Hypertension is a leading contributor to cardiovascular mortality worldwide. Despite this, its underlying mechanism(s) and the role of excess salt in cardiorenal dysfunction are unclear. Previously, we have identified cross-talk between mineralocorticoid receptor (MR), a nuclear transcription factor regulated by the steroid aldosterone, and the small GTPase Rac1, which is implicated in proteinuric kidney disease. We here show that high-salt loading activates Rac1 in the kidneys in rodent models of salt-sensitive hypertension, leading to blood pressure elevation and renal injury via an MR-dependent pathway. We found that a high-salt diet caused renal Rac1 upregulation in salt-sensitive Dahl (Dahl-S) rats and downregulation in salt-insensitive Dahl (Dahl-R) rats. Despite a reduction of serum aldosterone levels, salt-loaded Dahl-S rats showed increased MR signaling in the kidneys, and Rac1 inhibition prevented hypertension and renal damage with MR repression. We further demonstrated in aldosterone-infused rats as well as adrenalectomized Dahl-S rats with aldosterone supplementation that salt-induced Rac1 and aldosterone acted interdependently to cause MR overactivity and hypertension. Finally, we confirmed the key role of Rac1 in modulating salt susceptibility in mice lacking Rho GDP-dissociation inhibitor α. Therefore, our data identify Rac1 as a determinant of salt sensitivity and provide insights into the mechanism of salt-induced hypertension and kidney injury.

ABSTRACTgpl3O, a signal-transducing receptor component of interleukin 6 (IL-6), associates with an IL-6 and IL-6 receptor (IL-6R) complex and transduces signals. To examine the role of gpl3O signaling in the expansion of human hemopoietic progenitor cells, we tested the effects of a recombinant soluble human and/or combination with other cytokines on purified human umbilical cord blood CD34+ cells, using methylcellulose clonal assay and suspension culture in the presence or absence of serum. A combination of sIL-6R and IL-6 (sIL-6R/IL-6), but not sIL-6R or IL-6 alone, was found to dramatically stimulate expansion of hemopoietic progenitor cells as well as CD34+ cells in the presence of stem cell factor. Significant generation of multipotential hemopoietic progenitors over a period of 3 weeks in suspension culture and efficient formation of colonies, especially multilineage and blast cell colonies, in methylcellulose assay supplemented with a combination of sIL-6R/IL-6 together with stem cell factor were observed in serum-containing and serum-free culture. Addition of antigpl3O monoclonal antibodies or anti-IL-6R monoclonal antibodies to the above cultures dose-dependently inhibited the expansion of progenitor cells in suspension culture and also completely blocked the formation of multilineage colonies in methylcellulose culture. These findings demonstrated that the significant expansion of human primitive hemopoietic progenitors could be achieved with the gpl3O and c-Kit signalings initiated by the sIL-6R/IL-6 complex in the presence of stem cell factor and suggested the possible application of this method for ex vivo expansion of CD34+ cells for bone marrow transplantation.

SummaryWe recently demonstrated that stimulation of gp 130 by a combination of soluble interleukin 6 receptor (slL-6R) and IL-6 but not IL-6 alone significantly stimulates the ex vivo expansion of primitive hematopoietic progenitors and the generation of erythroid cells from human CD34 + cells in the presence of stem cell factor (SCF). Here, we show that gp130 is found low positively on most CD34 + cells, whereas IL-6R is expressed on only 30-50% of these cells. Although most of the colonies generated from FACS| CD34+IL-6R + cells were granulocyte/macrophage (GM) colonies, CD34+IL-6R -cells gave rise to various types of colonies, including erythroid bursts, GM, megakaryocytes, and mixed colonies in methylcellulose culture with a combination of IL-6, slL-6R, and SCF. Similar results were obtained in culture supplemented with a combination of IL-3, IL-6, SCF, granulocyte colony-stimulating factor, erythropoietin, and thrombopoietin. A limiting dilution analysis of long-term culture-initiating cells (LTC-IC) showed that the CD34+IL-6P, -cells contained a larger number of LTC-IC than did the CD34+IL-6R + cells. In a serum-free suspension ofCD34+IL-61:( -cells, the addition of slL-6P, to the combination oflL-6 and SCF dramatically increased the total and multipotential progenitors, whereas CD34+IL-6R. + cells failed to do so under the same conditions. These results indicate that most of the erythroid, megakaryocytic, and primitive human hematopoietic progenitors are included in the IL-61:(-populations, and the activation of gp130 on these progenitors can be achieved by a complex of IL-6-slL-6R, but not by IL-6 alone. The present culture system using IL-6, slL-6R., and SCF may provide a novel approach for ex vivo expansion of human primitive hematopoietic progenitors.

