Ser38-His93-Asn91 triad confers resistance of JFH1 HCV NS5A-Y93H variant to NS5A inhibitors

HCV NS5A is a dimeric phosphoprotein involved in HCV replication. NS5A inhibitors are among direct-acting antivirals (DAA) for HCV therapy. The Y93H mutant of NS5A is resistant to NS5A inhibitors, but the precise mechanism remains unclear. In this report, we proposed a Ser38-His93-Asn91 triad to dissect the mechanism. Using pymol 1.3 software, the homology structure of JFH1 NS5A was determined based on the dimer structure of genotype 1b extracted from the database Protein DataBank (www.ebi.ac.uk/pdbsum) with codes 1ZH1 and 3FQM/3FQQ. FLAG-NS5A-WT failed to form dimer in the absence of nonstructural proteins from subgenomic replicon (NS3-5A); however, FLAG-NS5A-Y93H was able to form dimer without the aid of NS3-5A. The Ser38-His93-Asn91 triad in the dimer of the Y93H variant predicts a structural crash of the cleft receiving the NS5A inhibitor daclatasvir. The dimerization assay revealed that the existence of JFH1-NS5A-1ZH1 and -3FQM homology dimers depended on each other for existence and that both NS5A-WT 1ZH1 and 3FQM dimers cooperated to facilitate RNA replication. However, NS5A-Y93H 1ZH1 alone could form dimer and conduct RNA replication in the absence of the 3FQM structure. In conclusion, this study provides novel insight into the functional significance of the Ser38-His93-Asn91 triad in resistance of the Y93H variant to NS5A inhibitors.

Akt1 is involved in HCV release by promoting endoplasmic reticulum-to-endosome transition of infectious virions

AIMS

Hepatitis C virus (HCV) relies on the viral and host factors to complete its life cycle. It has evolved to profit from Akt activation at some stage in its life cycle through various mechanisms, notably by activating lipogenesis, which is crucial for infectious virions production.

MATERIALS AND METHODS

By employing an Akt-specific inhibitor, the impact of Akt on intracellular and extracellular infectivity was investigated. To ascertain the role of Akt in the HCV life cycle, the two-part cell culture-derived HCV infection protocol utilizing Akt1 small interfering RNAs (siRNAs) was implemented. The impact of Akt1 on intracellular HCV transition was determined using membrane flotation assay and proximity ligation assay coupled with Anti-Rab7 immunoprecipitation and immunofluorescence.

KEY FINDINGS

Akt1 silencing reduced infectious virions release to a degree comparable to that of ApoE, a host component involved in the HCV assembly and release, suggesting Akt1 was critical in the late stage of the HCV life cycle. Extracellular infectivity of HCV was inhibited by brefeldin A, and the inhibitory effect was augmented by Akt1 silencing and partially restored by ectopic Akt1 expression. Immunofluorescence revealed that Akt1 inhibition suppressed the interaction between HCV core protein and lipid droplet. Akt1 silencing impeded the transition of HCV from the endoplasmic reticulum to the endosome and hence inhibited the secretion of HCV infectious virions from the late endosome.

SIGNIFICANCE

Our study demonstrates that Akt1 has an impact on the lipogenesis pathway and plays a critical role in the assembly and secretion of infectious HCV.

Ser235 phosphorylation of hepatitis C virus NS5A is required for NS5A dimerization and drug resistance

Hepatitis C virus (HCV) infection is recognized as a major causative agent of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. HCV non-structural protein 5A (NS5A) is a dimeric phosphoprotein with a hyperphosphorylated form to act as a switch that regulates HCV replication and assembly. NS5A inhibitors have been utilized as the scaffold for combination therapy of direct-acting antiviral agents (DAA). However, the mode of action of NS5A inhibitors is still unclear due to the lack of mechanistic detail regarding NS5A phosphorylation and dimerization in the HCV life cycle. It has been demonstrated that phosphorylation of NS5A at Ser235 is essential for RNA replication of the JFH1 strain. In this report, we found that NS5A phosphomimetic Ser235 substitution (Ser-to-Asp mutation) formed a dimer that was resistant to disruption by NS5A inhibitors as was the NS5A resistance-associated substitution Y93H. Phosphorylation of NS5A at Ser235 residue was required for the interaction of two NS5A-WT molecules in JFH1-based cell culture system but not absolutely required for dimerization of the NS5A-Y93H mutant. Interestingly, HCV nonstructural proteins from the subgenomic replicon NS3-5A was required for NS5A-WT dimerization but not required for NS5A-Y93H dimerization. Our data suggest that spontaneous Ser235 phosphorylation of NS5A and ensuing dimerization account for resistance of the JFH1/NS5A-Y93H mutant to NS5A inhibitors.

