Ecosinoids Flashcards
Alprostadil (impotence and erectile dysfunction)
Prostaglandin
PGE1
Alprostadil (impotence and erectile dysfunction)
Site of action
corpus cavernosum smooth muscle
Alprostadil (impotence and erectile dysfunction)
Mechanism of Action
PGE1 analog thatworks via the EP2/4 receptors to increase cAMP which relaxes trabecular smooth muscle and dilates cavernous arteries leading to entrapment of blood
Alprostadil (impotence and erectile dysfunction)
Receptor
EP2 Receptor
PGE1 works on EP2 receptor
Alprostadil (impotence and erectile dysfunction)
Major adverse effect
priapism, erection lasting over 6 hours
Two therapuetic uses of Alprostadil
- Impotence and Erectile Dysfunction when PGE1 acts on EP2 receptor on corpus cavernosum smooth muscle causing an increase in cAMP
- Temporary Maintenance of patent ductus arteriosus when PGE1 acts on EP2 receptor on ductus arteriosus smooth muscle leading to increase in cAMP
Alprostadil (maintenance of patent ductus arteriosus)
Prostaglandin
PGE1
Alprostadil (maintenance of patent ductus arteriosus)
Site of Action
ductus arteriosus smooth muscle
Alprostadil (maintenance of patent ductus arteriosus)
Mechanism of Action
PGE1 analog that increases cAMP via EP2 receptor which relaxes ductus arteriosus smooth muscle
Alprostadil (maintenance of patent ductus arteriosus)
Adverse effect
apnea
Two therapeutic uses of Bimatoprost
- glaucoma
2. Eyelash hypotrichosis
Bimatoprost (glaucoma) prostaglandin
Prostamide F2a
Bimatoprost (glaucoma) Site of action
trabecular and uveoscleral aqueous humor outflow pathways
Bimatoprost (glaucoma) Mechanism of action
stimulation of specific Prostamide F2a receptor resulting in changes in genes that remodel cells to increase drainage
Bimatoprost (glaucoma) major adverse effect
increase length and number of eyelashes
Bimatoprost (eyelash hypotrichosis) Prostaglandin
Prostamide F2a
Bimatoprost (eyelash hypotrchosis) Site of action
hair follicles of eye
Bimatoprost (eyelash hypotrichosis) Mechanism of action
Stimulation of specific Prostamide F2a receptor causing increase in anagen phase of hair cycle
Two therapeutic uses for Carboprost
- Pregnancy termination
2. To control postpartum hemorrhage
Carboprost (pregnancy termination) Prostaglandin
PGF2a
Carboprost (pregnancy termination) Site of action
uterine smooth muscle
Carboprost (pregnancy termination) mechanism of action
increase in Ca via FP receptor causing uterine contraction
Carboprost (pregnancy termination) Major adverse effect
uterine rupture
Major adverse effect of bimatoprost (eyelash hypotrichosis)
eye redness, itching
dinoprostone therapeutic functions
- cervical ripening in pregnancy
2. early pregnancy termination
dinoprostone (cervical ripening in pregnancy) prostaglandin
PGE2
dinoprostone (cervical ripening in pregnancy) Site of action
cervix
dinoprostone (cervical ripening in pregnancy) Mechanism of action
- activation of collagenase via EP4 receptor which increases cAMP
- relaxes cervical smooth muscle
dinoprostone (cervical ripening in pregnancy) major adverse effect
uterine rupture
dinoprostone (early pregnancy termination) prostaglandin
PGE2
dinoprostone (early pregnancy termination) Site of action
uterine smooth muscle
dinoprostone (early pregnancy termination) Mechanism of action
EP1 mediated increase in Ca
OR
EP3 mediated decrease in cAMP
causes uterine contractions
dinoprostone (early pregnancy termination) Major adverse effect
uterine rupture
Epoprostenol protaglandin
PGI2
Epoprostenol site of action
Pulmonary artery smooth muscle
Epoprostenol Mechanism of action
increase in cAMP via IP receptor which dilates the pulmonary artery vascular smooth muscle
Epoprostenol major adverse effect
GI related and potential drug interations with other hypertensive therapy or anti-platelt therapy
Epoprostenol therapeutic use
idiopathic pulmonary arterial hypertension
misoprostol prostaglandin
PGE1
misoprostol site of action
parietal cell
misoprostol Mechnaism of action
PGE1 analog that suppresses gastric acid secretion via decrease in cAMP via EP3 receptor
misoprostol major adverse effect
diarrhea
CONTRAINDICATED IN PREGNANCY
misoprostol therapeutic use
replacement therapy for prevention of ulcers caused by long term administration with NSAIDs
take 4x a day
In humans what is the most abundant precursor of ecosinoids
arachidonic acid
Describe the biosynthesis of ecosinoids- release of arachidonic acid
