NO News is Good News
(An Update on Nitric Oxide)

By Ellen Kuwana
Neuroscience for Kids Staff Writer
April 27, 1999

Two stories have reported on new developments in the complex world of nitric oxide (NO). (For background information on NO, see the "In the News" story on NO: "NO is for Nobel.")

Nitric Oxide - The Defender?

Nitric Oxide (NO) is a gas that is found in air pollution. Cars, for example, give off NO in their exhaust. Scientists are now reporting that your body uses NO to defend against all sorts of nasty things, such as viruses, bacteria, and other microscopic enemies. What is it about NO that these small invaders do not like?

Because this story involves enzymes, it's important to understand what enzymes do. Enzymes (the names of which always end in "ase") are proteins that carry out chemical reactions. These reactions include tasks such as building up or breaking down other molecules. This process activates and inactivates chemicals, thus regulating important processes in your body.

In the case of one virus, research has shown that NO seems to inactivate an enzyme called a protease. The viral protease in this study has the job of splitting large proteins into smaller ones that are used in making more viruses. Nitric oxide stops this process, so the enzyme no longer works and in the process, prevents viruses from multiplying.


  1. Saura, M., Zaragoza, C., McMillan, A., Quick, R.A., Hohenadl, C., Lowenstein, J.M. and Lowenstein, C.J., "An Antiviral Mechanism of Nitric Oxide: Inhibition of a Viral Protease," Immunity, Vol. 10 (January 1999), page 21-28.
  2. "A gas just says NO to a virus," Science News, Vol. 155, No. 9, February 27, 1999, page 139.

Nitric Oxide and the Kissing Bug

In tropical climates, Rhodnius prolixus, commonly known as the kissing bug, sucks human blood for nourishment. Although this may not sound like a tasty meal to us, it is the bug's way of surviving. Like a mosquito, the kissing bug can get a good dinner by preventing the human blood in the vein from clotting. Imagine you are drinking a milk shake--you wouldn't want it to be so thick that the milkshake clogged the straw. You'd want the milkshake liquid enough that you could drink it easily. If the blood clotted, the meal would be over! How do the bugs prevent the blood from clotting and thickening?

Researchers in Arizona and in Amsterdam have collaborated and discovered that the kissing bug carries nitric oxide (NO) in its saliva. It is known that NO opens blood vessels. This finding was reported in the October 17, 1997 issue of Science. Let's take a closer look at this insect's newly discovered secrets.

Rhodnius prolixus
Kissing Bug
Image is courtesy of Prof. Marcelo de Campos Pereira, University of São Paulo Institute of Biomedical Sciences Department of Parasitology
The insect's saliva contains proteins called nitrophorins, which hold NO and then release it into the human tissue. This opens the blood vessels and prevents blood clotting. So far, "it's the only known natural NO storage and transport protein," commented Donald Champagne, the scientist who cloned the gene for nitrophorin. The nitrophorin protein is kind of like a cargo ship: it transports its goods to the port (the blood vessel) and then unloads its cargo (the NO).

You may have heard of kissing bugs because they transmit Chagas disease, a parasitic infection that attacks the heart muscle and sometimes causes death. Although the new information on NO may not help fight this disease, it may contribute to therapies for other diseases. For instance, drugs might be developed that deliver NO to fight heart attacks or strokes, both of which are conditions when the arteries become blocked and need to be opened up. Also, if part of the body had a bacterial infection, then a drug could be sent to that area to deliver NO to fight the infection (as described in the above story).

Nature is clever and there are various ways in which scientists can use the information they gain to study how different animals live, feed, and reproduce. You never know where you may find useful information!


  1. "A bug's kiss has chemistry in humans," Science News Vol. 155, No. 4, January 23, 1999, page 54.
  2. "Biologists Catch Their First Detailed Look at NO Enzyme," Science, Vol. 278, No. 5337, October 17, 1997, page 246.

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