Curcuminoids in Neurodegenerative Diseases

Neurodegeneration is a term used to describe progressive deterioration of structure and/or function of neurons that affects different parts of the central nervous system and leads to eventual death. Neurodegenerative diseases include Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and Down's syndrome (DS), multiple sclerosis (MS), glaucoma, age-related macular degeneration (AMD), and diabetic encephalopathy (DE). Although the initial events that trigger these disorders may be different from each other, they share similar biochemical reactions that lead to neurodegeneration. Curcuminoids, polyphenol compounds from turmeric (Curcuma longa), possess diverse biological properties that modulate debilitating biochemical processes involved in AD that include attenuation of mitochondrial dysfunction-induced oxidative stress and inflammatory responses to inflammatory cytokines, COX-2, and iNOS. Curcuminoids also bind to β-amyloid (Aβ) plaques to inhibit amyloid accumulation and aggregation in the brain, in addition to inhibiting the toxic Aβ oligomer formation and oligomer-dependent Aβ toxicity. These properties can be further elaborated to DS, glaucoma and AMD. Curcuminoids also prevent α-synuclein aggregation in PD; attenuate ROS-induced COX-2 expression in ALS; ameliorate the symptoms of MS, DE and traumatic brain injury, in addition to neurodamages caused by heavy metal poisoning. These results demonstrate curcuminoids may be potentially effective therapeutic means to treat neurodegenerative diseases. A bulk of patents discloses methods to improve bioavailability of curcuminoids for therapeutic development. This review provides a comprehensive description on the current progress on curcuminoids against neurodegenerative diseases.