New insights into Nod-like receptors (NLRs) in liver diseases.

Activation of inflammatory signaling pathways is of central importance in the pathogenesis of alcoholic liver disease (ALD) and nonalcoholic steatohepatitis (NASH). Nod-like receptors (NLRs) are intracellular innate immune sensors of microbes and danger signals that control multiple aspects of inflammatory responses. Recent studies demonstrated that NLRs are expressed and activated in innate immune cells as well as in parenchymal cells in the liver. For example, NLRP3 signaling is involved in liver ischemia-reperfusion (I/R) injury and silencing of NLRP3 can protect the liver from I/R injury. In this article, we review the evidence that highlights the critical importance of NLRs in the prevalent liver diseases. The significance of NLR-induced intracellular signaling pathways and cytokine production is also evaluated.

Effects of Contrast-Enhanced Ultrasonography in Monitoring Hepatic Microcirculation After Rat Liver Ischemia-Reperfusion Injury.

OBJECTIVES: Our objective was to evaluate the effects of contrast-enhanced ultrasonography in monitoring microcirculation after rat liver ischemia-reperfusion injury. MATERIALS AND METHODS: Male Wistar rats (n = 36) were divided into sham-operated and ischemia-reperfusion groups. Rats in the ischemia-reperfusion groups underwent normothermic liver ischemia for 15 minutes followed by 1, 6, or 24 hours of reperfusion. At different time points, contrast-enhanced ultrasonography was performed to determine peak intensity in monitoring hepatic microcirculation. In addition, serum levels of alanine aminotransferase, aspartate aminotransferase, tumor necrosis factor α, and interleukin 1ß levels were measured. Histopathologic changes were also observed. RESULTS: One hour after reperfusion, peak intensity values decreased, and serum levels of alanine aminotransferase, tumor necrosis factor α, and interleukin 1ß increased significantly in the ischemia-reperfusion group compared with the sham-operated group. Histology results showed mild injury. Six hours after reperfusion, peak intensity values decreased continuously, serum levels of alanine aminotransferase, tumor necrosis factor α, and interleukin 1ß decreased, and aspartate aminotransferase levels increased. Histology results showed severe injury compared with 1 hour after reperfusion. Twenty-four hours after reperfusion, peak intensity values increased, alanine aminotransferase and aspartate aminotransferase levels decreased, and histology results showed moderate injury compared with 6 hours after reperfusion. Peak intensity values were negatively correlated to alanine aminotransferase (P < .05; γ = -0.38) and aspartate aminotransferase (P < .01; γ = -0.78) levels. CONCLUSIONS: Microcirculation dysfunction after liver ischemia-reperfusion injury can be monitored by contrast-enhanced ultrasonography. The perfusion of contrast agents negatively correlates to the severity of injuries.

Enhancement of the nonamyloidogenic pathway by exogenous NGF in an Alzheimer transgenic mouse model.

Nerve growth factor (NGF) is an important nerve cell growth regulatory factor and has an indispensable role in the development, survival and regeneration of the cholinergic basal forebrain (CBF) neurons, and it has multiple targets when used for Alzheimer's Disease (AD) therapy. In this study, we observed whether NGF can affect cholinergic neurons to change amyloid-ß precursor protein (APP) metabolism process and reduce amyloidosis in AD brains. NGF was administered intranasally to APP/PS1 double-transgenic mice for 14weeks. We observed an increase in APP695 and ADAM10 and a decrease in BACE1 and PS1 protein levels and, subsequently, a reduction in Aß1-40 and Aß1-42 levels and Aß burden were present in NGF-treated mice brains, suggesting that NGF enhanced the APP nonamyloidogenic cleavage pathway and reduced the Aß generation in the APP/PS1 transgenic mice brains.

Kidins220/ARMS contributes to airway inflammation and hyper-responsiveness in OVA-sensitized mice.

