J Pharmacol Exp Ther 326(1): 196-208 (2008 July)
Begum AN, Jones MR, Lim GP, Morihara T, Kim P, Heath DD, Rock CL, Pruitt MA, Yang F, Hudspeth B, Hu S, Faull KF, Teter B, Cole GM, Frautschy SA
Departments of Medicine/Neurology UCLA, Greater Los Angeles Healthcare System, VA Medical Center, Sepulveda, CA 91343, USA
Curcumin can reduce inflammation and neurodegeneration, but its chemical instability and metabolism raise concerns, including whether the more stable metabolite tetrahydrocurcumin (TC) may mediate efficacy. We examined the antioxidant, anti-inflammatory, or anti-amyloidogenic effects of dietary curcumin and TC, either administered chronically to aged Tg2576 APPsw mice or acutely to lipopolysaccharide (LPS)-injected wild-type mice. Despite dramatically higher drug plasma levels after TC compared with curcumin gavage, resulting brain levels of parent compounds were similar, correlating with reduction in LPS-stimulated inducible nitric-oxide synthase, nitrotyrosine, F2 isoprostanes, and carbonyls. In both the acute (LPS) and chronic inflammation (Tg2576), TC and curcumin similarly reduced interleukin-1ß. Despite these similarities, only curcumin was effective in reducing amyloid plaque burden, insoluble ß-amyloid peptide (Aß), and carbonyls. TC had no impact on plaques or insoluble Aß, but both reduced Tris-buffered saline-soluble Aß and phospho-c-Jun NH2-terminal kinase (JNK). Curcumin but not TC prevented Aß aggregation. The TC metabolite was detected in brain and plasma from mice chronically fed the parent compound. These data indicate that the dienone bridge present in curcumin, but not in TC, is necessary to reduce plaque deposition and protein oxidation in an Alzheimer’s model. Nevertheless, TC did reduce neuroinflammation and soluble Aß, effects that may be attributable to limiting JNK-mediated transcription. Because of its favorable safety profile and the involvement of misfolded proteins, oxidative damage, and inflammation in multiple chronic degenerative diseases, these data relating curcumin dosing to the blood and tissue levels required for efficacy should help translation efforts from multiple successful preclinical models.
J Biol Chem 283(21): 14497–14505 (2008 May 23)
Kim SJ, Son TG, Park HR, Park M, Kim MS, Kim HS, Chung HY, Mattson MP, Lee J.
Department of Pharmacy, College of Pharmacy and Research Institute for Drug Development, Longevity Life Science and Technology Institutes, Pusan National University, Geumjeong-Gu, Busan, Korea
Curcumin is a natural phenolic component of yellow curry spice, which is used in some cultures for the treatment of diseases associated with oxidative stress and inflammation. Curcumin has been reported to be capable of preventing the death of neurons in animal models of neurodegenerative disorders, but its possible effects on developmental and adult neuroplasticity are unknown. In the present study, we investigated the effects of curcumin on mouse multi-potent neural progenitor cells (NPC) and adult hippocampal neurogenesis. Curcumin exerted biphasic effects on cultured NPC; low concentrations stimulated cell proliferation, whereas high concentrations were cytotoxic. Curcumin activated extracellular signal-regulated kinases (ERKs) and p38 kinases, cellular signal transduction pathways known to be involved in the regulation of neuronal plasticity and stress responses. Inhibitors of ERKs and p38 kinases effectively blocked the mitogenic effect of curcumin in NPC. Administration of curcumin to adult mice resulted in a significant increase in the number of newly generated cells in the dentate gyrus of hippocampus, indicating that curcumin enhances adult hippocampal neurogenesis. Our findings suggest that curcumin can stimulate developmental and adult hippocampal neurogenesis, and a biological activity that may enhance neural plasticity and repair.
Chinese Medical Journal 121(9): 832-839 (2008)
Pan R, Qiu S, Lu DX, Dong J.
Department of Orthopedics, the First Affiliated Hospital, Medical College of Jinan University, Guangzhou, Guangdong, China
Background Increasing evidence suggests that many neurons may die through apoptosis in Alzheimer's disease (AD). Mitochondrial dysfunction has been implicated in this process of neuronal cell death. One promising approach for preventing AD is based upon anti-apoptosis to decrease death of nerve cells. In this study, we observed the memory improving properties of curcumin in mice and investigated the neuroprotective effect of curcumin in vitro and in vivo.
Methods: The mice were given AlCl3 orally and injections of D-galactose intraperitoneally for 90 days to establish the AD animal model. From day 45, the curcumin group was treated with curcumin for 45 days. Subsequently, the step-through test, neuropathological changes in the hippocampus and the expression of Bax and Bcl-2 were carried out to evaluate the effect of curcumin on the AD model mice. In cultured PC12 cells, AlCl3 exposure induced apoptosis. The MTT assay was used to measure cell viabilities; flow cytometric analysis to survey the rate of cell apoptosis; DNA-binding fluorochrome Hoechst 33258 to observe nuclei changes in apoptotic cells and Western blot analysis of Bax, Bcl-2 to investigate the mechanisms by which curcumin protects cells from toxicity.
Results: Curcumin significantly improved the memory ability of AD mice in the step-through test, as indicated by the reduced number of step-through errors (P <0.05) and prolonged step-through latency (P <0.05). Curcumin also attenuated the neuropathological changes in the hippocampus and inhibited apoptosis accompanied by an increase in Bcl-2 level (P <0.05), but the activity of Bax did not change (P >0.05). AlCl3 significantly reduced the viability of PC12 cells (P <0.01). Curcumin increased cell viability in the presence of AlCl3 (P <0.01). The rate of apoptosis decreased significantly in the curcumin group (P <0.05) when measured by flow cytometric analysis. Curcumin protected cells by increasing Bcl-2 level (P <0.05), but the level of Bax did not change (P >0.05).
Conclusions: This study demonstrates that curcumin improves the memory ability of AD mice and inhibits apoptosis in cultured PC12 cells induced by AlCl3. Its mechanism may involve enhancing the level of Bcl-2.
Adv Exp Med Biol 595: 197-212 (2007)
Greg M. Cole, Bruce Teter, and Sally A. Frautschy
Greater Los Angeles Veterans Affairs Healthcare System, Geriatric Research, Education, and Clinic Center, Sepulveda, CA 91343, USA
Neurodegenerative diseases result in the loss of functional neurons and synapses. Although future stem cell therapies offer some hope, current treatments for most of these diseases are less than adequate and ourbest hope is to prevent these devastating diseases. Neuroprotective approaches work best prior to the initiation of damage, suggesting that some safe and effective prophylaxis would be highly desirable. Curcumin has an outstanding safety profile and a number of pleiotropic actions with potential for neuroprotective efficacy, including anti-inflammatory, antioxidant, and anti-protein-aggregate activities. These can be achieved at submicromolar levels. Curcumin's dose-response curves are strongly dose dependent and often biphasic so that in vitro data need to be cautiously interpreted; many effects might not be achievable in target tissues in vivo with oral dosing. However, despite concerns about poor oral bioavailability, curcumin has at least 10 known neuroprotective actions and many of these might be realized in vivo. Indeed, accumulating cell culture and animal model data show that dietary curcumin is a strong candidate for use in the prevention or treatment of major disabling age-related neurodegenerative diseases like Alzheimer's, Parkinson's, and stroke. Promising results have already led to ongoing pilot clinical trials.