Clinical depression and addiction can spin destructive realities – crushing careers, dreams, families, even life itself. Depression is considered a leading cause of disability in the Western world, affecting 120 million people, while some 90 million worldwide were diagnosed in 2003 with addictive disorders associated with alcohol and drug abuse. Recent studies show that these conditions share a common biological link in areas of the brain referred to collectively as the “reward system.”
 

Dr. Abraham Zangen of the Institute’s Neurobiology Department investigates the reward system's role in mitigating stress – one cause of depression. This part of the brain, he found in several experiments, produces chemical compounds in a number of stressful situations. For instance, rats pressing a lever received a mild electrical stimulus straight to their reward centers; when this pleasurable sensation was withheld, the brain released beta-endorphin – which has an effect much like a mild dose of morphine. This neurochemical response may be the reward system's way of coping – a sort of “consolation prize” to allow animals to adapt to a new situation and perhaps mitigate feelings of frustration and stress. Rats, humans and other mammals share a similar neurochemistry, suggesting that imbalances in these chemicals in the human brain’s reward system could be tied to depressive or addictive tendencies, in which stress is a key factor.
 

“In the black box of psycho-physics, the reward system is a small window to understanding how the mind and the brain relate,” says Zangen. He predicts that the several parallel paths of study he currently pursues will ultimately converge to improve understanding of the brain's reward system and its effects on behavior.

Another of his research paths targets chronic cocaine use, which can cause permanent changes to the network of neurons in the reward system, compromising its ability to mediate motivation and pleasure. Zangen wanted to see if stimulation to specific deep brain areas could reverse these neuro-logical changes. His team, which included Ph.D. student Dino Levy, found that rats treated with electrode stimulation of a specific reward-related brain region during cocaine detox exhibited 50% less cocaine-seeking behavior than the control group. There was also a measurable improvement in the treatment group’s brain chemistry: The electrode stimulation partly reversed cocaine-induced changes affecting glutamate, one of the reward system's key neuro-transmitters. Further study is in progress to elucidate the neurochemical effects of such electrode stimulation as well as the potential therapeutic benefits.
 

Could deep brain stimulation be applied to humans with problems related to reward system dysfunction? Zangen was interested in a non-invasive technique known as transcranial magnetic stimulation (TMS) – a method of triggering electrical responses in the brain through the use of external, rapidly alternating magnetic fields. TMS however, can penetrate only the outer layers of the brain – up to about 2 cm – whereas the reward system is buried much deeper. Efforts to increase its range by increasing the magnetic field intensity were unsuccessful, sometimes having an intolerably painful effect on subjects. Zangen conceived of a device that would produce low-level magnetic fields arranged radially so as to come together only at the desired deep brain region.

In collaboration with Yiftach Roth, a graduate student at Tel Aviv University, he designed and perfected the device, using computer modeling techniques and a “phantom” brain – a spherical container of a solution with the same conductivity as the brain. Their final design, the “H-coil,” was patented in 2002 by the National Institutes of Health, USA. Zangen and his colleagues recently tested the device on healthy volunteers in the U.S. and found it attained depths of up to 6 cm – deep enough to reach reward system centers.
 

The H-coil may, in the future, enhance many areas of brain research and treatment. For depression, Zangen believes the H-coil may offer an effective alternative to electroconvulsive therapy. Variations in the design of the H-coil may potentially be useful for the treatment of addiction, neurological disorders such as epilepsy, and diseases such as Alzheimer's and Parkinson's.    

Joystick

There is a large genetic component to depression. To link specific genetic factors to behavior, Zangen has employed a number of rat testing methods, including the swimming test – widely used for analyzing levels of motivation. Zangen and Ph.D. student Roman Gersner recently developed a novel approach that improves diagnostic accuracy and objectivity in this swimming test. Instead of timing periods of activity with a stopwatch, they use a joystick to measure the swimming rat’s limb motion, which is recorded and plotted by computer. Zangen predicts this methodology will contribute to a better mathematical analysis of behavior and potential drug effectiveness.

A Promising Career

Dr. Abraham "Boomy" Zangen received a B.Sc. in pharmacology from the Hebrew University of Jerusalem in 1991, and from Bar Ilan University, an M.Sc. in biochemical pharmacology and a Ph.D. in psychopharmacology. In 1999, he travled to the US on fulbright and Fogarty scholarships to comlete postdoctoral research at the National Institutes of Health. In 2003 he returned to Israel to a position as senior scientist in the Weizmann Institute's Neurobiology Department. He has reiicved the annual proze of the Israel Society for Biological Psychiatry (twice), a Fellows Award for Research Excellence for the NIH and published over 25 papers in scientific journals.

Zangen lives in Jeruslaem with his wife, Rachel, and their four children.

