Xinchuan Zheng

Geniposide suppresses LPS-induced nitric oxide, PGE2 and inflammatory cytokine by downregulating NF-κB, MAPK and AP-1 signaling pathways in macrophages.

Inflammatory responses are important to host immune reactions, but uncontrolled inflammatory mediators may aid in the pathogenesis of other inflammatory diseases. Geniposide, an iridoid glycoside found in the herb gardenia, is believed to have broad-spectrum anti-inflammatory effects in murine models but its mechanism of action is unclear. We investigated the action of this compound in murine macrophages stimulated by lipopolysaccharide (LPS), as the stimulation of macrophages by LPS is known to induce inflammatory reactions. We determined the effect of geniposide on LPS-induced production of the inflammatory mediators, nitric oxide (NO) and prostaglandin E2 (PGE2), the mRNA and protein expression of the NO and PGE2 synthases, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), respectively, and the mRNA and protein expression of the inflammatory cytokine, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Furthermore, nuclear factor (NF)-κB, mitogen-activated protein kinase (MAPK) and activator protein (AP)-1 activity were assayed. To understand the action of geniposide on the NF-κB and MAPK pathways, we studied the effect of NF-κB and MAPK inhibitors on the LPS-induced production of NO, PGE2 and TNF-α. Our findings clearly showed that geniposide mainly exerts its anti-inflammatory effects by inhibiting the LPS-induced NF-κB, MAPK and AP-1 signaling pathways in macrophages, which subsequently reduces overexpression of the inducible enzymes iNOS and COX-2 and suppresses the expression and release of the inflammatory factors, TNF-α, IL-6, NO and PGE2. Thus, geniposide shows promise as a therapeutic agent in inflammatory diseases.

Identification of a new anti-LPS agent, geniposide, from Gardenia jasminoides Ellis, and its ability of direct binding and neutralization of lipopolysaccharide in vitro and in vivo.

Lipopolysaccharide (LPS/endotoxin) is a key pathogen recognition molecule for sepsis. Currently, one of the therapeutic approaches for severe sepsis is focusing on the neutralization of LPS, and clinical trials have shown a lot of traditional Chinese herbs possess anti-sepsis function. Herein, to elucidate the bioactive components of traditional Chinese herbs that can neutralize LPS, the lipid A-binding abilities of sixty herbs were tested using affinity biosensor technology. The aqueous extract of Gardenia jasminoides Ellis, traditionally used to treat inflammation in Asian countries for centuries, was further investigated. Subsequently, a monomer, identified as geniposide, was isolated. In vitro, geniposide was found to directly bind LPS and neutralize LPS. It dose-dependently inhibited cytokines release from RAW264.7 cells induced by LPS without affecting the cell viability, and inhibited TNF-α mRNA expression up-regulated by LPS. However, geniposide did not decrease TNF-α release induced by CpG DNA, Poly I:C or IL-1β. Significantly, geniposide dose-dependently down-regulated TLR4 mRNA expression up-regulated by LPS, and suppressed the phosphorylations of p38 MAKP induced by LPS but not by IL-1β. In vivo, geniposide (40mg/kg) could significantly protect mice challenge with lethal heat-killed E. coli, and dose-dependently decreased the level of serum endotoxin which was tightly associated with the cytokine levels in endotoxemia mice. In summary, we successfully isolated geniposide from G. jasminoides Ellis. Geniposide directly bound LPS and neutralized LPS in vitro, and significantly protected sepsis model mice. Therefore, geniposide could be as a useful lead compound for anti-sepsis drug development.

Artesunate in combination with oxacillin protect sepsis model mice challenged with lethal live methicillin-resistant Staphylococcus aureus (MRSA) via its inhibition on proinflammatory cytokines release and enhancement on antibacterial activity of oxacillin.

