Mitochondrial targeted antioxidants, mitoquinone and SKQ1, not vitamin C, mitigate doxorubicin-induced damage in H9c2 myoblast: pretreatment vs. co-treatment

BACKGROUND

Preconditioning of the heart ameliorates doxorubicin (Dox)-induced cardiotoxicity. We tested whether pretreating cardiomyocytes by mitochondrial-targeted antioxidants, mitoquinone (MitoQ) or SKQ1, would provide better protection against Dox than co-treatment.

METHODS

We investigated the dose-response relationship of MitoQ, SKQ1, and vitamin C on Dox-induced damage on H9c2 cardiomyoblasts when drugs were given concurrently with Dox (e.g., co-treatment) or 24 h prior to Dox (e.g., pretreatment). Moreover, their effects on intracellular and mitochondrial oxidative stress were evaluated by 2,7-dichlorofluorescin diacetate and MitoSOX, respectively.

RESULTS

Dox (0.5-50 μM, n = 6) dose-dependently reduced cell viability. By contrast, co-treatment of MitoQ (0.05-10 μM, n = 6) and SKQ1 (0.05-10 μM, n = 6), but not vitamin C (1-2000 μM, n = 3), significantly improved cell viability only at intermediate doses (0.5-1 μM). MitoQ (1 μM) and SKQ1 (1 μM) significantly increased cell viability to 1.79 ± 0.12 and 1.59 ± 0.08 relative to Dox alone, respectively (both p < 0.05). Interestingly, when given as pretreatment, only higher doses of MitoQ (2.5 μM, n = 9) and SKQ1 (5 μM, n = 7) showed maximal protection and improved cell viability to 2.19 ± 0.13 and 1.65 ± 0.07 relative to Dox alone, respectively (both p < 0.01), which was better than that of co-treatment. Moreover, the protective effects were attributed to the significant reduction in Dox-induced intracellular and mitochondrial oxidative stress.

CONCLUSION

The data suggest that MitoQ and SKQ1, but not vitamin C, mitigated DOX-induced damage. Moreover, MitoQ pretreatment showed significantly higher cardioprotection than its co-treatment and SKQ1, which may be due to its better antioxidant effects.

Intravitreal aflibercept for macular oedema secondary to central retinal vein occlusion in patients with prior treatment with bevacizumab or ranibizumab

PurposeTo report the visual and anatomic outcomes in eyes with macular oedema (MO) secondary to central retinal vein occlusion (CRVO) that were switched from either intravitreal bevacizumab or ranibizumab to intravitreal aflibercept.MethodsTwo-center retrospective chart review. Eyes with MO secondary to CRVO that received a minimum of three intravitreal injections of bevacizumab or ranibizumab and were switched to intravitreal aflibercept for persistent or recurrent MO not responding to either bevacizumab and/or ranibizumab.ResultsIn all 42 eyes of 42 patients were included in the study. The median visual acuity before the switch was 20/126, 1 month after the first injection of aflibercept 20/89 (P=0.0191), and at the end of the follow-up 20/100 (P=0.2724). The median CRT before the switch was 536 μm, 1 month after the first injection of aflibercept 293.5 μm (P=0.0038), and at the end of the follow-up 279 μm (P=0.0013 compared to before the switch). The median number of weeks between injections before the switch was 5.6 and after the switch was 7.6 (P<0.0001).ConclusionConverting eyes with refractory MO due to CRVO to aflibercept can result in stabilization of the vision, improved macular anatomy, and extension of the injection interval.

Inhibition of long chain fatty acyl-CoA synthetase (ACSL) and ischemia reperfusion injury

Various triacsin C analogs, containing different alkenyl chains and carboxylic acid bioisoteres including 4-aminobenzoic acid, isothiazolidine dioxide, hydroxylamine, hydroxytriazene, and oxadiazolidine dione, were synthesized and their inhibitions of long chain fatty acyl-CoA synthetase (ACSL) were examined. Two methods, a cell-based assay of ACSL activity and an in situ [(14)C]-palmitate incorporation into extractable lipids were used to study the inhibition. Using an in vivo leukocyte recruitment inhibition protocol, the translocation of one or more cell adhesion molecules from the cytoplasm to the plasma membrane on either the endothelium or leukocyte or both was inhibited by inhibitors 1, 9, and triacsin C. The results suggest that inhibition of ACSL may attenuate the vascular inflammatory component associated with ischemia reperfusion injury and lead to a decrease of infarct expansion.

The effects of modulating eNOS activity and coupling in ischemia/reperfusion (I/R)

The in vivo role of endothelial nitric oxide synthase (eNOS) uncoupling mediating oxidative stress in ischemia/reperfusion (I/R) injury has not been well established. In vitro, eNOS coupling refers to the reduction of molecular oxygen to L-arginine oxidation and generation of L-citrulline and nitric oxide NO synthesis in the presence of an essential cofactor, tetrahydrobiopterin (BH(4)). Whereas uncoupled eNOS refers to that the electron transfer becomes uncoupled to L-arginine oxidation and superoxide is generated when the dihydrobiopterin (BH(2)) to BH(4) ratio is increased. Superoxide is subsequently converted to hydrogen peroxide (H(2)O(2)). We tested the hypothesis that promoting eNOS coupling or attenuating uncoupling after I/R would decrease H(2)O(2)/increase NO release in blood and restore postreperfused cardiac function. We combined BH(4) or BH(2) with eNOS activity enhancer, protein kinase C epsilon (PKC ε) activator, or eNOS activity reducer, PKC ε inhibitor, in isolated rat hearts (ex vivo) and femoral arteries/veins (in vivo) subjected to I(20 min)/R(45 min). When given during reperfusion, PKC ε activator combined with BH(4), not BH(2), significantly restored postreperfused cardiac function and decreased leukocyte infiltration (p < 0.01) while increasing NO (p < 0.05) and reducing H(2)O(2) (p < 0.01) release in femoral I/R veins. These results provide indirect evidence suggesting that PKC ε activator combined with BH(4) enhances coupled eNOS activity, whereas it enhanced uncoupled eNOS activity when combined with BH(2). By contrast, the cardioprotective and anti-oxidative effects of the PKC ε inhibitor were unaffected by BH(4) or BH(2) suggesting that inhibition of eNOS uncoupling during reperfusion following sustained ischemia may be an important mechanism.

The pulmonary vascular complications of hereditary haemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia (HHT) is a rare autosomal dominant disorder, characterised by the presence of vascular malformations. The pulmonary vascular complications of HHT include pulmonary arteriovenous malformations, pulmonary hypertension associated with high-output heart failure and liver vascular malformations and, finally, pulmonary arterial hypertension secondary to HHT. In the present review, the authors describe the clinical presentation, diagnosis and management of all three pulmonary vascular presentations of HHT, as well as the underlying genetics and pathophysiology.

International guidelines for the diagnosis and management of hereditary haemorrhagic telangiectasia

BACKGROUND

HHT is an autosomal dominant disease with an estimated prevalence of at least 1/5000 which can frequently be complicated by the presence of clinically significant arteriovenous malformations in the brain, lung, gastrointestinal tract and liver. HHT is under-diagnosed and families may be unaware of the available screening and treatment, leading to unnecessary stroke and life-threatening hemorrhage in children and adults.

