Transcript 2 necrosis - Univerzita Karlova v Praze

General Pathology - II
Cell
Death
Jaroslava Dušková
Inst. Pathol. ,1st Med. Faculty, Charles Univ. Prague
http://www1.lf1.cuni.cz/~jdusk/
Death
irreversible damage of the
morphological & functional
integrity of
cells
organism
Cell Death
apoptosis
 necrosis

Apoptosis
induced (from outside) or
 genetically programmed cell

death
(cell execution / suicide)
logical and functional contrary to mitosis
 a system for the removal of unnecessary,
aged, or damaged cells

Necrosis
cell death caused from
external insult
Apoptosis
Biochemistry
– expression of genes de novo
– production of apoptosis related proteins
 inductors of the cell death p53, MTS1 Multiple Tumor Suppressor, c-myc, Fas
inhibitors of the cell death bcl-2,
– activation of endonucleases
– fragmentation of DNA
– polymerisation of actin

Apoptosis -1
• Triggered by a wide range of stimuli.
• Cell surface receptors like Fas or
tumor necrosis factor receptor 1 (TNFR1).
• Interplay of proapoptotic (Bax, Bad, Bid, Bik,
and Bim) and antiapoptotic (Bcl-2 and Bcl-XL)
proteins
http://www.sigmaaldrich.com
Oxidative Damage -1
• Endogenous production of reactive
oxygen by mitochondria.
• Increased permeability transition
(PT) in the mitochondrial
membrane
Oxidative damage -2



Apoptogenic factors leak into the
cytoplasm
cytochrome c and apo - inducing
factor (AIF) a cascade of proteolytic
activity
DNA

fragmentation

mutations

cell death.
Mitochondria in Apoptosis
Oxidative damage - 3

Bcl-2 and Bcl-X
–prevent pore formation
–block the release of cytochrome c
from the mitochondria
– prevent activation of the caspase
cascade and apoptosis.
Caspase Cascade -1

Caspases - a class of cysteine
proteases involved in apoptosis.

A proteolytic cascade activates
enzymes that subsequently degrade
cellular targets.
Caspase Cascade - 2
 The
mitochondrial stress pathway release of cytochrome c from
mitochondria
 Granzyme
B and perforin (proteins
released by cytotoxic T cells) induce
apoptosis in target cells by forming
transmembrane pores
Caspase Cascade - 3
 Caspase-activated
DNAse (CAD) may
be activated through the cleavage of its
associated inhibitor ICAD. CAD is then
able to interact with components such
as topoisomerase II (Topo II) to
condense chromatin and lead to DNA
fragmentation.
Granzyme B
 forming
transmembrane pores
 cleavage of effector caspases such as
caspase-3
 In addition, caspase-independent
mechanisms of granzyme B-mediated
apoptosis have been suggested.
 Caspase-activated DNAse (CAD) is activated
through the cleavage of its associated
inhibitor ICAD by caspase-3.
 CAD interacts with topoisomerase II (Topo II)
to condense chromatin
– DNA fragmentation and ultimately apoptosis.
Fas Signaling Pathway






