Distribution of nitric oxide synthase in normal and cirrhotic human liver

The role of nitric oxide synthase/ nitric oxide in infection-related cancers: Beyond antimicrobial activity

As a free radical and endogenous effector molecule, mammalian endogenous nitric oxide (NO) is mainly derived from nitric oxide synthase (NOS) via L-arginine. NO participates in normal physiological reactions and provides immune responses to prevent the invasion of foreign bacteria. However, NO also has complex and contradictory biological effects. Abnormal NO signaling is involved in the progression of many diseases, such as cancer. In the past decades, cancer research has been closely linked with NOS/ NO, and many tumors with poor prognosis are associated with high expression of NOS. In this review, we give a overview of the biological effects of NOS/ NO. Then we focus on the oncogenic role of iNOS/ NO in HPV, HBV, EBV and H. pylori related tumors. In fact, there is growing evidence that iNOS could be used as a potential therapeutic target in cancer therapy. We emphasize that the pro-tumor effect of NOS/ NO is greater than the anti-tumor effect.

Albumin, an interesting and functionally diverse protein, varies from 'native' to 'effective' (Review)

Human serum albumins (HSAs) are synthesized in the liver and are the most abundant proteins in plasma of healthy human. They play an important role in the pathophysiological processes of the liver and even the whole organism. Previous studies have mainly focused on the regulation of HSAs' expression. However, with the progress of research in recent years, it has been found that the content of circulating albumin cannot fully reflect the biological function of albumin itself. Given the aforementioned fact, the concept of serum 'effective albumin concentration' has been proposed. It refers to the content of albumin that is structurally and functionally intact. Alterations in the molecular structure and function of albumin have been reported in a variety of diseases, including liver disease. Moreover, these changes have been verified to affect the progression of oxidative stress‑related diseases. However, the link between albumin structure and function has not been fully elaborated, and the mechanisms by which different forms of albumin affect disease also need to be further investigated. In this context, the present review mainly expounded the biological characteristics and functions of albumin, summarized the different types of post‑translational modification of albumin, and discussed their functional changes and possible mechanisms in non‑alcoholic fatty liver disease, alcoholic hepatitis, viral hepatitis and different stages of cirrhosis. This will help to improve understanding of the role of albumin in disease development and provide a more comprehensive physiological basis for it in disease treatment.

Esawy AELW. Evaluating the hepatotoxic versus the nephrotoxic role of iron oxide nanoparticles: One step forward into the dose-dependent oxidative effects

The present study has been designed to detect the dose-dependent effect of iron oxide nanoparticles (IONPs) on the liver and kidney of rats by evaluating three different doses 30, 300, 1000 mg/kg/day IONPs for 28 days. Forty rats were divided into four groups; I (control), II (low dose), III (medium dose) and IV (high dose). There also was a statistically-significant elevation in the serum levels of hepatic enzymes; AST and ALT in medium & high dose. The elevation of serum ALP, on the other hand, was significant in all IONPs doses. There was significant elevation in the levels of urea creatinine, and MDA in the medium and high doses of IONPs. The activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) showed significant decrease in the high dose only compared to the control group. The serum iron levels increased in a dose-dependent manner in the IONPs-treated groups with highly significant increase in the moderate and high dose groups. On comparing the effect of different doses of IONPs between the liver and kidney, the high dose revealed statistically significant difference (p < 0.05) in the area percent of collagen deposition (54.4 ± 3.9 versus 6.1 ± 2.6) and alpha smooth muscle actin (α-SMA) reaction (7.7 ± 1.5 versus 17.8 ± 4.3) in the liver relative to the kidney. The medium and high doses revealed statistically significant difference in optical density of Periodic acid Schiff (PAS) reaction (45 ± 3.4 versus 50.3 ± 1.8 in the medium dose, and 38.9 ± 6 versus 63 ± 3 in the high dose) and area percent of inducible nitric oxide synthase (iNOS) reaction (12.98 ± 2.7 versus 3.5 ± 0.5 in the medium dose, and 27.91 ± 1.5 versus 7.7 ± 0.6 in the high dose) in the liver relative to the kidney.

ASL mRNA-LNP Therapeutic for the Treatment of Argininosuccinic Aciduria Enables Survival Benefit in a Mouse Model

Argininosuccinic aciduria (ASA) is a metabolic disorder caused by a deficiency in argininosuccinate lyase (ASL), which cleaves argininosuccinic acid to arginine and fumarate in the urea cycle. ASL deficiency (ASLD) leads to hepatocyte dysfunction, hyperammonemia, encephalopathy, and respiratory alkalosis. Here we describe a novel therapeutic approach for treating ASA, based on nucleoside-modified messenger RNA (modRNA) formulated in lipid nanoparticles (LNP). To optimize ASL-encoding mRNA, we modified its cap, 5' and 3' untranslated regions, coding sequence, and the poly(A) tail. We tested multiple optimizations of the formulated mRNA in human cells and wild-type C57BL/6 mice. The ASL protein showed robust expression in vitro and in vivo and a favorable safety profile, with low cytokine and chemokine secretion even upon administration of increasing doses of ASL mRNA-LNP. In the ASL^Neo/Neo mouse model of ASLD, intravenous administration of the lead therapeutic candidate LNP-ASL CDS2 drastically improved the survival of the mice. When administered twice a week lower doses partially protected and 3 mg/kg LNP-ASL CDS2 fully protected the mice. These results demonstrate the considerable potential of LNP-formulated, modified ASL-encoding mRNA as an effective alternative to AAV-based approaches for the treatment of ASA.

Role of Nitric Oxide in Megakaryocyte Function

Megakaryocytes are the main members of the hematopoietic system responsible for regulating vascular homeostasis through their progeny platelets, which are generally known for maintaining hemostasis. Megakaryocytes are characterized as large polyploid cells that reside in the bone marrow but may also circulate in the vasculature. They are generated directly or through a multi-lineage commitment step from the most primitive progenitor or Hematopoietic Stem Cells (HSCs) in a process called "megakaryopoiesis". Immature megakaryocytes enter a complicated development process defined as "thrombopoiesis" that ultimately results in the release of extended protrusions called proplatelets into bone marrow sinusoidal or lung microvessels. One of the main mediators that play an important modulatory role in hematopoiesis and hemostasis is nitric oxide (NO), a free radical gas produced by three isoforms of nitric oxide synthase within the mammalian cells. In this review, we summarize the effect of NO and its signaling on megakaryopoiesis and thrombopoiesis under both physiological and pathophysiological conditions.

Effect of the Non-steroidal Anti-inflammatory Drug Diclofenac on Ischemia-Reperfusion Injury in Rat Liver: A Nitric Oxide-Dependent Mechanism

Ischemia/reperfusion injury (IRI) is an inevitable complication of liver surgery and transplantation. The purpose of this study was to examine the beneficial effects of diclofenac on hepatic IRI and the mechanism behind it. Wistar rats' livers were subjected to warm ischemia for 60 min followed by 24 h of reperfusion. Diclofenac was administered intravenously 15 min before ischemia at 10, 20, and 40 mg/kg body weight. To determine the mechanism of diclofenac protection, the NOS inhibitor L-Nitro-arginine methyl ester (L-NAME) was administered intravenously 10 min after diclofenac injection (40 mg/kg). Liver injury was evaluated by aminotransferases (ALT and AST) activities and histopathological analysis. Oxidative stress parameters (SOD, GPX, MPO, GSH, MDA, and PSH) were also determined. Then, eNOS gene transcription and p-eNOS and iNOS protein expressions were evaluated. The transcription factors PPAR-γ and NF-κB in addition to the regulatory protein IκBα were also investigated. Finally, the gene expression levels of inflammatory (COX-2, IL-6, IL-1β, IL-18, TNF-α, HMGB-1, and TLR-4) and apoptosis (Bcl-2 and Bax) markers were measured. Diclofenac, at the optimal dose of 40 mg/kg, decreased liver injury and maintained histological integrity. It also reduced oxidative stress, inflammation, and apoptosis. Its mechanism of action essentially depended on eNOS activation rather than COX-2 inhibition, since pre-treatment with L-NAME abolished all the protective effects of diclofenac. To our knowledge, this is the first study demonstrating that diclofenac protects rat liver against warm IRI through the induction of NO-dependent pathway. Diclofenac reduced oxidative balance, attenuated the activation of the subsequent pro-inflammatory response and decreased cellular and tissue damage. Therefore, diclofenac could be a promising molecule for the prevention of liver IRI.

