Catalase pretreatment attenuates oleic acid-induced edema in isolated rabbit lung

Because reactive O2 metabolites have been demonstrated to be potent mediators of vascular dysfunction and are synthesized by lung tissue, their involvement as mediators of oleic acid (OA)-induced pulmonary edema in the isolated Krebs-perfused rabbit lung was assessed. Injection of OA (0.1 ml) into the pulmonary artery after vehicle pretreatment induced marked increases in lung weight [50.4 +/- 13.9 vs. 4.2 +/- 2.0 (SE) g 45 min after OA or vehicle, respectively, P less than 0.05], an index of pulmonary edema, and airway pressure. OA also caused a significant though minimal increase in pulmonary arterial pressure. Pretreatment with catalase (1,000 U/ml), a scavenger of H2O2, significantly (P less than 0.05, Friedman's) attenuated the increases in lung weight (50.4 +/- 13.9 vs. 15.1 +/- 4.9 g), airway pressure, and pulmonary arterial pressure. In contrast to catalase, pretreatment with Cu-tryptophan (40 microM), a lipid-soluble scavenger of superoxide, provided no protective effect by itself, nor was there any potentiation of protection when combined with catalase. Further evidence implicating O2 metabolites in OA-induced edema was obtained by electron paramagnetic resonance (EPR) spectroscopy of perfusate samples to which the spin trap, sodium 3,5-dibromo-4-nitrosobenzenesulfonate (10 mM), was added. Analysis of these samples revealed the presence of free radicals after OA. Pretreatment with catalase (1,000 U/ml) and superoxide dismutase (250 U/ml) attenuated the EPR signal, indicating that proximal formation of O2 free radicals was in part responsible for the signal. These results suggest that reactive O2 metabolites are mediators of OA-induced pulmonary edema in the isolated perfused rabbit lung.     

Effect of endotoxin on oleic acid lung injury does not depend on priming.

Recent studies have demonstrated significant synergistic physiological and biochemical effects between low-dose endotoxin (Etx) administration and oleic acid (OA)-induced canine lung injury. To evaluate whether this interaction depends on Etx priming of some key cell population, we compared the effects of giving low-dose Etx both after as well as before inducing lung injury with OA. In addition to hemodynamic and blood-gas measurements, positron emission tomographic imaging was used to measure edema accumulation and intrapulmonary blood flow distribution. Biochemical measurements of the stable metabolites of prostacyclin and thromboxane were obtained as well as measurements of isoprostanes and reactive sulfhydryls as evidence for possible concomitant oxidant production. We found that the physiological and biochemical effects of low-dose Etx developed 30-45 min after its administration, regardless of whether Etx was administered before or after OA. No increase in either isoprostane or reactive sulfhydryl production after Etx and/or OA was detected. These data suggest that the synergistic effect of low-dose Etx and OA-induced lung injury is not due to a priming effect of Etx.     

Intravascular anti-IgE challenge in perfused lungs: mediator release and vascular pressor response.

Intravascular application of goat anti-rabbit immunoglobulin E (IgE) was used to stimulate parenchymal mast cells in situ in perfused rabbit lungs. Sustained pulmonary arterial pressure rise was evoked in the absence of lung vascular permeability increase and lung edema formation. Early prostaglandin (PG) D2 and histamine release into the perfusate was documented, accompanied by more sustained liberation of cysteinyl leukotrienes (LT), LTB4, and PGI2. The quantities of these inflammatory mediators displayed the following order: histamine greater than cysteinyl-LT greater than PGI2 greater than LTB4 greater than PGD2. Pressor response and inflammatory mediator release revealed corresponding bell-shaped dose dependencies. Cyclooxygenase inhibition (acetylsalicylic acid) suppressed prostanoid generation, increased LT release, and did not substantially affect pressor response and histamine liberation. BW755 C, a cyclo- and lipoxygenase inhibitor, blocked the release of cysteinyl-LT and markedly reduced the liberation of the other inflammatory mediators as well as the pressor response. The H1-antagonist clemastine caused a moderate reduction of the anti-IgE-provoked pressure rise. We conclude that intravascular anti-IgE challenge in intact lungs provokes the release of an inflammatory mediator profile compatible with in situ lung parenchymal mast cell activation. Pulmonary hypertension represents the predominant vascular response, presumably mediated by cysteinyl-LT and, to a minor extent, histamine liberation.     

