Molecular and cellular remodeling of HepG2 cells upon treatment with antitubercular drugs

Drug-induced liver injury (DILI) is an adverse outcome of the currently used tuberculosis treatment regimen, which results in patient noncompliance, poor treatment outcomes, and the emergence of drug-resistant tuberculosis. DILI is primarily caused by the toxicity of the drugs and their metabolites, which affect liver cells, biliary epithelial cells, and liver vasculature. However, the precise mechanism behind the cellular damage attributable to first-line antitubercular drugs (ATDs), as well as the effect of toxicity on the cell survival strategies, is yet to be elucidated. In the current study, HepG2 cells upon treatment with a high concentration of ATDs showed increased perforation within the cell, cuboidal shape, and membrane blebbing as compared with control/untreated cells. It was observed that ATD-induced toxicity in HepG2 cells leads to altered mitochondrial membrane permeability, which was depicted by the decreased fluorescence intensity of the MitoRed tracker dye at higher drug concentrations. In addition, high doses of ATDs caused cell damage through an increase in reactive oxygen species production in HepG2 cells and a simultaneous reduction in glutathione levels. Further, high dose of isoniazid (50–200 mM), pyrazinamide (50–200 mM), and rifampicin (20–100 µM) causes cell apoptosis and affects cell survival during toxic conditions by decreasing the expression of potent autophagy markers Atg5, Atg7, and LC3B. Thus, ATD-mediated toxicity contributes to the reduced ability of hepatocytes to tolerate cellular damage caused by altered mitochondrial membrane permeability, increased apoptosis, and decreased autophagy. These findings further emphasize the need to develop adjuvant therapies that can mitigate ATD-induced toxicity for the effective treatment of tuberculosis.     

Control of circadian rhythm in nitrate reductase activity in Wolffia microscopica Griff

In Wolffia microscopica, the activity of nitrate reductase showedstrong diurnal rhythmicity with a peak in the forenoon. Therhythmicity persists under extended dark conditions as wellas under continuous light. The phase of the rhythm shifts underinverted light-dark cycles. Studies with various inhibitorsof macromolecular synthesis suggest that the increase in enzymeactivity depends on the new synthesis of both RNA and protein. (Received February 14, 1979; )     

Overexpression of Glyoxalase III gene in transgenic sugarcane confers enhanced performance under salinity stress

Journal of Plant Research - The glyoxalase pathway is a check point to monitor the elevation of methylglyoxal (MG) level in plants and is mediated by glyoxalase I (Gly I) and glyoxalase II (Gly II)...     

Piriformospora indica?rescues growth diminution of rice seedlings during high salt stress

Piriformospora indica association has been reported to increase biotic as well as abiotic stress tolerance of its host plants. We analyzed the beneficial effect of P. indica association on rice seedlings during high salt stress conditions (200 and 300 mM NaCl). The growth parameters of rice seedlings such as root and shoot lengths or fresh and dry weights were found to be enhanced in P. indica-inoculated rice seedlings as compared with non-inoculated control seedlings, irrespective of whether they are exposed to salt stress or not. However, salt-stressed seedlings performed much better in the presence of the fungus compared with non-inoculated control seedlings. The photosynthetic pigment content [chlorophyll (Chl) a, Chl b, and carotenoids] was significantly higher in P. indica-inoculated rice seedlings under high salt stress conditions as compared with salt-treated non-inoculated rice seedlings, in which these pigments were found to be decreased. Proline accumulation was also observed during P. indica colonization, which may help the inoculated plants to become salt tolerant. Taken together, P. indica rescues growth diminution of rice seedlings under salt stress.     

Substrate specificity plays an important role in uncoupling the catalytic and scaffolding activities of rat testis DNA topoisomerase IIα

Abstract

Topoisomerase II (topo II) is a dyadic enzyme found in all eukaryotic cells. Topo II is involved in a number of cellular processes related to DNA metabolism, including DNA replication, recombination and the maintenance of genomic stability. We discovered a correlation between the development of postnatal testis and increased binding of topo IIα to the chromatin fraction. We used this observation to characterize DNA-binding specificity and catalytic properties of purified testis topo IIα. The results indicate that topo IIα binds a substrate containing the preferred site with greater affinity and, consequently, catalyzes the conversion of form I to form IV DNA more efficiently in contrast to substrates lacking such a site. Interestingly, topo IIα displayed high-affinity and cooperativity in binding to the scaffold associated region. In contrast to the preferred site, however, high-affinity binding of topo IIα to the scaffold-associated region failed to result in enhanced catalytic activity. Intriguingly, competition assays involving scaffold-associated region revealed an additional DNA-binding site within the dyadic topo IIα. These results implicate a dual role for topo IIα in vivo consistent with the notion that its sequestration to the chromatin might play a role in chromosome condensation and decondensation during spermatogenesis.     

Molecular heterogeneity among north Indian isolates of Group A Streptococcus

AIM: To monitor molecular heterogeneity among the clinical isolates of group A Streptococcus (GAS) from north India by Vir and emm typing. METHODS AND RESULTS: GAS isolates, 31 from pharyngitis and nine from rheumatic fever (RF)/rheumatic heart disease (RHD) patients were differentiated into 16 Vir types (VT). These isolates were further discriminated into 23 emm types. Most of emm types were Vir type specific, except few (7.5%), which revealed different Vir types within same emm type. The most prevalent emm type found was emm 49 (15%) followed by 7.5% of emm 69, emm 71 and emm 75 which were different from emm type distribution reported from south India. CONCLUSIONS: Analysis of data revealed 40% heterogeneity by Vir typing and 57.5% by emm typing among GAS isolates which is significant in view of small number of isolates studied. SIGNIFICANCE OF IMPACT OF THE STUDY: The molecular study for the first time demonstrates different emm types prevalent and circulating in northern region of India and such data may help in selection of types for vaccine development.     

Identification of SopE2, a Salmonella secreted protein which is highly homologous to SopE and involved in bacterial invasion of epithelial cells

Type III secreted Sop protein effectors are delivered into target eukaryotic cells and elicit cellular responses underlying Salmonella pathogenicity. In this work, we have identified another secreted protein, SopE2, and showed that SopE2 is an important invasion-associated effector. SopE2 is encoded by the sopE2 gene which is present and conserved in pathogenic strains of Salmonella. SopE2 is highly homologous to SopE, a protein encoded by a gene within a temperate bacteriophage and present in only some pathogenic strains.     

Functional genomics of Neisseria meningitidis pathogenesis

The pathogenic bacterium Neisseria meningitidis is an important cause of septicemia and meningitis, especially in childhood. The establishment and maintenance of bacteremic infection is a pre-requisite for all the pathological sequelae of meningococcal infection. To further understand the genetic basis of this essential step in pathogenesis, we analyzed a library of 2,850 insertional mutants of N. meningitidis for their capacity to cause systemic infection in an infant rat model. The library was constructed by in vitro modification of Neisseria genomic DNA with the purified components of Tn10 transposition. We identified 73 genes in the N. meningitidis genome that are essential for bacteremic disease. Eight insertions were in genes encoding known pathogenicity factors. Involvement of the remaining 65 genes in meningocoocal pathogenesis has not been demonstrated previously, and the identification of these genes provides insights into the pathogenic mechanisms that underlie meningococcal infection. Our results provide a genome-wide analysis of the attributes of N. meningitidis required for disseminated infection, and may lead to new interventions to prevent and treat meningococcal infection.