Unit 2a Flashcards
Major causes (etiologies) of cell injury (7)
1) Physical agents: trauma/heat/electric shock/radiation/aging…
2) Chemical and drugs: drug toxicity, poisoning
3) Infection: pathogenic bacteria, virus, fungi, protozoa
4) Immunologic reactions: anaphylaxis, autoimmunity
5) Genetic derangement: phenylketonuria, cystic fibrosis
6) Nutritional imbalance: atherosclerosis, protein and vitamin deficient
7) Hypoxia
Human diseases occur due to …
cell / tissue injury
Major mechanisms of cell injury (6)
1) ATP depletion
2) Mitochondrial damage
3) Influx of calcium
4) Accumulation of ROS
5) Increased permeability of cellular membranes
6) Accumulation of damaged DNA and misfolded proteins
ATP depletion –> ________, ________ and _________
1) Decrease in Na+ pump activity
→ influx Ca2+, H2O, and Na+ and efflux of K+ → ER swelling, cellular swelling, loss of microvilli, blebs
2) Increase in anaerobic glycolysis
→ decrease glycogen, increase in lactic acid, decrease in pH → clumping of nuclear chromatin
3) Detachment of ribosomes –> decreased protein synthesis
ATP is produced via ___________ or _________
oxidative phosphorylation of ADP in mitochondria OR glycolytic pathway in absence of O2
Tissues with greater _________ are better able to withstand ischemic injury
glycolytic capacity
Susceptibility of specific cells to ischemic injury:
- Neurons
- Cardiac myocytes, hepatocytes, renal epithelium
- Cells of soft tissue, skin, skeletal muscle
Neurons = 3-5 min
Cardiac myocytes, hepatocytes, renal epithelium = 30 min - 2 hr
Cells of soft tissue, skin, skeletal muscle = many hours
Failure of oxidative phosphorylation –> (4)
1) ATP depletion
2) Formation of ROS
3) Formation of high-conductance channel (mitochondrial permeability transition pore) and loss of membrane potential
4) Release of proteins that activate apoptosis
Influx of calcium and cell injury
Ordinarily - big calcium gradient between extra and intracellular Ca2+
Ischemia and toxins → release of Ca2+ from intracellular stores and increased influx across plasma membrane → membrane damage, nuclear damage, decreased ATP
Two major pathways to accumulate ROS
1) during cells redox reactions during normal mitochondrial respiration
2) Phagocytic leukocytes (neutrophils and macrophages)
How are ROS produced during mitochondrial respiration?
1) Fenton Reaction
O2 → superoxide (O2-) → H2O2 + Fe++ → OH* + OH-
2)
O2 → superoxide + NO → peroxynitrite ONOO-
Superoxide Dismutase (SOD)
removes superoxide
Converts superoxide to H2O2 (however, this reaction can also occur spontaneously)
Catalase and Glutathione Peroxidase
decomposes hydrogen peroxide (H2O2) to H2O
Phagocytic leukocytes produce ROS via…
oxidative burst –> peroxynitrite, hypochlorite
Consequences of free radicals (3)
1) Damage determined by rate of production vs. rate of removal
2) Increased production or ineffective scavenging → oxidative stress
3) Removal via spontaneous decay and specialized enzymatic systems
Pathologic effects of ROS (3)
Lipid peroxidation → membrane damage
Protein modification → breakdown, misfolding
DNA damage → mutations
Important sites of membrane damage include _______, _______ and _______
mitochondria, plasma membrane, lysosome
Reversible cell injury includes _______ and ________
cellular swelling
fatty change
Reversible cell injury
- Recoverable if damaging stimulus removed
- Injury has not progressed to severe membrane damage and nuclear dissolution
- CAN result in IRREVERSIBLE injury if changes persist (especially severe mitochondria damage and disturbances in membrane function)
Cellular swelling
failure of energy dependent ion pumps in plasma membrane → disrupted ionic and fluid homeostasis
Fatty change
- accumulation of lipid vacuoles WITHIN cytoplasm of cells (typically those participating in fat metabolism - hepatocytes, myocardial cells, etc.)
- Due to increased entry and synthesis of free fatty acids and decreased fatty acid oxidation
- NOT SPECIFIC FOR INJURY type (could be alcoholic liver disease, NAFLD, etc.)
Intracellular changes of reversibly damaged cell include…(4)
1) plasma membrane alteration
2) mitochondrial changes
3) Dilate of ER with detachment of ribosomes
4) Nuclear alterations (with clumping of chromatin)
Plasma membrane alterations due to cell injury can cause…
blebbing (bulging), blunting, distortion of microvilli, loosening of intercellular attachments
Myelin figures
phospholipid masses derived from damaged cellular membranes
Mitochondrial changes resulting from cell injury
swelling and appearance of phospholipid-rick amorphous densities
Irreversible cell injury includes… (2)
Necrosis
Apoptosis
aka cell death
Necrosis signs
Cell size = ? Nucleus = ? Plasma membrane = ? Inflammation? Pathologic or physiologic?
Cell size = enlarged (swelling)
Nucleus = pyknosis → karyorrhexis → karyolysis
Plasma membrane = disrupted (Cellular contents enzymatically digested, may leak out of cell)
Inflammation? YES
Pathologic or physiologic? - ALWAYS pathologic
Apoptosis
Cell size = ? Nucleus = ? Plasma membrane = ? Inflammation? Pathologic or physiologic?
