Biological functions of carbon monoxide

Carbon monoxide is produced naturally by the human body as a signaling molecule. Thus, carbon monoxide may have a physiological role in the body, such as a neurotransmitter or a blood vessel relaxant.[1] Because of carbon monoxide's role in the body, abnormalities in its metabolism have been linked to a variety of diseases, including neurodegenerations, hypertension, heart failure, and inflammation.[1]

Functional Summary[2]

In mammals, carbon monoxide is naturally produced by the action of heme oxygenase 1 and 2 on the heme from hemoglobin breakdown. This process produces a certain amount of carboxyhemoglobin in normal persons, even if they do not breathe any carbon monoxide.

Following the first report that carbon monoxide is a normal neurotransmitter in 1993,[3][4] as well as one of three gases that naturally modulate inflammatory responses in the body (the other two being nitric oxide and hydrogen sulfide), carbon monoxide has received a great deal of clinical attention as a biological regulator. In many tissues, all three gases are known to act as anti-inflammatories, vasodilators, and encouragers of neovascular growth.[5] However, the issues are complex, as neovascular growth is not always beneficial, since it plays a role in tumor growth, and also the damage from wet macular degeneration, a disease for which smoking (a major source of carbon monoxide in the blood, several times more than natural production) increases the risk from 4 to 6 times.

There is a theory that, in some nerve cell synapses, when long-term memories are being laid down, the receiving cell makes carbon monoxide, which back-transmits to the transmitting cell, telling it to transmit more readily in future. Some such nerve cells have been shown to contain guanylate cyclase, an enzyme that is activated by carbon monoxide.[4]

Studies involving carbon monoxide have been conducted in many laboratories throughout the world for its anti-inflammatory and cytoprotective properties. These properties have potential to be used to prevent the development of a series of pathological conditions including ischemia reperfusion injury, transplant rejection, atherosclerosis, severe sepsis, severe malaria, or autoimmunity. Clinical tests involving humans have been performed, however the results have not yet been released.[6]

References

  1. 1 2 Wu, L; Wang, R (December 2005). "Carbon Monoxide: Endogenous Production, Physiological Functions, and Pharmacological Applications". Pharmacol Rev. 57 (4): 585–630. doi:10.1124/pr.57.4.3. PMID 16382109.
  2. ↑ Olas, Beata (25 April 2014). "Carbon monoxide is not always a poison gas for human organism: Physiological and pharmacological features of CO". Chemico-Biological Interactions. 222 (5 October 2014): 37–43. doi:10.1016/j.cbi.2014.08.005. Retrieved 23 October 2014.
  3. ↑ Verma, A; Hirsch, D.; Glatt, C.; Ronnett, G.; Snyder, S. (1993). "Carbon monoxide: A putative neural messenger". Science. 259 (5093): 381–4. Bibcode:1993Sci...259..381V. doi:10.1126/science.7678352. PMID 7678352.
  4. 1 2 Kolata, Gina (January 26, 1993). "Carbon Monoxide Gas Is Used by Brain Cells As a Neurotransmitter". The New York Times. Retrieved May 2, 2010.
  5. ↑ Li, L; Hsu, A; Moore, PK (2009). "Actions and interactions of nitric oxide, carbon monoxide and hydrogen sulphide in the cardiovascular system and in inflammation—a tale of three gases!". Pharmacology & therapeutics. 123 (3): 386–400. doi:10.1016/j.pharmthera.2009.05.005. PMID 19486912.
  6. ↑ Johnson, Carolyn Y. (October 16, 2009). "Poison gas may carry a medical benefit". The Boston Globe. Retrieved October 16, 2009.
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