Orientador: Norma Sueli Pinheiro Módolo / Banca: Leandro Gobbo Braz / Banca: Laís Helena Navarro e Lima / Banca: Rogério Luiz da Rocha Videira / Banca: Alexandra Assad / Resumo: O pós-condicionamento em modelo de isquemia e reperfusão já mostrou evidências de efeito renoprotetor, mas ainda há alguma controvérsia sobre os protocolos e seus resultados. A administração de cetamina S(+) em dose subanestésica em infusão contínua, como estratégia anti-inflamatória, ainda não foi testada na lesão renal aguda, bem como sua interação com o pós-condicionamento isquêmico não é conhecida. Testamos a hipótese de que a cetamina S(+) atenua o dano tubular e melhora a função renal em ratos sob pós-condicionamento. Quarenta e um ratos machos Wistar (≥300g) foram divididos aleatoriamente em quatro grupos: GS-Sham; GC-Cetamina S(+) em dose subanestésica em infusão contínua; GP-Pós-condicionamento isquêmico; GCP-Cetamina S(+) em dose subanestésica em infusão contínua e pós-condicionamento. Todos os animais foram submetidos à nefrectomia direita. Nos ratos submetidos ao pós-condicionamento (GP e GCP) foi realizada oclusão da artéria renal esquerda por 30 minutos. A reperfusão plena foi precedida por três ciclos de 2 min de reperfusão, seguido por 2 min de reoclusão. A pressão arterial, a frequência cardíaca e a temperatura foram controladas durante o experimento. A hidratação foi realizada com solução de Ringer lactato em infusão contínua intravenosa (3,0 mL.Kg-1.h-1), além de bolus após cada coleta. A função renal foi avaliada pela dosagem plasmática de NGAL, creatinina e ureia em três momentos: C1 (após estabilização), C2 (após 30 min de reperfusão completa) e C3 (após 24h). Dano tubular foi avaliado pela histologia renal. Foram utilizados os critérios de RIFLE e AKIN para avaliação evolutiva da creatinemia entre momentos. A creatinina e a ureia apresentaram aumento estatisticamente significativo nos grupos com pós-condicionamento isquêmico (GS e GC), mas não a NGAL (p = 0,08). Dano tubular significativo foi encontrado apenas nos ... / Abstract: Postconditioning against ischaemia-reperfusion injury has shown renoprotective effects, but there is still some controversy about protocols and its outcomes. The potencial application of subanesthetic S(+) ketamine continuous infusion as an antiinflammatory strategy, is not yet available in acute kidney injury, as well as the interaction with ischaemic postconditioning (IP). We tested the hypothesis that it attenuates tubular damage and improves renal function in IP in rats. Forty-one male Wistar rats (≥300g) were randomized into four groups: GS-sham; GK-subanesthetic S(+) ketamine; GP-posconditioning and GKP-subanesthetic S(+) ketamine and postconditioning. All animals were subjected to right nephrectomy but only in postconditioned rats 30-min left kidney arterial occlusion was performed, in which complete reperfusion were preceded by three cycles of 2 min of reperfusion followed by 2 min of reocclusion. Animals were studied for 24 h. Renal function was assessed by measurement of serum NGAL, creatinine and blood urea nitrogen (BUN) at three moments: C1 (after stabilization), C2 (after 30-min complete reperfusion) and C3 (after 24h). Tubular damage was evaluated by renal histology. RIFLE and AKIN criteria were used to evaluate creatinine among moments. Creatinine and BUN significantly increased in IP groups as compared to rats in GS and GK, but not NGAL (P=0,08). Despite significant tubular damage found only in IP groups, there was no significant difference between IP and S(+) ketamine/IP. RIFLE and AKIN criteria showed identical functional lesions. S(+) ketamine infusion does not attenuate tubular damage or improve renal function. However, IP groups show identical results and postconditioning is unable to show a renoprotective effect in this model / Doutor

