Understanding how toxic compounds affect the body is an important aspect of toxicology, as toxins are known to affect biological structures and processes. This knowledge helps predict the toxicity of certain compounds. With this knowledge toxicologists can plan ways to prevent exposure to toxic compounds and develop ways to antagonize the effects of the toxins.
Toxins Affect Humans in Three Different Pathways
There are three main pathways that potential toxins use to affect the human body.
Direct interaction: In this case the toxins damage the target organs or cells directly by their mere presence at the organ or tissue.
Cellular Dysfunction: Toxins can interrupt the cells by causing the cells to malfunction.
Cellular Disrepair: This is a culmination of the above two pathways. It leads to complex interaction that involves different systems that result in the cells inability to repair itself.
Specific Toxic Target Specific Biomolecules Interrupting Specific Systems
Toxicity is apparent when the toxin reaches its specific target molecule or system. It imparts its effect either by direct contact to the target molecule or indirectly by affecting a molecule that is important in the functionality of a system. Toxicity via direct contact can cause changes to the target molecule. There are three different types of interactions that a toxin uses to change the target molecule.
- Non-covalent Binding: This binding does not necessitate the exchange of electrons. These bonds are relatively transient that do not change the chemical structures of the molecules. This kind of interaction is reversible.
- Covalent Binding: These bonds between toxins and their target molecules are basically irreversible.
- Hydrogen Abstraction: These reactions are started by the toxin. The toxic molecules remove hydrogen from the target molecule. The target molecule then goes on to remove hydrogen from other molecules. The result is the creation of free radicals. Radicals are unstable and tend to abstract hydrogen from stable biomolecules rendering them unstable.
- Other toxin reactions with biomolecules include electron transfer and enzymatic reactions.
Changes Caused by Toxic Exposure
Toxicants once in the system can create havoc in the body. They can either cause the biomolecules to dysfunction or the toxins will ultimately lead to the biomolecules destruction.
- Dysfunction: The toxicant can either activate or deactivate the target molecule erroneously. The dysfunction can result in the body’s inability to recognize the original biomolecule. The body then triggers an immune reaction against its own biomolecule.
- Destroy Target Molecules: By destroying the target molecule, toxins can render the target molecule ineffective. For example if the toxicant acts to produce biomolecule free radicals, the free radicals can start a chain reaction. Free radical chain reactions normally end with the destruction of DNA molecules.
By studying the different types of effects that toxins cause through their exposure, toxicologists are able to better predict how newly designed molecules such as drugs or pesticides could be expected to react when exposed to the human population.
Sources
Zoltan Gregus, Kurtis Klassen. "General Principles of Toxicology." In: Casarett &Doull's Toxicology: The Basic Science of Poisons (Klaassen CD, ed). 5th ed. New York:McGraw Hill. pp. 35-74.
