Moxifloxacin-Mediated Killing of Mycobacterium tuberculosis Involves Respiratory Downshift, Reductive Stress, and Accumulation of Reactive Oxygen Species.

Moxifloxacin is central to treatment of multidrug-resistant tuberculosis. Effects of moxifloxacin on the Mycobacterium tuberculosis redox state were explored to identify strategies for increasing lethality and reducing the prevalence of extensively resistant tuberculosis. A noninvasive redox biosensor and a reactive oxygen species (ROS)-sensitive dye revealed that moxifloxacin induces oxidative stress correlated with M. tuberculosis death. Moxifloxacin lethality was mitigated by supplementing bacterial cultures with an ROS scavenger (thiourea), an iron chelator (bipyridyl), and, after drug removal, an antioxidant enzyme (catalase). Lethality was also reduced by hypoxia and nutrient starvation. Moxifloxacin increased the expression of genes involved in the oxidative stress response, iron-sulfur cluster biogenesis, and DNA repair. Surprisingly, and in contrast with Escherichia coli studies, moxifloxacin decreased expression of genes involved in respiration, suppressed oxygen consumption, increased the NADH/NAD+ ratio, and increased the labile iron pool in M. tuberculosis. Lowering the NADH/NAD+ ratio in M. tuberculosis revealed that NADH-reductive stress facilitates an iron-mediated ROS surge and moxifloxacin lethality. Treatment with N-acetyl cysteine (NAC) accelerated respiration and ROS production, increased moxifloxacin lethality, and lowered the mutant prevention concentration. Moxifloxacin induced redox stress in M. tuberculosis inside macrophages, and cotreatment with NAC potentiated the antimycobacterial efficacy of moxifloxacin during nutrient starvation, inside macrophages, and in mice, where NAC restricted the emergence of resistance. Thus, NADH-reductive stress contributes to moxifloxacin-mediated killing of M. tuberculosis, and the respiration stimulator (NAC) enhances lethality and suppresses the emergence of drug resistance.

Hesperetin alleviates DMH induced toxicity via suppressing oxidative stress and inflammation in the colon of Wistar rats.

1,2-Dimethylhydrazine (DMH), a colon-specific environmental toxicant is one among the carcinogen responsible for the cause of colon cancer. The present study was designed to evaluate the protective effect of Hesperetin (HST) against colon toxicity induced by DMH in Wistar rats. HST, a flavonoid widely found in citrus fruits possesses several biological activities including anti-microbial, anti-oxidant properties among others. A single dose of DMH (40 mg/kg body weight) was administered subcutaneously on 1st day for induction of colon toxicity followed by oral treatment with HST at a dose of 20 mg/kg bodyweight for 14 consecutive days. DMH administration leads to excessive ROS generation, resulting in an imbalance in redox homeostasis and causing membrane lipid peroxidation, which is also partly due to the decrease in the level of tissue antioxidant machinery. Our result showed HST significantly ameliorates DMH-induced lipid peroxidation and also substantially increases the activity/level of various anti-oxidant proteins (GR, GPx, GST, GSH, and SOD). HST was also found to reduce the expression of inflammatory proteins (TNF-α, IL-6, i-NOS, COX-2, NF-kB-p65), goblet cell disintegration as well as mucin depletion (sulfo and sialomucin) in the colon that was found to be elevated upon administration of DMH. Our histological results further provide confirmation of the protective role of HST against DMH-induced pathological alterations. The results of the present study demonstrate supplementation of HST is beneficial in ameliorating DMH-induced toxicity by suppressing oxidative stress, inflammation, goblet cell disintegration as well mucin depletion in the colon of Wistar rats.

Meta-analysis of efficacy of iron and iodine fortified salt in improving iron nutrition status.

