Raquel López-Fontal

Specific Contribution of p19ARF to Nitric Oxide-Dependent Apoptosis

NO is an important bioactive molecule involved in a variety of physio- and pathological processes, including apoptosis induction. The proapoptotic activity of NO involves the rise in the tumor suppressor p53 and the accumulation and targeting of proapoptotic members of the Bcl-2 family, in particular Bax and the release of cytochrome c from the mitochondria. However, the exact mechanism by which NO induces p53 activation has not been fully elucidated. In this study, we describe that NO induces p19ARF through a transcriptional mechanism. This up-regulation of p19ARF activates p53, leading to apoptosis. The importance of p19ARF on NO-dependent apoptosis was revealed by the finding that various cell types from alternate reading frame-knockout mice exhibit a diminished response to NO-mediated apoptosis when compared with normal mice. Moreover, the biological relevance of alternative reading frame to p53 apoptosis was confirmed in in vivo models of apoptosis. Together, these results demonstrate that NO-dependent apoptosis requires, in part, the activation of p19ARF.

ILK mediates LPS-induced vascular adhesion receptor expression and subsequent leucocyte trans-endothelial migration

AIMS The inflammatory response to injurious agents is tightly regulated to avoid adverse consequences of inappropriate leucocyte accumulation or failed resolution. Lipopolysaccharide (LPS)-activated endothelium recruits leucocytes to the inflamed tissue through controlled expression of membrane-associated adhesion molecules. LPS responses in macrophages are known to be regulated by integrin-linked kinase (ILK); in this study, we investigated the role of ILK in the regulation of the LPS-elicited inflammatory response in endothelium. METHODS AND RESULTS This study was performed on immortalized mouse endothelial cells (EC) isolated from lung and coronary vasculature. Cells were thoroughly characterized and the role of ILK in the regulation of the LPS response was investigated by suppressing ILK expression using siRNA and shRNA technologies. Phenotypic and functional analyses confirmed that the immortalized cells behaved as true EC. LPS induced the expression of the inflammatory genes E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). ILK knockdown impaired LPS-mediated endothelial activation by preventing the induction of ICAM-1 and VCAM-1. Blockade of the LPS-induced response inhibited the inflammatory-related processes of firm adhesion and trans-endothelial migration of leucocytes. CONCLUSION ILK is involved in the expression of cell adhesion molecules by EC activated with the inflammatory stimulus LPS. This reduced expression modulates leucocyte adhesion to the endothelium and the extravasation process. This finding suggests ILK as a potential anti-inflammatory target for the development of vascular-specific treatments for inflammation-related diseases.

Supression of inflammatory responses by labdane-type diterpenoids

A series of 11 labdane-type diterpenoids (1-11) with various patterns of substitution were tested for potential anti-inflammatory activity. Of these compounds, 4 and 11 were selected to evaluate their influence on targets relevant to the regulation of the inflammatory response. These diterpenoids reduced the production of nitric oxide (NO), prostaglandin E2, and tumor necrosis factor-alpha in LPS-activated RAW 264.7 macrophages, with IC50 in the range 1-10 microM. Inhibition of these inflammatory mediators was related to inhibition of the expression of nitric oxide synthase-2 (NOS-2) and cyclooxygenase-2 (COX-2) at the transcriptional level, as determined by western-blot and RT-PCR. Examination of the effects of these diterpenoids on nuclear factor kappaB signaling showed that both compounds inhibit the phosphorylation of IkappaBalpha and IkappaBbeta, preventing their degradation and the nuclear translocation of the NF-kappaB p65 subunit. Inhibition of IKK activity was also observed. These derivatives displayed significant anti-inflammatory activity in vivo, suppressing mouse ear edema induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) and inhibiting myeloperoxidase activity, an index of neutrophil infiltration. The anti-inflammatory effects of these labdane diterpenoids, together with their low cell toxicity, suggest potential therapeutic applications in the regulation of the inflammatory response.

