HIF1α-Dependent Induction of TFRC by a Combination of Intestinal Inflammation and Systemic Iron Deficiency in Inflammatory Bowel Disease

Abstract

Background and Aims: Iron deficiency (ID) is a frequent extra-intestinal manifestation in patients with Inflammatory Bowel Disease (IBD), who often do not respond to iron supplementation. Iron is a cofactor for hydroxylases that suppress the hypoxia-inducible factor-1α (HIF1α), a transcription factor regulating iron homeostasis. We hypothesized that iron deficiency affects mucosal HIF1α activity in IBD.Methods: IBD patients (n = 101) were subdivided based on iron status (ferritin levels or transferrin saturation) and systemic inflammation (C-reactive protein levels). 154 corresponding ileal and colonic biopsies were analyzed for differential expression of 20 HIF1α pathway-associated genes and related to iron and inflammation status. In vitro expression of selected HIF1α pathway genes were analyzed in wild-type and HIF1A-null Caco-2 cells.Results: Gene expression of the mucosal HIF1α pathway was most affected by intestinal location and inflammatory status. Especially, ileal mucosal TFRC expression, encoding the transferrin receptor TFR1, was increased in inflamed tissue (p < 0.001), and further enhanced in ID. Accordingly, TFRC expression in inflamed tissue associated negatively with serum iron levels, which was not observed in the non-inflamed mucosa. The HIF1α pathway agonist DMOG increased TFRC expression in Caco-2 cells, which was blunted in HIF1A-null cells.Conclusion: We demonstrate that inflammation and anatomical location primarily determine HIF1α pathway activation and downstream TFRC expression in the intestinal mucosa. IBD patients with ID may benefit from treatment with HIF1α-agonists by 1) increasing TFRC-mediated iron absorption in non-inflamed tissue and 2) decreasing mucosal inflammation, thereby improving their responsiveness to oral iron supplementation.

Faecalibacterium prausnitzii promotes intestinal epithelial IL-18 production through activation of the HIF1α pathway

“…We propose that the increase in gene expression of both HIF1A and IL18 in inflamed biopsies is primarily driven by pathophysiological hypoxia, which is installed during inflammation in the intestinal mucosa (Fagundes and Taylor, 2017;Brown et al, 2020;Fagundes et al, 2022). Nonetheless, activation of the HIF1α pathway has been mechanistically linked to gut mucosal health, both in the context of prevention and recovery from intestinal inflammation.…”

“…Reads were aligned to the From the RNA sequencing data, expression levels of IL18, HIF1A, HIF2A, HIF-hydroxylases (EGLN1, EGLN2 and EGLN3), VHL and HIF1AN were selected for analysis. In addition, HIF1α and HIF2α scores (quotients calculated using the mRNA levels of either HIF-1α or HIF-2α divided by the sum total of the negative regulators of these factors), were calculating as described before (Brown et al, 2020;Fagundes et al, 2022).…”

“…Descriptive statistics of the patient cohort is described in Table 1. Mucosal IL18 expression in 760 intestinal mucosa biopsies from 371 IBD patients was obtained from an in-house dataset of RNA sequencing dataset (Hu et al, 2022) and was correlated to the abundance of bacterial genera, as established by 16S rRNA gene sequencing of the same biopsies. A significant positive correlation between IL18 expression and mucosal levels of prominent butyrate-producing bacteria was observed, including Ruminococcaceae, Ruminococcus species, Agathobacter, and Faecalibacterium (Table 2).…”

Hypoxia induces a glycolytic complex in intestinal epithelial cells independent of HIF-1-driven glycolytic gene expression

“…sgRNAs for HIF-1A (sequence 5′-GATGGTAAGCCTCATCACAG-3′) were designed via Benchling© online platform and cloned in pLenti-sgRNA backbone (Addgene, 71409), as described by ref. 41 . For generating a stable Caco-2-iCas9 cell line, cells were incubated with 1 mL lentivirus suspension, supplemented with 8 μg/mL polybrene (Sigma-Aldrich, TR-1003) before selection with Neomycin (2 mg/mL) for 7 d. For introduction of sgRNA, Caco-2-iCas9 cells were incubated with 1 mL lentivirus containing sgRNA (empty vector or against HIF-1A), supplemented with 8 μg/mL polybrene.…”

Transendothelial electrical resistance measurement by a microfluidic device for functional study of endothelial barriers in inflammatory bowel disease

“…Transferrin receptor protein 1 (TFRC) was significantly upregulated by more than five-fold in IBD exosomes. Transferrin receptor levels are reportedly increased in inflammatory tissues, while HIF a Frontiers in Bioengineering and Biotechnology frontiersin.org pathway agonists may benefit such patients by increasing non inflammatory tissue-mediated iron absorption and reducing mucositis (Fagundes et al, 2022). Annexin A5 (ANXA5), a calcium and phospholipid-binding protein, was significantly downregulated in IBD exosomes.…”