New drug offers promising possibility for treating adults with periodontitis

University of Pennsylvania researchers have been searching for ways to prevent, half and reverse periodontitis. In a report published in the Journal of Immunology, they describe a promising new target: a component of the immune system called complement. Treating monkeys with a complement inhibitor successfully prevented the inflammation and bone loss that is associated with periodontitis, making this a promising drug for treating humans with the disease.

George Hajishengallis, a professor in the School of Dental Medicine's Department of Microbiology, was the senior author on the paper, collaborating with co-senior author John Lambris, the Dr. Ralph and Sallie Weaver Professor of Research Medicine in the Department of Pathology and Laboratory Medicine in the Perelman School of Medicine. Their collaborators included Tomoki Maekawa, Toshiharu Abe, Evlambia Hajishengallis and Kavita B. Hosur of Penn Dental Medicine and Robert A. DeAngelis and Daniel Ricklin of Penn Medicine.

Earlier work by the Penn team had shown that the periodontal bacterium Porphyromonas gingivalis can hamper the ability of immune cells to clear infection, allowing P. gingivalisand other bacteria to flourish and inflame the gum tissue.

"P. gingivalis has many mechanisms to escape killing by the immune system, but getting rid of inflammation altogether is not good for them because they 'feed' off of it," Hajishengallis said. "So P. gingivalis helps suppress the immune system in a way that creates a hospitable environment for the other bacteria."

The researchers wanted to find out which component of the complement system might be involved in contributing to and maintaining inflammation in the disease. Their experiments focused on the third component of complement, C3, which occupies a central position in signaling cascades that trigger inflammation and activation of the innate immune system.

New drug offers promising possibility for treating adults with periodontitis

Drug may guard against periodontitis, related chronic diseases

A drug currently used to treat intestinal worms could protect people from periodontitis, an advanced gum disease, which untreated can erode the structures   including bone   that hold the teeth in the jaw. The research was published ahead of print in Antimicrobial Agents and Chemotherapy. Current treatment for periodontitis involves scraping dental plaque, which is a polymicrobial biofilm, off of the root of the tooth. Despite this unpleasant and costly ordeal, the biofilm frequently grows back. But the investigators showed in an animal model of periodontitis that the drug Oxantel inhibits this growth by interfering with an enzyme that bacteria require for biofilm formation, says corresponding author Eric Reynolds, of the University of Melbourne, Australia. It does so in a dose-dependent manner, indicating efficacy.

The researchers began their search for a therapy for periodontitis by studying the symbioses of the periodontal pathogens, using genomics, proteomics, and metabolomics, in animal models of periodontitis. They soon found that the periodontal biofilm depended for growth on the availability of iron and heme (an iron-containing molecule related to hemoglobin), and that restricting these reduced levels of the enzyme, fumarate reductase. Since Oxantel (see structure)  was known to inhibit fumarate reductase in some bacteria, they then successfully tested its ability to inhibit fumarate reductase activity in Porphyromonas gingivalis, one of the major bacterial components of periodontitis biofilms. Fumarate reductase is absent from humans, making it an ideal drug target.

They also showed that Oxantel disrupted the growth of polymicrobial biofilms containing P. gingivalis, Tannerella forsythia, and Treponema denticola, a typical composition of periodontal biofilms, despite the fact that the latter alone is unaffected by Oxantel.

The researchers found that treatment with Oxantel downregulated six P. gingivalis gene products, and upregulated 22 gene products, all of which are part of a regulon (a genetic unit) that controls availability of heme.

Periodontitis affects an estimated 30-47 percent of the adult population with severe forms affecting 5-10 percent. It also increases the risks of diabetes, heart disease, stroke, arthritis, and dementia, says Reynolds. These risks arise due to the pathogenic bacteria that enter the blood stream from periodontitis, as well as from the chronic inflammation caused by this disease, he says. Additionally, periodontitis correlates with increased risk of cancers of the head and neck, the esophagus, the tongue, and the pancreas, the investigators report.

http://aac.asm.org/content/early/2013/10/22/AAC.01375-13

Drug may guard against periodontitis, related chronic diseases