BALB/c mice were sensitized and challenged with ovalbumin. We hypothesized that Kidins220/ARMS influences airway inflammation and hyper-responsiveness during allergic airway challenge, and assessed it by intranasal administration of anti-NGF antibody or anti-ARMS antibody to mice. Airway resistance was measured using a sealed whole-body plethysmograph. Total cell numbers and the percentage of different inflammatory cells in BALF were counted. Expression of IL-1ß, IL-4 and TNF-α were determined by ELISA, and NF-κB activation determined by EMSA. Kidins220/ARMS expression was observed in ovalbumin-sensitized mice by immunofluorescence or western blotting. IL-1ß, IL-4, and TNF-α were overexpressed and NF-κB activation increased after allergen challenge compared with controls. After treatment with anti-ARMS or anti-NGF, levels of IL-1ß, IL-4 and TNF-α and NF-κB activation were reduced in comparison with those of ovalbumin-sensitized mice. These results suggest that NGF-mediated Kidins220/ARMS signaling participates in the pathogenesis of asthma, and contributes to airway inflammation and hyper-responsiveness in ovalbumin-sensitized mice.

NGF/TrkA-mediated Kidins220/ARMS signaling activated in the allergic airway challenge in mice.

BACKGROUND: Nerve growth factor (NGF), combined with its high-affinity receptor tyrosine kinase receptor A (TrkA), has been reported to be involved in the pathogenesis of asthma. OBJECTIVE: To investigate whether the downstream protein ankyrin-rich membrane spanning (ARMS), a novel transmembrane substrate of protein kinase D (Kidins220), is activated in the pathogenesis of asthma. METHODS: The asthmatic model was established by the inhalation of ovalbumin in BALB/c mice. The effects of NGF and TrkA on Kidins220/ARMS in an allergic airway challenge were assessed by administering anti-NGF or anti-TrkA antibody to the mice. Pathologic changes in the bronchi and lung tissues were examined by means of hematoxylin and eosin staining; the inflammatory cells in the bronchoalveolar lavage fluid (BALF) were counted; and co-expression of ARMS and TrkA in BALF cells was observed by means of immunofluorescence. In addition, Kidins220/ARMS, CrkL, NGF, TrkA protein, and Kidins220 messenger RNA levels were determined using Western blot or quantitative reverse transcription-polymerase chain reaction. RESULTS: Using fluorescence microscopy, we found that Kidins220 and TrkA were co-expressed on the membranes of the BALF cells of asthmatic mice. Compared with expression in control animals, Kidins220/ARMS, CrkL, NGF, and TrkA were overexpressed in the lungs after allergen challenge. Moreover, after the mice were treated with anti-NGF or anti-TrkA, the Kidins220/ARMS levels and allergen-induced airway inflammation decreased. CONCLUSIONS: These results suggest that Kidins220/ARMS partly participates in the pathogenesis of asthma through the NGF-TrkA signaling pathway, possibly representing a new mechanism in asthma.

Calcitonin gene-related peptide enhances CREB phosphorylation and attenuates tau protein phosphorylation in rat brain during focal cerebral ischemia/reperfusion.

Calcitonin gene-related peptide (CGRP) is a potent vasodilator and immune cell modulator. Exogenous CGRP could increase the cerebral blood flow significantly and protect the ischemic neurons, but its mechanism is not entirely clear. The effect of CGRP on the expressions of CREB and tau in the ipsilateral parietal cortex were detected in focal cerebral ischemia/reperfusion model. The expression of CREB mRNA decreased in ischemia/reperfusion group (I/R group) compared with that of the sham operation group, and it got highest in CGRP group. CREB expression was lesser in I/R group than sham group, but it became more in CGRP group than I/R group. Phospho-CREB became more in I/R group, and it got most in CGRP group in the cortex. No significant difference was observed on Tau mRNA expression in all the groups. The level of tau hyperphosphorylation at Ser199/202 site and total tau in rat parietal cortex were significantly higher in I/R group than sham group. CGRP significantly inhibited tau hyperphosphorylation and the level of total tau also significantly reduced in CGRP group than that in I/R group. CGRP can upregulate the expression of CREB and phospho-CREB and attenuate the level of tau hyperphosphorylation in the ischemic neurons of the parietal cortex during focal cerebral ischemia/reperfusion. Phosphorylating CREB and inhibiting tau phosphorylation are probably involved in the mechanism of protective effect of CGRP to ischemic neurons.

