Hit-to-lead optimization of phenylsulfonyl hydrazides for a potent suppressor of PGE2 production: Synthesis, biological activity, and molecular docking study.

Preliminary hit-to-lead optimization of a novel series of phenylsulfonyl hydrazide derivatives, which were derived from the high throughput screening hit compound 1 (IC50=5700nM against PGE2 production), for a potent suppressor of PGE2 production is described. Subsequent optimization led to the identification of the potent lead compound 8n with IC50 values of 4.5 and 6.9nM, respectively, against LPS-induced PGE2 production and NO production in RAW 264.7 macrophage cells. In addition, 8n was about 30- and >150-fold more potent against mPGES-1 enzyme in a cell-free assay (IC50=70nM) than MK-886 and hit compound 1, respectively. Molecular docking suggests that compound 8n could inhibit PGE2 production by blocking the PGH2 binding site of human mPGES-1 enzyme.

Synthesis, structure determination, and biological evaluation of phenylsulfonyl hydrazide derivatives as potential anti-inflammatory agents.

In our previous research, a novel series of phenylsulfonyl hydrazide derivatives were found to reduce LPS-induced PGE2 levels in RAW 264.7 macrophage cells via an inhibition of mPGES-1 enzyme. Recently, it was found that a regioisomeric mixture of phenylsulfonyl hydrazide was formed depending on the reaction conditions, which favor either of two regioisomers. One regioisomer corresponds to a kinetic product (7a-7c) and the other regioisomer corresponds to a thermodynamic product (8a-8c). Among them, the structure of kinetic product 7b was confirmed by measuring single X-ray crystallography. In vitro PGE2 assay studies showed that the kinetic product (7a and 7b; IC50=0.69 and 0.55µM against PGE2) is generally more potent than the thermodynamic product (8a and 8b; IC50=>10 and 0.79µM against PGE2). A molecular docking study also exhibited that the kinetic product (7a) has a higher MolDock Score (-147.4) than that of 8a (-142.4), which is consistent with the PGE2 assay results. A new potent phenylsulfonyl hydrazide (7d; IC50=0.06µM against PGE2) without affecting COX-1 and COX-2 enzyme activities was identified based on these overall results.

Recovery from welding-fume-exposure-induced lung fibrosis and pulmonary function changes in sprague dawley rats.

Welder's pneumoconiosis has generally been determined as benign based on the absence of pulmonary function abnormalities in welders with marked radiographic abnormalities. Yet, there have also been several reports on welders with respiratory symptoms, indicating lung function impairment, X-ray abnormalities, and extensive fibrosis. Accordingly, this study attempted to investigate the inflammatory responses and pulmonary function changes in rats during a 60-day welding-fume-inhalation exposure period to elucidate the process of fibrosis. The rats were exposed to manual metal-arc stainless-steel welding fumes (MMA-SS) with total suspended particulate concentrations of 64.8 +/- 0.9 (low dose) and 107.8 +/- 2.6 mg/m3 (high dose) for 2 h per day in an inhalation chamber for 60 days. Animals were sacrificed after the initial 2-h exposure and after 15, 30, and 60 days, and the pulmonary function was also measured every week after the daily exposure. Elevated cellular differential counts were also measured in the acellular bronchoalveolar lavage fluid of the rats exposed to the MMA-SS fumes for 60 days. Among the pulmonary function test parameters, only the tidal volume showed a statistically significant and dose-dependent decrease after 35 to 60 days of MMA-SS welding-fume exposure. When the rats exposed to the welding fumes were left for 60 days to recover their lung function and cellular differentiation, recovery was observed in both the high and low-dose rats exposed up to 30 days, resulting in the disappearance of inflammatory cells and restoration of the tidal volume. The rats exposed for 60 days at the low dose also recovered from the inflammation and tidal volume loss, yet the rats exposed for 60 days at the high dose did not fully recover even after a 60-day recovery period. Therefore, when taken together, the results of the current study suggest that a decrease in the tidal volume could be used as an early indicator of pulmonary fibrosis induced by welding-fume exposure in Sprague Dawley rats, and fibrosis would seem to be preventable if the exposure is short-term and moderate.

Micronuclei induction by 13 week-inhalation of 1,1-dichloro-1-fluoroethane in Sprague-Dawley rats.

