Activation of JAK-STAT pathway is required for platelet-derived growth factor-induced proliferation of pancreatic stellate cells

AIM: To clarify the role of Janus kinase-signal transducersand activators of transcription (JAK-STAT) pathway in platelet-derived growth factor (PDGF) induced proliferation in activated pancreatic stellate cells (PSCs).METHODS: PSCs were isolated from rat pancreas tissue, and used in their culture-activated, myofibroblast-like phenotype. STAT-specific binding activity was assessed by electrophoretic mobility shift assay. Activation of Src, JAK2,STAT1, STAT3, and ERK was determined by Western blotting using anti-phosphospecific antibodies. Cell proliferation was assessed by measuring the incorporation of 5-bromo-2′deoxyuridine.RESULTS: PDGF-BB induced STAT-specific binding activity, and activation of Src, JAK2, STAT1, STAT3, and ERK. Ethanol and acetaldehyde at clinically relevant concentrations decreased basal activation of JAK2 and STAT3. PDGFinduced activation of STAT1 and STAT3 was inhibited bya Src inhibitor PP1 and a JAK2 inhibitor AG490, whereasPDGF-induced activation of ERK was inhibited by PP1, and not by AG490. PDGF-induced proliferation was inhibited by PP1 and AG490 as well as by STAT3 antisense oligonucleotide.CONCLUSION: PDGF-BB activated JAK2-STAT pathwayvia Src-dependent mechanism. Activation of JAK2-STAT3pathway, in addition to ERK, may play a role in PDGF-induced proliferation of PSCs.

Establishment and characterization of a rat pancreatic stellate cell line by spontaneous immortalization

AIM: Activated pancreatic stellate cells (PSCs) have been implicated in the pathogenesis of pancreatic fibrosis and inflammation. Primary PSCs can be subcultured only several times because of their limited growth potential. A continuous cell line may therefore be valuable in studying molecular mechanisms of these pancreatic disorders. The aim of this study was to establish a cell line of rat PSCs by spontaneous immortalization.METHODS: PSCs were isolated from the pancreas of male Wistar rats, and conventional subcultivation was performed repeatedly. Telomerase activity was measured using the telomere repeat amplification protocol. Activation of transcription factors was assessed by electrophoretic mobility shift assay.Activation of mitogen-activated protein (MAP) kinases was examined by Western blotting using anti-phosphospecific antibodies. Expression of cytokine-induced neutrophil chemoattractant-1 was determined by enzyme immunoassay.RESULTS: Conventional subcultivation yielded actively growing cells. One clone was obtained after limiting dilution,and designated as SIPS. This cell line has been passaged repeatedly more than 2 years, and is thus likely immortalized.SIPS cells retained morphological characteristics of primary,culture-activated PSCs. SIPS expressed α-smooth muscle actin, glial acidic fibrillary protein, vimentin, desmin, type Ⅰ collagen, fibronectin, and prolyl hydroxylases. Telomerase activity and p53 expression were negative. Proliferation of SIPS cells was serum-dependent, and stimulated with platelet-derived growth factor-BB through the activation of extracellular signal-regulated kinase. Interleukin-1β activated nuclear factor-κB, activator protein-1, and MAP kinases.Interleukin-1β induced cytokine-induced neutrophil chemoattractant-1 expression through the activation of nuclear factor-κB and MAP kinases.CONCLUSION: SIPS cells can be useful for in vitro studies of cell biology and signal transduction of PSCs.

Green tea polyphenol epigallocatechin-3-gallate blocks PDGF-induced proliferation and migration of rat pancreatic stellate cells

AIM: To clarify the effects of epigallocatechin-3-gallate (EGCG) on the platelet-derived growth factor (PDGF)-BBinduced proliferation and migration of pancreatic stellate cells (PSCs).METHODS: PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype. Cell proliferation was assessed by measuring the incorporation of 5-bromo-2'-deoxyuridine. Cell migration was assessed using modified Boyden chambers. CyclinD1, p21waf1, and p27kip1 expression and phosphorylation of PDGF β-receptor, extracellular signal-regulated kinase, and Akt were examined by Western blotting. Activation of phosphatidylinositol 3-kinase was examined by kinase assay using phosphatidylinositol as a substrate. Cell cycle was assessed by flow cytometry after staining with propidium iodide. RESULTS: EGCG at non-cytotoxic concentrations inhibited PDGF-induced proliferation and migration. This effect was associated with the inhibition of cell cycle progression beyondthe G1 phase, decreased cyclin D1 and increased p27Kip1 expression. EGCG inhibited tyrosine phosphorylation of PDGF β-receptor and downstream activation of extracellular signal-regulated kinase and phosphatidylinositol 3-kinase/ Akt pathways.CONCLUSION: EGCG inhibited PDGF-BB-induced proliferation and migration of PSCs through the inhibrdon of PDGF-mediated signaling pathways.

Endothelin-1 stimulates contraction and migration of rat pancreatic stellate cells

AIM: To examine the ability of ET-1 to affect the cell functions of PSCs and the underlying molecular mechanisms.METHODS: PSCs were isolated from the pancreas of male Wistar rats after perfusion with collagenase, and cells between passages two and five were used. Expression of ET-1 and ET receptors was assessed by reverse transcription-PCR and immunostaining. Phosphorylation of myosin regulatory light chain (MLC), extracellular-signal regulated kinase (ERK), and Akt was examined by Western blotting. Contraction of PSCs was assessed on hydrated collagen lattices. Cell migration was examined using modified Boyden chambers. Cell proliferation was assessed by measuring the incorporation of 5-bromo-2'-deoxyuridine.RESULTS: Culture-activated PSCs expressed ETA and ETB receptors, and ET-1. ET-1 induced phosphorylation of MLC and ERK, but not Akt. ET-1 induced contraction and migration,but did not alter proliferation of PSCs. ET-1-induced contraction was inhibited by an ETA receptor antagonist BQ-123 and an ETB receptor antagonist BQ-788, whereas migration was inhibited by BQ-788 but not by BQ-123. A Rho kinase inhibitor Y-27632 abolished both contraction and migration.CONCLUSION: ET-1 induced contraction and migration of PSCs through ET receptors and activation of Rho-Rho kinase. ETA and ETB receptors play different roles in the regulation of these cellular functions in response to ET-1.

2.抗挤毁电阻焊套管的开发

制约钢管抗挤毁强度的主要因素有屈强比、残余应力和尺寸精度。提高屈强比,将大大改善钢管的抗挤毁性能。对D/S值(外径与壁厚之比)较小的钢管,即D/S≤20的钢管更是如此。在这类钢管中,屈服强度是导致塑性挤毀的主要因素。因此,在设计钢种时,降低含碳量和细化晶粒,是达到这一目的的有效措施。新日铁开发了一种可以提高热轧低碳带钢强度的新工艺,此工艺是在带钢热轧期间,控制轧材高温机械性能的控制轧制工艺。采用这项新工艺,用热轧带钢不经淬火与回火便能直接生产出552MPa级的高强度电阻焊石油套管,而淬火与回火一直是常规轧制不可缺少的过程。将减少含碳量的冶炼方法与以细化晶粒为目的的高温机械性能控制轧制方法相结合,能大幅度地改善钢材的屈强比。因此,由这一新工艺生产的电阻焊石油套管,其抗挤毁强度等同或优于传统工艺轧制,即热轧、淬火、回火工艺流程所生产的产品。要实施热轧工艺的这一革新,即只采用热轧就能获得低碳高强的细晶粒钢材,须将终轧温度准确地控制在Ar_3点之上,并在轧后冷却区的前半段进行急冷,以及降低带钢的打卷温度。