OBJECTIVE

The goal of this international HHT guidelines process was to develop evidence-informed consensus guidelines regarding the diagnosis of HHT and the prevention of HHT-related complications and treatment of symptomatic disease.

METHODS

The overall guidelines process was developed using the AGREE framework, using a systematic search strategy and literature retrieval with incorporation of expert evidence in a structured consensus process where published literature was lacking. The Guidelines Working Group included experts (clinical and genetic) from eleven countries, in all aspects of HHT, guidelines methodologists, health care workers, health care administrators, HHT clinic staff, medical trainees, patient advocacy representatives and patients with HHT. The Working Group determined clinically relevant questions during the pre-conference process. The literature search was conducted using the OVID MEDLINE database, from 1966 to October 2006. The Working Group subsequently convened at the Guidelines Conference to partake in a structured consensus process using the evidence tables generated from the systematic searches.

RESULTS

The outcome of the conference was the generation of 33 recommendations for the diagnosis and management of HHT, with at least 80% agreement amongst the expert panel for 30 of the 33 recommendations.

Boosting enrollment in neurology trials with Local Identification and Outreach Networks (LIONs)

OBJECTIVE

Our purpose was to develop a geographically localized, multi-institution strategy for improving enrolment in a trial of secondary stroke prevention.

METHODS

We invited 11 Connecticut hospitals to participate in a project named the Local Identification and Outreach Network (LION). Each hospital provided the names of patients with stroke or TIA, identified from electronic admission or discharge logs, to researchers at a central coordinating center. After obtaining permission from personal physicians, researchers contacted each patient to describe the study, screen for eligibility, and set up a home visit for consent. Researchers traveled throughout the state to enroll and follow participants. Outside the LION, investigators identified trial participants using conventional recruitment strategies. We compared recruitment success for the LION and other sites using data from January 1, 2005, through June 30, 2007.

RESULTS

The average monthly randomization rate from the LION was 4.0 participants, compared with 0.46 at 104 other Insulin Resistance Intervention after Stroke (IRIS) sites. The LION randomized on average 1.52/1,000 beds/month, compared with 0.76/1,000 beds/month at other IRIS sites (p = 0.03). The average cost to randomize and follow one participant was $8,697 for the LION, compared with $7,198 for other sites.

CONCLUSION

A geographically based network of institutions, served by a central coordinating center, randomized substantially more patients per month compared with sites outside of the network. The high enrollment rate was a result of surveillance at multiple institutions and greater productivity at each institution. Although the cost per patient was higher for the network, compared with nonnetwork sites, cost savings could result from more rapid completion of research.

AMP-activated protein kinase: a core signalling pathway in the heart

Over the past decade, AMP-activated protein kinase (AMPK) has emerged as an important intracellular signalling pathway in the heart. Activated AMPK stimulates the production of ATP by regulating key steps in both glucose and fatty acid metabolism. It has an inhibitory effect on cardiac protein synthesis. AMPK also interacts with additional intracellular signalling pathways in a coordinated network that modulates essential cellular processes in the heart. Evidence is accumulating that AMPK may protect the heart from ischaemic injury and limit the development of cardiac myocyte hypertrophy to various stimuli. Heart AMPK is activated by hormones, cytokines and oral hypoglycaemic drugs that are used in the treatment of type 2 diabetes. The tumour suppressor LKB1 is the major regulator of AMPK activity, but additional upstream kinases and protein phosphatases also contribute. Mutations in the regulatory gamma2 subunit of AMPK lead to an inherited syndrome of hypertrophic cardiomyopathy and ventricular pre-excitation, which appears to be due to intracellular glycogen accumulation. Future research promises to elucidate the molecular mechanisms responsible for AMPK activation, novel downstream AMPK targets, and the therapeutic potential of targeting AMPK for the prevention and treatment of myocardial ischaemia or cardiac hypertrophy.

Spectral domain optical coherence tomography for quantitative evaluation of drusen and associated structural changes in non-neovascular age-related macular degeneration

Background/aims:

To demonstrate how spectral domain optical coherence tomography (SDOCT) can better evaluate drusen and associated anatomical changes in eyes with non-neovascular age-related macular degeneration (AMD) compared with time domain optical coherence tomography (TDOCT).

Methods:

Images were obtained from three eyes of three patients with AMD using an experimental SDOCT system. Both a titanium–sapphire (Ti:sapphire) laser and a superluminescent diode (SLD) were used as a broadband light source to achieve cross-sectional images of the retina. A qualitative and quantitative analysis was performed for structural changes associated with non-neovascular AMD. An automated algorithm was developed to analyse drusen area and volume from SDOCT images. TDOCT was performed using the fast macular scan (StratusOCT, Carl Zeiss Meditec, Dublin, California).

Results:

SDOCT images can demonstrate structural changes associated with non-neovascular AMD. A new SDOCT algorithm can determine drusen area, drusen volume and proportion of drusen.

Conclusions:

With new algorithms to determine drusen area and volume and its unprecedented simultaneous ultra-high speed ultra-high resolution imaging, SDOCT can improve the evaluation of structural abnormalities in non-neovascular AMD.

Gö 6983: A Fast Acting Protein Kinase C Inhibitor that Attenuates Myocardial Ischemia/Reperfusion Injury

Reperfusion injury is characterized by a decrease in endothelial release of nitric oxide within 5 min after reperfusion, increased leukocyte-endothelium interaction, and transmigration of leukocytes into the myocardium, producing cardiac contractile dysfunction. Gö 6983 is a fast acting, lipid soluble, broad spectrum protein kinase C inhibitor. When administered at the beginning of reperfusion, it can restore cardiac function within 5 min and attenuate the deleterious effects associated with acute ischemia/reperfusion. Gö 6983 may offer greater cardioprotection than other broad-spectrum PKC inhibitors in postischemic reperfusion injury because it inhibits PKC(zeta) as well as four other isoforms. The cardioprotection is associated with decreased leukocyte superoxide release and increased endothelial derived nitric oxide from vascular tissue. In vitro studies of human tissue showed that Gö 6983 significantly inhibited antigen-induced superoxide release from leukocytes of patients previously sensitized to tree pollen. In human vascular tissue, Gö 6983 inhibited intracellular Ca(2+) accumulation, suggesting a mechanism for its vasodilator properties. These studies suggest that Gö 6983 would be an effective compound to use in a clinical ischemia/reperfusion setting of organ transplantation and/or cerebral ischemia where inhibiting superoxide release and vasoconstriction in postischemic tissues would allow for better restoration of organ function during reperfusion. However, given the broad-spectrum action of Gö 6983, careful titration of the dose regimen would be recommended to ensure a successful outcome in the setting of organ transplantation and/or cerebral ischemia.

