Short-term akt activation in cardiac muscle cells improves contractile function in failing hearts.

Akt is a serine/threonine protein kinase that is activated by a variety of growth factors or cytokines in a phosphatidylinositol 3-kinase-dependent manner. By using a conditional transgenic system in which Akt signaling can be turned on or off in the adult heart, we previously showed that short-term Akt activation induces a physiological form of cardiac hypertrophy with enhanced coronary angiogenesis and maintained contractility. Here we tested the hypothesis that induction of physiological hypertrophy by short-term Akt activation might improve contractile function in failing hearts. When Akt signaling transiently was activated in murine hearts with impaired contractility, induced by pressure overload or doxorubicin treatment, contractile dysfunction was attenuated in both cases. Importantly, improvement of contractility was observed before the development of cardiac hypertrophy, indicating that Akt activation improves contractile function independently of its growth-promoting effects. To gain mechanistic insights into Akt-mediated positive inotropic effects, transcriptional profiles in the heart were determined in a pressure overload-induced heart failure model. Biological network analysis of differentially expressed transcripts revealed significant alterations in the expression of genes associated with cell death, and these alterations were reversed by short-term Akt activation. Thus, short-term Akt activation improves contractile function in failing hearts. This beneficial effect of Akt on contractility is hypertrophy-independent and may be mediated in part by inhibition of cell death associated with heart failure.

Intrathecal injection of adenosine 2A receptor agonists reversed neuropathic allodynia through protein kinase (PK)A/PKC signaling.

A single intrathecal dose of adenosine 2A receptor (A2AR) agonist was previously reported to produce a multi-week reversal of allodynia in a chronic constriction injury (CCI) model of neuropathic pain. We aimed to determine if this long-term reversal was induced by A2AR agonism versus more generalized across adenosine receptor subtypes, and begin to explore the intracellular signaling cascades involved. In addition, we sought to identify whether the enduring effect could be extended to other models of neuropathic pain. We tested an A1R and A2BR agonist in CCI and found the same long duration effect with A2BR but not A1R agonism. An A2AR agonist (ATL313) produced a significant long-duration reversal of mechanical allodynia induced by long established CCI (administered 6 weeks after surgery), spinal nerve ligation and sciatic inflammatory neuropathy. To determine if ATL313 had a direct effect on glia, ATL313 was coadministered with lipopolysaccharide to neonatal microglia and astrocytes in vitro. ATL313 significantly attenuated TNFα production in both microglia and astrocytes but had no effect on LPS induced IL-10. Protein kinase C significantly reversed the ATL313 effects on TNFα in vitro in microglia and astrocytes, while a protein kinase A inhibitor only effected microglia. Both intrathecal PKA and PKC inhibitors significantly reversed the effect of the A2AR agonist on neuropathic allodynia. Therefore, A2AR agonists administered IT remain an exciting novel target for the treatment of neuropathic pain.

Microsomal prostaglandin e2 synthase-1 modulates the response to vascular injury.

BACKGROUND: Microsomal (m) prostaglandin (PG) E2 synthase (S)-1 catalyzes the formation of PGE2 from PGH2, a cyclooxygenase product that is derived from arachidonic acid. Previous studies in mice suggest that targeting mPGES-1 may be less likely to cause hypertension or thrombosis than cyclooxygenase-2-selective inhibition or deletion in vivo. Indeed, deletion of mPGES-1 retards atherogenesis and angiotensin II-induced aortic aneurysm formation. The role of mPGES-1 in the response to vascular injury is unknown. METHODS AND RESULTS: Mice were subjected to wire injury of the femoral artery. Both neointimal area and vascular stenosis were significantly reduced 4 weeks after injury in mPGES-1 knockout mice compared with wild-type controls (65.6 ± 5.7 versus 37.7 ± 5.1 × 10³ pixel area and 70.5 ± 13.4% versus 47.7 ± 17.4%, respectively; P < 0.01). Induction of tenascin-C, a proproliferative and promigratory extracellular matrix protein, after injury was attenuated in the knockouts. Consistent with in vivo rediversion of PG biosynthesis, mPGES-1-deleted vascular smooth muscle cells generated less PGE2 but more PGI2 and expressed reduced tenascin-C compared with wild-type cells. Both suppression of PGE2 and augmentation of PGI2 attenuate tenascin-C expression and vascular smooth muscle cell proliferation and migration in vitro. CONCLUSIONS: Deletion of mPGES-1 in mice attenuates neointimal hyperplasia after vascular injury, in part by regulating tenascin-C expression. This raises for consideration the therapeutic potential of mPGES-1 inhibitors as adjuvant therapy for percutaneous coronary intervention.