Effects of iNOS in Hepatic Warm Ischaemia and Reperfusion Models in Mice and Rats: A Systematic Review and Meta-Analysis

Warm ischaemia is usually induced by the Pringle manoeuver (PM) during hepatectomy. Currently, there is no widely accepted standard protocol to minimise ischaemia-related injury, so reducing ischaemia-reperfusion damage is an active area of research. This systematic review and meta-analysis focused on inducible nitric oxide synthase (iNOS) as an early inflammatory response to hepatic ischaemia reperfusion injury (HIRI) in mouse- and rat-liver models. A systematic search of studies was performed within three databases. Studies meeting the inclusion criteria were subjected to qualitative and quantitative synthesis of results. We performed a meta-analysis of studies grouped by different HIRI models and ischaemia times. Additionally, we investigated a possible correlation of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) regulation with iNOS expression. Of 124 included studies, 49 were eligible for the meta-analysis, revealing that iNOS was upregulated in almost all HIRIs. We were able to show an increase of iNOS regardless of ischemia or reperfusion time. Additionally, we found no direct associations of eNOS or NO with iNOS. A sex gap of primarily male experimental animals used was observed, leading to a higher risk of outcomes not being translatable to humans of all sexes.

Selective gene expression profiling contributes to a better understanding of the molecular pathways underlying the histological changes observed after RHMVL

Background

In previous studies, five vasoactive drugs were investigated for their effect on the recovery process after extended liver resection without observing relevant improvements. We hypothesized that an analysis of gene expression could help to identify potentially druggable pathways and could support the selection of promising drug candidates.

Methods

Liver samples obtained from rats after combined 70% partial hepatectomy and right median hepatic vein ligation (n = 6/group) sacrificed at 0 h, 24 h, 48 h, and 7days were selected for this study. Liver samples were collected from differentially perfused regions of the median lobe (obstruction-zone, border-zone, normal-zone). Gene expression profiling of marker genes regulating hepatic hemodynamics, vascular remodeling, and liver regeneration was performed with microfluidic chips. We used 3 technical replicates from each sample. Raw data were normalized using LEMming and differentially expressed genes were identified using LIMMA.

Results

The strongest differences were found in obstruction-zone at 24 h and 48 h postoperatively compared to all other groups. mRNA expression of marker genes from hepatic hemodynamics pathways (iNOS,Ptgs2,Edn1) was most upregulated.

Conclusion

These upregulated genes suggest a strong vasoconstrictive effect promoting arterial hypoperfusion in the obstruction-zone. Reducing iNOS expression using selective iNOS inhibitors seems to be a promising approach to promote vasodilation and liver regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01364-z.

Evaluation of statins as a new therapy to alleviate chronotropic dysfunction in cirrhotic rats

AIMS

Liver cirrhosis defines by regenerative nodules and fibrotic septa, causing a complication called cirrhotic cardiomyopathy (CCM) with chronotropic hypo-responsiveness. In addition to lowering cholesterol levels, statins yield antioxidant and anti-inflammatory effects. In liver diseases animal models, statins have been shown to decrease hepatic inflammation, fibrogenesis, and portal pressure (PP). Therefore, we evaluated the atorvastatin effect on the heart in cirrhotic rats.

MATERIALS AND METHODS

Bile duct ligation (BDL) or sham operation performed on male Wistar rats and grouped as cirrhotic; BDL/Saline, BDL/Ator-7d(days) (Atorvastatin 15 mg/kg/day), and BDL/Ator-14d groups, or control; Sham/Saline, Sham/Ator-7d, and Sham/Ator-14d groups. Corrected QT interval (QTc interval), chronotropic responses, serum brain natriuretic peptides (BNP), heart tumor necrosis factor-α (TNF-α), nuclear factor erythroid 2-related factor 2 (Nrf2), and malondialdehyde (MDA) levels were studied along with atrial Ras homolog family member A (RhoA) and endothelial nitric oxide synthase (eNOS) gene expression.

KEY FINDINGS

The chronotropic responses decreased in BDL/Saline and increased in BDL/Ator-7d group. The QTc interval, BNP, TNF-α, and MDA levels increased in BDL/Saline and decreased in BDL/Ator-14d group. The Nrf2 level did not change in BDL/Saline and increased in BDL/Ator-14d group. The liver inflammation and fibrosis increased in BDL/Saline and did not affect BDL/Ator-7d and BDL/Ator-14d groups. The RhoA expression was down-regulated in BDL/Saline, BDL/Ator-7d, and BDL/Ator-14d groups. The eNOS expression did not change in BDL/Saline and down-regulated in BDL/Ator-14d group.

SIGNIFICANCE

Atorvastatin alleviates the chronotropic hypo-responsiveness and down-regulates the atrial RhoA and eNOS gene expression along with anti-inflammatory, antioxidant, and anti-stress effects in CCM.

Nitric oxide-releasing biomaterials for promoting wound healing in impaired diabetic wounds: State of the art and recent trends

Impaired diabetic wounds are serious pathophysiological complications associated with persistent microbial infections including failure in the closure of wounds, and the cause of a high frequency of lower limb amputations. The healing of diabetic wounds is attenuated due to the lack of secretion of growth factors, prolonged inflammation, and/or inhibition of angiogenic activity. Diabetic wound healing can be enhanced by supplying nitric oxide (NO) endogenously or exogenously. NO produced inside the cells by endothelial nitric oxide synthase (eNOS) naturally aids wound healing through its beneficial vasculogenic effects. However, during hyperglycemia, the activity of eNOS is affected, and thus there becomes an utmost need for the topical supply of NO from exogenous sources. Thus, NO-donors that can release NO are loaded into wound healing patches or wound coverage matrices to treat diabetic wounds. The burst release of NO from its donors is prevented by encapsulating them in polymeric hydrogels or nanoparticles for supplying NO for an extended duration of time to the diabetic wounds. In this article, we review the etiology of diabetic wounds, wound healing strategies, and the role of NO in the wound healing process. We further discuss the challenges faced in translating NO-donors as a clinically viable nanomedicine strategy for the treatment of diabetic wounds with a focus on the use of biomaterials for the encapsulation and in vivo controlled delivery of NO-donors.

Cyclic GMP in Liver Cirrhosis-Role in Pathophysiology of Portal Hypertension and Therapeutic Implications

The NO-cGMP signal transduction pathway plays a crucial role in tone regulation in hepatic sinusoids and peripheral blood vessels. In a cirrhotic liver, the key enzymes endothelial NO synthase (eNOS), soluble guanylate cyclase (sGC), and phosphodiesterase-5 (PDE-5) are overexpressed, leading to decreased cyclic guanosine-monophosphate (cGMP). This results in constriction of hepatic sinusoids, contributing about 30% of portal pressure. In contrast, in peripheral arteries, dilation prevails with excess cGMP due to low PDE-5. Both effects eventually lead to circulatory dysfunction in progressed liver cirrhosis. The conventional view of portal hypertension (PH) pathophysiology has been described using the "NO-paradox", referring to reduced NO availability inside the liver and elevated NO production in the peripheral systemic circulation. However, recent data suggest that an altered availability of cGMP could better elucidate the contrasting findings of intrahepatic vasoconstriction and peripheral systemic vasodilation than mere focus on NO availability. Preclinical and clinical data have demonstrated that targeting the NO-cGMP pathway in liver cirrhosis using PDE-5 inhibitors or sGC stimulators/activators decreases intrahepatic resistance through dilation of sinusoids, lowering portal pressure, and increasing portal venous blood flow. These results suggest further clinical applications in liver cirrhosis. Targeting the NO-cGMP system plays a role in possible reversal of liver fibrosis or cirrhosis. PDE-5 inhibitors may have therapeutic potential for hepatic encephalopathy. Serum/plasma levels of cGMP can be used as a non-invasive marker of clinically significant portal hypertension. This manuscript reviews new data about the role of the NO-cGMP signal transduction system in pathophysiology of cirrhotic portal hypertension and provides perspective for further studies.

