iNOS Gene Expression Levels Research Articles

Protective and curative effects of unconjugated bilirubin on gene expression of LOX-1 and iNOS in the heart of rats receiving high-fat diet and low dose streptozotocin: a histomorphometric approach

BackgroundAtherosclerosis is a chronic inflammatory condition affecting the large arteries and is a major cause of cardiovascular diseases (CVDs) globally. Increased levels of adhesion molecules in cardiac tissue serve as prognostic markers for coronary artery occlusion risk. Given the antioxidant properties of bilirubin and its inverse correlation with atherosclerosis, this study aimed to assess the beneficial effects of bilirubin on atherosclerotic indices and heart structure in high-fat diet-fed diabetic rats with atherosclerosis.MethodsAtherosclerosis was induced in three out of five groups of adult male Sprague Dawley rats through a 14-week period of high-fat diet (HFD) consumption and a single low dose of streptozotocin (STZ) (35 mg/kg). The atherosclerotic rats were then treated with intraperitoneal administration of 10 mg/kg/day bilirubin for either 6 or 14 weeks (treated and protected groups, respectively), or the vehicle. Two additional groups served as the control and bilirubin-treated rats. Subsequently, the mRNA expression levels of vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1), lectin-like LDL receptor 1 (LOX-1), and the inducible nitric oxide synthase (iNOS) were analyzed using quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Histopathological and stereological analyses were performed to assess changes in the heart structure.ResultsBilirubin significantly decreased the expression of VCAM-1, ICAM-1, LOX-1, and iNOS genes in the treated group. Moreover, bilirubin mitigated pathological damage in the left ventricle of the heart. Stereological analysis revealed a decrease in the left ventricle and myocardium volume, accompanied by an increase in vessel volume in rats treated with bilirubin.ConclusionThese findings demonstrate that mild hyperbilirubinemia can protect against the progression of atherosclerosis and heart failure by improving lipid profile, modulating adhesion molecules, LOX-1, and iNOS gene expression levels.

Unveiling of the antileishmanial activities of Linalool loaded zinc oxide nanocomposite through its potent antioxidant and immunomodulatory effects

This study aimed to produce linalool loaded zinc oxide nanocomposite (LZNPs) and assess its in vitro and in vivo antileishmanial effects against Leishmania major. LZNPs was produced through the synthesis of an ethanolic solution containing polyvinyl alcohol. The average size of LZNPs was determined to be 105 nm. The findings indicated that LZNPs displayed significant (p < 0.01) antileishmanial effects on promastigotes and amastigotes. Following exposure of promastigotes to LZNPs, there was a notable rise in the percentage of early and late apoptotic cells from 9.0 to 57.2 %. The gene expression levels of iNOS, IFN-γ, and TNF-α in macrophages were upregulated in a dose-dependent approach following exposure to LZNPs. LZNPs alone and in conjunction with glucantime (Glu) resulted in a reduction in the diameter and parasite load of CL lesions in infected mice. Treatment of the CL-infected mice with LZNPs at 25 and 50 mg/kg mainly in combination with Glu-reduced the tissue level of malondialdehyde (MDA), increased both gene and protein expression of the antioxidant enzymes as well as raised the expression level of IFN-γ and IL-12 cytokines, whereas caused a significant reduction in the expression level of IL-4. The present study shows that LZNPs has potent antileishmanial effects and controls CL in a mice model through its antioxidant and immunomodulatory properties. Further investigation, especially in clinical trials, could explore the potential use of this nanocomposite in managing and treating CL.

Histological and molecular characterization of the protective effect of Eugenia caryophyllata against renal toxicity induced by vitamin D in male wistar rats

Vitamin D can be harmful if taken for a long time, or taken in large acute dose, cause many problems including hypercalcemia. Here, we examined the protective effects of Eugenia Caryophyllata against vitamin D toxicity induced renal inflammation in rats. This study employed four experimental groups (n = 10) that underwent two months of treatment as follows: control group animal received saline (0.9% NaCl), vitamin D group that was received (100 mg/kg) of vitamin D, Eugenol group that was received Eugenol (100 mg/kg), vitamin D + eugenol group that was received vitamin D (100 mg/kg) then will be orally given Eugenol (100 mg/kg). The current study showed that a significant upregulation in the IL-2, TNF- α and iNOS gene expression levels caused by vitamin D compared to the control group. Eugenol treatment caused a significant decreased IL-2, TNF-α and iNOS activity and also upregulated gene expression levels. Histological features investigated showed that administered with vitamin D intoxication showed distinct alterations from that of the untreated control groups, such Shrinkage of glomeruli, hypercellularity of the glomeruli and necrosis. However, retreatment with Eugenol showed improvement in the histological features in by slight infiltration, fibrosis, minimal pleomorphism and less disarrangement and compared with that of Vitamin D treated rats. In conclusion, the Eugenol exhibited renoprotective effects against vitamin D-induced nephrotoxicity. These renoprotective effects could be achieved by the antioxidant and anti-inflammatory activities of the Eugenol. Thus, for vitamin D-induced nephrotoxicity, the use of Eugenol could be beneficial.

