NEW YORK CITY—March 16, 2008
Tumor necrosis factor (TNF) is known to play a role in several important inflammatory diseases including rheumatoid arthritis. While much is known about early signaling pathways activated by TNF, little is known about delayed and chronic TNF responses. In addition, cells called macrophages produce TNF, but little is known about the effects of TNF on the macrophages themselves.
In studies using human blood cells and mice, scientists examined the responses of macrophages during a two-day period after being stimulated with TNF. They found that macrophages secreted TNF and that then the TNF activated surface receptors on the macrophages themselves, spurring the cells into a low and sustained production of a protein called interferon-beta. This protein acted synergistically with TNF signals to induce 1) sustained expression of genes encoding inflammatory molecules and 2) delayed expression of genes encoding interferon-response molecules.
"The striking thing about many of these genes that came to our attention first was that there were these classic interferon response genes which had previously not been associated with TNF," said Lionel Ivashkiv, M.D., director of Basic Research at Hospital for Special Surgery, who led the study. "It suggests a new mechanism by which TNF can drive and sustain inflammation."
Experiments also revealed that the so-called autocrine loop was dependent on so-called interferon-response factor 1. "This was the first implication that IRF1 was linked to TNF inflammatory pathways," said Dr. Ivashkiv.
The researchers say that these findings could lead scientists to ways of preventing the bone destruction that is associated with some diseases. "There is the potential to control inflammation and also to control bone destruction. This interferon response is very effective at preventing the destruction of bones, which is one of the major issues with rheumatoid arthritis," said Dr. Ivashkiv. "So, what it does is sets up the next series of studies, in animal models, to try to determine whether this induction of interferon is beneficial or not."
The new research could also help explain how a patient involved in a University of Pennsylvania gene therapy experiment that used an adenovirus to deliver the gene died. Host response to adenoviral vectors is dependent on both IRF1 and TNF.
"What we have described is that TNF has both pathogenic affects-it helps to sustain some of these inflammatory chemokines, but it also has a potential protective effect, because some of these interferon responses limit the amount of cell proliferation and they can also help to limit inflammation."
In addition to HSS researchers, investigators from the Weill Graduate School of Medical Sciences of Cornell University contributed to the study. The National Institutes of Health supported the work.
About HSS | Hospital for Special Surgery
HSS is the world’s leading academic medical center focused on musculoskeletal health. At its core is Hospital for Special Surgery, nationally ranked No. 1 in orthopedics (for the eighth consecutive year) and No. 3 in rheumatology by U.S. News & World Report (2017-2018). Founded in 1863, the Hospital has one of the lowest infection rates in the country and was the first in New York State to receive Magnet Recognition for Excellence in Nursing Service from the American Nurses Credentialing Center four consecutive times. The global standard total knee replacement was developed at HSS in 1969. An affiliate of Weill Cornell Medical College, HSS has a main campus in New York City and facilities in New Jersey, Connecticut and in the Long Island and Westchester County regions of New York State. In 2017 HSS provided care to 135,000 patients and performed more than 32,000 surgical procedures. People from all 50 U.S. states and 80 countries travelled to receive care at HSS. In addition to patient care, HSS leads the field in research, innovation and education. The HSS Research Institute comprises 20 laboratories and 300 staff members focused on leading the advancement of musculoskeletal health through prevention of degeneration, tissue repair and tissue regeneration. The HSS Global Innovation Institute was formed in 2016 to realize the potential of new drugs, therapeutics and devices. The culture of innovation is accelerating at HSS as 130 new idea submissions were made to the Global Innovation Institute in 2017 (almost 3x the submissions in 2015). The HSS Education Institute is the world’s leading provider of education on the topic on musculoskeletal health, with its online learning platform offering more than 600 courses to more than 21,000 medical professional members worldwide. Through HSS Global Ventures, the institution is collaborating with medical centers and other organizations to advance the quality and value of musculoskeletal care and to make world-class HSS care more widely accessible nationally and internationally.