Mice Lacking Thyroid Hormone Receptor β Show Enhanced Apoptosis and Delayed Liver Commitment for Proliferation after Partial Hepatectomy

Background The role of thyroid hormones and their receptors (TR) during liver regeneration after partial hepatectomy (PH) was studied using genetic and pharmacologic approaches. Roles in liver regeneration have been suggested for T3, but there is no clear evidence distinguishing the contribution of increased amounts of T3 from the modulation by unoccupied TRs. Methodology/Principal Findings Mice lacking TRα1/TRβ or TRβ alone fully regenerated liver mass after PH, but showed delayed commitment to the initial round of hepatocyte proliferation and transient but intense apoptosis at 48h post-PH, affecting ∼30% of the remaining hepatocytes. Pharmacologically induced hypothyroidism yielded similar results. Loss of TR activity was associated with enhanced nitrosative stress in the liver remnant, due to an increase in the activity of the nitric oxide synthase (NOS) 2 and 3, caused by a transient decrease in the concentration of asymmetric dimethylarginine (ADMA), a potent NOS inhibitor. This decrease in the ADMA levels was due to the presence of a higher activity of dimethylarginineaminohydrolase-1 (DDAH-1) in the regenerating liver of animals lacking TRα1/TRβ or TRβ. DDAH-1 expression and activity was paralleled by the activity of FXR, a transcription factor involved in liver regeneration and up-regulated in the absence of TR. Conclusions/Significance We report that TRs are not required for liver regeneration; however, hypothyroid mice and TRβ– or TRα1/TRβ–deficient mice exhibit a delay in the restoration of liver mass, suggesting a specific role for TRβ in liver regeneration. Altered regenerative responses are related with a delay in the expression of cyclins D1 and E, and the occurrence of liver apoptosis in the absence of activated TRβ that can be prevented by administration of NOS inhibitors. Taken together, these results indicate that TRβ contributes significantly to the rapid initial round of hepatocyte proliferation following PH, and improves the survival of the regenerating liver at later times.

IL10 Released by a New Inflammation-regulated Lentiviral System Efficiently Attenuates Zymosan-induced Arthritis

Administration of anti-inflammatory cytokines is a common therapeutic strategy in chronic inflammatory diseases. Gene therapy is an efficient method for delivering therapeutic molecules to target cells. Expression of the cell adhesion molecule E-selectin (ESEL), which is expressed in the early stages of inflammation, is controlled by proinflammatory cytokines, making its promoter a good candidate for the design of inflammation-regulated gene therapy vectors. This study describes an ESEL promoter (ESELp)-based lentiviral vector (LV) that drives localized transgene expression during inflammation. Mouse matrigel plug assays with ESELp-transduced endothelial cells showed that systemic lipopolysaccharide (LPS) administration selectively induces ESELp-controlled luciferase expression in vivo. Inflammation-specific induction was confirmed in a mouse model of arthritis, showing that this LV is repeatedly induced early in acute inflammation episodes and is downregulated during remission. Moreover, the local acute inflammatory response in this animal model was efficiently blocked by expression of the anti-inflammatory cytokine interleukin-10 (IL10) driven by our LV system. This inflammation-regulated expression system has potential application in the design of new strategies for the local treatment of chronic inflammatory diseases such as cardiovascular and autoimmune diseases.

The Tumor Suppressor ARF Regulates Innate Immune Responses in Mice

The innate immune system is the first line of defense against invading organisms, and TLRs are the main sensors of microbial components, initiating signaling pathways that induce the production of proinflammatory cytokines and type I IFNs. An antiviral action for the tumor suppressor alternative reading frame (ARF) has been reported; however, the precise role of ARF in innate immunity is unknown. In this study, we show that ARF plays an important role in regulation of inflammatory responses. In peritoneal macrophages and bone marrow-derived macrophages from ARF-deficient animals, the induction of proinflammatory cytokines and chemokines by TLR ligands was severely impaired. The altered responses of ARF−/− cells to TLR ligands result from aberrant activation of intracellular signaling molecules including MAPKs, IκBα degradation, and NF-κB activation. Additionally, animals lacking ARF were resistant to LPS-induced endotoxic shock. This impaired activation of inflammation in ARF−/− mice was not restricted to TLRs, as it was also shown in response to non-TLR signaling pathways. Thus, ARF−/− mice were also unable to trigger a proper inflammatory response in experimental peritonitis or in 12-O-tetradecanoylphorbol-13-acetate–induced edema. Overexpression of ARF, but not its downstream target p53, rescued the ARF-deficient phenotype, increasing TLR4 levels and restoring inflammatory reaction. An increase in the E2F1 protein levels observed in ARF−/− macrophages at basal condition and after LPS stimulation may be involved in the impaired response in this system, as E2F1 has been described as an inflammatory suppressor. These results indicate that tumor suppressor ARF is a new regulator of inflammatory cell signaling.

