Genetic factors associated with acquired phenotypic drug resistance and its compensatory evolution during tuberculosis treatment

OBJECTIVES

We elucidated the factors, evolution, and compensation of antimicrobial resistance (AMR) in Mycobacterium tuberculosis (MTB) isolates under dual pressure from the intra-host environment and anti-tuberculosis (anti-TB) drugs.

METHODS

This retrospective case-control study included 337 patients with pulmonary tuberculosis from 15 clinics in Tianjin, China, with phenotypic drug susceptibility testing results available for at least two time points between January 1, 2009 and December 31, 2016. Patients in the case group exhibited acquired AMR to isoniazid (INH) or rifampicin (RIF), while those in the control group lacked acquired AMR. The whole-genome sequencing (WGS) was conducted on 149 serial longitudinal MTB isolates from 46 patients who acquired or reversed phenotypic INH/RIF-resistance during treatment. The genetic basis, associated factors, and intra-host evolution of acquired phenotypic INH/RIF-resistance were elucidated using a combined analysis.

RESULTS

Anti-TB interruption duration of ≥30 days showed association with acquired phenotypic INH/RIF resistance (aOR = 2·2, 95% CI, 1·0-5·1) and new rpoB mutations (p = 0·024). The MTB evolution was 1·2 (95% CI, 1·02-1·38) single nucleotide polymorphisms per genome per year under dual pressure from the intra-host environment and anti-TB drugs. AMR-associated mutations occurred before phenotypic AMR appearance in cases with acquired phenotypic INH (10 of 16) and RIF (9 of 22) resistances.

DISCUSSION

Compensatory evolution may promote the fixation of INH/RIF-resistance mutations and affect phenotypic AMR. The TB treatment should be adjusted based on gene sequencing results, especially in persistent culture positivity during treatment, which highlights the clinical importance of WGS in identifying reinfection and AMR acquisition before phenotypic drug susceptibility testing.

The Humanization and Maturation of an Anti-PrPc Antibody

The cellular prion protein (PrPc) is a cell surface glycoprotein that is highly expressed in a variety of cancer tissues in addition to the nervous system, and its elevated expression is correlated to poor prognosis in many cancer patients. Our team previously found that patients with colorectal cancer (CRC) with high-level PrPc expression had significantly poorer survival than those with no or low-level PrPc expression. Mouse antibodies for PrPc inhibited tumor initiation and liver metastasis of PrPc-positive human CRC cells in mouse model experiments. PrPc is a candidate target for CRC therapy. In this study, we newly cloned a mouse anti-PrPc antibody (Clone 6) and humanized it, then affinity-matured this antibody using a CHO cell display with a peptide antigen and full-length PrPc, respectively. We obtained two humanized antibody clones with affinities toward a full-length PrPc of about 10- and 100-fold of that of the original antibody. The two humanized antibodies bound to the PrPc displayed significantly better on the cell surface than Clone 6. Used for Western blotting and immunohistochemistry, the humanized antibody with the highest affinity is superior to the two most frequently used commercial antibodies (8H4 and 3F4). The two new antibodies have the potential to be developed as useful reagents for PrPc detection and even therapeutic antibodies targeting PrPc-positive cancers.

In vitro evolution of diagnostic antibodies targeting native antigens in plasma by sandwich flow cytometry

Monoclonal antibodies (mAbs) that recognize and bind to specific antigens (Ags) have a wide range of applications in research, therapy, and diagnostics. However, many of these antibodies cannot bind well to the native Ags. In this study, based on the Chinese hamster ovary (CHO) cell display platform developed previously in our lab, we reported a novel artificial evolution procedure to improve the affinity of mAb against the native Ag directly using the plasma samples without purification of the native Ag. In this procedure, a pair of antibodies able to bind the Ag in sandwich manner are first confirmed (Ab1/Ab2) and the antibody (Ab) to be affinity-improved (Ab1) is displayed on CHO cells for Ab mutation. Then the cells were detected and sorted with flow cytometry in the form of Ab1-Ag-fluorescence labeled Ab2, which we named sandwich flow cytometry. Here, we used soluble isoform of suppression of tumorigenicity 2 (sST2) protein as model Ag, carried out "sandwich" maturation directly using the plasma samples containing the native sST2 protein and optimized a pair of antibodies with significantly improved sensitivity in the detection of the native sST2 in plasma. This method could be very useful in optimization of the diagnostic Ab pairs working in a "sandwich" manner if more antibodies were also successfully affinity-matured with this method.

