Polyphenols are natural products that are consumed by humans as vegetables, fruits, and herbs.
Plant polyphenols possess antioxidant, anti-inflammatory, and anti-carcinogenic properties.
“Resveratrol, a polyphenol found in grapes, is known to have pronounced immunomodulatory and anti-inflammatory effects on animal models of colitis ulcer,” said Dr. Takuya Yashiro, a researcher in the Department of Biological Science and Technology at Tokyo University of Science.
“We investigated the possibility of other compounds structurally similar to resveratrol as a new type of treatment for inflammatory bowel disease.”
In patients with inflammatory bowel disease, the gastrointestinal tract lining contains long-lasting ulcers caused by chronic inflammation due to an elevated immune response in the body. This involves the excessive production of immune system-related molecules called cytokines.
Moreover, two types of immune cells — dendritic cells and T cells — are also involved: at the onset of an immune response, dendritic cells produce inflammatory cytokines and activate T cells to initiate a defense response.
These processes together form a complex pathway that result in a hyperimmune response.
In the study, Dr. Yashiro and colleagues examined the effects of several plant-derived compounds on dendritic cell-mediated T cell proliferation.
Pterostilbene showed stronger immunosuppressive activity than the other candidate compounds.
The researchers found that pterostilbene treatment prevents T cells from differentiating into Th1 and Th17 (subtypes of T cells that elevate the immune response), while increasing their differentiation into regulatory T cells (another subtype known to inhibit inflammation).
They also revealed that pterostilbene inhibits inflammatory cytokine production from dendritic cells by attenuating the DNA-binding activity of a crucial transcription factor PU.1.
When they further tested pterostilbene in mice with inflammatory bowel disease, they found that oral intake of the compound improved symptoms of the disease.
“For disease prevention, it is important to identify the beneficial components in foods and to understand the underlying mechanism by which immune responses and homeostasis are modulated in body,” Dr. Yashiro said.
“Our findings showed that pterostilbene possesses a strong immunosuppressive property, paving the way for a new, natural treatment for inflammatory bowel disease.”
Takuya Yashiro et al. Pterostilbene reduces colonic inflammation by suppressing dendritic cell activation and promoting regulatory T cell development. The FASEB Journal, published online September 22, 2020; doi: 10.1096/fj.202001502R