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Updated: Aug 12, 2026
High Content Screening in Neurodegenerative Diseases
Published on: January 6, 2012
Organophosphorus compound-induced modification of SH-SY5Y human neuroblastoma mitochondrial transmembrane potential
1Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, Virginia 24061, USA.
Abstract:
Organophosphorus (OP) compounds inhibit mitochondrial enzymes, respiration, and ATP generation, in addition to inducing structural changes such as matrix swelling. This implicates mitochondria as primary subcellular targets for these compounds. In this study, the health and function of cellular mitochondria following OP compound exposure were assessed by evaluating the mitochondrial transmembrane potential (DeltaPsi(m)). This was done by measuring the changes in DeltaPsi(m) in SH-SY5Y human neuroblastoma cells incubated with the cationic fluorochrome, rhodamine 123 (5 microg/ml), and the OP compounds tri-ortho-tolyl phosphate (TOTP), triphenyl phosphite (TPPi), or parathion for 7.5 to 960 minutes. OP compounds (100 microM to 1 mM) induced significant concentration-dependent mitochondrial hyperpolarization with peak maxima occurring at 60 (TOTP, TPPi) or 120 (parathion) min. Following this, the mitochondrial membranes gradually depolarized. Pretreatment with cyclosporin A (500 nM, 30 h), a mitochondrial permeability transition pore (PTP) inhibitor, decreased the hyperpolarization. In contrast, 30-h pretreatment with the muscarinic receptor agonist carbachol (1 mM) significantly increased DeltaPsi(m) and delayed subsequent depolarization. Hyperpolarization and subsequent depolarization of mitochondrial membranes occurred 16 to 24 h prior to a loss of substrate adhesion or an increase in DNA fragmentation, indicating that mitochondria were a primary target in OP compound-initiated cytotoxicity.
Insights
Organophosphorus compounds target cellular mitochondria, initially causing hyperpolarization then depolarization. This mitochondrial dysfunction precedes cell damage, indicating mitochondria are key targets in organophosphate toxicity.
Area of Science:
- Biochemistry
- Cell Biology
- Toxicology
Background:
- Organophosphorus (OP) compounds are known to disrupt mitochondrial function, affecting enzymes, respiration, and ATP generation.
- Mitochondria exhibit structural changes like matrix swelling upon OP exposure, suggesting they are primary subcellular targets.
Purpose of the Study:
- To assess cellular mitochondrial health and function after OP compound exposure.
- To evaluate changes in mitochondrial transmembrane potential (DeltaPsi(m)) as an indicator of OP toxicity.
Main Methods:
- SH-SY5Y human neuroblastoma cells were incubated with rhodamine 123 and OP compounds (tri-ortho-tolyl phosphate, triphenyl phosphite, parathion).
- Mitochondrial transmembrane potential (DeltaPsi(m)) was measured over time (7.5 to 960 minutes).
- Effects of cyclosporin A (PTP inhibitor) and carbachol (muscarinic agonist) on DeltaPsi(m) were investigated.
Main Results:
- OP compounds induced concentration-dependent mitochondrial hyperpolarization, peaking at 60-120 minutes, followed by gradual depolarization.
- Cyclosporin A pretreatment reduced OP-induced hyperpolarization.
- Carbachol pretreatment increased DeltaPsi(m) and delayed depolarization.
Conclusions:
- Mitochondrial hyperpolarization and subsequent depolarization are early events in OP compound-initiated cytotoxicity.
- These changes in mitochondrial membranes precede observable cell damage like loss of adhesion or DNA fragmentation.
- Mitochondria are confirmed as primary subcellular targets in the toxic mechanism of OP compounds.
