Platelets act as a fundamental component of the hemostatic process and their activation leads to the formation of a stable clot at the injured endothelium surface. Thrombin, as the important physiological agonist, activates platelets through protease-activated receptors (PARs). Protease-activated receptors are one of the major receptors in platelets and belong to the seven-transmembrane G-protein couple receptor family. Four protease-activated receptors are found, named as PAR1, PAR2, PAR3 and PAR4. Human platelets express PAR1 and PAR4 and murine platelets express PAR4 and PAR3 instead of PAR1. Thrombin activates PARs through a unique mechanism, involving the cleavage of N-terminus of PAR receptors and the newly exposed N-terminus acts as its own tethered ligand to bind and activate the receptor. In this study, we characterized a new PAR1 specific activating peptide (TFRRRLSRATR), generated from the c-terminus of human platelet P2Y1 receptor, and evaluated its biological function. This peptide activated platelets in a concentration-dependent manner, causing shape change, aggregation, secretion and calcium mobilization. Its activation is completely inhibited by using BMS200261, a PAR-1 specific antagonist. Its specificity to PAR1 receptor is further confirmed by using TFRRR-peptide-pretreated washed platelets and murine platelets. The shape change induced by 10 microM peptide was totally abolished by Y-27632, an inhibitor of p160ROCK which is the downstream signal of G12/13 pathways. The TFRRR-peptide, YFLLRNP, and the physiological agonist thrombin selectively activated G12/13 pathways at low concentrations and began to activate both Gq and G12/13 pathways with increased concentrations. Similar to SFLLRN, the TFRRR-peptide caused phosphorylation of Akt and Erk in a P2Y12 receptor-dependent manner, and p-38 MAP kinase activation in a P2Y12-independent manner. The effects of this peptide are elicited by the first six amino acids (TFRRRL) whereas the remaining peptide (LSRATR), TFERRN, or TFEERN had no effects on platelets. Beside thrombin, PARs also can be activated by other proteases. Previous studies in our lab show that plasmin, a major extracellular protease, activates both human and murine platelets through prototypical cleavage of PAR4 (Quinton et al., 2004). In this study, we continue our study and investigate the molecular basis for the differential activation of murine and human platelets by plasmin. Plasmin-induced full aggregation is achieved at lower concentrations (0.1 U/mL) in murine platelets as compared to human platelets (1 U/mL). In COS7 cells expressing the murine PAR4 (mPAR4) receptor, 1 U/mL plasmin caused a higher intracellular calcium mobilization than in cells expressing the human PAR4 (hPAR4) receptor. This difference was reversed when the tethered ligand sequences of mPAR4 and hPAR4 were interchanged through site-directed mutagenesis. This difference between human and murine PAR4 is not because of the cofactor effect of PAR3 in murine platelets by showing that in both transfected cell lines and platelet system, PAR3 inhibits plasmin-induced PAR4 stimulation. All of the data suggest that murine platelets are more sensitive to activation by plasmin than human platelets due to differences in the primary sequence of PAR4. In contrast to thrombin-dependent activation of platelets, wherein PAR3 acts as a co-receptor, mPAR3 inhibits plasmin-induced PAR4 activation. Abnormal platelet activation causes thrombus formation and induces pathological conditions including stroke and atherosclerosis. Antithrombotic therapy is a widely used therapeutic method for stroke. However, currently used agents based on the irreversible inhibition of the platelet cyclooxygenases 1 and 2 or inhibition of P2Y12 receptors can cause unexpected bleeding or resistant side effects. Antithrombotic therapy targeting thrombin signaling is one of the new treatments under investigation and PAR1 antagonists are now in clinical trials. In this study, we investigate the effect of one of thrombin receptors, protease-activated