Tuesday, September 17, 2013

Chemistry in the News: Redefining our Understanding of Brown Recluse Venom

              Most of us who grew up in North Carolina have heard of the brown recluse.  Though the spiders are more common in the southern part of the central US, we still encounter the brown recluse in NC.  As the name recluse implies, the spider is not aggressive and rarely attacks.  Studies have shown that most people who are bitten by the brown recluse were bitten because the spider was inside of their clothing or shoes, to which the victim wasn't aware.  In fact, the fangs of the brown recluse are so small that they cannot penetrate fabric.  The venom of the brown recluse is a hemotoxin, and can produce tissue damage near the site of the wound or in more severe cases the victim can have a systemic reaction and the person can experience heart failure or death.  In one study, "Clinical presentation and outcome of brown recluse spider bite." showed that in 37% of bites that the person suffered necrotizing skin wounds.  Many of these wounds resulted in later skin grafts by plastic surgery.  Though the bites by these spiders can be very dangerous, until recently we had little idea about how the venom of the black widow works.
                Researchers at the UA BIO5 institute recently isolated and identified the protein that causes the tissue damage when a brown recluse bites an animal.  When introduced into tissue, the protein cleaves off the head of the lipids in the cell membrane.  Up until now, scientists thought that the reaction ended with the headless lipid being vulnerable to break down from the venom. Instead, we know that the protein actually causes the lipids to form cyclical structures.  Many other insect bites create the same headless lipid structure, which very rarely in other insect bites causes systemic reactions.  This discrepancy between other insect bites and brown recluse bites and their respective effects was one of the sources of inspiration for this study.  When the ring structure forms, it initiates an immune response.  This immune response is "basically our tissues committing suicide".  The cells in the tissues begin to lose blood flow and begin to die, which stops the blood containing the venomous toxin from entering healthy tissues.  If we have better understanding of the function of the cyclical structure that forms in the lipid tissue after a brown recluse bite, we could potentially develop an anti-venom to inhibit the protein and stop tissue damage or systemic reaction.  


  1. Daniel M. Lajoie, Pamela A. Zobel-Thropp, Vlad K. Kumirov, Vahe Bandarian, Greta J. Binford, Matthew H. J. Cordes.Phospholipase D Toxins of Brown Spider Venom Convert Lysophosphatidylcholine and Sphingomyelin to Cyclic PhosphatesPLoS ONE, 2013; 8 (8): e72372 DOI:10.1371/journal.pone.0072372
  2.  Wright SW, Wrenn KD, Murray L, Seger D. Clinical presentation and outcome of brown recluse spider bite. Ann Emerg Med 1997;30: 28–3


  1. It's pretty interesting that other insect bites that create a similar headless lipid structure don't have the same systemic reaction as a brown recluse bite. I also wonder why it is that the headless lipids form a cyclic structure that eventually causes the tissue to die due to lack of blood flow. It's comforting to know that the spider can't bite through fabric though!

  2. This is an interesting article, speaking as someone who lived in the desert the past decade and who is new to the area. I am not used to seeing soo many little critters and am completely clueless about the wild life in NC. I will definitely have to make sure to check my clothes for these little guys. I am curious as to how these cells are committing suicide though. I wonder if it has anything to do with leaving holes or entering the phospholipid bilayer of the cell's membrane or if it is all exterior of the cell.

  3. I was captivated by your choice of article Phospholipase D Toxins of Brown Spider Venom Convert Lysophosphatidylcholine and Sphingomyelin to Cyclic Phosphates, partly by the nature of it but mostly by the chemical reaction that causes tissue damage. I looked up the sources that were cited and I found them a bit difficult to follow so I found a similar article. You mentioned UA BIO5. From there I found an article titled, “The Bite of the Brown Recluse,” which I am certain you read. Dr. Boyer, the director of the VIPER Institute, gives the reader a lot of insight, but I was take back because she says, “The [chemical] protein [that attacks the cell] clips off the molecules' heads, causing the normally straight molecules to bend into rings. This affects the body in ways that are not yet fully understood.” She continues explaining that, this recognition of damaged cells causes blood cells and antibodies to swarm to the site of the wound to the point where the arterioles squeeze tight and cannot supply blood to that area. I liked how you said, “basically our tissues commit suicide.” Although there is no anti-venom I was curious enough to research what to do just in case someone I know gets bitten by a brown recluse spider. Just for your insight, www.emedicinehealth.com mentions that you should apply ice to decrease pain and swelling, elevate the area of interest above the heart, wash the area and use acetaminophen for pain. What was more interesting however was what NOT to do. The article says do not apply heat because it will accelerate tissue destruction, do not apply steroid creams, do not try to remove the venom, do not apply electrotherapy and do not apply a tourniquet. Great job! I enjoyed your blog response.