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Biomedical subjects

E Imai

Publications and source records attributed to E Imai.

At least 91 records · Page 5Linked to original sources
PubMed1997

Gene therapy for the treatment of renal disease: prospects for the future.

Human gene therapy has been progressing at a remarkable rate, but information from basic research on gene therapy is still generally lacking. Gene transfer to the kidney has been attempted using various strategies, yet we still have no satisfactory and reliable gene transfer technique to the kidney. More effective and more selective gene transfer techniques are required for gene therapy, as well as for use as a research tool, to improve understanding of the pathophysiology of renal diseases.

Adenoviridae↗
PubMed1997

Osmotic regulation of amino acids and system A transport in Madin-Darby canine kidney cells.

The effects of hypertonicity on the intracellular amino acid content and system A transport activity were studied in Madin-Darby canine kidney (MDCK) cells. Total content of 20 amino acids increased from 274 to 689 nmol/mg protein after 8 h of hypertonicity (500 mosmol/ kg), remaining almost constant until after 6 days of hypertonicity. The content of neutral amino acids increased from 77 to 307 and 395 nmol/mg protein after 8 h and 6 days of hypertonicity, respectively, accounting for 73% of the increased amount of total amino acids. In the hypertonic MDCK cells, system A transport activity, measured by Na+-dependent 2-(methylamino)isobutyric acid (MeAIB) uptake, increased approximately 60-fold relative to the uptake in isotonic cells. MeAIB was taken up primarily on the basal side in the isotonic MDCK cells cultured on permeable supports. Extracellular hypertonicity stimulated the MeAIB uptake predominantly on the basal side. These results indicated that amino acids, especially neutral amino acids, can function as volume-regulating osmolytes and that the stimulation of system A activity appears to contribute to the accumulation of neutral amino acids in hypertonic MDCK cells.

Amino Acids↗
PubMed1997

Effects of inhibition of myo-inositol transport on MDCK cells under hypertonic environment.

To investigate the role of myo-inositol under hypertonic conditions, we examined the effects of inhibition of myo-inositol transport in Madin-Darby canine kidney (MDCK) cells using an analog of myo-inositol, 2-O,C-methylene-myo-inositol (MMI). We first characterized the inhibitory effects of MMI on myo-inositol transport in MDCK cells. The Na+-dependent component of [3H] myo-inositol uptake was inhibited by MMI in a concentration-dependent manner, although MMI did not inhibit the activities of the betaine transporter and system A neutral amino acid transporter. We found decreased affinity for myo-inositol in the presence of MMI, whereas the maximal velocity (Vmax) of the transporter did not change. Thus MMI behaves as a competitive inhibitor of myo-inositol transport with a relatively high inhibition constant (K(i)) value (1.6 mM). Myo-inositol content in hypertonic MDCK cells was markedly reduced in the presence of 5 mM MMI, but MMI itself did not accumulate in these cells. The hypertonic cells began to detach in the presence of MMI 3 days after increasing medium osmolality, whereas MMI did not affect the cells in isotonic medium. We also examined the effects of MMI on colony-forming efficiency of MDCK cells. MMI decreased colony-forming efficiency in a concentration-dependent manner, and addition of myo-inositol returned the efficiency to the value without MMI. Addition of betaine also increased colony-forming efficiency in the presence of MMI. These results indicate that myo-inositol plays an important role in survival and growth under hypertonic environment.

Animals↗
PubMed1997

Osmolarity in renal medulla of transgenic mice regulates transcription via 5'-flanking region of canine BGT1 gene.

Betaine is a major compatible osmolyte accumulated in the mammalian kidney medulla and in Madin-Darby canine kidney cells in response to hypertonicity. The accumulation is the result of an increase in maximal velocity of the Na(+)- and Cl-coupled betaine transporter designated BGT1. We have previously cloned the canine BGT1 gene and identified a tonicity-responsive enhancer element (TonE) in its 5'-flanking region. Here we report studies of transgenic mice that have in their genome 2.4 kb of the 5'-flanking region of the canine BGT1 gene in front of a chloramphenicol acetyl-transferase (CAT) reporter. Expression of CAT mRNA was detected only in the renal medulla and was increased by experimental manipulations that increase the tonicity of the renal medulla and decreased by manipulations that decrease medullary tonicity. We conclude that the 2.4-kb 5'-flanking region of the BGT1 gene mediates an increase in transcription in response to hyperosmolarity in the renal medulla.

Animals↗
PubMed1997

A young man with acute renal failure and severe loin pain.

