" "
Satellite Banner
Technology
Networks
Scientific Communities
 
Become a Member | Sign in
Home>News>This Article
  News
Return

Gum Disease Bacteria Selectively Disarm Immune System, Penn Study Finds

Published: Friday, June 13, 2014
Last Updated: Friday, June 13, 2014
Bookmark and Share
New study shows that bacteria responsible for many cases of periodontitis cause dysbiosis.

The human body is comprised of roughly 10 times more bacterial cells than human cells. In healthy people, these bacteria are typically harmless and often helpful, keeping disease-causing microbes at bay. But, when disturbances knock these bacterial populations out of balance, illnesses can arise. Periodontitis, a severe form of gum disease, is one example.

In a new study, University of Pennsylvania researchers show that bacteria responsible for many cases of periodontitis cause this imbalance, known as dysbiosis, with a sophisticated, two-prong manipulation of the human immune system.

Their findings, reported in the journal Cell Host & Microbe, lay out the mechanism, revealing that the periodontal bacterium Porphyromonas gingivalis acts on two molecular pathways to simultaneously block immune cells’ killing ability while preserving the cells’ ability to cause inflammation.

The selective strategy protects “bystander” gum bacteria from immune system clearance, promoting dysbiosis and leading to the bone loss and inflammation that characterizes periodontitis. At the same time, breakdown products produced by inflammation provide essential nutrients that “feed” the dysbiotic microbial community. The result is a vicious cycle in which inflammation and dysbiosis reinforce one another, exacerbating periodontitis.

George Hajishengallis, a professor in the Penn 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 Penn’s Perelman School of Medicine. Collaborators included Tomoki Maekawa and Toshiharu Abe of Penn Dental Medicine.

Work by Hajishengallis’s group and collaborators had previously identified P. gingivalis as a “keystone pathogen.” Drawing an analogy from the field of ecology, in which a species such as a grizzly bear is thought of as a keystone species because of the influence it has over a number of other species in the community, the idea suggests that, although P. gingivalis may be relatively few in number in the mouth, their presence exerts an outsized pull on the overall microbial ecosystem. Indeed, the team has shown that, although P. gingivalis is responsible for instigating the process that leads to periodontitis, it can’t cause the disease by itself.

“Scientists are beginning to suspect that keystone pathogens might be playing a role in irritable bowel disease, colon cancer and other inflammatory diseases,” Hajishengallis said. “They’re bugs that can’t mediate the disease on their own; they need other, normally non-pathogenic bacteria to cause the inflammation.”

In this study, they wanted to more fully understand the molecules involved in the process by which P. gingivalis caused disease.

“We asked the question, how could bacteria evade killing without shutting off inflammation, which they need to obtain their food,” Hajishengallis said.

The researchers focused on neutrophils, which shoulder the bulk of responsibility of responding to periodontal insults. Based on the findings of previous studies, they examined the role of two protein receptors: C5aR and Toll-like receptor-2, or TLR2.

Inoculating mice with P. gingivalis, they found that animals that lacked either of these receptors as well as animals that were treated with drugs that blocked these receptors had lower levels of bacteria than untreated, normal mice. Blocking either of these receptors on human neutrophils in culture also significantly enhanced the cells’ ability to kill the bacteria. Microscopy revealed that P. gingivalis causes TLR2 and C5aR to physically come together.

“These findings suggest that there is some crosstalk between TLR2 and C5aR,” Hajishengallis said. “Without either one, the bacteria weren’t as effective at colonizing the gums.”

Further experiments in mice and in cultured human neutrophils helped the researchers identify additional elements of how P. gingivalis operates to subvert the immune system. They found that the TLR2-C5aR crosstalk leads to degradation of the protein MyD88, which normally helps clear infection. And in a separate pathway from MyD88, they discovered that P. gingivalis activates the enzyme PI3K through C5aR-TLR2 crosstalk, promoting inflammation and inhibiting neutrophils’ ability to phagocytose, or “eat,” invading bacteria.

Inhibiting the activity of either PI3K or a molecule that acted upstream of PI3K called Mal restored the neutrophils’ ability to clear P. gingivalis from the gums.

“P. gingivalis uses this connection between C5aR and TLR2 to disarm and dissociate the MyD88 pathway, which normally protects the host from infection, from the proinflammatory and immune-evasive pathway mediated by Mal and PI3K,” Hajishengallis said.

Not only does the team’s discovery open up new targets for periodontitis treatment, it also suggests a bacterial strategy that could be at play in other diseases involving dysbiosis.