Expression of immunoreactive inducible nitric oxide synthase in pancreatic islet cells from newly diagnosed and long-term type 1 diabetic donors is heterogeneous and not disease-associated

Exposure of isolated human islets to proinflammatory cytokines leads to up-regulation of inducible nitric oxide synthase (iNOS), raised NO, and beta cell toxicity. These findings have led to increasing interest in the clinical utility of iNOS blockade to mitigate beta cell destruction in human type 1 diabetes (T1D). However, recent studies show that iNOS-derived NO may also confer beta cell protection. To investigate this dichotomy, we compared islet cell distributions and intensity of iNOS immunostaining in pancreatic sections, co-stained for insulin and glucagon, from new-onset T1D donors (group 1), with non-diabetic autoantibody-negative (group 2), non-diabetic autoantibody-positive (group 3) and long-term diabetic donors (group 4). The cellular origins of iNOS, its frequency and graded intensities in islets and number in peri-islet, intra-islet and exocrine regions were determined. All donors showed iNOS positivity, irrespective of disease and presence of beta cells, had variable labelling intensities, without significant differences in the frequency of iNOS-positive islets among study groups. iNOS was co-localised in selective beta, alpha and other endocrine cells, and in beta cell-negative islets of diabetic donors. The number of peri- and intra-islet iNOS cells was low, being significantly higher in the peri-islet area. Exocrine iNOS cells also remained low, but were much lower in group 1. We demonstrate that iNOS expression in islet cells is variable, heterogeneous and independent of co-existing beta cells. Its distribution and staining intensities in islets and extra-islet areas do not correlate with T1D or its duration. Interventions to inactivate the enzyme to alleviate disease are currently not justified.

Four weeks exercise training enhanced the hepatic insulin sensitivity in high fat- and high carbohydrate-diet fed hyperinsulinemic rats

Aim

Hyperinsulinemia is considered the primary defect underlying the development of type 2 diabetes. The liver is essential for the regular glucose homeostasis. In this study, we examined the effect of physical training on the insulin signaling, oxidative stress enzymes and Glucose-6-phosphatase(G6Pase) activity in the liver of Wistar rats.

Methods

Adult male Wistar rats were divided into Control diet group(C), High carbohydrate diet(HCD), High fat diet(HFD), HCD and HFD with training(HCD Ex & HFD Ex). HFD Ex and HCD Ex were trained on a small animal treadmill running at 20 m/min for 30 min, 5 days/wk. The present work investigated the effect of training on hepatic insulin receptor(InsR) signaling events, oxidative stress marker expressions and G6Pase activity in hyperinsulinemic rats.

Results

High carbohydrate and fat feeding led to hyperinsulinemic status with increased hepatic G6Pase activity and impaired phosphorylation of insulin receptor substrate 1(IRS1) and reduced expression of antioxidant enzymes.Training significantly reduced hepatic G6Pase activity, upregulated phosphoinositide 3 kinase(PI3K) docking site phosphorylation and downregulated the negative IRS1 phosphorylations thereby increasing the glucose transporter(GLUT) expressions (aa(P < 0.001) when compared to HFD, b(P < 0.01),bb (P < 0.001 when compared to HCD). Anti oxidant enzymes like CAT, SOD, eNOS expression were increased with reduction in the expression of inflammatory enzymes like TNF-α and COX-2 (*(P < 0.05),**(P < 0.01),***(P < 0.001) when compared to control, †(P < 0.05),††(P < 0.01),†††(P < 0.001) when compared to HFD and HCD).

Conclusion

Thus, our study shows that four weeks training enhanced the hepatic insulin sensitivity in high fat and high carbohydrate-diet fed hyperinsulinemic rats.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-020-00694-y.

Insulin secretion: The nitric oxide controversy

Nitric oxide (NO) is a gas that serves as a ubiquitous signaling molecule participating in physiological activities of various organ systems. Nitric oxide is produced in the endocrine pancreas and contributes to synthesis and secretion of insulin. The potential role of NO in insulin secretion is disputable - both stimulatory and inhibitory effects have been reported. Available data indicate that effects of NO critically depend on its concentration. Different isoforms of NO synthase (NOS) control this and have the potential to decrease or increase insulin secretion. In this review, the role of NO in insulin secretion as well as the possible reasons for discrepant findings are discussed. A better understanding of the role of NO system in the regulation of insulin secretion may facilitate the development of new therapeutic strategies in the management of diabetes.

Phosphodiesterases in the Liver as Potential Therapeutic Targets of Cirrhotic Portal Hypertension

Liver cirrhosis is a frequent condition with high impact on patients' life expectancy and health care systems. Cirrhotic portal hypertension (PH) gradually develops with deteriorating liver function and can lead to life-threatening complications. Other than an increase in intrahepatic flow resistance due to morphological remodeling of the organ, a functional dysregulation of the sinusoids, the smallest functional units of liver vasculature, plays a pivotal role. Vascular tone is primarily regulated by the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway, wherein soluble guanylate cyclase (sGC) and phosphodiesterase-5 (PDE-5) are key enzymes. Recent data showed characteristic alterations in the expression of these regulatory enzymes or metabolite levels in liver cirrhosis. Additionally, a disturbed zonation of the components of this pathway along the sinusoids was detected. This review describes current knowledge of the pathophysiology of PH with focus on the enzymes regulating cGMP availability, i.e., sGC and PDE-5. The results have primarily been obtained in animal models of liver cirrhosis. However, clinical and histochemical data suggest that the new biochemical model we propose can be applied to human liver cirrhosis. The role of PDE-5 as potential target for medical therapy of PH is discussed.

Systemic Insulin Resistance and Metabolic Perturbations in Chow Fed Inducible Nitric Oxide Synthase Knockout Male Mice: Partial Reversal by Nitrite Supplementation

iNOS, an important mediator of inflammation, has emerged as an important metabolic regulator. There are conflicting observations on the incidence of insulin resistance (IR) due to hyperglycemia/dyslipidemia in iNOS^−/− mice. There are reports that high fat diet (HFD) fed mice exhibited no change, protection, or enhanced susceptibility to IR. Similar observations were also reported for low fat diet (LFD) fed KO mice. In the present study chow fed iNOS^−/− mice were examined for the incidence of IR, and metabolic perturbations, and also for the effect of sodium nitrite supplementation (50 mg/L). In IR-iNOS^−/− mice, we observed significantly higher body weight, BMI, adiposity, blood glucose, HOMA-IR, serum/tissue lipids, glucose intolerance, enhanced gluconeogenesis, and disrupted insulin signaling. Expression of genes involved in hepatic and adipose tissue lipid uptake, synthesis, oxidation, and gluconeogenesis was upregulated with concomitant downregulation of genes for hepatic lipid excretion. Nitrite supplementation restored NO levels, significantly improved systemic IR, glucose tolerance, and also reduced lipid accumulation by rescuing hepatic insulin sensitivity, glucose, and lipid homeostasis. Obesity, gluconeogenesis, and adipose tissue insulin signaling were only partially reversed in nitrite supplemented iNOS^−/− mice. Our results thus demonstrate that nitrite supplementation to iNOS^−/− mice improves insulin sensitivity and metabolic homeostasis, thus further highlighting the metabolic role of iNOS.

