Objective:To discuss the effect of sericin on the phosphatidylinositol 3-kinase(PI3K)/protein kinase B(Akt)/nuclear factor-κB(NF-κB)signaling pathway and apoptosis in the streptozotocin(STZ)-damaged INS-1 cells,and to clarify its mechanism.Methods:The INS-1 cells were cultured with complete medium containing 0,0.1,0.3,1.0,3.0,and 10.0 μmol·L-1 Akt1 inhibitor A-674563,10 mmol·L-1 STZ,and 600 mg·L-1 sericin,and divided into 0,0.1,0.3,1.0,3.0,and 10.0 μmol·L-1 A-674563 groups,and the control group(complete medium without drugs)was set up.Cell counting kit-8(CCK-8)method was used to detect the survival rates of the INS-1 cells,and the half-maximal inhibitory concentration(IC50)value was calculated to determine the optimal inhibitory concentration of A-674563,which was further verified by Western blotting method.The INS-1 cells were divided into normal control group(complete medium),model group(10 mmol·L-1 STZ+complete medium),and low,medium,and high doses of sericin groups(10 mmol·L-1 STZ+150 mg·L-1 sericin+complete medium,10 mmol·L-1 STZ+300 mg·L-1 sericin+complete medium,and 10 mmol·L-1 STZ+600 mg·L-1 sericin+complete medium).CCK-8 method was used to detect the survival rates of the INS-1 cells in various groups to determine the optimal concentration of sericin.Additionally,the INS-1 cells were divided into normal control group(complete medium),model group(10 mmol·L-1 STZ+complete medium),sericin group(10 mmol·L-1 STZ+600 mg·L-1 sericin+complete medium),and A-674563 group(10 mmol·L-1 STZ+600 mg·L-1 sericin+0.3 μmol·L-1 A-674563+complete medium).Flow cytometry was used to detect the apoptotic rates of the INS-1 cells in various groups;real-time fluorescence quantitative PCR(RT-qPCR)method was used to detect the expression levels of Akt1,NF-κB,tumor necrosis factor-α(TNF-α),and interleukin-6(IL-6)mRNA in the INS-1 cells in various groups;Western blotting method was used to detect the expression levels of phosphorylated Akt1(p-Akt1)and NF-κB proteins in the INS-1 cells in various groups;enzyme linked immunosorbent assay(ELISA)method was used to detect the levels of TNF-α and IL-6 in the INS-1 cells in various groups.Results:The survival rates of the INS-1 cells in control group was 100.00%±0.00%;in 0,0.1,0.3,1.0,3.0,and 10.0 μmol·L-1 A-674563+10 mmol·L-1 STZ+600 mg·L-1 sericin+complete medium groups,which were 82.50%±2.28%,69.47%±1.94%,51.51%±1.74%,38.94%±1.57%,24.79%±1.14%,and 19.85%±1.03%,respectively.The IC?? value of A-674563 for INS-1 cells was 0.3 μmol·L-1,and 0.3 μmol·L-1 A-674563 was selected for subsequent experiments.Compared with 0 μmol·L-1 A-674563,the expression level of p-Akt1 protein in the INS-1 cells after treated with 0.3 μmol·L-1 A-674563+10 mmol·L-1 STZ+600 mg·L-1 sericin+complete medium was significantly decreased(P<0.05).The CCK-8 results showed that compared with normal control group,the survival rate of the INS-1 cells in model group was significantly decreased(P<0.05);compared with model group,the survival rates of the INS-1 cells in low,medium,and high doses of sericin groups were significantly increased(P<0.05);compared with low and medium doses of sericin groups,the survival rate of the INS-1 cells in high dose of sericin group was significantly increased(P<0.05).Thus,600 mg·L-1 sericin was selected for subsequent experiments.The CCK-8 results showed that compared with normal control group,the survival rate of the INS-1 cells in model group was significantly decreased(P<0.05);compared with model group,the survival rate of the INS-1 cells in sericin group was significantly increased(P<0.05);compared with sericin group,the survival rate of the INS-1 cells in A-674563 group was significantly decreased(P<0.05).The flow cytometry results showed that compared with normal control group,the apoptotic rate of the INS-1 cells in model group was significantly increased(P<0.05);compared with model group,the apoptotic rate of the INS-1 cells in sericin group was significantly decreased(P<0.05);compared with sericin group,the apoptotic rate of the INS-1 cells in A-674563 group was significantly increased(P<0.05).The RT-qPCR results showed that compared with normal control group,the expression level of Akt1 mRNA in the INS-1 cells in model group was significantly decreased(P<0.05);compared with model group,the expression levels of Akt1 mRNA in the INS-1 cells in low,medium,and high doses of sericin groups were significantly increased(P<0.05);compared with low and medium doses of sericin groups,the expression level of Akt1 mRNA in the INS-1 cells