Cultured macrophages cause dissolucytosis of metallic silver

The present study proves that cultured macrophages can liberate silver ions from metallic silver surfaces by a process called dissolucytosis. Macrophages (J774) were grown on a silver plate for different periods of time and after fixation in glutaraldehyde, they were subjected to autometallograhy in order to amplify possible cellular silver-sulphur nanocrystals. Light and electron microscopic analysis of the cells revealed that silver ions released from the plate had been taken up by the macrophages and accumulated in lysosome- like structures. We found that the liberation of silver ions takes place extracellularly and is caused by chemical activity in a dissolution membrane, most likely secreted and organized by the macrophages. The liberation and the subsequent uptake of silver ions in the macrophages is a relatively fast process and the resulting silver-sulphur nanocrystals can be observed in macrophages that have been in contact with metallic silver for only a few minutes. Our findings indicate that the speed of dissolucytosis is highly influenced by the chemical nature of the object exposed to the dissolucytotic process which is likely to occur whenever macrophages encounter a non-phagocytosable foreign object

Uptake of silver from metallic silver surfaces induces cell death and a pro-inflammatory response in cultured J774 macrophages

In clinical medicine metallic silver is used as anti-bacterial coating on various catheters, bandages and prostheses. By means of dissolucytosis, i.e. extracellular macrophage-mediated bio-liberation of metal ions, silver ions are continuously liberated from silver surfaces starting within minutes of exposure. The present study investigates how bio-liberation and subsequent cellular uptake of silver ions affects cell viability and cell signalling within the first 3-24 hours of exposure when J774 macrophages are grown directly on a silver surface. Autometallography (AMG) was applied to demonstrate cytoplasmatic silver uptake and localisation after 1, 3, 12 and 24 hours of exposure to metallic silver. From 12 hours onwards the cells were completely filled with silver enhanced silver-sulphur nanocrystals (AMG-silver grains). At the ultrastructural level, the silver accumulations were located to lysosome-like structures. An immunoassay cell death kit found silver-induced apoptosis after 12 and 24 hours of exposure. Necrosis was seen at the same times. Judged by mRNA analysis silver exposure statistically significantly induces TNF-α and m-CSF gene expression, especially at 3 hours. Furthermore, anti-inflammatory IL-10 transcription is reduced by silver uptake and 24 hours of silver exposure induces massive iNOS-2 gene expression. At the same time silver exposure increases the gene expression of metallothionein (MT-I/MT-II), a cystein-rich protein known for its role in detoxifying heavy metals. Our data suggest that silver ions liberated from metallic silver surfaces accumulate in lysosomes, reduce macrophage viability by apoptosis and necrosis and induce a proinflammatory response

Toxicological aspects of injectable gold-hyaluronan combination as a treatment for neuroinflammation

Secondary inflammatory reactions to stroke or trauma contribute to irreplaceable loss of brain tissue of the affected patients. Likewise, neuroinflammatory processes are the main pathophysiological feature in Multiple Sclerosis (MS), a common neurodegenerative disease among young adults. In the search for safe and efficient ways to reduce inflammation within nervous tissue older immunosuppressive remedies have been re-investigated. The anti-inflammatory properties of gold salts are well known but result in uncontrollable systemic spread of gold ions, generating side effects such as nephrotoxicity, limiting their use. Recent studies have circumvented this obstacle by introducing metallic gold implants as a localized source of immune-modulating gold ions and suspension in hyaluronic acid (HA) enables injection of small amounts of gold in the natural spaces of the brain. By injecting >25 µm gold beads in HA intracerebrally we recently showed a slowing of disease progression in a rodent model of MS. The toxicological aspects were, however, not assessed. The present study investigates the viability of neuronal and macrophage cell cultures exposed to the gold/HA combination and the possible risk associated with unilateral gold/HA injection in young Balb/CA mice in the first 7 to 21 days of gold-exposure. Tracing by autometallography of gold accumulations throughout the brain exhibited sparse gold uptake in glia and neurons of hippocampus and cortex, and striatum and cerebellum were void of staining. No systemic spread of gold was seen in liver or kidney, nor were there signs of obstruction of the ventricular system. Both cell cultures of J774 macrophages and CCL neurons accumulated gold from gold/HA-exposure with no signs of reduced viability. In conclusion, our findings indicate that gold/HA is not overtly neuro- or cytotoxic, nor does intraventricular exposure result in widespread gold accumulation or tissue damage, warranting further studies into the pharmacological properties of this novel form of gold treatment. Histol Histopathol 29, 447-456 (2014