receptor 4 (PAR4) in mice transient middle cerebral artery occlusion/ reperfusion (tMCAO/R) model. Our data show that PAR4 -/- mice have more than 80% reduction in infarct volume and significant improved neurological and motor function after 1 h MCAO followed by 23 h reperfusion. Examination of cellular responses to tMCAO/R indicates that PAR4-/- mice have less cellular death. Platelet/endothelial and leukocyte/endothelial interactions have been shown to play a critical role in the inflammatory responses during cerebral ischemic/reperfusion injury. Comparing wild-type with PAR4-/- mice platelets/endothelial and leukocyte/endothelial interactions, deficiency of PAR4 causes a significant decrease in both platelet/endothelial and leukocyte/endothelial interactions. In addition, PAR4-/- mice attenuate blood-brain barrier (BBB) disruption during tMCAO/R. All the data suggest that deficiency of PAR4 will protect against brain ischemic injury though attenuation of cerebral inflammatory responses including inflammatory cells extravasation and BBB disruption. Protease-activated receptor 4 (PAR4) is the only thrombin receptor existing in both human and murine platelets. The data we get in this study also have a beneficial effect for human study and inhibition of PAR4 may provide a novel potential therapeutic strategy for ischemic injury. / Physiology

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Background: Exacerbated or prolonged inflammatory responses can be detrimental to the host, then any antiinflammatory mediators act to regulate the properties of pro-inflammatory factors and ensure the homeostasis of the organic systems. Objectives: Aims: This study has focused in the regulation of expression and the immunomodulatory properties of annexin A1, a protein of 37 KDa, originally known as the second messenger action of glucocorticoids, in inflammatory and infectious processes. Methods: Using molecular (qPCR), biochemical (luminometry) and immunological (flow cytometry, immunofluorescence) tools, we investigated the endogenous and exogenous of ANXA1 and its mimetic peptide (Ac2-26) in different conditions in vitro and in vivo: fungi infection, HIV/SIV infecion, bowel inflammatory disease and renal ischemic injury. Results: The Ac2-26 pre-treatment of PMN and PBMC of human peripheral blood stimulated with opsonized-zymosan inhibited the production of reactive oxygen species in a dose-dependent manner. In parallel, incubation of phagocytes with the peptide was shown to decrease expression of TLR2 receptor, responsible for the recognition of zymosan on phagocyte, suggesting a regulatory mechanism of surface receptor by ANXA1 peptide. Due to last data, the expression of CCR5, chemokine receptor and HIV co-receptor, was investigated in the same in vitro conditions. CCR5 transcription was down-regulated in PBMC from HIV-infected and healthy subjects, partially by ANXA1/FPR pathway. Consistently, both PBMC subject groups showed an impairment of percentage of CCR5+CD4+ T cells after Ac2-26 incubation. In contrast, Ac2-26 showed an up-regulation of CCR5 surface expression in monocytes, however the peptide switched the profile of monocyte subsets, increasing CD14highCD16- and decreasing CD14lowCD16+ populations. The last one is the most susceptible to HIV infection. In conclusion, the data suggest that the action of N-terminal ANXA1 is cell-dependent and may contribute indirectly modulating the HIV-1. Coherently, the study in vivo of ANXA1 expression in a non-human model of AIDS, showed that ANXA1 is regulated during the progression of the disease in the main compartments of infection, the blood and the gut. In comparison with samples of uninfected animals, the ANXA1 transcripts in peripheral blood increased from acute to chronic SIV infection, whereas in the intestinal mucosa it was down-regulated, reaching baseline levels only in chronic infection. Analysis of typical markers of AIDS progression, showed that increased ANXA1 transcripts was significantly correlated with the activation of T