Allodynia In Diabetic Mice Research Articles

Role of Spinal Cholecystokinin Octapeptide, Nociceptin/Orphanin FQ, and Hemokinin-1 in Diabetic Allodynia.

A complication of diabetes is neuropathic pain, which is difficult to control with medication. We have confirmed that neuropathic pain due to mechanical allodynia in diabetic mice is mediated by a characteristic neuropeptide in the spinal cord. We evaluated the strength of mechanical allodynia in mice using von Frey filaments. When mice were intravenously injected with streptozotocin, mechanical allodynia appeared 3 days later. Antibodies of representative neuropeptides were intrathecally (i.t.) administered to allodynia-induced mice 7 days after the intravenous administration of streptozotocin, and allodynia was reduced by anti-cholecystokinin octapeptide antibodies, anti-nociceptin/orphanin FQ antibodies, and anti-hemokinin-1 antibodies. In contrast, i.t.-administered anti-substance P antibodies, anti-somatostatin antibodies, and anti-angiotensin II antibodies did not affect streptozotocin-induced diabetic allodynia mice. Mechanical allodynia was attenuated by the i.t. administration of CCK-B receptor antagonists and ORL-1 receptor antagonists. The mRNA level of CCK-B receptors in streptozotocin-induced diabetic allodynia mice increased in the spinal cord, but not in the dorsal root ganglion. These results indicate that diabetic allodynia is caused by cholecystokinin octapeptide, nociceptin/orphanin FQ, and hemokinin-1 released from primary afferent neurons in the spinal cord that transmit pain to the brain via the spinal dorsal horn.

The selective TRPV4 channel antagonist HC-067047 attenuates mechanical allodynia in diabetic mice

Painful diabetic neuropathy (PDN) is a serious symptom that compromises quality of life and remains without effective pharmacological treatment. The transient receptor vanilloid 4 (TRPV4) is a cation-permeable channel implicated in sensory transduction and pain signalling. Therefore, drugs that act on TRPV4 may have therapeutic applications to treat PDN. In the present work, we assessed the effect of the selective TRPV4 channel antagonist HC-067047 on painful neuropathy associated with streptozotocin (STZ)-induced diabetes in mice. STZ-treated animals presented both mechanical and cold allodynia at 6 weeks after diabetes induction. Notably, HC-067047 (1 mg/kg, s.c.) given daily between 2 and 6 weeks after diabetes induction significantly prevented the development of mechanical allodynia. Additionally, both single and repeated treatments with HC-067047 (10 mg/kg, s.c.) significantly reverted established mechanical allodynia induced by STZ. However, HC-067047 was not capable of affecting either thermal cold allodynia or hyperglycemia. Similarly, HC-067047 treatments showed no effect on body weight, temperature, locomotor activity or motor coordination of control mice. Immunohistochemistry assay showed that TRPV4 expression was not different in sciatic nerve, dorsal root ganglia (DRG) or hind paw plantar skin from diabetic and non-diabetic mice, suggesting that HC-067047 acts on constitutive receptors to inhibit mechanical allodynia. Taken together, the data generated in the present study show the potential relevance of using TRPV4 antagonists to treat painful neuropathy associated with diabetes.

PREGABALIN TREATMENT OF PERIPHERAL NERVE DAMAGE IN A MURINE DIABETIC PERIPHERAL NEUROPATHY MODEL.