Protein kinase C-ζ inhibition exerts cardioprotective effects in ischemia-reperfusion injury

Ischemia followed by reperfusion (I/R) in the presence of polymorphonuclear leukocytes (PMNs) results in marked cardiac contractile dysfunction. A cell-permeable PKC-ζ peptide inhibitor was used to test the hypothesis that PKC-ζ inhibition could attenuate PMN-induced cardiac contractile dysfunction by suppression of superoxide production from PMNs and increase nitric oxide (NO) release from vascular endothelium. The effects of the PKC-ζ peptide inhibitor were examined in isolated ischemic (20 min) and reperfused (45 min) rat hearts reperfused with PMNs. The PKC-ζ inhibitor (2.5 or 5 μM, n = 6) significantly attenuated PMN-induced cardiac dysfunction compared with I/R hearts ( n = 6) receiving PMNs alone in left ventricular developed pressure (LVDP) and the maximal rate of LVDP (+dP/d tmax) cardiac function indexes ( P < 0.01), and these cardioprotective effects were blocked by the NO synthase inhibitor, NG-nitro-l-arginine methyl ester (50 μM). Furthermore, the PKC-ζ inhibitor significantly increased endothelial NO release 47 ± 2% (2.5 μM, P < 0.05) and 54 ± 5% (5 μM, P < 0.01) over basal values from the rat aorta and significantly inhibited superoxide release from phorbol-12-myristate-13-acetate-stimulated rat PMNs by 33 ± 12% (2.5 μM) and 40 ± 8% (5 μM) ( P < 0.01). The PKC-ζ inhibitor significantly attenuated PMN infiltration into the myocardium by 46–48 ± 4% ( P < 0.01) at 2.5 and 5 μM, respectively. In conclusion, these results suggest that the PKC-ζ peptide inhibitor attenuates PMN-induced post-I/R cardiac contractile dysfunction by increasing endothelial NO release and by inhibiting superoxide release from PMNs thereby attenuating PMN infiltration into I/R myocardium.

Protein kinase C betaII peptide inhibitor exerts cardioprotective effects in rat cardiac ischemia/reperfusion injury

Ischemia followed by reperfusion (I/R) in the presence of polymorphonuclear leukocytes (PMNs) results in a marked cardiac contractile dysfunction. A cell-permeable protein kinase C (PKC) betaII peptide inhibitor was used to test the hypothesis that PKC betaII inhibition could attenuate PMN-induced cardiac dysfunction by suppression of superoxide production from PMNs and increase NO release from vascular endothelium. The effects of the PKC betaII peptide inhibitor were examined in isolated ischemic (20 min) and reperfused (45 min) rat hearts with PMNs. The PKC betaII inhibitor (10 microM; n = 7) significantly attenuated PMN-induced cardiac dysfunction compared with I/R hearts (n = 9) receiving PMNs alone in left ventricular developed pressure (LVDP) and the maximal rate of LVDP (+dP/dt(max)) cardiac function indices (p < 0.01). The PKC betaII inhibitor at 10 microM significantly increased endothelial NO release from a basal value of 1.85 +/- 0.18 pmol NO/mg tissue to 3.49 +/- 0.62 pmol NO/mg tissue from rat aorta. It also significantly inhibited superoxide release (i.e., absorbance) from N-formyl-L-methionyl-L-leucyl-L-phenylalanine-stimulated rat PMNs from 0.13 +/- 0.01 to 0.02 +/- 0.004 (p < 0.01) at 10 microM. Histological analysis of the left ventricle of representative rat hearts from each group showed that the PKC betaII peptide inhibitor-treated hearts experienced a marked reduction in PMN vascular adherence and infiltration into the postreperfused cardiac tissue compared with I/R + PMN hearts (p < 0.01). These results suggest that the PKC betaII peptide inhibitor attenuates PMN-induced post-I/R cardiac contractile dysfunction by increasing endothelial NO release and by inhibiting superoxide release from PMNs.

Inhibiting long chain fatty Acyl CoA synthetase increases basal and agonist-stimulated NO synthesis in endothelium

OBJECTIVES

Endothelial nitric oxide synthase (eNOS) activation/deactivation is associated with cyclic depalmitoylation/repalmitoylation of specific Cys residues. The mechanism of depalmitoylation has been identified recently, but repalmitoylation remains undefined. We hypothesized that long chain fatty acyl CoA synthetase (LCFACoAS) modulates endothelial nitric oxide synthase repalmitoylation by limiting palmitoyl CoA availability.

METHODS

Human coronary endothelial cells were treated with triacsin-C, an inhibitor of long chain fatty acyl CoA synthetase, for 24 h. Media nitrite accumulation, eNOS activity, and eNOS palmitoylation were measured. Methacholine-induced NO synthesis or vascular relaxation were measured in endothelium-intact rat aortae in the presence and absence of triacsin-C.

RESULTS

Triacsin-C significantly reduced incorporation of [3H] palmitate into immunoreactive endothelial nitric oxide synthase and over a concentration range of 0.1 to 10 microM, increased media nitrite accumulations 2- to 2.5-fold over baseline. Total in vitro catalytic activity of nitric oxide synthase in triacsin-C treated cells did not differ significantly from control. Triacsin-C significantly increased methacholine-induced NO synthesis in the isolated rat aorta, and significantly enhanced methacholine-induced relaxation of rat aortic rings.

CONCLUSIONS

These data are consistent with the interpretation that inhibition of palmitoylation increases endothelial nitric oxide synthase activity without changing endothelial nitric oxide synthase expression, suggesting that inhibiting palmitoylation increases the catalytically active fraction of endothelial nitric oxide synthase.

Gö 6983 Exerts Cardioprotective Effects in Myocardial Ischemia/Reperfusion

Ischemia followed by reperfusion (I/R) in the presence of polymorphonuclear leukocytes (PMNs) results in cardiac contractile dysfunction. Inhibiting protein kinase C (PKC) inhibits the release of superoxide from PMNs. The compound Gö 6983 is an inhibitor of all five PKC isoforms present in PMNs. Therefore, we hypothesized that Gö 6983 could attenuate PMN-induced cardiac dysfunction by suppression of superoxide production from PMNs. We studied isolated rat hearts following ischemia (20 minutes) and reperfusion (45 minutes) infused with activated PMNs. In hearts reperfused with PMNs and Gö 6983 (100 nM, n = 7), left ventricular developed pressure (LVDP) and the rate of LVDP (+dP/dt max) recovered to 89 +/- 7% and 74 +/- 2% of baseline values, respectively, at 45 minutes postreperfusion compared with I/R hearts (n = 9) receiving PMNs alone, which only recovered to 55 +/- 3% and 45 +/- 5% of baseline values for LVDP and +dP/dtmax, respectively (P < 0.01). Gö 6983 (100 nM) significantly reduced PMN adherence to the endothelium and infiltration into the myocardium compared with I/R + PMN hearts (P < 0.01), and significantly inhibited superoxide release from PMNs by 90 +/- 2% (P < 0.01). In the presence of PMNs, Gö 6983 attenuated post-I/R cardiac contractile dysfunction, which may be related in part to decreased superoxide production.

