Background & Aims HFE and transferrin receptor 2 (TFR2) are each necessary for the normal relationship between body iron status and liver hepcidin expression. In murine Hfe and Tfr2 knockout models of hereditary hemochromatosis (HH), signal transduction to hepcidin via the bone morphogenetic protein 6 (Bmp6)/Smad1,5,8 pathway is attenuated. We examined the effect of dietary iron on regulation of hepcidin expression via the Bmp6/Smad1,5,8 pathway using mice with targeted disruption of Tfr2, Hfe, or both genes. Methods Hepatic iron concentrations and mRNA expression of Bmp6 and hepcidin were compared with wild-type mice in each of the HH models on standard or iron-loading diets. Liver phospho-Smad (P-Smad)1,5,8 and Id1 mRNA levels were measured as markers of Bmp/Smad signaling. Results While Bmp6 expression was increased, liver hepcidin and Id1 expression were decreased in each of the HH models compared with wild-type mice. Each of the HH models also demonstrated attenuated P-Smad1,5,8 levels relative to liver iron status. Mice with combined Hfe/Tfr2 disruption were most affected. Dietary iron loading increased hepcidin and Id1 expression in each of the HH models. Compared with wild-type mice, HH mice demonstrated attenuated (Hfe knockout) or no increases in P-Smad1,5,8 levels in response to dietary iron loading. Conclusions These observations demonstrate that Tfr2 and Hfe are each required for normal signaling of iron status to hepcidin via Bmp6/Smad1,5,8 pathway. Mice with combined loss of Hfe and Tfr2 up-regulate hepcidin in response to dietary iron loading without increases in liver BMP6 mRNA or steady-state P-Smad1,5,8 levels.

Pulmonary hypertension (PH), a risk factor for mortality in sickle cell disease (SCD), has pathologic features of both pulmonary arterial hypertension (PAH) and PH related to left-sided heart disease (LHD) suggesting a link between these two entities. We hypothesized that both are characterized by endothelial dysfunction and increased adhesion molecule expression. SCD patients and normal volunteers underwent a screening questionnaire, echocardiogram, and blood donation for preparation of platelet-poor plasma. PAH was defined as a tricuspid regurgitant jet (TRJ) velocity ≥ 2.5 m/sec and/or the presence of isolated right ventricular hypertrophy or decreased systolic function. LHD was defined as either left-sided systolic/diastolic dysfunction or significant valvular disease. Plasma vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), P-and E-selectin, nitric oxide (NO x ), erythropoietin, and vascular endothelial growth factor (VEGF) levels were assayed by enzyme-linked immunoassay. Forty-three percent of sickle cell anemia (HbSS) and 28% of hemoglobin SC disease (HbSC) disease patients had PAH. Additionally, 10-15% of SCD patients had LHD. VCAM-1 levels were significantly increased in HbSS patients compared with HbSC patients and normal volunteers. VCAM-1 and P-selectin levels correlated positively with TRJ velocity in HbSS patients (r 5 0.45, P 5 0.03, r 5 0.2, P 5 0.05, respectively). ICAM-1, E-selectin, NO x , erythropoietin, and VEGF levels were similar across subject groups. PH is common in SCD and, at times, due to LHD. Increased VCAM-1 and P-selectin expression was associated with TRJ elevation regardless of etiology suggesting a similar effect on endothelial gene expression and possibly providing a pathologic link between PAH and PH related to LHD in SCD. Am. J. Hematol. 83:547-553, 2008. V

Inflammation may play an important role in the pathophysiology of sickle cell disease (SCD), and recent studies have identified the 70-kDa heat shock protein (Hsp70) as an important mediator of inflammatory responses. Here we demonstrate a significant increase in circulating serum Hsp70 level in SCD during vaso-occlusive crisis (VOC) as compared with baseline steady-state levels (P < 0.05) and a significant increase in Hsp70 levels in SCD at baseline compared with normal controls (P < 0.05). Taken together, these results indicate that circulating serum Hsp70 might be a marker for VOC in SCD. Am.