A new wave of research links inflammation to almost all chronic disease.
Sixty years ago, Patricia Mabe took her first-ever breath, inflating new pink lungs with the air of Carbondale, Pennsylvania, home of the nation’s first underground mine; a town that today, despite a long-ago demise of the anthracite industry, still smolders from burning veins of coal.
Mabe’s subsequent inhalations—even before she acquired, at age 15, a smoking habit that would be lifelong—no doubt contained vestiges of a variety of toxins, no matter whether she was outside or in. Her dad, who worked in a mine, was a smoker. Her mother smoked, too.
Whenever Mabe inhaled anything noxious, her body’s defense system recognized foreign molecules in her lungs as the interlopers they were and mounted a functional inflammatory response. Brawny cells called macrophages, among others, stormed her lungs to do away with pathogens and debris while unleashing a barrage of molecular messengers that orchestrated strategic battles and mended damaged cells. Then—and this is every bit as important as their SWAT-team-like arrival—the macrophages would leave with all their assorted artillery in tow once the mission was over. In a healthy system, inflammatory cells are both highly regulated and self-disciplined; they go where ordered, expertly distinguish friend from foe, exert only necessary firepower, tidy up after themselves and then retreat, ultimately restoring calm—also known as homeostasis.
Precise though the immune system may be, some level of self-attack occurs even when all parts are working well. The key is keeping the collateral damage in check.
In fact, how effectively and efficiently any one person controls inflammation is a key determinant of health and disease. Some individuals regulate inflammation better than others. It’s likely that many of us are able to control inflammation at certain times of our lives better than at other times. Why—and how—is the focus of intriguing research that’s implicating how nutrition and inflammation interact in just about every major chronic disease.
"The inflammatory system is like the ocean. It’s beautiful, but also deadly." —Josef Coresh
“There appear to be windows of opportunity when we are good at adapting to what is in our environment, which is intimately related to how we meet and greet and defend ourselves from potential invaders,” says Keith West, DrPH ’86, MPH ’79, the George G. Graham Professor of Infant and Child Nutrition. “We get less good at that as life goes on.”
Over time—likely in response to the toxicity and persistence of cigarette smoke in her lungs—Mabe’s inflammatory response turned pathological. The composition of immune molecules and cells became qualitatively and quantitatively different. Inflammation became too too: There was too much of it; it was too strong for too long. Complicating that scenario, macrophages also became unfit and lingered incompetently in her lungs, clogging her airways.
What once defended her from disease now was causing it.
There's a new buzz among scientists about inflammation, even though it’s been known for ages to be one of the first responses by the immune system to infection and irritation. Inflammation is hot. And not in just a classical “calor” kind of way. Calor—as in heat or fever—is one of four characteristics of inflammation recorded in De medicina, an ancient Roman medical text. The remaining three—dolor, rubor and tumor—translate to pain, redness and swelling, respectively.
“Inflammation is something we have rediscovered in the 21st century,” explains Shyam Biswal, PhD, MS, a professor in Environmental Health Sciences (EHS), “specifically, inflammation as a focal point of chronic disease. People used to think of it as a bystander of disease. But it’s actually a driver.”
If attention to inflammation is spreading like wildfire throughout the research world, an early spark was ignited by Noel Rose, MD, PhD, director of the Center for Autoimmune Disease Research. Having introduced the concept of autoimmunity as a cause of chronic thyroiditis in 1956, Rose now is investigating the causes of magnified inflammatory responses in the hearts of young men for whom transplant is the only cure. A muscle that needs to pump, Rose concedes, is a bad location for excessive scarring to occur as a result of inflammation.
“We’re now looking at the details of inflammation,” he says, “and realizing the benefits from targeting specific parts of the inflammatory response. You have to know which part is doing good and which is doing bad and tailor drugs accordingly.”
It’s not simply the presence or amount of inflammation that’s important, Rose says: “It’s the texture of it; the makeup of the cells that are attracted, the ways in which they are stimulated and the products they release. If you’re getting down to that level, that’s where you find the causes of diseases.”
Among chronic, noninfectious disorders now commonly regarded as “inflammatory” is atherosclerosis, often called hardening of the arteries, says Josef Coresh, MD, PhD ’92, MHS ’92, director of the George W. Comstock Center for Public Health Research and Prevention.
“We’ve known for a long time that inflammation is central to atherosclerosis,” says Coresh, principal investigator of the Johns Hopkins Field Center of the Atherosclerosis Risk in Communities (ARIC) study. “You can see inflammatory cells in the lesions.” (Known as plaques, lesions form in the arteries, hardening them.)