To investigate the genotoxic effect of l,1-dichloro-1-fluoroethane (HCFC-141b), which was currently widely used as a cleaning solvent in the electronic parts industry and suggested as a potential reproductive effector, in vivo micronucleus tests were performed. Groups of 10 male and 10 female Sprague-Dawley rats were exposed, by inhalation (6h/day, 5 days/week) to the vapors of HCFC-141b for 13 weeks using whole body exposure chambers at the concentrations of 0 (control), 1500, 3000, and 6000 ppm. The micronuclei frequencies among the polychromatic erythrocytes (PCEs) and the percentage of polychromatic erythrocytes among the total number of erythrocytes were counted in the bone marrow of rats, and body weights, organ weights, histopathology, clinical chemistry and hematologic changes were also observed. Statistically significant and dose-dependant increases were found in the micronuclei frequencies in the male rats (P<0.01), yet not in the females. The decreases in the percentage of polychromatic erythrocytes among the total number of erythrocytes were also statistically significant (P<0.05) in both sexes of the high concentration groups. However, no exposure-related effects of toxicological significance were noted with respect to organ weights, clinical chemistry and histopathology. Apart from it, only slightly decreased mean corpuscular hemoglobin concentration (MCHC) was noted in the females of 6000 ppm group (P<0.05). These results suggest that HCFC 141b can induce the genetic effects, micronuclei in the rat bone marrows, especially in males, at earlier stages before the other general clinical and histopathologic changes occur if with more prolonged exposure.

Inflammatory and genotoxic responses during 30-day welding-fume exposure period.

Welder's pneumoconiosis has generally been determined to be benign and unassociated with respiratory symptoms based on the absence of pulmonary-function abnormalities in welders with marked radiographic abnormalities. In previous studies, the current authors suggested a three-phase lung fibrosis process to study the pathological process of lung fibrosis and found that the critical point for recovery was after 30 days of welding-fume exposure at a high dose, at which point early and delicate fibrosis was observed in the perivascular and peribronchiolar regions. Accordingly, the current study investigated the inflammatory and genotoxic responses during a 30-day period of welding-fume exposure to elucidate the process of fibrosis. As such, rats were exposed to manual metal arc-stainless steel (MMA-SS) welding fumes at concentrations of 65.6 +/- 2.9 (low dose) and 116.8 +/- 3.9 mg/m3 (high dose) total suspended particulate for 2 h per day in an inhalation chamber for 30 days. Animals were sacrificed after the initial 2 h exposure, and after 15 and 30 days of exposure. The rats exposed to the welding fumes exhibited a statistically significant (P < 0.05) decrease in body weight when compared to the control during the 30-day exposure period, yet an elevated cellular differential count and higher levels of albumin, LDH, and beta-NAG, but not elevated TNF-alpha, and IL-1beta in the acellular bronchoalveolar lavage fluid. In addition, the DNA damage resulting from 30 days of welding-fume exposure was confirmed by a comet assay and the inmmunohistochemistry for 8-hydroxydeoxyguanine (8-OH-dG). Consequently, the elevated inflammatory and genotoxic indicators confirmed the lung injury and inflammation caused by the MMA-SS welding-fume exposure.

Changes of 8-OH-dG levels in DNA and its base excision repair activity in rat lungs after inhalation exposure to hexavalent chromium.

According to the toxicological and epidemiological studies, hexavalent chromium (Cr) is associated with increase of lung cancer risk. Genotoxic effects, such as chromosomal aberrations, and cellular oxidative DNA damage by reactive oxygen species produced by hexavalent Cr exposure may play an important role in its carcinogenesis. To clarify whether reactive oxygen species are involved in its mechanism, we examined the levels of 8-hydroxydeoxyguanine (8-OH-dG) and its base excision repair activities in the lung tissues of rats that repeatedly inhaled a sodium chromate solution mist for 1, 2, and 3 weeks. The levels of 8-OH-dG increased significantly in the lung tissues of the rats exposed for 1 week at the low concentration (0.18 mg/m(3), P<0.05), as compared with the controls. However, there was no difference in the 8-OH-dG levels at the higher concentration or with more than 2 weeks of exposure. The 8-OH-dG repair activities decreased in a dose-dependent manner during 2 weeks of exposure, on the contrary they recovered at 3 weeks of repeated exposure. These results suggest that the DNA damage caused by hexavalent Cr inhalation is induced by the generation of reactive oxygen species and by inhibition of base excision repair activity during the earlier phase of exposure. However, the 8-OH-dG levels and its repair activities recovered to the level of the controls in the latter inhalation exposure period.

Recent advances in occupational health research in Korea.

