Controlling CRISPR-Cas9 by guide RNA engineering.

The clustered regularly interspaced short palindromic repeats (CRISPR) system is a product of million years of evolution by microbes to fight against invading genetic materials. Around 10 years ago, scientists started to repurpose the CRISPR as genetic tools by molecular engineering approaches. The guide RNA provides a versatile and unique platform for the innovation to improve and expand the application of CRISPR-Cas9 system. In this review, we will first introduce the basic sequence and structure of guide RNA and its role during the function of CRISPR-Cas9. We will then summarize recent progress on the development of various guide RNA engineering strategies. These strategies have been dedicated to improve the performance of CRISPR-Cas9, to achieve precise spatiotemporal control of CRISPR-Cas9, and to broaden the application of CRISPR-Cas9. Finally, we will briefly discuss the uniqueness and advantage of guide RNA-engineering based systems versus those with engineered Cas9 proteins and speculate potential future directions in guide RNA engineering. This article is categorized under: RNA Methods > RNA Analyses In Vitro and In Silico RNA Methods > RNA Nanotechnology Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.

Vesicle transport related protein Synaptotagmin-1 mediates paraquat transport to antagonize paraquat toxicity.

In this study, A549/PQ cells with moderate resistance to paraquat (PQ) were obtained by treating A549 cells with PQ, their growth rate was slowed down, the accumulation concentration of PQ and the levels of growth inhibition, injury and early apoptosis induced by PQ were significantly lower than those of parental A549 cells. Microarray screening and RT-qPCR detection found that Synaptotagmin-1 (SYT1) expression in drug-resistant cells was significantly increased, and PQ further enhanced its expression. After inhibiting SYT1 expression in A549/PQ cells, cell viability, intracellular PQ concentration and the expression of Bcl-2, SNAP25 and RAB26 were significantly reduced, while the mortality, early apoptosis rate and Bax expression were significantly increased. In vivo experiments also further showed that PQ promoted the expression of SYT1, SNAP25 and RAB26 in PQ-poisoned mice; when inhibiting SYT1 expression, PQ concentration in lung tissues was significantly increased, and the levels of lung injury and apoptosis were also significantly enhanced, while the expression of SNAP25 and RAB26 was significantly reduced. This indicates that PQ poisoning leads to compensatory up-regulation of vesicle transport related proteins such as SYT1 in vivo, thereby promoting PQ transmembrane transport, and then reducing the pulmonary accumulation of PQ and PQ-caused lung injury.

A microRNA-inducible CRISPR-Cas9 platform serves as a microRNA sensor and cell-type-specific genome regulation tool.

microRNAs (miRNAs) are small noncoding RNAs that play important regulatory roles in plants, animals and viruses. Measuring miRNA activity in vivo remains a big challenge. Here, using an miRNA-mediated single guide RNA (sgRNA)-releasing strategy and dCas9-VPR to drive a transgene red fluorescent protein, we create an miRNA sensor that can faithfully measure miRNA activity at cellular levels and use it to monitor differentiation status of stem cells. Furthermore, by designing sgRNAs to target endogenous loci, we adapted this system to control the expression of endogenous genes or mutate specific DNA bases upon induction by cell-type-specific miRNAs. Finally, by miRNA sensor library screening, we discover a previously undefined layer of heterogeneity associated with miR-21a activity in mouse embryonic stem cells. Together, these results highlight the utility of an miRNA-induced CRISPR-Cas9 system as miRNA sensors and cell-type-specific genome regulation tools.

Simvastatin prevents and ameliorates depressive behaviors via neuroinflammatory regulation in mice.