The Emerging Role of Hepatocellular eNOS in Non-alcoholic Fatty Liver Disease Development

Non-alcoholic fatty liver disease (NAFLD) is comprised of a spectrum of liver injury ranging from excess fat accumulation in the liver (steatosis), to steatohepatitis (NASH), to its end stage of cirrhosis. A hallmark of NAFLD progression is the decline in function of hepatic mitochondria, although the mechanisms remain unresolved. Given the important role endothelial nitric oxide synthase (eNOS) plays in mitochondrial dynamics in other tissues, it has emerged as a potential mediator of maintaining mitochondrial function in the liver. In this mini review, we summarize the most relevant findings that extends current understanding of eNOS as a regulator of mitochondrial biogenesis, and identifies a potential additional role in mitochondrial turnover and attenuating inflammation during NAFLD development and progression.

Antifibrotic Effects of Amyloid-Beta and Its Loss in Cirrhotic Liver

The function and regulation of amyloid-beta (Aβ) in healthy and diseased liver remains unexplored. Because Aβ reduces the integrity of the blood-brain barrier we have examined its potential role in regulating the sinusoidal permeability of normal and cirrhotic liver. Aβ and key proteins that generate (beta-secretase 1 and presenilin-1) and degrade it (neprilysin and myelin basic protein) were decreased in human cirrhotic liver. In culture, activated hepatic stellate cells (HSC) internalized Aβ more efficiently than astrocytes and HSC degraded Aβ leading to suppressed expression of α-smooth muscle actin (α-SMA), collagen 1 and transforming growth factor β (TGFβ). Aβ also upregulated sinusoidal permeability marker endothelial NO synthase (eNOS) and decreased TGFβ in cultured human liver sinusoidal endothelial cells (hLSEC). Liver Aβ levels also correlate with the expression of eNOS in transgenic Alzheimer’s disease mice and in human and rodent cirrhosis/fibrosis. These findings suggest a previously unexplored role of Aβ in the maintenance of liver sinusoidal permeability and in protection against cirrhosis/fibrosis via attenuation of HSC activation.

Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism

Nitric oxide (NO) contributes to carbohydrate metabolism and decreased NO bioavailability is involved in the development of type 2 diabetes mellitus (T2DM). NO donors may improve insulin signaling and glucose homeostasis in T2DM and insulin resistance (IR), suggesting the potential clinical importance of NO-based interventions. In this review, site-specific roles of the NO synthase (NOS)-NO pathway in carbohydrate metabolism are discussed. In addition, the metabolic effects of physiological low levels of NO produced by constitutive NOS (cNOS) versus pathological high levels of NO produced by inducible NOS (iNOS) in pancreatic β-cells, adipocytes, hepatocytes, and skeletal muscle cells are summarized. A better understanding of the NOS-NO system in the regulation of glucose homeostasis can hopefully facilitate the development of new treatments for T2DM.

Regulation of carbohydrate metabolism by nitric oxide and hydrogen sulfide: Implications in diabetes

Nitric oxide (NO) and hydrogen sulfide (H₂S) are two gasotransmitters that are produced in the human body and have a key role in many of the physiological activities of the various organ systems. Decreased NO bioavailability and deficiency of H₂S are involved in the pathophysiology of type 2 diabetes and its complications. Restoration of NO levels have favorable metabolic effects in diabetes. The role of H₂S in pathophysiology of diabetes is however controversial; H₂S production is decreased during development of obesity, diabetes, and its complications, suggesting the potential therapeutic effects of H₂S. On the other hand, increased H₂S levels disturb the pancreatic β-cell function and decrease insulin secretion. In addition, there appear to be important interactions between NO and H₂S at the levels of both biosynthesis and signaling pathways, yet clear an insight into this relationship is lacking. H₂S potentiates the effects of NO in the cardiovascular system as well as NO release from its storage pools. Likewise, NO increases the activity and the expression of H₂S-generating enzymes. Inhibition of NO production leads to elimination/attenuation of the cardioprotective effects of H₂S. Regarding the increasing interest in the therapeutic applications of NO or H₂S-releasing molecules in a variety of diseases, particularly in the cardiovascular disorders, much is to be learned about their function in glucose/insulin metabolism, especially in diabetes. The aim of this review is to provide a better understanding of the individual and the interactive roles of NO and H₂S in carbohydrate metabolism.

In vivo hepatotoxicity of chemically modified nanocellulose in rats

Chemical modification of cellulose is currently attracting attention as researchers attempt to take advantage of the abundance of hydroxyl groups on its surface to introduce extra biological functionality. However, the possible deleterious effect of exposure to functionalized nanocellulose (CSN) remains a concern. Therefore, this study aims to explore the potential mechanisms of hepatotoxicity of CSN modified with oxalate ester (NCD) in rats. A 7-day repeated oral toxicity study of NCD at the doses of 50 and 100 mg kg−1body weight was conducted, and plasma and liver tissue samples were assayed using biochemical analysis, liver histopathology, and protein expression. NCD, at both doses, did not significantly ( p > 0.05) alter the relative weight of liver, alkaline phosphatase activity, and lipid peroxidation levels of the animals. However, NCD at the dose of 100 mg kg−1body weight significantly elevated aspartate aminotransferase, alanine aminotransferase, and myeloperoxidase activities. NCD also enhanced the immunohistochemical expression of inducible nitric oxide synthase and Bcl-2-associated X protein in the liver of rats. Histological observations revealed necrosis and severe cellular infiltration at the high-dose treatment. Our study provides an experimental basis for the safe application of NCDs.

eNOS deletion impairs mitochondrial quality control and exacerbates Western diet-induced NASH

Dysregulated mitochondrial quality control leads to mitochondrial functional impairments that are central to the development and progression of hepatic steatosis to nonalcoholic steatohepatitis (NASH). Here, we identify hepatocellular localized endothelial nitric oxide synthase (eNOS) as a novel master regulator of mitochondrial quality control. Mice lacking eNOS were more susceptible to Western diet-induced hepatic inflammation and fibrosis in conjunction with decreased markers of mitochondrial biogenesis and turnover. The hepatocyte-specific influence was verified via magnetic activated cell sorting purified primary hepatocytes and in vitro siRNA-induced knockdown of eNOS. Hepatic mitochondria from eNOS knockout mice revealed decreased markers of mitochondrial biogenesis (PPARγ coactivator-1α, mitochondrial transcription factor A) and autophagy/mitophagy [BCL-2-interacting protein-3 (BNIP3), 1A/1B light chain 3B (LC3)], suggesting decreased mitochondrial turnover rate. eNOS knockout in primary hepatocytes exhibited reduced fatty acid oxidation capacity and were unable to mount a normal BNIP3 response to a mitophagic challenge compared with wild-type mice. Finally, we demonstrate that eNOS is required in primary hepatocytes to induce activation of the stress-responsive transcription factor nuclear factor erythroid 2-related factor 2 (NRF2). Thus, our data demonstrate that eNOS is an important regulator of hepatic mitochondrial content and function and NASH susceptibility.

Thymoquinone protection from amikacin induced renal injury in rats

We investigated whether thymoquinone (TQ) exerts a beneficial effect on renal injury due to amikacin (AK) administration in rats. To generate kidney damage with AK, a single 1.2 g/kg dose of AK was administered intraperitoneally. TQ was administered orally to the AK treated group at a dose of 40 mg/kg for five days. At the end of the experiment, rats were sacrificed and blood samples were used to measure blood urea nitrogen (BUN) and creatinine (Cr) levels. Kidney samples were taken to measure the oxidative stress biomarker, malondialdehyde (MDA), and expression of the antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT). Because reactive oxygen species (ROS) and apoptosis contribute to tissue damage associated with NADPH oxidase (NOX), we also investigated NOX-2, NOX-4 and apoptosis marker, caspase-3, expression using immunohistochemistry. MDA, BUN, Cr, NOX-2, NOX-4 and caspase-3 production were increased, and SOD and CAT were decreased in the AK treated group compared to controls. MDA, BUN, Cr, NOX-2, NOX-4 and caspase-3 levels were decreased, and SOD and CAT levels were increased in TQ + AK treated rats compared to AK treated animals. TQ appears to protect the kidney from the toxic effects of AK.

