Intrathecal edaravone, a free radical scavenger, is effective on inflammatory-induced pain in rats

Multiple biological active 4-aminopyrazoles containing trifluoromethyl and their 4-nitroso-precursors: Synthesis and evaluation

4-Nitroso-3-trifluoromethyl-5-alkyl[(het)aryl]pyrazoles were synthesized via one-pot nitrosation of 1,3-diketones or their lithium salts followed by treatment of hydrazines. Reduction of nitroso-derivatives made it possible to obtain 4-amino-3-trifluoromethylpyrazoles chlorides. According to computer-aided calculations, all synthesized compounds are expected to have acceptable ADME profile for drug design. Tuberculostatic, antibacterial, antimycotic, antioxidant and cytotoxic activities of the compounds were evaluated in vitro, while their analgesic and anti-inflammatory action was tested in vivo along with acute toxicity studies. N-Unsubstituted 4-nitrosopyrazoles were the most effective tuberculostatics (MIC to 0.36 μg/ml) and antibacterial agents against Streptococcus pyogenes (MIC to 7.8 μg/ml), Staphylococcus aureus,S. aureus MRSA and Neisseria gonorrhoeae (MIC to 15.6 μg/ml). 4-Nitroso-1-methyl-5-phenylpyrazole had the pronounced antimycotic action against a wide range of fungi (Trichophytonrubrum, T. tonsurans, T. violaceum, T. interdigitale, Epidermophytonfloccosum, Microsporumcanis with MIC 0.38-12.5 μg/ml). N-Unsubstituted 4-aminopyrazoles shown high radical-scavenging activity in ABTS test, ORAC/AAPH and oxidative erythrocyte hemolysis assays. 1-Methyl-5-phenyl-3-trifluoromethylpyrazol-4-aminium chloride revealed potential anticancer activity against HeLa cells (SI > 1351). The pronounced analgesic activity was found for 4-nitroso- and 4-aminopyrazoles having phenyl fragment at the position 5 in "hot plate" test. The most of the obtained pyrazoles had a moderate acute toxicity.

Phytochemical and anti-neuropathic investigations of Crocus sativus via alleviating inflammation, oxidative stress and pancreatic beta-cells regeneration

Objective

The aim of this study is to investigate the phytochemical and the long-term anti-neuropathic potentials of Crocus sativus cultivated in the University botanical garden, and explore its most bioactive compounds and their underlying mechanisms of action.

Methods

Phytochemical analysis and bio-guided isolation-procedures including RP-HPLC and ¹H and ¹³C NMR utilizing biological models of diabetes, inflammation, and diabetic-neuropathy were used. Cultivated saffron (S-RCED) and Spanish-saffron stigma (S-SP) alone or in combination with Camellia sinus (CS) were investigated.

Results

The RP-HPLC analyses showed the presence of picrocrocin, crocin I, crocin II, crocin I’, crocin II’, and safranal (SAF) in both S-SP and S-RCED extracts with higher-concentrations. It had been shown that SAF was the most bioactive-compound in Crocus sativus. Both S-SP and S-RCED possessed significant (P < 0.05) anti-diabetic activities in acute (6 h), subchronic (8 d) and chronic (8 weeks) models. S-RCED had been proven with more hypoglycemic potentials when compared to S-SP and SAF. S-SP, S-RCED, and SAF produced significant anti-inflammatory and anti-nociceptive activities against carrageenan-induced inflammatory, hyperalgesic and tactile diabetic-neuropathy models, respectively. S-SP, S-RCED, and SAF elevated serum catalase, reduced glutathione, and insulin serum levels, ameliorated lipid peroxidation and HbA1c levels, and histopathologically regenerated the pancreatic beta-cells. Combinations with CS showed more significant efficacy than the single component.

Conclusion

The oxidative stress reduction, insulin secretagogue, and pancreatic beta-cells regeneration potentials might be responsible for the mechanism underlying the anti-diabetic, anti-inflammatory and anti-diabetic neuropathy activities. Thus, the cultivated Crocus sativus might be clinically useful for protecting against many serious-disorders.

Synthesis and Biological Evaluation of Polyfluoroalkylated Antipyrines and their Isomeric O-Methylpyrazoles

Background:

Formally belonging to the non-steroidal anti-inflammatory drug class pyrazolones have long been used in medical practices.

