The document provides an overview of apoptosis, a programmed cell death process crucial for development and homeostasis, differentiating it from necrosis. It details the historical background, mechanisms, examples, and both physiological and pathological roles of apoptosis, along with detection methods and recent advances in treatment approaches. It highlights the significance of apoptosis in various diseases, including cancer and neurodegenerative disorders.

1. OBJECTIVES
Introduction
Example of apoptosis
History of apoptosis
Difference between apoptosis and necrosis
Reasons for apoptosis
Mechanism of apoptosis
Regulation of apoptosis
Changes in apoptosis
Detection and recent advances

2. INTRODUCTION
Apoptosis is the programmed cell death.
Greek word meaning ‘falling off ’ or ‘dropping off ’.
First described in1972.
It is a form of coordinated and internally planned cell death,
which is of greater significance in a variety of physiologic and
pathologic conditions.
Apoptosis has genetic control.
Genes of the own cells play important role in this
programmed cell death.

3. Example of apoptosis
Apoptosis is a natural process & examples are:
 Death of neurons in central nervous system during brain
development and synapse formation.
 During fetal development, degeneration of many tissues
like web in the fingers.
 Many blood cells like eosinophils undergo apoptosis.

4. History of apoptosis
German scientist Carl Vogt put
forth the principle of
apoptosis in 1842.

5. Walther Flemming an
anatomist described the
process of programmed
cell death in 1885.

6. John Kerr in 1965 while studying
tissues using electron microscopy,
was able to distinguish apoptosis
from traumatic cell death.
In an article published in1972 John
Kerr, Andrew H. Wyllie and A.R. Curie
coined the term apoptosis.
Kerr received the Paul Ehrlich and
Ludwig Dermstaedter prize on March
14, 2000 for his description of
apoptosis.

7. The 2002 Nobel prize in
Physiology and Medicine was
awarded to Sydney Brenner, H.
Robert Hovitz and John E.
Sulston for their work is
identifying genes that control
apoptosis.

8. Necrosis vs. Apoptosis
 Cellular shrinkage
 Membranes remain intact
 Active process-requires ATP
 Cell is phagocytosed, no tissue
reaction
 In vivo, individual cells appear
affected
 Maybe physiological or
pathological.
 Cellular swelling
 Membranes are broken
 Passive process
 Cell lyses, eliciting an
inflammatory reaction
 In vivo, whole areas of the
tissue are affected
 Always pathological
Necrosis Apoptosis

9. Apoptosis vs. Necrosis

10. Why should a cell commit suicide?
Apoptosis is needed for proper development examples:
 The formation of the fingers and toes of the fetus
 The sloughing off of the inner lining of the uterus
 The formation of the proper connections between neurons
in the brain
 Apoptosis is needed to destroy cells examples:
 Cells infected with viruses
 Cells of the immune system
 Cells with DNA damage
 Cancer cells.

11. Mechanisms of Apoptosis
Apoptosis is stimulated by two stimuli-
Extrinsic pathway- stimulus received from outside of cell.
Intrinsic pathway-stimulus arises within the cell.
Both the pathways lead to activation of cysteine proteases in
the cell called caspases which trigger apoptosis.
Caspase are synthesized in the cell as precursor named
procaspase.

12. There are three types of caspases
 Inflammatory caspases : Caspases 1,4 & 5
 Initiator caspases : Caspases 2,8,9,10
 Effector caspases : Caspases 3,6 & 7
In the case of apoptosis the process starts with activation of
caspases 8 or 9 which activates caspases 3 and 7 which then
activates other caspases resulting in a cascade.

13. Regulation of Apoptosis
Once apoptosis is initiated, certain intracellular proteins provide
signal for the final programmed cell death, which actually determine
the outcome.
Apoptosis depends on the balance between the proapoptotic
proteins and anti-apoptotic proteins.
Proapoptotic proteins - BAX and BAK
Anti-apoptotic proteins-BCL-2, BCL-XL, MCL-1
Proteins which regulate between proapoptotic proteins and anti-
apoptotic proteins : BAD, BIM, BID, Puma and Noxa
Other apoptotic regulatory protein-TP53(p53) protein, caspases, BAX
& certain viruses like adenovirus, papiloma virus, HBV.

