Bone II - Osteoclast Activity and Regulation
parathyroid hormone, calcitonin
What 2 hormones control osteoclast activity?
RANK, RANK-L, OPG
What 3 molecules control osteoclast activity at the cellular level?
corticosteroids, glucocorticoids, IL-1
What are some examples of cytokines influencing RANK, RANK-L and OPG levels?
carbonic, citric, lactic
What are some organic acids involved in focal decalcification?
Howship's lacunae
What are the depression left in eroded bone by osteoclasts?
cathespins
What can inhibitors attack to regulate osteoclast activity?
levels of various cytokines
What determines the levels of RANK, RANK-L and OPG?
osteoprotegerin
What does OPG stand for?
binds to RANK to stimulate primitive osteoclast development into mature osteoclasts
What does RANK-L do?
denosumab, antibody which binds to RANK-L
What drug inhibits RANK-L and how?
calcium supplements, vitamin D, increase calcium levels
What drugs inhibit PTH and how?
hormonal replacement therapy, biphosphonates
What drugs/treatments reduce osteoclast activity?
cathespins
What enzymes digest collagen?
PTH, exercise, anti-sclerostin antibodies
What inhibits sclerostin?
acid hydrolases digest extracellular material
What is involved in the second step of bone resorption?
molecule involved in osteoclast/osteoblast interaction
What is sclerostin?
focal decalcification by organic acids
What is the first step of bone resorption by osteoclasts?
decoy molecule that blocks RANK-L preventing binding to primitive osteoclasts
What is the function of OPG?
forms seal so secretions don't leak to other areas of bone
What is the importance of the collar on osteoclasts?
increase surface area for secretion and resorption
What is the importance of the ruffled border of osteoclasts?
primitive osteoclasts
Where is RANK found?
osteoblasts
Where is RANK-L found?
thyroid gland
Where is calcitonin produced?
digesting osteoid
How can osteoblasts prepare a surface for osteoclast activity?
increases osteoblast and osteoclast activity, bone mass decreased
How does PTH affect bone resorption?
reduces osteoclast activity by reducing no. of folds, no. of osteoclasts and osteoclast movement
How does calcitonin affect bone resorption?
