Isoniazid induces apoptosis: Role of oxidative stress and inhibition of nuclear translocation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2).

AIMS: Long-term treatment of Isoniazid (INH) in tuberculosis (TB) patients can lead to anti-tuberculosis drug-induced hepatotoxicity. To understand the mechanism of hepatotoxicity, an attempt has been made to elucidate the role of Nrf2, a transcription factor induced by oxidative stress, in INH induced apoptosis liver cancer cell lines. MATERIALS AND METHODS: Cytotoxicity was evaluated by MTT assay. Apoptosis and reactive oxygen species (ROS) generation was performed by flow cytometry. mRNA and protein expression of various genes involves in INH induced toxicity was evaluated via Real-time PCR and western blot analysis respectively. Differential protein expression was performed by two-dimensional gel electrophoresis followed by identification using MALDI TOF/TOF. KEY FINDINGS: INH induced ROS and apoptosis in HepG2 as well as THLE-2 cells. Nuclear damage was also observed by INH treatment in HepG2 cells. Expression of apoptotic (Cytochrome C and Caspase 9) and antioxidative (Keap1 and Nrf2) genes were observed to increase. INH induced PKCδ phosphorylation and released Nrf2 from its inhibitor Keap1 in the cytoplasm of HepG2 cells. However, over-expression of Nrf2 did not affect nuclear Nrf2 protein level as well as its downstream target NQO1. Nrf2 importer, Karyopherin ß1 level was observed to decrease in HepG2 as well as THLE-2 cells following INH treatment. SIGNIFICANCE: These findings suggest that INH prevented Nrf2 translocation into the nucleus by inhibiting its importer Karyopherin ß1. Therefore Nrf2 might not able to bind ARE sequences from inducing antioxidative response for protecting the cells undergoing apoptosis.

Isoniazid prevents Nrf2 translocation by inhibiting ERK1 phosphorylation and induces oxidative stress and apoptosis.

Isoniazid is used either alone or in combination with other drugs for the treatment of tuberculosis. It is also used for the prevention of tuberculosis. Chronic treatment of Isoniazid may cause severe liver damage leading to acute liver failure. The mechanism through which Isoniazid causes liver damage is investigated. Isoniazid treatment generates reactive oxygen species and induces apoptosis in Hep3B cells. It induces antioxidative and apoptotic genes leading to increase in mRNA expression and protein levels in Hep3B cells. Whole genome expression analysis of Hep3B cells treated with Isoniazid has resulted in differential expression of various genes playing prime role in regulation of apoptotic, antioxidative, DNA damage, cell signaling, cell proliferation and differentiation pathways. Isoniazid increased cytosolic Nrf2 protein level while decreased nuclear Nrf2 protein level. It also decreased ERK1 phosphorylation and treatment of Hep3B cells with ERK inhibitor followed by Isoniazid resulting in increased apoptosis in these cells. Two dimensional gel electrophoresis results have also shown differential expression of various protein species including heat shock proteins, proteins playing important role in oxidative stress, DNA damage, apoptosis, cell proliferation and differentiation. Results suggest that Isoniazid induces apoptosis through oxidative stress and also prevents Nrf2 translocation into the nucleus by reducing ERK1 phosphorylation thus preventing cytoprotective effect.

Rosiglitazone induces cardiotoxicity by accelerated apoptosis.

