1,355,116 research outputs found
BDNF and TrkB mediated mechanisms in the spinal cord. In "Synaptic plasticity in pain", Editor Marzia Malcangio
No full textBDNF acts as a synaptic modulator in spinal cord, inducing short and long term changes in pain transmissio
Cytotoxic drugs regulate VEGF and IL-8 expression in human melanoma cells by A2A and A3 adenosine receptors.
No full textCancer patients undergoing treatment with systemic cancer chemotherapy drugs often have abnormal growth factor and cytokine profiles. Thus, serum levels of interleukin-8 (IL-8) are elevated in patients with malignant melanoma. In addition to IL-8, aggressive melanoma cells secrete, through its transcriptional regulator Hypoxia-inducible Factor 1 (HIF-1), vascular endothelial growth factor (VEGF), which promotes angiogenesis and metastasis of human cancerous cells.1,4 Whether these responses are related to adenosine, a ubiquitous mediator expressed at high concentrations in cancer and implicated in numerous inflammatory processes, is not known and is the focus of this study. We have examined whether the DNA-damaging agents etoposide (VP-16) and doxorubicin can affect IL-8, VEGF and HIF-1 expression in human melanoma cancer cells. In particular, we have investigated whether these responses are related to the modulation of the adenosine receptor subtypes, named A1, A2A, A2B and A3. We have demonstrated that A2B receptor blockade can modulate IL-8 production while blocking A3 receptors it is possible to further decrease VEGF reduction due to VP-16 and doxorubicin in melanoma cells. This understanding may present the possibility of using adenosine antagonists to reduce chemotherapy-induced inflammatory cytokine production and to improve the ability of chemotherapeutic drugs to block angiogenesis. Consequently, we conclude that adenosine receptor modulation may be useful for refining the use of chemotherapeutic drugs to treat human cancer more effectively.
(1) Merighi, S.; Benini, A.; Mirandola, P.; Gessi, S.; Varani, K.; Simioni, C.; Leung, E.; Maclennan, S.; Baraldi, P.G.; Borea, P.A. Caffeine inhibits adenosine-induced accumulation of hypoxia-inducible factor-1alpha, vascular endothelial growth factor, and interleukin-8 expression in hypoxic human colon cancer cells. Mol Pharmacol. 2007, 72, 395-406.
(2) Merighi S, Benini A, Mirandola P, Gessi S, Varani K, Leung E, Maclennan S, Baraldi, P.G.; Borea PA. Hypoxia inhibits paclitaxel-induced apoptosis through adenosine-mediated phosphorylation of bad in glioblastoma cells. Mol Pharmacol. 2007, 72, 162-72.
(3) Merighi, S.; Benini, A.; Mirandola, P.; Gessi, S.; Varani, K.; Leung, E.; Maclennan, S.; Borea, P.A. Adenosine modulates vascular endothelial growth factor expression via hypoxia-inducible factor-1 in human glioblastoma cells. Biochem Pharmacol. 2006, 72, 19-31.
(4) Merighi, S.; Benini, A.; Mirandola, P.; Gessi, S.; Varani, K.; Leung, E.; Maclennan, S.; Baraldi, P.G.; Borea, P.A. A3 adenosine receptors modulate hypoxia-inducible factor-1alpha expression in human A375 melanoma cells. Neoplasia 2005, 7, 894-90
A3 ADENOSINE RECEPTORS MODULATE HYPOXIA-INDUCIBLE FACTOR-1ALPHA EXPRESSION IN HUMAN CANCER CELLS
No full textHypoxia appears to induce a program which shifts the cellular phenotype toward an increase in intracellular adenosine. Hypoxia-inducible factor-1 (HIF-1) is a key regulator of genes crucial to many aspects of cancer biology (1). Since the levels of both HIF-1 and adenosine are elevated within the hypoxic environment of solid tumors, we investigated whether adenosine may regulate HIF-1. In particular, we investigated the effect of A3 receptor antagonists on HIF-1 and vascular endothelial growth factor expression (2-5). The response to adenosine was generated at the cell surface because the inhibition of A3 receptor expression, by using small interfering RNA, abolished nucleoside effects. Furthermore, we characterized the signaling pathways induced by A3 receptors in hypoxia and provide results of how human tumor growth may be influenced through the adenosinergic system (6).
(1) Semenza GL. Targeting HIF-1 for cancer therapy. Nat Rev Cancer 2003, 3, 721–732.
