Journal of neurochemistry
-
Journal of neurochemistry · Nov 2006
Rapid co-release of interleukin 1beta and caspase 1 in spinal cord inflammation.
Mounting evidence supports the hypothesis that pro-inflammatory cytokines secreted by astrocytes and microglia modulate nociceptive function in the injured CNS and following peripheral nerve damage. Here we examine the involvement of interleukin-1beta (IL-1beta) and microglia activation in nociceptive processing in rat models of spinal cord inflammation. Following application of lipopolysaccharide (LPS) to an ex vivo dorsal horn slice preparation, we observed rapid secretion of IL-1beta which was prevented by inhibition of glial cell metabolism and by inhibitors of either p38 mitogen-activated protein kinase (MAPK) or caspase 1. ⋯ Extensive microglial cell activation in the dorsal horn, as determined by immunoreactivity for phosphorylated p38 MAPK, was found to correlate with the occurrence of IL-1beta secretion. In behavioural studies, intrathecal injection of LPS in the lumbar spinal cord produced mechanical hyperalgesia in the rat hind-paws which was attenuated by concomitant injections of a p38 MAPK inhibitor, a caspase 1 inhibitor or the rat recombinant interleukin 1 receptor antagonist. These data suggest a critical role for the cytokine IL-1beta and caspase 1 rapidly released by activated microglia in enhancing nociceptive transmission in spinal cord inflammation.
-
Journal of neurochemistry · Nov 2006
The age-related attenuation in long-term potentiation is associated with microglial activation.
It is well established that inflammatory changes contribute to brain ageing, and an increased concentration of proinflammatory cytokine, interleukin-1beta (IL-1beta), has been reported in the aged brain associated with a deficit in long-term potentiation (LTP) in rat hippocampus. The precise age at which changes are initiated is unclear. In this study, we investigate parallel changes in markers of inflammation and LTP in 3-, 9- and 15-month-old rats. ⋯ Associated with these changes, we observed a significant impairment of hippocampal LTP in the same rats. The importance of microglial activation in the attenuation of long-term potentiation (LTP) was demonstrated using an inhibitor of microglial activation, minocycline; partial restoration of LTP in 15-month-old rats was observed following administration of minocycline. We propose that signs of neuroinflammation are observed in middle age and that these changes, which are characterized by microglial activation, may be triggered by IL-18.
-
Journal of neurochemistry · Nov 2006
TRPV1b overexpression negatively regulates TRPV1 responsiveness to capsaicin, heat and low pH in HEK293 cells.
Transient receptor potential channel type V (TRPV) 1 is a non-selective cation channel that can be activated by capsaicin, endogenous vanilloids, heat and protons. The human TRPV1 splice variant, TRPV1b, lacking exon 7, was cloned from human dorsal root ganglia (DRG) RNA. The expression profile and relative abundance of TRPV1b and TRPV1 in 35 different human tissues were determined by quantitative RT-PCR using isoform-specific probes. ⋯ These results demonstrate that exon 7, which encodes the third ankyrin domain and 44 amino acids thereafter, is required for normal channel function of human TRPV1. Moreover, when co-expressed with TRPV1, TRPV1b formed complexes with TRPV1, and inhibited TRPV1 channel function in response to capsaicin, acidic pH, heat and endogenous vanilloids, dose-dependently. Taken together, these data support the hypothesis that TRPV1b is a naturally existing inhibitory modulator of TRPV1.
-
Journal of neurochemistry · Aug 2006
Comparative StudyThe radical scavenger CR-6 protects SH-SY5Y neuroblastoma cells from oxidative stress-induced apoptosis: effect on survival pathways.
Reactive oxygen species (ROS) and oxidative stress have long been linked to cell death of neurons in many neurodegenerative conditions. However, the exact molecular mechanisms triggered by oxidative stress in neurodegeneration are at present unclear. In the current work we have used the human neuroblastoma SH-SY5Y cell line as a model for studying the molecular events occurring after inducing apoptosis with H2O2. ⋯ Furthermore, we show that pre-treatment of SH-SY5Y cells with a cocktail containing CR-6, the pan-caspase inhibitor zVAD-fmk (zVal-Ala-Asp-fluoro-methylketone) and the calpain inhibitor SJA6017 confers almost total protection against apoptosis. In summary, the present work characterizes the molecular mechanisms involved in oxidative stress-induced apoptosis in SH-SY5Y cells. Our findings highlight the relevance of CR-6, alone or in combination with other drugs, as potential therapeutic strategy for the treatment of neurodegenerative diseases.
-
Journal of neurochemistry · Jun 2006
Minocycline neuroprotects, reduces microgliosis, and inhibits caspase protease expression early after spinal cord injury.
Minocycline, a clinically used tetracycline for over 40 years, crosses the blood-brain barrier and prevents caspase up-regulation. It reduces apoptosis in mouse models of Huntington's disease and familial amyotrophic lateral sclerosis (ALS) and is in clinical trial for sporadic ALS. Because apoptosis also occurs after brain and spinal cord (SCI) injury, its prevention may be useful in improving recovery. ⋯ We have since found decreased tumor necrosis factor-alpha, as well as caspase-3 mRNA expression, as possible mechanisms of action for minocycline's ameliorative action. These results support reports that modulating apoptosis, caspases, and microglia provide promising therapeutic targets for prevention and/or limiting the degree of functional loss after CNS trauma. Minocycline, and more potent chemically synthesized tetracyclines, may find a place in the therapeutic arsenal to promote recovery early after SCI in humans.