Ciliary neurotrophic factor infused intracerebroventricularly shows reduced catabolic effects when linked to the TAT protein transduction domain

Toxic effects of phytol and retinol on human glioblastoma cells are associated with modulation of cholesterol and fatty acid biosynthetic pathways

Glioblastoma (GBM) is the most common primary brain tumor. Genetic mutations may reprogram the metabolism of neoplastic cells. Particularly, alterations in cholesterol and fatty acid biosynthetic pathways may favor biomass synthesis and resistance to therapy. Therefore, compounds that interfere with those pathways, such as phytol (PHY) and retinol (RET), may be appropriate for cytotoxic approaches. We tested the effect of PHY or RET on the viability of human GBM cell lines (U87MG, A172 and T98G). Since the compounds showed a dose-dependent cytotoxic effect, additional analyses were performed with IC₅₀ values. Transcriptome analyses of A172 cells treated with PHY IC₅₀ or RET IC₅₀ revealed down-regulated genes involved in cholesterol and/or fatty acid biosynthetic pathways. Thus, we investigated the expression of proteins required for cholesterol and/or fatty acid synthesis after treating all lineages with PHY IC₅₀ or RET IC₅₀ and comparing them with controls. Sterol regulatory element-binding protein 1 (SREBP-1) expression was reduced by PHY in U87 and T98G cells. However, fatty acid synthase (FAS) protein expression, which is regulated by SREBP-1, was down-regulated in all lineages after both treatments. Moreover, farnesyl-diphosphate farnesyltransferase (FDFT1) levels, a protein associated with cholesterol synthesis, were reduced in all lineages by PHY and in U87MG and A172 cells by RET. Our results suggest that SREBP-1, FAS and FDFT1 are potential target(s) for future in vivo approaches against GBM and support the use of inhibitors of their synthesis, including PHY and RET, for such approaches.

Ciliary neurotrophic factor (CNTF) delivery to retina: an overview of current research advancements

The intraocular administration of the ciliary neurotrophic factor (CNTF) has been found to attenuate the photoreceptor degeneration and preserve retinal functions in the animal research models of the inherited or induced retinal disease. Studies with the aim of CNTF transfer to the posterior segment inside the eye have been directed to determine the best method for its administration. An ideal delivery method would overcome the eye drug elimination mechanisms or barriers and provide the sustained release of the CNTF into retina in the safest fashion with the minimum harm to the quality of life. This review focuses on the present state of CNTF delivery to retina, also provides an overview of available technologies and their challenges.

In vitro neuroprotective effects of ciliary neurotrophic factor on dorsal root ganglion neurons with glutamate-induced neurotoxicity

Ciliary neurotrophic factor has neuroprotective effects mediated through signal transducer and Janus kinase (JAK) 2/activator of transcription 3 (STAT3) and phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways. Whether ciliary neurotrophic factor is neuroprotective for glutamate-induced excitotoxicity of dorsal root ganglion neurons is poorly understood. In the present study, the in vitro neuroprotective effects of ciliary neurotrophic factor against glutamate-induced excitotoxicity were determined in a primary culture of dorsal root ganglion neurons from Wistar rat embryos at embryonic day 15. Whether the JAK2/STAT3 and PI3K/Akt signaling pathways were related to the protective effects of ciliary neurotrophic factor was also determined. Glutamate exposure inhibited neurite outgrowth, cell viability, and growth-associated protein 43 expression and promoted apoptotic neuronal cell death, all of which were reversed by the administration of exogenous ciliary neurotrophic factor. Additionally, preincubation with either JAK2 inhibitor AG490 or PI3K inhibitor LY294002 blocked the neuroprotective effect of ciliary neurotrophic factor. These data indicate that the two pathways JAK2/STAT3 and PI3K/Akt play major roles in mediating the in vitro neuroprotective effects of ciliary neurotrophic factor on dorsal root ganglion neurons with glutamate-induced neurotoxicity.