Peripheral nerve lesions are a major complication of diabetes mellitus, the main clinical manifestations of which are numbness and pain involving the limbs. To determine the correlation between pregabalin treatment and diabetic peripheral neuropathic pain. An experimental animal study in BALB/c mice. Diabetes models are established by injecting streptozotocin (STZ) into the abdominal cavities of mice. The correlation between the treatment effect, time, and dosage of pregabalin was determined. The effect of a type 1 organic cation transporter (Octn1) in the absorption of pregabalin was evaluated. Pregabalin reduced tactile allodynia in diabetic mice. The best analgesic effect occurred when intestinal absorption was increased. Octn1 mediated pregabalin entry into intestinal epithelial cells, which influenced the absorption of pregabalin with a time-dependent fluctuation in the small intestine. Peripheral nerve damage caused by diabetes was dependent on time and dose of pregabalin, which was related to the regular expression of Octn1 in small intestinal epithelium. Peripheral nerve damage caused by diabetes was dependent on time and dosage of pregabalin, which was related to the regular expression of Octn1 in small intestinal epithelium.

Secoisolariciresinol diglycoside, a flaxseed lignan, exerts analgesic effects in a mouse model of type 1 diabetes: Engagement of antioxidant mechanism

Peripheral painful neuropathy is one of the most common complications in diabetes and necessitates improved treatment. Secoisolariciresinol diglycoside (SDG), a predominant lignan in flaxseed, has been shown in our previous studies to exert antidepressant-like effect. As antidepressant drugs are clinically used to treat chronic neuropathic pain, this work aimed to investigate the potential analgesic efficacy of SDG against diabetic neuropathic pain in a mouse model of type 1 diabetes. We subjected mice to diabetes by a single intraperitoneal (i.p.) injection of streptozotocin (STZ, 200mg/kg), and Hargreaves test or von Frey test was used to assess thermal hyperalgesia or mechanical allodynia, respectively. Chronic instead of acute SDG treatment (3, 10 or 30mg/kg, p.o., twice per day for three weeks) ameliorated thermal hyperalgesia and mechanical allodynia in diabetic mice, and these analgesic actions persisted about three days when SDG treatment was terminated. Although chronic treatment of SDG to diabetic mice did not impact on the symptom of hyperglycemia, it greatly attenuated excessive oxidative stress in sciatic nerve and spinal cord tissues, and partially counteracted the condition of weight decrease. Furthermore, the analgesic actions of SDG were abolished by co-treatment with the reactive oxygen species donor tert-butyl hydroperoxide (t-BOOH), but potentiated by the reactive oxygen species scavenger phenyl-N-tert-butylnitrone (PBN). These findings indicate that chronic SDG treatment can correct neuropathic hyperalgesia and allodynia in mice with type 1 diabetes. Mechanistically, the analgesic actions of SDG in diabetic mice may be associated with its antioxidant activity.

Central or peripheral delivery of an adenosine A1 receptor agonist improves mechanical allodynia in a mouse model of painful diabetic neuropathy

Diabetic peripheral neuropathy is a common complication of diabetes mellitus, and a significant proportion of individuals suffer debilitating pain that significantly affects their quality of life. Unfortunately, symptomatic treatment options have limited efficacy, and often carry significant risk of systemic adverse effects. Activation of the adenosine A1 receptor (A1R) by the analgesic small molecule adenosine has been shown to have antinociceptive benefits in models of inflammatory and neuropathic pain. The current study used a mouse model of painful diabetic neuropathy to determine the effect of diabetes on endogenous adenosine production, and if central or peripheral delivery of adenosine receptor agonists could alleviate signs of mechanical allodynia in diabetic mice. Diabetes was induced using streptozocin in male A/J mice. Mechanical withdrawal thresholds were measured weekly to characterize neuropathy phenotype. Hydrolysis of AMP into adenosine by ectonucleotidases was determined in the dorsal root ganglia (DRG) and spinal cord at 8 weeks post-induction of diabetes. AMP, adenosine and the specific A1R agonist, N6-cyclopentyladenosine (CPA), were administered both centrally (intrathecal) and peripherally (intraplantar) to determine the effect of activation of adenosine receptors on mechanical allodynia in diabetic mice. Eight weeks post-induction, diabetic mice displayed significantly decreased hydrolysis of extracellular AMP in the DRG; at this same time, diabetic mice displayed significantly decreased mechanical withdrawal thresholds compared to nondiabetic controls. Central delivery AMP, adenosine and CPA significantly improved mechanical withdrawal thresholds in diabetic mice. Surprisingly, peripheral delivery of CPA also improved mechanical allodynia in diabetic mice. This study provides new evidence that diabetes significantly affects endogenous AMP hydrolysis, suggesting that altered adenosine production could contribute to the development of painful diabetic neuropathy. Moreover, central and peripheral activation of A1R significantly improved mechanical sensitivity, warranting further investigation into this important antinociceptive pathway as a novel therapeutic option for the treatment of painful diabetic neuropathy.

