Chronic exposure to environmentally relevant concentration of fluoride alters Ogg1 and Rad51 expressions in mice: Involvement of epigenetic regulation.

Chronic exposure to fluoride (F) beyond the permissible limit (1.5 ppm) is known to cause detrimental health effects by induction of oxidative stress-mediated DNA damage overpowering the DNA repair machinery. In the present study, we assessed F induced oxidative stress through monitoring biochemical parameters and looked into the effect of chronic F exposure on two crucial DNA repair genes Ogg1 and Rad51 having important role against ROS induced DNA damages. To address this issue, we exposed Swiss albino mice to an environmentally relevant concentration of fluoride (15 ppm NaF) for 8 months. Results revealed histoarchitectural damages in liver, brain, kidney and spleen. Depletion of GSH, increase in lipid peroxidation and catalase activity in liver and brain confirmed the generation of oxidative stress. qRT-PCR result showed that expressions of Ogg1 and Rad51 were altered after F exposure in the affected organs. Promoter hypermethylation was associated with the downregulation of Rad51. F-induced DNA damage and the compromised DNA repair machinery triggered intrinsic pathway of apoptosis in liver and brain. The present study indicates the possible association of epigenetic regulation with F induced neurotoxicity.

Raman spectroscopy reveals distinct differences between two closely related bacterial strains, Mycobacterium indicus pranii and Mycobacterium intracellulare.

A common technique used to differentiate bacterial species and to determine evolutionary relationships is sequencing their 16S ribosomal RNA genes. However, this method fails when organisms exhibit high similarity in these sequences. Two such strains that have identical 16S rRNA sequences are Mycobacterium indicus pranii (MIP) and Mycobacterium intracellulare. MIP is of significance as it is used as an adjuvant for protection against tuberculosis and leprosy; in addition, it shows potent anti-cancer activity. On the other hand, M. intracellulare is an opportunistic pathogen and causes severe respiratory infections in AIDS patients. It is important to differentiate these two bacterial species as they co-exist in immuno-compromised individuals. To unambiguously distinguish these two closely related bacterial strains, we employed Raman and resonance Raman spectroscopy in conjunction with multivariate statistical tools. Phenotypic profiling for these bacterial species was performed in a kinetic manner. Differences were observed in the mycolic acid profile and carotenoid pigments to show that MIP is biochemically distinct from M. intracellulare. Resonance Raman studies confirmed that carotenoids were produced by both MIP as well as M. intracellulare, though the latter produced higher amounts. Overall, this study demonstrates the potential of Raman spectroscopy in differentiating two closely related mycobacterial strains. Graphical abstract.

Targeted photodynamic therapy in visible light using BODIPY-appended copper(ii) complexes of a vitamin B6 Schiff base.

Copper(ii) complexes [Cu(L1/L2/L3)(A)] (1-3), where H2A·HCl is a vitamin B6 Schiff base, viz. 3-hydroxy-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylpyridin-1-ium chloride, L1 and L2 are 2-(2-pyridyl)benzimidazole based borondipyrromethene (BODIPY) ligands and L3 is 2-(2-pyridyl)benzimidazole, were prepared, characterized and their visible light-induced anti-cancer activity was studied. Complex 3, characterized by X-ray crystallography, exhibits a distorted square-pyramidal geometry for copper (τ = 0.33). Complexes 1 and 2 showed absorption bands at 500 and 535 nm, respectively, in 20% DMSO/Dulbecco's phosphate buffered saline (DPBS) medium. Complex 1 exhibited emission at ∼510 nm (λexc = 480 nm) (ΦF = 0.1) in 20% DMSO/DPBS, while the non-emissive diiodo-BODIPY complex 2 is an efficient photosensitizer. The green fluorescent complex 1 enabled us to study its cellular uptake and localization. It showed selective uptake in proliferating cancer cells and significant mitochondrial localization (Pearson's coefficient = 0.7). Complex 2 showed excellent photocytotoxicity (400-700 nm, 10 J cm-2) in HeLa, MCF-7 and HepG2 cancer cells with IC50 values within 0.4-0.6 µM, while remaining less toxic in the dark and in non-cancerous HPL1D cells (photocytotoxic index ∼50). Complex 2, remarkable in targeting cancer cells over non-cancerous cells, showed photoinduced generation of singlet oxygen, causing apoptotic cell death, thus satisfying the major requirements of targeted photodynamic therapy.

Dual-Mode Optical Sensing of Histamine at Nanomolar Concentrations in Complex Biological Fluids and Living Cells.

