Antibacterial mechanism of high-mobility group nucleosomal-binding domain 2 on the Gram-negative bacteria Escherichia coli.

OBJECTIVE: To investigate the antibacterial mechanism of high-mobility group nucleosomal-binding domain 2 (HMGN2) on Escherichia coli K12, focusing on the antibacterial and antibiofilm formation effects. Its chemotactic activity on human neutrophils was also investigated. METHODS: Human tissue-derived HMGN2 (tHMGN2) was extracted from fresh uterus fiber cystadenoma and purified by HP1100 reversed-phase high-performance liquid chromatography (RP-HPLC). Recombinant human HMGN2 (rHMGN2) was generated in E. coli DE3 carrying PET-32a-c(+)-HMGN2. Antibacterial activity of HMGN2 was determined using an agarose diffusion assay and minimum inhibitory concentration (MIC) of HMGN2 was determined by the microdilution broth method. Bacterial membrane permeability assay and DNA binding assay were performed. The antibiofilm effect of HMGN2 was investigated using a crystal violet assay and electron microscopy scanning. The activating effect and chemotactic activity of HMGN2 on neutrophils were determined using a nitroblue tetrazolium (NBT) reduction assay and Transwell chamber cell migration assay, respectively. RESULTS: HMGN2 showed a relatively high potency against Gram-negative bacteria E. coli and the MIC of HMGN2 was 16.25 µg/ml. Elevated bacterial membrane permeability was observed in HMGN2-treated E. coli K12. HMGN2 could also bind the bacterial plasmid and genomic DNA in a dose-dependent manner. The antibiofilm effect of HMGN2 on E. coli K12 was confirmed by crystal violet staining and scanning electron microscopy. However, the activating effects and chemotactic effects of HMGN2 on human neutrophils were not observed. CONCLUSIONS: As an antimicrobial peptide (AMP), HMGN2 possessed a good capacity for antibacterial and antibiofilm activities on E. coli K12. This capacity might be associated with disruption of the bacterial membrane and combination of DNA, which might affect the growth and viability of E. coli.

Knockdown of HMGN2 increases the internalization of Klebsiella pneumoniae by respiratory epithelial cells through the regulation of α5ß1 integrin expression.

Integrin receptors, a large family of adhesion receptors, are involved in the attachment of Klebsiella pneumoniae to respiratory epithelial cells, and subsequently cause the internalization of K. pneumoniae by host cells. Although a number of molecules have been reported to regulate the expression and activity of integrin receptors in respiratory epithelial cells, the specific underlying molecular mechanisms remain largely unknown. High mobility group nucleosomal binding domain 2 (HMGN2), a non-histone nuclear protein, is present in eukaryotic cells as a ubiquitous nuclear protein. Our previous studies have demonstrated that HMGN2 affects chromatin function and modulates the expression of antibacterial peptide in A549 cells exposed to lipopolysaccharide, which indicates the critical role of HMGN2 in innate immune responses. In addition, our cDNA microarray analysis suggested that HMGN2 knockdown induced the enhanced expression of α5ß1 integrin in A549 cells. Therefore, we hypothesized that intercellular HMGN2 may mediate the internalization of K. pneumoniae by altering the expression of α5ß1 integrin. Using the A549 cell line, we demonstrated that HMGN2 knockdown induced the increased expression of α5ß1 integrin on cell membranes, which resulted in a significant increase in K. pneumoniae internalization. Further results revealed that HMGN2 silencing induced the expression of talin and the activation of α5ß1 integrin, which led to actin polymerization following the phosphorylation of FAK and Src. This study suggests a possible therapeutic application for bacterial internalization by targeting HMGN2 in order to treat K. pneumoniae infection.

The chromosomal protein HMGN2 mediates the LPS-induced expression of ß-defensins in mice.

Human ß-defensin-2 (HBD-2), an antimicrobial peptide produced by epithelial cells, plays an important role in the body's innate and adaptive immunity. High-mobility group N2 (HMGN2), a member of the HMG superfamily, binds to chromatin to modulate gene transcription. Previously, we have shown that HMGN2 acts as a positive modulator of the signal transduction cascade in the process of inducible human ß-defensin expression. In our current study, we found that down-regulation of HMGN2 reduces the expression level of murine ß-defensin-3 and -4 (mBD-3 and mBD-4), but not mBD-1 upon LPS stimulation in various tissues of pregnant ICR mice, as well as in embryonic and neonatal lungs and livers at different developmental time points. In the control group, murine HMGN2 expression decreased, while mBD-1 and mBD-4 expression increased slightly during development. In the LPS-treated groups, murine HMGN2 and mBD-1 expression did not change significantly, whereas mBD-3 and mBD-4 expression significantly increased in maternal, embryonic, and neonatal tissues, especially the mBD-3 expression. HMGN2 shRNA interference led to decreased mBD-3 and mBD-4 expression, while mBD-1 expression did not significantly change. These results demonstrate that HMGN2 is a component of the LPS-induced mouse ß-defensin response.

