3T3-L1 adipocytes possess anandamide- and epinephrine-responsive machinery for MDM2 distribution to the plasma membrane.

The effects of biomolecules on peripheral tissues and their responsive machinery are not well understood. We examined MDM2 level in the plasma membrane (PM) and total MDM2 level of 3T3-L1 adipocytes treated with biomolecular anandamide, epinephrine, and other agents for 15 min. We also examined biomolecular responses in cells treated with mithramycin A, a binding inhibitor, or cells exposed to cooling and cell viability. Immunoblotting revealed that PM MDM2 level increased and total MDM2 level was not altered following treatment with anandamide, epinephrine, capsaicin, CL316243, and aluminum fluoride. PM MDM2 distribution caused by a biomolecular concentration was maintained by treatment with mithramycin A and exposure of cells to 28°C or 32°C but not to 18°C, and PM MDM2 levels after treatment with high concentrations of biomolecules were altered upon exposure to the inhibitor and mild hypothermia. These conditions did not decrease cell viability. Our findings indicate that 3T3-L1 adipocytes possess molecular machinery that responds differentially to anandamide and epinephrine under the inhibitor treatment and cool temperature conditions and that is sensitive to other agents (which mimic biomolecular responses); these machineries can induce subcellular alterations in molecular interactions. We provide information helpful for clarifying biomolecular responsive machinery present in 3T3-L1 adipocytes.

Cooling-increased phospho-ß-arrestin-1 and ß-arrestin-1 expression levels in 3T3-L1 adipocytes.

Cooling induces several responses that are modulated by molecular inhibitors and activators and receptor signaling. Information regarding potential targets involved in cold response mechanisms is still insufficient. We examined levels of the receptor-signaling mediator ß-arrestin-1 and phospho-Ser-412 ß-arrestin-1 in 3T3-L1 adipocytes exposed to 4-37 °C or treated with some molecular agents at 37°C. We also cooled cells with or without modification and signal-modulating agents. These conditions did not decrease cell viability, and western blot analysis revealed that exposure to 4 °C for 1.5h and to 28 and 32 °C for 24 and 48 h increased phospho-ß-arrestin-1 and ß-arrestin-1 levels and that exposure to 4 and 18 °C for 3 and 4.5h increased ß-arrestin-1 level. Serum removal and rewarming abolished ß-arrestin-1 alterations induced by cooling. Mithramycin A (a transcription inhibitor) treatment for 4 and 24h increased the level of ß-arrestin-1 but not that of phospho-ß-arrestin-1. The level of phospho-ß-arrestin-1 was increased by okadaic acid (a phosphatase inhibitor), decreased by epinephrine and aluminum fluoride (receptor-signaling modulators), and unaffected by N-ethylmaleimide (an alkylating agent) at 37 °C. N-Ethylmaleimide and the receptor-signaling modulators did not alter ß-arrestin-1 expression at 37 °C but impaired the induction of phospho-ß-arrestin-1 at 28 and 32 °C without affecting the induction of ß-arrestin-1. We show that cold-induced ß-arrestin-1 alterations are partially mimicked by molecular agents and that the responsive machinery for ß-arrestin-1 requires serum factors and N-ethylmaleimide-sensitive sites and is linked to rewarming- and receptor signaling-responsive machinery. Our findings provide helpful information for clarifying the cold-responsive machinery for ß-arrestin-1 and elucidating low-temperature responses.

MDM2-related responses in 3T3-L1 adipocytes exposed to cooling and subsequent rewarming.

