Carlo Gaetano

Functional and morphological recovery of dystrophic muscles in mice treated with deacetylase inhibitors

Pharmacological interventions that increase myofiber size counter the functional decline of dystrophic muscles. We show that deacetylase inhibitors increase the size of myofibers in dystrophin-deficient (MDX) and α-sarcoglycan (α-SG)–deficient mice by inducing the expression of the myostatin antagonist follistatin in satellite cells. Deacetylase inhibitor treatment conferred on dystrophic muscles resistance to contraction-coupled degeneration and alleviated both morphological and functional consequences of the primary genetic defect. These results provide a rationale for using deacetylase inhibitors in the pharmacological therapy of muscular dystrophies.

Common micro-RNA signature in skeletal muscle damage and regeneration induced by Duchenne muscular dystrophy and acute ischemia

The aim of this work was to identify micro‐RNAs (miRNAs) involved in the pathological pathways activated in skeletal muscle damage and regeneration by both dystrophin absence and acute ischemia. Eleven miRNAs were deregulated both in MDX mice and in Duchenne muscular dystrophy patients (DMD signature). Therapeutic interventions ameliorating the mdx‐phenotype rescued DMD‐signature alterations. The significance of DMD‐signature changes was characterized using a damage/regeneration mouse model of hind‐limb ischemia and newborn mice. According to their expression, DMD‐signature miRNAs were divided into 3 classes. 1) Regeneration miRNAs, miR‐31, miR‐34c, miR‐206, miR‐335, miR‐449, and miR‐494, which were induced in MDX mice and in DMD patients, but also in newborn mice and in newly formed myofibers during postischemic regeneration. Notably, miR‐206, miR‐34c, and miR‐335 were up‐regulated following myoblast differentiation in vitro. 2) Degenerative‐miRNAs, miR‐1, miR‐29c, and miR‐135a, that were down‐modulated in MDX mice, in DMD patients, in the degenerative phase of the ischemia response, and in newborn mice. Their down‐modulation was linked to myofiber loss and fibrosis. 3) Inflammatory miRNAs, miR‐222 and miR‐223, which were expressed in damaged muscle areas, and their expression correlated with the presence of infiltrating inflammatory cells. These findings show an important role of miRNAs in physiopathological pathways regulating muscle response to damage and regeneration.—Greco, S., De Simone, M., Colussi, C., Zaccagnini, G., Fasanaro, P., Pescatori, M., Cardani, R., Perbellini, R., Isaia, E., Sale, P., Meola, G., Capogrossi, M. C., Gaetano, C., Martelli, F. Common micro‐RNA signature in skeletal muscle damage and regeneration induced by Duchenne muscular dystrophy and acute ischemia. FASEB J. 23, 3335–3346 (2009). www.fasebj.org

HDAC2 blockade by nitric oxide and histone deacetylase inhibitors reveals a common target in Duchenne muscular dystrophy treatment

The overlapping histological and biochemical features underlying the beneficial effect of deacetylase inhibitors and NO donors in dystrophic muscles suggest an unanticipated molecular link among dystrophin, NO signaling, and the histone deacetylases (HDACs). Higher global deacetylase activity and selective increased expression of the class I histone deacetylase HDAC2 were detected in muscles of dystrophin-deficient MDX mice. In vitro and in vivo siRNA-mediated down-regulation of HDAC2 in dystrophic muscles was sufficient to replicate the morphological and functional benefits observed with deacetylase inhibitors and NO donors. We found that restoration of NO signaling in vivo, by adenoviral-mediated expression of a constitutively active endothelial NOS mutant in MDX muscles, and in vitro, by exposing MDX-derived satellite cells to NO donors, resulted in HDAC2 blockade by cysteine S-nitrosylation. These data reveal a special contribution of HDAC2 in the pathogenesis of Duchenne muscular dystrophy and indicate that HDAC2 inhibition by NO-dependent S-nitrosylation is important for the therapeutic response to NO donors in MDX mice. They also define a common target for independent pharmacological interventions in the treatment of Duchenne muscular dystrophy.