Summary.Congenital amegakaryocytic thrombocytopenia (CAMT) is an uncommon disorder in newborns and infants, characterized by isolated thrombocytopenia and megakaryocytopenia in the first year without physical anomalies. The defect of thrombopoiesis is not well understood. Recently, thrombopoietin (TPO), the ligand for the c-mpl receptor, was cloned. Accumulating evidence from in vitro and in vivo studies indicate that TPO plays a key role in the regulation of megakaryocytopoiesis. In this study we examined the effect of TPO on megakaryocyte colony formation from a patient with CAMT using a plasma-containing methylcellulose clonal culture. The in vitro results demonstrated a defective response to TPO in megakaryocyte colony formation from bone marrow mononuclear cells (MNC) of the patient, although interleukin-3 (IL-3) but not stem cell factor (SCF) induced only a small number of megakaryocyte colonies. These findings indicated that thrombocytopenia in CAMT could not be corrected by administration of TPO in vitro.Additionally, clonal cultures containing SCF, IL-3, IL-6 and erythropoietin showed decreased numbers of erythroid and myelocytic progenitors in the bone marrow of the patient. The serum TPO level measured by enzyme-linked immunosorbent assay was significantly higher than that in healthy controls. By PCR, marrow MNC from healthy children and from a patient with essential thrombocytosis expressed c-mpl mRNA, whereas no c-mpl mRNA was detected in marrow MNC from the patient with CAMT. There was no difference in the CD34 expression and c-kit mRNA between the CAMT patient and healthy children. The results of this study suggest that the pathophysiology in CAMT may be a defective response to TPO in haemopoietic cells through impaired expression of c-mpl mRNA.

Potential effects of aerobic and resistance training in peritoneal dialysis (PD) patients have been partially elucidated. We investigated effects of a home-based exercise program on physical functioning and health-related quality of life (HRQOL) in PD patients. Patients were randomly assigned to exercise (n = 24) and usual care (n = 23) groups. The exercise patients performed aerobic exercise thrice weekly and resistance training twice weekly at home for 12 weeks. The usual care patients received no specific intervention. The distance in incremental shuttle walking test significantly improved in the exercise group compared with the usual care group ( P = 0.02). Among the HRQOL subscales assessed using the Kidney Disease Quality of Life-Short Form questionnaire, kidney disease component summary ( P = 0.03), physical role functioning ( P = 0.01), emotional role functioning ( P < 0.01), and role/social component summary ( P < 0.01) significantly improved in the exercise group. Moreover, serum albumin was significantly maintained in the exercise group ( P = 0.03). There were no reported adverse events associated with the intervention. To our knowledge, this is the first randomized controlled trial to indicate the beneficial effects of a 12-week home-based exercise program exclusively in PD patients.

