Apoptosis And Necrosis Flashcards
Give 4 cell accumulation disorders
- cancer
- lupus erythematous
- glomerulonephritis
- viral infections
Give 4 cell loss disorders
- AIDS
- Alzeihmers disease
- Parkinson’s disease
- aplastic anemia
- myocardial infarction
What are neoplasms?
- “new growth”
- Abnormal mass of cells
What are the two main groups of neoplasms ?
- Benign neoplasms
- Grow slowly & remain localized to site of origin
- Malignant neoplasms= cancer
- Grow rapidly and May spread
- Abnormal growth of tissue- Clusters of cells that are capable of growing and dividing uncontrollably
- Growth is not regulated
- Rapid cell proliferation ignoring normal restraints on cell division
- Restriction of space
- Nutrients
- Cell cycle regulation
- Cell death (apoptosis )
- RES/
What are the hallmarks of cancer?
- Tumor promoting inflammation
- Limitless ability to reproduce
- Ignores anti-growth signals
- Self- sufficient growth signals
- Avoids apoptosis
- Sustained angiogenesis
- Tissue invasion and metastasis
- Genomic instability and mutations
- Avoiding immune destruction
- Deregulating energy metabolism
Briefly describe cancer nomenclature
Malignant neoplasms are classified according to tissue and cell type from which they originated
What is a carcinoma?
- Malignant tumor growing from epithelial tissue
- Many carcinomas affect glands that are involved with secretion
What is sarcoma?
Malignant tumor growing from connective tissues
- Cartilage, fat, muscle, tendons, and bones
- Ex. Osteosarcoma (bone) and chondrosarcoma (cartilage)
What is leukemia?
Cancer of blood or bone marrow
What is melanoma ?
Malignant tumor of melanocytes
What is a malignant neoplasm?
Locally invasive
-Tumor invades the tissues surrounding it by sending out “fingers” of cancerous cells into the normal tissue
Explain what’s metastasis
Distant spread of the tumor cells into other tissues in the body
Modes:
1. Vascular - veins
- Lymphatic -lymphatic vessels
- Transcoelemic- across coelemic spaces
- Ex. Peritoneal & pleural cavities
How are cancers classified?
Classified according to tissue and cell tyroe from which they arise
About 90% of human cancers are carcinomas
-Most of the cell proliferation in the body occurs in epithelial tissue
-Epithelial tissue frequently exposed to physical and chemical damage
Describe cancer growth
- Origins can usually be traced to a single primary tumor
- Derived by cell division of a single cell
- Typical tumor can contain more than a billion cells before first detection
- Doubling time of a typical breast tumor is about 100 days
Summarize tumor formation and proliferation
Tumor formation
- Clonal evolution- develops through repeated rounds kf mutation and proliferation
- cells aquire a selective growth advantage over neighbor cells - Stem cell
- Tumors contain cancer stem cells
- indefinite proliferative potential
- linked initially to leukemia’s
Tumor progression
- most human cancer cells are genetically unstable
- defective repair of DNA damage or replication errors
- Loss of chromosome integrity
- abnormal karyotype
Contrast cell swelling and cell shrinking for necrosis and apoptosis
Necrosis-causes cell swelling
Apoptosis- causes cell shrinkage
Contrast plasma membrane related events in necrosis and apoptosis
Damage to plasma membrane- necrosis
Plasma membrane blabbing- apoptosis
Contrast Nucleus activities in apoptosis and necrosis
Aggregation of chromatin- apoptosis
Fragmentation of nucleus- apoptosis
Necrosis doesn’t do either
Contrast DNA activities in relation to necrosis and apoptosis
Oligosaccharide DNA fragmentation- apoptosis
Random DNA degradation- necrosis
Caspase cascade activation- apoptosis
How are chromosomes sorted in karyotypes?
Chromosomes sorted by size, shape & fluorescent Chrimoeome 1 is the biggest and first, decreased in s8ze as numbers increase
Comeback to see translocation between chromosomes 8 and 14 that. Leads to tumors
A karyotype is made of a Breast cancer patient, what is to be expected?
A. General stain
-48 chromosomes rather than the normal 46
B. Fluorescent stains
-Evidence of multiple translocations
What are the 2 general mechanisms of cell death?
- Necrosis
- Principle outcome in many injuries
- Ex. Ischemia, toxins, infections & trauma - Apoptosis
- Regulated cell suicide program
- Occurs during development &throughout adulthood
- Physiological-development, tissue homeostasis
- Some pathological conditions (DNA Damage, Misfolded proteins, some viral infections)
Distinct morphological differences
Distinct biochemical differences
Summarize necrosis
- Pathologicial
- Acute cell injury
- Cell unable to maintain homeostasis
- Cell swelling
- Loss of plasma membrane integrity
- Cell contents released
- Surrounding tissue damage
- Inflammation
Summarize apoptosis
- Physiological
- Genetic
- Programmed cell death
- Cell shrinking
- DNA aggregation
- Maintains plasma membrane integrity
- No surrounding tissue damage
- No inflammation
Describe the morphological assessment of necrosis
Morphological
- Propidium iodide(PI) staining
- Live cell imaging
- PI intercalates & labels DNA
- PI positive = leaky /discontinuous plasma membrane = necrosis
H&E staining
- Increased eosinphilia
- Loss of cytoplasmic RNA
- Increase in denatured proteins
- Variable nuclear staining
- Typical loss of basophilia & total loss of nuclear staining after a couple of days; sometimes pyknosis visible
TEM
-discontinuous plasma & organelle membranes
What are the biochemical assessments of necrosis?
