Biomedical subjects

Yun Jung Lee

Publications and source records attributed to Yun Jung Lee.

At least 19 recordsLinked to original sources

PubMed2007

Dopamine stimulates 45Ca2+ uptake through cAMP, PLC/PKC, and MAPKs in renal proximal tubule cells.

We have examined the effect of dopamine on Ca(2+) uptake and its related signaling pathways in primary renal proximal tubule cells (PTCs). Dopamine increased Ca(2+) uptake in a concentration (>10(-10) M) and time- (>8 h) dependent manner. Dopamine-induced increase in Ca(2+) uptake was prevented by SCH 23390 (a DA(1) antagonist) rather than spiperone (a DA(2) antagonist). SKF 38393 (a DA(1) agonist) increased Ca(2+) uptake unlike the case with quinpirole (a DA(2) agonist). Dopamine-induced increase in Ca(2+) uptake was blocked by nifedipine and methoxyverapamil (L-type Ca(2+) channel blockers). Moreover, dopamine-induced increase in Ca(2+) uptake was blocked by pertussis toxin (a G(i) protein inhibitor), protein kinase A (PKA) inhibitor amide 14/22 (a PKA inhibitor), and SQ 22536 (an adenylate cyclase inhibitor). Subsequently, dopamine increased cAMP level. The PLC inhibitors (U 73122 and neomycin), the PKC inhibitors (staurosporine and bisindolylmaleimide I) suppressed the dopamine-induced increase of Ca(2+) uptake. SB 203580 (a p38 MAPK inhibitor) and PD 98059 (a MAPKK inhibitor) also inhibited the dopamine-induced increase of Ca(2+) uptake. Dopamine-induced p38 and p42/44 MAPK phosphorylation was blocked by SQ 22536, neomycin, and staurosporine. The stimulatory effect of dopamine on Ca(2+) uptake was significantly inhibited by the NF-kappaB inhibitors SN50, TLCK, and Bay 11-7082. In addition, dopamine significantly increased the level of NF-kappaB p65, which was prevented by either SQ 22536, neomycin, staurosporine, PD 98059, or SB 203580. Thus, dopamine stimulates Ca(2+) uptake in PTCs, initially through by G(s) coupled dopamine receptors, PLC/PKC, followed by MAPK, and ultimately by NF-kappaB activation.

Adenylyl Cyclases↗

PubMed2006

Uric acid inhibits renal proximal tubule cell proliferation via at least two signaling pathways involving PKC, MAPK, cPLA2, and NF-kappaB.

The accumulation of uric acid, an end-product of purine metabolism, is responsible for the many deleterious effects observed in gouty arthritis, including renal injury. Here, we present evidence that under conditions of hyperuricemia (>10(-4) M uric acid) [(3)H]thymidine incorporation into primary renal proximal tubule cells (PTCs) is inhibited, and we delineate the signaling pathways involved. Elevated uric acid was observed to stimulate MAPK phosphorylation. The uric acid induced p38 MAPK phosphorylation was also blocked by H-7 (a PKC inhibitor), indicating that p38 MAPK was a downstream target of PKC. Evidence that cytoplasmic phospholipase A(2) (cPLA(2)) was involved further downstream included 1) the stimulatory effect of uric acid on [(3)H]-labeled arachidonic acid (AA) release; 2) the stimulation of AA release in response to uric acid was blocked by the PKC inhibitor H-7 as well as by the p38 MAPK inhibitor SB 203580; and 3) the uric acid-induced inhibition of [(3)H]thymidine incorporation was prevented by SB 203580, as well as by the cPLA(2) inhibitor arachidonyl trifluoromethyl ketone, and mepacrine (another PLA(2) inhibitor). Evidence of a uric acid-induced activation of NF-kappaB as well as PLA(2) was obtained. Moreover the uric acid-induced inhibition of [(3)H]thymidine incorporation was also blocked by two NF-kappaB inhibitors, pyrrolidine dithiocarbamate and SN 50. However, SN 50 did not block the uric acid induced [(3)H]AA release. Thus the inhibition of [(3)H]thymidine incorporation caused by uric acid can be explained by two distinct mechanisms, the activation of NF-kappaB as well as the activation of PLA(2).

Animals↗

PubMed2006

EGF-induced inhibition of glucose transport is mediated by PKC and MAPK signal pathways in primary cultured chicken hepatocytes.

