Grapes help limit brain cell death following strokes

Grapes help limit brain cell death following strokes

These days, it's true, the French are not so well liked by some. But, pardonnez-moi, let's give credit where it's due. It is the French, after all, who helped inspire Grace and Albert Sun to pursue a line of research that could lead to big improvements in the way doctors treat patients with strokes. The key to that improvement turns out to be that old French favorite, red wine.

The Suns are a husband-wife team of MU biochemists who have been studying how substances in red wine may have important health benefits. In the process they've shown that red wine has the potential to protect against damage both to the brain and liver caused by chronic drinking.

More recently, the Suns have become the first researchers to demonstrate that one of the antioxidants in red wine, a substance called resveratrol, may play a role in limiting the destruction of brain cells that follows a stroke. It's a discovery that has the potential to enhance the recovery and subsequent quality of life for the thousands of Americans who survive, or are threatened with, strokes.

The Suns were not always so keen about things alcoholic. They began their career in alcohol research back in the 1970s looking at drink's harmful effects. Now, moderate wine consumption is something they no longer caution against. "The lifestyle of French people, you can use that as an example," Grace Sun says. "They drink two glasses of wine at dinner."

What drew the Suns to red wine was the famous French Paradox: How is it that the French can devour all that cheese and foie gras and butter and pastry with unrestrained joie de vivre yet have lower rates of cardiovascular disease than people in many other Western countries, including the United States? The question has perplexed the world's scientists for more than a decade. Some have proposed that it might be the olive oil in the French diet that makes the difference, or perhaps even the onions and garlic.

Researchers have now focused their attention on the wine the French are so fond of drinking. Some have suggested that it is the alcohol in wine that provides the benefits. And indeed, studies have found that moderate consumption of any alcoholic beverage is associated with lower blood pressure.

Wine, particularly red wine, also contains an abundance of compounds called polyphenols that can't be found in a can of Bud or a dry martini. Polyphenols, such as resveratrol, quercetin, catechin and proanthocyanidins, are potent antioxidants that occur naturally in a variety of fruit, vegetables and teas. Grape skins and seeds contain substantial quantities.

Antioxidants scavenge chemicals called oxygen free radicals that can injure tissues. Scientists believe antioxidants might slow aging and help prevent a number of diseases. Other researchers looking into the French Paradox already had demonstrated that the polyphenols in red wine could benefit heart health in a number of ways, such as inhibiting the aggregation of blood platelets into clots.

The Suns already had years of experience studying the oxidative damage alcohol can cause, particularly to brain cells. So they decided to investigate whether polyphenols have the same protective benefits for the brain that they do for the heart. "In many age-related diseases of the brain, Alzheimer's, Parkinson's, and stroke, oxidative damage is a problem," Grace Sun says. "We figured, ¡®Hey, these polyphenols may be good for the brain.'"

The couple acquired the assistance of researchers across the MU campus when they became charter members several years ago of the University's Center for Phytonutrient and Phytochemical Studies, a multidisciplinary program funded by the National Institutes of Health to investigate the health benefits of botanical compounds and herbs.

MU nutritionist and professor Ruth MacDonald helped put the polyphenols into the diets of the Suns' test animals. Another colleague, analytical chemist George Rottinghaus, determined whether the substances reached the animals' brains and livers. The Suns began their research off campus, with a trip to a winery in Hermann, Mo., to see how wine is made. To craft a red wine, winemakers often add grape skins to the juice as it ferments.

This fermentation process, the Suns found, extracts polyphenols naturally, fortifying red wine with the compounds. "Polyphenols are not easily dissolved in water, but they can be dissolved by alcohol. So they get into red wine just by nature's process," Grace Sun says.

In their first studies, the Suns treated rats with ethanol by adding it to their diets for a period of two months. Some of the rats also got fed an extract of grape polyphenols. The Suns made the extract from grape skins and seeds collected from wineries in Rocheport and New Haven immediately after the grapes had been pressed.

Rats fed just the alcohol showed definite declines in the function of two proteins in brain cell membranes that are sensitive to oxidative stress. But when grape polyphenols were added to their diet, they completely prevented these decreases in protein activity. In a similar experiment, the Suns demonstrated that the grape polyphenol extract prevented some of the damage chronic alcohol consumption causes to liver cells.

As the Suns and other researchers began to study the individual polyphenols in red wine, they found that one, resveratrol, stood out from the pack. For example, resveratrol alone has been shown to be just as effective as a combination of red wine polyphenols in protecting against heart attack damage.

"This group of compounds is all good, but resveratrol is particularly good," Grace Sun says.

The Suns found that in cell cultures resveratrol was more effective than such popular antioxidants as vitamins C and E at reducing oxidative damage. And their animal studies demonstrated for the first time that resveratrol is highly effective in crossing the blood-brain barrier.

"We can show that resveratrol can get to the brain really fast," Albert Sun says. That made resveratrol an ideal candidate for the Suns to try as a protective measure against the damage strokes can inflict on brain cells.

