Meningeal dendritic cells drive neuropathic pain through elevation of the kynurenine metabolic pathway in mice.

Neuropathic pain is one of the most important clinical consequences of injury to the somatosensory system. Nevertheless, the critical pathophysiological mechanisms involved in neuropathic pain development are poorly understood. In this study, we found that neuropathic pain is abrogated when the kynurenine metabolic pathway (KYNPATH) initiated by the enzyme indoleamine 2,3-dioxygenase 1 (IDO1) is ablated pharmacologically or genetically. Mechanistically, it was found that IDO1-expressing dendritic cells (DCs) accumulated in the dorsal root leptomeninges and led to an increase in kynurenine levels in the spinal cord. In the spinal cord, kynurenine was metabolized by kynurenine-3-monooxygenase-expressing astrocytes into the pronociceptive metabolite 3-hydroxykynurenine. Ultimately, 3-hydroxyanthranilate 3,4-dioxygenase-derived quinolinic acid formed in the final step of the canonical KYNPATH was also involved in neuropathic pain development through the activation of the glutamatergic N-methyl-D-aspartate receptor. In conclusion, these data revealed a role for DCs driving neuropathic pain development through elevation of the KYNPATH. This paradigm offers potential new targets for drug development against this type of chronic pain.

Lapachol, a compound targeting pyrimidine metabolism, ameliorates experimental autoimmune arthritis.

BACKGROUND: The inhibition of pyrimidine biosynthesis by blocking the dihydroorotate dehydrogenase (DHODH) activity, the prime target of leflunomide (LEF), has been proven to be an effective strategy for rheumatoid arthritis (RA) treatment. However, a considerable proportion of RA patients are refractory to LEF. Here, we investigated lapachol (LAP), a natural naphthoquinone, as a potential DHODH inhibitor and addressed its immunosuppressive properties. METHODS: Molecular flexible docking studies and bioactivity assays were performed to determine the ability of LAP to interact and inhibit DHODH. In vitro studies were conducted to assess the antiproliferative effect of LAP using isolated lymphocytes. Finally, collagen-induced arthritis (CIA) and antigen-induced arthritis (AIA) models were employed to address the anti-arthritic effects of LAP. RESULTS: We found that LAP is a potent DHODH inhibitor which had a remarkable ability to inhibit both human and murine lymphocyte proliferation in vitro. Importantly, uridine supplementation abrogated the antiproliferative effect of LAP, supporting that the pyrimidine metabolic pathway is the target of LAP. In vivo, LAP treatment markedly reduced CIA and AIA progression as evidenced by the reduction in clinical score, articular tissue damage, and inflammation. CONCLUSIONS: Our findings propose a binding model of interaction and support the ability of LAP to inhibit DHODH, decreasing lymphocyte proliferation and attenuating the severity of experimental autoimmune arthritis. Therefore, LAP could be considered as a potential immunosuppressive lead candidate with potential therapeutic implications for RA.

Nitric oxide and fever: immune-to-brain signaling vs. thermogenesis in chicks.

Nitric oxide (NO) plays a role in thermogenesis but does not mediate immune-to-brain febrigenic signaling in rats. There are suggestions of a different situation in birds, but the underlying evidence is not compelling. The present study was designed to clarify this matter in 5-day-old chicks challenged with a low or high dose of bacterial LPS. The lower LPS dose (2 µg/kg im) induced fever at 3-5 h postinjection, whereas 100 µg/kg im decreased core body temperature (Tc) (at 1 h) followed by fever (at 4 or 5 h). Plasma nitrate levels increased 4 h after LPS injection, but they were not correlated with the magnitude of fever. The NO synthase inhibitor (N(G)-nitro-l-arginine methyl ester, l-NAME; 50 mg/kg im) attenuated the fever induced by either dose of LPS and enhanced the magnitude of the Tc reduction induced by the high dose in chicks at 31-32°C. These effects were associated with suppression of metabolic rate, at least in the case of the high LPS dose. Conversely, the effects of l-NAME on Tc disappeared in chicks maintained at 35-36°C, suggesting that febrigenic signaling was essentially unaffected. Accordingly, the LPS-induced rise in the brain level of PGE2 was not affected by l-NAME. Moreover, l-NAME augmented LPS-induced huddling, which is indicative of compensatory mechanisms to run fever in the face of attenuated thermogenesis. Therefore, as in rats, systemic inhibition of NO synthesis attenuates LPS-induced fever in chicks by affecting thermoeffector activity and not by interfering with immune-to-brain signaling. This may constitute a conserved effect of NO in endotherms.

