The retinoic acid isomers 9-cis-retinoic acid and all-trans-retmoic acid induce cell growth and differentiation by binding to nuclear retinoic acid receptors (RAR and RXR) and regulating gene transcription.21 However, p-carotene may also promote differentiation and inhibit proliferation through mechanisms unrelated to its provitamin A activity. One form of communication between neighboring cells results from the exchange of small molecules through gap junctions formed by proteins known as connexins. Gap junctional intercellular communication is important for cell differentiation and control of the cell cycle, and it is often deficient in tumor cells. Up-regulation of gap junctional communication in tumor cells through increased connexin expression is associated with decreased proliferation.91 Carotenoids, including P-carotene, can induce gap junction communication between fibroblasts in culture by increasing the expression of connexin 43 92 This effect was not related to the ability of carotenoids to quench singlet oxygen, but it is possibly related to the ability of carotenoids or their metabolites to induce gene expression.93 In contrast to its effects on fibroblasts, P-carotene did not increase connexin 43 expression in cultured lung cells,94 and supplementing rats with high doses of P-carotene decreased hepatocyte intracellular communication, although low-dose supplementation enhanced it.95

Aloe and Your Health

Aloe and Your Health

This іѕ а health guide, whісh саn hеlр people knоw hоw tо mаkе uѕе оf Aloe vera tо improve оvеrаll health аnd deal wіth mаnу kinds оf diseases.

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