x-Irradiation in Rat Liver: Consequent Upregulation of Hepcidin and Downregulation of Hemojuvelin and Ferroportin-1 Gene Expression

Modeling the Effects of Protracted Cosmic Radiation in a Human Organ-on-Chip Platform

Galactic cosmic radiation (GCR) is one of the most serious risks posed to astronauts during missions to the Moon and Mars. Experimental models capable of recapitulating human physiology are critical to understanding the effects of radiation on human organs and developing radioprotective measures against space travel exposures. The effects of systemic radiation are studied using a multi-organ-on-a-chip (multi-OoC) platform containing engineered tissue models of human bone marrow (site of hematopoiesis and acute radiation damage), cardiac muscle (site of chronic radiation damage) and liver (site of metabolism), linked by vascular circulation with an endothelial barrier separating individual tissue chambers from the vascular perfusate. Following protracted neutron radiation, the most damaging radiation component in deep space, a greater deviation of tissue function is observed as compared to the same cumulative dose delivered acutely. Further, by characterizing engineered bone marrow (eBM)-derived immune cells in circulation, 58 unique genes specific to the effects of protracted neutron dosing are identified, as compared to acutely irradiated and healthy tissues. It propose that this bioengineered platform allows studies of human responses to extended radiation exposure in an "astronaut-on-a-chip" model that can inform measures for mitigating cosmic radiation injury.

Radiation-induced liver disease: beyond DNA damage

Radiation-induced liver disease (RILD), also known as radiation hepatitis, is a serious side effect of radiotherapy (RT) for hepatocellular carcinoma. The therapeutic dose of RT can damage normal liver tissue, and the toxicity that accumulates around the irradiated liver tissue is related to numerous physiological and pathological processes. RILD may restrict treatment use or eventually deteriorate into liver fibrosis. However, the research on the mechanism of radiation-induced liver injury has seen little progress compared with that on radiation injury in other tissues, and no targeted clinical pharmacological treatment for RILD exists. The DNA damage response caused by ionizing radiation plays an important role in the pathogenesis and development of RILD. Therefore, in this review, we systematically summarize the molecular and cellular mechanisms involved in RILD. Such an analysis is essential for preventing the occurrence and development of RILD and further exploring the potential treatment of this disease.

Studying ferroptosis and iron metabolism pre- and post-radiotherapy treatment in breast cancer patients

BACKGROUND

Radiotherapy (RT) is an important part of the treatment of many tumors. Radiotherapy causes oxidative damage in all cellular compartments, including lipid membrane, on a random basis. Toxic lipid peroxidation accumulation has only lately been linked to a regulated type of cell death known as ferroptosis. Iron is required for ferroptosis sensitization in cells.

AIM OF THE WORK

This work aimed to study ferroptosis and iron metabolism before and after RT in BC patients.

SUBJECTS AND METHODS

Eighty participants were included divided into two main groups: group I: 40 BC patients treated with RT. Group II: 40 healthy volunteers' age and sex matched as control group. Venous blood samples were collected from BC patients (prior to and after RT) and healthy controls. Glutathione (GSH), malondialdehyde (MDA), serum iron levels and % of transferrin saturation were measured by colorimetric technique. Ferritin, ferroportin, and prostaglandin-endoperoxide synthase 2 (PTGS2) levels were assessed by ELISA.

RESULTS

Serum ferroportin, reduced glutathione, and ferritin showed significant decrease after radiotherapy in comparison to before radiotherapy. However, there was significant increase in serum PTGS2, MDA, % of transferrin saturation and iron levels after radiotherapy in comparison to before radiotherapy.

CONCLUSION

Radiotherapy induced ferroptosis in breast cancer patients as a new cell death mechanism and PTGS2 is a biomarker of ferroptosis. Iron modulation is a useful approach for the treatment of BC especially if combined with targeted therapy and immune-based therapy. Further studies are warranted to be translated into clinical compounds.

Protective effect of acrocarpus fraxinifolius extract against hepatic fibrosis induced by Gamma irradiation and carbon tetrachloride in albino rats

PURPOSE

Liver fibrosis is considered as one of the ultimate outcomes of chronic liver disorders, characterized by outrageous cell proliferation and abnormal deposition of extracellular matrix, resulting in sever pathological distortions in the architecture and performance of liver tissues. The present study aimed to investigate the protective properties of aqueous methanol extract of Acrocarpus fraxinifolius leaves (AFL) against liver fibrosis induced by dual toxicity of γ-irradiation and carbon tetrachloride (CCl₄) in rats.

METHODS

The animals were exposed to 2 Gy irradiation once/week concurrently with intraperitoneal administration of CCl₄ (0.2 mL/100 g body weight) for seven weeks. Afterwards, liver toxicity and fibrosis were assessed biochemically at cellular and molecular as well as histopathological levels.

RESULTS

The livers of intoxicated rats showed distinct structural and functional changes, compared with the normal rats. The administration of AFL (500 mg/kg, p.o) significantly ameliorated the histopathological manifestations of fibrotic liver evidenced by mitigated steatosis progression, necrosis, fibrotic septa, apoptotic bodies, and immunochistochemical studies of alpha-smooth muscle actin. Also, AFL increased the final body weight, total protein, albumin levels and albumin/globulin ratio. While, the absolute liver weight, liver enzymes, total cholesterol and triglycerides were reduced. A significant modulation was observed in hydroxyproline, transforming growth factor-β and collagen-1expression. Furthermore, AFL exerted a direct effect on liver fibrosis by promoting extracellular matrix degradation via overexpression of the tissue inhibitor metalloproteinase-1, coupled with decease of metalloproteinase-9 activity.

CONCLUSIONS

Our findings suggested that AFL effectively improved the architecture of fibrotic liver and modified the biochemical markers of liver fibrosis.

Protective effects of apocynin against ionizing radiation-induced hepatotoxicity in rats

Radiation hepatotoxicity is thought to be due to free oxygen radicals. We investigated the protective effects of apocynin (APO) against ionizing radiation induced oxidative stress in liver tissue following whole body ionizing radiation. We divided rats into four groups. The control group was injected intraperitoneally (i.p.) with saline for five consecutive days. A second group was injected i.p. with saline for 5 days and after 24 h, a single-dose of radiation (800 cGy) was administered to the whole abdomen. A third group was injected i.p. with 20 mg/kg APO for 5 days. A fourth group was injected i.p. with APO for 5 days and after 24 h, the rats were exposed to radiation. Ionizing radiation induced hepatotoxicity was demonstrated biochemically by significant changes in oxidative and antioxidant parameters. Our findings suggest that APO treatment may be protective against radiation induced hepatic injury by decreasing oxidative stress and increasing antioxidant activity.

Hepcidin and Iron Metabolism in Experimental Liver Injury

The liver plays a pivotal role in the regulation of iron metabolism through its ability to sense and respond to iron stores by release of the hormone hepcidin. Under physiologic conditions, regulation of hepcidin expression in response to iron status maintains iron homeostasis. In response to tissue injury, hepcidin expression can be modulated by other factors, such as inflammation and oxidative stress. The resulting dysregulation of hepcidin is proposed to account for alterations in iron homeostasis that are sometimes observed in patients with liver disease. This review describes the effects of experimental forms of liver injury on iron metabolism and hepcidin expression. In general, models of acute liver injury demonstrate increases in hepcidin mRNA and hypoferremia, consistent with hepcidin's role as an acute-phase reactant. Conversely, diverse models of chronic liver injury are associated with decreased hepcidin mRNA but with variable effects on iron status. Elucidating the reasons for the disparate impact of different chronic injuries on iron metabolism is an important research priority, as is a deeper understanding of the interplay among various stimuli, both positive and negative, on hepcidin regulation. Future studies should provide a clearer picture of how dysregulation of hepcidin expression and altered iron homeostasis impact the progression of liver diseases and whether they are a cause or consequence of these pathologies.

