Hsp104 and ClpB are hexameric ATPases that resolubilize aggregated proteins in collaboration with the Hsp70 chaperone system. Hsp104/ClpB functionally interact only with their respective Hsp70 system and this specificity is mapped to the Hsp104/ClpB coiled-coil domain (CCD). We hypothesize that the interaction between Hsp70 and Hsp104/ClpB CCD stimulates nucleotide exchange and release of substrate from Hsp70. In the current study, the CCDs of E. coli ClpB and S. cerevisiae Hsp104 have been purified. Isolated domains are monomeric and well folded. They inhibit refolding of aggregated firefly luciferase in a species-specific manner. We found that the ATPase activity of E. coli DnaK is stimulated at low concentrations of the E. coli ClpB CCD but not by yeast Hsp104 CCD. However, in another bacterial system (Thermus thermophilus) we found that the ClpB CCD inhibits The ATPase activity of DnaK suggesting that the interaction may have different consequences in distinct chaperone networks.

Orientador: Eliana Aguiar Petri Nahas / Resumo: Objetivo: Avaliar os fatores de risco cardiovascular em mulheres na pós-menopausa tratadas de câncer de mama comparadas a mulheres na pós-menopausa sem câncer de mama e a associação das heat shock proteins (HSP) 60 e 70 com o câncer de mama em mulheres na pós-menopausa. Métodos: Realizou-se estudo clínico de corte transversal com 96 mulheres tratadas de câncer de mama comparadas a 192 mulheres na pós-menopausa (controle), com idades entre 45 e 75 anos. Foram incluídas no grupo principal mulheres com amenorréia > 12 meses e idade ≥ 45 anos, com diagnóstico histológico de câncer de mama, sem doença metastática e sem doença cardiovascular (DCV) estabelecida. O grupo controle foi constituído por mulheres com amenorréia > 12 meses, idade ≥ 45 anos, sem câncer de mama e DCV. Os grupos foram pareados por idade, tempo de menopausa e índice de massa corpórea (IMC) na proporção 1 caso para 2 controles, conforme cálculo amostral, com o mínimo de 92 pacientes tratadas de câncer de mama. Dados clínicos e antropométricos (IMC e circunferência da cintura) foram coletados por meio de entrevista e exame físico. Para análise bioquímica foram solicitados colesterol total, HLD, LDL, triglicerídeos, glicose e insulina. Foram consideradas com síndrome metabólica (SM), as mulheres que apresentaram três ou mais critérios diagnósticos: circunferência da cintura (CC) > 88 cm; TG ³ 150 mg/dL; HDL colesterol < 50 mg/dL; pressão arterial ³ 130/85 mmHg; glicose ³ 100 mg/dL. Para determinação das concentra... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: To evaluate cardiovascular risk factors in postmenopausal breast cancer survivors as compared to postmenopausal women without breast cancer and the association of heat shock proteins (HSP) 60 and 70 with breast cancer in postmenopausal women. Methods: In this cross-sectional study, 96 postmenopausal breast cancer survivors were compared with 192 postmenopausal women (controls), aged 45 to 75 years. The principal group included women with amenorrhea > 12 months and age ≥45 years, with histological diagnosis of breast cancer, without metastatic disease and without established cardiovascular disease (CVD). The control group consisted of women with amenorrhea > 12 months, age ≥45 years, without breast cancer and CVD. The groups were matched by age, time since menopause, and body mass index (BMI) in the proportion 1 case for 2 controls, according to the sample calculation, with a minimum of 92 breast cancer survivors. Clinical and anthropometric data (BMI and waist circumference) were collected by interview and physical examination. For biochemical analysis, total cholesterol, HLD, LDL, triglycerides, glucose and insulin levels were measured. Women who presented three or more of the following criteria were diagnosed as having metabolic syndrome (MetS): waist circumference (WC)> 88 cm; TG≥ 150 mg/dL; HDL cholesterol <50 mg/dL; blood pressure ≥ 130/85 mmHg; glucose ≥ 100 mg/dL. For measuring plasma concentrations of HSP 60 and 70, immunoassays by ELISA technique were used. Atheroscl... (Complete abstract click electronic access below) / Doutor

