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Owenpharm Block 2 > Eicosanoids > Flashcards

Eicosanoids Flashcards

1
Q

What is the relative availability of Arachidonic acid in cells?

A

Low

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2
Q

What enzyme releases arachidonic acid from phospholipids?

A

Phospholipase A2

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3
Q

Cyclooxygenase converts arachidonic acid to what?

A

PGG2

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4
Q

Peroxidase converts PGG2 into what?

A

PGH2

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5
Q

Arachidonic acid is converted to PGG2 by what enzyme?

A

Cyclooxygenase

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6
Q

PGG2 is converted to PGH2 by what enzyme?

A

Peroxidase

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7
Q

Where is COX-1 expressed?

A

In all tissues

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8
Q

Where is COX-2 commonly seen?

A

In inflammation

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9
Q

To what extent are the structures of COX1 and COX2 similar?

A

60%

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10
Q

How is the active site of COX2 different from COX1

A

It is bigger and more accessible

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11
Q

What are the various fates of PGH2?

A
  1. PGE2
  2. PGD2
  3. PGF2a
  4. PGI2
  5. TxA2
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12
Q

What is the structural difference between E1 and E2?

A

The number subscript refers to number of double bonds. E2 has two double bonds.

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13
Q

Cyclooxygenases convert Arachidonic acid into what two substances?

A

PGs and Thromboxanes

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14
Q

5-lipoxygenases convert Arachidonic acid into what substance?

A

Leukotrienes

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15
Q

What is the prototype 5-lipoxygenase inhibitor?

A

Zileuton

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16
Q

What effect does Zileuton have and how does it achieve this?

A

Decreased production of Leukotrienes

Achieved by inhibition of 5-LO

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17
Q

What is the prototype Leukotriene receptor antagonist for this class?
What is its effect on Leukotriene biosynthesis?

A

Zafirlukast

It has no effect on biosynthesis

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18
Q

What specific types of leukotrienes does Zafirlukast inhibit the effects of?

A

CYS-containing Leukotrienes

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19
Q

How is Zileuton administered?

A

orally

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20
Q

How is Zileuton metabolized?

A

CYP enzymes (CYP1A2, 2C9, 3A4)

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21
Q

What is the mechanism of action for Zileuton?

A

It inhibits 5-LO and prevents any production of Leukotrienes

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22
Q

What is the only adverse effect of Zileuton?

A

Increases liver enzymes in some

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23
Q

What is the therapeutic use of Zileuton?

A

Prophylaxis and chronic treatment of asthma

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24
Q

What is the common route of administration for Zafirlukast?

A

Oral

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25
Q

What enzyme metabolizes Zafirlukast?

A

CYP2C9

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26
Q

What is the mechanism of action for Zafirlukast?

A

Cys-Leukotriene receptor antagonism

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27
Q

What is the therapeutic use for Zafirlukast?

A

Prophylaxis and chronic treatment of asthma

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28
Q

Describe the inactivation of eicosanoids.

A

Rapid inactivation. Infusion of PGE1 is 95% inactivated through one pass in lung.

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29
Q

There are two steps to the catabolism of eicosanoids. Describe them.

A
  1. Initial step is rapid - 15OH dehydrogenase oxidation and PGdelta13 reductase reduction
  2. Second step is relatively slow - beta oxidation of side chains
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30
Q

What are the two primary second messengers for prostaglandin and thromboxane receptors?

A

Ca2+ and cAMP

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31
Q

Leukotriene LTB4 affects what receptors and to what effect? What second messenger is used?

A

BLT1 and BLT2
chemotaxis
Ca2+

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32
Q

Leukotrienes LTC4, LTD4, and LTE4 affect what receptors and to what effect?
What second messenger is used?

A

cysLT1 and cysLT2
bronchoconstriction and increased vascular permeability
Ca2+

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33
Q

PGE2 and PGI2 have what effects in the periphery regarding pain? (4 items)

A
  1. Sensitize pain receptors
  2. Lower the threshold of nociceptors of C fibers
  3. Hyperalgesia
  4. Potentiate pain-producing activity of other mediators
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34
Q

Where in the CNS is there COX2 expression?

To what end?

A

In the spinal cord

May contribute to neuropathic pain

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35
Q

Do PGs alone cause pain?

A

Only in high concentrations. They mainly lower the threshold for pain for other mediators.

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36
Q

How do PGs cause fever?