Expression of HMGB1 and HMGN2 in gingival tissues, GCF and PICF of periodontitis patients and peri-implantitis

High mobility group chromosomal protein B1 (HMGB1) and N2 (HMGN2), two members of High mobility group (HMG) family, play important role in inflammation. The purposes of this study were to investigate the expression of HMGB1 and HMGN2 in periodontistis. The expression of HMGB1 and HMGN2 mRNA in gingival tissues and gingival crevicular fluid (GCF) in chronic periodontitis (CP), generalized aggressive periodontitis (G-AgP) patients and healthy subjects was detected by real-time PCR. The protein level of HMGB1 and HMGN2 in peri-implant crevicular fluid (PICF), peri-implant crevicular fluid of peri-implantitis (PI-PICF) and normal patients was determined by Western blotting. Furthermore, IL-1â, IL-6, IL-8, TNF-á and HMGB1 levels in GCF, PI-PICF and healthy-PICF samples from different groups were determined by ELISA. HMGN2 expression was increased in inflamed gingival tissues and GCF from CP and G-ApG groups compared to control group. HMGB1 expression was the highest in the gingival tissues and GCF from CP patients and was accompanied by increased concentrations of IL-1â, IL-6, IL-8 proinflammaory cytokines. To our knowledge, this is the first study reporting that the expression of HMGB1 and HMGN2 was increased in the gingival tissues and GCF in CP and G-AgP and the PICF in PICF. Our data suggest that HMGB1 may be a potential target for the therapy of periodontitis and PI.

Expression of HMGB1 and HMGN2 in gingival tissues, GCF and PICF of periodontitis patients and peri-implantitis.

BACKGROUND AND OBJECTIVE: High mobility group chromosomal protein B1 (HMGB1) and N2 (HMGN2), two members of high mobility group (HMG) family, play important role in inflammation. The purpose of this study was to investigate the expression of HMGB1 and HMGN2 in periodontistis. MATERIALS AND METHODS: The expression of HMGB1 and HMGN2 mRNA in gingival tissues and gingival crevicular fluid (GCF) in chronic periodontitis (CP), generalised aggressive periodontitis (G-AgP) patients and healthy subjects was detected by real-time PCR. The protein level of HMGB1 and HMGN2 in peri-implant crevicular fluid (PICF), peri-implant crevicular fluid of peri-implantitis (PI-PICF) and normal patients was determined by Western blotting. Furthermore, IL-1ß, IL-6, IL-8, TNF-α and HMGB1 levels in GCF, PI-PICF and healthy-PICF samples from different groups were determined by ELISA. RESULTS: HMGN2 expression was increased in inflamed gingival tissues and GCF from CP and G-ApG groups compared to control group. HMGB1 expression was the highest in the gingival tissues and GCF from CP patients and was accompanied by increased concentrations of IL-1ß, IL-6, IL-8 proinflammaory cytokines. CONCLUSION: To our knowledge, this is the first study reporting that the expression of HMGB1 and HMGN2 was increased in the gingival tissues and GCF in CP and G-AgP and the PICF in PICF. Our data suggest that HMGB1 may be a potential target for the therapy of periodontitis and PI.

The chromosomal protein HMGN2 mediates lipopolysaccharide-induced expression of ß-defensins in A549 cells.

Human ß-defensin-2 (HBD-2) is an antimicrobial peptide produced by the epithelial cells that plays an important role in innate and adaptive immunity. Here we report that high mobility group protein N2 (HMGN2), a member of the high mobility group superfamily that affects chromatin function, modulates the expression of HBD-2 in A549 cells treated by lipopolysaccharide. Mechanistically, HMGN2 prolongs the retention time and enhances the accumulation of nuclear factor κB p65 in the nucleus, and promotes the acetylation of p65 through increasing histone acetyltransferase activity and enhancing p65-Ser536 phosphorylation. Additionally, chromatin immunoprecipitation reveals that HMGN2 and p65 synergistically promote their specific binding to HBD-2 promoter, thereby affecting the downstream transcription. Taken together, these results suggest that HMGN2 acts as a positive modulator of nuclear factor κB signalling to promote lipopolysaccharide-induced ß-defensin expression.

