Biomedical subjects

Corina Ehnert

Publications and source records attributed to Corina Ehnert.

8 recordsLinked to original sources

PubMed2006

Impaired acute and inflammatory nociception in mice lacking the p50 subunit of NF-kappaB.

The transcription factor NF-kappaB is thought to play an essential role in inflammatory processes and pain. However, the in vivo function of individual NF-kappaB subunits in the development and processing of nociceptive responses is not clarified. In this study we investigated the role of the p50 subunit of NF-kappaB in models of acute and persistent nociception using NF-kappaB p50(-/-) mice. We found that these mice showed impaired basal responses to mechanical as well as thermal noxious stimulation in the dynamic plantar as well as the hot plate test, respectively, in comparison with wild-type mice. In the formalin test we observed a decreased nociceptive behavior in the first and the second phase in NF-kappaB p50(-/-) mice. In a model of persistent inflammatory hyperalgesia these mice also showed a reduced hyperalgesia to a thermal stimulus, which was in accordance with a lower cyclooxygenase-2 expression in the spinal cord after peripheral inflammatory stimulation. Taken together, our data indicate that the p50 subunit of NF-kappaB is of importance in acute and persistent inflammatory pain. The participation to persistent pain might rely on activation of NF-kappaB by inflammatory stimuli while the contribution to acute pain responses might be related to constitutive NF-kappaB activity in neurons of the nociceptive system.

Animals↗

PubMed2006

GTP cyclohydrolase and tetrahydrobiopterin regulate pain sensitivity and persistence.

We report that GTP cyclohydrolase (GCH1), the rate-limiting enzyme for tetrahydrobiopterin (BH4) synthesis, is a key modulator of peripheral neuropathic and inflammatory pain. BH4 is an essential cofactor for catecholamine, serotonin and nitric oxide production. After axonal injury, concentrations of BH4 rose in primary sensory neurons, owing to upregulation of GCH1. After peripheral inflammation, BH4 also increased in dorsal root ganglia (DRGs), owing to enhanced GCH1 enzyme activity. Inhibiting this de novo BH4 synthesis in rats attenuated neuropathic and inflammatory pain and prevented nerve injury-evoked excess nitric oxide production in the DRG, whereas administering BH4 intrathecally exacerbated pain. In humans, a haplotype of the GCH1 gene (population frequency 15.4%) was significantly associated with less pain following diskectomy for persistent radicular low back pain. Healthy individuals homozygous for this haplotype exhibited reduced experimental pain sensitivity, and forskolin-stimulated immortalized leukocytes from haplotype carriers upregulated GCH1 less than did controls. BH4 is therefore an intrinsic regulator of pain sensitivity and chronicity, and the GTP cyclohydrolase haplotype is a marker for these traits.

Adult↗

PubMed2006

The glutamate transporter GLAST is involved in spinal nociceptive processing.

GLAST and GLT-1 are the most abundant glutamate transporters in the CNS and protect neurons from glutamate neurotoxicity. Here, we investigated the role of GLAST in spinal nociceptive processing. GLAST protein expression was not altered after treatment of rats with either formalin or zymosan. Surprisingly, knock-down of GLAST in the spinal cord using antisense-oligonucleotides decreased glutamate concentrations in cerebrospinal fluid (CSF) and reduced the nociceptive behaviour in the rat formalin assay. However, it did not influence thermal hyperalgesia in the zymosan-induced paw inflammation model indicating that GLAST is associated with spontaneous rather than inflammatory nociception. Mechanisms that might explain the decreased response in the formalin assay may include compensatory activation of other glutamate transporters, inhibition of glutamate release or disturbance of glutamate recycling. In conclusion, these data suggest that inhibition of GLAST expression in the spinal cord reduces excitatory synaptic activity and thereby spontaneous responses after nociceptive stimulation of the paw.

Amino Acid Transport System X-AG↗

PubMed2006

Bradykinin and peripheral sensitization.

Pain hypersensitivity after tissue injury and inflammation is contributed to by a reduction in the threshold and an increase in the responsiveness of the peripheral terminals of high-threshold nociceptor neurons, the phenomenon of peripheral sensitization. Bradykinin, acting via G-protein-coupled receptors expressed by the sensory neurons, links to multiple intracellular signaling pathways that in turn interact with voltage-gated and ligand-gated ion channels, changing their properties in such a way as to enhance the response to peripheral stimuli.

Animals↗

PubMed2005

Essential role of the synaptic vesicle protein synapsin II in formalin-induced hyperalgesia and glutamate release in the spinal cord.

