Hemojuvelin-mediated hepcidin induction requires both bone morphogenetic protein type I receptors ALK2 and ALK3.

ABSTRACT: Hemojuvelin (HJV) is a glycosylphosphatidylinositol-anchored protein of the repulsive guidance molecule family acting as a bone morphogenetic protein (BMP) coreceptor to induce the hepatic iron regulatory protein hepcidin. Hepcidin causes ubiquitination and degradation of the sole known iron exporter ferroportin, thereby limiting iron availability. The detailed signaling mechanism of HJV in vivo has yet to be investigated. In the current manuscript, we used an established model of adeno-associated virus (AAV)-mediated liver-specific overexpression of HJV in murine models of hepatocyte-specific deficiency of the BMP type I receptors Alk2 or Alk3. In control mice, HJV overexpression increased hepatic Hamp messenger RNA (mRNA) levels, soluble HJV (sHJV), splenic iron content (SIC), as well as phosphorylated small mothers against decapentaplegic protein (pSMAD1/5/8) levels. In contrast, in Alk2fl/fl;Alb-Cre and Alk3fl/fl;Alb-Cre mice, which present with moderate and severe iron overload, respectively, the administration of AAV-HJV induced HJV and sHJV. However, it did not rescue the iron overload phenotypes of those mice. Serum iron levels were induced in Alk2fl/fl;Alb-Cre mice after HJV overexpression. In phosphate-buffered saline-injected Alk3fl/fl;Alb-Cre mice, serum iron levels and the expression of duodenal ferroportin remained high, whereas Hamp mRNA levels were decreased to 1% to 5% of the levels detected in controls. This was reduced even further by AAV-HJV overexpression. SIC remained low in mice with hepatocyte-specific Alk2 or Alk3 deficiency, reflecting disturbed iron homeostasis with high serum iron levels and transferrin saturation and an inability to induce hepcidin by HJV overexpression. The data indicate that ALK2 and ALK3 are both required in vivo for the HJV-mediated induction of hepcidin.

Paclitaxel pre-medication: A comparison of two steroid pre-medication protocols.

Purpose To evaluate and compare the rate of hypersensitivity reactions between two low-dose steroid pre-medication regimens for paclitaxel-based treatments. Methods This was a single-center, retrospective, descriptive study, comparing the incidence of hypersensitivity reactions in two different dexamethasone pre-medication regimens that took place between July 2013 to December 2014. Patients who were paclitaxel-naïve with a diagnosis of breast or gynecological cancers were included. Patients in the early termination protocol were pre-medicated with a standard pre-medication regimen and if tolerated with no hypersensitivity reaction occurrence, all pre-medications were discontinued after the first two infusions. Patients in the low-dose steroid continuation protocol were pre-medicated with lower doses of dexamethasone, and if the infusion was tolerated with no hypersensitivity reaction, dexamethasone doses were further reduced after the first two infusions. Results A total of 120 patients were included for data analysis. The hypersensitivity reaction rate in the early termination protocol group was 7% (4 out of 60 patients). The hypersensitivity reaction rate in the low-dose continuation protocol group was 5% (3 out of 60 patients). All hypersensitivity reactions occurred during the first infusion, with no hypersensitivity reactions occurring once the dexamethasone pre-medications were discontinued or dose-reduced. All of the patients who experienced a hypersensitivity reaction were successfully re-challenged with paclitaxel and were able to continue their therapy uninterrupted. Conclusion Discontinuing dexamethasone pre-medication altogether after two uneventful infusions or decreasing the dose of dexamethasone paclitaxel pre-medication are both safe alternatives to high-dose steroid pre-medications recommended in product labeling.