Modification of Hyaluronan by Heavy Chains of Inter-α-Inhibitor in Idiopathic Pulmonary Arterial Hypertension

We previously reported an altered hyaluronan (HA) metabolism in idiopathic pulmonary arterial hypertension (IPAH) lung tissue and cultured smooth muscle cells. Hyaluronan was present in the smooth muscle cell layer surrounding the pulmonary vasculature and in plexigenic lesions. Additionally, cultured pulmonary artery smooth muscle cells produced spontaneous HA “cable” structures, without additional stimuli, that were leukocyte-adhesive. We now present evidence that the HA that accumulates in IPAH plexigenic lesions is a pathological form of HA in which heavy chains (HCs) from the serum-derived proteoglycan inter-α-inhibitor are covalently attached to the HA backbone to form a pathological HC-HA complex. CD45-positive leukocytes were identified within these HC-HA matrices. Elevated mRNA levels of the enzyme that transfers HCs to HA, known as tumor necrosis factor-stimulated gene 6, were detected in IPAH lung tissue.     

Identification of Epithelial to Mesenchymal Transition as a Novel Source of Fibroblasts in Intestinal Fibrosis

Intestinal fibrosis is a major complication of Crohn disease (CD), but the precise mechanism by which it occurs is incompletely understood. As a result, specific therapies to halt or even reverse fibrosis have not been explored. Here, we evaluated the contribution of epithelial to mesenchymal transition (EMT) to intestinal fibrosis associated with a mouse model of CD and also human inflammatory bowel disease. Mice administered intrarectal 2,4,6-trinitrobenzene sulfonic acid (TNBS) develop inflammation and fibrosis that resembles CD both histologically and by immunologic profile. We utilized this model to molecularly probe the contribution of EMT to intestinal fibrosis. Additionally, we utilized double-transgenic VillinCre;R26Rosa-lox-STOP-lox-LacZ mice, in which removal of the STOP cassette by Cre recombinase in villin⁺ intestinal epithelial cells activates permanent LacZ expression, to lineage trace epithelial cells that might undergo EMT upon TNBS administration. TNBS-induced fibrosis is associated with the presence of a significant number of cells that express both epithelial and mesenchymal markers. In the lineage tagged transgenic mice, the appearance of LacZ⁺ cells that also express the fibroblast marker FSP1 unequivocally demonstrates EMT. Transforming growth factor (TGF)-β1, a known inducer of EMT in epithelial cells, induces EMT in rat intestinal epithelial cells in vitro, and bone morphogenic protein-7, an antagonist of TGF-β1, inhibits EMT and fibrosis both in vitro and in the TNBS-treated mice. Our study demonstrates that EMT contributes to intestinal fibrosis associated with the TNBS-induced model of Crohn colitis and that inhibition of TGF-β1 with recombinant human bone morphogenic protein-7 prevents this process and prevents fibrosis.     

Proteome Variations in Pancreatic Stellate Cells upon Stimulation with Proinflammatory Factors

Pancreatic stellate cells are key mediators in chronic pancreatitis and play a central role in the development of pancreatic fibrosis, stromal formation, and progression of pancreatic cancer. This study was aimed at investigating molecular changes at the level of the proteome that are associated with the activation of pancreatic stellate cells by proinflammatory factors, namely TNF-α, FGF2, IL6, and chemokine (C-C motif) ligand 4 (CCL4). They were added individually to cells growing in serum-free medium next to controls in medium supplemented with serum, thus containing a mixture of them all, or in serum-free medium alone. Variations were detected by means of a microarray of 810 antibodies targeting relevant proteins. All tested factors triggered increased proliferation and migration. Further analysis showed that TNF-α is the prime factor responsible for the activation of pancreatic stellate cells. CCL4 is associated with cellular neovascularization, whereas FGF2 and IL6 induction led to better cellular survival and decreased apoptotic activity of the stellate cells. The identified direct effects of individual cytokines on human pancreatic stellate cells provide new insights about their contribution to pancreatic cancer promotion.     

