Serum ferritin: Past,present and future

Background

Serum ferritin was discovered in the 1930s, and was developed as a clinical test in the 1970s. Many diseases are associated with iron overload or iron deficiency. Serum ferritin is widely used in diagnosing and monitoring these diseases.

Scope of review

In this chapter, we discuss the role of serum ferritin in physiological and pathological processes and its use as a clinical tool.

Major conclusions

Although many aspects of the fundamental biology of serum ferritin remain surprisingly unclear, a growing number of roles have been attributed to extracellular ferritin, including newly described roles in iron delivery, angiogenesis, inflammation, immunity, signaling and cancer.

General significance

Serum ferritin remains a clinically useful tool. Further studies on the biology of this protein may provide new biological insights.     

Lysosomal membrane permeabilization causes oxidative stress and ferritin induction in macrophages

Moderate lysosomal membrane permeabilization (LMP) is an important inducer of apoptosis. Macrophages are professional scavengers and are rich in hydrolytic enzymes and iron. In the present study, we found that LMP by lysosomotropic detergent MSDH resulted in early up-regulation of lysosomal cathepsins, oxidative stress and ferritin up-regulation, and cell death. Lysosomotropic base NH₄Cl reduced the ferritin induction and oxidative stress in apoptotic cells induced by MSDH. Cysteine cathepsin inhibitors significantly protected cell death and oxidative stress, but had less effect on ferritin induction. We conclude that oxidative stress induced by lysosomal rupture causes ferritin induction with concomitant mitochondrial damage, which are the potential target for prevention of cellular oxidative stress and cell death induced by typical lysosomotropic substances in different disorders.     

Iron in arterial plaque: A modifiable risk factor for atherosclerosis

It has been proposed that iron depletion protects against cardiovascular disease. There is increasing evidence that one mechanism for this protection may involve a reduction in iron levels within atherosclerotic plaque. Large increases in iron concentration are seen in human atherosclerotic lesions in comparison to levels in healthy arterial tissue. In animal models, depletion of lesion iron levels in vivo by phlebotomy, systemic iron chelation treatment or dietary iron restriction reduces lesion size and/or increases plaque stability. A number of factors associated with increased arterial disease or increased cardiovascular events is also associated with increased plaque iron. In rats, infusion of angiotensin II increases ferritin levels and arterial thickness which are reversed by treatment with the iron chelator deferoxamine. In humans, a polymorphism for haptoglobin associated with increased cardiovascular disease is also characterized by increased lesional iron. Heme oxygenase 1 (HO1) is an important component of the system for mobilization of iron from macrophages. Human HO1 promoter polymorphisms causing weaker upregulation of the enzyme are associated with increased cardiovascular disease and increased serum ferritin. Increased cardiovascular disease associated with inflammation may be in part caused by elevated hepcidin levels that promote retention of iron within plaque macrophages. Defective retention of iron within arterial macrophages in genetic hemochromatosis may explain why there is little evidence of increased atherosclerosis in this disorder despite systemic iron overload. The reviewed findings support the concept that arterial plaque iron is a modifiable risk factor for atherogenesis.     

Adiponectin differentially regulates cytokines in porcine macrophages

Adiponectin, an adipocyte-derived hormone, attenuates the production of TNFalpha by activated human macrophages. In the present study, we used porcine blood-derived macrophages to test the hypothesis that the anti-inflammatory action of adiponectin includes suppression of IL6 and an induction of IL10. Adiponectin suppressed both TNFalpha and IL6 production in macrophages activated with lipopolysaccharide (P<0.01). In contrast, adiponectin increased IL10 expression (P<0.05) and augmented (P<0.05) the induction of this cytokine by lipopolysaccharide (LPS). Mechanistically, the attenuation of proinflammatory cytokine production by adiponectin was associated with an attenuation of the translocation of NFkappaB to the nucleus. Either adiponectin or inhibition of ERK1/2 with U0126 diminished the induction of IL6 by LPS (P<0.05), but the combination of adiponectin and the inhibitor did not further reduce IL6 production. In contrast, the inhibitory actions of adiponectin and a p38 MAPK inhibitor (SB203580) were additive (P<0.05). These data indicate that the anti-inflammatory actions of adiponectin include suppression of IL6 and induction of IL10. In addition, we provide evidence that some of the anti-inflammatory actions of adiponectin are mediated in part by suppression of NFkappaB signaling and ERK1/2 activity.     

