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Involvement of actin cytoskeleton in macrophage apoptosis induced by cationic liposomes

Katsuki Takano1, Kaori Sato, Yoichi Negishi

  • 1Tokyo University of Pharmacy and Life Sciences, Horinouchi, Hachioji, Tokyo, Japan.

Archives of Biochemistry and Biophysics
|December 29, 2011
PubMed

Insights

Cationic liposomes trigger macrophage apoptosis via the actin cytoskeleton. Inhibiting actin polymerization with cytochalasin D blocked apoptosis, phosphatidylserine externalization, and reactive oxygen species generation.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Immunology

Background:

  • Cationic liposomes, such as stearylamine liposomes (SA-liposomes), are utilized in drug delivery.
  • Macrophage apoptosis can be induced by various stimuli, including certain liposomal formulations.
  • The precise mechanisms underlying SA-liposome-induced macrophage apoptosis are not fully elucidated.

Purpose of the Study:

  • To investigate the role of the actin cytoskeleton in macrophage apoptosis induced by SA-liposomes.
  • To explore the involvement of protein kinase C delta (PKCδ) and reactive oxygen species (ROS) in this process.
  • To identify potential upstream regulators, such as proteoglycans, in the SA-liposome-induced apoptotic pathway.

Main Methods:

  • Utilized cytochalasin D, an F-actin polymerization inhibitor, to assess its effect on SA-liposome-induced apoptosis.
  • Measured phosphatidylserine externalization as an indicator of apoptosis.
  • Assessed PKCδ activation and ROS generation.
  • Employed fluorescence microscopy to visualize the co-localization of DiI-labeled SA-liposomes and F-actin (using fluorescein-labeled phalloidin).
  • Investigated the effect of chondroitinase ABC pre-treatment on SA-liposome and F-actin co-localization.

Main Results:

  • Cytochalasin D significantly suppressed SA-liposome-induced phosphatidylserine externalization, indicating reduced apoptosis.
  • The activation of PKCδ and ROS generation were also inhibited by cytochalasin D.
  • Microscopy confirmed the co-localization of SA-liposomes and F-actin, which was disrupted by cytochalasin D.
  • Pre-treatment with chondroitinase ABC inhibited the co-localization of SA-liposomes and F-actin.

Conclusions:

  • The actin cytoskeleton plays a crucial role in SA-liposome-induced macrophage apoptosis.
  • The proteoglycan-actin cytoskeleton-ROS generation pathway is implicated in SA-liposome-induced apoptosis in macrophages.
  • These findings provide novel insights into the mechanism of liposome-induced cell death.

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