Finding Clues
to Alzheimer's Disease
words by Mary Ann Littell / photograph by Andrew Hanenberg
LEFT TO RIGHT: NICK CORETTI, MS STUDENT; MIN HAN, PHD STUDENT; ELI LEVIN, DO/PHD STUDENT; DALIA LEMUS, MS STUDENT; robert nagele, phd, PROFESSOR OF MEDICINE; NIMISH ACHARYA, PHD STUDENT (SITTING IN FOREGROUND),ALL FROM UMDNJ-SCHOOL OF OSTEOPATHIC MEDICINE.
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obert Nagele has seen the ravages of Alzheimer’s disease first-hand. His mother-in-law, grandmother, two uncles and and one aunt battled this serious and life-altering illness. Witnessing family members progress into memory loss and dementia fueled the researcher’s desire to discover effective therapies for the disorder.
“I’ve been researching Alzheimer’s disease for a decade and all our work points in the same direction — toward the blood-brain barrier,” he says. “Our studies indicate that once this barrier becomes defective, harmful substances in the blood can enter the brain and cause damage. We believe this is a key contributor to Alzheimer’s and also speeds its progression.”
In this scientist’s opinion, all elderly individuals have at least a touch of Alzheimer’s. “It’s just a matter of degree,” he says. Research indicates that half of all people at age 85 have this degenerative brain disease. “Once you start to show symptoms and go to the doctor, you’ve probably had it for several years. The projection is that by the year 2020, 23 million people will be living with Alzheimer’s. Who’s going to take care of them?”
The researcher, a native of south Jersey, received his undergraduate degree, master’s and PhD at Rutgers. As a student, his first love was physics, “particularly astrophysics,” he says, “but there were few jobs in this field. I’d always been interested in the sciences, so I focused on biology.” In 1980, he came to UMDNJ as a postdoctoral fellow in the department of anatomy at Robert Wood Johnson Medical School and moved in 1983 to UMDNJ-School of Osteopathic Medicine (SOM), where he has stayed. He’s spent his entire career here, teaching and doing research. He oversees a busy lab that includes one student in the combined DO/PhD program at SOM, two PhD students, two master’s degree students and a research associate.
“My graduate students are fantastic — smart and hard-working,” he says. “This work wouldn’t have advanced without them.”
Nagele’s focus on Alzheimer’s came about in an unexpected way. A professional colleague working at Johnson & Johnson was preparing a presentation on Alzheimer’s disease. Knowing Nagele had a special microscope equipped with a 3-D imaging system, the colleague asked for help. “He sent me some tissue samples to photograph,” Nagele recalls. “When I looked at them under the microscope I was fascinated.” He ended up making an extensive study of the cells and soon switched his research efforts to Alzheimer’s. He’s currently running studies funded by pharmaceutical companies, including a project with GlaxoSmithKline aimed at developing drugs that prevent blood-brain barrier breakdown. The patent he holds is for the development of a diagnostic kit that tests a person’s blood for the presence of antibodies and proteins linked to the disease.
Because Alzheimer’s disease tends to run in families, Nagele believes he’s at high risk for developing the disorder sooner rather than later. “It’s vitally important to maintain vascular health to prevent blood-brain barrier breakdown,” he emphasizes. For others at high risk, he advises following the guidelines for protecting cardiovascular health: a healthy diet, weight control and exercise. “Getting on the treadmill for early-morning cardiovascular workouts is one of the things I do to stay healthy.”
When he’s not in the lab or working out, Nagele looks towards the sky, armed with a powerful telescope. “While studying the stars is my first love, the work I do in the lab is very rewarding because it combines all my interests — biology, chemistry and physics.”
Above all, it’s his natural curiosity that keeps him making new discoveries. “I tell my graduate students not to go into a project with a preconceived plan,” he says. “Let the data take you. In research, things are not always what you expect, so keep an open mind.”