Heat shock protein 90 (HSP90), a conserved molecular chaperone, has become a potential molecular target for cancer therapeutics. HSP90 inhibition (HSP90i) causes inhibition of several oncogenic pathways simultaneously and leads to anti-cancer activities in multiple cancers including in triple-negative breast cancer (TNBC). TNBC is a subtype of breast cancer with poor prognosis and lack of approved targeted therapies. Although HSP90i has shown promising initial clinical data, resistance to HSP90i can still arise in TNBC patients and its resistance mechanisms are not yet understood. In this study, using an in vitro system, we report for the first time the isolation of TNBC cells with acquired resistance to HSP90i. Proteome and whole transcriptome profiling, and a bioactive small molecule screen were performed to identify the molecular basis of resistance to HSP90i and potential therapeutic approaches to overcome acquired resistance to HSP90i in TNBC cells. Two independent HSP90i-resistant clones were acquired through prolonged exposure of a TNBC cell line (Hs578T) to HSP90i. The clones showed significant resistance to HSP90i, notably to resorcinol-based HSP90i. The HSP90i-resistant clones also shared genomic sequence variants, suggesting a pre-existing population of resistant cells within the parental cells. We demonstrate that upregulated expression of UGT1A9, possibly due to an increased intrinsic oxidative stress, is associated with acquired resistance to resorcinol-based HSP90i in TNBC cells, and sensitivity to HSP90i can be restored with a competitive inhibitor of UGT1A9. The HSP90i-resistant clones also exhibited slower growth and upregulated IL6- mediated JAK2-STAT3 survival signalling pathway, which might contribute to the crossresistance to chemotherapeutics and other targeted therapies seen in the clones. Finally, we demonstrate that inhibition of JAK2-STAT3 signalling pathway is able to increase the cytotoxic effects of HSP90i to TNBC cells. We conclude that by using in vitro assays, we are able to identify potential mechanisms of acquired resistance to HSP90i in TNBC cells. We propose that expression of UGT1A9 or STAT3 might be a potential biomarker of sensitivity to HSP90i in TNBC cells. A combined inhibition of HSP90 and JAK2 might be a potential therapeutic approach for the development of effective targeted therapies in TNBC patients.

Heat shock proteins (HSPs) play important roles in the process of maintaining proteostasis in a cell. HSP72, the inducible form of the HSP70 family, is expressed in response to stress on the cell or tissue, including those stresses caused by tumor growth. Increasing evidence suggests that HSP72 is necessary for a cancerous cell to survive under the stresses of a tumor microenvironment. This has naturally raised interest in identifying an inhibitor selective for HSP72. The Haystead Laboratory at Duke University identified such a small-molecule inhibitor, referred to as HS-72, and proposed the scaffold as an ideal starting point to develop a family of therapeutic agents targeting HSP72. This work examines the potency and effectiveness of HS-72 and a number of its analogs developed by the Haystead Laboratory. These results suggest that HS-159 is a more effective inhibitor of HSP72 on a range of human tumor cell lines than HS-72. Further studies are needed to quantify how much more potent HS-159 is than HS-72 and potentially identify even more potent compounds.

