Rapid detection of mexX in Pseudomonas aeruginosa based on CRISPR-Cas13a coupled with recombinase polymerase amplification.

The principal pathogen responsible for chronic urinary tract infections, immunocompromised hosts, and cystic fibrosis patients is Pseudomonas aeruginosa, which is difficult to eradicate. Due to the extensive use of antibiotics, multidrug-resistant P. aeruginosa has evolved, complicating clinical therapy. Therefore, a rapid and efficient approach for detecting P. aeruginosa strains and their resistance genes is necessary for early clinical diagnosis and appropriate treatment. This study combines recombinase polymerase amplification (RPA) and clustered regularly interspaced short palindromic repeats-association protein 13a (CRISPR-Cas13a) to establish a one-tube and two-step reaction systems for detecting the mexX gene in P. aeruginosa. The test times for one-tube and two-step RPA-Cas13a methods were 5 and 40 min (including a 30 min RPA amplification reaction), respectively. Both methods outperform Quantitative Real-time Polymerase Chain Reactions (qRT-PCR) and traditional PCR. The limit of detection (LoD) of P. aeruginosa genome in one-tube and two-step RPA-Cas13a is 10 aM and 1 aM, respectively. Meanwhile, the designed primers have a high specificity for P. aeruginosa mexX gene. These two methods were also verified with actual samples isolated from industrial settings and demonstrated great accuracy. Furthermore, the results of the two-step RPA-Cas13a assay could also be visualized using a commercial lateral flow dipstick with a LoD of 10 fM, which is a useful adjunt to the gold-standard qRT-PCR assay in field detection. Taken together, the procedure developed in this study using RPA and CRISPR-Cas13a provides a simple and fast way for detecting resistance genes.

Gold nanoparticle-based colorimetric method for the detection of prostate-specific antigen.

BACKGROUND: Prostate-specific antigen (PSA), a serine protease, is a biomarker for preoperative diagnosis and screening of prostate cancer and monitoring of its posttreatment. METHODS: In this work, we reported a colorimetric method for clinical detection of PSA using gold nanoparticles (AuNPs) as the reporters. The method is based on ascorbic acid (AA)-induced in situ formation of AuNPs and Cu2+-catalyzed oxidation of AA. Specifically, HAuCl4 can be reduced into AuNPs by AA; Cu2+ ion can catalyze the oxidation of AA by O2 to inhibit the formation of AuNPs. In the presence of the PSA-specific peptide (DAHSSKLQLAPP)-modified gold-coated magnetic microbeads (MMBs; denoted as DAHSSKLQLAPP-MMBs), complexation of Cu2+ by the MMBs through the DAH-Cu2+ interaction depressed the catalyzed oxidation of AA and thus allowed for the formation of red AuNPs. However, once the peptide immobilized on the MMB surface was cleaved by PSA, the DAHSSKLQ segment would be released. The resultant LAPP fragment remaining on the MMB surface could not sequestrate Cu2+ to depress its catalytic activity toward AA oxidation. Consequently, no or less AuNPs were generated. RESULTS: The linear range for PSA detection was found to be 0~0.8 ng/mL with a detection limit of 0.02 ng/mL. Because of the separation of cleavage step and measurement step, the interference of matrix components in biological samples was avoided. CONCLUSION: The high extinction coefficient of AuNPs facilitates the colorimetric analysis of PSA in serum samples. This work is helpful for designing of other protease biosensors by matching specific peptide substrates.

Sonic hedgehog improves ischemia-induced neovascularization by enhancing endothelial progenitor cell function in type 1 diabetes.

The Sonic hedgehog (Shh) pathway is downregulated in type 1 diabetes, and it has been reported that augmentation of this pathway may alleviate diabetic complications. However, the cellular mechanisms underlying these protective effects are poorly understood. Recent studies indicate that impaired function of endothelial progenitor cells (EPCs) may contribute to cardiovascular problems in diabetes. We hypothesized that impaired Shh signaling contribute to endothelial progenitor cell dysfunction and that activating the Shh signaling pathway may rescue EPC function and promote diabetic neovascularization. Adult male C57/B6 mice and streptozotocin (STZ)-induced type 1 diabetic mice were used. Gli1 and Ptc1 protein levels were reduced in EPCs from diabetic mice, indicating inhibition of the Shh signaling pathway. EPC migration, tube formation ability, and mobilization were impaired in diabetic mice compared with non-diabetic controls (p < 0.05 vs control), and all were improved by in vivo administration of the Shh pathway receptor agonist SAG (p < 0.05 vs diabetes). SAG significantly increased capillary density and blood perfusion in the ischemic hindlimbs of diabetic mice (p < 0.05 vs diabetes). The AKT activity was lower in EPCs from diabetic mice than those from non-diabetic controls (p < 0.05 vs control). This decreased AKT activity led to an increased GSK-3ß activity and degradation of the Shh pathway transcription factor Gli1/Gli2. SAG significantly increased the activity of AKT in EPCs. Our data clearly demonstrate that an impaired Shh pathway mediated by the AKT/GSK-3ß pathway can contribute to EPC dysfunction in diabetes and thus activating the Shh signaling pathway can restore both the number and function of EPCs and increase neovascularization in type 1 diabetic mice.