The prospective ARIC study, which first examined 15,792 Americans in 1987 and has followed them ever since, is a key resource for the investigation of many inflammation-related chronic diseases—few of which show their hands so obviously as atherosclerosis.
Researchers who are sleuthing the origins of cancers and diabetes, for instance, have found themselves stumbling time and again on inflammatory roots. Apparently, long ago resolved and seemingly unrelated infections buried deep in people’s pasts might tip the precarious immune system balance, imperceptibly if irrevocably reprogramming it. So too might the persistently simmering, subclinical kind of inflammation caused by excess body fat, for example. One investigative focus is finding the mechanisms that link long ago infections to inflammation and later, chronic diseases. Another is dissecting and tinkering with processes that can block, enhance or otherwise regulate inflammation once the SWAT team has mutinied.
“It’s not simply the presence or amount of inflammation that’s important. It’s the texture of it. That’s where you find the causes of diseases.” —Noel Rose
For instance, Andy Pekosz, PhD, with collaborators from Johns Hopkins Medicine, has demonstrated that epithelial cells harvested from the noses of patients suffering from chronic sinusitis “remember” many generations later that they are different. These cells have comparatively heightened inflammatory responses to various stimuli a month after leaving a diseased nasal environment—despite having been grown and propagated under the same conditions as healthy cells in lab culture dishes.
“This tells us there’s something about these cells that has changed,” explains Pekosz, an associate professor in the W. Harry Feinstone Department of Molecular Microbiology and Immunology (MMI). “The detection machinery or the circuitry in the cells from sinusitis patients is reprogrammed to respond differently to factors that stimulate inflammation.”
Understanding this reprogramming of the inflammatory response itself is the holy grail for Pekosz.
“If we could understand how to tune down that heightened response by the epithelial cells, we could relieve the chronic sinusitis,” he says. “The flip side is, if we could, at an opportune and early time point, find a way to increase the inflammatory responses, we might have a very powerful broad tool to use against a number of different viruses, for instance.”
Fiddling even a bit with any discrete part of a delicate and complex system is not without unforeseen consequences, many of which could be perilous, if not immediately, then sometime in the future. (Case in point: Although it provided sweet relief for many with osteoarthritis pain, the anti-inflammatory drug Vioxx, which works by inhibiting an enzyme in the inflammatory pathway called COX-2, was withdrawn from the market in 2004 after a study showed it doubled patients’ risk of heart attacks and strokes after 18 months of use.)
The inflammatory system is like the ocean, according to Coresh: “It’s beautiful, but also deadly,” he says. “As long as it’s calm, you can conduct commerce and fish on it, and without it, you’re dead. But, if it storms, it’s incredibly powerful and can kill you.
“When there’s imbalance in one thing, it’s like a wave that pushes on other things and you get a whole cluster of effects.”
Among the things that both cause and react to system imbalances are messenger proteins called cytokines. The immune system communicates through these versatile factors that float around in the bloodstream. Unlike neurons in the hard-wired nervous system, cells in the immune system are not physically connected to one another.
"If you think of the nervous system as a landline, then the immune system is a cell phone," says Jay Bream, PhD, an MMI associate professor. "Different cocktails of cytokines, in various abundances, play a central role in determining immune responses."
A phenomenon known as a "cytokine storm" can occur if the reaction of the immune system to a pathogen is wildly exaggerated and stimulates too many of the messenger molecules, which in turn activate the same cells that stimulated them, resulting in a dangerous feedback loop. For example, cytokine storms are associated with severe bacterial infections and the onset of septic shock as well as avian influenza (H5N1) infection. Likewise, infection with the deadly Ebola virus is associated with a cytokine storm leading to uncontrolled inflammation.
Cytokine storms can happen in tissues throughout the body. That's because the component parts of the immune system spread far and wide, from the top layer of skin to the deepest recesses of the bowels.
Bream, whose mission is linking cytokines with disease outcomes, studies Interleukin-10 (IL-10): "a lynchpin" he says, "at the nexus of inflammation."
When the volume of IL-10 is turned down low, inflammation happens. When it's blasting, inflammation is tamped down. Bream, co-director of the Becton Dickinson Immune Function Laboratory at the Bloomberg School, has shown that mice prone to express higher levels of IL-10 are susceptible to certain types of persistent infections because they can't mount appropriate inflammatory responses. If there's an under-abundance of IL-10, they are susceptible to immunopathology caused by collateral damage from the excessive immune response. In this scenario, the original infections clear, but the animals' inflammatory responses set them up for autoimmune diseases and cancers. Animals whose IL-10 gene has been knocked out have extremely compromised anti-inflammatory responses. For example, under conditions that mimic septic shock, 100 percent die within 48 hours due to the cytokine storm, Bream says.
