Inhibition Of iNOS Expression Research Articles

Nitrosoglutathione modulation of platelet activation and nitric oxide synthase expression in promotion of flap survival after ischemia/reperfusion injury 1

Background Recent studies have shown that platelets play an important role in the pathogenesis of reperfusion injury. Using an inferior epigastric artery skin flap as a flap ischemia/reperfusion (I/R) injury model, we investigated whether the administration of a nitric oxide (NO) donor, nitrosoglutathione (GSNO), could decrease platelet activation and modulate the NO synthase (NOS) activity of platelets and promote flap survival. Methods Thirty minutes before flap reperfusion, normal saline (1 mL), nitrosoglutathione (GSNO 0.2, 0.6, 3 mg/kg), or N G-nitro- l-arginine-methyl ester (450 mg/kg) was injected intravenously in 10 rats, respectively. The p-selectin (CD62P) expression of platelet activation was detected by a flow cytometry. Immunohistochemical staining was performed to investigate the CD62P deposition on the microvasculature of the flap vessels. NOS isoform expression in the platelets was evaluated by Western blot. Tissue perfusion was monitored by using laser-Doppler flowmetry. Survival areas were assessed at 7 days postoperatively Results An optimal dose of GSNO (0.6 mg/kg), significantly decreased in CD62P expression on platelets ( P < 0.001) and its deposition on the flap vessels, selectively suppressed iNOS induction of platelet, and significantly improved blood perfusion and the flap survival rate (59.8 ± 4.9% versus 22.1 ± 6.1%, P < 0.001). In contrast, the NO synthase inhibitor, N G-nitro- l-arginine methyl ester, although inhibiting iNOS expression of platelets, compromised platelet activation, tissue perfusion, and flap survival. Conclusion This study suggests that GSNO can appropriately donate NO to suppress platelet activation and platelet iNOS induction, resulting in less platelet activation, better blood perfusion, and flap survival after I/R injury.

Angiotensin II Differentially Regulates Interleukin-1-β-inducible NO Synthase (iNOS) and Vascular Cell Adhesion Molecule-1 (VCAM-1) Expression: ROLE OF p38 MAPK

Angiotensin II is implicated in pathophysiological processes associated with vascular injury and repair, which include regulating the expression of numerous NF-kappaB-dependent genes. The present study examined the effect of angiotensin II on interleukin-1beta-induced NF-kappaB activation and the subsequent expression of inducible NO synthase (iNOS) and vascular cell adhesion molecule-1 (VCAM-1) in cultured rat vascular smooth muscle cells. Neither NF-kappaB activation nor iNOS or VCAM-1 expression was induced in cells treated with angiotensin II alone. However, when added together with interleukin-1beta, angiotensin II, through activation of the AT(1) receptor, inhibited iNOS expression and enhanced VCAM-1 expression induced by the cytokine. The inhibitory effect of angiotensin II on iNOS expression was associated with a down-regulation of the sustained activation of extracellular signal-regulated kinase (ERK) and NF-kappaB by interleukin-1beta, whereas the effect on VCAM-1 was independent of ERK activation. The effect of angiotensin II on iNOS was abolished by inhibition of p38 mitogen-activated protein kinase (MAPK) with SB203580, but not by inhibition of PI3 kinase with wortmannin or stress-activated protein kinase/c-Jun NH(2)-terminal kinase (JNK) with JNK inhibitor II. Thus, angiotensin II, by a mechanism that requires the participation of p38 MAPK, differentially regulates the expression of NF-kappaB-dependent genes in response to interleukin-1beta stimulation by controlling the duration of activation of ERK and NF-kappaB.

Annexin 1: more than an anti-phospholipase protein.