Hemopressin an Inverse Agonist of Cb1 Cannabinoid Receptors Reverses Mechanical Sensitivity on Diabetes-Induced Neuropathy in Mice

Peripheral neuropathy is one of the most common complications of diabetes affecting about 50% of patients with the disease. The most prominent symptoms involve the extremities and occur as both an exaggerated response to noxious stimuli (hyperalgesia), mild or non-painful stimuli (allodynia). Hemopressin (Hp) is a non apeptide first found in rat brain extracts, which selectively binds CB1 cannabinoid receptors (CB1R) and exerts antinociceptive actions in experimental inflammatory and neuropathic pain models. However there is no data about its efficacy in neuropathic metabolic-related disease, like diabetes mellitus. The aim of this study was to investigate the role of Hp on mechanical and thermal sensitivity of mice submitted to an experimental model of type 1 diabetes mellitus-induced neuropathy. Mechanical allodynia and thermal sensibility were assessed by von Frey filaments or plantar test, respectively, 7, 14, 21 and 28 days after streptozotocine injection (STZ; 200 mg/kg). Body weight and blood glucose were monitored once a week. Hp was administered orally, once a day (2.5 mg/kg) for 28 days. Hp reversed mechanical allodynia in diabetic mice without changing blood glucose levels or body weight. No effects were observed for thermal sensitivity. These results make hemopressin an attractive approach for the development of cannabinoid-based therapies for the treatment diabetic neuropathic pain.

The Dipeptide Phe-Phe Amide Attenuates Signs of Hyperalgesia, Allodynia and Nociception in Diabetic Mice Using a Mechanism Involving the Sigma Receptor System

BackgroundPrevious studies have demonstrated that intrathecal administration of the substance P amino-terminal metabolite substance P1-7 (SP1-7) and its C-terminal amidated congener induced antihyperalgesic effects in diabetic mice. In this study, we studied a small synthetic dipeptide related to SP1-7 and endomorphin-2, i.e. Phe-Phe amide, using the tail-flick test and von Frey filament test in diabetic and non-diabetic mice.ResultsIntrathecal treatment with the dipeptide increased the tail-flick latency in both diabetic and non-diabetic mice. This effect of Phe-Phe amide was significantly greater in diabetic mice than non-diabetic mice. The Phe-Phe amide-induced antinociceptive effect in both diabetic and non-diabetic mice was reversed by the σ1 receptor agonist (+)-pentazocine. Moreover, Phe-Phe amide attenuated mechanical allodynia in diabetic mice, which was reversible by (+)-pentazocine. The expression of spinal σ1 receptor mRNA and protein did not differ between diabetic mice and non-diabetic mice. On the other hand, the expression of phosphorylated extracellular signal-regulated protein kinase 1 (ERK1) and ERK2 proteins was enhanced in diabetic mice. (+)-Pentazocine caused phosphorylation of ERK1 and ERK2 proteins in non-diabetic mice, but not in diabetic mice.ConclusionsThese results suggest that the spinal σ1 receptor system might contribute to diabetic mechanical allodynia and thermal hyperalgesia, which could be potently attenuated by Phe-Phe amide.

