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Interaction of recombinant human interferon-gamma with liposomes
H Ishihara1, T Hara, Y Aramaki
1Tokyo College of Pharmacy, Japan.
Insights
Recombinant human interferon-gamma (IFN) interacts with liposomes, showing charge and pH-dependent binding. Prolonged interaction causes liposome aggregation and morphological changes, leading to marker leakage.
Area of Science:
- Biochemistry
- Materials Science
- Cell Biology
Background:
- Interferon-gamma (IFN) is a crucial cytokine involved in immune responses.
- Liposomes are widely used as drug delivery vehicles and model systems for membrane interactions.
- Understanding the interaction between proteins like IFN and liposomes is vital for drug delivery and biomaterial design.
Purpose of the Study:
- To investigate the binding characteristics of recombinant human interferon-gamma (IFN) with egg phosphatidylcholine liposomes.
- To elucidate the mechanisms underlying IFN-liposome interactions, including binding, aggregation, and morphological changes.
- To determine the influence of liposomal charge and pH on IFN binding and subsequent liposome behavior.
Main Methods:
- Liposome preparation using egg phosphatidylcholine.
- Binding studies of IFN to liposomes under varying pH and charge conditions.
- Turbidity measurements to assess liposome aggregation.
- Electron microscopy to visualize liposome morphology and aggregation.
- Leakage assays using a trapped marker (calcein) to evaluate membrane integrity.
Main Results:
- IFN binding to liposomes was dependent on liposomal charge and pH, with preferential binding to negatively charged liposomes at pH 7.4-10.
- IFN induced liposomal aggregation, evidenced by increased turbidity, which was partially reversible by NaCl, suggesting ionic binding.
- Extended incubation led to irreversible aggregation and morphological changes in liposomes, resulting in the leakage of entrapped calcein.
- Electron microscopy confirmed liposome aggregation and revealed structural alterations associated with marker leakage.
Conclusions:
- Ionic binding plays a role in the initial interaction between IFN and liposomes.
- Prolonged interaction can lead to significant morphological changes in negatively charged liposomes, impacting their structural integrity.
- These findings highlight the complex interplay between IFN and liposomal membranes, with implications for liposome-based therapeutics and understanding protein-lipid interactions.
Abstract:
The interaction of recombinant human interferon-gamma (IFN) with egg phosphatidylcholine liposomes was studied. IFN which binds to liposomes was dependent on the liposomal charge and pH, and a preferential binding was observed in negatively charged liposomes at pH 7.4-10. Electron-microscopic observation showed that the increased liposomal turbidity induced by IFN was due to liposomal aggregation, and the increased turbidity could be decreased by the addition of NaCl. Thus, ionic binding may participate in this interaction. But, when the incubation time was longer, the liposomal aggregation was not decreased by the addition of NaCl, and the leakage of the entrapped marker, calcein, was observed. Electron-microscopic analysis showed that this leakage resulted from the morphological change of liposomes. From these findings, ionic binding may participate in the interaction between IFN and liposomes and then develop a morphological change in negatively charged liposomes under the neutral pH condition.
