Search

Sulfonylurea receptor-containing ATP-sensitive potassium ([K.sub.ATP]) channels have been implicated in cardioprotection, but the cell type and constitution of channels responsible for this protection have not been clear. Mice deleted for the first nucleotide binding region of sulfonylurea receptor 2 (SUR2) are referred to as SUR2 null since they lack full-length SUR2 and glibenclamide-responsive [K.sub.ATP] channels in cardiac, skeletal, and smooth muscle. As previously reported, SUR2 null mice develop electrocardiographic changes of ST segment elevation that were shown to correlate with coronary artery vasospasm. Here we restored expression of the cardiomyocyte SUR2-[K.sub.ATP] channel in SUR2 null mice by generating transgenic mice with ventricular cardiomyocyte-restricted expression of SUR2A. Introduction of the cardiomyocyte SUR2A transgene into the SUR2 null background restored functional cardiac [K.sub.ATP] channels. Hearts isolated from rescued mice, referred to as MLC2A, had significantly reduced infarct size (27 [+ or -] 3% of area at risk) compared with SUR2 null mice (36 [+ or -] 3% of area at risk). Compared with SUR2 null hearts, MLC2A hearts exhibited significantly improved cardiac function during the postischemia reperfusion period primarily because of preservation of low diastolic pressures. Additionally, restoration of cardiac SUR2-[K.sub.ATP] channels significantly reduced the degree and frequency of ST segment elevation episodes in MLC2A mice. Therefore, cardioprotective mechanisms both dependent and independent of SUR2-[K.sub.ATP] channels contribute to cardiac function. ATP-sensitive potassium channel; SUR2; SUR2A; ischemia; vasospasm doi: 10.1152/ajpheart.00084.2010.

Recent clinical trials demonstrated that PPAR[alpha] agonist fenofibrate reduces cardiovascular events, including limb amputation in people with type 2 diabetes. Here, we investigated whether fenofibrate modulates the revascularization process in a mouse model of hindlimb ischemia. Treatment with fenofibrate led to acceleration of revascularization of ischemic hindlimb relative to the contralatereal limb in wild-type (WT) mice, as measured by laser Doppler blood flow and capillary density analyses. Treatment of WT mice with fenofibrate increased the serum levels of adiponectin, which has protective actions on the vasculature. Of importance, fenofibrate had no effects on the revascularization in ischemic limbs of adiponectin-deficient (APN-KO) mice. Fenofibrate stimulated the phosphorylation of AMPK and eNOS in the ischemic muscles in WT mice but not in APN-KO mice. AMPK inhibitor compound C suppressed fenofibrate-induced increase in limb perfusion and AMPK phosphorylation in ischemic muscle in WT mice without affecting adiponectin levels. NOS inhibitor L-NAME also blocked the increased blood flow of ischemic limbs in fenofibrate-treated WT mice. Our observations suggest that fenofibrate could promote revascularization in response to ischemia through adiponectin-dependent AMPK signaling. angiogenesis; endothelial nitric oxide synthase doi: 10.1152/ajpendo.00284.2010.

Anemia may accelerate angiogenesis in ischemic organs through its ability to augment tissue hypoxia-induced generation of several known angiogenic factors and to increase erythropoietin levels, which are also potently angiogenic. We examined the effect of controlled phlebotomy (bloodletting) on blood flow in a mouse ischemic leg model. We ligated the right femoral artery of BALB/c mice. In the phlebotomy group, 200 [micro]l of blood were drawn from the tail vein once a week. After 4 wk, blood flow in the ischemic leg was significantly better in the phlebotomy group (flow ratio of the ischemic to nonischemic leg, 0.87 [+ or -] 0.04) than the control group (0.59 [+ or -] 0.05, P < 0.05), and capillary density was significantly higher. Repeated phlebotomy increased serum erythropoietin levels as well as the expression of hypoxia-inducible transcription factor-let and vascular endothelial growth factor and both the expression and activity of Akt and endothelial nitric oxide synthase (eNOS) in ischemic legs. Treatment with wortmannin or [N.sup.[omega]] nitro-L-arginine methyl ester significantly attenuated the phlebotomy-induced improvement of blood flow. In addition, fluorescence-activated cell sorting analysis revealed an increase in circulating peripheral endothelial progenitor cells in the phlebotomy group, and treatment with AMD3100, a specific inhibitor of the chemokine receptor CXCR4, blocked the beneficial effect of phlebotomy. These findings suggest that repeated phlebotomy improves blood flow in ischemic legs through an angiogenic action that involves the Akt/ eNOS pathway, endothelial progenitor cell mobilization, and their complicated cross talk. An adequately controlled phlebotomy might be one method by which to induce therapeutic angiogenesis. ischemia; vascular biology doi: 10.1152/ajpheart.00035.2010.

Because of their ability to perfuse remote regions and deliver oxygen, hemoglobin-based oxygen carriers (HBOCs) may be considered in the treatment of several ischemic conditions such as acute coronary syndromes or high-risk percutaneous intervention. Here we studied the effects of intracoronary infusion of ex vivo preoxygenated HBOC-201 during brief total coronary artery occlusion (CAOs) on myocardial oxygenation and left ventricular (LV) function in a large animal model and investigated the influence of HBOC-201 temperature and infusion rate on these effects. Thirteen open-chest anesthetized swine were instrumented for measurement of global and regional LV function and metabolism. CAOs were induced by inflating an intracoronary balloon catheter; preoxygenated HBOC-201 (12 g/dL) was infused distally through the central lumen of the balloon catheter. Animals underwent consecutive 3-min CAOs interspersed by 30 min of reperfusion, accompanied by different HBOC-201 infusion rates (0, 15, 23, 30, 40, and 50 ml/min) and/or two infusion temperatures (18[degrees]C or 37[degrees]C) in random order. CAO elicited immediate loss of systolic shortening (SS) in the ischemic region (19 [+ or -] 1% at baseline vs. -3 [+ or -] 2% at end of CAO), resulting in decreases in maximum rate of rise in LV pressure (15 [+ or -] 5%) and stroke volume (12 [+ or -] 4%; all P < 0.05). Balloon deflation resulted in marked coronary reactive hyperemia (to 472 [+ or -] 74% of baseline), increases in coronary venous concentrations of adenosine or inosine (to 218 [+ or -] 26% of baseline; both P < 0.05) and rapid restoration of SS toward baseline. HBOC-201 ameliorated the CAO-induced changes in SS, stroke volume, reactive hyperemia, and coronary venous adenosine + inosine. The effects were temperature and flow dependent with full preservation of SS at 50 ml/min HBOC-201 of 37[degrees]C. In conclusion, intracoronary preoxygenated HBOC-201 preserved myocardial oxygenation and LV function in swine during CAO in a dose-and temperature-dependent manner. In our study setting, preoxygenated HBOC-201 can match the oxygen delivery role of endogenous blood in the heart on an almost equivalent-volume basis. coronary blood flow; intracoronary infusion; left ventricular function; myocardial metabolism doi:10.1152/ajpheart.00667.2009