Fas/APO-1/CD95 is a member of the tumor necrosis
factor (TNF) receptor superfamily
– mediator of apoptotic cell death,
– involved in inflammation.
Binding of the Fas ligand (Fas-L) induces
trimerization of Fas in the target cell membrane.
Activation of Fas causes the recruitment of Fasassociated protein with death domain (FADD)
activation of caspase-8.
Activated caspase-8 cleaves (activates) nine other
pro-caspases
a caspase cascade leads to apoptosis.
TNF Signaling Pathway -1
TNF
receptor (TNFR) transduces
growth regulatory signals into the
cell.
TNF is mitogenic for normal cells
 TNF initiates apoptosis in
transformed cells causing DNA
fragmentation and cytolysis.
TNF Signaling Pathway - 2
 The
TNF-induced cell survival pathway
is mediated by the transcription factor
NF-kB.
 cells in which the NF-kB signaling
pathway is blocked are more likely to
undergo apoptosis in response to TNF.
 The availability of NF-kB may play a
critical role in the ability of TNF to act as
an apoptosis-inducer and anti-tumor
agent.
ATM/p53 Signaling Pathway
 The
ataxia telangiectasia-mutated gene
(ATM) encodes a protein kinase that acts as a
tumor suppressor.
 ATM activation stimulates DNA repair and
blocks cell cycle progression.
 ATM-dependent phosphorylation of p53
 p53 can cause growth arrest of the cell at a
checkpoint to allow for DNA damage repair or
can cause the cell to undergo apoptosis if the
damage cannot be repaired.
 p53 is mutated in over 50% of all human
cancers.
Integrin Signaling
in Cell Survival and Death
 Integrins
are heterodimeric transmembrane
receptors composed of a- and b-subunits.
 Approximately 20 integrins have been
identified
 Focal adhesion kinase (FAK) is activated via
autophosphorylation when cells interact
through integrins.
 Depending on the integrin interactions, the
cell can either survive or undergo apoptosis.
Caspase Activation Intristic Pathway -1
 Cytochrome
c release from the
mitochondria of pre-apoptotic cells
 Binding to Apaf-1 in the presence of
dATP/ATP.
 Conformational change in Apaf-1
allowing the molecules of Apaf-1 to
associate with each other.
Caspase Activation Intristic Pathway - 2
 A wheel-like
structure that contains 7
molecules each of Apaf-1, cytochrome c
and ATP.
 Pro-Caspase-9 autoactivation
 Mature caspase-9 remains bound to
the apoptosome
 Activation of executioner caspases
such as caspase-3 and caspase-7.
Apoptosis
Morphology
– chromatin condensation
– cell shrinkage
– budding and forming of apoptotic bodies
(emission of pseudopodia)
– karyorrhexis
(not pathognomonic for apoptosis)
Apoptosis
Meaning
physiological process
necessary for right organ
formatting and life course
 pathological process leading to
organism damage - e.g. atrophy

Apoptosis
Ontogenesis
intestinal mucose, genit. tract,
immune system - T lymphocytes
Tissue & organ structures turnover
intestinal mucose, blood, endometrium
Physiological involution
Atrophy
neonatal adrenal cortex, thymus,
breast after lactation period
preassure, hyperplasia regression,
slight ischemia
Apoptosis
Detection

TUNEL
= Terminal deoxynukleotidyl transferasemediated dUTP Nick End Labeling

silver methenamin impregnation
Necrosis
Biochemistry
– no expression of genes de novo
– energy dependent membrane
systems damaged
hypoxia, toxins
– changes in concentrations of ions
– increased water volume (oncosis)
– autolysis
Necrosis
Morphology
– pyknosis, karyorhexis, karyolysis
– denaturation of proteins - eosinophilia
– cell swelling
– cell budding
(cytoplasmic protrusions)
Necrosis
Meaning
pathological process
leading to a temporary
organism damage or death
Necrosis
Classification
according to the tissue macroscopy:
–
–
–
simple
liquefaction
coagulation
+ special types: caseation,
Zenker´s of waxy appearance
Necrosis –
–
–
further development:
no
death of organism
gangrene
sicca
humida
emphysematosa (gas g.)
demarcation, sequestration
regeneration
repair
Necrosis

- Causes:
chemical
– chlorinated hydrocarbons, heavy metal
compounds, ethyl- alcohol, aphlatoxins, ...

physical
– mechanical trauma, UV light, ionizing
radiation, heat, cold, ….

biologic
– bacteria, viruses, fungi...
Atrophy
diminution of organ or tissue
after full development has
been attained
(versus hypoplasia, aplasia)


simple
numerical
(x hypertrophy)
(x hyperplasia)
Atrophy - causes:

vascular
pressure
inactivity
inanition
neurogenic

ionizing radiation









involution
senile
postinflammatory
endocrine
unknown cause
Atrophy - meaning:


may be reversible
loss of specialised structures
& hypofunction
clinically silent or unimportant
(involution)
 clinically apparent


metaplasia, increase of the supportive
tissues - pseudohypertrophy