Flashcards in Cellular Responses 4/23 Deck (103):
what causes cellular aging?
- telomere shortening (replicative senescence)
- environmental insults (free radicals --> damage to proteins and organelles)
- DNA repair defects (causes accumulation of DNA defects and damage)
- abnormal growth factor signaling
- appears to prevent aging in cells
- may reduce aging progress via insulin sensitization and prevention of apoptosis
- reduce oxidative stress and free radical prevention
- low calorie diets can increase sirtuin levels
ex. Resveratrol is found in red wines, and induces formations of sirtuins through Sirt1
role of telomeres
-Telomeres function in replicative senescence of cells. Germ cells retain a higher telomere length than stem cells, than normal somatic cells. If the telomere gets too short, the cell loses its ability to replicate.
- Telomerase directs RNA template dependent DNA synthesis in which nucleotides are added to one strand at the end of chromosomes
- (telomerase does not operate in normal somatic cells, but is active in cancer cells)
Decrease in cell number and/or size of tissue and/or organ
Cell increases in size
- cytoplasm increased, more ribosomes, more protein
- nucleolus is enlarged (this is where protein is made)
Cells increase in number
- nucleus enlarged but less basophilic (i.e. chromatin is dispersed because it is undergoing txn and replication)
- increased DNA txn
- conversion of one differentiated (mature) cell type into another
- ex: cigarette smoking: results in squamous metaplasia of ciliated columnar epithelium within bronchioles
- ex. chronic irritation of endocervix, results in squamous metaplasia of endocervical glandular epithelium
- ex. chronic reflux esophagitis: squamous epithelial changes to stomach or intestinal epithelium, gastric glandular metaplasia
***note*** if cell has been terminally differentiated (i.e. the top layer of epithelium) it will die and not change. however the stem cells and less differentiated reserve cells at the base of the epithelium will be reprogrammed to produce a new cell type
What are the causes of pathologic atrophy?
1. decreased workload/use (cast)
3. decreased blood supply - ischemia
4. decreased O2 - hypoxia
5. nutrition (marasmus, cachexia, kwashikorkor)
6. loss of endocrine stimulation (endometrium, breast, ovary)
7. pressure (tumor, decubitus ulcers)
9. senility (senile osteoporosis)
ubiquitin-proteasome protein breakdown pathway
- this is a primary mechanism of atrophy
- allows for accelerated proteolysis in catabolic conditions
- proteins are ubiquitinated, and then proteasomes will come and will break down the protein
- may be accompanied by autophagy --> resulting in residual bodies
- golden brown residual body, left over after breakdown via the ubiquitin-proteasome breakdown pathway
- remains in the cell, called "aging pigment"
- atrophy with lots of lipofuscin = brown atrophy (seen in atrophy organs)
What are residual bodies?
- left over particles resulting from autophagy, that are indigestible
- ex. lipofuscin
What is seen with marasmus?
- calorie deficient state, but protein levels are normal
- thin child, uses its own fats and proteins for energy - a form of atrophy
- seen normal hair, old man appearance, thin limbs with little muscle or fat, very underweight
What is seen with kwashiorkor?
- deficiency is purely in proteins, the fat content in these children is normal. protein levels are low.
- swelling of legs (oedema), sparse hair, moon face, little interest in surroundings, flaky appearance of skin, swollen abdomen, thin muscles, fat present
- fluid shifts (due to lack of proteins in blood), to cause edema
- this is the worse off disease compared to marasmus
What is seen with extracellular tissue atrophy due to immobilized limbs?
1. loss of proteoglycans in articular cartilage
2. decreased strength of ligaments
3. osteopenia = loss of bone mass
is atrophy reversible?
- if energy is kept from cell and it dies, it will result in complete atrophy and irreversible death
- starvation induced fat atrophy can result in complete regeneration
- motor denervation of skeletal muscle (return of function if repaired in 3-5 weeks, useless to repair after 20-24 months)
how do you get hypertrophy/hyperplasia?
- increased functional demands (i.e. physiologic hypertrophy during exercise)
- excessive nutrition
- increased blood flow
- endocrine stimulation
- mechanical factors
what happens in the heart and skeletal muscle in response to increased functional demands?