Evaluation of labdane derivatives as potential anti-inflammatory agents

In the present study, a series of labdane derivatives (2-9) were prepared from labdanediol (1) and their potential as anti-inflammatory agents were evaluated on lipopolysaccharide (LPS)-treated RAW 264.7 macrophages. All compounds were able to inhibit LPS-induced nitric oxide (NO), although compounds 1, 2, 5, 8 and 9 exhibited the most potent effects with a range of IC(50) values of 5-15 microM. Similarly to the inhibitory effects on NO release, these labdane derivatives also inhibited prostaglandin E(2) (PGE(2)) production. However, analysis of cell viability demonstrated that effects on NO release and (PGE(2)) production of compounds 1, 8 and 9 were due to citotoxicity, whereas compound 2 and 5 did not show any effect in the survival of RAW 264.7 macrophages. In addition to these in vitro data, compound 5 also showed anti-inflammatory activity in vivo, when tested in mice. They prevented the extent of swelling in the TPA-induced ear edema model and inhibited MPO activity, showing similar potency to that of the widely used anti-inflammatory drug indomethacin. These results indicate that compound 2 and in particular compound 5 might be used for the design of new anti-inflammatory agents.

Critical role of the death receptor pathway in the antitumoral effects induced by hispanolone derivatives

Labdane diterpenoids have a broad spectrum of biological activities including antibacterial, antiviral and anti-inflammatory properties. However, little is known about their possible role in the apoptotic cell death machinery. Here, we report that hispanolone derivatives, a group of labdane diterpenoids, induce apoptosis in different tumor cell lines by activating caspase-8 with subsequent participation of mitochondrial signaling. Activation of caspase-8 by hispanolone derivatives was followed by a decrease in mitochondrial membrane potential, the release of apoptotic factors from mitochondria to the cytosol, and activation of caspases-9 and 3. Hispanolone derivatives also led to a time-dependent cleavage of Bid. Inhibition of caspase-8 abrogated these processes, suggesting that the death receptor pathway has a critical role in the apoptotic events induced by hispanolone derivatives. In addition, silencing death receptors with small interfering RNA s or pretreating cells with neutralizing antibodies to Fas ligand, tumor necrosis factor receptor 1 (TNF-R1), and TNF-α receptor 2 (TRAIL) inhibited diterpenoid-induced apoptosis, revealing it to be dependent on these death receptors. Interestingly, hispanolone derivatives had no effect on non-tumor cells. Consistently, in vivo bioluminescence imaging corroborates this antineoplasic effect, as hispanolone derivatives significantly decrease cancer growth in tumor xenograft assays. These data demostrate the antitumoral effects of hispanolone derivatives and provide relevant preclinical validation for the use of these compounds as potent therapeutic agents in cancer treatment.

8,9-dehydrohispanolone-15,16-lactol diterpene prevents LPS-triggered inflammatory responses by inhibiting endothelial activation

Endothelial activation contributes to lung inflammatory disorders by inducing leucocyte recruitment to pulmonary parenchyma. Consequently, vascular-targeted therapies constitute promising strategies for the treatment of inflammatory pathologies. In the present study, we evaluated the effect of 8,9-dehydrohispanolone-15,16-lactol diterpene (DT) on lung endothelium during inflammation. Lung endothelial cells pre-treated with DT and activated with lipopolysaccharide (LPS) or tumour necrosis factor-α (TNF-α) exhibited reduced expression of the pro-inflammatory cytokines Cxcl10, Ccl5 and Cxcl1, whereas the anti-inflammatory molecules IL1r2 and IL-10 were induced. Consistent with this result, DT pre-treatment inhibited nuclear factor κB (NF-κB) nuclear translocation, by interfering with IκBα phosphorylation, and consequently NF-κB transcriptional activity in endothelium activated by LPS or TNF-α. Furthermore, DT, probably through p38 signalling, induced transcriptional activation of genes containing activator protein 1 (AP-1)-binding elements. Inhibition of p38 prevented IL1r2 mRNA expression in endothelium incubated with DT alone or in combination with LPS or TNF-α. Accordingly, conditioned medium (CM) from these cells failed to stimulate leucocytes as measured by a reduction in adhesive ability of the leucocyte cell line J774 to fibronectin (FN). Additionally, DT reduced the expression of the endothelial adhesion molecules E-selectin, vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) after activation. Similarly, expression of VCAM-1 and ICAM-1 molecules on the lung endothelial layer of C57/BL6 mice pre-treated with DT and challenged with LPS were unchanged. Finally, inhibition of vascular adhesion molecule expression by DT decreased the interaction of J774 cells with lung endothelial cells in an inflammatory environment. Our findings establish DT as a novel endothelial inhibitor for the treatment of inflammatory-related diseases triggered by Gram-negative bacteria or by the associated cytokine TNF-α.