Further Information

Join For Free

Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,900+ scientific posters on ePosters
  • More Than 4,200+ scientific videos on LabTube
  • 35 community eNewsletters


Sign In



Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into TechnologyNetworks.com you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Related Content

Machine Learning Uncovers Unknown Bacterial Features
Technique robustly identified characteristic gene expression patterns in response to antibiotics, low oxygen conditions.
Monday, January 25, 2016
Genetic Cause of Heart Disease
Penn study sheds light on a genetic cause of heart disease.
Wednesday, December 16, 2015
Gene Pair Plays Crucial Role in Colon Cancer
In a new study researchers from the University of Pennsylvania describe two related genes in the Musashi family that are required for colon cancer to develop, and that may be useful targets for effective treatment.
Monday, December 07, 2015
Penn Engineering Team Showcases ‘Eye-on-a-Chip’ Technology
These small plastic chips contain microfluidic channels, carefully designed so that human cells can grow in them in a way that simulates the three-dimensional environments they would normally inhabit in the body.
Thursday, November 19, 2015
How Different Treatments for Crohn's Effect the Microbiome
Different treatments for Crohn's disease in children affects their gut microbes in distinct ways, which has implications for future development of microbial-targeted therapies for these patients, according to a study led by researchers from the Perelman School of Medicine at the University of Pennsylvania.
Friday, October 16, 2015
Profiling Non-Protein-Coding RNAs
Growing insights about a significant, yet poorly understood, part of the genome – the “dark matter of DNA” -- have fundamentally changed the way scientists approach the study of diseases.
Wednesday, October 14, 2015
New Target for Preventing Breast Cancer Relapses
A surprising, paradoxical relationship between a tumor suppressor molecule and an oncogene may be the key to explaining and working around how breast cancer tumor cells become desensitized to a common cancer drug, found researchers at the Perelman School of Medicine at the University of Pennsylvania.
Wednesday, October 14, 2015
Chromosomal Chaos
Penn study forms basis for future precision medicine approaches for Sezary syndrome
Friday, October 09, 2015
Cell's Waste Disposal System Regulates Body Clock Proteins
New way to identify interacting proteins could identify potential drug targets.
Thursday, October 08, 2015
MYC Oncogene Disrupts Cancers Rhythm
Findings inform time-dependent treatment for reducing side effects and increasing effectiveness of cancer medications.
Monday, September 21, 2015
Genes' Found that Play Major Role in Skin and Organ Development
Disruptions of splicing proteins cause facial, skin, organ defects in young mice.
Thursday, September 17, 2015
Viral Product That Promotes Immune Defense Against RSV Identified
A new study has identified a subset of viral products that are responsible for eliciting a strong immune response against RSV in people who become infected.
Wednesday, September 09, 2015
Synthetic DNA Vaccine Against MERS Shows Promise
A novel synthetic DNA vaccine can, for the first time, induce protective immunity against the Middle East Respiratory Syndrome (MERS) coronavirus in animal species.
Friday, August 21, 2015
Cell Aging Slowed by Putting Brakes on Noisy Transcription
Experiments in yeast hint at ways to extend life of some human cells.
Monday, August 03, 2015
Disrupting Cells’ ‘Powerhouses’ Can Lead to Tumor Growth
University of Pennsylvania researchers find that mitochondrial defects have a key role in a cells becoming cancerous.
Monday, July 13, 2015
Scientific News
Criminal Justice Alcohol Program Linked to Decreased Mortality
Institute has announced that in the criminal justice alcohol program deaths dropped by 4.2 percent over six years.
Charting Kidney Cancer Metabolism
Changes in cell metabolism are increasingly recognized as an important way tumors develop and progress, yet these changes are hard to measure and interpret. A new tool designed by MSK scientists allows users to identify metabolic changes in kidney cancer tumors that may one day be targets for therapy.
Improving Regenerative Medicine
Lab-created stem cells may lack key characteristics, UCLA research finds.
Tick Genome Reveals Secrets of a Successful Bloodsucker
NIH has announced that decipher the genome of the blacklegged tick which could lead to new tick control methods.
"Dark Side" of the Transcriptome
New approach to quantifying gene "read-outs" reveals important variations in protein synthesis and has implications for understanding neurodegenerative diseases.
Individuals' Medical Histories Predicted by their Noncoding Genomes
Researchers have found that analyzing mutations in regions of the genome that control genes can predict medical conditions such as hypertension, narcolepsy and heart problems.
'Molecular Movie' Opens Door to New Cancer Treatments
An international team of scientists led by the University of Liverpool has produced a 'structural movie' revealing the step-by-step creation of an important naturally occurring chemical in the body that plays a role in some cancers.
New Source of Mutations in Cancer
Recently, a new mutation signature found in cancer cells was suspected to have been created by a family of enzymes found in human cells called the APOBEC3 family.
Advancing Synthetic Biology
Living systems rely on a dizzying variety of chemical reactions essential to development and survival. Most of these involve a specialized class of protein molecules — the enzymes.
Madison Researchers Begin Work on Zika Virus
Work will start with basic questions about Zika virus infection.
Scroll Up
Scroll Down
Skyscraper Banner

Skyscraper Banner
Go to LabTube
Go to eposters
 
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,900+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
4,200+ scientific videos
Close
Premium CrownJOIN TECHNOLOGY NETWORKS PREMIUM FOR FREE!