Interaction of Mitochondrial and Epigenetic Regulation in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a pathology preceded mainly by cirrhosis of diverse etiology and is associated with uncontrolled dedifferentiation and cell proliferation processes. Many cellular functions are dependent on mitochondrial function, among which we can mention the enzymatic activity of PARP-1 and sirtuin 1, epigenetic regulation of gene expression, apoptosis, and so on. Mitochondrial dysfunction is related to liver diseases including cirrhosis and HCC; the energetic demand is not properly supplied and mitochondrial morphologic changes have been observed, resulting in an altered metabolism. There is a strong relationship between epigenetics and mitochondrion since the first one is dependent on the correct function of the last one. There is an interest to improve or to maintain mitochondrial integrity in order to prevent or reverse HCC; such is the case of IFC-305 that has a beneficial effect on mitochondrial function in a sequential model of cirrhosis-HCC. In this model, IFC-305 downregulates the expression of PCNA, thymidylate synthase, HGF and its receptor c-Met and upregulates the cell cycle inhibitor p27, thereby decreasing cell proliferation. Both effects, improvement of mitochondria function and reduction of tumor proliferation, suggest its use as HCC chemoprevention or as an adjuvant in chemotherapy

Molecular and Cellular Aspects of Cirrhosis and How an Adenosine Derivative Could Revert Fibrosis

Hepatic fibrosis occurs in response to persistent liver damage and is characterized by an excessive accumulation of extracellular matrix. When the damage is prolonged, there is a chronic inflammation and persistent hepatic fibrosis eventually leads to cirrhosis, where in addition to the scar, there is an important vascular remodeling associated with portal hypertension and, if decompensated, leads to death or can develop hepatocellular carcinoma. We have been studying the pharmacologic functions of adenosine, finding that a derivative of this nucleoside, IFC-305, shows hepatoprotective effects in a CCl4-induced rat cirrhosis model where it reverses liver fibrosis through modulation of fibrosis-related genes and by ameliorating hepatic function. Furthermore, this compound has the property to rescue cell cycle inhibition in vivo, prevents hepatic stellate cell activation, modulates anti-inflammatory macrophage polarization, and favors a chromatin context that could decrease the genomic instability and characteristics of cirrhosis, enabling the recovery of gene expression profile. Here we show results that contribute to the comprehension of molecular and cellular mechanism of cirrhosis, give the opportunity to suggest biomarkers to the early diagnostic of this pathology, and constitute the fundaments to suggest IFC-305 as a coadjuvant for treatment of this disease

Hyperkalemic periodic paralysis M1592V mutation modifies activation in human skeletal muscle Na+ channel

Mutations in the human skeletal muscle Na+ channel underlie the autosomal dominant disease hyperkalemic periodic paralysis (HPP). Muscle fibers from affected individuals exhibit sustained Na+ currents thought to depolarize the sarcolemma and thus inactivate normal Na+ channels. We expressed human wild-type or M1592V mutant α-subunits with the β- subunit in Xenopus laevis oocytes and recorded Na+ currents using two- electrode and cut-open oocyte voltage-clamp techniques. The most prominent functional difference between M1592V mutant and wild-type channels is a 5- to 10-mV shift in the hyperpolarized direction of the steady-state activation curve. The shift in the activation curve for the mutant results in a larger overlap with the inactivation curve than that observed for wild- type channels. Accordingly, the current through M1592V channels displays a larger noninactivating component than does that through wild-type channels at membrane potentials near -40 mV. The functional propertie

Recovery of the Cell Cycle Inhibition in CCl

Introduction. Cirrhosis is a chronic degenerative illness characterized by changes in normal liver architecture, failure of hepatic function, and impairment of proliferative activity. The aim of this study is to know how IFC-305 compound induces proliferation of the liver during reversion of cirrhosis. Methods. Once cirrhosis has been installed by CCl(4) treatment for 10 weeks in male Wistar rats, they were divided into four groups: two received saline and two received the compound; all were euthanized at 5 and 10 weeks of treatment. Liver homogenate, mitochondria, and nucleus were used to measure cyclins, CDKs, and cell cycle regulatory proteins PCNA, pRb, p53, E2F, p21, p27, HGF, liver ATP, and mitochondrial function. Results. Diminution and small changes were observed in the studied proteins in the cirrhotic animals without treatment. The IFC-305-treated rats showed a clear increase in most of the proteins studied mainly in PCNA and CDK6, and a marked increased in ATP and mitochondrial function. Discussion/Conclusion. IFC-305 induces a recovery of the cell cycle inhibition promoting recovery of DNA damage through the action of PCNA and p53. The increase in energy and preservation of mitochondrial function contribute to recovering the proliferative function

Control of scavenger receptor-mediated endocytosis by novel ligands of different length

Abstract The scavenger receptor recognized as a multiligand family of receptors falls in the group that is internalised through endocytosis. In this report we used several recombinant fragments of the tapeworm protein paramyosin, known to form filamentous dimers that bind collagenous structures as ligands of different length for the class A type I scavenger receptor (SR-AI). While native CHO cells are unresponsive to any of the recombinant fragments, it is shown that CHO cells transfected with this receptor efficiently internalise recombinant fragments that correspond to two thirds of the full-length paramyosin. In contrast, recombinant products corresponding to one-third of the full-length paramyiosin are not internalised. It is also shown that important molecules in the organization of the coated pit, are enriched when the two-thirds long paramyosin fragments were bound and internalised through the SR-AI. Moreover, internalisation of these fragments trigger a classical apoptotic pathway shown by the presence of TUNEL positive cells and the appearance of apoptotic bodies. We report paramyosin as a new ligand for the scavenger receptor and provide evidence supporting the notion that these receptors upon the formation of arrays with length-specific molecules, not only trigger endocytosis but also seem to regulate the synthesis of molecules involved in the organization of coated pits. (Mol Cell Biochem 271: 123-132, 2005

Mitoepigenetics and hepatocellular carcinoma

Mitochondria are the center of energy production in eukaryotic cells and are crucial for several cellular processes. Dysfunctional mitochondria have been associated with cancer progression. Mitochondria contain their own circular DNA (mtDNA), which codes for 13 proteins, 2rRNA, 22tRNA and non-coding RNAs. Recent evidence showed the presence of 5-methylcytosine and 5-hydroximethylcytosine in mtDNA suggesting that the level of gene expression could be modulated like a nuclear DNA by direct epigenetic modifications. Mitoepigenetics is a bidirectional phenomenon in the epigenetic regulation of mitochondrial genes encoded in both the nucleus and the mitochondrion. This process is affected by SAM-mediated methylation and hydroxymethylation of mtDNA and by nuclear chromatin modulators from mitochondria, such as Acetyl-CoA and NAD+. There is some information about physiological and pathological methylated profiles, but information is scarce for hepatocellular carcinoma (HCC). The aim of this review is to summarize the mitoepigenetic knowledge in HCC already reported so far, through a keywords search in Medline. In addition, the deregulation of energy intermediaries needed for the mitoepigenetic regulation is described. As this is a new area of study, a rigorous analysis and careful interpretation and integration of results are needed