Cyclic-AMP response element binding protein and tau are involved in the neuroprotective mechanisms of nerve growth factor during focal cerebral ischemia/reperfusion in rats.

Nerve growth factor (NGF) has protective and therapeutic effects after cerebral ischemic injury. However, its mechanism of action is not clear. We explored the protective mechanism of exogenous NGF on rat hippocampal neurons after focal cerebral ischemia/reperfusion. Changes were detected in the expression of cyclic-adenosine monophosphate (AMP) response element binding protein (CREB) messenger ribonucleic acid (mRNA), CREB protein, phosphorylated CREB, tau mRNA, total tau protein and the state of phosphorylation of tau protein at the serine 199/202 site. NGF treatment significantly increased the expression of CREB mRNA, CREB and phosphorylated CREB in the hippocampal CA1 region. NGF alleviated the level of phosphorylation of tau and the expression level of total tau. It is possible that the protective effect of NGF on the ischemic neuron was due to the activation of transcription and translation of CREB, the reduction in the level of phosphorylation of tau protein, and the activation of a series of signal pathways.

Nerve growth factor mediated SH2-Bbeta/Akt signal pathway activated in allergic airway challenge in mice.

BACKGROUND AND OBJECTIVE: Nerve growth factor (NGF) contributes to airway inflammation and bronchoconstriction in allergic asthma. The Src homology 2beta/serine/threonine kinase (SH2-Bbeta/Akt) pathway is one of the avenues through which NGF regulates the biological activity of pheochromocytoma (PC)12 cells. It has also been reported that NGF upregulates the expression of SH2-Bbeta in the lung tissue of asthmatic mice. The present study investigated the effects of NGF and SH2-Bbeta on Akt activation during allergic airway challenge. METHODS: BALB/c mice were sensitized and challenged with ovalbumin. The effects of NGF and SH2-Bbeta on Akt in allergic airway challenge were assessed by intravenously administering anti-NGF antibody or a mutant of SH2-Bbeta (R555E) to these mice. Pulmonary histological changes were then assessed and the inflammatory cells in the BAL fluid (BALF) were counted. Additionally, phosphorylated Akt (p-Akt) expression was determined by fluorescence microscopy, western blotting and quantitative RT-PCR. Airway resistance was also measured using closed-type body plethysmography. RESULTS: We observed p-Akt overexpression in the lungs after allergen challenge by fluorescence microscopy, Western blotting and RT-PCR, as compared with the control. However, after treatment with anti-NGF or R555E, p-Akt levels and allergen-induced airway inflammation were reduced in comparison with those of allergen-challenged mice. Anti-NGF and R555E also decreased airway hyperresponsiveness caused by allergen challenge in response to methacholine (MCH). CONCLUSIONS: These results suggest that SH2-Bbeta regulation of Akt partly participates in the NGF-mediated development of allergic airway challenge.

Toll-like receptor 4-mediated myeloid differentiation factor 88-dependent signaling pathway is activated by cerebral ischemia-reperfusion in hippocampal CA1 region in mice.

The Toll-like receptor 4 (TLR4)-mediated myeloid differentiation factor 88 (MyD88)-dependent signaling pathway plays an essential role in inflammation resulting from invading microbes. However, whether the signaling pathway is activated in the inflammatory reaction of cerebral ischemia-reperfusion and its mechanism is still unclear. In this experiment mice were randomly divided into sham group, ischemia/reperfusion group and TLR4-blocked group with different time points of reperfusion at 12, 24, 48 and 72 h . Mice cerebral ischemia was induced by occlusion of common carotid arteries (CCA) bilaterally. TLR4 signaling pathway was inhibited using specific anti-TLR4 binding protein to prevent TLR4 from interacting with its receptors. We determined the result of TLR4 antibodies-blocking and mice cerebral ischemia-reperfusion injuries by Western blot, and evaluated neuronal damage in the hippocampus. We also determined expression of TLR4 mRNA and MyD88 mRNA by in situ hybridization (ISH), activation of nuclear factor (NF)-kappaB by electrophoretic mobility-shift analysis (EMSA), and expression of interrleukin (IL)-1beta protein by Western blot. The results demonstrated that TLR4-mediated MyD88-dependent signaling pathway activated by ischemia-reperfusion may be involved in the mechanism of ischemia-reperfusion through upregulation of NF-kappaB, IL-1beta.

