Fig. 5

a Bioactive analogues of MECO-1. Murine macrophage-like RAW 264.7 cells were incubated with lipopolysaccharide (LPS, 4 ng/ml) in the absence or presence of MECO-1 or BACTN or BACFR, synthetic peptides based on the C-termini of EF-G of Bacteroides thetaiotamicron and Bacteroides fragilis. EFG-2 refers to human mitochondrial EFG-2 (mtEFG2). For Bacteroides thetaiotamicron, we used a 38-mer consisting of residues 681–703 shown in Fig. 4c followed by 704–718 QDKLIKDFEAKQTEE. For Bacteroides fragilis, we used a 33-mer consisting of residues, 681–703 shown in Fig. 4c followed by 704–713 = QDKLIKDFES. At 6 h after stimulation, aliquots of cell-free medium were examined. In other experiments, the synthetic peptide based on human mitochondrial EF-G1 (mtEFG1) gave results indistinguishable from EF-G2 (data not shown). The precise structure of the synthetic peptides is indicated in the text (see section “Results” and Table 1). Shown is a representative experiment. Similar results were observed in four other experiments. In this particular experiment MECO-1 showed effects at 10⁻¹⁰ M but not at 10⁻¹² M. In most experiments, it was effective at 10⁻¹² M. *p < 0.05 vs. LPS alone. b Bacteroides fragilis attenuates TNF release HMGB-1 stimulates release of TNF from RAW cells. Peptide based on structure of C-terminal region of EF-G of Bacteroides fragilis inhibited HMGB-1 accumulation so that at 10⁻⁷ M, TNF release was totally suppressed