Aminoguanidine inhibits IL-1β-induced protein expression of iNOS and COX-2 by blocking the NF-κB signaling pathway in rat articular chondrocytes.

Osteoarthritis is a chronic joint disease which has a serious impact on the health and quality of life of affected humans and animals. As an inhibitor of inducible nitric oxide synthase (iNOS), aminoguanidine (AG) displays anti-inflammatory effects. The purpose of the present study was to investigate the effect of AG on the expression of iNOS and cyclooxygenase-2 (COX-2), and the activity of the NF-κB signaling pathway in rat chondrocytes stimulated by interleukin-1β (IL-1β). The viability of chondrocytes treated with AG (0.3, 1 or 3 mM) alone was determined using a Cell Counting Kit-8 assay. Subsequently, the chondrocytes were treated with either 10 ng/ml IL-1β alone, or co-treated with increasing concentrations of AG (0.3, 1 or 3 mM) and 10 ng/ml IL-1β. The protein levels of COX-2, iNOS, phosphorylated (p)-p65, p65, p-NF-κβ inhibitor α (IκBα), IκBα, p-inhibitor of NF-κβ-β (IKKβ) and IKKβ were evaluated by western blotting. NF-κB translocation was determined by immunofluorescence analysis. Western blotting and reverse transcription-quantitative PCR were used to detect expression levels of relevant proteins/genes. The results suggested that the inhibitory effect of AG on the protein and gene expression levels of iNOS and COX-2 in IL-1β-treated chondrocytes was dose-dependent. In addition, AG decreased the level of phosphorylation of IKKβ, IκBα and NF-κB p65, the degradation of IKKβ, IκBα and p65, and the translocation of NF-κB in IL-1β-stimulated chondrocytes. The most significant inhibitory effect of AG was observed at a concentration of 1 mM. Therefore, the present study suggested that AG may serve as a potential agent to reduce the inflammatory response of chondrocytes stimulated by IL-1β.

Study the effect of indomethacin administration on breast tumor growth and iNOS gene expression in tumor-bearing mice

Breast cancer is a public health concern among the women. iNOS is stated by the effect of various inflammatory factors and is thus called inducible NOS. Investigating iNOS expression is a potent tool for understanding effective molecular parameters in tissue and cellular responses to external factors. In this research study, iNOS expression in mice with breast cancer was investigated and the effects of various doses of indomethacin on the iNOS gene expression in breast tumors was evaluated.4T1 cells were grown in RPMI 1640 Medium. 200 µl of cell suspension (107 cells)were injected into the mice right flank, subcutaneously. 35 Balb/C albino mice divided into five groups each group consist of 7 mice. First group was healthy control group, second group was tumor control, and the 3rd, 4th and 5th groups were treated by 25μg, 50μg and 100μg of indomethacin, respectively. The rate of breast tumor growth was measured in treated groups for two months. The levels of iNOS gene expression was determined using real time RT-PCR technique.Our results demonstrated, iNOS expression in tumor tissue increased with the growth of breast cancer cells. Furthermore, Administration of 25μg and 100μg indomethacin neither had significant effect on breast tumor growth nor effect on iNOS gene expression. While 50μg indomethacin decreased the tumor growth (P>0.05) and decreased iNOS gene expression. Further studies such as evaluating the effects of indomethacin on the other anti-tumor immunosuppressing factor and additional tests western blot, flow cytometry and immunohistochemistry recommended in order to obtain more practical findings.