Aldo-keto reductase family 1 B10 protein detoxifies dietary and lipid-derived alpha, beta-unsaturated carbonyls at physiological levels.

Alpha, beta-unsaturated carbonyls are highly reactive mutagens and carcinogens to which humans are exposed on a daily basis. This study demonstrates that aldo-keto reductase family 1 member B10 (AKR1B10) is a critical protein in detoxifying dietary and lipid-derived unsaturated carbonyls. Purified AKR1B10 recombinant protein efficiently catalyzed the reduction to less toxic alcohol forms of crotonaldehyde at 0.90 microM, 4-hydroxynonenal (HNE) at 0.10 microM, trans-2-hexanal at 0.10 microM, and trans-2,4-hexadienal at 0.05 microM, the concentrations at or lower than physiological exposures. Ectopically expressed AKR1B10 in 293T cells eliminated immediately HNE at 1 (subtoxic) or 5 microM (toxic) by converting to 1,4-dihydroxynonene, protecting the cells from HNE toxicity. AKR1B10 protein also showed strong enzymatic activity toward glutathione-conjugated carbonyls. Taken together, our study results suggest that AKR1B10 specifically expressed in the intestine is physiologically important in protecting the host cell against dietary and lipid-derived cytotoxic carbonyls.

SH2-B beta expression in alveolar macrophages in BAL fluid of asthmatic guinea pigs and its role in NGF-TrkA-mediated asthma.

BACKGROUND AND OBJECTIVE: Nerve growth factor (NGF)/tyrosine kinase receptor A (TrkA) signalling may play an important role in the pathogenesis of asthma, and SH2-B beta, a TrkA-binding protein, modulates the NGF signalling pathway. In this study, SH2-B beta expression in alveolar macrophages (AM) in guinea pig BAL fluid and its role in asthma pathogenesis through the NGF-TrkA signalling pathway were investigated. METHODS: Guinea pigs were randomized into five groups: control, a model of asthma, anti-SH2-B beta antibody treatment, anti-NGF antibody treatment and anti-TrkA antibody treatment. The asthmatic model was established in guinea pigs by inhalation of ovalbumin. Specific anti-SH2-B beta, anti-NGF and anti-TrkA antibodies were administered and AM were isolated from BAL fluid to assess SH2-B beta expression using an immunofluorescence assay. SH2-B beta and TrkA protein expression were determined by western blotting, IL-1 beta and IL-4 levels in the BAL fluid supernatants were determined by ELISA, and pathological changes in the bronchi and lung tissues were examined by HE staining. RESULTS: Lymphocyte, eosinophil and total inflammatory cell numbers in BAL fluid were significantly higher in the asthma model group than in the other groups (P < 0.01). NGF expression in the asthma model group was significantly higher than that in the PBS control group (P < 0.01). SH2-B beta was expressed in AM of control animals and expression was significantly higher in the asthma model than in the other groups (P < 0.01). TrkA protein expression was significantly higher in the asthma model group than in the PBS group (P < 0.01), and treatment with anti-NGF antibody resulted in significant reduction of TrkA expression (P < 0.01). CONCLUSIONS: SH2-B beta is expressed in AM of normal guinea pigs, and SH2-B beta may participate in asthma pathogenesis through the NGF-TrkA signalling pathway.

TLR4-mediated MyD88-dependent signaling pathway is activated by cerebral ischemia-reperfusion in cortex in mice.

