Progressive iron overload enhances chemically mediated tumor promotion in murine skin

Regulation of Epidermal Ferritin Expression Influences Systemic Iron Homeostasis

Absorption of dietary iron is largely regulated by the liver hormone hepcidin, which is released under conditions of iron overload and inflammation. Although hepcidin-dependent regulation of iron uptake and circulation is well-characterized, recent studies have suggested that the skin may play an important role in iron homeostasis, including transferrin receptor-mediated epidermal iron uptake and direct hepcidin production by keratinocytes. In this study, we characterized direct keratinocyte responses to conditions of high and low iron. We observed potent iron storage capacity by keratinocytes in vitro and in vivo and the effects of iron on epidermal differentiation and gene expression associated with inflammation and barrier function. In mice, systemic iron was observed to be coupled to epidermal iron content. Furthermore, topical inflammation, as opposed to systemic inflammation, resulted in a primary iron-deficiency phenotype associated with low liver hepcidin. These studies suggest a role for keratinocytes and epidermal iron storage as regulators of iron homeostasis with direct contribution by the cutaneous inflammatory state.

Epidemiological and nonclinical studies investigating effects of iron in carcinogenesis--a critical review

The efficacy and tolerability of intravenous (i.v.) iron in managing cancer-related anemia and iron deficiency has been clinically evaluated and reviewed recently. However, long-term data in cancer patients are not available; yet, long-term i.v. iron treatment in hemodialysis patients is not associated with increased cancer risk. This review summarizes epidemiological and nonclinical data on the role of iron in carcinogenesis. In humans, epidemiological data suggest correlations between certain cancers and increased iron exposure or iron overload. Nonclinical models that investigated whether iron can enhance carcinogenesis provide only limited evidence relevant for cancer patients since they were typically based on high iron doses as well as injection routes and iron formulations which are not used in the clinical setting. Nevertheless, in the absence of long-term outcome data from prospectively defined trials in i.v. iron-treated cancer patients, iron supplementation should be limited to periods of concomitant anti-tumor treatment.

Natural polyamine inhibits mouse skin inflammation and macrophage activation

OBJECTIVE

Natural polyamines are some of the most abundant polycationic molecules in eukaryotic cells, regulating gene expression. Polyamines have been reported to possess anti-inflammatory activities in many model inflammation systems. However, there is no report on their role in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced dermal edema.

METHODS

Mouse ear edema was induced by TPA. Edema biopsies were investigated using H&E staining. Levels of nitric oxide (NO) were determined using the Griess reaction. Tumor necrosis factor α (TNFα) and interleukin (IL)-1β levels in cell supernatants were measured by TNFα and IL-1β ELISA kits.

RESULTS

Spermidine and spermine caused significant decreases in ear thickness, water content, and neutrophil infiltrations in comparison with negative control (p < 0.05). External polyamines reduced the levels of inflammatory mediators such as NO, TNFα, and IL-1β in lipopolysaccharide (LPS)-stimulated RAW264.7 murine macrophages. Spermine had a higher inhibitory effect on the production of cytokines such as IL-1β and TNFα in LPS-stimulated murine macrophages compared to other polyamines.

CONCLUSION

Our findings clearly demonstrated that polyamines are involved in the anti-inflammatory effect by reducing dermal edema thickness and other inflammatory mediators like NO and cytokines in a dose-dependent manner.

Skin iron deposition characterises lipodermatosclerosis and leg ulcer

BACKGROUND

It is commonly reported that chronic venous disease (CVD) increases the skin iron content in which the excess is stored as haemosiderin. Despite increasing interest in the role of haemosiderin in venous ulceration, no study has systematically evaluated the occurrence of iron overload in the limbs of patients with CVD.

PURPOSE

To evaluate skin haemosiderin deposition in relation to the presence and severity of skin changes in CVD legs designated according to the clinical, etiologic, anatomic and pathophysiologic (CEAP) classification.

METHODS

A total of 85 skin biopsies were taken from the medial aspect of 49 limbs with CVD of CEAP clinical stages C2, C3, C4 and C6. The content of ferric ions was assessed by Perl's Prussian Blue (PPB) stain.

RESULTS

No haemosiderin deposition was found in normal skin of C2, C3 and C4A legs, in less severe regions of pigmentation and in some parts of more severely affected limbs. Haemosiderin was always present in lipodermatosclerotic skin and ulcers. Occasionally, haemosiderin was found in the apparently normal perilesional skin of C4b and C6 legs. The regenerating dermis at the base of healing ulcers showed none or light haemosiderin deposition.