Cell size = reduced (shrinkage)
Nucleus = fragmentation into nucleosome size fragments
Plasma membrane = remains intact (may have altered structure - e.g. lipid orientation)
Inflammation? NO
Pathologic or physiologic? - often physiologic BUT can be pathologic (due to DNA/protein damage)
5 patterns of tissue necrosis
- Coagulative
- Liquefactive
- Caseous
- Fat
- Fibrinoid
Pyknosis
nuclear shrinkage and increased basophilia (DNA condenses)
Karyorrhexis
pyknotic nucleus fragments
Karyolysis
dissolution of nucleus (basophilia of chromatin fades secondary to deoxyribonuclease activity - breakdown of denatured chromatin)
Cytoplasmic changes present with necrosis (2)
increased eosinophilia (increase binding of eosin to denatured cytoplasmic proteins)
loss of RNA basophilia in cytoplasm
Apoptosis
- Programmed cell death
- tends to involve individual, scattered cells
- Pathway of cell death - cells activate enzymes that degrade cells nuclear DNA and nuclear and cytoplasmic proteins which then fragment (“falling off”)
- Does NOT elicit inflammatory response
Apoptotic bodies
membrane bound vesicles containing cytosol and organelles → taken up by macrophages
Physiologic causes of apoptosis
Programmed cell destruction during embryogenesis
Involution of hormone-dependent tissues upon hormone deprivation
Cell loss in proliferating cell populations
Elimination of cells that have served their purpose
Elimination of self reactive lymphocytes
Cell death induced by cytotoxic T-lymphocytes
Pathologic causes of apoptosis (4)
1) DNA damage (Radiation, cytotoxic drugs, temp extremes, hypoxia) where repair mechanisms inadequate → better to eliminate cell than risk propagating mutated DNA
2) Accumulation of misfolded proteins (ER stress)
3) Cell injury in certain infections (especially viral)
4) Pathologic atrophy in parenchymal organs after duct obstruction (pancreas, parotid, kidney)
Two pathways of apoptosis:
1) Mitochondrial (intrinsic pathway) = caspase 9
2) Death receptor (extrinsic pathway) = caspase 8
Anti-apoptotic species (3)
BCL2, BCL-XL MCL1
pro-apoptotic species (2)
BAX, BAK
Mitochondrial (intrinsic) apoptosis pathway steps (4)
1) Cell injury –> BCl-2 family effectors activated (BAX, BAK)
2) Mitochondria releases cytochrome C and other pro-apoptotic proteins
3) –> caspase 9 activated
4) –> executioner caspases activated –> apoptosis
Death receptor (extrinsic) apoptosis pathway steps (4)
1) Binding to Fas or TNF receptor on cell membrane surface
2) –> adaptor proteins activated (FADD)
3) –> Caspase 8 activate
4) –> Executioner caspases activated –> apoptosis
Autophagy
- process in which cell eats its own contents
- Adaptive response/survival mechanism in times of nutrient deprivation
- Dysregulation implicated in many diseases (cancers, inflammatory bowel disease, neurodegenerative disorders)
- Role in host defense - some pathogens degraded by autophagy (e.g. mycobacteria, HSV-1, etc)
4 main pathways of intracellular accumulations
1) Inadequate removal (fatty change liver - buildup of triglycerides)
2) Accumulation of abnormal endogenous substance (alpha1-antitrypsin)
3) Failure to degrade due to inherited enzyme deficiencies (storage diseases)
4) Deposition and accumulation of abnormal exogenous substances (anthracosis)
Pathologic calcification
abnormal deposition of Ca2+ salts (together with smaller amounts of iron, magnesium, and other minerals)
-Dystrophic or metastatic calcification
Dystrophic Calcification
Occurs in dead or dying tissues
Absence of systemic derangements in Ca2+ metabolism
Metastatic calcification
Normal tissues
Secondary to derangement in Ca2+ metabolism (hypercalcemia, hyperparathyroidism, Paget disease, etc.)
Necrosis
cell death due to loss of membrane integrity → leakage of cellular contents → dissolution of cells due to degradation by enzymes
Most commonly seen with ischemia (blood flow to tissues is compromised) = Ischemic/Coagulative necrosis
Large portions of tissue die all at once
4 ways cells/tissues can adapt to injury
1) Hypertrophy
2) Hyperplasia
3) Atrophy
4) Metaplasia
Hypertrophy
increase in SIZE of cells → increase in size of organ
- Corresponding increase in # of mitochondria and ER, etc.