The first case of exercise-induced acute renal failure (EIARF) is reported measuring the blood flow and arterial resistance in the kidney by pulsed Doppler ultrasound. A 20-year-old Japanese male suffered from severe loin pain and non-oliguric acute renal failure after strenuous exercise. Serum myoglobin and creatine phosphokinase were normal and urinary myoglobin was not detectable. The Doppler pattern in several segmental arteries showed a slow end-diastolic velocity (EV) and a high resistance index (RI), indicating increased renal vascular resistance, which suggested severe renal vasoconstriction. Three days later, the EV had apparently increased and the RI normalized in accordance with improvement of renal function. The ultrasound Doppler technique is useful for the detection of a decrease in arterial blood flow on real time and for the diagnosis of EIARF.

Acute Kidney Injury↗
PubMed1997

[A case of recurrent IgA nephropathy following renal transplantation under tacrolimus (FK506)].

We report a case of recurrent IgA nephropathy following renal transplantation under tacrolimus (FK506). A 23-year-old female who had been diagnosed with IgA nephropathy was transplanted from her HLA two-mismatched mother under tacrolimus, prednisolone and azathioprine. Two years after transplantation, suddenly she noticed macroscopic hematuria. At that time, functional renal deterioration (serum creatinine: 2.3 mg/dl) and mild proteinuria were observed. Allograft biopsy disclosed acute cellular rejection. She was administered a bolus injection of methylprednisolone, 15-deoxyspergualin and anti-lymphocyte globulin. However, the response to the treatment was poor. A transplant biopsy revealed focal segmental glomerulosclerosis by PAS staining and granular IgA and C3 deposits on immunofluorescence examination. There was no sign of acute rejection and toxicity by tacrolimus. We diagnosed recurrent IgA nephropathy. At the present time, she has normal urinalysis and renal function is stable (serum creatinine: 1.9 mg/dl). No proteinuria was observed after total dosage of immunosuppressants was increased. Although recurrence of IgA nephropathy in renal allograft is frequent, allograft dysfunction is rare. However, IgA nephropathy has several types with different prognosis. For functional renal deterioration after renal transplantation, we should consider not only an acute rejection or the toxicity of immunosuppressants but also recurrent nephropathy.

Adult↗
PubMed1997

TCV-116 inhibits interstitial fibrosis and HSP47 mRNA in rat obstructive nephropathy.

Unilateral ureteral obstruction (UUO) is a well established disease model leading to fibrosis of the obstructed kidney. In this model, involvement of enhanced renin-angiotensin system in the pathogenesis of interstitial fibrosis has been demonstrated. A 47-kDa heat-shock protein (HSP47) was originally identified as a collagen-binding stress protein, and is currently considered to be a collagen-specific molecular chaperone that plays a pivotal role during the biosynthesis and secretion of procollagen from endoplasmic reticulum. To test if HSP47 is involved in interstitial fibrosis in UUO, we examined the expression of HSP47 mRNA in rat UUO kidneys after 12 hours. 1, 4, 7 days of obstruction. HSP47 mRNA expression was significantly increased as early as 12 hours after obstruction and was sustained at the increased level until seven days. Type I collagen mRNA significantly increased after four days of UUO. Fibrotic changes of interstitium appeared in Masson's trichrome stained section after four days. To explore the possible involvement of angiotensin II (Ang II) in HSP47 induction, the effect of Ang II receptor antagonist (TCV-116) and angiotensin converting enzyme inhibitor (lisinopril) was tested. TCV-116 or lisinopril was given to the animals orally once a day at the dose of 10 mg/kg. TCV-116 or lisinopril significantly ameliorated the fibrotic change of interstitium seven days after obstruction. HSP47 and type I collagen mRNA levels in the TCV-116- or lisinopril-treated groups were reduced to about 60% of untreated UUO. A possible involvement of HSP47 in the pathogenesis of interstitial fibrosis in UUO is suggested; however, further investigation is required to identify the signals involved in the induction of HSP47 in UUO.

Angiotensin II↗
PubMed1996

Na+/myo-inositol transport is regulated by basolateral tonicity in Madin-Darby canine kidney cells.

