Chronic iron overload enhances inducible nitric oxide synthase expression in rat liver

The role of tetrahydrocurcumin in disease prevention and treatment

In recent decades, natural compounds derived from herbal medicine or dietary sources have played important roles in prevention and treatment of various diseases and have attracted more and more attention. Curcumin, extracted from the Curcumae Longae Rhizoma and widely used as food spice and coloring agent, has been proven to possess high pharmacological value. However, the pharmacological application of curcumin is limited due to its poor systemic bioavailability. As a major active metabolite of curcumin, tetrahydrocurcumin (THC) has higher bioavailability and stability than curcumin. Increasing evidence confirmed that THC had a wide range of biological activities and significant treatment effects on diseases. In this paper, we reviewed the research progress on the biological activities and therapeutic potential of THC on different diseases such as neurological disorders, metabolic syndromes, cancers, and inflammatory diseases. The extensive pharmacological effects of THC involve the modulation of various signaling transduction pathways including MAPK, JAK/STAT, NF-κB, Nrf2, PI3K/Akt/mTOR, AMPK, Wnt/β-catenin. In addition, the pharmacokinetics, drug combination and toxicology of THC were discussed, thus providing scientific basis for the safe application of THC and the development of its dietary supplements and drugs.

Oxidative Stress and Redox-Dependent Pathways in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a primary liver tumor that accounts for 2% of all cancer-related deaths worldwide yearly. It can arise from cholangiocytes of biliary tracts, peribiliary glands, and possibly from progenitor cells or even hepatocytes. CCA is characterized by high chemoresistance, aggressiveness, and poor prognosis. Potentially curative surgical therapy is restricted to a small number of patients with early-stage disease (up to 35%). Accumulating evidence indicates that CCA is an oxidative stress-driven carcinoma resulting from chronic inflammation. Oxidative stress, due to enhanced reactive oxygen species (ROS) production and/or decreased antioxidants, has been recently suggested as a key factor in cholangiocyte oncogenesis through gene expression alterations and molecular damage. However, due to different experimental models and conditions, contradictory results regarding oxidative stress in cholangiocarcinoma have been reported. The role of ROS and antioxidants in cancer is controversial due to their context-dependent ability to stimulate tumorigenesis and support cancer cell proliferation or promote cell death. On these bases, the present narrative review is focused on illustrating the role of oxidative stress in cholangiocarcinoma and the main ROS-driven intracellular pathways. Heterogeneous data about antioxidant effects on cancer development are also discussed.

Mitochondrial Dysfunction-Associated Mechanisms in the Development of Chronic Liver Diseases

The liver is a major metabolic organ that performs many essential biological functions such as detoxification and the synthesis of proteins and biochemicals necessary for digestion and growth. Any disruption in normal liver function can lead to the development of more severe liver disorders. Overall, about 3 million Americans have some type of liver disease and 5.5 million people have progressive liver disease or cirrhosis, in which scar tissue replaces the healthy liver tissue. An estimated 20% to 30% of adults have excess fat in their livers, a condition called steatosis. The most common etiologies for steatosis development are (1) high caloric intake that causes non-alcoholic fatty liver disease (NAFLD) and (2) excessive alcohol consumption, which results in alcohol-associated liver disease (ALD). NAFLD is now termed "metabolic-dysfunction-associated steatotic liver disease" (MASLD), which reflects its association with the metabolic syndrome and conditions including diabetes, high blood pressure, high cholesterol and obesity. ALD represents a spectrum of liver injury that ranges from hepatic steatosis to more advanced liver pathologies, including alcoholic hepatitis (AH), alcohol-associated cirrhosis (AC) and acute AH, presenting as acute-on-chronic liver failure. The predominant liver cells, hepatocytes, comprise more than 70% of the total liver mass in human adults and are the basic metabolic cells. Mitochondria are intracellular organelles that are the principal sources of energy in hepatocytes and play a major role in oxidative metabolism and sustaining liver cell energy needs. In addition to regulating cellular energy homeostasis, mitochondria perform other key physiologic and metabolic activities, including ion homeostasis, reactive oxygen species (ROS) generation, redox signaling and participation in cell injury/death. Here, we discuss the main mechanism of mitochondrial dysfunction in chronic liver disease and some treatment strategies available for targeting mitochondria.

Investigating the Role of Ferroptosis-Related Genes in Ovarian Aging and the Potential for Nutritional Intervention

With advancing age, women experience irreversible deterioration in the quality of their oocytes, resulting in reduced fertility. To gain a deeper understanding of the influence of ferroptosis-related genes on ovarian aging, we employed a comprehensive approach encompassing spatial transcriptomics, single-cell RNA sequencing, human ovarian pathology, and clinical biopsy. This investigation revealed the intricate interactions between ferroptosis and cellular energy metabolism in aging germ cells, shedding light on the underlying mechanisms. Our study involved 75 patients with ovarian senescence insufficiency, and we utilized multi-histological predictions of ferroptosis-related genes. Following a two-month supplementation period with DHEA, Ubiquinol CoQ10, and Cleo-20 T3, we examined the changes in hub genes. Our results showed that TFRC, NCOA4, and SLC3A2 were significantly reduced and GPX4 was increased in the supplement group, confirming our prediction based on multi-omic analysis. Our hypothesis is that supplementation would enhance the mitochondrial tricarboxylic acid cycle (TCA) or electron transport chain (ETC), resulting in increased levels of the antioxidant enzyme GPX4, reduced lipid peroxide accumulation, and reduced ferroptosis. Overall, our results suggest that supplementation interventions have a notable positive impact on in vitro fertilization (IVF) outcomes in aging cells by improving metal ion and energy metabolism, thereby enhancing oocyte quality in older women.

