apoptosis in relation to necrosis

1. Presented by
R.PRATHISHA
Department of fish pathology
FC & RI-Tuticorin

2. Features of Apoptosis
Cell death may occur via at least two broadly
defined mechanisms:
• necrosis
• apoptosis

3. NECROSIS
• Usually affects large areas
of contiguous cells
• Control of intracellular
environment is lost early
• Cells swell and organelles
swell
APOPTOSIS
• Usually affects scattered
individual cells
• Control of intracellular
environment maintained in
early stages
• Cells contract

4. • Nuclear chromatin
marginates early,
• while injury is still
reversible
• When DNA is cleaved,which
is usually a late event,
fragments are random in
size (smear pattern in gels)
• Nuclear chromatin
marginates and chromatin
condenses,becoming very
compact
• Chromatin condensation
and DNA fragmentation
occur together; DNA
cleaved into multiples of
200 base pair units (ladder
pattern in gels)

5. • Cell membrane ruptures as
terminal event and cell
contents are released,which
are chemotactic
• Chemotactic factors lead to
neutrophil infiltration to
degrade dead cells
• Blebs form and apoptotic
bodies containing nuclear
Fragments are shed
• Phagocytosis of intact
apoptotic bodies, no
chemotactic factors are
generated

6. Apoptosis
• Pathway of cell death induced by a tightly
regulated suicide program.
• Controlled by specific genes.
• Fragmentation of DNA.
• Fragmentation of nucleus.
• Blebs form and apoptotic bodies are released.
• Apoptotic bodies are phagocytized.

8.  As many as 1011 cells die in an adult human per day to ensure
tissue homeostasis, and it is estimated that within a typical year,
the mass of cells a person loses through cell death is almost
equivalent to their entire body weight.
Apoptosis is also a protective mechanism, directing lysis of
virus-infected cells, foreign cells or incipient neoplasm.
Excess cell death can contribute to the acquired immune
deficiency syndrome (AIDS) and neurodegenerative diseases like
Alzheimer and Parkinson syndromes, and ischaemic injury such as
myocardial infarction.
Too little cell death could lead to cancer, persistent viral
infection, or autoimmune disorders.

9. Apoptosis plays a central role in the immune system
•Immature lymphocytes that bind to autoantigens are eliminated
by apoptosis
•Apoptosis in thymocytes is associated with the elimination of
self-reactive clones of developing T cells following their
interaction with antigens in the thymus
•B cells are subject to death by apoptosis throughout most
stages of their maturation and 60–70% cell loss has been
calculated during the pre-B to B cell transition in bone marrow

10. Inducers of Apoptosis and
Apoptotic Signalling
• Activators of apoptosis include
• Tumour necrosis factor α(TNFα),
• Fas ligand (FasL),
• Transforming growth factor β (TGFβ),
• Bax (and other proapoptotic Bcl-2 familymembers),and
• glucocorticoids
• In addition, aberrant oncogene expression (e.g. c-
myc), or normal tumour
• suppressor gene function (such as p53) may trigger
apoptosis under specific conditions.

11. Causes of Apoptosis
• Physiologic
• Pathologic

12. PHYSIOLOGIC APOPTOSIS
•Embryogenesis and fetal development.
• Hormone dependent involution.
• Cell loss in proliferating cell populations.
• Immature lymphocytes
• Epithelial cells in the GI tract
• Elimination of self-reactive lymphocytes.
• Death of cells that have served their function.
• Neutrophils, Lymphocytes

14. Pathologic
apoptosis:
• DNA damage due ‘to
radiation, chemotherapy.
• Accumulation of misfolded
proteins leads to ER stress
which ends with apoptosis.
• Cell death in viral
infections that induce
• apoptosis such as HIV and
Adenovirus or by the host
immune response such as
hepatitis.
• Organ atrophy after duct
obstruction

15. Genes that Regulate Apoptosis
• The ‘point of no return’ in apoptosis is
reached when caspases become
enzymatically active in cleaving target
proteins

16. The apoptosis cascade

17. • The Bcl-2 family of factors regulate caspase
activation either negatively (e.g. Bcl-2itself)or
positively(e.g. Bax)
• Among these upstream modulators are
oncogenes such as c-myc which activates
apoptosis in a manner which may be important
in tumorigenesis or cancer therapy.
• The tumour suppressor p53 induces apoptosis
under certain conditions, thereby accounting for
at least a portion of its tumour suppressive
activity.

18. cleavage of chromosomal DNA to a size
of several 100 kb,
then to 50 kb and
eventually to 200 bp
These oligosomal DNA fragments result in a distinct
laddering pattern on an ethidium bromide-stained
agarose gel that represents a hallmark of apoptosis

20. A - early apoptosis; chromatin
margination & condensation
B - later in apoptosis; nucleus
is fragmented

21. C - phagocytosis of apoptotic
cellular remnants by
adjacent cell
D - swollen, necrotic cell for
comparison

22. Mechanisms of Apoptosis
• Death receptor (Extrinsic)
pathway
• Mitochrondrial (Intrinsic)
pathway
• Execution Phase
• Removal of dead cells

24. Intrinsic -Mitochrondrial pathway
• Increased mitochondrial permeability with release of pro-
apoptotic molecules into the cytoplasm (cytochrome c).
• Synthesis of anti-apoptotic molecules (Bcl-2) promoted by
Growth factors.
• When cells are deprived of growth factors or subjected to
stress antiapoptotic molecules (Bcl-2) are lost.
• Mitochondrial membrane becomes permeable and proteins
that activate caspase leak out.

