Cell death, caspase activation, and HMGB1 release of porcine choroid plexus epithelial cells during Streptococcus suis infection in vitro.
The choroid plexus epithelium constitutes the structural basis of the blood-cerebrospinal fluid barrier. We previously demonstrated that Streptococcus suis (S. suis), a relevant cause of bacterial meningitis in pigs and humans, affects porcine choroid plexus epithelial cell (PCPEC) barrier function and integrity. We now characterized PCPEC cell death and investigated whether apoptosis or necrosis is responsible for the cytotoxicity after infection with different S. suis isolates. We found S. suis strain-dependent histone associated DNA-fragments quantified by ELISA. This response could partially be inhibited by cylcoheximide, cytochalasin D, dexamethasone, herbimycin A, but most effectively by the pan-caspase inhibitor zVAD-fmk. We further detected caspase-3 and -9 activation after infection with all tested S. suis isolates that could also be blocked by zVAD-fmk. However, we found a significantly stronger caspase activity with the protein kinase inhibitor staurosporine. All tested S. suis isolates induced loss of cell viability in PCPEC as shown with the Live/Dead assay, but strain dependent lactate dehydrogenase-release. Both parameters could not be influenced by zVAD-fmk. Immunostaining showed release of high-mobility group box 1 (HMGB1) protein from the nucleus, indicative of necrosis. Transmission electron microscopy showed cell swelling, cytoplasmic vacuolization, loss of membrane integrity, nuclear fermentation but no nuclear condensation, indices for a primarily necrotic cell morphology. Taken together, our findings indicate that S. suis causes cell death in PCPEC by different mechanisms. Although apoptosis may be involved in the process of PCPEC cell death, necrosis seems to be the predominant mechanism. Through inflammation in the choroid plexus during bacterial meningitis, the blood-cerebrospinal fluid barrier function will be compromised.
Tenenbaum
Tobias
T
Pediatric Infectious Diseases, Department for General Pediatrics, University Children's Hospital, Heinrich Heine University Düsseldorf, Moorenstr. 5, 40225 Düsseldorf, Germany. tenenbaum@med.uni-duesseldorf.de
Essmann
Frank
F
Adam
Rüdiger
R
Seibt
Annette
A
Jänicke
Reiner U
RU
Novotny
Gerd E K
GE
Galla
Hans-Joachim
HJ
Schroten
Horst
H
D000818:Animals; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D002467:Cell Nucleus / Q000473:pathology / Q000648:ultrastructure; D002478:Cells, Cultured; D002831:Choroid Plexus / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D053938:DNA Fragmentation; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D024243:HMGB1 Protein / Q000378:metabolism*; D007150:Immunohistochemistry; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D013290:Streptococcal Infections / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D017011:Streptococcus suis; D013552:Swine
D024243:HMGB1 Protein; D007770:L-Lactate Dehydrogenase; D020169:Caspases