Matt Baumann, Elizabeth Hervey, Corey Love University of New Mexico Biology of Toxins April 2009

 Aflatoxins are naturally occuring mycotoxins  Produced by two species of Aspergillus fungus: A. flavus A. parasiticus  18 different types of aflatoxins  Aspergillus is an opportunistic pathogen of stored food products  Aflatoxin B1 (AFB1) most common in cultures and in food products

History  Affects a wide variety of animals, namely livestock and humans  Originally described as “Turkey X Disease” in England in 1960 until it proliferated in other animals  FDA has established action levels regarding allowable content  The Food Additives Amendment of 1958 raised the question as to whether mycotoxins would fall under control of the FDA

Relevance of aflatoxins  No animals have known immunity but humans have elevated tolerance levels.  There is a separation of genetic and nongenetic damage caused by aflatoxins which are species specific.  Mice have relatively high tolerance level but adverse effects are seen in chicken, ducks, trout, dogs, guinea pigs, and monkeys.  Necrosis is most common. More often seen in ducklings and turkeys exposed to aflatoxins.

Concern for Humans  Aflatoxins cause mutation of p53 gene  Mutated p53 gene can cause cell division to continue regardless of the mistakes in the DNA sequences  This can lead to CANCER!!!

 Aflatoxins spread via colonization and contamination of crops such as maize, wheat, rice and cotton.  May contaminate vertebrate milk  Foods found in: Peanuts and various other nuts Corn Cottonseed Stored Food Products

Absorption  Ingestion is the main route into the body  Gastrointestinal system will the be the first site of absorption  The toxin is found in three types of substrate: Living plants Non-living plant parts Harvested seeds All of which play important roles in agriculture, human resources and the existence of livestock

Distribution  After ingestion, Aflatoxins are absorbed by the blood stream  Moved through the fluid compartments  Enters Intracellular Fluid Compartment to disrupt DNA and Protein Synthesis

Action Aflatoxin →→→ Epoxide ↑ P450

 P53 gene can go through a mutation: Mutation from GC to TA Occurs on third position of codon 249 Mutated p53 allows cells to go through division despite transcription errors

Action  Once converted, aflatoxins react with nucleic acids  They react with guanine in DNA and RNA leading to depurination  Aflatoxins can inhibit protein and DNA synthesis  DNA damage can also be mutagenic

Metabolism  Biotransformation of Aflatoxin Multi-pathway Determines the toxicity of the aflatoxin Dose that binds to DNA is determined by how much of the aflatoxin is converted to the epoxide

Metabolism  Our bodily responses to aflatoxin:  Hepatic necrosis  Tremorgenic  Nephrotoxicity  Ascites- peritoneal cavity fluid  Hemorrhages of Lungs and Brain (Cerebral Edema and Death)  Carcinogenic

Excretion  Urine - The main pathway for excretion  Milk  Feces

 Everyone is affected  Livestock more so than humans  Irreversible; there is no cure or known immunities  Progress has been made in refining samples to be used for food This process involves alkali refining, washing and bleaching of vegetable oils

Relevance- Immediate, US and Worldwide  New Mexico Importance of agricultural lifestyles involving livestock and crops  Crops and livestock losses Financial impact on farming communities  US and Worldwide Important for foreign trade purposes Overall cost of regulatory and preventative programs  Relatively developed countries with food enforcement policies stand a significant chance of preventing aflatoxin ingestion

 Implications for undeveloped countries Peoples in poor economic status have a slimmer reliance on caloric intake Food sources generally include more grain and products easier to come by Such products are main sources of Aflatoxins Lack of variety increases susceptibility

Broader Implications  Limited food resources for humans- FAMINE?  Dairy industry would be hit hard as the toxin can be excreted through vertebrate milk  Conditions that favor fungal growth include extremely stressful environments  Humidity/Drought- ability to proliferate in a variety of conditions  Potential use for biological warfare- “Cancer Bombs”

Future Research:  Effects of Global Warming on the ability of aflatoxins to spread  Can aflatoxins be used as biomarkers? They are inactivated by a variety of reagents. Aflatoxins may therefore provide insight into the effects on health by environmental agents.  Preventing contamination? Can we control genetic resistance to adverse effects of aflatoxins?

 Aflatoxin: Scientific background, control and implications. Goldblatt, Leo A. New York: Academic Press,  Eaton, D.L. and Gallagher, E.P “Mechanisms of Aflatoxin Carcinogenesis.” Annu. Rev. Pharmacol. Toxicol.  Genetics and Physiology of Aspergillus. Smith, John E. and Pateman, John A. London: Academic Press,  The Genus Aspergillus: From Taxonomy and Genetics to Industrial Application. Powell, Keith A., Renwick, Annabel and Peberdy, John F. New York: Plenum Press,  Groopman, J.D., Kensler, T.W “Role of metabolism and viruses in aflatoxin-induced liver cancer.” Toxicology and Applied Pharmacology. 206(2): :  Ramsdell, Howard S. and Eaton, David L “Species Susceptibility to Aflatoxin B1 Carcinogenesis: Compartive Kinetics of Microsomal Biotransformation.” Cancer Research. 50:  Raper, Kenneth B. and Fennell, Dorothy I. The Genus Aspergillus. Baltimore: The Williams & Wilkins Company,  Smela, M.E, Currier, S.S., Bailey, E.A. and Essigmann, J.M “The chemistry and biology of aflatoxin B1: from mutational spectromety to carcinogenesis.” Carcinogenesis. 22 (4):  Thom, Charles and Raper, Kenneth. A Manual of the Aspergilli. Baltimore: The Williams & Wilkins Company,  Tiwari, R.P., Dham, C.K., Bhalla, T.C., Saini, S.S., Badehra, D.V “Mechanism of Action of Aflatoxin B 1 in Bacillus megaterium.” Applied and Environmental Microbiology. 49(4):