Annexin 1 (ANXA1) is the first characterized member of the annexin family of proteins able to bind (i.e. to annex) to cellular membranes in a calcium-dependent manner. ANXA1 may be induced by glucocorticoids in inflammatory cells and shares with these drugs many anti-inflammatory effects. Originally described as a phospholipase A2 (PLA2)-inhibitory protein, ANXA1 can affect many components of the inflammatory reaction besides the metabolism of arachidonic acid. Recent data have shown that ANXA1 may specifically target cytosolic PLA2 by both direct enzyme inhibition and suppression of cytokine-induced activation of the enzyme. ANXA1 inhibits the expression and/or activity of other inflammatory enzymes like inducible nitric oxide synthase (iNOS) in macrophages and inducible cyclooxygenase (COX-2) in activated microglia. The inhibition of iNOS expression may be caused by the stimulation of IL-10 release induced by ANXA1 in macrophages. Like glucocorticoids, ANXA1 exerts profound inhibitory effects on both neutrophil and monocyte migration in inflammation. Several mechanisms may contribute to the protein effect on cell migration, namely the activation of receptors like the formyl peptide receptor (FPR) and the lipoxin A4 receptor (ALXR), the shedding of L-selectin, the binding to alpha4beta1 integrin and carboxylated N-glycans. Furthermore, again mimicking the action of glucocorticoids, ANXA1 promotes inflammatory cell apoptosis associated with transient rise in intracellular calcium and caspase-3 activation. Finally, ANXA1 has been recently identified as one of the 'eat-me' signals on apoptotic cells to be recognised and ingested by phagocytes. Thus, ANXA1 may contribute to the anti-inflammatory signalling that allows safe post-apoptotic clearance of dead cells.

JNK signaling involved in the effects of cyclic AMP on IL-1β plus IFNγ-induced inducible nitric oxide synthase expression in hepatocytes

cAMP significantly inhibits IL-1β+IFNγ-induced iNOS gene expression in hepatocytes, but the signaling pathways responsible for the effect are not known. PKA inhibitors, H89, PKI, and KT5720, had no effect on the recovery of the inhibitory effects of cAMP on cytokine-induced hepatocyte iNOS expression and activity. The JNK inhibitor, SP 600125, effectively reversed the inhibitory effects of cAMP on iNOS expression and significantly increased iNOS promoter activity. A cAMP analogue, dbcAMP, significantly induced JNK signaling and increased AP-1 binding activity in hepatocytes. The JNK activator, anisomycin, inhibited iNOS expression and transcription in hepatocytes as well as AP-1 binding activity; and SP600125 reversed this effect of anisomycin. Overexpression of c-Jun in hepatocytes inhibited IL-1β+IFNγ-induced nitrite accumulation and iNOS promoter activity while dominant negative c-Jun partially reversed the inhibitory effects of cAMP on nitrite accumulation. We conclude that JNK signaling plays an important role in the inhibitory effects of cAMP on IL-1β+IFNγ-induced iNOS gene expression in cultured hepatocytes.

Suppressive effect of Kanzo-bushi-to, a Kampo medicine, on collagen-induced arthritis.

Kanzo-bushi-to (KBT) is a traditional Japanese herbal medicine (Kampo medicine), which is used in Japan to treat rheumatoid arthritis. In the present study, we investigated the suppressive effect of KBT on collagen-induced arthritis (CIA) and further studied the underlying mechanism. CIA was induced in male DBA/1J mice by immunization with bovine type II collagen, followed by a booster injection 21 d later. KBT was given at a dose of 430 mg/kg/d from three days before the first immunization to the end of the experiment. KBT suppressed CIA development effectively and further protected focal bone erosion and bone destruction as evidenced by the reduced histological score. Histochemical examination revealed that KBT decreased TRAP-positive cells at the synovium-bone interface and at the sites of focal bone erosion, coincident with the findings that RANKL/OPG mRNA ratio was significantly reduced by KBT treatment. KBT also decreased mRNA levels of M-CSF and iNOS in joints and of iNOS in peritoneal macrophages. In conclusion, KBT prevented osteoclast generation by decreasing RANKL/OPG ratio and M-CSF mRNA levels, resulting in reduction in bone erosion and destruction. In addition, KBT has anti-inflammatory effect such as the suppression of iNOS expression in peritoneal macrophages and joints of CIA mice. These finding suggests that KBT is a potential new therapeutic agent for the treatment of RA.