cells. However, the expression of ANXA1 had a positive correlation with antiinflammatory cytokines in the blood and in the intestine and a inverse dynamics of viral load and depletion of CD4 T cells, suggesting that activation of its transcription is related to an attempt to reduce the immune depletion during infection. In addition, based on the described differential modulation of the ANXA1 in the gut of primates, another goal was to analyze the expression of ANXA1 in patients with IBD (inflammatory bowel disease) or not treated with immunosuppressive drugs. The correlation among those factors and clinical data were analyzed. In IBD patients, the expression of ANXA1 is reduced in level of mRNA in peripheral blood and protein in the colonic mucosa. In these patients, immunotherapy with infliximab (anti-TNF-alpha) modulates the transcription of ANXA1 and TNF-α, and even systemic lymphocyte activation in accordance with the duration of treatment and the side effects of drugs, such as bacteremia. The dynamics of ANXA1 added to other clinical and immunological factors appear to be associated with the course of IBD. Finally, acute and chronic inflammatory process induced by ischemia/reperfusion (I/R) procedure, revealed that exogenous ANXA1 mimetic peptide granted a remarkable protection against kidney I/R injury, preventing glomerular filtration rate and urinary osmolality decreases and acute tubular necrosis development by affording striking structural protection due to the abortion of neutrophil extravasation, attenuation of macrophage infiltration and regulation of endogenous annexin A1 expression in renal epithelial cells. Conclusions: In a general analysis of all studies presented, we conclude that exogenous ANXA1 and its derived peptides act as key molecules in the modulation of specific activation, immunophenotype and distribution of phagocytes and lymphocytes participating as a line of defense or targeting of infectious agents, via FPRs or not. And, emphasizing the importance of ANXA1 in the defense of homeostasis, although it was found that the pathways related to the regulation of endogenous ANXA1 is differentially activated in tissues and fluids under acute and chronic inflammation caused by viral infection, autoimmunity or hypoxia. / Introdução: As respostas inflamatórias exacerbadas ou prolongadas podem ser prejudiciais para o hospedeiro, então muitos mediadores antiinflamatórios atuam para regular as propriedades dos fatores pró-inflamatórios e garantir a homeostasia dos sistemas. Objetivos: Assim, o foco do presente trabalho foi estudar a regulação da expressão e as propriedades imunomodulatórias da anexina A1, uma proteína de 37 KDa, inicialmente conhecida como a segunda mensageira da ação dos glicocorticóides, em processos inflamatórios e infecciosos. Metodologia: Para tanto, por meio de técnicas moleculares (qPCR), bioquímicas (luminometria) e imunológicas (citometria de fluxo, imunofluorescência), foi investigado o papel endógeno da ANXA1 e exógeno do peptídeo N-terminal da ANXA1 em diferentes condições in vitro e in vivo: infecção fúngica, infecção viral por HIV-1 e SIV, doença inflamatória intestinal e injúria isquêmica renal. Resultados: O peptídeo N-terminal da ANXA1, Ac2-26, quando usado como tratamento prévio de PMN e PBMC do sangue periférico humano estimuladas por zymosan-opsonizado, inibe a produção de espécies reativas de oxigênio de modo dose-dependente. Paralelamente, a incubação dos fagócitos com o peptídeo demonstrou diminuir a expressão do receptor TLR2, responsável pelo reconhecimento de zymosan nos fagócitos, sugerindo um mecanismo de regulação de receptores de superfície pelo Ac2-26. Frente a este dado e a sinalização de ANXA1 via FPRs, a expressão do receptor de quimiocina e coreceptor do vírus HIV-1, CCR5, também foi investigada em tais condições in vitro. Os transcritos de CCR5 diminuíram em PBMCs de indivíduos HIV+ e saudáveis, parcialmente pela via ANXA1/FPR. Consistentemente, Ac2-26 também diminuiu a expressão do CCR5 na superfície de células T CD4+, os principais alvos