Mice that are fed a high-fat diet display increased hepcidin expression in adipose tissue

Since the discovery that hepcidin is expressed in the adipose tissue of obese subjects, attention has been increasingly focused on alterations in iron homeostasis that are associated with adiposity. We examined the production of hepcidin, the expression of hepcidin-related genes and the iron content of the adipose tissue in obesity using Swiss mice fed a high-fat diet (HFD). The mice were maintained on a control diet or HFD for 12 or 24 wk, and body weight, adiposity and glucose homeostasis were evaluated. The expression of several genes (hepcidin, TfR1, TfR2, DMT1, FT-heavy, ferroportin, IRP-1, IRP-2 and HIF-1) and the protein expression of hepcidin and IL-6 were quantified. The iron level was assessed using a Prussian blue reaction in paraffin-embedded tissue. After 24 wk on the HFD, we observed increases in the levels of hepcidin in the serum and the visceral adipose tissue. The IL-6 levels also increased in the visceral adipose tissue. Adipocytes isolated from the visceral adipose tissues of lean and obese mice expressed hepcidin at comparable levels; however, isolated macrophages from the stromal vascular fraction expressed higher hepcidin levels. Adipose tissues from obese mice displayed increased tfR2 expression and the presence of iron. Our results indicate that IL-6 and iron may affect the signaling pathways governing hepcidin expression. Thus, the mice fed HFD for 24 wk represent a suitable model for the study of obesity-linked hepcidin alterations. In addition, hepcidin may play local roles in controlling iron availability and interfering with inflammation in adipose tissue.

Identification of target genes using gene expression profile of granulocytes from patients with chronic myeloid leukemia treated with tyrosine kinase inhibitors

Differential gene expression analysis by suppression subtractive hybridization with correlation to the metabolic pathways involved in chronic myeloid leukemia (CML) may provide a new insight into the pathogenesis of CML. Among the overexpressed genes found in CML at diagnosis are SEPT5, RUNX1, MIER1, KPNA6 and FLT3, while PAN3, TOB1 and ITCH were decreased when compared to healthy volunteers. Some genes were identified and involved in CML for the first time, including TOB1, which showed a low expression in patients with CML during tyrosine kinase inhibitor treatment with no complete cytogenetic response. In agreement, reduced expression of TOB1 was also observed in resistant patients with CML compared to responsive patients. This might be related to the deregulation of apoptosis and the signaling pathway leading to resistance. Most of the identified genes were related to the regulation of nuclear factor κB (NF-κB), AKT, interferon and interleukin-4 (IL-4) in healthy cells. The results of this study combined with literature data show specific gene pathways that might be explored as markers to assess the evolution and prognosis of CML as well as identify new therapeutic targets.

Altered red cell and platelet adhesion in hemolytic diseases: Hereditary spherocytosis, paroxysmal nocturnal hemoglobinuria and sickle cell disease

OBJECTIVES

Intravascular hemolysis may have important pathophysiological consequences, such as the induction of cellular adhesion and vasculopathy. We compared the adhesive properties of red cells (RBC) and platelets in hereditary spherocytosis (HS), paroxysmal nocturnal hemoglobinuria (PNH) and sickle cell disease (SCD) patients.

DESIGN AND METHODS

The adhesion of RBC and platelets, from patients and healthy subjects, was determined using static adhesion assays. RBC surface markers were characterized by flow cytometry and lactate dehydrogenase (LDH), plasma hemoglobin (pHb) and TNF-α were assayed in serum/plasma samples.

RESULTS

pHb levels were elevated in all three hemolytic diseases, indicating the incidence of intravascular hemolysis. RBC adhesion and TNF-α were augmented in HS and SCD, but not in PNH. Reticulocyte counts were raised in the three diseases, but were higher in HS and SCD than in PNH; high expressions of CD71, CD36 and CD49d were observed on SCD RBC, while CD71 alone was increased on HS and PNH RBC. Splenectomy was associated with reversals of increased pHb, RBC adhesion, reticulocytes, RBC marker expression and inflammation in HS. In contrast, platelet adhesion was elevated in SCD and PNH, but not HS. Platelet adhesion correlated significantly with serum LDH, but not pHb, in the hemolytic disease cohort; interestingly, LDH did not correlate with reticulocytes or pHb levels.

CONCLUSIONS

Results indicate that extravascular, rather than intravascular, hemolysis (and ensuing RBC production) may contribute to elevations in RBC adhesive properties in HS and SCD, while mechanisms peculiar to each disease may augment platelet adhesion in SCD and PNH.