BRAF silencing by short hairpin RNA or chemical blockade by PLX4032 leads to different responses in melanoma and thyroid carcinoma cells

BRAF-activating mutations have been reported in several types of cancer, including melanoma (∼70% of cases), thyroid (30-70%), ovarian (15-30%), and colorectal cancer (5-20%). Mutant BRAF has constitutive kinase activity and causes hyperactivation of the mitogen-activated protein kinase pathway. BRAF silencing induces regression of melanoma xenografts, indicating the essential role of BRAF for cell survival. We set up an inducible short hairpin RNA system to compare the role of oncogenic BRAF in thyroid carcinoma versus melanoma cells. Although BRAF knockdown led to apoptosis in the melanoma cell line A375, the anaplastic thyroid carcinoma cell ARO underwent growth arrest upon silencing, with little or no cell death. Reexpression of the thyroid differentiation marker, sodium iodide symporter, was induced after long-term silencing. The different outcome of BRAF down-regulation in the two cell lines was associated with an opposite regulation of p21CIP1/WAF1 expression levels in response to the block of the BRAF mitogenic signal. These results were confirmed using a specific BRAF small-molecule inhibitor, PLX4032. Restoration of p21CIP1/WAF1 expression rescued melanoma cells from death. Altogether, our data indicate that oncogenic BRAF inhibition can have a different effect on cell fate depending on the cellular type. Furthermore, we suggest that a BRAF-independent mechanism of cell survival exists in anaplastic thyroid cancer cells. (Mol Cancer Res 2008;6(5):751–9)

Epigenetic Histone Modification and Cardiovascular Lineage Programming in Mouse Embryonic Stem Cells Exposed to Laminar Shear Stress

Experimental evidence indicates that shear stress (SS) exerts a morphogenetic function during cardiac development of mouse and zebrafish embryos. However, the molecular basis for this effect is still elusive. Our previous work described that in adult endothelial cells, SS regulates gene expression by inducing epigenetic modification of histones and activation of transcription complexes bearing acetyltransferase activity. In this study, we evaluated whether SS treatment could epigenetically modify histones and influence cell differentiation in mouse embryonic stem (ES) cells. Cells were exposed to a laminar SS of 10 dyne per cm2/s−1, or kept in static conditions in the presence or absence of the histone deacetylase inhibitor trichostatin A (TSA). These experiments revealed that SS enhanced lysine acetylation of histone H3 at position 14 (K14), as well as serine phosphorylation at position 10 (S10) and lysine methylation at position 79 (K79), and cooperated with TSA, inducing acetylation of histone H4 and phosphoacetylation of S10 and K14 of histone H3. In addition, ES cells exposed to SS strongly activated transcription from the vascular endothelial growth factor (VEGF) receptor 2 promoter. This effect was paralleled by an early induction of cardiovascular markers, including smooth muscle actin, smooth muscle protein 22-&agr;, platelet-endothelial cell adhesion molecule-1, VEGF receptor 2, myocyte enhancer factor-2C (MEF2C), and &agr;-sarcomeric actin. In this condition, transcription factors MEF2C and Sma/MAD homolog protein 4 could be isolated from SS-treated ES cells complexed with the cAMP response element-binding protein acetyltransferase. These results provide molecular basis for the SS-dependent cardiovascular commitment of mouse ES cells and suggest that laminar flow may be successfully applied for the in vitro production of cardiovascular precursors.

