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Background There are currently limited effective pharmacotherapy agents for acute lung injury (ALI). Inflammatory response in the lungs is the main pathophysiological process of ALI. Our preliminary data have shown that colquhounia root tablet (CRT), a natural herbal medicine, alleviates the pulmonary inflammatory responses and edema in a rat model with oleic acid-induced ALI. However, the potential molecular action mechanisms underlining its protective effects against ALI are poorly understood. This study aimed to investigate the effects and mechanism of CRT in rat pulmonary microvascular endothelial cells (PMEC) with TNF-α-induced injury. Methods PMECs were divided into 6 groups: normal control, TNF-α (10 ng/mL TNF-α), Dex (1×10−6 M Dex + 10 ng/mL TNF-α), CRT high (1000 ng/mL CRT + 10 ng/mL TNF-α), CRT medium (500 ng/mL CRT + 10 ng/mL TNF-α), and CRT low group (250 ng/mL CRT + 10 ng/mL TNF-α). Cell proliferation and apoptosis were detected by MTT assay and flow cytometry. Cell micromorphology was observed under transmission electron microscope. The localization and expression of tight junction proteins Claudin-5 and ZO-1 were analyzed by immunofluorescence staining and Western blot, respectively. Results TNF-a had successfully induced an acute endothelial cell injury model. Dex and CRT treatments had significantly stimulated the growth and reduced the apoptosis of PMECs (all p < 0.05 or 0.01) and alleviated the TNF-α-induced cell injury. The expression of Claudin-5 and ZO-1 in Dex and all 3 CRT groups was markedly increased compared with TNF-a group (all p < 0.05 or 0.01). Conclusion CRT effectively protects PMECs from TNF-α-induced injury, which might be mediated via stabilizing the structure of tight junction. CRT might be a promising, effective, and safe therapeutic agent for the treatment of ALI.

3-Phenyllactic acid (PLA) is a novel and natural antimicrobial compound. However, the concentration of PLA produced by native microbes was rather low. To enhance the production of PLA of Lactobacillus plantarum AB-1, the microcapsules of L. plantarum AB-1 cells with a high quorum-sensing capacity was established and investigated. In addition, the relation between PLA production and quorum sensing was further investigated and confirmed by adding the exogenous 4,5-dihydroxy-2,3-pentanedione (DPD, AI-2 precursor). The results indicated that the PLA production of L. plantarum AB-1 in microencapsulated cells (MC cells) was higher than that of the free cells, and the lactate dehydrogenase activity, autoinducer-2 (AI-2) levels and the relative expression of the luxS gene were also significantly increased in MC cells (P \ 0.05). In addition, the cell growth, AI-2 levels and PLA production of L. plantarum AB-1 were also significantly promoted after adding 24 lM exogenous DPD. The results suggest that the PLA production of L. plantarum was partly regulated by the AI-2/LuxS system, and microencapsulation can increase the local AI-2 level and enhance QS capacity, which are beneficial to PLA production. The results may provide a new insight and experimental basis for the industrial production of PLA.

Shewanella baltica is the predominant bacteria in spoiled shrimp (Litopenaeus vannamei), however, the spoilage ability and the mechanism of S. baltica is still unknown. S. baltica can't produce the signal molecule of acyl-homoserine-lactones (AHLs), so the aim of this study was to investigate how wild type S. baltica SA03 (WT SA03) eavesdrop exogenous AHLs to enhance its spoilage ability through LuxR receptor. The results indicated that Aeromonas spp. (Aer), Acinetobacter spp. (Aci) and Serratia spp. (Ser) isolated from refrigerated shrimp can produce different AHLs. WT SA03 can eavesdrop the AHLs of Aer (C4-HSL), Aci (O-C6-HSL) and Ser (C6-HSL, O-C6-HSL) to enhance its growth, especially Ser. Exogenous C4-HSL and C6-HSL enhanced biofilm formation of WT SA03, and C6-HSL and O-C6-HSL enhanced thioredoxin reductase trxB mRNA expression. However, the luxR mutant of WT SA03 (DluxR SA03) lost or weakened the role of using environmental AHLs. In vivo experiments, the lag time of WT SA03 was shortened by 6.4 h, 6.2 h and 14.4 h by co-inoculated with Aer, Aci and Ser, respectively. The total volatile basic nitrogen (TVB-N) were significantly enhanced in the samples co-inoculated with WT SA03 and Aer (or Aci, Ser) than those of DluxR SA03 and Aer (or Aci, Ser) (p \ 0.05). The results showed that S. baltica SA03 can utilize AHLs produced by other bacteria to enhance its growth and spoilage ability through LuxR receptor system. Quorum sensing based on AHLs of bacteria might as the potential targets for food spoilage control. KeywordsShewanella baltica Á Quorum sensing Á Eavesdropping Á Acyl-homoserine-lactones Á Spoilage ability Abbreviations WT SA03 Wild type Shewanella baltica SA03 DluxR SA03 The luxR mutant of Shewanella baltica SA03 Aer Aeromonas spp. Aci Acinetobacter spp. Ser Serratia spp. C4-HSL N-butanoyl-L-homoserine lactone C6-HSL N-hexanoyl-L-homoserine lactone C8-HSL N-3-hydroxyoctanoyl-L-homoserine lactone O-C6-HSL N-(3-oxohexanoyl)-L-homoserine lactone O-C8-HSL N-(3-oxo hydroxyoctanoyl)-L-homoserine lactone