• Journal of Korean Society for Atmospheric Environment
• /
• v.18 no.E2
• /
• pp.121-128
• /
• 2002

This study was carried out to investigate if nitric oxide synthase (NOS) inhibitors modulate airway inflammation induced by diesel exhaust particles (DEP). N$\^$G/-nitro-L-arginine methyl ester (L-NAME), a potent constitutive NOS (cNOS) inhibitor, and aminoguanidine (AG), a selective inducible NOS (iNOS) inhibitor, were administered to mice in their drinking water for 7 weeks. Airway inflammation was elicited by the repeated intratracheal administration of DEP. The results showed that macrophages, inflammatory eosinophils and neutrophils in bronchoalveolar lavage (BAL) fluids by intratracheal DEP instillation were significantly suppressed in the mice treated with two NOS inhibitors toghther with DEP. The suppression of these cells was more effective in AG treated groups than in L -NAME treated groups. NOS inhibitor treatment also reduced interleukin -5 (IL-5 in the BAL fluids and lung homogenates. Additionally, it was found that eosinophil peroxidase (EPO) activity in the BAL fluids was also decreased by NOS inhibitor treatment. These results suggest that nitric oxide (NO) is produced in airway inflammation by repeated DEP instillation, and that iNOS inhibition as well as cNOS inhibition can play a modulating role in this airway inflammation by DEP.

• The Korean Journal of Pharmacology
• /
• v.31 no.2
• /
• pp.233-239
• /
• 1995

To verify the effect of immunosuppressants on the endotoxin-induced increase in iNOS activity, the action of immunosuppressants, dexamethasone (1.5 mg/kg), azathioprine (5 mg/kg/day) and cyclosporine (10 mg/kg), were evaluated in mice pretreated with LPS. The intraperitoneal injection of lipopolysaccharide (10 mg/kg) increased the nitric oxide synthase (NOS) activity in the brain and liver to maximum at 1 and 3 hours, respectively. The increase in NOS activity was blocked by the treatment with NOS inhibitor, LNAME(300 mg/kg) and aminoguanidine(100 mg/kg); a protein inhibitor, cycloheximide (10 mg/kg); and a transcription inhibitor of inducible NOS(iNOS), dexamethasone(1.5 mg/kg). Immunosuppressants, azathioprine (5 mg/kg) and cyclosporine (10 mg/kg), effectively blocked the increase in NOS activity. These results suggest that iNOS expression plays an important role in LPS-induced the increase in NOS activity and that immunosuppressants can be used as candidate for therapeutic agents in endotoxemia.

• The Korean Journal of Physiology and Pharmacology
• /
• v.7 no.5
• /
• pp.283-287
• /
• 2003

While nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) is beneficial for host survival, it is also detrimental to the host. Thus, regulation of iNOS gene expression may be an effective therapeutic strategy for the prevention of unwanted reactions at various pathologic conditions. During the screening process for the possible iNOS regulators, we observed that esculetin is a potent inhibitor of cytokine-induced iNOS expression. The treatment of 3T3-L1 adipocytes with the tumor necrosis factor-${\alpha}$ (TNF) induced iNOS expression, leading to enhanced NO production. TNF-induced NO production was inhibited by esculetin in a dose-dependent manner. Esculetin inhibited the TNF-induced NO production at the transcriptional level through suppression of iNOS mRNA and subsequent iNOS protein expression. These results suggest esculetin, a component of natural products, as a naturally occurring, nontoxic means to attenuate iNOS expression and NO-mediated cytotoxicity.

• BMB Reports
• /
• v.41 no.1
• /
• pp.79-85
• /
• 2008

The source of nitric oxide (NO) in plants is unclear and it has been reported NO can be produced by nitric oxide synthase (NOS) like enzymes and by nitrate reductase (NR). Here we used wild-type, Atnos1 mutant and nia1, nia2 NR-deficient mutant plants of Arabidopsis thaliana to investigate the potential source of NO production in response to Verticillium dahliae toxins (VD-toxins). The results revealed that NO production is much higher in wild-type and Atnos1 mutant than in nia1, nia2 NR-deficient mutants. The NR inhibitor had a significant effect on VD-toxins-induced NO production; whereas NOS inhibitor had a slight effect. NR activity was significantly implicated in NO production. The results indicated that as NO was induced in response to VD-toxins in Arabidopsis, the major source was the NR pathway. The production of NOS-system appeared to be secondary.

• The Korean Journal of Physiology and Pharmacology
• /
• v.8 no.3
• /
• pp.161-165
• /
• 2004

Exogenous carbon monoxide (0.2%) increases L-type calcium $(Ca^{2+})$ current in human jejunal circular smooth muscle cells. The stimulatory effect of carbon monoxide (CO) on L-type $Ca^{2+}$ current is inhibited by pre-application of L-NNA, a classical competitive inhibitor of nitric oxide synthase (NOS) with no significant isoform selectivity (Lim, 2003). In the present study, we investigated which isoform of NOS affected CO induced stimulation of L-type $Ca^{2+}$ current in human jejunal circular smooth muscle cells. Cells were voltage clamped by whole-cell mode patch clamp technique, and membrane currents were recorded with 10 mM barium as the charge carrier. Before the addition of CO, cells were pretreated with each inhibitor of three NOS isoforms for 15 minutes. CO-stimulating effect on L-type $Ca^{2+}$ current was partially blocked by N-(3-(Amino-methyl) benzyl) acetamidine 2HCl (1400W, an iNOS inhibitor). On the other hand, 3-bromo-7-nitroindazole (BNI, a nNOS inhibitor) or $N^5-(1-Iminoethyl)-L-ornithine$ dihydrochloride (L-NIO, an eNOS inhibitor) completely blocked the CO effect. These data suggest that low dose of exogenous CO may stimulate all NOS isoforms to increase L-type $Ca^{2+}$ channel through nitric oxide (NO) pathway in human jejunal circular smooth muscle cells.

