PharmSci IV Exam 4 Flashcards
What about the structure of DNA/RNA makes it susceptible to damage by electrophiles?
The purine and pyrimidine bases are nucleophilic.
Where in the central dogma does DNA damage lead to carcinogenesis?
Replication
What are the three (3) stages in the Multistage model of carcinogenesis?
- Initiation
- Promotion
- Progression
What are the three (3) critical targets in the initiation stage?
- Proto-oncogenes
- Tumor suppressing genes
- DNA Repair enzymes
What is a complete carcinogen? (3 components)
A chemical that is able to act at all stages:
- damage DNA (initiation)
- promote clonal expansion (promotion)
- cause chromosome disarrangement [clastogenesis], polyclonal growth and angiogenesis (progression)
What are the four (4) metabolic forms of a carcinogen?
- Pre-carcinogen [not electrophile]
- Proximate carcinogen [may or may not be electrophile]
- Ultimate carcinogen [electrophile, free radical, ROS]
- Non-carcinogenic metabolites
What three (3) amino acid residues are susceptible to electrophilic binding?
- Cysteine
- Lysine
- Histamine
What are three (3) modes of DNA damage?
- Inter-strand crosslink (2 electrophiles)
- Intra-strand crosslink (2 electrophiles)
- Adduct (1 electrophile)
What are four (4) protection mechanisms against DNA damage?
- Glutathione and Glutathione-S-Transferase
- Superoxide Dismutase and Catalase
- Dietary and endogenous antioxidants
- DNA repair mechanisms
What is the process of bioactivation of benzo[a]pyrene?
Ultimate carcinogen contains epoxide and dihydrodiol:
- CYP-catalyzed alkyl oxidation forms epoxide.
- Epoxide hydrolase forms dihydrodiol.
- Alkyl oxidations forms an epoxide.
What are three (3) classes of deleterious or toxic drug effects?
- Pharmacological [overactivation]
- Pathological [cell/tissue damage]
- Genotoxic [can lead to cancer]
Define toxicology
study of adverse effects o living organism
Define hazard
Possible source of danger
Define toxin
Biological hazard
Define toxicant
Human made hazard
Poison
Capable of adverse response in biological systems
What is an idiosyncratic reaction?
An undesired effect that can occur at any dose
What is the distinction between immediate and delayed undesired effects?
- Immediate is quickly seen
2. Delayed has a latent period; may be carcinogenic or teratogenic.
What is the distinction between reversible and irreversible?
For a reversible effect, removing the toxicant will reduce the adverse effects.
What are two (2) mechanisms of chemical interactions?
- Pharmacokinetic [alter ADME]
2. Pharmacodynamic [compete for target]
What are four (4) classifications of chemical interactions?
- Additivity
- Synergy
- Potentiation
- Antagonism
Define additivity
Response is the sum of two agents
Define synergy
Combined effect is greater than the sum
Define potentiation
An agent does not have a response until a second agent is present.
Define antagonism
Interference between two agents decreases total response
What are four (4) classifications of antagonism?
- Functional
- Chemical
- Dispositional
- Receptor
What is functional antagonism?
Two agents balance opposite effects.
What is chemical antagonism?
Two agents inactivate one another.
What is dispositional antagonism?
One another alters the ADME of another.
What is receptor antagonism?
Receptors compete with another for a target.
What are three (3) assumptions in dose response?
- The response is due to the chemical administered.
- The magnitude of the response is related to the dose.
- There is a means of measuring and expressing toxicity.
When quantifying dose-response, what is the distinction between individual/graded and quantal?
- Individual/graded looks at the magnitude of response in an individual.
- Quantal looks at an all-or-nothing threshold response in a population.
What does the slope of the probit plot tell you about the population?
- A steep slope indicates greater variability
2. A shallow slope indicates less variability
What are EC50 and ED50?
Concentration or dose when 50% of test group responds.
What are LC50 and LD50?
Concentration or dose when 50% of the test group dies.
What is NOAEL?
No Observed Adverse Effect Level
Define the Therapeutic Index
TI = TD50/ED50
Define Margin of Safety
MS = TD1/ED99
Define potency
The range of doses overwhich the chemical causes an increasing response.
Define maximal efficacy
The limit of the response given an increasing dose. (horizontal asymptote)
What are four (4) steps in the development of toxicity?
- Delivery
- Interaction with Target Molecule
- Cellular dysfunction/injury
- Inappropriate repair and adaption
What are four (4) examples of Ultimate Toxicants?