Orientador: Norma Suelei Pinheiro Módolo / Banca: Geraldo Rolim Rodrigues Junior / Banca: Luiz Antonio Vane / Banca: Antonio Argolo Sampaio Filho / Banca: Rodrigo Leal Alves / Resumo: Justificativa e Objetivo: a lesão renal aguda(LRA) determina um aumento na morbidade e na mortalidade de pacientes hospitalizados. O diagnóstico precoce e a realização de medidas de proteção renal são essenciais. Foi observado que o pantoprazol possui efeito similar ao précondicionamento isquêmico em corações de ratos, promovendo efeito protetor. O objetivo deste experimento foi analisar o emprego do pantoprazol na proteção de rins submetidos à lesão de isquemia e reperfusão em ratos sob anestesia geral inalatória com isoflurano. Método: quarenta ratos, Wistar, machos, foram distribuídos aleatoriamente em quatro grupos: PIR (pantoprazol + isquemia artéria renal esquerda), P (pantoprazol), IR (isquemia renal esquerda) e Sham. O tempo de isquemia renal foi de 20 minutos e o de reperfusão, 30 minutos. Anestesia inalatória com isoflurano foi a técnica anestésica realizada. A dose administrada de pantoprazol foi de 192 mcg/kg. Todos os animais foram submetidos à nefrectomia direita e ao final do experimento procedeu-se nefrectomia esquerda, para posterior avaliação histológica e classificação por meio de escala de necrose tubular. Os atributos estudados foram: pressão arterial média (PAM), temperatura retal, os critérios de RIFLE e AKIN, dosagem urinária dos biomarcadores NGAL, KIM-1 e IL-8 e avaliação histológica. A creatinina sérica foi coletada em três momentos: M1, após monitorização; M2, após a reperfusão; e M3, 24 horas após o inicio do experimento. As coletas de urina para dosagem dos biomarcadores ocorreram antes (Urina 1) e após o experimento (Urina 2). Os atributos foram submetidos à análise estatística e as diferenças foram consideradas estatisticamente significativas quando p<0,05. Resultados: diferenças estatisticamente significativas foram observadas entre os grupos com aplicação dos critérios de RIFLE (p=0,007) e AKIN (p-0,003). Os grupos PIR e IR evoluíram com maior incidência de... / Abstract: Background and Objective: acute kidney injury (AKI) determines an increase in morbidity and mortality of hospitalized patients. Early diagnosis and the realization of renal protection measures are essential. It was observed that pantoprazole has effect similar to ischemic preconditioning in rat hearts, promoting protective effect. The objective was to analyze the use of pantoprazole in protecting kidneys subjected to ischemia and reperfusion in rats under inhalation anesthesia with isoflurane. Method: forty rats, Wistar male rats, were randomly divided into four groups: RIP (pantoprazole + left renal ischemia), P (pantoprazole), IR (left renal ischemia) and Sham. Renal ischemia time was 20 minutes and reperfusion 30 minutes. The anesthetic technique performed: inhalation anesthesia with isoflurane. The pantoprazole dose was 192 mcg/kg. All animals underwent right nephrectomy and at the end of the experiment proceeded to left nephrectomy for subsequent histological evaluation and classification through tubular necrosis scale. The parameters were: mean arterial pressure (MAP), rectal temperature, the criteria of RIFLE and AKIN, urinary dosage of biomarkers NGAL, KIM-1 and IL-8 and histological evaluation. Serum creatinine was collected in three moments: M1, after monitoring, M2, and M3 after reperfusion, 24 hours after the beginning of the experiment. The urine