Submitted by Daniel De Araujo Brito Buttros (danielbuttros@hotmail.com) on 2018-06-14T10:28:06Z No. of bitstreams: 1 DOUTORADO DANIEL BUTTROS.pdf: 8920662 bytes, checksum: 8d3d25caa8f04b9c86ef89d60f2cab83 (MD5) / Approved for entry into archive by Sulamita Selma C Colnago null (sulamita@btu.unesp.br) on 2018-06-14T17:51:10Z (GMT) No. of bitstreams: 1 buttros_dab_dr_bot.pdf: 8920662 bytes, checksum: 8d3d25caa8f04b9c86ef89d60f2cab83 (MD5) / Made available in DSpace on 2018-06-14T17:51:10Z (GMT). No. of bitstreams: 1 buttros_dab_dr_bot.pdf: 8920662 bytes, checksum: 8d3d25caa8f04b9c86ef89d60f2cab83 (MD5) Previous issue date: 2018-04-19 / Objetivo: Avaliar os fatores de risco cardiovascular em mulheres na pós-menopausa tratadas de câncer de mama comparadas a mulheres na pós-menopausa sem câncer de mama e a associação das heat shock proteins (HSP) 60 e 70 com o câncer de mama em mulheres na pós-menopausa. Métodos: Realizou-se estudo clínico de corte transversal com 96 mulheres tratadas de câncer de mama comparadas a 192 mulheres na pós-menopausa (controle), com idades entre 45 e 75 anos. Foram incluídas no grupo principal mulheres com amenorréia > 12 meses e idade ≥ 45 anos, com diagnóstico histológico de câncer de mama, sem doença metastática e sem doença cardiovascular (DCV) estabelecida. O grupo controle foi constituído por mulheres com amenorréia > 12 meses, idade ≥ 45 anos, sem câncer de mama e DCV. Os grupos foram pareados por idade, tempo de menopausa e índice de massa corpórea (IMC) na proporção 1 caso para 2 controles, conforme cálculo amostral, com o mínimo de 92 pacientes tratadas de câncer de mama. Dados clínicos e antropométricos (IMC e circunferência da cintura) foram coletados por meio de entrevista e exame físico. Para análise bioquímica foram solicitados colesterol total, HLD, LDL, triglicerídeos, glicose e insulina. Foram consideradas com síndrome metabólica (SM), as mulheres que apresentaram três ou mais critérios diagnósticos: circunferência da cintura (CC) > 88 cm; TG ³ 150 mg/dL; HDL colesterol < 50 mg/dL; pressão arterial ³ 130/85 mmHg; glicose ³ 100 mg/dL. Para determinação das concentrações plasmáticas de HSP 60 e 70 foram empregados imunoensaios pela técnica de ELISA. A doença aterosclerótica foi determinada pela espessura do complexo médio-intimal (CMI > 1mm) das artérias carótidas e/ou pela presença de placa ateromatosa, avaliadas pela ultrassonografia carotídea (scanner 14 duplex). Para análise estatística foram empregados: Teste t-student, Distribuição Gama (variáveis assimétricas), Teste do Qui-Quadrado e Regressão Logística (odds ratio-OR). Resultados: A média de idade das pacientes tratadas de câncer de mama foi de 59,8 ± 9,0 anos com tempo médio de seguimento de 4,2 ± 2,0 anos. Na comparação entre os grupos, mulheres tratadas de câncer de mama apresentaram valores médios elevados da pressão sistólica e diastólica (p<0.001) e valores médios de triglicerídeos e glicose, acima dos valores desejáveis (p<0.05). As pacientes do grupo principal apresentaram valores mais altos de HSP 60 e mais baixos de HSP 70 quando comparados ao controle (p<0.05). Foi observada maior ocorrência de diabetes, SM e placa ateromatosa entre as mulheres tratadas de câncer mama quando comparadas ao controle (19,8% vs 6,8%; 54,2% vs 30,7%; 19.8% vs 9.4%, respectivamente) (p<0.05). Na análise de risco ajustado para idade, tempo de menopausa e IMC, as mulheres tratadas de câncer de mama apresentaram risco significativamente aumentado para SM (OR=4.21; IC 95% 2.28-7.76), presença de placa ateromatosa (OR=2.61; IC 95% 1.19-5.72), diabetes (OR=4.42; IC 95% 1.86-10.49), hipertrigliceridemia (OR=2.32; IC 95% 1.33-4.0) e circunferência de cintura aumentada (OR=11.22; IC 95% 4.0 – 31.65), quando comparadas as mulheres sem câncer de