The synaptic vesicle protein synapsin II plays an important role in the regulation of neurotransmitter release and synaptic plasticity. Here, we investigated its involvement in the synaptic transmission of nociceptive signals in the spinal cord and the development of pain hypersensitivity. We show that synapsin II is predominantly expressed in terminals and neuronal fibers in superficial laminae of the dorsal horn (laminae I-II). Formalin injection into a mouse hindpaw normally causes an immediate and strong release of glutamate in the dorsal horn. In synapsin II deficient mice this glutamate release is almost completely missing. This is associated with reduced nociceptive behavior in the formalin test and in the zymosan-induced paw inflammation model. In addition, the formalin evoked increase in the number of c-Fos IR neurons is significantly reduced in synapsin II knockout mice. Touch perception and motor coordination, however, are normal indicating that synapsin II deficiency does not generally disrupt sensory and/or motor functions. Antisense-mediated transient knockdown of synapsin II in the spinal cord of adult animals also reduced the nociceptive behavior. As the antisense effect is independent of a potential role of synapsin II during development we suggest that the hypoalgesia in synapsin II deficient mice does involve a direct 'pain-facilitating' effect of synapsin II and is not essentially dependent on potentially occurring developmental alterations. The distinctive role of synapsin II for pain signaling probably results from its specific localization and possibly from a specific control of glutamate release.

Animals↗

PubMed2004

Effects of the selective COX-2 inhibitors celecoxib and rofecoxib on human vascular cells.

Rheumatoid arthritis (RA) is associated with a reduced life expectancy considered to be partly caused by cardiovascular events. A growing concern is that accelerated atherosclerosis is driven by inflammatory mechanisms similar to those responsible for RA. Therefore, selective COX-2 inhibitors, which are widely used for the symptomatic treatment of pain and inflammation in RA, may have an impact on atherosclerotic processes. Their anti-inflammatory properties might provoke anti-atherogenic effects but on the other hand, selective inhibition of anti-thrombotic prostacyclin and COX-2 independent effects might promote the risk of increased prothrombotic activity. In the current study, the effects of the presently marketed selective COX-2 inhibitors celecoxib and rofecoxib on vascular cells have been investigated. Celecoxib inhibited the proliferation of human umbilical vein endothelial cells (HUVECs) in a concentration-dependent manner. At high concentrations, it induced apoptosis and the modulation of inhibitory cell cycle proteins. In contrast rofecoxib-even at high concentrations-had no effect on cell proliferation, apoptosis or cell cycle distribution indicating that celecoxib and rofecoxib do not affect the same signal transduction pathways in endothelial cells. Both drugs did not affect apoptosis induction or cell cycle proliferation in human vascular smooth muscle cells. The observed effects on endothelial cells appear to be COX-independent since both drugs selectively inhibited COX-2-activity and the applied concentrations lay beyond the IC(50) for inhibition of prostacyclin production. Regarding endothelial apoptosis as a relevant event in the initiation and progression of atherosclerosis the present data put forward the hypothesis that the presently marketed COX-2 inhibitors have a different impact on atherosclerotic processes.

Apoptosis↗

PubMed2004

The calpain inhibitor MDL 28170 prevents inflammation-induced neurofilament light chain breakdown in the spinal cord and reduces thermal hyperalgesia.

Since long-term hyperexcitability of nociceptive neurons in the spinal cord has been suggested to be caused and maintained by changes of protein expression we assessed protein patterns in lumbar spinal cord during a zymosan induced paw inflammation employing two-dimensional (2D) gel electrophoresis. 2D PAGE revealed a time-dependent breakdown of scaffolding proteins one of which was neurofilament light chain (NFL) protein, which has been previously found to be important for axonal architecture and transport. Nociception induced breakdown of NFL in the spinal cord and dorsal root ganglias was prevented by pretreatment of the animals with a single dose of the specific inhibitor of the protease calpain (MDL-28170) which has been shown to be the primary protease involved in neurofilament degradation in neurodegenerative diseases. Treatment with the calpain inhibitor also provided anti-inflammatory and anti-hyperalgesic effects in the zymosan-induced paw inflammation model irrespective of whether the drug was administered systemically (i.p.) or delivered onto the lumbar spinal cord. This suggests that the activation of calpain is involved in the sensitization of nociceptive neurons what is partly due to neurofilament breakdown but cleavage of other calpain substrates may also be involved. Our results indicate that inhibition of pathological calpain activity may present an interesting novel drug target in the treatment of pain and inflammation.

Animals↗

PubMed2004

Protein associated with Myc (PAM) is involved in spinal nociceptive processing.

PAM (protein associated with Myc) is a potent inhibitor of adenylyl cyclases (ACs) which is primarily expressed in neurones. Here we describe that PAM is highly expressed in dorsal horn neurones and motoneuron of the spinal cord, as well as in neurones of dorsal root ganglia in adult rats. PAM mRNA expression is differentially regulated during development in both spinal cord and dorsal root ganglia of rats, being strongest during the major respective synaptogenic periods. In adult rats, PAM expression was up-regulated in the spinal cord after peripheral nociceptive stimulation using zymosan and formalin injection, suggesting a role for PAM in spinal nociceptive processing. Since PAM inhibited Galphas-stimulated AC activity in dorsal root ganglia as well as spinal cord lysates, we hypothesized that PAM may reduce spinal nociceptive processing by inhibition of cAMP-dependent signalling. Accordingly, intrathecal treatment with antisense but not sense oligonucleotides against PAM increased basal and Galphas-stimulated AC activity in the spinal cord and enhanced formalin-induced nociceptive behaviour in adult rats. Taken together our findings demonstrate that PAM is involved in spinal nociceptive processing.

Adaptor Proteins, Signal Transducing↗