- Parent xenobiotics
- Metabolite (e.g. reactive electrophiles)
- Reactive Oxygen Species
- Endogenous (altered biomolecules)
What are two (2) pathways involved in the delivery of a toxicant?
- Bioactivation
2. Detoxification
What are three (3) outcomes of toxicant reactions with a target molecule?
- Dysfunction [inactivation]
- Destruction [adduct; breakdown]
- Neoantigen formation [immune system]
What are four (4) types of reaction between a toxicant and a target molecule?
- Noncovalent [reversible]
2 . Covalent [adduct formation; irreversible] - H-Abstraction [ROS]
- Electron transfer [redox; heme groups]
Describe HSAB Theory
- Soft Electrophiles prefer Soft Nucleophiles
2. Hard electrophiles prefer hard nucleophiles
Using HSAB theory, describe the susceptibility of cysteine residues.
The soft cysteine bases are susceptible to soft =O.
Using HSAB theory, describe the susceptibility of histamine residues.
The medium-soft histamine residues are susceptible to epoxides.
Using HSAB theory, describe the susceptibility of lysine residues.
The medium-soft histamine residues are susceptible to epoxides.
Using HSAB theory, describe the susceptibility of DNA/RNA bases.
The hard DNA/RNA bases are susceptible to carbocations and nitrenium ions.
What determines the injury that develops upon binding of the toxicant to the target molecule?
The role of the target molecule
What are two categories of target molecule roles?
- Cell regulation
2. Cell maintenance
What injury can develop when a toxicant affects a target molecule involved with regulation?
- Dysregulation of gene expression
2. Dysregulation of ongoing cell function
What injury can develop when a toxicant affects a target molecule involved with cell maintenance?
- Impaired internal maintenance
2. Impaired external maintenance (e.g. bleeding)
What are three (3) outcomes that occur when there is dysrepair from cellular injury?
- Oragn ailure
- Fibrosis
- Carcinogenesis
What are four (4) types of toxicity?
- Cell death/tissue injury
- Altered phenotype/function
- Immunological hypersensitivity
- Cancer
What are two (4) mechanisms of drug toxicity?
- On-target (mechanism based) toxicity
- Off-target (unintended receptor) toxicity
- Immunological (hypersensitivity)
- Biological activation
What are two (2) drug examples of on-target toxicities?
- Statins
2. Diphenhydramine
What is a drug example of an off-target toxicity?
Thalidomide
What are three (3) broad considerations when determining toxicity?
- Overdose
- Drug-drug interactions
- Adverse effects (of the drug)
What are two (2) key anatomical parts of the liver?
- Portal triad [blood enters liver]
2. Terminal hepatic vein [blood exits liver]
What are the three (3) parts of the Portal triad?
- Portal vein
- Hepatic artery
- Bile duct
What is the difference between the orientations of the lobule and the acinus of the liver? (2 components)
- The lobule is oriented with the Terminal Hepatic Vein in the center.
- The Acinus is oriented with the Portal triad in the center.
Describe the acinus (2 components)
- Centered at the portal triad,
2. Three zones of metabolic regions that are increasingly distant from blood supply.
What are notable component gradients in Zone 1 of the acinus?
- Higher O2
2. Higher Glutathione (GSH)
What are notable component gradients in Zone 3 of the acinus?
- Higher CYP
2. Higher Epoxide Hydrolase
What are four (4) notable liver injuries?
- Fatty liver [steatosis]
- Immune-mediated response
- Canalicular cholestasis
- Fibrosis and Cirrhosis
What are two (2) serum biomarkers for liver injury?
- ALT [alanine transaminase]
2. AST [aspartate transaminase]
What is a biomarker for biliary duct obstruction (cholestasis)?
ALP [alkaline phosphatase]
In the bioactivation of ultimate carcinogens, what are three (2) ways to yield the nitrenium ion?
- Oxidation of amine (CYP, NADPH, O2, H+)
- Acetylation (NAT, Acetyl CoA) on N-OH followed by leaving of acetic acid.
- Sulfation (SULT/PAPS) on N-OH followed by leaving of HOSO3-
In the metabolism of DNA-reactive metabolites, what is a detoxification mechanism?
Glutathione (GSH) + Glutathione-S-Transferase (GST)
Describe a probit plot (3 components)
- Generated from population data where the response is all-or-none.
- Constructing using standard deviations, with 1 standard deviation from the mean representing 68% of the population.
- Provides information on how a population responds to a drug at varying doses.