1. APOPTOSIS and NECROSIS

2. The Morphology of Apoptosis
Engulfment of the cell corpse
Chromosomes condense and fragment
Nuclear membrane breaks down
Apoptotic body formation
Cytoplasm shrinks

3. Difference Between Apoptosis and Necrosis
Necrosis (pathological cell death): dying cells swell and lyse; toxic contents leak out and result in inflammatory response.
Apoptosis (physiological or programmed cell death): dying cells shrink, are engulfed by other cells, leave no trace, and don’t result in harmful outcomes

4. Forms of cell death "Classic" Necrosis Apoptosis Mitotic catastrophe
Passive Active Passive
Pathological Physiological or Pathological
pathological
Swelling, lysis Condensation, Swelling, lysis
cross-linking
Dissipates Phagocytosed Dissipates
Inflammation No inflammation Inflammation
Externally induced Internally or Internally induced
externally induced

5. APOPTOSIS Evolutionarily conserved
Occurs in all multicellular animals studies (plants too!)
Stages and genes conserved from nematodes (worms)
and flies to mice and humans

6. Functions of apoptosis
Sculpt body structures, e.g. hand digit
Serve some function but no longer needed
e.g. tadpole tail of frog.
Needed in one sex but not another
e.g. Mullerian duct important for female
is eliminated in males by apoptosis.
Produced in excess, e.g. extra neurons are
removed by apoptosis during neurogenesis.
Serve in immune system as a defense
mechanism to get rid of harmful or
damaged cells.

7. STAGES OF CLASSIC APOPTOSIS
Healthy cell
DEATH SIGNAL (extrinsic or intrinsic)
Commitment to die (reversible)
EXECUTION (irreversible)
Dead cell (condensed, crosslinked)
ENGULFMENT (macrophages, neighboring cells)
DEGRADATION

8. STAGES OF CLASSIC APOPTOSIS
Genetically controlled: Caenorhabditis elegans
soil nematode (worm)
ces2
ces1
ced9
ced3,4
Dead cell
Healthy cell
Committed cell
BCL2
Caspases
(proteases)
C. elegans genes == mammalian genes

9. Cells are balanced between life and death
DAMAGE
Physiological death signals
DEATH SIGNAL
PROAPOPTOTIC
PROTEINS
(dozens!)
ANTIAPOPTOTIC
PROTEINS
(dozens!)
DEATH

10. APOPTOSIS: important in embryogenesis
Morphogenesis (eliminates excess cells):
Selection (eliminates non-functional cells):

11. APOPTOSIS: important in embryogenesis
Immunity (eliminates dangerous cells):
Self antigen
recognizing cell
Organ size (eliminates excess cells):

12. APOPTOSIS: important in adults
Tissue remodeling (eliminates cells no longer needed):
Apoptosis
Late pregnancy, lactation
Involution
(non-pregnant, non-lactating)
Virgin mammary gland
- Testosterone
Apoptosis
Prostate gland

13. APOPTOSIS: important in adults
Tissue remodeling (eliminates cells no longer needed):
Apoptosis
Resting lymphocytes
+ antigen (e.g. infection)
- antigen (e.g. recovery)
Steroid immunosuppressants: kill
lymphocytes by apoptosis
Lymphocytes poised to die by apoptosis

14. X APOPTOSIS: important in adults Maintains organ size and function:
+ cell division
Cells lost by apoptosis are replaced by cell division
(remember limited replicative potential of normal cells
restricts how many times this can occur before
tissue renewal declines)

15. APOPTOSIS: control Receptor pathway (physiological): Death
FAS ligand
TNF
Death receptors:
(FAS, TNF-R, etc)
Death
domains
Adaptor proteins
Pro-caspase 8 (inactive)
Caspase 8 (active)
Pro-execution caspase (inactive)
Execution caspase (active)
MITOCHONDRIA
Death

16. APOPTOSIS: control Intrinsic pathway (damage): Mitochondria Death
Cytochrome c release
BAX
BAK
BOK
BCL-Xs
BAD
BID
B IK
BIM
NIP3
BNIP3
BCL-2
BCL-XL
BCL-W
MCL1
BFL1
DIVA
NR-13
Several
viral
proteins
Pro-caspase 9 cleavage
Pro-execution caspase (3) cleavage
Caspase (3) cleavage of cellular proteins,
nuclease activation,
etc.
Death

17. APOPTOSIS: control Physiological Intrinsic
receptor pathway damage pathway
MITOCHONDRIAL SIGNALS
Caspase cleavage cascade
Orderly cleavage of proteins and DNA
CROSSLINKING OF CELL CORPSES; ENGULFMENT
(no inflammation)

