Impact of cytokine gene variants on the prediction and prognosis of hepatocellular carcinoma in patients with cirrhosis.

BACKGROUND & AIMS: Genetic polymorphisms modulate the expression of proinflammatory cytokines. We prospectively assessed the influence of 6 single nucleotide polymorphisms (SNPs) in TNFα, IL6, and IL1ß genes on the risk of hepatocellular carcinoma (HCC) in patients with cirrhosis. METHODS: TNFα (G-238A, C-863A, G-308A), IL6 (C-174G), and IL1ß (C-31T, C-511T) SNPs were assessed in 232 alcoholics and 253 HCV-infected patients with biopsy-proven cirrhosis, prospectively followed-up and screened for HCC. Their influence on HCC development was assessed using the Kaplan-Meier method. RESULTS: These variants did not influence the risk of HCC in alcoholic patients. Conversely, two variants influenced the risk of HCC occurrence in patients with HCV-related cirrhosis, namely the TNFα-308 (A) allele (HR = 2.4 [1.6-3.7], Log-rank <0.0001) and the IL1ß-31 (T) allele (HR = 1.5 [1.1-2.1], Log-rank = 0.004). When stratifying HCV-infected patients into four genotypic associations expected to progressively increase TNFα and IL1ß production, we observed increasing risk of HCC occurrence (Log-rank <0.0001) from group 1 to 4. The TNFα-308 (A) allele was the only genetic trait independently associated with risk of HCC in these patients, along with older age, male gender, BMI, and platelet count. These variables led to construction of a predictive score able to separate patients with HCV-related cirrhosis into three subgroups with progressively increasing 5-year cumulative incidences of 4.7%, 14.1%, and 36.3%, respectively (Log-rank <0.0001). CONCLUSIONS: Genetic heterogeneity in the TNFα and IL1ß gene promoters influences the risk of HCC in patients with HCV-induced cirrhosis. These genetic data, when incorporated into clinical scores, are able to refine selection of risk classes of HCC.

Lipopolysaccharide-induced mitochondrial DNA depletion.

Hepatic energy depletion has been described in severe sepsis, and lipopolysaccharide (LPS) has been shown to cause mitochondrial DNA (mtDNA) damage. To clarify the mechanisms of LPS-induced mtDNA damage and mitochondrial alterations, we treated wild-type (WT) or transgenic manganese superoxide dismutase-overerexpressing (MnSOD(+++)) mice with a single dose of LPS (5 mg/kg). In WT mice, LPS increased mitochondrial reactive oxygen species formation, hepatic inducible nitric oxide synthase (NOS) mRNA and protein, tumor necrosis factor-alpha, interleukin-1 beta, and high-mobility group protein B1 concentrations. Six to 48 h after LPS administration (5 mg/kg), liver mtDNA levels, respiratory complex I activity, and adenosine triphosphate (ATP) contents were decreased. In addition, LPS increased interferon-ß concentration and decreased mitochondrial transcription factor A (Tfam) mRNA, Tfam protein, and mtDNA-encoded mRNAs. Morphological studies showed mild hepatic inflammation. The LPS (5 mg/kg)-induced mtDNA depletion, complex I inactivation, ATP depletion, and alanine aminotransferase increase were prevented in MnSOD(+++) mice or in WT mice cotreated with 1400W (a NOS inhibitor), (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl)triphenylphosphonium chloride, monohydrate (a superoxide scavenger) or uric acid (a peroxynitrite scavenger). The MnSOD overexpression delayed death in mice challenged by a higher, lethal dose of LPS (25 mg/kg). In conclusion, LPS administration damages mtDNA and alters mitochondrial function. The protective effects of MnSOD, NOS inhibitors, and superoxide or peroxynitrite scavengers point out a role of the superoxide anion reacting with NO to form mtDNA- and protein-damaging peroxynitrite. In addition to the acute damage caused by reactive species, decreased levels of mitochondrial transcripts contribute to mitochondrial dysfunction.

MnSOD overexpression prevents liver mitochondrial DNA depletion after an alcohol binge but worsens this effect after prolonged alcohol consumption in mice.

Both acute and chronic alcohol consumption increase reactive oxygen species (ROS) formation and lipid peroxidation, whose products damage hepatic mitochondrial DNA (mtDNA). To test whether manganese superoxide dismutase (MnSOD) overexpression modulates acute and chronic alcohol-induced mtDNA lesions, transgenic MnSOD-overexpressing (TgMnSOD(+++)) mice and wild-type (WT) mice were treated by alcohol, either chronically (7 weeks in drinking water) or acutely (single intragastric dose of 5 g/kg). Acute alcohol administration increased mitochondrial ROS formation, decreased mitochondrial glutathione, depleted and damaged mtDNA, durably increased inducible nitric oxide synthase (NOS) expression, plasma nitrites/nitrates and the nitration of tyrosine residues in complex V proteins and decreased complex V activity in WT mice. These effects were prevented in TgMnSOD(+++) mice. In acutely alcoholized WT mice, mtDNA depletion was prevented by tempol, a superoxide scavenger, L-NAME and 1400W, two NOS inhibitors, or uric acid, a peroxynitrite scavenger. In contrast, chronic alcohol consumption decreased cytosolic glutathione and increased hepatic iron, lipid peroxidation products and respiratory complex I protein carbonyls only in ethanol-treated TgMnSOD(+++) mice but not in WT mice. In chronic ethanol-fed TgMnSOD(+++) mice, but not WT mice, mtDNA was damaged and depleted, and the iron chelator, deferoxamine (DFO), prevented this effect. In conclusion, MnSOD overexpression prevents mtDNA depletion after an acute alcohol binge but aggravates this effect after prolonged alcohol consumption, which selectively triggers iron accumulation in TgMnSOD(+++) mice but not in WT mice. In the model of acute alcohol binge, the protective effects of MnSOD, tempol, NOS inhibitors and uric acid suggested a role of the superoxide anion reacting with NO to form mtDNA-damaging peroxynitrite. In the model of prolonged ethanol consumption, the protective effects of DFO suggested the role of iron reacting with hydrogen peroxide to form mtDNA-damaging hydroxyl radical.