[Cone-beam CT analysis of the correlation between incisor root resorption rate and tooth movement index in adult patients with fixed orthodontics appliance]

Objective: To analyze the correlation between the root resorption rate and tooth movement of the maxillary and mandibular incisors before and after orthodontic treatment in adult patients using cone-beam CT (CBCT), and to explore the related factors that affect the apical root resorption. Methods: In this retrospective study, 23 adult patients with classⅠor class Ⅱ division 1 malocclusion [2 males and 21 females, mean age (23.4±6.3) years, treatment time (2.1±0.7) years] who received orthodontic treatment with fixed appliance in Department of Oral & Cranio-Maxillofacial Surgery, Shanghai Ninth People's Hospital from January 2017 to June 2021 were enrolled. Full-column CBCT examination was performed before and after treatment. A three-dimensional model was established to observe and record the volume of the maxillary and mandibular central and lateral incisors before and after treatment. The change of the incisal edge, the angle of rotation of the incisal edge, and the direction of the long axis of the tooth were also measured. The root resorption in each tooth before and after treatment was compared, and the root resorption rate was calculated. Pearson correlation analysis was performed on the root absorption rate before and after treatment with age, treatment time and tooth movement. Results: After treatment, the tooth volume of the maxillary and mandibular central and lateral incisors decreased significantly (P<0.01). The root absorption volumes were (20.2±6.0) mm3 and (11.2±4.7) mm3 in maxillary central and lateral incisors, and (14.7±4.6) mm3 and (14.8±5.0) mm3 in mandibular central and lateral incisors, respectively. The root absorption rates were (9.49±1.75)% and (9.13±3.24)% in maxillary central and lateral incisors, and (8.56±3.43)% and (9.13±3.24)%, in mandibular central and lateral incisors, respectively (F=0.56, P=0.640). The root resorption rate of maxillary central incisors had a weak positive correlation with the change of sagittal distance of incisal edge (r=0.36, P=0.015). The root resorption rate of mandibular central incisors had a moderate positive correlation with the vertical movement distance (r=0.48, P=0.001). The root resorption rate of mandibular lateral incisors was weakly positively correlated with the vertical movement of incisal edge and the treatment time (r=0.35, P=0.016; r=0.34, P=0.021), and was moderately positively correlated wit the change of sagittal movement of incisal edge (r=0.44, P=0.002). Conclusions: During orthodontic treatment, both maxillary and mandibular incisors had a certain degree of root resorption, which was related to sagittal and vertical movement of the incisors and the time of orthodontic treatment.

Antiviral effect of saikosaponin B2 in combination with daclatasvir on NS5A resistance-associated substitutions of hepatitis C virus

BACKGROUND

Hepatitis C virus (HCV) is a major causative agent of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. The rapid progress in the development of direct-acting antivirals has greatly elevated the cure rate to ≥95% in recent years. However, the high cost of treatment is not affordable to patients in some countries, necessitating the development of less expensive treatment.

METHODS

We adopted a cell culture-derived HCV system to screen a library of the pure compounds extracted from herbs deposited in the chemical bank of the National Research Institute of Chinese Medicine, Taiwan.

RESULTS

We found that saikosaponin B2 inhibited viral entry, replication, and translation. Saikosaponin B2 is a plant glycoside and a component of xiao-chai-hu-tang, a traditional Chinese herbal medicine extracted from the roots of Bupleurum falcatum. It also inhibited daclatasvir-resistant mutant strains of HCV, especially in combination with daclatasvir.

CONCLUSION

Our results may aid the development of a new combination therapy useful for patients with HCV who are intolerant or refractory to the currently available medications, including pegylated interferon and direct-acting antiviral agents.

Inhibitory Effects of Amentoflavone and Orobol on Daclatasvir-Induced Resistance-Associated Variants of Hepatitis C Virus

Hepatitis C virus (HCV) is recognized as a major causative agent of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Despite rapid progress in the development of direct-acting antivirals (DAA) against HCV infection in recent years, cost-effective antiviral drugs with more affordable prices still need to be developed. In this study, we screened a library of natural compounds to identify natural HCV inhibitors. The library of the pure compounds extracted from Chinese herbs deposited in the chemical bank of National Research Institute of Chinese Medicine (NRICM), Taiwan was screened in the cell culture-derived HCV (HCVcc) system. We identified the flavone or flavan-based compounds amentoflavone, 7,4[Formula: see text]-dihydroxyflavanone, and orobol with the inhibition of viral entry, replication, and translation of the HCV life cycle. Amentoflavone and orobol also showed inhibitory effects on resistant-associated variants to the NS5A inhibitor daclatasvir. The results of this study have the potential to benefit patients who are intolerant to the adverse effect of pegylated interferon or who harbor resistant strains refractory to treatment by current direct-acting antiviral agents.