- pure hypertrophy WITHOUT hyperplasia
- this occurs in the heart and skeletal mm.
- may be physiologic or pathologic
- increased RNA and DNA in nucleus, increased amount of cytoplasm
what happens in kidney with increased fn. demands?
hypertrophy AND hyperplasia
what happens in striated mm. in response to increased fn. demand?
- Endurance mm - increased number and volume of mitochondria
- Resistance mm- hypertrophy of contractile elements and
increased capillary network
what happens to smooth mm with increased fn. demand?
- hypertorphy and hyperplasia
- *** smooth muscle polyploidy (increased number of DNA)***
what happens with cardiac remodeling? biochemical pathways? what gene expressions will change in response to increased stress?
- hypertrophy ONLY
Two main biochemical pathways:
- phosophinositide3-kinase/AKT pathway (exercise induced, will make more proteins)
- Growth factors or vasoactive amines will cause GPCR cascades (this is more pathological)
Things that may occur:
- switch of contractile protein to fetal forms (ex. alpha heavy chain myosin replaced with Beta heavy chain myosin, which is more energetically economical)
- early development genes re-expressed (i.e. increased ANF, results in increased sodium excretion in kidney, results in decreased intravascular volume and pressure)
what are signals to myocardial hypertrophy?
1. increased mechanical stress, will stimulate genes to be turned on
2. agonists (i.e. alpha adrenergic hormones and ANG)
3. Growth factors
these things will all increase mechanical performance and decrease workload
look at myocardial hypertrophy slides
is cardiac hypertrophy reversible?
- yes, portions of it.
- mm. mass and RNA can return to normal
- DNA does not change, results in increased nuclear size (doesn't return to normal size)
- see fibrosis (scarring) does not change, results in decreased compliance
- cytochrome P-450: breaks down toxins in the body, detoxification
- barbituates and ethanol will induce cytochrome P-450, this is how people develop resistance to their medications
- results in hypertrophy of ER
- P-450 can result in toxic products: ROS from oxidative metabolisms
- creates toxic metabolites
physiologic hyperplasia vs. pathologic hyperplasia?
- hormonal stimulation (i.e. breast development with estrogen, ACTH)
- compensatory (partial hepectomy, nephrectomy)
- hormonal stimulation (gigantism, prostatic)
- increased fn. demand (bone marrow in chronic blood loss and infections, secondary hyperparathyroidism)
- persistent cell injury (lichen simplex chronicus)
- infectious agents (papillomaviruses have viral genes for growth factors)
What occurs with liver partial hepatectomy? what is the mechanism?
- it is not regeneration
- called "compensatory hyperplasia" (hepatocytes proliferate)
1. growth factor driven proliferation of mature cells
2. increased output of new cells from stem cells (backup hyperplasia mechanism)
Stem cells of liver = oval cells: generate lineage only in situations in which hepatocyte proliferation is blocked or delayed
What is seen in endometrial menstrual cycle?
- proliferative phase = hyperplasia
- secretory phase = hypertrophy
- menstrual phase = atrophy and necrosis
- look at slide #45, the histology of the menstrual cycle- must identify these for the exam!!!
what does retinoic acid/ vitamin A do?
- this is a hormone, because it can regulate gene txn through retinoid receptors: retinoic acid regulates gene transcription through retinoid receptors (Vitamin A)
- can get squamous metaplasia with deficiency or excess
- behaves as a steroid hormone, because can diffuse directly into the cytoplasm of the cell
- ex. Acutane
- vitamin A deficiency: major consequence in the eye is in the production of keratinizing metaplasia of specialized epithelial surfaces, results in problems with cornea
Know SLIDE 50
- the most common example of metaplasia is that of columnar to squamous epithelium
- often protective
- double edged sword:
- in bronchi decreased cilia results in increased mucus. This can lead to malignant transformation
- squamous metaplasia that happens to 90% of smokers within the breast ducts
- ductal epithelium goes from glandular to squamous epithelium
- initiated by keratin trapped after metaplasia
- results in duct rupture, and strong inflammatory response to keratin
- fistulas occur if disease is recurrent
- glandular metaplasia
- physiologic sphincter does not function well and acid moves into esophagus.