Autologous cell implantation and angiogenic gene therapy have been evaluated in critical limb ischemic patients. Here, we compared the features of these strategies individually and in combination. C57BL/6J mice with ischemic hindlimbs were injected with adherent mononuclear cells (aMNCs) from bone marrow or adenovirus encoding the hepatocyte growth factor (HGF) gene (Ad-HGF). Under comparable angiogenic conditions, 10 x [10.sup.5] aMNCs produced significantly higher amounts of VEGF and FGF-2 and stimulated the number of arterioles in ischemic muscle compared with 1 x [10.sup.8] plaque-forming units (pfu) of Ad-HGF. Ad-HGF produced 10 times more HGF in ischemic muscle compared with aMNCs. Injection of 0.3 x [10.sup.5] aMNCs previously transfected with Ad-HGF (aMNC/Ad-HGF) increased blood flow and elevated the numbers of capillaries and arterioles to levels comparable with that seen with 10 x [10.sup.5] aMNCs or 1 x [10.sup.8] pfu of Ad-HGF. Hypoxic conditions induced the apoptotic death of aMNCs. However, coincubation with HGF or aMNC/Ad-HGF protected cells against apoptosis. HGF stimulated the migration of aMNCs, and the migration capacity of the aMNC/Ad-HGF group was significantly higher than that in the aMNC/Ad-LacZ group. In conclusion, cell-based HGF gene therapy decreased the number of cells required for neovascularization. This strategy can be an effective angiogenic therapy. angiogenesis; apoptosis doi: 10.1152/ajpheart.00321.2009

Adjunctive cardio-protective strategies for ameliorating the reversible and irreversible injuries with ischemia-reperfusion (I/R) are highly desirable. However, after decades of research, the promise of clinical cardioprotection from I/R injury remains poorly realized. This may arise from the challenges of trialing and effectively translating experimental findings from laboratory models to patients. One can additionally consider whether features of the more heavily focused upon candidates could limit or preclude therapeutic utility and thus whether we might shift attention to alternate strategies. The phenomena of preconditioning and postconditioning have proven fertile in identification of experimental means of cardioprotection and are the most intensely interrogated responses in the field. However, there is evidence these processes, which share common molecular signaling elements and end effectors, may be poor choices for clinical exploitation. This includes evidence of age dependence, limiting efficacy in target aged or senescent hearts; refractoriness to conditioning stimuli in diseased myocardium; interference from a variety of relevant pharmaceuticals; inadvertent induction of these responses by prior ischemia or commonly used drugs, precluding further benefit; and sex dependence of protective signaling. This review focuses on these features, raising questions about current research strategies, and the suitability of these widely studied phenomena as rational candidates for clinical translation. acute myocardial infarction; aging; cardiac ischemia; clinical translation; diabetes; obesity; preconditioning; postconditioning; reperfusion

Previous studies from our laboratory have demonstrated that altering muscle temperature of the exercising forearm can elicit changes in muscle sympathetic nerve activity (MSNA) during ischemic isometric handgrip. The purpose of the current study was to determine the interactive effect of muscle temperature and blood flow on MSNA responses during dynamic handgrip (DHG). Eight subjects performed two bouts of graded DHG to fatigue followed by 2 min of postexercise muscle ischemia (PEMI). Local heating of the forearm increased muscle temperature from 33.6 [+ or -] 0.3 to 38.3 [+ or -] 0.5[degrees]C (P < 0.05). Mean arterial pressure and heart rate increased in a linear fashion during graded DHG (P < 0.05) but were not affected by muscle temperature. MSNA (burst frequency and total activity) at fatigue and PEMI were elevated in all conditions (P < 0.05). However, MSNA responses were not different between temperature conditions. To ascertain the effect of blood flow, eight additional subjects completed two trials of ischemic DHG under control or warm conditions followed by 2 min of PEMI. MSNA, expressed as burst frequency and total activity, was significantly greater in warm compared with the control trial ([DELTA]14 [+ or -] 3 and [DELTA]9 [+ or -] 2 bursts/30 s, and [DELTA]1,234 [+ or -] 260 and [DELTA]751 [+ or -] 199 units/30 s, respectively). This finding supports the concept that muscle heating sensitizes skeletal muscle afferents during muscle contractions and augments MSNA in humans. However, on the basis of these findings, we conclude that muscle blood flow modulates the effect of muscle temperature on MSNA during exercise. metaboreflex; mechanoreflex; perfusion; ischemia; muscle thermoreflex

Cardiac cellular [Ca.sup.2+] transient (CAT) alternans and electrocardiographic T-wave alternans (TWA) often develop in myocardial ischemia, but the mechanisms for this relationship have not been elucidated. Acidosis is a major component of ischemia, but there is no direct evidence linking acidosis-induced cellular CaT alternans to ischemia-induced CaT alternans and TWA in whole heart. We used laser-scanning confocal microscopy to measure intracellular [Ca.sup.2+] ([Ca.sup.2+.sub.i]) cycling in individual myocytes of fluo-4 AM-loaded rat hearts and simultaneously recorded pseudo-ECGs to investigate changes in CaTs and late-phase repolarization, respectively, during baseline and rapid pacing under control and either globally acidic or globally ischemic conditions. Acidosis (hypercapnia; pH 6.6) increased diastolic [Ca.sup.2+.sub.i] levels, prolonged CaT duration, and shifted to slower heart rates both the development of pacing-induced acidosis-induced CaT alternans (both concordant and discordant) and of repolarization alternans (RPA, a measure of TWA in rat ECGs). The magnitudes of these shifts were equivalent for both CaT alternans and RPA, suggesting a close association between them. Nearly identical results were found in low-flow global ischemia. Additionally, ischemic preconditioning reduced the increased propensity for CaT altemans and RPA development and was mimicked by preconditioning by acidosis alone. Our results demonstrate that global acidosis or ischemia modifies [Ca.sup.2+.sub.i] cycling in myocytes such that the diastolic [Ca.sup.2+.sub.i] rises and the cellular CaT duration is prolonged, causing spatially concordant as well as spatially discordant cellular CaT alternans to develop at slower heart rates than in controls. Since RPA also developed at slower heart rates, our results suggest that acidosis is a major contributor to CaT alternans, which underlies the proarrhythmic state induced by myocardial ischemia and therefore may play a role in its modulation and prevention. arrhythmia; calcium cycling

