The tip of an immune molecule known for its ability to fight cancer may also help patients survive pneumonia, scientists report. A synthesized version of the tip of tumor necrosis factor (TNF) (see image) appears to work like a doorstop to keep sodium channels open inside the air sacs of the lungs so excess fluid can be cleared, according to a study published online on July 16, 2014 in the American Journal of Respiratory Critical Care Medicine. This TIP peptide is attracted to the sugar coating at the mouth of the sodium channel. Once the two connect, they move inside the small but essential number of cells that help keep the lungs clear by taking up sodium, said Dr. Rudolf Lucas, vascular biologist at the Medical College of Georgia (MCG) at Georgia Regents University and the study's corresponding author. Inside these cells, TIP binds to the most critical part of the sodium pump, the alpha subunit, and fluid starts moving again. Sodium comes in the channel, water follows, and the sodium pump pushes the fluid into the body's natural drainage network, called the lymphatic system. "The more sodium you take up, the more water will be taken up by these cells," Dr. Lucas said. "That is the way it's supposed to work.” Fluid in the lungs' 266 million air sacs interferes with breathing as well as the important transfer of oxygen from air sacs to capillaries so it can be distributed throughout the body. TNF, known for its tumor-killing capacity, actually has been viewed as a "bad guy" in the lungs where it can block the sodium channel. In fact, excessive TNF production can put patients into shock. "We found that there is another side on the tip of this molecule, which recognizes sugar groups and this side counteracts that side," Dr. Lucas said.
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