Rifamycins, a group of bacterial RNA polymerase inhibitors, are the firstline antimicrobial drugs to treat tuberculosis. In light of the emergence of rifamycinresistant bacteria, development of new RNA polymerase inhibitors that kill rifamycinresistant bacteria with high bioavailability is urgent. Structural analysis of bacterial RNA polymerase in complex with inhibitors by crystallography and cryo-EM indicates that RNA polymerase inhibitors function through five distinct molecular mechanisms:inhibition of the extension of short RNA; competition with substrates; inhibition of the conformational change of the'bridge helix'; inhibition of clamp opening;inhibition of clamp closure. This article reviews the research progress of these five groups of RNA polymerase inhibitors to provide references for the modification of existing RNA polymerase inhibitors and the discovery of new RNA polymerase inhibitors.
Antitubercular Agents ; therapeutic use ; Bacteria ; drug effects ; enzymology ; DNA-Directed RNA Polymerases ; metabolism ; Drug Discovery ; trends ; Drug Resistance, Bacterial ; Enzyme Activation ; drug effects ; Enzyme Inhibitors ; pharmacology ; Humans ; RNA, Bacterial ; Tuberculosis ; drug therapy ; enzymology

Objective To evaluate the antagonistic effects of N-acetylcysteine (NAC) on mitogen-activated protein kinases (MAPK) pathway activation, oxidative stress and inflammatory responses in rats with lung injury induced by fine particulate matter (PM_2.5). Methods Forty eight male Wistar rats were randomly divided into six groups: blank control group (C1), water drip control group (C2), PM_2.5 exposed group (P), low-dose NAC treated and PM_2.5 exposed group (L), middle-dose NAC treated and PM_2.5 exposed group (M), and high-dose NAC treated and PM_2.5 exposed group (H). PM_2.5 suspension (7.5 mg/kg) was administered tracheally once a week for four times. NAC of 125 mg/kg, 250 mg/kg and 500 mg/kg was delivered intragastrically to L, M and H group respectively by gavage (10 ml/kg) for six days before PM_2.5 exposure. The histopathological changes and human mucin 5 subtype AC (MUC5AC) content in lung tissue of rats were evaluated. We investigated IL-6 in serum and bronchoalveolar lavage fluid (BALF) by Enzyme-linked immunosorbent assay (ELISA), MUC5AC in lung tissue homogenate by ELISA, glutathione peroxidase (GSH-PX) in serum and BALF by spectrophotometry, and the expression of p-ERK1/2, p-JNK1/2 and p-p38 proteins by Western blot. All the measurements were analyzed and compared statistically. Results Lung tissue of rats exposed to PM_2.5 showed histological destruction and increased mucus secretion of bronchial epithelial cells. Rats receiving NAC treatment showed less histological destruction and mucus secretion. Of P, L, M and H group, MUC5AC in lung tissue, IL-6 in serum and BALF were higher than controls (C1 and C2) (all P<0.05), with the highest levels found in the P group and a decreasing trend with increase of NAC dose. The activity of GSH-PX in serum and BALF of PM_2.5 exposed rats (P, L, M and H) was lower than that of controls (all P<0.05), with higher activities found in NAC treated rats (L, M, and H), and an increasing trend with increase of NAC dose. The expressions of p-ERK1/2, p-JNK1/2 and p-p38 proteins in PM_2.5 exposed lung tissue (P, L, M and H) was higher than controls (all P<0.05), with decreased levels and dose dependent downregulation found in NAC treated rats. Conclusion NAC can antagonize major MAPK pathway activation, lung oxidative stress and inflammatory injury induced by PM_2.5 in rats.
Acetylcysteine/pharmacology* ; Animals ; Bronchoalveolar Lavage Fluid ; Enzyme Activation/drug effects* ; Glutathione Peroxidase/metabolism* ; Inflammation/pathology* ; Interleukin-6/metabolism* ; Lung/pathology* ; Lung Injury/pathology* ; Male ; Mitogen-Activated Protein Kinases/metabolism* ; Mucin 5AC/metabolism* ; Mucus/metabolism* ; Oxidative Stress/drug effects* ; Particle Size ; Particulate Matter/toxicity* ; Phosphorylation/drug effects* ; Rats, Wistar

