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Biomedical subjects

R Kikkawa

Publications and source records attributed to R Kikkawa.

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

Beraprost sodium, an analogue of prostacyclin, induces the expression of mitogen-activated protein kinase phosphatase and inhibits the proliferation of cultured mesangial cells.

Beraprost sodium, an analogue of prostacyclin, increases intracellular cyclic adenosine monophosphate (cAMP) in cultured glomerular mesangial cells. We examined the effect of beraprost on mesangial cell proliferation. Beraprost was able to inhibit fetal bovine serum-stimulated proliferation of mesangial cells in concentrations enough to increase cellular cAMP. By northern blot analysis, beraprost induced the expression of MKP-1, a mitogen-activated protein kinase phosphatase, in a dose- and time-dependent manner, similarly to dibutyryl cAMP and adrenomedullin. These results indicate that beraprost inhibits the proliferation of mesangial cells and one of the mechanisms might be cAMP-dependent induction of MKP-1.

Animals↗
PubMed1997

Oxidized lipoproteins found in patients with NIDDM stimulate radical-induced monocyte chemoattractant protein-1 mRNA expression in cultured human endothelial cells.

Although oxidized low density lipoprotein (LDL) exists in plasma from diabetic patients, there are few studies on its biological activity. Thus, we investigated the biological potency of LDL plus intermediate density lipoprotein fraction isolated from 12 non-diabetic and 24 non-insulin-dependent diabetic subjects of similar age and body mass index, in order to induce monocyte chemoattractant protein-1 (MCP-1) mRNA expression in cultured human endothelial cells. MCP-1 mRNA content in the cells exposed to the lipoproteins isolated from the diabetic patients was significantly higher than that from the control subjects (p < 0.001). The increment of MCP-1 mRNA content was positively correlated with not only HbA1c (r = 0.58, p < 0.0001) but also lysophosphatidylcholine (LPC) content in the lipoprotein (r = 0.46, p < 0.005) and was negatively correlated with diene formation lag time as a marker of oxidizability of the lipoprotein (r = -0.33, p < 0.05). Treatments of the cells with either 50 mumol/l probucol, 50 mumol/l alpha-tocopherol, or 0.1 mmol/l deferoxamine suppressed the increase in MCP-1 mRNA content induced by diabetic lipoproteins, respectively. Furthermore, the diabetic lipoproteins activated nuclear transcription factor NF-kappa B in the cells, which was inhibited by pre-treatment of cells with 50 mumol/l probucol. These data indicate that oxidatively modified lipoproteins found in diabetic plasma stimulate MCP-1 gene expression in endothelial cells. The LPC content which reflects oxidative modification of lipoprotein is at least a possible marker of biological activity to increase an atherogenic cytokine in endothelial cells.

Antioxidants↗
PubMed1997

Microalbuminuria is not associated with cardiovascular death in Japanese NIDDM.

To evaluate whether the presence of microalbuminuria can predict cardiovascular death in Japanese subjects with non-insulin-dependent diabetes mellitus (NIDDM), we investigated 297 Japanese NIDDM patients with Albustix-negative urine. Patients were divided into two groups, normoalbuminuric (n = 201) and microalbuminuric (n = 96) and followed until death or the end of 1994 (the mean follow-up period was 6.4 years). During the follow-up period, 28 deaths (14 normoalbuminuric and 14 microalbuminuric patients) were confirmed and only 10 deaths were attributed to cardiovascular disease (6 normoalbuminuric and 4 microalbuminuric patients). Although the age- and sex-adjusted mortality rate from all-causes in the microalbuminuric group was significantly higher than that in the normoalbuminuric group (13.5 vs. 8.2 per 1000 person-years: P < 0.05), the mortality rate from cardiovascular disease was not significantly different between two groups (3.4 vs. 3.3 per 1000 person-years). On age-adjusted Cox proportional hazards analysis. HbA1c and triglyceride were independent risk factors in mortality from cardiovascular disease, while microalbuminuria was not associated with cardiovascular death. These results indicate that, unlike Caucasians, the presence of microalbuminuria can not predict cardiovascular death in Japanese subjects with NIDDM.

Aged↗
PubMed1997

Distribution of heparin-binding EGF-like growth factor protein and mRNA in the normal rat kidneys.

