Defective apoptosis, or programmed cell death, is implicated in a wide array of diseases, primarily due to either insufficient or excessive cell death.
Diseases Associated with Deficient Apoptosis
When apoptosis is inhibited or doesn't occur properly, cells that should be eliminated persist and can contribute to various diseases, including:
-
Cancer: Perhaps the most well-known consequence. Defective apoptosis allows mutated or damaged cells to survive and proliferate uncontrollably, leading to tumor formation and metastasis. This includes:
- Carcinomas
- Sarcomas
- Leukemias
- Lymphomas
- Myelomas
-
Autoimmune Diseases: Failure to eliminate self-reactive immune cells can result in these cells attacking the body's own tissues. Examples include:
- Systemic Lupus Erythematosus (SLE)
- Immune-mediated Thrombocytopenia
- Autoimmune Neutropenia
- Glomerulonephritis
- Rheumatoid Arthritis
-
Viral Infections: Some viruses can inhibit apoptosis to promote their own replication and survival within the host cell.
Diseases Associated with Excessive Apoptosis
Conversely, too much apoptosis can also be detrimental, leading to cell loss and tissue damage.
-
Neurodegenerative Diseases: Excessive neuronal apoptosis contributes to the progressive loss of neurons seen in conditions like:
- Alzheimer's Disease
- Parkinson's Disease
- Amyotrophic Lateral Sclerosis (ALS)
-
Ischemic Injury: Events like stroke or heart attack can trigger excessive apoptosis in the affected tissues, leading to further damage.
-
AIDS (Acquired Immunodeficiency Syndrome): While HIV doesn't directly inhibit apoptosis in infected cells, it leads to depletion of CD4+ T cells through various mechanisms, including increased apoptosis of uninfected cells, contributing to immunodeficiency.
In summary, defective apoptosis, whether insufficient or excessive, is a key factor in the pathogenesis of many diseases. Understanding the specific mechanisms involved in different conditions is crucial for developing targeted therapies.