- results in heartburn, and digestion of squamous mucosa.
- cells at base result in reprogramming towards gastric or intestinal mucosa
- will see goblet cells in esophagus (those are only seen in intestine normally), will also see a glandular mucosa
- glandular cells are being chronically irritated, will result in increased replication, will result in glandular cancer (adino carcinomas)
- need to be able to recognize these pictures on slide 52
what is the sequential development of biochemical and morphologic changes in cell injury?
(reversible cell injury)= decrease in cell function
(irreversible cell injury)
1. see biochemical changes, leading to cell death (not enough ATP)
2. see injury with ultrastructural changes (electromicroscope level, seen injury on mitochondria)
3. light microscopic changes (see histological changes)
4. gross morphologic changes (can see problem with the naked eye)
ex. takes 12-24 hours until you can see MI problems. at least 6 hours before you can see MI on histological slide
cell death with swelling (associated with necrosis)
- he doesn't like this word
what are three results of irreversible injury?
1. necrosis: see inflammation
2. apoptosis: no inflammation
3. autophagy: no inflammation
what are causes to cell death?
1. decreased ATP
2. damaged mitochondria: proapoptotic messengers released from mitochondria
3. entry of Ca2+: caused by hole in lysozomes or cytoplasmic membranes, stimulates digestive enzymes in cells
4. increased ROS: have free electrons that will cause damage to DNA, lipids, and proteins
5. membrane damage: plasma membrane is damaged resulting in loss of cellular components, if lysosomal membrane is ruptured, it will cause enzymatic digestion of cellular components.
6. protein misfolding and DNA damage: results in activation of pro-apoptotic proteins
what happens with mitochondrial damage?
- decreased ox phos
- decreased ATP
- decreased Na+/K+ pump, sodium will go up in cell, K+ will go down in cell (will see hyperkalemia in blood), results in increased ER swelling, cellular swelling and loss of microvilli blebs
- increased anaerobic glycolysis: decreased glycogen, increased lactic acid, and decreased pH. results in clumping of nuclear chromatin
- detachment of ribosomes, results in decreased protein synth, and lipid deposition
damage of plasma membrane
- cell will most likely die
- influx of Ca2+, activates phospholipases, cell membrane damage and dysfunction, results in more Ca2+ influx
- Ca2+ also activates proteases, ATPases, which will result in increased mitochondria damage
what does mitochondria release due to damage?
cytochrome C is released, results in cellular apoptosis
- seen with alcoholic liver disease, aging and other disorders.
- the hepatocytes of alcoholics will have this
what are species of free radicals?
- hydroxyl radical (most damaging) OH*
- hydrogen peroxide H2O2
- superoxide O2*
what is fenton reaction?
creates a hydroxyl radical (OH*) from hydrogen peroxide and Iron
Fe2 + H2O2 --> Fe3 + OH- + OH*
- hydroxyl radical is the worst
* this is important *
what are preventions/removals of free radicals?
- antioxidants (Vit E and A)
- storage and transport proteins (want iron to be bound, ex. transferrin, ferritin, lactoferrin)
- superoxide dismutases (SODs): will get rid of superoxide
- glutathione peroxidase (gets rid of hydroxyl radical), found in mitochondria
- catalases (peroxisomes), will get rid of hydrogen peroxide
hydroxyl radical - OH
- causes most damage in cells
- generated from H2O and Iron via the Fenton rxn.