- Arachidonic acid is the precursor and it is found in very low concentration in the blood bc it is bound to a phospholipid
- Phospholipase 2 (PLA2) cleaves the Sn-2 ester bond of membrane phospholipids
- this is Ca dependent
How do glucocorticoids suppress PLA2
they induce annexin-1 (lipocortin) which suppresses PLA2 activity
How many isoforms exist of COX
2
How many functions does each isoform of COX have
- oxygenase function and peroxidase function
SO there are ______- distinct ______ at _______ distinct __________ on both COX proteins
There are two distinct activities at two distinct active sites on BOTH COX proteins
2 Actions of COX
- oxygenates and cyclizes the free arachidonic acid to form
cyclic endoperoxide PGG2
- Occurs at cyclooxygenase active site of enzyme
*Site where NSAIDs bind - Peroxidase activity to reduce PGG2
to PGH2
-Occurs at peroxidase active site of enzyme
Where do NSAIDs bind
at the cyclooxygenase active site of the COX enzyme
What is the main difference between COX1 and COX2
-COX 1 is constitutive it is present in all tissues
- COX 2 is inducible. It has a promoter region that binds transcription factors. it is commonly seen in inflammation
- Nf-κB, C/EBP, ERK1/2, MAPK
Name the four prostaglandins
PGE2
PGD2
PGF2a
PGI2
Name the Thromboxane
TxA2
What are the 3 main things that Arachidonic Acid Can be turned into an what enzyme class makes that happen
- Leukotrienes when acted upon by 5-lipoxygenases
2. Prostaglandins and Thromboxanes when acted upon by Cyclooxygenases (COX)
Lipoxygenases
Also which is the most important and why
-family of cytosolic lipoxygenases that catalyze the
oxygenation of fatty acids to corresponding lipid
hydroperoxides
-lipoxygenases differ in specificity for placing the
hydroperoxy group, and tissues differ in the
lipoxygenase(s) they contain
**5-lipoxygenase is the most important because it produces Leukotrienes
FLAP
5 lipoxygenase activating protein
5-lipoxygenase inhibitor
Zileuton
Leukotriene receptor
antagonist
Zafirlukast -DOES NOT INHIBIT BIOSYNTHESIS -Inhibits the effect of the CYS-containing Leukotrienes (LTC4, LTD4, LTE4) meaning all except for LTB4
Which Leukotrienes increase vascular permeability
LTC4 and LTD4
Which Leukotrienes cause bronchoconstriction
LTC4 and LTD4
Which Leukotrienes serve as chemoattractant for neutophils
LTB4
Which Leukotrienes are increased in allergies and asthma
all
Zileuton
Inhibits 5-lipoxygenase
leads to No production of any LTs
-Not appropriate or indicated for the reversal of bronchospasm in acute asthma attacks
Zafirlukast
- Cysteinyl leukotriene receptor antagonist
- No effect on LTB4
Describe the catabolism of ecosanoids
rapidly inactivated
-95% of PGE1 is inactivated in one pass through the lungs
Prostaglandins/Thromboxane interact with what type of receptors
GPCRs therefore their effects involve secondary messengers
Receptor and second messenger
TXA2
TP and Ca mobilization
Receptor and second messenger
PGF2a
FP and Ca mobilization
Receptor and second messenger
PGE2
EP1/EP3 Ca mobilization
EP2/EP4 increase cAMP
Receptor and second messenger
PGI2
IP increase cAMP
Receptor and second messenger
PGD2
DP1 and DP2 increase cAMP
Leukotriene LTB4 causes
chemotaxis
Effector system=Increase intracellular
calcium
Leuktorienes LTC4 & LTD4 & LTE4 cause
-Bronchoconstriction
-Increase vascular
permeability
Effector system=Increase intracellular
calcium
PGE2 and PGI2 and peripheral pain
- act through specific GPCR
- sensitive pain receptors
- lead to hyperalgesia
How do PGs cause pain
they decrease the threshold of pain so that lower levels of other mediators are able to cause pain
sometimes when levels of PGs are high enough they can cause pain alone through a specific GPCR
Sequence of events for a fever
- increased formation of
cytokines
2 increases synthesis of PGE2
in areas of brain associated with temperature control
3 increases cAMP and
triggers hypothalamus to elevate body temperature
4 Hypothalamus regulates the
set point at which body temperature maintained = fever
Ecosinoids in Platelets
-Activation of platelet membrane PLA release of arachidonic acid and its metabolism to thromboxane by COX-1 (platelets make thromboxane specifically TXA2)
THEN
-TXA2 induces platelet aggregation
◦ Acts on TP receptor
◦ Increase in intracellular calcium
TXA2 induces
platelet aggregation
◦ Acts on TP receptor
◦ Increase in intracellular calcium
Activation of endothelial membrane PLA2 causes release of arachidonic acid which is then metabolized by COX1 and COX2 into…..