Changes in lung macrophages during disease

Abstract The alveolar macrophage pool is morphologically and phenotypically heterogenous. Using monoclonal antibodies, homogeneous populations were isolated from broncho-alveolar lavage for functional studies. Such investigations revealed that some alveolar macrophages exhibit phagocytic ad microbicidal capacity, thus being equipped to act as effector cells (MoAb RFD7 +), while othrs exhibit the characteristics of antigen presenting cells (MoAb RFD1 +) involved in the induction of acquired T cell responses. In the investigation of cells from sarcoid patients, a third population was revealed, exhibiting the phenotype RFD1 + and RFD7 +. Functional studies of such cells showed them to act by suppressing T-cell responsiveness. The balance between these three populations alters in different disease processes and, in the case of sarcoidosis, is related to disease severity. It is propose that changes in the balance of these populations may directly influence the pathogenesis of inflammatory lung disease.     

Modulation of cytokine expression in human macrophages by endocrine-disrupting chemical Bisphenol-A

Exposure to environmental endocrine-disrupting chemical Bisphenol-A (BPA) is often associated with dysregulated immune homeostasis, but the mechanisms remain unclear. In the present study, the effects of BPA on the cytokines responses of human macrophages were investigated. Treatment with BPA increased pro-inflammation cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production, but decreased anti-inflammation cytokines interleukin-10 (IL-10) and transforming growth factor-β (TGF-β) production in THP1 macrophages, as well as in primary human macrophages. BPA effected cytokines expression through estrogen receptor α/β (ERα/β)-dependent mechanism with the evidence of ERα/β antagonist reversed the expression of cytokines. We also identified that activation of extracellular regulated protein kinases (ERK)/nuclear factor κB (NF-κB) signal cascade marked the effects of BPA on cytokines expression. Our results indicated that BPA effected inflammatory responses of macrophages via modulating of cytokines expression, and provided a new insight into the link between exposure to BPA and human health.     

The significance of ferritin in cancer: Anti-oxidation,inflammation and tumorigenesis

The iron storage protein ferritin has been continuously studied for over 70 years and its function as the primary iron storage protein in cells is well established. Although the intracellular functions of ferritin are for the most part well-characterized, the significance of serum (extracellular) ferritin in human biology is poorly understood. Recently, several lines of evidence have demonstrated that ferritin is a multi-functional protein with possible roles in proliferation, angiogenesis, immunosuppression, and iron delivery. In the context of cancer, ferritin is detected at higher levels in the sera of many cancer patients, and the higher levels correlate with aggressive disease and poor clinical outcome. Furthermore, ferritin is highly expressed in tumor-associated macrophages which have been recently recognized as having critical roles in tumor progression and therapy resistance. These characteristics suggest ferritin could be an attractive target for cancer therapy because its down-regulation could disrupt the supportive tumor microenvironment, kill cancer cells, and increase sensitivity to chemotherapy. In this review, we provide an overview of the current knowledge on the function and regulation of ferritin. Moreover, we examine the literature on ferritin's contributions to tumor progression and therapy resistance, in addition to its therapeutic potential.     

