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Capsaicin (N-vanillyl-8-methyl-1-nonenamide) is a major pungent ingredient in hot peppers and induces apoptosis in malignant carcinoma cell lines. However, the adverse effects of capsaicin on neuronal development have not been fully explored. The aim of this study was to determine whether capsaicin affected murine-derived cerebellar multi-potent neural progenitor cells (NPC) or adult hippocampal neurogenesis in vivo. Capsaicin dose-dependently suppressed NPC proliferation, and higher concentrations were cytotoxic. Capsaicin decreased the activation of extracellular signal-regulated kinases (ERK) without markedly affecting p38 kinases. Capsaicin reduced the number of newly generated cells in the dentate gyrus of the hippocampus but did not significantly alter learning and memory performance in young adult mice. Interestingly, capsaicin decreased ERK activation in the hippocampus, suggesting that reduced ERK signaling may be involved in the capsaicin-mediated regulation of hippocampal neurogenesis. [ABSTRACT FROM AUTHOR]

In 2006, the Korea Food and Drug Administration reported that combinations of dietary colors such as allura red AC (R40), tartrazine (Y4), sunset yellow FCF (Y5), amaranth (R2), and brilliant blue FCF (B1) are widely used in food manufacturing. Although individual tar food colors are controlled based on acceptable daily intake (ADI), there is no apparent information available for how combinations of these additives affect food safety. In the current study, the potencies of single and combination use of R40, Y4, Y5, R2, and B1 were examined on neural progenitor cell (NPC) toxicity, a biomarker for developmental stage, and neurogenesis, indicative of adult central nervous system (CNS) functions. R40 and R2 reduced NPC proliferation and viability in mouse multipotent NPC, in the developing CNS model. Among several combinations tested in mouse model, combination of Y4 and B1 at 1000-fold higher than average daily intake in Korea significantly decreased numbers of newly generated cells in adult mouse hippocampus, indicating potent adverse actions on hippocampal neurogenesis. However, other combinations including R40 and R2 did not affect adult hippocampal neurogenesis in the dentate gyrus. Evidence indicates that single and combination use of most tar food colors may be safe with respect to risk using developmental NPC and adult hippocampal neurogenesis. However, the response to excessively high dose combination of Y4 and B1 is suggestive of synergistic effects to suppress proliferation of NPC in adult hippocampus. Data indicated that combinations of tar colors may adversely affect both developmental and adult hippocampal neurogenesis; thus, further extensive studies are required to assess the safety of these additive combinations. [ABSTRACT FROM AUTHOR]