samples to test for biomarkers occurred before (Urine 1) and after the experiment (Urine 2). The attributes were subjected to statistical analysis and differences were considered statistically significant when p <0,05. Results: significant differences were observed between the groups with application of RIFLE criteria (p=0.007) and AKIN (p=0.003). The PIR and IR groups evolved with higher incidence of AKI. The NGAL and KIM-1 biomarkers increased in all groups throughout the experiment, but with higher values in the PIR and IR groups. IL-18 revealed no group effect (p=0.38) nor the ... / Doutor

Orientador: Winston Bonetti Yoshida / Banca: Carlos Eli Piccinato / Banca: Marcone Lima Sobreira / Banca: Ana Terezinha Guilaumon / Banca: Valter Castelli / Resumo: O uso da circulação extracorpórea desencadeia uma resposta inflamatória sistêmica, que somada às reações em cadeia relacionadas à isquemia-reperfusão de coração e pulmões pode levar a lesões celulares e até falência de órgãos no pós-operatório de cirurgia cardíaca. Vários estudos foram feitos visando melhor entendimento desses processos inflamatórios associados à circulação extracorpórea. Assim, esta revisão abordará os mecanismos de isquemia-reperfusão cardiopulmonar a ativação da cascata inflamatória por esse processo e o papel dos leucócitos na fisiopatologia destas lesões. Serão consideradas as interações de proteínas imunomoduladoras na resposta leucocitária e o bloqueio das mesmas por meio de filtros biológicos, do uso de anticorpos monoclonais e do estímulo à apoptose. / Abstract: The use of extracorporeal circulation starts a whole body inflammatory response that when added with a chain reactions related to heart and lung ischemia-reperfusion may cause cellular injuries and organ failures in the cardiac surgery pos-operative period. Many studies were made to achieve better comprehension of the inflammatory process that occur with use of extracorporeal circulation. So, this review discusses the ischemia- reperfusion events, their large activated inflammatory cascade as well as the leukocytes role on the pathophysiology of their associated injuries. The interactions of immunomodulatory proteins with the leukocitary response and their blockade through leukocytes filters, the monoclonal antibody use and the apoptosis stimuli will be approached too. / Doutor

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Objetivo: Avaliar os efeito da ornitina &#945;-cetoglutarato (OKG) no sangue e tecido intestinal de ratos submetidos à isquemia/reperfusÃo intestinal atravÃs da determinaÃÃo das concentraÃÃes in vivo no sangue e no tecido do intestino delgado, submetido a isquemia/reperfusÃo, de glicose, G 6 PDH, piruvato, acetoacetato, lactato, 3 HBDH, glutationa, T-Bars, mieloperoxidase, CPK e LDH. MÃtodo: Sessenta ratos (Rattus norvergicus albinus, Rodentia Mammalia) foram distribuÃdos aleatoriamente em cinco grupos de 12 animais: Sham 0â (s0â), Sham 30â (s30â), Sham 60â (s60â), Isquemia (i30â), ReperfusÃo (r30â). Estes grupos foram distribuÃdos em subgrupos de acordo com o tempo e com o composto utilizado na gavagem. Todos os animais receberam gavagem de caseinato de cÃlcio ou OKG em dose Ãnica, trinta minutos antes da laparotomia exploradora (LE). Os subgrupos s0âCaCa s30âCaCa, s60âc, i30âCaCa e r30âCaCa receberam apenas caseinato, de cÃlcio. Os subgrupos s0âOKG, s30âOKG, s60âOKG, i30âOKG e r30âOKG receberam OKG na dose de 5g/kg de peso. As amostras foram colhidas em cinco momentos: imediatamente apÃs a LE; apÃs 30 minutos da LE; ApÃs 1h da LE; ApÃs 30 minutos de isquemia; ApÃs 30 minutos de reperfusÃo. A estatÃstica discritiva foi expressa atravÃs da mÃdia, erro