We investigated the effects of change in basolateral osmolality on Na(+)-dependent myo-inositol uptake in Madin-Darby canine kidney cells to test our hypothesis that the Na+/myo-inositol transporter (SMIT), an osmolyte transporter, is mainly regulated by osmolality on the basolateral surface. A significant osmotic gradient between both sides of the epithelium persisted at least 10 h after basolateral osmolality was increased. [3H]myo-inositol uptake increased in a basolateral osmolality-dependent manner. The magnitude of the increase is comparable to that for making both sides hypertonic. Apical hypertonicity also increased the uptake on the basal side, but the magnitude of the increase was significantly smaller than the basolateral or both sides hypertonicity. Betaine-gamma-amino-n-butyric acid transporter activity, measured by [3H]gamma-amino-n-butyric uptake, showed a pattern similar to SMIT activity in response to basolateral hypertonicity. The most plausible explanation for the polarized effect of hypertonicity is that the basal membrane is much more water permeable than the apical membrane. These results seem to be consistent with the localization and regulation of the SMIT in vivo.

Animals↗
PubMed1996

Inhibition of TGF-beta 1 expression by antisense oligonucleotides suppressed extracellular matrix accumulation in experimental glomerulonephritis.

Overproduction of transforming growth factor-beta 1 (TGF-beta 1) has been implicated in the pathogenesis of fibrotic diseases. TGF-beta 1 plays a crucial role in the accumulation of extracellular matrix (ECM) in human and experimental glomerular diseases. However, it remains unclear whether inhibition of TGF-beta 1 overproduction would suppress TGF-beta 1-induced ECM accumulation. To inhibit the overproduction of TGF-beta 1 in experimental glomerulonephritis induced by anti-Thy 1.1 antibody, we introduced antisense oligodeoxynucleotides (ODN) for TGF-beta 1 into the nephritic kidney by the HVJ-liposome-mediated gene transfer method. Sense, scrambled or reverse ODN were also introduced as controls. Transfected ODN accumulated mainly in the nuclei of mesangial cells in the glomeruli of transfected kidneys. In the antisense ODN-transfected rats, a marked decrease in expression of TGF-beta 1 mRNA was confirmed by Northern analysis. Consequently, the expression of TGF-beta 1 protein in the glomerulus was markedly reduced in the antisense ODN-transfected kidney with a comparable effect in preventing glomerular ECM expansion in experimental glomerulonephritis. In contrast, sense, scrambled and reverse ODNs failed to suppress TGF-beta 1 expression and ECM accumulation. Thus, these results suggested that inhibition of TGF-beta 1 overproduction could suppress progression to glomerulosclerosis.

Animals↗
PubMed1996

Expression of betaine transporter mRNA: its unique localization and rapid regulation in rat kidney.

Betaine is a major compatible osmolyte in the renal medulla. It is taken up into cells via the betaine gamma-amino-n-butyric acid transporter (BGT-1). We investigated the localization of BGT-1 mRNA and its acute regulation by NaCl and furosemide administration. In situ hybridization revealed that BGT-1 mRNA is predominantly present in the outer medulla and papilla. Less intense signals were seen in the inner medulla and no signals were found in the cortex. Microscopic examination suggested that intense signals were present in the medullary thick ascending limbs of Henle's loop (MTAL) and the inner medullary collecting ducts (IMCD). A reverse transcription and polymerase chain reaction assay of individual microdissected segments along the nephron confirmed its localization. Intraperitoneal administration of NaCl rapidly increased the signal in the MTAL, and furosemide prevented the increase in BGT-1 mRNA by NaCl loading. In contrast, BGT-1 mRNA in the IMCD is less sensitive to these kinds of acute regulation. These results suggest that BGT-1 expression in the MTAL is rapidly regulated in response to the magnitude of NaCl absorption, as suggested for the expression of Na+/myo-inositol cotransporter.

Aldehyde Reductase↗
PubMed1996

Gene therapy by skeletal muscle expression of decorin prevents fibrotic disease in rat kidney.

There are currently no effective therapies for progressive fibrotic diseases. Recent evidence has implicated overproduction of transforming growth factor-beta1 (TGF-beta1) as a major cause of tissue fibrosis. Furthermore, this evidence implies that inhibitors of TGF-beta1 may be clinically useful as antifibrotic agents. The proteoglycan decorin is a known inhibitor of TGF-beta1. In a rat model of glomerulonephritis we have shown that fibrosis is mediated by TGF-beta1. We report here that transfer of decorin cDNA into rat skeletal muscle increases the amount of decorin messenger RNA and protein present in skeletal muscle and decorin present in kidney, where it has a marked therapeutic effect on fibrosis induced by glomerulonephritis. Transfected glomerulonephritic rats showed a significant reduction in levels of glomerular TGF-beta1 mRNA and TGF-beta1 protein, extracellular matrix accumulation and proteinuria. These results demonstrate the potential of gene therapy as a novel treatment for fibrotic diseases caused by TGF-beta1.