Objective:

Our goal is to synthesize N-methylated 1-aryl-3-polyfluoroalkylpyrazolones as fluorinated analogs of antipyrine, their isomeric O-methylated derivatives resembling celecoxib structure and evaluate biological activities of obtained compounds.

Methods:

In vitro (permeability) and in vivo (anti-inflammatory and analgesic activities, acute toxicity, hyperalgesia, antipyretic activity, “open field” test) experiments. To suggest the mechanism of biological activity, molecular docking of the synthesized compounds was carried out into the tyrosine site of COX-1/2.

Conclusion:

The trifluoromethyl antipyrine represents a valuable starting point in design of the lead series for discovery new antipyretic analgesics with anti-inflammatory properties.

Redox regulation of neuronal voltage-gated calcium channels

SIGNIFICANCE

Voltage-gated calcium channels are ubiquitously expressed in neurons and are key regulators of cellular excitability and synaptic transmitter release. There is accumulating evidence that multiple subtypes of voltage-gated calcium channels may be regulated by oxidation and reduction. However, the redox mechanisms involved in the regulation of channel function are not well understood.

RECENT ADVANCES

Several studies have established that both T-type and high-voltage-activated subtypes of voltage-gated calcium channel can be redox-regulated. This article reviews different mechanisms that can be involved in redox regulation of calcium channel function and their implication in neuronal function, particularly in pain pathways and thalamic oscillation.

CRITICAL ISSUES

A current critical issue in the field is to decipher precise mechanisms of calcium channel modulation via redox reactions. In this review we discuss covalent post-translational modification via oxidation of cysteine molecules and chelation of trace metals, and reactions involving nitric oxide-related molecules and free radicals. Improved understanding of the roles of redox-based reactions in regulation of voltage-gated calcium channels may lead to improved understanding of novel redox mechanisms in physiological and pathological processes.

FUTURE DIRECTIONS

Identification of redox mechanisms and sites on voltage-gated calcium channel may allow development of novel and specific ion channel therapies for unmet medical needs. Thus, it may be possible to regulate the redox state of these channels in treatment of pathological process such as epilepsy and neuropathic pain.

Free radical signalling underlies inhibition of CaV3.2 T-type calcium channels by nitrous oxide in the pain pathway

Nitrous oxide (N2O, laughing gas) has been used as an anaesthetic and analgesic for almost two centuries, but its cellular targets remain unclear. Here, we present a molecular mechanism of nitrous oxide's selective inhibition of CaV3.2 low-voltage-activated (T-type) calcium channels in pain pathways. Using site-directed mutagenesis and metal chelators such as diethylenetriamine pentaacetic acid and deferoxamine, we reveal that a unique histidine at position 191 of CaV3.2 participates in a critical metal binding site, which may in turn interact with N2O to produce reactive oxygen species (ROS). These free radicals are then likely to oxidize H191 of CaV3.2 in a localized metal-catalysed oxidation reaction. Evidence of hydrogen peroxide and free radical intermediates is given in that N2O inhibition of CaV3.2 channels is attenuated when H2O2 is neutralized by catalase. We also use the adrenochrome test as an indicator of ROS in vitro in the presence of N2O and iron. Ensuing in vivo studies indicate that mice lacking CaV3.2 channels display decreased analgesia to N2O in response to formalin-induced inflammatory pain. Furthermore, a superoxide dismutase and catalase mimetic, EUK-134, diminished pain responses to formalin in wild-type mice, but EUK-134 and N2O analgesia were not additive. This suggests that reduced ROS levels led to decreased inflammation, but without the presence of ROS, N2O was not able to provide additional analgesia. These findings reveal a novel mechanism of interaction between N2O and ion channels, furthering our understanding of this widely used analgesic in pain processing.

