Thymosin α1 modifies podosome architecture and promptly stimulates the expression of podosomal markers in mature macrophages

Abstract

Background and aims: The immunomodulatory activity of thymosin α1 (Tα1) on innate immunity has been extensively described, but its mechanism of action is not completely understood. We explored the possibility that Tα1-stimulation could affect the formation of podosomes, the highly dynamic, actin-rich, adhesion structures involved in macrophage adhesion/chemotaxis.

Methods: The following methods were used: optical and scanning electron microscopy for analyzing morphology of human monocyte-derived macrophages (MDMs); time-lapse imaging for visualizing the time-dependent modifications induced at early times by Tα1 treatment; confocal microscopy and Western blot for analyzing localization and expression of podosome components; and Matrigel Migration Assay and zymography for testing MDM invasive ability and metalloproteinase secretion.

Results: We obtained data to support that Tα1 could affect MDM motility, invasion and chemotaxis by promptly stimulating assembly and disassembly of podosomal structures. At very early times after its addition to cell culture medium and within 1 h of treatment, Tα1 induces modifications in MDM morphology and in podosomal components that are suggestive of increased podosome turnover.

Conclusions: Since impairment of podosome formation leads to reduced innate immunity and is associated with several immunodeficiency disorders, we confirm the validity of Tα1 as a potent activator of innate immunity and suggest possible new clinical application of this thymic peptide.

Keywords:

• confocal microscopy
• cytoskeletal components
• macrophages
• podosomes
• thymosin α1

Acknowledgments

We thank Dr. Martino Tony Miele for scientific secretariat support, and Arianna Colini Baldeschi (graduating student) for contributing to sample preparation in the WB and confocal microscopy analyses.

Declaration of interest

This paper is part of a supplemental issue, sponsored by SciClone. This work was supported by two grants from the Italian Ministry of University and Research (MIUR): Research Projects of National Interest (PRIN) 2008, including MIUR Prot. No 10484 to E Garaci and PS Vallebona. In addition, E Garaci is a Thymosin patent holder. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

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