Helicobacter pylori CagA protein activates Akt and attenuates chemotherapeutics-induced apoptosis in gastric cancer cells

Infection with cagA-positive Helicobacter pylori is associated with a higher risk of gastric cancer. The cagA gene product, CagA, is translocated into gastric epithelial cells and perturbs host cellular biological functions. Etoposide, a topoisomerase II inhibitor widely used to couple DNA damage to apoptosis, is a common cytotoxic agent used for advanced gastric cancer. We investigate the effect of CagA on etoposide-induced apoptosis in gastric cancer cells to elucidate whether CagA play a role in gastric carcinogenesis via impairing DNA damage-dependent apoptosis. AGS cell lines stably expressing CagA isolated from H. pylori 26695 strain were established. In the presence of etoposide, viability of parental AGS cells was decreased in a time-and dose-dependent manner, whereas CagA-expressing AGS cells were less susceptible to etoposide induced cell-killing effect. Suppression of etoposide-induced apoptosis was shown in CagA-expressing but not in parental AGS cells by DNA fragmentation, cell cycle, and annexin-V assays. This inhibitory effect of etoposide-induced apoptosis conferred by CagA was also demonstrated in SCM1 and MKN45 gastric cancer cell lines, with two additional chemotherapeutics, 5-FU and cisplatin. The effect of Akt activation on inhibition of etoposide-induced cytotoxicity by CagA was also evaluated. CagA expression and etoposide administration activate Akt in a dose-dependent manner. Enhancement of etoposide cytotoxicity by a PI-3-kinase inhibitor, LY294002, was evident in parental but was attenuated in CagA-expressing AGS cells. CagA may activate Akt, either in the absence or presence of etoposide, potentially contributing to gastric carcinogenesis associated with H. pylori infection and therapeutic resistance by impairing DNA damage-dependent apoptosis.

Karyotype analysis with amniotic fluid in 12365 pregnant women with indications for genetic amniocentesis and strategies of prenatal diagnosis

We explored the strategies of prenatal diagnosis by foetal karyotype analysis in pregnant women with indications for genetic amniocentesis. Karyotype analysis of amniotic fluid was performed on 12365 pregnant women with indications for genetic amniocentesis. The detection rates and distributions of abnormal karyotypes were observed in a variety of indications for genetic amniocentesis. The detection rates of abnormal karyotype were 57.4% in either a mother or father with chromosomal abnormality, 8.5% in the pregnant women with pathological ultrasound finding (PUF), 2.79% in the pregnant women with advanced age (35 years and over) and 2.23% in the women with abnormal maternal serum screening (MSS) tests. Foetal abnormal karyotype was found in 86 pregnant women with PUF; of the 86 pregnant women, 42 had trisomy 13, 18 or 21. Of the 12365 pregnant women, foetal abnormal karyotype was found in 428 (3.46%); of the 428 foetuses, only 154 had trisomy 13, 18 or 21. In the pregnant women with abnormal MSS, 111 foetuses had abnormal karyotype, but only 36 foetuses had trisomy 13, 18 or 21. We conclude that (1) ultrasound is an important approach to prevent the birth of foetuses with chromosomal disease. (2) Non-invasive prenatal DNA detection cannot completely replace invasive prenatal diagnosis and MSS. (3) The strategies of prenatal diagnosis: Genetic amniocentesis is strongly recommended for the pregnant women with indications for genetic amniocentesis. For pregnant women who refuse invasive prenatal diagnosis, non-invasive prenatal DNA detection is first performed. If the results of non-invasive prenatal DNA detection are negative, the pregnant women are followed up by ultrasound; if the results of non-invasive prenatal DNA detection are positive, the pregnant women should undergo invasive prenatal diagnosis.

New compound heterozygous mutations of p. Thr101Ilefs 2 and p. Thr306Ale in a child from a Chinese family with 17α-hydroxylase/17, 20-lyase deficiency

We determined whether a child with 17α-hydroxylase/17, 20-lyase deficiency possessed the sex-determining region (SRY) gene, and examined the mutations present in the CYP17A1 gene that led to 17α-hydroxylase/17, 20-lyase deficiency. In the child, karyotype analysis was performed and polymerase chain reaction analysis and electrophoretic techniques were used to identify the SRY gene. A total of 50 normal individuals were included as a control group. Polymerase chain reaction and DNA sequencing were used to identify CYP17A1 gene mutations in all samples. The karyotype of the child was 46, XY, which was inconsistent with her social sex, SRY was positive, and a compound heterozygous mutation p. Thr101Ilefs*2 in exon 2 and p. Thr306Ale in exon 5 were identified in the CYP17A1 gene. These mutations were inherited from her parents. In the 20 normal individuals, these mutations were not identified. In the child, sex reversal may have been caused by CYP17A1 mutations. The compound heterozygous mutation of p. Thr101Ilefs*2 and p. Thr306Ale is a new gene mutation of 17α-hydroxylase/17, 20-lyase deficiency.

