Thianthrene is a novel inhibitor of Leishmania donovani pteridine reductase 1 (PTR1)

Pteridine reductase 1 (PTR1) from Leishmania donovani is a short chain reductase that catalyses the NADPH-dependent reduction of folates and pterins. It has gained attention as a therapeutic target because it acts as a metabolic bypass for dihydrofolate reductase (DHFR) targeting drugs and is thought to be responsible for the failure of conventional therapies against the trypanosomatids. In the present study, we report the identification of thianthrene as a potent inhibitor of L. donovani PTR1 (LdPTR1) based on both structure-based virtual screening and experimental verification. Thianthrene displayed uncompetitive mixed type inhibition in a recombinant enzyme inhibition assay. In addition, cell based assays and flow cytometry showed that the intracellular amastigotes were inhibited by thianthrene in vitro. The results of our study could be considered for the development of novel therapeutics based on PTR1 inhibition

Mycobacterium tuberculosis NAD(+)-dependent DNA ligase is selectively inhibited by glycosylamines compared with human DNA ligase I

DNA ligases are important enzymes which catalyze the joining of nicks between adjacent bases of double-stranded DNA. NAD(+)-dependent DNA ligases (LigA) are essential in bacteria and are absent in humans. They have therefore been identified as novel, validated and attractive drug targets. Using virtual screening against an in-house database of compounds and our recently determined crystal structure of the NAD(+) binding domain of the Mycobacterium tuberculosis LigA, we have identified N(1), N(n)-bis-(5-deoxy-α-d-xylofuranosylated) diamines as a novel class of inhibitors for this enzyme. Assays involving M.tuberculosis LigA, T4 ligase and human DNA ligase I show that these compounds specifically inhibit LigA from M.tuberculosis. In vitro kinetic and inhibition assays demonstrate that the compounds compete with NAD(+) for binding and inhibit enzyme activity with IC(50) values in the µM range. Docking studies rationalize the observed specificities and show that among several glycofuranosylated diamines, bis xylofuranosylated diamines with aminoalkyl and 1, 3-phenylene carbamoyl spacers mimic the binding modes of NAD(+) with the enzyme. Assays involving LigA-deficient bacterial strains show that in vivo inhibition of ligase by the compounds causes the observed antibacterial activities. They also demonstrate that the compounds exhibit in vivo specificity for LigA over ATP-dependent ligase. This class of inhibitors holds out the promise of rational development of new anti-tubercular agents

Physical activity and attitudes towards exercise in people with axial and peripheral spondyloarthritis

OBJECTIVE: To evaluate physical activity and attitudes towards exercise among people with axial and peripheral spondyloarthritis (SpA). METHODS: Using baseline information from an on-going, longitudinal, prospective SpA cohort study (n=264), self-reported attitudes and beliefs towards exercise were assessed using questionnaires. Total metabolic equivalent (MET) hours of self-reported physical activity per week, time spent in activities, and activity levels were calculated from the Nurses\u27 Health Study Physical Activity Questionnaire II (NHSPAQ II). Adjusted multivariable linear models estimated the relationship between physical activity and disease status (axial versus peripheral). RESULTS: Regardless of predominant anatomic distribution of disease, most participants were well-educated, non-Hispanic white men. Approximately 40% met the United States Department of Health and Human Services physical activity recommendations. Positive attitudes, beliefs, and perceived benefits towards exercise were similar by anatomic distribution of disease. Despite similar MET-hours per week, participants with axial disease had greater concerns regarding discomfort and joint injuries than those with peripheral disease. Compared to those with peripheral SpA (n=201), participants with axial SpA (n=63) spent less time engaging in light and moderate activities (adjusted beta in light activity: -1.94 minutes/week, 95% Confidence Interval (CI): -2.96 to -0.93; adjusted beta in moderate activity: -1.05 minutes/week, 95% CI: -2.12 to 0.02). CONCLUSION: Participants with axial SpA had greater concerns regarding discomfort and injuries from exercise than those with peripheral SpA. Although no differences in time spent in vigorous activities were observed, participants with axial SpA spent less time than those with peripheral SpA in light to moderate activities

Primary care physician perspectives on barriers to diagnosing axial Spondyloarthritis: a qualitative study

