Polyprenoic Acid Research Articles

E-5166 (polyprenoic acid) reduces rate of second primary HCC

E-5166 (polyprenoic acid) reduces rate of second primary HCC

Effects of a synthetic polyprenoic acid (E-5166) on the gap junction of rat hepatocytes treated with liver tumor promoters, phenobarbital, and p,p'-dichlorodiphenyltrichloroethane.

Effects of in vivo exposure to the synthetic polyprenoic acid, 3,7,11,15-tetramethyl-2,4,6,10,14-hexadecapentaenoic acid (E-5166) using 6 groups of rats treated simultaneously or individually with phenobarbital (PB) or with p,p'-dichlorodiphenyltrichloroethane (DDT) on the gap junctions of hepatocytes were examined by freeze-fracture analysis. Experimental groups were as follows: Group 1, basal diet alone; Group 2, E-5166 treatment; Group 3, 0.05% PB diet; Group 4, PB diet and E-5166 treatment; Group 5, 0.05% DDT diet; and Group 6, DDT diet and E-5166 treatment. E-5166 was given by gavage (40 mg/kg body weight, 3 times/wk). Experimental diets and E-5166 were started at 6 wk of age. All animals were sacrificed at 2 wk after the start of the experiments. The density of gap junctions in PB- or DDT-treated rats was higher and that in E-5166-treated rats was lower than that in controls. The density of gap junctions in rats given PB and E-5166-/or DDT and E-5166-treated rats was slightly increased when compared to controls. The average area of gap junctions in DDT- or PB and E-5166-treated rats was significantly smaller than in controls (p < 0.005), although no statistical differences were found among PB-, E-5166-, and DDT and E-5166-treated rats and controls. Unit area of gap junctions to membrane area in rats given E-5166, DDT, or PB and E-5166 was lower than in controls. However, the unit area of gap junctions in DDT and E-5166-treated rats did not differ from in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Stereochemical requirements for the modulation by retinoic acid of thyroid hormone activation of Ca(2+)-ATPase and binding at the human erythrocyte membrane.

Physiological concentrations of retinoic acid can block the activation of human erythrocyte Ca(2+)-ATPase in vitro by thyroid hormone [Smith, Davis & Davis (1989) J. Biol. Chem. 264, 687-689]. The present studies were undertaken to ascertain the nature of this blockade. Two binding sites for L-thyroxine (T4) were demonstrated on washed erythrocyte membranes; the high-affinity site had a Kd value of 2.7 x 10(-10)M and a Bmax. of 76 fmol/mg of protein. The lower-affinity site possessed a Kd of 1 x 10(-8) M. Retinoic acid was as potent a displacer of radiolabelled T4 as was the unlabelled hormone. Certain retinoic acid analogues with either ring or fatty acid side chain modifications retained some ability to displace [125I]T4 binding and to block iodothyronine activation of Ca(2+)-ATPase. The side chain terminal carboxyl group was essential for full activity of the retinoic acid molecule. Its absence or replacement with an ethylsulphone group rendered the molecule considerably less active in the ATPase model. Retinol, 13-cis-retinoic acid, benzene-substituted all-trans-retinoic acid and polyprenoic acid all failed to influence iodothyronine binding or to block activation of Ca(2+)-ATPase by T4. There was good agreement between the ability of an analogue to displace [125I]iodothyronine binding and its ability to inhibit the T4-dependent activation of the Ca(2+)-ATPase. It would appear from these observations that retinoic acid can modulate the activation of erythrocyte membrane Ca(2+)-ATPase by thyroid hormone through a mechanism which involves displacement of iodothyronine from binding sites. These activities apparently derive from both the ring structure and the fatty acid side chain of the retinoic acid molecule.

Structure-activity relationships of retinoids as inhibitors of calmodulin-dependent human erythrocyte Ca2+-ATPase activity and calmodulin binding to membranes

All-trans retinoic acid displaces the binding of radiolabelled calmodulin to human erythrocyte membranes, and inhibits the activity of plasma membrane Ca(2+)-stimulated, Mg(2+)-dependent ATPase (Ca(2+)-ATPase; EC 3.6.1.3). This enzyme is dependent upon the action of calmodulin. In this study we explored the structural attributes of the retinoids which confer this ability to inhibit enzyme activity and calmodulin binding. With respect to the fatty acid side-chain, a clear requirement for inhibition is a trans-configuration of the polar end-group. The importance of the ring structure is indicated by the ineffectiveness of polyprenoic acid and a benzene ring retinoid analogue as inhibitors of enzyme activity and calmodulin binding. There was good correlation between the relative potencies of the analogues as enzyme inhibitors and as inhibitors of calmodulin binding. The ability of selected retinoid analogues, at physiological concentrations with respect to all-trans retinoic acid, to inhibit erythrocyte Ca(2+)-ATPase activity and membrane binding of calmodulin underscores the structurally specific effects of these compounds on the interaction of calmodulin with the membrane-bound enzyme.

