Researchers from Imperial College London (ICL) report that sulforaphane, a compound most widely associated with broccoli, may activate a protein called Nrf2 in arteries, according to findings published in Arteriosclerosis Thrombosis and Vascular Biology. While the protein is normally protective, in areas of arteries that are susceptible to disease the London-based researchers found that Nrf2 is inactive.
"We found that the innermost layer of cells at branches and bends of arteries lack the active form of Nrf2, which may explain why they are prone to inflammation and disease,” explained Dr Paul Evans, from the National Heart and Lung Institute at ICL.
“[Exposure to] the natural compound sulforaphane reduced inflammation at the high-risk areas by 'switching on' Nrf2,” he added.
"Sulforaphane is found naturally in broccoli, so our next steps include testing whether simply eating broccoli, or other vegetables in their 'family’, has the same protective effect. We also need to see if the compound can reduce the progression of disease in affected arteries."
The tissue of cruciferous vegetables, like broccoli, cauliflower, cabbage and Brussels sprouts, contain high levels of the active plant chemicals glucosinolates. These are metabolised by the body into isothiocyanates, which are known to be powerful anti-carcinogens. The main isothiocyanate from broccoli is sulforaphane.
The study was described as “fascinating” by Professor Peter Weissberg, Medical Director at UK charity British Heart Foundation, which funded the study. “These fascinating findings provide a possible mechanism by which eating vegetables protects against heart disease,” said Prof Weissberg.
"As well as adding evidence to support the importance of eating 'five-a-day’, the biochemistry revealed in this research could lead to more targeted dietary or medical approaches to prevent or lessen disease that leads to heart attacks and strokes," he added.
The researchers used mice engineered to lack the Nrf2 protein and compared their arteries with those of normal mice. Prof Evans and his team found that in straight sections of arteries Nrf2 was present in the endothelial 'lining’ cells. Through its action on other proteins, it prevented the cells from becoming inflamed, which is an early stage in the development of atherosclerosis.
Atherosclerosis, known as hardening or furring of the arteries is a key risk factor for cardiovascular disease, the cause of over 50 per cent of deaths in Europe and the US.
When the researchers looked at the lining cells of disease-prone sites they found that Nrf2 was attached to a protein that made it inactive. This effectively prevented it from exhibiting its protective properties.
When these cells were exposed to sulforaphane, a re-activation of Nrf2 in the disease-prone regions of the artery was observed. This indicated that the cells’ ability to protect themselves from becoming inflamed was restored, said the researchers.
Previously, the potential benefits of broccoli and sulforaphane have focussed on anti-cancer effects. Epidemiological and animal studies have shown that diets high in cruciferous vegetables result in fewer instances of certain cancers, especially lung, colon, breast, ovarian and bladder cancer.
Source: Arteriosclerosis Thrombosis and Vascular Biology
Sep 2009; doi:10.1161/ATVBAHA.109.193375
“Activation of Nrf2 in Endothelial Cells Protects Arteries From Exhibiting a Proinflammatory State”
Authors: M. Zakkar, K. Van der Heiden, L.A. Luong, H. Chaudhury, S. Cuhlmann, S.S. Hamdulay, R. Krams, I. Edirisinghe, I. Rahman, H. Carlsen, D.O. Haskard, J.C. Mason, P.C. Evans