Expression of microRNAs miR-126, miR-133b and miR-221 associated with apoptosis in rats submitted to focal cerebral ischemia and physical exercise / Expresión de microRNAs miR-126, miR-133b y miR-221 asociados a apoptosis en ratas sometidas a isquemia cerebral focal y ejercicio físico

SUMMARY: Stroke is one of the main causes of death and disability worldwide. The great impact on the quality of life of the population and on the health system justifies that we seek relevant alternatives to reduce the incidence and improve the treatment and recovery of patients affected by this disease. Physical exercise appears as an important tool in this scenario, being already pointed out as a possible therapeutic approach for the prevention of non-contagious chronic diseases. In this context, biomarkers such as miRNAs that respond to physical exercise and are directly related to several epigenetic mechanisms appear. Therefore, explaining the molecular mechanisms involved during physical exercise will lead to a better understanding of each stimulus and the dose to be used to better respond to each situation, thus being a promising approach for the evolution of prescription and control of training and processes recovery from various diseases, including stroke. Forty-eight Wistar rats were used, divided into four experimental groups: control group, ischemia group, physical exercise group and exercise + ischemia group. Real-time PCR methodology was used to analyze the expression of miRNAs: miR-126, miR-133b and miR-221. In our study we observed a significant difference in the expression of miR- 221 between the control group and the others groups. However, microRNAs: miR-126 and miR-133b do not show significant differences in expression between groups.

El ictus es una de las principales causas de muerte y discapacidad en todo el mundo. El gran impacto en la calidad de vida de la población y en el sistema de salud justifica buscar alternativas pertinentes para reducir la incidencia y mejorar el tratamiento y recuperación de los pacientes afectados por esta enfermedad. El ejercicio físico aparece como una herramienta importante en este escenario, siendo ya señalado como un posible abordaje terapéutico para la prevención de enfermedades crónicas no contagiosas. En este contexto, aparecen biomarcadores como los miRNAs que responden al ejercicio físico y están directamente relacionados con varios mecanismos epigenéticos. Por lo tanto, explicar los mecanismos moleculares involucrados durante el ejercicio físico conducirá a una mejor comprensión de cada estímulo y la dosis a utilizar para responder mejor a cada situación, siendo así un enfoque prometedor para la evolución de la prescripción, el control del entrenamiento y los procesos de recuperación de diversas enfermedades, incluido el accidente cerebrovascular. Se utilizaron cuarenta y ocho ratas Wistar, divididas en cuatro grupos experimentales: grupo control, grupo isquemia, grupo ejercicio físico y grupo ejercicio + isquemia. Se utilizó la metodología de PCR en tiempo real para analizar la expresión de miRNAs: miR-126, miR-133b y miR-221. En nuestro estudio observamos una diferencia significativa en la expresión de miR-221 entre el grupo control y los demás grupos. Sin embargo, los microARN: miR-126 y miR-133b no mostraron diferencias significativas en la expresión entre grupos.

Expression of microRNAs miR-21 and miR-326 associated with HIF-1α regulation in neurospheres of glioblastoma submitted to ionizing radiation treatment.

Background: Glioblastoma is an incurable neoplasm. Its hypoxia mechanism associated with cancer stem cells (CSCs) demonstrates hypoxia-inducible factor 1α (HIF-1α) expression regulation, which is directly related to tumor malignancy. The aim of this study was to identify a possible tumor malignancy signature associated with regulation of HIF-1α by microRNAs miR-21 and miR-326 in the subpopulation of tumor stem cells which were irradiated by ion in primary culture of patients diagnosed with glioblastoma. Materials and methods: We used cellular cultures from surgery biopsies of ten patients with glioblastoma. MicroRNA expressions were analyzed through real-time polymerase chain reaction (PCR ) and correlated with mortality and recurrence. The ROC curve displayed the cutoff point of the respective microRNAs in relation to the clinical prognosis, separating them by group. Results: The miR-21 addressed high level of expression in the irradiated neurosphere group (p = 0.0028). However, miR-21 was not associated with recurrence and mortality. miR-326 can be associated with tumoral recurrence (p = 0.032) in both groups; every 0.5 units of miR-326 increased the chances of recurrence by 1,024 (2.4%). Conclusion: The high expression of miR-21 in the irradiated group suggests its role in the regulation of HIF-1α and in the radioresistant neurospheres. miR-326 increased the chances of recurrence in both groups, also demonstrating that positive regulation from miR-326 does not depend on ionizing radiation treatment.

microRNA-181d associated with the methylation status of the MGMT gene in Glioblastoma multiforme cancer stem cells submitted to treatments with ionizing radiation and temozolomide.

Despite the increased understanding of the oncological mechanisms underlying Glioblastoma multiforme (GBM) pathophysiology, and recent advances in therapeutic strategies such as maximal surgical resection and post-operative radiotherapy with concomitant and adjuvant temozolomide chemotherapy, the prognosis for patients with brain tumors remains limited. Evidences indicate that the assessment of DNA methylation status in cancer stem cells would allow identifying molecules expressed in these cells, to lead to targeted elimination of this critical population from brain tumors, making the glioblastoma treatment more effective. This study aimed to analyze the role of microRNA-181d associated with the methylation status of the O6-methylguanine methyl transferase (MGMT) gene in Glioblastoma multiforme cancer stem cells subjected to treatment with temozolomide and ionizing radiation. Such responses were analyzed in terms of cell survival, evaluation of the MGMT gene methylation status by MS-HRM (Methylation-Sensitive High Resolution Melting), and analysis of miRNA-181d and MGMT gene expression by relative quantification of mRNA levels in cancer stem cells subjected to treatment with temozolomide and ionizing radiation, isolated or combined. We showed that ionizing radiation and temozolomide reduced the viability of cancer stem cells from GBM patients, as well as modified MGMT gene and miRNA-181d expression in cancer stem cells, suggesting that miRNA-181d interferes in the glioblastoma cancer stem cell response to treatment with temozolomide and ionizing radiation.