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Previous studies have shown that exposure to chronic hypoxia protects against myocardial infarction, but little is known about the cellular and molecular mechanisms involved. Here we observed that chronic hypoxia for 3 wk resulted in improved survival of mice (from 64% to 83%), reduced infarction size (from 45 [+ or -] 4% to 32 [+ or -] 4%, P < 0.05), increased cardiac ejection fraction (from 19 [+ or -] 4% to 35 [+ or -] 5%, P < 0.05), coronary flow velocity under adenosine-induced hyperemia (from 58 [+ or -] 2 to 75 [+ or -] 5 cm/s, P < 0.05), myocardial capillary density (from 3,772 [+ or -] 162 to 4,760 [+ or -] 197 capillaries/[mm.sup.2], P < 0.01), and arteriolar density (from 8.04 [+ or -] 0.76 to 10.34 [+ or -] 0.69 arterioles/[mm.sup.2], P < 0.05) 3 wk after myocardial infarction. With two-dimensional gel electrophoresis, we identified that protein disulfide isomerase (PDI) was highly upregulated in hypoxic myocardial capillary endothelial cells. The loss of PDI function in endothelial cells by small interfering RNA significantly increased the number of apoptotic cells (by 3.4-fold at hypoxia, P < 0.01) and reduced migration (by 52% at hypoxia, P < 0.001) and adhesion to collagen I (by 42% at hypoxia, P < 0.01). In addition, the specific inhibition of PDI by PDI small interfering RNA (by 46%, P < 0.01) and bacitracin (by 72%, P < 0.001) reduced the formation of tubular structures by endothelial cells. Our data indicate that chronic hypoxic exposure improves coronary blood flow and protects the myocardium against infarction. These beneficial effects may be partly explained by the increased endothelial expression of PDI, which protects cells against apoptosis and increases cellular migration, adhesion, and tubular formation. The increased PDI expression in endothelial cells may be a novel mechanism to protect the myocardium against myocardial ischemic diseases. myocardial infarction; apoptosis; migration; adhesion

Ag2–TCNQF4 (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) was synthesized for the first time via a photo-induced charge transfer of the precursor of semiconductor Ag–TCNQF4 using Au nanoparticles (AuNPs) as a catalyst. We first prepared the one-dimensional Ag–TCNQF4 crystal wires on a solid-supported substrate via a solution process. Then, Ag–TCNQF4 was reacted with KAuCl4via the galvanic replacement reaction to form a metal–semiconductor complex, AuNPs decorated Ag–TCNQF4 (AuNPs@Ag–TCNQF4). The resulting Ag–TCNQF4 crystal wires and AuNPs@Ag–TCNQF4 complex were characterized by scanning electron microscopy (SEM), X-ray diffraction, ultraviolet-visible (UV-vis) and X-ray photoelectron spectroscopies. Under the plasmon-enhanced catalysis of AuNPs, a laser-induced charge transfer process occurred on Ag–TCNQF4, altering it to Ag2–TCNQF4. Time-resolved in situ Raman spectra were recorded to monitor the photo-induced charge transfer process. The Raman data show that this photo-induced charge transfer process is laser wavelength-dependant, power-dependant and irradiation time-dependant. It is also affected by the loading of AuNPs. The SEM images, UV-vis and infrared spectra of the AuNPs@Ag–TCNQF4 before and after laser irradiation further prove that the charge transfer product is Ag2–TCNQF4. The mechanism of the plasmon-enhanced catalysis of photo-induced charge transfer from TCNQF4− to TCNQF42− is suggested, which provides a good model to study the charge transfer process in metal–semiconductor systems. In addition, this material has significance for applications in memory storage and photoelectric devices. [ABSTRACT FROM AUTHOR]

Spin-trapping nitrones such as alpha-phenyl-N-tert-butylnitrone (PBN) have traditionally been used to trap and stabilize free radicals for detection by electron paramagnetic resonance (EPR) spectroscopy. Unlike classical antioxidants, these agents have never been evaluated therapeutically in allograft transplantation. In the present study, we examined potential mechanisms of action of treatment with PBN in a rat model of acute cardiac allograft transplantation. Graft rejection was determined by histological examination and graft function determined by in situ sonomicrometry. DNA binding for nuclear factor (NF)-kappaB and activator protein (AP-1) were determined by gel shift assays. Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed for inducible nitric-oxide synthase (iNOS) and inflammatory cytokines. Histological rejection scores were elevated in untreated allografts and decreased by treatment with PBN. In situ sonomicrometry revealed decreased heart rate and distended end diastolic and end systolic segment lengths with rejection. Although PBN did not alter heart rate, it did normalize the distention of both diastolic and systolic cardiac dimension. EPR spectroscopy revealed nitrosylation of myocardial heme protein in untreated allografts that was decreased by treatment with PBN. PBN also decreased iNOS protein and iNOS mRNA. RT-PCR analysis revealed enhanced cytokine gene expression for interferon-gamma, interleukin-6, and interleukin-10 in untreated allografts. Expression for these genes was potently inhibited or abolished in recipients treated with PBN. PBN treatment also decreased DNA binding of transcription factors, NF-kappaB and AP-1. Thus, PBN retains significant anti-inflammatory properties through its action to down-regulate cytokine gene expression that contribute to protection against acute alloimmune activation in cardiac allografts.

We examined the efficacy and mechanism of action of N(6)-(1-iminoethyl)-L-lysine (L-NIL), a highly selective inhibitor of inducible nitric oxide (NO) synthase (iNOS), on acute cardiac transplant rejection. L-NIL produced a concentration-dependent attenuation of plasma NO by-products and a decrease in nitrosylation of heme protein without altering protein levels of iNOS. At postoperative day 4, L-NIL did not alter the increased binding activities for transcription factors nuclear factor-kappaB and activator protein-1. Whereas L-NIL decreased inflammatory cell infiltration, graft survival was only prolonged at the dose of 1.0 microg/ml that incompletely blocked NO production. Higher L-NIL concentrations (30 and 60 microg/ml) ablated the increased NO production but failed to improve graft survival and even potentiated NF-kappaB binding activity examined at day 6. Alloimmune activation indicated by increased cytokine gene expression for interferon-gamma, interleukin-6, and interleukin-10 was inhibited in grafts only by treatment with 1.0 microg/ml L-NIL. These findings suggest a complex role of NO in acute cardiac allograft rejection. Partial inhibition of iNOS is beneficial to graft survival, whereas total ablation may oppose any benefits to graft survival. These studies have important implications in understanding the dual role of NO in acute rejection and help to reconcile discrepancies in the literature.