Critical role of Rho-kinase pathway for cardiac performance and remodeling in failing rat hearts

Pulmonary arteries (PA) are resistant to the vasodilator effects of extracellular acidosis in systemic vessels; the mechanism underlying this difference between systemic and pulmonary circulations has not been elucidated. We hypothesized that RhoA/Rho-kinase-mediated Ca2+ sensitization pathway played a greater role in tension development in pulmonary than in systemic vascular smooth muscle and that this pathway was insensitive to acidosis. In arterial rings contracted with the α1-agonist phenylephrine (PE), the Rho-kinase inhibitor Y-27632 (≤3 μM) induced greater relaxation in precontracted PA rings than in aortic rings. In PA rings stimulated by PE, the activation of RhoA was greater than in aorta. Normocapnic acidosis (NA) induced a smaller relaxation in precontracted PA than in aorta. However, in the presence of nifedipine and thapsigargin, when PE-induced contraction was predominantly mediated by Rho-kinase, the relaxant effect of NA was reduced and similar in both vessel types. Furthermore, in the presence of Y-27632, NA induced a greater relaxation in both PA and aorta, which was similar in both vessels. Finally, in α-toxin-permeabilized smooth muscle, PE-induced contraction at constant Ca2+ activity was inhibited by Y-27632 and unaffected by acidosis. These results indicate that Ca2+ sensitization induced by the RhoA/Rho-kinase pathway played a greater role in agonist-induced vascular smooth muscle contraction in PA than in aorta and that tension mediated by this pathway was insensitive to acidosis. The predominant role of the RhoA/Rho-kinase pathway in the pulmonary vasculature may account for the resistance of this circulation to the vasodilator effect of acidosis observed in the systemic circulation.

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Phosphatase inhibition promotes antiapoptotic but not proliferative signaling pathways in erythropoietin-dependent HCD57 cells

Blood ◽

10.1182/blood.v96.6.2084.h8002084_2084_2092 ◽

2000 ◽

Vol 96 (6) ◽

pp. 2084-2092

Author(s):

Amy E. Lawson ◽

Haifeng Bao ◽

Amittha Wickrema ◽

Sarah M. Jacobs-Helber ◽

Stephen T. Sawyer

Keyword(s):

Tyrosine Phosphatase ◽

Critical Role ◽

Mitogen Activated Protein Kinase ◽

Phosphatidylinositol 3 Kinase ◽

Erythroid Progenitors ◽

Murine Cell Line ◽

Mitogen Activated Protein ◽

Erk Activity ◽

Kinase Pathway

Erythropoietin (EPO) allows erythroid precursors to proliferate while protecting them from apoptosis. Treatment of the EPO-dependent HCD57 murine cell line with 70 μmol/L orthovanadate, a tyrosine phosphatase inhibitor, resulted in both increased tyrosine protein phosphorylation and prevention of apoptosis in the absence of EPO without promoting proliferation. Orthovanadate also delayed apoptosis in primary human erythroid progenitors. Thus, we investigated what survival signals were activated by orthovanadate treatment. Expression of Bcl-XL and BAD phosphorylation are critical for the survival of erythroid cells, and orthovanadate in the absence of EPO both maintained expression levels of antiapoptotic Bcl-XLand induced BAD phosphorylation at serine 112. Orthovanadate activated JAK2, STAT1, STAT5, the phosphatidylinositol-3 kinase (PI-3 kinase) pathway, and other signals such as JNK and p38 without activating the EPO receptor, JAK1, Tyk2, Vav, STAT3, and SHC. Neither JNK nor p38 appeared to have a central role in either apoptosis or survival induced by orthovanadate. Treatment with cells with LY294002, an inhibitor of PI-3 kinase activity, triggered apoptosis in orthovanadate-treated cells, suggesting a critical role of PI-3 kinase in orthovanadate-stimulated survival. Mitogen-activated protein kinase (MAPK) was poorly activated by orthovanadate, and inhibition of MAPK with PD98059 blocked proliferation without inducing apoptosis. Thus, orthovanadate likely acts to greatly increase JAK/STAT and PI-3 kinase basal activity in untreated cells by blocking tyrosine protein phosphatase activity. Activated JAK2/STAT5 then likely acts upstream of Bcl-XL expression and PI-3 kinase likely promotes BAD phosphorylation to protect from apoptosis. In contrast, MAPK/ERK activity correlates with only EPO-dependent proliferation but is not required for survival of HCD57 cells.

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Alkannin Inhibited Hepatic Inflammation in Diabetic Db/Db Mice

Cellular Physiology and Biochemistry ◽

10.1159/000488264 ◽

2018 ◽

Vol 45 (6) ◽

pp. 2461-2470 ◽

Cited By ~ 3

Author(s):

Wenhua Xue ◽

Zhirui Fan ◽

Yuanzhe Li ◽

Lifeng Li ◽

Tengfei Zhang ◽

...

