Thimerosal-induced cytosolic Ca2+ elevation and subsequent cell death in human osteosarcoma cells

Area of Science:

• Biochemistry
• Cell Biology
• Toxicology

Background:

• The impact of thimerosal on calcium signaling and cell death in human osteoblast-like cells remains uninvestigated.
• Understanding thimerosal's effects on calcium homeostasis is crucial for assessing its potential toxicity in bone cells.

Purpose of the Study:

• To investigate the effects of thimerosal on cytosolic free calcium concentration ([Ca(2+)]i) and cell viability in MG63 human osteosarcoma cells.
• To elucidate the mechanisms underlying thimerosal-induced calcium changes and cytotoxicity.

Main Methods:

• Measurement of intracellular calcium ([Ca(2+)]i) using fura-2 fluorescence.
• Assessment of cell death using the WST-1 assay.
• Pharmacological manipulation of calcium channels and stores, including thapsigargin and U73122.

Main Results:

• Thimerosal increased [Ca(2+)]i in a concentration-dependent manner above 5 microM.
• The calcium increase involved both release from endoplasmic reticulum stores and extracellular influx, sensitive to La(3+) and dithiothreitol.
• Thimerosal exhibited concentration-dependent cytotoxicity, with 5, 10, and 20 microM killing 33%, 55%, and 100% of cells, respectively.
• Cytotoxicity was partially reversed by chelating intracellular calcium.

Conclusions:

• Thimerosal induces a rise in cytosolic calcium in MG63 cells through endoplasmic reticulum release and extracellular influx.
• Thimerosal causes calcium-dependent cytotoxicity in a concentration-dependent manner.
• These findings highlight the potential toxic effects of thimerosal on bone cells via calcium signaling disruption.