General Pathology - II

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General Pathology - II

• Cell
• Death

Jaroslava Dušková Inst. Pathol. ,1st Med.
Faculty, Charles Univ. Prague http//www1.lf1.cuni
.cz/jdusk/
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Death

• irreversible damage of the morphological
  functional integrity of

cells
organism
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Cell Death

• apoptosis
• necrosis

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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

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Necrosis

• cell death caused from external insult

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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

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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

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http//www.sigmaaldrich.com
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Oxidative Damage -1

• Endogenous production of reactive
• oxygen by mitochondria.
• Increased permeability transition (PT) in the
  mitochondrial membrane

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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.

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Mitochondria in ApoptosisOxidative 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.

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Caspase Cascade -1

• Caspases - a class of cysteine proteases
  involved in apoptosis.
• A proteolytic cascade activates enzymes that
  subsequently degrade cellular targets.

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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

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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.

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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.

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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
  Fas-associated protein with death domain (FADD)
• activation of caspase-8.
• Activated caspase-8 cleaves (activates) nine
  other pro-caspases
• a caspase cascade leads to apoptosis.

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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.

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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.

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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.

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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.

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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.

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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.

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Apoptosis

• Morphology
• chromatin condensation
• cell shrinkage
• budding and forming of apoptotic bodies
• (emission of pseudopodia)
• karyorrhexis
• (not pathognomonic for apoptosis)

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Apoptosis

• Meaning
• physiological process necessary for right
  organ formatting and life course
• pathological process leading to organism damage
  - e.g. atrophy

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Apoptosis

• Ontogenesis
• intestinal mucose, genit. tract,
• immune system - T lymphocytes
• Tissue organ structures turnover
• intestinal mucose, blood, endometrium
• Physiological involution
• neonatal adrenal cortex, thymus,
• breast after lactation period
• Atrophy preassure, hyperplasia regression,
  slight ischemia

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Apoptosis

• Detection
• TUNEL
• Terminal deoxynukleotidyl transferase-mediated
  dUTP Nick End Labeling
• silver methenamin impregnation

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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

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Necrosis

• Morphology
• pyknosis, karyorhexis, karyolysis
• denaturation of proteins - eosinophilia
• cell swelling
• cell budding (cytoplasmic protrusions)

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Necrosis

• Meaning
• pathological process
• leading to a temporary
• organism damage or death

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Necrosis

• Classification
• according to the tissue macroscopy
• simple
• liquefaction
• coagulation
• special types caseation, Zenkers of
  waxy appearance

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Necrosis - further development

• no
• death of organism
• gangrene
• sicca
• humida
• emphysematosa (gas g.)
• demarcation, sequestration
• regeneration
• repair

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Necrosis - Causes

• chemical
• chlorinated hydrocarbons, heavy metal compounds,
  ethyl- alcohol, aphlatoxins, ...
• physical
• mechanical trauma, UV light, ionizing radiation,
  heat, cold, .
• biologic
• bacteria, viruses, fungi...

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Atrophy

• diminution of organ or tissue after full
  development has been attained
• (versus hypoplasia, aplasia)
• simple (x hypertrophy)
• numerical (x hyperplasia)

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Atrophy - causes

• vascular
• pressure
• inactivity
• inanition
• neurogenic
• ionizing radiation

• involution
• senile
• postinflammatory
• endocrine
• unknown cause

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Atrophy - meaning

• may be reversible
• loss of specialised structures
  hypofunction
• clinically silent or unimportant
  (involution)
• clinically apparent
• metaplasia, increase of the supportive
  tissues - pseudohypertrophy