EGF is a regulator of a wide variety of processes in various cell systems. Hepatocytes are important sites in the body's metabolism and function. Glucose transporter 2 (GLUT2) is a major transporter that is expressed strongly in hepatocytes. Therefore, this study examined the effect of EGF on GLUT2 and its related signal cascades in primary cultured chicken hepatocytes. EGF decreased [(3)H]deoxyglucose uptake in a dose- and time-dependent manner (>10 ng/ml, 2 h). AG-1478 (an EGF receptor antagonist) and genistein and herbimycin A (tyrosine kinase inhibitors) blocked the EGF-induced decrease in [(3)H]deoxyglucose uptake, which correlated with the GLUT2 expression level. In addition, the EGF-induced decrease in GLUT2 protein expression was inhibited by staurosporine, H-7, or bisindolylmaleimide I (PKC inhibitors), PD-98059 (a MEK inhibitor), SB-203580 (a p38 MAPK inhibitor), and SP-600125 (a JNK inhibitor), suggesting a role of both PKC and MAPKs (p44/42 MAPK, p38 MAPK, and JNK). In particular, EGF increased the translocation of PKC isoforms (PKC-alpha, -beta(1), -gamma, -delta, and -zeta) from the cytosol to the membrane fraction and increased the activation of p44/42 MAPK, p38 MAPK, and JNK. Moreover, PKC inhibitors blocked the EGF-induced phosphorylation of three MAPKs. In conclusion, EGF decreases the GLUT2 expression level via the PKC-MAPK signal cascade in chicken hepatocytes.

Animals↗

PubMed2006

Role of ATP in DNA synthesis of renal proximal tubule cells: involvement of calcium, MAPKs, and CDKs.

Although ATP has been shown to act as a modulator in various kidney functions, its effect on renal proximal tubule cell (PTC) proliferation has not been elucidated. This study investigated the effect of ATP on cell proliferation and the effect of its related signal pathways on primary cultured PTCs. Treatment with >10(-5) M ATP for 1 h stimulated incorporation of thymidine and bromodeoxyuridine. ATP (10(-4) M)-induced stimulation of thymidine incorporation was blocked by suramin (a P2X and P2Y receptor antagonist), reactive blue 2 (a P2Y receptor antagonist), MRS-2159 (a P2X1 receptor antagonist), and MRS-2179 (a P2Y1 receptor antagonist). ATP increased intracellular Ca2+ concentration, which was blocked by suramin, methoxyverapamil, and EGTA. ATP-induced stimulation of cell proliferation was also blocked by EGTA (an extracellular Ca2+ chelator), methoxyverapamil (a Ca2+ antagonist), and nifedipine (an L-type Ca2+ channel blocker), suggesting a role for Ca2+ influx. ATP-induced phosphorylation of p38 and p44/42 MAPKs was blocked by nifedipine. ATP increased expression levels of cyclin-dependent kinase (CDK)-2, CDK-4, and cyclin E, which were blocked by suramin, reactive blue 2, MRS-2179, MRS-2159, and nifedipine. However, ATP decreased expression levels of p21WAF1/Cip1 and p27kip1. ATP-induced stimulation of thymidine incorporation and increase of CDK-2 and CDK-4 expression were blocked by SB-203580 (a p38 MAPK inhibitor) and PD-98059 (an MEK inhibitor), but not by SP-600125 (a JNK inhibitor). In conclusion, ATP stimulates proliferation by increasing intracellular Ca2+ concentration and activating p38, p44/42 MAPKs, and CDKs in PTCs.

Adenosine Triphosphate↗

PubMed2006

Extracellular adenosine triphosphate protects oxidative stress-induced increase of p21(WAF1/Cip1) and p27(Kip1) expression in primary cultured renal proximal tubule cells: role of PI3K and Akt signaling.

