Brian Wuertz, Warren Wilson College
In my previous post, “Hiding in plain sight”, I introduced DOSS, a compound that has been recently identified as a probable obesogen. We are especially concerned about the potential of this compound to cause obesity symptoms in developing children through exposure from their mothers. While DOSS is in many products we use daily, such as homogenized milk and makeup products, it is commonly prescribed to pregnant women in the form of Colace stool softener. I am investigating both how much DOSS is in certain places in the body and how it may promote obesity.
One of the main concerns about obesity is that it elevates the risk of developing other diseases such as diabetes or cancer by causing a state of chronic inflammation (Bianchini 2002). Chronic inflammation in adipose tissue is regulated by immune cells, including macrophages. Macrophages are immune cells found throughout the body that help to fight against infection by recognizing invading bacteria and engulfing them in a process called phagocytosis, literally meaning to eat the other cells. In addition to phagocytosis macrophages are important regulators of the larger inflammatory response by secreting proteins that tell other cells to initiate or maintain a state of inflammation (Fujiwara 2005). This inflammatory reaction may be induced by DOSS. We have seen evidence of increased inflammation and obesity in mice treated with DOSS, so in order to figure out what causes that I am focusing on macrophages because of the way they regulate inflammation.
One way to study the inflammatory response of macrophages is to expose them to DOSS and then see if they produce the inflammatory proteins. Instead of trying to measure the secreted proteins, we can measure how much RNA is made in the cell. The RNA is the translator molecule that takes the plan for the protein from the DNA and makes it available for the cell to read and make the right protein. I identified genes for four different inflammatory proteins to measure the RNA so we can test if DOSS causes the macrophages to make more of any of them. I am testing macrophages that I am isolating from human placenta and breast milk tissue because the developing child is influenced by inflammation in the placenta and breast milk. Macrophages in these tissues could be the source of inflammation that influences how the child develops.
Okay so we have talked about cells, but what about the instruments? In my last post I introduced my instrument of choice, but did not call it that. It is not a guitar or a saxophone, but the HPLC, or high performance liquid chromatograph. This is simply a fancy instrument used to separate chemical compounds by forcing them through a tiny filter column filled with tiny beads. Some compounds stick more to the beads than others, so when you flow a liquid through the column the compounds come out of the column at different times. It is essential to separate the compounds in a sample because then you can measure the amounts of individual compounds.
We want to know where DOSS goes in the body, so we need to be able to measure how much of it is in a sample. I am working to get a system up and running to measure the amounts of DOSS in samples from different cells and tissues. We want to be able to measure DOSS in humans and in marine mammals such as dolphins. Dolphins are exposed to DOSS in the COREXIT oil spill dispersal agent that is applied to large and small scale oil spill issues along coastlines and in harbors. Dolphins are an important sentinel species, meaning that they can provide insight into human health issues.
I have to prepare a column and get the right mixture of solvents to make DOSS come off of the column in a timely fashion and in a way that we can measure it. The measurement is actually done with a mass spectrometer, which measures allows us to identify the compound based on how much it weighs. The number of atoms and types of atoms in the compound determine the mass of the compound. This mass is how the instrument measures the compound. The technique I am using is therefore called liquid chromatography mass spectrometry or LC-MS and the instrument is also referred to by LC-MS. Hopefully by the end of the summer I will be able to find beautiful data with this instrument that will make a coherent tune rather than a jumble of notes.
Funding for this REU program is generously provided by the National Science Foundation and hosted by the College of Charleston. Dr Demetri Spyropoulos at the Medical University of South Carolina is graciously hosting my research project and providing mentorship.