Animals↗
PubMed1996

Antifibrogenic effect of a deletion variant of hepatocyte growth factor on liver fibrosis in rats.

Hepatic fibrosis, which may lead to cirrhosis, is associated with most chronic liver diseases. Current therapies for hepatic fibrosis are, however, generally ineffective. In this report we assessed the efficacy of the treatment of hepatic fibrosis with a naturally occurring deletion variant of hepatocyte growth factor (dHGF). The administration of dHGF increased liver weight and suppressed the increase of hepatic collagen content in rats treated with dimethylnitrosamine (DMN) to induce hepatic fibrosis. Furthermore, dHGF exerted its mitogenic and antifibrogenic activities even after the liver fibrosis had been established with DMN. Northern blot analysis showed that dHGF suppressed the increase of messenger RNA (mRNA) levels of procollagen alpha 2(I), alpha l(III), alpha 1(IV), transforming growth factor beta 1 (TGF-beta1), desmin (a marker of hepatic lipocytes), and alpha-smooth muscle (sm)-actin (a marker of activated hepatic lipocytes). In addition to suppressing the elevated TGF-beta1, mRNA level in hepatic fibrosis, dHGF had a potent ability to decrease TGF-beta1 mRNA level even in a normal liver. Immunohistochemical analysis revealed that desmin-positive cells and alpha-sm-actin-positive cells were increased in the hepatic fibrosis, whereas neither cells were seen in livers of DMN-treated rats given dHGF. We conclude that dHGF prevents and improves the DMN-induced hepatic fibrosis in rats by reducing mRNA levels of procollagens and TGF-beta1, by inhibiting an activation of hepatic lipocytes, and by stimulating liver regeneration. dHGF may be useful for and applicable to the treatment of fibrosis in chronic liver diseases.

Actins↗
PubMed1996

A low-affinity vasopressin V2-receptor gene in a kindred with X-linked nephrogenic diabetes insipidus.

In this study, a mutation in vasopressin Type 2 receptor (V2R) in a patient with hereditary nephrogenic diabetes insipidus (NDI) has been identified and characterized. The sequencing of the V2R gene from the patient revealed that there was a missense mutation (TAT to TGT) resulting in the substitution of 205Tyr for Cys in the putative third extracellular domain. The expression analysis in COS cells showed that the binding affinity of the mutant receptor (KD = 19.8 nM) for arginine vasopressin was much lower than that of the wild-type receptor (KD = 1.8 nM) so that intracellular cAMP production stimulated by arginine vasopressin was impaired in cells with the mutant V2R. From these results, it was concluded that the single amino-acid substitution of V2R is responsible for this familial disease.

Adult↗
PubMed1996

Angiotensin I-converting enzyme insertion/deletion polymorphism: potential significance in nephrology.

Angiotensin I-converting enzyme (ACE) plays a pivotal role in cardiovascular homeostasis and by activating angiotensin I into angiotensin II and inactivating bradykinin. These two peptides play antagonistic roles on the cardiovascular system by regulating vascular tone and vascular smooth muscle cell proliferation. Identification of the ACE gene as a genetic marker for various forms of cardiovascular disease is a recent result of the progress made in molecular biology and genetics. The insertion/deletion (ID) polymorphism of the ACE gene defined by the presence or absence of the 287 base pair Alu sequence situated in intron 16 has been investigated as a possible genetic marker for a variety of cardiovascular disease including myocardial infarction, essential hypertension, cardiomyopathy, and diabetic vascular complications. This paper reviews prior reports and briefly describes our recent study on the association of the ACE I/D polymorphism and antiproteinuric effect of ACE inhibitors in patients with proteinuria.

Cardiovascular Diseases↗
PubMed1996

[Regulation of osmolyte transporter gene expression by tonicity].

In response to exposure to hypertonic environment, cells accumulate small organic solutes termed osmolytes that protect them from the adverse effects of hypertonicity. Some osmolytes (myo-inositol, betaine and taurine) are accumulated by specific transporters. Those transporters have been cloned by expression cloning techniques. Transcription of osmolyte transporters is induced by hypertonicity. In situ hybridization reveals the localization of the Na+/myo-inositol cotransporter and the betaine transporter (BGT1) mRNAs in the kidney. The BGT1 gene was cloned and its 5' flanking region has been characterized A 13 bp tonicity responsive enhancer (TONE) has been identified. Analysis of transgenic mice harboring a 5' flanking region of the BGT1 gene, that included TONE, showed that it provides inducible reporter expression in kidney medulla.

Animals↗