A high-fructose diet in rats induces systemic iron deficiency and hepatic iron overload by an inflammation mechanism

Nonalcoholic fatty liver disease (NAFLD) correlates with the high intake of fructose-rich soft drinks. Both inflammation and dysregulated iron metabolism are pathogenic factors in the development of NAFLD. The present investigation assessed the effects of a high-fructose diet (HF diet) on inflammation and iron metabolism. In this study, rats were fed a control or HF diet for 4, 8, or 12 weeks, after which insulin resistance, transaminases levels, serum and liver lipid profiles, inflammatory factors, and iron metabolism-related molecules were evaluated. The activities of the hepatic inflammation-associated pathways, IKKβ/NF-κB, and JAK2/STAT3, were detected by western blot. Result showed that the HF diet-fed animals developed a time-dependent serum lipid increase and hepatic lipid accumulation as well as insulin resistance. Serum iron (SI), serum ferritin (SF), and transferrin saturation (TS) decreased while total iron-binding capacity (TIBC) and serum transferrin (s-TF) increased at 8 and 12 weeks in the HF diet group. The HF diet led to increased transaminases levels at 8 and 12 weeks, and iron deposition was observed in the liver, accompanied by an upregulation of ferritin light chain (FTL), hepcidin (HEPC), transferrin (TF), transferrin receptor 1 (TfR1), iron regulatory protein 1 (IRP1), hemojuvelin (HJV), and divalent metal transporter 1 (DMT1). Moreover, ferroportin (FPN1) levels were downregulated, as expected from the increased HEPC. A progressive inflammation phenotype was apparent, with increased inflammatory factors, MDA, IL-1β, IL-6, and TNF-α, in the serum and liver tissue. Concomitantly, the hepatic IKKβ/NF-κB and JAK2/STAT3 pathways were activated. In summary, we verified that HF diet induces systemic iron deficiency and hepatic iron accumulation, likely due to the activation of inflammation via the NF-κB and JAK2/STAT3 pathways. PRACTICAL APPLICATIONS: As increasing numbers of individuals consume HF diets, the health implications of this type of over nutrition become globally relevant. Using a high-fructose diet rat model, our present study reveals inflammation as the link between a HF diet and dysregulated iron metabolism. Importantly, both inflammation and disrupted iron metabolism have been shown to be pathogenic factors in nonalcoholic fatty liver disease (NAFLD). The iron regulatory hormone, HEPC, is a link between the liver, inflammation, and iron metabolism. As fructose-rich foods become increasingly abundant and people's fructose intake increases, the impact of high fructose on health requires increased attention. Little research has been conducted on the effects of fructose on iron metabolism. Our study provides useful insights into the prevention and treatment of iron metabolism disorders arising from metabolic syndrome.

Organ-Specific Effects of Low Dose Radiation Exposure: A Comprehensive Review

Ionizing radiation (IR) is a high-energy radiation whose biological effects depend on the irradiation doses. Low-dose radiation (LDR) is delivered during medical diagnoses or by an exposure to radioactive elements and has been linked to the occurrence of chronic diseases, such as leukemia and cardiovascular diseases. Though epidemiological research is indispensable for predicting and dealing with LDR-induced abnormalities in individuals exposed to LDR, little is known about epidemiological markers of LDR exposure. Moreover, difference in the LDR-induced molecular events in each organ has been an obstacle to a thorough investigation of the LDR effects and a validation of the experimental results in in vivo models. In this review, we summarized the recent reports on LDR-induced risk of organ-specifically arranged the alterations for a comprehensive understanding of the biological effects of LDR. We suggested that LDR basically caused the accumulation of DNA damages, controlled systemic immune systems, induced oxidative damages on peripheral organs, and even benefited the viability in some organs. Furthermore, we concluded that understanding of organ-specific responses and the biological markers involved in the responses is needed to investigate the precise biological effects of LDR.

PECAM-1 modulates liver damage induced by synergistic effects of TNF-α and irradiation

The mechanisms of radiation‐induced liver damage are poorly understood. We investigated if tumour necrosis factor (TNF)‐α acts synergistically with irradiation, and how its activity is influenced by platelet endothelial cell adhesion molecule‐1 (PECAM‐1). We studied murine models of selective single‐dose (25 Gy) liver irradiation with and without TNF‐α application (2 μg/mouse; i.p.). In serum of wild‐type (wt)‐mice, irradiation induced a mild increase in hepatic damage marker aspartate aminotransferase (AST) in comparison to sham‐irradiated controls. AST levels further increased in mice treated with both irradiation and TNF‐α. Accordingly, elevated numbers of leucocytes and increased expression of the macrophage marker CD68 were observed in the liver of these mice. In parallel to hepatic damage, a consecutive decrease in expression of hepatic PECAM‐1 was found in mice that received radiation or TNF‐α treatment alone. The combination of radiation and TNF‐α induced an additional significant decline of PECAM‐1. Furthermore, increased expression of hepatic lipocalin‐2 (LCN‐2), a hepatoprotective protein, was detected at mRNA and protein levels after irradiation or TNF‐α treatment alone and the combination of both. Signal transducer and activator of transcription‐3 (STAT‐3) seems to be involved in the signalling cascade. To study the involvement of PECAM‐1 in hepatic damage more deeply, the liver of both wt‐ and PECAM‐1‐knock‐out‐mice were selectively irradiated (25 Gy). Thereby, ko‐mice showed higher liver damage as revealed by elevated AST levels, but also increased hepatoprotective LCN‐2 expression. Our studies show that TNF‐α has a pivotal role in radiation‐induced hepatic damage. It acts in concert with irradiation and its activity is modulated by PECAM‐1, which mediates pro‐ and anti‐inflammatory signalling.

Gene expression profiling of rat livers after continuous whole-body exposure to low-dose rate of gamma rays

PURPOSE

To study gene expression modulation in response to continuous whole-body exposure to low-dose-rate gamma radiation and improve our understanding of the mechanism of this impact at the molecular basis.

MATERIALS AND METHODS

cDNA microarray method with complete pooling of samples was used to study expression changes in the transcriptome profile of livers from rats treated with prolonged low-dose-rate ionizing radiation (IR) relative to that of sham-irradiated rats.

RESULTS

Of the 209 genes that were two-fold-up or down-regulated, 143 were known genes of which 27 were found in previous literatures to be modulated by IR. Remarkably, there were a significant number of differentially expressed genes involved in hepatic lipid metabolism.

CONCLUSION

This study showed changes in transcriptome profile of livers from low-dose irradiated rats when compared with that of sham-irradiated ones. This study will be useful for studying the metabolic changes of human exposed for long term to cosmic ray such as in space and in polar regions.

Persistent T2*-hypointensity of the liver parenchyma after irradiation to the SPIO-accumulated liver: An imaging marker for responses to radiotherapy in hepatic malignancies

PURPOSE

To determine whether T2*-weighted MRI has the ability to visualize the irradiated liver parenchyma and liver tumor after irradiation to the previously superparamagnetic iron oxide (SPIO)-accumulated liver.

MATERIALS AND METHODS

We examined 24 liver tumor-bearing rats. Nine rats (Group 1) received 20 µmol Fe/kg SPIO and subsequent 70-Gy irradiation to the tumor-bearing liver lobe. Four rats (Group 2) received SPIO and sham irradiation. Six rats (Group 3) received saline and irradiation. Finally, five rats (Group 4) received saline and sham irradiation. We acquired sequential 3 Tesla T2*-weighted images of the liver on day 7, and assessed MR image findings including signal intensity of the tumors and tumor-bearing liver lobes.

RESULTS

In six rats in Group 1, tumors shrunk by 39-100% (303-0 mm³ ), and severely, well-defined hypointense irradiated areas were observed. In the other two rats, tumors enlarged by 25 and 172% (595 and 1148 mm³ ), and hypointense rings surrounded the tumors. The normalized relative signal intensity of the irradiated areas was significantly lower than that of the tumor (0.53 ± 0.06 versus 0.94 ± 0.06; P < 0.05). The severely, well-defined hypointense areas were not observed in the other groups. Histologically, necrotic regions dominated and minimal nonnecrotic tumor cells remained in irradiated areas. The number of CD68-positive cells was higher in irradiated areas than in nonirradiated areas.

CONCLUSION

T2*-weighted MR imaging visualized the irradiated liver parenchyma as markedly, well-defined hypointense areas and liver cancer lesions as hyperintense areas only when SPIO was administered before irradiation. The visualization of the hypointense area was associated with tumor regression after irradiation.

