Lec 4/5 Adrenal MedChem Flashcards
Adrenal Medulla
- Can survive without it
- Secretes Catecholamines:
-
Epinephrine / Norepinephrine
- from tyrosine
-
Epinephrine / Norepinephrine
Adrenal Cortex
-
Essential for LIFE
- G - F - R
- Z. Glomerulosa:
- Mineralcorticoid = Aldosterone
- Z. Fasciculata:
- Glucocorticoid = Cortisol
- Z. Reticularis (innermost)
- Androgens
Zona Glomerulosa
- Grape-like Cluster of cells
- OUTER MOST
- Secretes Mineralcorticoids
-
Aldosterone
- Controlled by Renin-Angiotensin
-
Aldosterone
Zona Fasciculata
- Cells in Rows or Cords
- Fat droplets in cells, seperated by Capillaries
- Cholesterol is stored here
- Secretes Glucocorticoids:
-
Cortisol
- controlled by ACTH
-
Cortisol
Zona Reticularis
- Network of branching small / dark cells
- Secretes Androgens
- controlled by ACTH
Cortisol Secretion Pathway
- Stressors / Diurnal Rhythem -> Hypothalamus
- -> CRH = corticotropin releasing hormone
- -> Pituitary
- -> ACTH -> Adrenals
- CORTISOL
- -> ACTH -> Adrenals
- -> Pituitary
- -> CRH = corticotropin releasing hormone
- Cortisol Negative Feedback to Pituitary & Hypothalmus
Adrenocorticoids
= Corticosteroids
Adrenal Cortex Steroids
aka Corticosteroids
Mineralcorticoids + Glucocorticoids
Androgens
Glucocorticoids
Cortisol = Hydrocortisone
From Adrenal CORTEX
- Essential for LIFE
- Effects are Permissive
- not directly responsible for the activity
- but NECESSARY for FULL EXPRESSION
- not directly responsible for the activity
Glucocorticoid = Cortisol
METABOLIC effects
-
Carbohydrate Metabolism
-
INCREASE supply of glucose
- gluconeogenesis
-
INCREASE supply of glucose
-
Protein Metabolism
- Reduce utilization of AA’s for the formation of protein
-
Fat Metabolism
-
INCREASE mobilization of FA’s / Glycerol from adipose tissue
- to undergo gluconeogenesis
-
INCREASE mobilization of FA’s / Glycerol from adipose tissue
Primary Steroids
- 5a-Cholestane
- 5a-Estrane
-
5a - Androstane
- -> ANDROGENS
-
5a - Pregnane
- -> Mineralcorticoids / Glucocorticoids
Naming & Numbering Cholesterol Structure
Alpha = AWAY from plane
Beta = Above / outwards
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Sterene Ring Configuration
Sterene rings assume Chair Configuration
- Changing the stereochemistry of the BACKBONE carbons
- greatly change the steroid SHAPE
-
5-Beta -> PREVENTS BINDING
- no activity
-
5-Beta -> PREVENTS BINDING
- greatly change the steroid SHAPE
StAR Protein
Rate LIMITING step in Steroid Biosynthesis
Transports Cholesterol
Cytosol -> Mitochondria
Steroid Biosynthesis Pathway Image
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Second Messengers
in Steroid BioSynthesis Pathway
All very Small & Lipophylic
Diffuse very Quickly!
-
cAMP
- -> Activates PKA
-
DAG
- -> Activates PKC
-
IP3
- -> Opens Ca2+ channels in ER
Slow Response
in Steroid BioSynthesis Pathway
-
ACTH -> GPCRreceptor
- -> Adenyl Cyclase -> cAMP released
- -> Activate/phosphorylate PKA
- -> enter the nucleus
- Nuclear Receptor bound C
- Activate Transcription of Steroids
- -> enter the nucleus
- -> Activate/phosphorylate PKA
- -> Adenyl Cyclase -> cAMP released
Cholesterol -> Pregnenolone
Occurs in the Cytosol -> Mitochondria
StAR Protein does this transportation
LYASE
once it enters the Mito -> it is then
DEDICATED to be an Adrenal Hormone
Lyase
(Desmolase)
Catalyzes cleaveavage of a Carbon-Carbon Bond
in a substrate w/ formation of 2 products by
a process other than HYDROLYSIS
ex. Oxidoreductase / Transferase
Desmolase = Specific to Steroid Synthesis
Hydroxylase
Add or Remove a HYDROXYL MOIETY
Adds -OH
Removes -OH
Hydroxysteroid Dehydrogenase
HSD
Alcohol Oxidoreductase
Non-CYP Enzyme
=O to -OH
and the reverse
Reactions that occur in the MITOchondria
Cholesterol - lyase -> Pregnenolone
Deoxycorticosterone - aldosterone synthase -> Aldosterone
11-Deoxycortisol -Hydroxylase -> Cortisol
Mineralcorticoid Biosynthesis
- Occurs in the Zona Glomerulosa
-
lacks P450c17 expression
- = Prognenolone –/–> Hydroxypregnenolone or DHEA
- so can not become glucocorticoid or androgen
-
lacks P450c17 expression
- Can continue to become Progestrone -> Aldosterone
Mineralcorticoid Biosynthesis Pathway
Photo
Occurs in Zona Glomerulosa
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Mineralcorticoid Pathway
- Cholesterol - Lyase -> Pregnenolone
-
HSD -> Progesterone
-
Hydroxylase -> deoxycorticosterone
- Aldosterone Synthase -> ALDOSTERONE
-
Hydroxylase -> deoxycorticosterone
-
HSD -> Progesterone
- Occurs in Zona Glomerulosa
Glucocorticoid Biosynthesis
- Occurs in Zona Fasciculata
- P450c17 has impaired Lyase Activity (17-20-lyase)
- so Androgen synthesis is MINOR
- Lacks Aldosterone Synthase expression
-
