New Synthetic Molecules Treat Autoimmune Disease in Mice

A team of Weizmann Institute scientists has turned the tables on an autoimmune disease. In such diseases, including Crohn's and rheumatoid arthritis, the immune system mistakenly attacks the body's tissues. But the scientists managed to trick the immune systems of mice into targeting one of the body's players in autoimmune processes, an enzyme known as MMP9. The results of their research recently appeared in Nature Medicine. 

Left: Natural control mechanism blocks the enzyme's zinc active site. Right: Novel antibody works as effectively as the natural control mechanism [Credit: Weizmann Institute of Science]

Prof. Irit Sagi of the Biological Regulation Department and her research group have spent years looking for ways to home in on and block members of the matrix metalloproteinase (MMP) enzyme family. These proteins cut through such support materials in our bodies as collagen, which makes them crucial for cellular mobilization, proliferation and wound healing, among other things. But when some members of the family, especially MMP9, get out of control, they can aid and abet autoimmune disease and cancer metastasis. Blocking these proteins might lead to effective treatments for a number of diseases. 

Originally, Sagi and others had designed synthetic drug molecules to directly target MMPs. But these drugs proved to be fairly crude tools that had extremely severe side effects. The body normally produces its own MMP inhibitors, known as TIMPs, as part of the tight regulation program that keeps these enzymes in line. As opposed to the synthetic drugs, these work in a highly selective manner. An arm on each TIMP is precisely constructed to reach into a cleft in the enzyme that shelters the active bit -- a metal zinc ion surrounded by three histidine peptides -- closing it off like a snug cork. "Unfortunately," says Sagi, "it is quite difficult to reproduce this precision synthetically." 

Dr. Netta Sela-Passwell began working on an alternative approach as an M.Sc. student in Sagi's lab, and continued on through her Ph.D. research. She and Sagi decided that, rather than attempting to design a synthetic molecule to directly attack MMPs, they would try coaxing the immune system into targeting MMP-9 through immunization. Just as immunization with a killed virus induces the immune system to create antibodies that then attack live viruses, an MMP immunization would trick the body into creating antibodies that block the enzyme at its active site. 

Together with Prof. Abraham Shanzer of the Organic Chemistry Department, they created an artificial version of the metal zinc-histidine complex at the heart of the MMP9 active site. They then injected these small, synthetic molecules into mice and afterward checked the mice's blood for signs of immune activity against the MMPs. The antibodies they found, which they dubbed "metallobodies," were similar but not identical to TIMPS, and a detailed analysis of their atomic structure suggested they work in a similar way -- reaching into the enzyme's cleft and blocking the active site. The metallobodies were selective for just two members of the MMP family -- MMP2 and 9 -- and they bound tightly to both the mouse versions of these enzymes and the human ones. 

As they hoped, when they had induced an inflammatory condition that mimics Crohn's disease in mice, the symptoms were prevented when mice were treated with metallobodies. "We are excited not only by the potential of this method to treat Crohn's," says Sagi, but by the potential of using this approach to explore novel treatments for many other diseases." Yeda, the technology transfer arm of the Weizmann Institute has applied for a patent for the synthetic immunization molecules as well as the generated metallobodies. 

Also participating in this research were Drs. Orly Dym, Haim Rozenberg, Rina Arad-Yellin and Tsipi Shoham, and Raanan Margalit of the Structural Biology, Immunology and Biological Regulation Departments, Raghavendra Kikkeri of the Organic Chemistry Department, Miriam Eisenstein of the Chemical Research Support Department, Ori Brenner of the Veterinary Resources Department and Tamar Danon of the Molecular Cell Biology Department. 

Prof. Irit Sagi's research is supported by the Spencer Charitable Fund; the Leona M. and Harry B. Helmsley Charitable Trust; Cynthia Adelson, Canada; Mireille Steinberg, Canada; the Leonard and Carol Berall Post Doctoral Fellowship; and the Ilse Katz Institute for Material Sciences and Magnetic Resonance Research. Prof. Sagi is the incumbent of the Maurizio Pontecorvo Professorial Chair. This work was financially supported by Merck Serono S.A., a division of Merck KGaA, Darmstadt, Germany. 

Source: Weizmann Institute of Science [December 26, 2011]

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Researchers investigate link between autoimmune diseases and wounds that don't heal

Millions of Americans suffer from wounds that don't heal, and while most are typically associated with diabetes, new research has identified another possible underlying cause – autoimmune diseases. The finding represents an unappreciated link that could lead to important new insights in wound healing, say researchers at Georgetown University Medical Center. 

The research will be presented during a poster session on Tuesday, Nov. 8, 2011, at the annual meeting of the American College of Rheumatology in Chicago. 

The study was sparked by the keen observation of Georgetown rheumatologist Victoria Shanmugam, M.D., who began noticing something rather unusual in her patients with autoimmune diseases — any open wound they had was very slow to heal. Their recovery was even more protracted than in patients with wounds who have diabetes, a disease that is notoriously damaging to blood vessels and to normal skin repair. 

So Shanmugam and her colleagues conducted a chart review of people who sought care at a high-volume wound clinic at Georgetown University Hospital to determine the prevalence of autoimmune diseases. The study included patients with open wounds — usually leg ulcers who were treated during a three-month period in 2009. Of the 340 patients, 49 percent had diabetes, which she says is a typical rate. 

"But what was surprising is that 23 percent had underlying autoimmune diseases, and the connection between these relatively rare disorders and wounds that don't heal is under-recognized," she says. 

Of the 78 patients in the cohort who had autoimmune disease, most had rheumatoid arthritis, lupus or livedoid vasculopathy, a type of vascular disease. 

Shanmugam says her findings also show that autoimmune disease-associated wounds were significantly larger at the patient's first visit. These non-healing wounds can be "incredibly emotionally draining and financially costly," Shanmugam says, because they require doctor visits over many months as well as an ever-present risk of serious infections. Sometimes, infections can lead to surgery and the amputation of limbs. More often, they require skin grafts or use of skin substitutes, which may still not solve the problem. 

In fact, Shanmugam's study found that skin grafts were more likely to fail in patients with autoimmune disease-associated wounds. 

Shanmugam hopes the link she has made between autoimmune diseases and wound healing will make its way into the consciousness of the general practitioner. While it is much too invasive and costly to recommend that all patients with wounds be tested for autoimmune diseases, she says, "If a doctor has a patient with a leg ulcer that won't heal after three or four months and they have done all the appropriate treatments, I hope they will look for the presence of an autoimmune disorder." 

Source: Georgetown University Medical Center [November 05, 2011]

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