Different addictive drug exposure induces selective alterations of the Endogenous Opioid System : modulation of transcription and epigenetic mechanisms

Drug addiction manifests clinically as compulsive drug seeking, and cravings that can persist and recur even after extended periods of abstinence. The fundamental principle that unites addictive drugs is that each one enhances synaptic DA by means that dissociate it from normal behavioral control, so that they act to reinforce their own acquisition. Our attention has focused on the study of phenomena associated with the consumption of alcohol and heroin. Alcohol has long been considered an unspecific pharmacological agent, recent molecular pharmacology studies have shown that acts on different primary targets. Through gene expression studies conducted recently it has been shown that the classical opioid receptors are differently involved in the consumption of ethanol and, furthermore, the system nociceptin / NOP, included in the family of endogenous opioid system, and both appear able to play a key role in the initiation of alcohol use in rodents. What emerges is that manipulation of the opioid system, nociceptin, may be useful in the treatment of addictions and there are several evidences that support the use of this strategy. The linkage between gene expression alterations and epigenetic modulation in PDYN and PNOC promoters following alcohol treatment confirm the possible chromatin remodeling mechanism already proposed for alcoholism. In the second part of present study, we also investigated alterations in signaling molecules directly associated with MAPK pathway in a unique collection of postmortem brains from heroin abusers. The interest was focused on understanding the effects that prolonged exposure of heroin can cause in an individual, over the entire MAPK cascade and consequently on the transcription factor ELK1, which is regulated by this pathway. We have shown that the activation of ERK1/2 resulting in Elk-1 phosphorylation in striatal neurons supporting the hypothesis that prolonged exposure to substance abuse causes a dysregulation of MAPK pathway.

Streptococcus agalactiae adapts to glucose stress conditions by modulating gene expression profile

Diabetes mellitus is considered a risk factor for Group B Streptococcus (GBS) infections. Typically, this pathology is associated to high glucose levels in the bloodstream. Although clinical evidences support this notion, the physiological mechanisms underlying GBS adaptation to such conditions are not yet defined. In the attempt to address this issue, we performed comparative global gene expression analysis of GBS grown under glucose-stress conditions and observed that a number of metabolic and virulence genes was differentially regulated. Of importance, we also demonstrated that by knocking-out the csrRS locus the transcription profile of GBS grown in high-glucose conditions was profoundly affected, with more than a third of glucose-dependent genes, including the virulence factor bibA, found to be controlled by this two-component system. Furthermore, in vitro molecular analysis showed that CsrR specifically binds to the bibA promoter and the phosphorilation increases the affinity of the regulator to this promoter region. Moreover, we demonstrated that CsrR acts as a repressor of bibA expression by binding to its promoter in vivo. In conclusion, this work by elucidating both the response of GBS to pathological glucose conditions and the underlined molecular mechanisms will set the basis for a better understanding of GBS pathogenesis.

Role of the Transcription Factor Sox2 in the Osteogenic Lineage

The Sox2 transcription factor is modified by sumoylation at the K247 position although the addition of SUMO1 and Pias1 promotes the sumoylation of Sox2 at the additional K123 site. The role of sumoylation on Sox2 biological functions was analyzed by comparing the activity of WT and sumoylation mutants on the transcription of the FGF4 gene in HeLa cells and on the downregulation of the Wnt pathwayvin 293T cells. When SUMO1 and PIAS1 promote the sumoylation of WT Sox2, the transcriptional activity of the FGF4 promoter is inhibited showing that Sox2 sumoylation is necessary for the repression function. However, there is no effect of Sox2 sumoylation on β-Catenin activity. Since we were interested in osteoblast differentiation we set up an inducible system for Sox2 in primary osteoblasts. Following Sox2 doxycycline induction, 158 genes were differentially expressed: 120 up-regulated and 38 down-regulated. We annotated as direct Sox2 targets a number of genes involved in osteoblast biology and we further analyzed 3 of them involved in the BMP pathway. The results show that Sox2 regulates the BMP pathway without affecting SMAD phosphorylation, and that Sox2 sumoylation is not necessary for this function. We also found that genes involved in the Hippo pathway were direct Sox2 targets. As the Hippo pathway is activated by Sox2 and Sox2 interacts with the NF2 promoter, we checked the effect of Sox2 on the expression of NF2. We showed that Sox2 down-regulates the transcriptional activity of the NF2 promoter, allowing the transcription of the YAP/TEAD genes in osteoblasts, thus acting as an upstream regulator of the Hippo pathway. We conclude that Sox2 induction in osteoblasts triggers FGF dependent inhibition of the BMP, Wnt and Hippo pathways.