Adipose-derived exosomes impairs endothelial transient receptor potential vanilloid 4 channels and elevates blood pressure in abdominal obesity

Aim

Large epidemiological studies have found that abdominal obesity is a strong risk factor for hypertension. Impaired endothelium-dependent vasodilation is a hallmark of obesity-induced hypertension. Adipose-derived exosomes can regulate distant tissues as novel adipokines, providing a new mechanism for cell-cell interactions. However, the effects of adipose-derived exosomes on obesity-induced hypertension are unknown.

Methods

We extracted three adipose-derived exosomes, including high-fat diet (HFD) mouse serum exosome, adipose tissue exosome, and adipose-derived stem cell exosome, and further explored their effects on endothelium-dependent vasodilation in vivo and in vitro.

Results

Impairment of endothelial transient receptor potential vanilloid 4 (TRPV4) channel activity and vasodilation were observed in the arteries from abdominal obesity patients. Ca2+ influx through TRPV4 channels at myoendothelial projections to smooth muscle cells decreases resting blood pressure in nonobese mice, a response that is diminished in HFD mice. Administration of three exosomes elevated blood pressure by promoting artery endothelial barrier permeability, impairing the expression of adherens junctions, and aggravating inflammatory response in vivo and in vitro, accompanied by TRPV4/Ca2+ pathway inhibition.

Conclusions

Impairment of endothelial TRPV4 channels contributes to obesity-induced hypertension and imply that HFD-induced obesity plays a role in blood pressure by aggravating the artery endothelial barrier injury and inflammatory response via adipose-derived exosomes, at least partially, through inhibiting the TRPV4/Ca2+ pathway.

Funding Acknowledgement

Type of funding sources: None. Main funding source(s): This research was supported by grants from the National Natural Science Foundation of China (81970262) (P.J.W.), Innovation Team Project Department of Education of Sichuan Province (18TD0030) (PJW), Central Funds Guiding the Local Science and Technology Development of Sichuan Province (2020ZYD036, P.W.), and grants from the Scientific Research Fund of Chengdu Medical College (CYZYB20-07) (J.W.).

[Effect of fatty acid synthase gene silencing on lipid metabolism and biological behaviors of human hepatoblastoma HepG2 cells]

OBJECTIVE

To investigate the effect of fatty acid synthase (FASN) gene silencing on lipid metabolism and biological behaviors of human hepatoblastoma HepG2 cells.

OBJECTIVE

Small interfering RNA (siRNA) targeting FASN gene or a negative control siRNA sequence (NC-siRNA) was transfected into HepG2 cells, and the gene silencing efficiency was evaluated with qRT-PCR and Western blotting. Triglyceride level in the cells was detected using enzyme-linked immunosorbent assay, and Oil red O staining was performed to examine intracellular lipid droplets. The proliferation ability of the transfected cells was tested by CCK-8 assay, and cell apoptosis was evaluated using annexin V-FITC/PI apoptosis detection kit. Wound healing assay and Transwell assay were performed to assess the migration ability of the transfected cells.

OBJECTIVE

Transfection of the cells with FASN-siRNA, but not NC-siRNA, significantly lowered FASN expression at both the mRNA and protein level (P < 0.001) and decreased the number of lipid droplets (P < 0.001) and triglyceride level (P < 0.01) in the cells. FASN gene silencing significantly inhibited proliferation, increased apoptosis rate and suppressed migration of HepG2 cells (P < 0.001).

OBJECTIVE

FASN gene silencing inhibits proliferation and migration and promotes apoptosis of HepG2 cells possibly by suppressing lipid synthesis in the cells.

