Pharmacology - Immunomodulatory agents Flashcards
What are the major metabolic effects of glucocorticoids?
gluconeogenesis, protein catabolism and lipolysis
How do glucocorticoids cause an increase in glucose?
enhance gluconeogenesis in extrahepatic tissues, increase hepatic storage of glycogen, reduce uptake and utilization of glucose by tissues, may decrease expression of insulin receptor by target cells
What effect do glucocorticoids have on plasma protein levels?
increased levels of plasma and liver protein levels –> due to reduced tissue protein synthesis and increased protein catabolism; results in muscle atrophy
How do glucocorticoids suppress the inflammatory function of leukocytes?
stabilizing the membranes of those cells (specifically granulocytes, mast cells, and monocyte-macrophages) –> prevents release of inflammatory mediators such as histamine and arachidonic acid metabolites
Glucocorticoids suppress production of what pro-inflammatory cytokines?
IL-1, IL-6, TNF-alpha
What effect do glucocorticoids have on macrophages?
downregulate expression of Fc receptors on macrophages –> decreases phagocytosis of opsonized particles
T/F: Glucocorticoids directly inhibit antibody production by B lymphocytes.
False - B lymphocytes are more resistant to the suppressive effects of glucocorticoids, BUT they can indirectly suppress antibody production through the effect on T cells
T/F: Glucocorticoids inhibit complement.
TRUE
Why are glucocorticoids bound to esters of acetate, diacetate, tebutate, phenylpropionate, or isonicotinate released over days to weeks?
moderately insoluble
Glucocorticoids bound to esters of acetonide, hexacetate, pivalate, or diproprionate are short-acting or long-acting?
long-acting, are poorly soluble which allows steroid release over a period of weeks to months
Examples of topical cutaneous glucocorticoids - formulated as acetonide or valerate esters
hydrocortisone, prednisolone, betamethasone, dexamethasone
T/F: Endogenous cortisol has greater glucocorticoid and mineralocorticoid activity than synthetic glucocorticoids.
False - synthetic glucocorticoids have greater glucocorticoid activity and less mineralocorticoid activity than endogenous cortisol
What are the only synthetic glucocorticoids with mineralocorticoid activity?
hydrocortisone, cortisone, and prednisolone
Which diffuses more readily into tissues: endogenous cortisol or synthetic glucocorticoids?
synthetic glucocorticoids - bind with less avidity to serum proteins
Which has a greater affinity for the cytoplasmic steroid receptor: endogenous cortisol or synthetic glucocorticoids?
synthetic glucocorticoids - and are less rapidly degraded
Prednisone and cortisone require activation in the liver to what compounds?
prednisolone and cortisol
T/F: Increasd ALP with glucocorticoid treatment indicates hepatic damage and should prompt discontinuation of therapy.
False - increase in ALP is due to activation of the corticosteroid-induced alkaline phosphatase gene within canine hepatocytes. This does not have any pathological consequences
Concurrent administration of glucocorticoids and cyclosporine has what effect on the metabolism of each drug?
reduced hepatic metabolism of each drug –> elevated blood levels of both agents
What antibiotic REDUCES hepatic metabolism of methylprednisolone?
erythromycin
There is an increased risk of hypokalemia when glucocorticoids are used concurrently with what drugs?
acetazolamide, amphotericin B, potassium-depleting diuretics (furosemide, thiazides)
What drugs may accelerate the metabolism of glucocorticoids?
phenobarbital, primidone, rifampin
What is the cause of the leukocytosis seen with glucocorticoid administration?
glucocorticoids inhibit expression of adhesion molecules on endothelial cells (ELAM-1 and ICAM-1) and thereby interfere with movement of leukocytes from the vasculature into inflamed tissues
What is the cause of the mature neutrophilia seen with glucocorticoid administration?
increased release of mature neutrophils from the bone marrow, decreased margination, decreased migration of neutrophils out of the blood vessels
What is the cause of the lymphopenia seen with glucocorticoid administration?
redistribution of circulating lymphocytes to nonvascular lymphatic compartments such as lymph nodes
How is the arachidonic acid cycle inhibited with glucocorticoid administration?
glucocorticoids increase production of lipocortin 1 lipomodulin –> causes a reduction in the action of phospholipase A2 on cell membranes –> inhibits AA cycle
Why can synthetic glucocorticoids be more potent at low doses?
poorly protein bound – only free glucocorticoid is metabolically active
What effect does adding a methyl or fluoride group to the basic steroid molecule have on potency and duration of action?
increases potency and duration of action
What effect does hypoalbuminemia have on glucocorticoid activity?
animals with low serum albumin levels have a lower binding capacity of glucorticoids –> excessive unbound glucocorticoid becomes freely available –> increases toxicity
Glucocorticoid effect on: eosinophils
decrease formation in bone marrow; increase apoptosis and inhibit prolongation of eosinophil survival and function from IL-3 and IL-5
Glucocorticoid effect on: lymphocytes and monocytes
redistribution of circulating lymphocytes to nonvascular lymphatic compartments such as lymph nodes/bone marrow; reduced number of lymphocytes and monocytes that bear low-affinity IgE and IgG receptors; Decreased serum immunoglobulin levels; Decrease all lymphocyte subpopulations (T > B lymphocytes), CD4+ decreased more than CD8+; Decreased lymphocyte production of IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, and IFN-gamma; Inhibit release of IL-1 and TNF-alpha from monocytes
Glucocorticoid effect on: mast cells
May decrease number o mast cells and synthesis of histamine
Glucocorticoid effect on: neutrophils
neutrophilia due to release from bone marrow as well as decreased margination and diapedesis of neutrophils into tissues; decreased chemotaxis, adherence, and enzyme secretion
Glucocorticoid effect on: lipocortin 1
Causes upregulation of lipocortin 1 (phospholipid binding protein) – potent anti-inflammatory effects; inhibition of phospholipase A2; Decrased production of AA metabolites from COX and LOX pathways; Decreased production of platelet-activating factor
Glucocorticoid effect on: humoral immunity
decreased antibody synthesis only after high dose, long-term therapy; reduces degree of suppression of B-lymphocyte proliferation in response to mitogens
Glucocorticoid effect on: cellular immunity
decreased antigen survival, uptake, and migration; decreased maturation of dendritic cells; inhibition of transcriptional activators (NF-kB and AP-1); decreased macrophages expression of some inflammatory cytokines (IL-1, TNF-alpha); increased expression of some anti-inflammatory cytokines (IL-10), decreased T-lymphocyte proliferation in response to mitogens; decreased T-cell activation; Decreased T-cell cytokines (IL-2 and IFN-gamma); Decreased NK-cell-mediated lysis of target cells)
Local areas of alopecia, pigmentary changes, and epidermal and dermal atrophy are more commonly induced when glucocorticoids are administered via what route?
subcutaneous injection
What long-acting injectable glucocorticoids are available for use in dogs?
betamethasone acetate, methylprednisolone acetate, triamcinolone acetonide
What long-acting injectable glucocorticoids are available for use in cats?
methylprednisolone acetate, triamcinolone acetonide
Unique side effect of glucocorticoids in cats
curling of the pinnae, alopecia, thin and easily torn skin, hypertrophic cardiomyopathy, diabetes mellitus, steroid hepatopathy
Common side effects of glucocorticoids
PU, PD, PP (weight gain), behavioral changes (depression, hyperactivity, aggression), panting, diarrhea, risk of infections
What is the mechanism of PU/PD in dogs with glucocorticoids?
interference of glucocorticoids with ADH –> polyuria and compensatory polydipsia
What is the mechanism of PU/PD in cats with glucocorticoids?
glucosuria and osmotic diuresis; most cases commonly maintain normal USG
What steroid may have a greater diabetogenic effect in cats?
dexamethasone
Arachidonic acid is stored in cells and released by the action of what enzyme?
phospholipase A2
What is the proposed mechanism of action of how fatty acids function in controlling pruritus?
inhibition of AA metabolism (competing for COX and LOX enzymes), alteration of metabolic byproducts of fatty acid metabolism (produce less inflammatory byproducts)
Gamma-linolenic acid is found in what oils?
evening primrose, borage, and black currant oils