Exam 4 Flashcards
Are steroid hormones hydrophobic or hydrophilic? Where are the receptors that they bind? How do they effect changes in cells?
Made of cholesterol backbone, very hydrophobic, diffuse into cell through plasma membrane and bind intracellular receptors to change gene transcription.
What are examples of steroid hormone receptors and their ligands?
Glucocorticoid (GR): cortisol (dexamethasone)
Mineralocorticoid (MR): aldosterone (spironolactone)
Androgen (AR): testosterone, dihydrotestosterone
Estrogen (ER): estrogens, phytoestrogens, BPA
Progesterone (PR): progestins
Vitamin D (VDR): D3
Retinoic acid (RAR): retinoic acid (vitamin A)
Thyroid hormone (TR): T3
Describe the activation pathway of classical steroid receptors residing in the cytoplasm vs. those residing in the nucleus.
Classical receptors in cytoplasm: 1) Ligand binds 2) Hsp dissociates 3) Receptors dimerize 4) Dimers translocate into nucleus 5) Receptors bind DNA and Gene transcription initiated or repressed
Classical receptors in nucleus: 1) Ligand diffuses into nucleus 2) Ligand binds 3) Receptors dimerize 4) Receptors bind DNA and Gene transcription initiated or repressed
Distinguish non-classical steroid hormone receptor signaling from classical receptor signaling mechanisms (genomic, non-genomic and tethered).
There are two types of receptor proteins: 1) classical which are the direct DNA binding transcription factors, and 2) non-classical which are GPCRs or ion channels etc.
The mechanisms whereby the classical receptors can exert their effects are 1) genomic, where the classical receptor directly binds to DNA; 2) non-genomic, where the classical receptor influences second messenger pathways; and 3) tethered, where other transcription factors are altered by the steroid receptor, without them directly binding to DNA themselves.
The non-classical receptors can only have non-genomic effects since they are cell surface receptors that are not DNA binding proteins (transcription factors).
How do receptor tyrosine kinases signal in general? How does the insulin receptor function?
RTKs are enzymes- i.e. have intrinsic catalytic activity. When ligand is bound, RTK phosphorylates itself and then other proteins, on tyrosine residues. When insulin is bound to the IR, it phosphorylates itself, then phosphorylates Insulin Receptor Substrate (IRS). providing docking sites for PI3-kinase (to activate Akt- metabolic effects glucose uptake, downregulates gluconeogenesis) and Grb (to activate the MAP kinase pathway- mitogenic effects Adipocyte proliferation).
What are the key proteins involved in normal insulin receptor signaling and what are their functions?
IRS- insulin receptor substrate. When phosphorylated provides docking sites for PI3-kinase and Grb. When PI3-kinase and Grb bind they are activated. PI3-K involved in metabolism and Grb in mitogenic effects.
What is the role of the PI3-K in insulin receptor signaling?
PI3-K activates AKT to exert metabolic effects: 1) Stimulate glucose uptake by GLUT4 transporters 2) Inactivate glycogen synthase kinase, promoting glycogenesis 3) Inactivate PEPCK-preventing gluconeogenesis
What is the role of the MAP kinase pathway in insulin receptor signaling?
Grb activates Ras which activates MAP-K pathway which activates AP-1 transcription factor that controls cell cycle progression, causes Adipocyte proliferation
What are the 3 circulating adrenocorticoids? How are they transported in the blood? Where are they metabolized? What receptors do they bind and are effects specific or generalized?
Aldosterone, Cortisol, Corticosterone. All 3 bind cortisol binding protein (CBP) with high affinity and albumin with low affinity. All are metabolized by the liver. Mineralocorticoids (Aldosterone) bind the Mineralocorticoid receptor (MR) and have specific effects- promoting Na+ and H2O resorption in kidney tubules. Glucocorticoids (cortisol, corticosterone) bind the glucocorticoid receptor 1 (GR) and have some binding at the MR with very widespread effects.
What are the areas of the adrenal glands and what hormones are made in each area?
Capsule -> Cortex [[Zona Glomerulosa (Mineralocorticoids ALDOSTERONE) -> Zona Fasciculata (Glucocorticoids CORTISOL, CORTICOSTERONE) -> Zona Reticularis (Sex Steroids TESTOSTERONE, 17-B-ESTRADIOL)]] -> Medulla (Neurotransmitters DOPAMINE, EPINEPHRINE, NOREPINEPHRINE)
What are the species differences in Corticosteroids?
CORTISOL: cats, dogs, humans CORTICOSTERONE: rabbits, rodents, birds BOTH: cattle
What are the types of Hyperadrenocorticism in dogs/cats? In horses?
