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Cell Biology International (2008) 32, 417–426 (Printed in Great Britain)

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Aggregatibacter actinomycetemcomitans lipopolysaccharide affects human gingival fibroblast cytoskeletal organization

Gloria Gutiérrez‑Venegas^*, Luis Arturo Contreras‑Marmolejo, Patricia Román‑Alvárez and Carolina Barajas‑Torres

Departamento de Bioquímica, División de Estudios de Posgrado e Investigación, Facultad de Odontología, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico

Abstract

The cytoskeleton is a dynamic structure that plays a key role in maintaining cell morphology and function. This study investigates the effect of bacterial wall lipopolysaccharide (LPS), a strong inflammatory agent, on the dynamics and organization of actin, tubulin, vimentin, and vinculin proteins in human gingival fibroblasts (HGF). A time-dependent study showed a noticeable change in actin architecture after 1.5h of incubation with LPS (1μg/ml) with the formation of orthogonal fibers and further accumulation of actin filament at the cell periphery by 24h. When 0.01–10μg/ml of LPS was added to human gingival fibroblast cultures, cells acquired a round, flat shape and gradually developed cytoplasmic ruffling. Lipopolysaccharides extracted from Aggregatibacter actinomycetemcomitans periodontopathogenic bacteria promoted alterations in F-actin stress fibres of human gingival cells. Normally, human gingival cells have F-actin fibres that are organized in linear distribution throughout the cells, extending along the cell's length. LPS-treated cells exhibited changes in cytoskeletal protein organization, and F-actin was reorganized by the formation of bundles underneath and parallel to the cell membrane. We also found the reorganization of the vimentin network into vimentin bundling after 1.5h of treatment. HGF cells exhibited diffuse and granular γ-tubulin stain. There was no change in LPS-treated HGF. However, vinculin plaques distributed in the cell body diminished after LPS treatment.

We conclude that the dynamic and structured organization of cytoskeletal filaments and actin assembly in human gingival fibroblasts is altered by LPS treatment and is accompanied by a decrease in F-actin pools.

Key words: Lipopolysaccharide, Aggregatibacter actinomycetemcomitans, Cytoskeletal, Actin, Human gingival fibroblasts, F-actin.

^*Corresponding author. Laboratorio de Bioquímica, División de Estudios de Posgrado e Investigación, Facultad de Odontología, Universidad Nacional Autónoma de México, 04510 México, D.F., México. Tel./fax: +52 55 5622 5554.

Received 23 March 2007/5 December 2007; accepted 24 December 2007