Systemic and spinal administration of etanercept, a tumor necrosis factor alpha inhibitor, blocks tactile allodynia in diabetic mice

Painful diabetic neuropathy is one of the most common forms of neuropathic pain syndromes. Tumor necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine that has been implicated as a key pain mediator in the development and maintenance of neuropathic pain conditions. Recent studies showed that endogenous TNF-alpha production was also accelerated in neural tissues and spinal cord under chronic hyperglycemia. Thus, in this study, we investigated whether pharmacological inhibition of TNF-alpha by etanercept, a TNF-alpha antagonist, could block behavioral sign of diabetic neuropathic pain. Diabetes was induced by streptozotocin (STZ) (200 mg/kg, i.p.) in Balb-c mice and behavioral tests were performed between 45 and 60 days after STZ administration. Mechanical and thermal sensitivities were measured by a series of calibrated Von Frey filaments and hot plate test, respectively. Etanercept was given by either intravenous (i.v.), intrathecal (i.th.) or intraplantar (i.pl.) routes to the diabetic mice. Tactile allodynia, but not thermal hyperalgesia, developed in diabetic mice. Both i.v. (1, 10 and 20 mg/kg) or i.th. (1, 5 and 10 μg/mouse) treatments with etanercept produced dose dependent reversal of tactile allodynia in diabetic mice. However, etanercept was found to be inactive against allodynia when given i.pl. (1, 5 and 10 μg/mouse). Our results suggest that etanercept has promising effects on diabetic neuropathic pain with antiallodynic effects when given systemically or intrathecally.

RhoA/Rho kinase pathway contributes to the pathogenesis of thermal hyperalgesia in diabetic mice

Diabetic neuropathy is one of the most common complications of diabetes and causes various problems in daily life. Several investigations have noted that many factors in the spinal cord are involved in the symptoms of painful diabetic neuropathy, and there are very few effective therapeutic regimens. In the present study, we sought to elucidate the role of the RhoA/Rho kinase (ROCK) pathway in thermal hyperalgesia in diabetic mice. The intracellular localization of RhoA and the expression of eNOS were measured by western blotting. Thermal hyperalgesia was assessed by the tail-flick test and mechanical allodynia was assessed by automated von Frey filament test in streptozotocin(STZ)-induced diabetic mice. The spinal cord of STZ-treated diabetic mice showed increased membrane-bound RhoA compared to non-diabetic control. Treatment with the RhoA inhibitor exoenzyme C3, Clostridium botulinum, and the ROCK inhibitor Y27632 attenuated thermal hyperalgesia and mechanical allodynia in diabetic mice. Moreover, daily treatment with simvastatin attenuated all of those changes in diabetic mice. The expression of eNOS and NO metabolite contents in the spinal cord was decreased in diabetic mice, and these changes were normalized by treatment with simvastatin. The present results show that HMG-CoA reductase inhibitors have an inhibitory effect on thermal hyperalgesia in diabetic mice, which is mediated by an increase in NO production through the inhibition of RhoA/ROCK pathways. These results suggest that ROCK inhibitors and HMG-CoA inhibitors may be attractive compounds to relieve the symptoms of painful diabetic neuropathies.

Effect of acute topical application of (+)-pentazocine on the mechanical allodynia in diabetic mice

Mechanical allodynia is a major complication in diabetic mellitus. Peripheral σ 1 receptors were shown to be involved in nociceptive perception. We therefore investigated the effect of σ 1 receptor ligand (+)-pentazocine injected into the dorsal surface of the hindpaw on mechanical allodynia in streptozotocin-induced diabetic mice. Injection of (+)-pentazocine (30 μg) into the dorsal surface of the hindpaw did not affect the mechanical threshold and hindpaw NO contents in non-diabetic mice, whereas the mechanical allodynia and hindpaw contents of NO metabolites in diabetic mice were normalized by (+)-pentazocine. These effects of (+)-pentazocine in diabetic mice were inhibited by pretreatment with an σ receptor antagonist BD1047 into the same area, but not by systemic pretreatment with a κ-opioid receptor antagonist nor-binaltorphimine. These results suggest that (+)-pentazocine injected into the dorsal surface of the hindpaw increases the lowered mechanical threshold in diabetic mice through the activation of peripheral σ 1 receptors. This attenuation may be, in part, due to the normalization of increased peripheral NO contents in the hindpaw of diabetic mice.