Aberrant Transferrin and Ferritin Upregulation Elicits Iron Accumulation and Oxidative Inflammaging Causing Ferroptosis and Undermines Estradiol Biosynthesis in Aging Rat Ovaries by Upregulating NF-Κb-Activated Inducible Nitric Oxide Synthase: First Demonstration of an Intricate Mechanism

We report herein a novel mechanism, unraveled by proteomics and validated by in vitro and in vivo studies, of the aberrant aging-associated upregulation of ovarian transferrin and ferritin in rat ovaries. The ovarian mass and serum estradiol titer plummeted while the ovarian labile ferrous iron and total iron levels escalated with age in rats. Oxidative stress markers, such as nitrite/nitrate, 3-nitrotyrosine, and 4-hydroxy-2-nonenal, accumulated in the aging ovaries due to an aberrant upregulation of the ovarian transferrin, ferritin light/heavy chains, and iron regulatory protein 2(IRP2)-mediated transferrin receptor 1 (TfR1). Ferritin inhibited estradiol biosynthesis in ovarian granulosa cells in vitro via the upregulation of a nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and p65/p50-induced oxidative and inflammatory factor inducible nitric oxide synthase (iNOS). An in vivo study demonstrated how the age-associated activation of NF-κB induced the upregulation of iNOS and the tumor necrosis factor α (TNFα). The downregulation of the keap1-mediated nuclear factor erythroid 2-related factor 2 (Nrf2), that induced a decrease in glutathione peroxidase 4 (GPX4), was observed. The aberrant transferrin and ferritin upregulation triggered an iron accumulation via the upregulation of an IRP2-induced TfR1. This culminates in NF-κB-iNOS-mediated ovarian oxi-inflamm-aging and serum estradiol decrement in naturally aging rats. The iron accumulation and the effect on ferroptosis-related proteins including the GPX4, TfR1, Nrf2, Keap1, and ferritin heavy chain, as in testicular ferroptosis, indicated the triggering of ferroptosis. In young rats, an intraovarian injection of an adenovirus, which expressed iron regulatory proteins, upregulated the ovarian NF-κB/iNOS and downregulated the GPX4. These novel findings have contributed to a prompt translational research on the ovarian aging-associated iron metabolism and aging-associated ovarian diseases.

Renoprotective effects of dapagliflozin in an iron overload non-diabetic rat model

PURPOSE

Sodium glucose co-transporter (SGLT) 2 inhibitors are oral anti-diabetic drugs with proven kidney protective effects. Renal protective effects in non-diabetic individuals have also been shown in recent studies. The aim of this study was to determine the renal protective effects of dapagliflozin by evaluating the oxidative stress markers in the kidney tissue and demonstrating it in renal histological sections in an iron-overloaded rat model.

METHODS

A total of 24 Wistar Albino rats were separated into 3 groups of 8 rats. Iron sucrose (60 ​mg/kg/day) was administered intraperitoneally to the first group (Group Fe) (n ​= ​8), iron sucrose and dapagliflozin (0.1 ​mg/kg/day) to the second group (Group Fe ​+ ​D) (n ​= ​8) and intraperitoneal saline as placebo to the control group (Group C) (n ​= ​8) for 4 weeks. The glomerular changes were semi-quantitatively scored with Oxford Classification. Oxidative stress was analyzed from the tissue fluorescent oxidation product (FLOP), malondialdehyde (MDA) and total sulfhydryl (T-SH) levels.

RESULTS

Dapagliflozin prevented glomerular and mesangial damage of iron overload in the non-diabetic rat model. MDA levels were significantly higher in Group Fe compared to the Group C, and there was no significant difference between the Fe ​+ ​D group and Group C. T-SH levels were preserved in the Fe ​+ ​D group and were significantly higher than in the Fe group.

CONCLUSIONS

The results of this study showed that dapagliflozin helped preserve the glomerular and mesangial structure histologically and reduced oxidative stress markers in a non-diabetic iron overload rat model.

Tetrahydrocurcumin-Related Vascular Protection: An Overview of the Findings from Animal Disease Models

Tetrahydrocurcumin (THC), one of the major metabolites of CUR, possesses several CUR-like pharmacological effects; however, its mechanisms of action are largely unknown. This manuscript aims to summarize the literature on the preventive role of THC on vascular dysfunction and the development of hypertension by exploring the effects of THC on hemodynamic status, aortic elasticity, and oxidative stress in vasculature in different animal models. We review the protective effects of THC against hypertension induced by heavy metals (cadmium and iron), as well as its impact on arterial stiffness and vascular remodeling. The effects of THC on angiogenesis in CaSki xenografted mice and the expression of vascular endothelial growth factor (VEGF) are well documented. On the other hand, as an anti-inflammatory and antioxidant compound, THC is involved in enhancing homocysteine-induced mitochondrial remodeling in brain endothelial cells. The experimental evidence regarding the mechanism of mitochondrial dysfunction during cerebral ischemic/reperfusion injury and the therapeutic potential of THC to alleviate mitochondrial cerebral dysmorphic dysfunction patterns is also scrutinized and explored. Overall, the studies on different animal models of disease suggest that THC can be used as a dietary supplement to protect against cardiovascular changes caused by various factors (such as heavy metal overload, oxidative stress, and carcinogenesis). Additionally, the reviewed literature data seem to confirm THC's potential to improve mitochondrial dysfunction in cerebral vasculature during ischemic stroke through epigenetic mechanisms. We suggest that further preclinical studies should be implemented to demonstrate THC's vascular-protective, antiangiogenic, and anti-tumorigenic effects in humans. Applying the methods used in the presently reviewed studies would be useful and will help define the doses and methods of THC administration in various disease settings.

Steel wools microfibers causes iron overload and induces biochemical changes in Gallus gallus domesticus chicks (Galliformes: Phasianidae)

Steel wool (SW) has a broad-spectrum of applicability, particularly as abrasives, cleaning household utensils and surfaces in general. However, when present in the natural environment, they can be ingested by animals, such as birds, and may represent a risk to the survival of individuals. Accordingly, in this study, we attempted the hypothesis that the ingestion of SW microfibers (SWMs) by Gallus gallus domesticus chicks (model system used) alters growth/development, induces redox imbalance and cholinesterasic effect, as well as promotes iron overload in different organs. For this, the animals received SWMs twice (within a 24-h interval) in an amount corresponding to 12% of their total stomach volume. At the end of the experiment, we observed less weight gain and less head growth, increased production of hydrogen peroxide (in the brain, liver, crop, and gizzard), nitrite (liver, crop, proventriculus and gizzard), malondialdehyde (brain, liver, muscle, proventriculus, and gizzard), along with increased superoxide dismutase activity in the liver, muscle and crop of animals exposed to SWMs. Such results were associated with iron overload observed in different organs, especially in liver, crop, and gizzard. Furthermore, we evidenced an anti-cholinesterasic effect in birds that ingested the SWMs, marked by a reduction in the acetylcholinesterase activity (in brain). Thus, our study sheds light on the (eco)toxicological potential of SWMs in avifauna, conceding us to associate their ingestion (despite ephemeral and occasional) with damage to the health of individuals, requiring a greater attention spotted to disposal of these materials in ecosystems.