To study whether the signaling pathway is activated in the inflammatory reaction of cerebral ischemia-reperfusion and its mechanism. The mice were randomly divided into sham group, ischemia-reperfusion group and TLR4-blocked group with different time points of reperfusion 12h, 24h, 48h and 72h group. We observed the different expression of TLR4 mRNA and MyD88 mRNA, activation of NF-kappaB and the TNF-alpha and IL-1beta protein levels in each group at different time point after ischemia-reperfusion. Mice cerebral ischemia was induced by occlusion of common carotid arteries (CCA) bilaterally. TLR4 signaling pathway could be inhibited by specific anti-TLR4 binding protein to prevent TLR4 from interacting with its receptors. We determined the result of TLR4 antibodies-blocking and mice cerebral ischemia-reperfusion injuries by Western blot, and evaluated neuronal damage in cortex. We also determined the expression of TLR4 mRNA and MyD88 mRNA by in situ hybridization (ISH), the activation of NF-kappaB by EMSA, and the expression of TNF-alpha protein by Western blot. Anti-TLR4 binding TLR4 receptors before reperfusion was effective; There was distinct difference among each group respecting neuronal damage; The expression of TLR4 mRNA and MyD88 mRNA, the activation of NF-kappaB, and the expression of TNF-alpha protein showed clear difference as well. LR4-mediated MyD88-dependent signaling pathway activated by ischemia-reperfusion may be involved in the mechanism of ischemia-reperfusion through upregulation of NF-kappaB and TNF-alpha.

[Effect of adrenomedullin on neuron apoptosis and early growth response gene-1 after focal ischemia/ reperfusion in rats].

OBJECTIVE: To explore the influence of adrenomedullin (ADM) on apoptosis of neuron, volume of infarction and the expression of early growth response gene-1 (Egr-1) mRNA in the rat with focal ischemia/reperfusion (I/R) injury. METHODS: Fifty-four SD rats were randomly divided into sham operation group, ADM femoral vein group, internal carotid artery group and lateral cerebral ventricle group. The model was reproduced by ligating the middle cerebral artery (MCA) with a ligature for 2 hours followed by injection of ADM through femoral artery, internal carotid artery and lateral cerebral ventricle before reperfusion for 22 hours. The volume of infarction was estimated with tetrazolium chloride (TTC) staining, apoptosis of the neuron was detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method, the positive expression of Egr-1 mRNA was detected by in-situ hybridization. RESULTS: The volume of infarction were smaller after the injection of ADM through different ways than that of I/R group. The result was better when the internal carotid artery and the lateral cerebral ventricle were used than that after injection by the way of the femoral vein (both P<0.05). There were few positive cells with TUNEL staining in the cerebral cortex and hippocampus CA1 zone in the sham operation group, and more apoptotic cells were seen in the group with focal brain I/R injury (both P<0.01). After the administration of ADM, especially through the internal carotid artery and the lateral cerebral ventricle, the number of the positive cells with TUNEL staining was decreased obviously compared with I/R group (both P<0.01). There was a little positive expression of Egr-1 mRNA in the cerebral cortex and hippocampus CA1 zone in sham operation group. The expression was enhanced in the group with focal brain I/R injury (both P<0.01). With the injection of ADM, the expression was much more enhanced, especially when internal carotid artery and the lateral cerebral ventricle were used for injection compared with those in I/R group (both P<0.01). CONCLUSION: The injection of ADM through different ways can reduce the neural injury, decrease the apoptosis of the neurons and the volume of the infarction, and increase the expression of Egr-1 mRNA. Therefore, it is efficacious in the treatment of cerebral ischemia.

Effect of adrenomedullin on neuron apoptosis, infarction volume and expression of Egr-1 mRNA after focal ischemia-reperfusion in rats.

