BackgroundAscorbic acid is a water-soluble chain breaking antioxidant. It scavenges free radicals and reactive oxygen species (ROS), which are produced during metabolic pathways. Exercise can produce an imbalance between ROS and antioxidants, leading to oxidative stress-related tissue damages. This study was designed to determine the effects of ascorbic acid supplementation on circulating biomarkers of oxidative stress and muscle damage following a single bout of exercise.MethodsIn a crossover design with a 1 wk. wash-out period, 19 healthy women performed 30 min moderate-intensity cycling after ingesting 1000 mg of ascorbic acid (AA) or placebo. Blood samples were taken immediately before, immediately after and 30 min post-exercise to determine plasma albumin, total protein, glucose, oxidative stress and muscle damage markers.ResultsPlasma albumin and total protein levels increased immediately after exercise in placebo alongside slight reductions in glucose (p = 0.001). These effects were absent in AA cohort. Ferric reducing ability of plasma and vitamin C levels in AA cohort significantly increased after exercise (p < 0.05). Superoxide dismutase activity was significantly elevated after exercise (p = 0.002) in placebo but not AA. Plasma malondialdehyde did not change after exercise in placebo but was significantly decreased in AA (p < 0.05). The exercise protocol promoted slight muscle damage, reflected in significant increases in total creatine kinase in all subjects after exercise. On the other hand, plasma C-reactive protein and lactate dehydrogenase remained unchanged.ConclusionSupplementation with ascorbic acid prior exercise improves antioxidant power but does not prevent muscle damage.

Introduction: Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) remains a global health concern because of the development of drug resistance. The adaptability of MTB in response to a variety of environmental stresses is a crucial strategy that supports their survival and evades host defense mechanisms. Stress regulates gene expression, particularly virulence genes, leading to the development of drug tolerance. Mannose-capped lipoarabinomannan (ManLAM) is a critical component of the cell wall, functions as a virulence factor and influences host defense mechanisms.Purpose: This study focuses on the effect of isoniazid (INH) stress on the regulation of ManLAM-related genes, to improve our understanding of virulence and drug resistance development in MTB. Materials and Methods: MTB with distinct drug resistance profiles were used for gene expression analysis. Multiplex-real time PCR assay was performed to monitor stress-related genes (hspX, tgs1, and sigE). The expression levels of ManLAM-related genes (pimB, mptA, mptC, dprE1, dprE2, and embC) were quantified by qRT-PCR. Sequence analysis of drug resistance-associated genes (inhA, katG, and rpoB) and ManLAM-related genes were performed to establish a correlation between genetic variation and gene expression. Results: INH treatment activates the stress response mechanism in MTB, resulting in a distinct gene expression pattern between drug resistance and drug-sensitive TB. In response to INH, hspX was up-regulated in RIF-R and MDR. tgs1 was strongly up-regulated in MDR, whereas sigE was dramatically up-regulated in the drug-sensitive TB. Interestingly, ManLAM-related genes were most upregulated in drug resistance, notably MDR (pimB, mptA, dprE1, and embC), implying a role for drug resistance and adaptability of MTB via ManLAM modulation. Conclusion:This study establishes a relationship between the antibiotic stress response mechanism and the expression of ManLAMrelated genes in MTB samples with diverse drug resistance profiles. The novel gene expression pattern in this work is valuable knowledge that can be applied for TB monitoring and treatment in the future.

Isoniazid (INH) is an antibiotic that is widely used to treat tuberculosis (TB). Adaptation to environmental stress is a survival strategy for Mycobacterium tuberculosis and is associated with antibiotic resistance development. Here, mycobacterial adaptation following INH treatment was studied using a multi-stress system (MS), which mimics host-derived stress. Mtb H37Rv (drug-susceptible), mono-isoniazid resistant (INH-R), mono-rifampicin resistant (RIF-R), and multidrug-resistant (MDR) strains were cultivated in the MS with or without INH. The expression of stress-response genes (hspX, tgs1, icl1, and sigE) and lipoarabinomannan (LAM)-related genes (pimB, mptA, mptC, dprE1, dprE2, and embC), which play important roles in the host–pathogen interaction, were measured using real-time PCR. The different adaptations of the drug-resistant (DR) and drug-susceptible (DS) strains were presented in this work. icl1 and dprE1 were up-regulated in the DR strains in the MS, implying their roles as markers of virulence and potential drug targets. In the presence of INH, hspX, tgs1, and sigE were up-regulated in the INH-R and RIF-R strains, while icl1 and LAM-related genes were up-regulated in the H37Rv strain. This study demonstrates the complexity of mycobacterial adaptation through stress response regulation and LAM expression in response to INH under the MS, which could potentially be applied for TB treatment and monitoring in the future.

Tuberculosis (TB) is a global health problem caused by Mycobacterium tuberculosis (MTB) infection. The main problem of TB treatment is the emergence of drug resistance, which can occur by inappropriate of antibiotic used. Isoniazid (INH) is the first-line anti-TB drug that inhibits mycolic acid synthesis, an important part of the mycobacterial cell wall. Mannose-capped lipoarabinomannan (ManLAM) is an essential cell wall part that plays a role as an immunomodulator and acts as a virulence factor. In this study, MTB clinical isolates with different drug resistant profiles were used to determine the expression of ManLAM related genes including pimB, mptA, mptC, dprE1, dprE2 and embC by qRT-PCR. Stress-related genes including hspX, tgs1, and sigE were determined by multiplex real-time PCR with probe assay. Sanger sequencing of ManLAM related genes and genes associated with drug resistance (inhA, katG, and rpoB) were analyzed. In response to INH, the expression pattern of ManLAM related genes was different among four strains. Interestingly, MDR-TB markedly up-regulated ManLAM related genes greater than others. Stress-related genes hspX and tgs1 were significantly upregulated in MDR response to INH, whereas sigE was significantly upregulated in MDR response to RIF and INH-R. DprE1 is crucial for MTB and it is a valuable target for anti-TB drugs. RIF-R and MDR isolates show C→T mutation at nucleotide position 459 of the dprE1 gene leading to the same amino acid at codon 153. Codon usage analysis for DprE1 showed that RIF-R and MDR preferred ACT codon over drug sensitive strains. This work provides the expression pattern of ManLAM related genes and stress responder genes, which are key factors in the interaction between MTB and host. Moreover, ManLAM is a possible factor that plays an important role in the adaptive mechanism and the drug resistance mechanism of mycobacteria.Author summaryThe adaptive mechanism of mycobacteria in response to stressors is an important strategy to promote their virulence and pathogenesis. This study determined the effect of antibiotic stress on Mycobacterium tuberculosis (MTB) focusing on mannose-capped lipoarabinomannan (ManLAM), which is one of the virulence factors that modulate host immune response. Multiplex real-time PCR with probe assay targeting stress responder genes and qRT-PCR targeting ManLAM related genes were performed. Isoniazid acts as a stressor to induce stress response in mycobacteria, as shown in the up-regulation of stress-related genes including hspX, tgs1, and sigE. The expression pattern of ManLAM related genes in drug resistant and drug sensitive-MTB in response to INH was different, causing a unique pattern. ManLAM related genes respond to isoniazid mostly in drug resistant strains and are present at high expression levels in INH-R and MDR. The results suggest that ManLAM is one factor involved in the adaptive mechanism of MTB response to antibiotic stress and probably associated with the emergence of MTB drug resistance. This work provides new insights into the adaptive mechanism of mycobacterial response to isoniazid that will improve understanding of how mycobacteria develop drug resistance.