[Expression of inducible nitric oxide synthase in restenosis rats and function of Astragalus membranaceus and Angelica sinensis].

OBJECTIVE: To explore the expression of inducible nitric oxide synthase (iNOS) in restenosis rats and function of Astragalus membranaceus and Angelica sinensis. METHOD: The restenosis model was established by denuding aorta endothelium, rats were randomly divided into control group, model group, A. membranaceus treatment group, A. sinensis treatment group, combined A. membranaceus with A. sinensis treatment group. After intramuscular injection of drugs for 21 dayss, the changes of iNOS in restenosis rats were observed by histomorphology and immunohistochemisty, the effects of A. membranaceus and A. sinensis on iNOS in restenosis rats was also investigated. RESULT: A small quantity of iNOS were detected in the intima and media of normal aorta, the expression of iNOS was increased on 3 day after denuding aorta endothelium, the expression of iNOS increasd and the color darken along with injury damage and intima thickening. Compared with model group, the expression of iNOS decreasd in A. membranaceus, A. sinensis treated group, A. membranaceus and A. sinensis treated group changed more significantly. CONCLUSION: iNOS was involved in blood vessel restenosis by denuding aorta endothelium, A. membranaceus, A. sinensis could inhibit intimal proliferation through iNOS.

Optimal timing for Soave primary pull-through in short-segment Hirschsprung disease: A meta-analysis.

BACKGROUND: The optimal age for endorectal pull-through (ERPT) surgery in infants with short-segment Hirschsprung disease varies, with a trend toward earlier surgery. However, it is unclear if the timing of surgery impacts functional outcomes. We undertook the present study to determine the optimal timing of ERPT in infants with short-segment Hirschsprung disease. METHODS: The NCBI PubMed database was searched for English-language manuscripts published between 2000 and 2019 analyzing functional outcomes for patient following the initial Soave ERPT for short-segment Hirschsprung disease. Raw data from these studies was obtained from the corresponding author for each manuscript. We combined data from these papers with our own institutional data and performed a meta-analysis. RESULTS: A total of 780 infants were included in our meta-analysis. Constipation occurred in 1.0-31.7%, soiling 1.3-26.0%, anastomotic stricture 0.0-14.6%, and anastomotic leak 0.0-3.4%. Regarding age at ERPT, younger infants at the time of initial corrective surgery had higher rates of soiling, stricture, and leak. On sub-group analysis, patients <2.5 months at their initial corrective surgery had higher rates of soiling (25.9% vs. 11.4%, p<0.01), as well as stricture (10.0% vs 1.7%, p<0.01) and leak (5.5% vs 1.3%, p<0.01). CONCLUSION: While age at Soave endorectal pull-through for short-segment Hirschsprung disease has decreased over time, functional outcomes associated with this trend have only recently been examined. Our findings suggest that patients <2.5 months old at the time of endorectal pull-through may have worse functional outcomes, emphasizing the need to consider further study of the timing of surgery in this population.

ROCK inhibition prevents fetal serum-induced alteration in structure and function of organ-cultured mesenteric artery.