mama. Conclusão: Mulheres tratadas de câncer de mama apresentaram maior risco para síndrome metabólica, diabetes, doença aterosclerótica, hipertrigliceridemia e obesidade abdominal, importantes fatores de risco para doença cardiovascular, quando comparadas as mulheres na pós-menopausa sem câncer de mama. Assim como, mulheres tratadas de câncer de mama apresentaram valores elevados de HSP 60 e diminuídos de HSP 70 quando comparadas às mulheres sem câncer. / To evaluate cardiovascular risk factors in postmenopausal breast cancer survivors as compared to postmenopausal women without breast cancer and the association of heat shock proteins (HSP) 60 and 70 with breast cancer in postmenopausal women. Methods: In this cross-sectional study, 96 postmenopausal breast cancer survivors were compared with 192 postmenopausal women (controls), aged 45 to 75 years. The principal group included women with amenorrhea > 12 months and age ≥45 years, with histological diagnosis of breast cancer, without metastatic disease and without established cardiovascular disease (CVD). The control group consisted of women with amenorrhea > 12 months, age ≥45 years, without breast cancer and CVD. The groups were matched by age, time since menopause, and body mass index (BMI) in the proportion 1 case for 2 controls, according to the sample calculation, with a minimum of 92 breast cancer survivors. Clinical and anthropometric data (BMI and waist circumference) were collected by interview and physical examination. For biochemical analysis, total cholesterol, HLD, LDL, triglycerides, glucose and insulin levels were measured. Women who presented three or more of the following criteria were diagnosed as having metabolic syndrome (MetS): waist circumference (WC)> 88 cm; TG≥ 150 mg/dL; HDL cholesterol <50 mg/dL; blood pressure ≥ 130/85 mmHg; glucose ≥ 100 mg/dL. For measuring plasma concentrations of HSP 60 and 70, immunoassays by ELISA technique were used. Atherosclerotic disease was determined by the intima-media thickness (IMT> 1mm) of the carotid arteries and / or by the presence of atheromatous plaque, assessed by carotid ultrasound (scanner duplex). For statistical nalysis, Student's t-test, Gamma Distribution (asymmetric variables), Chi-Square Test, and Logistic Regression (odds ratio-OR) were used. Results: The mean (± SD) age of breast cancer survivors was 59.8 ± 9.0 years, with a mean (± SD) follow-up of 4.2 ± 2.0 years. The breast cancer survivors presented high mean values of systolic and distal pressure (p <0.001), and mean values of triglycerides and glucose, above the desirable values (p <0.05). Patients with breast cancer had higher levels of HSP 60 and lower HSP 70 when compared to control (p <0.05). There was a higher occurrence of diabetes, MetS, and atheromatous plaque among the breast cancer survivors when compared to the control group (19.8% vs 6.8%, 54.2% vs. 30.7%, 19.8% vs. 9.4% respectively) (p <0.05). In the risk analysis adjusted for age, time since menopause and BMI, women treated for breast cancer had a significantly increased risk for MetS (OR = 4.21, 95% CI 2.28-7.76), presence of atheromatous plaque (OR = 2.61, CI 95% CI 1.19-5.72), diabetes (OR=4.42; IC 95% 1.86-10.49), hypertriglyceridemia (OR = 2.32, 95% CI 1.33-4.0) and large waist circumference (OR = 11.22, 95% CI 4.0 - 31.65 ) when compared to women without breast cancer. Conclusion: Postmenopausal breast cancer survivors had a higher risk for metabolic syndrome, diabetes, atherosclerotic disease, hypertriglyceridemia and abdominal obesity, important risk factors for cardiovascular disease when compared to postmenopausal women without breast cancer. Similarly, women treated for breast cancer presented high levels of HSP 60 and decreased HSP 70 when compared to women without cancer.