- also made due to radiation
- can be converted to H2O via glutathione and peroxidase
- this is the principal ROS, responsible for damaging lipids, proteins and DNA
What is CCl4
- free radical that when acted up by P450 oxidases of smooth endoplasmic reticulum forms the reactive radical CCl3
- this reactive species inhibits protein synth by damaging RER
- inhibits apoprotein synth by liver, causing steatosis
- products of lipid peroxidation results in PM damage, calcium influx and cell death
- Decrease in cell membrane transport systems secondary to decreased ATP
- decreased oxidative phosphorylation
- decreased protein synthesis
- Changes in ion concentrations lead to influx of water
- Altered cytoskeletal elements lead to light microscopic changes
↑ toxic products of metabolism if have concurrent ischemia
see swollen cells with bubbles inside, this is the result of extensive vacuolation due to hypoxia
- results from hypoxia causing decrease in ATP, increase of ions in cell and water in cell, resulting in cisternae and ER distension and rupture, which forms vacuoles
hypoxia repurfusion injury
- after you do repurfusion you will kill some cells, due to creation of ROS and allowing more iron into the area (increased fenton reaction)
- also will allow inflammatory cells into area, resulting in activation of complement system: will release enzymes into the area, causing lysis of dead cells and neighboring cells
- some cells will be brought back to life, thus overall it is good
- if reperfuse within 20 minutes, the ischemic area can be salvaged, sometimes up to 6 hours
- after 6 hours, the ischemic cells will be completely dead
what can cause membrane damage?
lipid breakdown products
the cell spills out all of its entire contents, leading to inflammation (huge release of cytokines)
- protein denaturation
- enzymatic digestion
- controlled cell death due to cytochrome C, instructing nucleus to turn on endonuclease, which breaks DNA up and are packaged
- apoptotic body does not release anything into environment, thus you will have no swelling
what are nuclear changes in morphological features of necrosis?
- karyolysis: DNA is all dissolved and goes away
- Pyknosis: DNA is all crunched up
- Karyorrhexis: DNA broken up into small pieces
what are other morph. features of necrosis?
- cytoplasmic eosinophilia: see dark pink/red due to loss of basophilia of ribosomes, eosin dye uptake by denatured proteins
- also see subcellular swelling, Ca2+ containing bodies, breaks in cell membranes
- see nuclear changes: pyknosis, karyorrhexis, karyolysis
best sign for irreversibility of cell death?
big hole in cell plasma membrane
- denaturation of protein is primary pattern
- see preservation of general architecture of tissue despite the death of its constituent cells (cytoplasm is normally seen pinker than normal, due to contracted proteins)
- seen in hypoxic death of cells (but NOT brain)
- ex. myocardial infarct
KNOW SLIDE PICTURE ON 76
- a distinct form of amorphous necrosis (looks "cheesy")
- ex. myobacterium tuberculosis
- gross: firm, dry, white appearance
- micro: amorphous granular debris composed of fragmented, coagulated cells and inflamm. granulomatous rxn.
- seen in the BRAIN
- enzyme digestion is dominant - cell spills out its enzymes and they digest everything (looks like a pool of liquid)
- will completely digest cells and turn tissue into liquid viscous mass
- ex. bacterial abscess or cerebral infarct in brain
- necrosis with or without putrefaction
- results from gradual ischemia of distal extremities. the affected tissues appear black due to deposition of iron sulphide from degraded Hgb
- subtype of liquefactive necrosis or ischemic necrosis
- begins as coagulative necrosis (pure ischemia), results in "dry" gangrene (black, brown mummified appearance)
- if neutrophils invade it results in "wet" gangrene (bacterial superinfection)= liquefactive necrosis
- "gas gangrene" can be due to wet gangrene with infarction of bowel and gas build up (myonecrosis)
fat necrosis: what are two types that are seen?
1. Pancreatic fat necrosis: seen with acute pancreatitis (release of pancreatic digestive enzymes, will digest away the fat surrounding the organ)
- "saponification": release of fat (calcium will deposit here easily, can be seen on xray)
2. traumatic fat necrosis: can occur by bumping into something, will spill out contents and cause inflammation
- special type of amorphous pink necrosis occuring in arteriole walls. caused by again, HTN, immune complex deposits
- necrosis and damage to vessel results in leakage of fibrin and other proteins into vessel walls
- fibrin is part of coagulation, anytime you get this, it will look pink under microscope
- term just means that it is protein rich deposit necrosis (not always fibrin)
- seen with hypertension
- immune complexes
What are two types of coagulative necrosis?