Previous studies have demonstrated an increase in the arterial baroreflex (ABR) control of muscle sympathetic nerve activity (MSNA) during isolated activation of the muscle metaboreflex with postexercise muscle ischemia (PEMI). However, the increased ABR-MSNA control does not appear to manifest in an enhancement in the ABR control of arterial blood pressure (BP), suggesting alterations in the transduction of MSNA into a peripheral vascular response and a subsequent ABR-mediated change in BP. Thus we examined the operating gains of the neural and peripheral arcs of the ABR and their interactive relationship at rest and during muscle metaboreflex activation. In nine healthy subjects, graded isolation of the muscle metaboreflex was achieved by PEMI following isometric handgrip performed at 15% and 30% maximal voluntary contraction (MVC). To obtain the sensitivities of the ABR neural and peripheral arcs, the transfer function gain from BP to MSNA and MSNA to femoral vascular conductance, respectively, was analyzed. No changes from rest were observed in the ABR neural or peripheral arcs during PEMI after 15% MVC handgrip. However, PEMI following 30% MVC handgrip increased the low frequency (LF) transfer function gain between BP and MSNA (ABR neural arc; +58 [+ or -] 28%, P = 0.036), whereas the LF gain between MSNA and femoral vascular conductance (ABR peripheral arc) was decreased from rest (-36 [+ or -] 8%, P = 0.017). These findings suggest that during high-intensity muscle metaboreflex activation an increased ABR gain of the neural arc appears to offset an attenuation of the peripheral arc gain to help maintain the overall ABR control of systemic BP. blood pressure; isometric handgrip exercise; transfer function analysis

Bone marrow mesenchymal stem cells (MSCs) may be a novel treatment modality for organ ischemia, possibly through the release of beneficial paracrine factors. However, an age threshold likely exists as to when MSCs gain their beneficial protective properties. We hypothesized that 1) VEGF would be a crucial stem cell paracrine mediator in providing postischemic myocardial protection and 2) small-interfering (si)RNA ablation of VEGF in adult MSCs (aMSCs) would equalize the differences observed between aMSC- and neonatal stem cell (nMSC)-mediated cardioprotection. Female adult Sprague-Dawley rat hearts were subjected to ischemia-reperfusion injury via Langendorff-isolated heart preparation (15 min equilibration, 25 min ischemia, and 60 min reperfusion). MSCs were harvested from adult and 2.5-wk-old neonatal mice and cultured under normal conditions. VEGF was knocked down in both cell lines by VEGF siRNA. Immediately before ischemia, one million aMSCs or nMSCs with or without VEGF knockdown were infused into the coronary circulation. The cardiac functional parameters were recorded. VEGF in cell supernatants was measured via ELISA. aMSCs produced significantly more VEGF than nMSCs and were noted to increase postischemic myocardial recovery compared with nMSCs. The knockdown of VEGF significantly decreased VEGF production in both cell lines, and the pretreatment of these cells impaired stem cell-mediated myocardial function. The knockdown of VEGF in adult stem cells equalized the myocardial functional differences observed between adult and neonatal stem cells. Therefore, VEGF is a critical paracrine mediator in facilitating postischemic myocardial recovery and likely plays a role in mediating the observed age threshold during stem cell therapy. ischemia-reperfusion

Reductions in vascular density occur following acute ischemia-reperfusion (I/R) injury that may predispose the development of chronic kidney disease. The mechanisms mediating vascular loss are not clear but may relate to the lack of effective vascular repair responses. To determine the regulation of the VEGF/VEGFR pathway following I/R injury, male SpragueDawley rats were subjected to bilateral renal ischemia (45 min) and allowed to recover for 1, 3, 7, and 35 days. VEGF mRNA expression was repressed by greater than 50% of control values up to 3 days postischemia, while VEGF protein was repressed for up to 7 days postischemia. The renal mRNA expression of receptors was not altered postischemia; however, VEGFR1 (flt-1) protein was transiently reduced in kidney while soluble flt-1 was elevated in plasma at 7 days following injury. Microarray analysis of angiogenesis-related genes identified the enhanced expression of a number of genes, among these was ADAMTS-1 (a disintegrin and metalloproteinase with thrombospondin motif-l), a secreted VEGF inhibitor. The altered expression of ADAMTS-1 was confirmed using RT-PCR and Western blot analysis; immunofluorescence localized its expression to proximal tubules following I/R injury. Other genes identified using microarray included aminopeptidase N, Smad-1, and Id-3 and their localization was also examined using immunohistochemistry. In summary, the data indicate no clear pattern of anti-angiogenic gene expression following renal I/R injury. However, the studies do suggest an overall inhibition of the VEGF pathway during the early injury and repair phase of renal ischemia that may contribute to an overall reduction in renal microvascular density. microarray; rarefaction

The JAK-STAT pathway is activated in the early and late phases of ischemic preconditioning (IPC) in normal myocardium. The role of this pathway and the efficacy of IPC in hypertrophied hearts remain largely unknown. We hypothesized that phosphorylated STAT-3 (pSTAT-3) is necessary for effective IPC in pressure-overload hypertrophy. Male Sprague-Dawley rats 8 wk after thoracic aortic constriction (TAC) or sham operation underwent echocardiography and Langendorff perfusion. Randomized hearts were subjected to 30 min of global ischemia and 120 min of reperfusion with or without IPC in the presence or absence of the JAK-2 inhibitor AG-490 (AG). Functional recovery and STAT activation were assessed. TAC rats had a 31% increase in left ventricular mass (1,347 [+ or -] 58 vs. 1,028 [+ or -] 43 mg, TAC vs. sham, P < 0.001), increased anterior and posterior wall thickness but no difference in ejection fraction compared with sham-operated rats. In TAC, IPC improved end-reperfusion maximum first derivative of developed pressure (+dP/[dt.sub.max]; 4,648 [+ or -] 309 vs. 2,737 [+ or -] 343 mmHg/s, IPC vs. non-IPC, P < 0.05) and minimum -dP/dt (-dP/[dt.sub.min]; -2,239 [+ or -] 205 vs. -1,215 [+ or -] 149 mmHg/s, IPC vs. non-IPC, P < 0.05). IPC increased nuclear pSTAT-1 and pSTAT-3 in sham-operated rats but only pSTAT-3 in TAC. AG in TAC significantly attenuated +dP/ [dt.sub.max] (4,648 [+ or -] 309 vs. 3,241 [+ or -] 420 mmHg/s, IPC vs. IPC + AG, P < 0.05) and -dP/[dt.sub.min] (-2,239 [+ or -] 205 vs. -1,323 [+ or -] 85 mmHg/s, IPC vs. IPC + AG, P < 0.05) and decreased only nuclear pSTAT-3. In myocardial hypertrophy, JAK-STAT signaling is important in IPC and exhibits a pattern of STAT activation distinct from nonhypertrophied myocardium. Limiting STAT-3 activation attenuates the efficacy of IPC in hypertrophy. ischemia-reperfusion; Janus-activated kinase; signal transducer and activator of transcription; cardiac preconditioning; myocardial hypertrophy doi:10.1152/ajpheart.01334.2005