Oxidative stress, the result of cellular production of reactive oxygen species (ROS), has been implicated in causing many renal diseases. Adenosine triphosphate (ATP) is an important extracellular signal in the regulation of many intracellular processes in normal tubular cells as well as in the pathogenesis of cell injury. This study investigated the effect of ATP on H(2)O(2)-induced increase of cyclin kinase inhibitors (CKI) expression and its related signal molecules in primary cultured renal proximal tubule cells (PTCs). H(2)O(2) inhibited DNA synthesis in a concentration- (>50 microM) and time-dependent manner (>2 h), as determined by thymidine and BrdU incorporation, and by increase in the p21(WAF/Cip1) and p27(Kip1) expression levels. In contrast, ATP increased the level of thymidine, BrdU incorporation (>10(-5) M), and decreased the p21(WAF/Cip1) and p27(Kip1) expression levels, suggesting that ATP has a protective effect against H(2)O(2)-induced oxidative damage. Suramin, reactive blue 2 (RB-2), MRS 2159, and MRS 2179 did block the reversing effect of ATP. In addition, AMP-CPP or 2-methylthio-ATP blocked H(2)O(2)-induced inhibition of DNA synthesis, suggesting all these P2 purinoceptors may be potentially involved. ATP-induced stimulation of DNA synthesis was blocked by phosphatidylinositol 3-kinase (PI3K) and Akt inhibitors. These results suggest the involvement of P2 purinoceptors-mediated PI3K/Akt signal pathway in the protective effect of ATP against H(2)O(2)-induced oxidative damage. Indeed, pre-treatment with PI3K or Akt inhibitors did not protect H(2)O(2)-induced lipid peroxide (LPO) production and inhibition of thymidine incorporation. In conclusion, ATP, in part, blocked H(2)O(2)-induced increase of p21(WAF1/Cip1) and p27(Kip1) expression through PI3K and Akt signal pathway in renal PTCs.

Adenosine Triphosphate↗

PubMed2006

High glucose-induced inhibition of 2-deoxyglucose uptake is mediated by cAMP, protein kinase C, oxidative stress and mitogen-activated protein kinases in mouse embryonic stem cells.

Abnormally high glucose levels may play an important role in early embryo development and function. In the present study, we investigated the effect of high glucose on 2-deoxyglucose (2-DG) uptake and its related signalling pathway in mouse embryonic stem (ES) cells. 2. 2-Deoxyglucose uptake was maximally inhibited by 25 mmol/L glucose after 24 h treatment. However, 25 mmol/L mannitol and dextran did not affect 2-DG uptake. Indeed, 25 mmol/L glucose decreased GLUT-1 mRNA and protein levels. The glucose (25 mmol/L)-induced inhibition of 2-DG uptake was blocked by pertussis toxin (a G(i)-protein inhibitor; 2 ng/mL), SQ 22,536 (an adenylate cyclase inhibitor; 10(-6) mol/L) and the protein kinase (PK) A inhibitor myristoylated PKI amide-(14-22) (10(-6) mol/L). Indeed, 25 mmol/L glucose increased intracellular cAMP content. 3. Furthermore, 25 mmol/L glucose-induced inhibition of 2-DG uptake was prevented by 10(-4) mol/L neomycin or 10(-6) mol/L U 73,122 (phospholipase C (PLC) inhibitors) and staurosporine or bisindolylmaleimide I (protein kinase (PK) C inhibitors). At 25 mmol/L, glucose increased translocation of PKC from the cytoplasmic fraction to the membrane fraction. The 25 mmol/L glucose-induced inhibition of 2-DG uptake and GLUT-1 protein levels was blocked by SQ 22,536, bisindolylmaleimide I or combined treatment. In addition, 25 mmol/L glucose increased cellular reactive oxygen species and the glucose-induced inhibition of 2-DG uptake were blocked by the anti-oxidants N-acetylcysteine (NAC; 10(-5) mol/L) or taurine (2 yen 10(-3) mol/L). 4. Glucose (25 mmol/L) activated p38 mitogen-activated protein kinase (MAPK) and p44/42 MAPK. Staurosporine (10(-6) mol/L), NAC (10(-5) mol/L) and PD 98059 (10(-7) mol/L) attenuated the phosphorylation of p44/42 MAPK. Both SB 203580 (a p38 MAPK inhibitor; 10(-7) mol/L) and PD 98059 (a p44/42 MAPK inhibitor; 10(-7) mol/L) blocked 25 mmol/L glucose-induced inhibition of 2-DG uptake. 5. In conclusion, high glucose inhibits 2-DG uptake through cAMP, PLC/PKC, oxidative stress or MAPK in mouse ES cells.

Alkaline Phosphatase↗

PubMed2006

[A study on the related factors of the wellbeing of family caregivers in elderly with stroke].