LEVEL OF EVIDENCE

2 J. Magn. Reson. Imaging 2017;45:303-312.

Disruption of Iron Regulation after Radiation and Donor Cell Infusion

Iron overload is common in patients undergoing hematopoietic cell transplantation (HCT). Peritransplant events, such as total body irradiation (TBI), and the effects of donor cell infusion may contribute to iron overload, in addition to disease-associated anemia and RBC transfusions. Using murine models we show complex time- and dose-dependent interactions of TBI and transplanted donor cells with expression patterns of iron regulatory genes in the liver. Infusion of allogeneic or syngeneic donor T lymphocytes increased serum iron, transiently up-regulated interleukin-6 (IL-6) and hepcidin (Hamp), and down-regulated ferroportin1 (Fpn1). After 7 to 14 days, however, changes were significant only with allogeneic cells. TBI (200 to 400 Gy) also induced IL-6 and Hamp expression but had little effect on Fpn1. TBI combined with allogeneic donor cell infusion resulted in modest early up-regulation of IL-6, followed by a decline in IL-6 levels and Hamp as well as Fpn1, and was accompanied by increased liver iron content. Injection of Fas ligand-deficient T lymphocytes from gld mice resulted in substantially lower alterations of gene expression than infusion of wild-type T cells. The agonistic anti-Fas antibody, JO2, triggered early up-regulation of Stat3 and IL-6, followed by an increase in Hamp and decreased expression of Fpn1 by 7 to 14 days, implicating Fas as a key modulator of gene expression in HCT. Minimal histologic changes were observed in mouse liver and duodenum. These data show profound and interacting effects of TBI and cell transplantation on the expression of iron regulatory genes in murine recipients. Alterations are largely related to induction of cytokines and Fas-dependent signals.

Hepcidin-2 in mouse urine as a candidate radiation-responsive molecule

We used high-performance liquid chromatography to separate urine obtained from whole-body gamma-irradiated mice (4 Gy) before analyzing each fraction with matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry to identify radiation-responsive molecules. We identified two candidates: hepcidin antimicrobial peptide 2 (hepcidin-2) and peptide fragments of kidney androgen-regulated protein (KAP). We observed that peak increases of hepcidin-2 in urine were delayed in a dose-dependent manner (1 Gy and above); however, the amount of KAP peptide fragments showed no correlation with radiation dose. In addition, an increase in hepcidin-2 after exposure to relatively low radiation doses (0.25 and 0.5 Gy, respectively) was biphasic (at 8-48 h and 120-168 h, respectively, after irradiation). The increase in hepcidin-2 paralleled an increase in hepcidin-2 gene (Hamp2) mRNA levels in the liver. These results suggest that radiation exposure directly or indirectly induces urinary excretion of hepcidin-2 at least in part by the upregulation of Hamp2 mRNA in the liver.

Role of PECAM-1 in radiation-induced liver inflammation

Platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31) is known to play an important role in hepatic inflammation. Therefore, we investigated the role of PECAM-1 in wild-type (WT) and knock-out (KO)-mice after single-dose liver irradiation (25 Gy). Both, at mRNA and protein level, a time-dependent decrease in hepatic PECAM-1, corresponding to an increase in intercellular cell adhesion molecule-1 (ICAM-1) (6 hrs) was detected in WT-mice after irradiation. Immunohistologically, an increased number of neutrophil granulocytes (NG) (but not of mononuclear phagocytes) was observed in the liver of WT and PECAM-1-KO mice at 6 hrs after irradiation. The number of recruited NG was higher and prolonged until 24 hrs in KO compared to WT-mice. Correspondingly, a significant induction of hepatic tumour necrosis factor (TNF)-α and CXC-chemokines (KC/CXCL1 interleukin-8/CXCL8) was detected together with an elevation of serum liver transaminases (6–24 hrs) in WT and KO-mice. Likewise, phosphorylation of signal transducer and activator of transcription-3 (STAT-3) was observed in both animal groups after irradiation. The level of all investigated proteins as well as of the liver transaminases was significantly higher in KO than WT-mice. In the cell-line U937, irradiation led to a reduction in PECAM-1 in parallel to an increased ICAM-1 expression. TNF-α-blockage by anti-TNF-α prevented this change in both proteins in cell culture. Radiation-induced stress conditions induce a transient accumulation of granulocytes within the liver by down-regulation/absence of PECAM-1. It suggests that reduction/lack in PECAM-1 may lead to greater and prolonged inflammation which can be prevented by anti-TNFα.

Mesenchymal stem cell-conditioned medium prevents radiation-induced liver injury by inhibiting inflammation and protecting sinusoidal endothelial cells

Current management of radiation-induced liver injury is limited. Sinusoidal endothelial cell (SEC) apoptosis and inflammation are considered to be initiating events in hepatic damage. We hypothesized that mesenchymal stem cells (MSCs) possess anti-apoptotic and anti-inflammatory actions during hepatic irradiation, acting via paracrine mechanisms. This study aims to examine whether MSC-derived bioactive components are protective against radiation-induced liver injury in rats. MSC-conditioned medium (MSC-CM) was generated from rat bone marrow-derived MSCs. The effect of MSC-CM on the viability of irradiated SECs was examined by flow cytometric analysis. Activation of the Akt and ERK pathways was analyzed by western blot. MSC-CM was also delivered to Sprague-Dawley rats immediately before receiving liver irradiation, followed by testing for pathological features, changes in serum hyaluronic acid, ALT, and inflammatory cytokine levels, and liver cell apoptosis. MSC-CM enhanced the viability of irradiated SECs in vitro and induced Akt and ERK phosphorylation in these cells. Infusion of MSC-CM immediately before liver irradiation provided a significant anti-apoptotic effect on SECs and improved the histopathological features of injury in the irradiated liver. MSC-CM also reduced the secretion and expression of inflammatory cytokines and increased the expression of anti-inflammatory cytokines. MSC-derived bioactive components could be a novel therapeutic approach for treating radiation-induced liver injury.

The anti-TNF-α antibody infliximab inhibits the expression of fat-transporter-protein FAT/CD36 in a selective hepatic-radiation mouse model

Previously, we reported a radiation-induced inflammation triggering fat-accumulation through fatty-acid-translocase/cluster of differentiation protein 36 (FAT/CD36) in rat liver. Furthermore, inhibition of radiation-induced FAT/CD36-expression by anti-tumor necrosis factor-α (anti-TNF-α) (infliximab) was shown in vitro. The current study investigates fat-accumulation in a mouse-model of single-dose liver-irradiation (25-Gray) and the effect of anti-TNF-α-therapy on FAT/CD36 gene-expression. Mice livers were selectively irradiated in vivo in presence or absence of infliximab. Serum- and hepatic-triglycerides, mRNA, and protein were analyzed by colorimetric assays, RT-PCR, Immunofluorescence and Western-Blot, respectively. Sudan-staining was used demonstrating fat-accumulation in tissue. In mice livers, early (1–3 h) induction of TNF-α-expression, a pro-inflammatory cytokine, was observed. It was followed by elevated hepatic-triglyceride level (6–12 h), compared to sham-irradiated controls. In contrast, serum-triglyceride level was decreased at these time points. Similar to triglyceride level in mice livers, Sudan staining of liver cryosections showed a quick (6–12 h) increase of fat-droplets after irradiation. Furthermore, expression of fat-transporter-protein FAT/CD36 was increased at protein level caused by radiation or TNF-α. TNF-α-blockage by anti-TNF-α showed an early inhibition of radiation-induced FAT/CD36 expression in mice livers. Immunohistochemistry showed basolateral and cytoplasmic expression of FAT/CD36 in hepatocytes. Moreover, co-localization of FAT/CD36 was detected with α-smooth muscle actin (α-SMA⁺) cells and F4/80⁺ macrophages. In summary, hepatic-radiation triggers fat-accumulation in mice livers, involving acute-phase-processes. Accordingly, anti-TNF-α-therapy prevented early radiation-induced expression of FAT/CD36 in vivo.

