Neurotoxicity of pneumolysin, a major pneumococcal virulence factor, involves calcium influx and depends on activation of p38 mitogen-activated protein kinase.
Neuronal injury in bacterial meningitis is caused by the interplay of host inflammatory responses and direct bacterial toxicity. We investigated the mechanisms by which pneumolysin, a cytosolic pneumococcal protein, induces damage to neurons. The toxicity after exposure of human SH-SY5Y neuroblastoma cells and hippocampal organotypic cultures to pneumolysin was time- and dose-dependent. Pneumolysin led to a strong calcium influx apparently mediated by pores on the cell membrane formed by the toxin itself and not by voltage-gated calcium channels. Buffering of intracellular calcium with BAPTA-AM [1, 2-bis (o-aminophenoxy) ethane N, N, N', N'-tetraacetic acid tetra(acetomethoxyl) ester] improved survival of neuronal cells following challenge with pneumolysin. Western blotting revealed increased phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) as early as 30 min after challenge with pneumolysin. SB 203580, a potent and selective inhibitor of p38 MAPK, rescued human neuronal cells from pneumolysin-induced death. Inhibition of the mitochondrial permeability transition pore using bongkrekate and caspase inhibition also improved survival following challenge with the toxin. Modulation of cell death pathways activated by pneumolysin may influence the outcome of pneumococcal meningitis.
Stringaris
Argyrios K
AK
Department of Neurology, University of Göttingen, 37075, Göttingen, Germany.
Geisenhainer
Jens
J
Bergmann
Friederike
F
Balshüsemann
Christoph
C
Lee
Unaa
U
Zysk
Gregor
G
Mitchell
Timothy J
TJ
Keller
Bernhard U
BU
Kuhnt
Ulrich
U
Gerber
Joachim
J
Spreer
Annette
A
Bähr
Mathias
M
Michel
Uwe
U
Nau
Roland
R
D000818:Animals; D001426:Bacterial Proteins; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D018929:Cell Culture Techniques; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008586:Meningitis, Pneumococcal / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009447:Neuroblastoma / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D009924:Organ Culture Techniques; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D013301:Streptolysins / Q000633:toxicity*; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases
D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; D002118:Calcium