PURPOSE: The purpose of this study was to identify the factors related to the wellbeing of the family caregivers of the elderly with a stroke. METHODS: The subjects of this study were 199 elderly treated in four oriental hospitals in Korea, and their primary family caregivers. The data was collected by interviews and a self-reported questionnaire, during the period from October, 2003 to April, 2004. RESULTS: The results of this study were as follows. The mean score of wellbeing of family caregivers was 60.6412.63. The factors related to wellbeing of family caregivers were sex, age, education, depression, illness severity, ADL, paralysis, and speech disability in elderly characteristics. Among family caregivers characteristics, education, relation, and burden were significantly related. In situational variables, family income and the previous relationship between the elderly and family caregivers were related to wellbeing. Stepwise multiple regression analysis revealed that the most powerful predictor of wellbeing was the burden of family caregivers. A combination of the depression of elderly and age of family caregivers accounted for 50.3% of the variance of wellbeing. CONCLUSIONS: On developing the nursing intervention for improving wellbeing of family caregivers, many factors should be considered, especially caregiver burden, and elderly depression.

Aged↗

PubMed2005

Estradiol-17beta stimulates proliferation of mouse embryonic stem cells: involvement of MAPKs and CDKs as well as protooncogenes.

Although the importance of estradiol-17beta (E(2)) in many physiological processes has been reported, to date no researchers have investigated the effects of E(2) on embryonic stem (ES) cell proliferation. Therefore, in the present study, we have examined the effect of E(2) on the DNA synthesis of murine ES (ES-E14TG2a) cells and its related signaling pathways. The results of this study show that E(2) (10(-9) M) significantly increased [(3)H]thymidine incorporation at >4 h and that E(2) (>10(-12) M) induced an increase of [(3)H]thymidine incorporation after 8-h incubation. Moreover, E(2) (>10(-12) M) also increased 5'-bromo-2'-deoxyuridine (BrdU) incorporation and cell number. Indeed, E(2) stimulated estrogen receptor (ER)-alpha and -beta protein levels and increased mRNA expression levels of protooncogenes (c-fos, c-jun, and c-myc). Tamoxifen (antiestrogen) completely inhibited E(2)-induced increases in [(3)H]thymidine incorporation. In addition, estradiol-6-O-carboxymethyl oxime-BSA (E(2)-BSA; 10(-9) M) increased [(3)H]thymidine incorporation at >1 h, and E(2)-BSA (>10(-12) M) increased [(3)H]thymidine incorporation after 1-h incubation. E(2)-BSA-induced increase in BrdU incorporation also occurred in a dose-dependent manner. Tamoxifen had no effect on E(2)-BSA-induced increase of [(3)H]thymidine incorporation. Also, E(2) and E(2)-BSA displayed maximal phosphorylation of p44/42 MAPKs at 10 and 5 min, respectively. E(2) increased cyclins D1 and E as well as cyclin-dependent kinase (CDK)2 and CDK4. In contrast, E(2) decreased the levels of p21(cip1) and p27(kip1) (CDK-inhibitory proteins). Increases of these cell cycle regulators were blocked by 10(-5) M PD-98059 (MEK inhibitor). Moreover, E(2)-induced increase of [(3)H]thymidine incorporation was inhibited by PD-98059 or butyrolactone I (CDK2 inhibitor). In conclusion, estradiol-17beta stimulates the proliferation of murine ES cells, and this action is mediated by MAPKs, CDKs, or protooncogenes.

Animals↗

PubMed2005

ANG II increases 2-deoxyglucose uptake in mouse embryonic stem cells.

It is now suggested that all components of the renin-angiotensin system are present in many tissues, including the embryo and may play a major role in embryo development and differentiation. However, little is known regarding whether ANG II regulates glucose transport in mouse embryonic stem (ES) cells. Thus, the effects of ANG II on [3H]-2-deoxyglucose (2-DG) uptake and its related signal pathways were examined in mouse ES cells. ANG II significantly increased cell proliferation and 2-DG uptake in concentration- and time-dependent manner (>18 h, >10(-8) M) and increased mRNA and protein level of GLUT1 by 31+/-7% and 22+/-5% compared to control, respectively. Actinomycin D and cycloheximide completely blocked the effect of ANG II on 2-DG uptake. ANG II-induced increase of 2-DG uptake was blocked by losartan, an ANG II type 1 (AT1) receptor blocker, but not by PD 123319, an ANG II type 2 (AT2) receptor blocker. In addition, ANG II-induced stimulation of 2-DG uptake was attenuated by phospholipase C (PLC) inhibitors, neomycin and U 73122 and ANG II increased inositol phosphates (IPs) formation by 37+/-8% of control. Protein kinase C (PKC) inhibitors, staurosporine, bisindolylmaleimide I, and H-7 also blocked ANG II-induced stimulation of 2-DG uptake. Indeed, ANG II activated a PKC translocation from the cytosolic to membrane fraction, suggesting a role of PKC. A 23187 (Ca2+ ionophore) increased 2-DG uptake and nifedifine (L-type Ca2+ channel blocker) blocked it. In conclusion, ANG II increased 2-DG uptake by PKC activation via AT1 receptor in mouse ES cells.