Participation of leptin in the determination of the macrophage phenotype: an additional role in adipocyte and macrophage crosstalk

Macrophages develop into specialized cell types with special functional properties, depending on locally produced stimuli. Adipose tissue macrophages present particular characteristics, such as the M2 cell phenotype, and produce cytokines and chemokines usually produced by M1 cells. Our aim was to study the role of leptin, which is an adipokine produced and released by adipocytes, in the induction of these characteristics in macrophages found in the adipose tissue. Human CD14(+) cells were obtained and maintained in culture with IFN-γ (classical M1 phenotype), IL-4 (alternative M2 phenotype) or leptin for 5 d. Surface marker expression was then analyzed by cytometry. In addition, the release of tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1β, IL-10, IL-1ra, MCP-1, MIP-1α, and RANTES was quantified by ELISA after an LPS stimulus, in the culture supernatant. Macrophages exposed to leptin in culture expressed surface markers that were more similar to the M2 phenotype, but they were able to produce TNF-α, IL-6, IL-1β, IL-1ra, IL-10, MCP-1, and MIP-1α, as observed for M1 cells. Results suggest that leptin strongly contributes to the phenotype observed in macrophages found in adipose tissue.

Design, synthesis, and pharmacological evaluation of novel hybrid compounds to treat sickle cell disease symptoms. part II: furoxan derivatives

Phthalimide derivatives containing furoxanyl subunits as nitric oxide (NO)-donors (3a-g) were designed, synthesized, and evaluated in vitro and in vivo for their potential uses in the oral treatment of sickle cell disease symptoms. All compounds (3a-g) demonstrated NO-donor properties at different levels. Moreover, compounds 3b and 3c demonstrated analgesic activity. Compound 3b was determined to be a promising drug candidate for the aforementioned uses, and it was further evaluated in K562 culture cells to determine its ability to increase levels of γ-globin expression. After 96 h at 5 μM, compound 3b was able to induce γ-globin expression by nearly three times. Mutagenic studies using micronucleus tests in peripheral blood cells of mice demonstrated that compound 3b reduces the mutagenic profile as compared with hydroxyurea. Compound 3b has emerged as a new leading drug candidate with multiple beneficial effects for the treatment of sickle cell disease symptoms and provides an alternative to hydroxyurea treatment.

Therapy with hydroxyurea is associated with reduced adhesion molecule gene and protein expression in sickle red cells with a concomitant reduction in adhesive properties

Propagation of the vaso-occlusive process in sickle cell anaemia (SCA) is a complex process involving the adhesion of steady-state SCA patients red cells and reticulocytes to the vascular endothelium. The effect of hydroxyurea therapy (HUT) on the adhesive properties of sickle cells and the expression of adhesion molecule genes by erythroid cells of SCA individuals is not yet fully understood. The expressions of the CD36 gene and the VLA-4-integrin subunit genes, CD49d (alpha-subunit) and CD29 (beta-subunit), were compared in the reticulocytes of steady-state SCA patients and patients on HUT using real-time PCR. Basal adhesion of red cells from these subjects was also compared using static adhesion assays, as was surface protein expression, using flow cytometry. Basal sickle red cell adhesion to fibronectin was significantly greater than that of normal cells (P < 0.01); in contrast, HUT was associated with significantly lower levels (P < 0.01) of red cell adhesion that were similar to those of control cells; this decrease could not be justified solely by altered reticulocyte numbers in this population. Accordingly, flow cytometry demonstrated that reticulocytes from patients on HUT had significantly lower CD36 and CD49d surface expressions (P < 0.01) and, importantly, significantly lower expressions of the CD36, CD49d and CD29 genes (P < 0.05) than reticulocytes of SCA patients not on HUT. Taken together, data support the hypothesis that HUT reduces the adhesive properties of sickle cells and that this decrease appears to be mediated, at least in part, by a decrease in the gene and, consequently, surface protein expression of adhesion molecules such as VLA-4 and CD36.

Gene expression profiles of erythroid precursors characterise several mechanisms of the action of hydroxycarbamide in sickle cell anaemia

Hydroxycarbamide (HC) (or hydroxyurea) has been reported to increase fetal haemoglobin levels and improve clinical symptoms in sickle cell anaemia (SCA) patients. However, the complete pathway by which HC acts remains unclear. To study the mechanisms involved in the action of HC, global gene expression profiles were obtained from the bone marrow cells of a SCA patient before and after HC treatment using serial analysis of gene expression. In the comparison of both profiles, 147 differentially expressed transcripts were identified. The functional classification of these transcripts revealed a group of gene categories associated with transcriptional and translational regulation, e.g. EGR-1, CENTB1, ARHGAP4 and RIN3, suggesting a possible role for these pathways in the improvement of clinical symptoms of SCA patients. The genes involved in these mechanisms may represent potential tools for the identification of new targets for SCA therapy.