Abstract
LPS (lipopolysaccharide), an outer membrane component of Gram-negative bacteria, plays an important role in the pathogenesis of sepsis and lipid A is known to be essential for its toxicity. Therefore it could be an effective measure to prevent sepsis by neutralizing or destroying LPS. Numerous studies have indicated that many traditional Chinese medicines are natural antagonists of LPS in vitro and in vivo. The goal of this study is to develop a rapid method to screen anti-sepsis components from Chinese herbs by use of a direct lipid A-based affinity biosensor technology based on a resonant mirror. The detergent OG (n-octyl β-D-glucopyranoside) was immobilized on a planar non-derivatized cuvette which provided an alternative surface to bind the terminal hydrophilic group of lipid A. A total of 78 herbs were screened based on the affinity biosensor with a target of lipid A. The aqueous extract of PSA (Paeonia suffruticosa Andr) was found to possess the highest capability of binding lipid A. Therefore an aqueous extraction from this plant was investigated further by our affinity biosensor, polyamide chromatography and IEC–HPLC. Finally, we obtained a component (PSA-I-3) from Paeonia suffruticosa Andr that was evaluated with the affinity biosensor. We also studied the biological activities of PSA-I-3 against sepsis in vitro and in vivo to further confirm the component we screened with the biosensor. In vitro, we found that PSA-I-3 could decrease TNFα (tumour necrosis factor α) release from RAW264.7 cells induced by LPS in a dose-dependent manner. In vivo, it increased remarkably the survival of KM (KunMing) mice by challenging both lethal-dose LPS and heat-killed Escherichia coli compared with control groups. Our results suggest that the constructed affinity biosensor can successfully screen the anti-sepsis component from Chinese herbs.
Highlights
Sepsis is a complex syndrome that is defined as the presence of infection plus systemic inflammatory response syndrome (SIRS) [1]
Aqueous extracts of 12 Chinese herbs bound to the indicated LPS concentration In previous experiments, we found that 12 out of the 78 herbs possess high lipid A-binding activities and the tannins have a great impact on binding between lipid A and Chinese herbs
Lipid A-binding fractions from Paeonia suffruticosa Andr (PSA) To determine which components of PSA could inhibit LPS, we isolated the aqueous extracts and tested their lipid A-binding abilities via polyamide chromatography and an affinity biosensor
Summary
Sepsis is a complex syndrome that is defined as the presence of infection plus SIRS (systemic inflammatory response syndrome) [1]. In the USA, sepsis syndrome is responsible for a tenth of all deaths. Gram-negative bacteria are no longer the number one cause of sepsis in recent years, as people pay more attention [4,5], infections still result in severe outcomes such as sepsis, severe sepsis and septic shock in most of these critically ill populations who do not receive appropriate and timely therapy [6]. LPS (lipopolysaccharide) is an outer membrane component of Gram-negative bacteria and more than 2×106 LPS molecules comprise a polysaccharide part, O-antigen and core regions, and a lipid anchor, called lipid A, known to be essential for its toxicity [7].
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