity to oxidised cardiolipin by 80%, without affecting that to HSA-APP or HSA-MDA. CONCLUSIONS Ethanol induced oxidative injury is associated with the development of antibodies targeting complexes between oxidised cardiolipin and β2-GP1. These antibodies might account for high aPL titres observed in patients with severe ALD.

Immune responses against oxidative stress-derived antigens are associated with increased circulating tumor necrosis factor-α in heavy drinkers

Growing evidence indicates that pro-inflammatory cytokines play a key role in alcoholic liver disease (ALD). This study investigates whether immune response toward oxidative stress-derived antigens could be involved in promoting cytokine production in alcohol abusers. Cytokine profile and circulating IgG against human serum albumin modified by malondialdehyde (MDA-HSA) and against oxidized cardiolipin (Ox-CL) were evaluated in 59 heavy drinkers (HD) with (n=30) or without (n=29) ALD and 34 healthy controls. IgG against MDA-HSA and Ox-CL were significantly higher in HD with ALD than in HD without liver injury or healthy controls. The elevation of these antibodies was associated with higher circulating levels of IL-2 (p=0.005) and TNF-alpha (p=0.001), but not of IL-6 or IL-8. The prevalence of abnormal TNF-alpha was 5-fold higher in HD with oxidative stress-induced IgG than in those without. HD with the combined elevation of both TNF-alpha and oxidative stress-induced IgG had 11-fold (OR 10.7; 95%CI 1.2-97.2; p=0.023) greater risk of advanced ALD than those with high TNF-alpha, but no immune responses. Moreover, the combined elevation of TNF-alpha and lipid peroxidation-derived IgG was an independent predictor of ALD in HD. We propose that immune responses towards oxidative stress-derived antigen promote TNF-alpha production and contribute to liver damage in alcohol abusers.

Combination of oxidative stress and steatosis is a risk factor for fibrosis in alcohol-drinking patients with chronic hepatitis C.

BACKGROUND AND AIMS:Alcohol and HCV have been shown to interact in stimulating hepatic oxidative damage. Thus, we investigated the contribution of oxidative mechanisms in the progression of chronic hepatitis C (CHC) in alcohol consumers.METHODS: An increased IgG reactivity against lipid peroxidation-derived antigens was used as the marker for alcohol-induced oxidative damage in 125 CHC patients.RESULTS:Alcohol intake significantly increased the frequency of the subjects with elevated lipid peroxidation-related IgG. However, no association was evident between oxidative stress markers and the severity of steatosis, necroinflammation, or fibrosis. Multivariate analysis revealed that age (P = 0.014) and hepatic iron content (P = 0.034) were the only independent predictors of fibrosis in these patients. However, the risk of fibrosis in the subjects with both steatosis and oxidative stress-induced immune responses was 6- (OR 6.2, 95% CI 1.2–31.0) and 14-fold (OR 14.6, 95% CI 3.1–68.1) higher than in the subjects with steatosis alone or without steatosis, respectively. Multivariate analysis confirmed that the combination of steatosis and oxidative stress (P = 0.045) was, together with age (P = 0.021) and hepatic iron content (P = 0.027), an independent risk factor for fibrosis in CHC patients with alcohol intake.CONCLUSIONS:These results demonstrate that oxidative stress interacts with steatosis to promote the progression of CHC in alcohol-consuming patients.