The rhizome (root) of turmeric (Curcuma longa Linn.) has long been used in traditional Asian medicine to treat gastrointestinal upset, arthritic pain, and "low energy." Laboratory and animal research has demonstrated anti-inflammatory, anti-oxidant, and anti-proliferative properties of turmeric and its constituent curcumin. Preliminary human evidence, albeit poor quality, suggests possible efficacy in the management of dyspepsia (upset stomach), hyperlipidemia (high cholesterol) and scabies (topical therapy). However, due to methodological weaknesses in the available studies, an evidence-based recommendation cannot be made regarding the use of turmeric or curcumin for any specific indication.
In traditional Indian Ayurvedic medicine, turmeric has been used to strengthen the body, tone the digestive system and the liver, dispel worms, regulate menstruation, dissolve gallstones and relieve arthritis. Ancient Hindu texts refer to its carminative, aromatic and stimulant properties. Mixed with slaked lime, it has been used as a topical treatment for sprains and strains.
In Chinese medicine, turmeric is an important herb for digestive and urinary complaints, gallstones and menstrual pain. Turmeric has been used in Asian food preparation, medicine, cosmetics and fabric dying for more than 2,000 years. Marco Polo described turmeric in his memoirs, and the herb became popular in Europe during Medieval times for its coloring value and medicinal uses.
A study by researchers from The University of Texas M.D. Anderson Cancer Center found that curcumin induces the degradation of cyclin E expression through ubiquitin-dependent pathway and up-regulates cyclin-dependent kinase inhibitors p21 and p27 in multiple human tumor cell lines.
Study authors explained that curcumin is a well-known chemopreventive agent and has been shown to suppress the proliferation of a wide variety of tumor cells through a mechanism that is not fully understood.
Cyclin E, a proto-oncogene that is overexpressed in many human cancers, mediates the G(1) to S transition, is a potential target of curcumin. Researchers demonstrated a dose- and time-dependent down-regulation of expression of cyclin E by curcumin that correlates with the decrease in the proliferation of human prostate and breast cancer cells. The suppression of cyclin E expression was not cell type dependent as down-regulation occurred in estrogen-positive and -negative breast cancer cells, androgen-dependent and -independent prostate cancer cells, leukemia and lymphoma cells, head and neck carcinoma cells, and lung cancer cells.
Curcumin-induced down-regulation of cyclin E was reversed by proteasome inhibitors, lactacystin and N-acetyl-L-leucyl-L-leucyl-L-norleucinal, suggesting the role of ubiquitin-dependent proteasomal pathway. Researchers found that curcumin enhanced the expression of tumor cyclin-dependent kinase (CDK) inhibitors p21 and p27 as well as tumor suppressor protein p53 but suppressed the expression of retinoblastoma protein. Curcumin also induced the accumulation of the cells in G1 phase of the cell cycle.
Researchers concluded that proteasome-mediated down-regulation of cyclin E and up-regulation of CDK inhibitors may contribute to the antiproliferative effects of curcumin against various tumors.
In a related study, researchers from The James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, University of British Columbia-St. Paul's Hospital in Canada, investigated the anti-inflammatory, antioxidant and antiproliferative properties or curcumin.
Researchers found that curcumin inhibits several intracellular signaling pathways, including the mitogen-activated protein kinases (MAPKs), casein kinase II (CKII), and the COP9 signalosome (CSN), in various cell types. Researchers noted that it has also been recently demonstrated that exposure to curcumin leads to the dysregulation of the ubiquitin-proteasome system (UPS).
Coxsackievirus infection is associated with various diseases, including myocarditis (inflammation of heart muscle) and dilated cardiomyopathy (weakness of heart muscle).
In searching for new antiviral agents against coxsackievirus, researchers found that treatment with curcumin significantly reduced viral RNA expression, protein synthesis and virus titer and protected cells from virus-induced cytopathic effect and apoptosis.
The study demonstrated that reduction of viral infection by curcumin was unlikely due to inhibition of CVB3 binding to its receptors or CVB3-induced activation of MAPKs. Moreover, said study authors, gene silencing of CKII and Jab1, a component of CSN, by small interfering RNAs did not inhibit the replication of coxsackievirus, suggesting that the antiviral action of curcumin is independent of these pathways.
Lastly, researchers found that curcumin treatment reduced both the 20S proteasome proteolytic activities and the cellular deubiquitinating activities, leading to increased accumulation of ubiquitinated proteins and decreased protein levels of free ubiquitin.
Researchers concluded that there might be an important antiviral effect of curcumin wherein it potently inhibits coxsackievirus replication through dysregulation of the UPS.
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