1-α,25-Dihydroxyvitamin D 3 regulates inducible nitric oxide synthase messenger RNA expression and nitric oxide release in macrophage-like RAW 264.7 cells

The expression of inducible nitric oxide synthase (iNOS) expression and release of nitric oxide (NO) from macrophages are markedly increased in granulomatous infections. Activation of macrophages 1α-hydroxylase results in an increase of 1α,25-dihydroxyvitamin D 3 [1,25(OH) 2D 3]. However, the significance of this increased production is not completely understood. In this study, we analyzed 1,25(OH) 2D 3 and NO production in patients with tuberculosis infection and hypercalcemia and used lipopolysaccharide (LPS) to stimulate RAW 264.7 cells in an attempt to assess iNOS expression and gaseous NO production regulated by 1,25(OH) 2D 3. Peroxynitrite (OONO −) production and lactate dehydrogenase activity were also examined. Without additional stimulation, peripheral-blood mononuclear cells (PBMCs) from patients with tuberculosis converted more 25-hydroxyvitamin D 3 to 1,25(OH) 2D 3 than did those from normal controls. These PBMCs released less NO than did those from control subjects, at baseline and in the stimulated state. We found that 1,25(OH) 2D 3 dose-dependently inhibited iNOS messenger RNA expression of the LPS-stimulated RAW 264.7 cells and also significantly reduced the gaseous NO release and OONO − production. Paralleling the 1,25(OH) 2D 3-induced inhibition of NO release were reductions in OONO − and LDH production. In conclusion, 1,25(OH) 2D 3 inhibited iNOS expression and reduced NO production by LPS-stimulated macrophages in the range of physiological doses. Inhibition of the NO surge was coupled with a reduction in OONO − and LDH production. Increased 1,25(OH) 2D 3 production and decreased release of NO from the PBMCs of patients with tuberculosis and hypercalcemia were also noted. We propose that 1,25(OH) 2D 3 production by macrophages may protect themselves against oxidative injuries caused by the NO burst. In the case of tuberculosis infection, increased 1,25(OH) 2D 3 synthesis may further contribute to the development of an unwanted phenomenon—hypercalcemia.

Inhibition of inducible nitric oxide synthase expression by baicalein in endotoxin/cytokine-stimulated microglia

Excessive production of nitric oxide (NO) in the central nervous system (CNS) mediated by activation of microglia has been implicated in neurotoxicity after stresses such as ischemia. Baicalein, a polyphenolic flavonoid antioxidant, is known to have anti-inflammatory, anticarcinogenic, and neuroprotective effects. In the present study, we report the inhibitory effect of baicalein on endotoxin/cytokine-induced NO production and inducible nitric oxide synthase (iNOS) gene expression in microglia. Baicalein abolished the endotoxin/cytokine-induced expression of iNOS protein, iNOS mRNA, and iNOS promoter activity in a parallel concentration-dependent manner. The suppression of iNOS expression was not mediated through the down-regulation of tumor necrosis factor-alpha (TNF-α) by baicalein because TNF-α failed to enhance endotoxin/cytokine-induced NO production in microglia. From the electrophoretic mobility shift assay (EMSA), we found that baicalein exerted a distinct inhibitory effect on the DNA binding activity of transcription factors, and this was significantly greater in nuclear factor IL-6 (NF-IL6) than in nuclear factor kappa B (NF-κB) and activated protein 1 (AP-1). Although extracellular signal-regulated kinase (ERK) is critical to iNOS expression, endotoxin/cytokine-stimulated phosphorylation of ERK1/2 was not significantly inhibited by baicalein. These results indicate that NF-IL6 inactivation could be the major determinant for the suppression of NO production by baicalein in microglia. Furthermore, it suggests that the inhibitory effect of baicalein on microglia activation and neurotoxic factor production is responsible for its neuroprotective action.

Candidate's thesis: Platelet-activating factor-induced hearing loss: mediated by nitric oxide?