Hyperadrenocorticism (HAC) can be primary (adrenal tumor), secondary (pituitary tumor aka Cushing’s), or iatrogenic (OD steroids for immunosuppression). In horses, Equine PPID secondary due to excess ATCH production by pituitary
What are the types of Hypoadrenocorticism?
Hypoadrenocorticism can be primary (loss of adrenal cortical tissue due to infection, autoimmune etc aka Addison’s), secondary (Loss of ACTH secretion by pituitary), congenital, or Iatrogenic (abrupt withdrawal of GC treatment or cytotoxic Hyperadrenocorticism drugs like mitotane).
What general drug categories are used to treat hyperadrenocorticism in horses? Dogs and cats?
For equine PPID: Dopamine agonists (reduce ACTH secretion, treat secondary disease). For primary HAC: 3B hydroxysteroid dehydrogenase inhibitors to reduce synthesis of GC and MCs or Selective adrenal cytotoxic agents to kill cortex cells directly (reduce GC secretion from adrenal cortex to treat primary disease, indirectly treat secondary), For MC effects, could use Aldosterone antagonists or Thiazide diuretics (counteract hyperaldosteronism).
What classes of drugs are used to treat hypoadrenocorticism?
Synthetic corticosteroids (replace adrenocorticoids)
What drug is used to treat equine hypperadrenocorticism?
Pergolide
What are the tissue targets and methods of action for Pergolide?
Dopamine agonist, tissue target: Pars Intermedia (Equine PPID)
What specific drugs are used to treat hyperadrenocorticism in dogs? Primary vs secondary?
Mitotane used to treat secondary HAC. Trilostane used to treat both primary and secondary HAC.
What are the tissue targets and methods of action for Mitotane?
Cytotoxic, inhibits CYP11B1 (enzyme in adrenal steroid biosynthesis pathway), tissue target: specific to zona fasciculata
What are the tissue targets and methods of action for Trilostane?
3B-Hydroxysteroid Dehydrogenase inhibitor that reduces glucocorticoid biosynthesis, tissue target: Adrenal cortex in general
What specific drug is used to treat hypoadrenocorticism?
Prednisone.
What are the tissue targets and methods of action for Prednisone?
Synthetic Steroid to treat hypoadrenocorticism. Glucocorticoid Receptor (GR) agonist, some Mineralocorticoid receptor (MR). Bioactivated to prednisolone. Tissue targets: WIDE! CNS, liver, fat…
What 2 specific drugs are used to treat mineralocorticoid deficiency? How are they different?
DOCP and Fludrocortisone. DOCP activity at MR only (not GR. Fludrocortisone activity at MR but also some at GR. DOCP is very long-acting injectable.
What are the tissue targets and methods of action for DOCP? How is it dosed?
Replacement therapy for mineralocorticoid deficiency. MR agonist (NO GR activity). LONG ACTING INJECTABLE ~1 MONTH. Tissue target: kidney
What are the tissue targets and methods of action for Fludrocortisone?
Replacement therapy for mineralocorticoid deficiency. MR agonist (some GR activity). Tissue target: kidney.
What specific drug is used to treat hypermineralocorticism?
Spironolactone
What are the tissue targets and methods of action for Spironolactone?
Treats hypermineralocorticism. MR antagonist. Tissue target: kidney.
What are common adverse effects of Mitotane?
anorexia, vomiting, diarrhea, ataxia, hypoadrenocorticism
What are common adverse effects of Trilostane?
GI, CNS, hyperkalemia, musculoskeletal effects
What are common adverse effects of Prednisone?
Polydipsia, polyphagia, polyuria, weight gain, lymphopenia, eosinopenia, neutrophilia, thrombocytosis, will suppress HPA axis
What are common adverse effects of DOCP?
Vomiting, diarrhea, anorexia, polydipsia, polyuria, fluid/electrolyte imbalance (especially hypokalemia), edema, cardiomegaly, and hypertension, lymphopenia, eosinopenia, neutrophilia, thrombocytosis.
What are common adverse effects of Fludrocortisone?
Fluid and electrolyte imbalance (esp. hypokalemia), edema, CHF, cardiomegaly, and hypertension.
What are common adverse effects of Spironolactone?
Hyperkalemia, life-threatening arrhythmias, contraindicated with dehydration
What is the major concern about rapid cessation of corticosteroid therapy?
Long term use of glucocorticoids suppress the Hypothalamus-Pituitary-Adrenal (HPA) axis and endogenous glucocorticoids can be suppressed for up to a year after cessation of therapy.
What is the rationale for using dopamine agonists to treat hyperadrenocorticism?
Dopamine is inhibitory to ACTH secretion from Pars Intermedia, so dopamine antagonists reduce ACTH and stimulation of adrenocorticoid release.
