Skeletal muscle proteolysis is associated with sympathetic activation and TNF-α-ubiquitin-proteasome pathway in liver cirrhotic rats.

BACKGROUND AND AIM: This study examined the effects of adrenergic blockade on muscle wasting and expression of the ubiquitin-proteasome system, tumor necrosis factor-α (TNF-α) and its signaling pathways in skeletal muscles of cirrhotic rats. METHODS: Cirrhosis was induced by bile duct ligation in adult male Sprague-Dawley rats for 5 weeks. Oral administration of propranolol (75 mg/kg per day) and intraperitoneal administration of TNF-α receptor antagonist (100 µg/kg per day) were delivered for the last 7 and 14 days experimental periods, respectively. RESULTS: Bile duct ligation caused a reduction of myosin heavy chain protein and muscle wasting. The release of free tyrosine and 3-methylhistidine, MAFbx and MuRF-1 ubiquitin ligase expression, myosin heavy chain protein ubiquitination, and 20S proteasome activity were higher in skeletal muscles of cirrhotic rats than in sham controls. In addition, circulating norepinephrine, protein levels of muscle TNF-α, TNF-α receptor-1, and TNF receptor-associated factor-2, phosphorylation of IKK-α/ß, IκB-α, and p65, and NF-κB activity were also increased. Administration of propranolol and TNF-α receptor antagonist led to reduction of post-receptor actions of TNF-α and ubiquitin-proteasome activity in cirrhotic rats. CONCLUSIONS: Our findings suggest a potential role of the sympathetic system, in association with pro-inflammatory responses, in the pathogenesis of muscle wasting in liver cirrhosis.

Hypomimia May Influence the Facial Emotion Recognition Ability in Patients with Parkinson's Disease.

BACKGROUND: Hypomimia is a clinical feature of Parkinson's disease (PD). Based on the embodied simulation theory, the impairment of facial mimicry may worsen facial emotion recognition; however, the empirical results are inconclusive. OBJECTIVE: We aimed to explore the worsening of emotion recognition by hypomimia. We further explored the relationship between the hypomimia, emotion recognition, and social functioning. METHODS: A total of 114 participants were recruited. The patients with PD and normal controls (NCs) were matched for demographic characteristics. All the participants completed the Mini-Mental State Examination and the Chinese Multi-modalities Emotion Recognition Test. In addition to the above tests, the patients were assessed with the Movement Disorder Society-Unified Parkinson's Disease Rating Scale and Parkinson's Disease Social Functioning Scale (PDSFS). RESULTS: Patients with PD with hypomimia had worse recognition of disgust than NCs (p = 0.018). The severity of hypomimia was predictive of the recognition of disgust (ß= -0.275, p = 0.028). Facial emotion recognition was predictive of the PDSFS score of PD patients (ß= 0.433, p = 0.001). We also found that recognizing disgust could mediate the relationship between hypomimia and the PDSFS score (ß= 0.264, p = 0.045). CONCLUSION: Patients with hypomimia had the worst disgust facial recognition. Hypomimia may affect the social function of PD patients, which is related to recognizing the expression of disgust. Emotion recognition training may improve the social function of patients with PD.

Adipose proinflammatory cytokine expression through sympathetic system is associated with hyperglycemia and insulin resistance in a rat ischemic stroke model.