25. Intrinsic
(Mitochondrial)
Pathway of
Apoptosis

26. Extrinsic (Death receptor initiated) pathway
• Death receptors are members of the tumor necrosis factor
receptor family and a related protein called Fas (CD95).
• These molecules contain a death domain.

27. Fas and TNFa Receptor-mediated
Apoptotic Signalling
• Fas receptor (CD95) belongs to a family of receptors
including the tumour necrosis factor (TNF) and nerve
growth factor (NGF) receptors that utilize related
signalling pathways to regulate cell proliferation,
differentiation or death.
• Fas serves as a receptor on the cell surface for a ligand
(FasL), and the
• crosslinking of FasL to Fas receptor triggers
apoptosis on the target cells.
• The Fas apoptotic pathway is implicated in eliminating
unwanted activated lymphocytes or virus-infected
cells

29. Extrinsic (Death
Receptor-initiated)
Pathway of
Apoptosis

30. Executioners of Apoptosis: Caspases
• Caspases (cysteinyl aspartate-specific
proteinases) are a family of proteases containing
cysteine at their active sites.
• They are related to mammalian interleukin 1b-
converting enzyme (ICE/caspase1) and to the
nematode apoptotic gene product Ced-3
• That these proteases play critical roles in
executing programmed cell death
Eg: caspase-3 dominates in regulating neuronal
apoptosis

31. • The inhibition of caspases is also one of the major
strategies adopted by viruses to elude their
destruction through suicide of the infected cell
• Cytokine response modifier A (CrmA) -cowpox
virus- caspase-1 and caspase-8
• P35- baculovirus- all caspases
• Leakage of cytochrome c from mitochondria
might serve as a key signal to activate
procaspases and initiate the biochemical events
of death.

32. • Infectious pancreatic necrosis virus (IPNV), the
causative agent of a highly infectious disease
in salmonid fish, encodes a small
nonstructural protein designated VP5.
• This protein contains Bcl-2 homologous
domains and inhibits apoptosis

33. Execution Phase
• The intrinsic and extrinsic pathways converge to a caspase
activation cascade
• Caspases (cysteine-aspartic-acid-proteases) are conserved
across species
• Synthesized as inactive precursors; activated by proteolytic
cleavage
• Family of at least 12 proteases, a few of which are involved in
inflammation, and many of which are involved in apoptosis

34. How Caspases Disassemble a Cell
• Cleave structural proteins leading
to nuclear breakdown.
• Converts cytoplasmic DNase to
active form.
• DNase causes characteristic
internucleosomal cleavage of DNA.

35. Removal of Dead Cells
• Dying cells secrete factors the recruit phagocytes.
• This facilitates prompt clearance before they undergo
secondary necrosis.
• Dead cells disappear without a trace and do not
produce inflammation.

37. Antiapoptotic genes
Heavily studied antiapoptotic genes include
• Bcl-2 and
• Bcl-XL in mammalian cells,
• Ced-9 in C. elegans,
• p35 in baculovirus,
• and E1B 19K protein in adenovirus.

38. • Overexpression of Bcl-2 is capable of
antagonizing apoptosis triggered by c-myc or
p53
• Bcl-XL acts to inhibit apoptosis similarly to Bcl-
2,(Recent study shows that Bcl-X can be embedded into
either synthetic lipid vesicles or planar lipid bilayers Bcl-X may
sustain cell survival by maintaining mitochondrial membrane
potential)

39. Proapoptotic genes that prevent
apoptosis
Bcl-2 family
Bax
Bad Bid

40. • Bax expression has been shown to be
transcriptionally upregulated by p53 in certain
contexts
• Bad, is directly phosphorylated by the
phosphatidylinositol 3-kinase target Akt, a
potentially important regulator of survival
signals emanating from the cell membrane.

41. • Bid direct target of the Fas signalling pathway

42. Refrences
• Apoptosis:Molecular Mechanisms
Min Wu, Harvard Medical School, Boston,
Massachusetts, USA
Han-Fei Ding, Harvard Medical School, Boston,
Massachusetts, USA
David E Fisher, Harvard Medical School, Boston
Massachusetts, USA
• The Cellular Basis of Disease Cell Injury 3
Apoptosis and Necrosis Cellular Aging
Christine Hulette MD

43. • Infectious pancreatic necrosis virus induces apoptosis in vitro
and in vivo independent of VP5 expression
Nina Santia, Ane Sandtrøb, Hilde Sindrec, Haichen Songd, Jiann-
Ruey Honge, Beate Thub,
Jen-Leih Wuf, Vikram N. Vakhariad, Øystein Evensenb,*
VIROLOGY ELSIVIER
• ApoReview Introduction to Apoptosis
• Extrinsic and Intrinsic Apoptosis Signal Pathway Review
Zhao Hongmei
Additional information is available at the end of the chapter
http://dx.doi.org/10.5772/50129

44. • Fish & Shell fish Immunology Apoptosis in thymus of teleost fish
Nicla Romano a,*, Giuseppina Ceccarelli a, Cecilia Capreraa,
Elisabetta Caccia a, Maria Rosaria Baldassini a, Giovanna Marino ba
Department of Ecology and Biology, Tuscia University, Viterbo, Italy
b National Institute for Environmental Protection and Research
(ISPRA), Rome, Italy
• APOPTOSIS: PROGRAMMED CELL DEATH AND ITS CLINICAL
IMPLICATIONS
Goran Bjelaković1, Aleksandar Nagorni1, Marija Bjelaković2, Ivanka
Stamenković1, Rade Arsić1, Vuka Katić3
1Department of Internal Medicine-Gastroenterology and Hepatology,
2Institute of Anatomy, 3Institute of Pathology, Medical Faculty,
Niš, Serbia and Montenegro E-mail: goranb@junis.ni.ac.yu