Alkaline Phosphatase↗

PubMed2005

EGF stimulates proliferation of mouse embryonic stem cells: involvement of Ca2+ influx and p44/42 MAPKs.

We examined the effect of EGF on the proliferation of mouse embryonic stem (ES) cells and their related signal pathways. EGF increased [3H]thymidine and 5-bromo-2'-deoxyuridine incorporation in a time- and dose-dependent manner. EGF stimulated the phosphorylation of EGF receptor (EGFR). Inhibition of EGFR tyrosine kinase with AG-1478 or herbimycin A, inhibition of PLC with neomycin or U-73122, inhibition of PKC with bisindolylmaleimide I or staurosporine, and inhibition of L-type Ca2+ channels with nifedipine or methoxyverapamil prevented EGF-induced [3H]thymidine incorporation. PKC-alpha, -betaI, -gamma, -delta, and -zeta were translocated to the membrane and intracellular Ca2+ concentration ([Ca2+]i) was increased in response to EGF. Moreover, inhibition of EGFR tyrosine kinase, PLC, and PKC completely prevented EGF-induced increases in [Ca2+]i. EGF also increased inositol phosphate levels, which were blocked by EGFR tyrosine kinase inhibitors. Furthermore, EGF rapidly increased formation of H2O2, and pretreatment with antioxidant (N-acetyl-L-cysteine) inhibited EGF-induced increase of [Ca2+]i. In addition, we observed that p44/42 MAPK phosphorylation by EGF and inhibition of EGFR tyrosine kinase, PLC, PKC, or Ca2+ channels blocked EGF-induced phosphorylation of p44/42 MAPKs. Inhibition of p44/42 MAPKs with PD-98059 (MEK inhibitor) attenuated EGF-induced increase of [3H]thymidine incorporation. Finally, inhibition of EGFR tyrosine kinase, PKC, Ca2+ channels, or p44/42 MAPKs attenuated EGF-stimulated cyclin D1, cyclin E, cyclin-dependent kinase (CDK)2, and CDK4, respectively. In conclusion, EGF partially stimulates proliferation of mouse ES cells via PLC/PKC, Ca2+ influx, and p44/42 MAPK signal pathways through EGFR tyrosine kinase phosphorylation.

Animals↗

PubMed2005

ATP stimulates Na+-glucose cotransporter activity via cAMP and p38 MAPK in renal proximal tubule cells.

Extracellular ATP plays an important role in the regulation of renal function. However, the effect of ATP on the Na(+)-glucose cotransporters (SGLTs) has not been elucidated in proximal tubule cells (PTCs). Therefore, this study was performed to examine the action of ATP on SGLTs and their related signal pathways in primary cultured rabbit renal PTCs. ATP increased [(14)C]-alpha-methyl-d-glucopyranoside (alpha-MG) uptake in a time-dependent (>1 h) and dose-dependent (>10(-6) M) manner. ATP stimulated alpha-MG uptake by increasing in V(max) without affecting K(m). ATP-induced increase of alpha-MG uptake was correlated with the increase in both SGLT1 and SGLT2 protein expression levels. ATP-induced stimulation of alpha-MG uptake was blocked by suramin (nonspecific P2 receptor antagonist), RB-2 (P2Y receptor antagonist), and MRS-2179 (P2Y(1) receptor antagonist), suggesting a role for the P2Y receptor. ATP-induced stimulation of alpha-MG uptake was blocked by pertussis toxin (PTX, a G(i) protein inhibitor), SQ-22536 (an adenylate cyclase inhibitor), and PKA inhibitor amide 14-22 (PKI). ATP also increased cAMP formation, which was blocked by PTX and RB-2. However, pretreatment of adenosine deaminase did not block ATP-induced cAMP formation. In addition, ATP-induced stimulation of alpha-MG uptake was blocked by SB-203580 (p38 MAPK inhibitor), but not by PD-98059 (p44/42 MAPK inhibitor) or SP-600125 (JNK inhibitor). Indeed, ATP induced phosphorylation of p38 MAPK. In conclusion, ATP increases alpha-MG uptake via cAMP and p38 MAPK in renal PTCs.