Gnaphalium affine D. Don, a medicinal and edible plant, has been used to treat gout in traditional Chinese medicine and popularly consumed in China for a long time. A detailed phytochemical investigation on the aerial part of G. affine led to the isolation of two new esters of caffeoylquinic acid named (-) ethyl 1, 4-di-O-caffeoylquinate (1) and (-) methyl 1, 4-di-O-caffeoylquinate (2), together with 35 known compounds (3-37). Their structures were elucidated by spectroscopic data and first-order multiplet analysis. All the isolated compounds were tested for their xanthine oxidase inhibitory activity with an in vitro enzyme inhibitory screening assay. Among the tested compounds, 1 (IC 11.94 μmol·L) and 2 (IC 15.04 μmol·L) showed a good inhibitory activity. The current results supported the medical use of the plant.
Adenine ; analogs & derivatives ; chemistry ; isolation & purification ; Drugs, Chinese Herbal ; chemistry ; pharmacology ; Enzyme Activation ; drug effects ; Flavonoids ; chemistry ; isolation & purification ; Gnaphalium ; chemistry ; Gout Suppressants ; chemistry ; isolation & purification ; pharmacology ; Hydroxybenzoates ; chemistry ; isolation & purification ; Molecular Structure ; Nuclear Magnetic Resonance, Biomolecular ; Phytochemicals ; chemistry ; isolation & purification ; pharmacology ; Plant Components, Aerial ; chemistry ; Plant Extracts ; chemistry ; isolation & purification ; pharmacology ; Quinic Acid ; analogs & derivatives ; chemistry ; isolation & purification ; Xanthine Oxidase ; antagonists & inhibitors

OBJECTIVETo investigate the effect of telomerase activation on biological behaviors of neural stem cells after hypoxic-ischemic insults.

METHODSThe neural stem cells passaged in vitro were divided into four groups: control, oxygen-glucose deprivation (OGD), OGD+cycloastragenol (CAG) high concentration (final concentration of 25 μM), and OGD+CAG low concentration (final concentration of 10 μM). The latter three groups were subjected to OGD. Telomerase reverse transcriptase (TERT) expression level was evaluated by Western blot. Telomerase activity was detected by telomerase repeat amplification protocol (TRAP). Cell number and neural sphere diameter were measured under a microscope. The activity of lactate dehydrogenase (LDH) was examined by chemiluminescence. Cell proliferation rate and apoptosis were detected by flow cytometry.

RESULTSAfter OGD insults, obvious injury of neural stem cells was observed, including less cell number, smaller neural sphere, more dead cells, lower proliferation rate and decreased survival rate. In CAG-treated groups, there were higher TERT expression level and telomerase activity compared with the control group (P<0.05). In comparison with the OGD group, CAG treatment attenuated cell loss (P<0.05) and neural sphere diameter decrease (P<0.05), promoted cell proliferation (P<0.05), and increased cell survival rate (P<0.05). Low and high concentrations of CAG had similar effects on proliferation and survival of neural stem cells (P>0.05). In the normal cultural condition, CAG treatment also enhanced TERT expression (P<0.05) and increased cell numbers (P<0.05) and neural sphere diameter (P<0.05) compared with the control group.

CONCLUSIONSTelomerase activation can promote the proliferation and improve survival of neural stem cells under the state of hypoxic-ischemic insults, suggesting telomerase activators might be potential agents for the therapy of hypoxic-ischemic brain injury.

Animals ; Cell Survival ; drug effects ; Enzyme Activation ; Hypoxia-Ischemia, Brain ; etiology ; Neural Stem Cells ; drug effects ; physiology ; Rats ; Sapogenins ; pharmacology ; Telomerase ; physiology

Specific gene expressions of host cells by spontaneous STAT6 phosphorylation are major strategy for the survival of intracellular Toxoplasma gondii against parasiticidal events through STAT1 phosphorylation by infection provoked IFN-γ. We determined the effects of small molecules of tyrosine kinase inhibitors (TKIs) on the growth of T. gondii and on the relationship with STAT1 and STAT6 phosphorylation in ARPE-19 cells. We counted the number of T. gondii RH tachyzoites per parasitophorous vacuolar membrane (PVM) after treatment with TKIs at 12-hr intervals for 72 hr. The change of STAT6 phosphorylation was assessed via western blot and immunofluorescence assay. Among the tested TKIs, Afatinib (pan ErbB/EGFR inhibitor, 5 µM) inhibited 98.0% of the growth of T. gondii, which was comparable to pyrimethamine (5 µM) at 96.9% and followed by Erlotinib (ErbB1/EGFR inhibitor, 20 µM) at 33.8% and Sunitinib (PDGFR or c-Kit inhibitor, 10 µM) at 21.3%. In the early stage of the infection (2, 4, and 8 hr after T. gondii challenge), Afatinib inhibited the phosphorylation of STAT6 in western blot and immunofluorescence assay. Both JAK1 and JAK3, the upper hierarchical kinases of cytokine signaling, were strongly phosphorylated at 2 hr and then disappeared entirely after 4 hr. Some TKIs, especially the EGFR inhibitors, might play an important role in the inhibition of intracellular replication of T. gondii through the inhibition of the direct phosphorylation of STAT6 by T. gondii.
Antiparasitic Agents/pharmacology ; Blotting, Western ; Cell Line ; Enzyme Activation/drug effects ; Fluorescent Antibody Technique ; Humans ; Janus Kinase 1/metabolism ; Janus Kinase 3/metabolism ; Phosphorylation/drug effects ; Quinazolines/*pharmacology ; STAT6 Transcription Factor/*metabolism ; Signal Transduction/*drug effects ; Toxoplasma/*drug effects/physiology ; Toxoplasmosis/physiopathology