Patients who experience acute ischemic stroke may develop hyperglycemia, even in the absence of diabetes, but the exact mechanisms are still unclear. Adipose tissue secretes numerous proinflammatory cytokines and is involved in the regulation of glucose metabolism. This study aimed to determine the effects of acute stroke on adipose inflammatory cytokine expression. In addition, because sympathetic activity is activated after acute stroke and catecholamines can regulate the expression of several adipocytokines, this study also evaluated whether alterations in adipose proinflammatory cytokines following acute stroke, if any, were medicated by sympathetic system. Acute ischemic brain injury was induced by ligating the right middle cerebral artery and bilateral common carotid arteries in male adult Sprague-Dawley rats. Adipose tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) mRNA and protein levels were determined by RT-PCR and enzyme-linked immunoassay, respectively. The stroke rats developed glucose intolerance on days 1 and 2 after cerebral ischemic injury. The fasting blood insulin levels and insulin resistance index measured by homeostasis model assessment were higher in the stroke rats compared with the sham group. Epididymal adipose TNF-α and MCP-1 mRNA and protein levels were elevated one- to twofold, in association with increased macrophage infiltration into the adipose tissue. When the rats were treated with a nonselective ß-adrenergic receptor blocker, propranolol, before induction of cerebral ischemic injury, the acute stroke-induced increase in TNF-α and MCP-1 was blocked, and fasting blood insulin concentration and homeostasis model assessment-insulin resistance were decreased. These results suggest a potential role of adipose proinflammatory cytokines induced by the sympathetic nervous system in the pathogenesis of glucose metabolic disorder in rats with acute ischemic stroke.

Stearic acid attenuates cholestasis-induced liver injury.

Inflammation is involved in cholestasis-induced hepatic damage. Stearic acid has been shown to possess anti-inflammatory potential. We assessed whether stearic acid has protective effects against cholestasis-related liver damage. Cholestasis was produced by bile duct ligation (BDL) in male Sprague-Dawley rats for 3weeks. Daily administration of stearic acid was started 2weeks before injury and lasted for 5weeks. In comparison with the control group, the BDL group showed hepatic damage as evidenced by elevation in serum biochemicals, ductular reaction, fibrosis, and inflammation. These pathophysiological changes were attenuated by chronic stearic acid supplementation. The anti-fibrotic effect of stearic acid was accompanied by reductions in alpha-smooth muscle actin-positive matrix-producing cells and critical fibrogenic cytokine transforming growth factor beta-1 production. Stearic acid also attenuated BDL-induced leukocyte accumulation and NF-kappaB activation. The data indicate that stearic acid attenuates BDL-induced cholestatic liver injury. The hepatoprotective effect of stearic acid is associated with anti-inflammatory potential.

Detrimental effects of post-treatment with fatty acids on brain injury in ischemic rats.

Studies have illustrated that fatty acids, especially polyunsaturated fatty acids (PUFA), have a role in regulating oxidative stress via the enhancement of antioxidative defense capacity or the augmentation of oxidative burden. Elevated oxidative stress has been implicated in the pathogenesis of brain injury associated with cerebral ischemia/reperfusion (I/R). The objective of this study was to assess whether treatment with fatty acids after focal cerebral I/R induced by occlusion of the common carotid arteries and the middle cerebral artery has effects on brain injury in a rat model. PUFA, including arachidonic acid (AA) and docosahexaenoic acid (DHA), and the saturated fatty acid, stearic acid (SA), were administrated 60 min after reperfusion via intraperitoneal injection. AA and DHA aggravated cerebral ischemic injury, which manifested as enlargement of areas of cerebral infarction and increased impairment of motor activity, in a concentration-dependent manner. However, there were no remarkable differences in post-ischemic alterations between the SA and saline groups. The post-ischemic augmentation of injury in AA and DHA treatment groups was accompanied by increases in the permeability of the blood-brain barrier (BBB), brain edema, metalloproteinase (MMP) activity, inflammatory cell infiltration, cyclooxygenase 2 (COX-2) expression, caspase 3 activity, and malondialdehyde (MDA) production, and by a decrease in the brain glutathione (GSH) content. Furthermore, we found that either AA or DHA alone had little effect on free radical generation in neuroglia, but they greatly increased the hydrogen peroxide-induced oxidative burden. Taken together, these findings demonstrate the detrimental effect of PUFA such as AA and DHA in post-ischemic progression and brain injury after cerebral I/R is associated with augmentation of cerebral I/R-induced alterations, including oxidative changes.

Activation of hepatic inflammatory pathways by catecholamines is associated with hepatic insulin resistance in male ischemic stroke rats.