A asma alérgica é uma doença pulmonar de inflamação crônica caracterizada por uma resposta imune do tipo Th2 e uma das principais abordagens terapêuticas para o seu tratamento no futuro, poderia ser a imunoterapia baseada na modulação da resposta imune Th2 para um perfil Th1 e anti-inflamatório. Nosso grupo já demonstrou a eficácia de uma imunoterapia, baseada em um plasmídeo de DNA contendo o gene hsp65 de M. Leprae (DNAHsp65) em modelo murino de asma alérgica. No entanto, apesar dos excelentes resultados, o grupo está procurando outras alternativas imunoterapêuticas, usando a Hsp65 micobacteriana, para futura utilização clinica na área de saúde humana e veterinária. Efeitos benéficos na prevenção e tratamento de doenças alérgicas vêm sendo obtidos com o uso de probióticos. Nossa hipótese é de que uma nova formulação terapêutica, como o probiótico Lactococcus lactis expressando Hsp65 micobacteriana (LLHsp65), apresentaria vantagens significativas no desenvolvimento de pesquisas translacionais. Diante disso, este estudo teve como objetivo avaliar se o probiótico LLHsp65 apresenta atividades imunoterapêuticas no modelo de asma experimental induzida por ovalbumina (OVA). Em diferentes grupos experimentais, 5x109 CFU de LLHsp65 ou de L. lactis selvagem (LLSELV), foram administrados por via oral durante 10 dias consecutivos aos camundongos BALB/c previamente sensibilizados e desafiados com OVA. Em seguida, investigamos os efeitos do tratamento na inflamação alérgica, modulação do padrão de citocinas, produção de anticorpos específicos, hiper-responsividade das vias aéreas e inflamação pulmonar. Nossos resultados demonstraram que o tratamento oral com LLhsp65 modula a resposta imune alérgica de padrão Th2 para o perfil Th1 com aumento dos níveis de IFN-?, IL-12, TNF-?, IL-10, IL-6 e IL- 17, e com a redução das citocinas IL-4, IL-5 e IL-13. Os níveis de IgE e IgG1 anti-OVA no soro também foram significativamente diminuídos. Como consequência desses resultados, também observamos diminuição significativa do infiltrado de eosinófilos no lavado broncoalveolar, na hiper-responsividade nas vias aéreas e a atenuação da inflamação e produção de muco no tecido pulmonar, quando comparados com o grupo controle (OVA/SAL). Por conseguinte, nossos resultados demonstraram que a administração oral de LLHsp65 proporciona uma melhora significativa do processo inflamatório alérgico induzido por OVA, sendo portanto, uma estratégia terapêutica promissora para o desenvolvimento de pesquisa translacional no tratamento de asma alérgica. / Allergic asthma is a chronic inflammatory lung disease characterized by a Th2-type immune response and one of the main therapeutic approaches to its treatment in the future could be immunotherapy based on the modulation of the Th2 immune response to a Th1 and anti-inflammatory profile. Our group has already demonstrated the efficacy of an immunotherapy based on a DNA plasmid carrying the mycobacterial hsp65 gene (DNAHsp65) in murine model of allergic asthma. However, despite the excellent results, our group is looking for other immunotherapeutic alternatives, using mycobacterial Hsp65, for future clinical use in the area of human and veterinary health. Beneficial effects in the prevention and treatment of allergic diseases have been obtained with the use of probiotics. Our hypothesis is that a new therapeutic formulation, such as the probiotic Lactococcus lactis expressing mycobacterial Hsp65 (LLHsp65), would present significant advantages in the development of translational research. The objective of this study was to evaluate whether the probiotic LLHsp65 has immunotherapeutic activities in the ovalbumin-induced asthma model. In different experimental groups, 5x109 CFU of LLHsp65 or control L. lactis (ctLL) were administered orally for 10 consecutive days to BALB/c mice previously sensitized and challenged with OVA. We then investigated the effects of treatment on allergic inflammation, modulation of the cytokine pattern, production allergen-specific antibodies, airway hyperresponsiveness and pulmonary inflammation. Our results demonstrated that oral treatment with LLhsp65 modulates the allergic Th2 immune response to Th1 profile with increased levels of IFN-?, IL-12, TNF-?, IL-10, IL-6 and IL-17 and with the reduction of IL-4, IL-5 and IL-13 cytokines. Serum anti-OVA IgE and IgG1 levels were also significantly decreased. Correspondingly with these results, we also observed a significant decrease in eosinophil infiltrate in bronchoalveolar lavage, airway hyper responsiveness and attenuation of inflammation and mucus production in lung tissue when compared to the control group (OVA/SAL). Therefore, our results demonstrated that oral administration of LLHsp65 provides a significant improvement of the OVA-induced allergic inflammatory process and is therefore a promising therapeutic strategy for the development of translational research in the treatment of allergic asthma.