ANTI-INFLAMMATORY AND ANTIOXIDANT EFFECTS OF POMEGRANATE ON ACETIC ACID-INDUCED ULCERATIVE COLITIS IN RATS

The present study was designed to investigate the protective effect of pomegranate extract on some blood and antioxidant parameters in addition to interleukin-1 (IL-1) and inducible nitric oxide (iNOS) gene expression of colon tissue in acetic acid-induced ulcerative colitis in rats. Forty rats were divided into four equal groups. Group I (c) group (control normal group) received no drugs. Group II (AA) group (Acetic acid induced ulcerative colitis group) rats were administrated with 2 ml of acetic acid (AA) 4% intracolonic as a single dose. Group III (PGFE) group (Pomegranate group) rats were administrated with pomegranate orally (500 mg/kg, b.wt/day for 14 days. Group VI (PGFE+AA) group (PGFE protected plus AA 4% induced ulcerative colitis group) rats were administrated with PGFE orally (500 mg/kg, b.wt/day for 14 days and at the 11th day was administrated intracolonic as a single dose with 2 ml of AA 4%. The obtained results showed that a significant decrease in neutrophils to lymphocytes ratio (N/LR) and increase in lymphocytes to monocytes ratio (L/MR) in (PGFE+AA) group when compared with (AA) group. Meanwhile, malondialdehyde (MDA) and nitric oxide (NO) were significantly decreased with significant down-regulation in IL-1s and iNOS gene expression levels were obtained in colon tissue of (PGFE+AA) group when compared with (AA) group. The results revealed that pomegranate has protective, anti-inflammatory and antioxidant effects in experimental model of ulcerative colitis in induced rats.

Carnosol and Related Substances Modulate Chemokine and Cytokine Production in Macrophages and Chondrocytes.

Phenolic diterpenes present in Rosmarinus officinalis and Salvia officinalis have anti-inflammatory and chemoprotective effects. We investigated the in vitro effects of carnosol (CL), carnosic acid (CA), carnosic acid-12-methylether (CAME), 20-deoxocarnosol and abieta-8,11,13-triene-11,12,20-triol (ABTT) in murine macrophages (RAW264.7 cells) and human chondrocytes. The substances concentration-dependently reduced nitric oxide (NO) and prostaglandin E2 (PGE2) production in LPS-stimulated macrophages (i.e., acute inflammation). They significantly blunted gene expression levels of iNOS, cytokines/interleukins (IL-1α, IL-6) and chemokines including CCL5/RANTES, CXCL10/IP-10. The substances modulated the expression of catabolic and anabolic genes in chondrosarcoma cell line SW1353 and in primary human chondrocytes that were stimulated by IL-1β (i.e., chronic inflammation In SW1353, catabolic genes like MMP-13 and ADAMTS-4 that contribute to cartilage erosion were down-regulated, while expression of anabolic genes including Col2A1 and aggrecan were shifted towards pre-pathophysiological homeostasis. CL had the strongest overall effect on inflammatory mediators, as well as on macrophage and chondrocyte gene expression. Conversely, CAME mainly affected catabolic gene expression, whereas ABTT had a more selectively altered interleukin and chemokine gene exprssion. CL inhibited the IL-1β induced nuclear translocation of NF-κBp65, suggesting that it primarily regulated via the NF-κB signalling pathway. Collectively, CL had the strongest effects on inflammatory mediators and chondrocyte gene expression. The data show that the phenolic diterpenes altered activity pattern of genes that regulate acute and chronic inflammatory processes. Since the substances affected catabolic and anabolic gene expression in cartilage cells in vitro, they may beneficially act on the aetiology of osteoarthritis.

Adrenomedullin attenuates interleukin-1β-induced inflammation and apoptosis in rat Leydig cells via inhibition of NF-κB signaling pathway

The aim of this paper is to investigate the protective effects of adrenomedullin (ADM) on interleukin-1β (IL-1β)-induced inflammation and apoptosis in rat Leydig cells and its underlying molecular mechanisms. Leydig cells were isolated from adult Sprague–Dawley rats. The cell culture was established by adding ADM 2h prior to 24h treatment with IL-1β-induced cytotoxicity. We detected cell viability and concentrations of testosterone, reactive oxygen species (ROS), malondialdehyde (MDA), and reduced glutathione (GSH). Gene expression levels were measured for inducible nitric oxide synthase (iNOS) and cyclo-oxygenase-2 (COX-2). Concentrations were detected for nitric oxide (NO) and prostaglandin E2 (PGE2). Apoptosis was assessed using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Levels of gene expression and protein were detected for Bcl-2, Bax, caspase-3, and poly adenosine diphosphate-ribose polymerase (PARP). Protein levels were measured for nuclear factor kappa B (NF-κB) p65 and IκBα. ADM reduced IL-1β-induced cytotoxicity. ADM pretreatment significantly increased testosterone concentrations and decreased ROS, MDA, and GSH concentrations. ADM pretreatment inhibited IL-1β-induced inflammation in Leydig cells by decreasing the gene expression levels of iNOS and COX-2, as well as the concentrations of NO and PGE2. ADM pretreatment further decreased the number of TUNEL-positive stained Leydig cells, as confirmed by the increase in gene expression and protein levels of Bcl-2 and the decrease of Bax, caspase-3, and PARP levels. Moreover, ADM pretreatment inhibited NF-κB p65 phosphorylation and IκBα phosphorylation and degradation. ADM has potential anti-inflammatory and anti-apoptotic properties in IL-1β-induced rat Leydig cells, which might be related to NF-κB signaling pathway.