BACKGROUND: Statins play a beneficial role in the treatment of coronary artery disease and are widely prescribed to prevent hypercholesterolemia. Previous studies have demonstrated that statins also have anti-inflammatory and immunomodulatory properties, and these are being explored for potential benefits in depression. However, the role of statins in the treatment of depression has not been well examined. METHODS: We investigated the effects of simvastatin on depressive behaviors and neuroinflammation in lipopolysaccharide (LPS) and chronic mild stress (CMS) induced depression model in mice. Sucrose preference test (SPT), forced swimming test (FST), novelty-suppressed feeding test (NSFT) were used to detect the depressive behaviors. The microglial activation was detected by immunohistochemistry analysis and the pro-inflammatory cytokines expressions including IL-1ß, TNF-α and IL-6 were examined by Western blot analysis. RESULTS: Our data indicated that oral administration of simvastatin at 20 mg/kg significantly prevented and ameliorated depressive behaviors reflected by better performance in the SPT, FST and NSFT. Moreover, simvastatin markedly prevented and ameliorated LPS and CMS-induced neuroinflammation, as shown by the suppressed activation of microglia in hippocampus and decreased hippocampal pro-inflammatory cytokines expressions including IL-1ß, TNF-α, IL-6, which might be mediated via the inhibition of NF-κB pathway, as shown by the decreased nuclear NF-κB p65 expression. LIMITATIONS: The interpretation of the evidence of a positive treatment effect of simvastatin on the depressive manifestations, multifaceted etiology of depression, and confirmation of this finding from animal models to humans is needed. CONCLUSION: These results suggest that simvastatin has the potential to be employed as a therapy for depression associated with neuroinflammation.

Nrf2 overexpression protects against paraquat-induced A549 cell injury primarily by upregulating P-glycoprotein and reducing intracellular paraquat accumulation.

Paraquat (PQ) intoxication causes thousands of mortalities every year, worldwide. Its pulmonary-targeted accumulation and the acute lung injury it subsequently causes, remain a challenge for detoxification treatment. A previous study has demonstrated that the upregulation of nuclear factor erythroid-2 related factor 2 (Nrf2) prevents PQ toxicity in cell line and murine models. As Nrf2 target genes include a group of membrane transporters, the current study assessed the protective mechanism exerted by Nrf2 against PQ toxicity and intracellular PQ accumulation via its effects on P-glycoprotein (P-gp), a downstream transporter of Nrf2. Adenovirus vectors containing the Nrf2 gene were transfected into A549 cells. Cell proliferation was assessed by Cell Counting Kit-8. The levels of LDH, MDA, SOD, TNF-α, IL-6 levels were detected using their respective ELISA kits. In addition, the levels of Nrf2 and P-gp protein expression were detected by western blot analysis. The concentration of PQ was measured by HPLC. The results revealed that overexpressed Nrf2 significantly increased P-gp protein levels, decreased the intracellular accumulation of PQ and attenuated PQ-induced toxicity. However, the protective effects of Nrf2 overexpression on PQ-challenged A549 cells were abrogated following cyclosporine A treatment, a competitive inhibitor of P-gp, which also increased intracellular PQ levels. These data indicated that Nrf2 gene overexpression prevented PQ toxicity in A549 cells, potentially via the upregulation of P-gp activity and the inhibition of intracellular PQ accumulation. Thus, Nrf2 and P-gp may serve as potential therapeutic targets for the treatment of PQ-induced injury.

Effects of repeated allopurinol administration on rat cytochrome P450 activity.

Allopurinol is a popular and widely-prescribed anti-hyperuricemic agent that has been implicated in drug interactions with substrates of several cytochrome P450 (CYP) enzymes. The effect of repeated allopurinol administration (20 mg/kg, once daily for 14 days) on metabolic activity of CYP was assessed in rats. This was a randomized, double-blind, two-way crossover study with a 4-week washout period between phases. The substrates used in this study were phenacetin (CYP1A2), tolbutamide (CYP2C9), omeprazole (CYP2C19) and dextromethorphan (CYP2D6). Validated HPLC-MS/MS was used to quantify all compounds. Our study showed that allopurinol administration inhibited CYP1A2 activity, causing a significant increase in AUC (0-infinity) (P < 0.01) and t1/2 (P < 0.05) of phenacetin, and a distinct decline in CL (P < 0.01). However, there were no significant differences of another three probe drugs in plasma concentrations and the corresponding pharmacokinetic parameters between the allopurinol-treated and normal saline-treated rats. The findings in this study suggested that allopurinol could inhibit CYP1A2 but did not influence CYP2C9, CYP2C19 and CYP2D6 enzymes.

Therapeutic drug monitoring in voriconazole-associated hyponatremia.

Voriconazole is a second generation triazole antifungal agent and the first choice therapy for invasive aspergillosis (IA). Although voriconazole may be associated with many adverse events, hyponatremia has been rarely reported which potentially could result in death. Therapeutic drug monitoring (TDM) and individualization of therapy by measuring voriconazole plasma concentrations improved the efficacy and safety in patients. We report the effect of TDM to adjust voriconazole dosage in a voriconazole-related hyponatremia patient.