The Interplay between Insulin Resistance, Inflammation, Oxidative Stress, Base Excision Repair and Metabolic Syndrome in Nonalcoholic Fatty Liver Disease

One of the most common chronic liver disorders, affecting mainly people in Western countries, is nonalcoholic fatty liver disease (NAFLD). Unfortunately, its pathophysiological mechanism is not fully understood, and no dedicated treatment is available. Simple steatosis can lead to nonalcoholic steatohepatitis and even to fibrosis, cancer, and cirrhosis of the liver. NAFLD very often occurs in parallel with type 2 diabetes mellitus and in obese people. Furthermore, it is much more likely to develop in patients with metabolic syndrome (MS), whose criteria include abdominal obesity, elevated blood triacylglycerol level, reduced high-density lipoprotein cholesterol level, increased blood pressure, and high fasting glucose. An important phenomenon in MS is also insulin resistance (IR), which is very common in NAFLD. Liver IR and NAFLD development are linked through an interaction between the accumulation of free fatty acids, hepatic inflammation, and increased oxidative stress. The liver is particularly exposed to elevated levels of reactive oxygen species due to a large number of mitochondria in hepatocytes. In these organelles, the main DNA repair pathway is base excision repair (BER). The present article will illustrate how impairment of BER may be related to the development of NAFLD.

Ameliorating Iron Overload in Intestinal Tissue of Adult Male Rats: Quercetin vs Deferoxamine

OBJECTIVE

The aim of our study is to compare the role of the new natural alternative (Quercetin) with the current iron-chelation therapy (Deferoxamine (DFO)) in the effect of iron overload on small intestinal tissues and to investigate the possible underlying molecular mechanisms of such toxicity.

METHODS

Forty-two adult male albino rats were divided into six groups: control groups, DFO, Quercetin, iron overload, iron overload+DFO, and iron overload+Quercetin groups. Animals received daily intraperitoneal injection of Deferoxamine (125 mg /kg), Quercetin (10 mg/kg), and ferric dextran (200 mg/kg) for 2 weeks.

RESULTS

Iron overloaded group showed significant increase in serum iron, total iron binding capacity (TIBC), transferrin saturation percentage (TS %) hepcidin (HEPC), serum ferritin, nontransferrin bound iron (NTBI), and small intestinal tissues iron levels. Iron overload significantly increased the serum oxidative stress indicator (MDA) and reduced serum total antioxidant capacity (TAC). On the other hand, iron overload increased IL6 and reduced IL10 in small intestinal tissues reflecting inflammatory condition and increased caspase 3 reactivity indicating apoptosis and increased iNOs expressing cell indicting oxidative stress especially in ileum. In addition, it induced small intestinal tissues pathological alterations. The treatment with Quercetin showed nonsignificant differences as compared to treatment with DFO that chelated the serum and tissue iron and improved the oxidative stress and reduced tissue IL6 and increased IL10 and decreased caspase 3 and iNOs expressing cells in small intestinal tissues. Moreover, it ameliorated the iron overload induced pathological alterations.

CONCLUSION

Our study showed the potential role of Quercetin as iron chelator like DFO in case of iron overload induced small intestinal toxicity in adult rats because of its serum and tissue iron chelation, improvement of serum, and small intestinal oxidative stress, ameliorating iron induced intestinal inflammation, apoptosis, and histopathological alterations.

Quercetin modulates iron homeostasis and iNOS expression of splenic macrophages in a rat model of iron deficiency anemia

Iron deficiency anemia is one of the most common micronutrient deficient conditions around the globe with various consequences, including the weakened immune system. Quercetin is widely distributed bioflavonoid; it has been debated for its dual roles in iron regulation. Quercetin-iron interaction in the body is a complex mechanism which has not been completely understood. The present study aimed to investigate the effect of quercetin on iron supplementation in iron deficiency anemia and on iNOS expression in splenic macrophages. The rat model of iron deficiency anemia was induced by feeding low iron diet to weanling rats for 20 days. The animals were then administered with ferrous sulfate, quercetin, and their combination for 30 days. Blood parameters, histopathological analysis, iron storage, CD68, iNOS and SLC40 expression in rat spleen were investigated. Our results showed that quercetin regulated iron absorption, despite SLC40 down-expression, indicating possible alternate route of iron transport, and that quercetin modulated iNOS production in splenic macrophages.

Role of Oxidative Stress in Pathophysiology of Nonalcoholic Fatty Liver Disease

Liver steatosis without alcohol consumption, namely, nonalcoholic fatty liver disease (NAFLD), is a common hepatic condition that encompasses a wide spectrum of presentations, ranging from simple accumulation of triglycerides in the hepatocytes without any liver damage to inflammation, necrosis, ballooning, and fibrosis (namely, nonalcoholic steatohepatitis) up to severe liver disease and eventually cirrhosis and/or hepatocellular carcinoma. The pathophysiology of fatty liver and its progression is influenced by multiple factors (environmental and genetics), in a "multiple parallel-hit model," in which oxidative stress plays a very likely primary role as the starting point of the hepatic and extrahepatic damage. The aim of this review is to give a comprehensive insight on the present researches and findings on the role of oxidative stress mechanisms in the pathogenesis and pathophysiology of NAFLD. With this aim, we evaluated the available data in basic science and clinical studies in this field, reviewing the most recent works published on this topic.

Oral administration of liquid iron preparation containing excess iron induces intestine and liver injury, impairs intestinal barrier function and alters the gut microbiota in rats

The aim of this study was to determine the toxicological effects of excess iron in a liquid iron preparation (especially on intestinal barrier function) and the possible etiology of side effects or diseases caused by the excess iron. In study 1, forty male Sprague-Dawley rats (4-5 wk old) were subjected to oral gavage with 1 ml vehicle (0.01 mol/L HCl) or 1 ml liquid iron preparation containing 8 mg, 16 mg or 24 mg of iron for 30 d. Iron status, oxidative stress, histology (H&E staining), ultrastructure (electron microscopy) and apoptosis (TUNEL assay) in the intestines and liver were assessed. The cecal microbiota was evaluated by 16S rRNA sequencing. In study 2, twenty rats with the same profile as above were subjected to oral gavage with 1 ml vehicle or 24 mg Fe for 30 d. The intestinal barrier function was determined by in vivo studies and an Ussing chamber assay; tight junction proteins and serum pro-inflammatory cytokines were observed by enzyme-linked immunosorbent assay. In study 1, the intestinal mucosa and liver showed apparent oxidative stress. In addition, iron concentration-dependent ultrastructural alterations to duodenal enterocytes and hepatocytes and histological damage to the colonic mucosa were detected. Notably, apoptosis was increased in duodenal enterocytes and hepatocytes. Impaired intestinal barrier function and lower expression of intestinal tight junction proteins were observed, and the phenotype was more severe in the colon than in the duodenum. A trend toward higher expression of serum pro-inflammatory cytokines might indicate systemic inflammation. Furthermore, the caecal microbiota showed a significant change, with increased Defluviitaleaceae, Ruminococcaceae, and Coprococcus and reduced Lachnospiraceae and Allobaculum, which could mediate the detrimental effects of excess iron on gut health. We concluded that excessive iron exposure from liquid iron preparation induces oxidative stress and histopathological alterations in the intestine and liver. Impaired intestinal barrier function could increase iron transportation, and inflammation along with oxidative stress-enhanced liver iron deposition may cause further liver injury in a vicious circle. These effects were accompanied by lower intestinal segment damage and altered gut microbial composition of rats toward a profile with an increased risk of gut disease.

