An extracellular protozoan parasite, Giardia is responsible for a significant number of intestinal infections, causing diarrhoea, cramps, headaches, dehydration and malabsorption, with the potential for chronic, post-infection illness and extraintestinal complications.[1,2]
Curcumin, from turmeric, has been shown to be antiparasitic against a number of protozoan, including Giardia. However, its mechanism of action has been unknown, which was the objective of a recent in vitro study.
Giardia trophozoites (the active, motile feeding stage) initially adhere to the epithelial cells of the upper small intestine, replicating and interacting with the three distinct barriers of the gut wall—microbiota, mucus layer and epithelial barrier. Attachment to the microvilli involves an adhesive ventral disk, flagella movements and chemical bonds involving proteins.
Giardia disrupts the homeostasis of the entire intestinal tract by competing with the commensal microbiota for nutrients and attachment sites, disrupting commensal microbiota biofilms, depleting mucus and reducing immune system activity. During the peak growing phase, studies show giardiasis increases intestinal epithelial permeability, and may induce epithelial apoptosis, promote bacterial translocation, and increase the production of pro-inflammatory cytokines.
An in vitro study published this year examined the cytotoxic effects and changes in morphology of 50,000/mL Giardia parasites when treated with curcumin. Through the use of multiple tests and analyses, researchers confirmed that curcumin inhibited trophozoite adhesion, proliferation and growth. It disrupted the dorsal and ventral surfaces, membranes, ventral disk and flagella, and caused loss in normal morphology. Analysis showed that curcumin can bind to and interact directly with the most abundant protein in the cytoskeleton of Giardia, the tubulins, which form microtubules within the parasite. The results showed a defragmentation of the microtubules.
This is the first study to evaluate tubulin as a target of curcumin against Giardia trophozoites. In addition to its antiparasitic activity, curcumin also has antioxidant and anti-inflammatory activities. With clinical manifestations of giardiasis often occurring several years after infection1 and the potential resultant inflammatory damage caused within the intestinal environment, a safe and natural agent, such as curcumin with its multiple pharmacological actions, may be a worthwhile addition to an antiparasitic treatment protocol.
- Allain T, Amat CB, Motta JP, et al. Interactions of Giardia sp. with the intestinal barrier: epithelium, mucus, and microbiota. Tissue Barriers 2017;5(1):e1274354. [Full Text]
- Gutierrez-Gutierrez F, Palomo-Ligas L, Hernandez-Hernandez JM, et al. Curcumin alters the cytoskeleton and microtubule organization on trophozoites of Giardia lamblia. Acta Tro. 2017;172:113-121. [Abstract]