Apoptotic gene expression in neuropathic pain

Pain initiated or caused by a primary lesion or dysfunction in the nervous system is defined as neuropathic pain. It results from direct injury to nerves in the peripheral or central nervous system and is associated with several clinical symptoms. Neuropathic pain treatment is extremely difficult, as it is a very complex disease, involving several molecular pathways. Excitatory or inhibitory pathways controlling neuropathic pain development show altered gene expression, caused by peripheral nerve injury.
This study used several experimental pain models to demonstrate the occurrence of programmed cell death in the centers controlling pain induction and maintenance, such as spinal cord and pre-frontal cortex. We combined behavioural, molecular and morphological approaches to assess the involvement of bcl-2 gene family and caspases in neuropathic pain. Chronic constriction injury (CCI) and spared nerve injury (SNI) of rodent sciatic nerve induced the appearance of pain-like behaviours, such as hyperalgesia and allodynia. An early (2-3 days post-CCI) apoptosis appeared in the spinal cord neurons as the pro-apoptotic bax gene increased (320±19%). The incidence of apoptosis appeared to be limited to the first few days following nerve injury. Subsequently, increased expression of anti-apoptotic bcl-2 family genes may inhibit further neuron loss. SNI triggered apoptotic pathway and caspases activation in pre-frontal cortex 7, 14, and 21 days post-injury. Among the time-points analyzed, RT-PCR analysis showed increased expression of the bax/bcl-2 ratio (40±2%), bid (16±2%), caspase-1 (84±3%), caspase-8 (53±6%), caspase-9 (25±6%), caspase-12 (58±2%), TNF (32±2%) genes in the cortex by 7 days post-injury. Western blot analysis showed increased active Caspase-3 protein levels in the cortex at 3, 7, 14, and 21 post-surgery. This study shows that apoptotic genes could be an useful pharmacological target in neuropathic pain controlling.
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Hybridase activity of human ribonuclease-1 revealed by a real-time fluorometric assay

Human ribonuclease-1 (hRNase-1) is an extracellular enzyme found in exocrine pancreas, blood, milk, saliva, urine and seminal plasma, which has been implicated in digestion of dietary RNA and in antiviral host defense. The enzyme is characterized by a high catalytic activity toward both single-stranded and double-stranded RNA. In this study, we explored the possibility that hRNase-1 may also be provided with a ribonuclease H activity, i.e. be able to digest the RNA component of RNA:DNA hybrids. For this purpose, we developed an accurate and sensitive real-time RNase H assay based on a fluorogenic substrate made of a 12 nt 5′-fluorescein-labeled RNA hybridized to a complementary 3′-quencher-modified DNA. Under physiological-like conditions, hRNase-1 was found to cleave the RNA:DNA hybrid very efficiently, as expressed by a k(cat)/K(m) of 330 000 M(−1) s(−1), a value that is over 180-fold higher than that obtained with the homologous bovine RNase A and only 8-fold lower than that measured with Escherichia coli RNase H. The kinetic characterization of hRNase-1 showed that its hybridase activity is maximal at neutral pH, increases with lowering ionic strength and is fully inhibited by the cytosolic RNase inhibitor. Overall, the reported data widen our knowledge of the enzymatic properties of hRNase-1 and provide new elements for the comprehension of its biological function

Intraperiaqueductal gray glycine and D-serine exert dual effects on rostral ventromedial medulla ON- and OFF-cell activity and thermoceptive threshold in the rat.

We have studied the involvement of the N-methyl-D-aspartate receptor (NMDAR) glycine site and the strychnine-sensitive glycine receptor (GlyR) in the ventrolateral periaqueductal gray (VL-PAG) on nociceptive behavior (tail flick) and pain-related changes on neuronal activity in the rostral ventromedial medulla (RVM). Glycine or D-serine increased the tail-flick latency, reduced OFF-cell pause, and delayed its onset and increased the time between the onset of the OFF-cell pause and the tail withdrawal. Conversely, they decreased the ongoing activity of the ON cell, the tail-flick-induced ON-cell firing, whereas they delayed the onset of increased tail-flick-induced ON-cell firing. Also, glycine or D-serine reduced the interval between the onset of the increased ON-cell firing and tail withdrawal. Whereas 7-Cl-kynurenic acid (7-Cl-KYN) prevented such effects, strychnine did not do so. A higher dose of 7-Cl-KYN or strychnine was per se able to reduce or increase tail-flick latency and increase or reduce ON-cell activities, respectively. A higher dose of glycine was hyperalgesic in the presence of 7-Cl-KYN, whereas such an effect was prevented by strychnine. These data suggest 1) a dual role of glycine in producing hyperalgesia or analgesia by stimulating the GlyR or the NMDARs within the VL-PAG, respectively; 2) consistently that RVM ON and OFF cells display opposite firing patterns to the stimulation of the VL-PAG NMDAR glycine site and GlyR activation; and 3) a tonic role of these receptors within the VL-PAG-RVM antinociceptive descending pathway.This work was supported by Ministero dell'Università e della Ricerca (Italy) Grant PRIN 2005 and Ministry of Education and Science (Spain) Grant SAF2005-3185.Peer reviewe

Michaelis–Menten plot for cleavage of the double-helical substrate by hRNase-1

<p><b>Copyright information:</b></p><p>Taken from "Hybridase activity of human ribonuclease-1 revealed by a real-time fluorometric assay"</p><p>Nucleic Acids Research 2006;34(10):2906-2913.</p><p>Published online 31 May 2006</p><p>PMCID:PMC1474055.</p><p>© The Author 2006. Published by Oxford University Press. All rights reserved</p> Assays were performed as detailed in , except that substrate concentration was 20–400 nM and enzyme concentration was 0.14–1.4 nM