Metallothionein (MT)-I+II synthesis is induced in the central nervous system (CNS) in response to practically any pathogen or disorder, where it is increased mainly in reactive glia. MT-I+II are involved in host defence reactions and neuroprotection during neuropathological conditions, in which MT-I+II decrease inflammation and secondary tissue damage (oxidative stress, neurodegeneration, and apoptosis) and promote post-injury repair and regeneration (angiogenesis, neurogenesis, neuronal sprouting and tissue remodelling). Intracellularly the molecular MT-I+II actions involve metal ion control and scavenging of reactive oxygen species (ROS) leading to cellular redox control. By regulating metal ions, MT-I+II can control metal-containing transcription factors, zinc-finger proteins and p53. However, the neuroprotective functions of MT-I+II also involve an extracellular component. MT-I+II protects the neurons by signal transduction through the low-density lipoprotein family of receptors on the cell surface involving lipoprotein receptor-1 (LRP1) and megalin (LRP2). In this review we discuss the newest data on cerebral MT-I+II functions following brain injury and experimental autoimmune encephalomyelitis.

Traumatic brain injury results in loss of neurons caused as much by the resulting neuroinflammation as by the injury. Gold salts are known to be immunosuppressive, but their use are limited by nephrotoxicity. However, as we have proven that implants of pure metallic gold release gold ions which do not spread in the body, but are taken up by cells near the implant, we hypothesize that metallic gold could reduce local neuroinflammation in a safe way. Bio-liberation, or dissolucytosis, of gold ions from metallic gold surfaces requires the presence of disolycytes i.e. macrophages and the process is limited by their number and activity. We injected 20-45 mum gold particles into the neocortex of mice before generating a cryo-injury. Comparing gold-treated and untreated cryolesions, the release of gold reduced microgliosis and neuronal apoptosis accompanied by a transient astrogliosis and an increased neural stem cell response. We conclude that bio-liberated gold ions possess pronounced anti-inflammatory and neuron-protective capacities in the brain and suggest that metallic gold has clinical potentials. Intra-cerebral application of metallic gold as a pharmaceutical source of gold ions represents a completely new medical concept that bypasses the blood-brain-barrier and allows direct drug delivery to inflamed brain tissue.

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