An easily synthesized fluorescein-based luminescent dye has been utilized for the dual-mode detection of histamine at nanomolar concentrations at pH 7.0 in water. The specific response to histamine was achieved by imidazole-catalyzed 'imine formation' reaction. The protocol was subsequently applied for the estimation of histamine in complex biological milieu such as human blood serum and urine samples. Furthermore, the dose-dependent cellular uptake of histamine and de novo synthesis (by thapsigargin treatment) was visualized in RAW 264.7, a mouse macrophage cell line. We have also developed portable paper strips for rapid, on-site detection of histamine without involving costly instruments.

Targeted photocytotoxicity by copper(II) complexes having vitamin B6 and photoactive acridine moieties.

Copper(II) pyridoxal Schiff base complexes [Cu(L(1)/L(2))(B)]ClO4 (1-4), where HL(1) is 4-(((2-(1H-imidazol-4-yl)ethyl)imino)methyl)-5-(hydroxymethyl)-2-methylpyridin-3-ol (in 1 and 2), HL(2) is 2-(((2-(1H-imidazol-4-yl)ethyl)imino)methyl)phenol (in 3, 4), B is 11-(9-acridinyl)dipyrido[3,2-a:2',3'-c]phenazine (acdppz in 1 and 3), dipyrido[3,2-a:2',3'-c]phenazine (in 2) and 1,10-phenanthroline (in 4), were synthesized, characterized and their photocytotoxicity in visible light, intracellular localization, cellular uptake and DNA photocleavage activity were studied. Complex 4 was characterized by X-ray crystallography. Complexes 1 and 3 having acdppz as photosensitizer showed significant photocytotoxicity in visible light in HeLa and MCF7 cells giving IC50 value of <0.6 µM, while being relatively non-toxic in dark. The complexes were non-toxic to non-tumorigenic HPL1D cells both in light and dark conditions. Complex 1 showed significant localization in the cytoplasm of HeLa cells within 4 h of treatment, as evidenced from confocal microscopy. DCFDA assay on 1 suggested generation of intracellular reactive oxygen species in HeLa cells upon photo-exposure. Importantly, Annexin-V-FITC/PI assay indicated photo-induced apoptotic cell death.

Interferon-gamma and nitric oxide synthase 2 mediate the aggregation of resident adherent peritoneal exudate cells: implications for the host response to pathogens.

Interferon-gamma (Ifnγ), a key macrophage activating cytokine, plays pleiotropic roles in host immunity. In this study, the ability of Ifnγ to induce the aggregation of resident mouse adherent peritoneal exudate cells (APECs), consisting primarily of macrophages, was investigated. Cell-cell interactions involve adhesion molecules and, upon addition of Ifnγ, CD11b re-localizes preferentially to the sites of interaction on APECs. A functional role of CD11b in enhancing aggregation is demonstrated using Reopro, a blocking reagent, and siRNA to Cd11b. Studies with NG-methyl-L-arginine (LNMA), an inhibitor of Nitric oxide synthase (Nos), NO donors, e.g., S-nitroso-N-acetyl-DL-penicillamine (SNAP) or Diethylenetriamine/nitric oxide adduct (DETA/NO), and Nos2-/- mice identified Nitric oxide (NO) induced by Ifnγ as a key regulator of aggregation of APECs. Further studies with Nos2-/- APECs revealed that some Ifnγ responses are independent of NO: induction of MHC class II and CD80. On the other hand, Nos2 derived NO is important for other functions: motility, phagocytosis, morphology and aggregation. Studies with cytoskeleton depolymerizing agents revealed that Ifnγ and NO mediate the cortical stabilization of Actin and Tubulin which contribute to aggregation of APECs. The biological relevance of aggregation of APECs was delineated using infection experiments with Salmonella Typhimurium (S. Typhimurium). APECs from orally infected, but not uninfected, mice produce high amounts of NO and aggregate upon ex vivo culture in a Nos2-dependent manner. Importantly, aggregated APECs induced by Ifnγ contain fewer intracellular S. Typhimurium compared to their single counterparts post infection. Further experiments with LNMA or Reopro revealed that both NO and CD11b are important for aggregation; in addition, NO is bactericidal. Overall, this study elucidates novel roles for Ifnγ and Nos2 in regulating Actin, Tubulin, CD11b, motility and morphology during the aggregation response of APECs. The implications of aggregation or "group behavior" of APECs are discussed in the context of host resistance to infectious organisms.

Interaction of DNA-lesions induced by sodium fluoride and radiation and its influence in apoptotic induction in cancer cell lines.