Rodent studies suggest that peroxisome proliferator-activated receptor-[alpha] (PPAR-[alpha]) activation reduces myocardial ischemia-reperfusion (I/R) injury and infarct size; however, effects of PPAR-[alpha] activation in large animal models of myocardial I/R are unknown. We determined whether chronic treatment with the PPAR-[alpha] activator fenofibrate affects myocardial I/R injury in pigs. Domestic farm pigs were assigned to treatment with fenofibrate 50 mg * [kg.sup.-1] * [day.sup.-1] orally or no drug treatment, and either a low-fat (4% by weight) or a high-fat (20% by weight) diet. After 4 wk, 66 pigs underwent 90 min low-flow regional myocardial ischemia and 120 min reperfusion under anesthetized open-chest conditions, resulting in myocardial stunning. The high-fat group received an infusion of triglyceride emulsion and heparin during this terminal experiment to maintain elevated arterial free fatty acid (FFA) levels. An additional 21 pigs underwent 60 min no-flow ischemia and 180 min reperfusion, resulting in myocardial infarction. Plasma concentration of fenofibric acid was similar to the [EC.sub.50] for activation of PPAR-[alpha] in vitro and to maximal concentrations achieved in clinical use. Myocardial expression of PPAR-[alpha] mRNA was prominent but unaffected by fenofibrate treatment. Fenofibrate increased expression of carnitine palmitoyltransferase (CPT)-I mRNA in liver and decreased arterial FFA and lactate concentrations (each P < 0.01). However, fenofibrate did not affect myocardial CPT-I expression, substrate uptake, lipid accumulation, or contractile function during low-flow I/R in either the low- or high-fat group, nor did it affect myocardial infarct size. Despite expression of PPAR-[alpha] in porcine myocardium and effects of fenofibrate on systemic metabolism, treatment with this PPAR-[alpha] activator does not alter myocardial metabolic or contractile responses to I/R in pigs. nuclear receptor; fibric acid derivative; energy metabolism; cytokine; ventricular function

Reactive oxygen and nitrogen species play a key role in the pathophysiology of renal ischemia-reperfusion (I/R) injury. Recent studies have shown that nitrite (N[O.sup.-.sub.2]) serves as an endogenous source of nitric oxide (NO), particularly in the presence of hypoxia and acidosis. Nanomolar concentrations of N[O.sup.-.sub.2] reduce injury following I/R in the liver and heart in vivo. The purpose of this study was to evaluate the role of N[O.sup.-.sub.2] in renal I/R injury. Male Sprague-Dawley rats underwent a unilateral nephrectomy followed by 45 min of ischemia of the contralateral kidney or sham surgery under isoflurane anesthesia. Animals received normal saline, sodium N[O.sup.-.sub.2], or sodium nitrate (N[O.sup.-.sub.3]; 1.2 nmol/g body wt ip) at 22.5 min after induction of ischemia or 15 min before ischemia. A separate set of animals received saline, N[O.sup.-.sub.2], or N[O.sup.-.sub.3] (0.12, 1.2, or 12 nmol/g body wt iv) 45 min before ischemia. Serum creatinine and blood urea nitrogen were increased following I/R injury but were not significantly different among treatment groups at 24 and 48 h after acute renal injury. Interestingly, N[O.sup.-.sub.3] administration appeared to worsen renal injury. Histological scoring for loss of brush border, tubular necrosis, and red blood cell extravasation showed no significant differences among the treatment groups. The results indicate that, contrary to the protective effects of N[O.sup.-.sub.2] in I/R injury of the liver and heart, N[O.sup.-.sub.2] does not provide protection in renal 1/R injury and suggest a unique metabolism of N[O.sup.-.sub.2] in the kidney. nitric oxide; nitrate; acute renal injury; tubular necrosis; hypoxia

Ischemia-induced acute renal failure (ARF) is a disorder with high morbidity and mortality. ARF is characterized by a regeneration phase, yet its molecular basis is still under study. Changes in gene expression have been reported in ARF, and some of these genes are specific for nephrogenic processes. We tested the hypothesis that the regeneration process developed after ischemia-induced ARF can be characterized by the reexpression of important regulatory proteins of kidney development. The distribution pattern and levels of nephrogenic proteins in rat kidneys after ischemia were studied by immunohistochemistry and immunoblot analysis. Ischemic damage was assessed by conventional morphology, serum creatinine, and the apoptotic markers terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and caspase 3. The hypoxia levels induced by ischemia were assessed by specific markers: hypoxia induced factor (HIF)-1[alpha] and 2-pimonidazole. In kidneys with ARF, an important initial damage was observed through periodic acid Schiff staining, by the induction of damage markers [alpha]-smooth muscle actin ([alpha]-SMA) and macrophages (ED-1) and by apoptosis induction. In agreement with diminishing renal damage at the initial reparation phase, the expression of the mesenchymal proteins vimentin, neural cell adhesion molecules (Ncam), and the epithelial markers, Pax-2, Noggin, and basic fibroblast growth factor was observed; after, in a second phase, the tubular markers bone morphogen protein 7, Engrailed, and Lim-1, as well as the transcription factors Smad and p-Smad, were observed. Additionally, the endothelial markers VEGF and Tie-2 were induced at the initial and middle stages of regeneration phase, respectively. The expression of these proteins was restricted in time and space, as well as spatially and temporally. Because all of these proteins are important in maintaining a functional kidney, these results suggest that during the regeneration process after induced hypoxia, these nephrogenic proteins can be reexpressed in a similar fashion to that observed during development, thus restoring mature kidney function. kidney; morphogen; regeneration