Dr. Abraham Zangen’s research is supported by the Nella and Leon Benoziyo Center for Neurological Diseases; the Carl and Micaela Einhorn-Dominic Brain Research Institute; the Abisch Frenkel Foundation for the Promotion of Life Sciences; the Charles and M.R. Shapiro Foundation Endowed Biomedical Research Fund; and the Lord Sieff of Brimpton Memorial Fund. Dr. Zangen is the incumbent of the Joseph and Celia Reskin Career Development Chair.

They volunteer in the largest army in the world. They don't get uniforms, or boots, or a paycheck, but they're heavily armed. They patrol, check identification, isolate and render harmless all suspicious objects, and fight every battle to the death. Their mission: to guard against invasion. Their unit name: the immune system.
 

As in any army, however, mistakes are made. Communication breaks down and casualties result from friendly fire. Physicians generally lack information about the immune system’s overall battle plan, relying instead on limited information obtained through the questioning of a few scouts. “Medical strategies could be more effective with global information about the system,” says Prof. Irun Cohen of the Immunology Department. Meanwhile, researchers at the Weizmann Institute have developed a way to eavesdrop on the immune system's communication network for clues about the battles being waged.

Communications are critical, for instance, to antibodies, the specialized soldiers of the immune system. Antibodies fight against foreign agents (antigens), but they must be trained to distinguish antigens from normal parts of the body (self-antigens). One small breakdown in identification or communication can trigger an autoimmune response – a deadly attack on self-antigens.  Autoimmune diseases are typically chronic and range from slight allergies, to painful and disfiguring diseases like rheumatoid arthritis and multiple sclerosis, to potentially fatal diseases like diabetes. One’s susceptibility or resistance is dependent on the collective state of the immune system, which may be vulnerable for a number of reasons, ranging from inheritance to lifestyle.

Recognizing that an effective defense initiative requires cooperation, Cohen formed an alliance with Prof. Eytan Domany of the Physics of Complex Systems Department. Drawing upon their combined knowledge of biology, immunology, bioinformatics and physics, the two researchers teamed up to develop a comprehensive analysis of the immune system. They hoped to find patterns in an individual’s repertoire of antibodies that might make it possible to predict resistance or susceptibility to various diseases.

The team elected to study Type 1 diabetes. Prediction is particularly important for diabetes because most of the pancreatic cells producing insulin have already been destroyed by the disease by the time the patient experiences any symptoms. There is no cure, and the prognosis is lifelong insulin dependence, susceptibility to kidney damage, loss of eyesight, leg amputation, coma and death.  
    
In their first collaborative study, the two groups obtained the “immune fingerprints” of both diabetic and healthy subjects – finding each person’s unique complement of antibodies by testing blood samples for interaction with 80 different antigens. They were able to demonstrate that such fingerprints can be used to identify diabetic subjects. This type of trial, however, is very labor-intensive, making it impractical for large-scale, multiple-antigen testing.
 

Cohen’s lab, therefore, took the lead in developing a chip that would allow testing for a large number of antibodies. The antigen chip contains many hundreds of minuscule antigen dots. Each of these dots attracts a different antibody out of a blood sample, which will hook on to it, just as it would attach to a natural antigen in the body. Researchers from Domany's lab assisted in perfecting the chip for clear and consistent results – a process that took eight months to complete. In theory, data from this exercise could be used to create an extensive profile of an individual’s immune system and perhaps even enable a physician to predict susceptibility to various diseases before they develop.
 

Obtaining a reading entails shining a laser light on the chip, which gives researchers information not only about the presence of antibodies that bind to the antigens printed on each spot, but also about their relative concentrations. The chip yields unwieldy quantities of information, so to make sense of the numbers, Domany’s group used an algorithm they developed to detect clusters and patterns in large amounts of data. From the original hundreds of antigens, 27 could be used to predict into which of two groups tested mice would fall: those that would become diabetic in the future and those endowed with resistance to the disease.
 

The researchers credit their in-vention to the cross-fertilization of ideas between their respective scientific fields: “Our multi-disciplinary approach,” says Domany, “led to new questions and new methods for finding answers.”
 

“Solutions for many types of illnesses and diseases have their foundations in understanding the collective behavior of the immune system,” explains Cohen. Armed with antigen chips, immunologists may gain a new advantage in the fight against silent and deadly enemies. The possible applications range from treating autoimmune diseases to fighting bioterrorism.

A number of people were involved over several years in researching and developing the antigen chip; they include Francisco Quintana, Gaddy Getz, Gad Elizur, Ilan Tzafrir, Dafna Tzafrir and Peter Hagedorn.

 

Prof. Irun Cohen’s research is supported by the Minna James Heineman Stiftung; the Robert Koch Minerva Center for Research in Autoimmune Disease; and Mr. and Mrs. Samuel Theodore Cohen, Chicago, IL.  Prof. Cohen holds the Helen and Morris Mauerberger Professorial Chair in Immunology.