What drug elicits a dopamine response?
pergolide
What drug is cytotoxic to the adrenals?
mitotane
What drug is a 3beta hydroxysteroid dehydrogenase inhibitor?
trilostane
What are 3 drugs that are synthetic steroids used to treat hypoadrenocorticism?
prednisone, desoxycorticosterone pivalate (DOCP), fludrocortisone
What drug is a mineralocorticoid receptor antagonist?
spironolactone
What is an adrenal emergency? How to treat?
Severe hypoadrenocorticism aka Addisonian crisis. Give prednisone or dexamethasone +/- fluids, mineralocorticoids.
What are the Biological Effects of GCs on-
Adipose tissue?
Cardiovascular system?
CNS?
Hypothalamus?
Immune system?
Liver?
Muscle?
Pancreas?
Glucose homeostasis?
Adipose tissue: increase lipolysis
Cardiovascular: positive inotropic, chronotropic effects
CNS:↑ mood, ↑ motor activity, ↓ sleep, ↓ memory
Hypothalamus: inhibits its own secretion by feedback inhibition on the H-P-A axis
Immune system: immunosuppression, anti-inflammatory effects
Liver: increase gluconeogenesis, glycogenesis
Muscle: increase glycogenolysis, proteolysis
Pancreas: increase insulin secretion -but antagonizes insulin action
Serum: increase blood glucose
How is thyroid hormone synthesized and secreted? What enzyme is important to this process? What stimulates release of thyroid hormones?
Thyroglobulin (TG) stored in thyroid follicle cells. Thyroid follicle cells actively transports and concentrates Iodine. Iodine oxidized by thyroperoxidase (TPO) enzyme. TG iodinated on tyrosines by TPO enzyme- called Iodide organification. Further esterified by TPO to produce Triiodothyronine (T3) and Thyroxine (T4)- called coupling. TSH stimulates T3 and T4 release into blood. Iodothyronine deiodinases (DIOs) located in peripheral tissues (eg liver) metabolize T4 to more active T3.
Where is Thyroglobulin (TG) located? How is iodine collected? Where is TPO located? Where is thyroid hormone stored prior to release? Where are TSH receptors located?
TG in follicle cells. Follicle cells actively transport in and concentrate iodine. TPO (thyroperoxidase) enzyme is located in the Colloid. T3/T4 are stored in the follicle cells until stimulated to release by TSH. TSH receptors are located on the Follicle cells.
Compare and contrast T4 and T3. How do they compare in their receptor affinity and half-lives?
Both agonists of Thyroxine Receptor (TR). Both highly bound to thyroxine binding globulin (TBG) and albumin proteins. Only unbound has activity. T3 higher TR affinity, Shorter ½ life. T4 is major secretory hormone, longer ½ life, converted in tissues to T3
What converts T4 to T3 in peripheral tissues?
Deiodinases (DIOs)
How are thyroid hormones transported in the blood?
Highly bound to serum proteins: Thyroxine binding globulin (TBG), Albumin
What classes of drugs treat hypothyroid? Hyperthyroid? Non-drug treatments?
T4 hormone replacement- hypothyroidism. Thyroperoxidase inhibitors or cytotoxic drugs- hyperthyroidism. Non-drug: Thyroidectomy, Iodine deficient diet for cats- hyperthyroidism.
What specific drugs are used to treat hyperthyroidism?
MMI and 131I
How do MMI and 131I work to treat hyperthyroid disease?
MMI- A thioureylene that inhibits thyroperoxidase (TPO) decreases thyroid hormone synthesis
[131I] Sodium iodide- Selectively targets thyroid, emits beta particles and gamma rays to cause DNA strand breaks and cell death.
What specific drug is used to treat hypothyroidism?
Levothyroxine
How does levothyroxine work to treat hypothyroid disease?
Thyroid hormone receptor (TR) agonist
What drug is a synthetic thyroid hormone?
levothyroxine
What drug is an Iodide?
131iodide
What drug is a thioureylene?
methimazole
What are the effects of Thyroid hormone on:
Adipose tissue?
Cardiovascular system?
CNS?
Hypothalamus?
Immune system?
Liver?
Muscle?
Pancreas?
Glucose homeostasis?
Adipose tissue: increases lipolysis
Cardiovascular: positive inotropic, chronotropic effects
CNS: too much causes anxiety, too little causes lethargy
Hypothalamus: inhibits its own secretion by feedback inhibition on the H-P-T axis
Immune system: causes immunosuppression, anti-inflammatory effects
Liver: increases gluconeogenesis, glycogenolysis, degrades cholesterol to bile acids
Muscle: increases glycogenolysis, proteolysis but decreased glucose utilization
Bone: Increases Ca2+mobilization, osteolyticaction
Pancreas: increases insulin secretion -but antagonizes insulin action
Glucose homeostasis: increase blood glucose
How are different insulin formulations categorized and when would they be best used?