Hepatic Lysosomal iNOS Activity Impairs Autophagy in Obesity

BACKGROUND & AIMS

The lysosome is an acidic organelle that is important for maintaining cellular and metabolic homeostasis in hepatocytes. Lysosomal dysfunction and chronic inflammation coexist, and both contribute to obesity-associated hepatic insulin resistance. However, in the context of obesity, the interplay between inflammatory signals and hepatic lysosomal function remains largely unknown. Inducible nitric oxide synthase (iNOS) is a hallmark for inflammation, and is activated in obesity. The aim of this study is to understand the molecular link between iNOS-mediated lysosomal nitric oxide (NO) production, hepatic lysosomal function, and autophagy in the context of obesity-associated insulin resistance.

METHODS

The role of iNOS in hepatic autophagy, as related to insulin and glucose homeostasis were studied in mice with diet-induced obesity (DIO). The effects and mechanisms of iNOS-mediated lysosomal NO production on lysosomal function and hepatic autophagy were studied in primary hepatocytes as well as in a mouse model of DIO.

RESULTS

We demonstrate that obesity promotes iNOS localization to the lysosome and decreases levels of lysosomal arginine, resulting in an accumulation of NO in hepatic lysosomes. This lysosomal NO production is attenuated by treatment with a NO scavenger, while co-overexpression of mTOR and a lysosomal arginine transporter (SLC38A9) enhances lysosomal NO production and suppresses autophagy. In addition, we show that deletion of iNOS ameliorates lysosomal nitrosative stress in the livers of DIO mice, promotes lysosomal biogenesis by activating transcription factor EB (TFEB), and enhances lysosomal function and autophagy. Lastly, deletion of iNOS in mice with DIO improves hepatic insulin sensitivity, which is diminished by suppression of TFEB or autophagy related 7 (Atg7).

CONCLUSIONS

Our studies suggest that lysosomal iNOS-mediated NO signaling disrupts hepatic lysosomal function, contributing to obesity-associated defective hepatic autophagy and insulin resistance.

Hepatic cytochrome P450 metabolism suppressed by mast cells in type 1 allergic mice

Mast cells and Kupffer cells secrete interleukin (IL)-1β, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α, which stimulate excess nitric oxide (NO) producing-inducible NO synthase (iNOS). Unlike Kupffer cells, immunoglobulin E-sensitized mast cells elicit sustained NO production. We investigated the participation of mast cell-released NO and cytokine-derived iNOS activation in type 1 allergy-suppressed hepatic cytochrome P450 (CYP) metabolism. Aminoguanidine, a selective iNOS inhibitor, completely suppressed serum nitrate plus nitrite (NOx) concentrations after primary and secondary sensitization of ICR mice and markedly attenuated allergy-suppressed hepatic CYP1A2, CYP2C, CYP2E1, and CYP3A activities. In the liver, primary and secondary sensitization enhanced iNOS-stimulating IFN-γ (5-15-fold) and TNF-α (3-5-fold) mRNA levels more than IL-1β (2-fold) and F4/80-positive Kupffer cell (2-fold) mRNA levels. When mast cell-deficient (-/-) mice were sensitized, hepatic CYP activities were not suppressed. Serum NOx levels in the sensitized -/- mice were similar with those in saline-treated ICR and -/- mice. In the liver of -/- mice, secondary sensitization markedly enhanced mRNA expression of iNOS (20-fold), IFN-γ (15-fold), and TNF-α (3-fold). However, hepatic total NOS activities in -/- mice were not significantly different between saline treatment and sensitization. Similarly, primary and secondary ICR mice did not significantly enhance total NOS activities in the liver and hepatocytes. The total NOS activities observed did not relate to the high levels of iNOS, IFN-γ, and TNF-α mRNA in the liver. Hepatic c-kit-positive mast cells in sensitized ICR mice were maintained at control levels. Therefore, our data suggest that mast cell-released NO participates in type 1 allergy-suppressed CYP1A2, CYP2C, CYP2E1, and CYP3A metabolism.

Hepatoprotective Role of Thymol in Drug-Induced Gastric Ulcer Model

INTRODUCTION AND AIM

Indo is widely one of the non-steroidal anti-inflammatory drugs and one of the common toxic effects of this drug is hepatic failure. Thymol is a monoterpene phenol with many different pharmacological activities. However, up to now its hepatoprotective effects on Indo-induced gastric ulcer model in rats have not been explored yet.

MATERIAL AND METHODS

Thirty five Sprague-Dawley rats were divided into seven groups: control, ulcer control (30 mg/kg Indo), Indo + reference standard (50 mg/kg Rantidine), Indo + Thymol (75, 100, 250 and 500 mg/kg) groups. 10 minutes after the induction of ulcer with Indo; Thymol was orally administered to the rats. Liver function enzymes (AST, ALT and LDH) were measured from serum samples. TOS/TAC, TNF-α and PGE2 levels, eNOS and Caspase-3 activity were assessed from tissue homogenate samples. In addition, histopathologic analysis on liver sections was performed.

RESULTS

Indo significantly increased the levels of hepatic enzymes, TNF-α and eNOS, and caspase-3 activation, while decreased PGE2 levels. Furthermore, it induced oxidative stress as evidenced by elevated TOS and decreased TAC levels. However, Thymol treatment induced a significant improvement in these parameters, especially in 250 mg/kg dose. On the other hand, treatment with Thymol 500 mg/kg dramatically affected the parameters much worse than the Indo treated group.

CONCLUSION

The findings of the current study demonstrated that Thymol administration significantly ameliorated liver injury due to Indo toxicity. This effect of Thymol (250 mg/kg) may be mediated by its anti-oxidative or anti-inflammatory effect, and up-regulation the synthesis of PGE2.

Green tea infusion protects against alcoholic liver injury by attenuating inflammation and regulating the PI3K/Akt/eNOS pathway in C57BL/6 mice

Alcohol intake is a major risk factor for the pathogenesis of alcoholic liver diseases. Accumulating evidence suggests that green tea protects against alcoholic liver injury; however, the underlying mechanisms remain unclear. The present study investigated the role of endothelial nitric oxide synthase (eNOS) in the protective effects of green tea against alcohol-induced liver injury and inflammation. Ethanol was intragastrically administered to male C57BL/6 mice once a day, and the mice were allowed free access to green tea infusion or water for two weeks. We assessed the plasma levels of alanine aminotransferase and aspartate aminotransferase, hepatic contents of thiobarbituric acid reactive substances, malondialdehyde and triglyceride and hepatic mRNA expression of pro-inflammatory cytokines (interleukin-1β, tumor necrosis factor-α, and interleukin-6). Our results showed that compared with water alone, green tea infusion markedly reduced liver damage, hepatic oxidative stress, hepatic lipid accumulation and inflammatory response. Green tea infusion also significantly reduced hepatic nuclear factor-κB expression and its downstream inflammatory mediators (inducible nitric oxide synthase and cyclooxygenase-2) mRNA levels in ethanol-treated mice. Additionally, green tea infusion significantly activated hepatic phosphorylated phosphatidylinositol 3-kinase (PI3K) and phosphorylated protein kinase B (Akt), which are associated with the upregulation of phosphorylated eNOS expression and the increase of plasma nitric oxide levels in ethanol-treated mice. Furthermore, the protective effects of green tea infusion were considerably inhibited by the eNOS inhibitor N^G-nitro-l-arginine methyl ester in ethanol-treated mice. In conclusion, our study demonstrated that the protective effects of green tea infusion on alcohol-induced liver injury and inflammation involve the modulation of the PI3K/AKT/eNOS pathway.