Platelet-activating factor (PAF)in middle ear effusion is thought to induce hearing loss. The purpose of this study is to investigate the role of nitric oxide (NO) in the mechanism of PAF-induced hearing loss by studying the effects of PAF application on the round window membrane (RWM) with and without PAF-antagonist NO-blocker. Longitudinal study on randomized guinea pigs using PAF to induce hearing loss. METHODS Guinea pigs were divided into four groups: PBS, PAF, PAF-antagonist, and L-NAME. The PBS group received phosphate buffered saline (PBS) and the PAF groups received 10, 20, and 40 microg of PAF soaked into gelfoam and placed on the RWM. PAF-antagonist (WEB 2170) and NOS inhibitor NG-nitro-l-arginine-methylester (L-NAME) were injected intraperitoneally prior to PAF 20 microg application on the RWM. The following three tests were performed on each animal group: Hearing was tested with an auditory brainstem response (ABR) test over 24 hours. At the end of 24 hours, cochlear hair cells were examined by scanning electron microscopy (SEM) and immunohistochemistry was carried out on the cochlea to test the expression of inducible nitric oxide synthase (iNOS). The PAF group developed significant elevation of ABR threshold and cochlear hair cell damage in the SEM group as compared with the PBS control group. The PAF-antagonist (WEB 2170) and the L-NAME groups did not show significant elevation of ABR threshold and cochlear hair cell damage compared with the group administered PAF 20 microg, but in the PAF-antagonist group, the elevation of ABR threshold was significant compared with that of the PBS control group, whereas it was not significant compared with the PBS group in the L-NAME group. Strong expression of iNOS on cochlea was observed in the PAF group and lighter expression was seen in PBS, WEB 2170, and L-NAME groups. This study demonstrated that PAF placed on the RWM induced hearing loss and cochlear hair cell damage. The PAF-antagonists and L-NAME prevented the PAF-induced hearing loss and inhibited iNOS expression in the cochlea. These findings suggest that the PAF-induced hearing loss caused by cochlear hair cell damage may have been mediated by NO. PAF-antagonists and L-NAME may have future therapeutic implications in preventing sensorineural hearing loss associated with chronic otitis media. The results of this study have significant potential clinical application.

Flavopiridol downregulates the expression of both the inducible NO synthase and p27(kip1) in malignant cells from B-cell chronic lymphocytic leukemia.

Flavopiridol, an inhibitor of cyclin-dependent kinases and other protein kinases, induces in vitro apoptosis of malignant cells from B-cell chronic lymphocytic leukemia (B-CLL). Previously, we reported that nitric oxide (NO), produced by an inducible NO synthase (iNOS), spontaneously expressed by the B-CLL cells, contributed to their deficiency in apoptosis. In the present work, we show that ex vivo treatment of leukemic cells from B-CLL patients with flavopiridol results in the inhibition of iNOS expression, as determined by immunofluorescence and Western blotting, and in a marked inhibition of NO production measured in situ with a specific fluorescent probe (DAF-2 DA). These effects are accompanied by membrane, mitochondrial and nuclear events of apoptosis. Flavopiridol exposure also results in the stimulation of caspase 3 activity and in caspase-dependent cleavage of p27(kip1), a negative regulator of the cell cycle, which is overexpressed in B-CLL. Thus, flavopiridol is capable of downregulating both iNOS and p27(kip1) expression in B-CLL cells. Furthermore, flavopiridol-promoted apoptosis is partly reverted by an NO donor, suggesting that inhibition of the NO pathway could participate in the apoptotic effects of flavopiridol on the leukemic cells.

혈관평활근세포에서 Phorbol 12-Myristate 13-Acetate의 전처리가 Interleukin-1&amp;#x03B2;에 의한 Nitrite생성에 미치는 영향

