The words behind the science.
Plain-English definitions of the terms that come up in cartilage glutathione research, each linked to a fuller explanation.
Aggrecanaggregating proteoglycan, ACAN (its gene)
Aggrecan is the large proteoglycan of cartilage, a protein core carrying many sugar chains that draw in water and let cartilage resist compression. It sits within the type II collagen network.
Alpha-lipoic acidALA, lipoic acid, thioctic acid
Alpha-lipoic acid is a small sulphur-containing fatty acid that the body makes in small amounts and uses as a helper for energy-producing enzymes in mitochondria. Inside cells it is reduced to dihydrolipoic acid, its antioxidant form.
Antioxidantantioxidant defence
An antioxidant is a molecule that neutralises reactive oxygen species or limits the damage they cause, usually by giving up electrons. Some come from food; others, such as glutathione, cells make for themselves.
Articular cartilagejoint cartilage, hyaline cartilage
Articular cartilage is the smooth, slippery tissue that covers the ends of bones in moving joints, letting them glide and spreading load with low friction. It has no blood vessels, lymphatics or nerves.
Avascularwithout a blood supply, avascularity
Avascular means without blood vessels. Adult articular cartilage is avascular, so its cells get oxygen and nutrients by diffusion through the tissue rather than from a blood supply.
Chondrocytecartilage cell
A chondrocyte is the resident cell of cartilage, the cell that makes and maintains the surrounding tissue. In articular cartilage, chondrocytes make up only about 2% of the volume.
CysteineL-cysteine, Cys
Cysteine is a sulphur-containing amino acid and the building block that gives glutathione its working thiol group. Its supply is one of the two key controls on how fast cells make glutathione.
Dihydrolipoic acidDHLA, reduced lipoic acid
Dihydrolipoic acid (DHLA) is the reduced, active form of alpha-lipoic acid, with two free thiol groups that can give up electrons. Cells make it from alpha-lipoic acid.
Glutamateglutamic acid, L-glutamate, Glu
Glutamate is an amino acid and one of glutathione's three building blocks, joined to cysteine in the first step of glutathione synthesis. Cells get it from food, from other amino acids and from glutamine.
Glutamate cysteine ligaseGCL, gamma-glutamylcysteine synthetase
Glutamate cysteine ligase (GCL) is the enzyme that carries out the first and rate-limiting step of glutathione synthesis, joining glutamate to cysteine. Its activity and the supply of cysteine are the two key controls on how much glutathione a cell makes.
GlutamineL-glutamine, Gln
Glutamine is the most abundant amino acid in the blood and a ready source of glutamate, one of glutathione's three building blocks. Cells convert it to glutamate with the enzyme glutaminase.
GlutathioneGSH, L-glutathione, gamma-glutamylcysteinylglycine
Glutathione is a tripeptide, a small molecule built from three amino acids (glutamate, cysteine and glycine), that cells make for themselves to defend against oxidative stress. It is the most abundant non-protein thiol in mammalian tissues.
Glutathione precursorglutathione building block
A glutathione precursor is a nutrient that cells use to make glutathione themselves, such as cysteine (often given as NAC), glycine, or glutamine as a source of glutamate. Precursors support the cell's own production rather than supplying finished glutathione.
Glutathione reductaseGR, GSR (its gene)
Glutathione reductase is the enzyme that recycles oxidised glutathione (GSSG) back into two molecules of working, reduced glutathione (GSH), using electrons from NADPH.
GlycineL-glycine, Gly
Glycine is the smallest amino acid and one of glutathione's three building blocks. It also makes up a third of the amino acids in collagen, so cartilage cells need it for both their antioxidant and their matrix.
GlyNACglycine and N-acetylcysteine, glycine plus NAC
GlyNAC is the combination of glycine and N-acetylcysteine (NAC), two glutathione precursors given together so cells have both glycine and cysteine for making glutathione.
GSH:GSSG ratioglutathione redox ratio, reduced to oxidised glutathione ratio, glutathione redox status
The GSH:GSSG ratio compares the amount of working, reduced glutathione (GSH) with the amount of used, oxidised glutathione (GSSG) in a cell or fluid. A lower ratio means more of the glutathione pool is oxidised, a common sign of oxidative stress.
N-acetylcysteine (NAC)NAC, acetylcysteine, N-acetyl cysteine, N-acetyl-L-cysteine
N-acetylcysteine (NAC) is a form of the amino acid cysteine with an acetyl group attached, which cells can use as a source of cysteine to make glutathione. It is widely used in research as a glutathione precursor and antioxidant.
Oxidative stressoxidant stress, redox imbalance
Oxidative stress is the state in which a cell's production of reactive oxygen species outpaces its antioxidant defences, so oxidants start damaging molecules and disturbing the cell's signalling.
Oxidised glutathione (GSSG)GSSG, glutathione disulphide
Oxidised glutathione (GSSG) is the used form of glutathione: two glutathione molecules joined through their sulphur atoms after neutralising an oxidant. The enzyme glutathione reductase turns it back into two molecules of working GSH.
Reactive oxygen speciesROS, oxidants
Reactive oxygen species (ROS) are oxygen-containing molecules, such as superoxide and hydrogen peroxide, that react readily with fats, proteins and DNA. Cells make them as by-products of normal metabolism and use some of them as signals.
Reduced glutathione (GSH)GSH, glutathione (reduced form)
Reduced glutathione (GSH) is the working, single-molecule form of glutathione, with a free thiol group on its cysteine that can neutralise oxidants. Once it has done that job it becomes oxidised glutathione (GSSG).
Synovial fluidjoint fluid, synovia
Synovial fluid is the thick, slippery fluid inside a joint capsule that lubricates the cartilage surfaces. Because cartilage has no blood supply, it is also the route by which nutrients reach the cartilage cells.
Type II collagencollagen II, collagen type II, COL2A1 (its gene)
Type II collagen is the main collagen of articular cartilage, forming the fibre network that gives the tissue its strength. It is made by chondrocytes, the cartilage cells.