Inhibitory Effects of Acyclic Retinoid (Polyprenoic Acid) and Its Hydroxy Derivative on Cell Growth and on Secretion of α‐Fetoprotein in Human Hepatoma‐derived Cell Line (PLC/PRF/5)

Acyclic retinoid (polyprenoic acid) has a slightly different structure from retinoic acid. However, acyclic retinoid acts similarly to retinoic acid, because both bind to cellular retinoic acid‐binding protein and cellular retinoid‐binding protein, F‐type, with the same strong binding affinity. We studied the effects of acyclic retinoid, the 7‐hydroxy derivative of acyclic retinoid (7OH‐acyclic retinoid) and retinoic acid on a human hepatoma‐derived cell line PLC/PRF/5 (Alexander cells). Acyclic retinoid inhibited cell growth with an ID50 value of 14 μM, and reduced cell viability with an LD50 value of 86 μM. The ratios of LD50 value to ID50 value were 6.1 for acyclic retinoid, 2.4 for 7OH‐acyclic retinoid and 1.4 for all‐trans‐retinoic acid. Taking this ratio as a parameter of relative cytotoxicity, we concluded that acyclic retinoid is the least toxic compound. Growth inhibition of cells by acyclic retinoid was associated with the incorporation of 3H‐thymidine in the logarithmic phase. Acyclic retinoid reduced secretion of α‐fetoprotein (AFP) and reciprocally increased secretion of albumin in the culture media, suggesting that acyclic retinoid influences gene expression of these proteins. Thus, acyclic retinoid, one of the less toxic retinoids, inhibits cell growth of human cancer cell line PLC/PRF/5 and appears to alter gene expression of AFP and albumin toward a “normal’direction.

Inhibitory effect of acyclic retinoid (polyprenoic acid) on hepatic fibrosis in CCl4-treated rats

A study was conducted to examine the inhibitory effect of acyclic retinoid (polyprenoic acid) on the development of hepatic fibrosis induced by CCl4 in rats. Oral administration of the compound brought about a significant reduction in both serum and tissue levels of immunoreactive prolyl hydroxylase, a key enzyme of collagen formation. The result indicated that the rate of collagen synthesis in the liver was decreased which was consistent with histological findings. Acyclic retinoid also decreased both AST and ALT activities in serum, demonstrating the reduction in hepatic parenchymal damage. This cytoprotective effect on parenchymal cells may be related, at least in part, to inhibition of hepatic fibrosis. No significant side effects were observed, despite a long-term administration of the acyclic retinoid. The present findings suggest the potential scope of therapy of hepatic fibrosis by retinoid.

Polyprenoic acid is effective to prevent the UVB induced skin tumors

Polyprenoic acid is effective to prevent the UVB induced skin tumors

Inhibitory effect of acyclic retinoid (polyprenoic acid) on the secretion of .ALPHA.-fetoprotein in CCl4-treated rats.

A study was conducted to examine the inhibitory effect of acyclic retinoid (polyprenoic acid) on the secretion of alpha-fetoprotein (AFP) in rats with chronic liver damage induced by CCl4. Oral administration of the compound brought about a significant reduction of serum AFP levels at the time when liver cirrhosis was formed. Acyclic retinoid also decreased the activities of serum aminotransferases and ornithine carbamyl transferase, while it increased serum albumin levels, demonstrating the reduction of hepatic parenchymal damage. Significant negative correlation was observed between serum AFP and albumin levels. This cytoprotective effect of the retinoid on the parenchymal cell may well be related to the inhibition of the synthesis and/or secretion of AFP. No significant side effect was observed, despite a long-term administration of the compound. The present finding will provide a potential scope for the future use of acyclic retinoid for the treatment of chronic liver damage.