Post-Transcriptional Regulation of Hepatic DDAH1 with TNF Blockade Leads to Improved eNOS Function and Reduced Portal Pressure In Cirrhotic Rats

Portal hypertension (PH) is a major cause of morbidity and mortality in chronic liver disease. Infection and inflammation play a role in potentiating PH and pro-inflammatory cytokines, including TNF, are associated with severity of PH. In this study, cirrhotic bile duct ligated (BDL) rats with PH were treated with Infliximab (IFX, a monoclonal antibody against TNF) and its impact on modulation of vascular tone was assessed. BDL rats had increased TNF and NFkB compared to sham operated rats, and their reduction by IFX was associated with a reduction in portal pressure. IFX treatment also reduced hepatic oxidative stress, and biochemical markers of hepatic inflammation and injury. IFX treatment was associated with an improvement in eNOS activity and increased l-arginine/ADMA ratio and DDAH1 expression. In vitro analysis of HepG2 hepatocytes showed that DDAH1 protein expression is reduced by oxidative stress, and this is in part mediated by post-transcriptional regulation by the 3′UTR. This study supports a role for the DDAH1/ADMA axis on the effect of inflammation and oxidative stress in PH and provides insight for new therapies.

Role of Nitric Oxide Pathway in Development and Progression of Chronic Kidney Disease in Rats Sensitive and Resistant to its Occurrence in an Experimental Model of 5/6 Nephrectomy

BACKGROUND Understanding the mechanisms conditioning development of chronic kidney disease (CKD) is still a challenge. The aim of this study was to evaluate the activity of the intrarenal nitric oxide (NO) pathway in the context of sensitivity or resistance of different animal strains to the development and degree of renal failure. MATERIAL AND METHODS Two rat strains were used: Wistar (WR) and Sprague-Dawley rats (SDR) in a model of CKD - 5/6 nephrectomy. We assessed parameters of renal failure and expression of nitric oxide synthase (NOS) isoforms in renal cortex and medulla. RESULTS We did not observe renal failure in WR, and CKD developed in SDR with increase of creatinine and urea concentration as well as decrease of diuresis and glomerular filtration. In the renal cortex, baseline expression of NOS2 was higher in WR than in SDR. 5/6 nephrectomy resulted in reduction of NOS2 in both strains and NOS3 in WR. In the renal medulla, baseline NOS2 expression was higher in SDR, and nephrectomy resulted in its decrease only in SDR. Although baseline NOS3 expression was higher in SDR, the NOS3 expression after nephrectomy was higher in WR rats. CONCLUSIONS In model of CKD - 5/6 nephrectomy, SDR proved to be sensitive and WR resistant to development of CKD. The intrarenal activity of the nitric oxide pathway was the factor that differentiated both strains. This mechanism may be responsible for insensitivity of WR to development of renal failure in this model of CKD.

Contribution of inducible and neuronal nitric oxide synthases to mitochondrial damage and melatonin rescue in LPS-treated mice

NOS isoform activation is related to liver failure during sepsis, but the mechanisms driving mitochondrial impairment remain unclear. We induced sepsis by LPS administration to inducible nitric oxide synthase (iNOS^-/-) and neuronal nitric oxide synthase (nNOS^-/-) mice and their respective wild-type controls to examine the contribution of iNOS to mitochondrial failure in the absence of nNOS. To achieve this goal, the determination of messenger RNA (mRNA) expression and protein content of iNOS in cytosol and mitochondria, the mitochondrial respiratory complex content, and the levels of nitrosative and oxidative stress (by measuring 3-nitrotyrosine residues and carbonyl groups, respectively) were examined in the liver of control and septic mice. We detected strongly elevated iNOS mRNA expression and protein levels in liver cytosol and mitochondria of septic mice, which were related to enhanced oxidative and nitrosative stress, and with fewer changes in respiratory complexes. The absence of the iNOS, but not nNOS, gene absolutely prevented mitochondrial impairment during sepsis. Moreover, the nNOS gene did not modify the expression and the effects of iNOS here shown. Melatonin administration counteracted iNOS activation and mitochondrial damage and enhanced the expression of the respiratory complexes above the control values. These effects were unrelated to the presence or absence of nNOS. iNOS is a main target to prevent liver mitochondrial impairment during sepsis, and melatonin represents an efficient antagonist of these iNOS-dependent effects whereas it may boost mitochondrial respiration to enhance liver survival.

Nitrative and oxidative DNA damage in infection-related carcinogenesis in relation to cancer stem cells

Infection and chronic inflammation have been recognized as important factors for carcinogenesis. Under inflammatory conditions, reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from inflammatory and epithelial cells, and result in the formation of oxidative and nitrative DNA lesions, such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-nitroguanine. The DNA damage can cause mutations and has been implicated in inflammation-mediated carcinogenesis. It has been estimated that various infectious agents are carcinogenic to humans (IARC group 1), including bacterium Helicobacter pylori (H. pylori), viruses [hepatitis B virus (HBV), hepatitis C virus (HCV), human papillomavirus (HPV) and Epstein-Barr virus (EBV)] and parasites [Schistosoma haematobium (SH) and Opisthorchis viverrini (OV)]. H. pylori, HBV/HCV, HPV, EBV, SH and OV are important risk factors for gastric cancer, hepatocellular carcinoma, nasopharyngeal carcinoma, bladder cancer, and cholangiocarcinoma, respectively. We demonstrated that 8-nitroguanine was strongly formed via inducible nitric oxide synthase (iNOS) expression at these cancer sites of patients. Moreover, 8-nitroguanine was formed in Oct3/4-positive stem cells in SH-associated bladder cancer tissues, and in Oct3/4- and CD133-positive stem cells in OV-associated cholangiocarcinoma tissues. Therefore, it is considered that nitrative and oxidative DNA damage in stem cells may play a key role in infection-related carcinogenesis via chronic inflammation.

Preventive effects of dietary walnuts on high-fat-induced hepatic fat accumulation, oxidative stress and apoptosis in mice

We hypothesized that dietary walnut would prevent high-fat-diet (HFD)-induced hepatic apoptosis based on its antioxidant properties. Male C57BL/6J mice were fed a rodent chow or HFD (45% energy-derived)±walnuts (21.5% energy-derived) for 6 weeks. Liver histological and biochemical analyses revealed significantly elevated fat accumulation in mice fed HFD compared to mice fed the chow or HFD±walnuts. Walnut supplementation prevented HFD-mediated alteration of the levels of key proteins in lipid homeostasis such as Sirt1, AMPK and FAS, leading to decreased fat accumulation. In addition, walnut supplementation to HFD significantly decreased the hepatic levels of cytochrome P450-2E1, nitrated proteins and lipid peroxidation. Furthermore, walnut supplementation decreased the activated cell-death-associated p-JNK and p-p38K accompanied with increased hepatocyte apoptosis in HFD group. The beneficial effects of dietary walnut likely result, at least partially, from its antioxidant ingredients and attenuating HFD-induced hepatic steatosis, nitroxidative stress and apoptosis.