Mechanism of phosgene-induced lung toxicity: role of arachidonate mediators

We have previously shown that phosgene markedly increases lung weight gain and pulmonary vascular permeability in rabbits. The current experiments were designed to determine whether cyclooxygenase- and lipoxygenase-derived mediators contribute to the phosgene induced lung injury. We exposed rabbits to phosgene (1,500 ppm/min), killed the animals 30 min later, and then perfused the lungs with a saline buffer for 90 min. Phosgene markedly increased lung weight gain, did not appear to increase the synthesis of cyclooxygenase metabolites, but increased 10-fold the synthesis of lipoxygenase products. Pre- or posttreatment with indomethacin decreased thromboxane and prostacyclin levels without affecting leukotriene synthesis and partially reduced the lung weight gain caused by phosgene. Methylprednisolone pretreatment completely blocked the increase in leukotriene synthesis and lung weight gain. Posttreatment with 5,8,11,14-eicosatetraynoic acid (ETYA), a nonmetabolized competitive inhibitor of arachidonic acid metabolism, or the leukotriene receptor blockers, FPL 55712 and LY 171883, also dramatically reduced the lung weight gain caused by phosgene. These results suggest that lipoxygenase products contribute to the phosgene-induced lung damage. Because phosgene exposure did not increase cyclooxygenase synthesis or pulmonary arterial pressure, we tested whether phosgene affects the lung's ability to generate or to react to thromboxane. Infusing arachidonic acid increased thromboxane synthesis to the same extent in phosgene-exposed lungs as in control lungs; however, phosgene exposure significantly reduced pulmonary vascular reactivity to thromboxane but not to angiotension II and KCl.     

Release of prostaglandins from healthy and sensitized guinea-pig lung and trachea by histamine.

The effects of histamine and its antagonists on the release of prostaglandin E and F2alpha (PGE and PGF2alpha) and the 15-keto-13,14-dihydro PGF2alpha/E (metabolites) were examined in minced and whole perfused guinea pig lung. Lung fragments released considerable amounts of prostaglandins into the incubation media with time alone: parenchyma more PGF2alpha than PGE, trachea more PGE than PGF2alpha. The levels of PGF2alpha found in the filtrates of both tissues on per gram basis were about the same, whereas the concentrations of PGE were several fold higher in the media of incubated trachea. In contrast to lung, trachea released only trace amounts of metabolites. These differences in synthesis and turnover are probably of importance for maintenance of the adequate ventilation-perfusion ratios. The process of sensitization caused a significant increase in the outflows of PGF2alpha and metabolites from the lung fragments. The PGE to PGF2alpha ratio was decreased in both parenchymal and tracheal tissues. Increased spontaneous release of prostaglandins was also found in whole perfused sensitized lung. This was consistent with the hypothesis that sensitization with antigen alters the biochemical properties of the organism. Incubation of lung fragments with histamine had only a small additional effect on the liberation of prostaglandins, since the baseline release was high due to the trauma of mincing. However, histamine perfusion of whole lung caused severalfold increase in the outflows of prostaglandins. Pretreatment with pyrilamine (histamine receptor 1 antagonist) decreased the subsequent release of PGF2alpha by histamine. On the other hand, pretreatment with metiamide (histamine receptor 2 antagonist) diminished the subsequent release of PGE. It is suggested that stimulation of histamine receptor 1 is predominantly (but not solely) related to the synthesis of PGF2alpha, and stimulation of the receptor 2 is related to the synthesis of PGE.     

VEGF, Bcl-2 and Bad regulated by angiopoietin-1 in oleic acid induced acute lung injury

Molecular mechanisms of acute lung injury (ALI) are poorly defined. Our previous study demonstrated that recombinant angiopoietin-1 (Ang1) can protect against oleic acid (OA) induced ALI at an early stage. The purpose of this study was to elucidate whether vascular endothelial growth factor (VEGF), Bcl-2, and Bad, phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) play any role in the protective mechanism of recombinant Ang1 in OA-induced ALI. All BALB/C mice were administered a single dose of OA to induce lung injury. Lungs, bronchoalveolar lavage fluid (BALF), and serum were harvested at certain time points. The expression of VEGF, Bcl-2, Bad, PI3K/Akt, and the histological changes in the lung, and the levels of VEGF, IL-6, and IL-10 in serum and BALF were examined. A second cohort of mice was followed for survival for 7 days. We observed increased expression of VEGF in BALF and serum and reduced expression of VEGF in lung tissue. Recombinant Ang1 treatment, however, up-regulated VEGF expression and p-Akt/Akt in lung tissue but down-regulated VEGF expression in BALF and serum. OA led to a decrease of anti-apoptotic marker Bcl-2 and a marked increase of pro-apoptotic marker Bad. Compared with the ALI group, in the recombinant Ang1 treated group, Bcl-2 expression was restored, and Bad expression was clearly attenuated. In addition, recombinant Ang1 attenuated the lung pathological changes and improved the survival of mice. These findings suggest that recombinant Ang1 may be a promising potential treatment for ALI. It seems that VEGF is mediated by PI3K/Akt pathway which is required for Ang1-mediated protection of lung injury. Activation of Akt stimulates expression of Bcl-2 and inhibits the expression of Bad, thus inhibiting the execution of apoptosis.     