Objective To observe the influence of adrenomedullin (ADM) on neuron apoptosis, infarction volume of brain, and the expression of early growth response 1 (Egr-1) mRNA in ischemia-reperfusion rats. Methods The arteria cerebri media was tied for 2 h to construct the ischemia model. Infarction volume was detected by triphenltetrazolium chloride (TTC) staining, neuronal apoptosis and necrosis was detected with terminal deoxynucleotidyl transferase nick labeling (TUNEL) method, and the Egr-1 mRNA expression was examined by in situ hybridization (ISH). Results Infarction volume after ischemia-reperfusion is (269 +/- 20) mm(3). Infarction volume after injection of ADM through different ways are femoral vein (239 +/- 17) mm(3) (decreased by 11.2%), arteria carotis (214 +/- 14) mm(3) (by 20.4%) and lateral cerebral ventricle (209 +/- 13) mm(3) (by 22.3%), respectively. The results indicate that injecting ADM through arteria carotis and lateral cerebral ventricle is much more effective than it through femoral vein (P < 0.05). The TUNEL-positive cells in cerebral cortex or hippocampus are few in the sham operation group, but much more in the ischemia-reperfusion group. After being supplied with ADM, especially through arteria carotis interna or lateral cerebral ventricle way, the TUNEL-positive cells decreased obviously. Expression of Egr-1 mRNA was low in the cerebral cortex of the sham operation group rats, enhanced in the ischemia and reperfusion group rats, and enhanced markedly after treatment with ADM, especially through arteria carotis interna or lateral cerebral ventricle way (P < 0.01). Conclusion Injection of ADM through different ways could alleviate neural dysfunction, decrease neuron apoptosis and brain infarction volume, and increase the expression of Egr-1 mRNA.

[The expression of protein kinase C and the regulatory effect of nerve growth factor in the lung and the visceral sensory afferent system of asthmatic guinea pigs].

OBJECTIVE: To explore the expression of protein kinase C (PKC) and the regulatory effect of nerve growth factor (NGF) in the lung and the visceral sensory afferent system (C(7)-T(5) spinal ganglia and the corresponding posterior horn of the spinal cord) of asthmatic guinea pigs. METHODS: Forty guinea pigs were divided to four groups, a saline control group (group A, n = 8), a provocation alone control group (group B, n = 8), an asthmatic group (group C, n = 12) and an anti-NGF group (group D, n = 12). The alterations of PKC immunoreactivity were investigated by means of immunohistochemistry in the C(7)-T(5) spinal ganglia and the corresponding posterior horn of the spinal cord of all groups. The expressions of NGF and PKC were investigated by Western blot in the lung, C(7)-T(5) spinal ganglia and the corresponding posterior horn of the spinal cord of all groups. The results were analyzed by the Luzex-F real time image analysis system and the gel imaging analysis system respectively. RESULTS: (1) Immunohistochemistry results: The absorbency (A) values of PKC were 0.102 +/- 0.009, 0.113 +/- 0.009, 0.106 +/- 0.005 and 0.116 +/- 0.007 in the C(7)-T(5) spinal ganglia and the corresponding posterior horn of the spinal cord of group A and group B respectively. There was no significant difference between group A and group B (P > 0.05). The A values of PKC were 0.215 +/- 0.014 and 0.176 +/- 0.010 respectively in the C(7)-T(5) spinal ganglia and the corresponding posterior horn of the spinal cord of group C, which were significantly different compared with group A (P < 0.01). The A values of PKC were 0.140 +/- 0.008 and 0.130 +/- 0.011 respectively in the C(7)-T(5) spinal ganglia and the corresponding posterior horn of the spinal cord of group D, which were significantly different compared with group C (P < 0.01). (2) Western blot results: Compared with group A (the relative A values were 0.51 +/- 0.02, 0.43 +/- 0.01 and 0.92 +/- 0.02 respectively) and group B, the expression of PKC (the relative A values were 1.51 +/- 0.01, 1.40 +/- 0.03 and 2.22 +/- 0.02 respectively) increased markedly in the lung, C(7)-T(5) spinal ganglia and the corresponding posterior horn of the spinal cord of group C; however, the expression of PKC of group D (the relative A values were 0.80 +/- 0.03, 0.83 +/- 0.01 and 1.12 +/- 0.02 respectively) decreased markedly in comparison with group C. CONCLUSION: The present results indicate that PKC might be involved in the pathogenesis of bronchial asthma, and NGF can upregulate the expression of PKC.