[The role of JNK in apoptosis of renal tubular epithelial cells in diabetic rats with fluctuant high blood glucose].

OBJECTIVE: To explore the signal transduction mechanisms of apoptosis in renal tubular epithelial cells in diabetic rats with fluctuant high blood glucose. METHODS: Healthy SD rats were randomly divided into 3 groups: normal control group (A), stable high blood glucose group (B) and fluctuant high blood glucose group (C). Diabetic rats were induced by intraperitoneal injection of streptozotocin (STZ, 65 mg/kg), and the fluctuant high blood glucose animal model was induced by intraperitoneal injection of ordinary insulin and glucose at different time point every day. The superoxide dismutase (SOD) activity and the content of malonaldehyde (MDA) in renal tissue homogenate were detected with colorimetry. The protein expression of Nox4 and JNK were examined by immunohistochemistry and Western blot. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL). RESULTS: After 12 experimental weeks, significantly increased cell apoptosis, up-regulation of Nox4 and P-JNK expression in renal tubular epithelial cells were observed in B and C groups compared with those in A group. The MDA content increased and SOD activity decreased in renal tissue in B and C groups. Above effects were more obviously shown in C group. CONCLUSION: Fluctuant high blood glucose induced more apoptosis of renal tubular epithelial cell than stable high blood glucose in diabetic kidney, which might be related to the activation of JNK signal transduction pathway.

Inhibition of hepatitis C virus replication by single and dual small interfering RNA using an HCV-infected cell model.

Dual siRNA against different regions of gene in hepatitis C virus (HCV) synergistically inhibited replication of HCV RNA. An HCV-infected cell model was established, and HCV RNA and core protein were detected by RT-PCR and Western blot, respectively. Four HCV-specific siRNAs (siCore, siNS3, siNS4B, siNS5B) were designed and transfected into HCV-infected Huh7.5.1 cells. The antiviral efficacies of the siRNAs were compared using real time PCR and agarose gel electrophoresis. HCV replication in infected cells was inhibited by IFNα-2b in a dose-dependent manner. Synergistic inhibition effects were achieved with combination treatment of any two of the siRNAs (siCore, siNS3 and siNS5B) at low doses (0.1 and 10 nM), as compared to single siRNA treatment (P < 0.05). Furthermore, CCK-8 assay showed no toxicity of the siRNAs to Huh7.5.1 cells. These findings indicate a promising new therapeutic approach for treatment of HCV.

[Influence of miR-122 on IFN-α treatment for HCV infection].

OBJECTIVE: To investigate the influence of miR-122 on IFN-α treatment for HCV infection. METHODS: Huh7.5.1 cells infected with HCV were treated with miR-122 mimics (20 nmol/L, 100 nmol/L, 400 nmol/L) and/or IFN-α (1000 IU/ml). The relative expression of HCV RNA was detected by real-time polymerase chain reaction (PCR). Huh7.5.1 cells were treated with different amounts of HCV (107 copies, 106 copies and 105 copies) and/or IFN-α (1000 IU/ml). RESULTS: IFN-α suppressed the replication of HCV in a time-dependent manner, resulting in a ≊ 83% reduction of HCV at 48 h. MiR-122 mimics facilitated replication of HCV RNA in a dose-dependent manner (P<0.05). The antiviral effect of IFN-α was inverted to levels of miR-122 mimics (20 nmol/L, 100 nmol/L, 400 nmol/L), (73.3% ± 3.5% compared with 84% ± 4.5%, P>0.05; 64.67% ± 5.5% compared with 84% ± 4.5%, P>0.05; 56.33% ± 5.1% compared with 84% ± 4.5%, P<0.05). The antiviral effect of IFN-α was inverted to HCV load (105 copies group compared with 107 copies group, P<0.05). CONCLUSION: MiR-122 facilitates replication of HCV RNA in the cell culture system; and the expression of miR-122 may partly counteract the anti-HCV effect of IFN-α.