Characterization of intestinal absorption of C-glycoside flavonoid vicenin-2 from Lychnophora ericoides leafs in rats by nonlinear mixed effects modeling

AbstractVicenin-2 (apigenin-6,8-di-C-β-d-glucopyranoside) is present in hydroalcoholic extracts of the Brazilian species Lychnophora ericoides Mart., Asteraceae, leaves, and the biological effects of this compound have been demonstrated including anti-inflammatory, antioxidant and anti-tumor effects in rat models. Given the potential of this compound as a pharmacological agent, the aims of this investigation were to evaluate the extent of intestinal absorption of vicenin-2, and to determine the intestinal permeation profile using an in situ single-pass intestinal perfusion technique. A validated HPLC–UV method was applied to measure the amount of unabsorbed vicenin-2 in the gut after an oral administration of 180 mg kg-1 in five rats. A nonlinear mixed effects model was used to determine the absorption pharmacokinetic parameters assuming a first order absorption and active secretion processes for this compound, wherein the active secretion was characterized by a zero-order process. The population pharmacokinetic parameters obtained were 0.274 min-1 for the first-order absorption rate constant, 16.3% min-1 for the zero-order rate constant; the final percentage of the original dose that was absorbed in vivo was 40.2 ± 2.5%. These parameters indicated that vicenin-2 was rapidly absorbed in the small intestine. In contrast to literature information indicating no absorption of vicenin-2 in Caco-2 cells, our results suggested that vicenin-2 can be absorbed in the small intestine of rats. The finding supports further investigation of vicenin-2 as a viable oral phytopharmaceutical agent for digestive diseases.

Pharmacokinetic evaluation of avicularin using a model-based development approach.

The aim of this study was to use the pharmacokinetic information of avicularin in rats to project a dose for humans using allometric scaling. A highly sensitive and specific bioanalytical assay to determine avicularin concentrations in the plasma was developed and validated for UPLC-MS/MS. The plasma protein binding of avicularin in rat plasma determined by the ultrafiltration method was 64%. The pharmacokinetics of avicularin in nine rats was studied following an intravenous bolus administration of 1 mg/kg and was found to be best described by a two-compartment model using a nonlinear mixed effects modeling approach. The pharmacokinetic parameters were allometrically scaled by body weight and centered to the median rat weight of 0.23 kg, with the power coefficient fixed at 0.75 for clearance and 1 for volume parameters. Avicularin was rapidly eliminated from the systemic circulation within 1 h post-dose, and the avicularin pharmacokinetic was linear up to 5 mg/kg based on exposure comparison to literature data for a 5-mg/kg single dose in rats. Using allometric scaling and Monte Carlo simulation approaches, the rat doses of 1 and 5 mg/kg correspond to the human equivalent doses of 30 and 150 mg, respectively, to achieve comparable plasma avicularin concentrations in humans.

Freqüência das alterações dos níveis séricos de imunoglobulinas dos pacientes atendidos no Hospital Universitário, Londrina, Paraná / Frequency of the changes in the serum immunoglobulins levels of the patients attended at the University Hospital, Londrina, Paraná

As imunoglobulinas constituem um grupo de glicoproteínas presentes no soro e nos líquidos orgânicos e são produzidas pelos linfócitos B ativados que se diferenciam em plasmócitos. São divididas em cinco classes ou isotipos: IgG, IgA, IgM, IgD e IgE. O objetivo deste trabalho foi determinar a freqüência das alterações dos níveis séricos das imunoglobulinas nos pacientes atendidos pelo Hospital Universitário (HU), Londrina, PR, no período de agosto de 2001 a fevereiro de 2006, avaliados pelo método de nefelometria. Foram analisadas 773 amostras de soro de pacientes, 410 (53,0%) do sexo feminino e 363 (47,0%) do sexo masculino, com idade variando de um mês a 86 anos. Das 1719 dosagens de imunoglobulinas séricas realizadas, os níveis de IgA sérica foram avaliados em 568 amostras e foram observadas alterações em 88 (15,5%) das amostras. Das 495 dosagens de IgG, 107 (21,6%) estavam com os níveis séricos alterados. A dosagem de IgM sérica foi realizada em 465 amostras e 142 (30,5%) estavam com os níveis séricos alterados. Os níveis de IgE sérica foram avaliados em 191 amostras e 129 (67,5%) amostras apresentaram níveis aumentados. Os dados obtidos confirmam a ocorrência de diferentes alterações nos níveis séricos das imunoglobulinas e a importância destas dosagens laboratoriais no diagnóstico de doenças infecciosas, parasitárias, alérgicas, auto-imunes e das imunodeficiências humorais congênitas ou adquiridas.