Alzheimer’s Disease: A Diagnostic Test
Alzheimer’s disease (AD) is an aging-linked, neurodegenerative disorder that currently produces a dramatic and progressive decline in learning and memory in more than four million Americans. Increases in lifespan coupled with the failure to effectively prevent or treat AD forecast a three-fold increase in disease incidence by 2050. Recent studies in our laboratory at the New Jersey Institute for Successful Aging (NJISA) in Stratford have shown that breakdown of the blood-brain barrier (BBB), which normally blocks entry of blood components into the brain, is a key contributor to this disease. Among the things that leak from blood vessels into the brain through a defective BBB are autoantibodies, some of which can target and bind to neurons in the brain. We have recently shown that binding of autoantibodies to neurons can drive amyloid deposition in these cells, one of the earliest pathological hallmarks of AD that eventually leads to the death of these cells. The widespread presence of neuron-binding autoantibodies in human sera has opened up both diagnostic and therapeutic opportunities for AD. For a diagnostic, we are developing autoantibody target protein microarrays that — when reacted with human serum — generate a personal autoantibody profile that reveals the identity and amount of each brain-reactive autoantibody in that serum. These autoantibody profiles will provide important information pertaining to one’s risk for developing AD as well as prognostic information on the expected rate of disease progression in those already afflicted with this devastating AD evolves over a period of years with widespread loss of neurons and their synaptic interconnections in targeted brain areas that include the cerebral cortex and hippocampus. This devastation is accompanied by severe cognitive and memory loss and is evident grossly in MRI images as a general shrinkage of the brain. At the microscopic level, an early and consistent pathological hallmark is the intraneuronal deposition of amyloid b‚1-42 (Ab42), a 42 amino acid protein fragment, followed by the death and rupture of Ab42-overburdened cells. This terminal event frequently leaves behind a small, spherical cloud of non-degradable, Ab42-rich residue at the site formerly occupied by the now dead neuron, a structure referred to as an amyloid plaque. Amyloid plaques are both abundant and widely scattered throughout AD brains and, for many years, have been used by pathologists to confirm the disease. In view of this, the therapeutic potential of reducing the production of Ab42 and/or blocking its entry into vulnerable neurons is obvious. Strategies to block body-wide production of Ab42 by inhibiting its proteolytic cleavage from its parent protein have been extensively tested, albeit with disappointing results thus far. On the other hand, strategies aimed at blocking the deposition of Ab42 within neurons have not yet gotten underway, in part because the mechanisms of intraneuronal Ab42 deposition are not yet well-delineated. Changing the focus of research efforts to defining events going on within neurons emphasizes the need to identify the source of the Ab42 that invariably accumulates in these cells. Recent work in our laboratory at the NJISA strongly supports the notion that the blood, through a defective BBB, serves as a major, chronic source of the soluble Ab42 that sticks selectively to the surfaces of certain neuronal subtypes and eventually accumulates within them. We have also found that Ab42 gets unexpected help from another blood component that also leaks into the brain through a defective BBB: antibodies. Human serum, in addition to harboring soluble Ab42, commonly contains autoantibodies that can leak into the brain and, for reasons currently unknown, can bind selectively to the surfaces of the same neurons that are well-known to accumulate excessive Ab42 in AD brains. Support for a link between autoantibodies and intraneuronal Ab42 deposition comes from the observation that neurons containing Ab42 deposits also have autoantibodies attached to their surfaces in post-mortem AD brains. These findings have led us to hypothesize that (1) breakdown of the BBB allows access of both neuron-binding autoantibodies and soluble Ab42 to brain neurons and (2) binding of these autoantibodies to neurons triggers the internalization and accumulation of cell surface-bound Ab42 in vulnerable neurons as a byproduct of their natural tendency to clear surface-bound autoantibodies. In experimental support of this possibility, we have shown that human autoantibodies that strongly bind to neurons in sections of AD brain tissue also dramatically enhance the internalization and deposition of soluble, exogenous Ab42 in neurons in vitro (in mouse brain slice cultures) and in vivo (in mouse brains receiving direct intracranial injections of diluted human serum and Ab42 peptide). These results suggest that elderly individuals with high titers of specific neuron-binding autoantibodies in their blood may generally be at higher risk for developing AD than those with lower titers or lacking these autoantibodies. If so, then detection of “good” and “bad” autoantibody profiles in human sera could be used to identify those at risk for developing AD long before the onset of the disease, and should open up new possibilities for both early therapeutic intervention and treatment of those already afflicted. In view of this, we are developing a diagnostic test that will detect and quantify disease-related, brain-reactive autoantibodies in human sera. To accomplish this, we are employing protein microarrays containing identified, AD-relevant autoantibody target proteins spotted on a special type of glass specimen slide. When reacted with human serum, the resulting autoantibody-to-target protein binding will generate a color reaction or fluorescence signal at a specific address on the slide occupied by the appropriate target protein. In addition to detecting the presence of a particular brain-reactive autoantibody, the magnitude of the color or fluorescent signal will be directly proportional to the amount of that specific autoantibody in the blood. In this way, a brain-reactive autoantibody profile for each individual will be generated. The types and amounts of brain-reactive autoantibodies present in the profile will be compared with an ever-growing database of autoantibody profiles that have already been confirmed to represent a risk for AD or be the result of ongoing AD progression. For younger individuals (e.g., at 55 years of age), determination of one’s brain-reactive autoantibody profile well before the onset of the disease may allow sufficient time to implement lifestyle changes and treatments that would tend to delay AD onset or ward it off altogether. Such lifestyle changes would be focused on promoting vascular health, including the health of blood vessels in the brain that maintain the BBB. These changes would include diet, cardiovascular exercise, the use of statins and other preventatives of atherosclerosis and better control of hypertension. For individuals coming to their physicians with mild cognitive impairment (MCI), often a prelude to AD, a determination of the MCI patient’s autoantibody profile may provide valuable information on the expected rate of progression of the MCI as well as whether or not the profile is consistent with others that were obtained from patients who went on to progress to AD. Lastly, for individuals who have already been diagnosed with AD, an autoantibody profile could provide the physician with important information as to the expected rate of AD progression. This is especially true since BBB compromise occurs in all AD patients. A patent application has been filed on this novel AD antibody profiling technology. Such information is important to the patient as well as to the caregivers who often shoulder the burden of responsibility for the future care of the patient. . |