Insulin-like growth factor-I and insulin induce the production of phospho-Ser-166 MDM2, a target of Akt, and influence the formation of the MDM2 complex. The glycolipid hormone insulin differentially activates phosphatidylinositol 3-kinase (PI3K)/Akt pathways in 3T3-L1 (L1) adipocytes incubated at 19 °C. Responses of L1 adipocytes to different temperature changes and their regulatory mechanisms are poorly understood. We exposed L1 adipocytes to cooling and subsequent rewarming in the presence or absence of wortmannin, a PI3K inhibitor, or mithramycin A, a transcription inhibitor, and examined the induction of phospho-Ser-166 MDM2 and MDM2 and the subcellular formation of the MDM2 complex using western blot analysis. Exposure to 28 and 18 °C induced phospho-MDM2 in cells and increased the level of MDM2 in the plasma membrane of cells. These temperatures did not affect the total MDM2 level. Similar results were obtained when the cells were treated with insulin. Exposure to 4 °C increased the total MDM2 level and did not induce phospho-MDM2, which was induced by rewarming at 37 °C after cooling at 4°C without any alteration in the protein level. Mithramycin A (10 µM) did not alter the increase in protein level induced at 4 °C. The induction of phospho-molecules at 28 and 18 °C was impaired slightly by 1 µM of wortmannin but not by 0.1 µM of wortmannin. This low concentration of wortmannin completely blocked the induction of phospho-MDM2 by rewarming. Our results indicate that temperature changes induce MDM2-related responses, including those that are stimulated by receptor responses and dependent on a kinase inhibitor, in L1 adipocytes.

Induction of phospho-Thr-172 AMPK in 3T3-L1 adipocytes exposed to cold or treated with anisomycin, mithramycin A, and ionic compounds.

Cold exposure induces cellular responses, including subcellular molecule expression and transport responses, similar to those stimulated by insulin in 3T3-L1 (L1) adipocytes. The transport response is induced in L1 adipocytes treated with translation inhibitors. We examined the level of phospho-Thr-172 AMPK (an active form of AMPK, a known energy-state sensor) in L1 adipocytes exposed to different temperatures of 4-37 degrees C or stressors, including chemical inhibitors and activators. The phospho-AMPK level increased in cold-exposed cells and their subcellular fractions and decreased after rewarming and serum depletion. The phospho-molecule was also induced by anisomycin, which induces protein kinase activation and translation inhibition; mithramycin A, an inhibitor of transcription factor binding; and ionic compounds, which stimulate molecular signaling and alter several gene expression. These results indicate that temperature responses are mimicked by metabolic stressors through phospho-molecule alteration. Our results provide possible clues for clarifying the mechanisms underlying cold responses in L1 adipocytes.

Polymorphisms in promoter sequences of the p15 ( INK4B ) and PTEN genes of normal Japanese individuals.

Gene promoter regions of p15(INK4B), a cyclin-dependent kinase inhibitor, and phosphatase and tensin homolog (PTEN), a dual-function protein and lipid phosphatase, interact with regulatory factors for gene transcription and methylation. Normal individuals exhibit sequence polymorphisms in these regulatory genes. We isolated genomic DNA from whole blood of healthy Japanese individuals and sequenced promoter regions of the p15 ( INK4B ) and PTEN genes. We also examined the influence of polymorphisms on promoter activity in several cell lines. We identified polymorphisms at positions -699, -394, and -242 and an insertion at position -320 in the p15 ( INK4B ) gene and a polymorphism at position -1142 in the PTEN gene. Reporter gene analysis revealed that these polymorphisms influenced transcriptional regulation in their cell lines. Our results indicate for the first time that promoter sequences of the p15 ( INK4B ) and PTEN genes differ among normal Japanese individuals and that promoter polymorphisms can influence gene transcription.

Polymorphisms in promoter sequences of MDM2, p53, and p16 genes in normal Japanese individuals.

Research has been conducted to identify sequence polymorphisms of gene promoter regions in patients and control subjects, including normal individuals, and to determine the influence of these polymorphisms on transcriptional regulation in cells that express wild-type or mutant p53. In this study we isolated genomic DNA from whole blood of healthy Japanese individuals and sequenced the promoter regions of the MDM2, p53, and p16(INK4a) genes. We identified polymorphisms comprising 3 nucleotide substitutions at exon 1 and intron 1 regions of the MDM2 gene and 1 nucleotide insertion at a poly(C) nucleotide position in the p53 gene. The Japanese individuals also exhibited p16(INK4a) polymorphisms at several positions, including position -191. Reporter gene analysis by using luciferase revealed that the polymorphisms of MDM2, p53, and p16(INK4a) differentially altered luciferase activities in several cell lines, including the Colo320DM, U251, and T98G cell lines expressing mutant p53. Our results indicate that the promoter sequences of these genes differ among normal Japanese individuals and that polymorphisms can alter gene transcription activity.

