Evaluation of antinociceptive and antioxidant properties of 3-[4-(3-trifluoromethyl-phenyl)-piperazin-1-yl]-dihydrofuran-2-one in mice

Kinga Saat Katarzyna Gawlik Jadwiga Witalis Dorota Pawlica-Gosiewska Barbara Filipek Bogdan Solnica Krzysztof Wickowski Barbara Malawska The aim of this study was to evaluate the influence of 3-[4-(3-trifluoromethyl-phenyl)-piperazin-1-yl]dihydrofuran-2-one (LPP1) on nociceptive thresholds in mouse models of persistent pain. Influence of LPP1 on motor coordination and its antioxidant capacity in mouse brain tissue homogenates were also assessed. Pain sensitivity thresholds in animals treated with LPP1 were established using 5 % formalin solution in normoglycemic mice and in streptozotocin (STZ)-treated diabetic mice in the von Frey, hot plate, innocuous, and noxious cold water tests (water at 10 C and 4 C, respectively). Motor deficits were assessed in the rotarod test, whereas antioxidant capacities were evaluated using ferric reducing ability of plasma (FRAP) assay, catalase (CAT), and superoxide dismutase (SOD) activities. LPP1was antinociceptive in both phases of the formalin test, in particular, in the late phase (at doses 0.930 mg/kg for 66-99 % vs. control normoglycemic mice) and in a statistically significant manner increased nociceptive thresholds in response to mechanical, heat, and noxious cold stimulation in neuropathic mice (at 30 mg/kg for 274, 192, and 316 %, respectively vs. diabetic control). LPP1 did not impair motor coordination of mice in the rotarod revolving at 6 or 18 rpm. In brain tissue homogenates, it demonstrated antioxidant capacity in FRAP assay and increased SOD activity for 63 % (acute administration) and 28 % (chronic administration) vs. control. No influence on CAT activity was observed. LPP1 has significant antinociceptive properties in the formalin model and elevates pain thresholds in neuropathic mice. It has antioxidant capacity and is devoid of negative influence on animals' motor coordination. - Neuropathic pain is a debilitating form of chronic pain that results from dysfunction or damage to the peripheral or central nervous system (CNS). This type of pain is considered as a drug-resistant complication that still remains a serious medical problem worldwide. The term neuropathic pain comprises a variety of painful conditions, including postamputation pain, painful neuropathies (e.g., painful diabetic neuropathy and postherpetic neuralgia), posttraumatic neuralgia, and others. So far, multiple factors responsible for development of neuropathic pain have been identified: metabolic diseases (e.g., diabetes), neuronal tissue injuries caused by ischemia, toxicological factors or mechanical damage to the spinal cord, and others (Nickel et al. 2012; Woolf and Mannion 1999). Hence, pharmacotherapy used to relieve neuropathic pain comprises several pharmacological classes, of which antiepileptic drugs (AEDs), antidepressant drugs, opioid analgesics, and local anesthetic agents play a pivotal role (Christoph et al. 2011; Davis 2007; Davis 2010; Gilron et al. 2009; Miranda et al. 2012; Takeuchi et al. 2007; Yamama et al. 2010). Despite this, approximately 1030 % of patients suffering from neuropathic pain syndromes are drug resistant (Blackburn-Munro and Erichsen 2005), so still, there is a great need for seeking new analgesic compounds able to attenuate neuropathic pain episodes. Many lines of evidence indicate that oxidative stress is implicated in a variety of disorders, including degenerative diseases (Kasznicki et al. 2012; Reynolds et al. 2007; Trushina and McMurray 2007; Uttara et al. 2009), atherosclerosis, inflammation (Barton et al. 2007; Reuter et al. 2010; Salvemini et al. 2011), and chronic pain (Janes et al. 2012; Salvemini et al. 2011). Painful diabetic neuropathy is one of the most serious complications of diabetes in which the role of oxidative stress has been postulated. Imbalance between enhanced generation of reactive oxygen and nitrogen species and diminished activity of enzymatic and nonenzymatic antioxidant defenses as a key factor underlying diabetic neuropathy in mammals has been demonstrated (Di Naso et al. 2011; Pacher et al. 2005). In our previous studies, we demonstrated significant antinociceptive, antiinflammatory, and local anesthetic activities (Salat et al. 2009; Salat et al. 2012a; Salat et al. 2012b; Wickowski et al. 2012) as well as antioxidant properties (Salat et al. 2012a; Salat et al. 2012b) of several dihydrofuran-2-one derivatives, including the 3-[4-(3-trifluoromethyl-phenyl)piperazin-1-yl]-dihydrofuran-2-one (LPP1). Observed cell membrane-stabilizing properties of these derivatives, together with their antioxidant capacity, suggest that they might be effective as antiallodynic and antihyperalgesic agents in diabetes-induced neuropathic pain models. In the present study, we focus on antinociceptive activity of the compound LPP1. We evaluate its efficacy in tonic (formalin) and neuropathic pain models in normoglycemic and diabetic mice, respectively. In view of the observed significant antioxidant capacity in 2,2'-azino-bis3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical cation scavenging assay, we assess influence of LPP1 on selected markers of oxidative stress in mouse brain tissues (total antioxidant status in ferric reducing ability of plasma (FRAP) assay, activity of superoxide dismutase (SOD), and catalase (CAT)). The influence of LPP1 on motor coordination of diabetic animals in the rotarod test is also presented below. Materials and methods Animals and housing conditions Adult male Albino Swiss (CD-1) mice weighing 1824 g were used in behavioral experiments. The animals were kept in groups of 15 mice in cages at room temperature of 222 C under light/dark (12:12) cycle and had free access to food and water before experiments. Ambient temperature of the room and humidity were kept consistent throughout all tests. For the experiments, the animals were randomly selected. Each group consisted of eight to 18 animals per dose and each mouse was used only once. The mice were allowed to acclimate to holding cages prior to the test for a minimum of 30 min. The experiments were performed between 8 a.m. and 3 p.m. Behavioral measures were scored by trained observers blind to experimental conditions. The animals were killed by cervical dislocation immediately after the assay. All the procedures were approved by the local ethics committee of the Jagiellonian University in Cracow (ZI/595/2011). Chemicals used in pharmacological tests Synthesis of the investigated compound, LPP1, was described previously (Salat et al. 2009). For behavioral experiments, LPP1, pregabalin (a reference drug in the neuropathic pain model), and morphine (a reference compound in the formalin test) were suspended in a 0.5 % methylcellulose solution (Loba Chemie, Germany) and administered by the intraperitoneal (i.p.) route 30 min before the test. Control animals were given an appropriate amount of vehicle (0.5 % methylcellulose suspension; i.p.) 30 min before the test. To evaluate antioxidant capacity, LPP1 and prega (...truncated)