Prostaglandins/Inflammation Flashcards
Inflammation in general
Essential to alter the immune system of injury/infections
Recruits leukocytes
Aberrant inflammation is detrimental
Cytokines - function
Infection: macrophages sense pathogen
release:
Cytokines: modulate immune cell activation
Chemokines: attract specific immune cells
Also: endothelial permeability increases
TLR activation
LPS from gram negative bacteria
binds to TLR-4, spec. MD2 part
Clustering of TLRs via their PAMP ligands
TLR signal downstream
IKB destroyed
releases NFKB
Now transcription factor for cytokine genes - activated
Receptor clustering
… General mechanism for immune modulation
TLRs and cytokines
TLRs + macrophages –> release of immunostimulating cytokines
Inflammatory cytokines act on other cells, initiate inflammation, several mechanisms
5 cytokines
IL-1beta
TNF-al
IL-6
CXCL8
IL-12
IL-1beta
Activates vascular endothelium,
lymphocytes
Local tissue destruction
Access of effector cells ^^
Effect: Fever, produce IL-6
TNF-alpha
Vascular endo
increases vascular permeability
IgG entry
Incr. fluid to lymph node
Effect: Fever
Mobilize metabolites
Shock
IL-6
Lymphocyte activation
Ab production
Effect: Fever
acute-phase protein production
CXCL8
Chemotactic factor
neutrophil recruiter
Basophil
T cell to site of infection
IL-12
NK cells activation
Differentiation of CD4 –> Th1
Macrophages –> phospholipids
Immune cell –> release cytokine –> receptor –> activate Phospholipase A2 (macrophage can be activated by same cytokine it produced)
Pathway of PLA2 and therapeutics
PL –> Arachidonic acid –> Prostaglandins –> inflammation
Phospholipase: inhibited by Glucocorticoids (dexamethasone)
Cyclooxygenase –> prostaglandins: can be inhibited by NSAIDs (aspirin, ibuprofen)
Eicosanoids and PL damage
Membrane damage increases [phospholipid] for PLA2 processing
Pathway from PL –> prosta…
PL –> PLA2 –> arachidonic acid –> COX1/2 –> PGG2 –> PGH2 –> prostaglandins, prostacyclin, thromboxanes
Eicosanoid: biosynthesis
Major classes: Prostaglandins, leukotrienes, thromboxanes
All from arachidonic acid AA
COX1/2 + prostaglandin synthases –> most biosynthetic transformations
3 parts of conversion to PG-in
- Cyclization
- Adding peroxide bridge
- Secondary peroxide acid OOH
highly potent, reactive, small 1/2 life
Prostaglandin nomenclature
Labelled with PG
20 carbons
5 membered ring - dictate A-K
number of double bonds not in ring –> subscript
Stereochemistry at C9, if ketone reduced, alpha/beta
4 Prostaglandin overall structure
PGD: C9 is OH, C11 is ketone (flipped than usual)
PGE: ketone is C9; C11 is OH
PGF alpha: C9 and 11 has OH
PGI: prostacyclin: double ring, new one connected with ether
Prostaglandins: local action, 1/2 life, pathological, generally
PG biosynthesized, acts locally
Degradation rapid, occurs catabolically and spontaneously
Spatial control over signalling, to limit inflammation to tissue damage
Chronic prod. of PGs: inflammation, disease
Catabolism of prostaglandins:
Hydroxyprostaglandin dehydrogenase HPGD
Carbonyl reductase 1: can deactivate PGs
HPGD oxidize OH at C15 –> ketone
CBR1 –> reduced C9 ketone
Some PH unstable and hydrolyze easily
Prostacyclin (PGI2) –> 6ketoPGF1alpha
Eicosanoids: tissue specificity
PGs act on every tissue type, numerous effects
Specific effect depend on receptor at tissue
Tissue-specific effects
Vessels: PGF2, PGI2, PGE2, PGD2
Platelets: PGE1, PGI2
Intestines: PGE1, PGFalpha
Stomach: PGE2, PGI2
Uterus: PGE2, PGF2
Kidney: PGH2, PGE1
HPA: PGE2, PGE2
Prostaglandin receptors
Designated by ring identity by corresponding ligand
PGE2 –> EP (4types)
PGI2–> IP
All GPCR
Alter IC Ca++, cAMP
