Glutathione (γ-glutatamylcysteinylglycine, GSH) is a tripeptide containing a γ-amide bond and a sulfhydryl group, consisting of glutamate, cysteine and glycine, and is present in almost every cell of the body. Glutathione is widely found in animals and plants and has an important role in living organisms. Glutathione is available in both reduced (GSH) and oxidized (GSSG) states, with reduced glutathione predominating under physiological conditions. Glutathione reductase can catalyze the interchange between the two states.
As an important intracellular regulatory metabolite, GSH is both a cofactor for glyceraldehyde phosphate dehydrogenase and a coenzyme for glyoxalase and malonose dehydrogenase, participating in the tricarboxylic acid cycle and glucose metabolism in the body, and GSH can activate various enzymes, such as sulfhydryl enzyme-coenzyme, thus promoting sugar, fat and protein metabolism.
The sulfhydryl group on cysteine is the glutathione active group, which can easily bind with certain drugs (such as paracetamol), toxins (such as free radicals, iodoacetic acid, mustard gas, heavy metals such as lead, mercury and arsenic), and has integrated detoxification effect. Therefore, glutathione especially in hepatocytes can participate in biotransformation, thus converting harmful toxic substances in the organism into harmless ones and excreting them out of the body.
Application of Glutathione
- Cell Culture
Complete medium for culturing cells consists of a basal medium (such as MEM) and additives (such as serum or certain defined hormones and growth factors for serum-free culture). The vast majority of culture media are based on balanced salt solutions (BSS) with added amino acids, vitamins and other nutrients in concentrations similar to those found in serum. The most widely used medium is a mixture of MEM, which contains 13 essential amino acids and 8 vitamins. Cells cannot survive in basal medium alone, and in specific types of cell cultures certain trace nutrients and growth factors must be provided to allow cells to grow and maintain growth. The basal medium is often supplemented with serum, most often at a final concentration of 5 to 20%. The source of serum for special applications must be determined empirically, and the most widely used types of serum are horse and fetal bovine serum.
Serum-free medium
Neural cell survival and growth can be maintained with chemical additives without the addition of serum to the medium. The basis of this work was the replacement of components of the medium with a suitable combination of hormones, nutrients, and pro-adhesive substances, resulting in a formulation of reagents suitable for most cell cultures, called N2, specifically for neuronal cell culture. Its base medium is a 1:1 mixture of DMEM and H12 with the addition of insulin, transferrin, progesterone, putrescine and selenium.
Why glutathione for cell culture
It is worth noting that selenium is a component of the glutathione peroxidase (GSH-Px enzyme), an important peroxidolytic enzyme, which can catalyze the change of GSH to GSSG and reduce toxic peroxides to non-toxic hydroxyl compounds, thus protecting the structure and function of cell membranes from interference and damage by peroxides. Glutathione can be added to cell culture medium as an antioxidant for use in neural cell culture.
Researchers have found that neurons are particularly vulnerable to peroxide and free radical injury when grown in serum-free medium when lacking serum proteins. Peroxidases prevent the accumulation of peroxides and superoxides in the medium. Thus, the formulation of serum-free media often contains reagents of antioxidants.
- Clinical Drugs
Glutathione drugs, widely used in clinical practice, are used in hepatitis, hemolytic diseases, and keratitis, cataract and retinal diseases as therapeutic or adjuvant drugs, in addition to using its sulfhydryl group to chelate heavy metals, fluoride, mustard gas, and other toxins poisoning. In recent years, glutathione has been discovered that it has the function of inhibiting HIV.
Cancer
The role of GSH in cancer is a complex one. glutathione metabolism is able to play both protective and pathogenic roles. It is crucial in the removal and detoxification of carcinogens, and alterations in this pathway, can have a profound effect on cell survival. However, by conferring resistance to a number of chemotherapeutic drugs, elevated levels of glutathione in tumour cells are able to protect such cells in bone marrow, breast, colon, larynx and lung cancers. The inhibitors of GSH synthesis (such as BSO) or GSH- transferases (GST) have been used to modulate activity of cells to anticancer drugs. The depletion of GSH can be seen to enhance the antitumour cytotoxicity of various drugs without increasing toxicity to normal tissue.
Alzheimer’s disease
Glutathione serves as an important anti-oxidant in the brain by scavenging harmful reactive oxygen species that are generated during different molecular processes. The GSH level in the brain provides indirect information on oxidative stress of the brain. Depletion of the GSH in the hippocampus may be a potential early diagnostic biomarker for Alzheimer’s disease.
Antioxidants
Glutathione, as an important antioxidant in the body, can scavenge free radicals in the body. Since GSH itself is easily oxidized by certain substances, it can protect the sulfhydryl groups in many proteins and enzymes and other molecules in the body from being oxidized by harmful substances, thus ensuring the normal performance of physiological functions of proteins and enzymes and other molecules. Human red blood cells contain a lot of glutathione, which is important for protecting the sulfhydryl groups of proteins on the red blood cell membrane in a reduced state and preventing hemolysis.