Chronic treatment with fetal bovine serum (FBS) causes contractility reduction, morphological alteration and DNA synthesis in organ-cultured vascular tissues. Here, we tested the hypothesis that chronic inhibition of ROCK has a protective effect on FBS-induced alterations in small arteries. Rabbit mesenteric arterial rings were cultured in FBS-supplemented culture medium with or without Y-27632, a reversible ROCK inhibitor. Chronic Y-27632 treatment prevented FBS-induced gradual arterial constriction, wall thickening, reduced contractility, and increased ROCK-specific MYPT1 Thr853 phosphorylation. Treatment with Y-27632 also prevented decreased eNOS mRNA expression, and reduced acetylcholine-induced relaxation. Sudden application of Y-27632 to pre-cultured rings reduced MYPT1 phosphorylation and re-widened the constricted rings. Chronic treatment with Y-27632, however, rather augmented than reduced the FBS-induced RhoA over-expression, also increased ROCK1 and MYPT1 expression and averted the FBS-induced reduction of MLC expression, suggesting a compensation of inhibited RhoA/ROCK activity. Sudden removal of Y-27632 caused a rebound in MYPT1 phosphorylation and vasoconstriction in rabbit mesenteric artery. To test which ROCK isoform has greater involvement in FBS-induced contraction, haploinsufficient Rock1+/- and Rock2+/- mouse mesenteric arterial rings were subjected to organ-culture. FBS-induced contraction and RhoA over-expression in either heterozygous animal was not different from wild-type animals. These results suggest that FBS-induced contraction is mediated by up-regulation of RhoA and subsequent activation of ROCK. In conclusion, chronic ROCK inhibition produces some effects that protect against FBS-stimulated vasoconstriction and remodeling. There are also negative effects that a sudden withdrawal of ROCK inhibitor might cause a stronger vasoconstriction than before it was used.

Pressure-overload magnitude-dependence of the anti-hypertrophic efficacy of PDE5A inhibition.

Increased myocardial cGMP, achieved by enhancing cyclase activity or impeding cGMP hydrolysis by phosphodiesterase type-5 (PDE5A), suppresses cellular and whole organ hypertrophy. The efficacy of the latter also requires cyclase stimulation and may depend upon co-activation of maladaptive signaling suppressible by cGMP-stimulated kinase (cGK-1). Thus, PDE5A inhibitors could paradoxically be more effective against higher than lower magnitudes of pressure-overload stress. To test this, mice were subjected to severe or moderate trans-aortic constriction (sTAC, mTAC) for 6 wks +/-co-treatment with oral sildenafil (SIL 200 mg/kg/d). LV mass (LVM) rose 130% after 3-wks sTAC and SIL blunted this by 50%. With mTAC, LVM rose 56% at 3 wks but was unaffected by SIL, whereas a 90% increase in LVM after 6 wks was suppressed by SIL. SIL minimally altered LV function and remodeling with mTAC until later stages that stimulated more hypertrophy and remodeling. SIL stimulated cGK-1 activity similarly at 3 and 6 wks of mTAC. However, pathologic stress signaling (e.g. calcineurin, ERK-MAPkinase) was little activated after 3-wk mTAC, unlike sTAC or later stage mTAC when activity increased and SIL suppressed it. With modest hypertrophy (3-wk mTAC), GSK3beta and Akt phosphorylation were unaltered but SIL enhanced it. However, with more severe hypertrophy (6-wk mTAC and 3-wk sTAC), both kinases were highly phosphorylated and SIL treatment reduced it. Thus, PDE5A-inhibition counters cardiac pressure-overload stress remodeling more effectively at higher than lower magnitude stress, coupled to pathologic signaling activation targetable by cGK-1 stimulation. Such regulation could impact responses of varying disease models to PDE5A inhibitors.

Rho-kinase inhibitors Y-27632 and fasudil prevent agonist-induced vasospasm in human radial artery.