Melatonin Prevents Oxidative Stress and Hepatocyte Cell Death Induced by Experimental Cholestasis

The induction of oxidative stress precedes liver injury during experimental obstructive jaundice (OJ). In this sense, different evidences suggest that melatonin (MEL), as antioxidant, may be useful in the protection against apoptosis and necrosis during experimental cholestasis. In addition, we will also assess if MEL-dependent protection is related to a recovery of antioxidant status disturbances induced by OJ. Cholestasis was achieved by double ligature and sectioning of the principal bile duct. MEL was injected intraperitoneally (500?μg/kg/day). Lipid peroxidation was evaluated by the measurement of malondialdehyde (MDA) content in liver. Different parameters related to antioxidant status, such as reduced glutathione (GSH), glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD) were determined in liver. Liver injury was assessed by alanine aminotransferase (ALT) in serum, histological examination, DNA fragmentation and TUNEL assay. The activation of perisinusoidal stellate cells was evaluated by immunohistochemical measurement of α-smooth muscle actin in liver sections. The induction of OJ increased all the parameters related to apoptosis and necrosis in liver. The induction of liver injury was associated with stellate cell activation, as well as an increase in MDA (p<0.0001) and a reduction in GSH, GPx, catalase and SOD content (p<0.0001) in liver. MEL reduced hepatic apoptosis and necrosis (p<0.004) with a significant improvement in all oxidative stress markers. In conclusion, our results showed that MEL recovered the antioxidant status and reduced apoptosis and necrosis induced by experimental cholestasis.     

Poly(ADP-ribose) signaling in cell death

Poly(ADP-ribosyl)ation (PARylation) is a reversible protein modification carried out by the concerted actions of poly(ADP-ribose) polymerase (PARP) enzymes and poly(ADP-ribose) (PAR) decomposing enzymes such as PAR glycohydrolase (PARG) and ADP-ribosyl hydrolase 3 (ARH3). Reversible PARylation is a pleiotropic regulator of various cellular functions but uncontrolled PARP activation may also lead to cell death. The cellular demise pathway mediated by PARylation in oxidatively stressed cells has been described almost thirty years ago. However, the underlying molecular mechanisms have only begun to emerge relatively recently. PARylation has been implicated in necroptosis, autophagic cell death but its role in extrinsic and intrinsic apoptosis appears to be less predominant and depends largely on the cellular model used. Currently, three major pathways have been made responsible for PARP-mediated necroptotic cell death: (1) compromised cellular energetics mainly due to depletion of NAD, the substrate of PARPs; (2) PAR mediated translocation of apoptosis inducing factor (AIF) from mitochondria to nucleus (parthanatos) and (3) a mostly elusive crosstalk between PARylation and cell death/survival kinases and phosphatases. Here we review how these PARP-mediated necroptotic pathways are intertwined, how PARylation may contribute to extrinsic and intrinsic apoptosis and discuss recent developments on the role of PARylation in autophagy and autophagic cell death.     

人IL-6和TNF突变体重组融合蛋白表达质粒的构建及在大肠杆菌中的表达

本文利用PCR技术,对人肿瘤坏死因子α(hTNFα)基因进行了改造,并将其与人白细胞介素-6(hIL-6)成熟肽编码区cDNA进行融合,构建了5′IL-6-TNF△融合蛋白的表达质粒pBVIL6-TNFA△。DNA序列分析证明,PCR扩增片段核苷酸序列与引物设计序列及相应的cDNA序列完全一致;重组子用限制性内切酶酶切鉴定,含有正确的IL6-TNF△融合cDNA片段;表达产物经SDS-聚丙烯酰胺凝胶电泳,分子量约为37kD,与预计的相符合;生物学活性分析初步表明,该融合蛋白具有抗肿瘤活性。     

The Structure and Ubiquitin Binding Properties of TRAF RING Heterodimers

Tumour necrosis factor (TNF) receptor associated factor (TRAF) family members share a common domain architecture, but play non-redundant physiological roles in cell signalling. At the N terminus, most TRAFs have a RING domain, followed by a series of Zinc finger (ZF) domains. The RING domain of TRAF6 dimerizes, and the RING homodimer together with the first ZF assembles ubiquitin chains that form a platform which facilitates activation of downstream kinases. The RING dimer interface is conserved amongst TRAF proteins, suggesting that functional heterodimers could be possible. Here we report the structure of the TRAF5-TRAF6 RING heterodimer, which accounts for the stability of the heterodimer as well as its ability to assemble ubiquitin chains. We also show that the RING domain of TRAF6 heterodimerizes with TRAF3 and TRAF2, and demonstrate that the linker helix and first ZF of TRAF2 can cooperate with TRAF6 to promote chain assembly. Collectively our results suggest that TRAF RING homo- and hetero-dimers have the potential to bridge interaction of nearby TRAF trimers and modulate TRAF-mediated signalling.     

