Cationic liposomes induce apoptosis through p38 MAP kinase-caspase-8-Bid pathway in macrophage-like RAW264.7 cells

Area of Science:

• Cell Biology
• Biochemistry
• Toxicology

Background:

• Cationic liposomes, specifically stearylamine liposomes (SA-liposomes), are known to induce apoptosis.
• The precise molecular mechanisms underlying SA-liposome-induced apoptosis remain unclear.
• Understanding these pathways is crucial for evaluating the safety and efficacy of liposomal drug delivery systems.

Purpose of the Study:

• To elucidate the signaling pathways involved in SA-liposome-induced apoptosis in the RAW264.7 macrophage cell line.
• To identify key molecular players and intermediates in the apoptotic cascade.
• To investigate the role of reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) in this process.

Main Methods:

• Treatment of RAW264.7 cells with SA-liposomes.
• Assessment of MAPK activation (p38, JNK) using specific inhibitors.
• Measurement of reactive oxygen species (ROS) levels using N-acetylcysteine.
• Analysis of caspase activation (caspase-8) and protein cleavage (Bid, Bax).
• Evaluation of Bcl-2 expression levels.

Main Results:

• SA-liposomes induced activation of p38 and c-jun N-terminal kinase (JNK) MAPKs.
• Inhibition of p38 significantly blocked SA-liposome-induced apoptosis.
• N-acetylcysteine, a ROS scavenger, prevented p38 activation and cell death, indicating ROS as an initial trigger.
• p38 activation led to caspase-8 activation and subsequent Bid cleavage.
• No significant changes in Bcl-2 expression or Bax cleavage were observed.

Conclusions:

• SA-liposome-induced apoptosis in RAW264.7 cells is primarily mediated by the p38 MAPK pathway.
• The process involves ROS generation, p38 activation, caspase-8 activation, and Bid cleavage.
• This study clarifies a key apoptotic pathway for cationic liposomes, highlighting the roles of ROS and specific signaling molecules.