Serotonin enhances the production of type IV collagen by human mesangial cells

Serotonin enhances the production of type IV collagen by human mesangial cells.BackgroundThe plasma concentration of 5-hydroxytryptamine (5-HT) in diabetic patients is higher than that in normal subjects. Since recent reports have demonstrated the presence of 5-HT2A receptor in glomerular mesangial cells, it is possible that 5-HT may be involved in the development of diabetic nephropathy through the 5-HT2A receptor in mesangial cells. Because expansion of the glomerular mesangial lesion is a characteristic feature of diabetic nephropathy, we examined the effect of 5-HT on the production of type IV collagen by human mesangial cells.MethodsHuman mesangial cells were incubated with 5-HT with or without 5-HT receptor antagonists, protein kinase C (PKC) inhibitor or transforming growth factor-β (TGF-β) antibody. Type IV collagen mRNA and protein concentration in medium were measured by Northern blot analysis and enzyme-linked immunosorbent assay (ELISA), respectively. TGF-β mRNA and bioactivity in the medium were measured by Northern blot analysis and bioassay using mink lung epithelial cells, respectively.Results5-HT stimulated the production of type IV collagen by human mesangial cells, which was inhibited by ketanserin and sarpogrelate hydrochloride, 5-HT2A receptor antagonists, but not by ondansetron, a 5-HT3 receptor antagonist. 5-HT increased the bioactivities of both active and total TGF-β. However, the 5-HT-enhanced production of type IV collagen was completely inhibited by an anti-TGF-β antibody. Furthermore, a PKC inhibitor, calphostin C, inhibited the 5-HT-induced increase in type IV collagen secretion, and the activity of membrane PKC was increased by 5-HT. Phorbol ester activated type IV collagen production as well as active and total TGF-β. Calphostin C completely inhibited the 5-HT-enhanced activity of active TGF-β, but did not inhibit exogenous TGF-β-induced increase in type IV collagen secretion.ConclusionsOur results suggest that 5-HT-enhanced production of type IV collagen by human mesangial cells is mediated by activation of PKC and subsequent increase in active TGF-β activity

Electric-field control of interfacial in-plane magnetic anisotropy in CoFeB/MgO junctions

Magnetoelectric coupling in metal/oxide heterostructures has opened up the possibility of controlling magnetization by voltage, i.e., electric field. However, the electric-field excitation of magnetization dynamics in perfectly in-plane and out-of-plane magnetized films have not been demonstrated so far due to zero electric-field torque originating from voltage control of perpendicular magnetic anisotropy. This limits the application of voltage-controlled magnetic anisotropy in magnetic field free control of magnetization dynamics. Here we show that magnetic annealing can induce an interfacial in-plane magnetic anisotropy of CoFeB/MgO junctions, thereby controlling the symmetry of interfacial magnetic anisotropy. The magnetic anisotropy is modulated by applying voltage: a negative bias voltage increases perpendicular magnetic anisotropy, while a positive bias voltage decreases perpendicular magnetic anisotropy and increases the in-plane magnetic anisotropy. Such a control of symmetry of the interfacial magnetic anisotropy by magnetic annealing and its tunability by electric fields is useful for developing purely voltage-controlled spintronic devices

Electric field induced parametric excitation of exchange magnons in a CoFeB/MgO junction

Inspired by the success of field-effect transistors in electronics, electric field controlled magnetization dynamics has emerged as an important integrant in low-power spintronic devices. Here, we demonstrate electric field induced parametric excitation for CoFeB/MgO junctions by using interfacial in-plane magnetic anisotropy (IMA). When the IMA and the external magnetic field are parallel to each other, magnons are efficiently excited by electric field induced parametric resonance. The corresponding wavelengths are estimated to be tuned down to exchange interaction length scales by changing the input power and frequency of the applied voltage. A generalized phenomenological model is developed to explain the underlying role of the electric field torque. Electric field control of IMA is shown to be the origin for excitation of both uniform and parametric resonance modes in the in-plane magnetized sample, a crucial element for purely electric field induced magnetization dynamics. Electric field excitation of exchange magnons, with no Joule heating, offers a good opportunity for developing nanoscale magnonic devices and exploring various nonlinear dynamics in nanomagnetic systems

Electric-field control of interfacial in-plane magnetic anisotropy in CoFeB/MgO junctions

Magnetoelectric coupling in metal/oxide heterostructures has opened up the possibility of controlling magnetization by voltage, i.e., electric field. However, the electric-field excitation of magnetization dynamics in perfectly in-plane and out-of-plane magnetized films have not been demonstrated so far due to zero electric-field torque originating from voltage control of perpendicular magnetic anisotropy. This limits the application of voltage-controlled magnetic anisotropy in magnetic field free control of magnetization dynamics. Here we show that magnetic annealing can induce an interfacial in-plane magnetic anisotropy of CoFeB/MgO junctions, thereby controlling the symmetry of interfacial magnetic anisotropy. The magnetic anisotropy is modulated by applying voltage: a negative bias voltage increases perpendicular magnetic anisotropy, while a positive bias voltage decreases perpendicular magnetic anisotropy and increases the in-plane magnetic anisotropy. Such a control of symmetry of the interfacial magnetic anisotropy by magnetic annealing and its tunability by electric fields is useful for developing purely voltage-controlled spintronic devices