Protective effects of grape seed proanthocyanidins against iron overload-induced renal oxidative damage in rats

BackgroundExcessive exposure to iron can cause kidney damage, and chelating drugs such as deferoxamine and deferiprone have limited usefulness in treating iron poisoning. This study was designed to investigate the protective effects of grape seed proanthocyanidins (GSPAs) against iron overload induced nephrotoxicity in rats. The roles of GSPAs in chelating iron, antioxidant activity, renal function, pathological section, and apoptosis-related gene expression were assessed.MethodsNewly weaned male Sprague–Dawley rats aged 21 days (weight, 65 ± 5 g) were randomly divided into four groups containing 10 rats each: normal control (negative) group, iron overload (positive) group, GSPAs group, and GSPAs + iron overload (test) group. Iron dextran injections (2.5 mg⋅ kg⁻¹) and GSPAs (25 mg⋅ kg⁻¹) were intraperitoneally and intragastrically administered to rats daily for 7 weeks, respectively. Measurements included red blood cell (RBC) count and hemoglobin (Hb) level, serum total iron-binding capacity (TIBC), renal iron content, glutathione peroxidase (GSH-Px) activity, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, total antioxidant activity (T-AOC), creatinine (CR) and blood urea nitrogen (BUN) levels, pathological changes, and apoptotic Fas, Bax expressions in the kidney tissue. Differences among the dietary groups were determined using one-way analysis of variance with post-hoc Tukey’s test. P < 0.05 was considered statistically significant.ResultsRBC count, Hb level, renal iron content, MDA content, CR and BUN levels, and Fas, Bax expressions significantly increased in the positive group than in the negative group; contrarily, TIBC, GSH-Px activity, and T-AOC significantly decreased in the positive group than in the negative group (P < 0.05). Although not statistically significant, SOD activity was slightly reduced in the positive group than in the negative group. Inflammatory cell infiltration and fibrous tissue proliferation were observed in the kidney tissue of the rats in the positive group; in contrast, the rats exhibited better recovery when GSPAs were used instead of iron alone. Compared with the positive group, RBC counts, Hb levels, renal iron contents, the MDA content, CR and BUN levels, and Fas, Bax expressions significantly decreased, whereas the TIBC, the GSH-Px and SOD activities as well as T-AOC significantly increased in the test group rats (P < 0.05). There were no significant differences in the RBC counts, Hb levels, TIBC, renal iron contents, the SOD activity and MDA content, CR and BUN levels, and Fas expression between the GSPAs and negative groups. The GSH-Px activity and T-AOC were significantly increased whereas Bax expression was significantly decreased in the GSPAs group rats than in the negative group rats (P < 0.05). The rats in the GSPAs, test, and negative groups displayed glomeruli and tubules with a clear structure; further, the epithelial cells in the renal tubules were neatly arranged.ConclusionsGSPAs have protective effects on nephrotoxicity in rats with iron overload. Thus, further investigation of GSPAs as a new and natural phytochemo-preventive agent against iron overload is warranted.     

Hesperidin ameliorates cisplatin induced hepatotoxicity and attenuates oxidative damage,cell apoptosis,and inflammation in rats

Cisplatin is one of the most widely used chemotherapeutic anti-cancer drugs that is associated with multiple systemic toxicities limiting its use. The present study aimed to evaluate the hepato-protective effect of hesperidin against cisplatin-induced toxicity. Thirty-two adult male albino rats were equally split into four groups, the first group served as control received normal saline, the second group (CIS) received a single intraperitoneal dose of cisplatin (7.5 mg/kg bw) on the 22nd day of the experiment, the third group (HES) treated once daily with hesperidin (200 mg/kg bw, orally) for 21 days, and the last group (HES + CIS) pretreated once daily with hesperidin followed by a single intraperitoneal dose of cisplatin. Twenty-four hours later, samples were collected for further investigations. CIS-intoxication resulted in a significant decrease in the erythrogram along with thrombocytopenia leukopenia, and lymphopenia. Furthermore, CIS administration significantly elevated serum activity of liver enzymes, total, and indirect bilirubin as well serum glucose, total cholesterol, and triglycerides levels, meanwhile serum total protein, and globulin levels were significantly reduced. The hepatic MDA was markedly elevated with a concomitant decline in the hepatic antioxidant enzymes and severe alterations in the hepatic tissue architecture in CIS-intoxicated rats. Additionally, CIS-induced overexpression of hepatic Bax, caspase-3, and TNF-α, with no effect on hepatic expression of IL-10. Interestingly, HES pretreatment improved the CIS-induced hemato-biochemical, molecular and histopathological alterations. In conclusion, hesperidin hepato-protective effects against CIS might be mediated by its antioxidant, anti-inflammatory, and anti-apoptotic properties.     