do vírus. Em contraste, nos monócitos o peptídeo aumentou a expressão de CCR5, no entanto, induziu uma mudança na distribuição dos subfenótipos, diminuindo a quantidade dos monócitos com maior susceptibilidade a infecção por HIV-1 (CD14lowCD16+). A investigação da ANXA1 endógena em um modelo não humano de AIDS, realizado pela infecção de macacos por SIV, mostrou que a expressão transcricional da ANXA1 é regulada durante a progressão da doença nos principais compartimentos de infecção, o sangue e o intestino. Em comparação com as amostras de animais não-infectados, os transcritos de ANXA1 aumentaram gradualmente no sangue periférico entre as fases aguda e crônica da infecção por SIV, enquanto que na mucosa intestinal houve uma regulação negativa, atingindo os níveis basais apenas na infecção crônica. A análise de marcadores típicos da progressão da AIDS mostrou que a expressão de ANXA1 está relacionada à ativação de células T. No entanto, a expressão da ANXA1 tem uma correlação positiva com o número de transcritos de citocinas antiinflamatórias e uma correlação negativa com a carga viral e depleção de células T CD4+ no sangue e no intestino, sugerindo que a ativação da sua transcrição está relacionada a tentativa de diminuir a exaustão imunológica durante a infecção. Frente aos dados da modulação diferencial da ANXA1 no intestino de primatas, o próximo objetivo foi analisar a expressão da ANXA1 nos portadores de IBD (doença inflamatória intestinal) tratados ou não com drogas imunossupressoras. Nos indivíduos com IBD, a expressão da ANXA1 é diminuída em nível de RNAm, no sangue periférico, e proteína, na mucosa colônica. Nestes pacientes, a imunoterapia com infliximab (anti-TNF-α) modulou sistemicamente a transcrição da ANXA1 e do TNF-α, e ainda a ativação linfocitária e a bacteremia. Em suma, a dinâmica da ANXA1 somada a outros elementos imunológicos e clínicos parecem estar associados a progressão do curso das IBDs. Finalmente, os processos inflamatórios agudo e crônico induzidos pelo procedimento de isquemia e reperfusão (I/R) revelou que o peptídeo mimético ANXA1 exógeno protegeu significativamente contra a lesão por I/R renal. Os animais pré-tratados com Ac2-26 mostraram menores taxas de filtração glomerular, osmolalidade urinária e desenvolvimento da necrose tubular aguda, possivelmente, por manter a integridade tecidual devido ao bloqueio total do extravasamento de neutrófilos, à atenuação de infiltração de macrófagos e à regulação da expressão protéica da ANXA1 endógena em células epiteliais renais. Estes resultados apontam um importante papel da ANXA1 na defesa das células epiteliais contra a lesão de I/R e indicam que os neutrófilos são mediadores-chave para o desenvolvimento da lesão do tecido renal após I/R. Conclusões: Em uma análise geral do conjunto de estudos apresentados, é possível concluir que a ANXA1 exógena e seus peptídeos derivados atuam como moléculas chave na modulação específica da ativação, imunofenótipo e distribuição dos fagócitos e linfócitos que participam como linha de defesa ou como alvo de agentes infecciosos, por meio da ligação com os FPRs ou por uma via ainda não elucidada. E, enfatizando a relevância da ANXA1 na defesa da homeostasia, ainda foi constatado que as vias relacionadas à regulação da ANXA1 endógena são ativadas diferencialmente em tecidos e fluidos sob inflamação aguda e crônica iniciadas quer seja por infecção viral, autoimunidade ou hipóxia. / Doutor em Genética e Bioquímica