e desvio padrÃo, acompanhando-se pelo intervalo de confianÃa da mÃdia a 95% . Para comparar os valores prà e pÃs-procedimentos nas concentraÃÃes das variÃveis estudadas foram empregados os teste âtâ de Student pareado (para variÃncia homogÃnea e heterogÃnea) e ANOVA apÃs anÃlise de normalidade atravÃs do teste Kolmogorov-Smirnov. Quando observou a nÃo normalidade aplicou-se o teste de Kruskal-Wallis. Resultados: Os resultados apontaram um aumento significativo na lactacemia (1.186 + 0,18 versus 0,794 + 0,06, p<0,01) nos animais que receberam OKG em relaÃÃo ao controle nos subgrupos isquemia trinta minutos (i30â). No tecido intestinal reperfundido (r30â) ocorreu reduÃÃo significativa da concentraÃÃo de lactato (0,107 + 0,01 versus 0,266 + 0,02, p<0,05) nos animais recipientes de OKG em relaÃÃo ao animais controle, O piruvato plasmÃtico e tecidual se mostrou significantemente reduzido (0,146 + 0,24 versus 0,156 + 0,17 e 0,094 + 0,02 versus 0,248 + 0,03, p<0,05) apÃs o perÃodo de reperfusÃo de trinta minutos nos animais recipientes da OKG em relaÃÃo aos animais controle. Houve reduÃÃo significativa da concentraÃÃo do acetoacetato no tecido intestinal nos tempos pÃs isquemia e pÃs reperfusÃo dos animais recipientes da OKG (0,57 + 0,01 versus 0,0685 + 0,01 e 0,128 + 0,04 versus 0,156 + 0,03,*p<0,05) quando comparados ao animais nÃo tratados. A glicose 6 PDH apresentou reduÃÃo significativa da sua concentraÃÃo plasmÃtica no tempo isquemia trinta minutos dos animais recipientes da OKG em relaÃÃo aos nÃo tratados ( 0,1442 + 0,048 versus 1,1098 + 0,0796, *p<0,05) , ocorrendo o mesmo na concentraÃÃo tecidual, no pÃs isquemia (0,1002 + 0,02 versus 0,147 + 0,0264, p<0,05). A LDH apresentou elevaÃÃo significativa da sua concentraÃÃo nos animais recipientes da OKG em relaÃÃo ao controle (278,01 + 51,52 versus 132,93 + 12,54, *p<0,05) no grupo isquemia (i30â) . Ocorreu reduÃÃo significativa da CPK no grupo reperfusÃo (r30â) dos animais recipientes da OKG em comparaÃÃo aos animais controle (115,13 + 11,77 versus 166,70+6,23,p<0,05). A glutationa tecidual apresentou elevaÃÃo significativa no sham OKG 30 minutos em relaÃÃo ao nimais controle (59,17 + 2,39 versus 25,09 + 1.53, p<0,05) e reduÃÃo significante no tempo isquemia, tanto nos animais OKG quanto CaCa. Durante o perÃodo de reperfusÃo a glutationa nÃo apresentou alteraÃÃes significativas entre os animais tratados e controle. A OKG influenciou de maneira significativa na reduÃÃo da concentraÃÃo da 3HDBH tecidual no tempo i30â (0,062 + 0,01 versus 0,075 + 0,02,p<0,01) Esta diferenÃa significativa foi mantida no sangue dos animais tratados no grupo reperfusÃo 30âOKG em relaÃÃo aos animais r30âCaCa (0,03 + 0,00 versus 0,0615 + 0,01, p<0,01). A T-bars tecidual apresentou reduÃÃo significante no grupo r30âOKG em comparaÃÃo ao r30âCaCa (0,0522 + 0,03 versus 0,0745 + 0,02, p<0,05), com elevaÃÃo significativa no grupo sham 60âCaCa em relaÃÃo aos animais tratados 0,0937 + 0,02 versus 0,020 + 0,01, p<0,01). A oferta exÃgena da alfa-cetoglutarato nÃo ocasionou nenhuma alteraÃÃo significante nas concentraÃÃes de glicose e mieloperoxidase (MPO) entre os animais do subgrupo experimento quando comparados aos do subgrupo controle. ConclusÃes: Os procedimentos realizados foram suficientes para desencadear alteraÃÃes significativas em alguns metabÃlitos estudados. O modelo de isquemia-reperfusÃo demonstrou efetividade. A oferta exÃgena OKG, em dose Ãnica por gavagem, sugere aumento na atividade prÃ-glicolÃticas aerÃbica a nÃvel tecidual e sistÃmico; proteÃÃo contra lesÃo celular do tecido intestinal, e efeito antioxidante tecidual e sistÃmico durante a lesÃo de isquemia e apÃs a lesÃo de