Prostacyclin PGI2
What does PGI2 do?
-PGI2 is formed when endothelial membrane PLA2 releases arachidonic acid which is then metabolized by COX 1 and COX2 into PGI2 (Prostacyclin)
- PGI2 inhibits platelet aggregation
- It stimulates IP receptors and INCREASES cAMP
-PGI2 causes vasodilation via IP receptors and INCREASES cAMP
What synthesizes PGI2
endothelial cells (to inhibit platelet aggregation)
Role of PGI2 in uterus
- early pregnancy-keeps uterus in quiescent state
- relaxation via IP receptors and increases cAMP
Role of PGE2 in uterus
- initiation and progression of labor
- induces uterine contractility via EP1/EP3 mediated increase in calcium
- Mediates cervical ripening via EP2/Ep4 mediated increase in cAMP
Role of PGF2a in uterus
-contracts uterus during labor via FP receptor mediated increase in Ca
How does pregnancy influence COX
Pregnancy induces COX1 and COX2 which increase PGI2, PGE2, and PGF2a
Effect of PGF2a on the non-pregnant uterus
contributes to symptoms of primary dysmenorrhea (cramps)
disruption of the uterine membrane during mensration releases AA increasing PG synthesis via COX 1 and COX2
What two prostaglandins are vasodilators
PGE2 and PGI2
But in some cases PGE2 is a vasoconstrictor when it acts on a different receptor (EP1/EP3) which increases Ca and inhibits cAMP
What are two vasoconstrictors
PGF2a and TXA2
Prostaglandins in the kidneys
PGE2 and PGI2 increase renal blood flow and promote diuresis and natriuresis
Which os the following COX1 or COX2 is more important in disease in the kidney
COX2 (there is constituitive expression of COX2 in the macula densa cells, an there is a relationship between COX2 and PG mediated renin release)
Describe the role of PGs in blood pressure regulation
LOCALLY produced vasodilator PGs tend to predominate.
- PGE2 acts through EP4 (and EP2) to increase cAMP
- PGI2 acts through IP to increase cAMP
- they serve to counteract the effect of circulating vasoconstrictor autocoids (like angtiotensinII)
-they work to maintain blood flow to vital organs like the kidney, and increase Na and H2o excretion
How do prostaglandins influcence Na and H2 excretion
increase
During fetal life, the ductus arteriosus is
a normal structure that
allows most of the blood leaving the right ventricle to bypass the pulmonary circulation and pass into the descending aorta.
what maintains patency of the ductus arteriosus during fetal life (keeps it open)
PGs specifically PGE2.
it causes relaxation via the EP4 receptor (cAMP) and COX2
Function of Leukotrienes
bronchoconstriction and chemotaxis
Which COX is important in synthesis of cytoprotective PGs (PGs that protect lining of GI system)
COX1
Which PGs inhibit gastric acid secretion, and via which receptors
PGE2 (EP2/4) and PGI2)
Role of PGs in gastric ulceration
they suppress gastric ulceration
Name two reasons for why Prostaglandins have limited therapeutic use
- Significant adverse effects-PGs do so many different things all over the body there is great potential for adverse effects
- Short Half Lives in circulation-PG analogs that have chemical structures that prevent metabolism by 15-OH dehydrogenase and Delta 13-PG reductase have been developed
Carboprost (control postpartum hemorrhage) prostaglandin
PGF2a
Carboprost (control of postpartum hemorrhage) Site of Action
uterine smooth muscle
Carboprost (control of postpartum hemorrhage) mechanism of Action
increase in Ca via FP receptor causing uterine contraction
Carboprost (control of postpartum hemorrhage)
adverse reaction
uterine rupture