Radial artery (RA) vasospasm remains a potential cause of early graft failure after coronary artery bypass graft surgery, despite pretreatment with alpha-adrenergic or calcium channel blockers. Our aim was to investigate the mechanism of the vasorelaxant effects of Rho-kinase inhibitors (Y-27632 and fasudil) on the human RA. Segments were obtained from 30 patients undergoing coronary artery bypass graft and were divided into 3-4 mm vascular rings. The rings were stimulated with 10(-5) mol/L phenylephrine (PE) by using the isolated tissue bath technique and were relaxed with 10(-6) mol/L acetylcholine. Relaxation responses were recorded for Y-27632 (10(-9)-10(-4) mol/L), fasudil (10(-9)-10(-4) mol/L), and sodium nitroprusside (SNP) (10(-9)-10(-5) mol/L). Y-27632 and fasudil relaxation responses were repeated in either N(G)-nitro-L-arginine (L-NNA), which is a specific endothelial nitric oxide synthase inhibitor, or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), which is a guanylate cyclase inhibitor. SNP relaxation responses were repeated in 10(-8) mol/L Y-27632 and 10(-8) mol/L fasudil. Y-27632 and fasudil caused concentration-dependent vasorelaxation in RA rings precontracted with PE, and maximal relaxation (100%) was recorded at the highest concentration used (10(-4) mol/L). The vasorelaxant effects of Y-27632 and fasudil were significantly reduced in the presence of L-NNA and ODQ, and the pD2 values of Y-27632 and fasudil were not changed. The vasorelaxant effects of SNP were significantly increased in the presence of Y-27632 and fasudil, and the pD(2) values of SNP were not changed. These findings indicate that Y-27632 and fasudil caused concentration-dependent vasorelaxation in the RA rings. Because this effect was decreased in a dose-dependent manner by L-NNA and ODQ, the relaxant effects of Y-27632 and fasudil could be due to stimulation by nitric oxide that is being released. Rho-kinase inhibitors may have an important role in preventing vasospasm in arterial grafts used for coronary artery surgery.

Omega-3 fatty acid supplement reduces activation of NADPH oxidase in intracranial atherosclerosis stenosis.

Objectives Intracranial atherosclerotic stenosis (ICAS) is one of the most common causes of stroke worldwide. We adapted a rat model of atherosclerosis to study brain intracranial atherosclerosis, and further investigated how omega-3 fatty acids (O3FA) attenuated the development of ICAS by reducing the generation of reactive oxygen species (ROS) and the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) activity. Methods Adult male Sprague-Dawley rats were divided into control normal-cholesterol or high-cholesterol diet groups with or without O3FA for up to 6 weeks. NG-nitro-L-arginine methyl ester (L-NAME, 3 mg/mL), a nitric oxide synthase inhibitor, was added to the drinking water of the high-cholesterol groups during the first 2 weeks. The rats received supplementation with O3FA (5 mg/kg/day) by gavage. At 3 and 6 weeks, we measured blood lipid levels, including low-density lipoprotein (LDL), cholesterol (CHO), triglycerides (TG), and high-density lipoprotein (HDL) as atherosclerotic blood markers. The lumen of middle cerebral artery (MCA) and the thickness of the vessel wall were assessed histologically. ROS production was measured. NOX activity and mRNA and protein expression of NOX subunits (p47phox, gp91phox, p22phox, and p67phox) were measured. Results A high-cholesterol diet exhibited a significant increase in the classic blood markers (LDL, CHO, and TG) for atherosclerosis, as well as a decrease in HDL. These markers were found to be progressively more severe with time. Additionally, increased lumen stenosis and intimal thickening were observed in the MCA for this group. Rats given O3FA demonstrated attenuation of blood lipid levels with an absence of morphological changes.O3FA significantly reduced ROS production and NOX activity in the brain. Moreover, O3FA decreased the mRNA and protein expression of the NOX subunits p47phox, gp91phox, and p67phox. Conclusions Long-term O3FA dietary supplementation prevents the development of intracranial atherosclerosis. This O3FA effect appears to be mediated by its attenuation of NOX subunit expression and NOX activity, therefore reducing ROS production. O3FA dietary supplement shows promising results in the prevention of ICAS.

Matrix metalloproteinase promotes elastic fiber degradation in ligamentum flavum degeneration.

