• Skip to main content
  • Skip to primary sidebar
  • Skip to footer
  • Health
  • Presentation
  • Procedures
  • Diseases
  • Women
  • Subscribe
  • About
    • Privacy Policy
    • Contact Us

medcaretips.com

Health, Medicine and Medical Care

telegram channel medcaretips
You are here: Home / Basics / What Is Apoptosis?

What Is Apoptosis?

By Dr Arun Pal Singh

Apoptosis is programmed cell death that is carried out in a multicellular organism. Apoptosis leads to the production of cell fragments called apoptotic bodies that phagocytic cells engulf and quickly remove.

Apoptosis is designed to carry out functions of the body development. For example, the differentiation of fingers and toes in a developing human embryo occurs because cells between the fingers apoptose, separating the digits.

Between 50 and 70 billion cells die each day due to apoptosis in the average human adult.

Defective apoptotic processes have been implicated in an extensive variety of diseases which include atrophies in case of increased apoptosis and cancer when apoptosis is insufficient.

apoptosis image

Pathways of Apoptosis

Pathways That Lead to Cellular Apoptosis

Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Programmed cell death involves a series of biochemical events leading to a characteristic cell morphology and death. In more specific terms, it includes a series of biochemical events that lead to a variety of morphological changes, including blebbing, changes to the cell membrane such as loss of membrane asymmetry and attachment, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation.

Processes of disposal of cellular debris whose results do not damage the organism differentiate apoptosis from necrosis. Multiple triggers can lead to a cell undergoing apoptosis by one of two major pathways.

Death receptors

Fas (CD95), TNFR1, TRAIL receptors have a homologous intracellular region “death domain.” These death domains bind to adaptor protein (Fas binds to FADD, TNFRI to TRADD). These adaptor proteins can activate the cysteine protease, procaspase 8. This can be inhibited by FLIP or FLICE-inhibitory protein.

The activated caspase 8 activates the executioner caspases which in turn activate an endonuclease called caspase-activated DNase as well as others. These endonucleases cleave DNA causing fragmentation and cell death.

Caspases also activate proteases that act on actin microfilaments leading to blebbing of the membrane.

Mitochondria-cellular stress

As a result of mitochondria cellular stress, Bax, Bak, and/or Bid bind to mitochondria. This displaces Bcl-2 and Bcl-x, which are normally on the outer mitochondrial membrane and inhibit apoptosis. When this happens, cytochrome c is released from the mitochondria. Cytochrome c activates the adaptor protein, APAF-1, which is in the cytosol. APAF-1 activates procaspase-9, which activates caspases 3 and 7 causing apoptosis.

Akt inhibits this pathway.

Many tumors have chronically activated Akt, so the tumor cell doesn’t undergo apoptosis.

Others cytotoxic cells (T and NK cells) inject granzyme B, which activates caspases 3 and 7.  DNA damage is detected by p53, resulting in the activation of apoptosis. Defective p53 can be found in some tumors and also synoviocytes in rheumatoid arthritis, perhaps contributing to their proliferation.

Abnormalities in cellular apoptosis can lead to cancer and autoimmune disease. Apoptotic bodies can serve as a source of nuclear autoantigens for autoimmune diseases such as systemic lupus erythematosus.

Spread the Knowledge
  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  

Filed Under: Basics

Primary Sidebar

Subscribe to updates

Receive articles in your inbox !!
Enter your email address below

Iron Deficiency Anemia: Causes, Lab Diagnosis and Treatment

Iron deficiency anemia is a type of anemia which occurs when the body does not have enough iron to produce the hemoglobin it needs. Functions and … [Read More...] about Iron Deficiency Anemia: Causes, Lab Diagnosis and Treatment

Breast Cancer While Breastfeeding

Breast Cancer: Risk Factors, Classification, Diagnosis and Treatment

Breast cancer is a type of cancer that starts in the breast. It occurs when breast cells start growing out of control and proliferate rapidly forming … [Read More...] about Breast Cancer: Risk Factors, Classification, Diagnosis and Treatment

vagus nerve anatomy

Vagus Nerve Anatomy, Course and Function

Vagus nerve is a cranial nerve [arises from brain] that contains both … [Read More...] about Vagus Nerve Anatomy, Course and Function

Breast pump

Breast Pump – Types, Working, Uses and Selection Tips

A breast pump is a mechanical device used by breastfeeding mothers to … [Read More...] about Breast Pump – Types, Working, Uses and Selection Tips

breast engorgement

Breast Engorgement: Causes, Prevention and Treatment

Breast engorgement is the painful condition of breasts that occurs … [Read More...] about Breast Engorgement: Causes, Prevention and Treatment

breastfeeding

Breastfeeding – Benefits, Problems and Tips for Better Feeding

Breastfeeding or lactation is a natural and normal way of providing … [Read More...] about Breastfeeding – Benefits, Problems and Tips for Better Feeding

chylous ascites can occur due to bloackage or leakage of lymphatics

Chylous Ascites – Causes, Presentation and Treatment

Chylous ascites is a less common form of ascites resulting from a … [Read More...] about Chylous Ascites – Causes, Presentation and Treatment

Footer

Copyright © 2019 ·News Pro · Genesis Framework by StudioPress · WordPress · Log in