Hepatocyte growth factor gene-modified adipose-derived mesenchymal stem cells ameliorate radiation induced liver damage in a rat model

Liver damage caused by radiotherapy is associated with a high mortality rate, but no established treatment exists. Adipose-derived mesenchymal stem cells (ADSCs) are capable of migration to injured tissue sites, where they aid in the repair of the damage. Hepatocyte growth factor (HGF) is critical for damage repair due to its anti-apoptotic, anti-fibrotic and cell regeneration-promoting effects. This study was performed to investigate the therapeutic effects of HGF-overexpressing ADSCs on radiation-induced liver damage (RILD). ADSCs were infected with a lentivirus encoding HGF and HGF-shRNA. Sprague-Dawley (SD) rats received 60Gy of irradiation to induce liver injury and were immediately given either saline, ADSCs, ADSCs + HGF or ADSCs + shHGF. Two days after irradiation, a significant reduction in apoptosis was observed in the HGF-overexpressing ADSC group compared with the RILD group, as assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Scanning electron microscopy showed chromatin condensation after irradiation, which was ameliorated in the group that received ADSCs and was reversed in the group that received HGF-overexpressing ADSCs. HGF-overexpressing ADSCs ameliorated radiation- induced liver fibrosis through down regulation of α-SMA and fibronectin. Hepatocyte regeneration was significantly improved in rats treated with ADSCs compared with rats from the RILD group), as assessed by Ki-67 immunohistochemistry. Rats that received HGF-overexpressing ADSCs showed an even greater level of hepatocyte regeneration. HGF-overexpressing ADSCs completely blocked the radiation-induced increase in the enzymes ALT and AST. The effect of mitigating RILD was compromised in the ADSC + shHGF group compared with the ADSC group. Altogether, these results suggest that HGF-overexpressing ADSCs can significantly improve RILD in a rat model, which may serve as a valuable therapeutic alternative.

Investigation into the role of the cholinergic system in radiation-induced damage in the rat liver and ileum

It has been previously shown that acetylcholine (ACh) may affect pro-inflammatory and anti-inflammatory cytokines. The role of the cholinergic system in radiation-induced inflammatory responses and tissue damage remains unclear. Therefore, the present study was designed to determine the radio-protective properties of the cholinergic system in the ileum and the liver of rats. Rats were exposed to 8-Gy single-fraction whole-abdominal irradiation and were then decapitated at either 36 h or 10 d post-irradiation. The rats were treated either with intraperitoneal physiological saline (1 ml/kg), physostigmine (80 µg/kg) or atropine (50 μg/kg) twice daily for 36 h or 10 d. Cardiac blood samples and liver and ileal tissues were obtained in which TNF-α, IL-1β and IL-10 levels were assayed using ELISA. In the liver and ileal homogenates, caspase-3 immunoblots were performed and myeloperoxidase (MPO) activity was analyzed. Plasma levels of IL-1β and TNF-α increased significantly following radiation (P < 0.01 and P < 0.001, respectively) as compared with non-irradiated controls, and physostigmine treatment prevented the increase in the pro-inflammatory cytokines (P < 0.01 and P < 0.001, respectively). Plasma IL-10 levels were not found to be significantly changed following radiation, whereas physostigmine augmented IL-10 levels during the late phase (P < 0.01). In the liver and ileum homogenates, IL-1β and TNF-α levels were also elevated following radiation, and this effect was inhibited by physostigmine treatment but not by atropine. Similarly, physostigmine also reversed the changes in MPO activity and in the caspase-3 levels in the liver and ileum. Histological examination revealed related changes. Physostigmine experiments suggested that ACh has a radio-protective effect not involving the muscarinic receptors.

Bone marrow-derived stromal cell therapy in cirrhosis: clinical evidence, cellular mechanisms, and implications for the treatment of hepatocellular carcinoma

Current treatment options for hepatocellular carcinoma (HCC) are often limited by the presence of underlying liver disease. In patients with liver cirrhosis, surgery, chemotherapy, and radiation therapy all carry a high risk of hepatic complications, ranging from ascites to fulminant liver failure. For patients receiving radiation therapy, cirrhosis dramatically reduces the already limited radiation tolerance of the liver and represents the most important clinical risk factor for the development of radiation-induced liver disease. Although improvements in conformal radiation delivery techniques have improved our ability to safely irradiate confined areas of the liver to increasingly higher doses with excellent local disease control, patients with moderate-to-severe liver cirrhosis continue to face a shortage of treatment options for HCC. In recent years, evidence has emerged supporting the use of bone marrow-derived stromal cells (BMSCs) as a promising treatment for liver cirrhosis, with several clinical studies demonstrating sustained improvement in clinical parameters of liver function after autologous BMSC infusion. Three predominant populations of BMSCs, namely hematopoietic stem cells, mesenchymal stem cells, and endothelial progenitor cells, seem to have therapeutic potential in liver injury and cirrhosis. Preclinical studies of BMSC transplantation have identified a range of mechanisms through which these cells mediate their therapeutic effects, including hepatocyte transdifferentiation and fusion, paracrine stimulation of hepatocyte proliferation, inhibition of activated hepatic stellate cells, enhancement of fibrolytic matrix metalloproteinase activity, and neovascularization of regenerating liver. By bolstering liver function in patients with underlying Child's B or C cirrhosis, autologous BMSC infusion holds great promise as a therapy to improve the safety, efficacy, and utility of surgery, chemotherapy, and hepatic radiation therapy in the treatment of HCC.

Effect of ionizing radiation on liver protein oxidation and metabolic function in C57BL/6J mice

PURPOSE

Protein oxidation in response to radiation results in DNA damage, endoplasmic reticulum stress/unfolded protein response, cell cycle arrest, cell death and senescence. The liver, a relatively radiosensitive organ, undergoes measurable alterations in metabolic functions following irradiation. Accordingly, we investigated radiation-induced changes in liver metabolism and alterations in protein oxidation.

MATERIALS AND METHODS

C57BL/6 mice were sham irradiated or exposed to 8.5 Gy (60)Co (0.6 Gy/min) total body irradiation. Metabolites and metabolic enzymes in the blood and liver tissue were analyzed. Two-dimensional gel electrophoresis and OxyBlot™ were used to detect carbonylated proteins that were then identified by peptide mass fingerprinting.

RESULTS

Analysis of serum metabolites revealed elevated glucose, bilirubin, lactate dehydrogenase (LDH), high-density lipoprotein, and aspartate aminotransferase within 24-72 h post irradiation. Liver tissue LDH and alkaline phosphatase activities were elevated 24-72 h post irradiation. OxyBlotting revealed that the hepatic proteome contains baseline protein carbonylation. Radiation exposure increased carbonylation of specific liver proteins including carbonic anhydrase 1, α-enolase, and regucalcin.

CONCLUSIONS

8.5 Gy irradiation resulted in distinct metabolic alterations in hepatic functions. Coincident with these changes, radiation induced the carbonylation of specific liver enzymes. The oxidation of liver enzymes may underlie some radiation-induced alterations in hepatic function.

Hepatocyte senescence induced by radiation and partial hepatectomy in rat liver

PURPOSE

Exposure to radiation primes the liver for extensive replacement of the resident parenchymal cells by transplanted hepatocytes. The mechanisms underlying this repopulation remain to be clarified. In these studies, we examined the possible occurrence of cell senescence in vivo following radiation-associated preconditioning of the host liver.

MATERIALS AND METHODS

Fischer 344 rats underwent external-beam, computed-tomography-based partial liver irradiation. A single dose of 25 Gy was delivered to the right liver lobes (40% of liver mass). An additional group of animals received a 1/3 partial hepatectomy (removal of the left anterior lobe) four days after irradiation. Non-irradiated groups served as controls. All rats were sacrificed four weeks after the initial treatment.

RESULTS

The irradiated livers displayed several markers of cell senescence, including expression of senescence-associated-β-galactosidase (SA-β-gal), increase in cell size, and up-regulation of cyclin-dependent kinase inhibitors (CDK-I) p16 and p21. Furthermore, quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) analysis revealed activation of the senescence-associated secretory phenotype (SASP), including the cytokines interleukin 6 (IL6) and 1α (IL1α). The senescence-related changes were more prominent in rats undergoing partial hepatectomy (PH) following irradiation (IR).

CONCLUSIONS

We conclude that priming with radiation for liver repopulation results in the induction of cell senescence and the up-regulation of a senescence-associated secretory phenotype. The latter can contribute to the extensive growth of transplanted cells in this system.

