Cytotoxicity is the quality of being toxic to cells, meaning that it can cause cell damage or death.

– Cytotoxicity can be caused by various agents, such as chemicals, drugs, radiation, viruses, bacteria, or immune cells. Cytotoxicity can have different effects depending on the type and extent of the cell injury, such as inflammation, necrosis, apoptosis, or autophagy.

– Cytotoxicity can also have different consequences depending on the target and function of the affected cells, such as tissue damage, organ failure, infection, or cancer. Cytotoxicity can be measured by various methods that assess the viability, morphology, or function of the cells .

– Cytotoxic agents are substances that can induce cytotoxicity in cells.

Some examples of Cytotoxic Agents are:

🔅 Chemotherapy Drugs

– These are drugs that are used to treat cancer by killing or inhibiting the growth of rapidly dividing cancer cells. However, chemotherapy drugs can also affect normal cells that divide quickly, such as those in the bone marrow, hair follicles, or gastrointestinal tract. This can cause side effects such as anemia, hair loss, nausea, vomiting, or diarrhea .

🔅 Radiation Therapy

– This is a treatment that uses high-energy rays or particles to destroy cancer cells or shrink tumors. Radiation therapy can also damage normal cells near the tumor site, causing inflammation, swelling, pain, skin changes, or fatigue.

🔅 Venom

– This is a toxic substance produced by some animals, such as snakes, spiders, scorpions, bees, or jellyfish. Venom can contain various components that can affect different types of cells and organs. For example, some venom can cause hemolysis (destruction of red blood cells), neurotoxicity (damage to nerve cells), or cardiotoxicity (damage to heart cells).

🔅 Bacteria

– These are microscopic organisms that can cause infections in humans and animals. Some bacteria can produce toxins that can harm the cells and tissues of the host. For example, Clostridium botulinum produces botulinum toxin, which blocks the release of acetylcholine from nerve cells and causes paralysis

🔅 Immune Cells

– These are cells that are part of the immune system and help to protect the body from foreign invaders. However, sometimes immune cells can attack the body's own cells by mistake or in excess. This can cause autoimmune diseases or inflammatory disorders. For example, cytotoxic T cells can kill infected or abnormal cells by releasing perforin and granzymes.

– Cytotoxic activities are processes or mechanisms that involve cytotoxicity in cells.

Some examples of Cytotoxic Activities are:

🔅 Cell-mediated immunity: This is a type of immune response that involves cytotoxic T cells and natural killer (NK) cells. These cells recognize and eliminate infected or abnormal cells by releasing perforin and granzymes or by activating death receptors on the target cell surface.

🔅 Apoptosis: This is a type of programmed cell death that occurs in response to various stimuli, such as DNA damage, oxidative stress, or growth factor withdrawal. Apoptosis is characterized by cell shrinkage, chromatin condensation, DNA fragmentation, membrane blebbing, and phagocytosis by macrophages.

🔅 Necrosis: This is a type of accidental cell death that occurs due to severe injury or trauma. Necrosis is characterized by cell swelling, loss of membrane integrity, release of cytoplasmic contents into the extracellular space, and inflammation.

🔅 Autophagy: This is a type of self-digestion process that occurs in response to stress or nutrient deprivation. Autophagy involves the formation of double-membrane vesicles called autophagosomes that engulf and degrade cellular components in lysosomes.

▶️ What is the Difference Between Apoptosis and Necrosis?

– Apoptosis and necrosis are two different ways of cell death that have different causes, effects, and mechanisms.

Here are some of the main differences between Apoptosis and Necrosis:

1). Apoptosis is a programmed cell death that is triggered by normal, healthy processes in the body, such as development, tissue homeostasis, or immune response whereas necrosis is an accidental cell death that is triggered by external factors or disease, such as trauma, infection, or toxins.

2). Apoptosis is a regulated and orderly process that involves cell shrinkage, chromatin condensation, DNA fragmentation, membrane blebbing, and formation of apoptotic bodies that are phagocytosed by macrophages while necrosis is an unregulated and chaotic process that involves cell swelling, loss of membrane integrity, release of cytoplasmic contents into the extracellular space, and inflammation.

3). Apoptosis is usually beneficial and does not cause any noticeable symptoms or damage to the surrounding tissues whereas necrosis is always detrimental and can cause pain, fever, tissue death, decreased blood flow, and infection.

4). Apoptosis is caused by self-generated signals within a cell that activate specific enzymes called caspases that execute the cell death program whereas necrosis is caused by external agents that disrupt the cell structure and function by various mechanisms, such as oxidative stress, ATP depletion, calcium overload, or mitochondrial damage.

5). Apoptosis rarely needs any medical treatment, as it is a natural part of the cell cycle. Necrosis always requires medical treatment, as it can lead to serious complications such as sepsis, organ failure, or gangrene.

▶️ What are some Diseases that involve Apoptosis?

Some Diseases that involve Apoptosis are:

🔅 Cancer

– Cancer is a disease of uncontrolled cell growth and division, which can result from mutations or defects in the genes that regulate apoptosis. For instance, the tumor suppressor gene p53, which normally triggers apoptosis in response to DNA damage, can be mutated or inactivated in many types of cancer, allowing the damaged cells to survive and proliferate. Conversely, some cancer treatments, such as chemotherapy and radiation therapy, work by inducing apoptosis in the cancer cells.

🔅 Neurodegenerative Diseases

– Neurodegenerative diseases are disorders that affect the brain and nervous system, causing progressive loss of neurons and cognitive functions. Some examples are Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis (ALS). These diseases may involve abnormal or excessive apoptosis of neurons due to various factors, such as oxidative stress, inflammation, protein aggregation, or genetic mutations.

🔅 Autoimmune Diseases

– Autoimmune diseases are conditions in which the immune system attacks the body's own cells and tissues, causing inflammation and damage. Some examples are rheumatoid arthritis, lupus, multiple sclerosis, and type 1 diabetes. These diseases may involve impaired or dysregulated apoptosis of immune cells, such as T cells or B cells, leading to chronic activation and self-reactivity.

🔅 AIDS

– Acquired immunodeficiency syndrome (AIDS) is a disease caused by the human immunodeficiency virus (HIV), which infects and destroys CD4+ T cells, a type of white blood cell that is essential for immune defense. HIV induces apoptosis in CD4+ T cells by various mechanisms, such as direct viral infection, activation-induced cell death, bystander killing by infected cells, or Fas-mediated death. This leads to a progressive decline in the number and coo function of CD4+ T cells and increased susceptibility to opportunistic infections and cancers.