We tested the hypothesis that renal sympathetic nerve activity (RSNA) to the ischemic and nonischemic regions responded differently during partial ischemia of the kidney in pentobarbital-anesthetized cats. The renal artery divides into two branches at the front of the renal hilus: one branch perfuses predominantly the dorsal half of the kidney, and the other perfuses its ventral half. We identified the innervated area of a renal nerve bundle by supramaximal electrical stimulation and subsequently determined the changes in RSNA in response to occlusion of either renal arterial branch for 3 min. RSNA to the nonischemic region of the kidney gradually decreased by 23 [+ or -] 4% during partial renal ischemia, whereas RSNA to the ischemic region of the same kidney showed no significant change. Crushing either all renal nerve bundles or only the renal nerve bundles terminated to the ischemic region abolished the decrease in RSNA to the nonischemic region. Furthermore, intraarterial administration of a prostaglandin synthesis inhibitor (meclofenamate, 4 mg/kg) abolished the decrease in RSNA to the nonischemic region of the kidney. Following spinal transection at the level of [T.sub.7], the inhibitory response in RSNA to the nonischemic region disappeared, whereas the RSNA to the ischemic region was markedly augmented by 47 [+ or -] 17%. Thus it is likely that renal chemoreceptors activated during renal partial ischemia elicit heterogeneous control of renal sympathetic outflows to the ischemic and nonischemic regions of the same kidney, which may be determined by a net output between the supraspinal inhibitory and spinal excitatory reflexes. ipsilateral renorenal reflex; supraspinal inhibitory reflex; spinal excitatory reflex; complete renal ischemia; prostaglandins

During ischemia intracellular concentrations of [P.sub.i] and [H.sub.+] increase. Also, changes in myosin heavy chain (MHC) isoform toward [beta]-MHC have been reported after ischemia and infarction associated with coronary artery disease. The purpose of this study was to investigate the effects of myoplasmic changes of [P.sub.i] and [H.sup.+] on the loaded shortening velocity and power output of cardiac myocytes expressing either [alpha]- or [beta]-MHC. Skinned cardiac myocyte preparations were obtained from adult male Sprague-Dawley rats (control or treated with 5-n-propyl-2-thiouracil to induce [beta]-MHC) and mounted between a force transducer and servomotor system. Myocyte preparations were subjected to a series of isotonic force clamps to determine shortening velocity and power output during [Ca.sup.2+] activations in each of the following solutions: 1) pCa 4.5 and pH 7.0; 2) pCa 4.5, pH 7.0, and 5 mM [P.sub.i]; 3) pCa 4.5 and pH 6.6; and 4) pCa 4.5, pH 6.6, and 5 mM [P.sub.i]. Added [P.sub.i] and lowered pH each caused isometric force to decline to the same extent in [alpha]-MHC and [beta]-MHC myocytes; however, [beta]-MHC myocytes were more resistant to changes in absolute power output. For example, peak absolute power output fell 53% in [alpha]-MHC myocytes, whereas power fell only 38% in [beta]-MHC myocytes in response to elevated [P.sub.i] and lowered pH (i.e., solution 4). The reduced effect on power output was the result of a greater increase in loaded shortening velocity induced by [P.sub.i] in [beta]-MHC myocytes and an increase in loaded shortening velocity at pH 6.6 that occurred only in [beta]-MHC myocytes. We conclude that the functional response to elevated [P.sub.i] and lowered pH during ischemia is MHC isoform-dependent with [beta]-MHC myocytes being more resistant to declines in power output. ischemia; inorganic phosphate; loaded shortening velocity; power output

We examined the hypothesis that a stiff aorta is associated with reduced coronary blood flow (CBF) and CBF response to percutaneous coronary intervention (PCI). Aortic mechanical properties are thought to affect CBF, with increased stiffness associated with decreased coronary perfusion. Animal studies are conflicting, and human evidence is lacking. Even less is known about the effects of aortic stiffness on the CBF response to successful PCI. In 18 subjects undergoing elective PCI, a Doppler velocity guidewire was positioned proximal to a severe coronary stenosis to measure resting and adenosine-induced hyperemic CBF before and after PCI. Stenosis severity was assessed with Doppler velocity and pressure guidewires. Aortic mechanical indexes measured included central pulse-wave velocity (cPWV) and central pulse pressure (cPP). PCI was successful in all subjects (diameter stenosis: 88 [+ or -] 9% to 2 [+ or -] 7%; coronary flow velocity reserve: 1.8 [+ or -] 0.6 to 3.0 [+ or -] 0.8; fractional flow reserve: 0.57 [+ or -] 0.19 to 0.92 [+ or -] 0.06; all P < 0.001). With the adjustment for age and gender, resting and hyperemic CBF were inversely related to cPWV irrespective of the presence of stenosis (resting: before PCI, [r.sup.2] = 0.452, P < 0.01; after PCI, [r.sup.2] = 0.261, P = 0.043; hyperemic: before PCI [r.sup.2] = 0.503, P = 0.005; after PCI [r.sup.2] = 0.500, P = 0.002), whereas they were related to cPP in absence of stenosis (resting: [r.sup.2] = 0.368, P = 0.022; hyperemic: [r.sup.2] = 0.370, P = 0.016). Hyperemic CBF response (P = 0.005) and hyperemic CBF improvement from PCI (P = 0.025) were less marked in a stiff aorta than a compliant aorta. A stiff aorta is associated with a reduction in CBF, a lower hyperemic CBF response, and may reduce the improvement in hyperemic CBF after successful PCI. aorta; elasticity; angioplasty; ischemia

Although long QT syndrome (LQTS) and coronary occlusion-reperfusion (O/R) are arrhythmogenic, they affect ventricular action potential duration (APD) differently. In contrast to the prolonged APD in LQTS, ischemia abbreviates APD after a transient prolongation. Thus we hypothesized that the dynamic interactive effects of ischemia and LQTS on APD and its dispersion would affect ventricular arrhythmogenicity. We mapped transmural distribution of action potentials in 6 groups of 10 isolated wedges of canine ventricnlar walls: LQTS-O/R, LQTS only, and O/R only, with separate groups for pacing cycle lengths (PCL) of 1,000 and 2,000 ms. We created type 3 LQTS with anemone toxin (ATX) II followed >30 min later by arterial occlusion (40 min) and reperfusion (>100 min). Arterial occlusion initially (first 4 min) prolonged and then shortened APD. Early afterdepolarizations (EADs) occurred during the initial 4 min of occlusion in 4 of the 10 LQTS-O/R wedges at PCL of 2,000 ms but not in the other groups. Reperfusion restored APD in the O/R-only groups but caused APD to overshoot its original duration, indicating depressed repolarization reserve, in the LQTS-O/R group. Reperfusion increased the dispersion of APDs and initiated ventricular tachycardia-fibrillation in 7 of 10 and 6 of 10 LQTS-O/R wedges and in 2 of 10 and 1 of 10 O/R-only wedges at PCLs of 1,000 and 2,000 ms, respectively. The LQTS-only wedges exhibited neither EADs nor ventricular tachycardia. We conclude that coronary O/R increased the arrhythmogenicity of LQTS via cumulative prolongation of APD, increase in repolarization dispersion, and suppression of repolarization reserve. arrhythmias; ischemia; repolarization reserve