reperfusÃo / Objective: To evaluate the effect of ornithine alpha-ketoglutarate (OKG) in the blood and intestinal tissue of rats submitted to intestinal ischemia/reperfusion, using the blood concentrations of glucose, G6PDH, pyruvate, acetoacetate, lactate, 3HBDH, glutathione, T-Bars, myeloperoxydase, CPK and LHD, evaluated in vivo on these tissues. Methods: Sixty rats (Rattus norvergicus albinus, Rodentia Mammalia) were selected and aleatorily distributed in five groups of twelve animals, which were: Sham0â(s0â), Sham30â(s30â), Sham60â(s60â), Isquemia(i30â), ReperfusÃo(r30â). These groups were distributed in subgroups according to the time and the compost used to the âgavagemâ. All de animals received the âgavagemâ with calcium caseinate or okg, only one dosage, thirty minutes before the exploratory laparotomy (EL). The subgroups s0âCa, s30âCa, s60âCa, i30âCa and r30âCa received only calcium caseinate. The subgroups s0âokg, s30âokg, s60âokg, i30âokg and r30âokg received 5g of okg par each kilogram. The samples were taken in five moments: immediately passed the EL; passed 30 minutes of the EL; passed 60 minutes of the EL; passed 30 minutes of the isquemia; passed 30 minutes of the reperfusion. The descriptive statistics were media, error and standard deviation. The values before and after the procedures were compared using the âtâ test (âStudent pareadoâ to homogeny and heterogeny variation) and ANOVA. Then, it was used Kolmogorov-Smirnov to compare the normal results. The results were not normal, it was used the Kruskal-Wallis test. Results: It was shown an improvement on the blood lactate(1.186 + 0,18 versus 0,794 + 0,06, p<0,01) to the animals that received okg from i30â. A reduction on blood lactate lactato (0,107 + 0,01 versus 0,266 + 0,02, p<0,05) was noticed in the group r30â that received okg. It occurred a reduction on plasmatic and tissue pyruvate reduzido (0,146 + 0,24 versus 0,156 + 0,17 and 0,094 + 0,02 versus 0,248 + 0,03, p<0,05) to the group r30â that received okg. The acetoacetate was reduced to both groups, isquemia and reperfusion, that received okg0,57 + 0,01 versus 0,0685 + 0,01 e 0,128 + 0,04 versus 0,156 + 0,03,*p<0,05). The plasmatic glucose was reduced to the group i30â( 0,1442 + 0,048 versus 1,1098 + 0,0796, *p<0,05) treated with okg and the same happened to the tissue glucose after isquemia (0,1002 + 0,02 versus 0,147 + 0,0264, p<0,05). The LDH had an improvement (0,1002 + 0,02 versus 0,147 + 0,0264, p<0,05) to the group i30â treated with okg. CPK was reduced (115,13 + 11,77 versus 166,70+6,23,p<0,05) to the group r30â treated with okg. The tissue glutathione had an improvement to sham okg 30â (59,17 + 2,39 versus 25,09 + 1.53, p<0,05) and a reduction on isquemia period to the animals treated with okg and CaCa . 3HBDH was reduced (0,062 + 0,01 versus 0,075 + 0,02,p<0,01) in the blood and in the tissues from i30â. This difference was kept to animalsâ blood from r30âokg when related to r30âCaCa(0,03 + 0,00 versus 0,0615 + 0,01, p<0,01). There was a reduction on tissue T-BARS to r30âOKG when compared to r30âCaCa(0,0522 + 0,03 versus 0,0745 + 0,02, p<0,05) and an improvement to sham60âCaCa(0,0937 + 0,02 versus 0,020 + 0,01, p<0,01). Glicose and Myeloperoxydase were not affected by the use of okg. All the results were compared to the respective control groups. Conclusion: The used procedures could bring useful results to metabolites in study. The isquemia/reperfusion showed efficiency, offering exogen okg leads to a rising on glicolitic and aerobic activity to tissues and systems. This offer protects yet from the tissue injury and has antioxidant effect during the isquemia/reperfusion injury.