In vitro assessment of TAT - Ciliary Neurotrophic Factor therapeutic potential for peripheral nerve regeneration

In regenerative neurobiology, Ciliary Neurotrophic Factor (CNTF) is raising high interest as a multifunctional neurocytokine, playing a key role in the regeneration of injured peripheral nerves. Despite its promising trophic and regulatory activity, its clinical application is limited by the onset of severe side effects, due to the lack of efficient intracellular trafficking after administration. In this study, recombinant CNTF linked to the transactivator transduction domain (TAT) was investigated in vitro and found to be an optimized fusion protein which preserves neurotrophic activity, besides enhancing cellular uptake for therapeutic advantage. Moreover, a compelling protein delivery method was defined, in the future perspective of improving nerve regeneration strategies. Following determination of TAT-CNTF molecular weight and concentration, its specific effect on neural SH-SY5Y and PC12 cultures was assessed. Cell proliferation assay demonstrated that the fusion protein triggers PC12 cell growth within 6h of stimulation. At the same time, the activation of signal transduction pathway and enhancement of cellular trafficking were found to be accomplished in both neural cell lines after specific treatment with TAT-CNTF. Finally, the recombinant growth factor was successfully loaded on oxidized polyvinyl alcohol (PVA) scaffolds, and more efficiently released when polymer oxidation rate increased. Taken together, our results highlight that the TAT domain addiction to the protein sequence preserves CNTF specific neurotrophic activity in vitro, besides improving cellular uptake. Moreover, oxidized PVA could represent an ideal biomaterial for the development of nerve conduits loaded with the fusion protein to be delivered to the site of nerve injury.

Sulfasalazine intensifies temozolomide cytotoxicity in human glioblastoma cells

Temozolomide (TMZ) is an alkylating agent used to treat glioblastoma. This tumor type synthesizes the antioxidant glutathione through system X c (-) , which is inhibited by sulfasalazine (SAS). We exposed A172 and T98G human glioblastoma cells to a presumably clinically relevant concentration of TMZ (25 µM) and/or 0.5 mM SAS for 1, 3, or 5 days and assessed cell viability. For both cell lines, TMZ alone did not alter viability at any time point, while the coadministration of TMZ and SAS significantly reduced cell viability after 5 days. The drug combination exerted a synergistic effect on A172 cells after 3 and 5 days. Therefore, this particular lineage was subjected to complementary analyses on the genetic (transcriptome) and functional (glutathione and proliferating cell nuclear antigen (PCNA) protein) levels. Cellular pathways containing differentially expressed genes related to the cell cycle were modified by TMZ alone. On the other hand, SAS regulated pathways associated with glutathione metabolism and synthesis, irrespective of TMZ. Moreover, SAS, but not TMZ, depleted the total glutathione level. Compared with the vehicle-treated cells, the level of PCNA protein was lower in cells treated with TMZ alone or in combination with SAS. In conclusion, our data showed that the association of TMZ and SAS is cytotoxic to T98G and A172 cells, thus providing useful insights for improving TMZ clinical efficacy through testing this novel drug combination. Moreover, the present study not only reports original information on differential gene expression in glioblastoma cells exposed to TMZ and/or SAS but also describes an antiproliferative effect of TMZ, which has not yet been observed in A172 cells.

Peripheral inflammatory hyperalgesia depends on the COX increase in the dorsal root ganglion

It is well established that dorsal root ganglion (DRG) cells synthesize prostaglandin. However, the role that prostaglandin plays in the inflammatory hyperalgesia of peripheral tissue has not been established. Recently, we have successfully established a technique to inject drugs (3 μL) directly into the L5-DRG of rats, allowing in vivo identification of the role that DRG cell-derived COX-1 and COX-2 play in the development of inflammatory hyperalgesia of peripheral tissue. IL-1β (0.5 pg) or carrageenan (100 ng) was administered in the L5-peripheral field of rat hindpaw and mechanical hyperalgesia was evaluated after 3 h. Administration of a nonselective COX inhibitor (indomethacin), selective COX-1 (valeryl salicylate), or selective COX-2 (SC-236) inhibitors into the L5-DRG prevented the hyperalgesia induced by IL-1β. Similarly, oligodeoxynucleotide-antisense against COX-1 or COX-2, but not oligodeoxynucleotide-mismatch, decreased their respective expressions in the L5-DRG and prevented the hyperalgesia induced by IL-1β in the hindpaw. Immunofluorescence analysis demonstrated that the amount of COX-1 and COX-2, constitutively expressed in TRPV-1(+) cells of the DRG, significantly increased after carrageenan or IL-1β administration. In addition, indomethacin administered into the L5-DRG prevented the increase of PKCε expression in DRG membrane cells induced by carrageenan. Finally, the administration of EP1/EP2 (7.5 ng) or EP4 (10 µg) receptor antagonists into L5-DRG prevented the hyperalgesia induced by IL-1β in the hindpaw. In conclusion, the results of this study suggest that the inflammatory hyperalgesia in peripheral tissue depends on activation of COX-1 and COX-2 in C-fibers, which contribute to the induction and maintenance of sensitization of primary sensory neurons.