Gap junctions mediate direct communication between cells; however, toxicological cascade triggered by nonessential metals can abrogate cellular signaling mediated by gap junctions. Although cadmium (Cd) is known to induce apoptosis in organs and tissues, the mechanisms that underlie gap junction activity in Cd-induced apoptosis in BRL 3A rat liver cells has yet to be established. In this study, we showed that Cd treatment decreased the cell index (a measure of cellular electrical impedance) in BRL 3A cells. Mechanistically, we found that Cd exposure decreased expression of connexin 43 (Cx43), increased expression of p-Cx43 and elevated intracellular free Ca2+ concentration, corresponding to a decrease in gap junctional intercellular communication. Gap junction blockage pretreatment with 18β-glycyrrhizic acid (GA) promoted Cd-induced apoptosis, involving changes in expression of Bax, Bcl-2, caspase-3 and the mitochondrial transmembrane electrical potential (Δψm). Additionally, GA was found to enhance ERK and p38 activation during Cd-induced activation of mitogen-activated protein kinases, but had no significant effect on JNK activation. Our results indicated the apoptosis-related proteins and the ERK and p38 signaling pathways may participate in gap junction blockage promoting Cd-induced apoptosis in BRL 3A cells.
Animals ; Apoptosis/*drug effects ; Cadmium/*toxicity ; Calcium/metabolism ; Cell Communication/drug effects ; Connexin 43/genetics ; Enzyme Activation/drug effects ; Gap Junctions/*drug effects ; Gene Expression Regulation/drug effects ; Hepatocytes/cytology/*drug effects ; Rats ; Signal Transduction/drug effects

Matrine (MT), the effective component of Sophora flavescens Ait, has been shown to have anti-inflammation, immune-suppressive, anti-tumor, and anti-hepatic fibrosis activities. However, the pharmacological effects of MT still need to be strengthened due to its relatively low efficacy and short half-life. In the present study, we report a more effective thio derivative of MT, MD-1, and its inhibitory effects on the activation of hepatic stellate cells (HSCs) in both cell culture and animal models. Cytological experiments showed that MD-1 can inhibit the proliferation of HSC-T6 cells with a half-maximal inhibitory concentration (IC50) of 62 μmol/L. In addition, MD-1 more strongly inhibits the migration of HSC-T6 cells compared to MT and can more effectively induce G0/G1 arrest and apoptosis. Investigating the biological mechanisms underlying anti-hepatic fibrosis in the presence of MD-1, we found that MD-1 can bind the epidermal growth factor receptor (EGFR) on the surface of HSC-T6 cells, which can further inhibit the phosphorylation of EGFR and its downstream protein kinase B (Akt), resulting in decreased expression of cyclin D1 and eventual inhibition of the activation of HSC-T6 cells. Furthermore, in rats with dimethylnitrosamine (DMN)-induced hepatic fibrosis, MD-1 slowed the development and progression of hepatic fibrosis, protecting hepatic parenchymal cells and improving hepatic functions. Therefore, MD-1 is a potential drug for anti-hepatic fibrosis.
Alkaloids ; pharmacology ; Animals ; Cell Line ; Cyclin D1 ; metabolism ; Dimethylnitrosamine ; toxicity ; Enzyme Activation ; drug effects ; ErbB Receptors ; metabolism ; G1 Phase Cell Cycle Checkpoints ; drug effects ; Hepatic Stellate Cells ; metabolism ; pathology ; Liver Cirrhosis ; chemically induced ; metabolism ; pathology ; prevention & control ; Phosphorylation ; drug effects ; Proto-Oncogene Proteins c-akt ; metabolism ; Quinolizines ; pharmacology ; Rats

Drugs are exogenous compounds for human bodies, and will be metabolized by many enzymes after administration. CYP450 enzyme, as a major metabolic enzyme, is an important phase I drug metabolizing enzyme. In human bodies, about 75% of drug metabolism is conducted by CYP450 enzymes, and CYP450 enzymes is the key factor for drug interactions between traditional Chinese medicine( TCM) -TCM, TCM-medicine and other drug combination. In order to make clear the interaction between metabolic enzymes and TCM metabolism, we generally chose the enzymatic activity as an evaluation index. That is to say, the enhancement or reduction of CYP450 enzyme activity was used to infer the inducing or inhibitory effect of active ingredients and extracts of traditional Chinese medicine on enzymes. At present, the common method for measuring metabolic enzyme activity is Cocktail probe drugs, and it is the key to select the suitable probe substrates. This is of great significance for study drug's absorption, distribution, metabolism and excretion (ADME) process in organisms. The study focuses on the interaction between TCMs, active ingredients, herbal extracts, cocktail probe substrates as well as CYP450 enzymes, in order to guide future studies.
Animals ; Cytochrome P-450 Enzyme Inhibitors ; metabolism ; pharmacology ; Cytochrome P-450 Enzyme System ; chemistry ; metabolism ; Drugs, Chinese Herbal ; metabolism ; pharmacology ; Enzyme Activation ; drug effects ; Enzyme Activators ; metabolism ; pharmacology ; Humans