O fator derivado do epitélio pigmentado (PEDF) é um fator neurotrófico que possui um grande potencial trófico nos neurônios motores da medula espinal, bem como é capaz de modular o microambiente da lesão. Desta forma, analisamos a capacidade do tratamento com PEDF em promover a neuroplasticidade da medula espinal após lesão isquêmica. Ratos Wistar adultos foram submetidos à lesão medular isquêmica do tipo fototrombótica, segundo o método de Rose Bengal, na altura do 11° segmento torácico e foram imediatamente tratados com inoculação local de PEDF (grupo PEDF) ou solvente (grupo Salina). Ratos submetidos à cirurgia simulada (grupo Sham) receberam a injeção do solvente. Ao término do procedimento cirúrgico, os ratos foram submetidos a testes neurofuncionais durante 6 semanas. Após esse período, os animais sofreram eutanásia e o tecido medular foi dividido entre as técnicas de imunoistoquímica, western blot e PCR em tempo real. Foi analisada na região lombar anterior da medula espinal a modulação das CSPGs, a expressão dos fatores neurotróficos NT-3, GDNF, BDNF e FGF-2, bem como os níveis das moléculas associadas à angiogênese e apoptose (laminina e Bcl-2), das proteínas relacionadas à neuroplasticidade (MAP-2, GAP-43 e sinaptofisina) e do sistema Eph/efrina e a RhoA, que são capazes de modular o crescimento de fibras. Os resultados mostraram uma recuperação parcial e espontânea do comportamento sensório-motor dos animais que foram submetidos à lesão fototrombótica, onde o tratamento com PEDF foi capaz de potencializar alguns desses parâmetros. A análise da região lombar anterior da medula espinal, caudal à lesão, mostrou uma diminuição das CSPGs nos dois grupos lesados, o que pode ter favorecido os eventos de neuroplasticidade. O tratamento com PEDF foi capaz de promover a regulação dos fatores neurotróficos NT-3 e GDNF, diminuir a angiogênese local (diminuição da laminina) e potencializar o processo de neuroplasticidade (aumento da MAP-2) nessa região. A lesão medular isquêmica foi capaz de modular a expressão do receptor EphA4 e da efrina-B1 e o tratamento com PEDF possivelmente regulou o estado de ativação da efrina-A2 e da efrina-B3 e certamente modulou a ativação da efrina-B2. Ainda, os receptores Eph e as efrinas foram observados diferentemente nos neurônios e astrócitos. Nossos resultados confirmam a capacidade plástica da medula espinal após lesão e mostra que o tratamento com PEDF foi capaz de potencializar esse processo / The pigment epithelium derived factor (PEDF) is a neurotrophic factor that has a great trophic potential in the motor neurons of the spinal cord, and is able to modulate the lesion microenvironment. We analyzed the capacity of the treatment with PEDF to promote the neuroplasticity after ischemic spinal cord injury. Adult male Wistar rats were underwent to photothrombotic ischemic spinal cord injury, according to the Rose Bengal method, at the level of 11° thoracic segment, and were immediately treated with local injection of PEDF (PEDF group) or solvent (Saline group). Rats underwent to a sham surgery (Sham group) received solvent injection. At the end of surgery, the rats were submitted to neurofunctional tests during 6 weeks. After this period, the animals were euthanized, and the anterior lumbar region of the spinal cord tissue was submitted to immunohistochemistry, western blot and real-time PCR analyses. The inhibitory response of CSPGs, the expression of neurotrophic factors (NT-3, GDNF, BDNF and FGF-2), the molecules associated with angiogenisis and apoptosis (laminin and Bcl-2), the proteins related to neuroplasticity (MAP-2, GAP-43 and synaptophysin), as well the Eph/ephrin system and the RhoA, which is able to modulate the fibers growth, were evaluated. The results showed a spontaneous, and parcial, recovery of the sensory motor behavior of the animals that were underwent to a photothrombotic injury, and the treatment with PEDF was able to potentiate some of these parameters. The analysis of the anterior lumbar region of the spinal cord, caudally to the lesion, showed a decrease of CSPGs, which may have favored the neuroplasticity events. The treatment with PEDF was able to promote the regulation of NT-3 and GDNF, as well the reduction of laminin and the increase of MAP-2 in that region. In relation to the Eph/ephrin system, the ischemic spinal cord injury was able to modulate the EphA4 receptor and ephrin-B1 expression, and the treatment with PEDF possibly regulated the activation state of ephrin-A2 and ephrin-B3 and certainly modulated the ephrin-B2 activation. Eph receptors and ephrins have been found specifically in neurons and astrocytes. Our results confirmed the plastic capacity of the spinal cord after injury and showed that the treatment with PEDF was able to enhance this process

