ML Watson Lec 5 Flashcards
In RA, activated tissue cells produce ______ (especially ______)
Chemotaxins
- Especially chemokines
Chemokine attract leukocytes such as n____, m____ and _ and _ _____
Neutrophils, monocytes and T and B lymphocytes
Tissue cells and invading leukocytes can be further activated after being attracted to the synovium leading to the product of…
1) Cytokines (TNFalpha and IL-1b)
2) Chemoattractants
3) P______
4) R______ O____ and N_____ S_____
Proteases
Reactive Oxygen and Nitrogen Species (RONS)
Cartilage is made by _____ in the matrix
Chondrocytes
Joint cartilage comprises mainly
1) F____ _____ (collagen)
2) P_______
Fibrous Protein (collagen) Proteoglycan
Bone is a dense connective tissue made up of cells and matrix it comprises:
1) Mineralised (C_____ P____) matrix
2) Fibrous protein C_____
Mineralised Calcium Phosphate Matrix
Fibrous protein - Collagen
______ break down bone when activated by cytokines (that may be released from T cells and macrophages)
Osteoclasts
Osteoclasts release
1) ____ _____
2) _ _ _s
3) ____ _____
1) Carbonic anhydrase - H+
2) Matrix metallo proteinases
3) Cysteine proteases
P____ is lost rapidly in RA
- Shock absorption is impaired
- Loss of joint function, pain
Proteoglycans
P______ breakdown proteoglycans (in cartilage)
Proteinases
Native collagen is only susceptible to degradation by ______
Collagenases
S_____ F_____ secrete the following when activated:
- Lipid mediators (PGE2)
- Cytokines (IL-6, IL-8, etc.)
- Enzymes
- Matrix materials
They act to ‘nurse’ T cells and may exhibit ‘malignant’ phenotype
Synovial Fibroblasts
Proteoglycan has a ‘shock absorber’ function
1) - It consists of chondroitin sulphate (polysaccharide) linked to ______ (core protein)
2) - It is charged (as it is highly S______ ) and binds water
What happens if it breakdown and cannot bind water?
1) Aggrecan
2) Sulphated
Friction in the joint will increase
MMPs are activated by removal of the propeptide.
This is done by S____ P_____
Serine Proteases
What is important on a matrix metalloproteinases’ domain structure for specificity and regulation?
- The C terminus
What is the active site on a MMP?
Zn+
What series of MMP inhibitors target the active site?
- Hydroxamate series e.g marimastat
What are MMPs inhibited by?
- TIMPs - tissue inhibitors of Metallo-Proteinases
Synthetic MMP inhibitors include Peptidomimetics. What acid are these based on?
- Hydroxamic acid based molecules
- Zinc binding
- Mimic MMP substrate - collagen
- Inhibit MMP activity
Give an example of a Peptidomimetic that lacks specificity and acts on most metalloenzymes (similar structure to the substrate that acts on Zn binding region)
- Marimastat
Give an example of a Non-peptide hydroxamate that is involved in Zn binding by binding to the MMP active site.
- Prinomastat
Better selectivity for collagenases
Name the last type of MMP inhibitor after Peptidomimetics and Non-peptide hydroxcamates…
- Tetracycline and derivatives e.g Doxycycline (periostat)
Used in periodontal and skin disease
Name 3 roles the MMP’s have in the body involved with homeostatic connective tissue turnover…
1) Embryogenesis
2) Wound healing
3) Growth and repair
Serine and Cysteine proteases are products of _____?
- Leukocytes
Give an example of 3 Serine and Cysteine proteases that break down matrix proteins such as elastin, laminin and Chondroitin sulphate and proteoglycans.
1) Neutrophil elastase
2) Cathepsin G
3) Kallikrein
What are Serine and Cysteine proteinases inhibited by endogenously?
How are these inhibitors inactivated?
Serpins
(SERine Protease INhibitors)
- Inhibited by oxidation
What produces RONS?
- Infiltrating leukocytes and tissue resident cells
- NADPH catalyses formation of ______ (O2-)
- O2- dismuted to form _____ H2O2
- H2O2 further decomposes to form
- hydroxyl radical OH
- hypohalous acids e.g HOCl-
- These are powerful anti-bacterial agents
- Superoxide
- Peroxide
Leukocytes phagocytose:
- Bacteria
- Yeast
- Immune complexes
- DAMAGED TISSUE (produced in response to this)
What do leukocytes generate as part of their defence?
- ROS
- Reactive oxygen species
- These are released into the joint space and cause further damage and inflammation
Rheumatoid synovial tissue undergoes cycles of hypoxia and reperfusion leading to oxidative stress.
This can cause immune complex formation in some diseases leading to the generation of…
S______ (O2-), H2O2 and NO
Superoxide
Superoxide (O2-), ____ and __ can:
- Mediate important cell functions
- Promote formation of hydroxy radical (OH), peroxynitrite (ONOO-)
- Tissue injury, modulation of cell function
1) H2O2
2) NO
RONS can lead to DNA damage and activation of inflammatory gene transcription (NFkB)
RONS can also cause amino acid modifications that can make host proteins immunogenic and inactivate serpins
What happens when serpins are inactivated?
- Inactivation of serine protease inhibitors causes serine proteases to continue breaking down peptides in cartilage and bone
Tissue damage in RA:
1) Inflammatory mediators and RONS from infiltrating leukocytes act on resident cells such as C_____, O_____ and F_____
2) These produce Proteases, MMPs, Elastases and _ _ _s and so do infiltrating leukocytes
3) These destroy cartilage and bone
- Chondrocytes, osteoclasts and fibroblasts
- RONs (reactive oxygen and nitrogen species)