Rosuvastatin, a new HMG-CoA reductase inhibitor, protects ischemic reperfused myocardium in normocholesterolemic rats

The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have been shown to upregulate endothelial nitric oxide synthase in isolated endothelial cells in a manner that is independent of their lipid-lowering effects. Nitric oxide inhibits polymorphonuclear leukocyte (PMN) adherence and attenuates cardiac dysfunction caused by PMNs after ischemia/reperfusion. Therefore, the authors hypothesized that a new statin, rosuvastatin, could attenuate PMN-induced cardiac dysfunction, and examined the effects of rosuvastatin in isolated ischemic (20 min) and reperfused (45 min) rat hearts perfused with PMNs. Rosuvastatin (0.25 or 1.25 mg/kg) given 18 h before ischemia/reperfusion significantly improved left ventricular developed pressure (P < 0.01) and the maximal rate of development of left ventricular developed pressure (+dP/dt(max), P < 0.01) compared with ischemia/reperfused hearts obtained from rats given 0.9% NaCl. The time point for the improved cardiac performance caused by rosuvastatin (1.25 mg/kg) was 20 min after reperfusion. In addition, rosuvastatin significantly reduced PMN adherence to the vascular endothelium and subsequent infiltration into the postischemic myocardium (P < 0.01). The nitric oxide synthase inhibitor N omega-nitro-l-arginine methyl ester (50 micromol/l) blocked these cardioprotective effects. These results provide evidence that rosuvastatin significantly attenuates PMN-induced cardiac contractile dysfunction in the isolated perfused rat heart.

Attenuation of neutrophil-mediated myocardial ischemia-reperfusion injury by a calpain inhibitor

Calpains are ubiquitous neutral cysteine proteases. Although their physiological role has yet to be clarified, calpains seem to be involved in the expression of cell adhesion molecules. Therefore, we hypothesized that a selective calpain inhibitor could attenuate polymorphonuclear (PMN) leukocyte-induced myocardial ischemia-reperfusion (I/R) injury. We examined the effects of the calpain inhibitor Z-Leu-Leu-CHO in isolated ischemic (20 min) and reperfused (45 min) rat hearts perfused with PMNs. Z-Leu-Leu-CHO (10 and 20 microM, respectively) significantly improved left ventricular developed pressure (LVDP) (P < 0.01) and the maximal rate of development of LVDP (P < 0.01) compared with I/R hearts perfused without Z-Leu-Leu-CHO. In addition, Z-Leu-Leu-CHO significantly reduced PMN adherence to the vascular endothelium and subsequent infiltration into the postischemic myocardium (P < 0.01). Moreover, Z-Leu-Leu-CHO significantly inhibited expression of P-selectin on the rat coronary microvascular endothelium (P < 0.01). These results provide evidence that Z-Leu-Leu-CHO significantly attenuates PMN-mediated I/R injury in the isolated perfused rat heart to a significant extent via downregulation of P-selectin expression.

Vascular effects of poly-N-acetylglucosamine in isolated rat aortic rings

BACKGROUND

[corrected] Poly-N-acetylglucosamine (p-GlcNAc) is a secretion of marine diatoms that is known to be useful in controlling bleeding. As a component of promoting hemostasis, p-GlcNAc is thought to exert vasoconstrictor effects in arteries. The present study was undertaken to determine whether p-GlcNAc induced a significant vasoconstrictor effect and, if so, what the mechanism of this effect might be.

MATERIALS AND METHODS

We examined vascular effects of p-GlcNAc on isolated aortic rings obtained from Sprague-Dawley rats. The rings were suspended in organ baths and precontracted with U46619, a thromboxane A2 mimetic.

RESULTS

p-GlcNAc produced a concentration-dependent vasoconstriction over the range of 14 to 100 microg/ml. At a concentration of 100 microg/ml, p-GlcNAc significantly contracted aortic rings by 133 +/- 20 mg of developed force (P < 0.01). Neither a deacetylated derivative of p-GlcNAc nor a structurally related macromolecule, chitin, contracted rat aortic rings, indicating a specificity for p-GlcNAc. The vasoconstriction to p-GlcNAc was totally abolished in deendothelialized rat aortic rings, suggesting that an endothelial component is essential to the vasoconstriction. Pretreatment with the endothelin ET(A) receptor antagonist, JKC-301 (0.5 and 1 microM), significantly diminished p-GlcNAc-induced vasoconstriction by 57 to 61% (P < 0.01). However, p-GlcNAc did not significantly diminish nitric oxide release from rat aortic endothelium.

CONCLUSION

These results provide evidence that p-GlcNAc significantly contracts isolated rat aortic rings via an endothelium-dependent mechanism, partly via enhancement of endothelin-1 release from endothelial cells.

Chronic activation of AMP kinase results in NRF-1 activation and mitochondrial biogenesis

The underlying mechanism by which skeletal muscle adapts to exercise training or chronic energy deprivation is largely unknown. To examine this question, rats were fed for 9 wk either with or without beta-guanadinopropionic acid (beta-GPA; 1% enriched diet), a creatine analog that is known to induce muscle adaptations similar to those induced by exercise training. Muscle phosphocreatine, ATP, and ATP/AMP ratios were all markedly decreased and led to the activation of AMP-activated protein kinase (AMPK) in the beta-GPA-fed rats compared with control rats. Under these conditions, nuclear respiratory factor-1 (NRF-1) binding activity, measured using a cDNA probe containing a sequence encoding for the promoter of delta-aminolevulinate (ALA) synthase, was increased by about eightfold in the muscle of beta-GPA-fed rats compared with the control group. Concomitantly, muscle ALA synthase mRNA and cytochrome c content were also increased. Mitochondrial density in both extensor digitorum longus and epitrochlearis from beta-GPA-fed rats was also increased by more than twofold compared with the control group. In conclusion, chronic phosphocreatine depletion during beta-GPA supplementation led to the activation of muscle AMPK that was associated with increased NRF-1 binding activity, increased cytochrome c content, and increased muscle mitochondrial density. Our data suggest that AMPK may play an important role in muscle adaptations to chronic energy stress and that it promotes mitochondrial biogenesis and expression of respiratory proteins through activation of NRF-1.

Cardiac responses to insulin-induced hypoglycemia in nondiabetic and intensively treated type 1 diabetic patients

Insulin-induced hypoglycemia occurs commonly in intensively treated patients with type 1 diabetes, but the cardiovascular consequences of hypoglycemia in these patients are not known. We studied left ventricular systolic [left ventricular ejection fraction (LVEF)] and diastolic [peak filling rate (PFR)] function by equilibrium radionuclide angiography during insulin infusion (12 pmol. kg(-1). min(-1)) under either hypoglycemic (approximately 2.8 mmol/l) or euglycemic (approximately 5 mmol/l) conditions in intensively treated patients with type 1 diabetes and healthy nondiabetic subjects (n = 9 for each). During hypoglycemic hyperinsulinemia, there were significant increases in LVEF (DeltaLVEF = 11 +/- 2%) and PFR [DeltaPFR = 0.88 +/- 0.18 end diastolic volume (EDV)/s] in diabetic subjects as well as in the nondiabetic group (DeltaLVEF = 13 +/- 2%; DeltaPFR = 0.79 +/- 0.17 EDV/s). The increases in LVEF and PFR were comparable overall but occurred earlier in the nondiabetic group. A blunted increase in plasma catecholamine, cortisol, and glucagon concentrations occurred in response to hypoglycemia in the diabetic subjects. During euglycemic hyperinsulinemia, LVEF also increased in both the diabetic (DeltaLVEF = 7 +/- 1%) and nondiabetic (DeltaLVEF = 4 +/- 2%) groups, but PFR increased only in the diabetic group. In the comparison of the responses to hypoglycemic and euglycemic hyperinsulinemia, only the nondiabetic group had greater augmentation of LVEF, PFR, and cardiac output in the hypoglycemic study (P < 0.05 for each). Thus intensively treated type 1 diabetic patients demonstrate delayed augmentation of ventricular function during moderate insulin-induced hypoglycemia. Although diabetic subjects have a more pronounced cardiac response to hyperinsulinemia per se than nondiabetic subjects, their response to hypoglycemia is blunted.