(2) Merighi, S.; Benini, A.; Mirandola, P.; Gessi, S.; Varani, K.; Simioni, C.; Leung, E.; Maclennan, S.; Baraldi, P.G.; Borea, P.A. Caffeine inhibits adenosine-induced accumulation of hypoxia-inducible factor-1alpha, vascular endothelial growth factor, and interleukin-8 expression in hypoxic human colon cancer cells. Mol Pharmacol. 2007, 72, 395-406.
(3) Merighi S, Benini A, Mirandola P, Gessi S, Varani K, Leung E, Maclennan S, Baraldi, P.G.; Borea PA. Hypoxia inhibits paclitaxel-induced apoptosis through adenosine-mediated phosphorylation of bad in glioblastoma cells. Mol Pharmacol. 2007, 72, 162-72.
(4) Merighi, S.; Benini, A.; Mirandola, P.; Gessi, S.; Varani, K.; Leung, E.; Maclennan, S.; Borea, P.A. Adenosine modulates vascular endothelial growth factor expression via hypoxia-inducible factor-1 in human glioblastoma cells. Biochem Pharmacol. 2006, 72, 19-31.
(5) Merighi, S.; Benini, A.; Mirandola, P.; Gessi, S.; Varani, K.; Leung, E.; Maclennan, S.; Baraldi, P.G.; Borea, P.A. A3 adenosine receptors modulate hypoxia-inducible factor-1alpha expression in human A375 melanoma cells. Neoplasia 2005, 7, 894-903.
(6) Merighi S.; Benini A.; Mirandola P.; Gessi S.; Varani K.; Leung E.; Maclennan S.; Borea PA. A3 adenosine receptor activation inhibits cell proliferation via phosphatidylinositol 3-kinase/Akt-dependent inhibition of the extracellular signal-regulated kinase 1/2 phosphorylation in A375 human melanoma cells. J Biol Chem. 2005, 280, 19516-26
BDNF and TrkB mediated mechanisms in the spinal cord
No full textThe neurotrophin brain-derived neurotrophic factor (BDNF) plays an essential role during development, promoting the survival of specific populations of central and peripheral neurons. During adulthood, BDNF also acts as a synaptic modulator in several areas of the central nervous system (CNS), including the spinal cord, and is involved in short and long term changes of synaptic efficacy. In spinal cord dorsal horn BDNF is expressed in the peptidergic terminals originating from primary afferent fibres, while its high affinity receptor trkB has been detected on both primary afferent terminals and dorsal horn neurons. In superficial dorsal horn, exogenous BDNF modulates fast excitatory (glutamatergic) and inhibitory (GABAergic/glycinergic) signals, as well as slow peptidergic neurotransmission. Conditions of inflammatory and neuropathic pain alter the expression of BDNF and trkB receptors in dorsal horn. In experimental pain models, modulation of synaptic transmission by BDNF plays an important role in the induction and maintenance of central sensitization
GABAB receptors-mediated tonic inhibition of glutamate release from Aβ fibers in rat laminae III/IV of the spinal cord dorsal horn.
No full textPresynaptic GABAB receptors (GABABRs) are highly expressed in dorsal root ganglion neurons and spinal cord dorsal horn. GABABRs located in superficial dorsal horn play an important antinociceptive role, by acting at both pre- and postsynaptic sites. GABABRs expressed in deep dorsal horn could be involved in the processing of touch sensation and possibly in the generation of tactile allodynia in chronic pain. The objective of this study was to characterize the morphological and functional properties of GABABRs expressed on Aβ fibers projecting to lamina III/IV and to understand their role in modulating excitatory synaptic transmission. We performed high-resolution electron microscopic analysis, showing that GABAB2 subunit is expressed on 71.9% of terminals in rat lamina III-IV. These terminals were engaged in axodendritic synapses and, for the 46%, also expressed glutamate immunoreactivity. Monosynaptic excitatory postsynaptic currents, evoked by Aβ fiber stimulation and recorded from lamina III/IV neurons in spinal cord slices, were strongly depressed by application of baclofen (0.1-2.5 μM), acting as a presynaptic modulator. Application of the GABABR antagonist CGP 55845 caused, in a subpopulation of neurons, the potentiation of the first of two excitatory postsynaptic currents recorded with the paired-pulse protocol, showing that GABABRs are endogenously activated. A decrease in the paired-pulse ratio accompanied the effect of CGP 55845, implying the involvement of presynaptic GABABRs. CGP 55845 facilitated only the first excitatory postsynaptic current also during a train of four consecutive stimuli applied to Aβ fibers. These results suggest that GABABRs tonically inhibit glutamate release from Aβ fibers at a subset of synapses in deep dorsal horn. This modulation specifically affects only the early phase of synaptic excitation in lamina III-IV neuron
Cannabinoid CB2 receptor modulates microglial cell activation: role of ERK-1/2 Kinase signaling.
