Lecture 1: Cell Injury Flashcards
__ is an abnormal body process with a characteristic set of signs or symptoms and lesions that may affect the whole body or any of its parts.
Disease
The fundamental disease process begins with injury at the __ level
molecular and cellular
__ refers to damage or pathologic alterations in cell molecules or structure
cell injury
__ are cell alterations that are associated with disease
lesions
What are the 8 causes of cell injury
- hypoxia/hypoxemia
- physical agents
- chemicals/drugs
- infectious agents
- immunologic reactions
- Genetic defects
- nutritional imbalances
- aging
What are the responses to cell injury
- adaptation (hypertrophy)
- reversible cell injury
- irreversible cell injury and death (necrosis and apoptosis)
Necrosis (oncotic necrosis) is a pattern of cell death that often follows hypoxic, toxic and microbial injury and is characterized by __
Cell swelling with nuclear changes
__ is cell death induced by tightly regulated intracellular program where enzymes degrade the cell’s nuclear DNA and proteins leading to nuclear framentation w/o loss of plasma membrane integrity
Apoptosis
3 microscopically visible changes in reversible cell injury
- cell swelling
- chromatin clumping
- lipidosis
7 ultrastructural changes in reversible cell injury
- dilation of ER
- ribosomal detach from RER
- Loss of microvilli and cilia
- mitochondrial swelling
- chromatin clumping
- membrane blebs
- lipid accumulation
Many things that cause swelling are due to
mitochondrial damage
Ischemia causes a decrease in oxidative phosphorylation by the mitochondria which causes a decrease in __
ATP
Decrease in ATP due to ischemia causes what 3 things
- decrease Na pump (ER, cellular swell, loss of microvilli, blebs)
- increase anaerobic glycolysis
- decreased protein synthesis
What happens when ischemia causes decreased ATP leading to decreased Na pump activity
Ca, water, and Na flow into the cell and K flows out causing swelling
What happens when ischemia causes decreased ATP leading to an increase in anaerobic glycolysis
cell uses up glycogen (decreases) and pH decreases (acidic) causing chromatin clumping
When ischemia causes decreased ATP and protein synthesis what can be seen
lipid deposition
Irreversible cell injury (necrosis) has 2 microscopically visible changes
- nuclear changes (pyknosis, karyorrhexis, chromatolysis)
2. increased eosinophilia of cytoplasm
Irreversible cell injury (necrosis) has 4 ultrastructural changes
- high mitochondrial swelling
- membrane defects
- lysosomal membrane rupture
- nuclear condensation, fragmentation, dissolution
Necrotic tissue has what gross changes
pale/dull coloration
what are the 6 forms of necrosis discussed
- coagulation necrosis (simplest)
- liquefactive necrosis
- caseous necrosis
- gangrenous necrosis
- fat necrosis
- fibrinoid necrosis
What are 3 microscopic features seen in coagulative necrosis
- nuclear changes
- increased eosinophilia of cytoplasm
- cell borders STILL VISIBLE
__ necrosis pathogenesis is due to high influx of neutrophils (protease destruction) in tissue with high fat content (brain, lung)
liquefactive
Liquefactive necrosis has 3 microscopic features
- LOSS of cell borders (unlike in coagulative necrosis)
- granular basophilic and eosinophilic debris with nuclear fragments
- tissue structure is obliterated
__ necrosis involves recruitment of macrophages with persistence of stimulus and inflammatory cell component breakdown and is commonly seen in mycrobacterial infections
caseous
caseous necrosis is seen with __ infections
mycrobacterial (bovis, tuberculosis), corynebacterium ovis, fusobacterium necrophorum
Caseous necrosis has 3 microscopic features
- LOSS of cell borders (like liquefactive)
- center of lesions homogenously eosinophilic with scattered nuclear basophilia
- tissue structure is obliterated (like liquefactive)
__ necrosis is characterized by the loss of blood supply to distal extremities (toes, feet, ear) and hypoxia induced necrosis
gangrenous necrosis
___ necrosis can be seen in pancreatitis and vitamin E deficiency
fat necrosis
__ is characterized by enzymes cleaving triglycerides and making free FA wich form soaps of yellow-white areas in the fat
fat necrosis
