Transcript P450s is a weapon in plant

Are humans really are
what they eat?
Complexity of human drug
metabolism
by Olga Trubetskoy
Terminology
 Metabolism:
(Gk: metabole: change)
 Xenobiotics: xeno (Gk: foreign)… biotics
 Inhibition (Latin inhibitus, ): to prohibit from
doing something
 Induction (Latin inducere): to induce: to
call forth or bring about by influence or
stimulation
 Cytochrome P450s (CYPs)
P450s is a weapon in plant-animal chemical
warfare
“We are continually under threat from
chemical warfare in the guise of foreign
compounds in our diet and environment,
odorants, drugs and our bodies’ own waste
chemicals. CYP450s are a vital part of
defense system which reduce the toxicity of
potentially damaging chemicals and
facilitate their excretion”
- B. Burchell
Drug metabolism process (defense
mechanism against plants’ toxins)
P450
Food
Toxin
Individual’s metabolic signature

An individual exposure to food and environmental
compounds leaves a “metabolic signature” in our
body, changing the way we are interacting with
our environment
 Many factors, including genetic, environmental, in
uterus exposure, life style, diet and eating habits
contribute to a “metabolic fingerprint map” unique
for each individual organism
 This “metabolic signature” may serve as a basis
for the personalized drug therapy
Why is it important to know you
“metabolic signature”?
 Adverse
reactions to prescription drugs
are killing about 106,000 Americans each
year -- roughly three times as many as are
killed by automobiles.
 This makes prescription drugs the fourth
leading killer in the U.S., after heart
+
+
disease, cancer, and stroke
 What is behind adverse drug reactions
Why do you need to know your metabolic
profile (“metabolic signature”)?


This information may save your life!!!!!
Drug-drug and drug/food interactions are one
of the leading cases of patients’ mortality
 What
drugs to prescribe/avoid and dose
 What combination of drugs to avoid
 How your behavior affects your metabolism
 Do you really need “a pill”?
Get to know your P450s: body’s
own biochemical weapon

“Weapon’s” design:
P450s: where they are involved
Metabolism of xenobiotics*:
• toxification
• detoxification
• production of intermediate metabolites
(active, inactive, toxic)
* xenobiotics - non-biological compounds prevalent in the environment,
including drugs, nutrients, herbal and plant food components,
odorants, toxins, carcinogens and mutagens
Main P450s in drug metabolism
Major classes of “weapons” (P450s)
Families
CYP1 CYP2 CYP3
CYP3A, 2D6, 2C9, 2C19, 1A2, 2E1
Variability of drug clearance
(how fast drug is eliminated)
P450
enzyme
1A
2C
2D6
2E1
3A4
Extent of
variability
~40-folds
25-100-folds
>1000-fold
~20-fold
~20-fold
Simulated effect of P450 induction
Simulated effect of P450 inhibition
Do we have control over our own
weapons?
Levels of complexity in drug metabolism
response:

Genetics
 Epigenetic





In uterus exposure
Age, sex, disease
Diet and nutrition
Exposure to environmental toxins
Psychological factors
Control over sources of variability
(on/off switch programming)


Genes - individual, ethnic (initial conditions)
Physiology:
age, sex, diseases (uncontrolled conditions)
 nutrition and diet, alcohol and smoking, style of
life (partial control)
 Environment (environmental toxins, mutagens
carcinogens) (partial control?)


Psychology– anything will work in 40%
cases (placebo effect) – may be?
Genetics: P450 polymorphism
CYP2D6
PM (poor metabolizer) - inactive or absent enzyme
EM (extensive metabolizer) - at least 1 functional allele
UM (ultrarapid metabolizer) - multiple copies (up to 13) of
CYP2D6 gene
Frequency of PM phenotype:
Caucasian ~12 %
African-American ~1 - 3%
Asian <1 %
Frequency of EM phenotype:
Ethiopian ~13 %
Spanish ~3.5 %
Can you influence your genes?
The most interesting example: high expression of CYP2D6 in
many persons of Ethiopian and Saudi Arabian origin. 2D6 is
not inducible, so these people have developed a different
strategy to cope with the (presumed) high load of toxic
13
alkaloids in their diet - multiple copies of the gene (up to……)
Changing the diet (moving to Sweden) changed their CYP2D6
phenotype to 1 (not genotype).
Effect of fast metabolism may be dual - many antidepressants
and neuroleptics are quickly become ineffective. Conversely,
prodrugs will be extensively activated - codeine will be turned
into morphine almost immediately.
Others: through induction CYP2C9, 2D6, 2C19, 3A4
Interplay between nuclear receptors (NR), their
ligands and CYP450s
P450
Xeno-,
Endobiotics
X, E
P450 genes
On
off
NRs
On
off
Other genes
XO, EO metabolites
How dietary composition can
modulate on/off switch
 Unlike
that of other animal species, the human
diet is extremely variable among individuals.
 The compositions of diets vary according to
availability, religion and the method of
preparation
Which P450 enzymes are being
affected
Nutrition
1A1; 1A2; 2E1; 3A4, 5
Smoking
1A1; 1A2
Alcohol
2E1
Drugs
1A1; 1A2; 2A6; 2B6; 2C; 2D6; 3A3, 3A4,5
Enviroment
1A1; 1A2; 2A6; 1B; 2E1; 3A3, 3A4,5
Genetic
1A1; 2A6; 2C9, 19; 2D6; 2E1
Polymorphism
Does it matter if you had a glass of
coffee, grapefruit juice or milk for
breakfast? What else?