We hypothesized that activation of heat shock protein 70 (HSP70) by preconditioning, which is known to confer delayed cardioprotection, attenuates the impaired handling of C[a.sup.2+] at multiple sites. To test the hypothesis, we determined how the ryanodine receptor (RYR), sarco(endo)plasmic reticulum C[a.sup.2+]-ATPase (SERCA), and N[a.sup.+]/C[a.sup.2+] exchanger (NCX) handled C[a.sup.2+] in rat ventricular myocytes preconditioned with a [kappa]-opioid receptor agonist, U50488H (UP), followed by blockade of HSP70 with a selective antisense oligonucleotide and subsequently subjected to simulated ischemia. We determined the following: 1) the C[a.sup.2+] transients induced by electrical stimulation and caffeine, which provide the overall picture of C[a.sup.2+] homeostasis; 2) expression of RyR, SERCA, and NCX; and 3) C[a.sup.2+] fluxes via NCX by the use of [45.sup.C[a.sup.2+] in the rat ventricular myocyte. We found that UP increased the activity of RyR, SERCA, and NCX and the expression of RyR and SERCA. These effects led to increases in the release of C[a.sup.2+] from the sarcoplasmic reticulum via RyR and in the removal of C[a.sup.2+] from the cytoplasm by reuptake of C[a.sup.2+] to the SR via SERCA and by extrusion of C[a.sup.2+] out of the cell via NCX. UP also reduced mitochondrial C[a.sup.2+] accumulation. All of the effects of UP were either abolished or significantly attenuated by blockade of HSP70 synthesis with a selective antisense oligonucleotide. The results are evidence that activation of HSP70 by preconditioning improves the ischemia-impaired C[a.sup.2+] homeostasis at multiple sites in the heart, which may be responsible, at least partly, for attenuated C[a.sup.2+] overload, improved recovery in contractile function, and cardioprotection. intracellular C[a.sup.2+], [kappa]-opioid receptor; N[a.sup.+]/C[a.sup.2+] exchanger; ryanodine receptor; sarco(endo)plasmic reticulum C[a.sup.2+]-ATPase

Our laboratory showed previously that cardiac-specific overexpression of FGF-2 [FGF-2 transgenic (Tg)] results in increased recovery of contractile function and decreased infarct size after ischemia-reperfusion injury. MAPK signaling is downstream of FGF-2 and has been implicated in other models of cardioprotection. Treatment of FGF-2 Tg and wild-type hearts with U-0126, a MEK-ERK pathway inhibitor, significantly reduced recovery of contractile function after global low-flow ischemia-reperfusion injury in FGF-2 Tg (86 [+ or -] 2% vehicle vs. 66 [+ or -] 4% U-0126; P < 0.05) but not wild-type (61 [+ or -] 7% vehicle vs. 67 [+ or -] 7% U-0126) hearts. Similarly, MEK-ERK inhibition significantly increased myocardial infarct size in FGF-2 Tg (12 [+ or -] 3 % vehicle vs. 31 [+ or -] 2% U-0126; P < 0.05) but not wild-type (30 [+ or -] 4% vehicle vs. 36 [+ or -] 7% U-0126) hearts. In contrast, treatment of FGF-2 Tg and wild-type hearts with SB-203580, a p38 inhibitor, did not abrogate FGF-2-induced cardioprotection from postischemic contractile dysfunction. Instead, inhibition of p38 resulted in decreased infarct size in wild-type hearts (30 [+ or -] 4% vehicle vs. 11 [+ or -] 2% SB-203580; P < 0.05) but did not alter infarct size in FGF-2 Tg hearts (12 [+ or -] 3% vehicle vs. 14 [+ or -] 1% SB-203580). Western blot analysis of ERK and p38 activation revealed signaling alterations in FGF-2 Tg and wild-type hearts during early ischemia or reperfusion injury. In addition, MEK-independent ERK inhibition by p38 was observed during early ischemic injury. Together these data suggest that activation of ERK and inhibition of p38 by FGF-2 is cardioprotective during ischemia-reperfusion injury. extracellular signal-regulated kinase; p38; ischemia-reperfusion injury; myocardial infarction; signaling cross talk; mitogen-activated protein kinase

Adrenomedullin (AM) is a potent, long-fasting vasodilator peptide that was originally isolated from human pheochromocytoma. AM signaling is of particular significance in endothelial cell biology since the peptide protects cells from apoptosis, promotes angiogenesis, and affects vascular tone and permeability. The angiogenic effect of AM is mediated by activation of Akt, mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2, and focal adhesion kinase in endothelial cells. Both AM and its receptor, calcitonin receptor-like receptor, are upregulated through a hypoxia-inducible factor-1-dependent pathway under hypoxic conditions. Thus AM signaling plays an important role in the regulation of angiogenesis in hypoxic conditions. Recently, we have developed a nonviral vector~ gelatin. Positively charged gelatin holds negatively charged plasmid DNA in its lattice structure. DNA-gelatin complexes can delay gene degradation, leading to efficient gene transfer. Administration of AM DNA-gelatin complexes induces potent angiogenic effects in a rabbit model of hindlimb ischemia. Thus gelatin-mediated AM gene transfer may be a new therapeutic strategy for the treatment of tissue ischemia. Endothelial progenitor cells (EPCs) play, an important role in endothelial regeneration. Interestingly, EPCs phagocytose ionically linked DNA-gelatin complexes in coculture, which allows nonviral gene transfer into EPCs. AM gene transfer into EPCs inhibits cell apoptosis and induces proliferation and migration, suggesting that AM gene transfer strengthens the therapeutic potential of EPCs. Intravenous administration of AM gene-modified EPCs regenerate puhnonary endothelium, resulting in improvement of puhnonary hypertension. These results suggest that in vivo and in vitro transfer of AM gene using gelatin may be applicable for intractable cardiovascular disease. regeneration; endothelium; ischemia: pulmonary hypertension