Antifibrotic effect of xanthohumol in combination with praziquantel is associated with altered redox status and reduced iron accumulation during liver fluke-associated cholangiocarcinogenesis

Cholangiocarcinoma (CCA) caused by infection of the liver fluke Opisthorchis viverrini, (Ov) is the major public health problem in northeast Thailand. Following Ov infection the subsequent molecular changes can be associated by reactive oxygen species (ROS) induced chronic inflammation, advanced periductal fibrosis, and cholangiocarcinogenesis. Notably, resistance to an activation of cell death in prolonged oxidative stress conditions can occur but some damaged/mutated cells could survive and enable clonal expansion. Our study used a natural product, xanthohumol (XN), which is an anti-oxidant and anti-inflammatory compound, to examine whether it could prevent Ov-associated CCA carcinogenesis. We measured the effect of XN with or without praziquantel (PZ), an anti-helminthic treatment, on DNA damage, redox status change including iron accumulation and periductal fibrosis during CCA genesis induced by administration of Ov and N-dinitrosomethylamine (NDMA) in hamsters. Animals were randomly divided into four groups: group I, Ov infection and NDMA administration (ON); group II, Ov infection and NDMA administration and PZ treatment (ONP); the latter 2 groups were similar to group I and II, but group III received additional XN (XON) and group IV received XN plus PZ (XONP). The results showed that high 8-oxodG (a marker of DNA damage) was observed throughout cholangiocarcinogenesis. Moreover, increased expression of CD44v8-10 (a cell surface in regulation of the ROS defense system), whereas decreased expression of phospho-p38^MAPK (a major ROS target), was found during the progression of the bile duct cell transformation. In addition, high accumulation of iron and expression of transferrin receptor-1 (TfR-1) in both malignant bile ducts and inflammatory cells were detected. Furthermore, fibrosis also increased with the highest level being on day 180. On the other hand, the groups of XN with or without PZ supplementations showed an effective reduction in all the markers examined, including fibrosis when compared with the ON group. In particular, the XONP group, in which a significant reduction DNA damage occurred, was also found to have iron accumulation and fibrosis compared to the other groups. Our results show that XN administered in combination with PZ could efficiently prevent CCA development and hence provide potential chemopreventive benefits in Ov-induced cholangiocarcinogenesis.

Effects of ferric citrate supplementation on advanced glycation end products in a rat model of streptozotocin/nicotinamide-induced diabetes

SCOPE

Diabetes is associated with the increased risks of anemia and activation of advanced glycation end products (AGEs) and the receptor for AGEs (RAGE). However, the effects of pharmacological doses of iron supplementation on AGE metabolism are less clear. The aim was to investigate the effect of ferric citrate supplementation on AGE metabolism.

METHODS AND RESULTS

Diabetes was induced in overnight starved rats by intraperitoneal injections of 40 mg/kg streptozotocin and 120 mg/kg nicotinamide. Diabetic rats were fed a standard diet or pharmacological doses of ferric citrate (0.5, 1, 2, and 3 g of ferric iron/kg diet) for 10 weeks. Ferric citrate supplementation showed a dose-related effect on the hepatic steatosis score, malondialdehyde, cathepsin D, and glyoxalase I. A Western blot analysis revealed that >1 g of ferric iron suppressed hepatic AGE receptor 1 and high-mobility group-box 1 expressions but increased heme oxygenase-1 and RAGE expressions. Further analysis showed that high doses of ferric iron triggered sterol regulatory element-binding protein 1c, p38-mitogen-activated protein kinase, and nuclear factor-κB protein expressions.

CONCLUSION

Overall, the present results suggest a dose-related effect of ferric citrate supplementation on AGE metabolism, and this effect was more evident at high iron doses (>1 g of ferric iron/kg diet).

Tetrahydrocurcumin in combination with deferiprone attenuates hypertension, vascular dysfunction, baroreflex dysfunction, and oxidative stress in iron-overloaded mice

Excessive iron can generate reactive oxygen species (ROS), leading to oxidative stress that is closely associated with cardiovascular dysfunction. Iron overload was induced in male ICR mice by injection of iron sucrose (10mg/kg/day) for eight weeks. Iron overload was evidenced by increased serum iron indices. The mice developed increased blood pressure, impaired vascular function and blunted response of the autonomic nervous system. These effects were accompanied by increased malondialdehyde levels in various tissues, increased nitric oxide metabolites in plasma and urine, and decreased blood glutathione. Tetrahydrocurcumin (THU, 50mg/kg/day), deferiprone (or L1, 50mg/kg/day) or both was orally administered throughout the period of iron sucrose injection. The treatments significantly alleviated the deleterious cardiovascular effects of iron overload, and were associated with modulation of nitric oxide levels. An imbalance between endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS) expression in response to iron overload was normalized by THU, L1 or the combination treatment. Moreover, the treatment decreased the upregulated expression levels of gp91phox, p47phox and HO-1. The combination of THU and L1 exerted a greater effect than THU or L1 monotherapy. These results suggest beneficial effects of THU and L1 on iron-induced oxidative stress, hypertension, and vascular dysfunction.

The role of S-methylisothiourea hemisulfate as inducible nitric oxide synthase inhibitor against kidney iron deposition in iron overload rats

Background:

Iron dextran is in common use to maintain iron stores. However, it is potentially toxic and may lead to iron deposition (ID) and impair functions of organs. Iron overload can regulate the expression of inducible nitric oxide synthase (iNOS) in some cells that has an important role in tissue destruction. S-methylisothiourea hemisulfate (SMT) is a direct inhibitor of iNOS, and this study was designed to investigate the effect of SMT against kidney ID in iron overload rats.

Materials and Methods:

24 Wistar rats (male and female) were randomly assigned to two groups. Iron overloading was performed by iron dextran 100 mg/kg/day every other day for 2 weeks. In addition, during the study, groups 1 and 2 received vehicle and SMT (10 mg/kg, ip), respectively. Finally, blood samples were obtained, and the kidneys were prepared for histopathological procedures.