1. hemorrhagic or "red" infarct:
- in organs with dual blood supply (i.e. lungs and liver), if one is lost, it may result in infarct
2. pale or "anemic" infarct:
- sudden arrest of circ. blood flow, usually from thrombus or embolus
- cavity full of puss due to liquefactive necrosis
- cavities are green b/c neutrophils have a greenish color to them
- infection results in neutrophil influx, the enzyme release kills bacteria and digestion of neighboring cells, results in pus
- bacteremia: hole can be made in vessel wall, and bacteria can spread through blood
- local expansion: pus travels along fascial planes
- can makes its way all the way out to skin, resulting in fistulus tract.
bacterial superinfection of the necrotic material resulting in liquefactive necrosis
- black-brown, mummified in appearance
- due to coagulative necrosis
gas gangrene "myonecrosis"
- occurs when wet gangrene is present with infarction of the bowel
- results from rapid bacterial superinfection, which produces gas
- most gangrene caused by Clostridium welchii and Cl. Perfringes (capable of thriving under anaerobic conditions)
- triggered by DNA damage or abnormal protein accumulation
- results in mitochondrial release of Cytocrhome C
- p53 is released if DNA damage is unrepairable
- blocks Bax/Bak
Intrinsic Pathway, what blocks apoptosis?
- survival signal (aka growth factor) will signal to a viable cell
- will result in production of anti-apoptotic proteins (Bcl2)
- Bcl2 binds the mitochondria and blocks the release of cytochrome C, through inhibiting the Bak/Bax channel
"Death receptor pathway"
- FasL binds the Fas activating the FADD
- FADD activates pro-caspase 8, which results in active caspase 8, which acts on executioner caspases and results in apoptosis
- This can also be TNF mediated
Intrinsic pathway, what activates apoptosis?
- DNA damage is detected, resulting in activation of BH3-only proteins (which acts to inhibit Bcl2)
- this allows for activation of Bax/Bak channel which allows for the leakage of cytochrome C from mitochondria
- cytochrome C activates caspases which results in apoptosis
How do cytotoxic T-Lymphocytes mediate apoptosis?
- CTLs secrete perforin, a transmembrane pore-forming molecule
- promotes entry of CTL granzymes into cell
- activates a variety of cellular caspases
- induces the effector phase of apoptosis
What can cause defective apoptosis?
* increased cell survival can be due to p53 mutations.
- increased p53 with DNA damage prevents cell replications and can induce apoptosis
- p53 mutations allow cancer cells with unrepairable DNA damage to replicate
what can cause increased apoptosis?
* excessive cell death
(1) neurodegenerative diseases - misfolded proteins build up
(2) ischemic injury
(3) death of virus-infected cells
what happens when there is an abnormal amount of protein build up in the cell?
= "unfolded protein response"
- Stress (UV damage, heat, radical injury) can cause mutations of proteins, and protein folding to be messed dup
-abnormal proteins build up in ER. This results in inability to get rid of the protein, and will set off caspases in the cell. The cell will undergo apoptosis.
necrosis vs. apoptosis
apoptosis is controlled and results in turning on of endonucleases (will create DNA fragments). It will not set off inflammation
necrosis, breaks of DNA are random and will have a lot of inflammation
In an agarose gel electrophoresis you will see a ladder pattern of DNA with apoptosis, and a continuous smear with necrosis.
alpha1 antitrypsin deficiency (A1AT)
* necessary b/c inactivates neutrophil elastase to control tissue destruction *
- this genetic disorder results in inability for abnormal A1AT to be exported out of cell, it can't be metabolized, and builds up in ER.
- abnormal protein can cause hepatocyte death (apoptosis) and lung disease (enzymatic digestion, emphyzema)
- there is a large amount of elastic tissue in lungs, if neutrophils release elastase then it results in emphyzema
- if there is a large amount of smoking, then there will be a large amount of neutrophils, resulting in early emphyzema
how do people end up with fatty livers? malnutrition? starvation? hypoxia? Reye syndrome? CCl4? toxins?
* know these *
- with diabetes and starvation there is increased supply of FFA, it ends up in the liver
- malnutrition and CCl4 results in reduced apoprotein availability (can't move the fat), resulting in impaired export of triglyceride via lipoproteins and increased FFA in liver
- CCl4 breaks down apoproteins
- toxins: breakdown proteins and cause decreased oxidation of FFA
- hypoxia and Reye syndrome, results in decreased oxidation of FFA, leading to increased FFA in liver
- ethanol is a supplier of calories, resulting in fatty liver.
pathology of filaments? thin? and intermediate?
