4-(2-(5-6-7-8-tetrahydro-5-5-8-8-tetramethyl-2-naphthalenyl)-1-propenyl)benzoic-acid and astaxanthine

Carotenoids have been implicated in numerous epidemiological studies as being protective against cancer at many sites, and their chemopreventive properties have been confirmed in laboratory studies. Astaxanthin (AST), primarily a carotenoid of marine origin, responsible for the pink coloration of salmon, shrimp and lobster, has received relatively little attention. As with other carotenoids, its highly lipophilic properties complicate delivery to model systems. To overcome this issue we have synthesized a novel tetrasodium diphosphate astaxanthin (pAST) derivative with aqueous dispersibility of 25.21 mg/ml. pAST was delivered to C3H/10T1/2 cells in an aqueous/ethanol solution and compared with non-esterified AST dissolved in tetrahydrofuran. We show pAST to (i) upregulate connexin 43 (Cx43) protein expression; (ii) increase the formation of Cx43 immunoreactive plaques; (iii) upregulate gap junctional intercellular communication (GJIC); and (iv) cause 100% inhibition of methylcholanthrene-induced neoplastic transformation at 10(-6) M. In all these assays, pAST was superior to non-esterified AST itself; in fact, pAST exceeded the potency of all other previously tested carotenoids in this model system. Cleavage of pAST to non-esterified (free) AST and uptake into cells was also verified by HPLC; however, levels of free AST were approximately 100-fold lower than in cells treated with AST itself, suggesting that pAST possesses intrinsic activity. The dual properties of water dispersibility (enabling parenteral administration in vivo) and increased potency should prove extremely useful in the future development of cancer chemopreventive agents.

Topics: Animals; Anticarcinogenic Agents; Antineoplastic Agents; Benzoates; beta Carotene; Carotenoids; Cell Line; Cell Transformation, Neoplastic; Fibroblasts; Gap Junctions; Mice; Mice, Inbred C3H; Retinoids; Xanthophylls

Expression of connexin 43 (Cx43) is correlated with reduced indexes of neoplasia and is upregulated by cancer-preventive retinoids and carotenoids in nontransformed human and murine fibroblasts and keratinocytes. The molecular mechanism of upregulation, however, is poorly understood. Three retinoic acid receptor (RAR) antagonists (Ro 41-5253, BMS453, and BMS493) were capable of suppressing retinoid-induced Cx43 protein expression in 10T1/2 cells. However, Ro 41-5253 did not suppress protein expression by the non-provitamin A carotenoids astaxanthin or lycopene. In contrast, Cx43 induction by astaxanthin but not by a RAR-specific retinoid was inhibited by GW9662, an antagonist of peroxisome proliferator activated receptor-gamma activation. Simultaneous treatment with the maximally effective concentration of a retinoid and with beta-carotene or the non-provitamin A carotenoid astaxanthin resulted in supraadditive upregulation of Cx43 expression, again indicating separate mechanisms of gene regulation by these two cancer preventive agents.

Topics: Animals; Anticarcinogenic Agents; Antioxidants; Benzoates; beta Carotene; Carotenoids; Cell Line; Connexin 43; Gene Expression Regulation, Neoplastic; Humans; Mice; Neoplasms; PPAR gamma; Receptors, Retinoic Acid; Retinoids; Up-Regulation; Xanthophylls