Improved efficacy of gene therapy approaches for Pompe disease using a new, immune-deficient GSD-II mouse model

Glycogen storage disease type II (GSD-II) is a lysosomal storage disorder in which the lack of human acid-alpha glucosidase (hGAA) activity results in massive accumulations of glycogen in cardiac and skeletal muscle fibers. Affected individuals die of cardiorespiratory failure secondary to the skeletal and/or cardiac muscle involvement. Recombinant hGAA enzyme replacement therapy (ERT) is currently in clinical trials and, although promising, ERT may be limited by large-scale production issues and/or the need for frequent infusions. These limitations could be circumvented or augmented by gene therapy strategies. Previous findings in our lab demonstrated that hepatic targeting of a modified adenovirus vector expressing human GAA was able to correct the glycogen accumulation in multiple affected muscles in the GAA-KO mice, by virtue of high-level, hepatic secretion of hGAA. However, although the vector persisted and expressed hGAA for 6 months in the liver, plasma hGAA was not detectable beyond 10 dpi (days postinjection), and reaccumulation of glycogen was observed. Two possibilities may have contributed to this phenomenon, the shut down of the CMV promoter and/or the onset of high levels of anti-hGAA antibodies. In order to test these and other possibilities, we have now developed an immune-deficient mouse model of GSD-II by interbreeding GAA-KO mice with severe combined immune-deficient (SCID) mice, generating double knockout, GAA-KO/SCID mice. In this new mouse model, we evaluated the efficacy of an [E1-, polymerase-] AdhGAA vector, in the absence of anti-hGAA antibody responses. After intravenous injection, GAA detection in the plasma was prolonged for at least 6 months secondary to the lack of anti-hGAA antibody production in all of the treated mice. GAA-KO/SCID mice treated with high doses of viral vector demonstrated longer durations of glycogen correction in both skeletal and cardiac muscles, relative to mice injected with lower doses of the vector. Notably, within 2 weeks of vector injection, muscle strength and coordination was normalized, and the improved muscle function persisted for at least 6 months. In summary, this new mouse model of GSD-II now makes it possible to assess the full potential for efficacy of any GAA-expressing vector (and/or ERT) contemplated for use in GSD-II gene therapy, without the negative influence that anti-hGAA antibodies entail.

[Studies on chemical constituents in the root of Desmos grandifolius (I)]

OBJECTIVE

To investigate new compounds with anti-tumor activities from the root of Desmos grandifolius of Annonaceae.

METHOD

The chemical constituents were isolated by silica gel column chromatography, and the structures were elucidated by UV, IR, MS, 1H NMR, 13C NMR, H-H COSY and NOESY analysis.

RESULTS

Six compounds have been isolated from the CHCl3 extract of this plant and identified as lawinal(I), isolawinal(II), desmethoxymatteucinol(III), benzoic acid(IV), beta-sitosterol(V) and sitgmasterol (VI).

CONCLUSION

All compounds were found from this plant for the first time. Three dihydroflavonoids isolated from this species are characterized by A-ring substitution and no B-ring substitution.

[Studies on chemical constituents of Polygala arillata buch-ham]

Two new compounds were isolated from the roots of Polygala arillata Buch-Ham. On the basis of chemical reactions and spectral (UV, IR, MS, 1HNMR, DIFNOE, 13CNMR) analysis, they were identified as 1,3-dihydroxy-2-methoxyxanthone(I) and 7-hydroxy-1-methoxy-2,3-methylenedioxyxanthone(II). Pharmacological study indicated that I and II have inhibitory effect on aldose reductase activity.

[Chemical studies of Strobilanthes cusia]

Seven compounds have been isolated from the whole plant of Strobilanthes cusia (Nees) O. Ktze. Three of them are triterpenes (I-III), two are indole alkaloids (IV, V), two are quinazolinone alkaloids (VI, VII). On the basis of spectral analysis and physicochemical properties, their structures were established as lupeol (I), betulin (II), lupenone (III), indigo (IV), indirubin (V), 4(3H)-quinazolinone (VI), 2,4(1H,3H)-quinazolinedione (VII). VI and VII were found from natural plant for the first time. The results of the pharmacological tests demonstrate that compound V has anticancer activity and compound VI has hypotensive action. Compound VII can be quantitatively determined by HPLC, which may serve as a quality control standard for materia medica and its preparations. Compounds VI and VII have been confirmed by means of synthesis.