Polyprenoic acid, E-5166, is effective in inhibiting the proliferation of keratinocytes in vitro

E-5166 is a newly synthesized polyprenoic acid that has been reported to control epithelial differentiation and to have antiproliferative effects on various tumor cells in vitro. This study examined the effects of E-5166 on the proliferation of keratinocytes. Three kinds of keratinocytes were used: normal human keratinocytes, a human trichilemmoma-derived K-TL-1 cell line, and a Pam 212 cell line. Cell proliferation was measured by 3H-thymidine incorporation and also by determining cell numbers. E-5166 was found to have significant antiproliferative effects on each of the cell lines studied. When Pam 212 cells were cultured in the presence of E-5166, cell proliferation was inhibited in a dose-dependent fashion. The inhibitory effect appeared to be reversible, since removal of E-5166 from the culture medium resulted in a subsequent return of cell proliferation. For normal human keratinocytes and K-TL-1 cells, E-5166 inhibited 3H-thymidine incorporation in a dose-dependent fashion. Furthermore, E-5166 showed significantly stronger antiproliferative capacity than Ro 10-9359, one of the aromatic retinoids, on Pam 212 cells and normal human keratinocytes.

Diverse responses to retinoid in morphological differentiation, tumorigenesis and n‐myc expression in human neuroblastoma sublines

We established the subline RT-BMV-C6 from the parent human neuroblastoma cell line RT-BM by a process that required repeated subculture of cells, which were prone to disaggregation. RT-BMV-C6 and the parent cloned line, RT-BM-1, had an identical marker chromosome, confirming that both lines were derived from a common progenitor. In the analysis of surface antigen expression, RT-BMV-C6 did not react with UJ-127-11, Leu7 or KP-NAC2 MAbs to which RT-BM-1 showed positive binding. The levels of both N-myc amplification and expression in RT-BMV-C6 were twice as high as the level obtained in RT-BM-1. Colony-forming efficiency in soft agar was 2.0 +/- 0.8% for RT-BMV-C6 and 3 times greater than that for RT-BM-1 (0.6 +/- 0.1%). When 100 x 10(6) cells of RT-BM-1 and RT-BMV-C6 were inoculated into nude mice, tumor incidence was significantly higher for RT-BMV-C6 (6/6; 100%) than for RT-BM-1 (0/6; 0%). Our data show that N-myc is closely related to tumorigenicity in NB. When RT-BM-1 and RT-BMV-C6 were co-cultured with a new synthetic retinoid, polyprenoic acid (E5166), and dibutyryl cyclic AMP, RT-BM-1 was induced to neuronal differentiation, defined by the formation of neuronal processes and expression of neurofilaments, whereas RT-BMV-C6 was not. However, when exposed to E5166, N-myc expression of RT-BMV-C6 was more strongly reduced than that of RT-BM-1, and colony formation of RT-BMV-C6 was significantly inhibited as compared to RT-BM-1. These findings suggest that the reduction of N-myc expression might closely correlate with growth inhibition accompanying neuronal differentiation of neuroblastoma cells.

Differential expression of N-myc and c-src proto-oncogenes during neuronal and schwannian differentiation of human neuroblastoma cells.

Neuroblastoma (NB) cells can be induced to differentiate bidirectionally into either neuronal or schwannian cells by different inducers. However, the underlying mechanisms are poorly understood. We examined the expression of N-myc and c-src genes in 3 human NB-cell lines during either neuronal or schwannian differentiation in vitro, since proto-oncogenes are considered to play a pivotal role in regulating cell proliferation and differentiation. Decreased N-myc expression and increased c-src expression were observed during neuronal differentiation by retinoic acid, polyprenoic acid (E5166) and dibutyryl cyclic AMP, whereas the expression of N-myc and c-src genes was considerably reduced during schwannian differentiation by bromodeoxyuridine, demonstrating that the expression of N-myc and c-src genes was regulated independently in the bipolar differentiation processes of NB cells. Our results suggest that enhanced N-myc expression might be closely linked to the undifferentiated phenotypes of NB cells, that c-src expression might be related to the neuronal differentiation of NB cells, and that N-myc and c-src genes might be regulated independently in the determination of the bipolar differentiation of NB cells.

Inhibitory effects of synthetic acidic retinoid and polyprenoic acid on the development of hepatoma in rats induced by 3'-methyl-N, N-dimethyl-4-aminoazobenzene.

