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Effects of Clostridium difficile toxin B on human monocytes and macrophages: possible relationship with cytoskeletal
J C Siffert1, O Baldacini, J G Kuhry
1Département d'Immunologie, Immunopharmacologie et Pathologie, Université Louis Pasteur, Illkirch, France.
Abstract:
Toxin B from Clostridium difficile is cytopathic in vitro for various types of cells, including polymorphonuclear cells, lymphocytes, and monocytes. Since intestine lamina propria is rich in macrophages, we studied the effect of toxin B on human monocytes and on human macrophages generated in vitro by long-term culture of purified circulating blood monocytes. Upon addition of toxin B, human monocytes exhibited few modifications whereas macrophages adopted a stellate morphology, with rounding up of the perikaryon. Toxin B made microfilaments of actin disappear and induced an important reorganization of vimentin and a redistribution of tubulin. Membrane area increased by approximately 16%. Toxin B did not affect the viability of human mononuclear phagocytes and did not exert any significant lytic effect. It profoundly altered the phagocytic function of macrophages. When activated by gamma interferon in the presence of toxin B, monocytes were more cytotoxic for U-937 target cells than control monocytes activated in absence of toxin. Finally, the combined treatment of monocytes with gamma interferon and toxin B increased significantly the secretion of tumor necrosis factor alpha, whereas toxin B alone was unable to induce tumor necrosis factor production. These results suggest that morphological and functional alterations induced in human mononuclear phagocytes by toxin B from C. difficile are due to the disorganization of the cytoskeleton and the resulting impairment of the membrane traffic equilibrium.
Insights
Clostridium difficile toxin B alters human macrophage structure and function by disrupting the cytoskeleton. This impairs phagocytosis but enhances gamma interferon-induced cytotoxicity and tumor necrosis factor alpha secretion.
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Clostridium difficile Toxin B is a known cytotoxin affecting various cell types.
- Intestinal lamina propria contains numerous macrophages, making them a key target for C. difficile toxins.
Purpose of the Study:
- To investigate the effects of Toxin B on human monocytes and in vitro-derived macrophages.
- To elucidate the mechanisms underlying Toxin B-induced cellular alterations.
Main Methods:
- Human monocytes and macrophages were treated with Toxin B.
- Cytoskeletal components (actin, vimentin, tubulin) were analyzed.
- Membrane area, phagocytic activity, and cytokine production were assessed.
- Cytotoxicity assays were performed on U-937 target cells.
Main Results:
- Toxin B induced morphological changes in macrophages, including a stellate shape and perikaryon rounding.
- Disappearance of actin microfilaments and reorganization of vimentin and tubulin were observed.
- Macrophage phagocytic function was significantly impaired.
- Combined treatment with gamma interferon and Toxin B enhanced monocyte cytotoxicity and TNF-alpha secretion.
Conclusions:
- Toxin B-induced alterations in human mononuclear phagocytes are linked to cytoskeleton disorganization.
- Impaired membrane traffic equilibrium contributes to functional changes.
- Toxin B modulates immune responses, enhancing cytotoxic and pro-inflammatory activities under specific conditions.