Protein kinase C (PKC)가 interleukin-1 beta (IL-1<TEX>$\beta$</TEX>)에 의하여 산화질소(NO) 생성과정에 어떤 역할을 하는지를 검토하기 위하여, 혈관평활근세포에서 PKC 활성제인 phorbol 12-myristate 13-acetate (PMA)로 전처리한 후 IL-1<TEX>$\beta$</TEX>에 의하여 야기되는 NO생성을 nitrite (<TEX>$NO_2$</TEX>)로 정량하고, RT-PCR method를 이용하여 iNOS 발현에 미치는 영향을 검토하여 다음과 같은 결과를 얻었다. PMA (20, 200 nM)는 IL-1<TEX>$\beta$</TEX>에 의한<TEX>$NO_2$</TEX> 생성을 유의하게 증가시켰다. PMA 200 nM, phorbol 12,13-dibutyrate 500 nM로 전처리하여 8, 24시간 노출된 세포에서 IL-1<TEX>$\beta$</TEX>에 의한 NO2생성이 현저히 감소되었으나, PKC 비활성제인 4<TEX>$\alpha$</TEX>-phorbol-didecanoate 200 nM로 전처리한 경우는 영향을 받지 아니하였다. PMA 농도를 달리하여 24시간 전처리한 경우 IL-1<TEX>$\beta$</TEX>에 의한 <TEX>$NO_2$</TEX> 생성의 감소는 PMA의 농도가 20및 200 nM에서 현저하였다. RT-PCR method를 이용하여 iNOS 발현을 검토한바 IL-1<TEX>$\beta$</TEX> 100U/ml에 의한 iNOS발현이 PMA전처리 및 cycloheximide 또는 actinomycin D존재로서 현저히 억제 되었다. 이상의 결과로 미루어 혈관평활근세포에서 PMA 전처리로 야기되는 IL-1<TEX>$\beta$</TEX>에 의한 NO 생성의 감소는, PKC 조절저하작용에 의한 iNOS 발현의 억제로 야기되는 것 같다. To examine the role of protein kinase C (PKC) in regulation of interleukin-1 beta (IL-1<TEX>$\beta$</TEX>)-induced iNOS expression, IL-1<TEX>$\beta$</TEX>-induced nitrite production was observed in cultured vascular smooth muscle (VSM) cells pretreated with phorbol 12-myristate 13-acetate (PMA) and phorbol 12,13-butyrate (PDB) as PKC activator; 4<TEX>$\alpha$</TEX>-phorbol-didecanoate (PDD) as PKC non-activator. Nitrite production induced by IL-1<TEX>$\beta$</TEX> was increased by the presence of increasing concentration of PMA ranging from 2 to 200 nM. However, in VSM cells pretreated with PMA and PDB, IL-1<TEX>$\beta$</TEX>-induced <TEX>$NO_2$</TEX> production was decreased in proportion to the duration of pretreatment, and most significantly decreased in pretreatment time of 24 hours. Using RT-PCR method, the expression of iNOS mRNA induced by IL-1<TEX>$\beta$</TEX> was decreased in VSM cells pretreated with PMA 200 nM for 24 hours. These results suggest that decrease in IL-I<TEX>$\beta$</TEX>-induced nitrite production by the pretreatment of PMA result from inhibition of iNOS expression and the inhibition related to PMA-induced PKC down-regulation.

INOS activity is essential for endothelial stress gene expression protecting against oxidative damage.

In endothelial cells, the expression of the inducible nitric oxide synthase (iNOS) and the resulting high-output nitric oxide synthesis have often been assumed as detrimental to endothelial function, but recent publications have demonstrated a protective role resulting from iNOS espression and activity. To address this question, we used antisense-mediated iNOS knockdown during proinflammatory cytokine challenge in primary endothelial cell cultures and studied endothelial function by monitoring the expression of stress defense genes. Using antisense oligonucleotides, we achieved a block of iNOS protein formation, accompanied by a strong decrease in the expression of the protective stress response genes bcl-2, vascular endothelial growth factor, and heme oxygenase-1 (HO-1). Additionally, cells were also maintained in the presence of limited exogenous substrate concentrations during cytokine challenge, thereby mimicking a situation of low serum arginine level during inflammation. Under these conditions, cytokine addition results in full iNOS protein expression with minimal nitric oxide formation, concomitant with a significant reduction in stress response gene expression and susceptibility to cell death induced by reactive oxygen species. Taken together, our data suggest that cytokine-induced endogenous iNOS expression and activity have key functions in increasing endothelial survival and maintaining function. Thus suppression of iNOS expression or limited substrate supply, as has been reported to occur in atherosclerosis patients, appears to significantly contribute to endothelial dysfunction and death during oxidative stress.