Adenosine Triphosphate↗

PubMed2005

Insulin stimulates Ca2+ uptake via PKC, cAMP, and p38 MAPK in mouse embryonic stem cells.

Embryonic stem (ES) cells are provided as a powerful tool for developmental biology and have been shown to respond to insulin. However, little is known about the effect of insulin on [Ca2+]i regulation in the ES cells, although many cellular functions are tightly regulated by [Ca2+]i. Therefore, we examined the effect of insulin on Ca2+ uptake and its related signal pathways in the mouse ES cells. Mouse ES cells expressed alkaline phosphatase (AP), transcription factor Oct-4, and stage-specific embryonic antigen-1 (SSEA-1). Insulin increased the Ca2+ uptake in a time- and dose-dependent manner and the effect was blocked by L-type Ca2+ channel blockers, nifedifine and methoxyverapamil. Genistein or herbimycin A (tyrosine kinase inhibitors), wortmannin (PI-3K inhibitor), and staurosporine or bisindolylmaleimide I (PKC inhibitors) completely prevented insulin-induced increase of Ca2+ uptake. Wortmannin blocked insulin-induced PKC activation, but SQ 22536 (adenylate cyclase inhibitor) did not. Insulin also rapidly increased formation of inositol phosphates (IPs). We examined the involvement of MAPKs in mediating the effect of insulin on Ca2+ uptake. SB 203580 (p38 MAPK inhibitor) but not PD 98059 (p44/42 MAPKs inhibitor) blocked insulin-induced increase of Ca2+ uptake. Insulin significantly increased the phosphorylation of p38 MAPK but not p44/42 MAPKs. In addition, genistein, PKI, and bisindolylmaleimide I blocked the phosphorylation of p38 MAPK by insulin, suggesting a causal relationship. In conclusion, insulin partially stimulated Ca2+ uptake via PKC, cAMP, and p38 MAPK signaling pathways in mouse ES cells.

Analysis of Variance↗

PubMed2005

Effect of albumin on 14C-alpha-Methyl-D-Glucopyranoside uptake in primary cultured renal proximal tubule cells: involvement of PLC, MAPK, and NF-kappaB.

A growing body of evidence implicates albumin has an important regulatory function in renal proximal tubule cells (PTCs). In present study, the effect of bovine serum albumin (BSA) on 14C-alpha-methyl-D-glucopyranoside (alpha-MG) uptake and its related signal molecules were examined in the primary cultured rabbit renal PTCs. BSA significantly increased uptake of alpha-MG, a distinctive proximal tubule marker, as well as expression level of Na+/glucose cotransporters (SGLT1 and SGLT2) proteins. The BSA-induced increase of alpha-MG uptake was completely blocked by actinomycin D and cycloheximide. Neomycin or U 73122 (PLC inhibitors), BAPTA/AM or TMB-8 (intracellular Ca2+ mobilization inhibitors) completely abolished BSA-induced increase of alpha-MG uptake. BSA significantly increased IPs accumulation, but did not affect Ca2+ uptake. Effect of BSA on alpha-MG uptake was blocked by PD 98059, but did not SB 203580. BSA increased phosphorylation of p44/42 mitogen activated protein kinase (MAPK) in a time-dependent manner. NAC or catalase (antioxidants) significantly blocked BSA-induced increase of H2O2 formation and alpha-MG uptake. BSA activated NF-kappaB translocation into nucleus. PDTC, SN50, and TLCK (NF-kappaB inhibitors) also completely blocked BSA-induced increase of alpha-MG uptake, NF-kappaB p65 and phospho IkappaB-alpha activation. In conclusion, BSA stimulates alpha-MG uptake and its action is partially correlated with PLC, MAPK, or NF-kappaB signal molecules in primary cultured renal PTCs.

Active Transport, Cell Nucleus↗

PubMed2005

Effect of EGF on H2O2-induced inhibition of alpha-MG uptake in renal proximal tubule cells: involvement of MAPK and AA release.