Voluntary exercise attenuates obesity-associated inflammation through ghrelin expressed in macrophages

Chronic low-level inflammation is associated with obesity and a sedentary lifestyle, causing metabolic disturbances such as insulin resistance. Exercise training has been shown to decrease chronic low-level systemic inflammation in high-fat diet (HFD)-induced obesity. However, the molecular mechanisms mediating its beneficial effects are not fully understood. Ghrelin is a peptide hormone predominantly produced in the stomach that stimulates appetite and induces growth hormone release. In addition to these well-known functions, recent studies suggest that ghrelin localizes to immune cells and exerts an anti-inflammatory effect. The purpose of the current study was to investigate the role of ghrelin expressed in macrophages in the anti-inflammatory effects of voluntary exercise training. Expression of tumor necrosis factor-α (TNF-α), monocyte chemotactic protein (MCP)-1 and F4/80 was increased in adipose tissue from mice fed a HFD (HFD mice) compared with mice fed a standard diet (SD mice), whereas the expression of these inflammatory cytokines was markedly decreased in mice performing voluntary wheel running during the feeding of a HFD (HFEx mice). The expression of TNF-α was also increased in peritoneal macrophages by a HFD and exercise training inhibited the increase of TNF-α expression. Interestingly, expression of ghrelin in peritoneal macrophages was decreased by a HFD and recovered by exercise training. Suppression of ghrelin expression by siRNA increased TNF-α expression and LPS-stimulated NF-κB activation in RAW264 cells, which is a macrophage cell line. TNF-α expression by stimulation with LPS was significantly suppressed in RAW264 cells cultured in the presence of ghrelin. These results suggest that ghrelin exerts potent anti-inflammatory effects in macrophages and functions as a mediator of the beneficial effects of exercise training.     

Lipotoxicity in macrophages: evidence from diseases associated with the metabolic syndrome

Accumulation of lipid metabolites within non-adipose tissues can induce chronic inflammation by promoting macrophage infiltration and activation. Oxidized and glycated lipoproteins, free fatty acids, free cholesterol, triacylglycerols, diacylglycerols and ceramides have long been known to induce cellular dysfunction through their pro-inflammatory and pro-apoptotic properties. Emerging evidence suggests that macrophage activation by lipid metabolites and further modulation by lipid signaling represents a common pathogenic mechanism underlying lipotoxicity in atherosclerosis, obesity-associated insulin resistance and inflammatory diseases related to metabolic syndrome such as liver steatosis and chronic kidney disease. In this review, we discuss the latest discoveries that support the role of lipids in modulating the macrophage phenotype in different metabolic diseases. We describe the common mechanisms by which lipid derivatives, through modulation of macrophage function, promote plaque instability in the arterial wall, impair insulin responsiveness and contribute to inflammatory liver, muscle and kidney disease. We discuss the molecular mechanism of lipid activation of pro-inflammatory pathways (JNK, NFκB) and the key roles played by the PPAR and LXR nuclear receptors—lipid sensors that link lipid metabolism and inflammation.     

Sphingolipid-mediated inhibition of apoptotic cell clearance by alveolar macrophages

