Apoptosis.ppt 5c5og

APOPTOSIS Dr. MARUTHI DEVI PG STUDENT ORALPATHOLOGY 16-07-2007

CONTENTS           

INTRODUCTION DEFINITION CLASIFICATION MECHANISM MORPHOLOGIC CHANGES MOLECULAR CHANGES BIOCHEMICAL CHANGES HISTOPATHOGENESIS THE SIGNALS INDUCING APOPTOSIS TECHNIQUES TO IDENTIFY APOPTOTIC CELLS CONCLUSION

INTRODUCTION



In 1971,John Kerr,an Australian pathologist, described cell death in rat liver after ligation of a branch of the portal vein as shrinkage necrosis. Kerr&co-workers further described the morphology of this form of cell death & used the term Apoptosis .

DEFINITION Apoptosis is a genetically regulated evolutionary conserved process that removes damaged cells from a tissue or organ.  It is a form of co-ordinated and internally programmed cell death. Hence living cells posses inherent inhibitory mechanism to keep apoptotic process in check. 

CLASSIFICATION 1. 2.

Physiological apoptosis Pathological apoptosis

• 1.

2. 3. 4. 5. 6.

PHYSIOLOGICAL APOPTOSIS The programmed destruction of cells during embryogenesis Hormone dependent involution in the adult Cell deletion in proliferating cell population Death of host cells Cell death induced by cytotoxic Tcells Involution of Thymus in early life

PATHOLOGICAL APOPTOSIS 1.

Cell death by injurious stimuli



Radiation & cytotoxic anti cancer drugs Heat & Hypoxia Accumulations Viral diseases Pathological atrophy in parenchymal organ Cell death in tumors Cell death by cytotoxic T-cells in immune mechanism Progressive depletion of CD4 &T cells in AIDS In degenerative diseases of C.N.S

  2. 3. 4. 5. 6. 7.

MORPHOLOGICAL CHANGES  Death

of a single cell  No inflammatory reaction  Cell shrinkage  Cyotoplasmic blebs on membrane  Apoptotic bodies  Chromatin condensation  Phagocytosis of apoptotic bodies by macrophages

.CELL SHOWING APOPTOSIS

BIOCHEMICAL CHANGE  Proteolysis

of cytoskeletal proteins  Protein-protein cross linking  Fragmentation of nuclear chromatin by activation of nuclease  Appearance of phosphatidylserine on the outer surface of cell membrane  Appearance of an adhesive glycoprotein Thrombospondein on Apoptotic bodies

MECHANISM OF APOPTOSIS 1.

INITIATION



EXTRINSIC PATHWAY OR RECEPTOR INITIATED INTRINSIC PATHWAY OR MITOCHONDRIAL PATHWAY EXECUTION PHASEP PHAGOCYTOSIS



2. 3.

INITIATION PHASE  EXTRINSIC

PATHWAY

INTRINSIC PATHWAY

THE EXECUTION PHASE  A.

Execution caspases act & cleave cytoskeleton & nuclear matrix proteins. This disrupt the cytoskeleton& lead to break down of nucleus & DNA damage.

PHAGOCYTOSIS  Apoptotic

cells & their fragments have marker molecules on their surfaces which facilitates early recognition by adjacent cells or phagocytes for phagocytosis. Phosphatidylserine which is present in he inner membrane of the cell come to lie on the outer surface of the cell membrane as the cell undergoes apoptosis & acts as a marker.

HISTOPATHOLOGICAL CHANGES The characteristic changes by light microscopy, 1.condensation of the nuclear chromatin-pyknosis 2.cell shrinkage & loss of cell-cell . Increasing eosinophilia of the cytoplasm. 3.the cytoplasmic organelles are still preserved at this stage . 4.as the process continues the nuclear chromatin brakes up into fragments-karyohexis 5.Dissolution of nuclear membrane. 6.cytoplasmic blebs break away from the cell surface & entire cell breaks up to form membrane bound fragments. 7.cell fragments containing nuclear material are known as apoptotic bodies



THE SIGNALS THAT INDUSE APOPTOSIS  Apoptosis

after growth factor deprivation  DNA damage mediated apoptosis.  Apoptosis induced by tumor necrosis factor family receptors.  Cytotoxic T-lymphocyte mediated apoptosis.

TECHNIQUES TO IDENTIFY APOPTOTIC CELLS    





Haematoxylin ,Feulgen, or acridine orange For staining chromatin condensation. Flow cytometry to visualize rapid cell shrinkage. In situ technique or gel electrophoresis to detect DNA changes. Annexin-v as marker for apoptotic cell membrane having phosphatidylserine on the cell exterior. Agrose gel analysis, PCR analysis, COMET assays, ELISA system, TUNEL,to identify fragments.

CONCLUSION

Our understanding of Apoptosis and mechanism of normal development and pathogenesis of many diseases including AIDS ,Neurodegenarative diseases, and Cancer and the role of Apoptosis in these diseases has lead to the development of new and more specific therapies.

REFERENCES  ROBINS

&COTRAN -7th EDITION

 HARSHMOHAN

-4th EDITION

 JOURNAL

OF ORAL PATHOLOGY & MEDICINE, vol-32,no-3, March 2003

 JOURNAL

OF ORAL PATHOLOGY & MEDICINE, vol-31,no-3,March 2002