Neurotensin stimulates histamine release from the isolated, spontaneously beating heart of rats

Neurotensin (NT) evoked a transient, dose-dependent histamine release (ED50 170 ng ml-1) from the rat perfused heart. Histamine release by NT occurred within seconds and lasted less than 2 min. The histamine releasing effect of NT was followed by a dose-dependent increase of the perfusion pressure and a slight tachycardia. The histamine releasing effect of NT was completely abolished in hearts derived from rats pretreated for 3 days with high doses of compound 48/80. The coronary vasoconstrictor effect of NT was increased in hearts derived from compound 48/80-pretreated rats. The mast cell inhibitor cromoglycate markedly inhibited NT-induced histamine release without affecting the coronary vasoconstrictor effect of NT. The histamine releasing effect of NT was inhibited, while its coronary vasoconstrictor effect was markedly potentiated, in hearts derived from rats pretreated with the antiallergic and antiinflammatory steroid dexamethasone. The increase of perfusion pressure evoked by NT was not modified by antihistamine drugs. Infusions of exogenous histamine (10(-6)-10(-5) g ml-1) caused a dose-dependent coronary vasodilation in the rat perfused heart. The results suggest that NT stimulates histamine release from cardiac mast cells. These results together with those obtained in previous studies suggest that mast cell mediators (particularly histamine and serotonin) are unlikely to be responsible for the coronary vasoconstrictor effect of NT in the rat perfused heart.     

A novel and stable "two-hit" acute lung injury model induced by oleic acid in piglets

Background  

Children are susceptible to pulmonary injury, and acute lung injury (ALI) often results in a high mortality and financial cost in pediatric patients. Evidence has showed that oleic acid (OA) plays an important role in ALI. Therefore, it has special significance to study ALI in pediatric patients by using OA-induced animal models. Unfortunately, the animal model hs a high mortality due to hemodynamic instability. The aim of this study was to establish a novel hemodynamically stable OA-induced ALI model in piglets with two hits.     

Lung injury and complement activation: Role of neutrophils and xanthine oxidase

Evidence is presented that oxygen products generated from xanthine oxidase (XO) may also be involved in the pathogenesis of neutrophil-mediate lung injury following intravascular activation of complement with cobra venom factor (CVF). CVF injection in rats resulted a rapid increase in plasma of both XO activity (but not xanthine dehydrogenase) and its reaction product, uric acid. These changes were greatly attenuated in allopurinol-treated animals. The apperance of XO activity was paralleled by a raise in plasma of histamine. Prevention of histamine release by pretreatment of rats withy cromolyn abolished both the rise in plasma histamine and the increase in XO activity. Since we have previously shown that histamine can enhance XO activity in vitro and in vivo (Am. J. Pathol. 135:203, 1989), these observations suggest that the increase in plasma XO activity following CVF injection is related to the appearance in plasma of histamine. Accordingly, pretreatment of rats with xanthine oxidase inhibitors (allopurinol, lodoxamine) or prevention of histamine release by pretreatment with cromolyn significantly attenuated development of lung injury following injection of CVF. Our data support the concept that oxygen radicals derived from both neutrophils and XO are playing a role in the CVF-induced acute lung injury.     

