Lecture 2 Flashcards
Examples of Physical Injury to a cell?
trauma
heat
cold
radiation
electricity
O2 deprivation
Examples of Chemical Injury to a cell?
Carbontetrachloride injuring cells in the liver
pH
extremes free radicals
low or high oxygen concentration
poisons
drugs
Examples of Biological Causes to a cell?
factors arising from microorganisms
damaging factors released during immune responses
nutritional imbalances
lack of growth factors
Examples of Immunological injury Injury to a cell?
autoimmune reactions
autoimmune disease
Examples of Genetic Derangements to a cell?
range from severe cognital malformations
subtle variations in genetic makeup -both influence the susceptibility of cells to injury
- genome sequencing has increased our knowledge of how genetic determinates alter how cells respond
- not very strong determinents
- often large numbers which interact with one another and other aspects of the disease
Examples of Nutritional imbalances to a cell?
range from severe protein-calorie deficiencies in third world
starvation
anorexia nervosa
excess intake of lipids and cholesterol
- predisposing atherosclerosis
- directly injury
- modulate how other factors injure cells
What is the anagram to remember the causes of cell stress and injury?
PiC’N BIG
Physical
Chemical
Nutritional
Biological
Immunological
Genetic derangements
What are 4x things that cause damage to the cell membrane?
- Directly due to Free Radicals
- After Hypoxia (stress induced due to low O2)
- membrane targeting bacterial toxins (a-toxin of Clostridium Perfringens)
- Ca2= plasma membrane pump failure
What is an example of a bacterial toxin that targets the plasma membrane?
a-toxin of Clostridium Perfringens
What 4 things happen when the plasma membrane is damaged?
- loss of cellular contents
- loss of proteins, enzymes, co-enzymes and RNA (ribo-nucleic acids)
- loss of osmotic balance
- influx of fluids and ions
What is the function of transmembrane pumps and how can they be injured?
Transmembrane pumps control the ionic and iso-osmotic balance or cells and organelles
- injured directly
- decreased function due to decreased ATP availability
What is Autolysis?
Lysosomal membranes injured
= enzymes leak into cytoplasm
= digestion (autolysis) of cellular components
What is severe cell injury often associated with and how does this arise?
Severe cell injury = assoc. decreased content of membrane phospholipids
Caused by combination of two factors:
- cell injury activation of phospholipases +
- decreased ATP causing decreased synthesis of phospholipids
What happens when there is decreased Ca2+ membrane pump activity?
- increased Ca2+ influx into cytosol
- activation of destructive Ca2+ dependant enzymes
a) ATPases (faster ATP depletion)
b) Phosopholipases (damages lipid parts of membrane)
c) Proteases (breaks down both membrane and cytoskeletal proteins) - Endonucleases (breaks down both DNA and chromatin into fragments (fragmentation))
What do proteases break down?
both 1. Membrane and 2. Cytoskeletal proteins
What do endonucleases break down?
both 1. DNA and 2. Chromatin into fragments (fragmentation)
What is a secondary form of injury?
Free Radical damage
-occurs on cells which have been exposed to a variety of injurious agents or stressors
What are Free Radicals?
Reactive molecules
Single unpaired electron in outer orbit releases energy via reacting with adjacent molecules
What is oxidative stress?
an accumulation of free radicals
What are reactive oxygen species?
free radicals generated during cell injury
What is a generatlisation regarding the effects of stress and cell injury on individual cells?
Multiple components of cells are often injured at the same time
Often the effects of injuring one compoenents, flow through to alter another components
LINKAGE
Not one thing going on at once
Series of events will differ slightly due to what part has beendamage –> but will flow on to later effect other components
What are the elements behind a decrease in ATP?
Production: Mitochondrial Oxidative phosphorylation or Glycolysis
Common for ATP to be depleted
- Lack of O2- Infarction. BV blocked, tissue becomes hypoxic and low in O2 = cell injury via loss of ATP
- Damage to enzymes. Cell mediators. Directly. Sunburn injury enzyme in keratinosites + cell DNA
- Mitochondria. most important. Produce ATP via ox. phosphorylation
Results:
- Repair needs energy. Enzymes need the ATP to repair damaged DNA and proteins.
- ATP driven membrane ion pumps (maintin conc). Inability to pump cations and anions through membrane pumps. - Na pump doesnt work as well, NA and H2O accumulate inside. Cell Swelling. - Ca2+ pump, Ca2+ influx into cytocol . Activates Destructie Ca2+ dependant enzymes
- Protein Synthesis - in order to repair cell.
What are the elements behind damage to cell membranes?
- Lysosomes - release of digestive lysosomal enzymes into cytosol, digets cell from inside=Autolysis = major amount of damage
- Mitochondria (ATP oxidative phosphorylation dependant on complex membranes). Non selective high conductance channel formation. Removes transmembrane potential and cytochrome C required for oxidative phosphorylation. Signalling cell cytochrome C also leaks into cytosol and primes cell for Apoptosis
- Plasma membrane - loss of cell contents + osmotic balance(H2o influc cell swelling) + Influx of fluids and ions + loss of proteins, enzymes, coenzymes and RNA
What are the elements behind Increase in Intracellular Ca2+ levels?