Sepsis induced by methicillin-resistant Staphylococcus aureus (MRSA) has worse outcome because of multiresistance to a large group of antibiotics, which may lead to death from septic shock. In the present study, we firstly found that artesunate in combination with oxacillin was capable of protecting mice challenged with live MRSA WHO-2 (WHO-2) and the protection was related to the reduced TNF-α and IL-6 levels and decreased bacterial load. Based on above results, artesunate was further investigated from two aspects in vitro, anti-inflammation effect and antibacterial enhancement effect on antibiotics. Artesunate not only inhibited TNF-α and IL-6 release but also inhibited mRNA and protein expressions of TLR2 and Nod2, two important receptors, in murine peritoneal macrophages stimulated with heat-killed WHO-2, further demonstrating anti-inflammatory effect of artesunate was related to the inhibition of TLR2- and Nod2-mediated proinflammatory cytokines. Significantly, artesunate enhanced antibacterial activity of oxacillin and ampicillin not levofloxacin against WHO-2 and a clinical MRSA strain; the fractional inhibitory concentration indexes were lower than 0.5. Further, artesunate possessed moderate affinity for penicillin-binding protein 2a (PBP2a) and reduced the mecA mRNA expression up-regulated by oxacillin, suggesting that artesunates enhancement on antibacterial activity of β-lactams was related to the inhibition of PBP2a and down-regulation of mecA mRNA expression. In conclusion, our results demonstrated that artesunate in combination with oxacillin protected mice challenged with lethal live MRSA via its inhibition on proinflammatory cytokines release and enhancement on antibacterial activity of oxacillin. Artesunate could be further investigated as a candidate drug for MRSA sepsis.

Ulinastatin is a novel candidate drug for sepsis and secondary acute lung injury, evidence from an optimized CLP rat model

Ulinastatin is a potent multivalent serine protease inhibitor, which was recently found with therapeutic potentials in treating sepsis, and the most life-threatening complication of critically ill population. However, the pharmacological features and possible mechanisms need to be further elucidated in reliable and clinical relevant sepsis models. As known, sepsis induced by surgery of cecal ligation and puncture (CLP) is widely accepted as the gold standard animal model, but the inconsistency of outcomes is the most obvious problem. In the present experiments, we reported an improved rat CLP model with much more consistent outcomes using self-made three edged puncture needles in our lab. Results from this optimized model revealed that ulinastatin improved survivals of CLP rats, attenuated proinflammatory response and prevented systemic disorder and organ dysfunction. Ulinastatin was also found to be effective in ameliorating sepsis-related ALI, a syndrome most frequent and fatal in sepsis. The molecular mechanism investigation showed that ulinastatins protection against ALI was probably related to the down-regulation of NF-κB activity and inhibition of TNF-α, IL-6 and elastase expressions in the lung tissue. In conclusion, based on a successful establishment of optimized rat CLP model ulinastatin is proved to be an effective candidate for sepsis treatment, due to its anti-inflammation and anti-protease activities that ameliorate systemic disorders, prevent organ injuries and thus improve the survival outcomes of sepsis in animals.

Kukoamine B, a novel dual inhibitor of LPS and CpG DNA, is a potential candidate for sepsis treatment

BACKGROUND AND PURPOSE Lipopolysaccharides (LPS) and oligodeoxynucleotides containing CpG motifs (CpG DNA) are important pathogenic molecules for the induction of sepsis, and thus are drug targets for sepsis treatment. The present drugs for treating sepsis act only against either LPS or CpG DNA. Hence, they are not particularly efficient at combating sepsis as the latter two molecules usually cooperate during sepsis. In this study, a natural alkaloid compound kukoamine B (KB) is presented as a potent dual inhibitor for both LPS and CpG DNA.

Dual targets guided screening and isolation of Kukoamine B as a novel natural anti-sepsis agent from traditional Chinese herb Cortex lycii