Induction of chemokines and cytokines before neutrophils and macrophage recruitment in different regions of rat liver after TAA administration

Single-dose thioacetamide (TAA) administration induces inflammation and acute liver damage. The mechanism of inflammatory cell recruitment in the liver is still unclear. The aim of this study was to examine the sequence and recruitment of inflammatory cells in different liver regions in relation to CXC- and CC-chemokine and cytokine expression during acute liver injury. Single-dose TAA was administered to rats intraperitoneally, and animals were killed at different time points thereafter. Serum and liver tissue were taken and frozen immediately. Tissue was used for immunostaining cryostat sections, RNA, and protein extraction. RT-PCR and western blotting were performed for RNA and protein analysis, respectively. An early increase (3 h) in CXCL8/IL-8 levels was measured followed by a marked release in MCP1/CCL2 (24 h) serum levels after TAA administration compared with controls. Similarly, an early increase in specific RNA of hepatic chemokines CXCL1/KC and CXCL8/IL-8 was found at 3 h, followed by an upregulation of CXCL5/LIX (6 h), CXCL2/MIP-2 (12 h), and MCP1/CCL2 gene expression at 24-48 h. Further, an induction of pro-inflammatory cytokines IFN-γ and IL-1β followed by IL-6 and TNF-α was observed with a maximum at 12 h. The magnitude of increase in gene expression of TNF-α and MCP1/CCL2 was the highest among all cytokines and chemokines, respectively. By means of immunohistochemistry, an early (12-24 h) increase in the number of only neutrophil granulocytes (NGs) attached to and around portal vessel walls was observed, followed by increased numbers of mononuclear phagocytes (24-48 h) along the sinusoids. Treatment of the human monocytic cell line U-937 with TNF-α increased the gene expression of CXCL1/KC, CXCL8/IL-8, and MCP1/CCL2. Conversely, adding of infliximab (IFX) to the culture medium inhibited this upregulation significantly. In conclusion, single-dose TAA administration induces a sequence of events with a defined upregulation of gene expression of inflammatory chemokines and cytokines and a transient accumulation of NGs within the portal area and macrophages along the sinusoids throughout the liver. Periportal inflammation seems to precede hepatocellular damage.

Differential regulation of ferritin subunits and iron transport proteins: an effect of targeted hepatic X-irradiation

The current study aimed to investigate radiation-induced regulation of iron proteins including ferritin subunits in rats. Rat livers were selectively irradiated in vivo at 25 Gy. This dose can be used to model radiation effects to the liver without inducing overt radiation-induced liver disease. Sham-irradiated rats served as controls. Isolated hepatocytes were irradiated at 8 Gy. Ferritin light polypeptide (FTL) was detectable in the serum of sham-irradiated rats with an increase after irradiation. Liver irradiation increased hepatic protein expression of both ferritin subunits. A rather early increase (3 h) was observed for hepatic TfR1 and Fpn-1 followed by a decrease at 12 h. The increase in TfR2 persisted over the observed time. Parallel to the elevation of AST levels, a significant increase (24 h) in hepatic iron content was measured. Complete blood count analysis showed a significant decrease in leukocyte number with an early increase in neutrophil granulocytes and a decrease in lymphocytes. In vitro, a significant increase in ferritin subunits at mRNA level was detected after irradiation which was further induced with a combination treatment of irradiation and acute phase cytokine. Irradiation can directly alter the expression of ferritin subunits and this response can be strongly influenced by radiation-induced proinflammatory cytokines. FTL can be used as a serum marker for early phase radiation-induced liver damage.

Dietary iron concentration may influence aging process by altering oxidative stress in tissues of adult rats

Iron is an essential element. However, in its free form, iron participates in redox-reactions, leading to the production of free radicals that increase oxidative stress and the risk of damaging processes. Living organisms have an efficient mechanism that regulates iron absorption according to their iron content to protect against oxidative damage. The effects of restricted and enriched-iron diets on oxidative stress and aging biomarkers were investigated. Adult Wistar rats were fed diets containing 10, 35 or 350 mg/kg iron (adult restricted-iron, adult control-iron and adult enriched-iron groups, respectively) for 78 days. Rats aged two months were included as a young control group. Young control group showed higher hemoglobin and hematocrit values, lower levels of iron and lower levels of MDA or carbonyl in the major studied tissues than the adult control group. Restricted-iron diet reduced iron concentrations in skeletal muscle and oxidative damage in the majority of tissues and also increased weight loss. Enriched-iron diet increased hematocrit values, serum iron, gamma-glutamyl transferase, iron concentrations and oxidative stress in the majority of tissues. As expected, young rats showed higher mRNA levels of heart and hepatic L-Ferritin (Ftl) and kidneys SMP30 as well as lower mRNA levels of hepatic Hamp and interleukin-1 beta (Il1b) and also lower levels of liver protein ferritin. Restricted-iron adult rats showed an increase in heart Ftl mRNA and the enriched-iron adult rats showed an increase in liver nuclear factor erythroid derived 2 like 2 (Nfe2l2) and Il1b mRNAs and in gut divalent metal transporter-1 mRNA (Slc11a2) relative to the control adult group. These results suggest that iron supplementation in adult rats may accelerate aging process by increasing oxidative stress while iron restriction may retards it. However, iron restriction may also impair other physiological processes that are not associated with aging.

Ferroportin-1 is a 'nuclear'-negative acute-phase protein in rat liver: a comparison with other iron-transport proteins

Liver is the central organ of iron metabolism. During acute-phase-response (APR), serum iron concentration rapidly decreases. The current study aimed to compare expression and localization of iron transport protein ferroportin-1 (Fpn-1) and of other iron import proteins after experimental tissue damage induced by injecting turpentine oil in the hind limbs of rats and mice. Serum and spleen iron concentration decreased with an increase in total liver, cytoplasmic and nuclear iron concentration. In liver, mRNA amount of Fpn-1, Fpn-1a, Fpn-1b, HFE, hemojuvelin (HJV) and hephaestin (heph) genes showed a rapid decrease. Hepcidin, divalent metal transporter-1 (DMT-1), transferrin (Tf) and Tf-receptor-1 (TfR1), TfR-2 (TfR2) gene expression was increased. Western blot analysis of liver tissue lysate confirmed the changes observed at mRNA level. In spleen, a rapid decrease in gene expression of Fpn-1, Fpn-1a, Fpn-1b, DMT-1, Tf, TfR1 and TfR2, and an increase in hepcidin was observed. Immunohistochemistry of DMT-1 and TfR2 were mainly detected in the nucleus of rat liver and spleen, whereas TfR1 was clearly localized in the plasma membrane. Fpn-1 was mostly found in the nuclei of liver cells, whereas in spleen, the protein was mainly detected in the cell membrane. Western blot analysis of liver fractions confirmed immunohistochemical results. In livers of wild-type mice, gene expression of Fpn-1, Fpn-1a and Fpn-1b was downregulated, whereas hepcidin gene expression was increased. In contrast, these changes were less pronounced in IL-6ko-mice. Cytokine (IL-6, IL-1b and TNF-a) treatment of rat hepatocytes showed a downregulation of Fpn-1, Fpn-1a and Fpn-1b, and upregulation of hepcidin gene expression. Moreover, western blot analysis of cell lysate of IL-6-treated hepatocytes detected, as expected, an increase of a2-macroglobulin (positive acute-phase protein), whereas albumin (negative acute-phase protein) and Fpn-1 were downregulated. Our results demonstrate that liver behaves as a 'sponge' for iron under acute-phase conditions, and Fpn-1 behaves as a negative acute-phase protein in rat hepatocytes mainly, but not exclusively, because of the effect of IL-6. These changes could explain iron retention in the cytoplasm and in the nucleus of hepatocytes during APR.

Radiation-induced damage in different segments of the rat intestine after external beam irradiation of the liver

INTRODUCTION

The out-of-field effects on the intestine, caused by radiation treatment of a parenchymatous organ, have not previously been studied.

METHODS

A single dose of 25Gy was administered percutaneously to the liver of male Wistar rats after a planning CT-scan. Sham-irradiated animals served as controls. At 1, 6, 24, 96h, 1.5 and 3months the duodenum, jejunum, ileum and distal colon were removed, washed and deep-frozen or prepared for paraffin staining.