Lung tumor progression is regulated by proangiogenic factors. Heat shock protein A12B (HSPA12B) is a recently identified regulator of expression of proangiogenic factors. However, whether HSPA12B plays a role in lung tumor growth is unknown. To address this question, transgenic mice overexpressing HSPA12B (Tg) and wildtype littermates (WT) were implanted with Lewis lung cancer cells to induce lung tumorigenesis. Tg mice showed significantly higher number and bigger size of tumors than WT mice. Tg tumors exhibited increased angiogenesis and proliferation while reduced apoptosis compared with WT tumors. Interestingly, a significantly enhanced upregulation of Cox-2 was detected in Tg tumors than in WT tumors. Also, Tg tumors demonstrated upregulation of VEGF and angiopoietin-1, downregulation of AKAP12, and increased eNOS phosphorylation compared with WT tumors. Celecoxib, a selective Cox-2 inhibitor, suppressed the HSPA12B-induced increase in lung tumor burden. Moreover, celecoxib decreased angiogenesis and proliferation whereas increased apoptosis in Tg tumors. Additionally, celecoxib reduced angiopoietin-1 expression and eNOS phosphorylation but increased AKAP12 levels in Tg tumors. Our results indicate that HSPA12B stimulates lung tumor growth via a Cox-2-dependent mechanism. The present study identified HSPA12B as a novel facilitator of lung tumor growth and a potential therapeutic target for the treatment of lung cancer.

Cardiac dysfunction is a major consequence of septic shock and may be responsible for the high mortality of sepsis. We have reported that transgenic mice with cardiac-specific overexpression of heat shock protein 27 (Hsp27 Tg) exhibited the protection against doxorubicin-induced cardiac dysfunction. We hypothesized that overexpression of Hsp27 will attenuate cardiac dysfunction during endotoxemia. Hsp27 Tg and age-matched wild-type (WT) mice were injected with LPS. Cardiac function was evaluated by echocardiography, survival rate was carefully monitored, and activities of signaling pathways were determined by immunoblot. LPS administration significantly decreased cardiac function in WT mice. In Hsp27 Tg mice, LPS-induced cardiac dysfunction was significantly attenuated as evidenced by increased ejection fraction (27.3%) and fractional shortening (37.1%), respectively, compared with LPS-treated WT mice. Heat shock protein 27 Tg mice were more resistant to LPS-induced mortality than WT. The levels of phospho-Akt and phospho-glycogen synthase kinase 3β (phospho-GSK-3β) in the myocardium were significantly increased in Hsp27 Tg mice compared with WT after LPS administration. Nuclear factor κB-binding activity was significantly decreased in Hsp27 Tg mice compared with WT mice after LPS challenge. Similar results were observed in in vitro studies using Hsp27-transfected rat cardiomyoblasts. Importantly, phosphoinositide 3-kinase inhibition abolished the protective effect of Hsp27 in LPS-induced cardiac dysfunction and mortality of endotoxemia. Our results suggest that Hsp27 plays an important role in attenuation of cardiac dysfunction and mortality in endotoxemia and that the mechanisms of the protection may involve activation of the PI3K/Akt signaling pathway.