CONCLUSION

Iron overload is not present in the less severe stages of skin damage due to CVD but lipodermatosclerosis and leg ulcers are always accompanied by haemosiderin deposition. In fact, no severe skin changes occur in CVD legs until iron overload occurs. Our results are in agreement with previous reports suggesting that a genetic inability to counteract skin iron overload is present in these patients. A more detailed analysis of disordered iron metabolism should be undertaken in CVD patients.

Real-time observation of the effect of iron on receptor-mediated endocytosis of transferrin conjugated with quantum dots

The optical properties of antiphotobleaching and the advantage of long-term fluorescence observation of quantum dots are fully adopted to study the effects of iron on the endocytosis of transferrin. Quantum dots are labeled for transferrin and endocytosis of transferrin in HeLa cells is observed under the normal state, iron overloading, and an iron-deficient state. In these three states, the fluorescence undergoes a gradual process of first dark, then light, and finally dark, indicating the endocytosis of transferrin. The fluorescence intensity analysis shows that a platform emerges when fluorescence changes to a certain degree in the three states. Experienced a same period of time after platform, the fluorescence strength of cells in the normal state is 1.2 times the first value, and the iron-deficiency state is 1.4 times, but the iron overloading state was 0.85 times. We also find that the average fluorescence intensity in cells detected by the spectrophotometer in the iron-deficiency state is almost 7 times than that in a high iron state. All this proves that iron overloading would slow the process, but iron deficiency would accelerate endocytosis. We advance a direct observational method that may contribute to further study of the relationship of iron and transferrin.

Correlation of iron and colon adenomas

BACKGROUND AND OBJECTIVE

Better colon cancer screening guidelines are needed. This study was conducted to explore the relationship between serum transferrin saturation (as iron is a potential carcinogen) and presence of colon adenomas. This may aid to evolve better colon cancer screening guidelines.

METHODS

This study is a retrospective review of computer records. Patients who had colonoscopy and iron studies done between May 1996 and December 2003 were included in the study. The adjusted odds ratio, derived from multiple logistic regression analysis, was used to measure the association between transferrin saturation and colon adenomas.

RESULTS

Complete data were available for 124 subjects. The adjusted odds ratio, for predicting the presence of polyp in those patients with transferrin saturation above the median was 10.9 (CI 4.0-29.5, P<0.001). A one percent increase in transferrin saturation was associated with a 1.07 increase the odds of adenoma (CI 1.03-1.11, P<0.001).

CONCLUSIONS

Iron levels are directly linked to presence of colon polyps, and might help in evolving better screening guidelines.

Trace element concentration in primary liver cancers--a systematic review

BACKGROUND

The incidence of primary liver cancer varies between countries. Many of the etiological factors contributing to the geographical variations in incidence are unknown. Development of hepatocellular carcinoma has been linked to levels of trace elements. This review summarizes the evidence associating HCC with trace elements.

METHODS

MEDLINE, EMBASE, and CENTRAL databases were searched. Various inclusion and exclusion criteria were applied to select the articles for inclusion. Data extraction was performed using a custom designed data extraction form.

RESULTS

A total of 12,344 references were identified. Duplicates, 1,597, were excluded. Clearly irrelevant references, 10,676, were excluded through reading titles and abstracts. Some references (59) were excluded by applying the exclusion criteria. Twelve studies including 646 patients and measuring iron content (8), copper content (11), zinc (9), and selenium (2) qualified for the review. Although a meta-analysis was not possible due to heterogeneity between the studies, a clear pattern of distribution of the trace elements was discernible.

CONCLUSION

Iron and zinc content are lower in HCC than in surrounding tissues or normal controls. Copper content is lower in HCC than in surrounding tissues and cirrhotic controls. Epidemiological and physiological reasons for the trace element alterations should be further investigated.

A new deletion defect leading to ?-thalassaemia in a large Dutch Caucasian family

alpha-thalassaemia is a common inherited haemoglobin disorder that can cause only mild symptoms in carriers and is often either not diagnosed or mistaken for iron deficiency anaemia in the Netherlands. Although considered rare in North-Europeans, we also regularly observe common and rare defects in this population. It is important to be alert for the mild symptoms of these carriers because compound heterozygous and homozygous combinations can result in intermediate, severe or fatal disease in the progeny of healthy carriers. Using a new technical application, a novel alpha degrees -thalassaemia deletion was recently detected in our laboratories in a propositus of a large Dutch Caucasian family. We report the phenotypic and molecular study of this new form of alpha(o)-thalassaemia (called--(OH)alpha-thalassaemia deletion), which was observed in 10 of the 19 individuals studied in the index family. Our results indicate that the frequency of these unsuspected alpha(o)-thalassaemia defects is probably underestimated in the Netherlands.

Trace element concentration in metastatic liver disease: a systematic review

BACKGROUND

There are conflicting reports about the levels of trace elements in secondary liver cancers. This review summarises the evidence associating secondary liver tumours with trace elements.