Effects of Ougan juice on P450 activities using a cocktail method.

Ougan (Citrus suavissima Hort. ex Tanaka) is an important domesticated fruit which is used medicinally in China. To date, a number of methods for its identification and chemical analysis have been studied. However, the effects of Ougan juice on CYP isozymes have not been reported. Therefore, the objective of our study was to evaluate the potential effects of Ougan juice on the CYP isozymes CYP1A2, CYP2C9, CYP2C19 and CYP2D6 in rats using a cocktail approach involving the probe drugs phenacetin, tolbutamide, omeprazole and dextromethorphan. These four probe drugs were simultaneously administered to rats after single and multiple dosing of Ougan juice by gastric irrigation. The pharmacokinetics of the probes in the plasma were simultaneously determined by HPLC-MS. The main pharmacokinetic parameters of the four probe drugs were not significantly different in rats after single dose of Ougan juice. The t1/2 and AUC(0-infinity) of phenacetin and omeprazole increased significantly and their CL(z) decreased markedly after multiple dosing of Ougan juice. However, the t1/2 of tolbutamide decreased notably, while the t1/2 of dextromethorphan was not changed. The findings of this study suggest that a single administration of Ougan juice had little effect on P450 activities while multiple administration of Ougan juice tended to inhibit CYP1A2 and CYP2C19 and induce CYP2C9, but did not influence CYP2D6.

Dynamic monitoring of total plasma homocysteine in spontaneously hypertensive rats by LC-MS.

Hypertension has been recognized to be closely related to plasma homocysteine levels (tHcy). Spontaneously hypertensive rats (SHR) are used widely for hypertension research, but it is unclear whether hypertension is related to high levels of tHcy in rat plasma. To test whether hyperhomocysteinemia occurs in SHR we dynamically measured plasma total homocysteine (tHcy) in SHR by liquid chromatography-tandem mass spectrometry (LC-MS). This analytical method has good linearity within the range of 1-100 micromol/L for tHcy in rat plasma with a correlation coefficient of R = 0.9975. After dynamic monitoring (12 weeks) on the plasma tHcy in SHR and Wistar-Kyoto rats, we found that there was no significant difference in tHcy level between SHR and Wistar-Kyoto rats, which was 6.98 +/- 1.82 micromol/L and 8.04 +/- 1.64 micromol/L, respectively. And there was no significantly high level of plasma tHcy in SHR.

Adjudin targeting rabbit germ cell adhesion as a male contraceptive: a pharmacokinetics study.

Adjudin (1-(2,4-dichlorobenzyl)-1H-indazole-3-carbohydrazide; formerly called AF-2364) has been shown to inhibit spermatogenesis by disrupting anchoring junctions at the Sertoligerm cell interface. This, in turn, leads to germ cell loss from the seminiferous epithelium, and transient infertility. Adjudin's efficacyin inhibiting spermatogenesis, the recovery of spermatogenesis after cessation of the drug, and side effects were examined in adult male Japanese rabbits. The pharmacokinetics profiles of adjudin in rabbits after oral administration and after intravenous injection were compared. Rabbits received 25 mg/kg adjudin once weekly for 4 consecutive weeks either by intravenous injection or by gavage. Vehicle-treated rabbits were used as controls. At 1, 2, 3, 4, and 8 weeks after treatment, testes were removed for microscopic examination to assess the status of spermatogenesis. Four weeks after intravenous cessation of adjudin, the recovery of spermatogenesis also was monitored. Blood was withdrawn after first administration to measure plasma concentrations of adjudin by high-performance liquid chromatography. Four weeks after intravenous treatment, examination of testis sections showed rapid exfoliation of elongated/elongating spermatids and the presence of large multinucleated cells; more than 95% of germ cells were absent from the seminiferous epithelium. Intravenous treatment showed a more severe disturbance of spermatogenesis compared with gavage treatment, which was correlated with bioavailability of the drug. The areas under the curve for intravenous injection and gavage were 20.11 +/- 1.90 and 2.23 +/- 0.45 mg x h x L(-1), respectively. These results illustrate the potential of adjudin as a male contraceptive, and the efficacy is associated with the bioavailability of the drug.