1. Sarin Adarsh Vangala

2. Introduction: Why Sarin? It is one of the most famous and widely used agents of modern chemical warfare – It has been involved in many recent conflicts – We have a better understanding of its effects on humans than other nerve agents It serves as good illustration of the mechanism and effects of other nerve agents.

3. Introduction: Presentation Contents Uses of Nerve Agents History of Sarin Production Mechanism Physiological response and symptoms Detection Current Treatments

4. Nerve Agents Organophosphate compounds that disrupt transmission of information in nervous system – All act with similar mechanism Tabun (GA), Sarin (GB), Soman (GD), Cyclosarin (GF), VX are examples used in chemical warfare Smythies, Journal of the Royal Society of Medicine, 2004, 97.

5. Uses of Nerve Agents 1 st synthesized nerve agent Tabun developed by IG Farben in Germany as insecticide in late 30s – Toxic effects on humans discovered when lab assistants accidentally exposed Sarin and Tabun now used almost exclusively for chemical warfare Ivarsson, National Defence Research Establishment, 1992.

6. Civilian Uses of Nerve Agents Organophosphate compounds very similar to Sarin such as parathion and chloropyrifos are still used as pesticides in the U.S. today – Quickly degraded and rendered nontoxic by exposure to sunlight, air, etc. Reigart, EPA, 2013, 43-55

7. Potential Medical Uses of Organophosphates Cholinesterase inhibitors might be used to treat dementia Organophosphates pyridostigmine and physostigmine used to treat neruomuscular disease myasthenia gravis Ellis, J.M., 2005, J AM Osteopathic Assoc, 145-158 Flacke, W., 1973, N Engl J Med., 27-31

8. History of Sarin Sarin (C 4 H 10 FO 2 P) first synthesized by German scientist Gerhard Schrader part of G-series of synthetic nerve agents developed for use in chemical warfare by German military never actually used during WWII Sample, Guardian, 2013 Ivarsson, National Defence Research Establishment, 1992.

9. Use in Warfare and terrorism One of several chemical agents used by Iraqi government in 1988 Halabja attack killing over 5,000 Most famously used by terrorist Aum Shinrikyo sect during 1994 Matsumoto attack and 1995 Tokyo Subway attack in Japan killing over 20 people. Sample, Guardian, 2013

10. Modern Incidents rocket attacks on August 21 st 2013 on Ghouta area of Damascus during Syrian Civil war claimed between 350 and 1400 lives Sample, Guardian, 2013

11. Production of Sarin Several different methods used to synthesize Sarin – Many components such as isopropanol (rubbing alcohol) are very common – Most major precursors are heavily restricted by Chemical Weapons Convention guidelines that went into effect in 1997 Can only easily be made in large quantities by governments and militaries Sample, Guardian, 2013

12. Acetylcholine Common neurotransmitter involved in signaling muscle contraction. Acetylcholinesterase (AChE) is an enzyme that hydrolyzes ACh into choline and acetic acid. Pohanka, 2011, Biomed. Pap. Med. Fac. Univ. Palacky Olomouc Czech Repub., 219-230 CDC, 2007

13. Sarin Mechanism Sarin prevents the breakdown of Ach through competitive inhibition. Sarin forms phosphate ester bond to serine residue on AChe active site. CDC,2007 Wang, 2006, Phys. Chem. B. 7567-7573

14. Mechanism Continued sarin-AChE complex undergoes irreversible dealkylation that results in the cleavage of the phosphonate ester bond. – This irreversible process, called “aging”, permanently removes the enzyme’s functionality. CDC, 207 Wang, 2006, Phys. Chem. B. 7567-7573

15. Physiological response Sarin exposure causes buildup of ACh Causes uncontrollable muscle contractions – May cause paralysis when ATP depleted Most of the acute symptoms observed when 75-80% of the AChE inhibited – 1995 Tokyo subway victims showed decreased erythrocyte cholinesterase activity 3 years after the attack Yanagisawa, 2006, Journal of the Neurological Sciences, 76-85 Okumura, 2005, Toxicol. Appl. Pharmacol., 471-476

16. Symptoms Symptoms of inhalation usually appear within five minutes – symptoms of liquid exposure generally arise much later – Respiratory failure was main cause of death in 1994 Matsumoto attack weakness and paralysis in respiratory muscles, mixes with inhibition of the respiratory center of the CNS and thick mucus secretions in the respiratory tract Yanagisawa, 2006, Journal of the Neurological Sciences, 76-85 Okumura, 2005, Toxicol. Appl. Pharmacol., 471-476