14. INTRINSIC PATHWAY
Also known as mitochondrial pathway.
Internal stimuli may be due to cellular stress, viral infections,
increase in the concentration of intracellular oxidants, heat,
radiation, nutrient deprivation, hypoxia, increased
intracellular calcium concentration, damage to the DNA etc.

15. Mitochondrial proteins called SMACs (Second
Mitochondria derived Activator of Caspases) are also
released into the cell's cytosol following increased
mitochondrial permeability.
SMAC binds to anti-apoptotic proteins thereby
deactivating them and therefore allowing apoptosis to
proceed.

16. INTRINSIC PATHWAY
Internal
stlmuli
Damage to
mitochondrial
membrane increasing
permeability
Entry of
cytochrome- C into
the cytoplasm
Apoptosome activates
procaspase 9 to
caspase 9
Cytochrome binds to
Apaf – 1 forming
apoptosome

17. EXTRINSIC PATHWAY
The extrinsic pathway of apoptosis begins outside a cell,
when conditions in the extracellular environment determine
that a cell must die.
External stimuli are various ligands that bind with cell
surface to activate apoptosis.TNF and Fas Ligands are some
examples of ligands that activates Caspase 8.
These ligands are called death ligands and they bind with
Death receptors like TNFR1.

18. Mechanisms of Apoptosis

19. Steps
of
Apoptosis

20. Changes in Apoptosis
PATHOPHYSIOLOGIC CHANGES
 The apoptotic cells become round or oval & reduce in size.
 The cytoplasm becomes intensely eosinophilic containing
condensed or fragmented nuclear chromatin material.
 Cytoplasm is reduce but organelles remain almost normal.
 Cell membrane convolutes with formation of membrane
bound spherical structures called apoptotic bodies that
contain compacted organelles.
 Chromatic condensation occurs around the periphery of
nucleus.
 Phagocytosis of apoptotic bodies occurs by macrophages.

21. Biochemical Changes
 Proteolysis of cytoskeletal proteins.
 Cross linking of protein molecules.
 Fragmentation of nuclear chromatin by activation of nuclease.
 A glycoprotein molecule called thrombospondin and a
phosphoprotein called phosphatidylserine appear on the
outer surface of apoptotic bodies, which facilitate
recognition by macrophages for phagocytosis.

22. PHYSIOLOGICAL PROCESSES
The separation of fingers and toes in a developing human
embryo occurs because cells between the digits undergo
apoptosis.
Endometrial shedding in menstrual cycles.
Regression of lactating breast after cessation of breastfeeding.
Normal shedding of intestinal epithelium.
Involution of thymus after childhood.
Degeneration and regeneration of neurons within the CNS and
formation of synapse.
Regression of duct system during sex differentiation in the
foetus.

23. PATHOLOGICAL PROCESSES
Tumor cell death on exposure to chemotherapeutic agents.
Transplant cell death by cytotoxic T cells that cause
transplant rejection.
Cell death induced by viral infections.
Cell death induced by radiation, hypoxia.
Degenerative diseases like Alzheimer's disease, Parkinson's
disease.

24. Detection of Apoptosis
 DNA fragmentation assay by electrophoresis
 TUNEL staining
 Demonstration of chromatic condensation by H & E
 Estimation of cytosolic cytochrome-c, activated caspase,
and annexin V.

25. Application
Understanding the concept of apoptosis has promising role
in future regenerative medicine.
Disorder with reduced Apoptosis-
Cancers
Autoimmune diseases - SLE, Mysthenia Gravis
Inflammatory diseases - BA, IBD
Viral infections- herpres, pox, adenovirus
Disorder with increased Apoptosis-
Neurodegenerative-Alzheimer’s disease, Parkinson’s disease
Ischaemic injury-MI, Stroke

26. Recent Advances
Caspase inhibitors such as N-benzylioxicarbonyl-Val-Ala-Asp
fluoromethyl-ketone (Z-VAD-FMK) were being investigated
for the treatment of Neurodegenerative disorders like
Alzheimer’s disease, Parkinson’s disease, Huntington’s
disease
Another promising compound that is currently under
evaluation is Minocycline which is better than other caspase
inhibitors with less side effects

27. References
 Textbook Of Medical Physiology 4/e 2022 by G K Pal
 Ganong's Review of Medical Physiology
 Guyton and Hall textbook of Medical Physiology
 Robbins And Cotran Pathologic Basis Of Disease (2020)