Seihaito, a Kampo medicine, attenuates IL-13-induced mucus production and goblet cell metaplasia.

Goblet cell hyperplasia and increased mucus production are features of airway diseases, including asthma, and excess airway mucus often worsens these conditions. Even steroids are not uniformly effective in mucus production in severe asthma, and new therapeutic options are needed. Seihaito is a Japanese traditional medicine that is used clinically as an antitussive and expectorant. In the present study, we examined the effect of Seihaito on goblet cell differentiation and mucus production. In in vitro studies, using air-liquid interface culture of guinea-pig tracheal epithelial cells, Seihaito inhibited IL-13-induced proliferation of goblet cells and MUC5AC, a major component of mucus production. Seihaito suppressed goblet cell-specific gene expression, without changing ciliary cell-specific genes, suggesting that it inhibits goblet cell differentiation. In addition, Seihaito suppressed MUC5AC expression in cells transfected with SPDEF, a transcription factor activated by IL-13. Furthermore, Seihaito attenuated in vivo goblet cell proliferation and MUC5AC mRNA expression in IL-13-treated mouse lungs. Collectively, these findings demonstrated that Seihaito has an inhibitory effect on goblet cell differentiation and mucus production, which is at least partly due to the inhibition of SPDEF.

Bisacodyl Suppresses TGF-α-Induced MUC5AC Production in NCI-H292 Cells.

MUC5AC overproduction is commonly observed in chronic inflammatory lung diseases and worsens these conditions. Therefore, drugs that inhibit MUC5AC production are urgently needed. To identify novel drugs directly inhibiting MUC5AC production, 640 already approved drugs were screened. We found that the laxative bisacodyl suppressed transforming growth factor (TGF)-α-induced MUC5AC production in a concentration-dependent manner. Additionally, bisacodyl also suppressed TGF-α-induced MUC5AC mRNA expression in the same concentration range. These results suggested that bisacodyl could be a new drug for treating mucin overproduction.

Ibudilast Suppresses MUC5AC Mucus Production through Inhibition of ERK1/2 Phosphorylation.

Mucus hypersecretion is a hallmark of respiratory diseases, and excess airway mucus can worsen these conditions. Therefore, it is important to control the production of airway mucus in the treatment of respiratory diseases. The phosphodiesterase inhibitor ibudilast has been reported to be effective in treating sputum and postnasal drip in patients with chronic airway inflammation. On the basis of the hypothesis that ibudilast could inhibit mucus production in the airway, in the present study, we examined the effects of ibudilast on the production of MUC5AC, a major protein component of mucus. In in vitro studies using NCI-H292 cells, ibudilast suppressed MUC5AC production induced by various stimuli. In addition, ibudilast inhibited extracellular signal-regulated kinase (ERK)1/2 phosphorylation and MUC5AC gene transcription. Furthermore, it attenuated MUC5AC production and Muc5ac mRNA expression in lipopolysaccharide-treated mice in vivo. Collectively, these findings demonstrate that ibudilast has an inhibitory effect on mucus production, which could at least partly be attributed to the inhibition of ERK1/2 phosphorylation and the repression of MUC5AC gene transcription.

C-Terminal Domain of Aquaporin-5 Is Required to Pass Its Protein Quality Control and Ensure Its Trafficking to Plasma Membrane.

Aquaporin-5 (AQP5) is selectively expressed in the apical membrane of exocrine glands, such as salivary, lacrimal, and submucosal glands. It is important for the secretory function of exocrine glands because mice with the knockout of AQP5 exhibit a significant reduction in secretion from these glands. Previous reports indicated that the AQP5 C-terminal domain is crucial for the localization of AQP5 at the plasma membrane, but it remains unclear which motif or amino acid residues in the C-terminal domain are essential for this. In this study, we examined the effects of various AQP5 C-terminal deletions or mutations on the expression of AQP5 on the cell surface. AQP5 C-terminal domain mutants did not localize on the plasma membrane, and Leu262 was shown to be crucial for AQP5's plasma membrane localization. The mutants localized in the autophagosome or lysosome and showed decreased protein stability via lysosomal degradation. Taking these findings together, our study suggests that the C-terminal domain is required for AQP5 to pass protein quality control and be trafficked to the plasma membrane.

Ezrin Regulates Ca2+ Ionophore-Induced Plasma Membrane Translocation of Aquaporin-5.