Oxidative Stress and Epigenetic Regulation in Ageing and Age-Related Diseases

Recent statistics indicate that the human population is ageing rapidly. Healthy, but also diseased, elderly people are increasing. This trend is particularly evident in Western countries, where healthier living conditions and better cures are available. To understand the process leading to age-associated alterations is, therefore, of the highest relevance for the development of new treatments for age-associated diseases, such as cancer, diabetes, Alzheimer and cardiovascular accidents. Mechanistically, it is well accepted that the accumulation of intracellular damage determined by reactive oxygen species (ROS) might orchestrate the progressive loss of control over biological homeostasis and the functional impairment typical of aged tissues. Here, we review how epigenetics takes part in the control of stress stimuli and the mechanisms of ageing physiology and physiopathology. Alteration of epigenetic enzyme activity, histone modifications and DNA-methylation is, in fact, typically associated with the ageing process. Specifically, ageing presents peculiar epigenetic markers that, taken altogether, form the still ill-defined “ageing epigenome”. The comprehension of mechanisms and pathways leading to epigenetic modifications associated with ageing may help the development of anti-ageing therapies.

Shear Stress–Mediated Chromatin Remodeling Provides Molecular Basis for Flow-Dependent Regulation of Gene Expression

&NA; Shear stress (SS), the tangential component of hemodynamic forces, modulates the expression of several genes in endothelial cells. However, no information is available about its effect on chromatin structure, which plays a key role in gene transcription. In this study, a link between SS and chromatin remodeling was established in human umbilical vein endothelial cells (HUVECs). HUVECs were exposed to SS of 10 dyne/cm2 per second, in the presence or absence of the histone deacetylase inhibitor trichostatin A, and assayed for histone H3 and histone H4 modifications. SS induced histone H3 serine phosphorylation at position 10 (S10) and lysine acetylation at position 14 (K14) but required trichostatin A to induce H3 phosphoacetylation and H4 acetylation. The phosphatidylinositol 3‐kinase inhibitor wortmannin and the mitogen‐activated protein kinase inhibitor PD98059 decreased SS‐dependent histone H3 phosphorylation, without affecting its acetylation; the p38 inhibitor SB203580 reduced both H3 phosphorylation and acetylation, whereas the protein kinase A inhibitor PKI‐tide reduced histone H3 acetylation. Remarkably, the abrogation of histone acetylation inhibited SS‐dependent c‐fos expression. SS also activated ribosomal S6 kinase‐2 and mitogenand stress‐activated kinase‐1 protein kinases and promoted the formation of a cAMP‐responsive element‐binding protein (CREB)/CREB‐binding protein complex, providing the molecular basis for the increase in histone acetyltransferase activity observed in HUVECs exposed to SS. Finally, the effect of SS on chromatin remodeling was examined. In HUVECs exposed to SS, chromatin within c‐fos and c‐jun promoters was specifically immunoprecipitated by an antibody against acetylated histone H3 on K14. These results indicate that SS induces posttransduction modifications of histones; this is an early step toward the flow‐dependent regulation of gene expression. (Circ Res. 2003;93:155‐161.)

p66ShcA Modulates Tissue Response to Hindlimb Ischemia

Background—Oxidative stress plays a pivotal role in ischemia and ischemia/reperfusion injury. Because p66ShcA-null (p66ShcA−/−) mice exhibit both lower levels of intracellular reactive oxygen species and increased resistance to cell death induced by oxidative stress, we investigated whether tissue damage that follows acute ischemia or ischemia/reperfusion was altered in p66ShcA−/− mice. Methods and Results—Unilateral hindlimb ischemia was induced by femoral artery dissection, and ischemia/reperfusion was induced with an elastic tourniquet. Both procedures caused similar changes in blood perfusion in p66ShcA wild-type (p66ShcAwt) and p66ShcA−/− mice. However, significant differences in tissue damage were found: p66ShcAwt mice displayed marked capillary density decrease and muscle fiber necrosis. In contrast, in p66ShcA−/− mice, minimal capillary density decrease and myofiber death were present. When apoptosis after ischemia was assayed, significantly lower levels of apoptotic endothelial cells and myofibers were found in p66ShcA−/− mice. In agreement with these data, both satellite muscle cells and endothelial cells isolated from p66ShcA−/− mice were resistant to apoptosis induced by simulated ischemia in vitro. Lower apoptosis levels after ischemia in p66ShcA−/− cells correlated with decreased levels of oxidative stress both in vivo and in vitro. Conclusions—p66ShcA plays a crucial role in the cell death pathways activated by acute ischemia and ischemia/reperfusion, indicating p66ShcA as a potential therapeutic target for prevention and treatment of ischemic tissue damage.