A

Cytokine formation increases synthesis of PGE2 which increases cAMP and triggers hypothalamus to elevate body temperature

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37
Q

How is TXA2 produced in platelets?

A

activation of platelet membrane stimulates PLA2 to release arachidonic acid which is metabolized by COX1 into thromboxane

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38
Q

What effect does TXA2 have?

A

Induction of platelet aggregation by acting on TP receptor which increases intracellular calcium

39
Q

How are prostaglandins produced in the endothelium?

A

Activation of endothelial membrane PLA2 causes release of arachidonic acid and its metabolism to prostacyclin (PGI2) by COX1 and COX2

40
Q

What effect does PGI2 have on the endothelium and how?

A

Inhibition of platelet aggregation by stimulation of the IP receptors and an increase in cAMP

41
Q

What effect does TXA2 have on blood vessels and how?

A

Induction of vasoconstriction by acting on the TP receptor in vascular smooth muscle resulting in an increase in intracellular calcium

42
Q

What effect does PGI2 have on blood vessels and how?

A

PGI2 causes vasodilation by stimulation of IP receptors with an increase in cAMP.

43
Q

Is PGI2 synthesized by platelets or endothelial cells?

A

Endothelial cells

44
Q

What role does PGI2 have in pregnancy?

By what mechanism?

A

Keeps uterus in quiescent state

Relaxation is via IP and increase in cAMP

45
Q

What role does PGE2 have in pregnancy?

By what mechanism?

A

Initiation and progression of labor
Induction of uterine contractility through EP1/EP3 mediated increase in calcium
Mediation of cervical ripening by EP2/EP4 type increase in cAMP

46
Q

What role does PGF2a have in pregnancy?

By what mechanism?

A

Contracts uterus during labor through FP mediated increase in calcium

47
Q

Which prostaglandin contributes to the symptoms of primary dysmenorrhea?

48
Q

What is the mechanism for the PG contribution in dysmenorrhea?

A

Disruption of uterine membranes causes release of AA and increase PG synthesis by COX1 and COX2.

49
Q

What effect does PGF2a have during dysmenorrhea?

A
  1. Contraction of uterus
  2. Contraction of GI smooth muscle
  3. Sensitization of afferent pain fibers
50
Q

IV administration of PGE2 or PGI2 causes a fall in blood pressure through what receptors?

51
Q

What two PGs are vasodilators?

A

PGE2 and PGI2

52
Q

What two PGs are vasoconstrictors?

A

TXA2 and PGF2a

53
Q

What is peculiar about PGD2 in its relationship to blood vessels?

A

It is usually a vasodilator except in pulmonary circulation where it is a constrictor.

54
Q

When thinking about role of PGs in blood pressure regulation what two things should be remembered?

A
  1. Locally produces vasodilator PGs tend to predominate

2. They serve to counteract the effect of circulating vasoconstrictor autocoids like ANGII

55
Q

How do PGs relate to the Kidney?

A

Vasodilator PGs like PGE2 and PGI2 promote increased renal blood flow

56
Q

Which PG maintains the PDA? By what receptor? By which COX enzyme?

A

PGE4. Via EP4 receptor. By COX2.

57
Q

What causes a reduction in PGE2 in neonates and a closure of the PDA?

A
  1. Loss of placenta (major source of circulating PGE2 invitro)
  2. Decrease in PGE2 receptors (EP4/dilator subtype)
  3. Increase in pulmonary blood flow at birth (major site of PG catabolism)
58
Q

What are the roles of the different PGs in bronchial smooth muscle?

A

PGF2a & PGD2 constrict
PGE2 relaxes
TXA2 constricts
PGI2 relaxes

59
Q

What two roles do Leukotrienes have in the lungs?

A
  1. Bronchoconstriction

2. Chemotaxis

60
Q

What two effects do PGs have on the kidneys?

A
  1. Modulation of renal blood flow

2. Regulation of urine formation via direct effect on renal tubules

61
Q

Is COX1 or COX2 more important in renal disease?

62
Q

Which two PGs are most active in the kidneys?

What do they do?

A

PGE2 and PGI2

Increase blood flow and promote diuresis and natriuresis

63
Q

Which COX enzyme is most active in GI system?

64
Q

PGE2 (EP3) and PGI2(IP) do what in the stomach?

A

Inhibit gastric acid secretion and increase gastric mucosal blood flow

65
Q

What three additional effects does PGE2 have on the GI system?