Aquaporin-5 (AQP5) is selectively expressed in the apical membrane of exocrine glands, such as salivary, sweat, and submucosal airway glands, and plays important roles in maintaining their secretory functions. Because AQP5 is not regulated by gating, localization on the plasma membrane is important for its water-permeable function. Ezrin is an ezrin-radixin-moesin family protein that serves as a crosslinker between the plasma membrane and actin cytoskeleton network. It plays important roles in translocation of various membrane proteins to mediate vesicle trafficking to the plasma membrane. In this study, we examined the effects of ezrin inhibition on membrane trafficking of AQP5. Ezrin inhibition selectively suppressed an ionomycin-induced increase in AQP5 translocation to the plasma membrane of mouse lung epithelial cells (MLE-12) without affecting the steady-state level of plasma membrane AQP5. Taken together, our data suggest that AQP5 translocates to the plasma membrane through at least two pathways and that ezrin is selectively involved in a stimulation-dependent pathway.

Effects of nitrous acid exposure on baseline pulmonary resistance and Muc5ac in rats.

We examined the baseline pulmonary resistance (RLung), baseline dynamic lung compliance (Cdyn), cytokine inductions, and histological alterations in rats exposed to nitrous acid (HONO) with secondary products of nitrogen dioxide (NO2) and nitric oxide (NO) to assess its biological effects. We exposed three groups of nine male F344 rats to different doses of HONO for six weeks (24 h/day). The cumulative values of HONO concentration were measured twice. The average concentrations of nitrogen oxide for each group were 5.8 parts per million (ppm) HONO with secondary products of 0.7 ppm NO2 and 2.3 ppm NO, 4.1 ppm HONO with 0.1 ppm NO2 and 0.6 ppm NO, and a clean air control. We measured baseline RLung and baseline Cdyn using tracheal cannulation. A tracheal tube was inserted into the trachea by tracheostomy, and lung function measurements (baseline RLung and baseline Cdyn) were conducted in mechanically ventilated rats. We measured mRNA levels of Cxcl-1, TNF-α, and Muc5ac in the right lung using quantitative RT-PCR, and observed histological alterations and the alveolar mean linear intercept (Lm) on the left lung. Our results demonstrated that HONO exposure significantly increased baseline RLung, Lm and Muc5ac expression, but did not affect baseline Cdyn or expression of Cxcl-1 and TNF-α. Further, we identified bronchial smooth muscle hypertrophy, pulmonary emphysema-like alterations in the alveolar duct centriacinar regions, and increased goblet cells in HONO-exposed rats. The present results suggest that HONO (with secondary products) adversely affects respiratory function, but that these pathologies may be unrelated to inflammation.

Boiogito, a Kampo medicine, improves hydrarthrosis in a rat model of knee osteoarthritis.

BACKGROUND: Hydrarthrosis, which is associated with knee pain and limited range of motion, decreases the quality of life (QOL) of patients with osteoarthritis (OA). The Kampo medicine boiogito is prescribed for the treatment of knee OA with hydrarthrosis; however, its precise mechanisms of action remain unknown. The purposes of this study were to assess the pharmacological effects of boiogito and its mechanisms of action on joint effusion in rats with surgically induced OA. METHODS: A rat OA model was produced by transecting the anterior (cranial) cruciate ligament, medial collateral ligament, and medial meniscus in the right knee joints of 7-week-old female Wistar rats. The rats were given chow containing boiogito (1 or 2%) or indomethacin (0.002 %) for 4 weeks after surgical transection. Levels of interleukin-1ß (IL-1ß) and hyaluronic acid (HA) were measured by enzyme-linked immunosorbent assay. Knee joint pain was assessed using an incapacitance tester. Osmotic water permeability in cultured rabbit synovial cells was assessed using stopped-flow analysis. RESULTS: Increased synovial fluid volume and knee joint pain were observed in rats with surgically induced OA. In rats with OA, levels of IL-1ß and HA in the articular cavity were higher but concentration of HA in synovial fluid was lower than in sham-operated rats, suggesting excessive synovial fluid secretion. Administration of boiogito improved hydrarthrosis, IL-1ß, and HA concentrations and alleviated knee joint pain in rats with OA. Indomethacin reduced IL-1ß and knee joint pain but failed to improve hydrarthrosis or HA concentration in rats with OA. Osmotic water permeability in synovial cells, which is related to the function of the water channel aquaporin, was decreased by treatment with boiogito. CONCLUSION: Boiogito ameliorates the increased knee joint effusion in rats with OA by suppressing pro-inflammatory cytokine IL-1ß production in the articular cavity and regulating function of water transport in the synovium. The improvement of hydrarthrosis by boiogito results in the increased HA concentration in synovial fluid, thus reducing joint pain. Boiogito may be a clinically useful treatment of QOL in patients with OA with hydrarthrosis.