A study was conducted to investigate the inhibitory effects of acidic retinoid (trimethylmethoxyphenyl analog of retinoic acid ethylester or TMMP) and polyprenoic acid (3,7,11,15-tetramethyl-2,4,6,10,14-hexadecapentaenoic acid or E-5166) on the development of hepatoma induced by 3'-methyl-N, N-dimethyl-4-aminoazobenzene (3'-MeDAB) in rats. Morphometric analysis of liver specimens was employed to evaluate the antitumor effects of the compounds in detail, and revealed significant decreases in the number and area of tumors in the TMMP- and E-5166-treated groups. As for adverse effects, retarded growth and marked hypertriglyceridemia were observed only in TMMP-treated rats. During the hepatocarcinogenesis, cellular retinoid-binding protein, F-type or CRBP(F) and cellular retinoic acid-binding protein or CRABP newly appeared in the tumor tissue, particularly in hyperplastic nodules which are the precancerous state of hepatoma. These results suggest that the polyprenoic acid is a good candidate for clinical chemoprevention of hepatoma, targetting its precancerous stage when intracellular receptors for acidic retinoid have emerged.

In vitro and in vivo regulation of transglutaminase activity of mouse epidermal cells by various vitamin A compounds.

AbstractIn vitro and in vivo effects of various vitamin A analogues on the transglutaminase activity of mouse epidermal cells were investigated. In vitro addition of all‐trans‐retionic acid (retinoic acid), retinyl acetate, or Ro 10‐9359 (etretinate) to a culture medium induced transglutaminase activity in a transformed mouse epidermal cell line (PAM 212 cells). Induction by a new synthetic vitamin‐A‐like compound (E‐5166, polyprenoic acid derivative) was significant but less marked than that by other vitamin A analogues. Simultaneous addition of retinoic acid and the phorbol ester 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), which also induces transglutaminase, did not cause any increase in transglutaminase activity. These retinoic acid derivatives inhibited the proliferation of PAM 212 cells at concentrations of 10–5–10–6 M in the culture medium.In vivo analysis consisted of oral administration of retinoic acid and Ro 10‐9359 to adult mice. These mice were found to have increased liver transglutaminase activity in the soluble fraction but not in the particulate fraction. Orally administered retinoic acid did not induce transglutaminase activity in the epidermis in the whole skin. These results suggest that retinoids modify transglutaminase activity and epidermal proliferation and differentiation in vitro, but the induction of the enzyme seems not to be related to the clinical effects of orally administered retinoids on various skin diseases.

Effects of a Novel Synthetic Vitamin A-Like Compound (a Polyprenoic Acid Derivative, E-5166) on Neutrophil-Derived Reactive Oxygen Species

In order to elucidate the mechanisms of anti-inflammatory activity of a new synthetic vitamin A-like compound (polyprenoic acid derivative, E-5166), the anti-oxidant effect of the agent was evaluated by examining the levels of reactive oxygen species both in the zymosan-stimulated neutrophil system and in the cell-free, xanthine-xanthine oxidase system. E-5166 inhibited the generation of hydroxyl radicals but had little effect on superoxide, hydrogen peroxide, or chemiluminescence when used at therapeutic concentrations. The favorable effects of E-5166 on several inflammatory skin disorders are discussed in connection with the anti-oxidant activity of the drug.

A Novel Synthetic Vitamin A-like Compound (A Polyprenoic Acid Derivative, E-5166) Inhibits the Release of Arachidonic Acid Stimulated by Epidermal Growth Factor

Little is known about the mechanisms of anti-inflammatory activity of retinoids. A new synthetic vitamin A-like compound (polyprenoic acid derivative, E-5166) has a strong in vitro binding affinity to intracellular binding proteins for acidic retinoids. In order to elucidate the anti-inflammatory activity of E-5166, we studied the effect of E-5166 on the epidermal growth factor (EGF)-stimulated arachidonic acid (AA) release of pig epidermis. E-5166 significantly inhibited the EGF-stimulated AA release and this inhibitory effect of E-5166 required a longer incubation than hydrocortisone did. Furthermore, E-5166 inhibited the EGF-stimulated phosphatidylinositol (PI) turnover of pig epidermis. These results indicate that E-5166 inhibited the EGF-stimulated AA release through the inhibition of the EGF-stimulated PI turnover.