Darbo tikslas: Sukurti kiekybinius signalų morfologijos, atspindinčių širdies veiklos reguliavimą, jos audinių gyvybingumą bei centrinę hemodinamiką, vertinimo metodus. Uždaviniai: 1. Ištirti signalų dekompozicijos baigtiniu bazinių funkcijų rinkiniu (truncated signal representation) metodų tinkamum��, širdies veiklą, jos audinių gyvybingumą bei centrinę hemodinamiką aprašančių signalų, morfologijos analizei; 2. Sukurti signalų, atspindinčių širdies audinių gyvybingumą, optimalaus aprašymo metodą; 3. Sukurti centrinę hemodinamiką atspindinčio krūtinės ląstos impedanso signalo struktūrinės bei morfologinės analizės metodą; 4. Sukurti elektrokardiogramos P-bangos morfologijos dinamikos, atspindinčios širdies veiklos autonominį reguliavimą, kiekybinio įvertinimo metodą. / The aim: To elaborate the quantitative methods for evaluation of morphology of the signals reflecting viability of heart tissue, heart function control and central/peripheral hemodynamics. Objectives: 1. Investigation of usefulness truncated signal representation methods for analysis of morphology of the signals reflecting viability of heart tissue, heart function control and central/peripheral hemodynamics; 2. Elaboration of method for optimal representation of signals reflecting heart tissue viability; 3. Elaboration of method for quantitative evaluation of ECG P-wave morphology dynamics reflecting autonomous heart function control; 4. Elaboration of method for structural and morphological analysis of the chest impedance signals reflecting central hemodynamics.

O fator derivado do epitélio pigmentado (PEDF) é um fator neurotrófico que possui um grande potencial trófico nos neurônios motores da medula espinal, bem como é capaz de modular o microambiente da lesão. Desta forma, analisamos a capacidade do tratamento com PEDF em promover a neuroplasticidade da medula espinal após lesão isquêmica. Ratos Wistar adultos foram submetidos à lesão medular isquêmica do tipo fototrombótica, segundo o método de Rose Bengal, na altura do 11° segmento torácico e foram imediatamente tratados com inoculação local de PEDF (grupo PEDF) ou solvente (grupo Salina). Ratos submetidos à cirurgia simulada (grupo Sham) receberam a injeção do solvente. Ao término do procedimento cirúrgico, os ratos foram submetidos a testes neurofuncionais durante 6 semanas. Após esse período, os animais sofreram eutanásia e o tecido medular foi dividido entre as técnicas de imunoistoquímica, western blot e PCR em tempo real. Foi analisada na região lombar anterior da medula espinal a modulação das CSPGs, a expressão dos fatores neurotróficos NT-3, GDNF, BDNF e FGF-2, bem como os níveis das moléculas associadas à angiogênese e apoptose (laminina e Bcl-2), das proteínas relacionadas à neuroplasticidade (MAP-2, GAP-43 e sinaptofisina) e do sistema Eph/efrina e a RhoA, que são capazes de modular o crescimento de fibras. Os resultados mostraram uma recuperação parcial e espontânea do comportamento sensório-motor dos animais que foram submetidos à lesão fototrombótica, onde o tratamento com PEDF foi capaz de potencializar alguns desses parâmetros. A análise da região lombar anterior da medula espinal, caudal à lesão, mostrou uma diminuição das CSPGs nos dois grupos lesados, o que pode ter favorecido os eventos de neuroplasticidade. O tratamento com PEDF foi capaz de promover a regulação dos fatores neurotróficos NT-3 e GDNF, diminuir a angiogênese local (diminuição da laminina) e potencializar o processo de neuroplasticidade (aumento da MAP-2) nessa região. A lesão medular isquêmica foi capaz de modular a expressão do receptor EphA4 e da efrina-B1 e o tratamento com PEDF possivelmente regulou o estado de ativação da efrina-A2 e da efrina-B3 e certamente modulou a ativação da efrina-B2. Ainda, os receptores Eph e as efrinas foram observados diferentemente nos neurônios e astrócitos. Nossos resultados confirmam a capacidade plástica