- Thin filaments: need ATP to get rid of the last contraction, resulting in Rigor Mortis
- this is the target of toxins, i.e. mushrooms
- Mallory (alcoholic) Hyaline
* this inactivates toxins
- this is inducible, and once induced may require larger doses of mediations (they breakdown medications more quickly)
- induced by ethanol, phenobarbital, tobacco
- smokers and others may need higher doses of medications
Alcohol induced cell injury results in activation of what and what cellular changes?
- induces cytochrome P-450
- hydropic change (injured cell membrane, or messed up)- swollen cells
- fatty change in liver
- hyaline degeneration ( see Mallory Bodies)
- also causes pancreatitis
- leads to fibrosis of liver, which results in cirrhosis
Kartagener syndrome: what are the symptoms? what is the defect?
- genetic syndrome: a pathology of cilia
- abnormal cilia, primary ciliary dyskinesia (lung problems: brochiectasis, chronic sinusitis, infertile males, subfertile females)
- results in defective dynein arms
** situs inversus is also present **
what do you see with fatty liver?
- yellow and bloated
- build up of triglycerides, appears yellow
accumulation of cholesterol?
seen in cholesterolosis (cholesterol-laden macrophages) called "foam cells" are seen in the gallbladder
also see this buildup with atherosclerosis - atheroma
neurofilaments that bunch up in alzheimer's disease
Mallory hyaline (bodies)
keratin intermediate filaments that build up in liver
*** be able to recognize in slide 118*** see dark pink staining within the cells
where do you see glycogen build up?
- diabetic hepatopathy
- you will see nuclear holes, when do a PAS stain, will see red material which stains the glycogen located in the cells.
- golden brown pigment
- need to be able to recognize it!
- this is breakdown products from cell membranes
- golden brown pigment- resulting from buildup of iron
- results from breakdown product of hemoglobin
- this is seen with hemolytic anemia, or with patients with too many transfusions (often seen in macrophages)
- hemochromotosis (genetic defect, will see accumulation in liver)
** prove that its iron with prussian blue stain
Melanin (blue nevus)
- bluish-black pigment
- if its black, its melanin, melanoma
- this is the only naturally black pigment found in the skin
- kernicterus in babies
- exogenous mimic: carotenemia (from too much yellow veggies, carrots, yams)
Copper buildup: how do you visualize
- Won't see with H&E, have to use Rhodamine stain
- see kaiser fuscher ring around the eye - results in wilson's disease (iron turns gold)
exogenous black pigment (anthracosis)
exogenous pigments (lead = plumbism)
- exposure can result in gingival lead line
- this causes hemolytic anemia and renal tubular necrosis from toxic effects of lead.
- calcification deposit in site of previous tissue damage
- may end up with bony metaplasia (i,e, dystrophic ossification)
- scar --> fibrous tissue --> fibrous tissue calcifies
- systemic hypercalcemia with deposits possible in all tissues
- likes to deposit in alkaline environment, thus will deposit in interstitium of acid secreting organs (stomach, kidneys, lungs)
- seen with hyperparthyroidism, bone destruction, vitamin D excess, aluminum intoxication, milk-alkali syndrome.
the cause of a disease
sequence of evens in cells and tissue in response to disease products
what is leaked from necrosis? liver, heart, pancreas, muscles?
hepatocyes: GGT, AST, ALT
Biliary obstruction: Alk phos
Myocardial cells: Creatine kinases (CK), LDH, troponins
Pancreas: lipase, amylase
what is cytokine TNF?
- an inflammatory mediator capable of inducing extrinsic apoptosis
- also induces thrombosis of tumor blood vessels leading to ischemic death of tumor
What is Reye's syndrome?
- in children with viral infection and concomitant use of aspirin there is mitochondrial injury which leads to decreased FFA oxidation.
- this results in increased esterification of FFA to triglyceride and liver develops statosis with a microvesicular pattern.
- this disorder also results in vomiting, liver failure, and neurologic symptoms
- "Mallory Bodies"
- tissue degeneration chiefly of connective tissues in which structural elements of affected cells are replaced by homogeneous translucent material that stains intensely with acid stains