Ligamentum flavum (LF) hypertrophy in lumbar spinal canal stenosis (LSCS) is characterized by a loss of elastic fibers and fibrosis. Chronic inflammation is thought to be responsible for the histological change but the mechanism underlying elastic fiber degradation remains unclear. Given that matrix metalloproteinase (MMP)-2 and -9 have elastolytic activity and are partly regulated by inflammatory cytokines such as interleukin (IL)-6, in this study, we investigated whether MMPs mediate LF degeneration using 52 LF samples obtained during lumbar surgery, including 31 LSCS and 21 control specimens. We confirmed by histological analysis that the LSCS samples exhibited severe degenerative changes compared with the controls. We found that MMP-2 was upregulated in LF tissue from patients with LSCS at the mRNA and protein levels, whereas MMP-9 expression did not differ between the two groups. The MMP-2 level was positively correlated with LF thickness and negatively correlated with the area occupied by elastic fibers. IL-6 mRNA expression was also increased in LF tissue from patients with LSCS and positively correlated with that of MMP-2. Signal transducer and activator of transcription (STAT)3, a component of the IL-6 signaling pathway, was activated in hypertrophied LF tissues. Our in vitro experiments using fibroblasts from LF tissue revealed that IL-6 increased MMP-2 expression, secretion, and activation via induction of STAT3 signaling, and this effect was reversed by STAT3 inhibitor treatment. Moreover, elastin degradation was promoted by IL-6 stimulation in LF fibroblast culture medium. These results indicate that MMP-2 induction by IL-6/STAT3 signaling in LF fibroblasts can degrade elastic fibers, leading to LF degeneration in LSCS.

Estrogen receptor beta protects the murine heart against left ventricular hypertrophy.

BACKGROUND: Left ventricular hypertrophy (LVH) displays significant gender-based differences. 17beta-estradiol (E2) plays an important role in this process because it can attenuate pressure overload hypertrophy via 2 distinct estrogen receptors (ERs): ERalpha and ERbeta. However, which ER is critically involved in the modulation of LVH is poorly understood. We therefore used ERalpha-deficient (ERalpha-/-) and ERbeta-deficient (ERbeta-/-) mice to analyze the respective ER-mediated effects. METHODS AND RESULTS: Respective ER-deficient female mice were ovariectomized and were given E2 or placebo subcutaneously using 60-day release pellets. After 2 weeks, they underwent transverse aortic constriction (TAC) or sham operation. In ERalpha-/- animals, TAC led to a significant increase in ventricular mass compared with sham operation. E2 treatment reduced TAC induced cardiac hypertrophy significantly in wild-type (WT) and ERalpha-/- mice but not in ERbeta-/- mice. Biochemical analysis showed that E2 blocked the increased phosphorylation of p38-mitogen-activated protein kinase observed in TAC-treated ERalpha-/- mice. Moreover, E2 led to an increase of ventricular atrial natriuretic factor expression in WT and ERalpha-/- mice. CONCLUSIONS: These findings demonstrate that E2, through ERbeta-mediated mechanisms, protects the murine heart against LVH.

Roles of chymase in stenosis occurring after polytetrafluoroethylene graft implantations.

Chymase is an important enzyme for the generation of angiotensin (Ang) II and in the activation of transforming growth factor (TGF)-beta1. Therefore, chymase may be involved in the hemodialysis access dysfunction, which is caused by intimal hyperplasia that occurs after polytetrafluoroethylene (PTFE) graft implantations. Bilateral U-shaped PTFE grafts were placed between the femoral vein and artery in dogs. Chymase inhibitor (NK3201, 1 mg/kg per day, p.o.) treatments were initiated 3 days before the operation. After the implantation, the stenosis by neointima proliferation was most frequently observed in the venous side of the PTFE grafts. In the hyperplastic neointima, myofibroblasts were the main cellular components. On the other hand, fibroblasts only occupied cellular components in a much smaller proportion in the neointima. However, these cells seem to be rich in the properties of proliferation and migration. After PTFE graft implantations, extensive accumulations of chymase-positive mast cells were found mainly in the tissue surrounding the grafts. The Ang II- and TGF-beta-positive cells were found in an adjacent section that was in close proximity to the chymase-positive cells. In contrast, the AT(1) receptors, as well as TGF-beta type II receptors, were expressed either in the neointima or in the outside adventitia of the PTFE grafts. Chymase inhibitor treatment resulted in a reduction of chymase, Ang II and TGF-beta1 expression, leading to a significant inhibition of neointimal formation. These findings indicating that an increase of chymase via promoting Ang II and TGF-beta1 generation plays a pivotal role in the neointimal formation after the implantation of PTFE grafts and also suggesting that chymase inhibition may be a new strategy that can be used to prevent PTFE graft dysfunctions in clinical settings.