Increased plasma phenylacetic acid in patients with end-stage renal failure inhibits iNOS expression

NO prevents atherogenesis and inflammation in vessel walls by inhibition of cell proliferation and cytokine-induced endothelial expression of adhesion molecules and proinflammatory cytokines. Reduced NO production due to inhibition of either eNOS or iNOS may therefore reinforce atherosclerosis. Patients with end-stage renal failure show markedly increased mortality due to atherosclerosis. In the present study we tested the hypothesis that uremic toxins are responsible for reduced iNOS expression. LPS-induced iNOS expression in mononuclear leukocytes was studied using real-time PCR. The iNOS expression was blocked by addition of plasma from patients with end-stage renal failure, whereas plasma from healthy controls had no effect. Hemofiltrate obtained from patients with end-stage renal failure was fractionated by chromatographic methods. The chromatographic procedures revealed a homogenous fraction that inhibits iNOS expression. Using gas chromatography/mass spectrometry, this inhibitor was identified as phenylacetic acid. Authentic phenylacetic acid inhibited iNOS expression in a dose-dependent manner. In healthy control subjects, plasma concentrations were below the detection level, whereas patients with end-stage renal failure had a phenylacetic acid concentration of 3.49 ± 0.33 mmol/l (n = 41). It is concluded that accumulation of phenylacetic acid in patients with end-stage renal failure inhibits iNOS expression. That mechanism may contribute to increased atherosclerosis and cardiovascular morbidity in patients with end-stage renal failure.

Increased plasma phenylacetic acid in patients with end-stage renal failure inhibits iNOS expression.

NO prevents atherogenesis and inflammation in vessel walls by inhibition of cell proliferation and cytokine-induced endothelial expression of adhesion molecules and proinflammatory cytokines. Reduced NO production due to inhibition of either eNOS or iNOS may therefore reinforce atherosclerosis. Patients with end-stage renal failure show markedly increased mortality due to atherosclerosis. In the present study we tested the hypothesis that uremic toxins are responsible for reduced iNOS expression. LPS-induced iNOS expression in mononuclear leukocytes was studied using real-time PCR. The iNOS expression was blocked by addition of plasma from patients with end-stage renal failure, whereas plasma from healthy controls had no effect. Hemofiltrate obtained from patients with end-stage renal failure was fractionated by chromatographic methods. The chromatographic procedures revealed a homogenous fraction that inhibits iNOS expression. Using gas chromatography/mass spectrometry, this inhibitor was identified as phenylacetic acid. Authentic phenylacetic acid inhibited iNOS expression in a dose-dependent manner. In healthy control subjects, plasma concentrations were below the detection level, whereas patients with end-stage renal failure had a phenylacetic acid concentration of 3.49 +/- 0.33 mmol/l (n = 41). It is concluded that accumulation of phenylacetic acid in patients with end-stage renal failure inhibits iNOS expression. That mechanism may contribute to increased atherosclerosis and cardiovascular morbidity in patients with end-stage renal failure.

Cytokine induction of prolactin receptors mediates prolactin inhibition of nitric oxide synthesis in pulmonary fibroblasts

Prolactin (PRL) has been implicated as a modulator of immune function, and some of its actions may be linked to NO synthesis. Because NO acts as a mediator of inflammation, we speculated that an inflammatory milieu could unmask pathways by which PRL could affect NO synthesis. Here, we show that pro-inflammatory cytokines induce the expression of PRL receptors in pulmonary fibroblasts, allowing PRL to inhibit cytokine-induced NO production and the expression of the inducible nitric oxide synthase (iNOS). Inhibition of iNOS expression by PRL correlates with the phosphorylation of STAT-5b (signal transducer and activator of transcription 5b) and the suppression of expression of IRF-1 (interferon regulatory factor 1), a transcription factor for iNOS. These results reveal previously unrecognized mechanisms by which PRL and PRL receptors may play significant modulatory roles during immune–inflammatory processes.

Melatonin counteracts lipopolysaccharide-induced expression and activity of mitochondrial nitric oxide synthase in rats.

