Nuclear translocation of cytochrome c during apoptosis

Release of cytochrome c from mitochondria is a major event during apoptosis. Released cytochrome c has been shown to activate caspase-dependent apoptotic signals. In this report, we provide evidence for a novel role of cytochrome c in caspase-independent nuclear apoptosis. We showed that cytochrome c, released from mitochondria upon apoptosis induction, gradually accumulates in the nucleus as evidenced by both immunofluorescence and subcellular fractionation. Parallel to nuclear accumulation of cytochrome c, acetylated histone H2A, but not unmodified H2A, was released from the nucleus to the cytoplasm. Addition of purified cytochrome c to isolated nuclei recapitulated the preferential release of acetylated, but not deacetylated, histone H2A. Cytochrome c was also found to induce chromatin condensation. These results suggest that the nuclear accumulation of cytochrome c may be directly involved in the remodeling of chromatin. Our results provide evidence of a novel role for cytochrome c in inducing nuclear apoptosis.

Influence of Egr-1 in cardiac tissue-derived mesenchymal stem cells in response to glucose variations

Mesenchymal stem cells (MSCs) represent a promising cell population for cell therapy and regenerative medicine applications. However, how variations in glucose are perceived by MSC pool is still unclear. Since, glucose metabolism is cell type and tissue dependent, this must be considered when MSCs are derived from alternative sources such as the heart. The zinc finger transcription factor Egr-1 is an important early response gene, likely to play a key role in the glucose-induced response. Our aim was to investigate how short-term changes in in vitro glucose concentrations affect multipotent cardiac tissue-derived MSCs (cMSCs) in a mouse model of Egr-1 KO (Egr-1-/-). Results showed that loss of Egr-1 does not significantly influence cMSC proliferation. In contrast, responses to glucose variations were observed in wt but not in Egr-1 -/- cMSCs by clonogenic assay. Phenotype analysis by RT-PCR showed that cMSCs Egr-1-/- lost the ability to regulate the glucose transporters GLUT-1 and GLUT-4 and, as expected, the Egr-1 target genes VEGF, TGFβ-1, and p300. Acetylated protein levels of H3 histone were impaired in Egr-1-/- compared to wt cMSCs. We propose that Egr-1 acts as immediate glucose biological sensor in cMSCs after a short period of stimuli, likely inducing epigenetic modifications. © 2014 Daniela Bastianelli et al.

An investigation into the effects of metabolic disturbance on monocyte inflammatory response and regulation

The presence of chronic inflammation is associated with increased nutrient availability during obesity or type 2 diabetes which contributes to the development of complications such as atherosclerosis, stroke and myocardial infarction. The link between increased nutrient availability and inflammatory response remains poorly understood. The functioning of monocytes, the primary instigators of the inflammatory response was assessed in response to obesity and increased glucose availability. Monocyte microRNA expression was assessed in obese individuals prior to and up to one year after bariatric surgery. A number of microRNAs were identified to be dysregulated in obesity, some of which have previously been linked to the regulation of monocyte inflammatory responses including the microRNAs 146a-5p and 424-5p. Weight loss in response to bariatric surgery lead to the reversal of microRNA changes towards control values. In vitro treatments of THP-1 monocytes with high concentrations of D-glucose resulted in decreased intracellular NAD+:NADH ratio, decreased SIRT1 deacetylase activity and increased P65 acetylation. However the increased osmotic concentration inhibited LPS induced inflammatory response and TNFα mRNA expression. In vitro treatment of primary human monocytes with increased concentrations of D-glucose resulted in increased secretion of a number of inflammatory cytokines and increased expression of TNFα mRNA. Treatment also resulted in decreased intracellular NAD+:NADH ratio and increased binding of acetylated P65 to the TNFα promoter region. In vitro treatments of primary monocytes also replicated the altered expression of the microRNAs 146a-5p and miR-424-5p, as seen in obese individuals. In conclusion a number of changes in monocyte function were observed in response to obesity and treatment with high concentrations of D-glucose. These may lead to the dysregulation of inflammatory responses contributing to the development of co-morbidities.