No full textCannabinoid (CB) receptor agonists have potential utility as anti-inflammatory drugs for the treatment of many disease conditions (Atwood et al., 2010). In the present study, we characterized the signal transduction pathways mediated by CB2 receptors in resting and lipopolysaccharide (LPS)-stimulated murine microglia. We examined the effects of the synthetic CB2 ligand, JWH-015 (Merighi et al., 2010), on phosphorylation of MAPKs and on nitric oxide (NO) production. Stimulation of CB2 receptors by JWH-015 activates JNK-1/2 and ERK-1/2 in resting microglial cells. Furthermore, CB2 receptor activation increased p-ERK-1/2 at 15 minutes in LPS-stimulated microglia. Surprisingly, in the presence of both LPS and JWH-015, phosphorylation of ERK-1/2 was reduced after 30 minutes. The NO synthetase inhibitor L-NAME blocked the ability of JWH-015 to downregulate LPS-induced p-ERK increase, indicating that CB2 reduces LPS-effects on ERK-1/2 phosphorylation through NO. JWH-015 increased LPS-induced NO release at 15 minutes, while at 48 hours CB2 receptor stimulation had an inhibitory effect. All of the effects of JWH-015 were significantly blocked by the CB2 antagonist AM 630 and were mediated specifically by activation of CB2 receptors since the inhibition of CB2 expression by siRNA abolished the agonist’s effects. Our results demonstrate that CB2 receptor stimulation activates MAPK pathway, but the presence of a second stimulus switches off MAPK signal transduction then inhibiting pro-inflammatory LPS-induced NO production. Therefore, CB2 receptor agonists may promote anti-inflammatory therapeutic response in activated microglia.
Atwood et al. (2010). Br J Pharmacol 160, 467-479.
Merighi et al. (2010). Biochem Pharmacol 79, 471-477
“[3H]MRE 3008F20: a novel antagonist radioligand for the pharmacological and biochemical characterization of human A3 adenosine receptors”.
No full textPharmacological and biochemical characterization of A3 adenosine receptors in Jurkat cells, a human leukemia line.
No full textAdenosine modulates various physiological effects on many cell types by activating four different subtypes of G protein coupled receptors classified as A1, A2A, A2B and A3. Recently, 5-N-(4-methoxyphenyl-carbamoyl)amino-8-propyl-2-(2-furyl)-pyrazolo-[4,3-e]1,2,4-triazolo[1,5-c]-pyrimidine, [3H]MRE3008F20, has been identified as a potent and selective radiolabelled antagonist of human recombinant A3 receptors (1). In this study we investigated the pharmacological and biochemical profile of A3 subtypes in Jurkat T cells, a human leukemia line, where the presence of A2B and A2A but not A3 receptors has been previously demonstrated. A3 receptors were first revealed by RT-PCR experiments; then saturation of [3H]MRE3008F20 binding to A3 receptors (range 0.2-2nM) showed a single high affinity binding site with Kd of 1.90.2 nM and Bmax of 1.30.1 pmol/mg of protein. Competition studies of [3H]MRE3008F20 binding (2nM) using typical adenosine ligands displayed a pharmacological profile typical of the A3 subtype. Agonist competition curves yelded both a high (30%) and a low-affinity state of A3 receptors. Cl-IB-MECA and IB-MECA were the most potent compounds with KH of 1.6, 2.7 nM and KL of 83, 150 nM, respectively. Functional studies showed that Cl-IBMECA and IB-MECA, were able to inhibit cAMP accumulations with EC50 values of 3.50.3 and 120.1 nM, respectively. The same agonists (30 M) stimulated Ca2+ release from intracellular Ca2+ pools from a basal level of 100-150 nM to a stimulated level of 250-300 nM. Finally, A3 agonists (30-40M) and antagonists (1-10M) produced a cell death effect, reducing cell number to 40% of control (p<0.05, ANOVA and Dunnett’s test) as demonstrated by different viability assays: trypan blue, JAM and MTT assays. These data are the first evidence of the presence of functional A3 adenosine receptors in Jurkat cells.
1. Varani K., Merighi S., Gessi S., Klotz K.N., Leung E., Baraldi P.G., Cacciari B., Romagnoli R., Spalluto G., and Borea P.A. (2000) Mol. Pharmacol. 57:968-975
A model of public resources allocation for social investments on urban districts; the case of a northern italian metropolitan area
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