Mitochondrial nitric oxide synthase (mtNOS) is expressed constitutively, although it might be induced. Nitric oxide (NO) is a physiological regulator of mitochondrial respiration. Melatonin prevents mitochondrial oxidative damage and inhibits iNOS expression induced by bacterial lipopolysaccharide (LPS). The loss of melatonin with age may be related to the age-dependent mitochondrial damage. Thus, we examined the protective role of melatonin against the effects of LPS on mtNOS and on respiratory complexes activity in liver and lung mitochondria from young and old rats. The activity of mtNOS in control lung was low and did not change with age. LPS administration (10 mg/kg, i.v.) significantly increased mtNOS expression and activity and NO production in lung mitochondria, and the effect was greater in old rats. LPS administration also reduced the age-dependent decrease of the respiratory complexes I and IV. Melatonin administration (60 mg/kg, i.p.) prevented the LPS toxicity, decreasing mitochondrial NOS activity and NO production. Melatonin also counteracted LPS-induced inhibition of complexes I and IV. In general, the actions of melatonin were stronger in older animals than in younger ones. The results suggest that an inducible component of mtNOS, together with mitochondrial damage, occurs during sepsis, and melatonin prevents the mitochondrial failure that occurs during endotoxemia.

Ascorbate inhibits iNOS expression and preserves vasoconstrictor responsiveness in skeletal muscle of septic mice.

Inducible nitric oxide synthase (iNOS) expression in blood vessels contributes to the vascular hyporeactivity characteristic of sepsis. Our previous work demonstrated in vitro that ascorbate inhibits iNOS expression in lipopolysaccharide- and interferon-gamma-stimulated skeletal muscle endothelial cells (ECs) through an antioxidant mechanism. The present study evaluated in vivo the hypothesis that administration of ascorbate decreases oxidative stress, prevents endothelial iNOS expression, and improves vascular reactivity in septic skeletal muscle. Sepsis was induced in C57BL/6 mice by cecal ligation and puncture (CLP). Plasma nitrite and nitrate (NOx) levels were elevated by 6 h after CLP. Prior ascorbate bolus injection (200 mg/kg body wt iv) blocked the elevation of plasma NOx and abolished the expression of iNOS protein and activity in the septic skeletal muscle. We also demonstrated that iNOS mRNA determined by RT-PCR was induced in the microvascular ECs of the muscle at 3 h after CLP. This induction was attenuated by prior ascorbate administration. Ascorbate inhibition of iNOS expression was associated with decreased oxidant levels in the septic muscle. Moreover, ascorbate administration restored partially the baseline arterial pressure and preserved completely the microvascular constriction and arterial pressure responses to norepinephrine in CLP mice. These results suggest that early administration of ascorbate may be a valuable adjunct treatment of sepsis.

Propofol reduces nitric oxide biosynthesis in lipopolysaccharide-activated macrophages by downregulating the expression of inducible nitric oxide synthase.

Nitric oxide is an active oxidant that contributes to the physiology and pathophysiology of macrophages. Propofol has been widely used in intravenous anesthesia. It possess antioxidant and immunomodulating effects. This study aimed to evaluate the effects of propofol on nitric oxide production in lipopolysaccharide-activated macrophages. Exposure of macrophages to propofol (25, 50 and 75 micro M), to lipopolysaccharide (0.5, 1, 1.5 and 2 ng/ml) or to a combination of propofol and lipopolysaccharide did not affect cell viability. However, propofol at 100 micro M led to significant cell death ( P<0.05). The levels of nitrite, an oxidative product of nitric oxide, were increased in lipopolysaccharide-treated macrophages in a concentration-dependent manner ( P<0.01), while propofol could concentration-dependently decrease the lipopolysaccharide-enhanced nitrite levels ( P<0.01). Immunoblotting analysis revealed that lipopolysaccharide increased the protein level of inducible nitric oxide synthase (iNOS). The co-treatment of propofol and lipopolysaccharide significantly reduced this lipopolysaccharide-induced iNOS protein (357+/-49 x 10(3) versus 92+/-6 x 10(3) arbitrary units, P<0.01). Analysis by reverse transcriptase-polymerase chain reaction showed that lipopolysaccharide induced mRNA of iNOS, but that the inductive effect was inhibited by propofol (95+/-7 x 10(2) versus 30+/-4 x 10(2) arbitrary units, P<0.01). This study has demonstrated that propofol, at therapeutic concentrations, could suppress nitric oxide biosynthesis by inhibiting iNOS expression in lipopolysaccharide-activated macrophages. The mechanism of suppression was at a pretranslational level.

