New research has found that a chemical abundant in fruits, vegetables and plant products can suppress the immune response seen in food allergies. It paves the way to developing a natural treatment for this globally increasing problem.
Flavonoids are natural compounds found in fruits, vegetables, plants and leaves that possess a number of medicinal benefits. In the past, New Atlas has reported on studies finding that flavonoids may safeguard against dementia, possess anti-aging properties, and help make diabetes-friendly bread.
Now, a new study out of the Tokyo University of Science (TUS) has found that a particular flavonoid, kaempferol, can dampen the body’s allergic response – including food allergies – via its effect on the immune system.
Allergic conditions like food allergies, hay fever, eczema and asthma have become much more common. There are a few explanations about why this might be the case, but that’s a discussion for another time. The bottom line is this: allergies are rife.
In the gut are a subset of specialized antigen-presenting cells called dendritic cells (DCs) that prime immune responses crucial to the development of food allergies. Antigen-presenting cells, or APCs, literally do what their name suggests: present antigens (foreign substances that trigger an immune response) to T cells, activating them. DCs produce an enzyme called retinaldehyde dehydrogenase 2 (RALDH2), which converts the chemical retinal, derived from vitamin A, to retinoic acid. Retinoic acid then triggers the development of regulatory T cells (T-regs), immune cells that suppress the body’s allergic response.
In the present study, the researchers examined around 40 different flavonoids to see if they increased the expression and efficiency of RALDH2 in DCs. They found that kaempferol was the most effective at this, so they studied it more thoroughly.
Kaempferol is abundant in tea, beans, broccoli, apples, and strawberries. It’s also found in medicinal herbs like aloe vera, Ginkgo biloba, and rosemary (Rosemarinus officinalis). Kaempferol is a flavonol, a type of flavonoid that is known to have an anti-inflammatory effect and that existing studies have associated with a reduced risk of cancer and heart disease, tumor growth prevention, and alleviating damage caused by free radicals, among other health benefits.
In the lab, the researchers observed that kaempferol-treated DCs produced more RALDH2. Digging deeper, the researchers examined the molecular mechanisms underlying kaempferol’s effects on RALDH2. Focusing on the aryl hydrocarbon (AhR) receptor, which kaempferol targets, they found that the flavonol acted as an antagonist, blocking the AhR receptor and, in turn, accelerating T-reg development.
They then moved to testing kaempferol in animal models, inducing food allergy in mice using the ovalbumin (OVA) protein found in egg whites. Administering kaempferol increased the number of T-regs and “significantly suppressed” the physical symptoms caused by the food allergy, namely a decreased body temperature and diarrhea.
The researchers will investigate further to see whether these effects can be replicated in human cells. They maintain that kaempferol’s anti-inflammatory and immune-suppressing effect could be a promising way to treat allergies.
“When taken as a daily food, they [flavonoids] are expected to reduce allergies, inflammation, and autoimmune diseases that are caused or aggravated by excessive immune response,” said Professor Chiharu Nishiyama, from TUS’s Department of Biological Science and Technology and the study’s corresponding author.
The study was published in the journal Allergy.
Source: Tokyo University of Science