Involvement of a Caspase-3-Like Cysteine Protease in 1-Methyl-4-Phenylpyridinium-Mediated Apoptosis of Cultured Cerebellar Granule Neurons

Abstract: Exposure of various neuronal cells or cell lines to high concentrations of 1-methyl-4-phenylpyridinium (MPP⁺), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), results in cell death. Recently, it has been reported that low concentrations of MPP⁺ induce apoptosis in susceptible neurons. We have further characterized MPP⁺-mediated toxicity of cultured cerebellar granule neurons (CGNs) and found that exposure of CGNs to relatively low concentrations of MPP⁺ results in apoptosis, whereas higher concentrations result in necrosis. Cotreatment of CGNs with MPP⁺ and the tetrapeptide inhibitor of caspase-3-like proteases, acetyl-DEVD-CHO, markedly attenuates apoptotic but not necrotic death of these neurons. The more specific inhibitor of caspase-1-like proteases, acetyl-YVAD-CHO, however, was ineffective against MPP⁺ neurotoxicity. Moreover, cytoplasmic extracts prepared from MPP⁺-treated CGNs contain markedly increased protease activity that cleaves the caspase-3 substrate acetyl-DEVD- p -nitroaniline. Finally, the cytoplasmic concentration of the apoptogenic protein cytochrome c was increased in a time-dependent fashion in MPP⁺-treated CGNs before the onset of apoptosis. Our data confirm that the neurotoxicity of MPP⁺ is due to both necrosis and apoptosis and suggest that the latter is mediated by activation of a caspase-3-like protease.     

Screening of Necrotizing Spiders in Korea Using Nonradioactive Sphingomyelinase Assay(II) Web-building Spiders

Spider bites cause a range of symptoms from simple swellings to disfiguring necrotic lesions, and occasionally death. While spider bites are not a major medical problem in Korea, it would be of great value to know which species of spiders pose a threat to human health. A middle molecular weight protein, sphingomyelinase D, has been identified in the venom of the brown recluse spider and strong evidence suggests that they have a major role in spider bite necrosis. For the identification of necrotizing species, we have investigated using recently developed non‐radioactive assay of sphingomyelinase for rapidly screening the necrotizing venoms. Here, we demonstrate the fetal toxicity of total 65 species (24 genera, 9 families) of the web‐building spiders among 622 identified spider species in Korea. It has been revealed that four species of the orb‐weaving spider, Araneus ventricosus (family Araneidae, 0.3509), Dipoena castrata (0.2413, family Theridiidae), Argiope minuta (0.1836, family Araneidae), and Paracoelotes spinivulva (0.1760, family Amaurobiidae) have relatively strong activities among themselves. However, comparing to that of the brown recluse spider, Loxosceles recluse (1.814) in North America, the necrotizing shpingomyelinase activities of these Korean web‐building spiders are still very low. Based on our results, we may thus conclude that there would be little possibilities in South Korea to create serious medical problems caused by necrotizing arachnidism.     

Estrogens and cell death in murine uterine luminal epithelium

Summary The luminal epithelium of adult ovariectomized mice responds to estradiol-17 with a synchronised wave of DNA synthesis and mitosis. Estriol, however, although producing a similar DNA-synthetic and mitotic response fails to cause an increase in cell number owing to a wave of cell death occurring at mitosis. In the present study it was shown that cells died by two different routes. The majority died by apoptosis but, unusually, a minority also died by necrosis. In the apoptotic cells the cytoplasm became dense, the endoplasmic reticulum and nuclear cisternae dilated; chromatin became marginated the nucleus shrank and became deeply infolded and contorted. Apoptosis, however, was uncharacteristic in that the nucleus failed to fragment, form caps or show disruption before the cells died by membrane rupture. Furthermore, the cells were frequently lost in sheets from the epithelium into the lumen. Part of the biochemical explanation for this onset of cell death comes from the accelerated loss from the tissue of estriol when compared to estradiol-17. This resulted in a decline in protein and rRNA biosynthesis and a failure to complete ribosomal maturation. Evidence in favour of this explanation came from experiments that showed a return to the estradiol-17 level of response and an inhibition of cell death when the occupancy of the estriol receptor was maintained.