Caveolin-1 peptide exerts cardioprotective effects in myocardial ischemia-reperfusion via nitric oxide mechanism

Caveolin-1 is a protein constituent of cell membranes. The caveolin-1 scaffolding region (residues 82-101) is a known inhibitor of protein kinase C. Inhibition of protein kinase C results in maintained nitric oxide (NO) release from the endothelium, which attenuates cardiac dysfunction after ischemia-reperfusion (I/R). Therefore, we hypothesized that the caveolin-1 scaffolding region of the molecule, termed caveolin-1 peptide, might attenuate postischemia polymorphonuclear neutrophil (PMN)-induced cardiac dysfunction. We examined the effects of caveolin-1 peptide in isolated ischemic (20 min) and reperfused (45 min) rat hearts reperfused with PMNs. Caveolin-1 peptide (165 or 330 microg) given intravenously 1 h before I/R significantly attenuated postischemic PMN-induced cardiac dysfunction, as exemplified by left ventricular developed pressure (LVDP) (P < 0.01) and the maximal rate of developed pressure (+dP/dt(max)) (P < 0.01), compared with I/R hearts obtained from rats given 0.9% NaCl. In addition, caveolin-1 peptide significantly reduced cardiac PMN infiltration from 195 +/- 5 PMNs/mm2 in untreated hearts to 103 +/- 5 and 60 +/- 5 PMNs/mm2 in hearts from 165 and 330 microg caveolin-1 peptide-treated rats, respectively (P < 0.01). PMN adherence to the rat coronary vasculature was also significantly reduced in rats given either 165 or 330 microg caveolin-1 peptide compared with rats given 0.9% NaCl (P < 0.01). Moreover, caveolin-1 peptide-treated rat aortas exhibited a 2.2-fold greater basal release of NO than vehicle-treated aortas (P < 0.01), and this was inhibited by NG-nitro-L-arginine methyl ester. These results provide evidence that caveolin-1 peptide significantly attenuated PMN-induced post-I/R cardiac contractile dysfunction in the isolated perfused rat heart, probably via enhanced release of endothelium-derived NO.

Effect of 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside infusion on in vivo glucose and lipid metabolism in lean and obese Zucker rats

Activation of AMP-activated protein kinase (AMPK) with 5-aminoimidazole-4-carboxamide-1-beta-D-ribofurano-side (AICAR) increases glucose transport in skeletal muscle via an insulin-independent pathway. To examine the effects of AMPK activation on skeletal muscle glucose transport activity and whole-body carbohydrate and lipid metabolism in an insulin-resistant rat model, awake obese Zuckerfa/fa rats (n = 26) and their lean (n = 23) littermates were infused for 90 min with AICAR, insulin, or saline. The insulin infusion rate (4 mU.kg(-1).min(-1)) was selected to match the glucose requirements during AICAR (bolus, 100 mg/kg; constant, 10 mg.kg(-1).min(-1)) isoglycemic clamps in the lean rats. The effects of these identical AICAR and insulin infusion rates were then examined in the obese Zucker rats. AICAR infusion increased muscle AMPK activity more than fivefold (P < 0.01 vs. control and insulin) in both lean and obese rats. Plasma triglycerides, fatty acid concentrations, and glycerol turnover, as assessed by [2-13C]glycerol, were all decreased in both lean and obese rats infused with AICAR (P < 0.05 vs. basal), whereas insulin had no effect on these parameters in the obese rats. Endogenous glucose production rates, measured by [U-13C]glucose, were suppressed by >50% during AICAR and insulin infusions in both lean and obese rats (P < 0.05 vs. basal). In lean rats, rates of whole-body glucose disposal increased by more than two-fold (P < 0.05 vs. basal) during both AICAR and insulin infusion; [3H]2-deoxy-D-glucose transport activity increased to a similar extent, by >2.2-fold (both P < 0.05 vs. control), in both soleus and red gastrocnemius muscles of lean rats infused with either AICAR or insulin. In the obese Zucker rats, neither AICAR nor insulin stimulated whole-body glucose disposal or soleus muscle glucose transport activity. However, AICAR increased glucose transport activity by approximately 2.4-fold (P < 0.05 vs. control) in the red gastrocnemius from obese rats, whereas insulin had no effect. In summary, acute infusion of AICAR in an insulin-resistant rat model activates skeletal muscle AMPK and increases glucose transport activity in red gastrocnemius muscle while suppressing endogenous glucose production and lipolysis. Because type 2 diabetes is characterized by diminished rates of insulin-stimulated glucose uptake as well as increased basal rates of endogenous glucose production and lipolysis, these results suggest that AICAR-related compounds may represent a new class of antidiabetic agents.

Protein kinase inhibition exerts cardioprotective effects in myocardial ischemia/reperfusion via inhibition of superoxide release

Staurosporine, a selective inhibitor of protein kinase C (PKC) in the low nanomolar range suppresses superoxide production from polymorphonuclear leukocytes (PMNs). Therefore, we hypothesized that staurosporine could attenuate PMN-induced cardiac dysfunction by inhibiting superoxide production from PMNs. We examined the effects of staurosporine in isolated ischemic (I) (20 min) and reperfused (R) (45 min) rat hearts perfused with PMNs. Staurosporine given at 5 or 20 nM to hearts at R significantly improved left ventricular developed pressure (LVDP) (p < 0.01) and the maximal rate of development of LVDP (+dP/dtmax) (p < 0.05, 5 nM, and p < 0.01, 20 nM) compared to similar hearts perfused in the absence of staurosporine. Recombinant human superoxide dismutase (hSOD, 4 micrograms/ml) restored LVDP and +dP/dtmax to that of initial baseline at 45 min postreperfusion. Staurosporine also significantly reduced PMN adherence to the endothelium and infiltration into the myocardium by 38 to 48% (p < 0.01), whereas hSOD attenuated PMN infiltration and adherence by 74% (p < 0.001). These results provide clear evidence that inhibition or scavenging of superoxide release from PMNs significantly attenuates PMN-induced cardiac contractile dysfunction in the ischemic-reperfused rat heart and that a significant component of superoxide release from PMNs is mediated by PKC.

Establishment of a rabbit model of extrascleral extension of ocular melanoma

PURPOSE

To establish an animal model of extrascleral extension of choroidal melanoma.

