Effects of co-administration of methanol leaf extract of Catharanthus roseus on the hypoglycemic activity of metformin and glibenclamide in rats

Objective:To investigate the interacting effects of co-administration of methanol leaf extract of Catharanthus roseus（C.roseus） on the hypoglycemic activity of metformin as well as glibenclamide using experimental rats.Methods:Phytochemical analysis as well as acute toxicity and lethality(LD50) test were carried out on its methanol leaf extract.The alloxan model for experimental induction of diabetes in rats was employed.Six groups comprising five rats each were used.GroupsⅡ,ⅢandⅣreceived 250 mg/kg of extract,100 mg/kg of metformin and 1 mg/kg of glibenclamide respectively,while V and VI were administered metformin-extract and glibenclamide-extract combinations respectively at doses as above.Group I served as negative control and received only distilled water.All administration was done once daily for seven days. Fasting blood glucose was determined at 2,12,24,72 and 168 h using a glucometer.One-way ANOVA with post-hoc tests was used to assess for significant difference due to administration of drug alone and with co-administration of drug and extract.Results:The LD50 was 2 121.32 mg/kg. The phytochemical studies indicated the presence of saponins,tannins,alkaloids,phlotatannins, flavonoids,triterpenoids,reducing sugars,anthraquinones and glycosides.All medicaments significantly reduced blood glucose levels when compared with control alone（P【0.05） with the highest percentage reduction in blood glucose（64.86%） exhibited by metformin-extract combination.Conclusions:The leaf extract of C.roseus significandy increases the hypoglycemic effect of metformin.

The use of melittin to enhance transgene expression mediated by recombinant adeno-associated virus serotype 2 vectors both in vitro and in vivo

Objective: Melittin, a cell-penetrating peptide, improves the efficiency of many non-viral gene delivery vectors, yet its application in viral vectors has not been well studied. The non-pathogenic recombinant adeno-associated virus(rAAV) vector is an ideal in vivo gene delivery vector. However, its full potential will only be achieved after improvement of its transduction efficiency. To improve the transduction efficiency of rAAV2 vectors, we attempted to develop a melittin-based r AAV2 vector delivery strategy.Methods: The melittin peptide was inserted into the rAAV2 capsid either in the loop Ⅷ of all viral proteins(VPs) or at the N terminus of VP2. Various r AAV2-gfp or-fluc vectors were subjected to quantitative real-time polymerase chain reaction and Western blot assays to determine their titers and integrity of capsid proteins, respectively. Alternatively, the vectors based on wild-type capsid were pre-incubated with melittin, followed by transduction of cultured cells or tail vein administration of the mixture to C57BL/6 and BALB/c nude mice. In vivo bioluminescence imaging was performed to evaluate the transgene expression.Results: rAAV2 vectors with melittin peptide inserted in the loop Ⅷ of VPs had low transduction efficiency, probably due to dramatically reduced ability to bind to the target cells. Fusing the melittin peptide at the N-terminus of VP2 produced vectors without the VP2 subunit. Interestingly, among the commonly used rAAV vectors, pre-incubation of r AAV2 and rAAV6 vectors with melittin significantly enhanced their transduction efficiency in HEK293 and Huh7 cells in vitro. Melittin also had the ability to increase the rAAV2-mediated transgene expression in mouse liver in vivo. Mechanistically, melittin did not change the vector-receptor interaction. Moreover, cell counting kit-8 assays of cultured cells and serum transaminase levels indicated melittin had little cytotoxicity.Conclusion: Pre-incubation with melittin, but not insertion of melittin into the rAAV2 capsid, significantly enhanced rAAV2-mediated transgene expression. Although further in vivo evaluations are required, this research not only expands the pharmacological potential of melittin, but also provides a new strategy to improve gene therapy mediated by rAAV vectors.

GSH-responsive SN38 dimer-loaded shape-transformable nanoparticles with iRGD for enhancing chemo-photodynamic therapy

Accurate tumor targeting,deep penetration and superb retention are still the main pursuit of developing excellent nanomedicine.To achieve these requirements,a stepwise stimuli-responsive strategy was developed through co-administration tumor penetration peptide iRGD with shape-transformable and GSH-responsive SN38-dimer(d-SN38)-loaded nanoparticles(d-SN38@NPs/iRGD).Upon intravenous injection,d-SN38@NPs with high drug loading efficiency(33.92±1.33%)could effectively accumulate and penetrate into the deep region of tumor sites with the assistance of iRGD.The gathered nanoparticles simultaneously transformed into nanofibers upon 650 nm laser irradiation at tumor sites so as to promote their retention in the tumor and burst release of reactive oxygen species for photodynamic therapy.The loaded d-SN38 with disulfide bond responded to the high level of GSH in tumor cytoplasm,which consequently resulted in SN38 release and excellent chemo-photodynamic effect on tumor.In vitro,coadministering iRGD with d-SN38@NPs+laser showed higher cellular uptake,apoptosis ratio and multicellular spheroid penetration.In vivo,d-SN38@NPs/iRGD+laser displayed advanced penetration and accumulation in tumor,leading to 60.89%of tumor suppression in 4 T1 tumor-bearing mouse model with a favorable toxicity profile.Our new strategy combining iRGD with structural transformable nanoparticles greatly improves tumor targeting,penetrating and retention,and empowers anticancer efficacy.

Pharmacokinetic interaction of Forsythia suspensa extract and azithromycin injection after single and co-intravenous administration in rats

Azithromycin and Chinese medicine forsythia are often used together to treat pediatric mycoplasma infections in China. We aimed to investigate the pharmacokinetic interaction of Forsythia suspensa extract and azithromycin after single and co-intravenous administration in rats. Male Sprague-Dawley rats received single(Forsythia suspensa extract or azithromycin) treatment or co-administration of Forsythia suspensa extract and azithromycin. Blood samples were collected at scheduled times, and drug concentrations were determined by HPLC-UV or HPLC-MS/MS methods. Both non-compartmental analyses and nonlinear mixed-effects modeling approaches were applied to fit pharmacokinetic data and evaluate the impact of co-administration. Pharmacokinetic analysis showed that the area under the curve of azithromycin and forsythiaside increased, and clearance decreased significantly(P < 0.05),after co-administration. The in vivo behavior of both azithromycin and forsythiaside could be appropriately described by the two-compartmental model. The final population pharmacokinetic model indicated that co-administration decreased the central volume of azithromycin and forsythiaside clearance significantly. Co-administration of Forsythia suspensa extract and azithromycin significantly decreased the clearance and increased exposure for both drugs. Pharmacokinetic data suggest that drug co-administration may increase efficiency.