Biomedical subjects

Shoukang Zhu

Publications and source records attributed to Shoukang Zhu.

7 recordsLinked to original sources

PubMed2006

Aging in the atherosclerosis milieu may accelerate the consumption of bone marrow endothelial progenitor cells.

OBJECTIVE: We have demonstrated that bone marrow cells from young and wild-type (WT), but not old apoE-/-, mice are capable of preventing atherosclerosis. This study was performed to elucidate the numerical and functional changes underlying the efficacy difference between young and old bone marrow. METHODS AND RESULTS: CD34+/VEGFR2+ conventional endothelial progenitor cells and lin-/cKit+/Sca-1+ hematopoietic stem cells did not differ numerically or functionally between young and old apoE-/- bone marrow. Fluorescence-activated cell sorter analysis, however, showed that a group of cells (simple little cells or SLCs), characteristically located in the lower left quadrant of forward scatter/side scatter flow cytometric plot, were markedly decreased in old WT and apoE-/- marrow, but abundantly present in young WT and apoE-/- bone marrow. The SLC fraction was mainly composed of lin-/cKit-/Sca-1- cells. In vitro differentiation assay demonstrated substantially more efficient endothelial differentiation of lin-/cKit-/Sca-1- SLCs than other bone marrow fractions at a single cell level and en masse. Furthermore, old lin-/cKit-/Sca-1- SLCs had a trend of decreased endothelial differentiation capability. CONCLUSIONS: Lin-/cKit-/Sca-1- SLCs may represent a previously unrecognized cell population, enriched for endothelial progenitors. The identification of these cells may help improve the efficacy of cell therapy.

Animals↗

PubMed2005

Paclitaxel modulates TGFbeta signaling in scleroderma skin grafts in immunodeficient mice.

BACKGROUND: Systemic sclerosis (SSc) is characterized by excessive fibrosis and obliterative vascular lesions. Abnormal TGFbeta activation is implicated in the pathogenesis of SSc. Aberrant TGFbeta/Smad signaling can be controlled by stabilization of microtubules with paclitaxel. METHODS AND FINDINGS: SSc and healthy human skin biopsies were incubated in the presence or absence of paclitaxel followed by transplantation into severe combined immunodeficient mice. TGFbeta signaling, fibrosis, and neovessel formation were evaluated by quantitative RT-PCR and immunohistochemical staining. Paclitaxel markedly suppressed Smad2 and Smad3 phosphorylation and collagen deposition in SSc grafts. As a result, the autonomous maintenance/reconstitution of the SSc phenotype was prevented. Remarkably, SSc grafts showed a 2-fold increase in neovessel formation relative to normal grafts, regardless of paclitaxel treatment. Angiogenesis in SSc grafts was associated with a substantial increase in mouse PECAM-1 expression, indicating the mouse origin of the neovascular cells. CONCLUSION: Low-dose paclitaxel can significantly suppress TGFbeta/Smad activity and lessen fibrosis in SCID mice. Transplantation of SSc skin into SCID mice elicits a strong angiogenesis-an effect not affected by paclitaxel. Although prolonged chemotherapy with paclitaxel at higher doses is associated with pro-fibrotic and anti-angiogenic changes, the findings described here indicate that low-dose paclitaxel may have therapeutic benefits for SSc via modulating TGFbeta signaling.

Adult↗

PubMed2005

A crucial role for GRK2 in regulation of endothelial cell nitric oxide synthase function in portal hypertension.

Nitric oxide (NO) production by endothelial cell nitric oxide synthase (eNOS) in sinusoidal endothelial cells is reduced in the injured liver and leads to intrahepatic portal hypertension. We sought to understand the mechanism underlying defective eNOS function. Phosphorylation of the serine-threonine kinase Akt, which activates eNOS, was substantially reduced in sinusoidal endothelial cells from injured livers. Overexpression of Akt in vivo restored phosphorylation of Akt and production of NO and reduced portal pressure in portal hypertensive rats. We found that Akt physically interacts with G-protein-coupled receptor kinase-2 (GRK2), and that this interaction inhibits Akt activity. Furthermore, GRK2 expression increased in sinusoidal endothelial cells from portal hypertensive rats and knockdown of GRK2 restored Akt phosphorylation and NO production, and normalized portal pressure. Finally, after liver injury, GRK2-deficient mice developed less severe portal hypertension than control mice. Thus, an important mechanism underlying impaired activity of eNOS in injured sinusoidal endothelial cells is defective phosphorylation of Akt caused by overexpression of GRK2 after injury.

Animals↗

PubMed2005

Inactivation of monocarboxylate transporter MCT3 by DNA methylation in atherosclerosis.

BACKGROUND: Monocarboxylate transporters (MCTs) mediate lactate transport across the plasma membrane of cells. The molecular mechanisms regulating monocarboxylate transport in smooth muscle cells (SMCs) remain poorly characterized. The aim of this study was to investigate the effects of DNA methylation on MCT expression and lactate transport in SMCs in relation to atherosclerosis. METHODS AND RESULTS: MCT expression was determined by real-time reverse transcription-polymerase chain reaction, Western blotting, and immunohistochemistry in SMCs isolated from human aortas and coronary arteries. Bisulfite sequencing and confocal microscopic analysis were used to study DNA methylation and lactate transport in SMCs, respectively. Downregulation of MCT3 and impaired lactate transport were detected in proliferating/synthetic SMCs, relative to the contractile phenotype. A passage number- and atherosclerotic lesion-dependent methylation pattern of MCT3 was demonstrated in the CpG island located in exon 2. Treatment of SMCs with the demethylating agent 5-aza-2'-deoxycytidine restored MCT3 expression and normalized lactate transport. Furthermore, small interfering RNA-mediated specific MCT3 knockdown substantially stimulated SMC proliferation. CONCLUSIONS: These data indicate that DNA methylation may modify monocarboxylate transport by suppressing MCT3 expression, which could be important in regulating SMC function and the development of atherosclerosis.