An Efficient Exogenous Gene Insertion Site in CHO Cells with High Transcription Level to Enhance AID-Induced Mutation

Antibodies have been extensively used for the purpose of scientific research, clinical diagnosis, and therapy. Combination of in vitro somatic hypermutation and mammalian cell surface display has been an efficient technology for antibody or other proteins optimization, in which the efficiency of activation-induced cytidine deaminase (AID) mutations in genes is one of the most important key factors. Gene transcriptional level has been found to be positively proportional to AID-induced mutation frequency. Thus, construction of the cell clone bearing a gene of interest (GOI) with high transcription level can increase AID-induced mutations. In this study, a retargetable gene cassette is inserted onto predetermined chromosome site (ywhae gene site) which is among the genes with the highest as well as stable transcription, and is found that one subsite is suitable to be retargeted for efficient protein display in Chinese hamster ovary (CHO) cells. The resultant cell clone (T31) has higher and more stable transcription/expression than CHO-puro clone which was previously established through the strategy of random insertion followed by a high-throughput selection. It also possesses a significantly higher mutation frequency to GOI than CHO-puro cells; thus, it is a better clone for the in vitro improvement of antibody affinity, and probably other properties.

The Trends in Global Gene Expression in Mouse Embryonic Stem Cells During Spaceflight

The environment in space differs greatly from the environment on the ground. Spaceflight causes a number of physiological changes in astronauts, such as bone loss and immune system dysregulation. These effects threaten astronauts’ space missions, and understanding the underlying cellular and molecular mechanisms is important to manage the risks of space missions. The biological effects of spaceflight on mammalian cells, especially with regards to DNA damage, have attracted much attention. Rad9^−/− mouse embryonic stem cells (mESCs) are known to be extremely sensitive to DNA damage agents. In this study, a project of the SJ-10 satellite programme, we investigated the gene expression profiles of both Rad9^−/− mESCs and Rad9^+/+ (wild-type) mESCs in space with a focus on genes critical for inducing, preventing, or repairing genomic DNA lesions. We found that spaceflight downregulated more genes than it upregulated in both wild-type and Rad9^−/− mESCs, indicating a suppressive effect of spaceflight on global gene expression. In contrast, Rad9 deletion upregulated more genes than it downregulated. Of note, spaceflight mainly affected organ development and influenced a wide range of cellular functions in mESCs, while Rad9 deletion mainly affected the development and function of the hematological system, especially the development, differentiation and function of immune cells. The patterns of gene expression in mouse embryonic stem cells in space is distinct from those in other types of cells. In addition, both spaceflight and Rad9 deletion downregulated DNA repair genes, suggesting a possibility that spaceflight has negative effects on genome for embryonic stem cells and the effects are likely worsen when the genome maintenance mechanism is defective.

Simulated microgravity potentiates generation of reactive oxygen species in cells

Microgravity (MG) and space radiation are two major environmental factors of space environment. Ionizing radiation generates reactive oxygen species (ROS) which plays a key role in radiation-induced DNA damage. Interestingly, simulated microgravity (SMG) also increases ROS production in various cell types. Thus, it is important to detect whether SMG could potentiate ROS production induced by genotoxins including radiation, especially at a minimal level not sufficient to induce detectable ROS. In this study, we treated mouse embryonic stem (MES) cells with H₂O₂ and SMG for 24 h. The concentration of H₂O₂ used was within 30 μmol/L at which intracellular ROS was the same as that in untreated cells. Exposure of cells to SMG for 24 h did not induce significantly higher levels of intracellular ROS than that of control cells either. Simultaneous exposure of cells to both SMG- and H₂O₂-induced ROS and apoptosis in MES cells. Although incubation in medium containing 5 or 30 μmol/L H₂O₂ induced a small enhancement of DNA double-strand breaks (DSBs), the addition of SMG treatment dramatically increased DSB levels. Taken together, SMG can significantly potentiate the effects of H₂O₂ at a low concentration that induce a small or negligible change in cells on ROS, apoptosis, and DNA damage. The results were discussed in relation to the combined effects of space radiation and MG on human body in this study.

