RESUMEN
Uric acid is the final product of purine metabolism in humans and is considered to be quantitatively the main antioxidant in plasma. In vitro studies showed that the oxidation of uric acid by peroxidases, in presence of superoxide, generates urate free radical and urate hydroperoxide. Urate hydroperoxide is a strong oxidant and might be a relevant intermediate in inflammatory conditions. However, the identification of urate hydroperoxide in cells and biological samples has been a challenge due to its high reactivity. By using mass spectrometry, we undoubtedly demonstrated the formation of urate hydroperoxide and its corresponding alcohol, hydroxyisourate during the respiratory burst in peripheral blood neutrophils and in human leukemic cells differentiated in neutrophils (dHL-60). The respiratory burst was induced by phorbol myristate acetate (PMA) and greatly increased oxygen consumption and superoxide production. Both oxygen consumption and superoxide production were further augmented by incubation with uric acid. Conversely, uric acid significantly decreased the levels of HOCl, probably because of the competition with chloride by the catalysis of myeloperoxidase. In spite of the decrease in HOCl, the overall oxidative status, measured by GSH/GSSG ratio, was augmented in the presence of uric acid. In summary, the present results support the formation of urate hydroperoxide, a novel oxidant in neutrophils oxidative burst. Urate hydroperoxide is a strong oxidant and alters the redox balance toward a pro-oxidative environment. The production of urate hydroperoxide in inflammatory conditions could explain, at least in part, the harmful effect associated to uric acid.
Asunto(s)
Inflamación/sangre , Neutrófilos/metabolismo , Peróxidos/metabolismo , Especies Reactivas de Oxígeno/sangre , Ácido Úrico/análogos & derivados , Catálisis , Línea Celular Tumoral , Radicales Libres/química , Radicales Libres/metabolismo , Humanos , Inflamación/patología , Espectrometría de Masas , Neutrófilos/química , Oxidación-Reducción , Peroxidasa/genética , Peroxidasa/metabolismo , Peróxidos/química , Peróxidos/aislamiento & purificación , Especies Reactivas de Oxígeno/aislamiento & purificación , Superóxidos/química , Superóxidos/metabolismo , Ácido Úrico/química , Ácido Úrico/aislamiento & purificación , Ácido Úrico/metabolismoRESUMEN
Spinal cord injury (SCI) results in loss of movement, sensibility, and autonomic control at the level of the lesion and at lower parts of the body. Several experimental strategies have been used in attempts to increase endogenous mechanisms of neuroprotection, neuroplasticity, and repair, but with limited success. It is known that glucose-dependent insulinotropic peptide (GIP) and its receptor (GIPR) can enhance synaptic plasticity, neurogenesis, and axonal outgrowth. However, their role in the injury has never been studied. The aim of this study was to evaluate the changes in expression levels of both GIP and GIPR in acute and chronic phases of SCI in rats. Following SCI (2 to 24 h after damage), the rat spinal cord showed a lesion in which the epicenter had a cavity with hemorrhage and necrosis. Furthermore, the lesion cavity also showed ballooned cells 14 and 28 days after injury. We found that SCI induced increases in GIPR expression in areas neighboring the site of injury at 6 h and 28 days after the injury. Moreover, higher GIP expression was observed in these regions on day 28. Neuronal projections from the injury epicenter showed an increase in GIP immunoreactivity 24 h and 14 and 28 days after SCI. Interestingly, GIP was also found in progenitor cells at the spinal cord canal 24 h after injury, whereas both GIP and GIPR were present in progenitor cells at the injury epicenter 14 days after in SCI animals. These results suggest that GIP and its receptor might be implicated with neurogenesis and the repair process after SCI.
