Using the zebrafish as an animal model, researchers in the lab of Harvard Medical School professor of systems biology Timothy Mitchison and Dana Farber Cancer Institute professor Thomas Look have discovered that when the tail fins of these creatures are injured, a burst of hydrogen peroxide is released from the wound and into the surrounding tissue. Teams of rescue-working white blood cells respond to this chemical herald, crawl to the site of damage, and get to work.
“We’ve known for quite some time that when the body is wounded, white blood cells show up, and it’s really a spectacular piece of biology because these cells detect the wound at some distance,” says Mitchison. “But we haven’t known what they’re responding to. We do know something about what summons white blood cells to areas that are chronically inflamed, but in the case of an isolated physical wound, we haven’t really known what the signal is.”
These findings are reported in the June 4 issue of the journal Nature.
Philipp Niethammer, a postdoc in Mitchison’s lab, and Clemmens Grabber, a postdoc in Look’s lab, initiated this research project with no interest in wound healing. Rather, they were studying a groups of molecules called reactive oxygen species, or ROS. These small oxygen-derived molecules, of which hydrogen peroxide is one, have the potential to be both helpful and hurtful. Niethammer and Grabber were simply curious to find ways to detect ROS molecules in an organism.
To do this, they took a gene engineered to change color in the presence of hydrogen peroxide and inserted it into zebrafish embryos. Once the embryos entered the larvae stage after a few days, this synthetic gene spread throughout the entire body, essentially “wiring” the fish so that any discreet location in which hydrogen peroxide appears would glow.
But how do you coax the fish to produce a reactive chemical like hydrogen peroxide in the first place?
Since white blood cells have long been known to produce hydrogen peroxide, one obvious way to initiate chemical production would be to inflict a small wound onto the fish, and then, using microscopy, observe patterns of this chemical as white blood cells gathered around the wound. But much to the researchers surprise, they found that hydrogen peroxide immediately appeared at the wound site, prior to the arrival of any white blood cell, and quickly disseminated into neighboring tissue.
They repeated the experiment, this time in zebrafish where they’d disabled a protein that was previously discovered to produce hydrogen peroxide in the human thyroid gland. Not only did hydrogen peroxide not appear at the wound site, but white blood cells failed to respond to the injury.
“This was our real eureka! moment,” says Niethammer. “We weren’t too surprised that we could block hydrogen peroxide production through this technique, but what we didn’t expect at all was that white blood cells wouldn’t respond. This proved that the white blood cells needed hydrogen peroxide to sense the wound, and move towards it.”
Of course, zebrafish are not people, and while our genomes share many similarities with these tiny fish, it isn’t yet clear that natural selection has conserved this process throughout the evolutionary family tree. Still, these findings offer something of a conceptual shift in how to view human conditions where hydrogen peroxide plays a role.
“When we look at how hydrogen peroxide works in people, this really starts getting intriguing,” says Mitchison.
In the human body, hydrogen peroxide is produced primarily in three places: lung, gut, and thyroid gland. Because hydrogen peroxide, and the proteins responsible for producing other ROS molecules, are especially present in lung and gut, the researchers hypothesize that human diseases relevant to these findings would include any in the lung and gut that involve disproportionate levels of white blood cells, like asthma, chronic pulmonary obstruction, and some inflammatory gut diseases.
“Our lungs are supposed to be sterile; our guts are anything but,” says Mitchison. “It’s very logical that both those tissues produce hydrogen peroxide all the time. Perhaps in conditions like asthma, the lung epithelia is producing too much hydrogen peroxide because it’s chronically irritated, which, if our findings translate to humans, would explain inappropriate levels of white blood cells. This is certainly a question worth pursuing.”
Mitchison is currently laying the groundwork for investigating this hypothesis.
This research was funded by the National Institutes of Health.
Nature, June 3, 2009; 459 (7247)
“A tissue-scale gradient of hydrogen peroxide mediates rapid wound detection in zebrafish”
Philipp Niethammer(1), Clemens Grabher(2, 3), A. Thomas Look(2, 4), Timothy J. Mitchison(1)1-Departement of Systems Biology, Harvard Medical School, Boston MA
4-Division of Hematology/Oncology, Department of Pediatrics, Children’s Hospital, Harvard Medical School, Boston, MA
Harvard Medical School http://hms.harvard.edu has more than 7,500 full-time faculty working in 11 academic departments located at the School's Boston campus or in one of 47 hospital-based clinical departments at 17 Harvard-affiliated teaching hospitals and research institutes. Those affiliates include Beth Israel Deaconess Medical Center, Brigham and Women's Hospital, Cambridge Health Alliance, Children's Hospital Boston, Dana-Farber Cancer Institute, Forsyth Institute, Harvard Pilgrim Health Care, Hebrew SeniorLife, Joslin Diabetes Center, Judge Baker Children's Center, Massachusetts Eye and Ear Infirmary, Massachusetts General Hospital, McLean Hospital, Mount Auburn Hospital, Schepens Eye Research Institute, Spaulding Rehabilitation Hospital, and VA Boston Healthcare System.
David Cameron | Newswise Science News
NTU scientists build new ultrasound device using 3-D printing technology
07.12.2016 | Nanyang Technological University
How to turn white fat brown
07.12.2016 | University of Pennsylvania School of Medicine
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
07.12.2016 | Health and Medicine
07.12.2016 | Life Sciences
07.12.2016 | Health and Medicine