Distinct DNA methylation patterns of lysophosphatidic acid receptor genes during rat hepatocarcinogenesis induced by a choline-deficient L-amino acid-defined diet. Arch Toxicol. 2011;85:1303-1310. [PMID: 21290119 DOI: 10.1007/s00204-011-0656-7]

Autotaxin and lysophosphatidic acid signalling in lung pathophysiology

Autotaxin (ATX or ENPP2) is a secreted glycoprotein widely present in biological fluids. ATX primarily functions as a plasma lysophospholipase D and is largely responsible for the bulk of lysophosphatidic acid (LPA) production in the plasma and at inflamed and/or malignant sites. LPA is a phospholipid mediator produced in various conditions both in cells and in biological fluids, and it evokes growth-factor-like responses, including cell growth, survival, differentiation and motility, in almost all cell types. The large variety of LPA effector functions is attributed to at least six G-protein coupled LPA receptors (LPARs) with overlapping specificities and widespread distribution. Increased ATX/LPA/LPAR levels have been detected in a large variety of cancers and transformed cell lines, as well as in non-malignant inflamed tissues, suggesting a possible involvement of ATX in chronic inflammatory disorders and cancer. In this review, we focus exclusively on the role of the ATX/LPA axis in pulmonary pathophysiology, analysing the effects of ATX/LPA on pulmonary cells and leukocytes in vitro and in the context of pulmonary pathophysiological situations in vivo and in human diseases.

Choline's role in maintaining liver function: new evidence for epigenetic mechanisms

PURPOSE OF REVIEW

Humans eating diets low in choline develop fatty liver and liver damage. Rodents fed choline-methionine-deficient diets not only develop fatty liver, but also progress to develop fibrosis and hepatocarcinoma. This review focuses on the role of choline in liver function, with special emphasis on the epigenetic mechanisms of action.

RECENT FINDINGS

Dietary intake of methyl donors like choline influences the methylation of DNA and histones, thereby altering the epigenetic regulation of gene expression. The liver is the major organ within which methylation reactions occur, and many of the hepatic genes involved in pathways for the development of fatty liver, hepatic fibrosis, and hepatocarcinomas are epigenetically regulated.

SUMMARY

Dietary intake of choline varies over a three-fold range and many humans have genetic polymorphisms that increase their demand for choline. Choline is an important methyl donor needed for the generation of S-adenosylmethionine. Dietary choline intake is an important modifier of epigenetic marks on DNA and histones, and thereby modulates the gene expression in many of the pathways involved in liver function and dysfunction.

DNA methylome alterations in chemical carcinogenesis

Carcinogenesis, a complex multifactorial process of the transformation of normal cells into malignant cells, is characterized by many biologically significant and interdependent alterations triggered by the mutational and/or non-mutational (i.e., epigenetic) events. One of these events, specific to all types of cancer, is alterations in DNA methylation. This review summarizes the current knowledge of the role of DNA methylation changes induced by various genotoxic chemicals (carcinogenic agents that interact with DNA) and non-genotoxic carcinogens (chemicals causing tumor by mechanisms other than directly damaging DNA) in the lung, colorectal, liver, and hematologic carcinogenesis. It also emphasizes the potential role for epigenetic changes to serve as markers for carcinogen exposure and carcinogen risk assessment.

Genetic and epigenetic alterations of lysophosphatidic Acid receptor genes in rodent tumors by experimental models

Lysophosphatidic acid (LPA) is a bioactive mediator and induces several biological effects, including cell proliferation, migration, morphogenesis and differentiation. LPA interacts with at least six G protein-coupled receptors (GPCRs), including LPA receptor-1 (LPA(1)), LPA(2), LPA(3), LPA(4), LPA(5) and LPA(6). These receptors show different biological functions through the binding of LPA, depending on the type of cells. In human malignancies, a high level of LPA production was found in plasma and ascites in ovarian cancer cases. Moreover, aberrant expression levels of LPA receptor genes were detected in some cancer cells. Therefore, it is suggested that LPA receptors may be involved in the pathogenesis of tumor cells as well as LPA per se. Recently, we have reported that alterations of LPA receptor genes also occur in rodent tumors. In this review, we summarize the recent evidence in the investigations of LPA receptor alterations in rodent tumors by experimental models.