Nitric oxide mediates selective degeneration of hypothalamic orexin neurons through dysfunction of protein disulfide isomerase.

We addressed the role of nitric oxide (NO) in orexin neuron degeneration that has been observed under various pathological conditions. Administration of an NO donor NOC18 (50 nmol) into the third ventricle of mice resulted in a significant decrease of orexin-immunoreactive (-IR) neurons, in contrast to a modest change in melanin-concentrating hormone-IR neurons. In addition, NOC18 promoted formation of orexin-A-IR aggregates within orexin neurons. An endoplasmic reticulum stress inducer tunicamycin replicated the effect of NOC18 with regard to decrease of orexin-IR neurons and formation of aggregates. We also found that NOC18 caused an increase in S-nitrosation of protein disulfide isomerase (PDI) and a decrease in PDI activity in hypothalamic tissues. Moreover, PDI inhibitors, such as cystamine and securinine, caused a selective decrease of orexin neurons and promoted formation of orexin-A-IR aggregates. Aggregate formation in orexin-IR neurons was also induced by local injection of small interfering RNA targeting PDI. Interestingly, sleep deprivation for 7 consecutive days induced a selective decrease of orexin-IR neurons, which was preceded by aggregate formation in orexin-IR neurons and an increase in S-nitrosated PDI in the hypothalamus. Activity of neuronal NO synthase (nNOS)-positive neurons in the lateral hypothalamus as assessed by c-Fos expression was elevated in response to sleep deprivation. Finally, sleep deprivation-induced decrease of orexin-IR neurons, formation of aggregates, and S-nitrosation of PDI were not observed in nNOS knock-out mice. These results indicate that nNOS-derived NO may mediate specific pathological events in orexin neurons, including neuropeptide misfolding via S-nitrosation and inactivation of PDI.

Aquaporin 5 increases keratinocyte-derived chemokine expression and NF-κB activity through ERK activation.

Aquaporin-5 (AQP5) is a water-selective channel protein that is expressed in submucosal glands and alveolar epithelial cells in the lungs. Recent studies have revealed that AQPs regulate not only water metabolism, but also some cellular functions such as cell growth and migration. Here, we report the role of AQP5 in inflammatory responses. In MLE-12 cells, knockdown of AQP5 using siRNA (10-50 nM) attenuated TNF-α-induced expression of keratinocyte chemoattractant (KC) mRNA and protein. Conversely, in NIH-3T3 cells, overexpression of AQP5 increased KC expression, NF-κB activation, and ERK phosphorylation. The AQP5-induced increase of KC expression was diminished by treatment with ERK inhibitors. Taken together, we propose a new function of AQP5 as an inflammatory signal potentiator, which may be mediated by increased activation of ERK and NF-κB.

Phosphorylation of epidermal growth factor receptor at serine 1047 by MAP kinase-activated protein kinase-2 in cultured lung epithelial cells treated with flagellin.

It has been reported that tumor necrosis factor α (TNFα) activated the p38 MAP kinase pathway, followed by phosphorylation of epidermal growth factor receptor (EGFR) at serine 1047 (Ser1047). Although the phosphorylation of Ser1047 reportedly induced an internalization of EGFR, a protein kinase responsible for the phosphorylation has not been elucidated. In the present study, we found that treatment with flagellin of A549 cells, an alveolar epithelial cell line, induced the activation of p38 MAP kinase, followed by phosphorylation of EGFR at Ser1047. The phosphorylation was strongly inhibited by SB203580, an inhibitor of p38 MAP kinase. The flagellin treatment activated MAP kinase-activated protein kinase-2 (MAPKAPK-2), a protein kinase downstream of p38 MAP kinase, and MK2a inhibitor, an inhibitor of MAPKAPK-2, inhibited the flagellin-induced phosphorylation of EGFR at Ser1047. Unlike the flagellin treatment, the TNFα treatment induced the phosphorylation of EGFR at both Ser1047 and Tyr1173. SB203580 and MK2a inhibitor strongly inhibited the phosphorylation of Ser1047 but not Tyr1173 in EGFR. Finally, bacterially expressed and activated MAPKAPK-2 phosphorylated EGFR at Ser1047 in vitro. These results suggest that flagellin regulates the residence time of EGFR on the plasma membrane and thus the signaling of EGFR through phosphorylation of Ser1047 by MAPKAPK-2.