Hybrid inhibitor of peripheral cannabinoid-1 receptors and inducible nitric oxide synthase mitigates liver fibrosis

Liver fibrosis, a consequence of chronic liver injury and a way station to cirrhosis and hepatocellular carcinoma, lacks effective treatment. Endocannabinoids acting via cannabinoid-1 receptors (CB₁R) induce profibrotic gene expression and promote pathologies that predispose to liver fibrosis. CB₁R antagonists produce opposite effects, but their therapeutic development was halted due to neuropsychiatric side effects. Inducible nitric oxide synthase (iNOS) also promotes liver fibrosis and its underlying pathologies, but iNOS inhibitors tested to date showed limited therapeutic efficacy in inflammatory diseases. Here, we introduce a peripherally restricted, orally bioavailable CB₁R antagonist, which accumulates in liver to release an iNOS inhibitory leaving group. In mouse models of fibrosis induced by CCl₄ or bile duct ligation, the hybrid CB₁R/iNOS antagonist surpassed the antifibrotic efficacy of the CB₁R antagonist rimonabant or the iNOS inhibitor 1400W, without inducing anxiety-like behaviors or CB₁R occupancy in the CNS. The hybrid inhibitor also targeted CB₁R-independent, iNOS-mediated profibrotic pathways, including increased PDGF, Nlrp3/Asc3, and integrin αvβ6 signaling, as judged by its ability to inhibit these pathways in cnr1^-/- but not in nos2^-/- mice. Additionally, it was able to slow fibrosis progression and to attenuate established fibrosis. Thus, dual-target peripheral CB₁R/iNOS antagonists have therapeutic potential in liver fibrosis.

S-nitrosylation of the Mitochondrial Chaperone TRAP1 Sensitizes Hepatocellular Carcinoma Cells to Inhibitors of Succinate Dehydrogenase

S-nitrosoglutathione reductase (GSNOR) represents the best-documented denitrosylase implicated in regulating the levels of proteins posttranslationally modified by nitric oxide on cysteine residues by S-nitrosylation. GSNOR controls a diverse array of physiologic functions, including cellular growth and differentiation, inflammation, and metabolism. Chromosomal deletion of GSNOR results in pathologic protein S-nitrosylation that is implicated in human hepatocellular carcinoma (HCC). Here we identify a metabolic hallmark of aberrant S-nitrosylation in HCC and exploit it for therapeutic gain. We find that hepatocyte GSNOR deficiency is characterized by mitochondrial alteration and by marked increases in succinate dehydrogenase (SDH) levels and activity. We find that this depends on the selective S-nitrosylation of Cys(501) in the mitochondrial chaperone TRAP1, which mediates its degradation. As a result, GSNOR-deficient cells and tumors are highly sensitive to SDH inhibition, namely to α-tocopheryl succinate, an SDH-targeting molecule that induced RIP1/PARP1-mediated necroptosis and inhibited tumor growth. Our work provides a specific molecular signature of aberrant S-nitrosylation in HCC, a novel molecular target in SDH, and a first-in-class therapy to treat the disease. Cancer Res; 76(14); 4170-82. ©2016 AACR.

Diet-induced dyslipidemia leads to nonalcoholic fatty liver disease and oxidative stress in guinea pigs

Chronic dyslipidemia imposed by a high-fat and high-caloric dietary regime leads to debilitating disorders such as obesity, nonalcoholic fatty liver disease (NAFLD), and insulin resistance. As disease rates surge, so does the need for high validity animal models to effectively study the causal relationship between diet and disease progression. The dyslipidemic guinea pig displays a high similarity with the human lipoprotein profile and may in this aspect be superior to other rodent models. This study investigated the effects of 2 long-term Westernized diets (0.35% cholesterol, 18.5% vegetable oil and either 15% or 20% sucrose) compared with isocaloric standard chow in adult guinea pigs. Biochemical markers confirmed dyslipidemia in agreement with dietary regimens; however, both high-fat groups displayed a decreased tissue fat percentage compared with controls. Macroscopic appearance, histopathologic evaluation, and plasma markers of liver function confirmed NAFLD in high-fat groups, supported by liver redox imbalance and markers suggesting hepatic endothelial dysfunction. Plasma markers indicated endothelial dysfunction in response to a high-fat diet, although atherosclerotic lesions were not evident. Evaluation of glucose tolerance showed no indication of insulin resistance. The 5% increase in sucrose between the 2 high-fat diets did not lead to significant differences between groups. In conclusion, we find the dyslipidemic guinea pig to be a valid model of diet imposed dyslipidemia, particularly with regards to hepatic steatosis and endothelial dysfunction. Furthermore, the absence of obesity supports the present study setup as targeting NAFLD in nonobese individuals.

Protective effect of Spirulina platensis against cell damage and apoptosis in hepatic tissue caused by high fat diet

Spirulina platensis is a microalga that may be a source of antioxidants that can reduce body fat deposition. Consumption of a high fat diet produces elevated blood lipid levels, inflammation and apoptosis. We investigated the possible effects of S. platensis on the blood lipid profile, and liver inflammation and apoptosis in rats fed a high fat diet. Sixty-four young male rats were divided into eight equal groups. The control group was fed a basic diet. The experimental groups were fed a diet for 60 days that was prepared by mixing variable amounts of 43% vegetable oil and 10% cholesterol with or without 3% S. platensis mixed with the basal diet. Blood and liver tissue samples were collected from each animal. Serum samples were used to analyze lipid parameters, total antioxidant status and total oxidant status. iNOS and eNOS were determined by immunohistochemistry. TUNEL staining was used to detect apoptosis to investigate a possible connection between inflammation and apoptosis in the liver tissue. The relations between fat deposition and liver degeneration were assessed by Sirius red staining and alpha-smooth muscle actin immunostaining. S. platensis reduced serum HDL-C, LDL-C and triglyceride, increased HDL-C levels in rats fed a high fat diet to near control levels, and reduced iNOS levels and increased eNOS levels in the liver tissue compared to vegetable oil and cholesterol treated groups. The apoptotic index was reduced in the groups that were fed a high fat or a basic diet when supplemented with S. platensis.

The transcriptome of the bowhead whale Balaena mysticetus reveals adaptations of the longest-lived mammal

Mammals vary dramatically in lifespan, by at least two-orders of magnitude, but the molecular basis for this difference remains largely unknown. The bowhead whale Balaena mysticetus is the longest-lived mammal known, with an estimated maximal lifespan in excess of two hundred years. It is also one of the two largest animals and the most cold-adapted baleen whale species. Here, we report the first genome-wide gene expression analyses of the bowhead whale, based on the de novo assembly of its transcriptome. Bowhead whale or cetacean-specific changes in gene expression were identified in the liver, kidney and heart, and complemented with analyses of positively selected genes. Changes associated with altered insulin signaling and other gene expression patterns could help explain the remarkable longevity of bowhead whales as well as their adaptation to a lipid-rich diet. The data also reveal parallels in candidate longevity adaptations of the bowhead whale, naked mole rat and Brandt's bat. The bowhead whale transcriptome is a valuable resource for the study of this remarkable animal, including the evolution of longevity and its important correlates such as resistance to cancer and other diseases.

Effects of pentoxifylline and alpha lipoic acid on methotrexate-induced damage in liver and kidney of rats

The aim of the current study was to investigate the probable protective effects of Pentoxifylline (PTX) and Alpha Lipoic Acid (ALA), which display anti-oxidative efficacy against hepatotoxicity and nephrotoxicity, those being the major side effects of Methotrexate (MTX). Rats were divided into four groups: a control group; MTX (20mg/kg/day) group; MTX+PTX (20mg/kg/day+50mg/kg/day) group; and an MTX+ALA (20mg/kg/day+100mg/kg/day) group. At the end of the experiment, biochemical, histochemical and immunohistochemical analyses were performed on liver and kidney tissues of rats. We determined Glutathione Peroxidase (GSH-Px), Superoxide Dismutase (SOD), Catalase (CAT), Malondialdehyde (MDA), Nitric Oxide (NO) and Xanthine Oxidase (XO) levels in the liver and kidney. Moreover, Gamma Glutamyl Transferase (GGT), Direct Bilirubin (DBil), Blood Urea Nitrogen (BUN), and urea levels were measured in the serum. The histochemical evaluation revealed a significant decrease in MTX caused damage in the PTX- and ALA-treated groups (especially in ALA group). On the other hand, the immune staining of iNOS and TNF-α were observed most densely in the MTX group, while the density decreased in the PTX- and ALA-administered groups. We determined increased GGT, BUN, urea and levels of CAT, MDA, NO, and XO values in both groups, while GSH-Px (an increase in liver tissue) and DBil levels were decreased in the group that received MTX. However, we determined decreased SOD levels in liver tissue. In the PTX and ALA groups, the levels of GGT, BUN and urea as well as the levels of CAT, MDA, NO and XO decreased (SOD increased in the liver tissue), and the levels of GSH-Px and DBil increased. In conclusion, it can be stated that, although ALA is more effective in preventing the toxic effects of MTX on the liver and kidney, PTX also has a preventive effect. As a result, we can readily suggest that ALA and PTX can have protective effects by decreasing MDA, NO, BUN and urea values as antioxidants against MTX-induced damage in liver and kidney of rats.