Results:

SMT significantly reduced the serum levels of creatinine and blood urea nitrogen. However, SMT did not alter the serum levels of iron and nitrite, and the kidney tissue level of nitrite. Co-administration of SMT with iron dextran did not attenuate the ID in the kidney.

Conclusion:

SMT, as a specific iNOS inhibitor, could not protect the kidney from ID while it attenuated the serum levels of kidney function biomarkers.

Ameliorating role of rutin on oxidative stress induced by iron overload in hepatic tissue of rats

Iron is an essential element that participates in several metabolic activities of cells; however, excess iron is a major cause of iron-induced oxidative stress and several human diseases. Natural flavonoids, as rutin, are well-known antioxidants and could be efficient protective agents. Therefore, the present study was undertaken to evaluate the protective influence of rutin supplementation to improve rat antioxidant systems against IOL-induced hepatic oxidative stress. Sixty male albino rats were randomly divided to three equal groups. The first group, the control, the second group, iron overload group, the third group was used as iron overload+rutin group. Rats received six doses of ferric hydroxide polymaltose (100 mg kg(-1) b.wt.) as one dose every two days, by intraperitoneal injections (IP) and administrated rutin (50 mg kg(-1) b.wt.) as one daily oral dose until the sacrificed day. Blood samples for serum separation and liver tissue specimens were collected three times, after three, four and five weeks from the onset of the experiment. Serum iron profiles total iron, Total Iron Binding Capacity (TIBC), Unsaturated Iron Binding Capacity (UIBC), transferrin (Tf) and Transferrin Saturation% (TS%)}, ferritin, albumin, total Protein, total cholesterol, triacylglycerols levels and aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were determined. Moreover, total iron in the liver, L-malondialdehyde (L-MDA), glutathione (GSH), Nitric Oxide (NO) and Total Nucleic Acid (TNA) levels and glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD) activities were also determined. The obtained results revealed that, iron overload (IOL) resulted in significant increase in serum iron, TIBC, Tf, TS% and ferritin levels and AST and ALT activities and also increased liver iron, L-MDA and NO levels. Meanwhile, it decreased serum UIBC, total cholesterol, triacylglycerols, albumin, total protein and liver GSH, TNA levels and Gpx, CAT and SOD activities when compared with the control group. Rutin administration to iron-overloaded rats resulted in significant decrease in serum total iron, TIBC, Tf, TS%, ferritin levels and AST and ALT activities and liver total iron, L-MDA and NO levels with significant increases in serum UIBC, albumin, total protein and total cholesterol levels and in liver GSH, CAT and SOD activities compared with the IOL group. This study provides in vivo evidence that rutin administration can improve the antioxidant defense systems against IOL-induced hepatic oxidative stress in rats. This protective effect in liver of iron-loaded rats may be due to both antioxidant and metal chelation activities.

Effects of iron overload on the bone marrow microenvironment in mice

OBJECTIVE

Using a mouse model, Iron Overload (IO) induced bone marrow microenvironment injury was investigated, focusing on the involvement of reactive oxygen species (ROS).

METHODS

Mice were intraperitoneally injected with iron dextran (12.5, 25, or 50 mg) every three days for two, four, and six week durations. Deferasirox(DFX)125 mg/ml and N-acetyl-L-cysteine (NAC) 40 mM were co-administered. Then, bone marrow derived mesenchymal stem cells (BM-MSCs) were isolated and assessed for proliferation and differentiation ability, as well as related gene changes. Immunohistochemical analysis assessed the expression of haematopoietic chemokines. Supporting functions of BM-MSCs were studied by co-culture system.

RESULTS

In IO condition (25 mg/ml for 4 weeks), BM-MSCs exhibited proliferation deficiencies and unbalanced osteogenic/adipogenic differentiation. The IO BM-MSCs showed a longer double time (2.07±0.14 days) than control (1.03±0.07 days) (P<0.05). The immunohistochemical analysis demonstrated that chemokine stromal cell-derived factor-1, stem cell factor -1, and vascular endothelial growth factor-1 expression were decreased. The co-cultured system demonstrated that bone marrow mononuclear cells (BMMNCs) co-cultured with IO BM-MSCs had decreased colony forming unit (CFU) count (p<0.01), which indicates IO could lead to decreased hematopoietic supporting functions of BM-MSCs. This effect was associated with elevated phosphatidylinositol 3 kinase (PI3K) and reduced of Forkhead box protein O3 (FOXO3) mRNA expression, which could induce the generation of ROS. Results also demonstrated that NAC or DFX treatment could partially attenuate cell injury and inhibit signaling pathway striggered by IO.

CONCLUSION

These results demonstrated that IO can impair the bone marrow microenvironment, including the quantity and quality of BM-MSCs.

Are oxidative stress mechanisms the common denominator in the progression from hepatic steatosis towards non-alcoholic steatohepatitis (NASH)?

Non-alcoholic fatty liver disease (NAFLD) is not a single disease entity, rather it describes a spectrum of liver conditions that range from fatty liver (steatosis) to more severe steatosis coupled with marked inflammation and fibrosis [non-alcoholic steatohepatitis (NASH)] to severe liver disease such as cirrhosis and possibly hepatocellular carcinoma. Obesity, notably abdominal obesity, is a common risk factor for NAFLD. The pathogenesis from steatosis to NASH is poorly understood, and the 'two hit' model, as suggested nearly two decades ago, provides a feasible starting point for characterization of underlying mechanisms. This review will examine the oxidative stress factors ('triggers') which have been implicated as a 'second hit' in the development of primary NASH. It would be reasonable to assume that multiple, rather than single, pro-oxidative intracellular and extracellular triggers act in conjunction promoting oxidative stress that drives the development of NASH. It is likely that the common denominator of these pro-oxidative triggers is mitochondrial dysfunction. Understanding the contribution of each of these 'triggers' is an essential step in starting to understand and elucidate the mechanisms responsible for progression from steatosis to NASH, thus enabling the development of therapeutic targeting to prevent NASH development and progression.