Heparin-binding EGF-like growth factor (HB-EGF), a newly discovered potent mitogen and chemoattractant for smooth muscle cells, is a member of the EGF superfamily and binds to EGF receptors. To investigate the role of HB-EGF in the kidney, we determined the distribution of HB-EGF immunohistochemically in normal rat kidneys. The localization of mRNA expression was also studied by in situ hybridization, using a synthesized digoxigenin-labeled anti-sense riboprobe of HB-EGF. Immunohistochemical and in situ hybridization studies revealed that the tubular epithelial cells of the S3 segment of the outer stripe in the outer medulla were the predominant renal source of HB-EGF. In addition, in the immunohistochemical analysis, HB-EGF was ubiquitously present in the epithelial cells of the proximal tubules and the arterial smooth muscle cells, while HB-EGF expression was not detected in other parts of the kidney, including the glomeruli. Although EGF receptors were found to be present in the proximal tubules as well as in the distal tubules and collecting ducts, EGF has not been found to be expressed in the proximal tubules. Therefore, the present results indicate that HB-EGF might be a ligand for EGF receptors in the proximal tubules and might play a role in the functions of proximal tubules.

Animals↗
PubMed1997

Endothelin-1 activates c-Jun NH2-terminal kinase in mesangial cells.

Endothelin-1 (ET-1) is known to induce the contraction and proliferation of glomerular mesangial cells. ET-1 has been shown to activate p42 and p44 mitogen-activated protein kinases (MAPKs), also known as extracellular signal regulated kinases (ERKs), through both protein kinase C (PKC) and protein tyrosine kinase (PTK)-dependent pathways. However, an involvement of c-Jun NH2-terminal kinase (JNK), one of members of the MAPK family, in ET-1 signaling in mesangial cells has not yet been elucidated. To clarify this point, we examined whether ET-1 could activate JNK and the mechanism of activation in cultured mesangial cells. ET-1 enhanced the activities of JNK in a dose-dependent (10(-8) M maximum) and time-dependent manner, with a peak at 15 minutes. ET-1-induced activation of JNK was blocked by BQ-123, an antagonist for the ETA receptor. The depletion of PKC by prolonged treatment with phorbol 12,13 dibutyrate or the inhibition of PKC by GF 109203X failed to inhibit ET-1-induced activation of JNK. In contrast, ET-1-induced activation of JNK was significantly reduced by calcium chelation (with BAPTA/AM and EGTA). In addition, ionomycin, a calcium ionophore, and thapsigargin, an intracellular calcium-rising agent, were able to induce the activation of JNK. ET-1-induced activation of JNK was also inhibited by PTK inhibitors (herbimycin A and genistein). Furthermore, ET-1 increased the DNA-binding activity of AP-1 containing c-Jun and c-Fos proteins. These results indicate that ET-1 is able to activate JNK in glomerular mesangial cells through PKC-independent and PTK-dependent pathways and intracellular calcium is necessary to the activation of JNK.

Animals↗
PubMed1997

Axonal contact regulates expression of alpha2 and beta2 isoforms of Na+, K+-ATPase in Schwann cells: adhesion molecules and nerve regeneration.

Three isoforms of catalytic alpha subunits and two isoforms of beta subunits of Na+,K+-ATPase were detected in rat sciatic nerves by western blotting. Unlike the enzyme in brain, sciatic nerve Na+,K+-ATPase was highly resistant to ouabain. The ouabain-resistant alpha1 isoform was demonstrated to be the predominant form in rat intact sciatic nerve by quantitative densitometric analysis and is mainly responsible for sciatic nerve Na+,K+-ATPase activity. After sciatic nerve injury, the alpha3 and beta1 isoforms completely disappeared from the distal segment owing to Wallerian degeneration. In contrast, alpha2 and beta2 isoform expression and Na+,K+-ATPase activity sensitive to pyrithiamine (a specific inhibitor of the alpha2 isoform) were markedly increased in Schwann cells in the distal segment of the injured sciatic nerve. These latter levels returned to baseline with nerve regeneration. Our results suggest that alpha3 and beta1 isoforms are exclusive for the axon and alpha2 and beta2 isoforms are exclusive for the Schwann cell, although axonal contact regulates alpha2 and beta2 isoform expressions. Because the beta2 isoform of Na+,K+-ATPase is known as an adhesion molecule on glia (AMOG), increased expression of AMOG/beta2 on Schwann cells in the segment distal to sciatic nerve injury suggests that AMOG/beta2 may act as an adhesion molecule in peripheral nerve regeneration.