Aorta↗

PubMed2004

Transforming growth factor-beta-induced inhibition of myogenesis is mediated through Smad pathway and is modulated by microtubule dynamic stability.

The expression of muscle-specific genes associated with myogenesis is controlled by several myogenic transcription factors, including myogenin and MEF2D. Transforming growth factor-beta (TGF-beta) has been shown to inhibit myogenesis, yet the molecular mechanisms underlying such inhibition are not known. In the present study, TGF-beta was shown to inhibit myogenin and MEF2D expression and myotube formation in C2C12 myoblasts cultured in differentiation medium in a cell density-dependent manner. Transfection of C2C12 cells with Smad7, an antagonist for TGF-beta/Smad signaling, restored the capacity of these cells to differentiate in the presence of TGF-beta or when cultured in growth medium at low confluence, conditions that hinder muscle differentiation. Moreover, nocodazole, a microtubule-destabilizing agent, enhanced the inhibition of myogenesis exerted by TGF-beta, an effect that could be restored by tubulin-polymerizing agent taxol, both of which have been shown to affect Smad-microtubule interaction and regulate TGF-beta/Smad signaling. Our results indicate that TGF-beta inhibits myogenesis, at least in part, via Smad pathway, and provide evidence that low-dose pharmacological agents taxol and nocodazole can be used as a means to modulate myogenesis without affecting cell survival.

Cell Differentiation↗

PubMed2002

Deficient Smad7 expression: a putative molecular defect in scleroderma.

Scleroderma is a chronic systemic disease that leads to fibrosis of affected organs. Transforming growth factor (TGF) beta has been implicated in the pathogenesis of scleroderma. Smad proteins are signaling transducers downstream from TGF-beta receptors. Three families of Smads have been identified: (i) receptor-regulated Smad2 and -3 (R-Smads); (ii) common partner Smad4 (Co-Smad); and (iii) inhibitory Smad6 and -7 (I-Smads, part of a negative feedback loop). We have investigated the signaling components for the TGF-beta pathway and TGF-beta activity in scleroderma lesions in vivo and in scleroderma fibroblasts in vitro. Basal level and TGF-beta-inducible expression of Smad7 are selectively decreased, whereas Smad3 expression is increased both in scleroderma skin and in explanted scleroderma fibroblasts in culture. TGF-beta signaling events, including phosphorylation of Smad2 and -3, and transcription of the PAI-1 gene are increased in scleroderma fibroblasts, relative to normal fibroblasts. In vitro adenoviral gene transfer with Smad7 restores normal TGF-beta signaling in scleroderma fibroblasts. These results suggest that alterations in the Smad pathway, including marked Smad7 deficiency and Smad3 up-regulation, may be responsible for TGF-beta hyperresponsiveness observed in scleroderma.

Adult↗

PubMed2002

Upregulation of PAI-1 is mediated through TGF-beta/Smad pathway in transplant arteriopathy.

BACKGROUND: Plasminogen activator inhibitor type 1 (PAI-1) is the primary physiologic inhibitor of plasminogen activator in vivo. Increased PAI-1 expression is associated with arteriosclerosis. Transforming growth factor-beta (TGF-beta) induces PAI-1 production via Smads. METHODS: In vivo, TGF-beta receptors (TbetaRs), Smad2, Smad3, and Smad4, PAI-1, and Smad2 phosphorylation were examined by immunohistochemistry in 3 native aortas, 14 rat aortic syngrafts, and 19 allografts collected at 15, 30, and 45 days post-transplantation. In vitro, phosphorylation of Smad2 and induction of PAI-1 mRNA in human aortic smooth muscle cells (SMCs) in response to TGF-beta treatment were detected by Western blot and by TaqMan real-time RT-PCR, respectively. RESULTS: Immunohistochemical staining revealed that vascular parenchymal cells contained TbetaRI, TbetaRII, Smad2, Smad3, and Smad4, known signaling transducers for TGF-beta/Smad pathway, in all samples. Intense staining for phospho-Smad2 was observed in 94% of endothelial cells (ECs), 86% of intimal cells, 27% of medial SMCs, and 38% of adventitial cells at all 3 time points in all aortic allografts, but only in 5% of ECs in syngrafts. PAI-1 immunoreactivity was detected in similar number of cells, and from consecutive sections, phospho-Smad2 colocalized with PAI-1, in the aortic allografts. Low basal level PAI-1 expression was observed in aortic syngrafts and native vessels. Smad2 phosphorylation and time-dependent PAI-1 induction were detected in cultured SMCs upon TGF-beta treatment. CONCLUSIONS: Phospho-Smad2 staining in aortic allografts indicates the activation of TGF-beta signaling in allo-transplantation; and co-localization of PAI-1 and phospho-Smad2 suggests that PAI-1 upregulation is mediated mainly by TGF-beta/Smad pathway in aortic allografts.

Animals↗