Role of oxidative stress in animal model of visceral pain

Reactive oxygen species play an important role both in physiological and pathophysiological reactions. The aim of this study was to determine the role of free radicals and antioxidants in the development of visceral pain. Visceral pain was produced by colorectal distension (CRD) in adult rats. CRD was caused by insertion of a lubricated latex balloon into the descending colon and rectum followed by inflation to 80mm Hg for 10min. During CRD, visceral pain was rated on 0-3.5 point scale. Oxidative stress was determined indirectly by measurement of free radical scavenging enzymes (glutathione peroxidase (GPx) and superoxide dismutase (SOD)) in the blood, liver and brain. Following CRD we observed (1) all rats expressed signs of visceral pain (overall rating was 1.83), (2) SOD and GPx levels were increased in the liver and blood, and decreased in the brain samples and (3) administration of the antioxidant Trolox, a water-soluble derivate of vitamin E, prior to CRD, prevented SOD and GPx changes in the liver, blood and brain, but did not affect pain scores. It was concluded, that CRD as a model of visceral pain, increases oxidative stress in animals, which could be prevented by prior administration of antioxidants; however, antioxidants did not attenuate signs of visceral pain caused by CRD.

Nitric oxide and pain: 'Something old, something new'

Challenges have emerged following the revival of nitric oxide (NO) from 'something old', a simple gas derived from nitrogen and oxygen with a role in the early stages of evolution, into 'something new', an endogenously formed biological mediator regulating a wide variety of physiological functions. Although pain is a common sensation, it encompasses multiple neurobiologic components, of which NO is only one. In pain research, the study of NO is complicated by convoluted problems related mostly to the effects of NO, which are pro- or anti-nociceptive depending on the circumstances. This dual function reflects the multi-faceted roles of the NO molecule described in physiology. This review covers current information about NO and its implications in pain mechanisms. In addition, it follows the pain pathways, demonstrating the role of NO in peripheral nociceptive transmission as well in central sensitization. This knowledge may provide the scientific basis for developing new drugs that are indicated for different types of pain, drugs that may be related to the chemical links of NO. A comprehensive approach to understanding the effects of NO will help clinicians identify novel agents that combine the pharmacological profile of native drugs with a controllable manner of NO release. Inhibitors of NO synthesis may have analgesic effects and would be of interest for treating inflammatory and neuropathic pain. Unfortunately, only a few of these compounds have reached the stage of clinical pain trials.

Protective effect of edaravone, a free-radical scavenger, on ischaemia-reperfusion injury in the rat testis

OBJECTIVE

To investigate the effect of edaravone, a radical scavenger, on ischaemia-reperfusion (I-R) injury in the testes.

MATERIALS AND METHODS

Eight-week-old male Sprague-Dawley rats were allocated to one of four groups: a no-drug group subjected to induction of 30-min of ischaemia and 60-min reperfusion; two drug groups administered edaravone at 1 or 10 mg/kg intraperitoneal and then subjected to 30-min ischaemia and 60-min reperfusion; and a sham-operated control group administered edaravone at 10 mg/kg intraperitoneal. To induce testicular I-R, the right testis was exposed outside of the body and the testicular artery was clamped with a small clip for 30 min. Blood flow and nitric oxide (NO) release were monitored in real time simultaneously with a laser Doppler flowmeter and an NO-selective electrode, respectively. After death the tissue levels of NO(2)-NO(3) (a marker of NO production), malondialdehyde (a marker of lipid peroxidation), 8-hydroxydeoxyguanosine (a marker of oxidative DNA damage), myeloperoxidase (a marker of neutrophil infiltration), and heat-shock protein 70 (HSP 70) and its mRNA were measured. The testicular tissue was also analysed histologically.

RESULTS

Clamping the testicular artery resulted in a decrease of blood flow to 0-5% of the basal level measured before clamping. NO release was increased during clamping and gradually recovered to the basal level on removing the clip. Interestingly, the peak of NO release in rats of the no-drug group occurred at the start of reperfusion, while that in the high-dose drug group occurred several minutes later. The levels of NO(2)-NO(3), malondialdehyde, 8-hydroxydeoxyguanosine, myeloperoxidase and HSP 70 and its mRNA, and histological variables, were significantly greater in the no-drug I-R group than in the control, and these variables were ameliorated by treatment with edaravone.

CONCLUSION

These results indicate that edaravone reduces the oxidative stress and prevents the testicular damage induced by I-R.

Ameliorative effects of Ocimum sanctum in sciatic nerve transection-induced neuropathy in rats

OBJECTIVES

The present study was aimed at investigating the ameliorative effect of Ocimum sanctum in sciatic nerve transection (axotomy)-induced peripheral neuropathy in rats.