Heat shock protein A12A (HSPA12A) is a newly discovered member of the Hsp70 family. The biological characteristics and functional roles of HSPA12A are poorly understood. This study investigated the effects of HSPA12A on ischaemic stroke in mice. Ischaemic stroke was induced by left middle cerebral artery occlusion for 1 h followed by blood reperfusion. We observed that HSPA12A was highly expressed in brain neurons, and neuronal HSPA12A expression was downregulated by ischaemic stroke and stroke-associated risk factors (aging, obesity and hyperglycaemia). To investigate the functional requirement of HSPA12A in protecting ischaemic brain injury, HSPA12A knockout mice (Hspa12a−/−) were generated. Hspa12a−/− mice exhibited an enlarged infarct volume and aggravated neurological deficits compared to their wild-type (WT) littermates after stroke. These aggravations in Hspa12a−/− mice were accompanied by more apoptosis and severer hippocampal morphological abnormalities in ischaemic hemispheres. Long-term examination revealed impaired motor function recovery and neurogenesis in stroke-affected Hspa12a−/− mice compared to stroke-affected WT controls. Significant reduced activation of GSK-3β/mTOR/p70S6K signalling was also observed in ischaemic hemispheres of Hspa12a−/− mice compared to WT controls. Administration with lithium (non-selective GSK-3β inhibitor) activated GSK-3β/mTOR/p70S6K signalling in stroke-affected Hspa12a−/− mice. Notably, lithium administration attenuated the HSPA12A deficiency-induced aggravation in infarct size, neurological deficits and neuronal death in Hspa12a−/− mice after stroke. Altogether, the findings suggest that HSPA12A expression encodes a critical novel prosurvival pathway during ischaemic stroke. We identified HSPA12A as a novel neuroprotective target for stroke patients.

Small heat shock proteins (hsp) have been implicated in mediation of classic preconditioning in the rabbit. Hsp27 is a terminal substrate of the p38 MAPK cascade. One and 2D gel electrophoresis and immunoblotting of cell fractions was used to determine p38 MAPK and hsp27 phosphorylation levels, respectively, during in vitro ischemia in control, calyculin A (Cal A)-treated (protein phosphatase inhibitor), SB203580-treated (p38MAPK inhibitor) and preconditioned (IPC) isolated adult rabbit cardiomyocytes. The dual phosphorylation of p38 MAPK was increased by early ischemia (30-60 min), after which there was a loss of total cytosolic p38 MAPK. The ischemic increase of p38 MAPK dual phosphorylation was enhanced by IPC. Cal A strongly activated dual phosphorylation of p38 MAPK in oxygenated cells and this was maintained into early ischemia. SB203580 inhibited the dual phosphorylation of p38 MAPK and attenuated the loss of total cytosolic p38 MAPK. In each protocol, ischemia translocated hsp27 from the cytosolic fraction to the cytoskeletal fraction at similar rates and extents. Hsp27 phosphorylation was quantitated as the fraction of diphosphorylated hsp27, based on IEF mobility shifts of hsp27 phosphorylation isoforms. In oxygenated control cells, cytosolic and cytoskeletal hsp27 was highly phosphorylated. After 90 min ischemia, cytoskeletal hsp27 was markedly dephosphorylaled. Cal A slightly increased control cytoskeletal hsp27 phosphorylation. During ischemic incubation, Cal A blocked ischemic dephosphorylation. SB203580 accelerated ischemic hsp27 dephosphorylation and injury. IPC insignificantly decreased the initial rate of ischemic dephosphorylation of hsp27, but not the extent of dephosphorylation in later ischemia. Phosphorylation is regulated by both kinase and phosphatase activities. IPC protection was not correlated with a significant increase in cytosolic or cytoskeletal hsp27 phosphorylation levels during prolonged (> 60-90 min) ischemia.