Membrane damage of membrane compartments that contain Ca2+
Membrane pumps not working as not enough Ca2+
Signalling molecule that can turn on destructive enzymes which breakdown proteins and DNA. Activates:
- ATPases - further decrease ATP
- Phosopholypates - decreased phospholypid (bilayers)
- Proteases: Disrupts enzyems and cytoskeletal membrane components - furthers membrane damage
- Exo/Endonucleases - digest DNA
What are the elements of Reactive Oxygen species?
Oxidative phosphorylation reduced
Build up of Reactive Ozygen species- e.g.Superoxide
further protein and DNA damage
Reactive oxidative species= Free radicals
e.g. Irradiation, Metabolism of chemicals or drufs, oxygen toxicity, inflammation, reperfusion
Set up autocatalytic chains- generate more free radicals - damage more molecules
- Attack Double bonds and Unsatruated Fatty Acids(UFAs) = Lipid Peroxidation which damages membrane
- Oxidise Enzyme AA side chains = damaged enzymes
- React with Thymine = DNA damage
What are the possible outcomes of Cell injury or stress?
Adaptation or cell injury
Cell injury: Physically and Functionally damaged after injury exposure. NOT unable to adapt. Injury is wrong sort or just too great.
Irreversible or Reversible(repair, reverse and replace mechanisms) Cell injury
Irreversible Necrotic death(overwhleming injury or cells murdered/ passively wiped out) or Apoptotic Death (preprogrammed suicide, when cannot repair, clean: packaged blebs, phagocytosed. Allows Reuse)
What is “Adaptation” in regards to cells?
Adaptation of cells so they can change their functions and sometimes their structure, in order to better function, stay alive and better resist an injury
What are the elements of the cell’s internal processes/adaption to damage?
Signalling Pathways
- Heat shock factors. transcriptions factors which regulate expression of heat shock proteins, which help damaged protein- chaperone/hold together and move to correct place for repair. Or arrange for targetted degridation.
- Stress enzymes. a) p38 MAP kinase & Jun N-terminal Kinase enzymes. Top of/intiiate phosphorylation cascades, cells damage response, so cells can try adapt and limit effects. b) DNA damage activates p53 which stops cell division (stops progression into daughter cells) and sometimes induced cell suidice/apotosis. c) BCL2 protein family, Integrates responses to cell stress, to adaption or suicide:BMF (detects actin cytoskeleton damage), Bim ( detect microtubule damage, Bad (detect cell stress due to inadequate stimulation by growth factors)
What are the elements of Adaptation?
Mild injurious agents: Chronic Irritant
Mild Stress: Altered environmental Conditions
allows cells to continue function, Without being injured, despite stress or change in environment
Manners which cells deal and adapt to stress:
- Hypertrophy (gym, muscle fibres stress, and individual cells adapt by becoming larger)-blocked aortic valve=ventricular thickening due to stress. Hyperplasia (demand on tissue greater than what the tissue can deliver, stem cells divide so Number of cells increases)
- Atrophy (cells get smaller - loss growth factor stimualtion, nerves that have lost innvervation)
- Metaplasia (Stem cells reprogrammed. Change cell type, as no longer right cells to deal with injurious agent) - Oesophagus. Squamous epithelium. Changed to be better at resisting gastric acid-acid reflux disease. Stem cells reprogrammed to form Glandular epithelium.
What does a cell need to die by Apoptosis and not Necrosis?
Energy- Lack of ATP
What are the elements of Necoris?
Passive= Happens when not enough ATP for apoptosis to occur
Murdered by overwhelming damage
OFten affects large numbers of adjacent cells in a tissue
Oncosis
Myocardial infarction, Coronary artery blockage- cells dont have enough BF and die.
- No nuclei - common feature.
- Contraction bands
- Homogneous
- RBC enter as BV are damaged. Die. Heamorrage in tissue
Cells swell. Nuclei breaks into parts=Cariorecsus. Nuclie dissolves completely = Cariolysis - featureles cell appeance
Autolysis: Lysosomal membrane rupture (inner digestion)= Eosinophilic red protein soup (proteins digestion)
Leakage of cytosolic contents induces inflammatory response (WBC Inflammation)
Featureless Cytoplasm and Faded/fragmented chromatin
Renal cortex- BV blockage. Pale as dont have basophilic Blue staining of DNA as have dissolved (endo/exonulceases + cariolysis)
Myocardium
What are the elements of Apoptosis?
Requires ATP - sufficent time and energy to commit suicide
When cells arent overwhelmingly damage
Package DNA, organelles and contents into Blebs. Then Phagocytosed by adjacent cells or Phagocytes.
Characterisitic: Membrane Blebs. Shrinakge. Pyknosis
Phagocytosed by Macrophages + Neighbouring cells
Alternative Apoptosis: cell suicide seen in specialised cells
2x pathways:
- Mitochondria. activation of UPSTREAM Caspase enzymes, which activate digestion and containing via membrane blebs
- Death receptors on cell surface. Tumornecrosis receptors. Activate siganls which use Upstream Caspase enzymes to intiate apoptotic wrapping of membranes
Liver. Virus. Individual cells dying, not whole tissue.
Thymus: cells which develop potential autoimmunitiy are deleted. White cells = Marcrophages, which Reuse Cellular debris