Identification of a New Pyrrolyl Pyridoindole Alkaloid, Melpyrrole, and Flazin from Honey and Their Cough-Suppressing Effect in Guinea Pigs.

The cough-suppressing effect of honey was demonstrated for the first time using a guinea pig model whereby cough was induced by citric acid and capsaicin, and a new pyrrolyl pyridoindole, 1-(5-(hydroxymethyl)-1H-pyrrol-2-yl)-9H-pyrido[3,4-b]indole-3-carboxylic acid (1), named melpyrrole, and flazin (2) were identified as the active principle components. The structures of 1 and 2 were estimated using a combination approach of an activity-guided survey and LC-MS/MS multivariate analysis and were finally established by total synthesis of 1 and comparison with an authentic standard for 2. Both compounds showed antitussive activity comparable to that of dextromethorphan in guinea pigs. Their antitussive effects were unaffected by an opioid antagonist and reversed by a nitric oxide (NO) synthase inhibitor, indicating that these natural products do not act directly on opiate receptors but through the NO signaling pathway.

Induction of epithelial-mesenchymal transition by flagellin in cultured lung epithelial cells.

Toll-like receptor 5 (TLR5) recognizes bacterial flagellin and activates host inflammatory responses, mainly through activation of the NF-κB pathway. Although pulmonary fibrosis occurs in some cases of lung infection by flagellated bacteria, the pathological roles of TLR5 stimulation in pulmonary fibrosis have yet to be elucidated. In the present study, we first confirmed that flagellin activated the NF-κB pathway in cultured A549 alveolar epithelial cells. Next, we examined the types of genes whose expression was modulated by flagellin in the cells. Microarray analysis of gene expression indicated that flagellin induced a change in gene expression that had a similar trend to transforming growth factor-ß1 (TGF-ß(1)), a key factor in the induction of epithelial-mesenchymal transition (EMT). Biochemical analysis revealed that TGF-ß(1) and flagellin increased the level of fibronectin protein, while they reduced the level of E-cadherin protein after 30 h of treatment. Interestingly, simultaneous treatment with TGF-ß(1) and flagellin significantly augmented these EMT-related changes. Flagellin strongly activated p38 MAP kinase, and the activation was sustained for longer than 30 h. SB203580, an inhibitor of p38 MAP kinase, inhibited the upregulation of fibronectin by both flagellin and TGF-ß(1). Simultaneous treatment with TGF-ß(1) and flagellin augmented the activation of p38 MAP kinase by TGF-ß(1) or flagellin alone. These results strongly suggest that flagellin cooperates with TGF-ß(1) in the induction of EMT in alveolar epithelial cells.

Midbrain dopaminergic neurons utilize nitric oxide/cyclic GMP signaling to recruit ERK that links retinoic acid receptor stimulation to up-regulation of BDNF.

Stimulation of retinoic acid receptors (RARs) protects midbrain dopaminergic neurons, presumably via up-regulation of brain-derived neurotrophic factor (BDNF) expression. The present study was focused on unexplored signaling mechanisms linking RAR stimulation to BDNF expression. Rat midbrain slice cultures treated with an RAR agonist Am80 showed increased tissue levels of BDNF mRNA and protein as compared to cultures without treatment. Am80-induced increase in BDNF expression was observed in dopaminergic neurons, which was blocked by inhibition of extracellular signal-regulated kinase (ERK) activation. We also found that Am80 increased neuronal nitric oxide synthase expression in dopaminergic neurons even during ERK inhibition, and this increase was accompanied by 8-nitro-cyclic GMP formation. Notably, the effect of Am80 on BDNF expression was attenuated by inhibitors of nitric oxide synthase, soluble guanylyl cyclase and cyclic GMP-dependent protein kinase (PKG). Am80-induced ERK phosphorylation in dopaminergic neurons was also attenuated by inhibition of soluble guanylyl cyclase and PKG. Moreover, 8-Br-cyclic GMP induced ERK phosphorylation and BDNF expression in dopaminergic neurons. These results suggest that, by recruiting cyclic GMP and PKG, neuronal nitric oxide synthase-derived nitric oxide plays a novel and essential role in RAR signaling leading to ERK-dependent BDNF up-regulation in midbrain dopaminergic neurons.

Anti-MUC1 antibody inhibits EGF receptor signaling in cancer cells.

