Thus, hepcidin expression during inflammation needs to be finely regulated. regulates Tmprss6 expression directly by binding to a Stat5 element located on the Tmprss6 promoter. Importantly, our results spotlight the functional role of inflammatory modulation ofTMPRSS6expression in the regulation of hepcidin. TMPRSS6 inhibition via decreased STAT5 phosphorylation may be an additional mechanism by which inflammation stimulates hepcidin expression to regulate iron homeostasis and immunity. == Introduction == The transmembrane serine protease matriptase-2, encoded by theTMPRSS6gene, is usually expressed in the liver and is a negative regulator of hepcidin expression[1]. In humans, mutations inTMPRSS6lead to a genetic disorder characterized by an iron refractory iron deficiency anemia (IRIDA) that is unresponsive to oral iron treatment but partially responsive to parenteral iron therapy[2]. The importance ofTMPRSS6in the control of iron homeostasis and normal erythropoiesis in humans has been highlighted by genome-wide association studies. These studies identified commonTMPRSS6variants associated with hematological parameters and serum iron concentration[3]. Hepcidin is usually a peptide hormone produced by the liver that controls iron absorption at the intestinal level, and iron release from macrophages and hepatocytes. Hepcidin binds to the plasma membrane iron exporter ferroportin and induces its endocytosis and proteolysis, preventing release of iron into the plasma[4]. It is now well established that hepcidin expression is regulated by the BMP-SMAD pathway in response Quarfloxin (CX-3543) to iron variation[5]. Mutated forms of matriptase-2 are unable to cleave membrane hemojuvelin[6], resulting in a stimulation of the BMP-SMAD signaling pathway and an inappropriately high hepcidin expression. Recently, matriptase-2 has been demonstrated to be induced by acute iron deprivation[7], hypoxia[8], and erythropoietin[9], and by activators of hepcidin expression such as BMP6 and iron[10]. It is likely that matriptase-2 is usually upregulated by these activators of hepcidin expression as a negative feedback mechanism to control excessive increases in hepcidin. Thus, matriptase-2 has a pleiotropic role in hepcidin regulation in response to a number of stimuli. Inflammation is usually a potent stimulator of hepcidin expression. The upregulation of hepcidin in response to inflammation promotes hypoferremia through the downregulation of ferroportin iron export activity. Hepcidin induction has been hypothesized to have Quarfloxin (CX-3543) a protective role in contamination by sequestering iron from invading pathogens. As an antimicrobial peptide, hepcidin itself may also have additional functions in Ptgfr immunity[11]. IL-6 is a major hepatic regulator of the acute-phase response to inflammatory stimuli including hepcidin induction[12]. IL-6 binding to the IL-6 receptor leads to activation of Janus kinases that phosphorylate STAT3. Translocation of STAT3 to the nucleus results in upregulation of hepcidin expression through STAT3 responsive element around the hepcidin promoter[13]. In response to inflammatory stimuli, the BMP-SMAD pathway is also required to activate hepcidin[14], which may involve the activation of activin B[15]. Although hepcidin expression is usually induced directly by inflammatory stimuli, we hypothesized that additional fine tuning of its expression may be required to maintain body iron balance through the regulation of other genes. Specifically, we hypothesized thatTMPRSS6expression could be regulated by inflammation in order to participate in the regulation of hepcidin. In this study, we show thatTMPRSS6expression is regulated by inflammation via STAT5. == Methods == == Cell Culture == Hep3B cells (HB-8064, ATCC, Manassas, VA) were cultured in ATCC-formulated EMEM (ATCC) supplemented with 10% fetal bovine serum (FBS, ATCC). Hepa16 cells (CRL-1830, ATCC) were cultured in ATCC-formulated DMEM (ATCC) supplemented with 10% fetal bovine serum (FBS, ATCC). == Treatment of Hep3B Cells with IL-6 == Hep3B Quarfloxin (CX-3543) cells (1.2105per well) were seeded onto 24-well plates. Twenty-four hours later, the culture medium was switched Quarfloxin (CX-3543) to 1% FBS medium. After 7 hours, cells were treated with recombinant human IL-6 (5, 20, 100 ng/mL, 16 h) (R&D Systems) and then.