Keyword(s):

Western Blotting ◽

Tumour Necrosis ◽

Rho Kinase ◽

Hepatic Inflammation ◽

Tnf Α ◽

Hepatoprotective Effects ◽

Kinase Pathway ◽

Necrosis Factor ◽

Pro Inflammatory Cytokines

Background/Aims: The current study was designed to investigate the protective role of alkannin (ALK) on liver injury in diabetic C57BL/KsJ-db/db mice and explore its potential mechanisms. Methods: An oral glucose tolerance test (OGTT) was performed. The levels of insulin, alanine aminotransferase (ALT), aspartate aminotransaminase (AST), total cholesterol (TC) and triglyceride (TG) were determined by commercial kits. The pro-inflammatory cytokines interleukin (IL)-1β, IL-6 and tumour necrosis factor (TNF)-α were determined by ELISA. The levels of the ROCK/NF-κB pathway were determined by Western blotting. Results: The contents of pro-inflammatory cytokines interleukin (IL)-1β, IL-6 and tumour necrosis factor (TNF)-α were inhibited by ALK, metformin or fasudil in diabetic db/db mice. Further, Western blotting analysis showed that the expression of Rho, ROCK1, ROCK2, p-NF-κBp65, and p-IκBα was significantly reversed by ALK treatment. In human hepatic HepG2 cells, the hepatoprotective effects of ALK were further characterized. With response to palmitic acid-challenge, increased amounts of insulin, ALT, AST, TG, and TC were observed, whereas ALK pretreatment significantly inhibited their leakage in HepG2 cells without appreciable cytotoxic effects. The inflammation condition was recovered with ALK treatment as shown by changes of IL-1β, IL-6 and TNF-α. Further, Western blotting analysis also suggested that ALK improves hepatic inflammation in a Rho-kinase pathway. Conclusion: The present study successfully investigated the role of Rho-kinase signalling in diabetic liver injury. ALK exhibited hepatoprotective effects in diabetic db/db mice, and it might act through improving hepatic inflammation through the Rho-kinase pathway.

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Phosphatase inhibition promotes antiapoptotic but not proliferative signaling pathways in erythropoietin-dependent HCD57 cells

Blood ◽

10.1182/blood.v96.6.2084 ◽

2000 ◽

Vol 96 (6) ◽

pp. 2084-2092 ◽

Cited By ~ 20

Author(s):

Amy E. Lawson ◽

Haifeng Bao ◽

Amittha Wickrema ◽

Sarah M. Jacobs-Helber ◽

Stephen T. Sawyer

Keyword(s):

Tyrosine Phosphatase ◽

Critical Role ◽

Mitogen Activated Protein Kinase ◽

Phosphatidylinositol 3 Kinase ◽

Erythroid Progenitors ◽

Murine Cell Line ◽

Mitogen Activated Protein ◽

Erk Activity ◽

Kinase Pathway

Abstract Erythropoietin (EPO) allows erythroid precursors to proliferate while protecting them from apoptosis. Treatment of the EPO-dependent HCD57 murine cell line with 70 μmol/L orthovanadate, a tyrosine phosphatase inhibitor, resulted in both increased tyrosine protein phosphorylation and prevention of apoptosis in the absence of EPO without promoting proliferation. Orthovanadate also delayed apoptosis in primary human erythroid progenitors. Thus, we investigated what survival signals were activated by orthovanadate treatment. Expression of Bcl-XL and BAD phosphorylation are critical for the survival of erythroid cells, and orthovanadate in the absence of EPO both maintained expression levels of antiapoptotic Bcl-XLand induced BAD phosphorylation at serine 112. Orthovanadate activated JAK2, STAT1, STAT5, the phosphatidylinositol-3 kinase (PI-3 kinase) pathway, and other signals such as JNK and p38 without activating the EPO receptor, JAK1, Tyk2, Vav, STAT3, and SHC. Neither JNK nor p38 appeared to have a central role in either apoptosis or survival induced by orthovanadate. Treatment with cells with LY294002, an inhibitor of PI-3 kinase activity, triggered apoptosis in orthovanadate-treated cells, suggesting a critical role of PI-3 kinase in orthovanadate-stimulated survival. Mitogen-activated protein kinase (MAPK) was poorly activated by orthovanadate, and inhibition of MAPK with PD98059 blocked proliferation without inducing apoptosis. Thus, orthovanadate likely acts to greatly increase JAK/STAT and PI-3 kinase basal activity in untreated cells by blocking tyrosine protein phosphatase activity. Activated JAK2/STAT5 then likely acts upstream of Bcl-XL expression and PI-3 kinase likely promotes BAD phosphorylation to protect from apoptosis. In contrast, MAPK/ERK activity correlates with only EPO-dependent proliferation but is not required for survival of HCD57 cells.

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