Effect of indomethacin on airway contraction and the release of LTC4-like material

Ovalbumin (OA) and arachidonic acid (AA) were used to induce contractions of sensitized guinea-pig tracheal and lung preparations in the presence and absence of indomethacin. Leukotriene (LT)C₄-like material released from these tissues was extracted from the bathing fluid and measured by radioimmunoassay. Challenge with either OA or AA induced release of LTC₄-like material from both parenchyma and trachea, AA inducing a greater release than OA although OA induced greater contractions. This suggested that OA-induced the synthesis of other bronchoconstrictor compounds than LTC₄. Although indomethacin enhanced OA- and AA-induced contractions of trachea, there was no enhancement of the release of LTC₄-like material, suggesting enhancement by indomethacin was a result of the inhibition of the synthesis of prostaglandin E₂ and not diversion of AA into the lipoxygenase pathway. Indomethacin had no effect on OA-induced contractions of parenchyma, but attenuated those induced by AA. Indomethacin had no modulatory effect on the release of LTC₄-like material in the parenchyma. The results demonstrate that indomethacin does not result in increased synthesis of LTs in the airways.     

Dietary phytoestrogens have anti-inflammatory activity in a guinea pig model of asthma

Phytoestrogens are a normal constituent of soy protein and have been shown to have anti-inflammatory activity in various in vitro and in vivo models. The present study was designed to determine if a diet enriched in the phytoestrogen isoflavones, genistin and daidzin, would alter the antigen-induced cellular infiltration, particularly eosinophilia, characteristic of a guinea pig model of asthma. Throughout the duration of the study, guinea pigs were maintained on a control diet (standard guinea pig chow) or the same diet enriched in isoflavones. The animals were placed on the diet 2 weeks prior to active sensitization with ovalbumin (OA). Three weeks after sensitization, animals were challenged with OA aerosol. The cellular infiltration into the lung and protein and red blood cells (RBC) in the bronchoalveolar lavage fluid (BAL) were determined 17 hr later. In animals maintained on the control diet, OA aerosol challenge resulted in the expected increase in eosinophils in both the BAL and the lung tissue, an increase in neutrophils in the BAL, and an increase in protein and the number of RBC in the BAL. In contrast, in animals maintained on the isoflavone diet, the OA-induced eosinophilia in the lung tissue was significantly attenuated. In addition, OA challenge caused a greater increase in BAL protein in animals maintained on the isoflavone diet compared with animals on the control diet. Our results indicated that a diet enriched in isoflavones results in reduced antigen-induced eosinophilia in the lung in the guinea pig model of asthma. However, this beneficial anti-inflammatory effect of dietary phytoestrogens is accompanied by a potentially detrimental increase in antigen-induced leakage of protein into the airspace.     

Mechanism of okadaic acid-induced neuronal death and the effect of estrogens

Serine/threonine protein phosphatases are important mediators of general cellular function as well as neurodegenerative processes. We have previously shown inhibition of protein phosphatases to be as neurotoxic as glutamate-induced neuronal death but resistant to neuroprotection by estrogens. In this study, the mechanism by which phosphatase inhibition via okadaic acid (OA) induced neurotoxicity is explored. Neurons were exposed to OA or glutamate in the presence or absence of various protein kinases inhibitors, and/or one of four estrogens. Both OA and glutamate induced cell death via increased reactive oxygen species, protein carbonylation, lipid peroxidation, caspase-3 activity, and mitochondrial dysfunction. All estrogens attenuated glutamate-mediated responses, but not OA-induced responses. In addition, inhibition of protein kinase C and mitogen-activated protein kinase pathway was neuroprotective against glutamate but not OA toxicity. Interestingly, inhibition of mitogen-activated protein kinase pathway with PD98096 or U0126 caused a decrease in reactive oxygen species production suggesting that activation of ERK1/2 could further exacerbate the oxidative stress caused by glutamate-induced toxicity; however, these inhibitors had no effect on OA-induced toxicity. Collectively, these results indicate that both glutamate and OA neurotoxicities are mediated by persistent activation of ERK1/2 and/or protein kinase C and a resulting oxidative stress, and that protein phosphatase activity is an important and necessary aspect of estrogen-mediated neuroprotection.     