RESULTS

All animals survived the treatment. Epithelial cell damage occurred in all small-intestinal segments. However, prolonged denudation of the villi together with destruction of the crypt lining was only observed in the ileum, resulting in deficient regeneration. In the colon, changes were minor. Radiation mucositis with granulocyte (MP0+) infiltration was seen from 1 to 24h in the duodenum and jejunum, when ED1+ macrophages, CD3+ T-lymphocytes, and CD34+ hematopoietic precursor cells were recruited, accompanied by an increase in the chemokines MCP-1, MIP-1α, MIP3α and Il-8. In the ileum, early granulocyte infiltration was delayed but continuous. Recruitment of macrophages and lymphocytes was deficient and induction of chemokines as of the adhesion molecules PECAM-1, ICAM-1 was lacking.

CONCLUSION

Post-irradiation damage to the ileum was delayed and followed by an altered repair process with structural changes of the villi. The observed changes might result from a higher sensitivity to oxidative stress mechanisms with subsequent damage of the regenerative capacity of the crypt-villus axis, accompanied by a sustained "inflammatory response" and vascular damage with a lack of regeneratory cell recruitment.

Transferrin receptor 1 in the zoonosis and pathogenesis of New World hemorrhagic fever arenaviruses

At least five New World arenaviruses cause severe human hemorrhagic fevers. These viruses are transmitted to humans through contact with their respective South American rodent hosts. Each uses human transferrin receptor 1 (TfR1) as its obligate receptor. Accidental similarities between human TfR1 and TfR1 orthologs of arenaviral host species enable zoonoses, whereas mice and rats are not infectable because they lack these TfR1 determinants of infection. All pathogenic New World arenaviruses bind to a common region of the apical domain of TfR1. The ability of a New World arenavirus to use human TfR1 is absolutely predictive of its ability to cause hemorrhagic fevers in humans. Nonpathogenic arenaviruses, closely related to hemorrhagic fever arenaviruses, cannot utilize human TfR1 but efficiently enter cells through TfR1 orthologs of their native rodent hosts. Mutagenesis studies suggest that minor changes in the entry glycoproteins of these nonpathogenic viruses may allow human transmission. TfR1 is upregulated as a result of iron sequestration during the acute-phase response to infection, and the severity of disease may result from amplification of viral replication during this response.

Administration of rat acute-phase protein α(2)-macroglobulin before total-body irradiation initiates cytoprotective mechanisms in the liver

Previously, we showed that administration of the acute-phase protein α(2)-macroglobulin (α(2)M) to rats before total-body irradiation with 6.7 Gy (LD(50/30)) of X-rays provides the same level of radioprotection as amifostine. Here, we compare the cytoprotective effects of α(2)M and amifostine on rat liver. The potential of the liver to replenish cells destroyed by ionizing radiation was assessed by immunoblot analysis with antibody to proliferating cell nuclear antigen (PCNA). After irradiation, in unprotected rats PCNA decreased 6-fold from the basal level. In rats pretreated with either α(2)M or amifostine, PCNA was increased throughout a 4 week follow-up period, indicating that hepatocyte proliferation was unaffected. Since PCNA is an important component of the repair machinery, its increased expression was accompanied by significantly lower DNA damage in α(2)M- and amifostine-treated rats. At 2 weeks after irradiation, the Comet assay revealed a 15-fold increase in DNA damage in unprotected rats, while in α(2)M- and amifostine-treated rats we observed 3- and 4-fold rise in damage, respectively. The improved protection to DNA damage was supported by elevated activity of the antioxidant systems. Compared to untreated rats, pretreatments with α(2)M and amifostine led to similar increases in levels of the inflammatory cytokine IL-6 and the redox-sensitive transcription factor NFκB, promoting upregulation of MnSOD, the major component of the cell's antioxidant axis, and subsequent increases in Mn/CuZnSOD and catalase enzymatic activities. The results show that α(2)M induces protein factors whose interplay underlies radioprotection and support the idea that α(2)M is the central effector of natural radioprotection in the rat.

The rat acute-phase protein α2-macroglobulin plays a central role in amifostine-mediated radioprotection

Previously we reported that elevated circulating concentrations of the acute-phase (AP) protein α(2)-macroglobulin (α(2)M), either as typically occurring in pregnant female rats or after administration to male rats, provides radioprotection, displayed as 100% survival of experimental animals exposed to total-body irradiation with 6.7 Gy (LD(50/30)) x-rays, that is as effective as that afforded by the synthetic radioprotector amifostine. The finding that amifostine administration induces a 45-fold increase in α(2)M in the circulation led us to hypothesise that α(2)M assumes an essential role in both natural and amifostine-mediated radioprotection in the rat. In the present work we examined the activation of cytoprotective mechanisms in rat hepatocytes after the exogenous administration of α(2)M and amifostine. Our results showed that the IL6/JAK/STAT3 hepatoprotective signal pathway, described in a variety of liver-injury models, upregulated the α(2)M gene in amifostine-pretreated animals. In both α(2)M- and amifostine-pretreated rats we observed the activation of the Akt signalling pathways that mediate cellular survival. At the cellular level this was reflected as a significant reduction of irradiation-induced DNA damage that allowed for the rapid and complete restoration of liver mass and ultimately at the level of the whole organism the complete restoration of body weight. We conclude that the selective upregulation of α(2)M plays a central role in amifostine-provided radioprotection.

Inactivation of kupffer cells by gadolinium chloride protects murine liver from radiation-induced apoptosis

PURPOSE

To determine whether the inhibition of Kupffer cells before radiotherapy (RT) would protect hepatocytes from radiation-induced apoptosis.

MATERIALS AND METHODS

A single 30-Gy fraction was administered to the upper abdomen of Sprague-Dawley rats. The Kupffer cell inhibitor gadolinium chloride (GdCl3; 10 mg/kg body weight) was intravenously injected 24 h before RT. The rats were divided into four groups: group 1, sham RT plus saline (control group); group 2, sham RT plus GdCl3; group 3, RT plus saline; and group 4, RT plus GdCl3. Liver tissue was collected for measurement of apoptotic cytokine expression and evaluation of radiation-induced liver toxicity by analysis of liver enzyme activities, hepatocyte micronucleus formation, apoptosis, and histologic staining.

RESULTS

The expression of interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha was significantly attenuated in group 4 compared with group 3 at 2, 6, 24, and 48 h after injection (p <0.05). At early points after RT, the rats in group 4 exhibited significantly lower levels of liver enzyme activity, apoptotic response, and hepatocyte micronucleus formation compared with those in group 3.

CONCLUSION

Selective inactivation of Kupffer cells with GdCl3 reduced radiation-induced cytokine production and protected the liver against acute radiation-induced damage.

Single-dose gamma-irradiation induces up-regulation of chemokine gene expression and recruitment of granulocytes into the portal area but not into other regions of rat hepatic tissue

Liver damage is a serious clinical complication of gamma-irradiation. We therefore exposed rats to single-dose gamma-irradiation (25 Gy) that was focused on the liver. Three to six hours after irradiation, an increased number of neutrophils (but not mononuclear phagocytes) was observed by immunohistochemistry to be attached to portal vessels between and around the portal (myo)fibroblasts (smooth muscle actin and Thy-1(+) cells). MCP-1/CCL2 staining was also detected in the portal vessel walls, including some cells of the portal area. CC-chemokine (MCP-1/CCL2 and MCP-3/CCL7) and CXC-chemokine (KC/CXCL1, MIP-2/CXCL2, and LIX/CXCL5) gene expression was significantly induced in total RNA from irradiated livers. In laser capture microdissected samples, an early (1 to 3 hours) up-regulation of CCL2, CXCL1, CXCL8, and CXCR2 gene expression was detected in the portal area but not in the parenchyma; with the exception of CXCL1 gene expression. In addition, treatment with an antibody against MCP-1/CCL2 before irradiation led to an increase in gene expression of interferon-gamma and IP-10/CXCL10 in liver tissue without influencing the recruitment of granulocytes. Indeed, the CCL2, CXCL1, CXCL2, and CXCL5 genes were strongly expressed and further up-regulated in liver (myo)fibroblasts after irradiation (8 Gy). Taken together, these results suggest that gamma-irradiation of the liver induces a transient accumulation of granulocytes within the portal area and that (myo)fibroblasts of the portal vessels may be one of the major sources of the chemokines involved in neutrophil recruitment. Moreover, inhibition of more than one chemokine (eg, CXCL1 and CXCL8) may be necessary to reduce leukocytes recruitment.

Phagocytosis of gadolinium chloride or zymosan induces simultaneous upregulation of hepcidin- and downregulation of hemojuvelin- and Fpn-1-gene expression in murine liver

The liver and the spleen are the organs in which cellular material and aged erythrocytes are eliminated from the blood. Within the liver, Kupffer cells (KCs) are mainly responsible for this task, as such KCs have a pivotal role in iron metabolism. The aim of this study is to investigate the changes of hepatic gene expression in two models of KC phagocytosis. Gadolinium chloride (GD) or zymosan was injected intraperitoneally into rats and to endotoxin-resistant mice (C3H/HeJ). The animals were killed at different time points and their livers were immediately frozen in liquid nitrogen for RNA isolation and immunohistological studies. RNA was analyzed by real-time PCR and northern blot. Sera were used to measure transaminases, hepcidin and iron levels. The expression of iron metabolism genes, hepcidin, hemojuvelin (Hjv), ferroportin-1 (Fpn-1) and of the inflammatory cytokines IL-6, IL-1beta, TNF-alpha and IFN-gamma was determined. Although phagocytosed material was detected in ED-1- and C1q-positive cells, no inflammatory cells were identified within the liver parenchyma. Serum levels of hepcidin, iron and transaminases did not differ from those of control animals. Both GD and zymosan induced an upregulation of hepcidin-gene expression in rat liver as early as 3 h, reaching a maximum 6 h after treatment. Hjv- and Fpn-1-gene expression was downregulated at the same time. IL-6 was by far the most induced acute-phase-cytokine in GD- and zymosan-treated livers, although IL-1beta and TNF-alpha were also strongly upregulated by zymosan and to a lesser extent by GD. Similar results were obtained in the C3H/HeJ mouse strain excluding the possible role of contaminating endotoxin. This study shows that phagocytosis upregulates hepcidin-gene expression and downregulates Hjv- and Fpn-1-gene expression within the liver. These changes in iron-regulating-gene expression may be mediated by the locally produced acute-phase-cytokines.

Effect of irradiation on gene expression of rat liver adhesion molecules: in vivo and in vitro studies

BACKGROUND AND PURPOSE

Migration of leukocytes into tissue is a key element of innate and adaptive immunity. An animal study showed that liver irradiation, in spite of induction of chemokine gene expression, does not lead to recruitment of leukocytes into the parenchyma. The aim of this study was to analyze gene expression of adhesion molecules, which mediate leukocyte recruitment into organs, in irradiated rat liver in vivo and rat hepatocytes in vitro.

MATERIAL AND METHODS

Rat livers in vivo were irradiated selectively at 25 Gy. Isolated hepatocytes in vitro were irradiated at 8 Gy. RNA extracted within 48 h after irradiation in vivo and in vitro was analyzed by real-time PCR (polymerase chain reaction) and Northern blot. Adhesion molecule concentration in serum was measured by ELISA (enzyme-linked immunosorbent assay). Cryostat sections of livers were used for immunohistology.

RESULTS

Significant radiation-induced increase of ICAM-1 (intercellular adhesion molecule-1), VCAM-1 (vascular cell adhesion molecule-1), JAM-1 (junctional adhesion molecule-1), beta1-integrin, beta2-integrin, E-cadherin, and P-selectin gene expression could be detected in vivo, while PECAM-1 (platelet-endothelial cell adhesion molecule-1) gene expression remained unchanged. In vitro, beta1-integrin, JAM-1, and ICAM-2 showed a radiation-induced increased expression, whereas the levels of P-selectin, ICAM-1, PECAM-1, VCAM-1, Madcam-1 (mucosal addressin cell adhesion molecule-1), beta2-integrin, and E-cadherin were downregulated. However, incubation of irradiated hepatocytes with either tumor necrosis factor-(TNF-)alpha, interleukin-(IL-)1beta, or IL-6 plus TNF-alpha led to an upregulation of P-selectin, ICAM-1 and VCAM-1.

CONCLUSION

The findings suggest that liver irradiation modulates gene expression of the main adhesion molecules in vivo and in cytokine-activated hepatocytes, with the exception of PECAM-1. This may be one reason for the lack of inflammation in the irradiated rat liver.

Changes in transcriptome after in vivo exposure to ionising radiation reveal a highly specialised liver response

PURPOSE

To identify transcriptional gene-networks involved in the early in vivo response of liver cells to radiation exposure and improve our understanding of the molecular processes responsible for tissue radiosensitivity.

MATERIALS AND METHODS

Transcriptome variations of liver RNA samples were measured 3 hours post-irradiation using microarray technology. The results were confirmed and extended using real-time polymerase-chain-reaction (RT-PCR).

RESULTS

We identified quantitative changes in the expression of 126 genes, most of which were observed for the first time. We show that some modifications, such as the upregulation of the cyclin-dependent kinase inhibitor 1A (Cdkn1A) gene, persisted for at least two months after the initial exposure. Other genes regulated by the transformation-related protein 53 (Trp53/p53) such as Bcl2-associated X protein (Bax) or etoposide-induced-2.4 (Ei24/PIG8) were not upregulated. Grouping differentially expressed genes into functional categories revealed that the primary response of liver cells to radiation exposure was the enhancement of oxidoreductase activity and inhibition of cell proliferation, involving cell cycle progression and apoptosis-related genes.

CONCLUSIONS

The data provides evidence of gene expression modifications associated with the hepatic response to radiation exposure. One of the main differences observed with radiation-sensitive tissues such as the spleen was cell proliferation. The comparison of our data with transcriptome modifications in different biological models enabled the identification of networks of genes that might be co-regulated. Overall, our expression data revealed genes and cellular pathways that might help to improve our understanding of the molecular basis underlying tissue radiosensitivity and to identify possible targets for novel therapeutic strategies.

Effect of tumour necrosis factor-alpha and irradiation alone or in combination on the viability of hepatocellular and biliary adenocarcinoma cell lines in vitro

BACKGROUND

Tumour necrosis factor alpha (TNF-alpha) may exhibit antitumoral activity and can influence the reaction of both tumour and normal tissue to radiation.

AIMS

To test the effect of TNF-alpha and/or irradiation on hepatocellular (HepG2, Hep3B, Sk-Hep1, HuH7) and cholangiocellular (Sk-chA1, Mz-chA1) tumour cell lines.

METHODS

Colony formation, apoptosis analysis and trypan blue exclusion were used to assess cell viability. Doses of radiation (2-25 Gy) and TNF-alpha (100-50,000 U) as well as their respective sequencing were varied (24 and 12 h before and 6 h after). The expression of TNF-alpha and TNF receptors 1/2 was determined using real-time polymerase chain reaction and IkappaBalpha protein expression was detected by Western blot.

RESULTS

Sole irradiation induced a reduction in colony formation in all cell lines and sole TNF-alpha in HepG2 and Sk-chA1 cells only. No difference in apoptosis induction after TNF-alpha or irradiation was observed. Cellular death induced by the combination of TNF-alpha and radiation was not superior to the use of any of the two agents alone. All cell lines revealed that radiation induced upregulation of TNF-alpha whereas the extent of TNF receptor-specific transcription did not change. Furthermore, radiation-induced changes in IkappaBalpha expression were not detectable.

CONCLUSIONS

Our data suggest that both TNF-alpha and radiation may be treatment options for hepatocellular and cholangiocellular carcinomas. Because TNF-alpha and radiation do not interact in terms of radiosensitization, anti-TNF-alpha treatment may have the potential to protect against hepatocellular injury after abdominal irradiation. However, further in vivo studies are needed to confirm that anti-TNF-alpha treatment does not compromise tumour control and actually attenuates radiation-induced liver injury.

Synergistic effect of radiation and interleukin-6 on hepatitis B virus reactivation in liver through STAT3 signaling pathway

PURPOSE

Hepatitis B virus (HBV) reactivation can occur after radiotherapy (RT) for hepatobiliary malignancies. Our previous in vitro culture study identified interleukin-6 (IL-6) as the main bystander mediator of RT-induced HBV replication. We attempted to examine the molecular mechanism in HBV-transgenic mice.

METHODS AND MATERIALS

HBV transgenic mice were treated with whole liver RT (4 Gy daily for 5 days) with or without administration of IL-6 (400 ng twice daily for 15 days). The serum level of HBV DNA was measured using real-time polymerase chain reaction, and the IL-6 concentration was measured using enzyme-linked immunosorbent assay. The intensity of immunostaining with antibodies to HBV core protein and phosphorylated signal transducer and activator of transcription (STAT)3 in the mouse liver was qualitatively analyzed. HepG2.2.15 cells (a human hepatoblastoma cell line that persistently produces HBV DNA) were used to investigate the molecular role of IL-6 plus RT in HBV reactivation.

RESULTS

HBV reactivation was induced in vivo with IL-6 plus RT (5.58-fold) compared with RT alone (1.31-fold, p = .005), IL-6 alone (1.31-fold, p = .005), or sham treatment (1.22-fold, p = .004). HBV core protein staining confirmed augmentation of intrahepatic HBV replication. IL-6 plus RT-induced HBV DNA replication in HepG2.2.15 cells was suppressed by the STAT3 inhibitor AG490 and by transfection with dominant-negative STAT3 plasmid. Phosphorylated STAT3 staining was strongest in liver tissue from mice treated with IL-6 plus RT. The mobility shift assay demonstrated that reactivation was mediated through the interaction of phosphorylated STAT3/hepatocyte nuclear factor-3 complex with HBV enhancer 1.

CONCLUSION

RT to the liver and longer sustained IL-6 induced HBV reactivation through the STAT3 signal transduction pathway.

Long-term changes in rat hematopoietic and other physiological systems after high-energy iron ion irradiation

PURPOSE

To assess the long-term consequences of high-linear energy transfer (LET) iron ion radiation on immune and other critical body systems in the context of assessing potential effects astronauts may experience during exploratory missions.

MATERIALS AND METHODS

Sprague-Dawley rats were nearly whole-body irradiated with 56-Fe (5 GeV/n) to total doses of 0, 1, 2, and 4 Gray (Gy) and euthanized 9 months post-exposure for analyses.

RESULTS

Irradiated groups consistently had low body mass. Numbers of circulating white blood cells (WBC), lymphocytes and monocytes were lower in the 2 Gy group compared to 0 Gy (p < 0.05); a trend for low granulocytes was also noted. Red blood cell counts, hemoglobin, and hematocrit were decreased in irradiated animals (p < 0.05), whereas platelet counts and volume were unaffected. In the spleen, WBC counts and DNA synthesis by T cells were similar among groups and there were no differences in secreted interferon-gamma and interleukin-6. However, trends were noted for increased splenocyte capacity to secrete tumor necrosis factor-alpha and increased level of vascular endothelial cell growth factor in plasma. One or more of the irradiated groups had significant (p < 0.05) aberrations in several blood chemistry parameters associated with liver and kidney function.

CONCLUSION

The data show that exposure to 56-Fe radiation induced pathological changes in important body systems long after exposure.

Effect of radiation on gene expression of rat liver chemokines: in vivo and in vitro studies

The aim of the study was to analyze the effect of a single irradiation on chemokine gene expression in the rat liver and in isolated rat hepatocytes. RNA extracted from livers and from hepatocytes within the first 48 h after irradiation was analyzed by real-time PCR and the Northern blot assay. The chemokine concentrations in the serum of irradiated rats were measured quantitatively by ELISA. A significant radiation-induced increase of CINC1, IP10, MCP1, MIP3alpha, MIP3beta, MIG and ITAC gene expression could be detected at the RNA level in the liver. CINC1, MCP1 and IP10 serum levels were significantly increased. In rat hepatocytes in vitro, only MIP3alpha showed a radiation-induced increase in expression, while CINC1, IP10, MIP3beta, MIG, MIP1alpha, ITAC and SDF1 RNA levels were significantly down-regulated. However, incubation of irradiated hepatocytes in vitro with either TNF-alpha, IL1beta, or IL6 plus TNF-alpha led to up-regulation of MCP1, IP10 and MCP1 or CINC1 and MIP3beta, respectively. Irradiation of the liver induces up-regulation of the genes of the main proinflammatory chemokines, probably through the action of locally synthesized proinflammatory cytokines. The reason for the lack of liver inflammation in this model has still to be clarified.

Changes of gene expression of iron regulatory proteins during turpentine oil-induced acute-phase response in the rat

In the present study, turpentine oil was injected in the hind limb muscle of the rat to stimulate an acute-phase response (APR). The changes in the gene expression of cytokines and proteins known to be involved in the iron regulatory pathway were then studied in the liver and in extra-hepatic tissue. In addition to the strong upregulation of interleukin-6 (IL-6) and IL-1 beta observed in the inflamed muscle, an upregulation of the genes for IL1-beta and tumor necrosis factor-alpha, but not IL-6, were detectable in the liver. Hepatic Hepc gene expression increased to a maximum at 6 h after the onset of APR. An upregulation of transferrin, transferrin receptor 1 (TfR1), TfR2, ferritin-H, iron responsive element binding protein-1 (IRP1), IRP2 and divalent metal transporter gene expression was also found. Hemojuvelin (Hjv)-, ferroportin 1-, Dcytb-, hemochromatosis-gene- and hephaestin gene expression was downregulated. Hepcidin (Hepc) gene expression was not only detectable in extra-hepatic tissues such as heart, small intestine, colon, spleen and kidney but it was also upregulated under acute-phase conditions, with the Hjv gene being regulated antagonistically. Fpn-1 gene expression was downregulated significantly in heart, colon and spleen. Most of the genes of the known proteins involved in iron metabolism are expressed not only in the liver but also in extra-hepatic tissues. Under acute-phase conditions, acute-phase cytokines (eg IL-6) may modulate the gene expression of such proteins not only in the liver but also in other organs.

Science to practice: why is the liver a radiosensitive organ?

Christiansen et al irradiated rat livers in vivo; isolated rat hepatocytes in vitro; and measured hepcidin, hemojuvelin, and ferroportin-1 gene expression. They also evaluated the influence of proinflammatory cytokines (interleukin [IL]- 1beta, IL-6, and tumor necrosis factor [TNF]-alpha) on the expression of these proteins. In this issue of Radiology, Christiansen et al conclude that radiation-induced cell-cell interactions by way of the cytokines can lead to death of irradiated hepatocytes.

Increase of hepcidin plasma and urine levels is associated with acute proctitis and changes in hemoglobin levels in primary radiotherapy for prostate cancer

PURPOSE

To analyse hepcidin serum and urine levels during radiotherapy for prostate cancer.

METHODS

In 18 patients undergoing radiotherapy for prostate cancer, blood, plasma, and urine samples were taken before and during radiotherapy. Complete blood cell count, pro-hepcidin-, ferritin-, transferrin-, IL-1beta-, IL-6-, and TNF-alpha concentration was determined. Pro-hepcidin concentration was additionally measured in urine samples. Toxicity was evaluated weekly. Differences among tested factors were tested by Wilcoxon rank sign test for paired data.

RESULTS

In ten patients developing acute radiation-induced proctitis, a significant increase in pro-hepcidin, IL-6, and TNF-alpha plasma levels (p < 0.05) was detected. Pro-hepcidin urine levels also showed a strong trend towards increase (p = 0.06). Concurrently, hemoglobin, and leucocytes were significantly decreased in the patients with acute proctitis (p < 0.05). In eight patients showing no symptoms of proctitis, solely a significant decrease for leucocytes was detected. Additive, these patients showed a significant increase of ferritin, and a decrease of transferrin levels (p < 0.05).

CONCLUSIONS

Hepcidin levels are increased and hemoglobin is decreased during radiotherapy for prostate cancer in patients who develop acute proctitis. Radiation-induced expression of cytokines may be responsible for increased hepcidin expression in the liver. Regulation of iron metabolism by hepcidin may be an underestimated response in radiotherapy.