18. APOPTOSIS: Role in Disease
TOO MUCH: Tissue atrophy
Neurodegeneration
Thin skin
etc
TOO LITTLE: Hyperplasia
Cancer
Athersclerosis
etc

19. APOPTOSIS: Role in Disease
Neurodegeneration
Neurons are post-mitotic (cannot replace themselves;
neuronal stem cell replacement is inefficient)
Neuronal death caused by loss of proper connections,
loss of proper growth factors (e.g. NGF), and/or
damage (especially oxidative damage)
Neuronal dysfunction or damage results in loss of synapses
or loss of cell bodies
(synaptosis, can be reversible; apopsosis, irreversible)
PARKINSON'S DISEASE
ALZHEIMER'S DISEASE
HUNTINGTON'S DISEASE etc.

20. APOPTOSIS: Role in Disease
Cancer
Apoptosis eliminates damaged cells
(damage => mutations => cancer
Tumor suppressor p53 controls senescence
and apoptosis responses to damage
Most cancer cells are defective in apoptotic response
(damaged, mutant cells survive)
High levels of anti-apoptotic proteins or
Low levels of pro-apoptotic proteins
===> CANCER

21. APOPTOSIS: Role in Disease
AGING
Aging --> both too much and too little apoptosis
(evidence for both)
Too much (accumulated oxidative damage?)
---> tissue degeneration
Too little (defective sensors, signals?
---> dysfunctional cells accumulate
hyperplasia (precancerous lesions)

22. OPTIMAL FUNCTION (HEALTH)
APOPTOSIS
AGING
APOPTOSIS
Neurodegeneration, cancer, …..

23. NECROSIS

24. Development of Necrosis (2 mechanisms)
irreversible damage to mitochondria
(failure of ATP generation) ↓
anaerobic respiration
lactic acid accumulation
↓ pH in intracellalar matrix (↑ acidity)
activation of lysosomal enzymes
proteolytic digestion of cell
dead tissue cleaned away
damage to cell membrane ↓
loss of phospholipids & damage due to lipid breakdown material
cytoskeleton detached from cell membrane
injury allows enzymes to escape into ECF
Influx of Ca2+ ions
Ca2+ causes permanent damage to mitochondria, inhibits cellular enzyme action & denatures protein
characteristic cell changes
(coagulative necrosis)

25. Cytoplasmic changes 1- Increased eosinophilia:
Increased binding of eosin to the denatured protein
Loss of basophilia of RNA
2- Glassy homogenous appearance: due to loss of glycogen particles.
3- Vacuolated cytoplasm: due to enzymatic degradation of the organelles.

26. Nuclear changes Pyknosis – shrinking & condensation
Karyorrhexis – rupture of nuclear membrane
Karyolysis – basophilia gradually fades

27. Types of Necrosis Coagulative necrosis (Ischaemia Infarction)
Colliquative necrosis (Liquefactive necrosis)
Caseous necrosis
Fat necrosis
Enzymatic fat necrosis
Traumatic fat necrosis
Gangrenous necrosis (putrefactive infection)

28. Coagulative necrosis

29. Many nuclei have become pyknotic (shrunken and dark) and have then undergone karorrhexis (fragmentation) and karyolysis (dissolution). The cytoplasm and cell borders are not recognizable.

30. Here is myocardium in which the cells are dying
Here is myocardium in which the cells are dying. The nuclei of the myocardial fibers are being lost. The cytoplasm is losing its structure, because no well-defined cross-striations are seen.

31. Liquefactive necrosis
The necrotic tissue is rapidly liquefied.
It occurs in:
1- Infarctions of the brain: due to high lipid and fluid content.
2- Pyogenic abscess: due to proteolytic enzymes released by pus cells
3- Amoebic abscess: due to liquefactive enzymes released by the parasite

33. Fat Necrosis Enzymatic Fat Necrosis Traumatic Fat Necrosis
acute pancreatitis ↓
enzymes escape into surrounding tissue
lipases hydrolyse true fat into glycerol & fatty acids
fatty acids saponify or form soaps
(white opaque masses or plaques)
diagnostic of acute pancreatitis
calcification may occur later
rupture of cell membrane ↓
release natural fat into tissues
phagocytosed by macrophages
foamy appearance
chronic inflammatory reaction
fibrosis & scarring
(no enzymatic fat breakdown)

34. Acute pancreatitis

35. Fat necrosis

36. Caseation necrosis
Distinctive type of necrosis in which there is coagulative necrosis with slow liquefaction