Result of receptor effects downstream:
Inflammation, pain, immunoreg, mitogenesis, plasticity and cell injury
Receptor expression
PG rec. expression + Biosynthesis of PGs restricted to certain tissue types
Restricting PG receptor expression
Control over local [active PG] –> regulation over PG signalling
see slide 17
Therapy via PG
Modulating PG levels
Overlapping receptor expression on cell types –> various consequences of changing amt of 1 PG in body
Patient can increase PG signalling or inhibit PG biosynthesis
Female reprod organ: PG and fxn
PGE2, PGF2a
Uterine contraction, oxytocic action
Male reproductive organ
PGE2 PGF2a
Fertility
CV system
PGI2 - Thrombosis
PGE2, PGI2 - Arterial vasodilation
PGF2 - Venous vasoconstriction
PGE2, PGI2 - Patency of fetal ductus arteriosus
Respiratory system
PGE2 - bronchodilation
PGF2a- bronchoconstriction
Renal system
PGE2 PGI1 = Renal blood flow GFR
PGE2, PGI2 = renin release
PGE2 = Inhibition of ADH
GI system
PGE2, PGI2 = cytoprotection
Immune system
PGE2, PGI2 = inhibition of T B lymphocyte activation/ prolif
CNS
PGE2 = Fever
PGD2 = sleep
PGE2, PGI2 = Pain
Rheumatoid arthritis
RA -autoimmune, destruction and inflammation of joint tissue
Local inflammation by immune cells - attack autoantigens
Inflammation in synovial membrane –> leukocytes in tissue
T cells activate macrophages –> Cytokines –> osteoclast activation –> break cartilage
Tissue destruction: prostaglandin release: pain, swelling, redness
Inhibiting PG synthesis
Glucocorticoids
Inhibit
PL –> AA
NSAIDs - inhibit COX2/1, AA–> PGG2
NSAIDs - inhibit COX2/1, PGG2 –> PGH2
Activating PG formation
Epoprostenol PGI2
Alprostadil - PGE1
Misoprostol - PGE1 analogue
Dinoprostone - PGE2
Dinoprost - PGF2a
Carboprost - analogue of PGF2a
Predominant PG in inflammation
PGE2 and PGI2
Both promote edema and leukocyte influx
Enhance blood flow at inflamed region
Target for RA
Inhibit PGE2 and PGI2 biosynthesis
Good PG inhibitors
Inhibition of PGE2 and PGI2
Corticosteroids
Nonsteroidal anti-inflammatory drugs
Negative + positive effects of PG
PGE2 and PGI2 - pain, fever, immune cell activation –> inflammatory cascades
Also: GI protection of mucosa, CV regulation
Corticosteroids - cannot be safely used long
Modern NSAIDs - more accurate control over local PG
Corticosteroids + when used
Decrease prod. of cytokines, lower PG
Increased production of IL-10 tho
Decreased recruitment of immune cells
Immunosuppressive, limits use
Used in acute inflammation (anaphylaxis, brain swelling, cyto release syndrome)
RA, lupus IBS MS
Transplant recipients
Example of corticosteroid
Dexamethasone
Additional effects of steroids
lower NOS, lower NO, vasoconstrction
Lower adhesion, reduced emigration of leukocytes from vessels
Increase endonucleases - induce apoptosis of lymphocytes and eosinophils
Corticosteroid mechanism
bind to EC GC receptor
Into cell
bind to NFKB
into nucleus –> transcription of anti-inflammatory cytokines (IL-10, TGF-beta) –> immunosuppression
Also, repress transcription of inflammatory cytokines
Broad effects of corticosteroids
Extreme changes in transcription
Broad side effects
Not used as chronic treatment
Prevent PLA2 from acting, preventing AA release
Immunosuppresant drugs without side effects need to act narrowly
2 major NSAIDs, compare
COX1/2
Tissue restricted expression, inducibility - COX2 better target
COX1 constitutively expressed in tissues required for homeostasis- renal, platelet function, gastric mucosal protection
COX2 - for acute and chronic inflammation, pain, fever, limited homeostatic effect
COX enzymes - dual action, which change results in which PG?
