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@#BACKGROUND: Streptococcus pneumoniae (S. pneumoniae) is a common pathogen that causes bacterial pneumonia. However, with increasing bacterial resistance, there is an urgent need to develop new drugs to treat S. pneumoniae infections. Nanodefensin with a 14-carbon saturated fatty acid (ND-C14) is a novel nanoantimicrobial peptide designed by modifying myristic acid at the C-terminus of human α-defensin 5 (HD5) via an amide bond. However, it is unclear whether ND-C14 is effective against lung infections caused by S. pneumoniae. METHODS: In vitro, three groups were established, including the control group, and the HD5 and ND-C14 treatment groups. A virtual colony-count assay was used to evaluate the antibacterial activity of HD5 and ND-C14 against S. pneumoniae. The morphological changes of S. pneumoniae treated with HD5 or ND-C14 were observed by scanning electron microscopy. In vivo, mice were divided into sham, vehicle, and ND-C14 treatment groups. Mice in the sham group were treated with 25 µL of phosphate-buffered saline (PBS). Mice in the vehicle and ND-C14 treatment groups were treated with intratracheal instillation of 25 µL of bacterial suspension with 2×108 CFU/mL (total bacterial count: 5×106 CFU), and then the mice were given 25 μL PBS or intratracheally injected with 25 μL of ND-C14 (including 20 µg or 50 µg), respectively. Survival rates were evaluated in the vehicle and ND-C14 treatment groups. Bacterial burden in the blood and bronchoalveolar lavage fluid were counted. The lung histology of the mice was assessed. A propidium iodide uptake assay was used to clarify the destructive effect of ND-C14 against S. pneumoniae. RESULTS: Compared with HD5, ND-C14 had a better bactericidal effect against S. pneumoniae because of its stronger ability to destroy the membrane structure of S. pneumoniae in vitro. In vivo, ND-C14 significantly delayed the death time and improved the survival rate of mice infected with S. pneumoniae. ND-C14 reduced bacterial burden and lung tissue injury. Moreover, ND-C14 had a membrane permeation effect on S. pneumoniae, and its destructive ability increased with increasing ND-C14 concentration.
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Objective To investigate the dynamic changes in intestinal alpha-defensin-5 (RD-5),beta-defensin-2 (BD-2) mRNA after acute liver failure(ALF),and to explore their role in ALF.Methods A total of 60 C57BL5 mice were divided into 4 groups by means of random number table method:normal control group,ALF group,E.coli via gavage group and ALF + E.coli via gavage group.Intraperitoneal injection of D-galactosamine (500 mg/kg) and lipopolysaccharide(10 μg/kg) to make the model,in addition,ALF mice were fed with E.coli,and the observation time was 6 hours,12 hours,and 24 hours after modeling,and each time point had 6 specimens.Real-time PCR was used to test the RD-5 mRNA and BD-2 mRNA levels in the ileum tissue.Results The levels of RD-5 and BD-2 showed dynamic change in the experiment of ALF.Compared with the levels of RD-5 and BD-2(11.25 ±0.74,23.86 ±0.39) of the normal control group,the levels of RD-5 and BD-2 in ALF group and E.coli via gavage group increased at 6 hours after modeling(14.19 ±0.39,26.79 ± 0.36 and 12.57 ± 0.68,26.45 ± 0.85),and the differences were significant(all P＜0.05);at 12 hours after modeling,the RD-5 and BD-2 reached to the maximum concentration(15.76 ±0.33,29.10 ± 0.61 and 12.90 ± 0.96,27.42 ± 0.71),and the differences were statistically signi-ficant (all P ＜ 0.05).The degree of elevation of BD-2 was higher than RD-5.Later,they gradually declined.Conclusions RD-5 and BD-2 may play an important role in the pathogenesis of intestinal endotoxemia in experimental ALF.
