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Protective effect of cell-permeable ceramide analogs against modeccin, ricin, Pseudomonas toxin, and diphtheria toxin
1Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799, USA.
Abstract:
We investigated the effects of various ceramide (Cer) analogs and related sphingolipids on the cytotoxicities of modeccin, ricin, Pseudomonas toxin, and diphtheria toxin in various cell lines. The most pronounced protective effect by C6Cer, a short-chain cell-permeable Cer analog, was observed in modeccin cytotoxicity in Vero, BER-40, and MDCK cells, whereas the cytotoxicity of diphtheria toxin was not affected by any of the ceramide analogs tested. C6Cer did not affect the binding and internalization of ricin and modeccin in Vero and BER-40 cells. C2Cer and C8Cer also protected against modeccin cytotoxicity, albeit less effectively than C6Cer. However, related sphingolipids including sphingosine, sphingomyelin, lactosylceramide, C18Cer (the naturally occurring ceramide), and dihydro C6Cer had no effect. A correlation was found between the ability of ceramides to inhibit bulk protein secretion and the inhibition of modeccin cytotoxicity by ceramides. Among Cer analogs tested, C6Cer, the most potent inhibitor of modeccin cytotoxicity, strongly inhibited bulk protein secretion in Vero, BER-40, and MDCK cells. PtK1 cells, which were not protected by ceramides against toxins, were resistant to ceramide-induced inhibition of bulk protein secretion. These results confirm that Cer may modulate the intracellular transport of proteins through the Golgi complex. Such Cer-sensitive processes may be involved in the intoxication of cells by plant and bacterial toxins, especially modeccin.
Insights
Short-chain ceramides like C6Cer protect cells from modeccin toxin by inhibiting protein secretion. This suggests ceramides may influence intracellular transport, impacting toxin intoxication.
Area of Science:
- Cell Biology
- Biochemistry
- Toxicology
Background:
- Ceramides (Cer) are sphingolipids involved in various cellular processes.
- Plant and bacterial toxins like modeccin, ricin, and diphtheria toxin pose significant cellular threats.
- Understanding cellular defense mechanisms against toxins is crucial.
Purpose of the Study:
- To investigate the protective effects of ceramide analogs and sphingolipids against modeccin, ricin, Pseudomonas toxin, and diphtheria toxin.
- To elucidate the mechanism by which ceramides confer protection, focusing on protein transport.
Main Methods:
- Testing cytotoxicity of various toxins in cell lines (Vero, BER-40, MDCK, PtK1) with and without ceramide analogs.
- Assessing the binding and internalization of toxins.
- Measuring bulk protein secretion inhibition by ceramides.
Main Results:
- C6Cer demonstrated significant protection against modeccin cytotoxicity in Vero, BER-40, and MDCK cells.
- Other sphingolipids and ceramide analogs showed minimal or no protective effects.
- Ceramides inhibited bulk protein secretion, correlating with protection against modeccin.
- PtK1 cells, resistant to ceramide protection, also resisted ceramide-induced inhibition of protein secretion.
Conclusions:
- Ceramides, particularly C6Cer, can protect cells from modeccin intoxication.
- The protective mechanism involves the inhibition of bulk protein secretion, likely through modulation of intracellular protein transport via the Golgi complex.
- These ceramide-sensitive processes are implicated in cellular intoxication by certain plant and bacterial toxins.