Endothelial NOS, estrogen receptor β, and HIFs cooperate in the activation of a prognostic transcriptional pattern in aggressive human prostate cancer

The identification of biomarkers that distinguish between aggressive and indolent forms of prostate cancer (PCa) is crucial for diagnosis and treatment. In this study, we used cultured cells derived from prostate tissue from patients with PCa to define a molecular mechanism underlying the most aggressive form of PCa that involves the functional activation of eNOS and HIFs in association with estrogen receptor beta (ERbeta). Cells from patients with poor prognosis exhibited a constitutively hypoxic phenotype and increased NO production. Upon estrogen treatment, formation of ERbeta/eNOS, ERbeta/HIF-1alpha, or ERbeta/HIF-2alpha combinatorial complexes led to chromatin remodeling and transcriptional induction of prognostic genes. Tissue microarray analysis, using an independent cohort of patients, established a hierarchical predictive power for these proteins, with expression of eNOS plus ERbeta and nuclear eNOS plus HIF-2alpha being the most relevant indicators of adverse clinical outcome. Genetic or pharmacologic modulation of eNOS expression and activity resulted in reciprocal conversion of the transcriptional signature in cells from patients with bad or good outcome, respectively, highlighting the relevance of eNOS in PCa progression. Our work has considerable clinical relevance, since it may enable the earlier diagnosis of aggressive PCa through routine biopsy assessment of eNOS, ERbeta, and HIF-2alpha expression. Furthermore, proposing eNOS as a therapeutic target fosters innovative therapies for PCa with NO inhibitors, which are employed in preclinical trials in non-oncological diseases.

Shear Stress Downregulation of Platelet-Derived Growth Factor Receptor-β and Matrix Metalloprotease-2 Is Associated With Inhibition of Smooth Muscle Cell Invasion and Migration

BACKGROUND After endovascular injury, smooth muscle cells (SMCs) may be exposed to hemodynamic shear stress (SS), and these forces modulate neointima accumulation. The effect of SS on SMC migration and invasion is unknown, and it was examined in the present study. METHODS AND RESULTS Bovine aortic SMCs were exposed to laminar SS of 12 dyne/cm(2) for 3 (SS3) or 15 (SS15) hours; control (C3 and C15) SMCs were kept under static conditions. Platelet-derived growth factor (PDGF)-BB-directed SMC migration and invasion were evaluated by a modified Boyden chamber assay with filters coated with either gelatin or reconstituted basement membrane proteins (Matrigel), respectively. SS15 inhibited both SMC migration and invasion (P<0.0001). There was no significant difference between SS3 and C3 cells. Media conditioned with SS15 cells exhibited a reduction in matrix metalloprotease-2 (MMP-2) by zymography and Western analysis. Northern blot analysis revealed no effect of SS15 on MMP-2 mRNA. In contrast, SS15 decreased MMP-2 activator and membrane-type MMP (MT-MMP or MMP-14) mRNA and protein. Furthermore, SS15 decreased PDGF receptor-beta (PDGF-Rbeta) mRNA and protein (P<0.05), and the SS-dependent decrease in PDGF-BB-directed cell migration was rescued by overexpressing PDGF-Rbeta. CONCLUSIONS SS inhibits SMC migration and invasion via diminished PDGF-Rbeta expression. This effect of SS is associated with decreased MMP-2 secretion and MT-MMP downregulation.