so it can NOT synthesize Mineralcorticoids
- = aldosterone
-
so it can NOT synthesize Mineralcorticoids
- P450c17 has impaired Lyase Activity (17-20-lyase)
- Main product is CORTISOL
Glucocorticoid Pathway
Photo
Occurs in teh Zona Fasciculata
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Androgen Biosynthesis
- Occurs @ Zona Reticularis
- lacks significant 21-hydroxylase expression
-
can not produce
- mineralcorticoids or corticosteroids
-
can not produce
- lacks significant 21-hydroxylase expression
-
Main product is DHEA -> Androsteneidone
- which becomes Testosterone / Androgen
- in peripheral issue
- which becomes Testosterone / Androgen
P450scc
CYP11A1
Cholesterol Side Chain Cleavage Enzyme
considered a Lyase
Cholesterol -> Pregnenolone
@Mitochondria
inhibited by AMINOGLUTETHIMIDE
Aminoglutethimide main function
At HIGH Dose –> for Cushings Syndrome
-
Inhibits Cholesterol side Chain Cleavage
- = P450scc = CYP11A1 @Mitochondria
-
Blocks the FIRST STEP
- so it controls the production of CORTICOSTEROIDS
- DEADLY since you need cortex to survive
Aminoglutethimide
at Low Dose
Low dose = for Breast Cancer etc.
-
Inhibits AROMATASE (CYP19) in Peripheral tissues
- Fat / Liver / Tumor
-
Androstenedione / Testosterone from Z. Reticularis
- conversion to Estrone / 17B-Estradiol is inhibited
Trilostane
For Cushing’s Disease in DOGS
and possibly Breast/Prostate cancer
- Very structurally similar to progestrone
-
Competitively Inhibits 3B- HSD (hydroxysteroid dehydrogenase)
-
2nd tier inhibition of all 3 pathways
- -/-> progestrone / androstenedione
-
2nd tier inhibition of all 3 pathways
Ketoconazole
Antifungal agent
Second line therapy for Castration resistant prostate Cancer
- MAJOR inhibition of 17,20-Lyase
- 3rd column steps producing Androstenedione / DHEA
-
Minor inhibition of 17A & 11B - Hydroxylase
- 2nd column steps
- Final tier step to Aldosterone / Cortisol
Metyrapone
Etomidate
Steroid Enzyme inhibitor
Corticosteroid Inhibitor
- Inhibits 11B-Hydroxylase (CYP11B1) @ ER
-
–/–> Cortisol
- final step of corticosteroid synthesis
-
–/–> Cortisol
Aldosterone Synthase Inhibitors
Still in Development
Fadrozole / 3 other products in development
Spironolactone
Mineralcorticoid Receptor Competitive Antagonist
@ Distal Tubule cells of KIDNEY
- Potent Diuretic activity –> for Hypertention
-
Side effects:
- also stimulates Progestrone receptor
-
inhibits Androgen receptor
- ED / Erectile issues with males
Eplerenone
Mineralocorticoid Receptor Competitive Antagonist
@ Distal tubule cells of Kidney
Diuretic for Hypertention
- Comapared to Spiranolactone,
-
it REDUCES its binding to:
- Androgen/Progestrone Receptor
-
it REDUCES its binding to:
Mifepristone
Glucocorticoid Receptor Antagonist
for Cushing’s Syndrome
- also a Progestrone Receptor Antagonist*
- an Abortion Pill*
Mitotane
Inhibits STEROID Biosynthesis
Destroys MITO
@ Ad Cortex
palliative treatment of Adrenocortical Carcinoma
- Requires metabolic activation by the adrenal gland
- Discovered from DDD / DDT insecticides
Adrenocorticoid Metabolism
Reduction / HSD / Side chain Cleavage
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Glucocorticoid Receptor
Ligand-Activated Ranscription Factors
Expressed in MANY TISSUES
- Easily crosses the membrane (LIPOPHILIC)
- Binding domain is normally INHIBITED (bound by inhibitor)
- Hormone/Cortisol –> RELEASES the inhibitor
-
enters the nucleus
- –> Transcription occurs
-
enters the nucleus
- Hormone/Cortisol –> RELEASES the inhibitor
- Binding domain is normally INHIBITED (bound by inhibitor)
CortiSOL (Hydrocortisone)
vs
Cortisone
Cortisone = Less Active Metabolite
Also it has NO activity on the mineralcorticoid receptor
11B-HSD converts between the two
but Cortisone –/–> CortiSOL in Kidney
Mineralcorticoid Receptor
Ligand-Activated Ranscription Factors
Limited expression to
Kidney / Colon / Salivary/Sweat Glands / Hippocampus
- Easily crosses the membrane (LIPOPHILIC)
- Binding domain is normally INHIBITED (bound by inhibitor)
- Hormone/Aldosterone –> RELEASES the inhibitor
-
enters the nucleus
- –> Transcription occurs
-
enters the nucleus
- Hormone/Aldosterone –> RELEASES the inhibitor
- Binding domain is normally INHIBITED (bound by inhibitor)
Nuclear Binding Domains
- Most DNA response elements for Nuclear receptors are almost exactly the same
- for Estrogen/Progestrone/Glucocorticoid/Thyroxine receptors
- Differences for recognition are from:
- opposite reading direction
-
Amount of Nucleotides that seperate
-
3-5 bases in BETWEEN
- make the BIGGEST DIFFERENCE in translation
-
3-5 bases in BETWEEN
How do Mineralcorticoids overcome the
10FOLD difference in concentration vs Glucocorticoids??