METHODS

Pigmented choroidal tumors were established in nine New Zealand albino rabbit eyes using B16F10 melanoma cell line. The sclerotomy site was not closed in the subgroup of six rabbits where extrascleral extension was desired. For the control group, the sclerotomy site was sutured with 8-0 nylon. Animals were treated with daily injections of cyclosporine and followed by serial fundus examinations, color Doppler imaging, and fundus photography. All tumor-bearing eyes were enucleated at the end of the follow-up period and examined for extrascleral extension.

RESULTS

Extrascleral extension of choroidal melanoma occurred in all six animals with open sclerotomy sites. No extrascleral extension was observed in the control group. Color Doppler imaging identified extrascleral extension which was confirmed on gross histology.

CONCLUSIONS

Our animal model of extrascleral extension of choroidal melanoma requires minimal surgery to establish, and is reproducible and easy to follow with standard diagnostic equipment.

Effects of vowel height and vocal intensity on anticipatory nasal airflow in individuals with normal speech

The purpose of this study was to determine the effects of vowel height and vocal intensity on the magnitude of anticipatory nasal airflow in normal speakers when producing vowel-nasal-vowel (VNV) sequences. Measurements of nasal and oral airflow were obtained from 15 men and 12 women with normal speech during production of the VNV sequences /ini/ and /ana/ at low, medium, and high intensity levels. Ratios of nasal to oral-plus-nasal airflow were calculated for the initial vowel of both utterances at each of the intensity levels. Analysis of variance (ANOVA) procedures indicated a significant main effect of intensity level and a significant vowel-by-sex interaction effect (p < .05) on the airflow ratios. Overall, the airflow ratio was reduced at high as compared to low intensity levels, regardless of sex of the speaker or vowel type. Female speakers exhibited greater airflow ratios during production of /ini/ than during productions of /ana/. Their airflow ratios were also greater during production of /ini/ than were those of male speakers. The results suggest that vocal intensity may affect velopharyngeal (VP) function in an assimilative nasal phonetic context. The results further suggest that anticipatory nasal airflow may be determined by the configuration of the oral cavity to a greater extent in women than in men. Theoretical and clinical implications are discussed.

PR-39, a proline/arginine-rich antimicrobial peptide, exerts cardioprotective effects in myocardial ischemia-reperfusion

OBJECTIVE

PR-39, a proline/arginine-rich antimicrobial peptide, has been shown to inhibit the NADPH oxidase activity of polymorphonuclear leukocytes (PMNs) by blocking assembly of this enzyme. We hypothesized that PR-39 could attenuate PMN-induced cardiac dysfunction by suppression of superoxide production.

METHODS

We examined the effects of PR-39 in isolated ischemic (20 min) and reperfused (45 min) rat hearts administered PMNs at the onset of reperfusion.

RESULTS

PR-39 (4 or 10 microg/ml) given i.v. 30 min prior to ischemia-reperfusion (I-R) significantly improved left ventricular developed pressure (LVDP, P<0.01) and the maximal rate of development of LVDP (i.e. +dP/dt max, P<0.01) compared to I-R hearts obtained from rats given 0.9% NaCl. PR-39-treated PMNs (10 microg/ml) also significantly attenuated cardiac contractile dysfunction after I-R (P<0.01). Superoxide release was significantly reduced (P<0.01) in N-formylmethionyl-leucylphenylalanine stimulated PMNs pretreated with 4 or 10 microg/ml PR-39. PR-39 also significantly attenuated P-selectin expression on the rat coronary microvascular endothelium and CD18 upregulation in rat PMNs. In addition, PR-39 significantly reduced PMN vascular adherence and infiltration into the post-ischemic myocardium.

CONCLUSION

These results provide evidence that PR-39 significantly attenuates PMN-induced cardiac contractile dysfunction in the I-R rat heart at least in part via suppression of superoxide release. This cardioprotection occurred both by inhibition of PMN and endothelial NADPH oxidase.

Effect of hyperinsulinemia on myocardial amino acid uptake in patients with coronary artery disease

Branched-chain amino acids (BCAAs) are oxidative energy substrates for the heart and may exert anabolic effects on myocardial protein. The factors regulating their myocardial uptake in patients with ischemic heart disease are therefore of interest. To examine whether myocardial BCAA utilization is influenced by the circulating insulin concentration, in 10 patients with chronic ischemic heart disease, we measured transmyocardial amino acid balance during fasting and again during a 90-minute euglycemic insulin infusion (plasma insulin, 218+/-25 microU x mL(-1)) with plasma BCAA concentrations held constant by coinfusion. In the fasting state, the myocardial fractional extraction of leucine (8%), isoleucine (9%), and valine (5%) from arterial plasma was slightly greater than that of glucose (3%), while net myocardial BCAA uptake (leucine, 409+/-207 nmol x min(-1); isoleucine, 220+/-144 nmol x min(-1); valine, 407+/-326 nmol x min(-1); and total BCAA uptake, 1.0+/-0.3 micromol x min(-1)) was about 13% that of glucose (8+/-2 micromol x min(-1)). During euglycemic hyperinsulinemia, myocardial glucose uptake increased 3-fold, but there was no change in the arterial-coronary sinus balance or net myocardial uptake of any BCAA under conditions where their plasma concentrations were held constant. Instead, the myocardial uptake of each BCAA correlated positively with its concentration in arterial plasma. These results demonstrate that in patients with cardiovascular disease, myocardial utilization of BCAAs is insensitive to the circulating insulin level and is regulated instead by their availability in arterial plasma. Hyperinsulinemia reduced the magnitude of both net glutamate uptake and alanine release, suggesting a possible salutary effect on myocardial oxidative efficiency.

Wortmannin, a potent antineutrophil agent, exerts cardioprotective effects in myocardial ischemia/reperfusion

Ischemia followed by reperfusion in the presence of polymorphonuclear leukocytes (PMNs) results in a marked cardiac contractile dysfunction. Wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase, suppresses superoxide production from PMNs. Therefore, we hypothesized that wortmannin could attenuate PMN-induced cardiac dysfunction by suppression of superoxide production from PMNs. We examined the effects of wortmannin in isolated ischemic (20 min) and reperfused (45 min) rat hearts perfused with PMNs. Wortmannin at 10, 20, or 40 nM given to hearts during the first 5 min of reperfusion, significantly improved left ventricular developed pressure (P < .01), and the maximal rate of development of left ventricular developed pressure (P < .01) compared with ischemic/reperfused hearts perfused with PMNs in the absence of wortmannin. In addition, wortmannin significantly reduced PMN infiltration into the myocardium by 50 to 75% (P < .001). Superoxide radical release also was significantly reduced in N-formylmethionyl-leucylphenylalanine-stimulated PMNs pretreated with 10 or 40 nM wortmannin by 70 and 95%, respectively (P < .001 versus untreated PMNs). Rat PMN adherence to rat superior mesenteric artery endothelium exposed to 2 U/ml thrombin was significantly attenuated by 10 to 40 nM wortmannin compared with untreated vessels (P < .001). These results provide evidence that wortmannin can significantly attenuate PMN-induced cardiac contractile dysfunction in the ischemic/reperfused rat heart via attenuation of PMN infiltration into the myocardium and suppression of superoxide release by PMNs.