in high dose of sericin group was significantly increased(P<0.05).Compared with normal control group,the expression levels of NF-κB,TNF-α,and IL-6 mRNA in the INS-1 cells in model group were significantly increased(P<0.05);compared with model group,the expression levels of NF-κB,TNF-α,and IL-6 mRNA in the INS-1 cells in sericin group were significantly decreased(P<0.05);compared with sericin group,the expression level of NF-κB mRNA in the INS-1 cells in A-674563 group was significantly increased(P<0.05).The Western blotting results showed that compared with normal control group,the expression level of p-Akt1 protein in the INS-1 cells in model group was significantly decreased(P<0.05);compared with model group,the expression levels of p-Akt1 protein in the INS-1 cells in low,medium,and high doses of sericin groups were significantly increased(P<0.05);compared with low and medium doses of sericin groups,the expression level of p-Akt1 protein in the INS-1 cells in high dose of sericin group was significantly increased(P<0.05).Compared with normal control group,the expression level of NF-κB protein in the INS-1 cells in model group was significantly increased(P<0.05);compared with model group,the expression level of NF-κB protein in the INS-1 cells in sericin group was significantly decreased(P<0.05);compared with sericin group,the expression level of NF-κB protein in the INS-1 cells in A-674563 group was significantly increased(P<0.05).The ELISA results showed that compared with normal control group,the levels of TNF-α and IL-6 in the INS-1 cells in model group were significantly increased(P<0.05);compared with model group,the levels of TNF-α and IL-6 in the INS-1 cells in sericin group were significantly decreased(P<0.05);compared with sericin group,the levels of TNF-α and IL-6 in the INS-1 cells in A-674563 group were significantly increased(P<0.05).Conclusion:Sericin alleviates the PI3K/Akt/NF-κB signaling pathway-mediated inflammatory response and apoptosis by targeting Akt1,exerting a protective effect against STZ-induced damage in INS-1 cells.

Objective To analyze the structures of atypical class 1 integrons in clinical Proteus isolates. Methods This study included 26 class 1 integron integrase gene-positive clinical Proteus isolates, from which the variable regions of class 1 integrons could not be amplified. Six isolates were chosen from them to amplify the flanking DNA segments of class 1 integron integrase gene using inverse PCR. The se-quences of PCR products were analyzed with BLAST to identify the target homologous sequences as well as their accession numbers in GenBank. Primers for overlap PCR were designed according to the flanking se-quences. Then the 26 clinical Proteus isolates were analyzed with overlap PCR and sequencing analysis. Re-sults The variable regions of class 1 integrons in 25 out of the 26 clinical Proteus isolates were completely or partly identified by using inverse PCR,overlap PCR and sequencing analysis. A gene cassette array of estX-psp-aadA2-cmlA1-aadA1a-qacI-tnpA-sul3 was detected in 22 isolates. The variable regions of class 1 integrons in the other three isolates were identified to be estX-psp-aadA2-cmlA1,dfrA14 and IS26,respectively. All of the 25 isolates lacked the 3'conserved segements in class 1 integron. Conclusion Inverse PCR can be used to analyze the structures of atypical class 1 integrons. Gene cassette psp and gene cassette arrays of estX-psp-aadA2-cmlA1-aadA1a-qacI-tnpA-sul3 and estX-psp-aadA2-cmlA1 in clinical Proteus isolates are reported for the first time.

Objective To establish a high resolution melting based method for the rapid identifica-tion of functional class 2 integron.Methods Nighty-nine non-repetitive Proteus spp.strains positive for genes encoding class 2 integrase were isolated from August, 2011 to August, 2012.The genomic DNAs were extracted and used as templates to amplify 60 base pair fragments containing the mutated point in class 2 in-tegrase gene by PCR.The high resolution melting analysis was conducted to identify the functional class 2 in-tegrons that were further compared by sequence analysis.Results There were remarkable differences with the high resolution melting curves between the functional class 2 integrons and the ordinary class 2 integrons. The results of high resolution melting analysis were consistent with those by using sequence analysis.Con-clusion High resolution melting analysis could be used for the rapid and accurate identification of functional class 2 integron.