内毒诱导肺动脉内皮细胞生成过氧亚硝基阴离子的意义

目的：探讨牛肺动脉内皮细胞（BPAEC）产生过氧亚硝基阴离子（ONOO^-）的能力及其作用。方法：用流式细胞免疫荧光技术,定量检测内毒素主要成分脂多糖（LPS）诱导培养的BPAEC中ONOO^-生成标志物硝基酪氨酸（NT）的含量,观察ONOO^-对BPAEC形态变化的影响。结果：LPS可剂量依赖性诱导BPAEC产生ONOO^-明显增多,并为氮基胍部分翻转;ONOO^-可导致BPAEC明显回缩,胞体变小,细胞间隙增宽。结论：LPS诱导BPAEC产生增多的ONOO^-可能参与介导LPS对BPAEC本身的损伤效应。     

Crystal structure of a Y-family DNA polymerase in action: a mechanism for error-prone and lesion-bypass replication

Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4) is a DinB homolog that belongs to the recently described Y-family of DNA polymerases, which are best characterized by their low-fidelity synthesis on undamaged DNA templates and propensity to traverse normally replication-blocking lesions. Crystal structures of Dpo4 in ternary complexes with DNA and an incoming nucleotide, either correct or incorrect, have been solved at 1.7 A and 2.1 A resolution, respectively. Despite a conserved active site and a hand-like configuration similar to all known polymerases, Dpo4 makes limited and nonspecific contacts with the replicating base pair, thus relaxing base selection. Dpo4 is also captured in the crystal translocating two template bases to the active site at once, suggesting a possible mechanism for bypassing thymine dimers.     

Lipopolysaccharide induces apoptosis in adult rat ventricular myocytes via cardiac AT(1) receptors

Lipopolysaccharide (LPS) from gram-negative bacteria circulates in acute, subacute, and chronic conditions. It was hypothesized that LPS directly induces cardiac apoptosis. In adult rat ventricular myocytes (isolated with depyrogenated digestive enzymes to minimize tolerance), LPS (10 ng/ml) decreased the ratio of Bcl-2 to Bax at 12 h; increased caspase-3 activity at 16 h; and increased annexin V, propidium iodide, and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining at 24 h. Apoptosis was blocked by the caspase inhibitor benzyloxycarbonyl-valine-alanine-aspartate fluoromethylketone (Z-VAD-fmk), captopril, and angiotensin II type 1 receptor (AT(1)) inhibitor (losartan), but not by inhibitors of AT(2) receptors (PD-123319), tumor necrosis factor-alpha (TNFRII:Fc), or nitric oxide (N(G)-monomethyl-L-arginine). Angiotensin II (100 nmol/l) induced apoptosis similar to LPS without additive effects. LPS in vivo (1 mg/kg iv) increased apoptosis in left ventricular myocytes for 1-3 days, which dissipated after 1-2 wk. Losartan (23 mg. kg(-1). day(-1) in drinking water for 3 days) blocked LPS-induced in vivo apoptosis. In conclusion, low levels of LPS induce cardiac apoptosis in vitro and in vivo by activating AT(1) receptors in myocytes.     

Functional and molecular evidence for Na+-HCO3- cotransporter in porcine vas deferens epithelia

This study focused on the role ofsodium-bicarbonate cotransporter (NBC1) in cAMP-stimulated iontransport in porcine vas deferens epithelium. Ion substitutionexperiments in modified Ussing chambers revealed that cAMP-mediatedstimulation was dependent on the presence of Na⁺,HCO, and Cl for a full response.HCO-dependent current was unaffected byacetazolamide, bumetanide, or amiloride but was inhibited bybasolateral 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid.Na⁺-driven, HCO-dependent,stilbene-inhibitable anion flux was observed across the basolateralmembrane of selectively permeabilized monolayers. Results ofradiotracer flux studies suggest a4,4'-dinitrostilbene-2,2'-disulfonate-sensitive stoichiometry of 2 baseequivalents per Na⁺. Antibodies raised against rat kidneyNBC epitopes (rkNBC; amino acids 338-391 and 928-1035)identified a single band of ~145 kDa. RT-PCR detected NBC1 message inporcine vas deferens epithelia. These results demonstrate that vasdeferens epithelial cells possess the proteins necessary for thevectoral transport of HCO and that these mechanismsare maintained in primary culture. Taken together, the results indicatethat vas deferens epithelia play an active role in male fertility andhave implications for our understanding of the relationship betweencystic fibrosis and congenital bilateral absence of the vas deferens.