C-peptide exerts cardioprotective effects in myocardial ischemia-reperfusion

Ischemia followed by reperfusion in the presence of polymorphonuclear leukocytes (PMNs) results in cardiac dysfunction. C-peptide, a cleavage product of proinsulin to insulin processing, induces nitric oxide (NO)-mediated vasodilation. NO is reported to attenuate cardiac dysfunction caused by PMNs after ischemia-reperfusion (I/R). Therefore, we hypothesized that C-peptide could attenuate PMN-induced cardiac dysfunction. We examined the effects of C-peptide in isolated ischemic (20 min) and reperfused (45 min) rat hearts perfused with PMNs. C-peptide (70 nmol/kg iv) given 4 or 24 h before I/R significantly improved coronary flow (P < 0.05), left ventricular developed pressure (LVDP) (P < 0.01), and the maximal rate of development of LVDP (+dP/dt(max)) compared with I/R hearts obtained from rats given 0.9% NaCl (P < 0.01). N(G)-nitro-L-arginine methyl ester (L-NAME) (50 micromol/l) blocked these cardioprotective effects. In addition, C-peptide significantly reduced cardiac PMN infiltration from 183 +/- 24 PMNs/mm(2) in untreated hearts to 44 +/- 10 and 58 +/- 25 PMNs/mm(2) in hearts from 4- and 24-h C-peptide-treated rats, respectively. Rat PMN adherence to rat superior mesenteric artery exposed to 2 U/ml thrombin was significantly reduced in rats given C-peptide compared with rats given 0.9% NaCl (P < 0.001). Moreover, C-peptide enhanced basal NO release from rat aortic segments. These results provide evidence that C-peptide can significantly attenuate PMN-induced cardiac contractile dysfunction in the isolated perfused rat heart subjected to I/R at least in part via enhanced NO release.

Cardioprotective effects of citrulline in ischemia/reperfusion injury via a non-nitric oxide-mediated mechanism

The effects of L-citrulline, the byproduct of nitric oxide (NO) synthesis, and its stereoisomer D-citrulline were studied in a polymorphonuclear leukocyte (PMN)-dependent isolated perfused rat heart model consisting of 20 min of global ischemia and 45 min of reperfusion. Ischemic hearts reperfused with either D- or L-citrulline (20 nM) exhibited a marked preservation of left ventricular developed pressure and of maximal rate of development of left ventricular developed pressure, compared to hearts perfused without either D- or L-citrulline (both p < 0.001). In addition, both D- and L-citrulline significantly attenuated PMN accumulation in the post-reperfused myocardium from 288 +/- 33 PMNs/mm2 in untreated hearts to 89 +/- 10 and 76 +/- 6 PMNs/mm2, respectively (both p < 0.001). In isolated rat aortic rings, neither D- or L-citrulline induced any vasodilation or release of nitric oxide from the vascular endothelium. However, expression of P-selectin on the coronary vascular endothelium was markedly attenuated in hearts perfused with either D- or L-citrulline compared to ischemic-reperfused hearts without citrulline (both p < 0.001). These results provide evidence that D- or L-citrulline significantly attenuates PMN-induced cardiac contractile dysfunction in the isolated perfused rat heart subjected to ischemia/reperfusion via a non-NO-mediated mechanism.

Translocation of myocardial GLUT-4 and increased glucose uptake through activation of AMPK by AICAR

Insulin increases glucose uptake through the translocation of GLUT-4 via a pathway mediated by phosphatidylinositol 3-kinase (PI3K). In contrast, myocardial glucose uptake during ischemia and hypoxia is stimulated by the translocation of GLUT-4 to the surface of cardiac myocytes through a PI3K-independent pathway that has not been characterized. AMP-activated protein kinase (AMPK) activity is also increased by myocardial ischemia, and we examined whether AMPK stimulates glucose uptake and GLUT-4 translocation. In isolated rat ventricular papillary muscles, 5-aminoimidazole-4-carboxyamide-1-beta-D-ribofuranoside (AICAR), an activator of AMPK, as well as cyanide-induced chemical hypoxia and insulin, increased 2-[(3)H]deoxyglucose uptake two- to threefold. Wortmannin, a PI3K inhibitor, did not affect either the AICAR- or the cyanide-stimulated increase in deoxyglucose uptake but eliminated the insulin-stimulated increase in deoxyglucose uptake. Immunofluorescence studies demonstrated translocation of GLUT-4 to the myocyte sarcolemma in response to stimulation with AICAR, cyanide, or insulin. Preincubation of papillary muscles with the kinase inhibitor iodotubercidin or adenine 9-beta-D-arabinofuranoside (araA), a precursor of araATP (a competitive inhibitor of AMPK), decreased AICAR- and cyanide-stimulated glucose uptake but did not affect basal or insulin-stimulated glucose uptake. In vivo infusion of AICAR caused myocardial AMPK activation and GLUT-4 translocation in the rat. We conclude that AMPK activation increases cardiac muscle glucose uptake through translocation of GLUT-4 via a pathway that is independent of PI3K. These findings suggest that AMPK activation may be important in ischemia-induced translocation of GLUT-4 in the heart.

Regulation of myocardial glucose uptake and transport during ischemia and energetic stress

Myocardial glucose utilization increases in response to the energetic stress imposed on the heart by exercise, pressure overload, and myocardial ischemia. Recruitment of glucose transport proteins is the cellular mechanism by which the heart increases glucose transport for subsequent metabolism. Moderate regional ischemia leads to the translocation of both glucose transporters, GLUT4 and GLUT1, to the sarcolemma in vivo. Myocardial ischemia also stimulates 5'-adenosine monophosphate-activated protein kinase, which may be a fuel gauge in the heart and other tissues signaling the need to turn on energy-generating metabolic pathways. Pharmacologic stimulation of this kinase increases cardiac glucose uptake and transporter translocation, suggesting that it may play an important role in augmenting glucose entry in the setting of ischemic or energetic stress. Thus, recent work has provided insight into the cellular and molecular mechanisms responsible for glucose uptake during energetic stress, which may lead to new approaches to the treatment of patients with coronary artery disease.