"One of the main roles of IL-10 is to control expression of pro-inflammatory cytokines," Bream explains. "That's how it tries to right the ship, by reducing inflammation to acceptable levels."
If inflammation, which dictates how we respond to vaccines and infectious pathogens, is not under stringent genetic control, the result is disease.
"In terms of public health, I see all these diseases—from heart disease to autoimmune disease to cancer to schizophrenia—as gene regulation issues, related to inflammation," he says. "Some people who get influenza end up hospitalized and die while others recover. Some people get colds and can go to work while others are bedridden. It's this diversity in the human population of response to disease threats that is at the center of my research program."
"When there's imbalance in one thing, it's like a wave that pushes on other things and you get a whole cluster of effects." —Josef Coresh
To find out why some individuals control inflammation better than others, he's looking at tiny genetic variations (known as single nucleotide polymorphisms, or SNPs) that make each human a unique individual, and noting how they affect the levels of IL-10 in various tissues, ultimately exerting control over inflammation and disease.
Because he wants to know how IL-10 works in people, Bream has inserted chunks of DNA containing the human IL-10 gene into the mice he's using. Some mice get human genes with variations associated with high IL-10 expression, and some get human genes with variations associated with low IL-10 expression.
Among other things, he's discovered that location is all-important: Where he manipulates IL-10—that is, which tissue type—matters. If, for instance, Bream turns down the IL-10-producing ability of a subset of cells in a very specific area of the colon, just below the surface cell layer, those mice end up with severe colitis.
"IL-10 is an attractive target for therapeutic interventions that either add back or neutralize IL-10," says Bream, who's now testing different expression levels of the human gene across various tissue types in response to different kinds of infectious pathogens in mice. "By identifying the triggers and genetic variations that regulate IL-10 levels, it will be feasible to develop more personalized therapies that restrict or enhance IL-10 in tissues where inflammation is occurring. But it's extremely complicated."
Another group of researchers at the Bloomberg School is looking at the anti-inflammatory IL-10 cytokine in the context of frailty in older adults. Some elderly people get frail in a clinical sense, meaning they spiral into a vicious cycle of decline characterized by exhaustion, slowness, weakness and muscle loss.
"It's hypothesized that there's at least a subset of older adults in whom inflammation essentially gets turned on all the time," says Karen Bandeen-Roche, PhD, the Frank Hurley and Catharine Dorrier Professor and Chair of Biostatistics, and co-principal investigator of the Older Americans Independence Center. "It's associated with muscle wasting and other adverse outcomes."
Bandeen-Roche is collaborating with Jeremy Walston, MD, a Johns Hopkins professor of Medicine and co-director of the Biology of Healthy Aging Program, who has developed a frail mouse model by knocking out expression of the IL-10 gene.
"In human studies, again and again, associations of high inflammation and adverse outcomes have been revealed, with frailty prominently among them," says Bandeen-Roche. "Pro-inflammation is thought by many to be one of the key hallmarks in a cycle of multisystem dysregulation that leads to frailty."
Human studies designed to discover how inflammation works and reveal its links to diseases require not only big funding and endless approvals but also plenty of participants, willing subjects who are healthy, as well as those who are sick.
People like Patricia Mabe, for instance.
Five years ago, Mabe visited her doctor complaining of asthma-like symptoms. Disconcerting as that was, it didn’t affect her everyday life. An inhaler was prescribed, and for a while, she used it only occasionally. Then, two years ago, it was like a switch had flipped.
“I was always very active—some people might say hyper,” she says. “Then, all of a sudden, I didn’t have any energy.”
An avid walker, Mabe grew depressed when she couldn’t exercise with Buddy, her Yorkshire terrier, and Holly, her English bulldog. Already petite, she lost weight, falling to an alarming 86 pounds.
Quite a few members of Mabe’s extended family had breathing issues. Her parents, both lifelong smokers, needed course after course of antibiotics to fight recurring infections before they died, one year apart, from chronic obstructive pulmonary disorder (COPD). Given her heredity and behavior—despite attempts to quit, Mabe still smokes—she envisioned a bleak future. COPD is an umbrella term that includes chronic bronchitis, emphysema and chronic asthma or asthmatic bronchitis. Most people have a little of this, a little of that, according to Robert Wise, MD, a Johns Hopkins School of Medicine professor of Pulmonary and Critical Care Medicine who holds a joint appointment in EHS at the Bloomberg School. All suffer declining lung function that can contribute to coughing, panic and death. COPD has no cure. Although smoking is a major risk factor, only one in seven smokers ends up with the disease.