     

LOX-1 inhibition in myocardial ischemia-reperfusion injury: modulation of MMP-1 and inflammation

A recently identified lectin-like oxidized low-density lipoprotein receptor (LOX-1) mediates endothelial cell injury and facilitates inflammatory cell adhesion. We studied the role of LOX-1 in myocardial ischemia-reperfusion (I/R) injury. Anesthetized Sprague-Dawley rats were subjected to 60 min of left coronary artery (LCA) ligation, followed by 60 min of reperfusion. Rats were treated with saline, LOX-1 blocking antibody JXT21 (10 mg/kg), or nonspecific anti-goat IgG (10 mg/kg) before I/R. Ten other rats underwent surgery without LCA ligation and served as a sham control group. LOX-1 expression was markedly increased during I/R (P < 0.01 vs. sham control group). Simultaneously, the expression of matrix metalloproteinase-1 (MMP-1) and adhesion molecules (P-selectin, VCAM-1, and ICAM-1) was also increased in the I/R area (P < 0.01 vs. sham control group). There was intense leukocyte accumulation in the I/R area in the saline-treated group. Treatment of rats with the LOX-1 antibody prevented I/R-induced upregulation of LOX-1 and reduced MMP-1 and adhesion molecule expression as well as leukocyte recruitment. LOX-1 antibody, but not nonspecific IgG, also reduced myocardial infarct size (P < 0.01 vs. saline-treated I/R group). To explore the link between LOX-1 and adhesion molecule expression, we measured expression of oxidative stress-sensitive p38 mitogen-activated protein kinase (p38 MAPK). The activity of p38 MAPK was increased during I/R (P < 0.01 vs. sham control), and use of LOX-1 antibody inhibited p38 MAPK activation (P < 0.01). These findings indicate that myocardial I/R upregulates LOX-1 expression, which through p38 MAPK activation increases the expression of MMP-1 and adhesion molecules. Inhibition of LOX-1 exerts an important protective effect against myocardial I/R injury.     

Importance of FADD signaling in serum deprivation- and hypoxia-induced cardiomyocyte apoptosis

Although cardiomyocyte (CM) apoptosis has been well described in both in vitro and in vivo models of ischemic heart disease, the intracellular pathways leading to CM death have not been fully characterized. To define the role of death receptor signaling in CM apoptosis, we constructed recombinant adenoviral vectors carrying wild-type (wt) or dominant negative (dn) forms of the death receptor adaptor protein FADD (Fas-associated death domain protein) and used these vectors to transduce rat neonatal CMs in models of hypoxia- and serum deprivation (SD)-induced apoptosis. The combination of SD and hypoxia induced rapid activation of caspase-3 and -8 as well as DNA fragmentation, reaching a plateau within 4-8 h. Adenoviral expression of FADD-dn inhibited caspase-8 activation as well as hypoxia/SD-induced apoptosis at 24 h in an moi (multiplicity of infection)-dependent manner. In contrast, adenoviral expression of FADD-wt increased apoptosis and caspase-3 activity in CMs under both normoxic and hypoxic conditions. Surprisingly, FADD-dn, as well as the specific caspase-8 inhibitor benzyloxycarbonyl-IETD-fluoromethylketone also inhibited the activation of caspase-9 and -3 in CMs subjected to hypoxia/SD. These data suggest a primary role for FADD/caspase-8 signaling that is necessary and sufficient for apoptosis of CMs subjected to hypoxia/SD.     