Matrix metalloproteinases as profibrotic factors in terminal ileum in Crohn's disease.

BACKGROUND: Returning stenosis in Crohn's disease (CD) patients is poorly understood. After resection, newly developed strictures are seen within 10 years in 50% to 70%. Matrix metalloproteinases (MMPs) are involved in matrix-turnover processes. This study analyzes spatial expression of MMP-1, MMP-3, MMP-9, tissue inhibitor of MMP-1, and collagen III to get better insight in tissue remodeling of terminal ileum of CD patients. METHODS: Expressions were analyzed on mRNA and the protein level (MMP-1, MMP-3) in segments from resected terminal ileum from CD and control patients. In CD, macroscopic distinction was made between proximal resection margin, prestenotic, and stenotic tissue. Immunohistochemistry allowed for expression analyses transmurally. RESULTS: MMP-1 and MMP-3 gene expression was up-regulated (P < 0.05) in both prestenotic and stenotic tissue. MMP-1 protein was significantly up-regulated in submucosal and muscular tissue of prestenotic parts and in muscular tissue of stenotic Crohn samples. MMP-3 protein was significantly up-regulated in all layers of prestenotic and stenotic Crohn samples. Even in submucosa of proximal resection margin tissue, MMP-3 expression was significantly higher than in controls. CONCLUSION: Surprisingly, in proximal resection margin tissue up-regulated MMP-3 was seen. This suggests that in nonresected terminal ileum, in which anastomosis is made, tissue turnover is present, which may account for the high recurrence of intestinal strictures.

Pulmonary vein stenosis: expression of receptor tyrosine kinases by lesional cells.

BACKGROUND: Primary pulmonary vein stenosis (PVS) is a progressive disorder of infants. Although catheter based intervention and chemotherapy are used to manage the disorder, the benefit of these approaches is reduced considerably by restenosis. The nature of the intimal cells causing the occlusive lesions in PVS is poorly understood. METHODS: Seven PVS cases were studied with antibodies for smooth muscle actin (SMA), muscle-specific actin (MSA), monoclonal desmin, S100 protein, CD31, CD34, CD45RO, CD68, CD99, Ki-67 (MIB-I), and with antibodies directed against several receptor tyrosine kinases (RTK), including platelet-derived growth factor alpha and beta receptor (PDGFR-alpha and -beta), epidermal growth factor receptor (EGFR), fibroblast growth factor receptor (FGFR), vascular endothelial growth factor 1 and 2 receptor (VEGFR), and stem cell factor receptor (c-kit). RESULTS: Lesional cells stained strongly and diffusely with SMA and MSA, but not for macrophage, lymphocyte, endothelial markers, or for Ki-67. RTK expression was strong and diffuse for PDGFR-alpha and -beta, FGFR, and VEGFR-2. Lesional cells stained for VEGF and PDGF beta receptor was phosphorylated. CONCLUSIONS: The histologic appearance, and the strong diffuse immunoreactivity for smooth muscle markers, indicates that the intimal lesional cells are myofibroblast-like. Expression of various receptor tyrosine kinases and some ligands suggests an autocrine or paracrine role of these proteins in the pathogenesis of the intimal occlusive lesion in PVS.

Endothelial nitric oxide synthase gene is associated with vessel stenosis in Korean population.

BACKGROUND: Nitric oxide (NO) produced by endothelial NO synthase (eNOS) mediates endothelium-dependent vasodilation and antithrombotic action. Controversial results regarding the association of eNOS gene polymorphisms with vessel stenosis have been reported. METHODS: Age- and sex-matched 932 individuals (656 subjects having 1-, 2-, and 3-stenosed vessels and 276 controls without stenosis) living in Seoul and surrounding suburbs were selected. A GT missense mutation in exon 7 (894GT) was screened using PCR-restriction fragment length polymorphism analysis. The genotypes of a 27-bp insertion/deletion in intron 4 (eNOS4b/a) and a TC mutation in promoter region of -786 (-786TC) were determined by the banding pattern on gel electrophoresis and a commercially available minisequencing protocol (SNaPshot), respectively. RESULTS: The eNOS4a allele was highly linked to the -786C allele (r=0.93, P<0.0001) while there was no linkage between eNOS4a allele and 894T allele or between 894T allele and -786C allele. Furthermore, 894T allele, but not eNOS4a (-786C) allele, was associated with the presence, but not the number, of stenosed vessels (odds ratio=1.57 for dominant effect of the T allele, P<0.05, and 1.49 for additive effect, P<0.05). Multiple logistic regression analysis revealed that 894T allele and hypertension were predictive independent risk factors for the presence of vessel stenosis. CONCLUSION: Our data suggest that eNOS gene polymorphisms may play an important role in the pathogenesis of vessel stenosis in Korean population.