JAK2 inhibition is neuroprotective and reduces astrogliosis after quinolinic acid striatal lesion in adult mice

Quinolinic acid (QA) striatal lesion in rodents induces neuronal death, astrogliosis and migration of neuroblasts from subventricular zone to damaged striatum. These phenomena occur in some human neurodegenerative illnesses, but the underlying mechanisms are unknown. We investigated the effect of AG490, a Janus-kinase 2 (JAK2) inhibitor, on astrogliosis, neuronal loss and neurogenesis in the striatum of adult mice after unilateral infusion of QA (30 nmol). Animals were given subcutaneous injections of AG490 (10 mg/kg) or vehicle immediately after lesion and then once daily for six days. Brain sections were used for neuronal stereological quantification, immunohistochemical and Western Blotting analyses for GFAP and doublecortin, markers of astrocytes and neuroblasts, respectively. The total area of doublecortin-positive cells (ADPC) and the number of neurons (NN) in the lesioned (L) and contralateral (CL) sides were evaluated. Neurogenesis index (NI=ADPC(L)/ADPC(CL)) and neuronal ratio (NR=NN(L)/NN(CL)) were calculated. After QA administration, blotting for GFAP showed an ipsilateral decrease of 19% in AG490- vs vehicle-treated animals. NR was 25% higher in mice given AG490 vs controls given vehicle. NI showed a decrease of 21% in AG490- vs vehicle-treated mice. Our results indicate that JAK2 inhibition reduces QA lesion and suggest that astrogliosis may impair neuronal survival in this model.

Ciliary neurotrophic factor (CNTF) protects non-obese Swiss mice against type 2 diabetes by increasing beta cell mass and reducing insulin clearance

AIMS/HYPOTHESIS

Ciliary neurotrophic factor (CNTF) improves metabolic variables of obese animals with characteristics of type 2 diabetes, mainly by reducing insulin resistance. We evaluated whether CNTF was able to improve other metabolic variables in mouse models of type 2 diabetes, such as beta cell mass and insulin clearance, and whether CNTF has any effect on non-obese mice with characteristics of type 2 diabetes.

METHODS

Neonatal mice were treated with 0.1 mg/kg CNTF or citrate buffer via intraperitoneal injections, before injection of 250 mg/kg alloxan. HEPG2 cells were cultured for 3 days in the presence of citrate buffer, 1 nmol/l CNTF or 50 mmol/l alloxan or a combination of CNTF and alloxan. Twenty-one days after treatment, we determined body weight, epididymal fat weight, blood glucose, plasma insulin, NEFA, glucose tolerance, insulin resistance, insulin clearance and beta cell mass. Finally, we assessed insulin receptor and protein kinase B phosphorylation in peripheral organs, as well as insulin-degrading enzyme (IDE) protein production and alternative splicing in the liver and HEPG2 cells.

RESULTS

CNTF improved insulin sensitivity and beta cell mass, while reducing glucose-stimulated insulin secretion and insulin clearance in Swiss mice, improving glucose handling in a non-obese type 2 diabetes model. This effect was associated with lower IDE production and activity in liver cells. All these effects were observed even at 21 days after CNTF treatment.

CONCLUSIONS/INTERPRETATION

CNTF protection against type 2 diabetes is partially independent of the anti-obesity actions of CNTF, requiring a reduction in insulin clearance and increased beta cell mass, besides increased insulin sensitivity. Furthermore, knowledge of the long-term effects of CNTF expands its pharmacological relevance.

