Targeted degradation of PCNA outperforms stoichiometric inhibition to result in programed cell death

Biodegraders are targeted protein degradation constructs composed of mini-proteins/peptides linked to E3 ligase receptors. We gained deeper insights into their utility by studying Con1-SPOP, a biodegrader against proliferating cell nuclear antigen (PCNA), an oncology target. Con1-SPOP proved pharmacologically superior to its stoichiometric (non-degrading) inhibitor equivalent (Con1-SPOPmut) as it had more potent anti-proliferative effects and uniquely induced DNA damage, cell apoptosis, and necrosis. Proteomics showed that PCNA degradation gave impaired mitotic division and mitochondria dysfunction, effects not seen with the stoichiometric inhibitor. We further showed that doxycycline-induced Con1-SPOP achieved complete tumor growth inhibition in vivo. Intracellular delivery of mRNA encoding Con1-SPOP via lipid nanoparticles (LNPs) depleted endogenous PCNA within hours of application with nanomolar potency. Our results demonstrate the utility of biodegraders as biological tools and highlight target degradation as a more efficacious approach versus stoichiometric inhibition. Once in vivo delivery is optimized, biodegraders may be leveraged as an exciting therapeutic modality.

STUB1 is an intracellular checkpoint for interferon gamma sensing

Immune checkpoint blockade (ICB) leads to durable and complete tumour regression in some patients but in others gives temporary, partial or no response. Accordingly, significant efforts are underway to identify tumour-intrinsic mechanisms underlying ICB resistance. Results from a published CRISPR screen in a mouse model suggested that targeting STUB1, an E3 ligase involved in protein homeostasis, may overcome ICB resistance but the molecular basis of this effect remains unclear. Herein, we report an under-appreciated role of STUB1 to dampen the interferon gamma (IFNγ) response. Genetic deletion of STUB1 increased IFNGR1 abundance on the cell surface and thus enhanced the downstream IFNγ response as showed by multiple approaches including Western blotting, flow cytometry, qPCR, phospho-STAT1 assay, immunopeptidomics, proteomics, and gene expression profiling. Human prostate and breast cancer cells with STUB1 deletion were also susceptible to cytokine-induced growth inhibition. Furthermore, blockade of STUB1 protein function recapitulated the STUB1-null phenotypes. Despite these encouraging in vitro data and positive implications from clinical datasets, we did not observe in vivo benefits of inactivating Stub1 in mouse syngeneic tumour models-with or without combination with anti-PD-1 therapy. However, our findings elucidate STUB1 as a barrier to IFNγ sensing, prompting further investigations to assess if broader inactivation of human STUB1 in both tumors and immune cells could overcome ICB resistance.

Accelerated Identification of Cell Active KRAS Inhibitory Macrocyclic Peptides using Mixture Libraries and Automated Ligand Identification System (ALIS) Technology

Macrocyclic peptides can disrupt previously intractable protein–protein interactions (PPIs) relevant to oncology targets such as KRAS. Early hits often lack cellular activity and require meticulous improvement of affinity, permeability, and metabolic stability to become viable leads. We have validated the use of the Automated Ligand Identification System (ALIS) to screen oncogenic KRAS^G12D (GDP) against mass-encoded mini-libraries of macrocyclic peptides and accelerate our structure–activity relationship (SAR) exploration. These mixture libraries were generated by premixing various unnatural amino acids without the need for the laborious purification of individual peptides. The affinity ranking of the peptide sequences provided SAR-rich data sets that led to the selection of novel potency-enhancing substitutions in our subsequent designs. Additional stability and permeability optimization resulted in the identification of peptide 7 that inhibited pERK activity in a pancreatic cancer cell line. More broadly, this methodology offers an efficient alternative to accelerate the fastidious hit-to-lead optimization of PPI peptide inhibitors.

Discovery of cell active macrocyclic peptides with on-target inhibition of KRAS signaling

Macrocyclic peptides have the potential to address intracellular protein–protein interactions (PPIs) of high value therapeutic targets that have proven largely intractable to small molecules. Here, we report broadly applicable lessons for applying this modality to intracellular targets and specifically for advancing chemical matter to address KRAS, a protein that represents the most common oncogene in human lung, colorectal and pancreatic cancers yet is one of the most challenging targets in human disease. Specifically, we focused on KRpep-2d, an arginine-rich KRAS-binding peptide with a disulfide-mediated macrocyclic linkage and a protease-sensitive backbone. These latter redox and proteolytic labilities obviated cellular activity. Extensive structure–activity relationship studies involving macrocyclic linker replacement, stereochemical inversion, and backbone α-methylation, gave a peptide with on-target cellular activity. However, we uncovered an important generic insight – the arginine-dependent cell entry mechanism limited its therapeutic potential. In particular, we observed a strong correlation between net positive charge and histamine release in an ex vivo assay, thus making this series unsuitable for advancement due to the potentially fatal consequences of mast cell degranulation. This observation should signal to researchers that cationic-mediated cell entry – an approach that has yet to succeed in the clinic despite a long history of attempts – carries significant therapy-limiting safety liabilities. Nonetheless, the cell-active molecules identified here validate a unique inhibitory epitope on KRAS and thus provide valuable molecular templates for the development of therapeutics that are desperately needed to address KRAS-driven cancers – some of the most treatment-resistant human malignancies.