Prof. Eytan Domany’s research is supported by the M.D. Moross Institute for Cancer Research; the Yad Abraham Research Center for Cancer Diagnostics and Therapy; and the Ridgefield Foundation, New York, NY. Prof. Domany is the incumbent of the Henry J. Leir Professorial Chair.

There are gambles, and there are gambles. In a lottery, a modest investment buys a tiny chance of winning a fortune, while in Russian roulette, you run a fairly high risk of losing big-time. Evolution is a high-stakes game that combines features of both. Its instrument, mutation, carries a serious threat: mutations are hundreds of times more likely to be harmful than advantageous. But the right mutation at the right time can grant an all-important winning edge against competition or predators.
 

Recently a team of scientists, headed by Dr. Dan Tawfik in the Biological Chemistry Department, demonstrated how evolving organisms may be hedging their bets in the evolutionary game. In a paper published in Nature Genetics the scientists focused on a group of proteins that exhibit so-called “promiscuous” or “moonlighting” activity. Though evolved to perform a given function, these proteins are able to take on other, often completely unrelated, tasks as well. For example, the enzyme PON1 both removes cholesterol from artery walls and breaks up chemicals used in pesticides. Yet its main function is the removal of a completely different class of compounds. Tawfik believed promiscuity might provide nature with ready-made starting points for the evolution of new functions.
 

To investigate what advantage promiscuity offers, the team, which included Amir Aharoni, Leonid Gaidukov, Olga Khersonsky, Stephen McQ. Gould and Cintia Roodveldt, created a speeded-up version of evolution in the lab. They introduced random mutations into genes coding for a number of promiscuous proteins and selected those mutants with higher levels of activity in one specific promiscuous trait. After several rounds of mutation and selection, the scientists checked their enzymes to see what had changed. As expected, they had managed to increase the targeted activity a hundredfold or more. But did increasing one skill affect the others?

How does one define the borderline between life and death?” asks Prof. David Wallach of the Biological Chemistry Department. Most doctors agree that cessation of heartbeat or brainwaves is the standard indication of human death. For the body’s cells, too, scientists have clear ideas as to the signs that indicate death. For instance, they can point to specific molecules that are intimately associated with the cell death process. But, as Wallach and an international team of researchers have recently demonstrated, at least one of the molecules most closely linked to cell death may be just as necessary for maintaining cell life.
 

Caspase-8 is a member of the caspase family of enzymes, known to play a central role in the complex process leading to cell death, also called apoptosis. This enzyme’s activation is, in itself, taken as a sign that the cell is on an irreversible path to suicide.
 

In the 20 years that Wallach has been studying apoptosis, he has brought to light some of the more important biological molecules and processes involved, including caspases. Around six years ago, he and his research team used a technique called “gene knock-out” to create mice lacking the gene that produces caspase-8. However, rather than breeding mice with immortal cells, as would be the case if caspase-8 was merely a link in the cell-suicide chain, they found their mice didn’t make it past the embryo stage. Apparently, this “cell death” enzyme also had important roles to play in growth and development.
 

“Unfortunately, when knocking out a gene causes so much havoc in the organism, it's very hard to study its function,” says Wallach. But a recent advance in knock-out technology inspired the team to try once again to unravel caspase-8's role. Called conditional knock-out, it allowed the scientists to delete the gene in only one organ at a time or to turn it off at a specific time.
 

When the caspase-8 gene was knocked out from the liver, the result was, indeed, the creation of cells that refused to die, giving scientists further proof that caspases are crucial to apoptosis in living mammal cells. In contrast, knocking out the caspase gene from the circulatory system produced nearly opposite results. Cells did not grow and develop properly, and the fine capillary blood vessels failed to form as they should. Similarly, knocking out the caspase gene from the stem cells that become various types of blood cells resulted in the complete arrest of blood-cell generation, while deleting it in unformed macrophages (a type of white blood cell) kept them from maturing, showing the “death” gene may be a “life” gene after all.

 

While this study raised some new questions about the mechanisms that control life, another study recently published by Wallach and his team settled the long-standing question of how a protein they had previously discovered helps the cell resist death. Called NIK, this protein relays messages from the immune system outside the cell to an intracellular “messenger service” called NF-kB, which sparks the production of proteins that, among other effects, endow cells with death resistance. But NIK works only some of the time, and the circumstances of its employment were the subject of scientific controversy. Wallach’s team showed that NIK comes into play only if specific receptors on the cell membrane - those tied to the functioning of white blood cells known as lymphocytes - are activated. Because an accumulation of death-resistant lymphocytes is tied to such problems as graft rejection and various autoimmune diseases, NIK is a promising target for new drugs to treat a variety of conditions.

Prof. David Wallach’s research is supported by the Kekst Family Center for Medical Genetics; the Dr. Josef Cohn Minerva Center for Biomembrane Research; the David and Fela Shapell Family Center for Genetic Disorders; the Joseph and Bessie Feinberg Foundation; and the Alfred and Ann Goldstein Foundation.