Cationic peptide mR18L with lipid lowering properties inhibits LPS-induced systemic and liver inflammation in rats

The cationic single domain peptide mR18L has demonstrated lipid-lowering and anti-atherogenic properties in different dyslipidemic mouse models. Lipopolysaccharide (LPS)-mediated inflammation is considered as one of the potential triggers for atherosclerosis. Here, we evaluated anti-inflammatory effects of mR18L peptide against LPS-mediated inflammation. First, we tested the efficacy and tolerance of 1, 2.5 and 5 mg/kg mR18L in normolipidemic rats stimulated with 5 mg/kg LPS. LPS and then mR18L were injected in different intraperitoneal regions. By 2 h post LPS, mR18L inhibited LPS-mediated plasma TNF-α elevation at all doses, with the effect being stronger for 2.5 mg/kg (P < 0.05 vs. 1 mg/kg, non-significant vs. 5 mg/kg). In a similar model, 2.5 mg/kg mR18L reduced LPS-mediated inflammation in the liver, as assessed by microscopic examination of liver sections and measurements of iNOS expression in the liver tissue. In plasma, 2.5 mg/kg mR18L decreased levels of TNF-α and IL-6, decreased endotoxin activity and enhanced HDL binding to LPS. In another similar experiment, mR18L administered 1 h post LPS, prevented elevation of plasma triglycerides by 6 h post LPS and increased plasma activity of anti-oxidant enzyme paraoxonase 1, along with noted trends in reducing plasma levels of endotoxin and IL-6. Surface plasmon resonance study revealed that mR18L readily binds LPS. We conclude that mR18L exerts anti-endotoxin activity at least in part due to direct LPS-binding and LPS-neutralizing effects. We suggest that anti-endotoxin activity of mR18L is an important anti-inflammatory property, which may increase anti-atherogenic potential of this promising orally active lipid-lowering peptide.