Bicyclic endoperoxide - formed in 1st active site C11
Result peroxide C15 (PGG2)
Second active site - reduced at peroxide at C15 –> chiral alcohol (PGH2)
Early NSAIDS + amino acids + active sites
Non-specific COX - non-aspirin inhibitors enter active site and physically block AA entry
Ion pair formation with Arg 120
Aspirin - covalently modifies ser529 in active site
Ser529 - acetylated, blocks AA from entering active site
COX2 selectivity
COX2 selectivity - deeper binding pocket
Not in COX1
COX2 inhibitor cannot enter the COX1
COX2 selectivity vs toxicity
Improved GI side effect
Rofecoxib/Vioxx - >270x more selective
increase risk of CV effects
These issues adhere to all COX2 inhibitors
Consequence of COX inhibition: kidney and vasculature
Inhibition of PGE2 and PGI2 synthesis in macrophages
Vasculature: Alter arteriosclerosis plaque formation from COX2 (Atherogenesis): Myocardial infarction, stroke
Kidney: Increase BP
Risk: Myocardial infarction, stroke, hypertension, heart failure
RA and NSAIDs, potential new therapeutics
Good, not efficacious for all patients
Upstream targeting: goal to reduce cytokines inflammatory activity like TNF-alpha
Antibodies for RA
mAbs - preferred for use
more homogenous than polyclonal
PK/PD more reproducible
mAbs raised against inflammatory cytokine - can have therapeutic effects
Poly vs mono clonal
Poly - each Ab is produced by different B cell lineage -from animals
Mono - accessed by cloning specific B cell, fused with immortalized cell line
Ab types
omab - fully mouse
ximab - chimeric
-zumab - humanized
-umab - fully human
mAb production
mAb are often first developed in mice
Animal mAb - elicit unwanted immune response in humans
mAb of animal origin are engineered to mostly have human domains
Action of infliximab, adalimumab, golimumab
Treating TNF-alpha inflammation in RA
anti-TNF-alpha therapy bind to TNF alpha
Do not bind TNGa receptor
Reduced TNFa signalling
Decrease inflammat. cytokine production by immune cells/macrophages
Broadly immunosuppressive - opportunistic infections
Reduce inflammation at arthritic points
Recombinant proteins therapy
Alternate RA treatment - TNF binding domain of receptor TNFR –> to Ab Fc
Fusion of Fc increases half-life
Etanercept
Chimeric protein binds soluble TNFa, inactivates
Fusion/recombinant protein
Paracetamol action
- reducing agent in peroxidase COX site
- Deacetylation of paracetamol in CNS –> Conjugate with AA –> AM404 –> inhibits endocannabinoid reuptake
Dinoprostone, Dinoprost, Carboprost
PGE2 PGF2a –> oxytotic agents
Treat Postpartum hemorrhage
Terminate pregancy at any stage - uterine contr.
t1/2 - short, limit usefulness
Synthetic analogues - longer T1/2 - Carboprost
1. Dinoprostone: PGE2 - only one with ketone
2. Dinoprost: PGF2a
3. Carboprost: PGF2a analogue
Alprostadil, what for, function, half life
PGE1
second line treatment for ED
Injected
Vasodilation
inhibit platelet aggregation
useful for infant congenital heart disease
T1/2 - 5-10 min
Misoprostol
Synthetic derivative PGE1
Longer 1/2 - + methyl group
Prevent peptic ulceration - oral dosing
Prevent gastric acid production by parietal cells
counteract GI effects of NSAIDs
Epoprosteol, action, half life, derivatives
Prostacyclin - PGI2
Treat pulmonary hypertension via vasodilation
Prevent platelet aggregation
Short 1/2 life: 3-5 min
Derivatives: Iloprost 30 min
Treprostinil 4H