da medula espinal após lesão e mostra que o tratamento com PEDF foi capaz de potencializar esse processo / The pigment epithelium derived factor (PEDF) is a neurotrophic factor that has a great trophic potential in the motor neurons of the spinal cord, and is able to modulate the lesion microenvironment. We analyzed the capacity of the treatment with PEDF to promote the neuroplasticity after ischemic spinal cord injury. Adult male Wistar rats were underwent to photothrombotic ischemic spinal cord injury, according to the Rose Bengal method, at the level of 11° thoracic segment, and were immediately treated with local injection of PEDF (PEDF group) or solvent (Saline group). Rats underwent to a sham surgery (Sham group) received solvent injection. At the end of surgery, the rats were submitted to neurofunctional tests during 6 weeks. After this period, the animals were euthanized, and the anterior lumbar region of the spinal cord tissue was submitted to immunohistochemistry, western blot and real-time PCR analyses. The inhibitory response of CSPGs, the expression of neurotrophic factors (NT-3, GDNF, BDNF and FGF-2), the molecules associated with angiogenisis and apoptosis (laminin and Bcl-2), the proteins related to neuroplasticity (MAP-2, GAP-43 and synaptophysin), as well the Eph/ephrin system and the RhoA, which is able to modulate the fibers growth, were evaluated. The results showed a spontaneous, and parcial, recovery of the sensory motor behavior of the animals that were underwent to a photothrombotic injury, and the treatment with PEDF was able to potentiate some of these parameters. The analysis of the anterior lumbar region of the spinal cord, caudally to the lesion, showed a decrease of CSPGs, which may have favored the neuroplasticity events. The treatment with PEDF was able to promote the regulation of NT-3 and GDNF, as well the reduction of laminin and the increase of MAP-2 in that region. In relation to the Eph/ephrin system, the ischemic spinal cord injury was able to modulate the EphA4 receptor and ephrin-B1 expression, and the treatment with PEDF possibly regulated the activation state of ephrin-A2 and ephrin-B3 and certainly modulated the ephrin-B2 activation. Eph receptors and ephrins have been found specifically in neurons and astrocytes. Our results confirmed the plastic capacity of the spinal cord after injury and showed that the treatment with PEDF was able to enhance this process

Calcium tolerant pig and rabbit cardiomyocytes were isolated using retrograde aortic perfusion of nominally calcium-free collagenase. Preconditioning protocols used 1 or 3 x l0-min episodes of ischemic pelleting or pre-incubation with 100 μM adenosine, followed by a 15-min post-incubation and 180-240-min ischemic pelleting. Control cells were incubated and washed in parallel with the experimental groups. Injury was assessed by determination of cell morphology, trypan blue permeability following osmotic swelling, lactate and HPLC analysis of adenine nucleotides. Preconditioned pig cardiomyocytes had a reduced rate of ischemic contracture, but protection occurred without conservation of ATP. Preconditioned rabbit cardiomyocytes were protected without significant changes in rates of ischemic contracture or ATP depletion. Incubation of ischemic cells with the protein phosphatase inhibitor, fostriecin, at PP2A-selective concentrations (0.1-10 μM), mimicked preconditioning in both rabbit and pig cardiomyocytes. In rabbits, the K(ATP) channel blocker, 5-hydroxydecanoate (5-HD), did not block preconditioning or fostriecin protection. In the pig, 5-HD blocked both preconditioning and fostriecin protection, with return of the rates of ischemic contracture to control. However, 5-HD was an effective blocker of protection only in early ischemia. Fostriecin mimicked preconditioning in the rabbit and the early responses of the preconditioned pig. Preconditioning appears associated with protein phosphorylation in both the rabbit and the pig, but major pathways leading to protection may differ in the two species.