Targeting undruggable intracellular proteins with peptides: novel on-target macrocyclic peptide inhibitors of KRAS with broad inhibition of proliferation of multiple KRAS-dependent cancer cell lines.

H. pylori Pattern Gastritis with Negative Helicobacter Immunohistochemical Stain: Does A Specific Comment in Pathology Report Impact Clinical Management?

Introduction/Objective

The clinical significance of H. pylori (HP) pattern of gastritis with a negative Helicobacter IHC stain on gastric biopsy is unclear. Some pathologists report this pattern in cases that are highly suggestive of HP infection with a comment raising the possibility of HP infection; however, the subsequent clinical management of these patients has not been well described.

Methods/Case Report

We conducted a retrospective comparison study of patients with gastric biopsy between 2016 and 2019. Group 1 included patients with chronic active or chronic inactive gastritis and negative HP IHC with a comment stating the gastritis pattern is suggestive of HP. Group 2 included patients with chronic active or chronic inactive gastritis and negative HP IHC with no comment about HP pattern.

Results (if a Case Study enter NA)

We identified 60 patients in Group 1 which were compared to 63 patients in Group 2. Group 1 more frequently had history of HP (48.3% vs. 29.1%, p<0.05). After diagnosis, Group 1 more frequently received treatment (51.7% vs. 20.6%, p<0.001). Of those who received treatment, Group 1 more frequently received HP treatment (triple or quadruple therapy; 21.7% vs. 1.6%, p<0.001). History of HP did not affect whether a patient was treated (p>0.05). Following post-biopsy HP treatment, more patients in Group 1 received fecal antigen test (23.7% vs. 5.5%, p<0.01). Age, gender, NSAID and PPI use did not differ between groups.

Conclusion

Adding the diagnostic comment raising the possibility of HP for patients with HP pattern gastritis with negative HP IHC changes clinical management and it is independent of patients’ prior HP history.

Exquisitely Specific anti-KRAS Biodegraders Inform on the Cellular Prevalence of Nucleotide-Loaded States

Mutations to RAS proteins (H-, N-, and K-RAS) are among the most common oncogenic drivers, and tumors harboring these lesions are some of the most difficult to treat. Although covalent small molecules against KRAS^G12C have shown promising efficacy against lung cancers, traditional barriers remain for drugging the more prevalent KRAS^G12D and KRAS^G12V mutants. Targeted degradation has emerged as an attractive alternative approach, but for KRAS, identification of the required high-affinity ligands continues to be a challenge. Another significant hurdle is the discovery of a hybrid molecule that appends an E3 ligase-recruiting moiety in a manner that satisfies the precise geometries required for productive polyubiquitin transfer while maintaining favorable druglike properties. To gain insights into the advantages and feasibility of KRAS targeted degradation, we applied a protein-based degrader (biodegrader) approach. This workflow centers on the intracellular expression of a chimeric protein consisting of a high-affinity target-binding domain fused to an engineered E3 ligase adapter. A series of anti-RAS biodegraders spanning different RAS isoform/nucleotide-state specificities and leveraging different E3 ligases provided definitive evidence for RAS degradability. Further, these established that the functional consequences of KRAS degradation are context dependent. Of broader significance, using the exquisite degradation specificity that biodegraders can possess, we demonstrated how this technology can be applied to answer questions that other approaches cannot. Specifically, application of the GDP-state specific degrader uncovered the relative prevalence of the "off-state" of WT and various KRAS mutants in the cellular context. Finally, if delivery challenges can be addressed, anti-RAS biodegraders will be exciting candidates for clinical development.

Pyrazinamide triggers degradation of its target aspartate decarboxylase

Pyrazinamide is a sterilizing first-line tuberculosis drug. Genetic, metabolomic and biophysical analyses previously demonstrated that pyrazinoic acid, the bioactive form of the prodrug pyrazinamide (PZA), interrupts biosynthesis of coenzyme A in Mycobacterium tuberculosis by binding to aspartate decarboxylase PanD. While most drugs act by inhibiting protein function upon target binding, we find here that pyrazinoic acid is only a weak enzyme inhibitor. We show that binding of pyrazinoic acid to PanD triggers degradation of the protein by the caseinolytic protease ClpC1-ClpP. Thus, the old tuberculosis drug pyrazinamide exerts antibacterial activity by acting as a target degrader, a mechanism of action that has recently emerged as a successful strategy in drug discovery across disease indications. Our findings provide the basis for the rational discovery of next generation PZA.

