Molecular Mechanism Of Inhibition Of Lipopolysaccharide-Induced Chronic Inflammation By Mangiferin

Inflammation is foremost one of basic pathological processes. Various kinds of inflammatory diseases play an important role in disease spectrum of human being. Many chronic inflammatory diseases were kept as common diseases that persecuted great quantity crowd even to this day. Furthermore, recent research shows that some diseases, which were deemed to have nothing on or less relation to the inflammation, were bound up with the inflammation. There have been a lot of research evidences to indicate that essential hypertension, coronary heart disease, metabolic syndrome and type 2 diabetes can be understood as one inflammatory process, and inflammatory mechanism continuously plays a key role in many complications about these diseases. The chronic inflammation is considered as a general and important promoting factor for malignancy, which is as dangerous as cardiovascular disease and diabetes to human life expectancy. Lipopolysaccharide (LPS) is an important component of outer membrane of Gram-negative bacteria and uppermost one of pathogen molecular inducing chronic inflammatory damage. Many diseases are closely involved in LPS-induced sustaining subclinical inflammation. Based on accumulating evidences similar to the above researches, it may be a key part for disease occurring and treating to inhibit the LPS-induced inflammation.Based on the understanding of various pathophysiological mechanisms in the chronic inflammation, it could be a reasonable choice to find anti-inflammatory drug from nature products with moderate function and broad-spectrum pharmacological effect. Mango leave comes from smell secco plant mango Mangifera indica L. and mangiferin, a natural polyphenol compound, is taken as major active constituent. Previous studies have shown that mangiferin may markedly inhibit various inflammations, such as experimental acute inflammation or chronic proliferative inflammation or immunity Inflammation. In addition, mangiferin has remarkable curative effect on cough, sputum, panting, fever due to respiratory infection inflammation and plus with a good safety record in its clinical application. The specific molecular mechanism of inhibition of lipopolysaccharide-induced chronic inflammation by mangiferin is not entirely clear, but these research evidences indicate that mangiferin might be developed into a potential drug which can effectively restrain the chronic inflammation.This study is designed to clarify the action mechanism of mangiferin on LPS-related chronic inflammation. A rat model with LPS-induced chronic inflammation will be used in this study to investigate the anti-inflammatory action and the molecular mechanism of inhibition of lipopolysaccharide-induced chronic inflammation by mangiferin. Partâ… Establishment of a rat model wi^th chronic lipopolysaccharide-induced inflammationObjective: To establish a rat model wi^th chronic inflammation induced by intermittent low dose lipopolysaccharide (LPS) injection and probe its feasibility.Me^thods: 48 SD rats were randomly divided into 6 groups wi^th 8 rats in each group. Rats in each group received caudal vein injection respectively wi^th isometric stroke-physiological saline solution or 40μg/kg, 80μg/kg, 120μg/kg, 160μg/kg, 200μg/kg LPS once a week wi^thin 4 weeks. An evaluation on chronic inflammatory reaction was been executed at ^the end of 4^th week to confirmed an appropriate LPS dose for establishing rat model. Afterwards, 40 rats were randomly divided into 5 groups wi^th 8 rats in each group. Rats in each group received caudal vein injection wi^th isometric stroke-physiological saline solution or above conformed dose of LPS once a week wi^thin 4 weeks. The evaluations on ^the chronic inflammatory reaction were executed respectively at ^the end of 1^st, 2^nd, 3^rd and 4^th week.Results: The animals were all survived up to ^the endpoint of experiment. The appropriately chronic system inflammation had been not caused by intermittent caudal vein injection respectively wi^th 40μg/kg, 80μg/kg, 120μg/kg or 160μg/kg dose of LPS wi^thin 4 weeks. Not only ^the peripheral white blood cell count and neutrophils ratio, but also ^the level of serum interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α) and high-sensitivity C-reactive protein (hs-CRP) of rats, who received 200μg/kg dose of LPS caudal vein injection wi^thin 4 weeks, were raised. The tissue injury due to inflammatory cells infiltrating and blood stasis plus hydroncus as primary pa^thological manifestations was observed after LPS treating.Conclusion: The SD rat model with classic chronic inflammation can be successfully established by intermittent low dose LPS caudal vein injection. It may be used to study the LPS-related chronic inflammation in the long term.Partâ…¡Anti-inflammatory actions of mangiferin on chronic lipopolysaccharide-induced inflammationObjective: To study the anti-inflammatory actions of mangiferin on the chronic inflammation induced by lipopolysaccharide.Methods: 90 SD rats were randomly divided into control group, model group, positive drug prednisone (PNS) group (5mg.kg^-1.d^-1, gavage) and mangiferin high dose (MGF_H, 