- Physiologic (e.g enlargement of uterus during pregnancy) or Pathologic (e.g. left ventricular hypertrophy due to HTN)
- Caused by increased functional demand or growth factor/hormonal stimulation
- Hypertrophy and hyperplasia can occur together
- Eventually limit is reached, enlargement cannot compensate for increased burden ( → injury)
Hyperplasia
- increased NUMBER of cells in response to stimulus or injury
- Physiologic (e.g. proliferation of glandular epithelium of female breast during puberty or pregnancy) or Pathologic (e.g. endometrial hyperplasia in abnormal menstrual bleeding)
- Cellular proliferation stimulated by growth factors or hormones
- If stimulation is removed, hyperplasia should abate (in contrast with cancer)
Atrophy
- decrease/shrinkage in SIZE and FUNCTIONAL capacity of cells
- Physiologic (e.g. loss of hormone stimulation in menopause) or Pathologic (e.g. skeletal muscle denervation or diminished blood supply)
- Mechanism: decreased protein synthesis and increased protein degradation (ubiquitin-proteasome pathway)
Metaplasia
one adult / differentiated cell type replaced by another adult / differentiated cell type
- REVERSIBLE change
- Adaptive measure in response to injury or environmental changes
EX) replacement of squamous epithelium in distal esophagus by columnar intestinal epithelium in chronic reflux esophagitis = Intestinal metaplasia in Barett esophagus
Coagulative necrosis
- tissue architecture preserved for at least several days - dead cells remain as ghost like remnants of their former selves.
- Eventually dead cells digested by lysosomal enzymes of leukocytes recruited to site
- Characteristic of INFARCTS (e.g. MI or following ischemia in any solid organ)
Liquefactive necrosis
dead cells completely digested and tissue transforms into a liquid viscous mass, which is eventually removed by phagocytes
- Seen in focal bacterial and fungal infections
- Microbes → stimulate accumulation of inflammatory cells → leukocyte enzymes digest (liquify) tissue
- Seen in hypoxic cell death in CNS
Caseous necrosis
- THINK TB
- central portion of an infected lymph node is necrotic and has a chalky white appearance (like the milk protein casein).
- Necrotic area appears as a collection of fragmented or lysed cells and amorphous granular debris enclosed within a distinctive inflammatory border = granulomatous inflammation
Fat necrosis
release of activated pancreatic lipases (s/p acute pancreatitis or trauma) → areas of fat destruction
Fats hydrolyzed into free fatty acids → Ca2+ precipitate → “peculiar” chalky gray material
Fibrinoid necrosis
- immune reaction in which complexes of antigens and antibodies are deposited in the walls of arteries
- Deposited immune complexes combine with fibrin and produce bright pink and amorphous appearance on H&E
- Seen in certain vasculitis (e.g. polyarteritis nodosa)
Acute inflammation characteristic features (5)
1) Fast onset (min, hrs)
2) Cellular infiltrate = mainly neutrophils
3) Usually mild and self-limited tissue injury/fibrosis
4) Prominent local and systemic signs
5) Mostly innate immune response
Chronic inflammation characteristic features (5)
1) Slow onset (days)
2) Cellular infiltrate = mostly monocytes/macrophages and lymphocytes
3) Often severe and progressive tissue injury/fibrosis
4) Less prominent local and systemic signs, may be subtle
5) Increasing chronicity → more coordinated response (innate + adaptive immunity)
3 clinical signs of acute inflammation and their causes
Increased blood flow → ERYTHEMA (due to congested capillary beds) and local warmth
Increased permeability → SWELLING (exudate of fluid in tissues)
Change in lymph channel/node drainage → LYMPHADENITIS
Stimuli for acute inflammation (4)
1) Infections
2) Trauma
3) Foreign Material
4) Immune reactions
Stimuli for chronic inflammation (3)
1) Persistent infections
2) Immune mediated disease (autoimmune or allergic)
3) Prolonged exposure to toxins
4 steps of acute inflammation
1) Recognition
2) Vascular changes
3) Leukocyte Recruitment
4) Leukocyte Activation
How is acute inflammation recognized by inflammatory (and some non-inflam) cells?
Pattern recognition receptors present on cells → pick up microbe-derived substance, toxins, material from necrotic cells (ATP, uric acid, DNA), Fc portions of Abs
pro-inflammatory receptors can be located in ________, _________, and __________
Plasma membrane for extracellular triggers
Endosome for ingested triggers
Cytosol for intracellular triggers
Toll-Like Receptors (TLRs)
pattern recognition receptors, detect variety of microbes
Present on plasma membrane and endosomes
Inflammasome
pattern recognition receptor, complex of proteins that mediates cellular response - especially respond to stuff from dead/damaged cells (but also microbes)
Stuff = uric acid (from DNA breakdown), ATP, decreased intracellular K+ (due to plasma membrane injury), DNA
Receptors in cytoplasm
TLR stimulated –> ?
Inflammasoee stimulated –> ?
TLR stimulated → transcription factors → mediators of inflammation and anti-microbial products (e.g. interferons)
Inflammasome stimulated –> caspase-1 activated –> cleaves IL-1 to active form, IL1B –> Inflammation
How is blood flow increased during acute inflammation?