little to no inflammation is seen with: necrosis or apoptosis
apoptosis (cell buds off keeping damaging enzymes contained)
__ is a process of cell death that occurs both physiologically and pathologically
apoptosis
DNA damage (UV, chemo, carcinogens), misfolded protein accumulation, drug/cytokine induced (glucocorticoid,TNF), viral induced (lentivirus), atrophy of organs after duct obstruction are examples of __ induced apoptosis
pathologic
embryogenesis, hormones, tissue repair, deleting autroreactive t cells in thymus, virus infected cells induced by cytotoxic t-cells are examples of __ induced apoptosis
physiologic
2 things that inhibit apoptosis
- neoplastic dz (P53 mutations)
2. viral-induced proliferative dz (Epstein Bar virus has protein homologe)
list intrinsic (changes in the mitochondrial) that initiate apoptosis
- withdraw of growth factors or
2. injury (radiation, toxins, free radicals)
list extrinsic (death receptor-initiated pathways) that initiate apoptosis
- receptor-ligand interations (FAS, TNF) or
2. Cytotoxic T lymphocytes
after apoptosis in initiated (intrisic or extrinsically) what happens
caspases are initiated
Caspases initiated
cytoskeleton breakdown (proteases) and DNA/nuclear fragmentation (endonucleases), apoptotic body formation
Apoptotic bodies express __ for phygocytic cell receptors
ligands (phophatidylserine or thrombospondin)
Apoptotic bodies contain cell material and allow apoptosis to occur without __ and __
swelling and minimal inflammation (unless they are lysed)
6 steps of the extrinsic apoptosis pathway
- stimulation of receptor by ligand
- alteration in second signals
- activation of caspases
- activation of endonucleases and cytoskeleton breakdown
- nuclear and cytoplasmic fragmentation
- phagocytosis of apoptotic bodies
Loss of stimuli, injury, or positive stimulus increases decreases ATP production and allows mitochondrial permeability which releases __ and other activators of the caspase system to initiate the intrinsic/mitochondrial pathway to apoptosis
cytochrome c
the extrinsic (death receptor-initiated) apoptotic pathway is initiated by __ which activates caspase system
FAS-FAS Ligand
TNF-TNF receptor
Apoptosis is detectable microscopically but there is rarely __
gross changes
__ is characterized by cell swellign and nuclear changes, is pathologic, grossly visible (coagulation, liquefactive, caseous), ussualy causes inflammation
necrosis
list 4 things that are pathogenetic mechanisms to necrosis
- ATP depletion
- membrane damage
- free radical injury
- calcium influx
__ is characterized by nuclear and cytoplasmic fragmentation (endonuclease/protease activation by caspases), NO CELL SWELLING, can be pathologic or physiologic, little/no inflammation, not usually detected grossly
apoptosis
2 pathogenic mechanisms of apoptosis
- intrinsic/mitochondrial permeability and cytochrome c release
- extrinsic (death receptors FAS, TNF, granzyme)
__ is a form of programmed cell death similar mechanically to apoptosis but morphologically appears like necrosis
necroptosis “programed necrosis”
4 features of necroptosis
- caspase 8 independent
- RIP signaling
- mitochondrial alterations and decreased ATP
- cell damage = inflammation
overall, not apoptotic bodies, looks like necrosis (swelling and nuclear changes) but is programmed
How does TNF cause apoptosis vs necroptosis
apoptosis - TNF activates caspase 8
necroptosis - TNF fails to activate capsase 8
___ caused when microbial products interact with NOD like receptors to induce activation of inflammasome and apoptotic like mechanisms
pyroptosis
during __ animal gets fevers and becomes leukopenic (IL 1), there is severe swelling and inflammation, cell death looks like necrosis (capsase 1 and 11)
pyroptosis
both apoptosis and necroptosis can be
regulated/programmed
__ is the oldest recognized programmed cell death where __ is the newest recognized programmed cell death
apoptosis, necroptosis
__ is programmed cell death via caspase 8 independent mechanisms involving mitochondrial permeability and “necrosis”
necroptosis
How can you the difference between necrosis and post-mortem autolysis?