MUC1 is a type I transmembrane glycoprotein aberrantly overexpressed in various cancer cells. High expression of MUC1 is closely associated with cancer progression and metastasis, leading to poor prognosis. We previously reported that MUC1 is internalized by the binding of the anti-MUC1 antibody, from the cell surface to the intracellular region via the macropinocytotic pathway. Since MUC1 is closely associated with ErbBs, such as EGF receptor (EGFR) in cancer cells, we examined the effect of the anti-MUC1 antibody on EGFR trafficking. Our results show that: (1) anti-MUC1 antibody GP1.4, but not another anti-MUC1 antibody C595, triggered the internalization of EGFR in pancreatic cancer cells; (2) internalization of EGFR by GP1.4 resulted in the inhibition of ERK phosphorylation by EGF stimulation, in a MUC1 dependent manner; (3) inhibition of ERK phosphorylation by GP1.4 resulted in the suppression of proliferation and migration of pancreatic cancer cells. We conclude that the internalization of EGFR by anti-MUC1 antibody GP1.4 inhibits the progression of cancer cells via the inhibition of EGFR signaling.

Therapeutic effect of nicotine in a mouse model of intracerebral hemorrhage.

Intracerebral hemorrhage (ICH) resulting from the leakage of blood into the brain parenchyma triggers severe tissue damage involving neurodegeneration and inflammation. Increasing lines of evidence indicate that the stimulation of central nicotinic acetylcholine receptors affords neuroprotection against various insults and also suppresses the proinflammatory activation of microglia. Therefore, the present study aimed to determine whether the administration of nicotine modifies the pathological consequences of ICH, using a mouse model of ICH induced by intrastriatal injection of collagenase. Daily intraperitoneal administration of nicotine (2 mg/kg), starting from 3 h after the induction of ICH, inhibited apoptosis and decreased the number of remaining striatal neurons at 3 days after the insult. We also found that nicotine administration increased the relative expression level of the antiapoptotic protein B cell lymphoma-2 versus that of the proapoptotic protein Bax in the brain. In addition, nicotine administration attenuated the activation of microglia/macrophages, infiltration of neutrophils, and increases in oxidative stress associated with ICH, without affecting hematoma expansion and brain edema. It is noteworthy that mice treated with nicotine exhibited improved sensorimotor performance and a marked increase in survival rate after ICH. These results indicate that nicotinic acetylcholine receptors may serve as a novel target for emergency therapy for ICH.

Inhibition of neural activity depletes orexin from rat hypothalamic slice culture.

Orexins (hypocretins) are neuropeptides produced by a small population of hypothalamic neurons whose dysregulation may lead to narcolepsy, a neurological disorder characterized by disorganization of sleep and wakefulness. Excessive stimulation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors causes preferential loss of orexin neurons in the hypothalamus, whereas an adequate level of neuronal excitatory activities is generally known to be important for the maintenance of central neurons. By examining the effect of manipulation of neural activity, we found that 24-72 hr application of tetrodotoxin (TTX) caused a substantial decrease in the number of orexin-immunoreactive neurons, but not of melanin-concentrating hormone-immunoreactive neurons, in hypothalamic slice culture. Similar results were obtained when neural activity was arrested by added extracellular Mg(2+). Reduction of orexin expression by TTX and Mg(2+) was also observed at mRNA level. The decrease of orexin-immunoreactive neurons was attributable to depletion of orexin, because it was reversible after washout of TTX or elevated extracellular Mg(2+) and was not associated with induction of cell death. Blockers of voltage-dependent Ca(2+) channels as well as of NMDA receptors also induced a significant and selective decrease of orexin-immunoreactive neurons. Moreover, TTX-induced decrease of orexin immunoreactivity was largely abrogated by concurrent application of a moderate concentration of NMDA. These results suggest that Ca(2+) entry associated with nontoxic levels of spontaneous activity of glutamatergic inputs plays an important role in the maintenance of orexin neurons in a tissue culture model.

Inhibition by ethyl pyruvate of the nuclear translocation of nuclear factor-kappaB in cultured lung epithelial cells.