Adenoviral transfer of endothelial nitric oxide synthase attenuates lesion formation in a novel murine model of postangioplasty restenosis.

OBJECTIVE: Restenosis remains a major late complication of percutaneous transluminal coronary angioplasty (PTCA), for which the development of prevention strategies has thus far been hampered by the lack of a representative and practical animal model. We have, therefore, developed a murine model of PTCA-induced restenosis. METHODS AND RESULTS: Rigid probe angioplasty of pre-existing atherosclerotic lesions in the carotid arteries of ApoE-deficient mice was found to result in an increase in lesion size (0.14+/-0.04x10(5) microm2 to 0.42+/-0.09x10(5) microm2, P=0.007) with a smooth muscle cell-rich, fibrotic lesion morphology. In an additional experiment, lesions were incubated immediately after angioplasty with adenovirus bearing an endothelial nitric oxide synthase (eNOS) transgene (Ad.APT.eNOS), or an "empty" control virus (Ad.APT.empty) at a titer of 1.5x10(9) pfu/mL. Ad.APT.eNOS treatment was seen to lead to a 73.1% reduction in plaque size (0.27+/-0.04x10(5) microm2 versus 1.02+/-0.39x10(5) microm2, P=0.07), which translated to a significantly lowered average degree of stenosis (33.6+/-4.1% versus 74.6+/-14.0%, P=0.02). Ad.APT.eNOS also decreased lesional collagen content from 29.1% to 4.8% (P<0.001). CONCLUSIONS: We believe that we have established a representative murine model of postangioplasty restenosis, which may serve to elucidate the mechanisms underlying restenosis and to evaluate potential antirestenotic therapies.

Sustained decrease in superoxide dismutase activity underlies constrictive remodeling after balloon injury in rabbits.

OBJECTIVE: The redox pathophysiology of vascular repair is incompletely understood. We assessed the role of vascular superoxide dismutase (SOD) activity in oxidative/nitrative stress and caliber loss postinjury (PI). METHODS AND RESULTS: Rabbits submitted to iliac artery balloon overdistension were followed for 14 days PI. Significant decrease in vascular SOD activity occurred at 7 and 14 days PI (by 45% and 34%, respectively, versus control, 96+/-1 U/mg, P<0.05). Separation in concanavalin-A column showed that both extracellular SOD (ecSOD) and CuZn SOD activities were reduced, whereas Western analysis showed normal or augmented protein expression. Immunoreactivity to nitrotyrosine, neuronal NO synthase (NOS), and inducible NOS (iNOS) increased in media and neointima PI; iNOS mRNA also augmented. Administration of ecSOD from days 7 to 14 PI corrected the SOD activity decrease and minimized caliber loss by 59% (P=0.007) despite unaltered neointima. Nitrate levels markedly increased with ecSOD in injured artery homogenates (26+/-5 versus 4+/-0.3 micromol/L per mg, P=0.001). Such increase was 70% inhibited by specific iNOS antagonist 1400w. Nitrotyrosine and neuronal NOS expression decreased after ecSOD. CONCLUSIONS: Sustained low vascular SOD activity has a key role in constrictive remodeling after injury, promoting oxidative/nitrative stress and impairment of iNOS-derived NO bioavailability. SOD function may critically determine whether iNOS induction is beneficial or deleterious in vivo.

Tissue-type plasminogen activator after venous occlusion in pregnancy and puerperium.

