Substrate specificity of glycoside hydrolase family 1 ß-glucosidase AtBGlu42 from Arabidopsis thaliana and its molecular mechanism.

Plants possess many glycoside hydrolase family 1 (GH1) ß-glucosidases, which physiologically function in cell wall metabolism and activation of bioactive substances, but most remain uncharacterized. One GH1 isoenzyme AtBGlu42 in Arabidopsis thaliana has been identified to hydrolyze scopolin using the gene deficient plants, but no enzymatic properties were obtained. Its sequence similarity to another functionally characterized enzyme Os1BGlu4 in rice suggests that AtBGlu42 also acts on oligosaccharides. Here, we show that the recombinant AtBGlu42 possesses high kcat/Km not only on scopolin, but also on various ß-glucosides, cellooligosaccharides, and laminarioligosaccharides. Of the cellooligosaccharides, cellotriose was the most preferred. The crystal structure, determined at 1.7 Å resolution, suggests that Arg342 gives unfavorable binding to cellooligosaccharides at subsite +3. The mutants R342Y and R342A showed the highest preference on cellotetraose or cellopentaose with increased affinities at subsite +3, indicating that the residues at this position have an important role for chain length specificity.

Transcriptional Suppression of Diabetic Nephropathy with Novel Gene Silencer Pyrrole-Imidazole Polyamides Preventing USF1 Binding to the TGF-ß1 Promoter.

Upstream stimulatory factor 1 (USF1) is a transcription factor that is increased in high-glucose conditions and activates the transforming growth factor (TGF)-ß1 promoter. We examined the effects of synthetic pyrrole-imidazole (PI) polyamides in preventing USF1 binding on the TGF-ß1 promoter in Wistar rats in which diabetic nephropathy was established by intravenous administration of streptozotocin (STZ). High glucose induced nuclear localization of USF1 in cultured mesangial cells (MCs). In MCs with high glucose, USF1 PI polyamide significantly inhibited increases in promoter activity of TGF-ß1 and expression of TGF-ß1 mRNA and protein, whereas it significantly decreased the expression of osteopontin and increased that of h-caldesmon mRNA. We also examined the effects of USF1 PI polyamide on diabetic nephropathy. Intraperitoneal injection of USF1 PI polyamide significantly suppressed urinary albumin excretion and decreased serum urea nitrogen in the STZ-diabetic rats. USF1 PI polyamide significantly decreased the glomerular injury score and tubular injury score in the STZ-diabetic rats. It also suppressed the immunostaining of TGF-ß1 in the glomerulus and proximal tubules and significantly decreased the expression of TGF-ß1 protein from kidney in these rats. These findings indicate that synthetic USF1 PI polyamide could potentially be a practical medicine for diabetic nephropathy.

Contribution of TGF-ß1 and Effects of Gene Silencer Pyrrole-Imidazole Polyamides Targeting TGF-ß1 in Diabetic Nephropathy.

TGF-ß1 has been known to induce diabetic nephropathy with renal fibrosis and glomerulosclerosis. DNA-recognized peptide compound pyrrole-imidazole (PI) polyamides as novel biomedicines can strongly bind promoter lesions of target genes to inhibit its transcription. We have developed PI polyamide targeting TGF-ß1 for progressive renal diseases. In the present study, we evaluated the contribution of TGF-ß1 in the pathogenesis of diabetic nephropathy, and examined the effects of PI polyamide targeting TGF-ß1 on the progression of diabetic nephropathy in rats. For in vitro experiments, rat renal mesangial cells were incubated with a high (25 mM) glucose concentration. Diabetic nephropathy was established in vivo in eight-week-old Wistar rats by intravenously administering 60 mg/kg streptozotocin (STZ). We examined the effects of PI polyamide targeting TGF-ß1 on phenotype and the growth of mesangial cells, in vitro, and the pathogenesis of diabetic nephropathy in vivo. High glucose significantly increased expression of TGF-ß1 mRNA, changed the phenotype to synthetic, and increased growth of mesangial cells. STZ diabetic rats showed increases in urinary excretions of protein and albumin, glomerular and interstitial degenerations, and podocyte injury. Treatment with PI polyamide targeting TGF-ß1 twice weekly for three months improved the glomerular and interstitial degenerations by histological evaluation. Treatment with PI polyamide improved podocyte injury by electron microscopy evaluation. These findings suggest that TGF-ß1 may be a pivotal factor in the progression of diabetic nephropathy, and PI polyamide targeting TGF-ß1 as a practical medicine may improve nephropathy.