Effect of AMPK activation on muscle glucose metabolism in conscious rats

The effect of AMP-activated protein kinase (AMPK) activation on skeletal muscle glucose metabolism was examined in awake rats by infusing them with 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside (AICAR; 40 mg/kg bolus and 7.5 mg. kg-1. min-1 constant infusion) along with a variable infusion of glucose (49.1 +/- 2.4 micromol. kg-1. min-1) to maintain euglycemia. Activation of AMPK by AICAR caused 2-deoxy-D-[1,2-3H]glucose (2-DG) uptake to increase more than twofold in the soleus and the lateral and medial gastrocnemius compared with saline infusion and occurred without phosphatidylinositol 3-kinase activation. Glucose uptake was also assessed in vitro by use of the epitrochlearis muscle incubated either with AICAR (0.5 mM) or insulin (20 mU/ml) or both in the presence or absence of wortmannin (1.0 microM). AICAR and insulin increased muscle 2-DG uptake rates by approximately 2- and 2.7-fold, respectively, compared with basal rates. Combining AICAR and insulin led to a fully additive effect on muscle glucose transport activity. Wortmannin inhibited insulin-stimulated glucose uptake. However, neither wortmannin nor 8-(p-sulfophenyl)-theophylline (10 microM), an adenosine receptor antagonist, inhibited the AICAR-induced activation of glucose uptake. Electrical stimulation led to an about threefold increase in glucose uptake over basal rates, whereas no additive effect was found when AICAR and contractions were combined. In conclusion, the activation of AMPK by AICAR increases skeletal muscle glucose transport activity both in vivo and in vitro. This cellular pathway may play an important role in exercise-induced increase in glucose transport activity.

Insulin-like growth factor I stimulates cardiac myosin heavy chain and actin synthesis in the awake rat

To determine the effect of insulin-like growth factor I (IGF-I) on cardiac contractile protein synthesis in vivo, we measured L-[ring-2, 6-3H]phenylalanine incorporation into myosin heavy chain and actin during intravenous infusions (4 h) of either saline or IGF-I (1 microgram. kg-1. min-1) in awake rats. After an overnight fast, IGF-I increased myosin synthesis by 29% compared with saline (11.5 +/- 0.8 vs. 8.9 +/- 0.6%/day, P < 0.01) and actin synthesis by 26% (7.2 +/- 0.3 vs. 5.7 +/- 0.3%/day, P < 0.01), with similar effects in left and right ventricles and a comparable effect on mixed cardiac protein. When amino acids were infused with IGF-I, a further increase in myosin synthesis was observed (P < 0.01). In fed rats, despite higher baseline synthesis rates than in fasted rats (P < 0. 01), IGF-I also increased the synthesis of myosin (12.3 +/- 0.5 vs. 9.9 +/- 0.5%/day, P < 0.01) and actin (8.8 +/- 0.3 vs. 7.5 +/- 0. 2%/day, P < 0.01) compared with saline. IGF-I infusion had no hypoglycemic effect and did not change heart rate or blood pressure. Thus relatively low-dose IGF-I has a direct action in vivo to acutely increase heart contractile protein synthesis in both fasted and fed awake rats.

Additive effects of hyperinsulinemia and ischemia on myocardial GLUT1 and GLUT4 translocation in vivo

BACKGROUND

Myocardial ischemia increases glucose uptake through the translocation of GLUT1 and GLUT4 from an intracellular compartment to the sarcolemma. The present study was performed to determine whether hyperinsulinemia causes translocation of myocardial GLUT1 as well as GLUT4 in vivo and whether there are additive effects of insulin and ischemia on GLUT1 and GLUT4 translocation. METHODS ADN RESULTS: Myocardial glucose uptake and transporter distribution were assessed by arteriovenous measurements, cell fractionation, and immunofluorescence. In fasted anesthetized dogs, hyperinsulinemia increased myocardial glucose extraction 3-fold (P<0.01) and the sarcolemmal content of GLUT4 by 90% and GLUT1 by 50% (P<0.05 for both) compared with saline infusion. In subsequent experiments, glucose uptake and transporter distribution were determined in ischemic and nonischemic regions of hearts from hyperinsulinemic animals during regional myocardial ischemia. Glucose uptake was 50% greater in the ischemic region (P<0.05). This was associated with a 20% increase in sarcolemmal GLUT1 and a 60% increase in sarcolemmal GLUT4 contents in the ischemic region (P<0.05 for both).

CONCLUSIONS

Insulin stimulates myocardial glucose utilization through translocation of GLUT1 as well as GLUT4. Insulin and ischemia have additive effects to increase in vivo glucose utilization and augment glucose transporter translocation. We conclude that recruitment of both GLUT1 and GLUT4 contributes to increased myocardial glucose uptake during moderate reductions in coronary blood flow under insulin-stimulated conditions.

Immunohistochemical localization of ganciclovir in the human retina

PURPOSE

To localize ganciclovir in the retina of human eyes treated with intravenous or intravitreal ganciclovir for cytomegalovirus (CMV) retinitis.

METHODS

Paraffin-embedded five-micron sections of autopsy eyes were obtained from seven patients as follows: two patients with CMV retinitis treated with intravenous ganciclovir; two patients with CMV retinitis treated with an intravitreal sustained-release ganciclovir device; one patient with CMV retinitis treated with intravenous foscarnet; and two patients with AIDS without CMV retinitis who did not receive any anti-CMV therapy. The paraffin was removed from the sections, and indirect immunofluorescent staining was performed, using an antiserum to ganciclovir.

RESULTS

Bright fluorescent staining was noted in the retinal pigment epithelium (RPE) and photoreceptor outer segments of eyes treated with intravenous or intravitreal ganciclovir, but not in eyes treated with foscarnet or without CMV retinitis. In addition, patches of bright fluorescent staining of the internal limiting membrane was noted in eyes treated with intravitreal ganciclovir.

CONCLUSIONS

Ganciclovir is detected in the outer retina of patients with CMV retinitis treated with intravenous or intravitreal therapy. The drug is detected also in the internal limiting membrane in eyes treated with the intravitreal sustained-release ganciclovir device.

Expression of a vitamin D-regulated gene (VDUP-1) in untreated- and MNU-treated rat mammary tissue

Previous studies showed that the expression of an mRNA corresponding to VDUP-1 was decreased within MNU-induced rat mammary tumors. RNA from mammary tissue was DNase treated and reverse transcribed and the resulting cDNA was amplified using primers designed to amplify VDUP-1 (382 bp fragment) and glyceraldehyde-6-phosphate dehydrogenase (GAPDH) (416 bp fragment). Analysis of mammary cDNA derived from untreated or MNU-treated rats indicated that VDUP-1 expression within tumor tissue was significantly decreased, a finding which agrees with previous Northern blotting experiments. The differential expression was confirmed in tissue sections using an antisense VDUP-1 riboprobe for in situ hybridization studies which demonstrated that VDUP-1 staining in all cell types within tumor tissue was greatly decreased. VDUP-1 mRNA was expressed to a greater extent within epithelial cells and to a much lesser extent within stromal cells, including endothelial cells, in untreated mammary tissue. A significant decrease in VDUP-1 expression was detected as early as six weeks after MNU treatment, before tumors had formed. Bilateral ovariectomy did not alter VDUP-1 expression in untreated mammary tissue and ovariectomy prior to MNU treatment prevented tumor formation, as well as the associated decrease in VDUP-1 expression. The relative expression of VDUP-1 was higher in lung tissue than in adrenal, heart, kidney, liver, mammary, muscle, and ovary. Treatment of a cell line derived from an MNU-induced rat mammary tumor (MNU cells) with 1,25-dihydroxyvitamin D3 resulted in a significant increase in VDUP-1 expression and also inhibited cell growth in the absence of serum. The data are consistent with a role for VDUP-1 in mediating the inhibitory effects of 1,25-dihydroxyvitamin D3 on tumor cell growth.