Both oxidative stress and epidermal growth factor (EGF) contribute to the initiation and progression of renal proximal tubular dysfunction under pathophysiologic conditions. Thus, this study was performed (1) to examine both the individual, and the combined effects of H2O2 and EGF on alpha-methyl-D-glucopyranoside uptake (alpha-MG uptake) in the primary cultured renal proximal tubule cells (PTCs), and (2) to elucidate the involvement of p44/42 mitogen activated protein kinase (MAPK) and phospholipase A2 in mediating these actions. Both H2O2 and EGF inhibited alpha-MG uptake individually, while the combination of H2O2 and EGF further potentiated the inhibitory effect on alpha-MG uptake, which was elicited by each agent. H2O2 not only caused a rapid increase in the phosphorylation of p44/42 MAPK, but also promoted the translocation of cytosolic phospholipase A2 (cPLA2) from the cytosolic to particulate fraction, and stimulated cellular [3H]-arachidonic acid (AA) release. EGF similarly activates phosphorylation of p44/42 MAPK and stimulates [3H]-AA release. When PTCs were exposed to 100 microM H2O2 and 50 ng/ml EGF simultaneously, a further increase in the phosphorylation of p44/42 MAPK, of [3H]-AA release, and of prostaglandin E2 (PGE2) production was elicited as compared with the effects of each individual agonist alone. Moreover, the additive phosphorylation of p44/42 MAPK, [3H]-AA release, and PGE2 production by H2O2 and EGF was almost completely inhibited by the p44/42 MAPK inhibitor, PD 98059. In conclusion, these results are consistent with the hypothesis that under conditions of oxidative stress, the H2O2-induced inhibition of alpha-MG uptake in the renal proximal tubule is mediated through a modulation of the EGF signaling pathway, promoting further phosphorylation of p44/42 MAPK, activation of PLA2.

Animals↗

PubMed2005

Effect of adenosine triphosphate in renal ischemic injury: involvement of NF-kappaB.

Renal ischemic/reperfusion injury in vivo results in a significant increase of acute renal failure (ARF) and death. Nevertheless, there are many limitations in using in vivo models of renal ischemic injury to elucidate the detailed mechanisms of renal injury. Adenosine triphosphate (ATP), an extracellular signal, has been shown to be an important factor in regulation of epithelial cell function. Thus, the present study was performed to establish in vitro ischemic model using primary cultured rabbit renal proximal tubule cells (PTCs) and to examine the effect of ATP in this model. We established an in vitro model of ischemic injury, causing severe depletion of intracellular ATP by using the combination of a mitochondrial respiration inhibitor (antimycin A), non-metabolizable glucose analog (2-deoxyglucose), and calcium ionophore (A23187) in PTCs. Indeed, this ischemic injury significantly increased LDH release, a marker of structural damage, and ATP blocked ischemic injury-induced LDH release. 2-Methylthio-ATP and ATP-gamma-S (P2Y purinoceptor agonists) also blocked ischemic injury-induced LDH release, whereas AMP-CPP (P2X purinoceptor agonist) did not block it. In experiments to examine the relationship between ischemic injury and NF-kappaB activation, ischemic injury increased NF-kappaB translocation, DNA binding activity, and CAT activity. On the other hand, ATP, ATP-gamma-S, or 2-methylthio-ATP protected ischemic injury-induced NF-kappaB activation. These results suggest that the protective effect of ATP on ischemic injury is, in part, related to inhibition of NF-kappaB activation via P2Y receptor in PTCs.

Adenosine Triphosphate↗

PubMed2005

Effect of adenosine triphosphate on phosphate uptake in renal proximal tubule cells: involvement of PKC and p38 MAPK.

ATP has been known to act as an extracellular signal and to be involved in various functions of kidney. Renal proximal tubular reabsorption of phosphate (Pi) contributes to the maintenance of phosphate homeostasis, which is regulated by Na+/Pi cotransporter. However, the effects of ATP on Na+/Pi cotransporters were not elucidated in proximal tubule cells (PTCs). Thus, the effects of ATP on Na+/Pi cotransporter and its related signal pathways are examined in the primary cultured renal PTCs. In the present study, ATP inhibited Pi uptake in a time (> 1 h) and dose (>10(-6)M) dependent manner. ATP-induced inhibition of Pi uptake was correlated with the decrease of type II Na+/Pi cotransporter mRNA. ATP-induced inhibition of Pi uptake may be mediated by P2Y receptor activation, since suramin (non-specific P2 receptor antagonist) and RB-2 (P2Y receptor antagonist) blocked it. ATP-induced inhibition of Pi uptake was blocked by neomycin, U73122 (phospholipase C (PLC) inhibitors), bisindolylmaleimide I, H-7, and staurosporine (protein kinase C (PKC) inhibitors), suggesting the role of PLC/PKC pathway. ATP also increased inositol phosphates (IPs) formation and induced PKC translocation from cytosolic fraction to membrane fraction. In addition, ATP-induced inhibition of Pi uptake was blocked by SB 203580 [a p38 mitogen activated protein kinase (MAPK) inhibitor], but not by PD 98059 (a p44/42 MAPK inhibitor). Indeed, ATP induced phosphorylation of p38 MAPK, which was not blocked by PKC inhibitor. In conclusion, ATP inhibited Pi uptake via PLC/PKC as well as p38 MAPK in renal PTCs.