It has been shown that the bioactive component of pyrazinamide, pyrazinoic acid (POA), blocks coenzyme A biosynthesis in M. tuberculosis by binding to the aspartate decarboxylase PanD. Here the authors show that pyrazinamide triggers degradation of PanD by stimulating its degradation by the caseinolytic protease Clp.

Pharmacological and Molecular Mechanisms Behind the Sterilizing Activity of Pyrazinamide

Inclusion of pyrazinamide (PZA) in the tuberculosis (TB) drug regimen during the 1970s enabled a reduction in treatment duration from 12 to 6 months. PZA has this remarkable effect in patients despite displaying poor potency against Mycobacterium tuberculosis (Mtb) in vitro. The pharmacological basis for the in vivo sterilizing activity of the drug has remained obscure and its bacterial target controversial. Recently it was shown that PZA penetrates necrotic caseous TB lung lesions and kills nongrowing, drug-tolerant bacilli. Furthermore, it was uncovered that PZA inhibits bacterial Coenzyme A biosynthesis. It may block this pathway by triggering degradation of its target, aspartate decarboxylase. The elucidation of the pharmacological and molecular mechanisms of PZA provides the basis for the rational discovery of the next-generation PZA with improved in vitro potency while maintaining attractive pharmacological properties.

Targeted protein degradation in antibacterial drug discovery?

Drug induced degradation of a target protein is a novel concept in drug discovery. Traditionally drugs modulate activity, as opposed to abundance, of their targets. Degradation inducing ligands act catalytically. Thus, one advantage of target degradation over the classical on-target mechanism is that lower drug concentration may be sufficient to cause the desired cellular effects. The first promoters of target degradation were discovered unintentionally: it turned out that some drugs 'accidently' promote degradation of their target by the cellular proteolytic machinery. Elegant methods were developed to target specific proteins of interest for degradation, thus enabling the rational discovery of degradation inducers. The application of targeted degradation has so far been limited to human cells. Recently, we discovered that an antibacterial drug, the anti-tuberculosis antibiotic pyrazinamide, functions as a promotor of degradation of its bacterial target. Increasing antimicrobial resistance makes the discovery of novel antibiotics more urgent than ever. Can rational target degradation be applied for the discovery of anti-bacterials? Here, we first discuss briefly some historic examples and then recent approaches in rational target degradation for human diseases. Then, we describe how the first anti-bacterial target degradation promoter pyrazinamide triggers removal of its target. Efforts are under way to exploit this specific mechanistic knowledge for the discovery of next generation pyrazinamide. We end with the big - and open - question whether targeted protein degradation as an approach to anti-bacterial drug discovery can be generalized, similar to what has been achieved in the area of drug discovery for human diseases.

Phase variation in Mycobacterium tuberculosis glpK produces transiently heritable drug tolerance

The length and complexity of tuberculosis (TB) therapy, as well as the propensity of Mycobacterium tuberculosis to develop drug resistance, are major barriers to global TB control efforts. M. tuberculosis is known to have the ability to enter into a drug-tolerant state, which may explain many of these impediments to TB treatment. We have identified a mechanism of genetically encoded but rapidly reversible drug tolerance in M. tuberculosis caused by transient frameshift mutations in a homopolymeric tract (HT) of 7 cytosines (7C) in the glpK gene. Inactivating frameshift mutations associated with the 7C HT in glpK produce small colonies that exhibit heritable multidrug increases in minimal inhibitory concentrations and decreases in drug-dependent killing; however, reversion back to a fully drug-susceptible large-colony phenotype occurs rapidly through the introduction of additional insertions or deletions in the same glpK HT region. These reversible frameshift mutations in the 7C HT of M. tuberculosis glpK occur in clinical isolates, accumulate in M. tuberculosis-infected mice with further accumulation during drug treatment, and exhibit a reversible transcriptional profile including induction of dosR and sigH and repression of kstR regulons, similar to that observed in other in vitro models of M. tuberculosis tolerance. These results suggest that GlpK phase variation may contribute to drug tolerance, treatment failure, and relapse in human TB. Drugs effective against phase-variant M. tuberculosis may hasten TB treatment and improve cure rates.

Thienopyrimidinone Derivatives That Inhibit Bacterial tRNA (Guanine37-N1)-Methyltransferase (TrmD) by Restructuring the Active Site with a Tyrosine-Flipping Mechanism

Among the >120 modified ribonucleosides in the prokaryotic epitranscriptome, many tRNA modifications are critical to bacterial survival, which makes their synthetic enzymes ideal targets for antibiotic development. Here we performed a structure-based design of inhibitors of tRNA-(N¹G37) methyltransferase, TrmD, which is an essential enzyme in many bacterial pathogens. On the basis of crystal structures of TrmDs from Pseudomonas aeruginosa and Mycobacterium tuberculosis, we synthesized a series of thienopyrimidinone derivatives with nanomolar potency against TrmD in vitro and discovered a novel active site conformational change triggered by inhibitor binding. This tyrosine-flipping mechanism is uniquely found in P. aeruginosa TrmD and renders the enzyme inaccessible to the cofactor S-adenosyl-l-methionine (SAM) and probably to the substrate tRNA. Biophysical and biochemical structure–activity relationship studies provided insights into the mechanisms underlying the potency of thienopyrimidinones as TrmD inhibitors, with several derivatives found to be active against Gram-positive and mycobacterial pathogens. These results lay a foundation for further development of TrmD inhibitors as antimicrobial agents.