Patients who experience acute ischemic stroke may develop hyperglycemia, even in the absence of diabetes. In the current study we determined the effects of acute stroke on hepatic insulin signaling, TNF-α expression, endoplasmic reticulum (ER) stress, the activities of c-Jun N-terminal kinase (JNK), inhibitor κB kinase ß (IKK-ß), and nuclear factor-κB (NF-κB) pathways. Rats with cerebral ischemia developed higher blood glucose, and insulin levels, and insulin resistance index, as well as hepatic gluconeogenic enzyme expression compared with the sham-treated group. The hepatic TNF-α mRNA and protein levels were elevated in stroke rats in association with increased ER stress, phosphorylation of JNK1/2 and IKK-ß proteins, IκB/NF-κB signaling, and phosphorylation of insulin receptor-1 (IRS-1) at serine residue. The basal and insulin-stimulated tyrosine phosphorylation of IRS-1 and AKT proteins was reduced. In addition, acute stroke increased circulating catecholamines in association with hepatic adrenergic signaling activation. After administration of a nonselective ß-adrenergic receptor blocker (propranolol) before induction of cerebral ischemic injury, hepatic adrenergic transduction, TNF-α expression, ER stress, and the activation of the JNK1/2, IKK-ß, and NF-κB pathways, and serine phosphorylation of IRS-1 were all attenuated. In contrast, the phosphorylated IRS-1 at tyrosine site and AKT levels were partially restored with improved poststroke hyperglycemia and insulin resistance index. These results suggest that acute ischemic stroke can activate proinflammatory pathways in the liver by the catecholamines and is associated with the development of hepatic insulin resistance.

Protective effects of rutin on liver injury induced by biliary obstruction in rats.

Rutin has been shown to possess beneficial health effects, including hepatoprotection. However, to date, it has not been demonstrated to have a hepatoprotective effect against cholestatic liver injury. This is the first report to show a protective effect of rutin on cholestatic liver injury. Cholestasis was produced by bile duct ligation (BDL) in male Sprague-Dawley rats for 3 weeks. Daily oral administration of rutin was started 1 week before injury and was maintained for 4 weeks. In comparison with the control group, the BDL group showed liver injury as evidenced by histological changes and elevation in serum biochemicals, ductular reaction, fibrosis, inflammation, and oxidative stress. These pathophysiological changes were attenuated by rutin supplementation. Rutin alleviated BDL-induced transforming growth factor ß1 (TGF-ß1), interleukin-1ß, connective tissue growth factor, and collagen expression. The antifibrotic effect of rutin was accompanied by reductions in α-smooth muscle actin-positive matrix-producing cells and Smad2/3 activity critical to the fibrogenic potential of TGF-ß1. Rutin attenuated BDL-induced oxidative stress, leukocyte accumulation, NF-κB activation, and proinflammatory cytokine production. Further studies demonstrated an inhibitory effect of rutin on the redox-sensitive intracellular signaling molecule extracellular signal-regulated kinase (ERK). Rutin also attenuated BDL-induced reduction in NF-E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and AMP-activated protein kinase (AMPK). Taken together, the beneficial effects of rutin were shown to be associated with antioxidative and anti-inflammatory effects as well as the downregulation of NF-κB and TGF-ß/Smad signaling, probably via interference of ERK activation and/or enhancement of Nrf2, HO-1, and AMPK activity.

Beneficial effect of quercetin on cholestatic liver injury.