Inhibitory Effect of Retinoid (E5166) on Cell Growth and Suppressive Effect on Epstein-Barr Virus Early-Antigen Induction by n-Butyrate in Nasopharyngeal Hybrid Cells

The in vitro proliferation and colony-forming activity (plating efficiency) of Epstein-Barr virus (EBV) nuclear antigen-positive nasopharyngeal hybrid cells were inhibited by one of the retinoid, polyprenoic acid; E5166. It was dependent on retinoid concentration. Furthermore, an induction of EBV early antigen after treatment with 4 mM n-butyrate was markedly suppressed by E5166 and this was similar to the previously reported effects of retinoid acid on iododeoxyuridine (IUDR) and 12-O-tetra-decanoyl-phorbol-13-acetate (TPA) induction. These results support to lead a clinical application of E5166 for combination chemotherapy in patients with nasopharyngeal carcinoma.

Effects of 12-o-tetradecanoylphorbol-13-acetate and polyprenoic acid derivative on calcium-activated phospholipid-dependent protein kinase of pig skin.

12-o-Tetradecanoylphorbol-13-acetate (TPA) activates calcium-activated, phospholipid-dependent protein kinase (protein kinase C) partially purified in an ion exchange column from pig epidermis. Protein kinase C was activated by TPA in a concentration-dependent manner with simultaneous addition of Ca2+ and phospholipid. Polyprenoic acid derivative (E5166) which is a newly synthesized retinoic acid derivative, inhibited the TPA activation of protein kinase C. This inhibition may explain the mechanisms by which retinoids inhibit TPA-induced tumor promotion.

A novel synthetic vitamin-A-like compound (a polyprenoic acid derivative: E-5166) inhibits UVB-stimulated epidermal ornithine decarboxylase activity.

Irradiation of skin with ultraviolet B (UVB) stimulates epidermal activity of ornithine decarboxylase (ODC), a rate limiting polyamine biosynthesing enzyme. The maximum stimulation of ODC activity by UVB was found at 24 after irradiation. Systemic administration of a polyprenoic acid derivative (E-5166) significantly inhibited the UVB-stimulated ODC activity in a dose-dependent manner. The inhibitory effect of E-5166 on the UVB-stimulated ODC activity was found to begin at 5 mg/kg body weight. These results indicate that because it inhibits ODC activity E-5166 can be utilized for the treatment of hyperproliferative skin diseases.

Inhibitory effects of polyprenoic acid (E-5166) on N-2-fluorenylacetamide-initiated hepatocarcinogenesis in rats.

The effects of the newly synthesized polyprenoic acid, 3,7,11,15-tetramethyl-2,4,6,10,14-hexadecapentaenoic acid (E-5166) on N-2-fluorenylacetamide (FAA)-initiated hepatocarcinogenesis were examined in 6 groups of male ACI rats. The numbers of altered hepatocellular foci in rats of group 1 given a basal diet containing 0.02% FAA for 13 weeks and in rats of group 2 which received E-5166 by gavage (40 mg/kg, 3 times/week) at the same time as receiving the FAA diet were almost the same, indicating that E-5166 had no effect at the stage of carcinogen exposure. However, the number of foci in group 4, in which rats were given the basal diet and E-5166 after the termination of the carcinogen exposure, and were sacrificed 16 weeks later, was significantly smaller than that in group 3 maintained on the basal diet alone (P less than 0.05). The results suggests some anticarcinogenic activity of E-5166, possibly involving the phenotypic expression of the preneoplastic foci. Furthermore, the number of altered foci in rats of group 6 (given the liver-tumor promoter phenobarbital with E-5166 for 16 weeks after the administration of carcinogen) was also significantly smaller than that in rats of group 5, which received the promoter (P less than 0.05). The incidence of neoplastic nodules of the liver in group 6 at the end of the experiment was also lower than in group 5 (P less than 0.0014). These results suggest an antipromoting effect of the polyprenoic acid E-5166 on rat chemical hepatocarcinogenesis.

Inhibitory effects of polyprenoic acid (E5166) on production and secretion of alpha-fetoprotein and on cell kinetics in human hepatoma cells.

We investigated the effects of polyprenoic acid, E5166, on the production and secretion of alpha-fetoprotein (AFP) and on cell kinetics in a human hepatoma cell line (HuH-7). The cellular AFP content, measured flow cytometrically for cells stained by an indirect immunofluorescence method, was decreased by treatment with E5166. AFP in the culture medium decreased exponentially during exposure of cells to the drug. These changes were dose-dependent. The growth of HuH-7 cells in vitro was clearly suppressed in the presence of E5166. The inhibition of growth depended on the concentration of the agent. The fraction of S phase cells decreased relatively in the cells treated with a high concentration of the drug, whereas it increased in the cells treated with lower doses.