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Objective To construct the prokaryotic expression vector for HD-5 and purify the recombinant HD-5 protein then analyze its antifungal activity. Methods The HD-5 gene was cloned by PCR, then was inserted into prokary-otic expression plasmid pQE-30Xa to construct pQE-30Xa/HD-5. After sequencing, pQE-30Xa/HD-5 was transformed in-to E.coli M15 cells. Its expression was induced by IPTG and confirmed by SDS-PAGE. The recombinant protein was purified through Ni-NTA affinity purification system. The antifungal activity was tested by disk diffusion method. Results HD-5 gene and pQE-30Xa/HD-5 vector were obtained successfully. E.coli M15 strains was used to express HD-5 fusion protein. After purification, the fusion protein was confirmed by Western blot. The disk diffusion test confirmed that the fusion pro-tein can inhibit Candida albicans. Conclusion Expression vector pQE-30Xa/HD-5 was successfully constructed. The HD-5 fusion protein was expressed in E.coli successfully, which showed a certain degree of antifungal activity.
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BACKGROUND:Sepsis has become the greatest threat to in-patients, with a mortality of over 25％.The dysfunction of gut barrier, especially the immunological barrier, plays an important role in the development of sepsis. This dysfunction occurs after surgery, but the magnitude of change does not differentiate patients with sepsis from those without sepsis. Increased intestinal permeability before surgery is of no value in predicating sepsis. The present study aimed to observe the changes of intestinal mucosal immunologic barrier in rat models of sepsis induced by cecal ligation and puncture. METHODS:Sixty Sprague-Dawley rats were randomly divided into a sepsis group (n=45) and a control group (n=15). The rats in the sepsis group were subjected to cecal ligation and puncture (CLP), whereas the rats in the control group underwent a sham operation. The ileac mucosa and segments were harvested 3, 6 and 12 hours after CLP, and blood samples were collected. Pathological changes, protein levels of defensin-5 (RD-5) and trefoil factor-3 (TFF3) mRNA, and lymphocytes apoptosis in the intestinal mucosa were determined. In an additional experiment, the gut-origin bacterial DNA in blood was detected. RESULTS:The intestinal mucosa showed marked injury with loss of ileal villi, desquamation of epithelium, detachment of lamina propria, hemorrhage and ulceration in the sepsis group. The expression of TFF3 mRNA and level of RD-5 protein were decreased and the apoptosis of mucosal lymphocyte increased (P<0.05) in the sepsis group compared with the control group. Significant differences were observed in RD-5 and TFF3 mRNA 3 hours after CLP and they were progressively increased 6 and 12 hours after CLP in the sepsis group compared with the control group (P<0.05, RD-5 F=11.76, TFF3 F=16.86 and apoptosis F=122.52). In addition, the gut-origin bacterial DNA detected in plasma was positive in the sepsis group. CONCLUSION:The immunological function of the intestinal mucosa was impaired in septic rats and further deteriorated in the course of sepsis.
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Objective To review the characteristics of human defensin 5 (HD 5), including molecular structure, antibacterial activity and gene expression, and to show its development prospect as a new drug in the treatment of enterogenic infection. Methods The published papers about HD 5 were reviewed to summarize its research progress. Results Being a 3-5 KDa cationic peptide rich in cysteine and arginine, especially without glycosylated side chain, HD 5 plays its antibacterial role against positive and negative Gram's bacterium, fungi, spirochete, protozoan and enveloped virus with the special active center composed of three disulfide bonds. HD 5 encoding gene alpha defensin 5 (DEFA 5) localizes at the 8th chromosome P21 pter with 449 bp, which includes five pieces of sequence: 5′ untranslated region (1-40),signal peptide (41-97), propiece (98-226), mature peptide (227-322),and Poly A (433-438).Conclusion As a broad spectrum and effective endogenous antimicrobial peptide, HD 5 would be a promising alternative peptide against enterogenic infection if the accessibility to its mass production is settled.