Actionable mechanisms of drug tolerance and resistance in Mycobacterium tuberculosis

The emergence of antimicrobial resistance (AMR) across bacterial pathogens presents a serious threat to global health. This threat is further exacerbated in tuberculosis (TB), mainly due to a protracted treatment regimen involving a combination of drugs. A diversity of factors contributes to the emergence of drug resistance in TB, which is caused by the pathogen Mycobacterium tuberculosis (Mtb). While the traditional genetic mutation-driven drug resistance mechanisms operate in Mtb, there are also several additional unique features of drug resistance in this pathogen. Research in the past decade has enriched our understanding of such unconventional factors as efflux pumps, bacterial heterogeneity, metabolic states, and host microenvironment. Given that the discovery of new antibiotics is outpaced by the emergence of drug resistance patterns displayed by the pathogen, newer strategies for combating drug resistance are desperately needed. In the context of TB, such approaches include targeting the efflux capability of the pathogen, modulating the host environment to prevent bacterial drug tolerance, and activating the host anti-mycobacterial pathways. In this review, we discuss the traditional mechanisms of drug resistance in Mtb, newer understandings and the shaping of a set of unconventional approaches to target both the emergence and treatment of drug resistance in TB.

Direct Molecular Detection of Drug-Resistant Tuberculosis from Transported Bio-Safe Dried Sputum on Filter-Paper

In 2019, amongst half a million new rifampicin-resistant tuberculosis (TB) cases, 78% were multi drug-resistant TB (MDR-TB). Access to rapid and Universal-Drug susceptibility testing (DST) to patients in remote areas is a major challenge to combat drug-resistant TB. To overcome this challenge, we had recently reported the development of 'TB Concentration & Transport kit' for bio-safe ambient temperature transport of dried sputum on filter-paper (Trans-Filter). The present study was conducted to evaluate the utility of DNA extracted from sputum on Trans-Filter in a Multiplex PCR-based sequencing assay (Mol-DSTseq) for diagnosing drug-resistant TB. The developed Mol-DSTseq assays were standardized on Mycobacterium tuberculosis clinical isolates (n = 98) and further validated on DNA extracted from sputum on Trans-Filter (n = 100). Using phenotypic DST as gold standard, the Mol-DSTseq assay showed 100% (95% Confidence Interval [CI] 79.4-100%) and 73.3% (95% CI 54.1-87.7%) sensitivity for detecting rifampicin and isoniazid resistance with a specificity of 85.1% (95% CI 66.2-95.8%) and 100% (95% CI:82.3-100%), respectively. For fluoroquinolones and aminoglycosides, the Mol-DSTseq assay showed a sensitivity of 78.5% (95% CI 49.2-95.3%) and 66.6% (95% CI 9.4-99.1%) with a specificity of 88.2% (95% CI 72.5-96.7%) and 100% (95% CI 93.1-100%), respectively. The Mol-DSTseq assays exhibited a high concordance of ~ 83-96% (κ value: 0.65-0.81) with phenotypic DST for all drugs. In conclusion, the 'TB Concentration and Transport kit' was compatible with Mol-DSTseq assays and has the potential to provide 'Universal-DST' to patients residing in distant areas in high burden countries, like India for early initiation of anti-tubercular treatment.