Categorized by duration of action. Rapid-, short-, intermediate-, long- and ultra long-acting. Rapid acting regular insulin best for emergency situations. Intermediate acting NPH and Lente used in most dogs/cats. Ultra long acting Glargine is very slowly released and has no serum peak.
What factors affect bioavailability/absorption of insulins?
All insulins must be given parenterally because they are proteins- degraded in stomach. Short-acting regular insulin is the only form that does not crystallize and therefore may be used IV.
Factors that affect bioavailability are-
Injection depth: ↑ absorption IM vs SQ
Insulin concentration: ↑ absorption low conc
Insulin dose: ↑ duration high dose
Exercise: ↑ absorption
Heat/massage at injection site: ↑ absorption
What is the role of the PI3-K in insulin receptor signaling?
PI3-K activates Akt to 1) Stimulate glucose uptake by GLUT4 transporters 2) Phosphorylate and inactivate glycogen synthase kinase, promoting glycogenesis 3) Transcriptionally inactivate PEPCK-preventing gluconeogenesis.
What is the role of the MAP kinase pathways in insulin receptor signaling?
Grb -> Ras -> MAP kinase pathway -> upregulate AP-1 TF (cell cycle progression) -> adipocyte proliferation. Adipocytes secrete factors that cause insulin resistance.
What mechanisms contribute to insulin receptor (IR) desensitization?
Chronic agonist exposure (high blood sugar, high insulin) leads to: receptor internalization (i.e. sequestration), receptor degradation, decreased synthesis.
What mechanisms contribute to insulin resistance and how might they be mitigated?
Increased Serine Phosphorylation. Adipose tissue synthesizes FFAs, TNF-a, Resistin which all activate protein kinase C (PKC) that phosphorylates serine and turns off IRS/IR, downregulate Insulin response. Also genetic polymorphisms in IRS/PI3K. Increased tyrosine phosphatase can contribute.
Could mitigate by inhibiting Tyrosine phosphatase, PKC, or TNF-a.
What are the primary treatments for DM in veterinary medicine?
Diet (reduce adipose, reduce serine phosphorylation) and give insulin.
Name all of the insulin drugs and length of action.
Regular Insulin, Intermediate: NPH Insulin, Lente Insulin, Ultra Long: Insulin Glargine
Which is the only insulin that can be administered IV?
Regular insulin (short-acting)
How does obesity predispose animals to DM?
1- Obese patients are hyperinsulinemic which causes insulin resistance over time. 2- Obese patients have high circulating FFA levels which impair insulin function.
What is the importance of COX-1 and COX-2 selectivity?
COX-1 is constitutively expressed and cytoprotective in gastric mucosa and kidney. COX-2 is inducible in response to inflammatory stimuli. Anti-inflammatory drug goal is to selectively inhibit COX-2 without inhibiting COX-1.
How does the COX1:COX2 IC50 ratio help determine selectivity?
IC50 is concentration needed to inhibit the enzyme. Want a low number for COX-2 (takes a little to inhibit the enzyme) and a high number for COX-1 (would take a whole lot to inhibit COX-1). Want IC50 ratio of COX-1/COX-2 to be HIGH and IC50 ratio of COX-2/COX-1 to be LOW.
What are prostaglandins? Are they short-lived or long-lived? What receptors do they act through?
PGs are lipid mediators that are produced by virtually every cell in the body, are released as soon as they are synthesized, short-lived, and act locally through GPCRs.
How are prostaglandins synthesized? What other molecules are synthesized in this same pathway?
Synthesis: Membrane phospholipids -> Phospholipase A2 (PLA2) enzyme activity -> Arachidonic Acid -> COXs enzyme activity -> PG and Thromboxanes
What mechanisms contribute to the side effects of NSAID usage?
NSAIDs inhibit COX enzymes that are involved in PG synthesis. PG normally have roles in reproduction, inflammation, maintaining mucosa which can be interrupted by NSAIDs and lead to detrimental side effects.
What are the main therapeutic uses of major NSAID classes?
In general, Musculoskeletal pain, post-operative pain/inflammation, fever, cancer.
What are important metabolic factors of NSAIDs?
NSAIDS undergo hepatic P450 biotransformation and glucuronidation, renal elimination.
Cats are deficient in glucuronidation, including NSAIDs
What are contraindications for use of NSAIDs?
Contraindicated with pre-existing GI ulcers, bleeding disorders, compromised renal/liver issues
What are side effects of NSAIDS on-
GI? What potentiates GI risks?
Kidney?
Hemostasis?
Liver?
Cardiovascular?