The Mycobacterial Membrane: A Novel Target Space for Anti-tubercular Drugs

Tuberculosis (TB) poses an enduring threat to global health. Consistently ranked among the top 10 causes of death worldwide since 2000, TB has now exceeded HIV-AIDS in terms of deaths inflicted by a single infectious agent. In spite of recently declining TB incident rates, these decreases have been incremental and fall short of threshold levels required to end the global TB epidemic. As in other infectious diseases, the emergence of resistant organisms poses a major impediment to effective TB control. Resistance in mycobacteria may evolve from genetic mutations in target genes which are transmitted during cell multiplication from mother cells to their progeny. A more insidious form of resistance involves sub-populations of non-growing (“dormant”) mycobacterial persisters. Quiescent and genetically identical to their susceptible counterparts, persisters exhibit non-inheritable drug tolerance. Their prevalence account for the protracted treatment period that is required for the treatment of TB. In order to improve the efficacy of treatment against mycobacterial persisters and drug-resistant organisms, novel antitubercular agents are urgently required. Selective targeting of bacterial membranes has been proposed as a viable therapeutic strategy against infectious diseases. The underpinning rationale is that a functionally intact cell membrane is vital for both replicating and dormant bacteria. Perturbing the membrane would thus disrupt a multitude of embedded targets with lethal pleiotropic consequences, besides limiting the emergence of resistant strains. There is growing interest in exploring small molecules as selective disruptors of the mycobacterial membrane. In this review, we examined the recent literature on different chemotypes with membrane perturbing properties, the mechanisms by which they induce membrane disruption and their potential as anti-TB agents. Cationic amphiphilicity is a signature motif that is required of membrane targeting agents but adherence to this broad physical requirement does not necessarily translate to conformity in terms of biological outcomes. Nor does it ensure selective targeting of mycobacterial membranes. These are unresolved issues that require further investigation.

Indolyl Azaspiroketal Mannich Bases Are Potent Antimycobacterial Agents with Selective Membrane Permeabilizing Effects and in Vivo Activity

The inclusion of an azaspiroketal Mannich base in the membrane targeting antitubercular 6-methoxy-1- n-octyl-1 H-indole scaffold resulted in analogs with improved selectivity and submicromolar activity against Mycobacterium tuberculosis H37Rv. The potency enhancing properties of the spiro-fused ring motif was affirmed by SAR and validated in a mouse model of tuberculosis. As expected for membrane inserting agents, the indolyl azaspiroketal Mannich bases perturbed phospholipid vesicles, permeabilized bacterial cells, and induced the mycobacterial cell envelope stress reporter promoter p iniBAC. Surprisingly, their membrane disruptive effects did not appear to be associated with bacterial membrane depolarization. This profile was not uniquely associated with azaspiroketal Mannich bases but was characteristic of indolyl Mannich bases as a class. Whereas resistant mycobacteria could not be isolated for a less potent indolyl Mannich base, the more potent azaspiroketal analog displayed low spontaneous resistance mutation frequency of 10^-8/CFU. This may indicate involvement of an additional envelope-related target in its mechanism of action.

Pyrazinoic Acid Inhibits Mycobacterial Coenzyme A Biosynthesis by Binding to Aspartate Decarboxylase PanD

Previously, we showed that a major in vitro and in vivo mechanism of resistance to pyrazinoic acid (POA), the bioactive component of the critical tuberculosis (TB) prodrug pyrazinamide (PZA), involves missense mutations in the aspartate decarboxylase PanD, an enzyme required for coenzyme A biosynthesis. What is the mechanism of action of POA? Upon demonstrating that treatment of M. bovis BCG with POA resulted in a depletion of intracellular coenzyme A and confirming that this POA-mediated depletion is prevented by either missense mutations in PanD or exogenous supplementation of pantothenate, we hypothesized that POA binds to PanD and that this binding blocks the biosynthetic pathway. Here, we confirm both hypotheses. First, metabolomic analyses showed that POA treatment resulted in a reduction of the concentrations of all coenzyme A precursors downstream of the PanD-mediated catalytic step. Second, using isothermal titration calorimetry, we established that POA, but not its prodrug PZA, binds to PanD. Binding was abolished for mutant PanD proteins. Taken together, these findings support a mechanism of action of POA in which the bioactive component of PZA inhibits coenzyme A biosynthesis via binding to aspartate decarboxylase PanD. Together with previous works, these results establish PanD as a genetically, metabolically, and biophysically validated target of PZA.