PAF potentiates protamine-induced lung edema: role of pulmonary venoconstriction

We studied the synergistic interaction between platelet-activating factor (PAF) and protamine sulfate, a cationic protein that causes pulmonary endothelial injury, in isolated rat lungs perfused with a physiological salt solution. A low dose of protamine (50 micrograms/ml) increased pulmonary artery perfusion pressure (Ppa) but did not increase wet lung-to-body weight ratio after 20 min. Pretreatment of the lungs with a noninjurious dose of PAF (1.6 nM) 10 min before protamine markedly potentiated protamine-induced pulmonary vasoconstriction and resulted in severe lung edema and increased lung tissue content of 6-keto-prostaglandin F1 alpha, thromboxane B2, and leukotriene C4. Pulmonary microvascular pressure (Pmv), measured by double occlusion, was markedly increased in lungs given PAF and protamine. These potentiating effects of PAF were blocked by WEB 2086 (10(-5) M), a specific PAF receptor antagonist. Pretreatment of the lungs with a high dose of histamine (10(-4) M) failed to enhance the effect of protamine on Ppa, Pmv, or wet lung-to-body weight ratio. Furthermore, PAF pretreatment enhanced elastase-, but not H2O2-, induced lung edema. To assess the role of hydrostatic pressure in edema formation, we compared lung permeability-surface area products (PS) in papaverine-treated lungs given either protamine alone or PAF + protamine and tested the effect of mechanical elevation of Pmv on protamine-induced lung edema. In the absence of vasoconstriction, PAF did not potentiate protamine-induced increase in lung PS. On the other hand, mechanically raising Pmv in protamine-treated lungs to a level similar to that measured in lungs given PAF + protamine did not result in a comparable degree of lung edema. We conclude that PAF potentiates protamine-induced lung edema predominantly by enhanced pulmonary venoconstriction. However, a pressure-independent effect of PAF on lung vasculature cannot be entirely excluded.     

Pulmonary clearance of three aerosolized solutes in oleic acid-induced lung injury

We studied the effects of oleic acid (OA) on pulmonary clearance of three aerosolized radioactive solutes: 99mTc-diethylenetriamine pentaacetate (99mTc-DTPA), 67Ga-desferoxamine (67Ga-DFOM), and 111In-transferrin (111In-TF). Either 0.09 ml/kg OA or an equivalent volume of 0.9% NaCl (controls) was administered intravenously to 48 anesthetized, paralyzed dogs. Each animal received one aerosolized solute either 60 min after (protocol A) or 30 min before (protocol B) the infusion of OA or NaCl. In protocol A clearances of all three solutes were similar in OA and control animals. In contrast, in protocol B clearances of all three solutes increased significantly during OA infusion; during the next 60 min clearances of 99mTc-DTPA and 67Ga-DFOM returned to control values but 111In-TF remained increased. We conclude that 1) in OA-induced permeability edema pulmonary clearance of aerosolized solutes is increased when the aerosol is delivered 30 min before but not 60 min after injury, and 2) increased clearance persists only for large molecules, presumably because smaller molecules cross injured epithelium quickly and completely. These phenomena are best explained by a nonhomogeneous distribution of OA-induced injury.     

Regulation of production and release of lipoprotein by the perfused rat liver

The relationship between protein and triglyceride release into d < 1.007 lipoprotein was studied in the isolated perfused rat liver. Livers were perfused with a medium either high or low in linoleate content. Perfusion with the linoleate-rich medium resulted in a marked increase in the net release of both d < 1.007 lipoprotein triglyceride and lipoprotein protein, and caused a significant increase in amino acid incorporation into the protein moiety. Amino acid incorporation into d 1.008-1.21 protein was not affected by fatty acid concentration, while incorporation into whole perfusate and tissue proteins was depressed by a perfusate high in fatty acid content. Electron microscopic studies demonstrated that the livers with the higher rate of triglyceride release also produced a greater number of lipoprotein particles. The particles they released were also somewhat larger. These studies suggest that the intracellular concentration of newly esterified triglyceride and (or) some other lipid metabolite can specifically influence the release and perhaps the synthesis of d < 1.007 lipoprotein protein. They also suggest that the liver increases its rate of triglyceride release primarily by producing more lipoprotein particles.     

Preventive effects of dehydroepiandrosterone acetate on the fatty liver induced by orotic acid in male rats.

Preventive effects of dehydroepiandrosteone acetate (DHEA-A) and clofibrate (positive control substance) on the fatty liver induced by orotic acid (OA) were examined on the male Sprague-Dawley rats fed a high sucrose based diet containing 1% OA and this diet further mixed with 0.5% DHEA-A or 0.5% clofibrate for 2 weeks. Numerous lipid droplets were observed in the hepatocytes of the rats treated with OA alone, but not in those treated with DHEA-A or clofibrate. In comparison to the group with OA alone, the DHEA-A or clofibrate treated rats showed a larger relative liver weight (to body weight) which was accompanied by increased peroxisomes in the hepatocytes. These results indicate that DHEA-A, as well as clofibrate, may prevent OA-induced fatty liver.     