Protective mechanism of grape seed oil on carbon tetrachloride-induced brain damage in γ-irradiated rats

This study investigated the possible beneficial effects of grape seed oil (GSO) on carbon tetrachloride (CCl4)-induced acute neurotoxicity in γ-irradiated rats. A statistical significant decrease in superoxide-dismutase (SOD), catalase (CAT), and glutathione-peroxidase (GPx) activities and reduced glutathione (GSH) content were exhibited. Further, a significant elevation in malondialdehyde (MDA), nitric oxide (NO), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and transforming growth factor-beta-1 (TGF-β1) levels was observed. Furthermore, xanthine oxidase (XO) and inducible nitric oxide synthase (iNOS) gene expression were elevated in the γ-irradiated animals treated with an acute dose of CCl4. The pretreatment of GSO exerts significant amelioration of the studied parameters. In conclusion, this study demonstrated that GSO has a neuroprotective effect against CCl4-induced brain injury in γ-irradiated rats, which is likely attributed to its ability to scavenge the free radicals, suppress the inflammatory responses, improve the activity of the antioxidant enzymes and inhibit the XO and iNOS gene expression levels.

γ-Irradiated cancer cells promote tumor growth by activation of Toll-like receptor 1-mediated inducible nitric oxide synthase in macrophages

RT is commonly used to treat malignant tumors. However, tumor regrowth is a major limitation to RT as an antitumor treatment. In the present study, we investigated the tumor-promoting effects of high-dose (or ablative) RT treatments on tumor-bearing mice. We focused on the role of macrophages that interact with IR-CCs in the TME, which cause tumor regrowth. We observed that CT26(H-2(d)) tumor growth was enhanced by i.v. injection of IR-CT26 cells compared with NR control CT26 cells. The levels of iNOS gene expression and NO production from RAW264.7 macrophages (H-2(d)) in response to the interaction with IR-CT26 cells were higher than with NR-CT26 cells. When CT26 tumor-bearing mice were treated i.v. with L-NMMA, a NOS inhibitor, the reduction in in vivo tumor growth was higher in the IR-CT26-injected group compared with the NR-CT26-injected control group. In vivo CT26 tumor growth was decreased after transplanting PEM extracted from L-NMMA-treated, tumor-bearing mice. Although iNOS activity was reduced by inhibiting TLR1 expression with TLR1-siRNA, it was enhanced by TLR1 overexpression. Transcriptional activation and protein expression levels of iNOS were also decreased in the presence of TLR1-siRNA but increased as a result of TLR1 overexpression. These results demonstrate that postradiotherapeutic tumor regrowth may be caused by interaction of IR-CCs with macrophages that induce TLR1-mediated iNOS expression and NO production. Our data suggest that iNOS in macrophages could be a useful target to regulate postradiotherapeutic responses in hosts and subsequently limit tumor regrowth.

Dysregulation of neurotrophic and inflammatory systems accompanied by decreased CREB signaling in ischemic rat retina

