Inhibition of SOC/Ca2+/NFAT pathway is involved in the anti-proliferative effect of sildenafil on pulmonary artery smooth muscle cells

<p>Abstract</p> <p>Background</p> <p>Sildenafil, a potent phosphodiesterase type 5 (PDE5) inhibitor, has been proposed as a treatment for pulmonary arterial hypertension (PAH). The mechanism of its anti-proliferative effect on pulmonary artery smooth muscle cells (PASMC) is unclear. Nuclear translocation of nuclear factor of activated T-cells (NFAT) is thought to be involved in PASMC proliferation and PAH. Increase in cytosolic free [Ca²⁺] ([Ca²⁺]_i) is a prerequisite for NFAT nuclear translocation. Elevated [Ca²⁺]_iin PASMC of PAH patients has been demonstrated through up-regulation of store-operated Ca²⁺channels (SOC) which is encoded by the transient receptor potential (TRP) channel protein. Thus we investigated if: 1) up-regulation of TRPC1 channel expression which induces enhancement of SOC-mediated Ca²⁺influx and increase in [Ca²⁺]_iis involved in hypoxia-induced PASMC proliferation; 2) hypoxia-induced promotion of [Ca²⁺]_ileads to nuclear translocation of NFAT and regulates PASMC proliferation and TRPC1 expression; 3) the anti-proliferative effect of sildenafil is mediated by inhibition of this SOC/Ca²⁺/NFAT pathway.</p> <p>Methods</p> <p>Human PASMC were cultured under hypoxia (3% O₂) with or without sildenafil treatment for 72 h. Cell number and cell viability were determined with a hemocytometer and MTT assay respectively. [Ca²⁺]_iwas measured with a dynamic digital Ca²⁺imaging system by loading PASMC with fura 2-AM. TRPC1 mRNA and protein level were detected by RT-PCR and Western blotting respectively. Nuclear translocation of NFAT was determined by immunofluoresence microscopy.</p> <p>Results</p> <p>Hypoxia induced PASMC proliferation with increases in basal [Ca²⁺]_iand Ca²⁺entry via SOC (SOCE). These were accompanied by up-regulation of TRPC1 gene and protein expression in PASMC. NFAT nuclear translocation was significantly enhanced by hypoxia, which was dependent on SOCE and sensitive to SOC inhibitor SKF96365 (SKF), as well as cGMP analogue, 8-brom-cGMP. Hypoxia-induced PASMC proliferation and TRPC1 up-regulation were inhibited by SKF and NFAT blocker (VIVIT and Cyclosporin A). Sildenafil treatment ameliorated hypoxia-induced PASMC proliferation and attenuated hypoxia-induced enhancement of basal [Ca²⁺]_i, SOCE, up-regulation of TRPC1 expression, and NFAT nuclear translocation.</p> <p>Conclusion</p> <p>The SOC/Ca²⁺/NFAT pathway is, at least in part, a downstream mediator for the anti-proliferative effect of sildenafil, and may have therapeutic potential for PAH treatment.</p

Sildenafil Reduces Insulin-Resistance in Human Endothelial Cells

The efficacy of Phosphodiesterase 5 (PDE5) inhibitors to re-establish endothelial function is reduced in diabetic patients. Recent evidences suggest that therapy with PDE5 inhibitors, i.e. sildenafil, may increase the expression of nitric oxide synthase (NOS) proteins in the heart and cardiomyocytes. In this study we analyzed the effect of sildenafil on endothelial cells in insulin resistance conditions in vitro

Improved Hole Transport by p-InxGa1-xN Layer in Multiple Quantum Wells of Visible LEDs

Studied is the effect of indium (In) mole fraction in p-InxGa(1-x)N: Mg layers with 0 &lt;= x(In) &lt;= 0.035 on hole injection and transport behaviors in InGaN/GaN multiple quantum wells (MQWs) using dual-wavelength and triple-wavelength active regions. Electro-optical characteristics of light-emitting diodes containing p-layers with different In content and with silicon doping in selected QW barriers (QWBs) are compared to evaluate hole transport in the active region. The results show that enhanced hole transport and corresponding more uniform distribution of holes across the MQW region are achieved by increasing x(In) in the p-InxGa1-xN:Mg layer, possibly due to modification in energy of holes by a potential barrier between the p-InGaN and GaN QWB

Distinct QTLs are linked to cardiac left ventricular mass in a sex-specific manner in a normotensive inbred rat intercross

Genetic mapping of the progeny of an F2 intercross between WKY and WKHA rats had previously allowed us to detect male-specific linkage between locus Cm24 and left ventricular mass index (LVMI). By further expanding that analysis, we detected additional loci that were all linked to LVMI in a sexspecific manner despite their autosomal location. In males, we detected one additional locus (Lvm8) on Chromosome 5 (LOD = 3.4), the two loci Lvm13 (LOD = 4.5) and Lvm9 (LOD = 2.8) on Chromosome 17, and locus Lvm10 (LOD = 4.2) on Chromosome 12. The locus Lvm13 had the same boundaries as locus Cm26 previously reported by others using a different cross. None of these loci showed linkage to LVM in females. In contrast, we identified in females the novel locus Lvm11 on Chromosome 15 (LOD = 2.8) and locus Lvm12 (LOD = 2.7) that had the same boundaries on Chromosome 3 as locus Cm25 detected previously by others using a cross of other normotensive strains. In prepubertal males, there were no differences in the width of cardiomyocytes from WKY and WKHA rats, but cardiomyocytes from WKHA became progressively wider than that of WKY as sexual maturation progressed. Altogether, these results provide evidence that distinct genes may influence LVMI of rats in a sexdependent manner, maybe by involving sex-specific interactions of sex steroids with particular genes involved in the determination of LVMI and/or cardiomyocyte width.Bastien Llamas, Zhibin Jiang, Marie-Line Rainville, Sylvie Picard and Christian F. Descheppe