17. Other Symptoms bradycardia (depressed heart rate) due to effects on muscarine ACh receptors tachycardia (elevated heart rate) due to effects on nicotinic ACh receptors blurred vision, headaches, and coughing. Yanagisawa, 2006, Journal of the Neurological Sciences, 76-85 Okumura, 2005, Toxicol. Appl. Pharmacol., 471-476

18. Detection Sarin is very volatile and can be very dangerous even in small quantities. – Degrades quickly under environmental conditions – Exposes workers to risk detection methods focus on identifying more stable Sarin metabolites Abu-Qare, 2002, Food and Chemical Toxicology, 1327-1333 Okumura, 2005, Toxicol. Appl. Pharmacol., 471-476

19. Methods of Detection Gas chromatography, mass spectrometry identify metabolites – Metabolites methylphosphonic acid (MPA) or IMPA) isolated from soil samples, urine of victims, etc. Abu-Qare, 2002, Food and Chemical Toxicology, 1327-1333 Okumura, 2005, Toxicol. Appl. Pharmacol., 471-476

20. Treatment Currently mostly focuses on alleviating symptoms – diazepam to treat seizure symptoms – Atropine injections limit ACh activity in muscarine response – oximes injections (such as 2-pralidoxime chloride) can reactivate AChE split sarin into easier to metabolize fragments Oximes are ineffective once enzyme aging has occurred Okumura, 2005, Toxicol. Appl. Pharmacol., 471-476. Newmark, 2004, Arch. Nerol, 649-652. Smythies, 2004, Journal of the Royal Society of Medicine, 32.

21. Reasons for use of Sarin Highly toxic – The LD 50 of sarin gas is 179 μg/kg in mice Highly volatile (mostly gas at room temperature) – Can be easily inhaled or absorbed through skin Sarin much less toxic and less stable than other G-series nerve agents and more modern V-series nerve gases developed by U.S. – But manufacturing generally easier

22. Barriers to effective treatment “Aging” is nearly impossible to reverse – Sarin-AChe complex relatively stable as well Sarin is quick acting and very toxic even in small quantities – Difficult to detect – Victims often die before they can receive medical care – Medical personnel in many areas not equipped/trained to treat Sarin exposure – Poor access to medical care in regions where Sarin most likely to be used Okumura, 2005, Toxicol. Appl. Pharmacol., 471-476. Newmark, 2004, Arch. Nerol, 649-652. Smythies, 2004, Journal of the Royal Society of Medicine, 32.

23. Conclusions Sarin is widely used in chemical warfare – Very toxic and relatively easy to produce Similar organophosphates are relevant for both chemical warfare and pesticides Current treatment methods are largely ineffective Likely to remain relevant in future conflicts due to effectiveness

24. Avenues for future research More effective treatments Better protective gear More rapid and efficient detection methods Potential long term health effects of exposure on cholinesterase activity

25. References Smythies, J, Golomb, B. 2004. Nerve gas antidotes. Journal of the Royal Society of Medicine. 97, 32. Ivarsson U, Nilsson H, Santesson J, eds. 1992 A FOA briefing book on chemical weapons: threat, effects, and protection. Umeå, National Defence Research Establishment. Reigart, J.R. and J.R. Roberts. 2013. "Recognition and Management of Pesticide Poisonings." (6 th ed.) United States Environmental Protection Agency Publication EPA-735K-13001. Sample, I., 2013. Sarin: the deadly history of the nerve agent used in Syria. The Guardian. Wang, J., Gu, J., Leszczynski, J. (2006) Phosphonylation Mechanisms of Sarin and Acetylcholinesterase: A Model DFT Study. J. Phys. Chem. B. 110, 7567-7573 CDC. 2007. Cholinesterase Inhibitors: Including Insecticides and Chemical Warfare Nerve Agents. Agency for Toxic Substances and Disease Registry. Yanagisawa, N., Morita, H., Nakajima, T. (2006) Sarin experience in Japan: Acute toxicity and long- term effects. Journal of the Neurological Sciences. 249(1), 76-85 Newmark, J. (2004) Therapy for Nerve Agent Poisoning. Arch. Nerol. 61(5):649-652 Okumura, T., Hisaoka, T., Yamada, A., Naito, T., Isonuma, H., Okumura, S., Miura, K., Sakurada, M., Maekawa, H., Ishimatsu, S., Takasu, N., Suzuki, K. (2005) The Tokyo subway sarin attack—lessons learned. Toxicol. Appl. Pharmacol. 207, 471-476 Smythies, J, Golomb, B. (2004). Nerve gas antidotes. Journal of the Royal Society of Medicine. 97, 32. Ellis, J.M., 2005. Cholinesterase Inhibitors in the treatment of dementia. J AM Osteopathic Assoc. 105, 145-158 Flacke, W., 1973, Treatment of Myasthenia Gravis. N Engl J Med., 288, 27-31