• Archives of Pharmacal Research
• /
• v.26 no.4
• /
• pp.301-305
• /
• 2003

Nitric oxide (NO) is an important bioactive agent that mediates a wide variety of physiological and pathophysiological events. NO overproduction by inducible nitric oxide synthase (iNOS) results in severe hypotension and inflammation. This investigation is part of a study to discover new iNOS inhibitors from medicinal plants using a macrophage cell culture system. Two sesquiterpenes (1 and 2) were isolated from Artemisia iwayomogi (Compositae) and were found to inhibit NO synthesis ($IC_{50} 3.64 \mu g/mL and 2.81 \mu$g/mL, respectively) in lipopolysaccharide (LPS)-activated RAW 264.7 cells. Their structures were identified as 3-Ο-methyl-iso-secotanapartholide (1) and iso-secotanapartholide (2). Compounds 1 and 2 inhibited the LPS-induced expression of the iNOS enzyme in the RAW 264.7 cells. The inhibition of NO production via the down regulation of iNOS expression may substantially modulate the inflammatory responses.

• The Korean Journal of Pain
• /
• v.13 no.1
• /
• pp.19-30
• /
• 2000

Background: Partial nerve injury to a peripheral nerve may induce the development of neuropathic pain which is characterized by symptoms such as spontaneous burning pain, allodynia and hyperalgesia. Though underlying mechanism has not fully understood, sensitization of dorsal horn neurons may contribute to generate such symptoms. Nitric oxide acts as an inter- and intracellular messenger in the nervous system and is produced from L-arginine by nitric oxide synthase (NOS). Evidence is accumulating which indicate that nitric oxide may mediate nociceptive information transmission. Recently, it has been reported that NOS inhibitor suppresses neuropathic pain behavior in an neuropathic pain animal model. This study was conducted to determine whether nitric oxide could be involved in the sensitization of dorsal horn neurons in neuropathic animal model. Methods: Neuropathic animal model was made by tightly ligating the left L5 and L6 spinal nerves and we examined the effects of iontophoretically applied NOS inhibitor (L-NAME) on the dorsal horn neuron's responses to mechanical stimuli within the receptive fields. Results: In normal animals, NOS inhibitor (L-NAME) specifically suppressed the responses to the noxious mechanical stimuli. In neuropathic animals, the dorsal horn neuron's responses to mechanical stimuli were enhanced and NOS inhibitor suppressed the dorsal horn neuron's enhanced responses to non-noxious stimuli as well as those to noxious ones. Conclusions: These results suggest that nitric oxide may mediate nociceptive transmission in normal animal and also mediate sensitization of dorsal horn neurons in neuropathic pain state.

• Archives of Pharmacal Research
• /
• v.21 no.4
• /
• pp.481-484
• /
• 1998

In activated macrophages the inducible form of nitric oxide synthase (i-NOS) generates high amounts of toxic mediator, nitric oxide (NO) which contributes to the circulatory failure associated with septic shock. A sesquiterpene lactone compound (yomogin) isolated from medicinal plant Artemisia princeps Pampan inhibited the production of NO in LPS-activated RAW 264.7 cells by suppressing i-NOS enzyme expression. Thus, yomogin may be a useful candidate for the development of new drugs to treat endotoxemia and inflammation accompanied by the overproduction of NO.

• Biomolecules & Therapeutics
• /
• v.14 no.3
• /
• pp.143-147
• /
• 2006

In the mouse leukemic monocyte cell line RAW 264.7, the vacuolar-type $(H^+)$-ATPase (V-ATPase) inhibitor bafilomycin $A_1$ at 10 and 100 nM decreased cell growth and survival as determined by 3-(4,5-dimethyl(thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in a concentration-dependent manner. At such concentrations, bafilomycin $A_1$ induced nitric oxide (NO) production through the expression of inducible nitric oxide synthase (iNOS). The bafilomycin $A_1$-induced NO production was inhibited by the NOS inhibitor $N^G$-monomethyl-L-arginine acetate (L-NMMA). Our findings suggest that the V-ATPase inhibitor bafilomycin $A_1$ induces NO production through the expression of iNOS protein.

• Biomedical Science Letters
• /
• v.19 no.3
• /
• pp.180-187
• /
• 2013

Hypoxia is an integral part of the environment during luteolysis. In this study we examined whether hypoxia could directly stimulate endothelial cells to produce nitric oxide (NO). Endothelial cells were cultured in hypoxic (5% $O_2$) or normoxic (20% $O_2$) conditions and the levels of total NO, inducible NO and endothelial NO was measured. We found that hypoxia but not normoxia upregulated NO production. The increased NO levels correlated with increased inducible NO synthase (iNOS) expression whereas expression of endothelial NOS (eNOS) expression remained constant. Addition of the iNOS specific inhibitor 1400W to hypoxic cultures prevented NO production suggesting that hypoxia-induced NO production in endothelial cells was due mainly to upregulation of iNOS. We also found that prostaglandin $F_{2{\alpha}}$ (PGF) production was unaffected by hypoxia suggesting that upregulation of NO was not due to increased synthesis of PGF. In summary, we report that endothelial cells cultured under hypoxic conditions produce NO via the iNOS pathway. This study provides the importance of the relation between the hypoxic environment and the induction of NO by endothelial cells during regression of the corpus luteum in the ovary.