Metallothioneins, a Part of the Retinal Endogenous Protective System in Various Ocular Diseases

Metallothioneins are the metal-rich proteins that play important roles in metal homeostasis and detoxification. Moreover, these proteins protect cells against oxidative stress, inhibit proapoptotic mechanisms and enhance cell differentiation and survival. Furthermore, MTs, mainly MT-1/2 and MT-3, play a vital role in protecting the neuronal retinal cells in the eye. Expression disorders of these proteins may be responsible for the development of various age-related eye diseases, including glaucoma, age-related macular degeneration, diabetic retinopathy and retinitis pigmentosa. In this review, we focused on the literature reports suggesting that these proteins may be a key component of the endogenous protection system of the retinal neurons, and, when the expression of MTs is disrupted, this system becomes inefficient. Moreover, we described the location of different MT isoforms in ocular tissues. Then we discussed the changes in MT subtypes' expression in the context of the common eye diseases. Finally, we highlighted the possibility of the use of MTs as biomarkers for cancer diagnosis.