GI: Vomiting, diarrhea, Gastric ulceration, GI bleeding (both Cox-1 and -2 inhibitors). Ulcer risk potentiated by glucocorticoids.
Renal: Renal decompensation- both COX-1 and -2 impair generation of protective renal prostaglandins.
Hemostasis: Hemorrhage due to impaired platelet function via COX-1 mediated thromboxane generation.
Liver: idiosyncratic toxicity
Cardiovascular: Hypertension, vasoconstriction (PGs are vasodilatory)
What other molecules besides PGs are part of the synthesis pathway affected by NSAIDs? How does aspirin work as an anticoagulant despite contradictory effects on these molecules?
Thromboxanes produced by COX enzymes in platelets (stimulate platelet aggregation). Prostacyclins are produced by COX in endothelial cells (inhibit platelet aggregation). Endothelial cell prostacyclin production is less sensitive to inhibition by NSAIDs than thromboxane production (by platelets) even though the production of both is inhibited, net effect is anticoagulant via platelets.
What drugs are Non-selective COX-1 and COX-2 inhibitors?
Aspirin, Ketoprofen, Phenylbutazone, Flunixin, Piroxicam
What drugs are preferential COX-2 inhibitors?
Carprofen, Meloxicam, Etodolac
What drugs are selective COX-2 inhibitors?
Deracoxib, Firocoxib, Robenacoxib
What drugs are non COX inhibiting NSAIDS?
Acetaminophen, Grapiprant
What types of drugs are Omeprazole/pantoprazole/ranitidine/misoprostol/sucralfate?
Drugs that can prevent NSAID-induced gastric ulcers.
Omeprazole/Pantoprazole-blocks gastric acid secretion (proton pump inhibitor)
Ranitidine(Zantac)-blocks histamine H2 receptors on parietal cells, reducing acid production
Misoprostol-synthetic PGE2 analog
Sucralfate-sucrose sulfate aluminum complex that binds to the ulcer and creates a physical barrier against stomach acid
What is the risk associated with using NSAIDS and Glucocorticoids simultaneously?
GCs inhibit phospholipase A2 which are involved in arachidonic acid synthesis. AA is the precursor to PGs acted on by COX enzymes. Using both doubly affect the PG synthesis pathway. GCs also inhibit gastric peroxidases. Risk of ulcers.
At high levels maintained chronically, what non-COX effect do NSAIDs have?
Inhibit NF-KB which blocks inflammatory gene transcription.
What is the first-line treatment for immune-mediated diseases in veterinary medicine? Does this treatment affect innate or adaptive immune responses?
Glucocorticoids. suppress innate immune cells, cell-mediated responses and antibody production- so all 3 arms of the immune system.
In general what disorders are glucocorticoids used to treat?
Sterile inflammatory diseases, auto-immune diseases, allergic diseases, allergic reactions, hypoadrenocorticism, septic mastitis in cows.
ALSO- management of hypercalcemia, maturation of fetal lungs, anaphylaxis.
What is the central mediator of the immune response that we can therapeutically target?
NF-kappa B (TF upregulates COX enzymes and Cytokines)
How is NF-KappaB regulated?
Inhibitor of NF-kappaB (IkappaB) is phosphorylated by ikappaB kinase and dissociated from NF-kappaB which can then go to the nucleus and influence inflammatory gene transcription and COX gene transcription
How do glucocorticoids function as anti-inflammatories? What mechanism is mot impactful?
Classical genomic: Activate Ikappa-B (inhibitsNF-kappa B), Other anti-inflammatory molecules.
Classical tethered: Inhibit NF-kappa B DNA binding, repress cytokines, COX, etc. MOST IMPORTANT.
List different GCs.
Cortisol, Corticosterone, Prednison, Prednisolone
What chemical modifications alter glucocorticoid activities?
Short-acting- succinate or phosphate esters. Long-acting- acetate or acetonide esters.
What are the chronic side effects of GC usage and why do they arise?
CHRONIC- GI and hepatic effects. Gastric ulcers, lowered gastric mucosal turnover, hepatopathy.
What are the metabolic/endocrine side effects of GC usage in various tissues and why do they arise?
METABOLIC/ENDOCRINE- decreases TSH release, iatrogenic Cushing’s (MUST TAPER WITHDRAWAL), HPA axis suppression, increased lipolysis/visceral adipogenesis, hyperglycemia, insulin resistance, muscle atrophy, osteoporosis
What are the renal side effects of GC usage and why do they arise?
RENAL- inhibition of vasopressin, ADH effects inhibited by GCs
What are the Reproductive side effects of GC usage and why do they arise?
REPRODUCTIVE- decrease FSH and LH secretion, teratogenic, transient infertility
What are the dermatological side effects of GC usage and why do they arise?