MATERIALS AND METHODS

Sciatic nerve transection-induced axonal degeneration was assessed histopathologically. Paw pressure, Von Frey Hair, tail cold-hyperalgesia, motor in-coordination tests were performed to assess the extent of neuropathy. Biochemical estimations of thiobarbituric acid reactive species (TBARS), reduced glutathione (GSH), and total calcium levels were also performed. Methanolic extract of Ocimum sanctum at different doses (50, 100 and 200mg/kg p.o.) was administered for 10 consecutive days starting from the day of surgery.

RESULTS

Administration of Ocimum sanctum attenuated sciatic nerve transection-induced axonal degeneration, reduction of nociceptive threshold and motor in-coordination. Moreover, it also attenuated axotomy-induced rise in TBARS, total calcium and decrease in GSH levels in a dose-dependent manner.

CONCLUSION

Anti-oxidant and calcium attenuating actions may be responsible for observed ameliorative effects of Ocimum sanctum in axotomy-induced neuropathy.

In vitro metabolism study of edaravone in Wistar and hairless rat skin

We investigated the skin metabolism of edaravone as a radical scavenger in Wistar and hairless rat skin. Approximately 1 g of abdominal skin was excised from 10-week-old Wistar and hairless rats, homogenized in 10 ml saline, and centrifuged at 10000 g for 20 min. The supernatant fluid was used for the examination of edaravone metabolism in the skin, and we also used supernatant fluid that was heated at 80 degrees C. Edaravone solution (0.05 ml, 2.4 micromol/ml) was added to 0.95 ml Wistar rat and hairless rat skin homogenate supernatant fluids. In Wistar rats, the residual amount of edaravone in skin homogenate supernatant fluid at 37 degrees C after 0, 5, 10, 20 and 30 min was 61.58+/-1.65, 41.84+/-8.52, 35.54+/-8.62, 19.73+/-5.99 and 13.89+/-4.40%, respectively. In hairless rats, the residual amount of edaravone in skin homogenate supernatant fluid at 37 degrees C after 0, 5 and 10 min was 50.19+/-14.17, 6.71+/-5.82 and 0.89+/-0.80%, respectively, and edaravone was not detected after 20 min. Although it was thought that metabolic enzyme activity in skin homogenate supernatant fluid was lost following heat treatment at 80 degrees C, the residual amount of edaravone in our skin homogenate supernatant fluid decreased with time. It is suggested that edaravone metabolism in the skin is necessary for non-enzymatic reactions.

Preventive and curative effect of edaravone on nerve functions and oxidative stress in experimental diabetic neuropathy

Oxidative stress is implicated as a final common pathway in the development of diabetic neuropathy and pharmacological interventions targeted at inhibiting free radical production have shown beneficial effects. In the present study, we have investigated the effects of edaravone (3 mg/kg; 3-Methyl-1-phenyl-2-pyrazolin-5-one), a free radical scavenger (relatively selective to hydroxyl radicals) in streptozotocin (50 mg/kg i.p.) induced diabetic neuropathy in male Sprague-Dawley rats. Significant reduction (18%) in motor nerve conduction velocity, nerve blood flow (55%) and tail flick latency in cold (53%) and hot (50%) immersion test was observed in diabetic rats compared to age matched non-diabetic rats. Preventive (8 week) and curative (2 week) treatment of edaravone significantly improved the nerve conduction velocity and nociception but not nerve blood flow in diabetic rats. The changes in lipid peroxidation status and anti-oxidant enzymes (Superoxide dismutase and Catalase) levels observed in diabetic rats were significantly restored by edaravone treatment. Increase in blood pressure and vascular resistance was also significantly attenuated by edaravone treatment. This study provides experimental evidence to preventive and curative effect of edaravone on nerve function and oxidative stress in animal model of diabetic neuropathy. Hence edaravone may be tried clinically for the treatment of diabetic neuropathy since it is clinically used in stroke patients.

Superoxide, peroxynitrite and oxidative/nitrative stress in inflammation

A considerable body of evidence suggests that formation of potent reactive oxygen species and resulting oxidative/nitrative stress play a major role in acute and chronic inflammation and pain. Much of the knowledge in this field has been gathered by the use of pharmacological and genetic approaches. In this mini review, we will evaluate recent advances made towards understanding the roles of reactive oxygen species in inflammation, focusing in particular on superoxide and peroxynitrite. Given the limited space to cover this broad topic, here we will refer the reader to comprehensive review articles whenever possible.