The anorexigenic cytokine ciliary neurotrophic factor stimulates POMC gene expression via receptors localized in the nucleus of arcuate neurons

Ciliary neurotrophic factor (CNTF) is a neural cytokine that reduces appetite and body weight when administrated to rodents or humans. We have demonstrated recently that the level of CNTF in the arcuate nucleus (ARC), a key hypothalamic region involved in food intake regulation, is positively correlated with protection against diet-induced obesity. However, the comprehension of the physiological significance of neural CNTF action was still incomplete because CNTF lacks a signal peptide and thus may not be secreted by the classical exocytosis pathways. Knowing that CNTF distribution shares similarities with that of its receptor subunits in the rat ARC, we hypothesized that CNTF could exert a direct intracrine effect in ARC cells. Here, we demonstrate that CNTF, together with its receptor subunits, translocates to the cell nucleus of anorexigenic POMC neurons in the rat ARC. Furthermore, the stimulation of hypothalamic nuclear fractions with CNTF induces the phosphorylation of several signaling proteins, including Akt, as well as the transcription of the POMC gene. These data strongly suggest that intracellular CNTF may directly modulate POMC gene expression via the activation of receptors localized in the cell nucleus, providing a novel plausible mechanism of CNTF action in regulating energy homeostasis.

Recombinant human TAT-OP1 to enhance NGF neurogenic potential: preliminary studies on PC12 cells

Osteogenic protein 1 (OP1), also known as bone morphogenic protein-7 (BMP7), is a multifunctional cytokine with demonstrated neurogenic potential. As the recombinant OP1 (rhOP1) was shown to provide axonal guidance cues and to prevent the reduction of dendritic growth in the injury-induced cortical cultures, it was suggested that an in vivo efficient rhOP1 delivery could enhance neurite growth and functional reconnectivity in the damaged brain. In the present work, we engineered a chimeric molecule in which rhBMP7 was fused to a protein transduction domain derived from HIV-1 TAT protein to deliver the denatured recombinant BMP7 into cells and obtain its chaperone-mediated folding, circumventing the expensive and not much efficient in vitro refolding procedures. When tested on rat PC12 cells, a widely used in vitro neurogenic differentiation model, the resulting fusion protein (rhTAT-OP1) demonstrated to enter fastly into the cells, lose HIV-TAT sequence and interact with membrane receptors activating BMP pathway by SMAD 1/5/8 phosphorylation. In comparison with nerve growth factor (NGF) and BMP7, it proved itself effective to induce the formation of more organized H and M neurofilaments. Moreover, if used in combination with NGF, it stimulated a significant (P < 0.05) and more precocious dendritic outgrowth with respect to NGF alone. These results indicate that rhTAT-OP1 fused with TAT transduction domain shows neurogenic activity and may be a promising enhancer factor in NGF-based therapies.

Microglial phenotype is regulated by activity of the transcription factor, NFAT (nuclear factor of activated T cells)

The transcription factor family, nuclear factor of activated T cells (NFAT), regulates immune cell phenotype. Four different calcium/calmodulin-regulated isoforms have been identified in the periphery, but isoform expression in microglia, the resident immune cells of the CNS, has not been fully defined. In this study microglial NFAT isoform expression and involvement in regulating inflammatory responses in murine primary microglia culture was examined. Western blot analysis demonstrated robust detection of NFATc1 and c2 isoforms in microglia. Electrophoretic mobility shift assays demonstrated increased NFAT-DNA binding from nuclear extracts of lipopolysaccharide (LPS) stimulated microglia. Moreover, LPS-stimulated microglia behaved similarly to T cell receptor agonist antibody-stimulated Jurkat cells demonstrating a transient increase in NFAT-driven luciferase reporter gene expression. LPS-induced NFAT-luciferase activity in microglia was attenuated by pretreatment with tat-VIVIT, a cell-permeable NFAT inhibitory peptide. Furthermore, LPS-mediated secretion of microglial cytokines, TNF-alpha and MCP-1, was decreased by treatment with tat-VIVIT but not with tat-VEET, a negative control peptide. These results demonstrate that NFAT plays a role in regulating proinflammatory responses in cultured murine microglia.