Activation of sympathetic nervous system is a key component of myocardial remodeling that generally occurs following ischemia/reperfusion (I/R) injury and myocardial infarction. It induces cardiac myocyte apoptosis and myocardial fibrosis, leading to myocardial dysfunction. Intracellular ubiquitin (UB) regulates protein turnover by the UB-proteosome pathway. The biological functions of extracellular UB in the heart remain largely unexplored. Previously, our lab has shown that β-adrenergic receptor (β-AR) stimulation increases extracellular UB levels, and extracellular UB inhibits β-AR-stimulated apoptosis in adult rat ventricular myocytes (ARVMs). This study explores the role of extracellular UB in myocyte apoptosis, fibroblast phenotype and function, and myocardial remodeling following β-AR stimulation and I/R injury. First, left ventricular (LV) structural and functional remodeling was studied 7 days after chronic β-AR-stimulation in the presence or absence of UB infusion. Echocardiographic analyses showed UB infusion decreases β-AR-stimulated increases in percent fractional shortening and ejection fraction. It decreased cardiac myocyte apoptosis and myocardial fibrosis. UB activated Akt, and inhibition of Akt inhibited β-AR-stimulated increases in matrix metalloproteinase-2 expression. Second, using cardiac fibroblasts, we provide evidence that extracellular UB interacts with the cell surface and co-immunoprecipitates with CXCR4. UB treatment increased expression of α-smooth muscle actin (myofibroblast marker), and induced rearrangement of actin into stress fibers. It inhibited lamellopodia and filopodia formation, and cell migration into the wound. Third, using isolated mouse heart and I/R injury as a model, we provide evidence that UB treatment decreases I/R-mediated increases in infarct size. UB treatment improved functional recovery of the heart as measured by increased % LV developed pressure. Activation of proapoptotic proteins, p-STAT-1 and caspase-9, was significantly lower in UB I/R hearts versus I/R alone. In ARVMs, UB treatment decreased simulated I/R-induced apoptosis. It activated Akt (anti-apoptotic kinase) and inhibited activation of GSK-3β (pro-apoptotic kinase). It decreased I/R-induced oxidative stress and protected anoxia-induced mitochondrial polarization. In fibroblast and ARVMs, CXCR4 antagonism negated the effects of UB, while mutated UBs (unable to interact with CXCR4) had no effect. Thus, extracellular UB, most likely acting via CXCR4, modulates myocardial remodeling with effects on heart function, fibroblast phenotype and function and myocyte apoptosis.