Selective [delta]-opioid agonists produce delayed cardioprotection that lasts for 24-48 h in rats; however, the maximum length of the cardioprotective window is unclear. In this study, we attempted to prolong the cardioprotective window using a unique [delta]-opioid agonist, fentanyl isothiocyanate (FIT), which binds irreversibly to the [delta]-receptor, and determined the role of the phosphatidylinositol 3-kinase (PI3K) pathway as a trigger or end effector of FIT-induced cardioprotection. Initially, male rats were administered FIT (10 [micro]g/kg) 10 min before hearts were subjected to 30 min of ischemia and 2 h of reperfusion followed by infarct size (IS) assessment. Acute FIT administration reduced IS when given before ischemia, 5 min before reperfusion, or 10 s after reperfusion compared with control. IS reduction also occurred following a single dose of FIT at 48, 72, 96, and 120 h after administration vs. control, with the maximum effect observed at 96 h. FIT-induced IS reduction at 96 h was completely abolished when the irreversible PI3K inhibitor wortmannin (15 [micro]g/kg) was given before FIT during the trigger phase; however, the effect was only partially abrogated when wortmannin was given 96 h later. These data suggest that FIT has a prolonged cardioprotective window greater than that of any previously described cardioprotective agent that requires PI3K primarily in the trigger phase but also partially, as a mediator or end effector. delayed cardioprotection; phosphatidylinositol 3-kinase; opioids; BW373U86; postconditioning

Angiogenesis within an ischemic region of the brain may increase tissue viability and act to limit the extent of an infarct. The ANG II pathway can both stimulate and inhibit angiogenesis depending on the tissue and the activated receptors. Previous work showed that 2-wk losartan administration (ANG II type 1 receptor blockade) initiates a significant cerebral angiogenic response. We hypothesized that administration of losartan in the drinking water of rats for 2 wk before initiation of focal ischemia would decrease the extent of the resulting infarct. Adult male Sprague-Dawley rats were given losartan (50 mg/day) in drinking water for 2 wk before initiation of cerebral focal ischemia produced by cauterization of cortical surface vessels. Controls received normal drinking water. In control animals, three main vessels feeding the whisker barrel cortex were cauterized, resulting in cessation of blood flow. The same protocol was followed for losartan-treated animals but did not result in cessation of blood flow in the whisker barrel cortex. Another group of losartan-treated animals received between 8 and 14 cauterizations of surface vessels feeding the whisker barrel cortex, and cessation of blood flow was verified. Rats were killed 72 h after surgery. Morphological examination revealed angiogenesis, maintained vascular delivery, and significantly decreased infarct size in losartan-treated animals compared with controls. These results demonstrate that pretreatment with losartan reduces infarct size after cerebral focal ischemia and support the hypothesis that cerebral angiogenesis may be one of the mechanisms responsible. cerebrovascular regulation; rat model; losartan; stroke

Experiments were designed to test whether nitric oxide (NO) and peroxynitrite trigger delayed coronary endothelial protection induced by preconditioning (PC) in rats. Prolonged ischemia reperfusion markedly reduced the response of isolated coronary arteries to acetylcholine, and this was prevented by PC performed 24 h earlier. The NO synthase (NOS) inhibitor [N.sup.G]-nitro-L-arginine methyl ester (L-NAME) administered during PC abolished its delayed endothelial protective effect, whereas the inducible NOS inhibitor N-(3(aminomethyl)benzyl) acetaminide had no effect. Delayed endothelial PC was also abolished by the peroxynitrite scavengers selenomethionine or uric acid given during PC. In parallel, the NO/peroxynitrite donor S-morpholinosydnonimine and authentic peroxynitrite, administered 24 h before prolonged ischemia-reperfusion mimicked endothelial PC, whereas the NO donor S-nitroso-N-acetylpencillamine had no effect. This suggests that peroxynitrite is an essential trigger of the delayed coronary endothelial protection induced by PC in rat hearts. delayed preconditioning; nitric oxide; free radicals

Dogs were treated with estrogen to determine if it could reduce ventricular arrhythmias incidences caused by regional myocardial ischemia and reperfusion. In treated dogs, estrogen eliminated ischemia arrhythmias and reduced reperfusion arrhythmias. Estrogen also increased coronary blood flow. These results indicate estrogen could be an effective treatment for stabilizing ventricular rhythmicity.

The postischemic cardiac contractile function of left ventricular developed pressure (LVDP) increases with reduced reperfusion flow rates from 20 to 70 percent of the ordinary, preischemic flow rate which did not affect LVDP. The amount of tissue sodium and calcium increased and tissue potassium and magnesium decreased with the prolonged failure of LVDP generation in ischemic-reperfused rat hearts subject to ordinary reflow. The success of postischemic contractile recovery when reperfused at reduced rates is most likely linked to the prevention of calcium and sodium overload through slower ischemia-reperfusion-induced myocardial calcium and sodium increases.

Physiological studies in the ischemic rabbit hindlimb reveal that intra-arterial injection of vascular endothelial growth factor (VEGF) results in an increase in the maximum flow velocity and blood flow in the rabbit. VEGF also causes moderate increases in the resting flow. The increases occur only at day 30 after injection and are not seen at day 10 after injection. VEGF administration is an effective treatment for patients suffering from ischemia of the lower limbs.

The pyridine nucleotide metabolism in neonatal heart muscle cells changes hydroperoxide-induced oxidative stress. The postischemic myocardial damage is caused by the oxidant burden derived from the hydrogen peroxide (H2O2) overload. The influence of the H2O2 induced oxidative stress on heart muscle pyridine nucleotide metabolism is also investigated. The pyridine-nucleotide redose balance of the 50 micro Moles to 1.0 milli Moles H2O2 exposed neonatal rat cardiomyocytes is shifted towards oxidation. The glutathione cycle activity has no influence on the NADPH oxidation.

A study was conducted to examine if any positive effects on survival following intestinal ischemia and reperfusion in immature rats was seen if cardiovascular degeneration was removed by enhanced fluid resuscitation. The confusing variable of intense hypovolemia leading to hypotension and hemoconcentration can be avoided by sustenance of cardiovascular stability through enhanced fluid therapy. Large quantities of liquid are required to provide a model which is hemodynamically stable due to immense enhancement in postischemic bowel permeability.

A study was conducted to investigate the immunoreactive epidermal growth factor (irEGF) in the soluble and crude membrane parts of kidney homogenates and to examine if enhancement in the epidermal growth factor (EGF) is caused by EGF precursors in control and ischemia-impaired rat kidneys. Soluble irEGF that were six times more than that of unimpaired kidneys were found in kidneys which had endured ischemic damage. Simple end-producted restriction caused by secretion of membrane-bound EGF, biologically active from its precursor, causes lowered transcription.