Bile duct obstruction and subsequent cholestasis are associated with hepatocellular injury, cholangiocyte proliferation, stellate cell activation, Kupffer cell activation, oxidative stress, inflammation and fibrosis. Flavonoids have been shown to confer beneficial health effects, including hepatoprotection. However, the molecular mechanism of flavonoid-mediated hepatoprotection is incompletely understood. In this study, we report the protective effect of quercetin on cholestatic liver injury. Cholestasis was produced by bile duct ligation (BDL) in male Sprague-Dawley rats for 3 weeks. Daily oral administration of quercetin was started 1 week before injury and lasted for 4 weeks. In comparison with the control group, the BDL group showed liver injury, as evidenced by histological changes, and elevation in serum biochemicals, ductular reaction, fibrosis, inflammation and oxidative stress. These pathophysiological changes were attenuated by daily quercetin supplementation. Quercetin alleviated BDL-induced transforming growth factor beta-1 (TGF-ß1), interleukin-1 beta, connective tissue growth factor and collagen expression. The antifibrotic effect of quercetin was accompanied by reductions in α-smooth muscle actin-positive matrix-producing cells and Smad 2/3 activity critical to the fibrogenic potential of TGF-ß1. Quercetin also attenuated BDL-induced oxidative stress, leukocyte accumulation, nuclear factor (NF)-κB activation and proinflammatory cytokine production. Further studies demonstrated an inhibitory effect of quercetin on MyD88 and TGF-ß-activated kinase-1 critical for linking toll-like receptor (TLR) and NF-κB. Taken together, the hepatoprotective, anti-inflammatory and antifibrotic effects of quercetin seem to be multifactorial. The beneficial effects of daily quercetin supplementation are associated with antioxidative and anti-inflammatory potential as well as down-regulation of NF-κB and TGF-ß/Smad signaling, probably via interference with TLR signaling.

Hyperglycemia is associated with enhanced gluconeogenesis in a rat model of permanent cerebral ischemia.

Hyperglycemia is common after acute stroke. In the acute phase of stroke (within 24h), rats with permanent cerebral ischemia developed higher fasting blood glucose and insulin levels in association with up-regulation of hepatic gluconeogenic gene expression, including phosphoenolpyruvate carboxykinase, glucose-6-phosphatase, and fructose-1,6-bisphosphatase. In addition, hepatic gluconeogenesis-associated positive regulators, such as FoxO1, CAATT/enhancer-binding proteins (C/EBPs), and cAMP responsive element-binding protein (CREB), were up-regulated. For insulin signaling transduction, phosphorylation of insulin receptor (IR), insulin receptor substrate-1 (IRS1) at the tyrosine residue, Akt, and AMP-activated protein kinase (AMPK), were attenuated in the liver, while negative regulators of insulin action, including phosphorylation of p38, c-Jun N-terminal kinase (JNK), and insulin receptor substrate-1 (IRS1) at the serine residue, were increased. In addition, the brains of rats with stroke exhibited a reduction in phosphorylation of IRS1 at the tyrosine residue and Akt. Circulating cortisol, glucagon, C-reactive protein (CRP), monocyte chemoattractant protein 1 (MCP-1), and resistin levels were elevated, but adiponectin was reduced. Our data suggest that cerebral ischemic insults might modify intracellular and extracellular environments, favoring hepatic gluconeogenesis and the consequences of hyperglycemia.

Beneficial effect of docosahexaenoic acid on cholestatic liver injury in rats.

Bile duct obstruction and subsequent cholestasis are associated with hepatocellular injury, cholangiocyte proliferation, stellate cell activation, Kupffer cell activation, oxidative stress, inflammation and fibrosis. Docosahexaenoic acid (DHA) is an essential polyunsaturated fatty acid that has been shown to possess health beneficial effects, including hepatoprotection. However, the molecular mechanism of DHA-mediated hepatoprotection is not fully understood. In the present study, we report the protective effect of DHA on cholestatic liver injury. Cholestasis was produced by bile duct ligation (BDL) in male Sprague-Dawley rats for 3 weeks. Daily administration of DHA was started 2 weeks before injury and lasted for 5 weeks. In comparison with the control group, the BDL group showed hepatic damage as evidenced by histological changes and elevation in serum biochemicals, ductular reaction, fibrosis, inflammation and oxidative stress. These pathophysiological changes were attenuated by chronic DHA supplementation. DHA alleviated BDL-induced transforming growth factor beta-1 (TGF-ß1), intereukin-1beta, connective tissue growth factor and collagen expression. The anti-fibrotic effect of DHA was accompanied by reductions in α-smooth muscle actin-positive matrix-producing cells and Smad 2/3 activity critical to the fibrogenic potential of TGF-ß1. DHA also attenuated BDL-induced leukocyte accumulation and nuclear factor-κB (NF-κB) activation. Further studies demonstrated an inhibitory effect of DHA on redox-sensitive intracellular signaling molecule extracellular signal-regulated kinase (ERK). Taken together, the hepatoprotective, anti-inflammatory and anti-fibrotic effects of DHA seem to be multifactorial. The beneficial effects of chronic DHA supplementation are associated with anti-oxidative and anti-inflammatory potential as well as down-regulation of NF-κB and transforming growth factor beta/Smad signaling probably via interference with ERK activation.