Polymorphisms in promoter sequences of MDM2, p53, and p16INK4a genes in normal Japanese individuals

Research has been conducted to identify sequence polymorphisms of gene promoter regions in patients and control subjects, including normal individuals, and to determine the influence of these polymorphisms on transcriptional regulation in cells that express wild-type or mutant p53. In this study we isolated genomic DNA from whole blood of healthy Japanese individuals and sequenced the promoter regions of the MDM2, p53, and p16INK4a genes. We identified polymorphisms comprising 3 nucleotide substitutions at exon 1 and intron 1 regions of the MDM2 gene and 1 nucleotide insertion at a poly(C) nucleotide position in the p53 gene. The Japanese individuals also exhibited p16INK4a polymorphisms at several positions, including position -191. Reporter gene analysis by using luciferase revealed that the polymorphisms of MDM2, p53, and p16INK4a differentially altered luciferase activities in several cell lines, including the Colo320DM, U251, and T98G cell lines expressing mutant p53. Our results indicate that the promoter sequences of these genes differ among normal Japanese individuals and that polymorphisms can alter gene transcription activity.

Cancer prevention by phytochemicals.

Information has been accumulated indicating that diets rich in vegetables and fruits can reduce the risk of a number of chronic diseases, including cancer, cardiovascular disease, diabetes and age-related macular degeneration. Phytochemicals (various factors in plant foods), such as carotenoids, antioxidative vitamins, phenolic compounds, terpenoids, steroids, indoles and fibers, have been considered responsible for the risk reduction. Among them, a mixture of natural carotenoids has been studied extensively and proven to show beneficial effects on human cancer prevention.

Phosphorylation of c-Jun N-terminal kinase in human hepatoblastoma cells is transiently increased by cold exposure and further enhanced by subsequent warm incubation of the cells.

During a cold preservation and reperfusion process of organs, cells are exposed to two major stresses, i.e. changes in oxygen concentration and temperature. c-Jun N-terminal kinase (JNK) /stress-activated protein kinase is activated by various stresses through its phosphorylation. Although hypoxia and subsequent reoxygenation is known to activate JNK, little is known about effects of hypothermia and subsequent rewarming on JNK activation. Thus, we investigated the activation of JNK in human hepatoblastoma (HepG2) cells exposed to a temperature of 5 degrees C and in those rewarmed at 37 degrees C. Western blot analysis using an anti-phospho-JNK antibody revealed that p54 JNK was transiently phosphorylated in cold-stressed cells. In addition, the phosphorylation of p54 JNK was further increased by rewarming of the cells. Since translational and transcriptional abilities were markedly reduced in the cold-stressed cells, effects of translation and transcription inhibitors on the phosphorylation of p54 JNK were determined. Cycloheximide, but not actinomycin D, increased the phosphorylation of p54 JNK in HepG2 cells. These results suggest that hypothermia alone transiently increases the p54 JNK phosphorylation possibly through reduction of protein synthesis and that rewarming after hypothermia stimulates the phosphorylation of p54 JNK.

Carotenoids in cancer chemoprevention.

Various natural carotenoids, besides beta-carotene, were proven to have anticarcinogenic activity, and some of them showed more potent activity than beta-carotene. Thus, these carotenoids (alpha-carotene, lutein, zeaxanthin, lycopene, beta-cryptoxanthin, fucoxanthin, astaxanthin, capsanthin, crocetin and phytoene), as well as beta-carotene, may be useful for cancer prevention. In the case of phytoene, the concept of 'bio-chemoprevention', which means biotechnology-assisted method for cancerchemoprevention, may be applicable. In fact, establishment of mammalian cells producing phytoene was succeeded by the introduction of crtB gene, which encodes phytoene synthase, and these cells were proven to acquire the resistance against carcinogenesis. Antioxidative phytoene-containing animal foods may be classified as a novel type of functional food, which has the preventive activity against carcinogenesis, as well as the ability to reduce the accumulation of oxidative damages, which are hazardous for human health.