The DmtA methyltransferase contributes to Aspergillus flavus conidiation, sclerotial production, aflatoxin biosynthesis and virulence

DNA methylation is essential for epigenetic regulation of gene transcription and development in many animals, plants and fungi. We investigated whether DNA methylation plays a role in the development and secondary metabolism of Aspergillus flavus, identified the DmtA methyltransferase from A. flavus, and produced a dmtA knock-out mutant by replacing the dmtA coding sequence with the pyrG selectable marker. The A. flavus dmtA null mutant lines produced white fluffy mycelium in liquid medium, and displayed a slightly flavescent conidial pigmentation compared with the normal yellow of the wild-type strain when grown on agar. The ΔdmtA lines exhibited decreased conidiation and aflatoxin (AF) biosynthesis, compared with the wild-type line, suggesting that the DmtA knock-out affected the transcriptional level of genes in the AF cluster. In particular, sclerotia development and host colonization were altered in the dmtA null mutants. Green fluorescent protein tagging at the C-terminus of DmtA showed that DmtA localized to the nucleus and cytoplasm. DNA methylation content measurements in the dmtA mutants revealed no widespread DNA methylation in the mutants or wild-type lines. Thus, our findings suggest that DmtA, apart from being a C-5 cytosine methyltransferase in A. flavus, contributes to asexual development, aflatoxin biosynthesis, sclerotial production and virulence.

Direct synthesis of heparin-like poly(ether sulfone) polymer and its blood compatibility

In this study, heparin-like poly(ethersulfone) (HLPES) was synthesized by a combination of polycondensation and post-carboxylation methods, and was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum and gel permeation chromatography. Owing to the similar backbone structure, the synthesized HLPES could be directly blended with pristine PES at any ratios to prepare PES/HLPES membranes. After the introduction of HLPES, the microscopic structure of the modified PES membranes was changed, while the hydrophilicity was significantly enhanced. Bovine serum albumin and bovine serum fibrinogen adsorption, activated partial thromboplastin time, thromb time and platelet adhesion for the modified PES membranes were investigated. The results indicated that the blood compatibility of the PES/HLPES membranes was significantly improved compared with that of pristine PES membrane. For the PES/HLPES membranes, obvious decreases in platelet activation on PF-4 level, in complement activation on C3a and C5a levels, and in leukocytes activation on CD11b levels were observed compared with those for the pristine PES membrane. The improved blood compatibility of the PES/HLPES membrane might due to the existence of the hydrophilic groups (-SO3Na, -COONa). Furthermore, the modified PES membranes showed good cytocompatibility. Hepatocytes cultured on the PES/HLPES membranes presented improved growth in terms of SEM observation, MTT assay and confocal laser scanning microscope observation compared with those on the pristine PES membrane. These results indicate that the PES/HLPES membranes present great potential in blood-contact fields such as hemodialysis and bio-artificial liver supports.

The Impact of Gastrocnemius Muscle Cell Changes in Chronic Venous Insufficiency

OBJECTIVE

To investigate the pathological and metabolic changes in the gastrocnemius muscle in patients with chronic vein insufficiency (CVI).

METHOD

Thirty-six patients with varicose veins were investigated by ambulatory venous pressure (AVP) and duplex ultrasonography. Twelve age and height-matched controls were used for comparison. Patients and controls consented to participate in this study. Twenty-one patients with primary vein varicose (group AI) and 15 patients (group AII) with primary deep venous valve incompetence (DVI) underwent biopsies of the gastrocnemius muscle during operation. Adductor biopsies obtained from the same limbs served as a control group (group B) and specimens from controls subjects without venous disease served as the second control group (group C). All the specimens were investigated by superoxide dismutase (SOD), nitric oxide (NO), Na+-K+-ATPase, Ca2+-ATPase and lactic acid (LD) determinations. Samples were subjected to light and electron microscopy following H & E staining, special ATPase, cytochrome oxidase/succinate dehydrogenase (COX/SDH) stains.