Fluoride is an essential trace element but also an environmental contaminant with major sources of exposure being drinking water, food and pesticides. Previous studies showed that sodium fluoride (NaF) at 5 mM or more is required to induce apoptosis and chromosome aberrations and proposed that DNA damage and apoptosis play an important role in toxicity of excessive fluoride. The aim of this study is directed to understand the nature of DNA-lesions induced by NaF by allowing its interaction with radiation induced DNA-lesions. NaF 5 mM was used after observing inability to induce DNA damages and apoptosis by single exposure with 50 µM or 1 mM NaF. Co-exposure to NaF and radiation significantly increased the frequency of aberrant metaphases and exchange aberrations in human lymphocytes and arrested the cells in G1 stage instead of apoptotic death. Flow cytometric analysis, DNA fragmentation and PARP-cleavage analysis clearly indicated that 5 mM NaF together with radiation (1 Gy) induced apoptosis in both U87 and K562 cells due to down regulation of expression of anti-apoptotic proteins, like Bcl2 in U87 and inhibitors of apoptotic proteins like survivin and cIAP in K562 cells. This study herein suggested that single exposure with extremely low concentration of NaF unable to induce DNA lesions whereas higher concentration induced DNA lesions interact with the radiation-induced DNA lesions. Both are probably repaired rapidly thus showed increased interactive effect. Coexposure to NaF and radiation induces more apoptosis in cancer cell lines which could be due to increased exchange aberrations through lesions interaction and downregulating anti-apoptotic genes.

Reduction in fluoride-induced genotoxicity in mouse bone marrow cells after substituting high fluoride-containing water with safe drinking water.

Treatment of mice with 15 mg l(-1) sodium fluoride (NaF) for 30 days increased the number of cell death, chromosomal aberrations (CAs) and 'cells with chromatid breaks' (aberrant cells) compared with control. The present study was intended to determine whether the fluoride (F)-induced genotoxicity could be reduced by substituting high F-containing water after 30 days with safe drinking water, containing 0.1 mg F ions l(-1). A significant fall in percentage of CAs and aberrant cells after withdrawal of F-treatment following 30 days of safe water treatment in mice was observed which was highest after 90 days, although their levels still remained significantly high compared with the control group. This observation suggests that F-induced genotoxicity could be reduced by substituting high F-containing water with safe drinking water. Further study is warranted with different doses and extended treatment of safe water to determine whether the induced damages could be completely reduced or not.

Fluoride-induced histopathology and synthesis of stress protein in liver and kidney of mice.

Selective low (15 mg sodium fluoride (NaF)/L) and relatively high (150 mg NaF/L) doses of in vivo fluoride (F) treatment to Swiss albino mice through drinking water elicited organ-specific toxicological response. All the F-exposed groups showed severe alterations in both liver and kidney architectures, but there was no significant change in the rate of water consumption and body weight. Vacuolar degeneration, micronecrotic foci in the hepatocytes, and hepatocellular hypertrophy were evident in the mice exposed to low dose (15 mg NaF/L for 30 days) while sinusoidal dilation with enlarged central vein surrounded by deep-blue erythrocytes were preponderant when treated with the same dose for a period of 90 days. Blood filled spaces, disintegration of tubular epithelium, and atrophy of glomeruli were also recorded in the kidney of the same treatment group. Change in reduced glutathione level (GSH), glutathione-s-transferase (GST) activity, malondialdehyde (MDA) production in both liver and kidney, disturbances in liver function, induction of heat shock protein 70 (Hsp 70) expression in kidney and its down regulation in liver were positively correlated with histopathological lesion.

Fluoride-induced genotoxicity in mouse bone marrow cells: effect of buthionine sulfoximine and N-acetyl-L-cysteine.

A significant level of reactive oxygen species generation was observed in sodium fluoride (NaF) treated mouse bone marrow cells (BMCs). Reduced glutathione (GSH) as a free radical scavenger could be an important determining factor in F-induced genotoxicity. We therefore attempted to monitor GSH to understand the mechanism of NaF-induced genotoxicity. NaF was injected intra-peritoneally in normal, buthionine sulfoximine (BSO) or N-acetyl-L-cysteine (NAC) treated mice (n = 5). After 13 h of NaF-treatment BMCs were collected to harvest them at the same divisional cycle and processed for analysis of cell cycle, induction of apoptosis and chromosomal aberrations (CAs). Level of GSH was also measured concomitantly. NaF induced significant CAs in all treatment groups except at 2.5 mg NaF kg(-1) body weight. BSO-treatment alone induced significantly high frequency of CAs. BSO treatment prior to injection of 2.5-7.5 mg NaF kg(-1) b.w. was found to increase the frequency of CAs, significantly when compared with the positive control group, but the level was not significant in case of higher doses of NaF treatment (15 and 30 mg kg(-1) b.w.). NaF-treated cells also showed a higher population of Annexin-V positive cells. NAC pre-treatment significantly reduced the extent of NaF-induced CAs, which clearly indicates the involvement of GSH in the NaF response. However, further study is warranted to evaluate the low synergistic effect of BSO on higher doses of NaF-induced CAs.