Studies

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Curcumin, an Active Constituent of the Ancient Medicinal Herb Curcuma Longa L.: Some Uses and the Establishment and Biological Basis of Medical Efficacy.

The root extract, curcumin (diferuloylmethane), is a constituent of the ancient herbal medicine Jiawei-Xiaoyao-san that has been used for dyspepsia, stress, and mood disorders. Curcumin engenders a diverse profile of biological actions that result in changes in oxidative stress, inflammation, and cell-death pathways. Combined with its historical use in medical practice and its safety profile, curcumin has been studied for its potential therapeutic applications in cancer, aging, endocrine, immunological, gastrointestinal, and cardiac diseases. In addition, data in animal models and in humans have also begun to be collected in stroke, Alzheimer's disease, and Parkinson's disease. A compelling new body of literature is also mounting to support the efficacy of curcumin in stress and mood disorders. Current understanding of the biological basis for antidepressant-relevant biochemical and behavioral changes shows convergence with some mechanisms known for standard antidepressants. In addition, the mechanisms of the antidepressant-like pharmacology of curcumin also appear to overlap with those of other disease states. Thus, ancient wisdom might be built into this interesting and newly-appreciated natural molecule. Although curcumin is a primary ingredient in anti-aging pills, cosmetic creams, eye treatments, diet products, etc, a key hurdle to the development of curcumin for disease treatment and prevention is overcoming its low oral bioavailability. Although multiple approaches to this problem are being examined, a solution to the bioavailability issue will be needed to ensure appropriate tissue exposures of curcumin in clinical investigation. Progress in this regard is underway.

Source: Witkin JM, Li X. CNS Neurol Disord Drug Targets. 2013 Apr 4.

 

Curcumin as a potential treatment for Alzheimer's disease: a study of the effects of curcumin on hippocampal expression of glial fibrillary acidic protein.

Curcumin, an agent traditionally utilized for its preventative action against tumorigenesis, oxidation, inflammation, apoptosis and hyperlipemia, has also been used in the treatment of Alzheimer's disease (AD). Recent advances in the study of AD have revealed astrocytes (AS) as being key factors in the early pathophysiological changes in AD. Glial fibrillary acidic protein (GFAP), a marker specific to AS, is markedly more manifest during morphological modifications and neural degeneration signature during the onset of AD. Several studies investigating the functionality of curcumin have shown that it not only inhibits amyloid sedimentation but also accelerates the disaggregation of amyloid plaque. Thus, we are interested in the relationship between curcumin and spatial memory in AD. In this study, we intend to investigate the effects of curcumin in amyloid-β (Aβ(1-40)) induced AD rat models on both the behavioral and molecular levels, that is to say, on their spatial memory and on the expression of GFAP in their hippocampi. Our results were statistically significant, showing that the spatial memory of AD rats improved following curcumin treatment (p < 0.05), and that the expression of GFAP mRNA and the number of GFAP positive cells in the curcumin treated rats was decreased relative to the AD group rats (p < 0.05). Furthermore, the expression level of GFAP mRNA in hippocampal AS in the AD rats significantly increased when compared with that in the sham control (p < 0.05). Taken together, these results suggest that curcumin improves the spatial memory disorders (such disorders being symptomatic of AD) in Aβ(1-40)-induced rats by down regulating GFAP expression and suppressing AS activity.

Source: Wang Y, Yin H, Wang L, Shuboy A, Lou J, Han B, Zhang X, Li J. Am J Chin Med. 2013;41(1):59-70. doi: 10.1142/S0192415X13500055.

 

Effects of curcumin and demethoxycurcumin on amyloid-β precursor and tau proteins through the internal ribosome entry sites: a potential therapeutic for Alzheimer's disease.

OBJECTIVE:

This study aims to determine the effects of curcumin and demethoxycurcumin on the internal ribosome entry site of the amyloid-β precursor protein (APP) and tau protein through a bi-cistronic reporter assay for screening of anti-Alzheimer's disease agents.

MATERIALS AND METHODS:

A bi-cistronic assay was performed wherein the expression of the first cistron, a β-galactosidase gene under the control of a cytomegalovirus promoter, represents the canonical cap-dependent mechanism of translation initiation; while the second cistron involves the utilization of the APP or the tau IRES elements to drive the expression of secreted alkaline phosphatase (SEAP) under a cap-independent mechanism. Bioactive natural products reported to have therapeutic potential for AD such as curcumin and demethoxycurcumin were screened in an murine neuroblastoma (N2A) cell model. Western blot analyses for the expression of APP C-terminal protein, human tau-1, and phosphorylated tau at Serine 262 (p(262)) and Serine 396 (pS(396)) were done after treatment of N2A cells with the test compounds.

RESULTS:

The bi-cistronic reporter assay revealed that curcumin was more effective than demethoxycurcumin, a structural analog of curcumin, in inhibiting both APP and tau IRES-dependent translation initiation. This result was further confirmed by Western blot analysis for the expression of APP C-terminal protein, human tau-1, pS(262) and pS(396) suggesting that curcumin may play a role in AD pathology alleviation through the inhibition of the APP and tau IRES-mediated translation mechanism. On the other hand, demethoxycurcumin was observed to inhibit the phosphorylation of both tau pS(262) and pS(396).