LAMINITIS- common in GC-treated horses, mechanism unknown DERMATOLOGICAL- lower fibroblast proliferation, inhibited wound-healing, alopecia
What are the immunological and cardiovascular side effects of GC usage and why do they arise?
IMMUNOLOGICAL- higher incidence of bacterial infections due to immune suppression
CARDIOVASCULAR- hypertension, CHF (water retention, vasoconstriction, volume overload)
What GCs/MCs are selective for GRs and/or MRs?
Mineralocorticoids: DOCP- MR only, Fludrocortisone: both GR/MR.
Glucocorticoids: both- Cortisol/Hydrocortisone, Prednisone/Prednisolone, esters. GR only: Dexamethasone, Triamcinolone, Budesonide.
What are some of the species differences in metabolism of the GCs? What is used most in SA? LA?
Horses/Cats poor converters of prednisone- give prednisolone instead. Cats need 2x dose than dogs. Pred in SA, Dex in LA.
What are the glucocorticoid drugs? Formulation? Which is most potent?
Prednisolone/Prednisone (pro) PO, Dexamethasone PO, Budesonide PO/INHALED, Short and long acting esters IM, Fluticasone INHALED, Hydrocortisone PO/TOPICAL, Triamcinolone TOPICAL. Dex is most potent!
What is the goal in dosing steroids?
Find lowest dose possible, with most infrequent dosing interval to minimize the significant side effects
What are the mineralocorticoid drugs?
DOCP, Fludrocortisone
What are indications for use of immunosuppressant drugs?
Hemolytic anemia, thrombocytopenia, neutropenia, arthritis, uveitis, vasculitis, myasthenia gravis, organ transplant, cancer.
What are the phases and therapeutic goal of immunosuppressant therapy?
Phases: Induction, Intensification (+/- multidrug therapy), Maintenance, Re-induction. Overall goal is REMISSION.
What are first line and second line drugs for immunosuppression?
1st line:
Glucocorticoids
2nd line:
DNA Synthesis inhibitors
Microtubule inhibitors
T cell inhibitors
Alkylating agents
Jak Kinase inhibitors
Monoclonal antibodies.
Explain the idea of a pro-drug.
Prodrug must be acted upon by an enzyme to become active.
Which immune suppressants are pro-drugs?
Prednisone -> Prednisolone, Azothiaprine -> 6-MP, Mycophenolate mofetil -> MPA, Cyclophosphamide -> 4-hydroxyphosphamide, metabolized to Acrolein- bladder toxicity, Clopidogrel
What are the 6 classes of immune suppressants?
DNA synth inhib
T cell inhib
Jak Kinase inhib
Microtubule inhib
Alkylating agents
Monoclonal antibodies
What is Azathioprine used for? What species is it not used in?
Suppresses T and B cells, suppresses antibody synthesis. DON’T USE IN CATS.
What is Mycophenolate mofetil used for generally and specifically?
Generally: Prevents B and T cell proliferation and accumulation at inflammation sites.
Specifically: Dogs with MG or refractory IMHA.
What is Vincristine used for?
Mild immunosuppression by impairing mononuclear, phagocytic cells, increases platelet production.
What type of drug is cyclophosphamide? What is it used for?
Nitrogen mustard derived alkylating agent that fragments DNA in cells at any stage of cell cycle and causes cytotoxicity. Directly cytotoxic to lymphocytes and suppresses B cell antibody formation. Also potent anti-neoplastic drug.
What is the major drawback of cyclophosphamide? Is there a way to mitigate this drawback? Other drugs with less side effects?
Metabolized to acrolein which causes sterile hemorrhagic cystitis. Can give MESNA to mitigate the effect. Cats less sensitive. Alternatively could use chlorambucil- less toxic and also still alkylating agent.
What is Cyclosporine used for? Does it cause bone marrow suppression?
Potent immunosuppressant targeting cell-mediated immunity (T cell inhibitor). No bone marrow suppression.
What is MOA for DNA synth inhibitors?
DNA synthesis inhibitors- Azathioprine interferes with Purine synthesis, Mycophenolate mofetil inhibits guanine synthesis. Targets T and B cells.
What is MOA for T cell inhibitors?
T Cell inhibitors- Cyclosporin binds Cyclophilin and inhibits T cells.
What is MOA Jak inhibitor?
Oclacitinib inhibits Jak kinase
What is MOA for microtubule inhibitor?
Vincristine destabilize microtubules to arrest cells in metaphase REQ DIV CELLS
What is MOA for Alkylating agents?
Cyclophosphamide and Chlorambucil fragment DNA DO NOT REQ DIV CELLS. T/B cells.
What is MOA for monoclonal Ab?
Lokivetmab is a monoclonal anti-IL-31 Ab
What are the side effects of immune suppressants, and how do they arise?
