Generation of reactive oxygen species is an early event in dolichyl phosphate-induced apoptosis

Area of Science:

• Cell Biology
• Biochemistry
• Mitochondrial Research

Background:

• Dolichyl phosphate (Dol-P) is a lipid involved in protein glycosylation.
• The role of Dol-P in cellular apoptosis is not fully understood.
• U937 cells are a human leukaemic cell line often used in apoptosis studies.

Purpose of the Study:

• To elucidate the mechanism by which dolichyl phosphate (Dol-P) induces apoptosis in U937 cells.
• To investigate the role of mitochondrial dysfunction and reactive oxygen species (ROS) in Dol-P-induced cell death.

Main Methods:

• Isolated mitochondria assays to assess respiratory complex activity.
• Measurement of cytochrome-c release and reactive oxygen species (ROS) generation.
• Flow cytometry for mitochondrial membrane potential (Δψm) analysis.
• Electron microscopy to observe mitochondrial morphology.
• Inhibition studies using antioxidants and specific enzyme inhibitors.

Main Results:

• Dol-P significantly inhibited mitochondrial respiratory complex II activity, and also affected complexes I and III.
• Dol-P induced cytochrome-c release, loss of mitochondrial membrane potential, and increased ROS generation.
• The antioxidant pyrrolidine dithiocarbamate (PDTC) reduced Dol-P-induced ROS and caspase-3 activation.
• Mitochondria treated with Dol-P showed swelling and a spherical shape.

Conclusions:

• Dolichyl phosphate (Dol-P) initiates apoptosis by directly disrupting mitochondrial respiratory complexes, particularly complex II.
• This disruption leads to increased reactive oxygen species (ROS) generation and mitochondrial dysfunction, triggering the apoptotic pathway.
• Targeting mitochondrial respiration is a key mechanism in Dol-P-induced cell death.