Arterioles serving involved cap beds dilate, flooding capillaries
Histamine acts on smooth muscle cells in vascular wall to dilate arterioles
How is blood vessel permeability increased during acute inflammation? (3)
1) Endothelial cells contract as a response to mediators → gaps between cells
2) Endothelial injury
3) Transcytosis
Early vs. Later mediators for increased vessel permeability
Early: histamine, bradykinin
Later: different mediators (IL1, TNF) - sustained vascular change
5 main phases of Leukocyte recruitment
1) Margination
2) Rolling
3) Adhesion
4) Transmigration
5) Chemotaxis
Margination
leukocytes accumulate in periphery of blood vessels (b/c they are slow and big) on endothelium
Rolling
Stimulated endothelial cells express adhesion molecules with affinity for sugars on leukocytes (transient, not strong binding)
Local tissues detect threat → chemical mediators released → associated small vessels become “sticky”
Mediators induce endothelium to move adhesion molecules to surface:
Histamine –> _______
While IL-1 –>_______
Histamine → P selectin
IL-1 → E-Selectin
Adhesion
Leukocyte reaches area of high ligand (ICAM-1) concentration on endothelium for CD11/CD18 Integrins on leukocyte
–> stable attachment at sites of inflammation
Transmigration
begins after adhesion arrests leukocyte on endothelium
Point of no return
Leukocytes (using CD31) squeeze between endothelial cells = diapedesis
Mostly occur in venules
Leukocytes also secrete enzymes (e.g. collagenase) to break up basement membrane of vessels
Chemotaxis
Leukocytes move toward site of inflammation following chemical gradients of increasing density
Leukocyte activation
leukocytes activated when they encounter certain substances (microbial products, cellular debris, certain cellular mediators)
Once activated, leukocytes…(4)
1) readily phagocytize materials
2) are poised to kill/degrade engulfed material
3) readily secrete material to kill/degrade
4) Produce inflammatory mediators (amplifies inflammatory process)
Phagocytosis by leukocytes occur in 3 steps:
1) Recognition/attachment of particle to leukocyte
2) Engulfment and formation of vacuole
3) Killing/degradation of vacuolated material
Leukocytes bind material for phagocytosis using _______
opsonins
Opsonins
host proteins present in blood or produced locally that coat microbes
includes: IgG, complement system (C3b), collectins
______, ______, _______, ________, and ______ are toxic chemicals produced by leukocytes used to kill microbes in phagosomes
Superoxide Ion
Hydrogen peroxide
Hypochlorous radical
Other toxic nitrogen compounds
Other lysosomal enzymes
Transudates
result of altered intravascular pressure (either hemodynamic or osmotic)
Protein content decreased
Cell content decreased (few cells)
Specific gravity = low
Exudates
result of increased vascular permeability usually related to inflammation
Protein content increased
Cell content increased (inflammatory cells and RBCs)
Specific gravity = high
3 possible outcomes of acute inflammation
1) Resolution
2) Chronic inflammation
3) Scarring
Systemic Effects of Inflammation mediated by ______, ______ and _____ mediators that distribute systemically to produce ________, __________ and _________ generalized effects
TNF, IL-1, and IL-6
Fever
Increased acute phase proteins in blood
Leukocytosis
Fever caused by ______ which bind ________ to produce _______ –> increase in central body temp
pyrogens (IL-1, TNF)
bind hypothalamus cells
prostaglandins
Exogenous pyrogens can act directly on _______, but can also cause ________
hypothalamic cells
can cause release of IL-1 and TNF (endogenous pyrogens)
Increased acute phase proteins in blood stimulated by ______, which causes _______ to produce more proteins including _______, _______ and ________
IL-6
hepatocytes
C-Reactive protein (CRP)
Serum Amyloid A (SAA)
Fibrinogen
CRP and SAA are released upon stimulation from IL-6 and act as ___________
opsonins - promote adherence of leukocytes to vessel endothelium
Fibrinogen is released upon stimulation from IL-6 and acts to …
bind RBCs → RBCs form stacks and sediments → Erythrocyte Sedimentation Rate (ESR) used as test for inflammation
Leukocytosis is stimulated by ______ and ______
May cause an increase number of immature WBCs = ____________
TNF and IL-1
Left Shift of leukocytes
General Rule:
Neutrophilia –>
Lymphocytosis –>
Eosinophilia –>
Leukopneia –>
Neutrophilia → Bacterial infections
Lymphocytosis = increased lymphocytes → viral infections
Eosinophilia = increased eosinophils → asthma, parasitic infections
Leukopenia = decreased leukocytes → specific infections (e.g. typhoid)
Whats the difference between a monocyte and a macrophage
Monocytes circulate for about 1 day, some → macrophages in peripheral tissues
Macrophage functions (4)
1) Ingest microbes and necrotic cellular debris (main phagocytes of adaptive immune system)
2) Initiate tissue repair (often results in fibrosis/scarring)
3) Secrete inflammatory mediators (cytokines, eicosanoids) that promote inflammation
4) Present antigens to adaptive immune system
Two pathways to activate macrophages
1) Alternative activation (M2)
2) Classical Activation (M1)
Classical Activation of Macrophages:
Activated by _____ and ______.
Leads to secretion of ________ that promote __________ and __________
Endotoxin IFN-y (T cell cytokine) and foreign material
Secrete inflammatory mediators (cytokines and eicosanoids)
chronic inflammation and killing of microbes
Alternative activation of macrophages:
Activated by ______ and ________.