METHODS

MEDLINE, EMBASE and CENTRAL databases were searched for the period up to January 2006 using a formal search strategy. Various inclusion and exclusion criteria were applied to select the articles for inclusion. Data extraction was performed using a custom designed data extraction form.

RESULTS

A total of 6917 references were identified. About 1359 duplicates were excluded using EndNote. About 5529 clearly irrelevant references were excluded through reading titles and abstracts. Of these 24 references were excluded by applying the exclusion criteria. Five studies including 239 patients and measuring iron content (2), copper content (4) and zinc (3) qualified for the review. Both studies on iron, three studies on copper and all the studies on zinc used quantitative methods to determine mineral content. A meta-analysis was performed using the random effects model.

CONCLUSION

Copper and zinc content are lower in secondary liver cancer compared to livers from healthy patients. Iron, copper and zinc content are lower in liver secondaries compared to the normal tissues surrounding the secondaries. Reasons and implications for the trace element alterations should be further investigated.

Inhibition of the TPA-induced cutaneous inflammation and hyperplasia by EC-SOD

This study reports the roles of extracellular superoxide dismutase (EC-SOD) in the cutaneous inflammation and hyperplasia with 12-O-tetradecanoylphorbol-3-acetate (TPA) application in EC-SOD transgenic mice (Tg EC-SOD). Topical double TPA treatment induced the various inflammatory changes including the epidermal thickness, elevated the PCNA-labeling index, the edema formation, and increased production of hydrogen peroxide (H2O2) in wild type mice (WT). These changes were markedly suppressed in TPA-treated Tg EC-SOD. The expressions of the inflammatory cytokines, IL-1alpha and IL-1beta, were reduced in the TPA-treated Tg EC-SOD compared with those in TPA-treated WT. The expression of IL-1alpha was significantly increased in the skin of TPA-treated WT, especially in the basal and suprabasal layers, but it was restricted focally in basal layer of the skin of TPA-treated Tg EC-SOD. The number of infiltrating inflammatory cells and the IL-1beta expressing cells was obviously reduced in TPA-treated Tg EC-SOD in comparison with TPA-treated WT. The result suggests that EC-SOD might play an important role in the suppression of TPA-induced cutaneous inflammation and epidermal hyperplasia by regulating the expression of IL-1alpha and IL-1beta, although the mechanisms remain to be elucidated.

Stratum-specific expression of human transferrin receptor increases iron in mouse epidermis

Epidermal desquamation accounts for 20% of the body's iron loss each day. Yet, little is known about how iron content in epidermis is regulated. To test the importance of the transferrin receptor in regulating iron content in epidermis, we created transgenic mice that have stratum-specific expression of the human transferrin receptor. The keratin 14 promoter targeted the receptor primarily to basal, proliferating keratinocytes; the involucrin (Inv) promoter targeted the receptor to suprabasal, differentiating keratinocytes. There were age- and site-dependent differences in iron content in the epidermis and hair. In both types of transgenic mice, epidermal iron content increased with age and at 8 weeks was 2-3-fold greater in transgenic mice compared to littermate controls. Iron was increased up to 2-fold in hair of keratin 14-human transferrin receptor (hTfR) transgenics and 30% in Inv-hTfR transgenics. No gross or histological changes were seen in transgenic animals with increased iron in the epidermis. Ferritin expression, which was low in normal epidermis, was greatly increased in both transgenic lines, indicating that it is the likely depot for the extra iron in these animals. These data show that control of transferrin receptor expression is sufficient to regulate iron content in proliferating or differentiating keratinocytes in the epidermis.

Iron in skin of mice with three etiologies of systemic iron overload

In human hemochromatosis, tissue toxicity is a function of tissue iron levels. Despite reports of skin toxicity in hemochromatosis, little is known about iron levels in skin of individuals with systemic iron overload. We measured skin iron and studied skin histology in three mouse models of systemic iron overload: mice with a deletion of the hemochromatosis (Hfe) gene, mice fed a high iron diet, and mice given parenteral injections of iron. In Hfe(-/-) mice, iron content in the epidermis and dermis was unexpectedly the same as in Hfe(+/+) mice, and there were no histological abnormalities detected after 30 wk. A high iron diet produced increased iron in the epidermis of both normal and Hfe(-/-) animals; a high diet increased iron in the dermis only in Hfe(-/-) mice. Increased skin iron was not associated with other histological changes, even after 19 wk. Parenteral administration of iron produced increased iron in the epidermis and dermis, and gave the skin a bronze hue. These results show that the amount and distribution of iron in the skin depends on the etiology of iron overload. It appears that neither Hfe deletion nor elevated skin iron alone can account for cutaneous manifestations reportedly seen in humans with hereditary hemochromatosis.