Preclinical Study of DNA-Recognized Peptide Compound Pyrrole-Imidazole Polyamide Targeting Human TGF-ß1 Promoter for Progressive Renal Diseases in the Common Marmoset.

Pyrrole-imidazole (PI) polyamides are novel gene silencers that strongly bind the promoter region of target genes in a sequence-specific manner to inhibit gene transcription. We created a PI polyamide targeting human TGF-ß1 (hTGF-ß1). To develop this PI polyamide targeting hTGF-ß1 (Polyamide) as a practical medicine for treating progressive renal diseases, we examined the effects of Polyamide in two common marmoset models of nephropathy. We performed lead optimization of PI polyamides that targeted hTGF-ß1 by inhibiting in a dose-dependent manner the expression of TGF-ß1 mRNA stimulated by PMA in marmoset fibroblasts. Marmosets were housed and fed with a 0.05% NaCl and magnesium diet and treated with cyclosporine A (CsA; 37.5 mg/kg/day, eight weeks) to establish chronic nephropathy. We treated the marmosets with nephropathy with Polyamide (1 mg/kg/week, four weeks). We also established a unilateral urethral obstruction (UUO) model to examine the effects of Polyamide (1 mg/kg/week, four times) in marmosets. Histologically, the renal medulla from CsA-treated marmosets showed cast formation and interstitial fibrosis in the renal medulla. Immunohistochemistry showed strong staining of Polyamide in the renal medulla from CsA-treated marmosets. Polyamide treatment (1 mg/kg/week, four times) reduced hTGF-ß1 staining and urinary protein excretion in CsA-treated marmosets. In UUO kidneys from marmosets, Polyamide reduced the glomerular injury score and tubulointerstitial injury score. Polyamide significantly suppressed hTGF-ß1 and snail mRNA expression in UUO kidneys from the marmosets. Polyamide effectively improved CsA- and UUO-associated nephropathy, indicating its potential application in the prevention of renal fibrosis in progressive renal diseases.

Effect of Sucroferric Oxyhydroxide on Fibroblast Growth Factor 23 Levels in Hemodialysis Patients.

OBJECTIVE: This study investigated the effects of sucroferric oxyhydroxide on fibroblast growth factor (FGF)-23 and dose reduction of erythropoiesis-stimulating agents (ESA) and intravenous saccharated ferric oxide in hemodialysis patients. METHODS: In this prospective, open-label, parallel-group, multicenter trial involving patients receiving lanthanum carbonate hydrate, eligible patients were randomized to a sucroferric oxyhydroxide group or a control group. Hemoglobin, serum phosphate, FGF-23, iron, and ferritin levels, as well as transferrin saturation, doses of intravenous saccharated ferric oxide and ESA administered, and the erythropoietin responsiveness index (ERI) were monitored for 24 weeks. RESULTS: Sixty-eight eligible patients were allocated to receive sucroferric oxyhydroxide (n = 34) or serve as controls (n = 34). Data for 31 patients in the sucroferric oxyhydroxide group and 32 in the control group were analyzed. Serum phosphate was equally well controlled in both groups. In the sucroferric oxyhydroxide group, intact FGF-23 levels decreased significantly from baseline at the end of the study (p = 0.01) and there was a significant difference compared with the control group (p = 0.035). Required doses of ESA and ERI were significantly reduced in the sucroferric oxyhydroxide group decreased significantly. The dose of intravenous saccharated ferric oxide required in the sucroferric oxyhydroxide group was significantly lower than that at baseline (p = 0.006) and in the control group (p = 0.003). CONCLUSIONS: Treatment of hyperphosphatemia with sucroferric oxyhydroxide was effective in patients on hemodialysis, resulting in decreased serum FGF-23 levels and a reduction in the required dose of saccharated ferric oxide.