Effect of indomethacin on airway contraction and the release of LTC4-like material

Ovalbumin (OA) and arachidonic acid (AA) were used to induce contractions of sensitized guinea-pig tracheal and lung preparations in the presence and absence of indomethacin. Leukotriene (LT)C4-like material released from these tissues was extracted from the bathing fluid and measured by radioimmunoassay. Challenge with either OA or AA induced release of LTC4-like material from both parenchyma and trachea, AA inducing a greater release than OA although OA induced greater contractions. This suggested that OA-induced the synthesis of other bronchoconstrictor compounds than LTC4. Although indomethacin enhanced OA- and AA-induced contractions of trachea, there was no enhancement of the release of LTC4-like material, suggesting enhancement by indomethacin was a result of the inhibition of the synthesis of prostaglandin E2 and not diversion of AA into the lipoxygenase pathway. Indomethacin had no effect on OA-induced contractions of parenchyma, but attenuated those induced by AA. Indomethacin had no modulatory effect on the release of LTC4-like material in the parenchyma. The results demonstrate that indomethacin does not result in increased synthesis of LTs in the airways.     

Regulatory effects of hydrogen sulfide on IL-6, IL-8 and IL-10 levels in the plasma and pulmonary tissue of rats with acute lung injury

We examined the possible role of hydrogen sulfide (H(2)S) in the pathogenesis of oleic acid (OA)-induced acute lung injury (ALI) and its regulatory effects on the inflammatory response. Compared to control rats, the OA-treated rats had decreased partial pressure of oxygen in the arterial blood (PaO(2)) levels, an increased pulmonary wet/dry weight (W/D) ratio, increased index of quantitative assessment (IQA) score and increased frequency of polymorphonuclear (PMN) cells in the lung 2, 4 or 6 h after OA injection (0.1 ml/kg, intravenous injection). In addition, significantly increased IL-6, IL-8 and IL-10 levels together with decreased H(2)S levels were observed in the plasma and lung tissue of OA-treated rats compared to controls. Administration of the H(2)S donor sodium hydrosulfide (NaHS, 56 mumol/L, intraperitoneal injection) into OA-treated rats increased the PaO(2) level, reduced the lung W/D ratio and infiltration of PMN cells, and alleviated the degree of ALI (measured by the IQA score). In addition, NaHS decreased IL-6 and IL-8 levels but increased IL-10 levels in the plasma and lung tissues, suggesting that H(2)S may regulate the inflammatory response during ALI via regulation of IL-6, IL-8 and IL-10. Thus, the down-regulation of endogenous H(2)S production might be involved in the pathogenesis of OA-induced ALI in rats.     

Protein kinase C-Fyn kinase cascade mediates the oleic acid-induced disassembly of neonatal rat cardiomyocyte adherens junctions

Oleic acid (OA) affects assembly of gap junctions in neonatal cardiomyocytes. Adherens junction (AJ) regulates the stability of gap junction integrity; however, the effect of OA on AJ remains largely unexplored. The distribution of N-cadherin and catenins at cell–cell junction was decreased by OA. OA induced activation of protein kinase C(PKC)-α and -? and Src family kinase, and all three kinases were involved in the oleic acid-induced disassembly of the adherens junction, since it was blocked by pretreatment with Gö6976 (a PKCα inhibitor), ?V1–2 (a PKC? inhibitor), or PP2 (a Src family kinase inhibitor). Src family kinase appeared to be the downstream of PKC-α and -?, as blockade of either PKC-α or -? activity prevented the OA-induced activation of Src family kinase. Immunoprecipitation analyses showed that OA activated Fyn and Fer. OA promoted the association of p120 catenin/β-catenin with Fyn and Fer and caused increased tyrosine phosphorylation of p120 catenin and β-catenin, resulting in decreased binding of the former to N-cadherin and of the latter to α-catenin. Pretreatment with PP2 abrogated this OA-induced tyrosine phosphorylation of p120 catenin and β-catenin and restored the association of N-cadherin with p120 catenin and that of β-catenin with α-catenin. In conclusion, these results show that OA activates the PKC-Fyn signaling pathway, leading to the disassembly of the AJ. Therefore, inhibitors of PKC-α/-? and Src family kinase are potential candidates as cardioprotection agents against OA-induced heart injury during ischemia-reperfusion.