SummaryErythropoietin (EPO) is the primary humoral regulator of erythropoiesis and no other factor has previously been reported to support proliferation and terminal maturation oferythroid cells from hemopoietic stem cells. Here we show that stimulation ofglycoprotein (gp130) by a combination of recombinant human soluble intedeukin 6 receptor (slL-6R) and IL-6 but not slL-6R or IL-6 alone can support proliferation, differentiation, and terminal maturation of erythroid cells in the absence of EPO from purified human CD34 + cells in suspension culture containing stem cell factor (SCF). A number of erythroid bursts and mixed erythroid colonies also developed in methylcellulose culture under the same combination. The addition ofanti-gpl30 monoclonal antibodies but not anti-EPO antibody to the same culture completely abrogated the generation of erythroid cells. These results clearly demonstrate that mature erythroid cells can be emerged from hemopoietic progenitors without EPO in vitro. Together with the previous reports that human sera contain detectable levels of slL-6R, IL-6, and SCF, current data suggest that gp130 signaling in association with c-kit activation may play a role in human erythropoiesis in vivo.

Kawarazaki H, Ando K, Fujita M, Matsui H, Nagae A, Muraoka K, Kawarasaki C, Fujita T. Mineralocorticoid receptor activation: a major contributor to salt-induced renal injury and hypertension in young rats. Am J Physiol Renal Physiol 300: F1402-F1409, 2011. First published April 6, 2011 doi:10.1152/ajprenal.00691.2010.-Excessive salt intake is known to preferentially increase blood pressure (BP) and promote kidney damage in young, salt-sensitive hypertensive human and animal models. We have suggested that mineralocorticoid receptor (MR) activation plays a major role in kidney injury in young rats. BP and urinary protein were compared in young (3-wk-old) and adult (10-wk-old) uninephrectomized (UNx) Sprague-Dawley rats fed a high (8.0%)-salt diet for 4 wk. The effects of the MR blocker eplerenone on BP and renal injury were examined in the high-salt diet-fed young UNx rats. Renal expression of renin-angiotensinaldosterone (RAA) system components and of inflammatory and oxidative stress markers was also measured. The effects of the angiotensin receptor blocker olmesartan with or without low-dose aldosterone infusion, the aldosterone synthase inhibitor FAD286, and the antioxidant tempol were also studied. Excessive salt intake induced greater hypertension and proteinuria in young rats than in adult rats. The kidneys of young salt-loaded rats showed marked histological injury, overexpression of RAA system components, and an increase in inflammatory and oxidative stress markers. These changes were markedly ameliorated by eplerenone treatment. Olmesartan also ameliorated salt-induced renal injury but failed to do so when combined with low-dose aldosterone infusion. FAD286 and tempol also markedly reduced urinary protein. UNx rats exposed to excessive salt at a young age showed severe hypertension and renal injury, likely primarily due to MR activation and secondarily due to angiotensin receptor activation, which may be mediated by inflammation and oxidative stress. salt sensitivity; aldosterone; oxidative stress; renin-angiotensin OBSERVATIONAL STUDIES HAVE suggested that increased blood pressure (BP) in childhood correlates with increased BP in adulthood (36). Hypertension is closely related to kidney dysfunction, which can cause increased BP. Therefore, both BP control and maintenance of kidney health at a young age may be critical for BP management later in life.Salt consumption among very young children has increased in developed countries at a faster rate than in developing countries (9,28,33). It is believed that high salt (HS) intake during prepuberty contributes to high BP later in life (1, 23). In addition, increased BP resulting from excessive salt consumption has been shown to be enhanced in the young in several animal models of salt-sensitive (SS) hypertension (35). We previously demonstrated that in Dahl SS rats, an SS hypertension model, HS intake at a young age accelerates the development of kidney injury and hypertension (12). Interestingly, salt restriction during infant weaning has been reported to lo...

Photoionization efficiency (PIE) curves were measured for sandwich vanadium-benzene clusters, V n -(benzene) n+1 (n ) 1-5), which were produced by the reaction of laser-vaporized vanadium atoms with benzene vapor. A two-rod laser vaporization source was used for enhancing the production of the larger clusters. The second lowest ionization energies of the sandwich clusters were probed experimentally for the first time. The PIE curves of the sandwich clusters clearly present evidence that the clusters take a quasi-band electronic structure which results from a one-dimensional sandwich structure.