Metallothionein-I/II in brain injury repair mechanism and its application in forensic medicine / 法医学杂志

Metallothionein (MT) is a kind of metal binding protein. As an important member in metallothionein family, MT-I/II regulates metabolism and detoxication of brain metal ion and scavenges free radicals. It is capable of anti-inflammatory response and anti-oxidative stress so as to protect the brain tissue. During the repair process of brain injury, the latest study showed that MT-I/II could stimulate brain anti-inflammatory factors, growth factors, neurotrophic factors and the expression of the receptor, and promote the extension of axon of neuron, which makes contribution to the regeneration of neuron and has important effect on the recovery of brain injury. Based on the findings, this article reviews the structure, expression, distribution, adjustion, function, mechanism in the repair of brain injury of MT-I/II and its application prospect in forensic medicine. It could provide a new approach for the design and manufacture of brain injury drugs as well as for age estimation of the brain injury.

Metallothionein: an overview on its metal homeostatic regulation in mammals / Metalotioneina: una visión general de su regulación homeostática de metales en mamíferos

Metallothionein (MT) is a ubiquitous protein with a low molecular weight of 6-7 kDa weight and it was first identified in the kidney cortex of equines as a cadmium (Cd)-binding protein responsible for the natural accumulation of Cd in the tissue. The mammalian MT contains 61 to 68 amino acid residues, in which 18 to 23 cysteine residues are present. The expression of MT starts by binding of metal transcription factor-1 (MTF-1) to the regulative region of MT gene called metal responsive elements (MREs). The induction of MT through the MREs region can be initiated by several metal ions such as zinc (Zn), copper (Cu) and Cd. However, Zn is the only heavy metal which can reversibly and directly activate the DNA-binding activity of MTF-1. In mammals four types of MT are expressed and they are termed metallothionein-1 (MT1), metallothionein-2 (MT2), metallothionein-3 (MT3), and metallothionein-4 (MT4). MT1 and MT2 are expressed in almost all tissues while MT3 and MT4 are tissue-specific. MT is a key compound involved in the intracellular handling of a variety of essential and nonessential post-transitional metal ions. In order to the heavy metal binding ability of MT, it is suggested to play roles both in the intracellular fixation of essential trace elements Zn and Cu, in controlling the concentrations, and in neutralizing the harmful influences of exposure to toxic elements...

Metalotioneina (MT) es una proteína, con bajo peso molecular de kDa 6-7 y que fue primero identificada en la corteza renal de equinos como cadmio (Cd)-proteína responsable por la acumulación natural de Cd en los tejidos. La MT en mamíferos contiene 61 a 68 residuos de aminoácidos, de los cuales están presentes 18 a 23 residuos de cisteína. La expresión de MT se inicia por la unión del factor-1 de transcripción de metal (MTF-1) a la región reguladora del gen de la MT llamado elementos metálicos responsable (MREs). La inducción de MT a través de la región MREs puede ser iniciada por varios iones metálicos tales como zinc (Zn), cobre (Cu) y Cd. Sin embargo, el Zn es el único metal pesado que puede revertir y activar directamente la unión ADN de MTF-1. En los mamíferos se expresan cuatro tipos de MT y ellos se denominan metalotioneína-1 (MT1), metalotioneína-2 (MT2), metalotioneína-3 (MT3), y metalotioneína-4 (MT4). MT1 y MT2 se expresan en casi todos los tejidos mientras que MT3 y MT4 son tejido-específico. La MT es un compuesto clave implicado en la manipulación intracelular de una variedad de iones metálicos esenciales y no esenciales post-transicionales. Con el fin de evaluar la capacidad de unión de metales pesados de MT, se sugiere que éste desempeña ambos roles tanto en la fijación intracelular de trazas de elementos de Zn y Cu como en el control de las concentraciones, y neutralizando las influencias perjudiciales a la exposición de elementos tóxicos...

Gene expression profiling in wild-type and metallothionein mutant fibroblast cell lines

The role of metallothioneins (MT) in copper homeostasis is of great interest, as it appears to be partially responsible for the regulation of intracellular copper levels during adaptation to extracellular excess of the metal. To further investigate a possible role of MTs in copper metabolism, a genomics approach was utilized to evaluate the role of MT on gene expression. Microarray analysis was used to examine the effects of copper overload in fibroblast cells from normal and MT I and II double knock-out mice (MT-/-). As a first step, we compared genes that were significantly upregulated in wild-type and MT-/- cells exposed to copper. Even though wild-type and mutant cells are undistinguishable in terms of their morphological features and rates of growth, our results show that MT-/- cells do not respond with induction of typical markers of cellular stress under copper excess conditions, as observed in the wild-type cell line, suggesting that the transcription initiation rate or the mRNA stability of stress genes is affected when there is an alteration in the copper store capacity. The functional classification of other up-regulated genes in both cell lines indicates that a large proportion (>80 percent) belong to two major categories: 1) metabolism; and 2) cellular physiological processes, suggesting that at the transcriptional level copper overload induces the expression of genes associated with diverse molecular functions. These results open the possibility to understand how copper homeostasis is being coordinated with other metabolic pathways.

Toxicología ambiental: metalotioneínas y metabolismo celular / Environmental toxicology: metallothioneins and cellular metabolism

Las metalotioneínas (MT) constituyen una familia de proteínas de bajo peso molecular (6-8 kDa), presentes en procariotes y eucariotes, con elevado contenido en cisteína (30-35 por ciento) y marcada capacidad para combinarse con iones metálicos. dentro del metabolismo celular, se le han asignado múltiples funciones, desde un papel central en la homeostasis celular de ciertos metales pesados esenciales ("pool" citosólico de Zn y/o Cu), la detoxificación de metales pesados no esenciales, hasta su participación en ciertos procesos inflamatorios y la inactivación de radicales libres. La variación en el nivel de MT es indicador de exposición a xenobióticos, de situaciones ambientales adversas así como de situaciones de estrés fisiológico. Como tal, esta respuesta puede utilizarse tanto a nivel de la toxicología laboral, clínica y en estudios ecotoxicológicos. A este respecto, se encuentra en fase experimental su utilización con fines de diagnóstico ambiental. Esta revisión tiene como objeto constituir una breve reseña sobre los principales conocimientos reunidos hasta la fecha. Se ha avanzado significativamente en los aspectos básicos y metodológicos de la inducción de metalotioneínas en situaciones de estrés. Sin embargo, y a pesar de contarse con un número importante de estudios específicos, y a diferencia de otras proteínas menos estudiadas, queda aún sin precisar su función básica dentro del metabolismo celular