Promotes secretion of factors that promote _______, _________ and _________
new vessel growth, fibroblast activation and initiation of tissue repair (often → fibrosis/scarring)
Lymphocytes
Involved in many inflammatory responses - especially autoimmune disease and other chronic inflammatory disorders
Activated by adaptive immune response
Share pathways of tissue migration with other inflammatory cells
3 types of CD4+T cells secrete different cytokines that promote inflammation:
TH1 CD4+ –>
TH2 CD3+ –>
TH17 CD4+ –>
TH1 CD4+ T lymphocytes → secrete IFN-y → activates classical pathway macrophages
TH2 CD3+ T lymphocytes → secrete IL-4, IL-5, IL-13 → activates alternative pathway of macrophages and activates eosinophils
TH17 CD4+ T lymphocytes → secrete IL-17 → recruit netorophils and monocytes
Eosinophils are found in many inflammatory reactions, especially _______ and _______
Recruited by _________
Parasitic infections
Allergic reactions
chemokines (eotaxin)
Mast Cells
- Involved in acute and chronic inflammation
- Widely distributed → wide, quick trigger response to infections
- Quick release of inflammatory mediators (histamine and arachidonic acid)
- Coated with IgE → triggers mediator release
- Involved in allergic reactions
Granulomatous inflammation
sign of chronic inflammation
Fibrosis often forms around longstanding granulomatous inflammation
Happens with: organisms not eradicated by inflammatory reactions (TB, leprosy, fungi), immune-mediated diseases (Crohn’s), foreign material, Sarcoidosis (chronic granulomatous disease)
Sites of mediator production (2)
- site of inflammation
2. Liver
Synthesis of mediators can be:
- Preformed, ready for secretion (fast acting) - EX histamine
- Synthesized (on demand) - rapidly decaying compounds or toxic mediators - EX ROS
Vasoactive amines (2)
Histamine and serotonin
Storrage of vasoactive amines
stored in cells and ready for quick release
Histamine is released by (3)
mast cells, basophils, and platelets
Histamine causes (2)
- arterial dilation
2. endothelial contraction
Mast cells release histamine for (5)
Physical features (mechanical, temp), immune (binding of IgE), Complement (C3a, C5a), Histamine releasing proteins (from leukocytes), neuropeptides, and cytokines (IL-1, IL-8)
Serotonin causes…
vasoconstriction to aid in clotting
Serotonin is present in
platelet granules
Release of serotonin is a response to
platelet aggregation
Arachidonic acids are derived from
cell membrane phospholipids
Arachidonic acids are released by (4)
- leukocytes
- mast celss
- endothelium
- platelets
Arachidonic acid metabolites are formed by 2 main pathways
- Cyclooxgenase → prostaglandins and thromboxanes
2. Lipoxygenase → leukotrienes and lipotoxins
3 characteristics of prostaglandins and thromboxanes
a. Large variety of actions (some opposite) depending on the specific compound and receptor
b. Prostaglandins → symptoms of pain and fever
c. Presence of specific enzymes determines which compounds are made
Regeneration
cell proliferation of residual (uninjured) cells, and proliferation of stem cells
-can occur in labile tissues
Labile Tissues
continuously dividing (GI, skin, bone marrow, urothelium, oral cavity)
-Injured cells rapidly replaced by proliferation of residual cells and differentiation of tissue stem cells (provided underlying basement membrane is intact)
Stable tissues
minimal replicative activity, although capable of proliferating in response to injury or loss of tissue mass (liver, kidney, pancreas, endothelial cells, fibroblasts, smooth muscle cells)
Regeneration can occur, but (with exception of liver) usually limited
Scar Formation
in cases where injury is severe, chronic, or involves non-dividing cells
Repair occurs by replacement of non-regenerated cells with connective tissue
Permanent Tissues
terminally differentiated, non proliferative (cardiac muscle cells, neurons)
Two types of tissue repair
Regeneration
Scar formation
Acute vs. Chronic Inflammation onset/duration
Acute = seconds to minutes onset / days duration
Chronic = days onset / weeks, months, years duration
Vascular response during acute inflammation phase
-Dilation / Increased Flow
-Increased Permeability
→ Transudate
→ Exudate
Vascular response during chronic inflammation phase
- Variable persistence of dilation and “leakiness”
- Endothelial cell activated (ready to proliferate if necessary)
The acute inflammation phase involves ________ cells from _________.
Chronic inflammation phase involves ________ and _______ cells from the _________ and ________
Acute = NEUTROPHils from peripheral blood
Chronic = MACROPHAGES and LYMPHOCYTES from peripheral blood and local cells in tissue (sentinel)
Is there repair processes in acute inflammation?
In chronic inflammation phase?
Acute = NO repair
Chronic = repair is stimulated
Repair during chronic phase inflammation include:
Macrophages –> ?
Fibroblasts –> ?
Endothelial cells –> ?
Macrophages –> growth factors
Fibroblasts –> fibrosis/scar
Endothelial cells –> neovascularization
Growth factor is secreted by _________, and act to ….
Macrophages
Proteins that stimulate survival and proliferation of particular cells - may also promote migration, differentiation, and other cellular responses
Neovacularization is done by _________ cells
endothelial
Collagen deposition is done by _______ and ________ cells and requires ________
Fibroblasts and Myofibroblasts
ECM intact for tissue regeneration (if ECM damaged, repair only be scar formation)
Myofibroblasts responsible for wound contracture
Collagen remodeling and retraction is done by _______ cells
fibroblast
Re-epithelialization and regeneration is done by _________ and _________ cells
epithelial and hepatocytes
Granulation tissues
Comprised of ______, _______, __________, and _________
named for pink, soft granular appearance grossly (seen beneath scab of skin wound)
Comprised of:
fibroblasts
new capillaries
loose extracellular matrix
inflammatory cells (mostly macrophages)
Re-epithelialization
first vs. second intention
cells rapidly replaced by proliferation of residual cells provided underlying basement membrane is intact
First intention: epithelial regeneration principal mechanism of repair
Second Intention: more complex repair, involving combination of regeneration and scarring
-Typically larger defect → larger clot/scab, more inflammation, wound contraction, more granulation tissue
Liver regeneration
unique and robust regenerative capacity
Can regenerate when 40-60% of liver removed, and regenerate after insults (hepatitis, etc.) if enough tissue framework intact
Triggered by cytokines and growth factors in response to loss of liver mass and/or inflammation
May occur by proliferation by surviving hepatocytes and/or re-population from progenitor cells
Steps of normal scar formation: (5)
1) angiogenesis →
2) migration/proliferation of fibroblasts →
3) deposition of connective tissue (granulation tissue) →
4) maturation and reorganization of fibrous tissue (remodeling) →
5) stable fibrous scar
Angiogenesis is mediated by growth factor _________
VEGF
Deposition of connective tissue is mediated by _____, _______ and ______.