BACKGROUND: The average delay in diagnosis for patients with axial spondyloarthritis (axSpA) is 7 to 10 years. Factors that contribute to this delay are multifactorial and include the lack of diagnostic criteria (although classification criteria exist) for axSpA and the difficulty in distinguishing inflammatory back pain, a key symptom of axSpA, from other highly prevalent forms of low back pain. We sought to describe reasons for diagnostic delay for axSpA provided by primary care physicians. METHODS: We conducted a qualitative research study which included 18 US primary care physicians, balanced by gender. Physicians provided informed consent to participate in an in-depth interview ( \u3c 60 min), conducted in person (n = 3) or over the phone (n = 15), in 2019. The analysis focuses on thoughts about factors contributing to diagnostic delay in axSpA. RESULTS: Physicians noted that the disease characteristics contributing to diagnostic delay include: back pain is common and axSpA is less prevalent, slow progression of axSpA, intermittent nature of axSpA pain, and in the absence of abnormal radiographs of the spine or sacroiliac joints, there is no definitive test for axSpA. Patient characteristics believed to contribute to diagnostic delay included having multiple conditions in need of attention, infrequent interactions with the health care system, and doctor shopping. Doctors noted that patients wait until the last moments of the clinical encounter to discuss back pain. Problematic physician characteristics included lack of rapport with patients, lack of setting appropriate expectations, and attribution of back pain to other factors. Structural/system issues included short appointments, lack of continuity of care, insufficient insurance coverage for tests, lack of back pain clinics, and a shortage of rheumatologists. CONCLUSION: Primary care physicians agreed that lengthy axSpA diagnosis delays are challenging to address owing to the multifactorial causes (e.g., disease characteristics, patient characteristics, lack of definitive tests, system factors)

Modulation of inhibitory activity of xylanase - α-amylase inhibitor protein (XAIP): binding studies and crystal structure determination of XAIP- II from Scadoxus multiflorus at 1.2 Å resolution

Background: Plants produce a wide range of proteinaceous inhibitors to protect themselves against hydrolytic enzymes. Recently a novel protein XAIP belonging to a new sub-family (GH18C) was reported to inhibit two structurally unrelated enzymes xylanase GH11 and α -amylase GH13. It was shown to inhibit xylanase GH11 with greater potency than that of α-amylase GH13. A new form of XAIP (XAIP-II) that inhibits α-amylase GH13 with a greater potency than that of XAIP and xylanase GH11 with a lower potency than that of XAIP, has been identified in the extracts of underground bulbs of Scadoxus multiflorus. This kind of occurrence of isoforms of inhibitor proteins is a rare observation and offers new opportunities for understanding the principles of protein engineering by nature. Results: In order to determine the structural basis of the enhanced potency of XAIP-II against α-amylase GH13 and its reduced potency against xylanase GH11 as compared to that of XAIP, we have purified XAIP-II to homogeneity and obtained its complete amino acid sequence using cloning procedure. It has been crystallized with 0.1 M ammonium sulphate as the precipitating agent and the three-dimensional structure has been determined at 1.2 Å resolution. The binding studies of XAIP-II with xylanase GH11 and α-amylase GH13 have been carried out with surface plasmon resonance (SPR). Conclusion: The structure determination revealed that XAIP-II adopts the well known TIM barrel fold. The xylanase GH11 binding site in XAIP-II is formed mainly with loop α3-β3 (residues, 102 - 118) which has acquired a stereochemically less favorable conformation for binding to xylanase GH11 because of the addition of an extra residue, Ala105 and due to replacements of two important residues, His106 and Asn109 by Thr107 and Ser110. On the other hand, the α-amylase binding site, which consists of α-helices α6 (residues, 193 - 206), α7 (residues, 230 - 243) and loop β6-α6 (residues, 180 - 192) adopts a stereochemically more favorable conformation due to replacements of residues, Ser190, Gly191 and Glu194 by Ala191, Ser192 and Ser195 respectively in α-helix α6, Glu231 and His236 by Thr232 and Ser237 respectively in α-helix α7. As a result, XAIP-II binds to xylanase GH11 less favorably while it interacts more strongly with α-amylase GH13 as compared to XAIP. These observations correlate well with the values of 4.2 × 10-6 M and 3.4 × 10-8 M for the dissociation constants of XAIP-II with xylanase GH11 and α-amylase GH13 respectively and those of 4.5 × 10-7 M and 3.6 × 10-6 M of XAIP with xylanase GH11 and α-amylase GH13 respectively

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy