Searching for analgesic drug candidates alleviating oxaliplatin-induced cold hypersensitivity in mice

Oxaliplatin is a third-generation, platinum-based derivative used to treat advanced colorectal cancer. Within the patient population on oxaliplatin therapy, a lower incidence of hematological adverse effects and gastrointestinal toxicity is noted, but severe neuropathic pain episodes characterized by increased cold and tactile hypersensitivity are present in ~95% of patients. This drug is also used to induce a rodent model of chemotherapy-induced peripheral neuropathy (CIPN)-related neuropathic pain which is widely used in the search for novel therapies for CIPN prevention and treatment. This paper provides a step-by-step, detailed description of the prevention and intervention protocols used in our laboratory for the assessment of oxaliplatin-induced cold allodynia in mice. To establish cold sensitivity in mice, the cold plate test was used. Latencies to pain reaction in response to cold stimulus (2.5°C) for vehicle-treated non-neuropathic mice, vehicle-treated mice injected with oxaliplatin (neuropathic control), and oxaliplatin-treated mice treated additionally with duloxetine are compared. Duloxetine is a serotonin/noradrenaline reuptake inhibitor which was found to produce significant pain relief in patients with CIPN symptoms. In our present study, duloxetine administered intraperitoneally at the dose of 30 mg/kg served as a model antiallodynic drug which attenuated or partially prevented cold allodynia caused by oxaliplatin.

Interventional and preventive effects of aripiprazole and ceftriaxone used alone or in combination on oxaliplatin-induced tactile and cold allodynia in mice

BACKGROUND AND PURPOSE

Chemotherapy-induced peripheral neuropathy (CIPN) is a pharmacoresistant neurological complication induced by some antitumor drugs. This study aimed to assess antiallodynic properties of aripiprazole and ceftriaxone used alone or in combination to attenuate neuropathic pain related to CIPN caused by oxaliplatin.

METHODS

Neuropathic pain was induced in mice by a single intraperitoneal dose of oxaliplatin (10 mg/kg). Aripiprazole and ceftriaxone were used in a single- or repeated dosing protocol. Their antiallodynic activity was assessed using von Frey and cold plate tests on the day of oxaliplatin injection and after 7 days. The influence of aripiprazole and ceftriaxone on animals' locomotor activity and motor coordination was also assessed.

RESULTS

Single-dose and repeated-dose aripiprazole 10 mg/kg and ceftriaxone 200 mg/kg used alone and in combination attenuated early-phase and late-phase tactile allodynia in oxaliplatin-treated mice. Repeated administrations of ceftriaxone 200 mg/kg prevented the development of late-phase tactile allodynia. Both drugs showed no antiallodynic properties in the cold plate test. Single-dose aripiprazole 1 and 10 mg/kg but not its repeated administration significantly decreased locomotor activity of oxaliplatin-treated mice. Single-dose aripiprazole 1 and 10 mg/kg, aripiprazole 1 mg/kg + ceftriaxone 50 mg/kg and aripiprazole 1 mg/kg + ceftriaxone 200 mg/kg impaired motor coordination in the rotarod test.

CONCLUSIONS

In mice, neither ceftriaxone nor aripiprazole attenuated cold allodynia. Ceftriaxone alone could attenuate tactile allodynia caused by oxaliplatin without inducing motor adverse effects. Although the administration of aripiprazole reduced tactile allodynia, this effect seems to be limited considering severe motor deficits induced by this drug.

Thiazoles with cyclopropyl fragment as antifungal, anticonvulsant, and anti-Toxoplasma gondii agents: synthesis, toxicity evaluation, and molecular docking study

Synthesis and investigation of antifungal, anticonvulsant and anti-Toxoplasma gondii activities of ten novel (2-(cyclopropylmethylidene)hydrazinyl)thiazole 3a-3j are presented. Among the derivatives, compounds 3a-3d and 3f-3j possess very high activity against Candida spp. ATCC with MIC = 0.015-7.81 µg/ml. Compounds 3a-3d and 3f-3j possess also very high activity towards most of strains of Candida spp. isolated from clinical materials with MIC = 0.015-7.81 µg/ml. The activity of these compounds is similar and even higher than the activity of nystatin used as positive control. Additionally, compounds 3c and 3e showed interesting anticonvulsant activities in the MES test, whereas compounds 3f and 3i demonstrated the anticonvulsant activity in PTZ-induced seizures. Noteworthy, none of these compounds impaired animals' motor skills in the rotarod test. Moreover, thiazoles 3a, 3h, and 3j showed significant anti-Toxoplasma gondii activity, with IC50 values 31-52 times lower than those observed for sulfadiazine. The results of the cytotoxicity evaluation, anti-Candida spp. and anti-Toxoplasma gondii activity studies showed that Candida spp. and Toxoplasma gondii growth was inhibited at non-cytotoxic concentrations for the mouse L929 fibroblast and the African green monkey kidney (VERO) cells. Molecular docking studies indicated secreted aspartic proteinase (SAP) as possible antifungal target.

Evaluation of cebranopadol, a dually acting nociceptin/orphanin FQ and opioid receptor agonist in mouse models of acute, tonic, and chemotherapy-induced neuropathic pain

BACKGROUND

Cebranopadol (a.k.a. GRT-6005) is a dually acting nociceptin/orphanin FQ and opioid receptor agonist that has been recently developed in Phase 2 clinical trials for painful diabetic neuropathy or cancer pain. It also showed analgesic properties in various rat models of pain and had a better safety profile as compared to equi-analgesic doses of morphine. Since antinociceptive properties of cebranopadol have been studied mainly in rat models, in the present study, we assessed analgesic activity of subcutaneous cebranopadol (10 mg/kg) in various mouse pain models.

METHODS

We used models of acute, tonic, and chronic pain induced by thermal and chemical stimuli, with a particular emphasis on pharmacoresistant chronic neuropathic pain evoked by oxaliplatin in which cebranopadol was used alone or in combination with simvastatin.

KEY RESULTS

As shown in the hot plate test, the analgesic activity of cebranopadol developed more slowly as compared to morphine (90-120 min vs. 60 min). Cebranopadol displayed a significant antinociceptive activity in acute pain models, i.e., the hot plate, writhing, and capsaicin tests. It attenuated nocifensive responses in both phases of the formalin test and reduced cold allodynia in oxaliplatin-induced neuropathic pain model. Its efficacy was similar to that of morphine. Used in combination and administered simultaneously, 4 or 6 h after simvastatin, cebranopadol did not potentiate antiallodynic activity of this cholesterol-lowering drug. Cebranopadol did not induce any motor deficits in the rotarod test.

CONCLUSION

Cebranopadol may have significant potential for the treatment of various pain types, including inflammatory and chemotherapy-induced neuropathic pain.

Acute cold allodynia induced by oxaliplatin is attenuated by amitriptyline

Oxaliplatin is a third-generation, platinum-based antitumor drug used to treat colorectal cancer. Since its main adverse effect is neuropathic pain resulting from chemotherapy‑induced peripheral neuropathy (CIPN), this drug is used to study the neurobiology of CIPN in rodents and to search for analgesics that could attenuate neuropathic pain symptoms - cold and tactile allodynia that develop in most of the oxaliplatin‑treated subjects. In this research, testing across various temperatures, we assessed the cold reactivity threshold of albino Swiss mice treated with oxaliplatin. We also investigated if amitriptyline, a tricyclic antidepressant drug and a sodium channel inhibitor, could attenuate cold allodynia caused by this chemotherapeutic drug. Cold allodynia was induced using a single intraperitoneal dose of oxaliplatin. In the cold plate test while testing various temperatures the pain sensitivity threshold was assessed at different time-points after oxaliplatin (late‑phase allodynia). Antiallodynic activity of intraperitoneal amitriptyline was assessed for doses of 1, 2.5 and 10 mg/kg. A statistically significant decrease in latency time to pain reaction was detected for all temperatures applied, but the earliest response (i.e., 2 h post‑injection) was noted at 2.5°C. In all experimental groups early‑phase cold allodynia was fully developed 3 h after oxaliplatin injection and it was maintained until the end of the observation period (7 days). Early‑phase cold allodynia induced by oxaliplatin can be effectively attenuated by amitriptyline.

Antinociceptive, antiallodynic and antihyperalgesic effects of the 5-HT1A receptor selective agonist, NLX-112 in mouse models of pain

BACKGROUND AND PURPOSE

NLX-112 (a.k.a. befiradol, F13640) is a drug candidate intended for the treatment of l-DOPA-induced dyskinesia. It is a highly selective serotonin 5-HT_1A receptor full agonist which has been previously tested in a variety of models of CNS effects including analgesic activity in rat. Its activity in mouse models of pain has not been previously investigated.

EXPERIMENTAL APPROACH

The activity of NLX-112 was tested in mouse models of acute pain (hot plate), tonic pain (intraplantar formalin test), in the oxaliplatin-induced neuropathic pain model of chemotherapy-induced peripheral neuropathy and in the streptozotocin (STZ)-induced model of painful diabetic neuropathy.

KEY RESULTS

The main findings indicate that (i) NLX-112 was markedly active in the formalin test with potent reduction of paw licking in both phases of the test (minimal effective dose (MED) 0.5 mg/kg i.p. and p.o. in acute phase, and 0.1 mg/kg i.p. and 1 mg/kg p.o. in late phase). The effects of NLX-112 in this test were completely abolished by the selective 5-HT_1A receptor antagonist, WAY100635; (ii) NLX-112 was active in the hot plate test and in the oxaliplatin-induced neuropathic pain model of chemotherapy-induced peripheral neuropathy, but at markedly higher doses (MED 2.5 mg/kg i.p.); (iii) NLX-112 was least active in the STZ-induced model of painful diabetic neuropathy (MED 5 mg/kg i.p.); (iv) NLX-112 did not affect locomotor activity.

CONCLUSIONS AND IMPLICATIONS

NLX-112 may have significant potential for treatment of tonic pain but may be less promising as a candidate for treatment of chemotherapy-induced or diabetic neuropathic pain.

Synthesis, antimicrobial and anticonvulsant screening of small library of tetrahydro-2H-thiopyran-4-yl based thiazoles and selenazoles

Synthesis and investigation of antimicrobial activity of 22 novel thiazoles and selenazoles derived from dihydro-2H-thiopyran-4(3H)-one are presented. Additionally, anticonvulsant activity of six derivatives is examinated. Among the derivatives, compounds 4a-f, 4i, 4k, 4 l, 4n, 4o-s and 4v have very strong activity against Candida spp. with MIC = 1.95-15.62 μg/ml. In the case of compounds 4a-f, 4i, 4k, 4 l, 4n, 4o, 4r and 4s, the activity is very strong against some strains of Candida spp. isolated from clinical materials, with MIC = 0.98 to 15.62 μg/ml. Additionally, compounds 4n-v are found to be active against Gram-positive bacteria with MIC = 7.81-62.5 μg/ml. The results of anticonvulsant screening reveal that compounds 4a, 4b, 4m and 4n demonstrate a statistically significant anticonvulsant activity in the pentylenetetrazole model, whereas compounds 4a and 4n showed protection in 6-Hz psychomotor seizure model. Noteworthy, none of these compounds impaired animals' motor skills in the rotarod test. We also performed quantum chemical calculation of interaction and binding energies in complex of 4a with cyclodextrin.

Prostaglandin-targeting agents and spectral heart rate variability in experimental partial bladder outlet obstruction in rats

The purpose of this study was to determine the activity of the autonomic nervous system (ANS), using spectral analysis of the heart rate variability (HRV) in the model of partial bladder outlet obstruction (PBOO) in rats treated with selected non-steroidal anti-inflammatory drugs (NSAID): piroxicam (PRX) or meloxicam (MLX), and following administration of PGF2a prostaglandin analogue (Enzaprost F5). Neither the use of PGF2a analogue nor of MLX, caused significant changes in the HRV spectrum (except for HRV spectrum total power reduction with MLX). The use of PRX caused reduction of the total power and powers of all components of the HRV spectrum (except for VLF). Moreover, increased nLF and reduced nHF were observed. The obtained results suggest that the total prostaglandin synthesis block with a non-selective cyclooxygenase inhibitor (PRX) results in reduced ANS total activity, with decreased parasympathetic activity and a relative sympathetic predominance. The preferential cyclooxygenase-2 block (MLX) caused reduction of the total ANS activity as well, however with no clear disproportion of any part of the ANS. Therefore, prostaglandin synthesis inhibition and associated decrease of parasympathetic activity may constitute an additional and favourable feature of NSAID pharmacodynamics in the treatment of BPH.

Dysfunction of the autonomic nervous system activity is responsible for gastric myoelectric disturbances in the irritable bowel syndrome patients

The pathogenesis of the irritable bowel syndrome (IBS) is still unsolved. Lately most attention has been focused on visceral hypersensitivity related to dysfunction of the autonomic nervous system (ANS). The aim of this study was to evaluate changes in the ANS activity and gastric motility in constipation-predominant IBS patients using the heart rate variability (HRV) and gastric myoelectric activity (EGG) recording. 23 patients (45+/-13 yrs) matching Manning criteria and 30 healthy volunteers (47+/-5 yrs) participated in the study. EGG and HRV in fasted and fed subjects with fasted serum catecholamine levels were measured in both groups. Fasting IBS pts showed gastric dysrrhythmia (29+/-14% vs. 11+/-7%), DP was 128.860 +/- 112.000 vs. 46.000+/- 23.200microV2, DF 2.37+/-0.8 vs. 2.9+/-0.2cpm. Feeding (300 kcal) improved dysrrhythmia to 20+/-13% vs. 8+/-5%, DP decreased to 74.500+/-57.720 vs. 165.600+/-89.000microV(2) and DF increased to 2.53+/-0.7 vs. 3.2+/-0.3cpm. In fasted and fed IBS pts SWC (channels 3-4) was about 60+/-11 vs. 84+/-8% and 68+/-14 vs. 92+/-8% respectively. In IBS pts resting HRV parameters were lower (LF - 650.3 vs. 811.6 ms2; HF - 508.8 vs. 854.6 ms2); with higher LF/HF ratio in IBS patients (1.52 vs. 1.2). The serum fasting level of adrenaline and noradrenaline in IBS pts were higher 1.28+/-0.06 vs. 0.65+/-0.05 nmol/L, and 3.54+/-1.2 vs. 2.89+/- 08 nmol/L, p<0.05 respectively. Increased sympathetic drive in IBS pts reflected by high catecholamine levels and LH/HF ratio is responsible for gastric dysrrhythmias and low DF and coupling. Meal has negligible effect on EGG parameters improvement. The ANS dysfunction observed in IBS patients is most probably responsible for disturbances in gastric myoelectric activity presented as gastric dysrrhythmias resulting in gastric emptying delay and dyspeptic symptoms.

The effect of the year angiotensin-converting enzyme inhibitors (ACE I) intake on circadian heart rate variability in patients with primary hypertension

INTRODUCTION

The autonomic nervous system (ANS) disturbances have been considered as one of the important factors in development of essential hypertension. However information about the effect of antyhypertensive treatment (angiotensin-converting enzyme inhibitors--ACEI) on cardiac ANS activity is ccscarce.

AIM

The purpose of the study was to evaluate the HRV circadian changes in patients with essential hypertension, treated with ACEI throughout the period of one year.

METHODS

Ten patients with essential hypertension, aged 26 to 64 years (mean 54.3 +/- 12.3) and 10 healthy volunteers, matched for age and gender were qualified for the investigation. Twenty four-hour arterial blood pressure measurements with simultaneous ECG monitoring were conducted in both mentioned groups. The hypertensive patients were examined before and after 1 year of ACE inhibitor (enalapril) intake. HRV analysis was carried out by the fast Fourier transformation (FFT). The time and spectral parameters were compared in 8 examined subjects characteristic for dippers, in time periods of day (6 a.m.-10 p.m.) and night (10 p.m.-6 a.m.).

RESULTS

The results obtained before the treatment, likewise in control group, presented night's increases of RMSSD (p < 0.05), pNN50 (NS, p > 0.05), VLF, LF (p < 0.05) and HF (NS) mean values with a decrease of LF/HF ratio (p < 0.05). Similar tendencies in the cardiac ANS activity were observed after 1 year of the enalapril intake. A comparison of day's HRV before and after one year of the ACE inhibition presented the increase in values of the parasympathetic system reflecting parameters: RMSSD, pNN50 (p = 0.01) and HF (NS) with a decrease of LF/HF ratio (p < 0.01). The evaluation of the night's HRV parameters presented the increase of HF mean value (p < 0.05), without any other significant changes between the trials.

CONCLUSIONS

After 1-year of ACE inhibitor administration the only improvement of the day's parasympathetic activity was observed. The night's vagal activity suggested as one of the essential factor in development of hypertension remained unchanged in patients qualified into "dippers" hypertension group.

The effect of transcutaneous nerve stimulation (TENS) on gastric electrical activity

TENS became widely accepted method of treatment pain syndromes in clinical practice. Lately has been shown that its affects also gastrointestinal tract by releasing NANC neurotransmitter VIP. The aim of this study was to evaluate the effects of TENS on gastric myoelectric activities measured by electrogastrography (EGG). Eighteen healthy men (mean age 23 +/- 1.7) were included in the study. Healthy volunteers were divided on 3 groups each 6 persons: with normogastria occurring at 94.5 +/- 7% of recording time--group A, with predominant bradygastria (36.6 +/- 14%)--group B and with tachygastria (33 +/- 14%)--group C. In fasted condition EGG (Synectics, Sweden) was recorded with skin electrodes. TENS 15 min was performed with use of Sinus 5 stimulator (6 Hz, 0.1 ms duration, intensities 10-20 mA, Zimmer, Germany). Stimulating electrodes were placed on non-dominant hand.

RESULTS

None of the subjects during TENS reported any side effects or symptoms, during the all studies. In group A in the fasting recordings, after TENS, an decrease of the normal values in the range 2-4 cpm down to 78.5 +/- 21% of recording time (p = 0.03) occurred. The dominant frequency in the bradygastric region increased up to 17.7 +/- 7% of the total recording. In group B TENS decreased bradygastria level from 36.6 +/- 14% to 20.6 +/- 15% (p = 0.02). TENS did not significantly affect tachygastria in group C. Amplitude of the EGG signal after TENS in group B and C increased by 40 and 150% respectively (p < 0.05). Significant decrease of the amplitude was observed in group A (13%). We conclude that TENS by activating centrally mediated somato-visceral reflexes affects gastric electrical activity. Our results suggest that TENS may be useful in treatment of the gastric dysrhythmia.