The complex interplay of iron metabolism, reactive oxygen species, and reactive nitrogen species: insights into the potential of various iron therapies to induce oxidative and nitrosative stress

Production of minute concentrations of superoxide (O2(*-)) and nitrogen monoxide (nitric oxide, NO*) plays important roles in several aspects of cellular signaling and metabolic regulation. However, in an inflammatory environment, the concentrations of these radicals can drastically increase and the antioxidant defenses may become overwhelmed. Thus, biological damage may occur owing to redox imbalance-a condition called oxidative and/or nitrosative stress. A complex interplay exists between iron metabolism, O2(*-), hydrogen peroxide (H2O2), and NO*. Iron is involved in both the formation and the scavenging of these species. Iron deficiency (anemia) (ID(A)) is associated with oxidative stress, but its role in the induction of nitrosative stress is largely unclear. Moreover, oral as well as intravenous (iv) iron preparations used for the treatment of ID(A) may also induce oxidative and/or nitrosative stress. Oral administration of ferrous salts may lead to high transferrin saturation levels and, thus, formation of non-transferrin-bound iron, a potentially toxic form of iron with a propensity to induce oxidative stress. One of the factors that determine the likelihood of oxidative and nitrosative stress induced upon administration of an iv iron complex is the amount of labile (or weakly-bound) iron present in the complex. Stable dextran-based iron complexes used for iv therapy, although they contain only negligible amounts of labile iron, can induce oxidative and/or nitrosative stress through so far unknown mechanisms. In this review, after summarizing the main features of iron metabolism and its complex interplay with O2(*-), H2O2, NO*, and other more reactive compounds derived from these species, the potential of various iron therapies to induce oxidative and nitrosative stress is discussed and possible underlying mechanisms are proposed. Understanding the mechanisms, by which various iron formulations may induce oxidative and nitrosative stress, will help us develop better tolerated and more efficient therapies for various dysfunctions of iron metabolism.

Macrophages, TGF-β1 expression and iron deposition in development of NASH

A wide range of molecular markers and different types of cells in liver are possible factors for progression of non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH) development of liver fibrosis. We investigated biopsies from 57 patients with NASH. The material was obtained from livers and was proceed immunohistochemistry antibodies against CD68 and TGF-beta 1. In addition, biopsies were evaluated for iron content. Macrophages/-positive/could be found in all 57 cases. The number of macrophages in the sinusoids correlated with the degree of portal fibrosis:64.% of the patients with mild or intensive fibrosis had high infiltration with CD68-positive cells, while 100% of the patients without fibrosis hadlow infiltration (χ2=8.56; p=0.003). In specimens we, 69.% of patients with different degree of fibrosis expressed TGF-β1 in their portal tracts, and 100% of patients without fibrosis did demonstrate expression of the protein (χ2=23.7; p<0.001). Hepatic iron was found in 100% (9) of patients with intensive fibrosis vs. 10.3% of the patients mild fibrosis (χ2=23.4; p<0.001). Our results suggest that the macrophages and macrophage-derived TGF-beta1 are the major factors responsible for development of fibrosis and progression of chronic liver disease.

Accelerated proliferation of hepatocytes in rats with iron overload after partial hepatectomy

Although iron overload is implicated in hepatocarcinogenesis, the precise mechanism was not known yet. In the present study, we investigated the effect of iron overload upon the induction of hepatocyte proliferation after 70% partial hepatectomy (PH) in rats fed with rat chow with 3% carbonyl iron for 3 months. In normal-diet rats, the increase in Ki-67 labeling index (LI) commenced at 24 h post-PH and the LIs of proliferating cell nuclear antigen (PCNA) incorporated 5-bromo-2'-deoxyuridine (BrdU) and phospho-histone H3 reached maximum values at 36 and 48 h after PH, respectively. In iron-overload rats, the above parameters occurred 12 h earlier compared to that of normal-diet rats, shortening the G0-G1 transition. Interestingly, nuclear staining for metallothionein (MT), which is essential for hepatocyte proliferation, was noted even at 0 h in iron-overload rats, while MT expression occurred at 6 h in the normal rats. Moreover, nuclear factor kappa B (NF-κB) expression, which is an essential early event leading to liver regeneration, was detected in Kupffer cells at 0 h in iron-overload rats. These results may indicate that overloaded iron, maybe through the induction of MT and NF-κB, may keep liver as a state ready to regenerate in response to PH, by bypassing signal transduction cascades involved in the initiation of liver regeneration.

Ferric citrate CYP2E1-independently promotes alcohol-induced apoptosis in HepG2 cells via oxidative/nitrative stress which is attenuated by pretreatment with baicalin

In the case of alcoholic liver injury, an iron overload is always present. Both alcohol and iron can individually induce oxidative stress in liver. However, the combined effect of physiological concentrations of alcohol and iron on oxidative stress in hepatocytes remains unknown. Baicalin has been demonstrated to be an antioxidant or iron chelator in animal experiments. In this study, we investigated the injury to hepatocytes CYP2E1-independently induced by the combination of alcohol and iron and the protective effect of baicalin. Compared with cells treated with ethanol alone, ferric citrate enhanced the accumulation of reactive oxygen and nitrogen species, increased the occurrence of protein carbonylation/nitration and the levels of 4-hydroxy-2-nonenal, changed the distribution of iNOS, and eventually resulted in apoptosis. However, pretreatment with baicalin inhibited the oxidative stress induced by the combination of alcohol and iron, mainly by chelating iron. Our findings therefore suggest that iron could CPY2E1-independently enhance the oxidative stress induced by alcohol, which probably contributes to the pathogenesis of alcoholic liver disease. Baicalin is a promising phytomedicine for preventing alcoholic liver disease.

Iron overload-induced rat liver injury: Involvement of protein tyrosine nitration and the effect of baicalin

Baicalin has been reported to protect against liver injury in iron-overload mice, however, the mechanisms underlying the hepatoprotective properties of baicalin are poorly understood. In this study, we systematically studied the protective effect of baicalin on iron overload induced liver injury, as well as the underlying mechanism based on nitrative stress in rat model. We found that when iron overload rats (500mgiron/kg) were fed baicalin-containing diet (0.3% and 1% w/w) for 45days, baicalin dose dependently protected against iron overload induced liver injury, including alleviation of hepatic pathological damage, decrease of SOD activity, iron content, carbonyl content, and the thiobarbituric acid-reactive substances level in hepatic tissues. It also increased serum iron content, SH content and GPx activity, decreased serum ALT and AST activities. Immunohistochemistry and immunoprecipitation analysis revealed that baicalin could also inhibit iron overload induced protein tyrosine nitration in liver. Moreover, in iron overload rat liver, we found that baicalin decreased the iron overload increased level of glutathione-S-transferases (GSTs) expression, oxidation and nitration. These results suggest that not only oxidative stress, but also nitrative stress, is involved in iron overload induced liver injury, and the underlying mechanism might partially relate to the involvement of GSTs expression and post-translational modification. Baicalin can effectively prevent iron overload caused abnormality and can be a candidate medicine for iron overload diseases.