β-Adrenergic receptor (β-AR) stimulation increases extracellular levels of ubiquitin (UB) in myocytes, and exogenous UB decreases β-AR-stimulated myocyte apoptosis and myocardial fibrosis. Here, we hypothesized that exogenous UB modulates the inflammatory response, thereby playing a protective role in cardiac remodeling after ischemia-reperfusion (I/R) injury. C57BL/6 mice infused with vehicle or UB (1 μg·g−1·h−1) were subjected to myocardial I/R injury. Functional and biochemical parameters of the heart were examined 3 days post-I/R. Heart weight-to-body weight ratios were similarly increased in I/R and UB + I/R groups. The area at risk and infarct size were significantly lower in UB + I/R versus I/R groups. Measurement of heart function using echocardiography revealed that I/R decreases percent fractional shortening and percent ejection fraction. However, the decrease in fractional shortening and ejection fraction was significantly lower in the UB + I/R group. The UB + I/R group displayed a significant decrease in inflammatory infiltrates, neutrophils, and macrophages versus the I/R group. Neutrophil activity was significantly lower in the UB + I/R group. Analysis of the concentration of a panel of 23 cytokines/chemokines in the serum using a Bio-Plex assay revealed a significantly lower concentration of IL-12 subunit p40 in the UB + I/R versus I/R group. The concentration of monocyte chemotactic protein-1 was lower, whereas the concentration of macrophage inflammatory protein-1α was significantly higher, in the UB+I/R group versus the sham group. Expression of matrix metalloproteinase (MMP)-2 and activity of MMP-9 were higher in the UB + I/R group versus the I/R group. Levels of ubiquitinated proteins and tissue inhibitor of metalloproteinase 2 expression were increased to a similar extent in both I/R groups. Thus, exogenous UB plays a protective role in myocardial remodeling post-I/R with effects on cardiac function, area at risk/infarct size, the inflammatory response, levels of serum cytokines/chemokines, and MMP expression and activity.

Hydrogen sulfide (H2S) reduces ischemia reperfusion (IR) injury by stimulating adenosine triphosphate (ATP) sensitive potassium channels (KATP) [1-5]. Demonstrating H2S stimulation is unique to KATP, as other inwardly rectifying potassium (Kir) channels demonstrate inhibition or are unaffected [6]. We recently showed that H2S inhibits Kir2 and Kir3 by decreasing channel sensitivity to phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2 or PIP2) [6]. Here, we test the hypothesis that H2S regulation of Kir6.2, a pore-forming subunit of the KATP channel, is also dependent on PIP2. Using whole-cell patch-clamp we show that H2S increases the activity of Kir6.2 channels expressed in HEK-293 cells. To study the mechanism, we modulated PIP2 levels by expressing a light- activated phosphatase, or by including high levels of a water-soluble PIP2 analog in the patch pipette. The results suggest that H2S augmentation of Kir6.2 channel activity is increased when PIP2 levels are elevated.

Includes bibliographical references (leaves 292-352) Determines the role of matrix metalloproteinases, MMP-2 and MMP-9 in reperfusion injury following skeletal muscle ischaemia; and, whether inhibition of MMPs by doxycycline protects against tissue damage.

Ischaemic heart disease is a major contributor to premature death and heart failure in the Westernised world. Ischaemic injury within the heart may be beneficially modulated by the nucleoside adenosine. Derived from catabolism of ATP, adenosine was initially known as a potent bradycardic and hypotensive agent. However, more recently the protective function of adenosine has been investigated. The protective effects of adenosine are mediated via activation of adenosine receptors: A1, A2A, A2B, and A3 receptors. Activation of these potentially protective (or retaliatory) adenosine receptors hinges upon accumulation of adenosine during ischaemia-reperfusion. This Thesis examines the role and mechanisms of adenosine mediated cardioprotection in young and aged hearts, exploring endogenous and exogenous adenosine receptor activation, genetic manipulation of A1 receptors and adenosine deaminase and pharmacological manipulation of adenosine metabolism. The effects of age on ischaemic responses and adenosine handling and protection are also assessed. The core approach to assess each of the above issues involved the Langendorff isolated mouse heart preparation. Experiments within Chapter 3 focuses on the contractile effects of adenosine receptors in normoxic hearts. This study indicates A2A receptors have no direct effect on