GI upset, Bone marrow suppression/myelosuppression EXCEPT CYCLOSPORIN and TARGETED DRUGS (Oclacitinib and Lokivetmab), corrosive if extravasated. Cyclophosphamide is converted to acrolein (Bladder toxin), mitigated by MESNA.
What are the important species differences in the metabolism of some immune suppressants?
Do not use Azathioprine in cats. Cats less susceptible to bladder toxicity of Cyclophosphamide
How do aspirin and clopidogrel work to block platelet aggregation?
Clopidogrel metabolite is irreversible antagonist of platelet clotting for life of platelet. Aspirin is an irreversible COX-1 inhibitor that blocks thromboxane production.
What drugs are DNA Synthesis Inhibitors?
Azathioprine, Mycophenolate
What drug is a T Cell Inhibitors?
Cyclosporine
What drug is a Jak Kinase Inhibitor?
Oclacitinib
What drug is a Microtubule Inhibitor?
Vincristine
What drugs are Alkylating agents?
Cyclophosphamide, MESNA, Chlorambucil
What drug is a Monoclonal Antibody?
Lokivetmab
What drugs are Anti-platelet?
Aspirin, Clopidogrel
What are the regulatory mechanisms of the Hypothalamic Pituitary Gonadal (HPG) axis?
Estradiol (E2) inhibits LH and FSH release from gonadotrophs in anterior pituitary. E2 positively feeds back on GnRH Surge center of the hypothalamus. E2 surge -> GnRH surge -> LH surge -> ovulation
What is the source and primary function of Progestin?
Progestin – Corpus luteum and placenta – maintenance of pregnancy
What is the source and primary function of Prostaglandin F2a?
Prostaglandin F2a – uterine endometrium and CL – Luteolysis, uterine tone/contraction
What is the source and primary function of GnRH?
Gonadotropin releasing hormone GnRH – Hypothalamus (surge + tonic centers) – release FSH/LH
What is the source and primary function of FSH?
Follicle stimulating hormone FSH – anterior pituitary – follicular development, estradiol synthesis
What is the source and primary function of Oxytocin?
accelerate parturition, evacuate debris, facilitate uterine involution, metritis, milk letdown (intranasal or IM)
What is the elevated steroid metabolism concept in high producing lactating dairy cows?
High milk production assc’d with high feed intake which is assc’d with high liver blood flow and high steroid metabolism. High steroid metabolism lead to repro changes related to level of milk production.
What are the basic classes of hormonal therapeutic agents used to modify or enhance reproductive performance in cattle?
Steroid hormones and peptides
What is the mechanism by which progesterone administration synchronizes estrus?
Inhibits LH secretion -> suppresses ovulation/estrus. Timed estrus resumes upon withdrawal (for timed breeding). Protects against myometrial contractions (premature labor)
Why does the day of ovulation vary after PGF 2 α administration?
Because CL must become responsive to PGF in order for luteolysis to be induced. Cows show variable time to estrus after responding to PGF due to stage of the follicular wave.
Which drugs can be used to synchronize estrus in cattle?
PGF (Dinoprost or Cloprostenol) and GnRH
hCG mimics the action of which naturally occurring hormone(s)?
Luteinizing hormone LH, induces ovulation, used to treat ovarian cysts
Why must FSH be administered twice daily for 4 to 5 days in superovulation programs?
Glycoprotein, biphasic elimination, short half life. Need to stimulate multiple waves of follicles.
What drugs are PGF analogues?
Dinoprost, Cloprostenol
What is the clinical use of Oxytocin?
To accelerate parturition, evacuate postpartum debris (for vaginal or caesarian birth),
facilitate uterine involution after cesarean delivery, for metritis, and to induce milk letdown
(intranasal or IM)
How does the intrinsic pathway of apoptosis differ from the extrinsic pathway generally?
Intrinsic involves mitochondria and cytochrome c and is a response to lack of growth factors, ECM detachment, Damaged DNA. Extrinsic involves specific soluble death signals and surface receptors, e.g. TNFα.
What cell death pathway causes inflammation? Which does not?
Necrosis causes inflammation, apoptosis does not.
What is the MOA of intrinsic, cytochrome c apoptotic pathway? What proteins are pro- and anti-apoptotic?
If cytochrome C leaves mitochondria, get apoptosis. Bcl is anti-apoptotic. Bax and Bad are pro-apoptotic. Cytochrome C in cytoplasm activates caspases.
Which caspases are important to intrinsic vs extrinsic apoptosis pathways?
Intrinsic: cytochrome C in cytoplasm -> Caspase 9 activation -> Caspase 3 activation -> apoptosis
Extrinsic: Death signal (TNFα) binds cell surface receptor -> Caspase 8 activated -> Caspase 3 activation -> apoptosis
How do glucocorticoids cause apoptosis? Is this classical or non-classical GC Receptor activity?