Animals↗
PubMed1997

Cilostazol, a cAMP phosphodiesterase inhibitor, attenuates the production of monocyte chemoattractant protein-1 in response to tumor necrosis factor-alpha in vascular endothelial cells.

The induction of monocyte chemoattractant protein-1 (MCP-1) in vascular endothelial cells is thought to be an initial event in the development of atherosclerotic lesions. Therefore, inhibition of MCP-1 production may exhibit some effects in preventing atherosclerosis. In the present study, we found that 10 microM cilostazol, a cAMP phosphodiesterase inhibitor, increased the intracellular cAMP content by a twenty-five times of the basal level and resulted in the reduction of basal MCP-1 release by 41% from 168 +/- 11 ng/24 hr/mg protein to 99 +/- 14 ng/24 hr/mg protein (P < 0.001) from cultured human umbilical vein endothelial cells. Furthermore, 10 microM cilostazol also significantly attenuated the dose-dependent increment of MCP-1 production by tumor necrosis factor-alpha. The inhibition was consistent with the reduction of MCP-1 mRNA level, possibly through reduced activation of transcription factor NF-kappa B level. Similarly, 1 mM dibutyryl cAMP inhibited MCP-1 production in endothelial cells. These data suggest that cilostazol inhibits MCP-1 production through increased intracellular cAMP levels and modulation of its expression in vascular endothelial cells.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1997

beta-Sitosterolemia with generalized eruptive xanthomatosis.

The clinical features of the first case of a patient with sitosterolemia and generalized eruptive xanthomatosis are described. A six-year-old girl with generalized eruption was referred to the lipid clinic because of the high plasma cholesterol levels determined by the enzymatic method. Neither clinical signs nor results of laboratory examinations appeared to be abnormal, except for the eruption and the increase in the plasma cholesterol concentration. A family survey revealed high plasma cholesterol concentrations in the mother and one of two other siblings. Histological examination showed the eruption to be a xanthoma. Plasma sterol analysis by high-performance liquid chromatography revealed a noticeable increase in plasma plant sterol as well as cholestanol concentrations in the proband and the hypercholesterolemic sibling. The other family members had slightly high plasma sterol concentrations. This is the first case of a sitosterolemic patient with eruptive xanthomatosis. The case indicates that the clinical features of the xanthoma in sitosterolemia are not only tuberous or tendon but also eruptive, and also suggests that sitosterolemia should be considered in the differential diagnosis of hypercholesterolemia in almost every case with tuberous or eruptive xanthoma. The diagnosis is clinically important, since the disease can be treated successfully by diet therapy and bile acid binding resins.

Child↗
PubMed1997

Diabetic lipemia with maturity-onset diabetes of the young.

A 19-year-old woman with diabetic lipemia and maturity-onset diabetes of the young (MODY) is reported. Though her insulin secretory activity was preserved, she fell into mild diabetic ketoacidosis (DKA) and showed type V hyperlipidemia. Post-heparin plasma activity of lipoprotein lipase (LPL) was decreased even 10 days after initiating insulin injection but not deficient. The abnormalities in lipid metabolism were improved by long-term insulin treatment. Though the contribution of the genetic background to the lipid abnormalities is not clear, the characteristics of MODY in this patient including insulin secretory capacity under stress conditions such as DKA might play a role in the development of diabetic lipemia.

Adult↗
PubMed1997

Pyruvate improves deleterious effects of high glucose on activation of pentose phosphate pathway and glutathione redox cycle in endothelial cells.