84 Folate-methionine cycle and folate transport in developing buffalo embryos

Periconceptional folic acid is known to have a major role in the prevention of neural tube defects, leading to global recommendations for folic acid supplementation before and in early pregnancy. Maternal folate throughout pregnancy may have other roles in offspring health, including neurodevelopment and cognitive performance in childhood. Folate and folic acid (vitamin B9) act as a co-enzyme essential for single carbon metabolism, a network of pathways involved in several biological processes including nucleotide synthesis, DNA repair, and methylation reactions. In general, rapidly growing and multiplying cells require an adequate supply of folate. A primary deficiency of natural folate resulting in an increase of the total homocysteine concentration may be detrimental to the quality of the oocyte, subsequent fertilisation, embryogenesis, implantation, and fetal development. However, to date, folate-methionine metabolism and folate transport have not been studied in developing buffalo embryos. The present study details transcript expression for genes encoding key enzymes in the linked folate-methionine cycles in the ovary tissue, cumulus cells, immature oocytes, IVM oocytes, and pre-implantation embryos and also estimates the folate concentration in follicular fluid (FF) of buffalo. The FF was pooled and collected by aspiration of different sizes of surface follicles (2-8mm diameter). The total number of analysed samples was three, with different dilutions and estimation of folate in FF of buffalo done by chemiluminescence assay. Total RNA was extracted from oocytes, cumulus cells, ovarian tissue, and embryos produced from IVF. RT-PCR was performed to analyse the expression of folate-methionine cycle enzymes and folate transporters. Transcripts for all the enzymes of the folate-methionine cycle (i.e. SHMT, MTR, MTRR, MAT1A, MAT2B, GNMT, AHCY, CBS, and DHFR) and folate transporters (FOLR1, FOLR2) and reduced folate carrier (SLC19A1) were expressed in ovarian tissue, cumulus cells, oocytes, and pre-implantation embryos. Immunocytochemical analysis revealed FOLR2 and SLC19A1 protein expression on the plasma membrane and/or cytoplasm of the oocytes and embryos, and FOLR1 in the nucleus of pre-implantation embryos. The folate concentration in FF was 24ngmL−1. This is the first report to examine the concentration of folate in FF and revealed the identification of transcripts in different samples of buffalo species. The presence of these enzymes could have a profound effect on single-carbon metabolism within the ovary and pre-implantation embryo, therefore indicating that folate from FF is being disseminated through folate receptors within oocytes and embryos to participate in the folate pathway. This study advocates the necessity for examination of the result of folate supplementation throughout invitro embryo production for improving the quality and quantity of transferable blastocysts and subsequently live calf births in buffalo.

220 Exploring the use of mesenchymal stem cells for treatment of mastitis and metritis in cattle

The present study was carried out to isolate mesenchymal stem cells (MSCs) from adipose tissue of cattle (Bos indicus), characterise them, and apply them for the treatment of mastitis and metritis in the cow. Cattle MSCs were isolated from adipose tissue near the loin region of cow. Isolated adipose tissue was subjected to enzymatic digestion using 2% collagenase with agitation at regular intervals. The cells obtained after digestion were resuspended in cell culture flasks containing growth enriched medium and cultured under standard culture conditions. Alkaline phosphatase staining was used as one of the parameters to confirm cultured putative MSCs. Bovine Ad-MSCs were further characterised using real time-PCR by amplification of MSC-specific markers: CD73, CD90, and CD105 as positive markers and CD34, CD45, and CD79a as negative markers. Immunocytochemistry showed the presence of CD73, CD90, and CD105 on the cell surface. Three groups-control (C), local (L), and intravenous (IV)-with 6 cows suffering from mastitis were taken in each group and subjected to MSC transplantation through local and intravenous routes. Control group animals were subjected to antibiotic treatment only. Similarly, another three groups were taken with 6 cows in each group suffering from metritis. Post-transplantation wound healing, tissue repair, and reduction in inflammation were monitored for 26 days, at different time intervals; that is, after Days 1, 3, 7, and 15. Blood samples were also collected from animals at the same time intervals for real time-PCR. A similar examination was also done in metritis groups along with the analysis of the reduction in turbidity of cervical fluid at the abovementioned time intervals. Real time-PCR was performed to determine relative expression of genes for proliferative factors, anti-inflammatory cytokines, and antimicrobial peptides on cells isolated from blood collected at different time intervals. Gene expression in the local group of mastitis subjected to MSC injection was significantly higher than that of the IV and control group. The somatic cell count declined in both local and IV groups compared with the control group. Whereas the expression of the same genes in the IV group of metritis was significantly higher than that of the local and control groups of cows. The turbidity of cervical fluid and mucus was reduced in the IV group compared with the local group. In conclusion, we demonstrated the healing potential of MSCs in a cow model via MSC injection. Promising results were obtained in curing mastitis in both local and IV groups, whereas healing in the case of metritis was significantly higher in the IV group compared with both the control and local groups of cows. The study indicates the potential use of MSc for treatment of mastitis and metritis in cattle through wound healing and decreasing microbial infection.

Neuroprotective effect of hemeoxygenase-1/glycogen synthase kinase-3β modulators in 3-nitropropionic acid-induced neurotoxicity in rats

The present study has been designed to explore the possible interaction between hemeoxygenase-1 (HO-1) and glycogen synthase kinase-3β (GSK-3β) pathway in 3-nitropropionic acid (3-NP)-induced neurotoxicity in rats. 3-NP produces neurotoxicity by inhibition of the mitochondrial complex II (enzyme succinate dehydrogenase) and by sensitizing the N-methyl-D-aspartate receptor. Recent studies have reported the therapeutic potential of HO-1/GSK-3β modulators in different neurodegenerative disorders. However, their exact role is yet to be explored. The present study is an attempt to investigate the effect of pharmacological modulation of HO-1/GSK-3β pathway against 3-NP-induced behavioral, biochemical and molecular alterations in rat. Behavioral observation, oxidative stress, pro-inflammatory [tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β)], HO-1 and GSK-3β activity were evaluated post 3-NP treatment. Findings of the present study demonstrate a significant alteration in the locomotor activity, motor coordination, oxidative burden (increased lipid peroxidation, nitrite concentration and decreased endogenous antioxidants), pro-inflammatory mediators [TNF-α, IL-1β], HO-1 and GSK-3β activity in 3-NP-treated animals. Further, administration of hemin (10- and 30-mg/kg; i.p.) and lithium chloride (LiCl) (25- and 50-mg/kg; i.p.) prevented the alteration in body weight, motor impairments, oxidative stress and cellular markers. In addition, combined administration of hemin (10-mg/kg) and LiCl (25-mg/kg) showed synergistic effect on 3-NP-treated rats. Pretreatment with Tin (IV) protoporphyrin (40 μM/kg), HO-1 inhibitor reversed the beneficial effect of LiCl and hemin. Outcomes of the present study suggest that HO-1 and GSK-3β enzymes are involved in the pathophysiology of HD. The modulators of both the pathways might be used as adjuvants or prophylactic therapy for the treatment of HD-like symptoms.

Mechanisms involved in attenuated cardio-protective role of ischemic preconditioning in metabolic disorders

Myocardial infarction is a pathological state which occurs due to severe abrogation of the blood supply (ischemia) to a part of heart, which can cause myocardial damage. The short intermittent cycles of sub-lethal ischemia and reperfusion has shown to improve the tolerance of the myocardium against subsequent prolonged ischemia/reperfusion (I/R)-induced injury, which is known as ischemic preconditioning (IPC). Although, IPC-induced cardioprotection is well demonstrated in various species, including human beings, accumulated evidence clearly suggests critical abrogation of the beneficial effects of IPC in diabetes mellitus, hyperlipidemia and hyperhomocysteinemia. Various factors are involved in the attenuation of the cardioprotective effect of preconditioning, such as the reduced release of calcitonin gene-related peptide (CGRP), the over-expression of glycogen synthase kinase-3β (GSK-3β) and phosphatase and tensin homolog (PTEN), impairment of mito-KATP channels, the consequent opening of mitochondrial permeability transition pore (MPTP), etc. In this review, we have critically discussed the various signaling pathways involved in abrogated preconditioning in chronic diabetes mellitus, hyperlipidemia and hyperhomocysteinemia. We have also focused on the involvement of PTEN in abrogated preconditioning and the significance of PTEN inhibitors.