PDGF
FGF-2
TGF-B ** (most important)
Cytokines and GFs released from inflammatory cells (especially M2 activated macrophages)
Remodeling of connective tissue is done by _________
matrix metalloproteinases (MMPs)
Pathologic scar
accumulation of excessive amounts of collagen
Hypertrophic scar
outside boundaries of injury / regress
Keloid
outside boundaries of injury / persists
Local factors that adversely influence repair/regeneration process
infection, persistence of insult, trauma (early movement prior to completion of repair), trauma (foreign material), size/location
Systemic factors that might adversely influence repair/regeneration process
1) Nutritional: impaired collagen synthesis - protein deficiency, vitamin C deficiency
2) Metabolic: delayed repair - diabetes, glucocorticoids (inhibit TGF-B synthesis)
3) Vascular:
Thrombosis, atherosclerosis, venous drainage impairment (varicose veins)
COX-1 acts in the GI tract to
decrease acid/pepsin secretion
increase mucous/bicarb production
increase smooth muscle contractions
COX-1 acts on platelets via ______ to…
TXA2 increase aggregation
COX-1 and COX-2 act on the kidneys to…
increase/maintain renal blood flow, promotion of diuresis
COX-1 acts on vascular smooth muscle via ______ to…
TXA2
promote vasoconstriction
COX-1 acts on bone to…
stimulate bone formation and resorption
COX 1 is expressed ________ while COX-2 is _________
constitutively
induced (by cytokines, growth factors), upregulated (need basis) - in inflamed/activated tissues
COX-2 acts in areas of pain/inflammation via _____ to…
PGI2 (prostacyclin)
enhance edema and leukocyte infiltration
pain sensitization
(vasodilation, potentiation of bradykinin pain-producing activity)
COX-2 effect on body temperature
Fever: Increase heat generation, decrease heat loss
COX-2 acts on endothelial cells via ______ to promote….
PGI2
vasodilation
ANTI-aggregatory platelet effects
COX-2 acts on uterine smooth muscle to…
enhance labor contractions near parturition
COX-2 acts on ductus arteriosus to…
maintenan of patent ductus arteriosus via vasodilatory effects
Thromboxane (TXA2) is produced by _______ and acts to…
COX-1
promote platelet aggregation
Prostacyclin (PGI2) is produced by _______ and acts to…
COX-2
Vasodilation
Inhibit platelet aggregation
Pain sensitization
Gastric cyto-protection
COX-1 + platelets = ?
COX-2 + endothelial cells = ?
thromboxane
prostacyclin
Mechanism of action:
tNSAIDs
inhibition of COX-1 and 2
reversible
Mechanism of action:
Celecoxib (celebrex)
Inhibition of COX-2
reversible
Mechanism of action:
Acetaminophen
inhibition of COX-2 in CNS
NO effect on COX in periphery
Mechanism of action:
Aspirin
inhibition of COX-1 and COX-2 (irreversible)
Aspirin can be used for…(4)
Analgesic injury
Anti-inflammatory injury
Anti-pyretic
Anti-platelet aggregation**
tNSAIDS can be used for…
but NOT for…
Analgesic injury
Anti-inflammatory injury
Anti-pyretic
NO anti-platelet aggregation effect
Acetaminophen can be used for…
but NOT for…
Analgesic injury
Anti-pyretic
NO anti-inflammatory injury effect **
NO anti-platelet aggregation effect
Celecoxib can be used for…
but NOT for…
Analgesic injury
Anti-inflammatory injury
Anti-pyretic
NO anti-platelet aggregation effect
Aspirin side effects include…
but NOT…
Stomach (1) - GI upset
Platelet (1) - Bleeding
Kidney (1/2) - decreased renal function
Uterus (2) - decreased labor
NO effect on vessels
tNSAIDs side effects include…
but NOT…
Stomach (1) - GI upset
Platelet (1) - Bleeding
Kidney (1/2) - decreased renal function
Uterus (2) - decreased labor
NO effect on vessels
Acetaminophen side effects include…
but NOT…
**NO SIDE EFFECTS on stomach, platelets, kidney, uterus, or vessels
Celecoxib side effects include…
but NOT…
Kidney (1/2) - decreased renal function
Uterus (2) - decreased labor
**Vessel endothelial cells (2) -increase in clotting
NO effect on:
**Stomach (GI upset)
Platelets (bleeding)
tNSAID OD results in…
acute renal failure (TX = supportive)
Incidence of GI toxicity when using tNSAIDs can be reduced by…
concomitant use of proton pump inhibitors (omeprazole)
Celecoxib is dangerous because….BUT is often used for patients
it has prothrombotic potential –> increased MI risk
with GI problems (has lower risk of GI toxicity)
Acetaminophen OD
liver failure
TX - N-acetylcysteine
Limit dose to 4 g/day due to concerns of hepatotoxicity
Aspirin OD
hyperthermia, acidosis
TX - NaHCO3
Reyes Syndrome: seizures, acute encephalopathy, liver damage, rash, fatty liver, AMS
DO NOT use in children under 12 years old (use acetaminophen instead)
Hydrocortisone (cortisol)
Anti-inflammatory Topical Salt-retaining Potency Routes
Anti-inflammatory - 1 Topical - 1 Salt-retaining - 1 Potency - 20 mg Routes - oral, injectable, TOPICAL
Cortisone and prednisone are NOT _______ because…
topical
Prednisone and cortisone are 11-keto forms so they are topically inactive
Cortisol MUST have a hydroxyl at 11 position
Dexamethasone, methylprednisolone, and triamcinolone all have…
zero salt retaining
Dexamethasone and triamcinolone have…
oral, injectable, AND TOPICAL application
Leukotrines
mediate specific functions of inflammation
LTB4
Chemotactic agent for neutrophils
LTC, LTD4, LTE4
Cause vascular permeability
Effects of platelet-activating factor
platelet aggregation, vasodilation, vascular permeability, bronchoconstriction, stimulation of platelets and cells to form other mediators
Cytokines
Polypeptides that function as mediators in innate and adaptive immune system
Two important acute inflammatory cytokines
TNF and IL-1
TNF and IL-1 are produced by (3)
macrophages, mast cells, endothelial cells
Production of TNF and IL-1 is stimulated by
microbial products, immune complexes, and T cell mediators
Acute inflammatory cytokines cause
endothelial activation (leukocyte binding and recruitment)
Induces systemic effects of inflammation: fever, acute phase protein synthesis
Chemokines are separated into 2 groups:
- CXC: chemotactic for neutrophils (e.g. IL-8)
2. CC: chemotactic for several cells (e.g. eotaxin for eosinophils)
2 chronic inflammatory cytokines and function
IFN-y: stimulates classical macrophage activation
IL-12: Stimulate growth and function of T cells
ROS are released from
activated neutrophils and macrophages
Production of ROS from NADPH oxidase pathways
O2 + e- → O2-* (superoxide)
Superoxide ->
H202
H2O2 -> (2)
- H2O2 → hydroxyl radical (OH*)
2. H2O2 → hypochlorous radical (HOCL*) - via myeloperoxidase in neutrophils
O2, OH, and HOCL* are highly toxic ____ that damage ____ and _____
oxidizers
microbes
host tissue
Endogenous _____ such as _____ mitigate effect of ROS on host
antioxidants
superoxide dismutase
NO
free radical that can kill microbes
NO is a mediator of ____, antagonizes _____, and reduces _____
- vasodialation
- antagonizes platelet activation
- Leukocyte recruitment
Nitric oxide is produced from
L-arginine
Type II NOS
Inducible NOS-> induce macrophages and endothelial cells
Type II NOS is induced by
IL-1, TNF, IFN-gamma, and bacterial endotoxins
Type III NOS
Endothelial NOS
Constitutively expressed in endothelial cells
EX of lysosomal enzyme
Azurophil granules
Azurophil granules
(neutrophils and monocytes) similar to lysosomes
Contain enzymes that can kill microbes and digest ingested materials
Significant source for substances that damage normal host tissues
Granules in neutrophils
NOT all the same
different constituents with different functions (intra vs. extracellular)
Acid proteases
active within phagolysosomes (low pH)
Neutral proteases
active outside the cell (neutral pH)
EX: collagenase
Protease inhibitors widely present in blood and body tissues (2)
- Alpha-1-antitrypsin: neutrophil elastase inhibitor → emphysema
- Alpha-2-Macroglobulin: inhibits a large variety of proteinases (e.g. collagenase)
Neuropeptides
- can initiate inflammation
- particularly active in vascular tone and permeability (lung and GI)
EX of neuropeptide
Substance P
Substance P
- 11 AA peptide
Secreted by nerves and inflammatory cells (macrophages, eosinophils, lymphocytes, dendritic cells) - Binds neurokinin-1 receptor
- Generates proinflammatory effects in immune and epithelial cells
Compliment
- Composed of large number of plasma proteins involved with inflammation and immunity
- Opsonize pathogens, induce series of inflammatory responses that help fight infections
Final activated complement forms
Membrane attack complex
Compliment increases ____ and ____
vascular permeability and leukocyte chemotaxis
C1-C9 circulate inactive in ____, activated by ___
plasma, proteolysis
___ cleaves C3 into ___ and ___
C3 convertase
C3a and C3b
___ bind C3 convertase, forming ___ convertase, which initiates formation of ___
C3b
C5 convertase
C5b-9 (the MAC)
Charlie, you are ______. I want to let you know ______. I ___ you.
- _____
so beautiful
how much you mean to me
LOVE
-Josh
C3 convertase formation via 3 pathways
- Classical: fixation of C1 to antigen-antibody complexes
- Alternative: microbe wall components combines with plasma proteins (factors B, D)
- Lectin: plasma lectin binds microbial mannose and stimulates classical pathway
C3a, C5a:
increase vascular permeability, stimulate mast cells to release histamine
C5a:
activates lipogenous pathway for AA metabolism
C5a, C4a, C3a:
activate leukocytes, increasing their endothelial adhesion
i. Also chemotactic agents for neuts, eos, basophils, and monocytes
C3b:
acts as opsonin for enhanced phagocytosis
Inhibitors are located where?
Free in plasma
2 inhibitors of complement
- C1 inhibitor
2. Decay-accelerating factor (DAF) + factor H
DAF + factor H
limit C3/5 convertase formation
Coagulation system overlaps with
inflammation mediators
Important clotting factor
Factor XII (Hageman factor)
Factor XII activates
Kinin system → bradykinins → increased vascular permeability, vascular dilation, and pain
Intermediate product Kallkrein = chemotactic and activates Factor XII
Factor XII stimulates
clotting cascade + inflammatory factors
i. Factor Xa → vascular permeability
ii. Thrombin:
1. Binds protease activated receptors on endothelial cells (activating them)
2. Cleaves fibrinogen → fibrinopeptides → increased vascular permeability and chemotactic
3. Cleaves complement factor 5 forming factor 5a
Whenever clotting system active, so is ___
fibrinolytic system
Multiple of these factors are active inflammatory mediators resulting in vascular permeability, dilation and C3a formation
Molecules and mechanisms that limit and/or terminate inflammatory reactions (5)
- Lipoxins: antagonize leukotrienes
- Complement regulatory proteins (C1 inhibitor)
- IL-10 (secreted by macrophages) down regulates activated macrophages
- TGF-beta (promotes fibrosis) is anti-inflammatory
- Intracellular compounds also antagonize pro-inflammatory cell states
Exogenous GC →
act at sites of inflammation in periphery AND to H-P-A axis and alter release of releasing factors and growth hormone
GC → hypothalamus, anterior pituitary, adrenal gland suppression →
less CRF/ACTH/cortisol release (but increase exogenous ACTH, so not typically a problem)
**Problem comes during times of stress when excess cortisol needed - more than you are giving
Metabolic effects of cortisol on carbohydrates
increase gluconeogenesis → increase blood glucose (increase insulin)
EXCESS → diabetes-like state
Metabolic effects of cortisol on protein
decrease protein synthesis → increase AA to glucose
EXCESS → muscle wasting, skin-connective tissue atrophy
Metabolic effects of cortisol on fat
increase lipolysis (peripherally) → increase free fatty acids
EXCESS → increased lipogenesis (centrally via insulin) -> centripetal obesity
Acute side effects of glucocorticoids
glucose intolerance in diabetics, mood changes (up and down), insomnia, GI upset
Side effects of high dose sustained therapy (2-4 weeks)
- Iatrogenic Cushing’s syndrome → hyperglycemia, protein wasting (muscle), lipid deposition (weight gain - buffalo hump, trunk obesity) → diabetes-like state
- HPA axis suppression → insufficient response to stress
i. More suppression with Dexamethasone and Betamethasone ii. Decrease ACTH, GH, TSH, LH, sex steroids
- Mood disturbance
- Impaired wound healing
- Increased susceptibility to infection
- Osteoporosis
Mineralocorticoid effects on aldosterone
Increase Na+ reabsorption at kidney → increase blood volume and BP AND increase K+ and H+ secretion
EXCESS → sodium-fluid retention, hypertension, hypokalemia, metabolic alkalosis
Mineralcorticoid = salt ____
retaining
Acute side effects of mineralcorticoids
salt and water retention -> edema, increased BP, hypokalemia
Pharmacology of glucocorticoids
anti-inflammation and immunosuppressive effects
GC effects on vascular events
reduced vasodilation, decreased fluid exudation
GC on cellular events
overall decrease in accumulation- activation of inflammatory and immune cells
GC effects on inflammatory and immune mediators
decrease in synthesis
Cortisol (hydrocortisone)
i. GC:MC actions 1:1
ii. Oral and parenteral administration
iii. Useful in adrenal crisis
Prednisone
i. Most commonly used for steroid burst (asthma,inflammatory reaction)
ii. GC:MC actions 5:1
iii. Activated to prednisolone in liver - NO topical activity
Methylprednisolone
i. IV or oral for steroid burst
ii. Minimal MC action
Dexamethasone
i. Most potent anti-inflammatory agent
ii. Use: cerebral edema, chemotherapy induced vomiting
iii. Minimal MC action
iv. Greatest suppression of ACTH secretion at pituitary
Triamcinolone
i. Potent systemic agent with excellent topical activity
ii. No MC action
Alternate day therapy glucocorticoids
minimize adrenal suppression
i. Anti-inflammatory actions outlast HPA suppression
1. Anti-inflammatory effects longer lasting (48hrs) -HPA suppression shorter acting (24 hrs)
2. Minimizes GC block of ACTH release which can significantly reduce adrenal atrophy
Tapered withdrawal
i. Required for chronic therapy with GCs
ii. Minimizes disease rebound and potential for symptoms of adrenal insufficiency (adrenal crisis)
Triamcilone
GC with excellent topical activity, potent (system effects as well)