Protein nitration is associated with increased proteolysis in skeletal muscle of bile duct ligation-induced cirrhotic rats.

Cirrhosis is characterized by skeletal muscle wasting. In this study, the effects of nitric oxide production on skeletal muscle protein nitration and degradation in cirrhosis were investigated. Cirrhosis was induced by bile duct ligation (BDL) in Sprague-Dawley rats for 4 weeks. The BDL-induced cirrhotic rats and sham-operated rats were then injected daily with either saline or N(G)-l-nitro-arginine methyl ester (l-NAME) for 7 days from week 4 to week 5, after which nitrite/nitrate, glutathione reduction, as well as protein nitration, ubiquitination, and degradation were assessed in skeletal muscle. Elevated muscular nitrite/nitrate concentrations, protein nitration, total ubiquitin conjugates, and degradation fragments of myosin heavy chain as well as diminished glutathione reduction levels were observed in BDL-induced cirrhotic rats as compared with controls. Administration of l-NAME for 1 week led to reduction of nitrite/nitrate levels; protein nitration was also decreased in the skeletal muscle. In addition, ubiquitination of muscular proteins and degradation of myosin heavy chain were significantly diminished after treatment of l-NAME. In conclusion, nitrosative stress occurred in the skeletal muscle of BDL-induced cirrhotic rats and may lead to increased proteolysis of muscle-specific structural proteins.

Protective effect of docosahexaenoic acid against brain injury in ischemic rats.

Evidence suggests that inactivation of cell-damaging mechanisms and/or activation of cell-survival mechanisms may provide effective preventive or therapeutic interventions to reduce cerebral ischemia/reperfusion (I/R) injuries. Docosahexaenoic acid (DHA) is an essential polyunsaturated fatty acid in the central nervous system that has been shown to possess neuroprotective effects. We examined whether different preadministrative protocols of DHA have effects on brain injury after focal cerebral I/R and investigated the potential neuroactive mechanisms involved. Sprague-Dawley rats were intraperitoneally pretreated with DHA once 1 h or 3 days being subjected to focal cerebral I/R or daily for 6 weeks before being subjected to focal cerebral I/R. Reduction of brain infarction was found in all three DHA-pretreated groups. The beneficial effect of DHA on the treatment groups was accompanied by decreases in blood-brain barrier disruption, brain edema, malondialdehyde (MDA) production, inflammatory cell infiltration, interleukin-6 (IL-6) expression and caspase-3 activity. Elevation of antioxidative capacity, as evidenced by decreased MDA level and increased superoxide dismutase activity and glutathione level, was detected only in the chronic daily-administration group. The two single-administration groups showed increased phosphorylation of extracellular-signal-regulated kinase (ERK). Elevation of Bcl-2 expression was detected in the chronic daily-administration and 3-day-administration groups. In vitro study demonstrated that DHA attenuated IL-6 production from stimulated glial cells involving nuclear factor kappaB inactivation. Therefore, the data suggest that the neuroprotective mechanisms of DHA pretreatment are, in part, mediated by attenuating damaging mechanisms through reduction of cytotoxic factor production and by strengthening survival mechanisms through ERK-mediated and/or Bcl-2-mediated prosurvival cascade.