0.05-0.20 vs 40-180 ug/ml
-
Cortisone (less active GC than CortiSOL):
- has NO activity on the mineralcorticoid receptor
- also does NOT convert back to CortiSOL in the KIDNEY
- no TYPE 2 of 11B-HSD unlike the liver
Insertion of bulky substituents** on the **β-side of the steroid does?
Abolishes
GLUCOCORTICOID ACTIVITY
no activity on mineralcorticoid activity
Insertion of bulky substituents on the α-side of the steroid does?
Does NOT abolish Glucocorticoid Activity
Significantly impairs
Mineralcorticoid Activity
Structure-Activity Relationship
Amoung Adrenocorticoids
C & D Rings
Esp Carbons 11-21 (except 14/15/19)
Are most important for receptor Binding
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3 Major Groups of Adrenal Steroids / Drugs
classified by Biological activities
-
Mineralcorticoids (aldosterone)
- Deoxycorticosterone
- Fludrocortisone
-
Glucocorticoids w/ moderate to low salt retention
- Prednisolone / Prednisone
- Cortisone / Hydrocortisone
-
Glucocorticoids w/ little or no salt retention
- Methylprednisolone
- Dexamethasone / Betamethasone
- Triamcinolone
Deoxycorticosterone
Natural MC, substrate for Aldosterone Synthase
Moderate MC Activity
no GC activity
- 1st synthesized corticosteroid
- in 1937, Nobel Prize
- Tadeusz Reichstein
Fludrocortisone
HIGH salt retention, oral for Addison’s Disease
Topical Antiinflammatory
Class = MC
- Halogen Inductive effect:
- Potent MC Activity (800x)
- some GC activity (10x)
- Prevents metabolix oxidation of 11B-OH
Cortisol (Hydrocortisone) & Cortisone
Glucocorticoid w/ Moderate-Low Salt retention
Some Anti-Inflammatory activity
- much less inflammatory activity than 1-ene forms*
- prednisolone / prednisone*
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Prednisolone & Prednisone
Δ corticoids for treatment of Rheumatoid Arthritis
GC w/ Moderate-low salt retention
4X more Anti-Inflammatory activity vs Cortisol/cortisone
- little more salt retention as well*
- 1-ene form of Cortisol/cortisone
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Δ corticoid’s Orientation & Metabolism
- Glucocorticoid Receptor prefers / Increased activity:
-
Flattened Boat > half-chair
- on the A-Ring
-
Flattened Boat > half-chair
-
Prednisolone is the active form, metabolized 3 ways:
-
20-Hydroxyprednisolone
- inactive, MAJOR pathway
- **6B-Hydroxyprednisolone
-
16a-Hydroxyprednisolone
- actually MORE ACTIVE (like a pro-drug)
-
20-Hydroxyprednisolone
Methylprednisolone
GlucoCorticoid w/ very little - NO salt retention
Inhibits CYP oxidation @ C6
6a-methyl decreases salt retention
Dexamethasone / Betamethasone
Traimcinolone / Beclomethasone
Glucocorticoid w/ very little - NO salt retention
Anti-Inflammatory
16-OH / 16-methyl helps eliminate salt retention
9a-F/Cl INCREASES Glucocorticoid Activity
16 a - OH
16a/b - methyl
6a - methyl
Substituants on steroids that:
DECREASE SALT RETENTION
ex: methylprednisolone / other GC w/ little to no salt retention
triamcinalone / betamethasone
1 - ene (double bond)
9a - F / Cl
Substituents on steroids that:
Increase BOTH Glucocorticoids & Mineralcorticoid activity
Numbering Primary Steroids
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Glucocorticoid pharmacological effects of
BLOCKING inflammatory / immune response
- Decrease permeability of capillaries - allowing less plasma and fewer lymphocytes to enter injured areas
- Depression of phagocytosis by white blood cells
- Suppression of thymus-derived lymphocytes
- Suppression of key enzymes (e.g., interleukin-1) necessary for inflammatory response