RESULTS

Normal muscle architecture was seen following H & E, ATPase and COX/SDH staining and normal cell metabolism was observed in specimens of groups B and C. In group A, pathological changes were encountered in the gastrocnemius muscle including disseminated myofibril atrophy, cell denaturation and necrosis, inflammatory cell infiltration, proliferation and dilation of interfascicular veins. ATPase staining (pH 9.4) demonstrated grouping of atrophic fibres, especially type I myofibril grouping, accompanied by moderate to severe atrophy of type II muscle fibres. However, no patient had selective type I fibre atrophy. Enhanced enzymatic activity in single or multiple myofibrils was demonstrated by COX/SDH staining in approximately half of the specimens in group AII. In group AII, electron microscopy showed swelling, myelin figure denaturation of mitochondria, disruption of the myofibrils and increased lipid droplets in the gastrocnemius muscle. Increased concentration of LD was found in most specimens from group A patients. There were also reductions of SOD, NO, biochemical activity of Na+-K+-ATPase, Ca2+-ATPase with increasing concentration of LD in these patients, most prominently in group AII. We found correlation between AVP assessments and the biochemical measurements as well as morphological appearances of the gastrocnemius muscle.

CONCLUSION

Venous hypertension results in pathophysiological changes in the gastrocnemius muscles of patients with DVI, associated with decreased calf pump function.

Effectiveness of fortnightly tooth brushing with amine fluorides in caries-prone subjects

The aim of this study was to assess the caries incidence and plaque accumulation in schoolchildren at caries risk, after brushing the teeth fortnightly with gels containing 0, 0.4% F, 1.25% F as amine fluoride (AmF) or the common amine fluoride toothpaste containing 0.125% F. The study was conducted double blind over an 18-month period, and after 6 months discontinuation of brushing. Only the group that brushed with the 1.25% AmF gel showed a significant decrease in caries development compared to the group that brushed with the 0.125% AmF toothpaste. During the 6-month discontinuation period, the incidence of caries increased in all groups; the differences in caries development between all groups were not significant. Plaque indices were significantly lower in the AmF-treated groups. The highest fluoride concentration in the gel reduced the development of caries to zero, probably due to increased fluoride levels in the oral milieu of caries risk children. In order to maintain a positive effect of fluoride over an extended time period, caries-prone subjects should continue an initiated fluoride programme.

The effect of fluoride drop administration on dental caries increment--a longitudinal study

The effect of fluoride drop supplementation was investigated in a longitudinal study initiated in 1980. The def-t and DMF-T indices were used to estimate the incremental caries rate of the deciduous and first molars of 211 children aged 7-8 and 9.5-10.5 years. No statistically significant differences between the experimental and control def-t and DMF-T scores were found after 3 years. The incremental caries rate of the deciduous dentition of the experimental group was found to be significantly lower than that of the control group (def-t = 0.61 and 1.07 respectively), whereas the difference in the caries increments of the first molars was not significant (DMF-T = 1.62 in both groups). It is estimated that the efficacy was due to the long-term cariostatic effect of the topically acting fluoride on the erupting primary dentition, whereas the permanent dentition (first molars) had already completed calcification of the crown, but had not erupted at initiation of the study. It was estimated that the most effective cariostatic benefits would be apparent in the late erupting teeth of this study group.

Declining dental caries in Jerusalem schoolchildren

There has been an increase of dental caries in Israel during the last decade (1970-80), while most developed industrialized countries reported a decline in dental caries since 1970. A survey carried out on 267 first graders (6 yr old) by the same investigator and with the same methods as in the previous survey (1977), showed a significant decrease in prevalence of dental caries in 1985 as follows: 78% affected children with a caries score of 4.9 compared to 86.2% with a caries score of 5.2 in 1977.

Prevalence of dental decay in Jewish and Arab schoolchildren in the Jerusalem area

The purpose of this survey was to gather up-to-date information on the prevalence of dental decay in schoolchildren in the Jerusalem area. Close to 650 Arab and Jewish schoolchildren aged 6-8 yr underwent oral examinations. The relationship between caries prevalence and treatment supplied with some secondary factors was studied. The results show that 92% of the children were affected by decay. Compared to former years there is an increase in the prevalence of dental caries throughout the population. No significant differences were found when sex, ethnic population or socioeconomic factors were related to caries prevalence. However, when DMF is broken down into its components, Arab children were seen to have a greater number of teeth affected by caries and in need of treatment (D). In contrast, treatment need has been met to a much greater degree among Jewish children than among Arab children. Data and explanations are offered.