Indolylalkyltriphenylphosphonium Analogues Are Membrane-Depolarizing Mycobactericidal Agents

Agents that selectively target the mycobacterial membrane could potentially shorten treatment time for tuberculosis, reduce relapse, and curtail emergence of resistant strains. The lipophilicity and extensive charge-delocalized state of the triphenylphosphonium cation strongly favor accumulation within bacterial membranes. Here, we explored the antimycobacterial activities and membrane-targeting properties of indolylalkyltriphenylphosphonium analogues. The most active analogues preferentially inhibited growth of Mycobacterium tuberculosis H37Rv (MIC₅₀ 2-4 μM) and were bactericidal against Mycobacterium bovis BCG (MBC₉₉ 3 μM). In spite of their propensity to accumulate within membranes, we found no evidence that these compounds permeabilized mycobacterial membranes or induced cell-envelope stress. Our investigations indicated that their bacterical effects stem from sustained depolarization of mycobacterial membranes and ensuing disruptive effects on electron transfer and cell division.

In Vivo-Selected Pyrazinoic Acid-Resistant Mycobacterium tuberculosis Strains Harbor Missense Mutations in the Aspartate Decarboxylase PanD and the Unfoldase ClpC1

Through mutant selection on agar containing pyrazinoic acid (POA), the bioactive form of the prodrug pyrazinamide (PZA), we recently showed that missense mutations in the aspartate decarboxylase PanD and the unfoldase ClpC1, and loss-of-function mutation of polyketide synthases Mas and PpsA-E involved in phthiocerol dimycocerosate synthesis, cause resistance to POA and PZA in Mycobacterium tuberculosis. Here we first asked whether these in vitro-selected POA/PZA-resistant mutants are attenuated in vivo, to potentially explain the lack of evidence of these mutations among PZA-resistant clinical isolates. Infection of mice with panD, clpC1, and mas/ppsA-E mutants showed that whereas growth of clpC1 and mas/ppsA-E mutants was attenuated, the panD mutant grew as well as the wild-type. To determine whether these resistance mechanisms can emerge within the host, mice infected with wild-type M. tuberculosis were treated with POA, and POA-resistant colonies were confirmed for PZA and POA resistance. Genome sequencing revealed that 82 and 18% of the strains contained missense mutations in panD and clpC1, respectively. Consistent with their lower fitness and POA resistance level, independent mas/ppsA-E mutants were not found. In conclusion, we show that the POA/PZA resistance mechanisms due to panD and clpC1 missense mutations are recapitulated in vivo. Whereas the representative clpC1 mutant was attenuated for growth in the mouse infection model, providing a possible explanation for their absence among clinical isolates, the growth kinetics of the representative panD mutant was unaffected. Why POA/PZA resistance-conferring panD mutations are observed in POA-treated mice but not yet among clinical strains isolated from PZA-treated patients remains to be determined.

Pyrazinamide Resistance Is Caused by Two Distinct Mechanisms: Prevention of Coenzyme A Depletion and Loss of Virulence Factor Synthesis

Pyrazinamide (PZA) is a critical component of first- and second-line treatments of tuberculosis (TB), yet its mechanism of action largely remains an enigma. We carried out a genetic screen to isolate Mycobacterium bovis BCG mutants resistant to pyrazinoic acid (POA), the bioactive derivative of PZA, followed by whole genome sequencing of 26 POA resistant strains. Rather than finding mutations in the proposed candidate targets fatty acid synthase I and ribosomal protein S1, we found resistance conferring mutations in two pathways: missense mutations in aspartate decarboxylase panD, involved in the synthesis of the essential acyl carrier coenzyme A (CoA), and frameshift mutations in the vitro nonessential polyketide synthase genes mas and ppsA-E, involved in the synthesis of the virulence factor phthiocerol dimycocerosate (PDIM). Probing for cross resistance to two structural analogs of POA, nicotinic acid and benzoic acid, showed that the analogs share the PDIM- but not the CoA-related mechanism of action with POA. We demonstrated that POA depletes CoA in wild-type bacteria, which is prevented by mutations in panD. Sequencing 10 POA-resistant Mycobacterium tuberculosis H37Rv isolates confirmed the presence of at least 2 distinct mechanisms of resistance to the drug. The emergence of resistance through the loss of a virulence factor in vitro may explain the lack of clear molecular patterns in PZA-resistant clinical isolates, other than mutations in the prodrug-converting enzyme. The apparent interference of POA with virulence pathways may contribute to the drug's excellent in vivo efficacy compared to its modest in vitro potency.