Cornelussen, Richard N. M., Ger J. Van Der Vusse, Theo H. M. Roemen, and Luc H. E. H. Snoeckx. Heat pretreatment differentially affects cardiac fatty acid accumulation during ischemia and postischemic reperfusion. Am J Physiol Heart Circ Physiol 280: H1736-H1743, 2001.--We investigated whether the cardioprotection induced by heat stress (HS) pretreatment is associated with mitigation of phospholipid degradation during the ischemic and/or postischemic period. The hearts, isolated from control rats and from heat-pretreated rats (42 [degrees] C for 15 min) either 30 min (HSO.5-h) or 24 h (HS24-h) earlier, were subjected to 45 min of no-flow ischemia, followed by 45 min of reperfusion. Unesterified arachidonic acid (AA) accumulation was taken as a measure for phospholipid degradation. Significantly improved postischemic ventricular functional recovery was only found in the HS24-h group. During ischemia, AA accumulated comparably in control and both HS groups. During reperfusion in control and HS0.5-h hearts, AA further accumulated (control hearts from 82 [+ or -] 33 to 109 [+ or -] 51 nmol/g dry wt, not significant; HS-0.5h hearts from 52 [+ or -] 22 to 120 [+ or -] 53 nmol/g dry wt; P [is less than] 0.05). In contrast, AA was lower at the end of the reperfusion phase in HS24-h hearts than at the end of the preceding ischemic period (74 [+ or -] 18 vs. 46 [+ or -] 23 nmol/g dry wt; P [is less than] 0.05). Thus accelerated reperfusion-induced degradation of phospholipids in control hearts is completely absent in HS24-h hearts. Furthermore, the lack of functional improvement in HSO.5-h hearts is also associated with a lack of beneficial effect on lipid homeostasis. Therefore, it is proposed that enhanced membrane stability during reperfusion is a key mediator in the heat-induced cardioprotection. heat shock proteins; lipid metabolism; cardioprotection; enzyme release

Badr, A. E., W. Yin, G. Mychaskiw, and J. H. Zhang. Dual effect of HBO on cerebral infarction in MCAO rats. Am J Physiol Regulatory Integrative Comp Physiol 280: R766-R770, 2001.--Various reports in the literature have shown that hyperbaric oxygen (HBO) reduces cerebral infarction both in animals and humans. After the initial ischemic insult, however, initiating HBO treatment at different intervals has yielded conflicting results. The present study was undertaken to determine the optimal therapeutic window in which to start HBO treatment for cerebral infarction after transient focal ischemia. In this study, the operator occluded the middle cerebral artery (MCA) of anesthetized rats by introducing a blunted nylon filament into the proximal MCA from the dissected external carotid artery. When the operator removed the filament after 2 h, focal ischemia and reperfusion occurred. The operator then placed the rat in the HBO chamber and administered 3 atm absolute HBO for 1 h according to the protocol. The rat was killed 24 h after reperfusion, and the percentage of infarction (infarct ratio) was calculated by dividing the infarction area by the total area of the ipsilateral hemisphere. The results showed that the percentage of infarcted area decreased significantly (P [is less than] 0.05) both in the 3- (7.59%) and 6-h (5.35%) HBO-treatment groups compared with the control (no treatment) group (11.34%). However, the percentage of infarcted area increased significantly (P [is less than] 0.01 and P [is less than] 0.05, respectively) both in the 12- (23%) and 23-h (20%) treatment groups. The results of this study suggest that applying HBO within 6 h of ischemia-reperfusion injury could benefit the patient but that applying HBO 12 h or more after injury could harm the patient. cerebral ischemia; hyperbaric oxygen; infarct ratio

Valen, Guro, Tsutomu Kawakami, Peeter Tohepold, Alexandra Dumitrescu, Christian Lowbeer, and Jarle Vaage. Glucocorticoid pretreatment protects cardiac function and induces cardiac heat shock protein 72. Am J Physiol Heart Circ Physiol 279: H836-H843, 2000.--Acute administration of glucocorticoids reduces inflammation. Increasing knowledge of the mechanisms of action indicate that pretreatment with glucocorticoids could have organ-protective effects. We investigated whether pretreatment with methylprednisolone (MP) protected the heart against ischemiareperfusion dysfunction, and we hypothetized that this protection might be due to induction of the cardioprotective heat shock protein 72 (HSP72). Rats were given vehicle or MP-40 mg/kg im as a double injection starting either 24 or 120 h (5 days) before their hearts were excised for Langendorff perfusion (n = 6-11 hearts in each group). MP improved left ventricular function and coronary flow during reperfusion after 30 min of global ischemia and reduced infarct size. Cardiac HSP72 gradually increased in a 24-h time course after MP treatment, and the increase was sustained 5 days afterward (immunoblotting). HSP72 mRNA was either reduced or unchanged, indicating a posttranscriptional regulation. Pretreatment with hydrocortisone or dexamethasone (n = 7-8 hearts of each) similarily increased cardiac HSP72 24 h afterward. This paper demonstrates that glucocorticoids increase cardiac HSP72 and protect organ function against ischemia-reperfusion injury. methylprednisolone; dexamethasone; hydrocortisone; ischemia-reperfusion

Buras, Jon A., Gregory L. Stahl, Kathy K. H. Svoboda, and Wende R. Reenstra. Hyperbaric oxygen downregulates ICAM-1 expression induced by hypoxia and hypoglycemia: the role of NOS. Am. J. Physiol. Cell Physiol. 278: C292-C302, 2000.--Hyperbaric oxygen (HBO) is being studied as a therapeutic intervention for ischemia/reperfusion (UR) injury. We have developed an in vitro endothelial cell model of I/R injury to study the impact of HBO on the expression of intercellular adhesion molecule-1 (ICAM-1) and polymorphonuclear leukocyte (PMN) adhesion. Human umbilical vein endothelial cell (HUVEC) and bovine aortic endothelial cell (BAEC) induction of ICAM-1 required simultaneous exposure to both hypoxia and hypoglycemia as determined by confocal laser scanning microscopy, ELISA, and Western blot. HBO treatment reduced the expression of ICAM-1 to control levels. Adhesion of PMNs to BAECs was increased following hypoxia/ hypoglycemia exposure (3.4-fold, P [is less than] 0.01) and was reduced to control levels with exposure to HBO (P = 0.67). Exposure of HUVECs and BAECs to HBO induced the synthesis of endothelial cell nitric oxide synthase (eNOS). The NOS inhibitor nitro-k-arginine methyl ester attenuated HBO-mediated inhibition of ICAM-1 expression. Our findings suggest that the beneficial effects of HBO in treating UR injury may be mediated in part by inhibition of ICAM-1 expression through the induction of eNOS. cell adhesion molecules; ischemia; reperfusion injury; hyperoxia; neutrophils