Treating sepsis remains challenging at present. Bacterial lipopolysaccharide (LPS) and bacterial DNA/CpG DNA are important pathogenic molecules and drug targets for sepsis. It is thus a promising strategy to treat sepsis by discovering agents that neutralize LPS and CpG DNA simultaneously. In this study, we present evidences of the biosensor based screening and isolation of active anti-sepsis fractions and monomers from traditional Chinese herbs using dual targets (LPS and CpG DNA) guided drug discovery strategy. Firstly, LPS or CpG DNA was immobilized on surfaces of cuvettes in the biosensor to establish a screening platform. Then, Cortex lycii with both highest affinities was selected out from one hundred and fourteen traditional Chinese herbs. In subsequent experiments, chromatography was utilized and coupled with the biosensor to purify fractions with a higher affinity for LPS and CpG DNA. In line with affinity assay, these fractions were shown to neutralize LPS and CpG DNA and inhibit their activity in vitro and in vivo. Lastly, the contributing monomer Kukoamine B (KB) was purified. KB neutralized LPS and CpG DNA in vitro. It inhibited TLR4, TLR9 and MyD88 mRNA expressions up-regulated by LPS and CpG DNA, and also attenuated the LPS and CpG DNA elicited nuclear translocation of NF-κB p65 protein in RAW264.7 cells. It also protected mice from lethal challenge of heat-killed E. coli, a mixture of LPS and CpG DNA. In conclusion, we presented a dual target guided discovery of a novel anti-sepsis agent KB from traditional Chinese herbs via combination of biosensor technology and chromatography methods.

The citrus flavonoid naringenin confers protection in a murine endotoxaemia model through AMPK-ATF3-dependent negative regulation of the TLR4 signalling pathway

Excessive activation of the TLR4 signalling pathway is critical for inflammation-associated disorders, while negative regulators play key roles in restraining TLR4 from over-activation. Naringenin is a citrus flavonoid with remarkable anti-inflammatory activity, but the mechanisms underlying its inhibition of LPS/TLR4 signalling are less clear. This study investigated the molecular targets and therapeutic effects of naringenin in vitro and in vivo. In LPS-stimulated murine macrophages, naringenin suppressed the expression of TNF-α, IL-6, TLR4, inducible NO synthase (iNOS), cyclo-oxygenase-2 (COX2) and NADPH oxidase-2 (NOX2). Naringenin also inhibited NF-κB and mitogen-activated protein kinase (MAPK) activation. However, it did not affect the IRF3 signalling pathway or interferon production, which upregulate activating transcription factor 3 (ATF3), an inducible negative regulator of TLR4 signalling. Naringenin was demonstrated to directly increase ATF3 expression. Inhibition of AMPK and its upstream calcium-dependent signalling reduced ATF3 expression and dampened the anti-inflammatory activity of naringenin. In murine endotoxaemia models, naringenin ameliorated pro-inflammatory reactions and improved survival. Furthermore, it induced AMPK activation in lung tissues, which was required for ATF3 upregulation and the enhanced anti-inflammatory activity. Overall, this study reveals a novel mechanism of naringenin through AMPK-ATF3-dependent negative regulation of the LPS/TLR4 signalling pathway, which thereby confers protection against murine endotoxaemia.

Leucine-rich Repeat 11 of Toll-like Receptor 9 Can Tightly Bind to CpG-containing Oligodeoxynucleotides, and the Positively Charged Residues Are Critical for the High Affinity

Background: Leucine-rich repeats (LRR) within the extracellular domain of human TLR9 (hTLR9) mediate binding to CpG ODN. Results: LRR11 of hTLR9 has high affinity for CpG ODN, whereas the mutants of five positively charge residues in LRR11 lack this affinity. Conclusion: LRR11 binds to CpG ODN with high affinity. Significance: LRR11 could be further investigated as an antagonist of hTLR9. TLR9 is a receptor for sensing bacterial DNA/CpG-containing oligonucleotides (CpG ODN). The extracellular domain (ECD) of human TLR9 (hTLR9) is composed of 25 leucine-rich repeats (LRR) contributing to the binding of CpG ODN. Herein, we showed that among LRR2, -5, -8, and -11, LRR11 of hTLR9 had the highest affinity for CpG ODN followed by LRR2 and -5, whereas LRR8 had almost no affinity. In vitro, preincubation with LRR11 more significantly decreased CpG ODN internalization, subsequent NF-κB activation, and cytokine release than with LRR2 and -5 in mouse peritoneal macrophages treated with CpG ODN. The LRR11 deletion mutant of hTLR9 conferred decreased cellular responses to CpG ODN. Single- or multiple-site mutants at five positively charged residues of LRR11 (LRR11m1–9), especially Arg-337 and Lys-367, were shown to contribute to hTLR9 binding of CpG ODN. LRR11m1–9 showed reduced inhibition of CpG ODN internalization and CpG ODN/TLR9 signaling, supporting the above findings. Prediction of whole hTLR9 ECD-CpG ODN interactions revealed that Arg-337 and Lys-338 directly contact CpG ODN through hydrogen bonding, whereas Lys-347, Arg-348, and His-353 contribute to stabilizing the shape of the ligand binding region. These findings suggested that although all five positively charged residues within LRR11 contributed to its high affinity, only Arg-337 and Lys-338 directly interacted with CpG ODN. In conclusion, the results suggested that LRR11 could strongly bind to CpG ODN, whereas mutations at the five positively charge residues reduced this high affinity. LRR11 may be further investigated as an antagonist of hTLR9.