Tumor necrosis factor alpha (TNFalpha) is a cytokine inducing inflammatory responses. It has been reported that ethyl pyruvate has anti-inflammatory actions through inhibition of the transcription mediated by nuclear factor-kappa B (NF-kappaB). By reporter gene assay, we first confirmed that TNFalpha activated the NF-kappaB pathway in cultured alveolar epithelial cells, A549 cells. This activation was strongly inhibited by ethyl pyruvate in a concentration-dependent manner. Treatment of the cells with TNFalpha-induced phosphorylation and degradation of IkappaBalpha within 15 min. The level of IkappaBalpha protein was increased from 30 min, suggesting an increase in the NF-kappaB-mediated transcription of IkappaBalpha. Ethyl pyruvate did not affect the changes in IkappaBalpha within 15 min, but strongly inhibited the increase in the IkappaBalpha protein level from 30 min. An immunoblot analysis revealed that ethyl pyruvate inhibited the nuclear translocation of RelA from 5 min of the treatment with TNFalpha. These results strongly suggested that ethyl pyruvate inhibited the NF-kappaB pathway through inhibition of the nuclear translocation of RelA. Ethyl pyruvate may be a good therapeutic drug for inflammation in which activation of the NF-kappaB pathway is involved.

Glycyrrhizin attenuates mucus production by inhibition of MUC5AC mRNA expression in vivo and in vitro.

We have previously indicated that glycyrrhizin (GL), a major component of licorice, has glucocorticoid-like anti-inflammatory effects in cultured airway epithelial cells and suggested its usefulness in the treatment of inflammatory respiratory diseases. On the other hand, mucus hypersecretion in the respiratory tract and goblet cell hyperplasia in the airway epithelium contribute to the morbidity and mortality associated with airway inflammatory diseases. This study, therefore, aimed to examine the effects of GL on airway mucus hyperproduction and define the mechanisms behind these effects. In an in vivo model, GL significantly attenuated goblet cell hyperplasia and MUC5AC mRNA expression in mice treated with lipopolysaccharide or interleukin-4. In addition, GL significantly attenuated MUC5AC protein and mRNA expression by tumor growth factor (TGF)-alpha in cultured NCI-H292 cells. GL also attenuated TGF-alpha-stimulated MUC5AC promoter activity in a luciferase reporter gene assay, but did not affect the stability of MUC5AC mRNA. Taken together, we concluded that GL has an inhibitory effect on mucus hyperproduction both in vivo and in vitro and that GL-mediated inhibition may be mediated through the inhibition of MUC5AC gene transcription.

Retinoic acid receptor stimulation protects midbrain dopaminergic neurons from inflammatory degeneration via BDNF-mediated signaling.

Functions of retinoic acid receptors (RARs) in adult CNS have been poorly characterized. Here we investigated potential neuroprotective action of tamibarotene (Am80), an RARalpha/beta agonist available for the treatment of acute promyelocytic leukemia, on midbrain dopaminergic neurons. Am80 protected dopaminergic neurons in rat midbrain slice culture from injury mediated by lipopolysaccharide-activated microglia, without affecting production of nitric oxide, a key mediator of cell injury. The effect of Am80 was mimicked by another RAR agonist, TAC-101, but not by a retinoid X receptor agonist, HX630, and HX630 did not synergize with Am80. We observed neuronal expression of RARalpha and RARbeta in midbrain slice culture and also found that Am80 increased tissue level of brain-derived neurotrophic factor (BDNF) mRNA. Exogenous BDNF prevented dopaminergic neurodegeneration, and the neuroprotective effect of Am80 was suppressed by a TrkB inhibitor, K252a, or by anti-BDNF neutralizing antibody. These results reveal a novel action of RARs mediated by enhancement of BDNF expression. Finally, oral administration of Am80 prevented dopaminergic cell loss in the substantia nigra induced by local injection of lipopolysaccharide in mice, indicating that RARs are a promising target of therapeutics for neurodegenerative disorders.

Bacterial neuraminidase increases IL-8 production in lung epithelial cells via NF-kappaB-dependent pathway.

Bacterial neuraminidase, a sialic acid-degrading enzyme, is one of the virulent factors produced in pathogenic bacteria like as other bacterial components. However little is known about whether bacterial neuraminidase can initiate or modify a cellular response, such as cytokine production, in epithelial cells at infection and inflammation. We demonstrate here that bacterial neuraminidase, but not heat-inactivated neuraminidase, up-regulates expression of interleukin-8 (IL-8) mRNA and protein in lung epithelial A549 and NCI-H292 cells. We also show that bacterial neuraminidase significantly up-regulates IL-8 promoter activity as well as nuclear factor-kappaB (NF-kappaB) reporter activity. Moreover, inhibition of NF-kappaB signaling suppressed IL-8 mRNA expression induced by bacterial neuraminidase. Taken together, desialylation-induced IL-8 production in lung epithelial cells may play an important role in infection-associated inflammatory events.