Michaela Potěšilová

Endonuclease G interacts with histone H2B and DNA topoisomerase II alpha during apoptosis

Apoptosis is a natural form of cell death involved in many physiological changes in the cell. Defects in the process of apoptosis can lead to serious diseases. During some apoptotic pathways, proteins apoptosis-inducing factor (AIF) and endonuclease G (EndoG) are released from the mitochondria and they translocate into the cell nuclei, where they probably participate in chromatin degradation together with other nuclear proteins. Exact mechanism of EndoG activity in cell nucleus is still unknown. Some interacting partners like flap endonuclease 1, DNase I, and exonuclease III were already suggested, but also other interacting partners were proposed. We conducted a living-cell confocal fluorescence microscopy followed by an image analysis of fluorescence resonance energy transfer to analyze the possibility of protein interactions of EndoG with histone H2B and human DNA topoisomerase II alpha (TOPO2a). Our results show that EndoG interacts with both these proteins during apoptotic cell death. Therefore, we can conclude that EndoG and TOPO2a may actively participate in apoptotic chromatin degradation. The possible existence of a degradation complex consisting of EndoG and TOPO2a and possibly other proteins like AIF and cyclophilin A have yet to be investigated.

Differential effects of insulin and dexamethasone on pulmonary surfactant-associated genes and proteins in A549 and H441 cells and lung tissue

In this study, the effects of insulin and dexamethasone on the expression and mRNA transcription of 4 pulmonary surfactant-associated proteins [surfactant protein (SFTP)A, SFTPB, SFTPC and SFTPD] were examined. The commercially available cell lines, A549 and H441, were used as acceptable models of lung surfactant-producing cells. Subsequently, the effects of insulin on the expression of surfactant-associated proteins were examined in patients with lung adenocarcinoma during lung resection. Our results demonstrated the inhibitory effects of insulin on the transcription of the SFTPB, SFTPC and SFTPD genes in H441 cells and the SFTPB gene in A549 cells. Treatment with insulin significantly decreased the protein expression of SFTPA1 and SFTPA2 in the H441 cells and that of proSFTPB in the A549 cells. Dexamethasone promoted the transcription of the SFTPB, SFTPC and SFTPD genes in the A549 and H441 cells and reduced the transcription of the SFTPA1 and SFTPA2 genes in the H441 cells (SFTPA mRNA expression was not detected in A549 cells). Furthermore, we demonstrated that the mRNA levels of the selected genes were significantly lower in the cell lines compared to the lung tissue. A549 and H441 cells represent similar cell types. Yet, in our experiments, these cells reacted differently to insulin and/or dexamethasone treatment, and the mRNA levels of their main protein products, surfactant-associated proteins, were significantly lower than those in real tissue. Therefore, the results obtained in this study challenge the suitability of A549 and H441 cells as models of type II pneumocytes and Clara cells, respectively. However, we successfully demonstrate the possibility of studying the effects of insulin on pulmonary surfactant-associated genes and proteins in patients with lung adenocarcinoma.

Intravenous insulin therapy during lung resection does not affect lung function or surfactant proteins

BackgroundThe surgical resection of lung disrupts glucose homeostasis and causes hyperglycemia, as in any other major surgery or critical illness. We performed a prospective study where we carefully lowered hyperglycemia by insulin administration during the surgery, and for the first time we monitored immediate insulin effects on lung physiology and gene transcription.MethodsThe levels of blood gases (pH, pCO2, pO2, HCO3-, HCO3- std, base excess, FiO2, and pO2/FiO2) were measured at the beginning of surgery, at the end of surgery, and two hours after. Samples of healthy lung tissue surrounding the tumour were obtained during the surgery, anonymized and sent for subsequent blinded qPCR analysis (mRNA levels of surfactant proteins A1, A2, B, C and D were measured). This study was done on a cohort of 64 patients who underwent lung resection. Patients were randomly divided, and half of them received insulin treatment during the surgery.ResultsWe demonstrated for the first time that insulin administered intravenously during lung resection does not affect levels of blood gases. Furthermore, it does not induce immediate changes in the expression of surfactant proteins.ConclusionAccording to our observations, short insulin treatment applied intravenously during resection does not affect the quality of breathing.