Pregnancy is associated with depressed fibrinolysis as judged from the decreased fibrinolytic response to venous occlusion. In order to elucidate if this decreased response is due to an increase in plasminogen activator inhibitors 1 and 2 (PAI-1, PAI-2), and/or to decreased release of tissue-type plasminogen activator (t-PA) antigen during venous occlusion, 36 women (18 women with normal pregnancy and 18 with gestational hypertension without proteinuria) were followed during pregnancy and puerperium. In each women a 20 min venous occlusion was performed in the second and in the third trimester of pregnancy and 3 days after delivery. The increase in t-PA antigen after venous occlusion relative to basal value was in the second trimester of pregnancy on average 3.7 fold, in the third trimester 4.4 fold, and so not reduced compared to non-pregnant women (3.7 fold increase). After delivery the increase in t-PA antigen was significantly enhanced (8.5 fold, p < 0.005). The fibrinolytic response to venous occlusion measured by euglobulin and t-PA activity was significantly decreased in the third trimester compared to non-pregnant values (both p < 0.005) and returned to somewhat higher (euglobulin clot lysis) or significantly higher (t-PA activity, p < 0.01) values 3 days after delivery. Decreased euglobulin and t-PA activity after venous occlusion in the third trimester coincided with significant increases in basal PAI activity, PAI-1 antigen and PAI-2 antigen (2.9, 2.5 and > 30 fold increase relative to non-pregnant values, respectively, all p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Role of neutral endopeptidase in exercise-induced bronchoconstriction in asthmatic subjects.

The membrane-bound metalloproteinase, neutral endopeptidase (NEP), is a degrading enzyme of both bronchoconstrictor and bronchodilator peptides within the airways. To examine the role of NEP in exercise-induced bronchoconstriction (EIB) in asthmatic subjects, we used inhaled thiorphan, a NEP inhibitor, as pretreatment to a 6-min standardized exercise challenge. Thirteen clinically stable asthmatic subjects participated in this double-blind, placebo-controlled, crossover study that was performed on 2 days separated by 48 h. Thiorphan was administered by two inhalations of 0.5 ml containing 1.25 mg/ml. Subsequently, exercise was performed on a bicycle ergometer at 40-50% of predicted maximal voluntary ventilation while inhaling dry air (20 degrees C, relative humidity 6%). The airway response to exercise was measured by forced expiratory volume in 1 s (FEV1) every 3 min, up to 30 min postexercise challenge, and was expressed both as the maximal percent fall in FEV1 from baseline and as the area under the time-response curve (AUC) (0-30 min). The acute effects of both pretreatments on baseline FEV1 were not different (P > 0.2), neither was there any difference in maximal percent fall in FEV1 between thiorphan and placebo (P > 0.7). However, compared with placebo, thiorphan reduced the AUC by, on average, 26% [AUC (0-30 min, +/-SE): 213.6 +/- 47.7 (thiorphan) and 288.6 +/- 46.0%fall.h (placebo); P = 0.047]. These data indicate that NEP inhibition by thiorphan reduces EIB during the recovery period. This suggests that bronchodilator NEP substrates, such as vasoactive intestinal polypeptide or atrial natriuretic peptide, modulate EIB in patients with asthma.

Local expression of inducible nitric oxide synthase in an animal model of neuropathic pain.

Peripheral nerve injury is associated with local inflammation and neuropathic pain. In this study we investigated the local expression of the inducible isoform of nitric oxide synthase (iNOS) following a chronic constriction injury (CCI) to the sciatic nerve, a rat model of neuropathic pain. Western blot analysis and immunohistochemical co-localization methods were used to identify temporal and spatial expression of iNOS and its cells of origin. Changes in mRNA were analyzed by RT-PCR and iNOS specific primers. We report that CCI injury induced local iNOS expression in both macrophages and Schwann cells within and distal to the injury site. The local increase in iNOS mRNA expression paralleled both the temporal and spatial protein expression. This study supports the hypothesis that CCI is associated with a local inflammatory reaction mediated at least in part by iNOS. Local activation of the iNOS-NO system may play an important role in the pathogenesis of peripheral nerve injury and neuropathic pain.