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Articles by L. Yue
Total Records ( 3 ) for L. Yue
  J Du , J Xie , Z Zhang , H Tsujikawa , D Fusco , D Silverman , B Liang and L. Yue
 

Rationale: Cardiac fibrosis contributes to pathogenesis of atrial fibrillation (AF), which is the most commonly sustained arrhythmia and a major cause of morbidity and mortality. Although it has been suggested that Ca2+ signals are involved in fibrosis promotion, the molecular basis of Ca2+ signaling mechanisms and how Ca2+ signals contribute to fibrogenesis remain unknown.

Objective: To determine the molecular mechanisms of Ca2+-permeable channel(s) in human atrial fibroblasts, and to investigate how Ca2+ signals contribute to fibrogenesis in human AF.

Methods and Results: We demonstrate that the transient receptor potential (TRP) melastatin related 7 (TRPM7) is the molecular basis of the major Ca2+-permeable channel in human atrial fibroblasts. Endogenous TRPM7 currents in atrial fibroblasts resemble the biophysical and pharmacological properties of heterologous expressed TRPM7. Knocking down TRPM7 by small hairpin RNA largely eliminates TRPM7 current and Ca2+ influx in atrial fibroblasts. More importantly, atrial fibroblasts from AF patients show a striking upregulation of both TRPM7 currents and Ca2+ influx and are more prone to myofibroblast differentiation, presumably attributable to the enhanced expression of TRPM7. TRPM7 small hairpin RNA markedly reduced basal AF fibroblast differentiation. Transforming growth factor (TGF)-β1, the major stimulator of atrial fibrosis, requires TRPM7-mediated Ca2+ signal for its effect on fibroblast proliferation and differentiation. Furthermore, TGF-β1–induced differentiation of cultured human atrial fibroblasts is well correlated with an increase of TRPM7 expression induced by TGF-β1.

Conclusions: Our results establish that TRPM7 is the major Ca2+-permeable channel in human atrial fibroblasts and likely plays an essential role in TGF-β1–elicited fibrogenesis in human AF.

  G. D. Xiang , J. H. Pu , L. S. Zhao , H. L. Sun , J. Hou and L. Yue
  Aims  Osteoprotegerin (OPG) is a recently identified inhibitor of bone resorption. Recent studies indicate that OPG is also associated with endothelial dysfunction in Type 2 diabetes. The aim was to investigate the relationship between plasma OPG levels and urinary albumin excretion (UAE) in Type 2 diabetic patients.

Methods  This study included 154 newly diagnosed Type 2 diabetic patients and 46 healthy subjects. Plasma OPG and 24-h UAE were measured. High-resolution ultrasound was used to measure flow-mediated (endothelium-dependent arterial) dilation (FMD).

Results  Compared with the normoalbuminuric subgroup, OPG levels in the microalbuminuric subgroup were significantly higher, and OPG levels in macroalbuminuria subgroup were significantly higher than those in the normoalbuminuria and albuminuria subgroups. Multiple regression analysis showed that only FMD (r = −0.26), C-reactive protein (r = 0.23), fasting blood glucose (r = 0.25), 2-h blood glucose (r = 0.21), HbA1c (r = 0.28), UAE (r = 0.27) and retinopathy (r = 0.27) were significant factors associated with OPG. Pearson's correlation analyses showed a positive correlation between OPG and logUAE (r = 0.440) and negative correlations between OPG and FMD (r = −0.284), and between FMD and logUAE (r = −0.602).

Conclusions  Plasma OPG levels are significantly associated with UAE in Type 2 diabetic patients.

  J Du , J Xie and L. Yue
 

TRPM2 is a Ca2+-permeable nonselective cation channel that plays important roles in oxidative stress–mediated cell death and inflammation processes. However, how TRPM2 is regulated under physiological and pathological conditions is not fully understood. Here, we report that both intracellular and extracellular protons block TRPM2 by inhibiting channel gating. We demonstrate that external protons block TRPM2 with an IC50 of pHo = 5.3, whereas internal protons inhibit TRPM2 with an IC50 of pHi = 6.7. Extracellular protons inhibit TRPM2 by decreasing single-channel conductance. We identify three titratable residues, H958, D964, and E994, at the outer vestibule of the channel pore that are responsible for pHo sensitivity. Mutations of these residues reduce single-channel conductance, decrease external Ca2+ ([Ca2+]o) affinity, and inhibit [Ca2+]o-mediated TRPM2 gating. These results support the following model: titration of H958, D964, and E994 by external protons inhibits TRPM2 gating by causing conformation change of the channel, and/or by decreasing local Ca2+ concentration at the outer vestibule, therefore reducing [Ca2+]o permeation and inhibiting [Ca2+]o-mediated TRPM2 gating. We find that intracellular protons inhibit TRPM2 by inducing channel closure without changing channel conductance. We identify that D933 located at the C terminus of the S4-S5 linker is responsible for intracellular pH sensitivity. Replacement of Asp933 by Asn933 changes the IC50 from pHi = 6.7 to pHi = 5.5. Moreover, substitution of Asp933 with various residues produces marked changes in proton sensitivity, intracellular ADP ribose/Ca2+ sensitivity, and gating profiles of TRPM2. These results indicate that D933 is not only essential for intracellular pH sensitivity, but it is also crucial for TRPM2 channel gating. Collectively, our findings provide a novel mechanism for TRPM2 modulation as well as molecular determinants for pH regulation of TRPM2. Inhibition of TRPM2 by acidic pH may represent an endogenous mechanism governing TRPM2 gating and its physiological/pathological functions.

 
 
 
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