- Random DNA degradation
- Increased levels of lactate dehydrogenase (LDH)
What can be contrasted from an H & E stain of the kidney in necrosis and being normal
Infarct- increased eosinophilia, loss of nuclei, increased inflammatory infiltrate
What are the mechanisms of apoptosis?
2 pathways:
- intrinsic
- extrinsic
Differ in induction & regulation
Both result in activation of initiator & executioner caspases
What is a use for apoptosis in normal e,bryological development?
Ex. Developing digits
What is a use for apoptosis in normal tissue homeostasis?
- Billions of cells undergo apoptosis daily
- Replaced by renewing cell populations
What is a use for apoptosis in abnormal tissue homeostasis?
- Loss of cells due to apoptosis
- Immune deficiency syndromes, some types of anemia
- Irreplaceable due to non-renewing cell populations
- Ahlzeimer’s, Parkinson’s, myocardial infarction
- Accumulation of cells due to failure of apoptosis
- Malignant neoplasia, autoimmune syndromes
How does apoptosis helps with indigitation?
- Digits, in this case in a mouse paw are sculpted by apoptosis
- Webbing of human toes may occur because of interrupted apoptosis
What are the characteristics of the intrinsic pathways?
Death signal
-Ex. DNA damage
- Pro-apoptotic proteins unregulated
- Ex. Bax
-Release of cytochrome c from mitochondria
- Apoptosome formation
- Apaf-1
- Apoptotic protease activating factor 1
- Cytochrome c
- Procaspase 9
- Apaf-1
Caspase cascade
- Activation of initiator caspase 9
- Activation of effector caspases
- Ex. Caspase 3
Summarize the steps of the intrinsic pathway
- Apoptotic stimulus triggers the mitochondria to release cytochrome c
- Release of cytochrome c triggers the activation of Apaf-1
- Apaf-1 molecules assemble together to form the apoptosome
- The recruitment and activation of procaspase-9 leads to binding if the CARD domain to the apoptosome
- This leads to activation of executioner pro caspases. Caspase cascade leading to apoptosis
What are the characteristics of the extrinsic pathway for apoptosis ?
Extrinsic
- Binding of ligand to death receptor
- Fas ligand
- Recruitment of death domain adaptor proteins
- FADD
- TRADD
-Formation of death inducing signaling complex (DISC)
- Caspase cascade
- Activation of initiator caspases
- Ex. Caspase 8
- Activation of effector or “executioner” caspases
- Ex. Caspase 3
- Activation of initiator caspases
Describe the extrinsic pathway
A killer lymphocyte presents a Fas ligand to the Fas death receptor on a cell-the inner part of the Fas death receptor holds a death domain within the cell
- The FADD adaptor protein contains a death domain as well and a death effector domain
- Procaspase 8 or 10 contains a death effector domain
- When the killer lymphocyte binds the target cell, this results in the assembly of DISC, the death domain of FADD receptor and FADD adaptor protein bind, also death effector domain of of lrivaspase 8 or 10
- The DISC includes the FADD death domain, FADD death effector domain, death effector domain in the pro caspase 8 or 19 and procsspase 8 or 10 itself
- Activation and cleavage of pro caspase 8 or 10 or both
- This leads to activation of executioner caspases and apoptosis occurs
What are the initiator caspases?
Caspases 2,8,9,10- initiator caspases
What are the effector caspases?
3,6,7
What caspases are related to inflammation?
Caspases 4,5
What caspases are involved in skin development ?
Caspase 14
What caspase isn’t Apoptotic?
Caspase 1- cytosine maturation
All the others are Apoptotic
What are caspases?
Family of protease enzymes
-Cysteine-dependent Aspartate-directed proteases
- Synthesized as inactive precursors-pro caspases
- Activated by proteolytic cleavage
- Target cytoplasmic & nuclear proteins and caspase-active DNAse
Describe the Bcl-2 family
-Intracellular regulators of apoptosis
2 functional classes
- Pro-Apoptotic
- Bid- links extrinsic & intrinsic pathways
- Bax & Bak- permeabilization of mitochondrial outer membrane
- Anti-Apoptotic - Bcl-2
Balance of pro- & Apoptotic proteins largely determines cell fare
What Bcl-2 proteins are pro and anti survival?
Pro-survival: Bcl- 2, Bcl-xL
Anti-survival/pro-death:
- Bax
- Bak
- Bid
What role does Bcl-2 do in apoptosis ?
- Death receptor signaling results in caspase 8 activation
- Caspase 8 cleaves to Bid and tBid
- Bak and Bax can now enter the Mitichondrial membrane
- Cytochrome c is released from mitichondria
- Caspases are activated and induce proteolysis resulting in apoptosis
Describe the assessment of apoptosis
- Caspase activity
- Annexin 5- protein binds to phosphatidylserine when exposed on the outer leaflet of the plasma membrane
- DNA laddering
- DNAse cleaves internucleosomal DNA
- 180-200 bp fragments
TUNEL
- terminal uridine deoxynucleotdyl transferase nick end labeling
- Detects DNA fragmentation
What is TUNEL?
Assay detects dna fragmentation
Tagged or labeled deoxynucleotides to 3’ DNA ends
Who won the Nobel prize in physiology of medicine in 2002?
Awarded jointly to Syndeny Brenner, H. Robert Horvitz and John E. Sulston “for their discoveries concerning genetic regulation of organ development and programmed cell death”
