TNF-alpha is a mediator of the anti-inflammatory response in a human neonatal model of the non-septic shock syndrome.
The anti-inflammatory/immunoparalytic phase of the systemic inflammatory response syndrome (SIRS) following major insult (surgery, thermal/traumatic injury) is of major clinical importance in the neonate, during which the risk of infection is particularly great. Here, the mechanisms by which TNF-alpha production is suppressed in response to infection are largely unknown. We questioned whether TNF-alpha itself could be a critical mediator of this suppression. Monocytes, isolated from cord blood (n=3), were treated with LPS (100 ng/ml), TNF-alpha (10 ng/ml, +/- anti-TNF-alpha antibody) for 18 and 36 h. Cells were then restimulated with LPS (Gram -ve) or Pam-3-Cys (Gram +ve) for 24 h. This was also done in the presence of selective inhibitors of MAP kinases p38, MEK and JNK. TNF-alpha, IL-6, IL-10 and IL-8 were quantified by ELISA CD86 and HLA-DR expression were determined flow cytometrically. Cells stimulated with LPS for 24 h produced TNF-alpha (282 pg/ml), IL-10 (1,236 pg/ml), IL-6 (2,694 pg/ml) and IL-8 (2,144 pg/ml). In cells pre-exposed to TNF-alpha for 36 h, there was a significant suppression in TNF-alpha and IL-6 levels (9 and 221 pg/ml, respectively) (P<0.05) with minimal impact on IL-10 (1,206 pg/ml) and IL-8 levels (1,886 pg/ml). A similar effect was seen with Pam-3-Cys with a tenfold decrease in levels of TNF-alpha and IL-6 (86-->8.5 pg/ml and 458-->46 pg/ml, respectively) with no effect on IL-10 and IL-8 levels. Anti-TNF-alpha antibody negated this effect. Inhibition of p38 kinase reversed the TNF-alpha effect. Inhibition of the JNK and MEK kinases had no effect. A reduction in the expression of CD86 and HLA-DR was observed. This ex-vivo model of non-septic SIRS demonstrates that TNF-alpha, released during a major insult, can suppress subsequent monocyte responses to bacterial agents through p38 MAP kinase, making it a potential therapeutic target.
Hassett
S
S
The Children's Research Centre, Our Lady's Hospital for Sick Children, Dublin, Ireland. sineadhassett@hotmail.com
Moynagh
P
P
Reen
D
D
D016207:Cytokines / Q000097:blood / Q000276:immunology; D005312:Fetal Blood; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology*; D066298:In Vitro Techniques; D007231:Infant, Newborn; D008070:Lipopolysaccharides; D008074:Lipoproteins; D009000:Monocytes / Q000276:immunology*; D018709:Statistics, Nonparametric; D018746:Systemic Inflammatory Response Syndrome / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000276:immunology
D016207:Cytokines; D008070:Lipopolysaccharides; D008074:Lipoproteins; D014409:Tumor Necrosis Factor-alpha; C061108:N-palmitoyl-S-(2,3-bis(palmitoyloxy)propyl)cysteinyl-seryl-lysyl-lysyl-lysyl-lysine; D048051:p38 Mitogen-Activated Protein Kinases