Differing effects of two iron compounds on experimental arthritis, TNF-α levels and immune response in mice

iTRAQ and PRM-Based Proteomic Analysis Provides New Insights into Mechanisms of Response to Triple Therapy in Patients with Rheumatoid Arthritis

Background

Approximately 30% of patients with rheumatoid arthritis (RA) respond poorly to combination therapy of multiple drugs. The molecular mechanisms of different responses to methotrexate + leflunomide + infliximab therapy in patients with RA were explored in this study.

Methods

Infliximab was administered to patients with RA whose disease activity score was higher than 5.1 after 1 month of combination therapy with methotrexate and leflunomide. After 14 weeks of undergoing triple therapy, patients with RA were classified as responders and non-responders. Protein profiles at baseline and 14th week were investigated via isobaric tags for relative and absolute quantification (iTRAQ), and proteins with significant differences ≥1.2 folds change or ≤0.8 folds change were defined as differentially expressed proteins (DEPs). Overlapping DEPs between responders and non-responders were confirmed by parallel reaction monitoring (PRM). Bioinformatic analyses were performed for DEPs.

Results

The results revealed 5 non-responders (NRs) and 15 responders (Rs). iTRAQ analysis indicated 13 overlapping DEPs and included 6 opposite change DEPs such as testicular tissue protein Li 70, cofilin 1, fibrinogen beta chain, galectin-10, serotransferrin (TF) and albumin. The difference in serotransferrin between responders and non-responders confirmed by PRM was significant. Verification by PRM indicated that TF was elevated in the Rs group and was reduced in the NRs group. Bioinformatic analysis indicated that serotransferrin was involved in the hypoxia-inducible factor-1 pathway and ferroptosis.

Conclusion

Serotransferrin-related molecular mechanism may be a new direction to study refractory RA.

Mutual interaction between iron homeostasis and obesity pathogenesis

Obesity is identified as an important medical problem. One of the pathologic conditions observed in obesity is systemic iron deficiency and hypoferremia. Along with a large number of studies indicating disturbed iron homeostasis in obesity, recent data indicate a cause-effect relationship between iron status and obesity-related pathologies. The primary objective of the article is to consider two aspects of the iron-obesity interplay: (1) the mechanisms leading to impaired iron balance, and (2) the pathways of iron participation in obesity-related pathogenesis. While considering disturbance of iron homeostasis in obesity, a number of potential mechanisms of hypoferremia are proposed. At the same time, the inflammation of obesity and obesity-related hepcidin and lipocalin 2 hyperproduction seem to be the most probable reasons of obesity-related hypoferremia. Oversecretion of these proteins leads to iron sequestration in reticuloendothelial system cells. The latter also leads to increased adipose tissue iron content, thus producing preconditions for adverse effects of local iron overload. Being a redox-active metal, iron is capable of inducing oxidative stress as well as endoplasmic reticulum stress, inflammation and adipose tissue endocrine dysfunction. Iron-mediated mechanisms of toxicity may influence aspects of obesity pathogenesis possibly even leading to obesity aggravation. Thus, a mutual interaction between disturbance in iron homeostasis and obesity pathogenesis is proposed. All sides of this interaction should be considered to design new therapeutic approaches to the treatment of disturbed iron homeostasis in obesity.

Acute immunomodulatory effects of iron polyisomaltosate in rats

Anti-anaemic drug ferric-sorbitol citrate showed immunomodulatory effects, activating NF-kappaB in peritoneal macrophages, which consequently secrete tumour necrosis factor-alpha (TNF-alpha). TNF-alpha activates NF-kappaB in spleen cells. The aim of this study was to investigate the effect of iron polyisomaltosate, an iron (Fe(3+)) compound, on serum iron, interleukin-6 (IL-6) and serotonin (5-HT) concentration, neutrophil activity, and NF-kappaB activation in peritoneal macrophages and spleen cells in rats. Female Wistar rats were injected i.p. with 7.5mg iron/kg of iron polyisomaltosate 1.5, 3, 6, 24 and 48h before sacrifice. Serum iron, 5-HT and IL-6 concentration was determined by colorimetric, spectrofluorimetric and ELISA methods, neutrophil activity by a chemiluminescence assay, and NF-kappaB expression/activation by a Dot-Blot method. Iron polyisomaltosate significantly increased serum iron and 5-HT concentrations during the first 6h, IL-6 levels 3 and 6h, and diminished respiratory burst of granulocytes 1.5h after the injection. Iron polyisomaltosate stimulated activation of p65, p50 and RelB subunits of NF-kappaB in the peritoneal macrophages after 6h, and RelB subunit was additionally increased after 24 and 48h. In the spleen cells iron polyisomaltosate stimulated p65 subunit after 48h and RelB subunit after 24h. The results showed time-dependent immunomodulatory effects of iron polyisomaltosate. These effects might be achieved via induction of the intracellular signalling for NF-kappaB activation in peritoneal macrophages and later in spleen cells, together with increase of serum 5-HT, and IL-6 but with diminished respiratory burst of granulocytes. Iron polyisomaltosate presumably activated reactive oxygen species resulting in the stimulation of the acute phase reactants in the liver.

Effect of Ferric Sorbitol Citrate (FSC) Administration on NF‐κB in Macrophages and Spleen Cells of Rats

Interaction of iron metabolism and the immune system is complex and pathological changes in one system affect the other. Ferric sorbitol citrate (FSC), non-toxic compound of ferric ions with sorbitol and citrate. has immunomodulatory effect in treated mice. We investigated an effect of FSC on NF-kappaB expression/activation in peritoneal macrophages and spleen cells of rats. TNF-alpha concentrations in sera of control and FSC intraperitoneal (i.p.) treated Wistar rats were measured by ELISA. Furthermore, peritoneal macrophages (PM) were counted and splenocytes were isolated. PM and splenocytes were lysed and their cytoplasmic and nuclear fractions were separated by centrifugation. The influence of FSC on NF-kappaB expression and/or activity as well as expression of its inhibitor IkappaB-alpha was measured by Western blot. 1.5 and three hours after FSC treatment TNF-alpha level in sera was significantly (p < or = 0.05) increased. Activation of transcription factor NF-kappaB in PM was detected three hours after treatment, followed by significant increment in PM number. In splenocytes NF-kappaB was activated six and 48 hours after FSC application. The results indicate that, after i.p. application, FSC acts as a modulator of the immune system activating NF-kappaB in PM. PM consequently secrete TNF-alpha that activates NF-kappaB in splenocytes.