Hepatoprotective effect of nitric oxide in experimental model of acute hepatic failure

AIM: To evaluate the effect of nitric oxide (NO) on the development and degree of liver failure in an animal model of acute hepatic failure (AHF).

METHODS: An experimental rat model of galactosamine-induced AHF was used. An inhibitor of NO synthase, nitroarginine methyl ester, or an NO donor, arginine, were administered at various doses prior to or after the induction of AHF.

RESULTS: All tested groups developed AHF. Following inhibition of the endogenous NO pathway, most liver parameters improved, regardless of the inhibitor dose before the induction of liver damage, and depending on the inhibitor dose after liver damage. Prophylactic administration of the inhibitor was more effective in improving liver function parameters than administration of the inhibitor after liver damage. An attempt to activate the endogenous NO pathway prior to the induction of liver damage did not change the observed liver function parameters. Stimulation of the endogenous NO pathway after liver damage, regardless of the NO donor dose used, improved most liver function parameters.

CONCLUSION: The endogenous NO pathway plays an important role in the development of experimental galactosamine-induced AHF.

Effect of biliary cirrhosis on neurogenic relaxation of rat gastric fundus and anococcygeus muscle: role of nitric oxide pathway

BACKGROUND

Cirrhosis, associated with a host of hemodynamic abnormalities, could affect the gastrointestinal (GI) tract motility. On the other hand, the nonadrenergic noncholinergic (NANC) neurotransmission has been shown to play a pivotal role in GI tract motility and has been linked with release of nitric oxide (NO) on electrical stimulation. In this study, we investigated the effect of biliary cirrhosis on the neurogenic relaxation of rat gastric fundus and anococcygeus muscle and also the possible role of nitric oxide system in this manner.

METHODS

Isolated gastric fundus and anococcygeus strips of sham-operated and biliary cirrhotic (4 weeks after bile duct ligation) rats were mounted under tension in a standard organ bath. Electrical stimulation was applied to obtain NANC-mediated relaxations in precontracted gastric fundus and anococcygeus muscle. The neurogenic relaxations were examined in the presence of different doses of NO synthase inhibitor, N (w)-Nitro-L-Arginine Methyl Ester (L-NAME). The concentration-dependent relaxant responses to the NO donor sodium nitroprusside were also evaluated.

RESULTS

The neurogenic relaxation of both gastric fundus and anococcygeus muscle was significantly (P < 0.001) increased in cirrhotic animals. L-NAME (0.03-1,000 µM) inhibited relaxations in both groups in a dose-dependent manner (P < 0.001), but cirrhotic groups were more resistant to the inhibitory effects of L-NAME (P < 0.01). Sodium nitroprusside-mediated relaxations were similar in two groups.

CONCLUSIONS

This study for the first time demonstrated that cirrhosis increases the NO-mediated neurogenic relaxation of both rat gastric fundus and anococcygeus muscle, suggesting a crucial role for the neurogenic NO in the pathophysiology of disturbed GI motility in cirrhosis.

The role of inflammation and liver cancer

Persistent inflammation is known to promote and exacerbate malignancy. Primary liver cancer, mostly hepatocellular carcinoma (HCC), is a clear example of inflammation-related cancer as more than 90 % of HCCs arise in the context of hepatic injury and inflammation. HCC represents the fifth most common malignancy and the third leading cause of cancer-related death worldwide with about one million new cases diagnosed every year with almost an equal number of deaths. Chronic unresolved inflammation is associated with persistent hepatic injury and concurrent regeneration, leading to sequential development of fibrosis, cirrhosis, and eventually HCC. Irrespective of the intrinsic differences among various etiological factors, a common denominator at the origin of HCC is the perpetuation of a wound-healing response activated by parenchymal cell death and the resulting inflammatory cascade. Hence, the identification of fundamental inflammatory signaling pathways causing transition from chronic liver injury to dysplasia and HCC could depict new predictive biomarkers and targets to identify and treat patients with chronic liver inflammation. This chapter critically discusses the roles of several major cytokines, chemokines, growth factors, transcription factors, and enzymes as well as a distinct network of inflammatory signaling pathways in the development and progression of HCC. It also highlights and analyzes preclinical animal studies showing innovative approaches of targeting inflammatory mediators and signaling by a variety of natural compounds and synthetic agents to achieve effective therapy as well as prevention of hepatic malignancy. Additionally, current limitations and potential challenges associated with the inhibition of inflammatory signaling as well as future directions of research to accelerate clinical development of anti-inflammatory agents to prevent and treat liver cancer are presented.

Hepatic inducible nitric oxide synthase expression increases upon exposure to hypergravity

Stimulation by a number of conditions, including infection, cytokines, mechanical injury, and hypoxia, can upregulate inducible nitric oxide synthase (iNOS) in hepatocytes. We observed that exposure to hypergravity significantly upregulated the transcription of the hepatic iNOS gene. The aim of this study was to confirm our preliminary data, and to further investigate the distribution of the iNOS protein in the livers of mice exposed to hypergravity. ICR mice were exposed to +3 Gz for 1 h. We investigated the time course of change in the iNOS expression. Hepatic iNOS mRNA expression progressively increased in centrifuged mice from 0 to 12 h, and then decreased rapidly by 18 h. iNOS mRNA levels in the livers of centrifuged mice was significantly higher at 3, 6, and 12 h than in uncentrifuged control mice. The pattern of iNOS protein expression paralleled that of the mRNA expression. At 0 and 1 h, weak cytoplasmic iNOS immunoreactivity was found in some hepatocytes surrounding terminal hepatic venules. It was noted that at 6 h there was an increase in the number of perivenular hepatocytes with moderate to strong cytoplasmic immunoreactivity. The number of iNOS-positive hepatocytes was maximally increased at 12 h. The majority of positively stained cells showed a strong intensity of iNOS expression. The expression levels of iNOS mRNA and protein were significantly increased in the livers of mice exposed to hypergravity. These results suggest that exposure to hypergravity significantly upregulates iNOS at both transcriptional and translational levels.

Pathogenic role of oxidative and nitrosative stress in primary biliary cirrhosis

Primary biliary cirrhosis is a multifactor autoimmune disease characterized by hepatic and systemic manifestations, with immune system dysregulation and abnormalities in the hepatic metabolism of bile salts, lipids, and nutrients, as well as destruction of membrane lipids and mitochondrial dysfunction. Both oxidative and nitrosative stress are associated with ongoing manifestations of the disease. In particular, abnormalities in nitric oxide metabolism and thiol oxidation already occur at early stages, thus leading to the hypothesis that these biochemical events play a pathogenic role in primary biliary cirrhosis. Moreover, the association of these metabolic abnormalities with the progression of the disease may indicate some biochemical parameters as early diagnostic markers of disease evolution, and may open up the potential for pharmacological intervention to inhibit intra- and extra-cellular stress events for resuming hepatocellular functions. The following paragraphs summarize the current knowledge by outlining molecular mechanisms of the disease related to these stress events.