TNF-α is a mediator of the anti-inflammatory response in a human neonatal model of the non-septic shock syndrome

Abstract

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-a production is suppressed in response to infection are largely unknown. We questioned whether TNF-a itself could be a critical mediator of this suppression. Monocytes, isolated from cord blood (n=3), were treated with LPS (100 ng/ml), TNF-a (10 ng/ml, +/À anti-TNF-a antibody) for 18 and 36 h. Cells were then restimulated with LPS (Gram Àve) 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-a, 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-a (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-a for 36 h, there was a significant suppression in TNF-a 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-a and IL-6 (86 fi 8.5 pg/ml and 458 fi 46 pg/ml, respectively) with no effect on IL-10 and IL-8 levels. Anti-TNF-a antibody negated this effect. Inhibition of p38 kinase reversed the TNF-a 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-a, released during a major insult, can suppress subsequent monocyte responses to bacterial agents through p38 MAP kinase, making it a potential therapeutic target.

Investigation of Lipopolysaccharide Receptor Expression on Human Monocytes after Major Orthopaedic Surgery

“…TNF-␣ is a pivotal mediator of normal immune function, and disability to produce TNF-␣ is associated with an increased risk of infection [16] . In the present study, we tested the hypothesis that impaired cytokine responses to LPS are caused by the altered expression of surface receptors involved in bacterial recognition and signal transduction.…”

“…This diminished release of pro-inflammatory cytokines has been shown in patients with trauma [5] , sepsis [16,17] , and hypovolaemic shock [18] . There is a similar suppression of wholeblood capacity to LPS-induced TNF-␣ release throughout 12 days after surgery, particularly in patients undergoing major orthopaedic surgery.…”

Immune depression in musculoskeletal trauma

“…Gram-negative endotoxin (lipopolysaccharide) is detected by TLR4, and Gram-positive endotoxin (peptidoglycan) is sensed by TLR2 [60]. A number of studies have shown that trauma is associated with impaired readiness of blood monocytes to release pro-inflammatory cytokines after in vitro stimulation with lipopolysaccharide or peptidoglycan [61][62][63][64][65]. Additionally, with injury of the skeletal system, it has been shown that macrophage cells of the liver undergo a graded alteration to a less inflammatory phenotype with reduced capacity to synthesise TNF-a when exposed to endotoxins [66].…”

Postnatal development of lipopolysaccharide-induced inflammatory response in the brain

“…Further studies have shown that the immune function in neonates is distinct from that in adults. For example, human neonatal cord blood monocytes have been reported to produce less interleukin (IL)-12 p70, interferon (IFN)-a, IFN-c, and tumor necrosis factor (TNF)-a, but as much or even more IL-1b, IL-6, IL-23, and IL-10 than adult human peripheral blood monocytes (PBMCs) in response to most Toll-like receptor (TLR) ligands including lipopolysaccharide (LPS), a major component of Gram-negative bacterial cell wall and a potent immune activator [3][4][5][6][7]. Polymorphonuclear leukocytes (PMNs) from preterm infants have been reported to exhibit a much reduced antibacterial activity from those from adults [8].…”