Present investigation explores the cardiotoxicity of rosiglitazone (ROSI) using rat heart cardiomyocytes and db/db mice. In H9c2 cells, ROSI at 50 and 60 µM induced an increase in the percentage of apoptotic cells and superoxide generation, along with an increase in the expression of various subunits of NADPH oxidase and nitric oxide synthases, confirmed that ROSI-induced apoptosis in H9c2 cells is by ROS generation. The increase in the expression of the antioxidants like superoxide dismutase (SOD), catalase, glutathione reductase (GR), glutathione-S-transferase (GST), and glutathione peroxidase (GPx) further confirmed this notion. Heme oxygenase-1, having an important role in cell protection against oxidative stress, was found to be increased along with induction of nuclear translocation of NF-E2-related factor and increased protein kinase C δ expression. Moreover, in db/db mice, oral administration of ROSI (10 mg/kg) for 10 days induced an increase in serum creatinine kinase-MB, tissue antioxidants like SOD, catalase, GR, GST, GPx expression, cardiac troponin T, and inducible nitric oxide synthase protein expression strongly support the in vitro findings. Furthermore, global gene expression studies also showed the perturbation of oxidative phosphorylation, fat cell differentiation, and electron transport chain following ROSI treatment in vivo. These results suggested that ROSI-induced cardiac damage is due to accelerated apoptosis both in vitro and in vivo.

Cyclooxygenase 2 gene polymorphisms and chronic periodontitis in a North Indian population: a pilot study.

PURPOSE: Cyclooxygenase (COX) enzyme catalyzes the production of prostaglandins, which are important mediators of tissue destruction in periodontitis. Single nucleotide polymorphisms of COX2 enzyme have been associated with increasing susceptibility to inflammatory diseases. The present study evaluates the association of two single nucleotide polymorphisms in COX2 gene (-1195G>A and 8473C>T) with chronic periodontitis in North Indians. METHODS: Both SNPs and their haplotypes were used to explore the associations between COX2 polymorphisms and chronic periodontitis in 56 patients and 60 controls. Genotyping was done by polymerase chain reaction followed by restriction fragment length polymorphism. Chi-square test and logistic regression analysis were performed for association analysis. RESULTS: By the individual genotype analysis, mutant genotypes (GA and AA) of COX2 -1195 showed more than a two fold risk (odds ratio [OR]>2) and COX2 8473 (TC and CC) showed a reduced risk for the disease, but the findings were not statistically significant. Haplotype analysis showed that the frequency of the haplotype AT was higher in the case group and a significant association was found for haplotype AT (OR, 1.79; 95% confidence interval, 1.03 to 3.11; P=0.0370) indicating an association between the AT haplotype of COX2 gene SNPs and chronic periodontitis. CONCLUSIONS: Individual genotypes of both the SNPs were not associated while haplotype AT was found to be associated with chronic periodontitis in North Indians.

Protective association exhibited by the single nucleotide polymorphism (SNP) rs1052133 in the gene human 8-oxoguanine DNA glycosylase (hOGG1) with the risk of squamous cell carcinomas of the head & neck (SCCHN) among north Indians.

BACKGROUND & OBJECTIVES: Imbalances in compactly regulated DNA repair pathways in the form of single nucleotide polymorphisms (SNPs) within vital DNA repair genes may result in insufficient DNA repair and increase in DNA breaks thus rendering the human system vulnerable to the debilitatory effects of grave diseases like cancers. The present study involves investigation of association of the non-synonymous SNP rs1052133 (C8069G/Ser326Cys) located in the exonic region of the gene human 8-oxoguanine DNA glycosylase (hOGG1) with the risk of squamous cell carcinomas of the head and neck (SCCHN). METHODS: Case-control based genetic association study was performed among 575 (250 SCCHN cases and 325 normal healthy controls) sub-population cluster-matched (Indo-Europeans linguistic subgroup + Caucasoid morphological subtype) samples from the north Indian States of Uttar Pradesh and Uttarakhand using polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing analysis. RESULTS: Our results demonstrated statistically significant protective association for the heterozygous CG [Odds Ratio (OR) 0.6587, 95% Confidence Interval (CI) 0.4615 to 0.9402, P=0.0238], homozygous mutant GG (OR 0.2570, 95% CI 0.1070 to 0.6175, P=0.0013) and combined mutant CG + GG (OR 0.6057, 95% CI 0.4272 to 0.8586, P=0.0059) genotypes. INTERPRETATION & CONCLUSIONS: The results indicate that the polymorphism rs1052133 is strongly associated with SCCHN susceptibility and the mutant (G) allele might be a protective factor for SCCHN among north Indian subpopulations.