Project description:Glucocorticoids play central roles in the regulation of energy metabolism by shifting it toward catabolism, while AMPK is the master regulator of energy homeostasis, sensing energy depletion and stimulating pathways of increasing fuel uptake and saving on peripheral supplies. We showed here that AMPK regulates glucocorticoid actions on carbohydrate metabolism by targeting the glucocorticoid receptor (GR) and modifying transcription of glucocorticoid-responsive genes in a tissue- and promoter-specific fashion. Activation of AMPK in rats reversed glucocorticoid-induced hepatic steatosis and suppressed glucocorticoid-mediated stimulation of glucose metabolism. Transcriptomic analysis in the liver suggested marked overlaps between the AMPK and glucocorticoid signaling pathways directed mostly from AMPK to glucocorticoid actions. AMPK accomplishes this by phosphorylating serine 211 of the human GR indirectly through phosphorylation and consequent activation of p38 MAPK and by altering attraction of transcriptional coregulators to DNA-bound GR. In human peripheral mononuclear cells, AMPK mRNA expression positively correlated with that of glucocorticoid-responsive GILZ, which correlated also positively with the body mass index of subjects. These results indicate that the AMPK-mediated energy control system modulates glucocorticoid action at target tissues. Since increased action of glucocorticoids is associated with development of metabolic disorders, activation of AMPK could be a promising target for developing pharmacologic interventions to these pathologies. We tested the hypothesis by treateing rats with the synthetic glucocorticoid dexamethasone and the AMPK activator 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR).
Project description:Astrocytes contribute to the pathogenesis of multiple sclerosis (MS); however, the mechanisms underlying the regulation of astrocytic responses remain unknown. Here we report an exhaustive molecular and functional characterization of astrocyte reactivity following exposure to cerebrospinal fluid (CSF) from MS patients classified according to the degree of inflammatory activity. We showed that mouse astrocytes exposed to CSF from patients with high inflammatory activity (MS-High) exhibited a specific pro-inflammatory reactive state that was characterized by enhanced NF-kB signalling. This reactive astrocyte state conferred a dysfunctional response through an altered pro-inflammatory secretome that drove neuronal dysfunction and impaired synaptic plasticity. SerpinE1 was identified as a potential downstream mediator of the non-cell-autonomous toxic effect on neuronal function based on its significant up-regulation in secretomes from astrocytes exposed to CSF from MS-high patients. Further, we identified chitinase 3-like 1 as a potential upstream modulator of astrocyte reactivity via activation of NF-kB signalling based on its significantly increased levels in the CSF from MS-High patients. Taken together our findings indicate that the inflammatory microenvironment in the central nervous system of MS patients can induce specific reactive astrocyte states that trigger neuronal degeneration and may ultimately contribute to disease progression.
Project description:Failed regeneration of myelin around neuronal axons following central nervous system damage contributes to nerve dysfunction and clinical decline in various neurological conditions, for which there is an unmet therapeutic demand. Here, we show that interaction between glial cells – astrocytes and mature myelin-forming oligodendrocytes – is a critical determinant of remyelination. Using in vivo/ ex vivo/ in vitro rodent models and human brain lesion analyses, we discover that astrocytes support the survival of regenerating oligodendrocytes, via downregulation of the Nrf2 pathway associated with increased astrocytic cholesterol biosynthesis pathway activation. Remyelination fails following sustained astrocytic Nrf2 activation in focally-lesioned mice yet is restored by either cholesterol biosynthesis/efflux stimulation, or Nrf2 inhibition using the existing therapeutic Luteolin. We identify that astrocyte-oligodendrocyte interaction regulates remyelination, and reveal a drug strategy for central nervous system regeneration centred on targeting this interaction.
Project description:Dysregulation of kinase signaling pathways via mutations favors tumor cell survival and resistance to therapy and it is common in cancer. Here, we reveal a novel mechanism of post-translational regulation of kinase signaling and nuclear receptor activity via deubiquitination in acute leukemia. We observed that the ubiquitin specific protease 11 (USP11) is highly expressed in lymphoblastic leukemia and associates with poor prognosis in this disease. USP11 ablation inhibits leukemia growth in vitro and in vivo, sparing normal hematopoiesis and thymus development, suggesting that USP11 could be a therapeutic target in leukemia. USP11 forms a complex with USP7 to deubiquitinate the oncogenic lymphocyte cell-specific protein-tyrosine kinase (LCK). Deubiquitination of LCK controls its activity, thereby altering T cell receptor signaling. Impairment of LCK activity leads to increased expression of the glucocorticoid receptor transcript, culminating into transcriptional activation of pro-apoptotic target genes, and sensitizes cells to glucocorticoids in primary T cell leukemia patient samples. The transcriptional activation of pro-apoptotic target genes, such as BCL2L11, is orchestrated by the deubiquitinase activity and mediated via an increase in enhancer-promoter interaction intensity. Pharmacological inhibition of USP7 or genetic knockout of USP7 in combination treatment of glucocorticoid displayed improved anti-T-ALL efficacy in vivo. Our data unveil how dysregulated deubiquitination controls signaling pathways, leading to cancer cell survival and drug non-response, and suggest novel therapeutic combinations towards targeting leukemia.
Project description:Glucocorticoids play central roles in the regulation of energy metabolism by shifting it toward catabolism, while AMPK is the master regulator of energy homeostasis, sensing energy depletion and stimulating pathways of increasing fuel uptake and saving on peripheral supplies. We showed here that AMPK regulates glucocorticoid actions on carbohydrate metabolism by targeting the glucocorticoid receptor (GR) and modifying transcription of glucocorticoid-responsive genes in a tissue- and promoter-specific fashion. Activation of AMPK in rats reversed glucocorticoid-induced hepatic steatosis and suppressed glucocorticoid-mediated stimulation of glucose metabolism. Transcriptomic analysis in the liver suggested marked overlaps between the AMPK and glucocorticoid signaling pathways directed mostly from AMPK to glucocorticoid actions. AMPK accomplishes this by phosphorylating serine 211 of the human GR indirectly through phosphorylation and consequent activation of p38 MAPK and by altering attraction of transcriptional coregulators to DNA-bound GR. In human peripheral mononuclear cells, AMPK mRNA expression positively correlated with that of glucocorticoid-responsive GILZ, which correlated also positively with the body mass index of subjects. These results indicate that the AMPK-mediated energy control system modulates glucocorticoid action at target tissues. Since increased action of glucocorticoids is associated with development of metabolic disorders, activation of AMPK could be a promising target for developing pharmacologic interventions to these pathologies.
