Mitogen-activated protein kinases and NF-kappa B are involved in TNF-alpha responses to group B streptococci.
TNF-alpha is a mediator of lethality in experimental infections by group B streptococcus (GBS), an important human pathogen. Little is known of signal transduction pathways involved in GBS-induced TNF-alpha production. Here we investigate the role of mitogen-activated protein kinases (MAPKs) and NF-kappa B in TNF-alpha production by human monocytes stimulated with GBS or LPS, used as a positive control. Western blot analysis of cell lysates indicates that extracellular signal-regulated kinase 1/2 (ERK 1/2), p38, and c-Jun N-terminal kinase MAPKs, as well as I kappa B alpha, became phosphorylated, and hence activated, in both LPS- and GBS-stimulated monocytes. The kinetics of these phosphorylation events, as well as those of TNF-alpha production, were delayed by 30-60 min in GBS-stimulated, relative to LPS-stimulated, monocytes. Selective inhibitors of ERK 1/2 (PD98059 or U0126), p38 (SB203580), or NF-kappa B (caffeic acid phenetyl ester (CAPE)) could all significantly reduce TNF-alpha production, although none of the inhibitors used alone was able to completely prevent TNF-alpha release. However, this was completely blocked by combinations of the inhibitors, including PD98059-SB203580, PD98059-CAPE, or SB203580-CAPE combinations, in both LPS- and GBS-stimulated monocytes. In conclusion, our data indicate that the simultaneous activation of multiple pathways, including NF-kappa B, ERK 1/2, and p38 MAPKs, is required to induce maximal TNF-alpha production. Accordingly, in septic shock caused by either GBS or Gram-negative bacteria, complete inhibition of TNF-alpha release may require treatment with drugs or drug combinations capable of inhibiting multiple activation pathways.
Department of Experimental Pathology and Microbiology, University of Messina, Messina, Italy.
Giuseppe
G
Mancuso
Angelina
A
Midiri
Concetta
C
Beninati
Giovanna
G
Piraino
Andrea
A
Valenti
Giacomo
G
Nicocia
Diana
D
Teti
James
J
Cook
Giuseppe
G
Teti
D004789:Enzyme Activation; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D009000:Monocytes / Q000502:physiology; D016328:NF-kappa B / Q000502:physiology*; D011493:Protein Kinase C / Q000502:physiology; D013292:Streptococcus agalactiae / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*
D008070:Lipopolysaccharides; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases