Effects of desferrioxamine on human cytomegalovirus replication and expression of HLA antigens and adhesion molecules in human vascular endothelial cells

Iron deficiency after kidney transplantation

Iron deficiency (ID) is highly prevalent in kidney transplant recipients (KTRs) and has been independently associated with an excess mortality risk in this population. Several causes lead to ID in KTRs, including inflammation, medication and an increased iron need after transplantation. Although many studies in other populations indicate a pivotal role for iron as a regulator of the immune system, little is known about the impact of ID on the immune system in KTRs. Moreover, clinical trials in patients with chronic kidney disease or heart failure have shown that correction of ID, with or without anaemia, improves exercise capacity and quality of life, and may improve survival. ID could therefore be a modifiable risk factor to improve graft and patient outcomes in KTRs; prospective studies are warranted to substantiate this hypothesis.

The growth-inhibitory and apoptosis-inducing effect of deferoxamine combined with arsenic trioxide on HL-60 xenografts in nude mice

OBJECTIVE

The aim of this study is to investigate the growth-inhibitory and apoptosis-inducing effect of deferoxamine (DFO) combined with arsenic trioxide (ATO) on the human HL-60 xenografts in nude mice and its mechanism.

METHOD

The highly tumorigenic leukemia cell line HL-60 cells were inoculated subcutaneously into nude mice to establish a human leukemia xenograft model. The HL-60 xenograft nude mice models were randomly divided into four groups: control (Normal saline, NS), 50mg/kg DFO, 3mg/kg ATO, the combined treatment (50mg/kg DFO+1.5mg/kg ATO) once HL-60 cells were inoculated. Tumor sizes, growth curves, inhibitory rates, cell apoptosis, and the expression of apoptosis related markers were measured to evaluate the tumor growth.

RESULTS

Xenografted tumors were observed in all nude mice since the 5th day of inoculation. The inhibitory rates of tumor weight were 2.67%, 10.69%, and 25.57% in DFO, ATO and combination therapy groups, respectively. The combination of DFO with ATO induces significantly more tumor cell apoptosis than either agent alone (p<0.05). The expression of NF-κBp65 and survivin proteins decreased significantly while the expression of Caspase-3 and Bax increased in the combination therapy group (p<0.05). Double immunofluorescence for Caspase-3 and NFκBp65 demonstrated an inverse relationship between Caspase-3-positive areas and NFκBp65-positive areas, as well as the co-localization of Bax and survivin in xenografted tumor cells.

CONCLUSIONS

Combination of DFO and ATO has synergistic effects on tumor growth inhibition and apoptosis-inducing in vivo with no significant side effects. The DFO and ATO can up-regulate the expression of Caspase-3 and Bax, and down-regulate the expression of NF-κBp65 and survivin, especially for their combination.

Serum iron parameters in the early post-transplant period and infection risk in kidney transplant recipients

BACKGROUND

The impact of iron metabolism on the risk of infectious complications has been demonstrated in various immunosuppressed populations. However, no previous studies have assessed this potential association in kidney transplant (KT) recipients.

METHODS

We prospectively analyzed 228 patients undergoing KT at our institution from November 2008 to February 2011. Serum iron parameters (iron level, ferritin, total iron-binding capacity, unsaturated iron-binding capacity, transferrin, and transferrin saturation) were assessed within the first 2 weeks after transplantation (median interval, 3 days; interquartile [Q1 -Q3 ] range, 1-6 days), and before the occurrence of the first infectious episode (median interval, 26 days; Q1 -Q3 range, 11-76 days). Primary outcome was the occurrence of any episode of infection during the first year. Multivariate-adjusted hazard ratios (aHRs) were estimated by Cox regression models.

RESULTS

Patients with ferritin level ≥ 500 ng/mL had higher incidence rates (per 1000 transplant-days) of overall infection (P = 0.017), bacterial infection (P = 0.002), and bloodstream infection (P = 0.011) during the first post-transplant year. One-year infection-free survival rate was lower in these recipients (26% vs. 41%; P = 0.004). On multivariate analysis, after adjusting for potential confounders, ferritin emerged as an independent predictor of overall infection (aHR [per unitary increment], 1.001; P = 0.006), and bacterial infection (aHR [per unitary increment], 1.001; P = 0.020).

CONCLUSION

Monitoring of serum iron parameters in the early post-transplant period may be useful in predicting the occurrence of infection in KT recipients, although further studies should be carried out to confirm this preliminary finding.

Iron overload and unique susceptibility of liver transplant recipients to disseminated disease due to opportunistic pathogens

The propensity of liver transplant recipients to develop more fulminant disease presentation and a higher risk of disseminated disease due to a number of opportunistic infections, including invasive aspergillosis, cryptococcosis, zygomycosis, may be related to iron overload. Abnormalities in iron homeostasis may also be a contributor to severe manifestations due to other pathogens such as cytomegalovirus and Staphylococcus aureus in liver transplant recipients. Iron is essential not only for microbial pathogenesis, but directly impairs pivotal pathogen specific host defenses. Studies to assess iron homeostasis and the mechanisms by which iron overload contributes to the pathogenesis of opportunistic infections in liver transplant recipients are warranted.

Expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in human endometrial stromal and epithelial cells is regulated by interferon-gamma but not iron

BACKGROUND/AIMS

Endometrial cells are chronically exposed to iron due to cyclic menstrual bleeding. Iron induces expression of adhesion molecules in endothelial cells. The purpose of this study was to investigate iron incorporation by human endometrial cells and to test whether iron may stimulate expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1.

METHODS

Endometrial stromal and epithelial cells were cultured in medium alone or supplemented with INF-gamma or transferrin (Tf). Iron incorporation by cells was quantified by densitometry of ferritin immunostaining. ICAM-1 and VCAM-1 expression were evaluated at the transcriptional level by real-time RT-PCR. Membrane-bound and soluble protein levels of ICAM-1 were measured by quantitative immunohistochemistry and ELISA, respectively.

RESULTS

Tf induced a significant increase in ferritin immunostaining in both endometrial cell types. Endometrial cells treated with INF-gamma expressed more ICAM-1 and VCAM-1 than untreated cells. By contrast, Tf treatment did not alter ICAM-1 and VCAM-1 expression in cultured endometrial cells.

CONCLUSIONS

Endometrial cells are able to incorporate iron from Tf and to metabolize it to ferritin. Iron, unlike interferon-gamma, does not appear to be involved in the regulation of ICAM-1 and VCAM-1 expression in cultured endometrial cells.

The effect of iron overload on in vitro HIV-1 infection

BACKGROUND

It has been shown that Fe is required by HIV-infected cells for production of viral particles. Excess iron in the cell is detrimental to the host but beneficial to the pathogen.

OBJECTIVES

Here, we investigated the effect of excess Fe (overload) and chelation of the metal on in vitro HIV infection by assessing host cell responses (viability/death, stress protein expression and cytokine production) as well as virus replication (core protein content and enzyme activity).

RESULTS AND CONCLUSION

Excess iron decreased viability (21%, P<0.01) of HIV-infected cells, increased p24 levels by 8.6% (P=0.32) and elevated reverse transcriptase (RT) activity (81.7%, P<0.01). The stimulation of viral replication was decreased when Fe was first complexed to desferrioxamine (DFO). DFO alone (in the absence of excess Fe), lowered cell viability (35%, P=0.039) and in the presence of virus lowered both p24 levels (66%, P=0.054) and RT activity (43%, P<0.01) and unexpectedly increased cell viability (25%, P=0.01047). Interleukin-2 (IL-2) production of infected cells was completely inhibited by DFO and excess iron while stress protein (Hsp70) levels were lowered in the presence of HIV in combination with excess iron (37%, P<0.01) or DFO (47.2%, P<0.01) when compared to untreated cells. According to flow cytometric data, HIV infection caused a two-fold increase in the numbers of necrotic (P=0.006) and decreased apoptotic cells (28.5%, P=0.15) cells. These findings indicate that Fe overload associated with HIV infection is detrimental to host cell responses against viral infection and that chelation can prevent and/or reverse this effect.

Human cytomegalovirus-induced host cell enlargement is iron dependent

A hallmark of human cytomegalovirus (HCMV) infection is the characteristic enlargement of the host cells (i.e., cytomegaly). Because iron (Fe) is required for cell growth and Fe chelators inhibit viral replication, we investigated the effects of HCMV infection on Fe homeostasis in MRC-5 fibroblasts. Using the metallosensitive fluorophore calcein and the Fe chelator salicylaldehyde isonicotinoyl hydrazone (SIH), the labile iron pool (LIP) in mock-infected cells was determined to be 1.04 +/- 0.05 microM. Twenty-four hours postinfection (hpi), the size of the LIP had nearly doubled. Because cytomegaly occurs between 24 and 96 hpi, access to this larger LIP could be expected to facilitate enlargement to approximately 375% of the initial cell size. The ability of Fe chelation by 100 microM SIH to limit enlargement to approximately 180% confirms that the LIP plays a major role in cytomegaly. The effect of SIH chelation on the mitochondrial membrane potential (DeltaPsi(M)) and morphology was studied using the mitochondrial voltage-sensitive dye JC-1. The mitochondria in mock-infected cells were heterogeneous with a broad distribution of DeltaPsi(M) and were threadlike. In contrast, the mitochondria of HCMV-infected cells had a more depolarized DeltaPsi(M) distributed over a narrow range and were grainlike in appearance. However, the HCMV-induced alteration in DeltaPsi(M) was not affected by SIH chelation. We conclude that the development of cytomegaly is inhibited by Fe chelation and may be facilitated by an HCMV-induced increase in the LIP.

Antiviral and immunomodulatory activity of the metal chelator ethylenediaminedisuccinic acid against cytomegalovirus in vitro and in vivo

Antiviral activity of the metal chelator ethylenediaminedisuccinic acid (EDDS) was examined in vitro against human cytomegalovirus (HCMV) wild type strains and strains that are resistant against ganciclovir (GCV) and cidofovir (HPMPC). EDDS inhibited the replication of wild-type as well as GCV- and HPMPC-resistant strains with a 50% effective concentration of 7.4-12 microg/ml. At concentrations of 100 microg/ml EDDS, unlike GCV or HPMPC, suppressed HCMV-induced up-regulation of intercellular adhesion molecule-1 (ICAM-1) and reduced T-cell adhesion to HCMV-infected cells in a monolayer adhesion model. In vitro EDDS inhibited murine cytomegalovirus (MCMV) replication (EC50 8.6 microg/ml) and caused in mice some protection against MCMV induced mortality at a non-toxic dose. Since immunopathological factors may play a significant role in HCMV disease it will be of interest to further study whether EDDS is effective in terms of modulation of inflammatory responses to HCMV infections.

Inhibition of cytomegalovirus immediate early gene expression: a therapeutic option?

The replication cycle of the human cytomegalovirus (HCMV) is characterized by the expression of immediate early (IE), early (E), and late (L) gene regions. Current antiviral strategies are directed against the viral DNA polymerase expressed during the early phase of infection. The regulation of the IE-1 and IE-2 gene expression is the key to latency and active replication due to their transactivating and repressing functions. There is growing evidence that the pathogenic features of HCMV are largely due to the abilities of IE-1 and IE-2 to transactivate cellular genes. Consequently, current drugs used to inhibit HCMV infection would have no impact on IE-1 and IE-2-induced effects that are produced before the early phase. Moreover, when HCMV DNA replication is inhibited, IE gene products accumulate in infected cells causing disturbances of host cell functions. This review summarizes the biological functions of HCMV-IE gene expression, their relevance in pathogenesis, as well as efforts to develop novel treatment strategies directed against HCMV-IE expression.

Antiviral and immunomodulatory effects of desferrioxamine in cytomegalovirus-infected rat liver allografts with rejection

BACKGROUND

Cytomegalovirus (CMV) infection is associated with acute and chronic allograft rejection. We have recently shown that rat CMV increases portal inflammation and bile duct destruction in a model of rat liver allograft rejection. Desferrioxamine (DFO), an iron chelator and antioxidant, has recently been demonstrated to have antiviral as well as immunomodulatory effects in vitro. We therefore investigated whether DFO inhibits (a) CMV infection and (b) graft destruction in our rat model.

METHOD

One day after liver transplantation, PVG (RT1c) into BN(RT1n), the rats were infected with rat CMV (RCMV, Maastricht strain; 10(5) plaque-forming units i.p.). The effects of 100 mg/kg body weight and 200 mg/kg body weight DFO were examined.

RESULTS

In the untreated group, the grafts were uniformly RCMV culture-positive. In the group receiving 200 mg/kg DFO, RCMV replication was effectively inhibited. Inflammatory response in the graft, and especially the number of macrophages, was significantly reduced by DFO. Portal inflammation and bile duct destruction were also significantly reduced. In the untreated group, the bile duct epithelial cells were found to be strongly positive for tumor necrosis factor-alpha and this expression was clearly decreased by DFO. In addition, DFO significantly inhibited vascular cell adhesion molecule-1 expression on sinusoidal endothelial cells.

CONCLUSIONS

Our in vivo transplant study strongly supports the inhibitory effects of metal chelators on CMV infection and their possible usefulness in the treatment of CMV-induced pathogenic changes.

Iron metabolism and HIV infection: reciprocal interactions with potentially harmful consequences?

Humans with advanced human immunodeficiency virus (HIV) infection present some evidence suggestive of iron accumulation. Ferritin concentrations increase with HIV disease progression, and iron accumulates in several tissues. Iron excess may exert negative effects in individuals with HIV. Indeed, iron accumulation seems to be associated with shorter survival, and a number of investigations point to an iron-mediated oxidative stress in subjects with HIV infection. The observations on humans infected with HIV are in part supported by in-vitro findings. Indeed, in-vitro HIV infection is associated with changes in iron metabolism, and an iron-mediated oxidative stress is likely to contribute to viral cytopathogenicity. Furthermore, it is interesting to point out that the interaction between iron and HIV may be reciprocal, since viruses with a life-cycle involving a DNA phase require chelatable iron for optimum replication. This combined evidence suggests that iron metabolism is an important area for virus/host interaction. These observations may be relevant to both laboratory monitoring and clinical treatment of individuals with HIV.

Modulation of surface transferrin receptors in lymphoid cells de novo infected with human immunodeficiency virus type-1

To investigate whether transferrin receptor (CD71) expression is affected by acute HIV-1 infection, three different lymphoid cell lines (MT-4, SUPT-1, H9) were infected with HIV-1 and tested for surface CD71 expression after different incubation periods depending on cell survival after infection. We found that expression of surface CD71 was lower in cells infected with HIV-1 than in uninfected controls: the timing and extent of this down-modulation depended apparently on the different susceptibility of the cell lines to HIV-1 infection and cytopathogenicity. Citrate, a molecule capable of chelating iron, dose-dependently prevented down-modulation of surface CD71 in HIV-1 infected cells as well as viral cytopathic effects. We conclude that (i) expression of surface transferrin receptors is down-modulated by acute HIV-1 infection in T lymphoid cells, that (ii) this cell phenotypic modulation is associated with the cytopathic effects of the virus, and that (iii) these phenomena are modulated by iron chelation. These results support the view that iron metabolism may be an important area for interaction between HIV-1 and human cells.

Immunomodulatory properties of the metal chelators desferrioxamine and diethylenetriamine penta-acetic acid in vitro

In this study, we investigated the effects of the intracellular metal chelator desferrioxamine (DFO) and the extracellular metal chelator diethylenetriamine penta-acetic acid (DTPA), which were previously shown to have strong anticytomegalovirus potencies, on their ability to elicit immunomodulatory effects in vitro[fcn,3]. The results showed that nontoxic and in vivo attainable concentrations of both DFO and DTPA inhibited mitogen- and allogen-induced proliferation of peripheral blood lymphocytes. The immunomodulatory effects of DFO/DTPA seem to be due to the impaired expression of interleukin-2 receptor and the reduced secretion of interleukin-2. However, metal chelators were more effective than cyclosporine or tacrolimus (FK506) in our in vitro experiments. Moreover, cytotoxicity mediated by lymphokine-activated killer cells and natural killer cells and the expression of HLA and adhesion molecules on cytokine-stimulated endothelial cells were differentially impaired by DFO/DTPA. These results warrant further study of the immunological effects of metal chelators in vivo.

Impact of oxidative stress on human cytomegalovirus replication and on cytokine-mediated stimulation of endothelial cells

Transplantation-related pathogenic factors such as ischemia or allograft-directed inflammation are associated with oxidative changes that might lead to cellular oxidative stress. The aim of this study was to investigate the impact of oxidative stress on: (1) CMV replication in cultured human endothelial cells and (2) the stimulation of endothelial cells by proinfiammatory cytokines. Both pathomechanisms are known to contribute to graft rejection crises in vivo. Oxidative stress was induced in endothelial cell cultures with 10-200 microM buthionine sulfoximine. Western blotting showed a significant increase in the production of CMV-specific immediate early and late proteins in buthionine sulfoximine-treated cultures. Immunocytochemical staining suggested that this effect was caused by increased numbers of CMV antigen expressing cells (66% immediate early; 78%, late). Quantitative polymerase chain reaction for CMV-specific DNA and virus titration revealed that enhanced viral replication levels correlated with increased virion production. As a measure for the endothelial cell activation status, the surface expression of HLA-ABC and HLA-DR and adhesion molecules (ICAM-1, ELAM-1, VCAM-1) was quantified by fluorometric methods. Whereas oxidative stress alone did not modulate any surface molecule expression, the IFN-gamma-mediated expression of HLA-ABC and HLA-DR and the IL-1-mediated expression of ICAM-1, but not of ELAM-1 and VCAM-1 (IL-1 + TNF-alpha), was amplified. Interestingly, the amplification of HLA molecule expression was even higher in CMV-infected endothelial cells. This study provides evidence that oxidative stress contributes to the regulation of CMV replication, virus shedding, and the activation of endothelial cells by proinflammatory cytokines as it is observed in transplant recipients.

In vitro inhibition of human cytomegalovirus replication by calcium trinatrium diethylenetriaminepentaacetic acid

Desferrioxamine (DFO) has been shown to inhibit human cytomegalovirus (CMV) replication in vitro. In the present study, we compared antiviral effects of DFO in human foreskin fibroblast (HFF) cells against several CMV strains with those of other chelators that interact with iron and other ions from different pools. DFO, a hydrophilic chelator, that may chelate both intracellular and extracellular ions inhibited production of CMV late antigen at 50% effective concentrations (EC50S) ranging from 6.2 to 8.9 microM. EC50S for calcium trinatrium diethylenetriaminepentaacetic acid (CaDTPA) ranged from 6.1 to 9.9 microM. EC50S for 2,2'-bipyridine (BPD), a hydrophobic chelator, which diffuses into cell membranes ranged from 65 to 72 microM. Concentrations which inhibited BrdU incorporation into cellular DNA by 50% (IC50S) ranged from 8.2 to 12.0 microM (DFO), from 65 to 89 microM (BPD), and from 139 to 249 microM (CaDTPA). CaDTPA was the only chelator which completely inhibited production of infectious virus in HFF and vascular endothelial cells at concentrations which had no significant effects on cellular DNA synthesis and growth. Addition of stoichiometric amounts of Fe3+ in the culture medium of HFF cells completely eliminated antiviral effects of DFO while antiviral effects of CaDTPA and BPD were only moderately affected. Fe2+ and Cu2+ were stronger inhibitors of CaDTPA than Fe3+; however, Mn2+ and Zn2+ completely suppressed antiviral effects of CaDTPA. The results show that CaDTPA is a novel nontoxic inhibitor of CMV replication. The antiviral activity of CaDTPA is suppressed by metal ions with a decreasing potency order of Mn2+/Zn2+ > Fe2+ > Cu2+ > Fe3+.