A
  1. Stimulation of viscous mucucs
  2. Stimulation of bicarb secretion
  3. Contraction of GI smooth muscle
66
Q

How do PGE2 and PGI2 promote inflammation?

A

Directly increase blood flow and indirectly enhance edema formation and leukocyte infiltration. This increases other mediators that reach the site of injury.

67
Q

How do Leukotrienes promote inflammation?

A
  1. slow reacting substance of anaphylaxis (SRS-A) released from mast cells
  2. LTC4/LTD4 increase vascular permeability
  3. LTB4 is a chemoattractant for neutrophils
68
Q

Which cancers are associated with an increased concentration of PGs?

A
  1. Colon cancer
  2. Breast cancer
  3. Renal cell adenocarcinoma
69
Q

What possible role do PGs have in cancer?

A

Induction of cellular proliferation

70
Q

What PGE2 agent is used for cervical ripening?

A

Dinoprostone

71
Q

How is DInoprostone administered for cervical ripening?

A

Cervical gel 0.5mg

72
Q

What is the mechanism of action for Dinoprostone for cervical ripening?

A

EP4 receptor increase in cAMP resulting in:

  • promotion of cervical ripening
  • breakdown of collagen
  • activation of collagenase
  • relaxation of cervical smooth muscle
73
Q

What adverse effects are related to Dinoprostone?

A

Nausea/Vomiting/Diarrhea
Fever
Uterine rupture

74
Q

What is the therapeutic use for higher dose Dinoprostone and what is the method of administration?

A

Termination of early pregnancy

Vaginal suppository 20mg

75
Q

What is the mechanism of action for higher dose Dinoprostone for termination of pregnancy?

A

EP1/EP3 receptor mediated calcium release resulting in uterine contraction.

76
Q

What PGF2a related drug is used for the termination of pregnancy or control of postpartum hemorrhage?

A

Carboprost

77
Q

What is the mechanism of action of Carboprost?

A

FP mediated calcium release resulting in uterine contraction

78
Q

What PGE1 analog is used as “replacement” therapy for prevention of ulcers caused by NSAIDs

A

Misoprostol

79
Q

What is the mechanism of action for Misoprostol?

A
  • EP3 mediated reduction in cAMP resulting in decrease in gastric acid secretion, increase in mucin, increase in bicarb
  • EP2/4 mediated increase in cAMP resulting in increased mucosal blood flow
80
Q

What are the adverse effects associated with Misoprostol?

A

Diarrhea, Termination of pregnancy

81
Q

What PGE1 related drug is used for Impotence and erectile dysfunction or temporary maintenance of PDA?

A

Alprostadil

82
Q

How is Alprostadil administered for impotence?

A

Intracavernous injection

83
Q

How is Alprostadil administered for maintenance of PDA?

A

IV infusion

84
Q

What is the mechanism of action of Alprostadil for impotence?

A

Induction of erection through relaxation of trabecular smooth muscle and dilation of cavernosal arteries via EP2/4 mediated increase in cAMP

85
Q

What is the mechanism of action for Alprostadil for maintenance of PDA?

A

EP2/4 receptor increase in cAMP resulting in relaxation of ductus arteriosus smooth muscle

86
Q

What adverse effect occurs from Alprostadil in about 10% of neonates < 2kg?

87
Q

What PGI2 related medication is used for primary pulmonary hypertension?

A

Epoprostenol

88
Q

How is Epoprostenol administered?

A

continuous IV infusion

89
Q

What is the mechanism of action for Epoprostenol?

A

IP receptor cAMP mediated dilation of pulmonary artery vascular smooth muscle

90
Q

What are the adverse effects of Epoprostenol?

A

Nausea/Vomiting
Headache
Flushing

91
Q

What PGF2a related medication is used for Glaucoma or Eyelash hypotrichosis?

A

Bimatoprost

92
Q

What is the mechanism of action Bimatoprost in glaucoma?

A

EP2/4 mediated increase in cAMP resulting in increased outflow of aqueous humor.

93
Q

What are the adverse effects of ophthalmic Bimatoprost?

A

Eye redness, itching, change in eye color, increase in eye lashes

94
Q

What is the mechanism of action of Bimatoprost in eyelash hypotrichosis?

A

Increase in the percent and duration of hairs in the growth phase

Owenpharm Block 2 (11 decks)

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