A decreased clearance of apoptotic cells (efferocytosis) by alveolar macrophages (AM) may contribute to inflammation in emphysema. The up-regulation of ceramides in response to cigarette smoking (CS) has been linked to AM accumulation and increased detection of apoptotic alveolar epithelial and endothelial cells in lung parenchyma. We hypothesized that ceramides inhibit the AM phagocytosis of apoptotic cells. Release of endogenous ceramides via sphingomyelinase or exogenous ceramide treatments dose-dependently impaired apoptotic Jurkat cell phagocytosis by primary rat or human AM, irrespective of the molecular species of ceramide. Similarly, in vivo augmentation of lung ceramides via intratracheal instillation in rats significantly decreased the engulfment of instilled target apoptotic thymocytes by resident AM. The mechanism of ceramide-induced efferocytosis impairment was dependent on generation of sphingosine via ceramidase. Sphingosine treatment recapitulated the effects of ceramide, dose-dependently inhibiting apoptotic cell clearance. The effect of ceramide on efferocytosis was associated with decreased membrane ruffle formation and attenuated Rac1 plasma membrane recruitment. Constitutively active Rac1 overexpression rescued AM efferocytosis against the effects of ceramide. CS exposure significantly increased AM ceramides and recapitulated the effect of ceramides on Rac1 membrane recruitment in a sphingosine-dependent manner. Importantly, CS profoundly inhibited AM efferocytosis via ceramide-dependent sphingosine production. These results suggest that excessive lung ceramides may amplify lung injury in emphysema by causing both apoptosis of structural cells and inhibition of their clearance by AM.     

IRS-2 deficiency in macrophages promotes their accumulation in the vascular wall

The aim of this study was to investigate the role of insulin receptor substrate-2 (IRS-2) mediated signal in macrophages on the accumulation of macrophages in the vascular wall. Mice transplanted with IRS-2^−/− bone marrow, a model of myeloid cell restricted defect of IRS-2, showed accumulation of monocyte chemoattractant protein-1-expressing macrophages in the vascular wall. Experiments using cultured peritoneal macrophages showed that IRS-2-mediated signal pathway stimulated by physiological concentrations of insulin, not by IL-4, contributed to the suppression of monocyte chemoattractant protein-1 expression induced by lipopolysaccharide. Our data indicated that IRS-2 deficiency in macrophages enhanced their accumulation in the vascular wall accompanied by increased expression of proinflammatory mediators in macrophages. These results suggest a role for insulin resistance in macrophages in early atherosclerogenesis.     

Induction of apoptosis in macrophages by cationic liposomes

The effects of liposomes on apoptosis in macrophages were evaluated from DNA content and DNA fragmentation. Cationic liposomes composed of different kinds of cationic lipids induced apoptosis in mouse splenic macrophages and the macrophage-like cell line, RAW264.7 cells. Generation of reactive oxygen radicals from macrophages treated with cationic liposomes was detected using flow cytometry, and further apoptosis was inhibited by the addition of oxidant scavenger, N-acetylcysteine. From these findings, the production of reactive oxygen species may be important in the regulation of apoptosis induced by cationic liposomes.     

Roles of heterogenous hepatic macrophages in the progression of liver diseases

Hepatic macrophages are key immune cells associated with the broad ranges of liver diseases including steatosis, inflammation and fibrosis. Hepatic macrophages interact with other immune cells and orchestrate hepatic immune circumstances. Recently, the heterogenous populations of hepatic macrophages have been discovered termed residential Kupffer cells and monocyte-derived macrophages, and identified their distinct population dynamics during the progression of various liver diseases. Liver injury lead to Kupffer cells activation with induction of inflammatory cytokines and chemokines, which triggers recruitment of inflammatory monocyte-derived macrophages. To understand liver pathology, the functions of different subtypes of liver macrophages should be regarded with different perspectives. In this review, we summarize recent advances in the roles of hepatic macrophages under liver damages and suggest hepatic macrophages as promising therapeutic targets for treating liver diseases.     