GCs inhibit Bcl and induce Bad via intrinsic pathway through classical receptor genomic activity
How are prostaglandins involved in tumor growth?
PGs are associated with loss of apoptosis, enhancement of proliferation and promotion of metastatic growth
What is the effect of NF-κB signaling on cancer cells?
NF-κB expression/activity is highly up-regulated in many tumors-pro-survivalfactor for tumor cells. NF-κB increases the expression of anti-apoptotic genes (e.g.Bcl, cyclin D, superoxide dismutase) and it decreases the expression of pro-apoptotic genes (e.g.IκB, death receptors, caspases, p53).
Why are NSAIDs useful for treating certain types of cancer?
Reduce PG production, Reduce the risk of developing certain GI cancers in the esophagus, stomach and colorectum, Reduce tumor cell growth by decreasing EGFR activation, Also effects on cellular pathways (kinases, phosphatases) involved in oncogenesis.
How do platelets affect cancers?
Tumor ability to aggregate platelets confers several advantages to the tumor:
Evade detection by immune system
Shield tumor cells from damaging high sheer forces in flowing blood
Protects tumors from death induced by TNF from host immune cells
Facilitate tumor cell attachment to the endothelium
Release factors that promote tumor growth
What is the rationale for new therapeutics targeting NF-κB?
Blocking NF-κB can cause tumor cells to stop proliferating, to die, or to become more sensitive to the action of other anti-tumor agents
What is the rationale for new therapeutics targeting kinase signaling pathways like c-Kit?
New cancer drugs aimed at targeting specific pathways used by different tumors in individual patients. Receptor tyrosine kinase involved in tumor cell survival and proliferation. More specific = less side effects
What is the MOA of Toceranib? Does this work through intrinsic or extrinsic pathway?
Tyrosine Kinase Inhibitor, inhibits c-Kit. Works through the intrinsic pathway- akin to removal of a growth factor.
What other drug that we learned about is a Receptor tyrosine kinase inhibitor (Jak inhibitor)?
Oclacitinib
What is a characteristic of cell types most affected by chemotherapy?
Rapidly/actively dividing cells
How wide is therapeutic range for chemo drugs? How are they dosed?
Narrow therapeutic range, give @ max tolerated dose based on body surface area.
What are toxicities that are common to all chemotherapeutic drugs?
B.A.G. Bone marrow suppression, Alopecia, Gastrointestinal.
What classes of chemo drugs are cell-cycle specific?
Anti-microtubule agents
What classes of chemo drugs are NOT cell-cycle specific?
Alkylating agents, Anti-tumor antibiotics, platinum agents
What is a major drawback of cyclophosphamide use? Is there a way to mitigate this drawback? Are there alternative drugs with less side effects?
Metabolized to Acrolein which causes hematuria and sterile hemorrhagic cytistis. Can give MESNA to counteract toxicity. Or use alternative drugs: Lomustine or Chlorambucil.
How do alkylating agents work? What type of cancers used for?
Cross-link DNA to cause cytotoxicity. Not cell phase specific. Hematopoetic tumors.
What are two drugs that are alkylating agents? Which one crosses the BBB?
Cyclophosphamide, Lomustine/CCNU. Only Lomustine/CCNU crosses the BBB.
What are the unique toxicities of the alkylating agents?
Lomustine/CCNU causes liver toxicity. Cyclophosphamide causes sterile hemorrhagic cystitis and hematuria due to Acrolein metabolite. Remember red urine and hemorrhagic, heart-shaped bladder images.
What is an example of an anti-tumor antibiotic? What is the MOA? What is a unique toxicity of this drug?
Doxorubicin. Intercalation of DNA and topoisomerase inhibitor. Also forms free radicals that cause cardiotoxicity. Unique side effects: Cardiac toxicity in Dogs, renal toxicity in cats.
What are 2 drugs that are platinum agents?
Cisplatin and Carboplatin.
Which drugs are a microtubule inhibitors? What are unique toxicities?
Vincristine. Vinblastine. Cell cycle phase specific. Peripheral neuropathy, Tissue corrosive (vesicant)
What is the clinical use of L-Asparaginase? What is a unique toxicity and unique factor to consider when dosing?
Lymphoma only, causes hypersensitivity reactions, Rapid development of resistance.
Why can chemotherapies be or become ineffective?
Tumor slows down growth, Tumor outgrows blood supply so drugs don’t reach it, tumor cells develop resistance.
What is Mycophenolate mofetil used for generally and specifically?
Generally: Prevents B and T cell proliferation and accumulation at inflammation sites.
Specifically: Dogs with MG or refractory IMHA.