Although permanent bilateral common carotid artery occlusion (2VO) has been demonstrated to induce retinal injury, there is still a lack of systematic research on the complex processing of retinal degeneration. In the present study, time-dependent (at three, 14, 60 days after 2VO surgery) changes of neurotrophic and inflammatory systems, as well as cAMP-responsive element binding protein (CREB) signaling, which has been previously reported to effectively regulate these two systems, were evaluated. First, a morphological study confirmed that 2VO surgery progressively induced severe inner retinal degeneration and down-regulation of synaptic proteins, PSD95 and synaptophysin. The mRNA or protein levels of neurotrophic factors (NGF, BDNF, NT-3 and GDNF) and their receptors (TrkA, TrkB and TrkC) showed marked and persistent down-regulation in the rat retina since three days after 2VO surgery, whereas the gene transcription levels of CNTF were increased and p75NTR mRNA levels remained unchanged. In contrast to inner retinal degeneration, retinal Müller cells displayed rapid and prolonged activation since three days after 2VO lesion, whereas the microglia cell number, and TNF-α and IL-1β levels showed a robust increase with a maximal effect at three days and returned to levels that were slightly over baseline at 14 and 60 days after 2VO lesion. Interestingly, the gene expression levels of iNOS significantly decreased in the rat retina at both three and 14 days after 2VO surgery. Finally, as we hypothesized, remarkable reduction of CREB and extracellular signal-regulated kinase (ERK) phosphorylation levels were observed in the rat retina at three days after 2VO surgery. Thus, for the first time, our study demonstrated that chronic ischemia induced long-term aberrant CREB signaling and time-dependent progressive dysregulation of neurotrophic and inflammatory systems in the retina, which may provide important clues for a better understanding of the pathogenesis of retinal ischemic damage.

Influence of olive-derived hydroxytyrosol on the toll-like receptor 4-dependent inflammatory response of mouse peritoneal macrophages

Macrophages play important roles in the host innate immune response and are involved in the onset of diseases caused by inflammation. Toll-like receptor 4 (TLR4)-mediated inflammatory responses of macrophages may be associated with diseases such as diabetes and diseases of the cardiovascular system. Hydroxytyrosol (HT) exerts strong antioxidant and anti-inflammatory effects and may be applied in the treatment of inflammatory diseases. In the present study conducted in vitro, we investigated the effects of the TLR4-dependent anti-inflammatory effect of HT on peritoneal macrophage of BALB/c mice. We show here that the elevated levels of iNOS gene expression and nitric oxide production induced by lipopolysaccharide (LPS) (0.25μg/ml) were suppressed by HT (12.5μg/ml). LPS-dependent NF-κB gene expression and phosphorylation of NF-κB were not affected by HT under these conditions. In contrast, the expression of TNF-α was significantly increased in the presence of LPS and HT. These results suggest that HT suppressed nitric oxide production by decreasing iNOS gene expression through a mechanism independent of the NF-κB signaling pathway. These novel findings suggest that the modulation by HT of the expression of genes involved in inflammation may involve multiple mechanisms.

Floridoside suppresses pro-inflammatory responses by blocking MAPK signaling in activated microglia

Inflammatory conditions mediated by activated microglia lead to chronic neuro-degenerative diseases such as Alzheimer’s, Parkinson’s, and Huntington’s diseases. This study was conducted to determine the effect of floridoside isolated from marine red algae Laurencia undulata on LPS (100 ng/ml) activated inflammatory responses in BV-2 microglia cells. The results show that floridoside has the ability to suppress pro-inflammatory responses in microglia by markedly inhibiting the production of nitric oxide (NO) and reactive oxygen species (ROS). Moreover, floridoside down-regulated the protein and gene expression levels of iNOS and COX-2 by significantly blocking the phosphorylation of p38 and ERK in BV-2 cells. Collectively, these results indicate that floridoside has the potential to be developed as an active agent for the treatment of neuro-inflammation. [BMB Reports 2013; 46(8): 398-403]

Green tea epigallocatechin-3-gallate attenuatesPorphyromonas gingivalis-induced atherosclerosis

The purpose of this study was to determine whether epigallocatechin-3-gallate (EGCG) ameliorates Porphyromonas gingivalis-induced atherosclerosis. EGCG is a polyphenol extract from green tea with health benefits and P. gingivalis is shown here to accelerate atheroma formation in a murine model. Apolipoprotein E knockout mice were administered EGCG or vehicle in drinking water; they were then fed high-fat diets and injected with P. gingivalis three times a week for 3 weeks. Mice were then killed at 15 weeks. Atherosclerotic plaques in the proximal aorta were determined by Oil Red O staining. Atherosclerosis risk factors in serum, liver or aorta were analysed using cytokine antibody arrays, enzyme-linked immunosorbent assay and real-time PCR. Atherosclerotic lesion areas of the aortic sinus caused by P. gingivalis infection decreased in EGCG-treated groups, wherein EGCG reduced the production of C-reactive protein, monocyte chemoattractant protein-1, and oxidized low-density lipoprotein (LDL), and slightly lowered LDL/very LDL cholesterol in P. gingivalis-challenged mice serum. Furthermore, the increase in CCL2, MMP-9, ICAM-1, HSP60, CD44, LOX-1, NOX-4, p22phox and iNOS gene expression levels in the aorta of P. gingivalis-challenged mice were reduced in EGCG-treated mice. However, HO-1 mRNA levels were elevated by EGCG treatment, suggesting that EGCG, as a natural substance, inhibits P. gingivalis-induced atherosclerosis through anti-inflammatory and antioxidative effects.