Cardioprotection by Hepc1 in cTnT(R141W) transgenic mice

Hepcidin 1 (Hepc1) is a peptide hormone secreted by the liver in response to iron loading. It is expressed in the heart and is thought to play a role in the regulation of iron homeostasis in an autocrine and paracrine fashion. We have shown that expression of Hepc1 is strongly down-regulated in the heart of the cTnT(R141W) transgenic mouse model of dilated cardiomyopathy (DCM) at 3 months of age. Transgenic mice with heart tissue-specific Hepc1 expression alone or in combination with the cTnT(R141W) mutation were produced to study the effects of Hepc1 on DCM. Transgenic expression of Hepc1 was found to be nonlethal and resulted in decreased mortality in cTnT(R141W) transgenic mice, from 29.6 to 7.4%(n  = 27; P < 0.05), through 7 months of age. Expression of Hepc1 also brought about increases in the left ventricular wall, as well as ejection fraction and fractional shortening. In addition, the expression of Hepc1 inhibited the fibrosis and ultra-structural alterations seen in cTnT(R141W) transgenic mice. Furthermore, transgenic expression of Hepc1 restored the iron level and phosphorylation level of extracellular signal-regulated kinases 1/2 (ERK1/2) in the heart tissues of cTnT(R141W) transgenic mice. It was concluded that transgenic expression of Hepc1 compensated for the loss of Hepc1 expression and the release of iron and brought about a marked improvement in the pathologic phenotype of DCM, in which the ERK1/2 signal pathway might play an important role.

Non-alcoholic fatty liver disease: is iron relevant?

Non-alcoholic fatty liver disease (NAFLD) is a common and ubiquitous disorder (Bedogni et al. in Hepatology 42:44-52, 2005; Bellentani et al. in Ann Intern Med 132:112-117, 2000) which in a proportion of subjects leads to non-alcoholic steatohepatitis (NASH), advanced liver disease and hepatocellular carcinoma. Although the factors responsible for progression of disease are still uncertain, there is evidence that insulin resistance (IR) is a key operative mechanism (Angulo et al. in Hepatology 30:1356-1362, 1999) and that two stages are involved. The first is the accumulation of triglycerides in hepatocytes followed by a "second hit" which promotes cellular oxidative stress. Several factors may be responsible for the induction of oxidative stress but hepatic iron has been implicated in various studies. The topic is controversial, however, with early studies showing an association between hepatic iron (with or without hemochromatosis gene mutations) and the progression to hepatic fibrosis. Subsequent studies, however, could not confirm an association between the presence of hepatic iron and any of the histological determinants of NAFLD or NASH. Recent studies have reactivated interest in this subject firstly, with the demonstration that hepatic iron loading increases liver cholesterol synthesis with increased lipid deposition in the liver increasing the cellular lipid burden and secondly, a large clinical study has concluded that hepatocellular iron deposition is associated with an increased risk of hepatic fibrosis, thus, strongly supporting the original observation made over a decade ago. An improvement in insulin sensitivity has been demonstrated following phlebotomy therapy but a suitably powered controlled clinical trial is required before this treatment can be implemented.

Glucose abnormalities in non-alcoholic fatty liver disease and chronic hepatitis C virus infection: the role of iron overload

Non-alcoholic fatty liver disease (NAFLD) and chronic hepatitis C virus (HCV) infection are major causes of liver disease frequently described in outpatient patients with glucose abnormalities. Hyperferritinemia, which suggests that iron overload plays a decisive role in the pathophysiology of insulin resistance and hyperglycemia, is a common finding in both disorders. However, the role of the hepatic iron deposition differs from one to the other. In NAFLD, a moderate liver iron accumulation has been observed and molecular mechanisms, including the downregulation of the liver iron exporter ferroportin-1, have been described. Iron overload will enhance intrahepatic oxidative stress that promotes hepatic fibrosis, interfere with insulin signalling at various levels and may hamper hepatic insulin extraction. Therefore, liver fibrosis, hyperglycemia and hyperinsulinemia will lead to increased levels of insulin resistance and the development of glucose abnormalities. Furthermore, iron depletion by phlebotomy removes liver iron content and reduces serum glucose and insulin resistance in NAFLD patients. Therefore, it seems that iron overload participates in those glucose abnormalities associated with NAFLD. Concerning chronic HCV infection, it has been classically assumed that iron overload contributes to insulin resistance associated with virus infection. However, recent evidence argues against the presence of iron overload in these patients and points to inflammation associated with diabetes as the main contributor to the elevated ferritin levels. Therefore, glucose abnormalities, and specially type 2 diabetes, should be taken into account when evaluating serum ferritin levels in patients with HCV infection.

Iron overload is associated with hepatic oxidative damage to DNA in nonalcoholic steatohepatitis

Several lines of evidence have suggested that oxidative stress plays an important role for the pathogenesis of nonalcoholic steatohepatitis (NASH). Therefore, by using immunohistochemical staining of liver biopsy samples, we measured hepatic 7,8-dihydro-8-oxo-2' deoxyguanosine (8-oxodG), a DNA base-modified product generated by hydroxyl radicals, of 38 NASH patients and compared with 24 simple steatosis and 10 healthy subjects. Relation of hepatic 8-oxodG with clinical, biochemical, and histologic variables and changes after iron reduction therapy (phlebotomy plus iron-restricted diet) were also examined. Hepatic 8-oxodG levels were significantly higher in NASH compared with simple steatosis (17.5 versus 2.0 8-oxodG-positive cells/10(5) microm(2); P < 0.0001). 8-oxodG was significantly related to iron overload condition, glucose-insulin metabolic abnormality, and severities of hepatic steatosis in NASH patients. Logistic regression analysis also showed that hepatic iron deposit and insulin resistance were independent variables associated with elevated hepatic 8-oxodG. After the iron reduction therapy, hepatic 8-oxodG levels were significantly decreased (from 20.7 to 13.8 positive cells/10(5) microm(2); P < 0.01) with concomitant reductions of serum transaminase levels in NASH patients. In conclusion, iron overload may play an important role in the pathogenesis of NASH by generating oxidative DNA damage and iron reduction therapy may reduce hepatocellular carcinoma incidence in patients with NASH.