In our previous study (Diabetes 44:520-526, 1995), endothelial cells cultured in high glucose condition showed impairment of an oxidant-induced activation of the pentose phosphate pathway (PPP) and a reduced supply of NADPH to the glutathione redox cycle. To gain insight into the mechanisms of this impairment, the protective effect of pyruvate was studied in human umbilical vein endothelial cells cultured in either 5.5 mmol/l glucose (normal glucose [NG] condition) or 33 mmol/l glucose (high glucose [HG] condition). Through pretreatment of cells with 0.2 mmol/l pyruvate for 5-7 days in the HG condition, glucose oxidation through the PPP and total cellular NADPH content in the presence of 0.2 mmol/l H2O2 were increased by 54 (P < 0.05) and 34%, respectively, and glutathione-dependent degradation of H2O2 in HG cells was enhanced by 41% (P < 0.01), when compared with those cells to which pyruvate was not added. The addition of pyruvate significantly reduced the fructose 1,6-bisphosphate (FDP) content and free cytoplasmic NADH/NAD ratio, estimated by increased pyruvate/lactate ratio in NG and HG cells exposed to H2O2. Furthermore, the addition of pyruvate also showed a 46% reduction (P < 0.01) of endothelial cell damage induced by H2O2 in HG cells. These results indicate that abnormalities in PPP activation and glutathione redox cycle activity induced by H2O2 in HG cells are compensated, and that the accentuated reductive stress is improved by an addition of pyruvate. These pyruvate effects are associated with protection against an oxidant-induced endothelial cell injury in the high glucose condition.

Adenosine Triphosphate↗
PubMed1997

Mitogen-activated protein kinase cascade is activated in glomeruli of diabetic rats and glomerular mesangial cells cultured under high glucose conditions.

The activation of protein kinase C (PKC) found in diabetic glomeruli and glomerular mesangial cells cultured under high glucose conditions has been proposed to contribute to the development of diabetic nephropathy. However, the abnormalities distal to PKC have not been fully elucidated yet. Herein, we provide the evidence that mitogen-activated protein kinase (MAPK) cascade, an important kinase cascade downstream to PKC and an activator of cytosolic phospholipase A2 (cPLA2) by direct phosphorylation, is activated in glomeruli isolated from streptozotocin-induced diabetic rats. MAPK cascade was also activated in glomerular mesangial cells cultured under high glucose (27.8 mmol/l) conditions for 5 days, and the activation of MAPK cascade was inhibited by treating the cells with calphostin C, an inhibitor of PKC. Furthermore, the activities of cPLA2 also increased in cells cultured under the same conditions and this activation was inhibited by both calphostin C and PD 098059, an inhibitor of MEK (MAPK or extracellular signal-regulated kinase [ERK] kinase). These results indicate that MAPK cascade is activated in glomeruli and mesangial cells under the diabetic state possibly through the activation of PKC. Activated MAPK, in turn, may induce various functional changes of mesangial cells at least through the activation of cPLA2 and contribute to the development of diabetic nephropathy.

Animals↗
PubMed1997

Mechanism of the progression of diabetic nephropathy to renal failure.

Although the evolution of diabetic nephropathy is brought about mostly by persistent hyperglycemia, its progression may be influenced by various other factors such as hypertension and dietary protein intake. It has been recently suggested in the literature that the gene polymorphism of angiotensin converting enzyme (ACE) might be associated with the development of diabetic nephropathy, because the DD genotype of ACE gene is closely associated with the presence of nephropathy in diabetic subjects. However, in our present analysis the frequency of the DD genotype in patients with non-insulin dependent diabetes is not significantly related to the presence or absence of nephropathy. It remains to be clarified by multi-center analysis using large numbers of patients whether the gene polymorphism of ACE is related to the progression of diabetic nephropathy to renal failure. Furthermore, it has been postulated that the interstitial fibrosis evaluated in renal biopsy specimens is significantly correlated with the declining of renal function in diabetic patients. However, it is not possible to clinically quantitate the interstitial fibrosis without performing renal biopsy. We have recently found that the urinary excretion of type IV collagen is significantly increased in diabetic patients. Moreover, the increase in urinary type IV collagen is well correlated with the amount of urinary albumin. Since type IV collagen in the urine is probably derived from tubulointerstitial tissue, it is likely that the increased amount of type IV collagen in the urine may reflect the fibrotic change in diabetic kidneys. Whether the increase in urinary type IV collagen is able to predict for the progression of diabetic nephropathy in the future should be examined.

Collagen↗