BACKGROUND: Salt fortification with iron is a potential strategy to increase population-level iron intake. The current evidence regarding double-fortified salt (DFS) in improving iron nutrition status is equivocal. OBJECTIVE: To study the efficacy of DFS as compared to iodine fortified salt (IS) in improving iron nutrition status. METHODS: Randomized controlled trials comparing DFS and IS until August 2016 were systematically searched across multiple databases to assess for change in mean hemoglobin (Hb), prevalence of anemia, iron deficiency (ID), ID anemia (IDA), serum ferritin, and serum transferrin receptor (TfR). Meta-analysis was performed using R software. RESULTS: Of the initial 215 articles retrieved using the predetermined search strategy, data from 10 comparisons of DFS and IS across 8 randomized controlled trials are included. There was significant heterogeneity across included studies and the studies were of low to very low quality as per GRADE criteria. DFS significantly increased mean Hb by 0.44 g/dl (95% confidence interval [CI]: 0.16, 0.71) and significantly decreased anemia (risk difference -0.16; 95% CI: -0.26, -0.06) and ID (risk difference -0.20; 95% CI: -0.32, -0.08) as compared to IS. There was no statistically significant difference in change in ferritin levels (mean difference 0.62 µg/L; 95% CI: -0.12, 1.37), serum TfR levels (mean difference -0.23 mg/dL; 95% CI: -0.85, 0.38), and IDA (risk difference -0.08; 95% CI: -0.28, 0.11). CONCLUSION: DFS is a potentially efficacious strategy of addressing anemia as a public health problem at population level. There is a need for effectiveness trials before DFS can be scaled up in program mode at population level.

Chitosan Derivatives Active against Multidrug-Resistant Bacteria and Pathogenic Fungi: In Vivo Evaluation as Topical Antimicrobials.

The continuous rise of antimicrobial resistance and the dearth of new antibiotics in the clinical pipeline raise an urgent call for the development of potent antimicrobial agents. Cationic chitosan derivatives, N-(2-hydroxypropyl)-3-trimethylammonium chitosan chlorides (HTCC), have been widely studied as potent antibacterial agents. However, their systemic structure-activity relationship, activity toward drug-resistant bacteria and fungi, and mode of action are very rare. Moreover, toxicity and efficacy of these polymers under in vivo conditions are yet to be established. Herein, we investigated antibacterial and antifungal efficacies of the HTCC polymers against multidrug resistant bacteria including clinical isolates and pathogenic fungi, studied their mechanism of action, and evaluated cytotoxic and antimicrobial activities in vitro and in vivo. The polymers were found to be active against both bacteria and fungi (MIC = 125-250 µg/mL) and displayed rapid microbicidal kinetics, killing pathogens within 60-120 min. Moreover, the polymers were shown to target both bacterial and fungal cell membrane leading to membrane disruption and found to be effective in hindering bacterial resistance development. Importantly, very low toxicity toward human erythrocytes (HC50 = >10000 µg/mL) and embryo kidney cells were observed for the cationic polymers in vitro. Further, no inflammation toward skin tissue was observed in vivo for the most active polymer even at 200 mg/kg when applied on the mice skin. In a murine model of superficial skin infection, the polymer showed significant reduction of methicillin-resistant Staphylococcus aureus (MRSA) burden (3.2 log MRSA reduction at 100 mg/kg) with no to minimal inflammation. Taken together, these selectively active polymers show promise to be used as potent antimicrobial agents in topical and other infections.

Molecular mechanisms of adefovir sensitivity and resistance in HBV polymerase mutants: a molecular dynamics study.

Molecular modeling studies of adefovir diphosphate with the wild type and the mutant HBV polymerase-DNA complex demonstrated that the increase in adefovir sensitivity toward HBV polymerase mutants (rtL180M, rtM204V/I, rtL180M-M204V/I) is a result of increased van der Waals interaction and is supplemented by the decreased affinity of natural substrate toward the mutant HBV polymerase. In the case of rtN236T mutant, loss of two hydrogen bonds accompanied by significant decrease in electrostatic interactions is observed, which explains the observed decrease in drug sensitivity and binding affinity of adefovir diphosphate toward the rtN236T mutant HBV polymerase.