Host-Mediated Bioactivation of Pyrazinamide: Implications for Efficacy, Resistance, and Therapeutic Alternatives

Pyrazinamide has played a critical role in shortening therapy against drug-sensitive, drug-resistant, active, and latent tuberculosis (TB). Despite widespread recognition of its therapeutic importance, the sterilizing properties of this 60-year-old drug remain an enigma given its rather poor activity in vitro. Here we revisit longstanding paradigms and offer pharmacokinetic explanations for the apparent disconnect between in vitro activity and clinical impact. We show substantial host-mediated conversion of prodrug pyrazinamide (PZA) to the active form, pyrazinoic acid (POA), in TB patients and in animal models. We demonstrate favorable penetration of this pool of circulating POA from plasma into lung tissue and granulomas, where the pathogen resides. In standardized growth inhibition experiments, we show that POA exhibits superior in vitro potency compared to PZA, indicating that the vascular supply of host-derived POA may contribute to the in vivo efficacy of PZA, thereby reducing the apparent discrepancy between in vitro and in vivo activity. However, the results also raise the possibility that subinhibitory concentrations of POA generated by the host could fuel the emergence of resistance to both PZA and POA. In contrast to widespread expectations, we demonstrate good oral bioavailability and exposure in preclinical species in pharmacokinetic studies of oral POA. Baseline exposure of oral POA can be further increased by the xanthine oxidase inhibitor and approved gout drug allopurinol. These promising results pave the way for clinical investigations of oral POA as a therapeutic alternative or an add-on to overcome PZA resistance and salvage this essential TB drug.

Effect of chronic hypoxia on RAGE and its soluble forms in lungs and plasma of mice

The receptor for advanced glycation end products (RAGE) is a multi-ligand receptor. Alternative splicing and enzymatic shedding produce soluble forms that protect against damage by ligands including Advanced Glycation End products (AGEs). A link between RAGE and oxygen levels is evident from studies showing RAGE-mediated injury following hyperoxia. The effect of hypoxia on pulmonary RAGE expression and circulating sRAGE levels is however unknown. Therefore mice were exposed to chronic hypoxia for 21 d and expression of RAGE, sheddases in lungs and circulating sRAGE were determined. In addition, accumulation of AGEs in lungs and expression of the AGE detoxifying enzyme GLO1 and receptors were evaluated. In lung tissue gene expression of total RAGE, variants 1 and 3 were elevated in mice exposed to hypoxia, whereas mRAGE and sRAGE protein levels were decreased. In the hypoxic group plasma sRAGE levels were enhanced. Although the levels of pro-ADAM10 were elevated in lungs of hypoxia exposed mice, the relative amount of the active form was decreased and gelatinase activity unaffected. In the lungs, the RAGE ligand HMGB1 was decreased and of the AGEs, only LW-1 was increased by chronic hypoxia. Gene expression of AGE receptors 2 and 3 was significantly upregulated. Chronic hypoxia is associated with downregulation of pulmonary RAGE protein levels, but a relative increase in sRAGE. These alterations might be part of the adaptive and protective response mechanism to chronic hypoxia and are not associated with AGE formation except for the fluorophore LW-1 which emerges as a novel marker of tissue hypoxia.

Preparation, characterization and analytical application of an electrochemical laccase biosensor towards low level determination of isoprenaline in human serum samples

A novel electrochemical biosensor has been developed based on the immobilization of multiwalled carbon nanotubes (MWCNT) followed by sol–gel entrapment of laccase (Lac) enzyme on to the GCE.

Meta-analysis: underutilisation and disparities of treatment among patients with hepatocellular carcinoma in the United States

BACKGROUND

Despite wide availability of treatment options for hepatocellular carcinoma (HCC), several studies have suggested underutilisation in clinical practice.

AIMS

To quantify utilisation rates for HCC treatment among patients with HCC in the United States, and to summarise patterns of association between utilisation rates and patient socio-demographic characteristics.

METHODS

We performed a systematic literature review using the Medline database from January 1989 to March 2013. Two investigators independently extracted data on patient populations, study methods and results using standardised forms. Pooled treatment rates for any treatment and curative treatment, with 95% confidence intervals, were calculated. Prespecified subgroup analysis was performed to identify patient-level correlates of treatment utilisation.

RESULTS

We identified 24 studies that met inclusion criteria. The pooled rates of any treatment and curative treatment were 52.8% (95% CI 52.2-53.4%) and 21.8% (95% CI 21.4-22.1%) respectively. Among patients diagnosed at an early stage, the pooled curative treatment rate was 59.0% (95% CI 58.1-59.9%). Elderly, non-Caucasians and patients of low socioeconomic status had lower treatment rates than their counterparts.

CONCLUSIONS

Rates of HCC treatment in the United States, including curative treatment rates among patients detected at an early stage, are disappointingly low. Future efforts should focus on identifying appropriate intervention targets to increase treatment rates and reduce socio-demographic disparities.

G9a mediates Sharp-1-dependent inhibition of skeletal muscle differentiation

Sharp-1, a basic helix-loop-helix transcription factor, is a potent repressor of skeletal muscle differentiation and is dysregulated in muscle pathologies. However, the mechanisms by which it inhibits myogenesis are not fully understood. Here we show that G9a, a lysine methyltransferase, is involved in Sharp-1-mediated inhibition of muscle differentiation. We demonstrate that G9a directly interacts with Sharp-1 and enhances its ability to transcriptionally repress the myogenin promoter. Concomitant with a differentiation block, G9a-dependent histone H3 lysine 9 dimethylation (H3K9me2) and MyoD methylation are apparent upon Sharp-1 overexpression in muscle cells. RNA interference-mediated reduction of G9a or pharmacological inhibition of its activity erases these repressive marks and rescues the differentiation defect imposed by Sharp-1. Our findings provide new insights into Sharp-1-dependent regulation of myogenesis and identify epigenetic mechanisms that could be targeted in myopathies characterized by elevated Sharp-1 levels.

Differential roles of C4 and betaC1 in mediating suppression of post-transcriptional gene silencing: evidence for transactivation by the C2 of Bhendi yellow vein mosaic virus, a monopartite begomovirus

Bhendi yellow vein mosaic disease (BYVMD) is caused by the association of a DNA beta satellite with a begomovirus component. The begomovirus component has two promoters, one in the virion sense (V-sense) and the other in the complementary sense (C-sense) in the intergenic region (IR). To study the promoter activities of V-sense and C-sense promoters, mGFP gene fusion was made downstream to the promoters. Transient and stable expressions in N. benthamiana leaves showed significant GFP expression under C-sense promoter whereas the expression under the V-sense promoter was very weak in the absence of the transactivator C2. Untransformed N. benthamiana plants were agroinfiltrated with binary vector constructs containing V-sense-GFP alone or along with C1, C2, C4, V1, V2 or betaC1 (in both sense and antisense orientations) to understand the roles of these gene products in transactivation and/or suppression of post-transcriptional gene silencing (PTGS). The results showed strong suppression of gene silencing activities for C4 and betaC1 but a weak activity for C2. The suppression activities were also confirmed using gfp-silenced GFP16c/GFPi plants by agroinfiltration and agroinoculation. The expression of C4 and betaC1 as transgenes produced abnormal phenotypic growth compared to the other viral genes mentioned above, further supporting their suppressor function.

Impact of consumption of different levels of Bifidobacterium lactis HN019 on the intestinal microflora of elderly human subjects

BACKGROUND

Age-related changes in the physiology and intestinal function of the elderly render them more susceptible to gut-related illnesses. Probiotic dietary supplementation has been shown to enhance the health indices in the elderly.

OBJECTIVE

To determine the effect of three different doses [5 x 109 CFU/day (high), 1.0 x 109 CFU/day (medium) and 6.5 x 107 CFU/day (low)] of Bifidobacterium lactis HN019 (DR10TM) on the intestinal flora of elderly human subjects and the dose response effect.

DESIGN

Randomised, double-blind and placebo-controlled human dietary intervention study consisting of four groups of 20 elderly (over 60 years old) volunteers. Each volunteer consumed 250 mL per day of reconstituted skim milk (RSM) which either did not contain any probiotic supplement (placebo group) or contained B. lactis HN019 at different levels (low, medium and high dose groups). The study comprised three stages: a 2-week pre-intervention (without any supplement), followed by 4 weeks of test feeding (dietary intervention) and then a 2-week washout period.

RESULTS

After dietary intervention, statistically significant increases in bifidobacteria, lactobacilli and enterococci were observed. At the end of the 4-week feeding period the mean number of bifidobacteria recorded in the placebo group were 9.31 +/- 0.01 log CFU/g of faeces. In the high, medium and low dose groups the bifidobacteria levels were significantly (p < 0.006) higher (9.88 +/- 0.1, 9.75 +/- 0.14 and 9.74 +/- 0.11 log CFU/g of faeces, respectively), when compared to the respective pre-intervention levels. There were no significant differences (p superior 0.05) between the responses of the different dose groups, indicating that even the lowest dose tested augmented the changes in bifidobacteria. Similar trends were observed for lactobacilli and enterococci. In contrast, the counts of enterobacteria were reduced in all the probiotic dose groups.

CONCLUSION

The present study showed that dietary supplementation with B. lactis HN019 significantly increased the number of resident bifidobacteria and reduced the enterobacteria counts. In addition, enterococci and lactobacilli were also increased. Based on this study and already published clinical evidence (4, 5, 8, 9) we conclude that, B. lactis HN019 is a suitable probiotic for elderly human subjects and even the lowest dose (6.5 x 107 CFU/day) tested is able to confer desired changes in the intestinal microflora.

Probiotic research in Australia, New Zealand and the Asia-Pacific region

Although the epicentres of probiotic research in the past decade have been Japan and Europe, researchers in the Asia-Pacific region have actively contributed to the growing understanding of the intestinal microbial ecosystem, and interactions between gut bacteria, diet and health of the human host. A number of new probiotic strains have been developed in the region that have been demonstrated to have beneficial impacts on health in animal and human trials, including improved protection against intestinal pathogens and modulation of the immune system. Probiotics targeted to animals, including aquaculture, feature heavily in many Asian countries. Developments in probiotic technologies have included microencapsulation techniques, antimicrobial production in fermented meats, and synbiotic combinations. In particular, the impact of resistant starch on the intestinal environment and fermentation by intestinal bacteria has been intensively studied and new probiotic strains selected specifically for synbiotic combinations with resistant starch. This paper provides an overview of probiotic research within Australia, New Zealand and a number of Asian countries, and lists scientists in the Asia-Pacific region involved in various aspects of probiotic research and development.

A mutation that prevents glucosylation of the lipid-linked oligosaccharide precursor leads to underglycosylation of secreted yeast invertase

A mutant of Saccharomyces cerevisiae with the genotype mnn1 mnn2 mnn9 gls1 synthesizes mannoproteins with oligosaccharides having the composition Glc3Man10Glc-NAc2- owing to the mnn9 defect, which prevents synthesis of the outer chain, the mnn1 defect, which prevents branching of the core, and the gls1 mutation, which prevents deglucosylation of the resultant glycoprotein as a consequence of a defective glucosidase-I [Tsai, P.-K., Ballou, L., Esmon, B., Schekman, R. & Ballou, C. E. (1984) Proc. Natl. Acad. Sci. USA 81, 6340-6343]. (The mnn2 defect is not expressed in presence of the mnn9 mutation.) This strain spontaneously forms new colonies in which gls1 is suppressed owing to a defect in synthesis of dolichol phosphoglucose, the glucosylation substrate. The new mutant, designated mnn1 mnn2 mnn9 gls1 dpg1, synthesizes and secretes invertase (EC 3.2.1.26) that has a higher mobility on native gel electrophoresis than that made by the parent strain, the consequence of a reduction in both the size and the number of carbohydrate chains. The mannoprotein chains have the mnn1 mnn9 structure (Man10Glc-NAc2-), and the invertase is resolved by gel electrophoresis in sodium dodecyl sulfate into two major and two minor bands that represent homologs with about 4-7 carbohydrate units, in contrast to about 8-11 chains in the parent strain. Thus, the inability to glucosylate the lipid-linked precursor reduces the efficiency of glycosylation of the protein chains. The genetic defect is in synthesis of the glucose donor dolichol phosphoglucose, but the mutation is nonallelic with the reported alg5-1 mutation, which has a similar phenotype [Runge, K. W., Huffaker, T. C. & Robbins, P. W. (1984) J. Biol. Chem. 259, 412-417].

Isolation and structure of glucan from regenerating spheroplasts of Candida albicans

Regenerating spheroplasts of Candida albicans formed organized glucan nets in liquid culture. The nets consisted of interwoven microfibrils about 50 nm wide, but of an undetermined length. Partial acid hydrolysis of the polysaccharide showed the presence of chains of beta(1----3)- and beta(1----6)-linked glucose residues, but no intrachain beta(1----3) and beta(1----6) linkages. Periodate oxidation and GLC of the methylated glucan indicated a highly branched polymer (9.5% branch points). Sequential enzymic degradation of the isolated nets confirmed the presence of chains of beta(1----3)- and beta(1----6)-linked glucose residues. Degradation by (1----3)-beta- and (1----6)-beta-glucanase released 23% (w/w) and 30% (w/w) respectively of the carbohydrate as glucose equivalents. The residual material was degraded by chitinase. Equal amounts of N-acetylglucosamine and glucose equivalents were detected in the chitinase hydrolysate, suggesting a possible linkage between glucan and chitin. Our data indicate that the cell wall of C. albicans contains at least two highly branched glucans with predominantly beta(1----3) or beta(1----6) linkages.

Metabolism of [14C]glucose by regenerating spheroplasts of Candida albicans

Spheroplasts of Candida albicans were regenerated in [14C]glucose and buffered magnesium sulphate (0.1 M-Tris/HCl; 0.5 M-MgSO4, pH 7.2) at 35 degrees C. Uptake of glucose by spheroplasts was faster than that by intact yeast cells. After 6 h, 65% of the glucose taken up by the yeast appeared as CO2 and 30% was incorporated into the cellular material. With spheroplasts, 55% of the glucose taken up was expired as CO2, 25% was excreted into the medium as other metabolites and 20% was incorporated into the cells. The regenerating spheroplasts excreted 14C-labelled carbohydrates into the medium which were fractionated on a Sephadex G-15 column. Acid hydrolysis of the low molecular-weight fraction yielded the following sugars: mannose (75.7%), fucose (3.8%), arabinose (3%), galactose (2.1%) and an unidentified monosaccharide (14%). Spheroplasts did not incorporate mannoprotein into the regenerated wall. The wall carbohydrate from regenerated spheroplasts was fractionated on the basis of solubility in sodium hydroxide. The alkali-insoluble fraction was analysed by sequential enzyme hydrolysis; 40% of the incorporated counts were associated with beta (1----3)-linked glucan and 50% with a mixed glucan comprising beta (1----3)- and beta (1----6)-linkages and chitin.