contractility, while adenosine exerts positive inotropy independently of coronary flow and perfusion pressure (i.e. Independent of the Gregg phenomenon). In addition, investigations in genetically modified hearts hint at positive inotropy in response to A1 receptors. Since the latter is only evidenced in modified lines, it is possible A1-mediated inotropy may be abnormal or supraphysiological. In Chapter 4 the impact of genetic 'deletion' of A1ARs and/or adenosine deaminase (ADA) on intrinsic tolerance to ischaemia were studied. Data demonstrate that genetic deletion of A1 receptors significantly limits the ability of the mouse myocardium to withstand injury during ischaemic insult. Thus, providing strong support for a role of A1ARs in determining intrinsic tolerance to ischaemia-reperfusion. ADA KO mice confirm protection afforded by endogenous adenosine and the notion of adenosine metabolism modification as a protective strategy. Interestingly, effects of A1AR KO differ from A1AR overexpression or A1AR agonism in that the latter decrease contractile diastolic dysfunction while A1AR KO selectively increase systolic dysfunction and increase oncosis without altering diastolic injury. This challenges current dogma regarding the action of A1 adenosine receptors on ischaemic injury. In Chapter 5 the effects of adenosine metabolism inhibition (via adenosine deaminase (ADA) and adenosine kinase (AK) inhibitors) were studied. Inhibition of adenosine deaminase with the drug EHNA, and adenosine phosphorylation with iodotubercidin significantly protected mouse hearts from ischaemia-reperfusion, reducing contractile dysfunction and cardiac enzyme efflux. However, inhibitors failed to improve the outcome of the aged myocardium. 8-SPT and 5-HD reduced the protective effects of EHNA and iodotubercidin demonstrating thus; cardioprotection via ADA and AK appears to rely on adenosine receptor activation and involves a mitoK ATP dependent mechanism. Since aging is of considerable importance with regard to outcomes of ischaemic heart disease, experiments in Chapter 6 focused on effects of aging (and gender) on cardiovascular function and injury during ischaemia-reperfusion. In assessing post ischaemic outcomes in hearts from young adult (2-4 months), mature adult (8 months), middle aged (12 months), aged (18 months) and senescent (24-28 months) C57/BL/6J mice, data reveal a substantial age-related decline in ischaemic tolerance (which appears selective for myocardial vs. vascular injury). The decline in ischaemic tolerance is expressed primarily within the initial 12 months in both males and females with relatively little further decline with continued aging. There is evidence of a modest improvement in tolerance in senescence vs. aged hearts possibly reflecting selection of a protected phenotype in senescent populations. In addition, mature and middle-aged female hearts showed improved tolerance to ischaemia-reperfusion compared to males, supporting a role for hormonal changes. Effects of aging and purine metabolism were studied in Chapter 7. Data suggest impaired tolerance to ischaemia-reperfusion in older hearts may stem in part from shifts in myocardial purine catabolism. Data reveal reduced accumulation of salvageable and cardioprotective adenosine and enhanced accumulation of poorly salvaged (and potentially injurious) hypoxanthine and xanthine. These changes may potentially predispose the aged myocardium to ischaemic injury and radical generation via the xanthine oxidase reaction. The final data Chapter of this Thesis describes preliminary data regarding aging, signalling and adenosine mediated protection. It was found that protein kinase C (PKC) and A1 receptors mediate protection in young hearts and also that A1 receptors appear to mediate protection via a PKC LindependentLi signalling cascade. In addition, experiments in aged hearts (attempting to elucidate mechanisms behind impaired adenosinergic protection with age) suggest a PKC-independent A1-mediated protection path may be preserved with aging, since A1 receptors continue to offer some protection while PKC activation does not. It is possible the failure of exogenous adenosine to offer protection in aged hearts may result from a lesion at or downstream of PKC.

Includes bibliographical references (leaves 292-352) / xvi, 352 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Determines the role of matrix metalloproteinases, MMP-2 and MMP-9 in reperfusion injury following skeletal muscle ischaemia; and, whether inhibition of MMPs by doxycycline protects against tissue damage. / Thesis (M.D.)--University of Adelaide, Dept. of Surgery, 2002