Artesunate has its enhancement on antibacterial activity of β-lactams via increasing the antibiotic accumulation within methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) has now emerged as a predominant and serious pathogen because of its resistance to a large group of antibiotics, leading to high morbidity and mortality. Therefore, to develop new agents against resistance is urgently required. Previously, artesunate (AS) was found to enhance the antibacterial effect of β-lactams against MRSA. In this study, AS was first found to increase the accumulation of antibiotics (daunorubicin and oxacillin) within MRSA by laser confocal microscopy and liquid chromatography-tandem MS method, suggesting the increased antibiotics accumulation might be related to the enhancement of AS on antibiotics. Furthermore, AS was found not to destroy the cell structure of MRSA by transmission electron microscope. AS was found to inhibit gene expressions of important efflux pumps such as NorA, NorB and NorC, but not MepA, SepA and MdeA. In conclusion, our results showed that AS was capable of enhancing the antibacterial activity of β-lactams via increasing antibiotic accumulations within MRSA through inhibiting gene expressions of efflux pumps such as NorA, NorB and NorC, but did not destroy the cell structure of MRSA. AS could be further investigated as a candidate drug for treatment of MRSA infection.

1400 W ameliorates acute hypobaric hypoxia/reoxygenation-induced cognitive deficits by suppressing the induction of inducible nitric oxide synthase in rat cerebral cortex microglia

&NA; Nitric oxide (NO) is involved in neuronal modifications, and overproduction of NO contributes to memory deficits after acute hypobaric hypoxia‐reoxygenation. This study investigated the ability of the iNOS inhibitor 1400 W to counteract spatial memory deficits following acute hypobaric hypoxia‐reoxygenation, and to affect expression of NOS, NO, 3‐NT and MDA production, and apoptosis in rat cerebral cortex. We also used primary rat microglia to investigate the effect of 1400 W on expression of NOS, NO, 3‐NT and MDA production, and apoptosis. Acute hypobaric hypoxia‐reoxygenation impaired spatial memory, and was accompanied by activated microglia, increased iNOS expression, NO, 3‐NT and MDA production, and neuronal cell apoptosis in rat cerebral cortex one day post‐reoxygenation. 1400 W treatment inhibited iNOS expression without affecting nNOS or eNOS. 1400 W also reduced NO, 3‐NT and MDA production, and prevented neuronal cell apoptosis in cerebral cortex, in addition to reversing spatial memory impairment after acute hypobaric hypoxia‐reoxygenation. Hypoxia‐reoxygenation activated primary microglia, and increased iNOS and nNOS expression, NO, 3‐NT, and MDA production, and apoptosis. Treatment with 1400 W inhibited iNOS expression without affecting nNOS, reduced NO, 3‐NT and MDA production, and prevented apoptosis in primary microglia. Based on the above findings, we concluded that the highly selective iNOS inhibitor 1400 W inhibited iNOS induction in microglial cells, and reduced generation of NO, thereby mitigating oxidative stress and neuronal cell apoptosis in the rat cerebral cortex, and improving the spatial memory dysfunction caused by acute hypobaric hypoxia‐reoxygenation. HIGHLIGHTS1400 W ameliorated spatial memory deficits caused by acute HH/R in rats.1400 W inhibited iNOS overexpression in cerebral cortex microglia after acute HH/R.1400 W reduced NO and MDA generation, 3‐NT, and apoptosis after acute HH/R.1400 W inhibited overexpression of iNOS and NO production by microglia after H/R.1400 W reduced 3‐NT, MDA production, and decreased apoptosis in microglia after H/R.