The role of kinin B[indice inférieur 1] receptor in diabetic hyperalgesia

Autoimmune insulin-dependent type 1 diabetes involves an overproduction of cytokines, including interleukin-1[bêta] (IL-1[bêta]) and tumour necrosis factor-[alpha] (TNF-[alpha]), which leads to T-cell-mediated pancreatic [bêta]-cell destruction. It is associated with a series of complications including nephropathy, retinopathy and painful diabetic neuropathy (PDN). Several neurovascular systems are activated in type 1 diabetes including the inducible bradykinin (BK)B[indice inférieur 1] receptor (BKB[indice inférieur 1]-R) subtype which is generally absent or of little impact in healthy states, but highly induced or over-expressed under pathological conditions among which type 1 diabetes, where the over-production of cytokines, the hyperglycemia and the oxidative stress are critical factors for its up-regulation. The present project aimed at studying the development of hyperalgesia in rodent models of type 1 diabetes and characterising the role of the inducible BKB[indice inférieur 1]-R in this diabetic complication, through the use of selective BKB[indice inférieur 1]-R agonists and antagonists. Nociception was evaluated with two types of thermal pain tests; spinal (tail immersion and tail flick tests) and supra-spinal (hot plate and plantar stimulation) tests. Chemically streptozotocin (STZ)-induced diabetic mice and rats showed a marked hyperalgesia that was stable over 4 weeks following the STZ injection. Non-obese diabetic (NOD) and BioBreeding/Worcester (BB/Wor) rats, models of autoimmune spontaneous type 1 diabetes, similarly developed significant hyperalgesia over time (4-32 and 4-24 weeks of age, respectively). Hyperalgesia observed in NOD mice and BB/Wor rats did not correlate with hyperglycemia, but rather preceded the increase in the animal plasma glucose concentration. This finding supports the hypothesis that type 1 diabetic complications start early during the progression of the disease, even before the diagnosis of the state of hyperglycemia. The selective BKB[indice inférieur 1]-R agonist, desArg[indice supérieur 9]BK (DBK), which did not affect nociception in control non-diabetic animals, potentiated hyperalgesia in STZ-diabetic and NOD mice. In addition, the acute and chronic administration of the selective BKB[indice inférieur 1]-R antagonists R-715 and R-954 significantly attenuated diabetic hyperalgesia in all tested animals models. Our results also showed that stimulation of the inducible BKB[indice inférieur 1]-R activates several neurotransmitter systems responsible for the mediation of diabetic hyperalgesia including the substance P (SP), nitric oxide (NO) and calcitonin gene-related peptide (CGRP). Nevertheless, the hyperalgesia observed in wild type diabetic mice was totally absent in the BKB[indice inférieur 1]-R-knockout (KO) diabetic mice in which DBK had no effect on nociceptive responses."--Résumé abrégé par UMI

Dualité fonctionnelle des récepteurs des kinines en physiopathologie

Les kinines sont des peptides autacoïdes (hormones locales) et des neuromédiateurs centraux impliqués dans le contrôle cardiovasculaire, l’inflammation et la douleur. Leurs effets sont relayés par deux types de récepteurs couplés aux protéines G: un récepteur B2, constitutif, et un récepteur B1, inductible en présence de cytokines, d’endotoxines ou de lésions tissulaires. Alors que le récepteur B2 contribue aux effets bénéfiques des inhibiteurs de l’enzyme de conversion de l’angiotensine-I utilisés dans le traitement des maladies cardiovasculaires, il participe à la phase aiguë de l’inflammation et de la douleur somatique et viscérale. Le récepteur B1 participe, quant à lui, à la phase chronique de ces réponses, et jouerait un rôle stratégique dans les maladies ayant une forte composante immune telles que l’arthrite rhumatoïde, la sclérose en plaques, le choc septique ou le diabète. Il posséderait également une dualité fonctionnelle, se manifestant par une action protectrice (vis-à-vis de la sclérose en plaques et du choc septique, par exemple) ou délétère (dans le cas de la douleur et de l’inflammation). Ainsi, l’utilisation d’antagonistes de ces récepteurs comme agents thérapeutiques nécessite une évaluation rigoureuse de leurs effets.Kinins are autacoid peptides and central neuromediators involved in cardiovascular regulation, inflammation and pain. Their effects are mediated by two transmembrane G-protein-coupled receptors denoted as B1 and B2. While the B2 receptor is constitutive, the B1 receptor is inducible and up-regulated in the presence of cytokines, endotoxins or during tissue injury. The B2 receptor is believed to play an important role in the beneficial effects of angiotensin-1 converting enzyme inhibitors used in the treatment of cardiovascular diseases, yet it is involved in the acute phase of inflammation and of somatic and visceral pain. Conversely, the B1 receptor participates in the chronic phase of these responses and is likely to play a strategic role in diseases with a strong immune component such as rheumatoid arthritis, multiple sclerosis, septic shock and diabetes. A dual function for the B1 receptor is also reported in some pathologies in which it can exert either a protective (multiple sclerosis and septic shock) or harmful (pain and inflammation) effect. Therefore, the use of antagonists for these receptors as clinical therapeutic agents requires a rigorous evaluation of the potential side effects

Reversal of Morphine Analgesic Tolerance by Ethanol in the Mouse

The chronic use of opioids in humans, accompanied by the development of tolerance, is a dangerous phenomenon in its own right. However, chronic opioid use is often made more dangerous by the coconsumption of other substances. It has been observed that the blood level of opioids in postmortem analyses of addicts, who consumed ethanol along with the opioid, was much less than that observed in individuals who died from opioids alone. This relationship between ethanol and opioids led us to investigate the hypothesis that ethanol alters tolerance to opioids. In the present study, we report that ethanol significantly and dose-dependently reduced the antinociceptive tolerance produced by morphine and the cross-tolerance between [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) and morphine in the mouse tail-flick test. The reversal of morphine tolerance was partially blocked by both the gamma receptor blocker bicuculline and by the g-aminobutyric acid (GABA)B receptor blocker phaclofen and the administration of both inhibitors completely reversed the effects of ethanol on morphine tolerance. Diazepam, like ethanol, decreased morphine tolerance. However, this inhibition was reversed by the GABAA antagonist bicuculline but not by the GABAB antagonist phaclo-fen. These findings have important implications for individuals who abuse opioids and ethanol as well as suggest a mechanism to reduce the amount of opioid needed in chronic pain treatment