Adenosine Triphosphate↗

PubMed2005

Effects of TCDD and estradiol-17beta on the proliferation and Na+/glucose cotransporter in renal proximal tubule cells.

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is a highly toxic environmental toxicant that alters cell proliferation and function. Estrogens are noted for their ability to stimulate cell proliferation in various tissues. However, little is known about any interaction between TCDD and estradiol-17beta (E(2)) that affects renal proximal tubule cell proliferation and Na(+)/glucose cotransporters' activity. Thus, the effects of TCDD and E(2) on [(3)H]-thymidine incorporation and on alpha-methyl-d-glucopyranoside (alpha-MG) uptake were investigated in the primary rabbit kidney proximal tubule cells (PTCs). TCDD (>10(-10) M >1 h) inhibited [(3)H]-thymidine incorporation and c-fos transcripts in real-time RT-PCR, whereas E(2) (>10(-9) M, 24 h) stimulated them. Aryl hydrocarbon receptor (AhR) agonists, beta-naphthoflavone (beta-NF) and polychlorinated biphenyls (PCBs) (10(-6) M) synergistically increased the TCDD-induced inhibition of [(3)H]-thymidine incorporation. However, the AhR antagonist, alpha-naphthoflavone (alpha-NF) as well as E(2) blocked TCDD-induced inhibition of [(3)H]-thymidine incorporation. TCDD (10(-8) M, 48 h) specifically inhibited alpha-MG uptake and its effect was due to V(max) value but not K(m) value. Indeed, TCDD decreased Na(+)/glucose cotransporter 1, 2 (SGLT1, 2) protein level compared with control. In addition, TCDD-induced inhibition of alpha-MG uptake was blocked by alpha-NF or E(2). In conclusion, TCDD inhibited [(3)H]-thymidine incorporation and alpha-MG uptake, and E(2) blocked TCDDs effects in primary cultured renal proximal tubule cells.

Animals↗

PubMed2005

Clinical course of distal ulcerative colitis in relation to appendiceal orifice inflammation status.

BACKGROUND: Although appendiceal orifice inflammation (AOI) is frequently observed as a skip lesion of ulcerative colitis (UC), its clinical significance is not clearly understood. We aimed to evaluate whether AOI is associated with the clinical course of UC. METHODS: Ninety-four patients with newly diagnosed distal UC were prospectively enrolled at the Asan Medical Center between March 1996 and October 2002. Clinical features and colonoscopic findings during the follow-up period were analyzed in relation to initial AOI status. RESULTS: Forty-eight patients were found to be initially AOI-positive and 46 to be initially AOI-negative. We found no difference in the baseline demographics and clinical characteristics between these two groups. The median follow-up periods for AOI-positive and AOI-negative groups were 45 and 41 months, respectively. Clinical remission was achieved in all patients of each group. The cumulative risk of relapse at 1, 3, and 5 years after remission was 31.2%, 59.8%, and 69.2%, respectively, in the AOI-positive group and 17.4%, 46.5%, and 67.2%, respectively, in the AOI-negative group (P = 0.124). The cumulative risk of proximal disease extension at 1, 3, and 5 years after diagnosis was 17.9%, 24.9%, and 44.5%, respectively, in the AOI-positive group and 9.8%, 21.5%, and 43.9%, respectively, in the AOI-negative group (P = 0.522). Proctocolectomy was performed in no patients in the AOI-positive group and in 1 patient in the AOI-negative group. No mortalities were observed in either group. CONCLUSIONS: In patients with distal UC, AOI may have no prognostic implications in terms of remission, relapse, or proximal disease extension.

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