Blockages in the arteries feeding the brain can cut off blood and oxygen to nerve cells just as clogged coronary arteries can stop blood flow to heart muscle. For that reason, these ischemic strokes are now called "brain attacks," analogous to heart attacks.

But even after a stroke, when blood flow to the brain has been restored, the damage to brain cells can continue for several more days. That's because the absence of oxygen and glucose signals a chemical chain reaction in the cells that leads to the production of damaging free radicals. This phenomenon, called delayed neuronal death, causes neurological symptoms to worsen in about a third of patients in the days following a stroke.

Working with Qun Wang, an MU postdoctoral fellow in biochemistry, the Suns used Mongolian gerbils to test the effectiveness of resveratrol in preventing delayed neuronal death. Gerbils are widely used as an animal model for stroke because a unique quirk in their anatomy makes it easier for researchers to induce strokes than in many other kinds of lab animals. Humans and other mammals have a ring of connecting arteries, called the circle of Willis, at the base of their brain.

In gerbils, that circle is incomplete and lacks the connection between the front and back of the brain. This ensures that cutting off blood flow to the carotid arteries in a gerbil's neck causes a stroke at the front of the animal's brain.

The researchers induced strokes by anesthetizing the gerbils, exposing their two carotid arteries, closing off circulation with clips and then reopening the arteries five minutes later. Some of the animals received injections of resveratrol either during or just after strokes were induced.

Four days later, the researchers examined the animals' brains. Microscopic images showed substantial numbers of dead neurons in the brains of gerbils that had not received resveratrol. But in gerbils that had received the compound, the damage clearly was minimized. The next question the Suns asked, according to Grace Sun, was this: "If we put polyphenols in our diet, is that good for stroke?"

The search for an answer began when the Suns obtained a standardized grape extract from the California Table Grapes Commission for another series of experiments that are now underway. They gave gerbils the freeze-dried grape powder as a drink once a day for four days before inducing strokes. Subsequent examination showed the extract had, in fact, minimized brain damage.

Another study showed the extract also had a protective effect when administered after a stroke. The results have been so good that the Suns believe that the extract should be given to stroke patients. "This is very practical and very useful," Albert Sun says. "Now, we think when a patient has had a stroke it may help to immediately feed them the extract."

The Suns are finding that the extract's value isn't limited to minimizing brain damage after a stroke occurs. They have evidence now that it may be worthwhile to use the extract to fortify the diets of elderly persons who are simply at risk for stroke.

The Suns determined this by adding the extract to gerbil chow and feeding it to the animals for two months. Again, after strokes were induced, the gerbils that had eaten the extract as part of their diets suffered less impairment. "It's not a medicine that would cure something," Grace Sun says. "But this is probably a good preventive measure for older people."

While there are plenty of grape extract supplements on the market, the Suns aren't proposing that people run out and buy any of them. On the contrary. Nutritional supplements aren't subjected to the same regulatory scrutiny that prescription drugs receive.

"You don't know what they put in them," she says. "But it is good to have a healthful diet with fruits and vegetables." And besides that, the protection grape extract provides isn't complete. So the Suns are looking for other natural compounds that may provide additional safeguards. One likely candidate is turmeric, a spice widely used in curry powder that is also an antioxidant. There's epidemiological evidence that people in India, where plenty of curry is consumed, have lower rates of Alzheimer's disease than people in the United States. The Suns are looking for a suitable animal model for Alzheimer's disease in order to give turmeric a try.

The Suns' careers have taken a number of serendipitous turns like this that have led them to potentially very useful results. "We stumbled into this very happily with a good ending," Albert Sun says.

The couple met in the early 1960s while they were graduate students at Oregon State University. Grace was born in Hong Kong and came to the U.S. to attend college at Seattle Pacific University. Albert was born on the Chinese mainland and raised on Taiwan. He came to the United States as a graduate student.

The Suns married in 1964. Three years later, they had their PhDs and moved to Cleveland, where Albert Sun held a position at Case Western Reserve University. A couple of years later, both were hired by the state of Ohio's mental health system and began their lifelong study of the brain.

The Suns joined the MU faculty in 1974 after she received an appointment to the biochemistry department and he earned a position with the department of medical pharmacology and physiology. While they each have their own labs and projects, they have always collaborated on research as well. "Do we have a choice?" Grace Sun quipped. "It's very good to team up," Albert Sun added quickly. "We compensate each other." His expertise is with proteins, for example, hers with lipids. "We can talk things over at the dinner table," Albert Sun says.

"We don't always agree," Grace Sun says. "We argue, but that's part of our life."

The couple's most important collaboration has been their daughter, a computer scientist who recently gave them a grandson. They live in New Jersey, and that's become a serious factor in the Suns' plans.

These days their chief domestic debate is whether, when the time comes, to retire in Columbia where they have strong ties to the University and their church, or to move closer to their family back East. In either case, the Suns still have more work ahead of them to see to it that victims of stroke benefit from the good things they've found in red wine.

"We would like this research to go on to the practice side," Grace Sun says. "That is our goal."