Korea has a short history in research on occupational health like as short history of industrialization. During last four decades, however, Korea has experienced what developed countries have experienced for more than a hundred year. Research on occupational health in Korea has also drastically developed. Since industrialization in 1970s, many workers were exposed to hazardous working environment and suffered from occupational accidents and diseases. The main research topics were pneumoconiosis, noise-induced hearing loss and some chemical poisoning. However, improving working condition was not the top priority until the late 1980s. Carbon disulfide poisoning gave a big impact to the society. It made the government take many actions to improve working condition through regulation, enforcement, supporting academia, raising research fund, and establishing a research institute. Recently, classical occupational diseases have decreased and the interest from researchers has also reduced. Many claims for stress-related cardio-cerebrovascular diseases brought much concern and research on job stress. Work-related musculoskeletal disease became a major issue. Many workers are interested in quality of life, such as health promotion. Therefore, research on health promotion, job stress, and psychological problem from work organization would be the main research topics in the future, although research on occupational diseases, such as asthma, cancer and various diseases caused by chemicals are still attractive to researchers.

Effect of water-soluble metal working fluid aerosols on respiratory system after 13 weeks of repeated inhalation exposure in F344 rats.

Three groups of male F344 rats were exposed to a water-soluble metal working fluid (MWF) aerosol at concentrations of 20, 60 or 180 mg/m3 for 6 h/day, five days a week, for 13 weeks in inhalation chambers. The aerosol particles were normally distributed and the mass median aerodynamic diameter was 1.56 microm. Despite the absence of clinical findings or significant changes in body weight during the 13-week exposure period, the numbers of white blood cells and lung weights were significantly higher at the end of the 13-week exposure period. Exposure to 20 mg/m3 of the MWF aerosol was found to have an effect on the respiratory system, including an accumulation of foamy macrophages in the bronchoalveolar lavage (BAL) fluid and thickening of the alveolar walls in the histopathology. The level of histamine and number of polymorphonuclear (PMN) cells were also higher in the BAL fluid from the rats exposed to 60 mg/m3 of the MWF aerosol, while the respiratory inflammation was most pronounced in the rats exposed to 180 mg/m3 of the MWF aerosol, including the accumulation of PMNs and foamy macrophages in the BAL cells, lung weight increase and thickening of the alveolar walls. Immunoglobulin IgG2a level was also lower in the sera from the rats exposed to 180 mg/m3 of the MWF aerosol. Therefore, even though no clinical symptoms were observed in the rats exposed to the high MWF concentration, respiratory inflammation was still induced by a relatively low concentration of the MWF, while the immune system was affected by the high MWF concentration.

Gene-expression profiling using suppression-subtractive hybridization and cDNA microarray in rat mononuclear cells in response to welding-fume exposure.

Welders with radiographic pneumoconiosis abnormalities have shown a gradual clearing of the X-ray identified effects following removal from exposure. In some cases, the pulmonary fibrosis associated with welding fumes appears in a more severe form in welders. Accordingly, for the early detection of welding-fume-exposure-induced pulmonary fibrosis, the gene expression profiles of peripheral mononuclear cells from rats exposed to welding fumes were studied using suppression-subtractive hybridization (SSH) and a cDNA microarray. As such, Sprague-Dawley rats were exposed to a stainless steel arc welding fume for 2 h/day in an inhalation chamber with a 1107.5 +/- 2.6 mg/m3 concentration of total suspended particulate (TSP) for 30 days. Thereafter, the total RNA was extracted from the peripheral blood mononuclear cells, the cDNA synthesized from the total RNA using the SMART PCR cDNA method, and SSH performed to select the welding-fume-exposure-regulated genes. The cDNAs identified by the SSH were then cloned into a plasmid miniprep, sequenced and the sequences analysed using the NCBI BLAST programme. In the SSH cloned cDNA microarray analysis, five genes were found to increase their expression by 1.9-fold or more, including Rgs 14, which plays an important function in cellular signal transduction pathways; meanwhile 36 genes remained the same and 30 genes decreased their expression by more than 59%, including genes associated with the immune response, transcription factors and tyrosine kinases. Among the 5200 genes analysed, 256 genes (5.1%) were found to increase their gene expression, while 742 genes (15%) decreased their gene expression in response to the welding-fume exposure when tested using a commercial 5.0k DNA microarray. Therefore, unlike exposure to other toxic substances, prolonged welding-fume exposure was found to substantially downregulate many genes.