Why Mabe’s parents? Why her?
Eager for answers, Mabe signed up for a research study investigating the link between genetics and COPD. More recently, she participated in a clinical trial instigated by Shyam Biswal’s research involving a new therapeutic agent: sulforaphane, a compound from broccoli sprout extract that was discovered in 1992 by Paul Talalay, MD, a professor in Pharmacology and Molecular Sciences who has a joint appointment in International Health at the Bloomberg School.
If scientists can prove in this study and successive clinical trials that sulforaphane works in people—like they previously demonstrated it worked in mice and in human cells in a dish—they will have found a potent intervention for a largely ignored public health issue affecting millions of Americans. (COPD is the No. 3 cause of death nationwide.) In addition, billions of people worldwide also might stand to benefit, mostly women and children whose lungs are chronically compromised from indoor air pollution caused by cooking fires fueled by cow dung and brush.
“Our discovery is not restricted to lung diseases only. If this pans out, it could be a big thing for public health.” —Shyam Biswal
Sulforaphane works differently than existing anti-inflammatory agents, Biswal explains. Rather than tamp down inflammation by interfering with its various pathways, it ramps up a host’s defense system that’s been compromised by chronic inflammation. It breathes new life into Nrf2, a vital molecular player that’s effectively strangled by the “bad” inflammation that underpins not only COPD but also nearly every chronic disease imaginable.
Already, Biswal’s group has published research demonstrating in the lungs of COPD patients that a defect in the host defense results from a decrease in Nrf2. Additionally, they have shown that sulforaphane boosts Nrf2 levels and this enhances host defense in the lungs by improving the ability of macrophages to kill bacteria and making them more responsive to anti-inflammatory drugs such as steroids.
The ongoing clinical trial in which Mabe participated is double-blind, meaning that nobody knows yet whether their purple pills are placebos or contain high or low doses of broccoli sprout extract. But Mabe has a sneaking suspicion that she ingested sulforaphane and that it helped her. During the month-long trial when she dutifully swallowed her pills daily, she felt different. “It seemed like my air passages opened up more,” she reports. “I didn’t have any flare-ups during that time, and it’s odd that I wasn’t on my nebulizer for a whole month.”
The multicenter trial, coordinated here at Johns Hopkins and taking place at Temple University and SUNY Buffalo, to date has enrolled about half of the 90 participants needed to test whether feeding sulforaphane to people alters Nrf2 activity as assessed by anti-oxidant enzymes in macrophages. Reducing inflammation is ancillary.
“If we can’t hit this target, then we’ll have to step back and say, well, this works great in mice and in the test tube, but not when people ingest sulforaphane,” says Wise, who’s heading up the broccoli sprout extract clinical trial.
This wouldn’t be the first inflammation-related wonder-compound to fall apart in a human trial. But Wise is confident in the predictive quality of Biswal’s previous research. In addition, others have shown Nrf2 was increased in the nasal tissue of people who eat broccoli sprouts.
“We think if you can show that in the nose, we can show it in the lung,” Wise says.
That this strategy potentially may benefit nonsmokers who have chronic inflammation in the lungs is notable in the context of public health. Not incidentally, the WHO lists indoor air pollution from primitive household cooking fires as the leading environmental cause of death in the world.
“There’s no question that women and children in South America, Africa and South Asia are exposed for many hours a day in cooking huts to amazingly high levels of particulates from burning biofuels like cow dung, and that this leads to a condition that is akin to COPD,” Wise says. “They develop chronic cough and mucus production. They have airflow obstruction and die early.”
How their lungs are similar to or different from those compromised by tobacco-related COPD is unknown, prompting Biswal to remain hot on the Nrf2 trail.
Currently, he’s implanting particulate collected from cooking huts in India into the lungs of mice and testing how manipulations of the Nrf2 pathway affect disease outcomes. Next, he’s working on developing a breathing chamber for mice that would be analogous to the interior of a cooking hut.
“Our understanding is very weak in this area,” Biswal says, “and half the world’s population is at risk.”
If sulforaphane does, in fact, tackle COPD by boosting the defense system and rendering the immune system once again competent, complete with robust macrophages, what’s to prevent it from doing the same for those suffering from a gamut of inflammation-related diseases, including cystic fibrosis, HIV, cancer, asthma, psoriasis, sepsis, schizophrenia, atherosclerosis …?
“Nothing,” says Biswal. “Our discovery is not restricted to lung diseases only. If this pans out, it could be a big thing for public health.”