Rimonabant, a cannabinoid CB1 receptor antagonist, attenuates mechanical allodynia and counteracts oxidative stress and nerve growth factor deficit in diabetic mice

Diabetes is one of the leading causes of painful neuropathy and to date, besides a tight glycemic control, a viable treatment for this complication is not available. Rimonabant is a selective cannabinoid CB(1) receptor antagonist that produces a significant increase in insulin sensitivity and a reduction of HbA(1c) in diabetic patients. This study aimed to investigate the therapeutic potential of rimonabant in relieving diabetes-induced neuropathic pain. The repeated treatment with rimonabant evoked a significant attenuation of mechanical allodynia in diabetic mice that was dose- and time-dependent. This effect occurred without alteration of hyperglycemia, but it was associated with significant effects on many key players in the pathogenesis of diabetic neuropathy. Metabolic changes induced by hyperglycemia lead to oxidative stress, deregulation of cytokine control and reduced production and transport of nerve growth factor (NGF), and all these factors contribute to neuropathic pain. Rimonabant treatment reduced oxidative stress in peripheral nerve, as revealed by the ability of the compound to counteract the reduced glutathione (GSH) depletion. The same repeated treatment inhibited tumor necrosis factor (TNFalpha) overproduction in the spinal cord and increased the NGF support. This rimonabant-induced improvement might favour the nerve regeneration; accordingly, the histological analysis of sciatic nerves showed a marked degeneration of myelinated fibers in diabetic mice, that was substantially reduced after rimonabant administration. These findings support the hypothesis that CB(1) antagonists would represent a new opportunity for diabetic patients, since currently there are no treatments for painful diabetic neuropathy other than treating the diabetic condition per se.

Involvement of protein isoprenylation in mechanical allodynia in diabetic mice

Involvement of protein isoprenylation in mechanical allodynia in diabetic mice

Modulation of P2X receptors in dorsal root ganglion neurons of streptozotocin-induced diabetic neuropathy

Painful diabetic neuropathy causes hyperalgesia and does not respond to commonly used analgesics such as non-steroidal anti-inflammatory drugs or opioids at doses below those producing disruptive side effects. In the present study, we examined the effect of P2X receptor antagonists, which are known to modulate the pain pathway, on mechanical hyperalgesia in streptozotocin (STZ)-induced diabetic mice. The paw withdrawal frequency measured by von Frey filaments, began to significantly increase 5 days after STZ injection and was maintained for more than 14 days. Intrathecal administration of P2X receptor antagonists (PPADS and TNP-ATP) inhibited the mechanical allodynia in diabetic mice. The levels of P2X2 and P2X3 receptors mRNA were significantly increased in diabetic mice at 14 days after the intravenous injection of STZ. These results suggest that the upregulation of P2X2, P2X3 and/or P2X2/3 receptor in DRG neurons is associated with mechanical allodynia in STZ-induced diabetic mice.

Sulfasalazine blocks the development of tactile allodynia in diabetic rats.