Measurements of tumor tissue oxygen tension using a time-resolved luminescence-based optical oxylite probe: comparison with a paired survival assay

Recently, a system that measures tissue oxygen tension using time-resolved luminescence-based optical sensors has become available commercially (Oxford Optronix, Oxford, England). Two experiments were conducted using this system. First, the oxygen tension distribution was measured in two tumor lines: a spontaneous mouse fibrosarcoma, FSa-II, and a human squamous cell carcinoma xenograft, FaDu. The area in which the pO(2) was equal to or lower than 2.5 mmHg was defined as the hypoxic lesion, and the hypoxic cell fraction was taken as the fraction of these measurements in a tumor. The measured hypoxic cell fractions were compared with those determined by the paired cell survival assay for tumors of various sizes. Second, the tumor tissue pO(2) was measured continuously after administration of two different anesthetics to evaluate the effect of these drugs on tissue pO(2). Results indicated a good agreement between the hypoxic cell fractions measured by this system and those determined by the paired cell survival curve assay for tumors smaller than approximately 500 mm(3). For tumors larger than approximately 500 mm(3), the hypoxic cell fractions measured by the oxygen probe system were higher than those measured by the paired cell survival assay. This may suggest that the hypoxic cell fraction measured by the oxygen probes included both hypoxic and necrotic areas in large tumors where necrotic lesions occupied a significant portion of the tumor. Continuous measurements of pO(2) after anesthesia (Nembutal, or ketamine plus xylazine) showed a consistent rise in the pO(2) during the first 20-30 min of measurement. Subsequently, the pO(2) values became constant or continued to rise slowly. For comparison, the tumor cell survivals were assayed after a dose of 20 Gy given in air at 5, 20 and 60 min after anesthesia. The result showed a decrease in cell survival only in tumors irradiated 20 min after an injection of Nembutal.     

A ribosome-free extract from cultured cells improves recovery of polysomes from the mosquito fat body: analysis of vitellogenin and ribosomal protein rpL34 gene expression

We have examined the association of ribosomal protein rpL34 mRNA with polysomes in Aedes albopictus C7-10 cells in culture using a simple, two-step sucrose gradient. In growing cells, 40-50% of the ribosomes were engaged on polysomes. This proportion could be increased to 80% when metabolism was stimulated by refeeding the cells with fresh medium. Conversely, ribosomes shifted off polysomes when cells were starved with phosphate-buffered saline or cell lysates were treated with puromycin. When similar approaches were used with fat body from blood-fed female Aedes aegypti mosquitoes, we were unable to obtain the polysome fraction that contained vitellogenin mRNA, which is abundantly translated after a blood meal. Addition of post-mitochondrial supernatant from fat body to polysomes from cultured cells shifted the polysome profile towards smaller polysomes and monosomes, in a dose-dependent fashion. Disruption of fat body tissue in a post-ribosomal supernatant from refed cells improved the recovery of polysomes, demonstrating both the engagement of vitellogenin mRNA on polysomes and the mobilization of rpL34 from messenger-ribonuceloprotein particles onto polysomes in blood-fed mosquitoes. These observations suggested that ribonucleases remain active when polysomes are prepared from mosquito fat body, and that cell culture supernatant contains a ribonuclease inhibitor.     

Elicitation of simian immunodeficiency virus-specific cytotoxic T lymphocytes in mucosal compartments of rhesus monkeys by systemic vaccination

Since most human immunodeficiency virus (HIV) infections are initiated following mucosal exposure to the virus, the anatomic containment or abortion of an HIV infection is likely to require vaccine-elicited cellular immune responses in those mucosal sites. Studying vaccine-elicited mucosal immune responses has been problematic because of the difficulties associated with sampling T lymphocytes from those anatomic compartments. In the present study, we demonstrate that mucosal cytotoxic T lymphocytes (CTL) specific for simian immunodeficiency virus (SIV) and simian HIV can be reproducibly sampled from intestinal mucosal tissue of rhesus monkeys obtained under endoscopic guidance. These lymphocytes recognize peptide-major histocompatibility complex class I complexes and express gamma interferon on exposure to peptide antigen. Interestingly, systemic immunization of monkeys with plasmid DNA immunogens followed by live recombinant attenuated poxviruses or adenoviruses with genes deleted elicits high-frequency SIV-specific CTL responses in these mucosal tissues. These studies therefore suggest that systemic delivery of potent HIV immunogens may suffice to elicit substantial mucosal CTL responses.