Ceruloplasmin protects injured spinal cord from iron-mediated oxidative damage

CNS injury-induced hemorrhage and tissue damage leads to excess iron, which can cause secondary degeneration. The mechanisms that handle this excess iron are not fully understood. We report that spinal cord contusion injury (SCI) in mice induces an "iron homeostatic response" that partially limits iron-catalyzed oxidative damage. We show that ceruloplasmin (Cp), a ferroxidase that oxidizes toxic ferrous iron, is important for this process. SCI in Cp-deficient mice demonstrates that Cp detoxifies and mobilizes iron and reduces secondary tissue degeneration and functional loss. Our results provide new insights into how astrocytes and macrophages handle iron after SCI. Importantly, we show that iron chelator treatment has a delayed effect in improving locomotor recovery between 3 and 6 weeks after SCI. These data reveal important aspects of the molecular control of CNS iron homeostasis after SCI and suggest that iron chelator therapy may improve functional recovery after CNS trauma and hemorrhagic stroke.

Hepatic tumor necrosis factor signaling and nuclear factor-kappaB: effects on liver homeostasis and beyond

The proinflammatory cytokine TNF has a pivotal role in liver pathophysiology because it holds the capacity to induce both hepatocyte cell death and hepatocyte proliferation. This dual effect of TNF on hepatocytes reflects its ability to induce both nuclear factor kappaB (NF-kappaB)-dependent gene expression and cell death. Multiple studies have demonstrated the crucial role of the transcription factor NF-kappaB in the decision between life and death of a hepatocyte. Massive hepatocyte apoptosis preceding embryonic lethality in NF-kappaB-deficient mice constituted the first indication of an essential antiapoptotic function of NF-kappaB in the liver. Although many studies confirmed this crucial cytoprotective role of NF-kappaB in adult liver, a number of genetic studies recently obtained conflicting results on the exact role of NF-kappaB in different mouse models of TNF hepatotoxicity, demonstrating that caution should be taken when interpreting studies using different NF-kappaB-deficient mice in distinct models of liver injury. Recent reports showing a role for hepatic NF-kappaB activation in the proliferation of malignant cells during hepatocarcinogenesis, and in the progression of fatty liver diseases to insulin resistance and type 2 diabetes mellitus demonstrate that NF-kappaB can also have more detrimental effects in the liver. Moreover, its role in the development of the metabolic syndrome emphasizes that hepatic NF-kappaB activation might also have adverse effects on the endocrine system. Therefore, understanding the regulation of hepatic TNF signaling and NF-kappaB activation is of critical therapeutic importance. In this review, we summarize how studies on the role of NF-kappaB in different mouse models of liver pathologies have contributed to this understanding.

Peripheral iron dextran induced degeneration of dopaminergic neurons in rat substantia nigra

Iron accumulation is considered to be involved in the pathogenesis of Parkinson's disease. To demonstrate the relationship between peripheral iron overload and dopaminergic neuron loss in rat substantia nigra (SN), in the present study we used fast cyclic voltammetry, tyrosine hydroxylase (TH) immunohistochemistry, Perls' iron staining, and high performance liquid chromatography-electrochemical detection to study the degeneration of dopaminergic neurons and increased iron content in the SN of iron dextran overloaded animals. The findings showed that peripheral iron dextran overload increased the iron staining positive cells and reduced the number of TH-immunoreactive neurons in the SN. As a result, dopamine release and content, as well as its metabolites contents were decreased in caudate putamen. Even more dramatic changes were found in chronic overload group. These results suggest that peripheral iron dextran can increase the iron level in the SN, where excessive iron causes the degeneration of dopaminergic neurons. The chronic iron overload may be more destructive to dopaminergic neurons than the acute iron overload.

Hepatoprotective role of nitric oxide in an experimental model of chronic iron overload

Chronic iron overload (CIO) enhances nitric oxide (*NO) production in the liver, which may represent a hepatoprotective mechanism against CIO toxicity. In order to test this hypothesis, the influence of CIO (diet enriched with 3% (wt/wt) carbonyl-iron for 8 weeks) in the absence or presence of the (*)NO synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) on NOS activity, extracellular signal-regulated kinase (ERK1/2) and NF-kappaB activation was studied, in relation to ferritin expression and liver morphology. CIO increased liver NOS activity, ERK1/2 phosphorylation, NF-kappaB DNA binding, and ferritin expression, with normal liver histology. These changes were suppressed by combined CIO and L-NAME treatment, with the resulting inflammatory response of the liver. It is concluded that (*)NO response induced by CIO represents a molecular mechanism affording protection against iron toxicity, which is related to both the activation of the ERK/NF-kappaB pathway involving inducible NOS expression and ferritin upregulation, changes that may be interrelated.

Iron-related transcriptomic variations in CaCo-2 cells, an in vitro model of intestinal absorptive cells

Regulation of iron absorption by duodenal enterocytes is essential for the maintenance of homeostasis by preventing iron deficiency or overload. Despite the identification of a number of genes implicated in iron absorption and its regulation, it is likely that further factors remain to be identified. For that purpose, we used a global transcriptomic approach, using the CaCo-2 cell line as an in vitro model of intestinal absorptive cells. Pangenomic screening for variations in gene expression correlating with intracellular iron content allowed us to identify 171 genes. One hundred nine of these genes are clustered into five types of expression profile. This is the first time that most of these genes have been associated with iron metabolism. Functional annotation of these five clusters indicates potential links between the immune response, proteolysis processes, and iron depletion. In contrast, iron overload is associated with cellular metabolism, especially that of lipids and glutathione involving redox function and electron transfer.

Inducible nitric oxide synthase up-regulation and mitochondrial glutathione depletion mediate cyanide-induced necrosis in mesencephalic cells

We have previously shown in rat primary cultured mesencephalic cells that cyanide induces a high level of oxidative stress and necrotic death. To evaluate the mechanism of the cytotoxicity, the effects of cyanide on intracellular glutathione (GSH) pools and inducible nitric oxide synthase (iNOS)-mediated reactive nitrogen species (RNS) generation were studied. Cyanide rapidly depleted intracellular GSH. Restoration of GSH blocked cell death, whereas depletion of GSH by synthesis inhibition increased the necrosis. Selective depletion of mitochondrial GSH (mtGSH) increased oxidative stress and enhanced cell death, whereas the cytoplasmic pool was not critical to cell survival. These actions were accompanied by increased iNOS expression as determined by Western blot analysis, RT-PCR and immunohistochemistry. Up-regulation of iNOS led to increased generation of NO as reflected by elevated nitrite levels (an end product of NO metabolism). It was determined by use of a selective inhibitor that up-regulation of iNOS expression was transcriptionally regulated by activation of nuclear factor-kappaB, a redox-sensitive transcription factor. It was concluded that, in cyanide-mediated neurotoxicity, mtGSH is a vital component of the cellular antioxidant defense, and its depletion can lead to oxidative stress-mediated iNOS up-regulation, thus enhancing RNS generation and necrosis.