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Changes in ovine erythrocyte morphology due to sphingomyelin degradation by Corynebacterium pseudotuberculosis
K A Brogden1, R L Engen, J G Songer
1National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, Iowa.
Abstract:
Corynebacterium pseudotuberculosis produces a sphingomyelin-specific phospholipase D exotoxin that is a major determinant in the pathogenesis of caseous lymphadenitis. We assessed the changes induced in the morphology and sphingomyelin concentration of ovine erythrocytes after incubation with broth culture filtrates or purified exotoxin. Sphingomyelin was hydrolysed nearly in parallel with shape change. Morphologically, spherostomatocytes were seen initially, and later these contained numerous vacuoles at the periphery. Vacuoles seen in thin sections with transmission electron microscopy appeared as pits with scanning electron microscopy. Pitting became progressively worse with time, leading to extensive scalloping of the membrane surface. Chemically, significant decreases (P less than or equal to 0.05) in erythrocyte membrane sphingomyelin content and significant increases (P less than or equal to 0.05) in the content of glycerophospholipids (i.e. phosphatidylglycerol) were observed in erythrocytes incubated with broth culture filtrates or purified exotoxin. These alterations may contribute to the pathophysiology of acute infections induced by C. pseudotuberculosis.
Insights
Corynebacterium pseudotuberculosis exotoxin degrades erythrocyte sphingomyelin, causing cell shape changes and membrane damage. This sphingolipid hydrolysis may contribute to caseous lymphadenitis pathogenesis.
Area of Science:
- Veterinary Microbiology
- Pathogen-Host Interactions
- Cell Biology
Background:
- Corynebacterium pseudotuberculosis is a significant veterinary pathogen.
- Its sphingomyelin-specific phospholipase D (SL-PLD) exotoxin is crucial in caseous lymphadenitis pathogenesis.
- Understanding SL-PLD's erythrocyte effects is key to elucidating disease mechanisms.
Purpose of the Study:
- To investigate the impact of C. pseudotuberculosis exotoxin on ovine erythrocyte morphology and sphingomyelin content.
- To correlate sphingomyelin hydrolysis with observed cellular changes.
Main Methods:
- Incubation of ovine erythrocytes with C. pseudotuberculosis broth culture filtrates and purified SL-PLD.
- Morphological analysis using scanning and transmission electron microscopy.
- Biochemical quantification of erythrocyte membrane lipids (sphingomyelin and glycerophospholipids).
Main Results:
- Sphingomyelin hydrolysis occurred in parallel with erythrocyte shape alteration.
- Initial morphological changes included spherostomatocyte formation and peripheral vacuolation.
- Electron microscopy revealed membrane pitting and progressive surface scalloping.
- Significant decreases in erythrocyte sphingomyelin and increases in phosphatidylglycerol were observed.
Conclusions:
- C. pseudotuberculosis SL-PLD directly alters erythrocyte membrane integrity.
- The observed lipid alterations and morphological damage may play a role in the pathophysiology of C. pseudotuberculosis infections.
- SL-PLD's action on erythrocytes provides insights into acute infection mechanisms.