diffuse change throughout body/organs
NO INFLAMMATORY reaction/no tissue response
microscopically tissue appears pale/washed out
ischeima/hypoxemia injury causes Increase in cytoplasmic __ from outside the cell, the mitochondria, and ER cause membrane damage via decreased ATP and phospholipids, nuclear changes, and disruption of cytoskeleton
Ca
__ is a chemical species that has a single unpaired electron in an outer orbital (highly reactive with proteins and nucleic acids)
free radical
list 2 common free radicals
superoxide radicals (O2-) and hydoxyl radical (OH-)
3 ways free radical damage occurs
- absorb radiant E (UV)
- reduction-oxidation rxn during normal physiologic processes
- exposure to toxins (oxygen, carbon tetrachloride, drugs)
What are some normal physiological process (redox rxns) that create free radicals
- respiratory enzymes and o2
- xanthine oxidase (purine metabolism)
- cytochrome P450 monooxygenase activity
- NADPH oxidase
- fenton reaction
radicals are trasferred to many different substrates via __ reactions forming free radical intermediates
autocatalytic
4 substrates most at risk for free radical propagation
- proteins - especially sulfur containing AA
- nucleic acids
- membrane lipids-unsaturated bond (lipid peroxidation)
- cytosolic molecules - Hemoglobin
when lipid peroxidation occurs at high levels it can become __ causing complete lipid hydroperoxide formation which leads to membrane dysfunction and permeability.
autocatylitic (chain reaction)
3 ways free radicals are terminated
- scavengers (vitamin E)
- Enzymatic degradation/adaptation ( SOD, catalase, glutathione)
- spontaneous decay
What enzymes degrade free radicals
- SOD (O2- to O2 and H2O2)
- Glutathione (OH- to water and O2)
- Catalase (H2O2 to water and O2)
3 antioxidant defense scavengers for free radicals
- sulfhydryl rich molecules (glutathione, cystine)
- vitamin E and C
- Ceruloplasmin and transferrin
How does Vitamin E and C scavenge free radicals
terminantes lipid peroxidation
how do ceruloplasmin and transferrin scavenge free radicals
apoproteins bind copper and Fe (stops fenton rxn?)
4 common pathways in cell death
- ischemia and hypoxic injury
- free radical injury
- chemical injury
- infectious agent injury
reperfusion injury is combined __ and __ damage
hypoxic (ischemia) AND free radical (O2 and inflammatory cells)
during reperfusion injury: reduced blood flow causes hypoxic damage through __. Ca activated proteases causing increased __. When blood flow is reestablished it brings __, __, and __. Oxygen and inflammatory cells create __ further damaging the membrane and causing __.
decreased ATP xanthine oxidase (makes free rads later) oxygen, Ca, inflammatory cells free radical increased intracellular Ca/cell death
__ causes CCl4 (carbon tetracholoride) to be converted into CCL3- (free radical). CCl3- radical damages hepatocytes via __. The enzymes that activate this toxin leads to centrilobular ___ . Toxin uses local generation of free rads by the cell to cause injury.
Cytochrome P450.
lipid peroxidation.
hepatocellular coagulation necrosis
exotoxin released by __ causes phospholipase induced membrane damage and immediately induce cell necrosis.
Clostridia bacteria (clostridium perfringens type C)
3 ways Endotoxin released by bacteria induce cell injury/death
- direct membrane damage
- endotoxin directly initiating apoptosis
- TNF alpha induced in macs and binds to TNF receptors to induce apoptosis in lymphocytes.
What is most likely the main mechanism of endotoxins to cause cell death
high levels of TNF and other cytokines inducing apoptosis via extrinsic mechanism
Cellular adaptation to injury in 4 ways (ie exposed to low levels of free radicals over time)
- atrophy
- hypertrophy
- hyperplasia
- metaplasia
hyperplasia and mataplasia are important events leading to neoplasias
__ is reduciton in size of an organ/tissue/cell due to decrease in cell size and number
atrophy (physiologic/development or pathologic)
pathologic response: immobilization, deinnervation, decrease blood/nutrition/hormones, increased pressure,
mechanisms of atrophy
protein degradation and autophagy (lysosomeal digestion of cell’s own components)
__ is increase in cell size that results in an increase in the affected organ size
hypertrophy (physiologic or pathologic)
physio = increase muscle size for increased workload path = increased liver size due to drug or toxin metabolism
mechanism of hypertrophy
increased and/or altered protein production
mechanism of hypertrophy
increased and/or altered protein production
what cell organelle proliferates during hypertrophy
SER (increase protein production)
__is an increase in the number of cells in an organ/tissue in response to stimulus and often occurs with __
hyperplasia (path or physiologic), hypertrophy
path = excess/inappropriate hormone/growth factors, chronic injury, viral infections
__ is a REVERSIBLE change in which one differentiated cell type (epithelial or mesenchymal) is replaced by another cell type.
metaplasia (path, i.e. heavy smoker gets squamous metaplasia in trachea)
mechanism of metaplasia
chronic injury (infection/toxin) causes reprogramming of tissue stem cells to a different type (columnar epi to stratified squamous metaplasia)