Hypoxia enhances gene expression of inducible nitric oxide synthase and matrix metalloproteinase‐9 in ras/myc‐transformed serum‐free mouse embryo cells under simulated inflammatory and infectious conditions

Ras/myc-transformed serum-free mouse embryo (ras/myc SFME) cells were treated with interferon-gamma (IFN-gamma; 100 U/ml) and/or lipopolysaccharide (LPS; 0.5 microg/ml) for 24 h to simulate inflammatory and infectious conditions and investigate their effects on the expression of inducible nitric oxide synthase (iNOS) mRNA, nitric oxide (NO) and matrix metalloproteinase-9 (MMP-9). In addition, aminoguanidine (AG; 1 mM), a NOS inhibitor, S-nitroso-N-acetyl-DL-penicillamine (SNAP; 10-200 microM), an NO donor or (+/-)-N-[(E)-4-ethyl-2-[(Z)-hydroxyimino]-5-nitro-3-hexene-1-yl]-3-pyridine carboxamide (NOR4; 10-200 microM), an NO donor, were added to analyze possible associations of NO with MMP-9. Tissue inhibitors of metalloproteinase (TIMP)-1 and TIMP-2 were also measured to analyze possible relationships of NO with the MMP-9/TIMP balance. Furthermore, the cells were treated with 1% O2 under the simulated inflammatory and infectious conditions and the mRNA expressions of iNOS and MMP-9 were analyzed to investigate the possible effects of hypoxia on the expression of genes involved in tumor malignant progression and distant metastasis. Co-treatment with IFN-gamma and LPS increased the expression levels of iNOS mRNA, NO and MMP-9, but NO may not be directly associated with MMP-9 or the MMP-9/TIMP balance. Treatment with 1% O2 markedly increased the gene expression levels of iNOS and MMP-9, indicating that ras/myc SFME cells alter the expression levels of tumor-associated genes and possibly enhance their malignancy as cancer cells under inflammatory, infectious and hypoxic conditions.

Suppression of Bleomycin-Induced Nitric Oxide Production in Mice by Taurine and Niacin

The effects of taurine (T) and niacin (N) on the influx of inflammatory cells and nitric oxide (NO) levels in bronchoalveolar lavage fluid (BALF) and expression of inducible NO synthase (iNOS) mRNA and iNOS protein in lungs were evaluated in the bleomycin (BL)–mouse model of lung fibrosis. Mice were placed into four groups: saline-instilled (SA) with a control diet (CD) (SA + CD); saline-instilled with TN (1% taurine in water + 2.5% (w/w) niacin in diet) (SA + TN); BL-instilled with CD (BL + CD); and BL-instilled with TN treatment (BL + TN). There was no difference in differential cell counts in BALF between the SA + CD and SA + TN control groups. Intratracheal instillation (IT) of BL (0.1 U/mouse) in mice stimulated an early influx of neutrophils followed by an increase in lymphocytes and macrophages in the BL + CD group. Taurine and niacin treatment significantly reduced the numbers of neutrophils, lymphocytes, and macrophages in the BL + TN group and caused significant reductions in BL-induced increases in the lung hydroxyproline content at 14 and 21 days in the BL + TN group. The mice in the SA + CD and SA + TN control groups had low levels of NO in BALF, whereas mice in the BL + CD group as compared to the SA + CD control group had elevated levels of NO from day 3 through day 21. Taurine and niacin treatment caused significant reductions in BL-induced increases in NO levels in BALF from mice in the BL + TN group at 7, 14, and 21 days as compared to the corresponding BL + CD group. The increases in NO levels in BALF from the BL + CD group were associated with elevated levels of iNOS gene expression and protein in the lungs. RT-PCR analysis of total RNA isolated from the lungs indicated that taurine and niacin treatment suppressed the BL-induced increases in iNOS message and iNOS protein. The ability of taurine and niacin to suppress the BL-induced increased production of NO secondary to decreases in iNOS mRNA and protein appears to be one of the mechanisms for their anti-inflammatory and antifibrotic effects.