Cytotoxicity is a term used for substances to describe how toxic or poisonous to the cells they can potentially be. Exposure to cytotoxic substances can result in permanent cellular damage or even death. To determine levels of cytotoxicity, laboratory tests and assays are often conducted on substances or ingredients that will be included in any medication or medical apparatus. As for its etymology, the term “cytotoxicity” is a combination of two Greek words: “kytos,” which refers to the cell, and “toxikon,” which pertains to poison.
Substances that can be described as cytotoxic can include some chemicals or even other types of cells. When it comes to chemicals, some naturally produced ones can come in the form of animal venom, such as in some spiders and snakes. The family of vipers, for example, is known to release a type of cytotoxin called the haemotoxin, which can rupture red blood cells and cause internal bleeding and organ damage. Another dangerous cytotoxin is the cardiotoxin, which is often associated with a king cobra’s venomous bite. The toxin attaches itself to the muscle cells in the heart, causing the organ to stop pumping blood, which can result in death.
As for synthetically produced chemicals, their cytotoxicity does not always bring a negative effect but can actually be used as a treatment. Such is the case for chemotherapy, a common treatment option for cancer patients. One distinctive characteristic of malignant or cancerous cells is that they multiply at an unusually rapid rate; what chemotherapy does is either stop these cells from multiplying or ultimately kill them.
The good thing about chemotherapy is that many important types of cells in the body — such as those in the heart, brain, and the bones — are not affected, since their normal regeneration rate is not as fast as those of malignant cells. Other cells that normally have a rapid turnover, however, may be affected by chemotherapy. These cells can include those in the gut, the hair, and the mouth. This is why cancer patients who are undergoing chemotherapy may experience diarrhea, hair loss, and soreness in the mouth, among other side effects caused by chemotherapy’s cytotoxicity.
The human body also produces cytotoxic cells that help fight off infection-causing viruses and foreign bodies. One of these cells is a type of white blood cell called the “cytotoxic T cell,” which has the ability to kill damaged cells due to a virus or a tumor. Another type is the “natural killer cell,” a white blood cell that discharges some proteins and somehow “programs” infected cells to die.