OBJECTIVE—Diabetic neuropathy is manifested either by loss of nociception (painless syndrome) or by mechanical hyperalgesia and tactile allodynia (pain in response to nonpainful stimuli). While therapies with vasodilators or neurotrophins reverse some functional and metabolic abnormalities in diabetic nerves, they only partially ameliorate neuropathic pain. The reported link between nociception and targets of the anti-inflammatory drug sulfasalazine prompted us to investigate its effect on neuropathic pain in diabetes.RESEARCH DESIGN AND METHODS—We examined the effects of sulfasalazine, salicylates, and the poly(ADP-ribose) polymerase-1 inhibitor PJ34 on altered nociception in streptozotocin-induced diabetic rats. We also evaluated the levels of sulfasalazine targets in sciatic nerves and dorsal root ganglia (DRG) of treated animals. Finally, we analyzed the development of tactile allodynia in diabetic mice lacking expression of the sulfasalazine target nuclear factor-κB (NF-κB) p50.RESULTS—Sulfasalazine completely blocked the development of tactile allodynia in diabetic rats, whereas relatively minor effects were observed with other salicylates and PJ34. Along with the behavioral findings, sciatic nerves and DRG from sulfasalazine-treated diabetic rats displayed a decrease in NF-κB p50 expression compared with untreated diabetic animals. Importantly, the absence of tactile allodynia in diabetic NF-κB p50−/− mice supported a role for NF-κB in diabetic neuropathy. Sulfasalazine treatment also increased inosine levels in sciatic nerves of diabetic rats.CONCLUSIONS—The complete inhibition of tactile allodynia in experimental diabetes by sulfasalazine may stem from its ability to regulate both NF-κB and inosine. Sulfasalazine might be useful in the treatment of nociceptive alterations in diabetic patients.

Contribution of Ca2+-Dependent Protein Kinase C in the Spinal Cord to the Development of Mechanical Allodynia in Diabetic Mice

In this paper, we directly demonstrate, for the first time, the activation of Ca(2+)-dependent protein kinase C (PKC) in the spinal cord of diabetic mice. In streptozotocin (STZ)-treated (200 mg/kg, i.v.) diabetic mice, hypersensitivity (allodynia) to mechanical stimulation appeared 7 d after STZ injection. This mechanical allodynia was inhibited by intrathecal injection of the PKC inhibitors 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) and calphostin C, but not the protein kinase A inhibitor N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89). The activity of membrane-associated Ca(2+)-dependent PKC in the spinal cords of STZ-induced diabetic mice was significantly higher than that observed in non-diabetic mice. These results suggest that activation of Ca(2+)-dependent PKC in the spinal cord, contributes to the mechanical allodynia in the pain associated with diabetic neuropathy.

Cannabinoids blocks tactile allodynia in diabetic mice without attenuation of its antinociceptive effect

Diabetic neuropathic pain is one of the most commonly encountered neuropathic pain syndromes. However, the treatment of diabetic neuropathic pain is challenging because of partial effectiveness of currently available pain relievers. It is well known that diabetic animals are less sensitive to the analgesic effect of morphine, and opioids are found to be ineffective in the treatment of diabetic neuropathic pain. Cannabinoids are promising drugs and they share a similar pharmacological properties with opioids. It has been reported that cannabinoid analgesia remained intact and to be effective in some models of nerve injury. Thus, we investigated antinociceptive efficacy and the effects of cannabinoids on behavioral sign of diabetic neuropathic pain in diabetic mice by using WIN 55, 212-2, a cannabinoid receptor agonist. Diabetes was induced by streptozotocin (STZ) (200 mg/kg) and animals were tested between 45 and 60 days after onset of diabetes. Antinociception was assessed using the radiant tail-flick test. Mechanical and thermal sensitivities were measured by Von Frey filaments and hot-plate test, respectively. Tactile allodynia, but not thermal hyperalgesia developed in diabetic mice. Systemic WIN 55, 212-2 (1, 5 and 10 mg/kg) produced a dose-dependent antinociception both in diabetic and control mice. WIN 55, 212-2-induced antinociception were found to be similar in diabetic mice when compared to controls suggesting efficacy of cannabinoid antinociception was not diminished in diabetic mice. WIN 55, 212-2 also produced a dose-dependent antiallodynic effect in diabetic mice. This study suggests that cannabinoids have a potential beneficial effect on experimental diabetic neuropathic pain.