TtCH, a selective inhibitor of inducible nitric oxide synthase expression with antiarthritic properties

In a previous work, we investigated the effects of a series of dimethoxy- and trimethoxychalcone derivatives, with various patterns of fluorination, on nitric oxide production in lipopolysaccharide-stimulated murine RAW 264.7 cells. The present study was designed to determine if 2,4,6-trimethoxy-2′-trifluoromethylchalcone (ttCH) could modulate the production of nitric oxide (NO) and/or prostaglandins in vitro and in vivo. On the mouse macrophage cell line RAW 264.7, ttCH inhibited dose-dependently NO and prostaglandin E 2 production, with IC 50 in the micromolar range. This compound had no direct inhibitory effect on inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 activities. NO reduction was the consequence of inhibition of the expression of iNOS. This compound also exhibited in vivo an inhibitory behaviour on nitrite and prostaglandin E 2 levels. We have assessed the effect of ttCH in the treatment of acute and chronic inflammatory processes such as the mouse carrageenan paw oedema and the rat adjuvant-induced arthritis. The present study demonstrated that ttCH exerts acute and chronic anti-inflammatory effects that may be related with the inhibition of iNOS expression.

1,3-selenazol-4-one derivatives inhibit inducible nitric oxide-mediated nitric oxide production in lipopolysaccharide-induced BV-2 cells.

Activated microglia extensively produce nitric oxide (NO) by inducing expression of inducible NO synthase (iNOS). NO plays a deleterious role in brain inflammation and neuronal death. In the present study, we investigated the effects of 1,3-selenazol-4-one derivatives (Sz-A, B, C, D and E) on NO production and iNOS expression in lipopolysaccharide (LPS)-induced BV-2 cells, a murine microglia cell line. Among these compounds, Sz-B and C remarkably inhibited LPS-induced NO production relative to that of Sz-A, D, and E at 5 microM in BV-2 cells. Sz-B and C dose-dependently inhibited NO production at 1, 5, and 10 microM without toxicity to BV-2 cells. Sz-B and C also dose-dependently suppressed iNOS expression at the same concentrations in LPS-induced BV-2 cells. This result suggests that Sz-B and C inhibit iNOS-mediated NO production in LPS-induced BV-2 cells. Structurally, Sz-B and C bear an ethyl or methyl group at the 5 positions of the 4-selenazolone skeletons, which could play an important role in inhibiting iNOS-mediated NO production.

Terlipressin inhibits in vivo aortic iNOS expression induced by lipopolysaccharide in rats with biliary cirrhosis

In cirrhosis, lipopolysaccharide (LPS, a product of Gram-negative bacteria) in the blood may cause septic shock. LPS-elicited induction of arterial inducible nitric oxide synthase (iNOS) results in nitric oxide (NO)-induced vasodilation, which causes arterial hypotension and hyporeactivity to α 1-adrenergic constrictors. In vitro studies have suggested that vasopressin inhibits iNOS expression in cultured vascular smooth muscle cells exposed to LPS. Thus, the aim of this study was to investigate the effects of terlipressin administration (a vasopressin analog) on in vivo LPS-induced aortic iNOS in rats with cirrhosis. LPS (1 mg/kg, intravenously) was administered followed by the intravenous administration of terlipressin (0.05 mg/kg, intravenously) or placebo 1 hour later. Arterial pressure was measured, and contractions to phenylephrine (an α 1-adrenoceptor agonist), iNOS activity, and iNOS expressions (mRNA and protein) were investigated in isolated aortas. LPS-induced arterial hypotension and aortic hyporeactivity to phenylephrine were abolished in rats that received terlipressin. LPS-induced aortic iNOS activity and expression were suppressed in terlipressin-treated rats. In conclusion, in LPS-challenged rats with cirrhosis, terlipressin administration inhibits in vivo LPS-induced aortic iNOS expression. Terlipressin administration may be a novel approach for the treatment of arterial hypotension and hyporeactivity to α 1-adrenergic constrictors in patients with cirrhosis and septic shock. (H EPATOLOGY 2002;36:1070-1078.)