Spices (saffron, cumin, ginger)
Flavonoids (soy, red wine)
Fruits (bergamottin – grapefruit juice)
Other herbs: St. John’s Wort
Cruciferable vegetables (sprouts, cabbage) due
to a presence of indols
Caffeine
Smoking (benzopyrene)
CYP1A induction by flavonoids
1 bottle
2 glasses
Curry
Red wine
(good wine
stored in brown bottle)
Food/spices modulate P450 activity
CYP3A4
Onion ,
garlic
Hot pepper
Root beer
CYP2E1
Cooking style modulates P450
activity
Individuals who ate a charcoal-broiled 8ounce hamburger at lunch and a 6-ounce
steak for dinner each day for 4 days had
>80% lower plasma concentrations of
phenacetin compared with those who ate
their usual home diet
A high-protein–low carbohydrate diet for 2
weeks increases the metabolism of
caffeine and aminopyrine
Grapefruit juice modulates (inhibits)
CYP3A4 activity
Effect of bergamottin on
CYP3A4
Drug clearance (felodipine)
500
%
% remaining CYP3A4
activity
100
50
0
0.0
1.0
10.0
100.0
250
0
No GP
1 glass GP juice
Bergamottin, uM
Bergamottin (present in grapefruit skin only)
Diet modulate P450 activity
Alcohol modulates P450 activity

Alcohol (dual effect– beneficial from red wine
flavonoids and induction from ethanol exposure)
 Alcohol – induced toxicity of acetaminophen
(Tylenol) Acetaminophen in small amounts is
metabolized by glucuronidation and sulfation.
Larger ingestions result in production of a toxic
metabolite N-acetyl-p-benzoquinoneimine (NAPQI)
by P450. The NAPQI is normally detoxified by
glutathione. However, chronic alcoholism depletes
glutathione, and also induces P450 to increase
toxicity. Thus, previous chronic alcohol ingestion
increases the risk for acetaminophen toxicity.
Smoking modulates P450 activity

Polycyclic hydrocarbons in cigarette smoke
induce the metabolism of CYP1A substrates as
a result of CYP1A induction
 The average content of CYP1A in the liver
biopsies from smokers (16.3 pmol/mg of protein)
was significantly higher than that from
nonsmokers (4.7)
 Theophylline, caffeine, fluvoxamine, clozapine,
and olanzapine clearance is significantly
increased in smokers compared with
nonsmokers
Herbal supplements modulate
P450 activity
 St.
John’s Wort (Hypericum perforatum)
extracts, preparations that are used in the
treatment of depression, inhibit CYP1A2,
CYP2C9, CYP2C19, CYP2D6, and CYP3A4
 Ginseng (CYP1A1, 1A2, 1B1)-inhibition
 The Licorice Root derived Isoflavan Glabridin
inhibits P450s 3A4, 2B6, and 2C9
Multiple drug interactions modulate
P450 activity
A 63 year old man receiving medication for major
depression showed he boarded a plane in Toronto to fly to
London. On arrival he was unrousable. In his Carry-on bag
he had Mefadazone (for depression), Ketoconazole (for
fungal infection) and Triazolam (an antipsychotic also used
for insomnia). All three of these drugs bind to CYP3A4.
Ketoconazole inhibits CYP3A4 and caused the other two
drugs to become overdosed during 6 hr flight (sitting still is a
factor).
Ketoconazole
CYP3A4
+
+
Triazolam
Mefadazone
Overdose
Do our eating (and other) habits
leave marks (metabolic signatures)
in our drug metabolism landscape?
Prescriptions based on genotype or
phenotype?
 E.g.,
do we need to know only initial
conditions (your genes) or the final picture
(on/off switch)?
 Can we regulate this complex picture?
 To a what degree?
 And if we can, then….
Can one do things right just for
himself?
 Presence
of drug metabolites in soil and
underground waters (contamination)
 Global environmental exposure
 Are all these factors triggers for human
adaptation?