Asunto(s)
Polipéptido Inhibidor Gástrico/metabolismo , Neurogénesis/fisiología , Receptores de la Hormona Gastrointestinal/metabolismo , Traumatismos de la Médula Espinal/metabolismo , Animales , Conducta Animal/fisiología , Modelos Animales de Enfermedad , Masculino , Actividad Motora/fisiología , Ratas , Ratas Wistar , Traumatismos de la Médula Espinal/patología , Traumatismos de la Médula Espinal/fisiopatologíaRESUMEN
A role for proteinase-activated receptor-4 (PAR-4) was recently suggested in itch sensation. Here, we investigated the mechanisms underlying the pruriceptive actions of the selective PAR-4 agonist AYPGKF-NH2 (AYP) in mice. Dorsal intradermal (i.d.) administration of AYP elicited intense scratching behavior in mice, which was prevented by the selective PAR-4 antagonist (pepducin P4pal-10). PAR-4 was found to be coexpressed in 32% of tryptase-positive skin mast cells, and AYP caused a 2-fold increase in mast cell degranulation. However, neither the treatment with cromolyn nor the deficiency of mast cells (WBB6F1-Kit(W/Wv) mice) was able to affect AYP-induced itch. PAR-4 was also found on gastrin-releasing peptide (GRP)-positive neurons (pruriceptive fibers), and AYP-induced itch was reduced by the selective GRP receptor antagonist RC-3095. In addition, AYP evoked calcium influx in â¼1.5% of cultured DRG neurons also sensitive to TRPV1 (capsaicin) and/or TRPA1 (AITC) agonists. Importantly, AYP-induced itch was reduced by treatment with either the selective TRPV1 (SB366791), TRPA1 (HC-030031), or NK1 (FK888) receptor antagonists. However, genetic loss of TRPV1, but not of TRPA1, diminished AYP-induced calcium influx in DRG neurons and the scratching behavior in mice. These findings provide evidence that PAR-4 activation by AYP causes pruriceptive itch in mice via a TRPV1/TRPA1-dependent mechanism.
Asunto(s)
Capsaicina/farmacología , Prurito/fisiopatología , Receptores de Bombesina/metabolismo , Receptores de Trombina/metabolismo , Canales de Potencial de Receptor Transitorio/efectos de los fármacos , Animales , Conducta Animal , Células Cultivadas , Modelos Animales de Enfermedad , Femenino , Ganglios Espinales/citología , Inmunohistoquímica , Inyecciones Intradérmicas , Mastocitos/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Prurito/inducido químicamente , Prurito/psicología , Distribución Aleatoria , Valores de Referencia , Transducción de Señal , Canales de Potencial de Receptor Transitorio/metabolismoRESUMEN
BACKGROUND: Multiple sclerosis (MS) is a demyelinating and neuroinflammatory disease of the human central nervous system (CNS). The expression of kinins is increased in MS patients, but the underlying mechanisms by which the kinin receptor regulates MS development have not been elucidated. METHODOLOGY/PRINCIPAL FINDINGS: Experimental autoimmune encephalomyelitis (EAE) was induced in female C57BL/6 mice by immunization with MOG(35-55) peptide emulsified in complete Freund's adjuvant and injected with pertussis toxin on day 0 and day 2. Here, we report that blockade of the B(1)R in the induction phase of EAE markedly suppressed its progression by interfering with the onset of the immune response. Furthermore, B(1)R antagonist suppressed the production/expression of antigen-specific T(H)1 and T(H)17 cytokines and transcription factors, both in the periphery and in the CNS. In the chronic phase of EAE, the blockade of B(1)R consistently impaired the clinical progression of EAE. Conversely, administration of the B(1)R agonist in the acute phase of EAE suppressed disease progression and inhibited the increase in permeability of the blood-brain barrier (BBB) and any further CNS inflammation. Of note, blockade of the B(2)R only showed a moderate impact on all of the studied parameters of EAE progression. CONCLUSIONS/SIGNIFICANCE: Our results strongly suggest that kinin receptors, mainly the B(1)R subtype, play a dual role in EAE progression depending on the phase of treatment through the lymphocytes and glial cell-dependent pathways.