Expression of HMGB1 and HMGN2 in gingival tissues, GCF and PICF of periodontitis patients and peri-implantitis.

High mobility group chromosomal protein B1 (HMGB1) and N2 (HMGN2), two members of High mobility group (HMG) family, play important role in inflammation. The purposes of this study were to investigate the expression of HMGB1 and HMGN2 in periodontistis. The expression of HMGB1 and HMGN2 mRNA in gingival tissues and gingival crevicular fluid (GCF) in chronic periodontitis (CP), generalized aggressive periodontitis (G-AgP) patients and healthy subjects was detected by real-time PCR. The protein level of HMGB1 and HMGN2 in peri-implant crevicular fluid (PICF), peri-implant crevicular fluid of peri-implantitis (PI-PICF) and normal patients was determined by Western blotting. Furthermore, IL-1ß, IL-6, IL-8, TNF-α and HMGB1 levels in GCF, PI-PICF and healthy -PICF samples from different groups were determined by ELISA. HMGN2 expression was increased in inflamed gingival tissues and GCF from CP and G-ApG groups compared to control group. HMGB1 expression was the highest in the gingival tissues and GCF from CP patients and was accompanied by increased concentrations of IL-1ß, IL-6, IL-8 proinflammaory cytokines. To our knowledge, this is the first study reporting that the expression of HMGB1 and HMGN2 was increased in the gingival tissues and GCF in CP and G-AgP and the PICF in PICF. Our data suggest that HMGB1 may be a potential target for the therapy of periodontitis and PI.

Hemoglobin and its derived peptides may play a role in the antibacterial mechanism of the vagina.

BACKGROUND: Hemoglobin is a precursor of antibacterial peptides. Our aim was to identify an antibacterial peptide in human endometrium. We tested the antimicrobial activities of hemoglobin and a derived peptide in vitro and in vivo in rats. METHODS: Samples (n = 3) were scraped from the surface of endometrium. Acid-soluble proteins underwent electrophoresis followed by gel overlay assay and reversed-phase high-performance liquid chromatography. Antibacterial activities were determined by agar radial diffusion assay. Purified peptides were further characterized by electrophoresis, mass spectrometry, N-terminal amino acid (AA) sequencing and protein structure analysis. A rat model was used to test the inhibitory activity of human hemoglobin on vaginal infection with Escherichia coli, using one experimental group (intravaginal hemoglobin, n = 9) and three control groups (n = 14). Vaginal histology was studied. RESULTS: The purified peptide exhibited potent antibacterial activities against E. coli ML-35P. The N-terminal AA sequence was F L S F P T T K T Y, identical to AA 32-41 of the human hemoglobin alpha chain, and it had the same mass (m/z = 6776.8) as the alpha chain 32-93 AA fragment, with at least three alpha-helices. Histology indicated that the hemoglobin group changed significantly compared with the matrix control group (no treatment after infection): the surface layer of stratified squamous epithelium was smoother, inflammatory cell infiltration was relieved in the lamina propria and congestion pattern was decreased. CONCLUSIONS: These results suggest that erythrocytes from endometrium are another source of the antimicrobial molecules. Hemoglobin and its derived peptides may play a role in the host defense against pathogens in human vagina.

[Study on antimicrobial activity of human hemoglobin and its fragments both in vitro and in vivo].

OBJECTIVE: To isolate human hemoglobin and its fragrments, compare their antimicrobial activity in vitro and pilot study of their antimicrobial activity in vivo. METHODS: The alpha and beta chains of hemoglobin were separated by cation exchange chromatography and gel chromatography; The alpha and beta chains were cleaved by cyanogens bromide respectively. The cleaved fragments were purified by reverse phase high performance liquid chromatography. Antimicrobial activity of hemoglobin and its fragments was determined by agrose radial diffusion assay. After establishment of E. coli vaginal infection model, the rats were randomized into the experimental group (hemoglobin group) and the control group. The histologically pathological section was observed. RESULTS: Hemoglobin, alpha/beta chain and their fragments had similar antibacterial activities in vitro, which were mainly against Gram-negative bacteria E. coli; except alpha1-32 had a comparatively lower activity. Antimicrobial activity in vivo: a comparison of the hemoglobin group with the matrix control group (no treatment after infection), the surface layer of vaginal stratified squamous epithelium was smoother, inflammatory cells were significantly reduced in the lamina propria and congestion was obviously decreased. CONCLUSION: Human hemoglobin and its fragments had antibacterial activity in vitro, hemoglobin might relieve the inflammation of E. coil vaginal infection in rats moreover.