Does iron overload in metabolic syndrome affect macrophage profile? A case control study

AimsDysmetabolic iron overload syndrome (DIOS) is common but the clinical relevance of iron overload is not understood. Macrophages are central cells in iron homeostasis and inflammation. We hypothesized that iron overload in DIOS could affect the phenotype of monocytes and impair macrophage gene expression.MethodsThis study compared 20 subjects with DIOS to 20 subjects with metabolic syndrome (MetS) without iron overload, and 20 healthy controls. Monocytes were phenotyped by Fluorescence-Activated Cell Sorting (FACS) and differentiated into anti-inflammatory M2 macrophages in the presence of IL-4. The expression of 38 genes related to inflammation, iron metabolism and M2 phenotype was assessed by real-time PCR.ResultsFACS showed no difference between monocytes across the three groups. The macrophagic response to IL-4-driven differentiation was altered in four of the five genes of M2 phenotype (MRC1, F13A1, ABCA1, TGM2 but not FABP4), in DIOS vs Mets and controls demonstrating an impaired M2 polarization. The expression profile of inflammatory genes was not different in DIOS vs MetS. Several genes of iron metabolism presented a higher expression in DIOS vs MetS: SCL11A2 (a free iron transporter, +76 %, p = 0.04), SOD1 (an antioxidant enzyme, +27 %, p = 0.02), and TFRC (the receptor 1 of transferrin, +59 %, p = 0.003).ConclusionsIn DIOS, macrophage polarization toward the M2 alternative phenotype is impaired but not associated with a pro-inflammatory profile. The up regulation of transferrin receptor 1 (TFRC) in DIOS macrophages suggests an adaptive role that may limit iron toxicity in DIOS.     

Targeting apoptotic signalling pathway and pro-inflammatory cytokine expression as therapeutic intervention in TPE induced lung damage

Tropical pulmonary eosinophilia (TPE) is an occult manifestation of filariasis, brought about by helminth parasites Wuchereria bancrofti and Brugia malayi. Treatment of patients suffering from TPE involves the administration of diethyl carbamazine and Ivermectin. Although the drugs are able to block acute inflammation, they are not able to alleviate chronic basal inflammation. We have attempted to examine the disease by targeting two important components; namely filarial parasitic sheath proteins (FPP) induced apoptosis and pro-inflammatory cytokine response in human laryngeal carcinoma cells of epithelial origin (HEp-2) cells an epithelial cell line. Earlier studies by us have shown that FPP exposure induced apoptosis in these cells. In this study with hydrocortisone, calpain inhibitor (ALLN) and phorbol myristate acetate (PMA) treatments we demonstrate that apoptosis is inhibited as shown by [3H] thymidine incorporation studies, propidium iodide staining and Annexin V staining. Hydrocortisone at a dose, which inhibits cell death also down regulated, the expression of pro-inflammatory cytokines IL-6 and IL-8. These findings give us insights into the multifaceted approach one may adopt to target critical signalling molecules using appropriate inhibitors, which could eventually be used to reduce lung damage in TPE.     

Carboxyfullerene prevents iron-induced oxidative stress in rat brain

Carboxyfullerene, a water-soluble carboxylic acid derivative of a fullerene, was investigated as a protective agent against iron-induced oxidative stress in the nigrostriatal dopaminergic system of anesthetized rats. Intranigral infusion of exclusive carboxyfullerene did not increase lipid peroxidation in substantia nigra or deplete dopamine content in striatum. Infusion of ferrous citrate (iron II) induced degeneration of the nigrostriatal dopaminergic system. An increase in lipid peroxidation in substantia nigra as well as decreases in K+-evoked dopamine overflow and dopamine content in striatum were observed 7 days after the infusion. Co-infusion of carboxyfullerene prevented iron-induced oxidative injury. Furthermore, tyrosine hydroxylase-immunoreactive staining showed that carboxyfullerene inhibited the iron-induced loss of the dopaminergic nerve terminals in striatum. The antioxidative action of carboxyfullerene was verified by in vitro studies. Incubation of brain homogenates increased the formation of the Schiff base fluorescent products of malonaldehyde, an indicator of lipid peroxidation. Both autooxidation (without exogenous iron) and iron-induced elevation of lipid peroxidation of brain homogenates were suppressed by carboxyfullerene in a dose-dependent manner. Our results suggest that intranigral infusion of carboxyfullerene appears to be nontoxic to the nigrostriatal dopaminergic system. Furthermore, the potent antioxidative action of carboxyfullerene protects the nigrostriatal dopaminergic system from iron-induced oxidative injury.