CONCLUSION:

A novel assay system using the bi-cistronic reporter constructs for the identification of compounds with activity against the translation directed by APP and tau IRES was developed. The results provide novel suggestive insights for the potential use of the mentioned compounds as prophylactic and therapeutic anti-AD agents.

Source: Villaflores OB, Chen YJ, Chen CP, Yeh JM, Wu TY. Taiwan J Obstet Gynecol. 2012 Dec;51(4):554-64. doi: 10.1016/j.tjog.2012.09.010.

 

Curcumin decreases amyloid-beta peptide levels by attenuating the maturation of amyloid-beta precursor protein.

Alzheimer disease (AD) is a devastating neurodegenerative disease with no cure. The pathogenesis of AD is believed to be driven primarily by amyloid-beta (Abeta), the principal component of senile plaques. Abeta is an approximately 4-kDa peptide generated via cleavage of the amyloid-beta precursor protein (APP). Curcumin is a compound in the widely used culinary spice, turmeric, which possesses potent and broad biological activities, including anti-inflammatory and antioxidant activities, chemopreventative effects, and effects on protein trafficking. Recent in vivo studies indicate that curcumin is able to reduce Abeta-related pathology in transgenic AD mouse models via unknown molecular mechanisms. Here, we investigated the effects of curcumin on Abeta levels and APP processing in various cell lines and mouse primary cortical neurons. We show for the first time that curcumin potently lowers Abeta levels by attenuating the maturation of APP in the secretory pathway. These data provide a mechanism of action for the ability of curcumin to attenuate amyloid-beta pathology.

Source: Zhang C, Browne A, Child D, Tanzi RE. J Biol Chem. 2010;285(37):28472-80.

 

Curcumin labels amyloid pathology in vivo, disrupts existing plaques, and partially restores distorted neurites in an Alzheimer mouse model.

Alzheimer's disease (AD) is characterized by senile plaques and neurodegeneration although the neurotoxic mechanisms have not been completely elucidated. It is clear that both oxidative stress and inflammation play an important role in the illness. The compound curcumin, with a broad spectrum of anti-oxidant, anti-inflammatory, and anti-fibrilogenic activities may represent a promising approach for preventing or treating AD. Curcumin is a small fluorescent compound that binds to amyloid deposits. In the present work we used in vivo multiphoton microscopy (MPM) to demonstrate that curcumin crosses the blood-brain barrier and labels senile plaques and cerebrovascular amyloid angiopathy (CAA) in APPswe/PS1dE9 mice. Moreover, systemic treatment of mice with curcumin for 7 days clears and reduces existing plaques, as monitored with longitudinal imaging, suggesting a potent disaggregation effect. Curcumin also led to a limited, but significant reversal of structural changes in dystrophic dendrites, including abnormal curvature and dystrophy size. Together, these data suggest that curcumin reverses existing amyloid pathology and associated neurotoxicity in a mouse model of AD. This approach could lead to more effective clinical therapies for the prevention of oxidative stress, inflammation and neurotoxicity associated with AD.

Source: Garcia-Alloza M. J Neurochem. 2007;102:1095-1104.

 

Curcumin interaction with copper and iron suggests one possible mechanism of action in Alzheimer's disease animal models.

Curcumin is a polyphenolic diketone from turmeric. Because of its anti-oxidant and anti-inflammatory effects, it was tested in animal models of Alzheimer's disease, reducing levels of amyloid and oxidized proteins and preventing cognitive deficits. An alternative mechanism of these effects is metal chelation, which may reduce amyloid aggregation or oxidative neurotoxicity. Metals can induce Abeta aggregation and toxicity, and are concentrated in AD brain. Chelators desferrioxamine and clioquinol have exhibited anti-AD effects. Using spectrophotometry, we quantified curcumin affinity for copper, zinc, and iron ions. Zn2+ showed little binding, but each Cu2+ or Fe2+ ion appeared to bind at least two curcumin molecules. The interaction of curcumin with copper reached half-maximum at approximately 3-12 microM copper and exhibited positive cooperativity, with Kd1 approximately 10-60 microM and Kd2 approximately 1.3 microM (for binding of the first and second curcumin molecules, respectively). Curcumin-iron interaction reached half-maximum at approximately 2.5-5 microM iron and exhibited negative cooperativity, with Kd1 approximately 0.5-1.6 microM and Kd2 approximately 50-100 microM. Curcumin and its metabolites can attain these levels in vivo, suggesting physiological relevance. Since curcumin more readily binds the redox-active metals iron and copper than redox-inactive zinc, curcumin might exert a net protective effect against Abeta toxicity or might suppress inflammatory damage by preventing metal induction of NF-kappaB.

Source: Baum L, Ng A. J Alzheimers Dis. 2004 Aug;6(4):367-77; discussion 443-9.

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