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Bromobenzene and furosemide hepatotoxicity: alterations in glutathione, protein thiols, and calcium
K K Grewal1, E Rafeiro, W J Racz
1Department of Pharmacology and Toxicology, Queen's University, Kingston, ON, Canada.
Abstract:
The nature of the events whereby the reactive intermediates resulting from the bioactivation of bromobenzene and furosemide induce hepatotoxicity is unknown. To examine a role for disturbances in intracellular calcium homeostasis, secondary to a depletion in cellular reduced glutathione (GSH) and reduced protein thiols (PSHs), isolated mouse hepatocytes were exposed to cytotoxic concentrations of bromobenzene or furosemide. Cytosolic calcium concentration, as well as thiol status, was determined. The incubation of hepatocytes with 3.0 mM bromobenzene, and subsequent additions (1.2 mM) of the agent every hour, resulted in significant GSH depletion. The loss of plasma membrane integrity at 1.5 h preceded both a rise in the cytosolic Ca2+ concentration and depletion of total PSH content. Furosemide (1.0 mM) produced a 70% depletion in cellular GSH content in isolated hepatocytes. The initiation of cell damage occurred concurrently with both a rise in the cytosolic Ca2+ concentration and a depletion of total PSH content 4 h following furosemide addition. Since the increase in cytosolic Ca2+ did not precede cytotoxicity, these results do not support an initiating role for Ca2+ deregulation in bromobenzene and furosemide hepatotoxicities. In addition, depletion of PSH content did not correlate with bromobenzene- or furosemide-induced cytotoxicity.
Insights
This study investigated hepatotoxicity from bromobenzene and furosemide. Researchers found that calcium deregulation and thiol depletion do not initiate cell damage, challenging previous theories on drug-induced liver injury.
Area of Science:
- Hepatotoxicity Research
- Cellular Toxicology
- Biochemical Mechanisms
Background:
- The mechanisms underlying drug-induced hepatotoxicity, particularly from bromobenzene and furosemide, remain unclear.
- Investigating the role of intracellular calcium homeostasis disturbances and thiol depletion in this process is crucial.
Purpose of the Study:
- To examine if disruptions in intracellular calcium homeostasis, caused by reduced glutathione (GSH) and protein thiols (PSHs) depletion, initiate hepatotoxicity.
- To determine the temporal relationship between calcium levels, thiol status, and cell damage in response to bromobenzene and furosemide.
Main Methods:
- Isolated mouse hepatocytes were exposed to cytotoxic concentrations of bromobenzene or furosemide.
- Cytosolic calcium concentration and thiol status (GSH and PSHs) were measured over time.
- Plasma membrane integrity was assessed to determine the onset of cell damage.
Main Results:
- Bromobenzene exposure led to significant GSH depletion, with plasma membrane damage preceding increases in cytosolic Ca2+ and PSH depletion.
- Furosemide caused substantial GSH depletion, and cell damage occurred concurrently with Ca2+ increase and PSH depletion.
- Cytosolic Ca2+ increases did not precede cytotoxicity, and PSH depletion did not correlate with the observed hepatotoxicity for either agent.
Conclusions:
- The findings do not support a primary role for calcium deregulation in initiating bromobenzene or furosemide-induced hepatotoxicity.
- Depletion of protein thiols (PSHs) is not directly correlated with the cytotoxic effects of these drugs.
- Further research is needed to elucidate the exact events leading to reactive intermediate-induced hepatotoxicity.