200mg.kg^-1.d^-1, gavage) group, mangiferin middle dose (MGF_M, 100mg.kg^-1.d^-1, gavage) group, mangiferin low dose (MGF_L, 50mg.kg^-1.d^-1, gavage) group with 15 rats in each group. The chronic inflammation models were established by intermittent lipopolysaccharide caudal vein injection. The treatment was executed within 4 weeks. The leucocyte count and the neutrophil ratio in blood were measured. The levels of serum high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor alpha (TNF_-α), interleukin-6 (IL-6) and soluble intercellular adhesion molecule 1 (sICAM^-1) were detected by enzyme-linked immunosorbent assay. Regular HE staining was applied to evaluate the inflammatory reaction of heart, liver, lung and kidney tissue.Results: Compared with the model group, not only the leucocyte count and the neutrophil ratio in blood but also the levels of serum hs-CRP, IL-6, TNF_-αand sICAM^-1 in MGF_H group were well down(P<0.01). Less damage due to chronic inflammation was observed in MGF_H group. However, there were no significant difference for the leucocyte count, the neutrophil ratio and the levels of serum hs-CRP, IL-6, TNF-α, sICAM-1 between model group and MGF_M or MGF_L group (P>0.05). And the damage due to chronic inflammation was relatively obvious in MGF_M and MGF_L group.Conclusion: Mangiferin may significantly inhibit the chronic inflammation induced by lipopolysaccharide, and the mechanism of its action may be involved in mangiferin inhibiting the activation of leucocytes, lowering the level of inflammatory cytokines and reducing the tissue damage due to inflammation.Partâ…¢Dual inhibitory effect of mangiferin on cyclooxygenase and lipoxygenase in chronic lipopolysaccharide-induced inflammationObjective: To study the inhibitory action of mangiferin on cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX), 12-lipoxygenase (12-LOX) and their metabolins in the chronic inflammation induced by lipopolysaccharide.Methods: 50 SD rats were randomly divided into control group, model group and mangiferin high dose (MGF_H, 200mg.kg^-1.d^-1, gavage) group, mangiferin middle dose (MGF_M, 100mg.kg^-1.d^-1, gavage) group, mangiferin low dose (MGF_L, 50mg.kg^-1.d^-1, gavage) group with 10 rats in each group. The chronic inflammation models were established by intermittent lipopolysaccharide caudal vein injection. The treatment was executed within 4 weeks. Either the levels of COX-1, COX-2 in the leucocytes and serum PG E₂, PG F_2α as their metabolins, or the levels of 5-LOX, 12-LOX in the leucocytes and serum LT-B₄, LT-C₄, LT-D₄, LT-E₄ as their metabolins, were detected by enzyme-linked immunosorbent assay. The reverse transcription-polymerase chain reaction was applied to evaluate the mRNA expressions of COX-1, COX-2, 5-LOX, 12-LOX in the leucocytes isolated from blood.Results: Not only the levels of COX-2 in the leucocytes and serum PG E₂, PG F_2α but also the levels of 5-LOX, 12-LOX in the leucocytes and serumLT-B₄, LT-C₄, LT-D₄, LT-E₄ in MGF_H and MGF_M group were markedly lower than in model group (P<0.01), and the level of leucocyte COX-1 in MGFH group was obviously lower than in model group (P<0.01). There were no significant difference for the levels of leucocyte COX-1, COX-2 5-LOX, 12-LOX and serum PG E₂, PG F_2α, LT-B₄, LT-C₄, LT-E₄ between model group and MGFL group (P>0.05), but the level of serum LT-D₄ in MGF_L group was lower than in model group (P<0.05).Conclusion: Mangiferin may simultaneously inhibit leucocyte COX-1, COX-2 and 5-LOX, 12-LOX in the chronic inflammation induced by lipopolysaccharide, and it may be one action mechanism of mangiferin inhibiting the chronic inflammation concerned with lipopolysaccharide.Partâ…£Effect of mangiferin on cellular CD14-TLR4-MAPK signal transduction pathway in chronic lipopolysaccharide-induced inflammationObjective: To investigate the effect of mangiferin on gene expressions of main signal molecules of CD14-TLR4-MAPK signal transduction pathway in the chronic inflammation induced by lipopolysaccharide.Methods: 90 SD rats were randomly divided into control group, model group, positive drug prednisone (PNS) group (5mg.kg^-1.d^-1, gavage) and mangiferin high dose (MGF_H, 200mg.kg^-1.d^-1, gavage) group, mangiferin middle dose (MGF_<sub>M, 100mg.kg^-1.d^-1, gavage) group, mangiferin low dose (MGF_L, 50mg.kg^-1.d^-1, gavage) group with 15 rats in each group. The chronic inflammation models were established by intermittent lipopolysaccharide caudal vein injection. The treatment was executed within 4 weeks. The reverse transcription-polymerase chain reaction was applied to evaluate the mRNA expressions of CD14, TLR4, MyD88, P38, ERK, JNK and NF_-κB in the leucocytes isolated from blood.Results: Compared with model group, lower mRNA expressions of CD14, TLR4, MyD88, ERK, JNK, NF-κB were detected in MGF_H group (P<0.01), but not for P38 (P>0.05). There were no significant difference for mRNA expressions of CD14, TLR4, MyD88, P38, ERK, JNK, NF_-κB between model group and MGF_M or MGF_L group (P>0.05).Conclusion: Mangiferin may availably down-regulate the mRNA expressions of CD14, TLR4, MyD88, ERK, JNK and NF-κB in leucocytes, and it may be one action mechanism of mangiferin inhibiting the chronic inflammation induced by lipopolysaccharide.