Retinoid X receptor α (RXRα) and its N-terminally truncated version tRXRα play important roles in tumorigenesis, while some RXRα ligands possess potent anti-cancer activities by targeting and modulating the tumorigenic effects of RXRα and tRXRα. Here we describe NSC-640358 (N-6), a thiazolyl-pyrazole derived compound, acts as a selective RXRα ligand to promote TNFα-mediated apoptosis of cancer cell. N-6 binds to RXRα and inhibits the transactivation of RXRα homodimer and RXRα/TR3 heterodimer. Using mutational analysis and computational study, we determine that Arg316 in RXRα, essential for 9-cis-retinoic acid binding and activating RXRα transactivation, is not required for antagonist effects of N-6, whereas Trp305 and Phe313 are crucial for N-6 binding to RXRα by forming extra π-π stacking interactions with N-6, indicating a distinct RXRα binding mode of N-6. N-6 inhibits TR3-stimulated transactivation of Gal4-DBD-RXRα-LBD by binding to the ligand binding pocket of RXRα-LBD, suggesting a strategy to regulate TR3 activity indirectly by using small molecules to target its interacting partner RXRα. For its physiological activities, we show that N-6 strongly inhibits tumor necrosis factor α (TNFα)-induced AKT activation and stimulates TNFα-mediated apoptosis in cancer cells in an RXRα/tRXRα dependent manner. The inhibition of TNFα-induced tRXRα/p85α complex formation by N-6 implies that N-6 targets tRXRα to inhibit TNFα-induced AKT activation and to induce cancer cell apoptosis. Together, our data illustrate a new RXRα ligand with a unique RXRα binding mode and the abilities to regulate TR3 activity indirectly and to induce TNFα-mediated cancer cell apoptosis by targeting RXRα/tRXRα.
Apoptosis ; drug effects ; Cell Line, Tumor ; Enzyme Activation ; drug effects ; Humans ; Ligands ; Molecular Docking Simulation ; Nuclear Receptor Subfamily 4, Group A, Member 1 ; genetics ; metabolism ; Oximes ; metabolism ; pharmacology ; Protein Conformation ; Proto-Oncogene Proteins c-akt ; metabolism ; Pyrazoles ; metabolism ; pharmacology ; Retinoid X Receptor alpha ; chemistry ; genetics ; metabolism ; Thiazoles ; metabolism ; pharmacology ; Transcription, Genetic ; drug effects ; Transcriptional Activation ; drug effects ; Tumor Necrosis Factor-alpha ; metabolism

Dioscin is a natural steroid saponin derived from several plants, showing potent anti-cancer effect against a variety of tumor cell lines. In the present study, we investigated the anti-cancer activity of dioscin against human LNCaP cells, and evaluated the possible mechanism involved in its antineoplastic action. It was found that dioscin (1, 2 and 4 μmol/L) could significantly inhibit the viability of LNCaP cells in a time- and concentration-dependent manner. Flow cytometry revealed that the apoptosis rate was increased after treatment of LNCaP cells with dioscin for 24 h, indicating that apoptosis was an important mechanism by which dioscin inhibited cancer. Western blotting was employed to detect the expression of caspase-3, Bcl-2 and Bax in LNCaP cells. The expression of cleaved caspase-3 was significantly increased, and meanwhile procaspase-3 was markedly decreased. The expression of anti-apoptotic protein Bcl-2 was down-regulated, whereas the pro-apoptotic protein Bax was up-regulated. Moreover, the Bcl-2/Bax ratio was drastically decreased. These results suggested that dioscin possessed potential anti-tumor activity in human LNCaP cells through the apoptosis pathway, which might be associated with caspase-3 and Bcl-2 protein family.
Apoptosis ; drug effects ; Blotting, Western ; Caspase 3 ; metabolism ; Cell Line, Tumor ; Cell Survival ; drug effects ; Diosgenin ; analogs & derivatives ; chemistry ; pharmacology ; Dose-Response Relationship, Drug ; Enzyme Activation ; drug effects ; Flow Cytometry ; Humans ; Male ; Molecular Structure ; Prostatic Neoplasms ; metabolism ; pathology ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; Time Factors ; bcl-2-Associated X Protein ; metabolism